organic-walled microfossilsfrom the proterozoic vindhyan...
TRANSCRIPT
Pnincobo/nllisl 54(2005) 13-600031-0174/2005/13-60 $200
Organic-walled microfossils from the ProterozoicVindhyan Supergroup of Son Valley, Madhya
Pradesh, India
BIJAI PRASAD', S. N. UN1YALAND RAMSON ASHER
KDM Institute ojPetroleum Exploration, Oil and Natural Gas Corporation Limited,9 Kaulagarh Road, Dehra Dun- 248 195, India .
.Email: [email protected]
(Received 03 January 2005; revised version accepted 16 August 2005)
ABSTRACT
Prasad B, Uniyal S N & Asher R 2005. Organic-walled microfossils from the Proterozoic VindhyanSupergroup of Son Valley, Madhya Pradesh, India. Palaeobotanist 54 : 13-60.
Well-preserved and diversified organic-walled microfossil assemblages are recorded from the Vindhyansediments of Son Valley and DMH-A well, in Madhya Pradesh. The microfossils include acritarchs, coccoidand filamentous taxa that suggest a Meso-Neoproterozoic age for the Vindhyan Supergroup which, hitherto,was assigned a Late Paleoproterozoic to Early Paleozoic age, based on fossil evidences and radiometricdatings.
The Kajrahat Limestone, within the basal Semri Group, recorded abundant filamentous microfossils,VIZ. Poly/hrichoides. Karamia, Arctacellularia and Siphonophycus along with simple unornamentedsphaeromorph acritarchs (Leio~phaeridia spp.), suggesting ca. 1500-1450 Ma age of Early Mesoproterozoic.The microfossil assemblage ofDeonar Formation also includes the above taxa; however, Sarka, Eomicrocyslisand acanthomorph acritarchs, Tappania spp., appear within this formation along with abundantpolygonomorph acritarchs referable to Ocloedryxium. The Deonar microfossil assemblage resembles theassemblage of Roper Group (northern Australia) and suggests ca. \450-1350 Ma age of Early to MiddleMesoproterozoic.
The sediments of Kheinjua Subgroup are marked by the appearance of various species of Navifusa,Simia and Plerospermopsimorpha in the Koldaha Shale with overall abundance of Tappania, Salka,EOlllicrocySlis, Kildinosphaera and Leiosphaeridia. The presence of Middle to Late Mesoproterozoic markertaxa, viz. Tappania plana, T lubala and NaVifusa segmenlala helps to correlate the Koldaha Shale andSalkhan Limestone assemblages with the assemblage of the Ruyang Group (China), suggesting an EctasianStenian (ca.1350-1 050 Ma) age. In additon to the above taxa, the appearance of Early Neoproterozoic markertaxa, such as, VandalosphaeridiullI, Bavline/la, Melanocyrillium and budding leiosphaerids in the RampurFormation indicates a Late Stenian-Tonian age (ca. I050-850 Ma) for this formation.
The microfossil assemblage of the Rohtas Subgroup is quite distinct as the marker taxa of the KheinjuaSubgroup, viz. Tappania spp.and Navifusa spp. disappear. The presence of Trachysphaeridium laufeldi,Vandalosphaeridiul1l reliculalum, Bavlinellafaveolala and Slictosphaeridiul1l spp., and the disappearance ofEomicrocySlis, Salka and budding leiosphaerids within this formation allow its correlation with MiddleNeoproterozoic Miroyedikha (Siberia) and Husar-Kanpa (central Australia) assemblages, suggesting anEarly Cryogen ian (ca.850-750 Ma) age for the Rohtas Subgroup.
The microfossil assemblages from the Kaimur and Rewa groups are represented by the species ofSymplassosphaeriditilll, Synsphaeridium and Leiosphaeridia. The occurrence of B.faveolala, T laufeldi andOcloedryxiulII Iruncalwn in their assemblages suggest a Middle to Late Neoproterozoic (Late Cryogenian;ca.750-650 Ma) age. The sediments of the Bhander Group also include the above taxa. However, the
© Birbal Sahni Institute of Palaeobotany, India
14 THE PALAEOBOTANIST
appearance of Ediacaran (Vendian) marker species of Obruchevella, viz. O. parva and 0. valdaica in theGanurgarh Shale, and their abundance in the overlying Nagod Limestone and Sirbu Shale, suggests a LateCryogenian-Early Ediacaran (ca. 650-570 Ma) age for the Bhander Group. Yel, the appearance ofObruchevelladelicata, Lophosphaeridium tentativum and Cymatiosphaera sp. in the Nagod Limestone, and Obruchevellaparvissima, CristalliniulII sp. and Dictyotidium sp. in the Sirbu Shale suggest that the age of the BhanderGroup extends into the Late Ediacaran (ca.570-544 Ma).
The record of Calymmian (ca.1500 Ma) to Late Ediacaran (ca. 544 Ma) organic-walled microfossilassemblages categorically suggests an Early Mesoproterozoic to Terminal Proterozoic age-range for theVindhyan Supergroup. The occurrence of well-developed Middle and Late Mesoproterozoic microfossilassemblages in the Deonar Formation and Kheinjua Subgroup negates the Late Paleoproterozoic (ca. 1630Ma) age assignment to them, based on radiometric datings. The presence of Ediacaran (Vendian) markerspecies of Obruchevella and the absence of distinctive Early Cambrian acritarchs in the Bhander Groupbrackets the upper age limits of Vindhyan Supergroup to the Late Ediacaran, and does not encompass theLower Paleozoic.
Key-words-Meso-Neoproterozoic, organic-walled microfossils, Vindhyan Supergroup, Son Valley,India, acritarch biostratigraphy.
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INTRODUCTION
T HE Vindhyan Basin represents an undisturbed anddistinctive Proterozoic sedimentary succession of
calcareous, argillaceous and arenaceous facies in Central Indiawhich is classed as the Vindhyan Supergroup. Yet, the age ofVindhyan Supergroup has long been remained a subject ofmajor controversy due to the scantiness of fossils and itsvaried absolute age datings. Diverse and controversial ageshave been assigned to the Vindhyan succession, mainly basedon fossil evidences and radiometric datings at differentstratigraphic levels that gave its age ranging from LatePaleoproterozoic to Early Paleozoic (Silurian). The various ageevidences, suggested by a number of workers, are stillunconceivable and even not accepted by many stratigraphersas doubts were raised on a number of micro-and macrofossilevidences and radiometric datings.
The fossil and absolute age evidences available from theVindhyan Supergroup leading to its diverse age assignmentare the organic-walled microfossils (acritarchs, filamentous andcoccoid forms), stromatolites, macrofossils, small shellymicrofossils (SSMs) and radiometric absolute datings.
Organic-Walled Microfossils
Studies on acritarchs and other organic-walledmicrofossils from the Vindhyan sediments have been made bya number ofworkers (Salujha et al., 1971 a, b; Maithy & Shukla,1977; Maithy & Babu, 1993, 1997,2000; Venkatachala et a!.,1990; Kumar & Srivastava, 1995) which were recently reviewed
and summarized by Maithy (1992), Venkatachala et a!. (1996)and Maithy and Babu (1997). These studies broadly suggestedan Early Mesoproterozoic to Terminal Proterozoic (EarlyRiphean to Vendian) age-range for the Vindhyan Supergroup.The above age inference was made on the basis of records ofmainly the smooth and microsculptured sphaeromorphacritarchs (Kildinosphaera. Leiosphaeridia, Lophosphaeridium, Trachysphaeridium, Orygmatosphaeri-dium) andabundant filamentous and coccoid microfossils(Siphonophycus, Glenobot rydion, Myxococcoides,Eosynec!zoccus and Archaeoellipsoides). However, Salujha(1973), based on the records ofsmall acanthomorph acritarchs(Micrhystridium spp.) and herkomorphs (Cymatiosphaera,Dictyotidium) from the Rohtas Limestone and Bijaigarh Shale(Salujha el aI., 1971 a, b), opined that the Vindhyan Supergroupencompasses the Early Paleozoic also and ranges in age fromLate Precambrian to Early Silurian. Anabarasu (200 I) recordedherkomorph acritarchs referable to ? Cymatiosphaeroideskullingii of Late Neoproterozoic aspect from the basal SemriGroup (Chitrakoot Formation) of the Chitrakoot area. Prasadand Asher (2001) suggested Middle Mesoproterozoic(Ectasian) to Tenninal Proterozoic (Vendian) age-range for theVindhyan Supergroup on the basis of rich organic-walledmicrofossil assemblages from the DMH-A well, drilled in theVindhyan Basin near Damoh in Madhya Pradesh.
Stromatolites
A variety of stromatolitic structures were recorded fromdifferent limestone bearing formations (Kajrahat, Salkhan,
16 THE PALAEOBOTANIST
Rohtas and Nagod limestones) of the Vindhyan Supergroupwhich were later systematically studied and summarized byKumar (1982, 1984). Kumar (1984) recognised two stromatoliteassemblage zones, viz. the Kussiella-Colonnella Zone andthe Conophyton-Colonnella Zone in the Semri Group (LowerVindhyan), and the Baicalia- Tungussia Zone in the BhanderGroup (Upper Vindhyan). Kumar (1982, 1999a, b) suggestedan Early to Middle Riphean age for the stromatoliticassemblages of Semri Group and Late Riphaen for that fromthe Bhander Group.
Macro-and Megafossils
The macro-and megafossil records from the Vindhyansediments are the carbonaceous megafossils referable to theChllaria-TawlIia complex and metaphytic algae. These formswere described from the Lower as well as Upper Vindhyansuccessions (for details Maithy & Babu, 1988; Sharma et aI.,1992; Venkatachala el aI., 1996; Kumar & Srivastava, 1997;Kumar, 200 I), and are broadly indicative of the Precambrianage. Macroscopic algal filaments, referable to Crypania, arereported from the Rohtas Limestone from Katni area in CentralMadhya Pradesh (Kumar, 1995). Seilacher et al. (1998) recordedtrace-fossils of probable triploblastic animals from the ChorhatSandstone (Kheinjua Subgroup). However, doubts were raisedon this finding by a number of workers and considered to besyneresis cracks (Kumar, 2001). A doubtful specimen ofSpriggina, an Ediacaran fossil, is also reported from the PulkoaShale (Rohtas Subgroup) by Kathal el al. (2000), and thisfinding too is considered to be questionable (Kumar, 200 I).
Small shelly microfossils and brachiopods
Azmi (1998) recorded Early Cambrian small shellymicrofossils (SSMs) and brachiopods from the RohtasLimestone from the Son valley. Based on his finding, Azmi(1998) recognised the Precambrian-Cambrian boundary at thebase of the Rohtas Limestone, and regarded the Kaimur, Rewaand Bhander groups as Lower Paleozoic representatives inthe Vindhyan Basin. However, this fmding too, has been ruledout by several workers (for details Kumar, 2001).
Geochronology
Radiometric datings of the Vindhyan sediments atdifferent stratigraphic levels have been attempted by a numberof workers. However, these datings also gave varied ages to anumber of lithounits. For instance, Deonar FOImation (ChopanPorcellanite) of the basal Semri Group is dated ca. 1073-920 ±30 Ma at high temperature and ca. 617 ± 3.5 Ma at lowtemperature through Ar'°jAr39 method by Banerjee and Frank(1999). This unit has also been dated as 1631 ± 5 Ma throughU-Pb Zircon method by Ray et al. (2002). Similarly, the
glauconitic sandstone of the Rampur Formation (KheinjuaSubgroup) is also variously dated as 1110 ± 60 Ma (Vinogradovet al. ,1964), 1080 ± 40 Ma (Kreuzer el al., 1977) and 1599 ± 8to1628 ± 5 Ma (Rasmussen et a/., 2002). Recently, Sarangi elal. (2004) dated the Rohtas Limestone as 1599 ± 48 Ma. Theabove absolute ages of the Rohtas Limestone is almost aliketo the radiometric ages of Deonar (1631± 5 Ma; Ray el aI.,2002) and Rampur formations (1599 ± 8 tol628 ± 5 Ma;Rasmussen et al., 2002), although, Deonar and Rampurformations lie at the lower sn'atigraphic levels in respect to theRohtas Limestone.
Vinogradov et al. (1964) estimated the age of the LowerKaimur 940 ± 30 Ma, and 910 ± 30 Ma for the upper Kaimurrocks; whereas, Crawford and Compston (1970) dated Kimberlitepipes of Kaimur rocks at Majhgawan as 1140 ± 12 Ma by theRb-Sr method. But Kreuzer el al. ( 1977) revised the Vinogradovet al. (1964) dating of the Kaimur Sandstone as 890± 40 Ma onthe basis of newly recommended decay constants (A).Srivastava and Rajagopalan (1988, 1990) dated the Upper RewaSandstone and Lower Bhander Sandstone as 710-675 Ma and625 ± 24 Ma respectively by the Fission-Track method whichis suggestive of the Late Neoproterozoic age for the Rewa andBhander groups. Crawford and Compston (1970) dated theMaihar sandstone as 550 Ma (Late Ediacaran); whereas,Friedman el al. (1996) and Friedman and Chakraborty (1997)suggested the Precambrian-Cambrian boundary at the base ofSirbu Shale (Magardha Limestone) in the Bhander Group onthe basis of 8 I3C data.
It is apparent from the above review that the radiometricdata from the Vindhyan sediments are also quite diverse, andgave varied ages to a number of lithounits which consequentlysuggested the age-range of the Vindhyan Supergroup fromLate Paleoproterozoic to Early Paleozoic (Early Cambrian).
The records of Late Neoproterozoic herkomorphacritarchs? Cymaliosphaeroides ku/lingii from basal partsofthe Semri Group (Anabarasu, 2001), Ediacaran fossils (Kathalet aI., 2000) from the Pulkoa Shale (Rohtas Subgroup) andEarly Cambrian small shelly microfossils (Azmi, 1998) from theRohtas Limestone broadly indicated a Late NeoproterozoicTerminal Proterozoic age for the Semri Group with thePrecambrian-Cambrian boundary within the Rohtas Limestone.On the other hand, the absolute ages of the Deonar, Rampurand Rohtas formations of the same group (Semri Group) as oldas ca.1635 Ma (Late Paleoproterozoic) are very perplexing.Adding to the above controversy, the Fission-Track methodgave a Late Neoproterozoic (ca. 700-600 Ma) age to the Rewaand Bhander groups (Srivatava & Rajagopalan, 1988, 1990),whereas stable 8 IJC isotope excursion values suggested thePrecambrian-Cambrian boundary within the Bhander Group(Friedman & Chakraborty, 1997) in the uppermost part of theupper Vindhyan succession.
A perusal of the above fossils and radiometric age dataindicates that there were no conclusive evidences to ascertain
PRASAD et al..-ORGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 17
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Maihar (section-I) and the Jhal-Bihara (section· II).
18 THE PALAEOBOTANIST
the authentic age of the Vindhyan Supergroup, and newfindings further adding to its age controversies. It appearsthat the diverse ages were given to this unique Proterozoicsedimentary succession because a number of studies werelimited to particular or some lithounits, and the completeVindhyan succession was not taken into account in manystudies, and the evidences were not interpreted with respectto its distinctive sedimentary history.
To overcome the above age controversies, a detailedorganic-walled microfossils study has been made on theVindhyan sediments of Madhya Pradesh in outcrops as wellas subsurface sections, covering almost the completeVindhyan succession. A number of samples recordedabundant and well-preserved organic-walled microfossilsincluding some age potential Meso-and Neoproterozoic taxathat provided a more authentic age for the different lithounitsofVindhyan Supergroup as well as to the complete succession.In the present work, a detailed account of organic-walledmicrofossil assemblages, recovered from different lithounitsof this succession, is presented with discussion on their ageand the total age-range of the Vindhyan Supergroup.
GEOLOGICAL SETTING
The Vindhyan Basin is a large arcuate intracratonicProterozoic basin developed in the Central India, coveringparts of eastern Rajasthan, Madhya Pradesh, southern UttarPradesh and western Bihar (Figs lA, IB). The southern marginof the basin is bounded by the Son-Nannada Lineament Zone;whereas the northern margin is marked by the southern limitsof the Ganga Basin (Fig. IB). Biswas e/ af. (1993) consideredthat the Vindhyan Basin was an Interior Sag basin fOlmed bythe localised simple sagging of the continental crust. However,Ram e/ af. (1996) are of the opinion that it is a pericratonicbasin having pre-rift, syn-rift and post-rift phases ofdevelopment. Detailed accounts on the geology ofVindhyanBasin are available by the classic works of Mallet (1869), Heron(1932) and Auden (1933). Later on, Prasad (1976, 1984), Sastriand Moitra (1984) and Ram e/ al. (1996) have added furtherdata on the geology, structure and sedimentary history of theVindhyan Basin.
The entire sedimentary succession (approx. 4500 m thick)of the Vindhyan Basin is classed as the Vindhyan Supergroup.It is characterised by two distinct shallow marine depositionalfacies, and accordingly subdivided into two, viz. Lower andUpper Vindhyan successions which are separated by a majorregional unconformity (Fig. 2A). A number of lithostratigraphicclacsifications were attempted on the Vindhyan Supergroupby many stratigraphers. However, Auden's (1933)classificatio'n is widely accepted. This classification wasmodified later by Sastri and Moitra (1984) considering the latestCode of Stratigraphic Nomenclature, which is followed in thepresent work. The entire Vindhyan succession is divided into
four groups, viz. Semri, Kaimur, Rewa and Bhander (Auden,1933; Sastri & Moitra, 1984). The Semri Group represents theLower Vindhyan succession, whereas the Kaimur, Rewa andBhander groups characterise the Upper Vindhyan succession(Fig. 2A). Sastri and Moitra (1984) further subdivided the SemriGroup of the Son valley into four subgroups. The lowermostis the Mirzapur Subgroup which includes the Deoland (BasalConglomerate) and Arangi formations, and the KajrahatLimestone. The porcellanite succession that rests over theMirzapur Subgroup is named the Deonar Fonnation. TheKheinjua Subgroup overlies the Deonar Formation andcomprises the Ko1daha Shale, Salkhan Limestone and RampurFonnation. The youngest succession of the Semri Groupincludes the Rohtas Limestone and Bhagwar Shale andcomprises the Rohtas Subgroup. The Kaimur, Rewa andBhander groups of the Upper Vindhyan succession are alsosubdivided into a number of lithounits as shown in Fig. 2A.
MATERIAL AND METHODS
Outcrop samples for microfossil studies were collectedin two sections from the Maihar-Govindhgarh area of westernSon Valley in northem Madhya Pradesh (Figs IB, IC), viz. theBarhi-Badanpur-Maihar section and the Jhal-Bihara section(Fig. IC). Dutta e/ af. (1998) and the first author (B.P.) madedetailed geological studies in these sections and collected thesamples. The stratigraphic position of the studied samples isshown in the lithocolullUl of the respective sections (Figs 2B,2C). The Vindhyan succession of DMH -A well (surface to3500 m drilled depth), recently drilled in the Vindhyan Basinnear Damoh town in Madhya Pradesh (Fig. IB), andrepresenting an almost complete Vindhyan succession (Fig.4), has also been studied for organic-walled microfossils to
suppliment the outcrop microfossil data. The organic-walledmicrofossils were isolated by acid maceration technique,applying the simple Schulz's method, and palynomorphs wereseparated by the heavy liquid method.
MICROFOSSIL ASSEMBLAGES ANDBIOSTRATIGRAPHY
The organic-walled microfossils from Vindhyansediments include acritarchs, cocco ids (synaplomorphs) aswell as filamentous (nematomol1'hs) fonns and vase-shaped
microfossils (Melanocyrillium). An account of the microfossilassemblages, recovered from different lithounits ofVindhyan
Supergroup, is outlined below with discussion on their age.The stratigraphic distribution of selected organic-walledmicrofossils in the Vindhyan Supergroup, in outcrops as wellas subsurface, is presented through frequency distributions(Figs 3, 4), and the distinguishing microfossils ofeach lithounit
is shown in Fig. 5.
PRASAD el al.. -ORGANIC-WALLED MICROFOSSILS FROM SON VALLEY. MADHYA PRADESH. INDIA 19
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Sastri and Moitra. 1984). 2B. C). Generalised lithological succession of Vindhyan sediments in the Maihar-Govindgarh area (after Dutlael al., 1998), showing stratigraphic position of studied samples; 2B. Barhi-Badanpur-Maihar Section, 2C. Jhal-Bihara section.
20 THE PALAEOBOTANIST
Semri Group (Lower Vindhyan)
Kajrahat Limestone
The limestone and the associated thin shale partings ofthe Kajrahat Limestone from the Barhi-Badanpur-Maihar (S-41B, S-4/D; S-5) and the Jhal-Bihara (IV 14) sections (Figs 2B,2C), and the depth intervals from 3500-3147 m in DMH-A well(Fig. 4) representing the Kajrahat Limestone, yielded abundantfilamentous microfossils along with frequent occurrence ofsimple unomamented sphaeromorph acritarchs (PI. 1.1-14). Thefilamentous forms include Polylhrichoides linealus, Karamiasegmenlala, Torlunema pseudoseplala, Arclacellulariaellipsoidea, Oscillaloriopsis psi/ala and Siphonophyeus spp.(s. seplalum, S. robuslum, S. rugosum, S. keslron), along witha large number of dark opaque filamentous sheaths (PI. I. 614). Kildinosphaera chagrinata, Leiosphaeridia asperala,L. lenuissima, L. crassa and L. minulissima represent theunornamented sphaeromorph acritarchs (PI. I 1-5).
The Kajrahat assemblage by and large compares withthe Early Mesoproterozoic microfossil assemblages ofBuryanFormation, Southern Urals (Jankauskas, 1982) and BillyakhGroup (Anabar Uplift), northern Siberia (Golovenok & Belova,1984; Yakshin, 1991; Sergeev el af.. 1995) which are roughlyestimated as 1600-1300 Ma. Acritarch assemblages from theabove two formations of the Russian Platform and the KajrahatLimestone are of low diversity, and represented by simpleunornamented sphaeromorph acritarchs (Leiosphaeridia spp.and Ki/dinosphaera chagrinala) only, and are associated withabundant filamentous microfossils. The Kajrahat assemblagealso broadly compares with the microfossil assemblage of theLate Paleoproterozoic (ca. 1800 Ma) Chuanlingguo Formationof northern China (Zhang, 1986; Hofmann & Chen, 1981), assimple unornamented sphaeromorph acritarchs andfilamentous forms are common in both the assemblages.However, the Kajrahat assemblage shows EarlyMesoproterozoic features as it also includes abundant coccoidand filamentous microfossils (Venkatachala el al., 1990) andLower to Middle Riphean stromatolites (Misra el af., 1977;Kumar, 1976). Venkatachala el al. (1990) recorded a richassemblage ofcoccoid and filamentous microfossils from theKajrahat Limestone ofRohtasgarh area (Bihar) which is mainlyrepresented by the various species of Eoenlophysalis,Sphaerophycus, Telraphycus, Eosynechococcus, Myxococcoides, Diplococcus, Glenobolrydion, Siphonophycus,EomycelOpsis, Paleoanacyslis and Biocalenoides. Although,Venkatachala el al. (1990) suggested a Middle to LateMesoproterozoic (ca.1400-1 000 Ma) age to this assemblage, itshows close resemblence with the Early Mesoproterozoic(ca. 1500 Ma) microfossil assemblage of the Balbirini Dolomite(McArthur Group) ofnorthern Australia, described by Oehler(1978). The radiometric age of the Balbirini Dolomite is
estimated to be approximately 1500 Ma (Oehler, 1978) which isoverlain by the Roper Group having a well constrainedabsolute age of 1492-1429Ma (Kralik, 1982; Jackson el af.,1999). The microfossil assemblage of the Jalboi and Corcoranformations (Early Mesoproterozoic; ca. 1450-1429 Ma) of theRoper Group, northern Australia (Peat el af., 1978; Javaux elal., 2001) also broadly correlates with the Kajrahat assemblage,as abundant filamentous forms and leiosphaerids are commonin both the assemblages. However, the Kajrahat assemblagelacks the presence of much developed forms, such asTappania, Valeria, Diclyosphaera and Salka, which arepresent in the Jalboi-Corcoran assemblage of the Roper Group(Javaux el al., 200 I) and appears little older than the Jalboi andCorcoran assemblages. It is worth mentioning that the KajrahatLimestone is overlain by the Deonar Formation in the VindhyanBasin which also contains a microfossil assemblage showingthe first appearance of the characteristic acanthomorphacritarch Tappania, along with Salka and Eomicroeyslis, andis comparable with the Jalboi-Corcoran microfossil assemblageofthe Roper Group that has been dated at 1450-1429 Ma (Kralik,1982; Jackson el af., 1999).
It appears that the Kajrahat assemblage is little older thanthe Jalboi-Corcoran assemblage, and represents an EarlyMesoproterozoic (Late Calymmian; ca.1500-1450 Ma)microfossil assemblage in the Vindhyan Basin. Knoll (1996)also opined that Early Mesoproterozoic (1600-1400 Ma)sediments are characterised by low diversity acritarchs, mainlyrepresented by simple unornamented leiosphaerids along withsmall leiosphaerids (Eomicrocyslis, Synsphaeridium) andcyanophycean filamentous sheaths, as is the case with themicrofossil assemblage of the Kajrahat Limestone.
Deonar Formation
This formation represents a very conspicuous lithologyin the Lower Vindhyan succession (Semri Group) and ischaracterised by a porcellanite succession having silicifiedtuffs, cherts and porcellanised silicified shale. Three samplesfrom the Ihal-Bihara section (IV48C-5B, IV48D, II155D-13H)and one (S-3B) from the Barhi-Badanpur-Maihar section (Figs2B, 2C) and the porcellanite succession ofDMH-A well from3147-1930 m depth intervals (Fig. 4) yielded moderate butsignificant organic-walled microfossils (PI. 21-17).
Simple unornamented sphaeromorph acritarchs are themain constituents of the Deonar assemblage which includeLeiosphaeridia asperala, L. lerna la, L. minutissima, L.lenuissima, Kildinosphara chagrinala, K. granulala andDiclyosphaera sp. (PI. 2 10-11, 14-16). Forms, such asEomicrocyslis elegans, E. malgiea, Synsphaeridiul/1sorediforme, Symplassosphaeridium lumidulum and Salkasp. cf. S. squamlfera represent the coccoid microfossils, andshow their first appearance here. Filamentous forms, viz.Siphonophycus spp., Karamia segmenlala, PolYlhrichoides
PRASAD et al.. -ORGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 21
lineatus, Tortunema pseudoseptata and Oscillatoriopsispsi/ata that occur in the Kajrahat Limestone, also persist inthis formation. However, the most distinctive feature ofDeonarassemblage is the appearance of acanthomorph acritarchs,viz. Tappania spp. (T plana & T tubata) in rarity (PI. 2 5-6),and several polygonomorph acritarchs attributable toOctoed,yxium (Rudavskaia) Vidal (PI. 21- 4) which are referredto as a new species of Octoedryxium, viz. 0. vindhyanense.
Except for the record of polygonomorphic acritarchs(Octoedryxium vindhyanense), the Deonar microfossilassemblage resembles the Early Mesoproterozoic assemblagesrecorded from the Jalboi, Corcoran and McMinn formations(Peat et al., 1978; Javaux et at., 200 I) of the Roper Group(northern Australia), which have been dated ca.1450-1429 Maby SHRIMP and Rb-Sr methods (Kralik, 1982; Jackson et al.,1999). Species of Tappania and Satka, unornamentedsphaeromorph acritarchs (Leiosphaeridia spp.,Ki/dinosphaera spp.) and filament (Siphonophycus spp.) aswell as coccoid forms (Synsphaeridium spp., Eomicrocystisspp.) are common in both the assemblages. The appearanceof Tappania in the Deonar Formation, though in rarity, is verysignificant. Tappania is an acanthomorph acritarch with theoldest record from the Early Mesoproterozoic Jalboi Formation(ca. 1450 Ma) ofthe Roper Group in northern Australia (Javauxet al., 2001). The Jalboi Formation is about 400 m above thestratigraphic level of Mainoru Formation that has beenradiometrically constrained approxin1ately 1492 ± 4 Ma (Jacksonet al., 1999), and about 700m down below the stratigraphiclevel of McMinn Formation which is dated ca. 1429 ± 31 Ma(Kralik, 1982). The absolute ages of the above two horizonssuggest the depositional age of the Jalboi and Corcoranformations of the Roper Group to ca.1450 Ma. Thus, theappearance of acanthomorph acritarchs, viz. Tappania planaand T tubata, coccoid forms Satka sp. cf. S. squamifera andEomicrocystis spp., with associated occurrence of smoothsphaeromorph acritarchs and abundant filamentousmicrofossils suggests an age similar to the Jalboi and Corcoranformations of the Roper Group for the Deonar Formation. 1l1isassemblage also resembles the late Early Mesoproterozoic(ca. 1400 Ma) Chamberlain Shale (lower Belt Supergroup)assemblage of Montana, U.S.A. (Horodyski, 1980) and theDismal Lakes Group, Arctic Canada (Horodyski andDonaldson, 1980, 1983) as abundant unornamentedsphaeromorph acritarchs (Kildinosphaera spp. &Leiosphaeridia spp.), filamentous (Siphonophycus spp.) andcoccoid (Satka spp.) forms are common in both theassemblages.
The occurrence of polygonomorph acritarchs(Octoed,yxium) in Deonar Formation is perplexing. Its oldestrecord is from the Late Neoproterozoic Upper Visingso Bedsof Sweden (Vidal, 1976a). The occurrence ofpolygonomorphacritarchs in this lithounit extend the age ofDeonar assemblageto a little younger than the Roper Group assemblage. But, inany case, this assemblage appears undoubtebly older than
the Middle to Late Mesoproterozoic Tappania dominatedassemblages ofRuyang Group (ca. 1256-1140 Ma) of EasternChina (Yin, 1997; Yin & Yuan, 2002) and the Bahr~ichGroup(ca. 1350-1150 Ma) ofNorthern India (Prasad & Asher, 2001),as Tappania is rarely represented in this assemblage and it isalso succeeded by a Tappania dominated assemblagecorresponding to the Koldaha Shale.
It is inferred that the Deonar Formation represents a lateEarly Mesoproterozoic to Middle Mesoproterozoic (LateCalymmian-Early Ectasian; ca.1450-1350 Ma) organic-walledmicrofossil assemblage in the Vindhyan Basin. This ageinference is corroborated by the fact that the Deonarassemblage is immediately succeeded by the Tappaniadominated microfossil assemblage of the Koldaha Shale in theVindhyan Basin which is well correiatable with the Middle toLate Mesoproterozoic (ca. 1350-1150 Ma) microfossilassemblages of the Ruyang Group (eastern China) and theBahraich Group (Ganga Basin, India) due to the dominantoccurrence of Tappania in these assemblages.
Recently, the absolute age dating of the DeonarFormation is estimated as 1631 ± 5 Ma (Late Paleoproterozoic)by the U-Pb zircon method (Ray et al., 2002). If this dating istaken into account, then the taxa, such as Tappania(acanthomorphs), Octoedryxium (polygonomorhs),Dictyosphaera and Satka, representing a well-developed anddiversified acritarch assemblage, seem appeared during theLate Paleoproterozoic (1631 ± 5 Ma). But, the well-developedacritarch assemblages having acanthomorph andmicrosculptured sphaeromorph acritarchs are known from thelater part of Early Mesoproterozoic and younger Proterozoicsequences only (for details Knoll, 1996). So, the recentabsolute dating of the Deonar Formation as 1631 ± 5 Ma needsreconsideration in view of the present record of a welldeveloped and rich late Early Mesoproterozoic to MiddleMesoproterozoic (ca. 1450-1350 Ma) microfossil assemblagefrom this forn1ation,
Koldaha Shale
This formation represents the lowermost lithounit in theKheinjua Subgroup and comprises a thick succession of greyto olive green shale, and unconformably overlies the DeonarFormation. It is about 500 m thick in the outcrop areas, butthicker (approx. 800 m) in the subsurface. Four samples (S-8A,B, C; S-9) from the Barhi-Badanpur-Maihar section (Fig. 2B)and three ( IV55D-5D, D-7; D-5 ) from the lhal-Bihara section(Fig. 2C), and the Koldaha Shale succession from 1930-940 mdepth intervals in the DMH-A well (Fig. 4) contain a rich anddiversified assemblage oforganic-walled microfossils ( PI. 3.1"16; PI. 4.1-18).
The abundant occurrence of acanthomorph acritarchs,viz. Tappania plana, T tubata and T gangaei (PI. 3.1-5);netromorph acritarchs, such as NaVIfusa segmentata, N.majensis and N. granulatus (PI. 3.6, 10) and filamentous forms,
22 THE PALAEOBOTANIST
viz. Arctacellularia ellipsoidea and A. tetragonala (PI. 3.1112) are the most distinctive features of the Koldaha Shaleassemblage. The above enlisted species of Navifusa maketheir first appearance in this formation along with Tappaniagangaei; whereas, Tappania plana. T tubata. Arctacellulariatetragonala and A. ellipsoidea persist from the underlyingDeonar Formation. In addition, taxa such asPterospermopsimorpha insolita, P saccata, Simia annulare(PI. 3.7-9) and Lophosphaeridium granulatum (PI. 4.18) alsoappear in this formation (Figs 3, 4,5). Besides, abundant simplesphaeromorph acritarchs, represented by various species ofLeiosphaeridia (L. asperata, L. jacutica. L. crassa. L.tenuissima) and Kildinosphaera (K. chagrinata. K. granulata)persist from the Deonar Formation.
Coccoid forms, such as Eomicrocystis malgica. E.elegans. Satka colonialica. S. squamifera. Synsphaeridiumsorediforme and Symplassosphaeridium tumidulum (PI. 4.56, 8-13, 15) continued to occur here from the underlying DeonarFormation with increased frequency. However, other coccoidforms, such as Eohyella dichotoma. Eosynechococcusmoorei, Tetraphycus diminutivus, A. acinulus, Eoentophysalissp.,Sphaerophycus parvum and Spumosina rubiginosa (PI.4.1-4,7) also make their appearance here, and form an importantconstituent of the assemblage. Filamentous microfossils, viz.Siphonophycus spp. and Oscillatoriopsis spp. are also verycommon in this assemblage and persist from the underlyingDeonar Formation (Figs 3, 4).
The Koldaha Shale assemblage closely resembles Middlet9 Late Mesoproterozoic microfossil assemblages ofRuyangGroup (ca. 1256.-1140Ma), southern Shanxi, Eastern China (Yin,1997; Yin & Yuan, 2002) and Bahraich Group ( ca. 1350-1150Ma), Northern India (Prasad & Asher, 200 I) as the variousspecies of Tappania occur abundantly in the above threeassemblages. The above three assemblages are also associatedwith the occurrence ofNavifusa spp. and Arctacellularia spp.along with a large number of unornamented sphaeromorphacritarchs and filamentous as well as coccoid microfossils.The record of acanthomorph acritarchs Tappania spp. (Tplana, T tubata, T gangaei), netromorph acritarchs Navifusaspp. (N. segmentata, N. majensis) and filamentous formArctacellularia spp. (A. tetragonala. A. ellipsoidea) is verysignificant in dating the Koldaha Shale assemblage. Tappaniawas first recorded in abundance from the Baicaoping andBeidajian formations of the Ruyang Group, Shanxi Province(eastern China) and forms an important constituent of theRuyang Group assemblage (Yin, 1997; Yin & Yuan, 2002). Theage ofthe Beidajian Formation was determined by K-Ar methodas 1256-1140 Ma (Ma et af., 1980; Guan et al., 1988). Later, Yinand Yuan' (2002) recorded Navifusa segmentata, and A.
tetragonala from the Ruyang Group and regarded them asimportant constituents of the Ruyang assemblage. Based onthe microfossil data and radiometric dates, the Ruyangmicrofossil assemblage was assigned to the Middle to LateMesoproterozoic (1256-1140 Ma) age (Yin, 1997; Yin & Yuan,2002). Prasad and Asher (200 I) also recorded a rich acritarchassemblage, quite similar to the Ruyang assemblage, from thesubsurface metasedimentary succession (Bahraich Group) ofthe Ganga Basin in Northern India which is also dominated byTappania plana, T tubata, Navifusa segmentata, N. granulataand Arctacellularia tetragonala. Prasad and Asher (200 I)assigned a Late Ectasian-Early Stenian (ca.1350-1150 Ma) ageof Middle to Late Mesoproterozoic to the Tappania-dominatedBahraich assemblage, as the radiometric dating of igneousintntsives in the Bahraich Group gave the absolute age of1320 ± 30 Ma (Chug et al., 1989) and its assemblage wasequated with Ruyang Group assemblage.
The Koldaha Shale assemblage also compares with theMiddle to Late Mesoproterozoic microfossil assemblages ofthe Eqalulik and Uluksan groups of the Bylot Supergroup(Hofmann & Jackson 1991, 1994) and the Baffm Bay Group ofthe Thule Supergroup (Hofmann & Jackson, 1996; Samuelssonet af., 1999) in having abundant sphaeromorph and netromorphacritarchs, with associated filamentous and coccoid forms.The diabase in the basal unit of the Thule Supergroup(Wolstenholme Formation) provided an isochron age of ca.1268 Ma (LeCheminant & Heaman, 1991), whereas Knight andJackson (1994) suggested the age of the Bylot Supergroup tobe the 1270-1190 Ma.
Thus, the close comparable relationship ofKoldaha Shaleassemblage with the known Middle to Late Mesoproterozoicorganic-walled microfossil assemblages suggests that theKoldaha Shale belongs to the Middle to Late Mesoproterozoic(ca.1350-1150Ma)age.
Salkhan Limestone
One sample (IIJ 55G/I 0) from the Jhal-Bihara section (Fig.2C), and from the 940-780 m depth interval in the DMH-A well(Fig. 4) recorded moderate occurrence of organic-walledmicrofossils in the Salkhan Limestone (PI. 5.1-19).Unornamented sphaeromorph acritarchs are the mainconstituents of the assemblage and represented by the variousspecies of Kildinosphaera and Leiosphaeridia. Importantforms of the underlying Koldaha Shale, viz. Tappania plana,r tubata. Navifusa majensis, N. segmentata.Pterospermopsimorpha saccata. Simia annulare, Satkasquamifera, Eomicrocystis spp., Sphaerophycus parvum,Eoentophysalis sp. cf. E. belcherensis. Tetraphycus gregalis
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Fig. 3-Stratigraphic distribution of selected Meso-Neoproterozoic organic-walled microfossils in outcropping Vindhyan sediments of western SonValley, northern Madhya Pradesh.
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24 THE PALAEOBOTANIST
and T dichotoma persist here (PI. 5.1-19); whereasLeiosphaeridea kulgunica (PI. 5.14-15) and Stictosphaeridiumsinapticulum (PI. 5.13) appear in this formation. Siphonophycusseptatum, S rugosum and Oscillatoriopsis psilata representthe filamentous forms (Figs 3, 4, 5).
Kumar and Srivastava (1995) also recorded a large numberof coccoid and filamentous microfossils from this unit in SonValley; these are represented by different species ofMyxococcoides, Eosynechococcus, Eoentophysalis, Sphaerophycus. Oscillatoriopsis Tetraphycus, Palaeolyngbya andSiphonophycus, along with Trachysphaeridium sp. andLeiosphaeridia jacutica.
The palynofossil assemblage of the Salkhan Limestoneis very similar to that from the underlying Koldaha Shale, exceptthat there are fewer individual taxa. It is also represented bythe age markers Tappania plana, T tubata NaviJusasegmentata. and suggestive of a Middle to LateMesoproterozoic age, similar to the Koldaha shale. However,the appearance of Leiosphaeridia kulgunica (PI. 5.14, 19),Stictosphaeridiuln sinapticulum (PI. 5.13) and S implexulnwhich, till now, are recorded from Late Mesoproterozoic andyounger sediments, suggest a little younger age to thisassemblage than the Koldaha Shale. It appears that the SalkhanLimestone represents a Late Mesoproterozoic (Late Stenian;1150-1050 Ma) assemblage in the Vindhyan Basin, as Tappaniaspp. and Navifusa spp. are the common constituents of theSalkhan microfossil assemblage. This inference is corroboratedby the fact that the Salkhan Limestone is immediately overlainby the Rampur Formation which has yielded a well-developedand diversified microfossil assemblage of latestMesoproterozoic-Early Neoproterozoic (1050-850 Ma) age.
Rampur Formation
This formation includes glauconitic sandstonesuccession with intercalated siltstones and shales. Three shalesamples (II/168, W171, II/178) from the Thal-Bihara section (Fig.2C) and the depth intervals between 780-620 m in DMH-A(Fig. 4), representing this formation, yielded a well-preservedand diversified organic-walled microfossil assemblage (PI. 6.113;PI. 7.1-19).
The microfossil assemblage of the Rampur Formation isbroadly similar to that of the Koldaha Shale and the SalkhanLimestone. However, the species ofSatka (S colonialica andS squamifera) and Navifusa (N. segmentata, N. majensis, N.granulata) dominate quantitatively over the acanthomorph(Tappania spp.), sphaeromorph (Kildinosphaera spp.,Leiosphaeridia spp.) and pterosprmorph (Pterospermopsimorpha spp., Simia spp.) acritarchs. Several coccoid forms,such as Eomicrocystis spp., Sphaerophycus parvum,Tetraphycus acinulus, Eoentophysalis sp. cf. E. belcherensis,Symplassosphaeridium spp., Synsphaeridium spp., andfilamentous forms, viz. Siphonophycus spp. andOscillatoriopsis spp. persist here from the underlying Koldaha
Shale and Salkhan Limestone with almost the same frequency.However, the age potential taxa, such as Tappania plana (PI.6 II), T tubata (PI. 6.12-13). Navifusa segmentata (PI. 7.10, 16)and Arctacellularia tetragonala (PI. 7.15), which wereabundant in underlying Koldaha Shale and Salkhan Limestone,become rare in this assemblage, and completely disappear inthe upper part of this formation (Figs 3, 4).
The most important feature of the Rampur assemblage isthe appearance of other acanthomorph acritarchs, viz.Vandalosphaeridium reticulatum (PI. 6.5-6), V varangeri (PI.6.7) and Trachyhystrichosphaera truncata (PI. 6.3), coccoidforms, viz. Bavlinella Javeolata, ornamented sphaeromorphacritarchs, viz. Kildinosphaera verrucata (PI. 7.19) andTrachysphaeridium laminaritum (PI. 6.1), and filamentousmicrofossils, viz. Chlorogloeaopsis kanshiensis and Ccontexta (PI. 7.7,9). In addition, a large number of buddingleiosphaerids (PI. 7.2-3, 5) and vase-shaped microfossilsassignable to Melanocyrillium Bloeser, 1985 (PI. 6.8-10) alsomake their appearance within this formation, and all the abovenewly appearing taxa form an important constituent of theRampur assemblage (Figs 3, 4).
The presence of various species of Tappania (T plana.T tubata), NaviJusa (N. segmentata, N. majensis) andArctacellularia (A. tetragonala, A. ellipsoidea), though inrarity, largely allow the comparison of Rampur assemblagewith Late Mesoproterozoic microfossil assemblages, asdiscussed above. Nevertheless, this assemblage also includesseveral taxa, such as Vandalosphaeridium spp.,Trachyhystrichosphaera truncata, Bavlinella Javeolata.ornamented sphaeromorph acritarchs (K. verrucata, Tlaminaritum), budding leiosphaerids and Melanocyrillium thatgenerally appear in Early Neoproterozoic or near the MesoNeoproterozoic boundary (Knoll, 1996, 2000). Indeed, themicrofossil assemblage of Rampur Formation shows moreakinness to Early Neoproterozoic assemblages and resemblesthe Lakhanda (ca. 1000-900 Ma) assemblage of Siberia(Jankauskas, 1989; German, 1990). Forms, such as, Navifusamajensis, N. bacillan's, Pterospermopsimorpha insolita,Leiosphaeridia spp., Arctacellularia tetragonala,Chlorogloeaopsis spp., Satka spp., Eomicrocystis spp.,Synsphaeridium spp., Symplassosphaeridiuln spp.)Siphonophycus spp. and budding leiosphaerids are commonin both the assemblages. The present assemblage alsocompares with the latest Mesoproterozoic-EarlyNeoproterozoic (ca. 1050-940 Ma) microfossil assemblage ofthe Bushimay Group (Zaire) from central Africa (Maithy, 1975),as the species of Siphonophycus, Arctacellularia.Pterospermopsimorpha, Chlorogloeaopsis, Navifusa.Leiosphaeridia and Kildinosphaera are common in both theassemblages. The microfossil assemblage from RampurFormation and one that from the Early Neoproterozoic (900800 Ma) Veteranen Group, Spitsbergen (Knoll & Swett, 1985)are also quite similar and broadly correiatable to each othersas majority of the forms are common in both the assemblages,
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26 THE PALAEOBOTANIST
except the species of Tappania and Navifusa which are absentin the Veteranen Group.
Thus, the appearance of ornamented sphaeromorphs (K.
verrucata, T lal11inaritum), newly incoming acanthomorphacritarchs (T truncata and V reticulatul11), vase-shapedmicrofossils (Melanocyrillium) and budding leiosphaeridsthat generally appear in Early Neoproterozoic (Knoll, 1996;Knoll, 2000) strongly favours for a Tonian (ca. 1000-850 Ma)age of Early Neoproterozoic to this formation. The presenceof above mentioned characteristic Early Neoproterozoic taxa,in association with the rare occurrence of LateMesoproterozoic marker taxa, viz. Tappania spp. and Navifilsasegmentata, suggests that the Rampur FOlmation ranges inage from latest Mesoproterozoic to Early Neoproterozoic (ca.1050-850 Ma).
The KiAI' absolute datings of Rampur Formation byKruezer et al. (1977) as 1080 ± 40 Ma broadly cOlToborates thepresent age assignement of this formation on the basis oforganic-walled microfossils. However, the recent dating ofthislithounit as old as 1628 ± 8 Ma (Late Paleoproterozoic) byRasmussen et af. (2002) needs reconsideration in view of therecord of a rich and diversified organic-walled microfossilassemblage of latest Mesoproterozoic-Early Neoproterozoicage.
Rohtas Subgroup
This subgroup represents the uppermost sedimentarysuccession in the Semri Group and includes two formations,viz. the Rohtas Limestone and the Bhagwar Shale in the SonValley. Two samples (IV388, 1l/395) from the Rohtas Limestoneand one sample ( IV411) from the Bhagwar Shale in the JhalBihara section (Fig. 2C) and depth intervals from 620- 575m inthe DMH-A well, representing Rohtas Limestone (Fig. 4),yielded moderate OCCUlTence of organic-walled microfossils(PI. 8.1-17).
The Rohtas assemblage is mainly represented byabundant sphaeromorph acritarchs. It includes Leiosphaeridiatenuissima. L. asperata, Kildinopshaera granulata. K.verrucata, Trachysphaeridium laminaritum, Stictosphaeridiul11 sinapticulum, S. implexum and Lophosphaeridiul11jansoniusii. They occur in association with coccoid forms,viz. Satka colonialica, S. squamifera, Synsphaeridiul11sorediforme and Syl11plassosphaeridium tUl11idulum.Filamentous forms are also present, but in rarity, and mainlyrepresented by various species of Siphonophycus.Oscillaloriopsis. Karamia and Chlorogloeaopsis (PI. 8.1-17).
Important taxa of the underlying Rampur Formation, viz.Vandalosp}lGeridium reticula tum, Trachysphaeridiumlaminaritum, Plerospermopsimorpha saccala, Bavlinellafaveolata and Stictosphaerdium sinapticulum persist in theRohtas Subgroup. In addition, taxa such as Satka spp..Eomicrocyslis spp., Pterospermopsimorpha insolila, Simia
annulare and budding leiosphaerids also continue to occurin this lithounit, but disappear at different stratigraphic levelswithin this subgroup. On the other hand, species of Tappnia,Navifusa and Arctacel!ularia. which were the importantconstituents in the underlying Kheinjua Subgroup, arecompletely absent in the Rohtas Subgroup (Figs 3,4).
The Rohtas assemblage compares with the MiddleNeoproterozoic Miroyedikha acritarch assemblage (ca. 850Ma) ofSiberia (Jankauskas, 1989; German, 1990) since smoothand ornamented sphaeromorph acritarchs are abundant in boththe assemblages, as are coccoid (Satka spp.,Symplassosphaeridiul11 spp., Synsphaeridiul1l spp.) andfilamentous forms (Siphonophycus spp, Chlorogloeaopsis).The characteristic budding leiosphaerids are also present inboth assemblages. The species of Eomicrocyslis andPterospermopsimorpha insolita, which were very common inthe immediately underlying assemblage of Rampur FOimationand its comparable asemblages of Lakhanda and Veteranengroups, are conspicuously absent in the Rohtas as well as inthe Miroyedikha assemblages. The Rohtas assemblage alsoresembles the Middle Neoproterozoic organic-walledmicrofossil assemblage of the Husar-Kanpa formations,recovered from the subsurface (Husar-I well) in the westernOfficer Basin, central Australia (Hill el af., 2000) as these formsare common in both the assemblages. The species of Satka,Eomicrocystis. Plerosperl11opsimorpha insolila and Simiadisappear at different stratigraphic levels in both assemblages.It is infened that the Rohtas assemblage is a little younger inage than: the Miroyedikha (ca. 850 Ma) assemblage, andresembles the Husar-Kanpa assemblage of the western OfficerBasin (Australia) which is assigned a Middle Neoproterozoic(ca. 802-777 Ma) age as its homotaxial sediments in AdelaideBasin were radiometrically constrained as 802 ± 10 Ma to 777±7Ma.
Based on the above comparisons and the stratigraphicrelationship of the Rohtas Limestone with the underlying latestMesoproterozoic-Early Neoproterozoic (1050-850 Ma) RampurFormation, an Early Cryogeruan (ca. 850-750 Ma) age ofMiddleNeoproterozoic is envisaged for the Rohtas Subgroup.
Kaimur Group
The sediments of the Kaimur Group rest with apronounced unconformity over the Lower Vindhyan SemriGroup, and are represented by the Domarkhoka Quartzite andthe Bijaigarh Shale in the studied area. Although the outcropsamples are poorly fossiliferous, the subsurface sediments inthe DMH-A well from the 575-480 m depth-interval,representing undifferentiated Kaimur Group (Fig. 4), yielded amoderate occurrence of organic-walled microfossils (PI. 9.117).
Coccoid forms are the main constituents of the Kaimurassemblage and are represented by Symplassosphaeridium
PRASAD el o/..-ORGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 27
tumidulum, Synsphaeridium soredlforme and BavlinellaJaveolata (PI. 9.4-9, 13-15). Sphaeromorph acritarchs are thesubdominant constituents and are represented byLeiosphaeridia minutissima, L. tenuissima, L. asperata, L.jacutica, L. crassa. Kildinopshaera chagrinata, K. granulataand K. verrucala. Important forms, such asVandalosphaeridium reticula tum, Pterospermopsimorphasaccala. Trachysphaeridium laufeldi, T laminaritum andSlictosphaeridium sinapticulum are also rarely representedalong with species of Siphonophycus and Oscillatoriopsis.Important taxa of the underlying Rohtas Subgroup, viz.Pterospermopsimorpha insolita. Simia annulare,Eomicrocystis spp., Satka spp. and budding leiosphaeridsbecome absent here (Figs 3, 4).
The correlation of the Kaimur assemblage is ratherdifficult due to its meagre microfossil content. However, theassemblage broadly compares with the Middle Visingsoassemblage of Sweden (Vidal, 1976a; Vidal & Knoll, 1983) andthe upper Eleonore Bay Group assemblage of East Greenland(Vidal, 1976b) which have been dated Middle to LateNeoproterozoic (ca. 800-700 Ma). The age potential taxa, suchas Bavlinella Javeolata, Trachysphaeridium lauJeldi andVandalosphaeridium reticulatum and other forms, such asStictosphaeridium spp., Trachysphaeridium laminaritum andPterospermopsimorpha saccata are common in both theassemblages. V reticulatum. T laufeldi and B. Javeolala areregarded as age marker taxa that range from MiddleNeoproterozoic (ca. 850 Ma.) to Late Ediacaran-Early Cambrianand occur quite abundantly in Late Neoproterozoic-TerminalProterozoic sediments (Vidal, 1981; Vidal & Knoll, 1983; Knoll,1996). Thus, the occurrence of the above marker taxa in theKaimur Group broadly suggests Middle to Late Neoproterozoicage that broadly corresponds to the Middle Cryogenian (ca.750-700 Ma).
Rewa Group
Four samples from the Panna and Thiri shales (S-14, RPI2,S-2/1, S-12 ) from the Barhi-Badanpur-Maihar section (Fig. 2B)and the subsurface sequence in the DMH-A well from 480320m depth-intervals, representing undifferentiated RewaGroup (Fig. 4), yielded a poor occurrence ofacritarchs, coccoidand filamentous microfossils (PI. 9.18-26).
The microfossil assemblage of the Rewa Group is markedby the abundant occurrence of coccoid forms that includeSynsphaeridium sorediforme. S. gotlandicum (PI. 9.18,21-22),Symplassosphaeridium tumidulum and Bavlinella Javeolata(PI. 9.24). Sphaeromorph acritarchs, viz. Leiospharidia crassa,L. asperata, L. tenuissima, Kildinosphaera chagrinata, K.granulata. K. verrucata. Trachysphaeridium laminaritum, TlauJeldi, Slictosphaeridium sinapticulum andVandalosphaeridium reticulatum (PI. 9.23) are also frequentin this assemblage along with PterospennopsimOlpha saccata.
and persist from the underlying Kaimur Group. In addition,polygonomorph acritarchs, viz. Octoedryxium truncatum (PI.9.20) appear in this formation.
The recovered assemblage from the Rewa Group is alsovery poor and less diversified. However, the assemblagebroadly compares with the Late Neoproterozoic microfossilassemblage from the Upper Visingso Beds of Sweden (Vidal,1976a). Marker taxa such as Octoedryxium truncatum,Vandalosphaeridium reticulatum and Bavlinella Javeolata(PI. 9.20, 23, 24) are common in both assemblages, and areassociated with the above mentioned abundant sphaeromorphacritarchs. Vidal (1976a) and Vidal and Knoll (1983) recordedthe above three taxa in abundance from the upper VisingsoBeds in Sweden, which is dated as ca. 700-610 Ma (Vidal, 1976a).Thus, a Late Cryogenian (ca. 700-650 Ma) age is suggested tothe Rewa Group on the basis of the above microfossils. Thisage inference is corroborated by the observation that theyoungest unit of Rewa Group, viz. Govindgarh Sandstone(Upper Rewa Sandstone) from eastern Rajasthan gave anabsolute age of ca. 710-675 Ma (Srivastava & Rajagopalan,1988), and the Rewa assemblage is succeeded by theObruchevella-dominated latest Neoproterozoic to TerminalProterozoic (Ediacaran) microfossil assemblage ofthe BhanderGroup.
Bhander Group
The Bhander Group represents the uppermostsedimentary succession in the Upper Vindhyan sequence, andincludes the Ganurgarh Shale, Nagod Limestone, Sirbu Shaleand Maihar Sandstone in the Son Valley. Samples from theGanurgarh Shale, Nagod Limestone and Sirbu Shale from theBarhi-Badanpur-Maihar section (Fig. 2B) and the DMH-A well(320-00 m) provided fairly rich and diversified organic-walledmicrofossil assemblages with some Ediacaran (Vendian) agediagnostic microfossils that help in age interpretation of theBhander Group (Figs 3, 4, 5).
Ganurgarh Shale
The microfossil contents of this fornlation are rathermoderate in the outcrop areas, and only the two samples fromthe Barhi-Badanpur-Maihar section (Fig. 2B; S-28/B-l, S-31/6)yielded the microfossils. The assemblage is represented bythe rare occurrence of coccoid forms, viz. SynsphaeridillmsorediJorme. Symplassosphaeridium tumidulum andBavlinella Javeolata along with a number of species ofLeiosphaeridia, Kildinosphaera. Trachysphaeridillm,Stictosphaeridillm. Siphonopphycus. Oscillatoriopsis(PI. 10.1) and Chlorogloeaopsis. However. this lithounit in thesubsurface (320-165 m) from DMH-A well (Fig. 4) yielded arich microfossil assemblage and includes the above forms inabundance.
28 THE PALAEOBOTANIST
Above all, the most important aspect of Ganurgarh Shaleassemblage is the appearance of Terminal Proterozoic(Ediacaran) age marker and helically coiled filamentousmicrofossils, referable to Obruchevella, in the upper part ofthis lithounit. It is represented by 0 parva (PI. 10. 4) and 0valdaica (PI. 10.5) and rarely occurs in this assemblage. Theabove species of Obruchevella occur in association with otherLate Neoproterozoic-Terminal Proterozoic marker taxa, viz.Vandalosphaeridium reticulatum, TrachysphaeridiumlauJeldi, Octoedryxium truncatum and Bavlinella Javeolatawhich persisted from the underlying Rewa Group (Figs 3, 4).
The appearance of various species of Obruchevella, viz.o parva and 0 valdaica in the Ganurgarh Shale. though rare,is very significant. Particularly the appearance of 0 parva inthis lithounit is very significant. This species, till now, is onlyrecorded from the Terminal Proterozoic and Lower Cambriansequences with its earliest records from the Early Ediacaran(Early Vendian) sediments (Golovenok & Belova, 1983; Knoll& Ohta, 1988; Knoll, 1992). Moreover, 0 parva is recorded inquite abundance from the Late Ediacaran (Late Vendian)sediments (Reitlinger, 1959; Yakshin & Luchinina, 1981;Kolosov, 1977, 1982; Cloud et aI., 1979) as well as EarlyCambrian sediments (Wanget al., 1983; Song, 1984; Peel, 1988),and seems to disappear in the Early Cambrian (Mankiewicz,1992). Similarly, Obruchevella valdaica is quite abundant inTerminal Proterozoic (Ediacaran = Vendian) sediments (Aseeva,1974; German, 1985; German et al., 1989) and observed todisappear in the Late Vendian (Mankiewicz, 1992). Althoughits oldest record is known from the Late Mesoproterozoicsediments of Greenland (Hofmann & Jackson,1994;Samuelsson et aI., 1999) and India (Prasad & Asher, 2001), itsabundance in the Ediacaran (Vendian) sediments is wellestablished (Mankiewicz, 1992; Knoll, 1996) and seams todisappear in Late Ediacaran (Late Vendian). Consequently, theappearance of 0 parva and 0 valdaica in the upper part ofthis unit suggests an Early Ediacaran (Early Vendian) age tothe upper part of the Ganurgarh Shale. However, the lowerpart of this unit appears to be latest Cryogenian (LateNeoproterozoic) in age as it is characterised by the occurrenceof Vandalosphaeridium reticula fum, TrachysphaeridiumlauJeldi and Bavlinella Javeolata, and the species ofObruchevella are evidently absent.
Thus, the microfossil data, suggest a latest Cryogenian(Late Neoproterozoic )-Early Terminal Proterozoic (EarlyEdiacaran) age (ca. 650-590 Ma) for the Ganurgarh Shale. Thisinference is corroborated by the fact that the absolute age ofthe Govindgarh Sandstone (Rewa Group), which immediatelyunderlies tpe Ganurgarh Shale, was estimated as 710-675 Maby the F-T method (Srivastava & Rajagopalan, 1988). Inaddition, the Ganurgarh Shale assemblage is succeeded bythe Obruchevella-dominated Terminal Proterozoic (Early toLate Ediacaran; ca. 590-560 Ma) assemblage in the NagodLimestone.
Nagod Limestone
The microfossil assemblage of this formation is quitesimilar to those from the Ganurgarh Shale, but relatively rich.Three samples from the Barhi-Badanpur-Maihar section (S·30, IV-625, IV-613) and depth intervals from 165-105 m in theDMH-A well (Fig. 4), representing Nagod Limestone, recordeda well preserved organic-walled microfossils (PI. 10.2-3,6-14,16-18). Various species of Leiosphaeridia, Kildinosphaera,Trachysphaeridium, Stictosphaeridium, Favososphaeridium,Vandalosphaeridium and Germinosphaera represent thesphaeromorph and acanthomorph acritarchs. SynsphaeridiumsorediJorme, Symplassosphaeridium tumidulum andBavlinella Javeolata include the coccoid forms; whereasfilamentous microfossils are represented by abundantoccurrences of various species of Obruchevella,Chlorogloeaopsis, Oscillatoriopsis and Siphonophycus (Figs3,4).
The most distinguishing aspect of the Nagod Limestoneassemblage is the abundance of the Ediacaran (Vendian) markerspecies ofObruchevella, viz. 0 delicata (PI. 10.7, II) and 0parva (PI. 10.12) along with 0 valdaica (PI. 10.6), and theappearance of 0 delicata. In addition, Germinosphaeraunispinosa (PI. 10.3), FavososphaerdiumJavosum (PI. 10.18),Lophosphaeridium sp. cf. L. truncatum (PI. 10.8, 14),Lophosphaeridium rarum (PI. 10.9-10) and Cymatiosphaerasp. (PI. 10.17) make their appearance in this formation (Figs 3,4).
The abundance of 0 parva and 0 delicata in the NagodLimestone is very important. As stated above, the oldestrecords of0. parva are from the Early Ediacaran (Early Vendian)sediments (Golovenok & Belova, 1983; Knoll & Ohta. 1988;Knoll, 1992). It become quite abundant in the Late Ediacaran(Reitlinger, 1959; Yakshin & Luchinina, 1981; Kolosov, 1977,1982; Cloud et al., 1979) and Early Cambrian (Wang et aI.,1983; Song, 1984; Peel, 1988) sediments, and appears to rangeupto Early Cambrian (for details Mankiewicz, 1992). Similarly,the earliest record of 0 delicata is from the Late Ediacaran(Late Vendian) sediments (Zabit Formation) ofSiberia (ShenfLi,1983). It is also recorded in abundance from the Early Cambriansediments ofthe Siberian Platform (Reitlinger, 1948; Luchinina,1975; Yakshin & Luchinina, 1981), western Mongolia(Drozdova, 1980), eastern China (Song, 1984), South Australia(Bengtson et aI., 1990) and Canada (Voronova et al.. 1987),and ranges upto Early Ordovician (Bykova, 1961; Mankiewicz,1992). 0 valdaica is also originally recorded in abundancefrom the Ediacaran (Vendian) sediments of USSR (Aseeva,1974; German, 1985; Germanetal., 1989). Although, 0. valdaicawas later recorded from the Late Mesoproterozoic (HofmalU1& Jackson, 1994; Samuelsson et al., 1999; Prasad & Asher,2001) sediments, its abundance in Terminal Proterozoic(Ediacaran=Vendian) is well established (Knoll, 1996;Mankiewicz, 1992), and seems to disappear in Late Ediacaran
PRASAD el al.. --0RGAN1C-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 29
AGEI c.. c..
0::::::> :::>~ 0 0:::> 0::: 0:::(I) C> C>
zo~:E0:::ou.
CHARACTERISTIC ORGANIC-WALLED MICROFOSSILSc~Q.s.0:: Q>W Ea..i=
~W
MAIHAR SST. Unfossiliferous 544
ca. 18001600
z~zWI-m U
1200 2oz 0::< W
- Im 0~ 0::U a..w 0
1400 mW
Z :i!:~:i!::i!:>...J<U '1600Unfossiliferous
Unfossiliferous - Late Paleoproterozoic
Abundance - Siphonophycus spp., Polythrichoides lineatus, Tortunemapseudoseptata, Karamia segmentata, opaque filamentous forms; rare Arctace/lularia spp. and unornamented sphaeromorphs - Leiosphaen'dia spp., K.f"h::mrinata (PI. 1, figs 1-14)
ucvLAND FM.
'I KAJRAHAT I~ LST.~ _.._~.
MAHAKOSHAL I BIJAWARGROUP
Abundance - Leiosphaeridia spp., Siphonophycus spp., Obruchevel/a spp. (0. parva, :i ~
SIRBU O. delicata); common- Kildinosphaera spp., Germinosphaera spp., V. reticulatum, T. w ~ 2laufeldi, B. faveolata, Lophosphaeridium spp., Cymatiosphaera sp.; appearance - O. ~ u Z ~
0:: SHALE parvissima, Cristallinium sp., Dictyotidium sp., small micrhystrids & G. bispinosa ..J ~ ~ ~W (PI. 11, figs 1-18) w < ~C .. 570 (J Q.~ Abundance- Obruchevella parva, O. ~eltcata, O. valdalca; common- B. faveolata, V. r--=;- ~ <l:I: NAGOD LST retIcula tum, Lelosphaerrdla spp., Kildmosphaera spp.; Appearance- O. dellcata, >- « C ~
al . Lophosphaeridium rarum, L.. truncatum, Cymatiosphaera sp., Germinosphaera ii! ~ w ~~ unispinosa, Favososphaeridium favosum (PI. 10, rest figs) ;i1 ~ ~
?r Abundance· Siphonophycus spp., Oscillatoriopsis spp., Chlorogloeaopsis spp., w-
c GA~~~~:RH Leiosphaeridia spp.; rare - V. reticula tum , B. faveolata, Kildinosphaera spp., T. 6005 laufeldi; Appearance - Obruchevel/a parva, O. valdaica (PI. 10. figs 1.4.5.15)
0:: GIVINOGARH SST. nfn~~ilih'rnIJ~ Z
W Abundance- Symplassosphaen'dium spp., Synsphaeridium spp.,Leiosphaeridia spp.; ~~ < JHIRI common - Kildinosphaera spp., Pterospermopsimorpha saccata, Siphonophycus w:;;:) 3: SHALE spp.; rare - Vandalosphaeridium reticulatum, Bavlinel/a faveolata, T. laufeldi; g
W Appearance - Octoedryxium truncatum (PI. 9. figs 18-26) ~
0:: ASAN SST. Unfossiliferous () Ua.. PANNA Synsphaeridium spp., Symplassosphaeridium spp., Trachysphaeridium spp., w 0::> SHALE Stictosphaeridium spp., Leiosphaeridia spp. (PI. 9, figs. 18-26) < ~o S NAM SsT. Unfossiliferous ..J 0::
c::: ~ BIJAIGARH Leiosphaeridia spp., Kildinosphaera spp., Plerospermopsimorpha saccata, ~~ :i!: SHALE Trachysphaeridium spp., T. laufeldi, Bavlinella foveolata, Vandalosphaeridium spp., ~ ~W ~ Symplassosphaeridium spp., Synsphaeridium spp. (PI. 9, Figs.1-17) z a..a.. OOMARKHOKA ORfZ Unfossiliferous ~ 0::> Ul BHAGAWAR Abundance -Stictosphaeridium spp., Satka spp, Trachysphaeridium spp.; common - ~ ~ ~en ~ SHALE Kildinosphaera spp., Leiosphaeridia spp., Oscil/atoriapsis spp., ;i1 g~ 5 Plerospermopsimorpha spp., Siphonophycus spp., Vandalosphaeridium reticulatum, i;:>- II: ROHTAS LST. Bavlinel/a faveolata, Trachysphaeridium laufeldi (PI. 8, figs.1-17) 85~
J: Abundance - Satka spp., Navifusa spp., Trachysphaeridium spp.; Common - zC Tappania spp., Eomicrocystis spp., Leiosphaeridia spp., Kildinosphaera spp., ~Z RAMPUR Arctacel/ularia spp.; Appearance - Mellanocyrillium spp., budding leiosphaerids, 0 I> =- Bavlinel/a faveolata, K. verrucata, Trachyhystrichosphaera truncata, I- 1000
~ < Vandalosphaeridium spp. (PI. 6, figs.1-13; PI. 7, figs.1-19)
~ ~ SALKHAN Abundance- Tappania spp., Navifusa spp., Satka spp.; common-Eomicrocystis spp.,~ ~ (FAWN) Plerospermopsimorpha spp., Kildinosphaera spp., Leiosphaeridia kulgunica,~ ~ LST. Siphonophycus spp., Tetraphycus spp. (PI. 5. figs. 1-19)
?r ~ Abundance - Tappania spp., Navifusa spp., Eomicrocystis spp.; common -~ KOLDAHA Arctace/lularia spp., Plerospermopsimorpha spp., Trachysphaeridium spp., Satka:> SHALE spp., Kildinosphaera spp., Leiosphaeridia spp.; rare - Sphaerophycus spp.,0:: Eosynechococcus spp., Siphonophycus spp., Tetraphycus spp.; Appearance -~ Navifusa spp., T. gangaei (PI. 3, figs. 1-16; PI. 4, figs. 1-18 )
o Abundance - Leiosphaeridia spp., Kildiosphaera chagrinata, K. granulata,...J DEONAR Polythrichoides lineatus, Siphonophycus spp., Synsphaeridium spp. Appearance-
(PORCELLANITE) Tappania spp., Satka spp., Eomicrocystis spp., Octoedryxium vindhyanense,Dictyosphaera sp. ( PI. 2, figs 1-17)
Fig. 5-Characteristic organic-walled microfossil assemblages from different Iithounits of Vindhyan Supergroup, and their inferred geological age.
30 THE PALAEOBOTANIST
(Late Vendian) ofTenninal Proterozoic (Gennan et aI., 1989).Thus, the abundance of above species of Obruchevella in theNagod Limestone is alone suggestive of the Early to LateEdiacaran (Vendian) age for this Iithounit.
The Nagod Limestone assemblage also resembles EarlyEdiacaran (upper Early Vendian; ca. 580-570 Ma) microfossilassemblage of the Scotia Group, Svalbard (Knoll, 1992) as thespecies of Obruchevella, Siphonophycus, Myxococcoides(Synsphaeridium), rrachyhystrichosphaera andLeiosphaeridia are common to both the assemblages, andsuggestive ofan age similar to the Scotia Group. However, thecharacteristic large acanthomorph acritarchs of the ScotiaGroup, viz. Papillomembrana, Ericiasphaera,Echinosphaeridium, Asterocapsoides and Briareus are absentin the the Nagod Limestone assemblage. The Germinosphaeraunispinosa (PI. 10.3) seems to be the lone representive of thepurported large acanthomorph acritarchs in this assemblagewhich is absent in the Scotia Group. Moreover the presenceof Ediacaran marker species of Obruchevella, viz. 0. parvaand 0. delicata in abundance, with associated occurrence of
Bavlinella Javeolata, rrachysphaeridium lauJeldi,Vandalosphaeridium reticulatum and Favososphaeridium
Javosum is undoubtedly suggestive of an Early to LateEdiacaran age for the Nagod Limestone. Yet themorphologically complex and distinctive large acanthomorphacritarchs of upper Early Ediacaran (ca. 580-570 Ma), viz.Eotylotopalla, Papillomembrana, Megahystrichosphaeridium, Ericiasphaera and Briareus, which were recorded fromthe Doushantuo Fonnation, eastern China (Zhang et aI., 1998),Biskopas Conglomerate, southern Norway (Vidal, 1990),Kursovsky Fonnation, eastern Siberia (Kolosova, 1990, 1991;Moczydlowska et aI., 1993), Scotia Group, Svalbard (Knoll,1992) and Partataka Fonnation, central Australia (Zang &Walter, 1989), are absent. It appears that the Nagod Limestoneassemblage is little older than the acritarch assemblages oflarge and complex acanthomorph acritarchs or coeval to them,and belongs to upper Early Ediacaran (ca. 590-570 Ma) age.Yet the occurrence of taxa, such as O. delicata.Lophosphaeridium sp. cf. L. truncatum. L. rarum andCymatiosphaera sp., which are known to appear in LateEdiacaran (Late Vendian), extends the age of this Iithounit intothe Late Ediacaran also.
Thus, the recovered microfossil assemblage suggestsan upper Early Ediacaran to Late Ediacaran (ca. 590-560 Ma)age for the Nagod Limestone, as the above species of
Lophosphaeridium, Cymatiosphaera and O. delicata alsomake their, appearances in this lithounit. It is worth mentioningthat the F-T dating ofthe immediately overlying Lower BhanderSandstone gave the absolute age of 625 ± 24 Ma (Srivastava& Rajagopalan, 1990) which is very close to the age inferredby the recovered microfossil assemblage.
Sirbu Shale
Four samples (S-I/I, IV-4, S-l/3, IV-63 I) from the BarhiBadanpur-Maihar section (Fig. 2B) and the subsurfacesedimentary succession from 105-00 m (surface) depthintervals in the DMH-A well (Fig. 4), representing Sirbu Shalesuccession, provided a well-preserved organic-walledmicrofossil assemblage. The microfossil contents are moderatein outcrops, but they are very rich and diversified in thesubsurface (PI. 11.1-18).
Helically coiled filamentous microfossils (Obruchevellaspp.) are the most common constituent of the Sirbu Shaleassemblage and are represented by 0. parva, 0. parvissimaand 0. delicata (PI. 11.9-11). These fonns are also associatedwith various species of Siphonophycus. Oscil!atoriopsis andChlorogloeaopsis (PI. 11.14). The acritarch assemblagecommonly includes sphaeromorph acritarchs, viz.Leiosphaeridia spp., Kildinosphaera spp., Trachysphaeridium laminaritum, T laufeldi (PI. 11.8) and Cymatiosphaerasp. (PI. 11.18). In addition, Gerrninosphaera unispinosa (PI.11.1-2), G. bispinosa (PI. 11.3) and Vandalosphaeridiumreticulatum (PI. 11.12-13) are also very abundant. Forms suchas Synsphaeridium sored/forme, Symplassosphaeridiul/1tumidulum, Myxococcoides spp. and Bavlinella Javeolatarepresent the coccoid forms and persist here from theunderlying Nagod Limestone, as do Obruchuvella pm-va, 0.delicata, Vandalosphaeridium reticulatum, rrachysphaeridium lauJeldi. Favososphaeridium Javosum, BavlinellaJaveolata, Lophosphaeridium sp. cf. L. rarum, Lophosphaeridium sp. cf. L. truncatum and Cymatiosphaera sp.
Yet the most distinctive feature of this assemblage is theconsistent occurrence of the purported acanthomorph acritarchGerminosphaera, which is represented by G. unispinosa andG. bispinosa. In addition, Obruchevella parvissima (PI. 11.10),Dictyotidium sp. (PI. 11.4-7) and Cristallinium sp. cf. C.cambriense (PI. 11.17), which generally make their appearanceat the Precanmbrian-Cambrian boundary or in the EarlyCambrian, appear in this fonnation (Figs 3,4).
The Sirbu Shale assemblage is broadly comparable withthe Late Ediacaran (Late Vendian) microfossil assemblagesrecorded from the Valdaian sequences of the NorthernEuropean Platfonn (Vidal, 1976b, 1981; Vidal & Knoll, 1983)and the Eastern European Platfonn (Volkova, 1968; Volkova etaI., 1979). Abundant leiosphaerids and filamentous microfossilsare common in the Sirbu Shale as well as in the above areas,except that Germinosphaera and Obruchevella are absent inthe Valdaian assemblages. Microfossil assemblages from thelatest Proterozoic (Late Ediacaran) Redkino and Kotlinfonnations (Volkova, 1985; Burzin, 1996) also compare withthe Sirbu Shale assemblage as simple leiosphaerids andfilamentous microfossils abundantly occur in theseassemblages. Knoll (1996, 2000), while reviewing theProterozoic microfossil assemblages, opined that the Late
PRASAD el al..-ORGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH. INDIA 31
Ediacaran (Late Vendian, ca. 570-544 Ma) assemblages aremainly characterised by the dominance of thin-walledLeiosphaeridia spp., abundant Obntchevella spp., acme ofvendotaenids, and appearance ofsmall micrhystrids. Althoughthe vendotaenids are absent in this assemblage, the abundanceof Vendian marker species of Obruchuvella (0. parva and 0.delicata), Leiosphaeridia and filamentous microfossils, andthe rare occurrence of unidentifiable small micrhystrids, withassociated occurrence of Vandalosphaeridium reliculalum,Trachysphaeridium laufeldi and Bavlinellafaveolala stronglysuggests a Late Ediacaran age for the Sirbu Shale assemblage.However the appearance of Dictyotidium sp. (PI. 11.4-7),Cristallinium sp. cf. C. cambriense (PI. 11.17) andObruchevella parvissima (PI. 11.10) in the Sirbu Shale thatappear in Early Cambrian indicates that the age of the SirbuShale extends into the Early Cambrian also. But, the absenceofdistinctive Early Cambrian marker acritarchs, viz. Asteridiumtornatum, Skiagia ciliosa, Lophosphaeridium tentativum,Dictyotidium birvetense, Globosphaeridium cerinum.Annulum squamaceum and Comasphaeridium spp.corresponding to the Rovno-Lontova (sub-Holmia Stage)assemblages of the Eastern European Platform (Volkova et aI.,1979; 1983) and the Lublin Slope, eastern Poland(Moczydlowska, 1991), favours a Late Ediacaran (ca. 560- 544Ma) age for the Sirbu Shale. Cloud et al. (1979) and Song(1984) observed that the filament diameters of VendianObruchevella species are generally small « 20 11m) and that ofEarly Cambrian are large (> 20 11m), although, Mankiewicz (1992)did not observe this type of trends. However, the absence ofEarly Cambrian marker species of Obruchevella, viz. 0.meishucunensis and other species of Obruchevella havinglarge filament diameter (> 20 11m) in this assemblage, alsosuggest that the Sirbu Shale microfossil assemblage belongsto the Late Ediacaran (ca. 560-544 Ma), and does notencompass into the Early Cambrian.
Maihar Sandstone
The Maihar Sandstone represents the youngest lithounitin the Bhander Group as well as the Vindhyan Supergroup. Itcomprises a massive reddish-brown sandstone successionand is devoid of organic-walled microfossils. It seems thatthis lithounit of the Bhander Group was also deposited duringLate Ediacaran (Terminal Proterozoic). Crawford and Compston(1970) estimated the radiometric (KJAr) age of this unit as ca.550 Ma; whereas, Rai (1999) reported some algal microbialmats, and suggested a Late Ediacaran (Late Vendian) age forthe Maihar Sandstone.
DISCUSSIONThe recovered organic-walled microfossils from Vindhyan
sediments of the Son valley and DMH-A well from MadhyaPradesh include acritarchs, coccoid and filamentous
microfossils that generally characterise Meso-Neoproterozoicsediments worldwide. Among these, some age marker taxa arealso present which helped in dating the different lithounits ofthe Vindhyan Supergroup and ascertaining its total age-range.The stratigraphic distribution of organic-walled microfossilsthrough different lithounits of the Vindhyan Supergroup alsoreflects the pattern of distribution of these microfossils in theMeso-Neoproterozoic sediments of India.
The basal two lithounits of the Semri Group, viz. Deolandand Arangi formations (Mirzapur Subgroup) are devoid oforganic-walled microfossils. However, the occurrence ofabundant filamentous forms (Siphonophycus, Polythri-choides, Karamia & Arctacellularia) and unornamentedsphaeromorph acritarchs (Leiosphaeridia spp) in KajrahatLimestone, which represents the youngest lithounit ofMirzapur Subgroup, suggests an Early Mesoproterozoic (LateCalymrnian; ca. 1500-1450 Ma) age. The earlier age evidencesthrough the records of stromatolitic assemblages (Misra elaI., 1977) and organic-walled microfossils (Venkatachala et aI.,1990) from this unit also suggested an Early to Middle Ripheanage, which is very close to the present suggested age. Theolder two units of the Mirzapur Subgroup, viz. Deoland andArangi formations seem to represent the basalMesoproterozoic (Early Calymmian; ca. 1550-1500 Ma)sediments in the Vindhyan Basin, as they immediately underlythe Kajrahat Limestone, and the Arangi Formation ischaracterised by the Early Riphean stromatolites (Kumar, 1976).It is noteworthy that the oldest mafic volcanics inter-beddedwith the Bijawar Group, above which the Vindhyan Supergrouprests, have been dated at ca. 1791 Ma (Crawford & Compston,1970; Sarkar et aI., 1997) and it was opined that the Bijawarsedimentation was initiated at ca. 1800 Ma and terminated atabout 1600 Ma corresponding to the Zhongyuean orogenicmovement (Shankar et aI., 1999). It appears that the basalVindhyan sediments are not older than the ca.1600 Ma, andthe sedimention in the Vindhyan Basin was initiated duringEarly Mesoproterozoic.
The appearance of Tappania (acanthomorph acritarch),Satka and Eomicrocystis in the Deonar Formation wasobserved to be the very important biostratigraphic event inVindhyan stratigraphy. The oldest record of Tappania is fromEarly Mesoproterozoic (ca.1450 Ma) sediments (JalboiFormation, Roper Group) in northern Australia (Javaux et al.,2001). It was recorded in abundance from Middle to LateMesoproterozoic sediments of eastern China (Yin, 1997) andIndia (Prasad & Asher, 200 I). Its appearance in the DeonarFormation indicated an age similar to the Roper Group (ca.1450-1400 Ma). However, the appearance of abundantpolygonomorph acritarchs (Octoedryxium) in the DeonarFormation extends its age to early Middle Mesoproterozoic(ca. 1400-1350 Ma). The record of Octoedryxium in thisformation also suggests that polygonomorph acritarchs wereflourishing even during early Middle Mesoproterozoic time.
32 THE PALAEOBOTANIST
The presence of a distinctive late Early to MiddleMesoproterozoic microfossil assemblage in the DeonarFormation does not support its absolute age of 1630 ± 5 Ma,as suggested by Ray et al. (2002). The well-developed acritarchassemblages having acanthomorph and microsculpturedsphaeromorph acritarchs are known from the later part ofEarlyMesoproterozoic and younger Meso-Neoterozoic sequencesonly (Knoll, 1996).
The dominance of acanthomorph acritarchs (Tappaniaspp.) in the Koldaha Shale is also a significant feature. Asstated earlier, Tappania was recorded in abundance fromMiddle to Late Mesoproterozoic (ca. 1200-1100 Ma) RuyangGroup sediments ofChina (Yin, 1997) and Bahraich Group (ca.1350-1150 Ma) from Northern India (Prasad & Asher, 2001).The abundance of Tappania in the Koldaha Shale and SalkhanLimestone assemblages is similar to the Mid- to LateMesoproterozoic Ruyang and Bahraich microfossilassemblages, suggesting a Late Ectasian-Early Stenian (ca.1350-1050 Ma) age for the above two units of the KheinjuaSubgroup. Although the presence of Tappania in the RampurFormation is indicative of a Late Mesoproterozoic (ca. 11001000 Ma) age, the appearance of Vandalosphaeridium,budding leiospharids and Melanocyrillium undoubtablysuggest an Early Neoproterozoic (ca. 850 Ma) age for thisformation. It appears that the Rampur Formation ranges in agefrom latest Mesoproterozoic to Early Neoproterozoic (ca. 1050850 Ma). The absolute age of the Rampur Formation by Kruezeret al. (1977) as 1080 ± 40 Ma is consistent with the present ageassignment. However, the 1628 ± 8 Ma radiometric dating ofthis lithounit (Rasmussen et aI., 2002) needs reconsiderationin view of the record of distinctive latest MesoproterozoicEarly Neoproterozoic microfossils assemblage.
As discussed earlier, the Rohtas assemblage equates withthe Middle Neoproterozoic (ca. 850 Ma) Miroyedikhaassemblage of Siberia (German, 1990), suggesting an EarlyCryogenian (ca. 850-750 Ma) age. The absolute dating of theRohtas Limestone as 1599± 48 Ma (Sarangi et aI., 2004) seemsincompatiable in view of the record of distinctive Middle
Neoproterozoic microfossil assemblage. Similarly, the absenceof Terminal Proterozoic or Early Cambrian organic-walledmicrofossils does not suggest Late Ediacaran or Early Cambrianage to this Iithounit, as suggested by Azami (1998).
The organic-walled microfossil assemblages of theKaimur and Rewa groups are quite different, as theSymplassosphaeridium-Synsphaeridium complex dominatesover the Leiosphaeridia-Kildinosphaera association of theSemri Group. The only innovative features of the Kaimur andRewa assemblages are the occurrence of Trachysphaeridiumlaufeldi, Vandalosphaeridium reticulatum and Bavlinellafaveolata, and the appearance of Octoedryxium truncatum inthe Rewa Group, whose oldest records are from the LateNeoproterozoic (Middle Visingso Beds; ca. 700-610 Ma) ofSweden (Vidal, 1976a). Thus, the presence of T laufeldi and V.reticulatum and the appearance of 0. truncatum favours aLate Neoproterozoic (ca. 750-650 Ma) age for the Kaimur andRewa groups collectively. The absolute dating of the RewaGroup as 710-675 Ma (Srivastava & Rajagopalan, 1988)corroborates the above age inference.
The most important aspect of the Bhander Groupassemblages is the abundance of different species ofObruchevella, viz. O. valdaica, 0. parva, 0. delicata and 0.parvissima. Among these O. valdaica and 0. parva appear inthe upper parts of the Ganurgarh Shale, and become abundantin the overlying Nagod Limestone and Sirbu Shale. Similarly,0. delicata, Lophosphaeridium spp., Cymatiosphaera sp. andGerminosphaera spp. appear in the Nagod Limestone, andcontinue to occur in the Sirbu Shale. However, some LateEdiacaran-Early Cambrian marker taxa, viz. Obruchevellaparvissimal.. Dictyotidium sp., Cristallinium sp. and smallunidentifiable micrhystrids also make their appearance in theSirbu Shale.
Although, the occurrence of V. reticulatum, T laufeldiand B.faveolata suggests a Late Neoproterozoic (ca. 650-600Ma) age for the Ganurgarh Shale, the appearence of variousspecies of Obruchevella (0. valdaica, 0. parva) in the upperpart of the Ganurgarh Shale extends its age into the Early
'"PLATEl ./
Organic-walled microfossils from the Kajrahat Limestone (Mirzapur Subgroup). Specimen nos. 1-2 from the Barhi-Badanpur-Maihar outcropsection, 3-14 from the DM H-A well, CC-' 0 (3479-3483 m depth interval), representing the Kajrahat Limestone succession. Scale bar =
10 ~m.
I, 2. Leiosphaeridia crassa (Naumova) Jankauskas. I. S-5/1; EFR L50. 2. S-5/1; EFR H 48/3.
3. Leiosphaeridia tenuissima Eisenack. CC-IO, Seg. 3/5/1; EFR N
58.4. Leiofphaeridia asperara (Naumova) Lindgren. CC-IO, Seg.l/
5/2; EFR F 25/4.
5. Kildinosphaera chagrinara Vidal in Vidal & Siedlecka. CC-IO,Seg. 1/5/2; EFR P 65.
6. Opaque filament. CC-IO, Seg. 1/5/1; EFR U 54.
7. SiphonophYClls robllstum (Schopf) Knoll, Swetl & Mark. CC10, Seg.I/5/2; EFR G 67/t.
8. Tortunema pseudoseptara (German) Butterfield, Knoll &Swett. CC-IO, Seg. 1/5/2; EFR H 68/t.
9. An enlarged part of T pseudosepfara in Fig. 8, showing incomplete transeverse septa on the filament. CC-IO, Seg.1 /5/2; EFRH 68/t.
10. Siphonophycus kestron Schopf. CC-I 0. Seg.I/5/2; EFR F 68/1.II, 12. Arctacellularia ellipsoidea German. 11. CC-IO, Seg.I/5/1; EFR
Q 36/2. 12. CC-IO, Seg.I/5/2; EFR G 28.13. Polythrichoides linearus (German) Knoll, Swett & Mark. CC
10, Seg.I/5/1; EFR G 42/3.14. Karamia segmentata Jankauskas, Mikhailova & German. CC
10, Seg.I/5/2; EFR P 64.
PRASAD et al.. --QRGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 33
13
7
~. ,...,.~ i':"
~
,. ..
11
-• # ~
".J •
\ . ..~~~-{ ..'~,-",. , :u: -.:'" ~. I~ ~ . ':
PLATE 1
34 THE PALAEOBOTANIST
Ediacaran (ca. 590 Ma). The abundance of Obruchevella spp.in the Nagod Limestone, and the appearance ofLate Ediacaranmarker taxa, such as 0. delicata, L. tuncatum, L. rarum andCymatiosphaera sp., is suggestive ofan Early Ediacaran ageof the Nagod Limestone, and it appears that it may extend intothe Late Ediacaran also. The persistence of these taxa in theSirbu Shale, including the various species of Obruchevella,and the appearance ofother Late Ediacaran and Early Cambrianmarker taxa, viz. Obruchevella parvissima, Dictyotidium sp.Cristallinium sp. and unidentifiable small micrhystrids indicatea Late Ediacaran (ca. 560-544 Ma)-Early Cambrian age for theSirbu Shale. But, the absence of specific Early Cambrianacritarch marker taxa, viz. Comasphaeridium spp., Asteridiumtornatum, Skiagia ciliosa, Fimbriaglomerella spp., Annulumsquamaceum and Baltisphaeridium spp. restricts the upperage limits for the Sirbu Shale to the Late Ediacaran of theTenninal Proterozoic.
CONCLUSIONS
1. The recovered organic-walled microfossil assemblagesfrom Vindhyan sediments suggest that the Semri Group (LowerVindhyan) ranges in age from Early Mesoproterozoic (EarlyCalymmian, ca. 1550 Ma) to Middle Neoproterozoic (EarlyCryogenian, ca. 750 Ma). On the other hand, the Kaimur, Rewaand Bhander groups of the Upper Vindhyan succession rangein age from Middle Neoproterozoic (ca. 750 Ma) to TerminalProterozoic (Late Ediacaran, ca. 544 Ma).
2. Organic-walled microfossils of Early Cambrian aspectare not recorded in the Rohtas Subgroup, from which Azmi(1998) reported the occurrence of Early Cambrian small shellymicrofossils and brachiopods. Even the sediments of theBhander Group, representing the youngest lithounit of theVindhyan succession, have not yielded any distinctive EarlyCambrian organic-walled index microfossils.
3. The recent absolute age datings of the Deonar,Rampur and Rohtas fonnations of the Semri Group as old asca. 1630-1599 Ma (Late Paleoproterozoic) need re-evaluationin the light of the record of the distinctive MiddleMesoproterozoic (ca. 1450-1350 Ma), latest MesoproterozoicEarly Neoproterozoic (ca.l050-850 Ma) and Middle
Neoproterozoic (ca. 850-750 Ma) organic-walled microfossilassemblages.
4. The age of the Vindhyan Supergroup appears to rangefrom the Early Mesoproterozoic ( ca. 1550 Ma) to Late Ediacaran(Terminal Proterozoic, ca. 544 Ma), and it does not encompassthe Lower Paleozoic.
LIST OFTAXA
The organic-walled microfossil taxa, recognised anddocumented from the sediments ofVindhyan Supergroup, arelisted below. Only the stratigraphic potential and age markertaxa, marked with asterisk (*), are described.
Acritarchs
SphaeromorphsLeiosphaeridia tenuissima Eisenack, 1958L. asperata (Naumova, 1949) Lindgren, 1982L.jacutica (Timofeev, 1966) Mikhailova & Jankauskas in
Jankauskas, 1989L. ternata (Timofeev, 1966) Mikhailova & Jankauskas in
Jankauskas, 1989L. crassa (Naumova, 1949) Jankauskas in Jankauskas,
1989L. minutissima (Naumova, 1949) Jankauskas, 1989* L. kulgllnica lankauskas, 1980bKildinosphaera chagrinata Vidal in Vidal & Siedlecka,
1983K. verrucata Vidal in Vidal & Siedlecka, 1983K. granlilata Vidal in Vidal & Siedlecka, 1983Gangasphaera bulbousus Prasad & Asher, 2001* Trachysphaeridium laminaritllm (Timofeev, 1966) Vidal,
1976a* r laufeldi Vidal, 1976ar levis (Lopukhin, 1972) Vidal, 1976aStictosphaeridium sinapticulum Timofeev, 1966S. implexum Timofeev, 1966* Favososphaeridiumfavosum Timofeev, 1966* Lophosphaeridium rarum Timofeev, 1959*Lophosphaeridium sp. cf. L. truncatum Volkova, 1969
'-PLATE 2 ,/
Organic-walled microfossils from the Deonar Formation (Chopan Porcellanite). Illustrated specimens from the Jhal-Bihara outcrop section(sample no. 11148C ). Scale bar = 101lm.
1- 4. Oc/oedryxium vindhyanense sp. nov. I. EFR T 67/3. 2. EFR U42. 3. EFR T 65/3. 4. EFR W 64/2.
5. Tappania tuba/a Yin. EFR H 40/1.6. Tapp(lIlia plana Yin. EFR N 67.7. Sa/ka squamifera Pyatiletov. EFR T 58.8. Siphonophycus rugosum (Maithy) Hofmann & Jackson. EFR
G 39/4.9. Eomicrocys/is elegans Golovenok & Belova. EFR N 32/2.10. Leiosphaeridia tenuissima Eisenack. EFR T 34/3.
II.12.
13.
14, 15.
16.17.
Leiosphaeridia aspernta (Naumova) Lindgren. EFR S 37.Polythrichoides linea/us (German) Knoll, Swett & Mark. EFRT 50.Siphonophycus septatum (Schopf) Knoll, Swett & Mark. EFRS 58.Kildinosphaern grnnulata Vidal in Vidal & Siedlecka. 14. EFRQ 47/3. 15. EFR K 30.Dictyosphaern sp. EFR T 63/3.Synsphaeridium sorediforme (Timofeev) Eisenack. EFR G SOl3.
PRASAD et al.. -ORGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 35
11
.
f~· ~:~.. .a:>. '~~.:
, ~. ·t't_(a ,.
• ~ :":: • .r; ~.~" •-..' •. _ ~., ...J.
•
2
,.
13
1•
r.
'-
PLATE 2
36 THE PALAEOBOTANIST
Lophosphaeridium granulatus Maithy, 1975L.jansoniusii Salujha et aI., 1971Netromorphs*Navifusa majensis Pyatiletov, 1980*N. segmentata Prasad & Asher, 2001N. granulata Prasad & Asher, 2001N. actinomorpha (Maithy, 1975) Hofmann & Jackson,
1994Acanthomorphs*Tappania plana Yin, 1997*T tubata Yin, 1997T gangaei Prasad & Asher, 200 I*Vandalosphaeridium reticlliatum (Vidal, 1976) Vidal,
1981II varangeri (Vidal, 1976) Vidal, 1981*Trachyhystrichosphaera truncata German &
Jankauskas in Jankauskas, 1989*Germinosphaera unispinosa Jankauskus, 1989*G. bispinosa Jankauskus, 1989PteromorphsPterospermopsimorpha insolita Timofeev, 1969P saccata Yin, 1987*Simia annulare (Timofeev, 1969) Mikhailova &
Jankauskas in Jankauskas, 1989Herkomorphs*Cymatiosphaera sp.*Dictyotidium sp.
*Cristallinum sp. cf. C. cambriense (Slavikova, 1968)Vanguestaine, 1978
Polygonomorphs*Octoedryxium vindhyanense sp. nov.*0. truncatum (Rudavskaia, 1973) Rudavskaia In
Jankauskas, 1989
Coccoid Microfossils
SynaplomorphsEoentophysalis sp. cf. E. belcherensis Hofmann, 1976Eoentophysalis sp.Eosynechococcus moorei Hofmann, 1976
E. medius Hofmann, 1976Sphaerophycus parvum Schopf, 1968Eohyella dichotoma Green et aI., 1988Tetraphycus acinulus Oehler, 1978T diminutivus Oehler, 1978T gregalis Oehler, 1978*Eomicrocystis elegans Golovenok & Belova, 1984*E. malgica Golovenok & Belova, 1986*Bavlinellafaveolata (Schepeleva, 1962) Vidal, 1976aSpumosina rubiginosa Andreeva, 1966Symplassosphaeridium tumidulum Timofeev, 1959Synsphaeridium sorediforme (Timofeev, 1959) Eisenack,
1965Synsphaeridium gotlandicum Eisenack, 1958*s. colonialica Jankauskas, 1979b*Satka squamifera Pyatiletov, 1980
Filamentous Microfossils
NematomorphsSiphonophycus septatum (Schopf, 1968) Knoll et aI.,
1991.S. robustum (Schopf, 1968) Knoll et aI., 1991S. rugosum (Maithy, 1975) Hofmann & Jackson, 1994S. kestron Schopf, 1968S. capitaneum Nyberg & Schopf, 1984*Polythrichoides lineatus (German, 1974) Knoll et aI.,
1991* Karamia segmentata Jankauskas et aI., 1989Tortunema pseudoseptata (Germann, 1990) Butterfield
etal.,1994Arctacellularia ellipsoidea German in Timofeev et aI.,
1976A. tetragonala (Maithy, 1975) Hofmann & Jackson, 1994Oscillatoriopsis psi/ata Maithy & Shukla, 1977Chlorogloeaopsis kanshiensis (Maithy, 1975) Hofmann
& Jackson, 1994C contexta (German, 1976) Hofmann & Jackson, 1994*Obruchevella valdaica (Shepeleva ex Aseeva, 1974)
Jankauskas et al. in Jankauskas, 1989
'-PLATE 3 ./
Organic-walled microfossils from the Koldaha Shale (Kheinjua Subgroup). Illustrated specimens from the Barhi-Badanpur-Maihar and the JhalBihara outcrop sections, and the DM H-A well (1930-940 m depth interval), representing the Koldaha Shale succession. Scale bar = 10 11m.
1, 3, 4. Tappania lubata Yin. I. DM H-A, 1390-95m/2 EFR G 72. 3.DMH-A, 1380-85mll; EFR N 45. 4. DMH-A, 1450-55m/2;EFR N 56.
2, 5. Tappania plana Yin. 2. DMH-A, 1400-05m/2; EFR F 35/4. 5.DMH-A, 1380-85m/2; EFR F 40.
6. Navifusa segmentata Prasad & Asher. DMH-A, I720-25mll ;EFR P 28.
7, 9. Pterospermopsimorpha insolita (Timofeev) Mikhailova. 7.DMH-A, 1675-80m/1 ; EFR F 63/1. 9. S-912; EFR 0 65/2.
8. Simia annulare (Timofeev) Mikhailova & Jankauskas. S-8/elI; EFR E 4312.
10. Navifusa majensis Pyatiletov. DMH-A, 1205-1 Om/I; EFR N44/1.
I I. Arctacellularia ellipsoidea Gennan. DMH-A, I575-80m/1 ; EFRo 62/4.
12. Arctacellularia rerragonala ( Maithy) Hofmann & Jackson.DMH-A, 1505-IOm/2; EFR N 54.
13, 14. Leiosphaeridia jacurica (Timofeev) Mikhaylova & Jankauskas.13 S-9/2; EFR S 64. 14. S-9/2; EFR K 4711.
15. Leiosphaeridia renuissima Eisenack. S-912; EFR U 41/4.16. Kildinosphaera chagrinara Vidal in Vidal & Siedlecka. 11/55DI
7; EFR X 55/4.
PRASAD et al..---0RGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, fNDIA 37
"
\'' ..
•
J ' .' "''' '"'t ~.'. :,' ...1 '
• ,"l:r'~.~, ;"~~ ;~J ..~ ""~i ",I<
--'
~11
/,.' ."", , '" ~.""".l'.' '.- ' ".... ~.t· • ..~.
I .' \l1. ","i ""',,,\, Q'1'" . ,'~;'" r;. ,.~ I.'U'~"~J"
i'''''·~~~_''.'~.~~. ..,..
'11
PLATE 3
38 THE PALAEOBOTANIST
*Obruchevella parva Reitlinger, 1959*Obruchevella delicata Reitlinger, 1948*0. parvissima Song, 1984
TRACHYSPHAERIDIUM LAMINARITUM (Timofeev,1966) Vidal, 1976a
(PI. 6.1 ; PI. 8.11)
Vase-shaped Microfossils
Melanocyrillium sp.
SYSTEMATICS
Group-ACRITARCHA Evitt, 1963
Subgroup-SPHAEROMORPHITAE Downie et al., 1963
Genus-LEIOSPHAERIDIA Eisenack 1958 emend. Downie& Sarjeant, 1963
Type species-LEIOSPHAERIDIA BALTICA Eisenack,1958.
LEIOSPHAERIDIA KULGUNICA Jankauskas, 1980b
(P1.5.14, 19)
Description-Vesicle sphaerical to subsphaerical, thin,single-walled; surface smooth to finely scabrate, with irregularfolds. A distinct circular pylome (? excystment) present on thevesicle, having a narrow and thickened lip-like margin aroundthe opening.
Dimensions-Vesicle diameter 36-70 ,.un, pylome diameter13-15pm
Occurrence-Leiosphaeridia kulgunica appears in theSalkhan Limestone and ranges upto the Bhander Group in theVindhyan basin. This species is mainly recorded from the Earlyto Middle Neoproterozoic sediments ofNorway (Vidal & Knoll,1983), Russian Platform (Jankauskas, 1980b) and China (Yin &Guan, 1999).
~nus-TRACHYSPHAERIDIUM Timofeev 1959 exTimofeev, 1966
Typespecies-TRACHYSPHAERIDIUM AlTENUATUMTimofeev,1959.
Description-Vesicle spherical, with thick vesicle- wall;surface ornamented by the sculptural elements ofrugulae andalveoli. Sculptural elements coalesced, fonning a pseudoreticulate texture. Vesicle appears enclosed in thin andtransparent envelope.
Dimensions-Vesicle diameter 37-52 pm.Occurrence-This species appears in the Rampur
Fornlation within Kheinjua Group and range upto the SirbuShale within the Bhander Group. Outside India, T laminaritumis recorded from the Early to Late Neoproterozoic (ca 850-600Ma) sediments ofSweden, Norway (Vidal, 1976a; Vidal & Knoll.1983) and North China (Yin & Guan, 1999).
TRACHYSPHAERIDIUM LAUFELDI Vida~ 19700
(PI. 7.13; PI. 11.8)
Description-Vesicle spherical, with thickened wall;surface ornamented by sparsely distributed sculptural elementsofgrana and echinae (small spines). A distinct, circular, rimmedopening present on the vesicle, opening often with a bulbousprotrusion.
Dimensions-Vesicle diameter 44-50 pm, circular openingdiameter 9-12 pm.
Occurrence-In Vindhyan Basin, this species appears inthe Rampur Formation, and ranges upto the Sirbu Shale withinthe Bhander Group. T laufeldi is recorded from the Early toLate Neoproterozoic (ca 850-600 Ma) sediments of Swedenand Norway (Vidal, 1976a; Vidal & Knoll, 1983) and North China(Yin & Guan, 1999).
Genus-FAVOSOSPHAERIDIUM Timofeev, 1966
Type species-FAVOSOSPHAERIDIUM SCANDICUMTimofeev, 1966.
FAVOSOSPHAERIDIUM FAVOSUM Timofeev, 1966
(pl.IO.18)
......PLATE 4 /'
Organic-walled microfossils from the Koldaha Shale (Kheinjua Subgroup). Illustrated specimens from the Barhi- Badanpur-Maihar and the JhalBihara outcrop sections, and the DM H-A well (1930-940 m depth interval), representing the Koldaha Shale succession. Scale bar ~ 10 f1m.
I. Eosynechococcus moorei Hofmann. S-8/C/I; EFR D 49/2.
2. Te/raphycus diminutivlIs Oehler. S-8/C/I; EFR V 34/2.
3, 4. Sphaerophycus sp. 3. S-9/2; EFR Q 44/3. 4. S-9/2; EFR S 70/4.
5. Eomicrocys/is elegans Golovenok & Belova. S-9/2; EFR 0 32.
6. Eohlicrocys/is malgica Golovenok & Belova. S-8/C; EFR S 66.
7. SphaerophyClIs parvum Schopf. S-9/2; EFR L 73/1.
8. Synsphaeridillm sorediforme (Timofeev) Eisenack. S-9/2; EFR
o 43/2.
9. Symplassosphaeridium tumidulum Timofeev. S-8/C; EFR W
47/2.
10, 13. Sarka squamifera Pyatiletov. 10. S-9/2; EFR P 63/1. 13. S-9/2;EFR L 61/1.
J I, 15. Sarka colonialica Jankauskas. 11. S-9/2; EFR M 74/3. 15. S-9/2; EFR Q 71.
12. Leiosphaeridia jacu/ica (Timofeev) Mikhailova & Jankauskas.S-9/2; EFR S 57/4.
14. Kildinosphaera granula/a Vidal. S-9/2; EFR X 64/1.16. Leiosphaeridia crassa (Naumova) Jankauskas. S-9/2; EFR Y
30.17. Leiosphaeridia /enllissima Eisenack. S-8/A/I; EFR T 67/218. Lophosphaeridium granula/um Maithy. S-8/C/2; EFR G 44/2.
PRASAD el al..---DRGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 39
15
7
10
14
,"
.... .~.~.~"
. ~.~, $-...'. f:'~~ -,.. . - .. ",~,,~~-,:
~ .. i'.~';'~ ~.'l'_ (,)' .I¥"~, '.,,~-- ..
" .
5
PLATE 4
40 THE PALAEOBOTANIST
Description-Vesicle spherical with oval outline, stout;surface covered with well-developed, irregular, microreticulatednetworks. Vesicle associated with irregular thin folds.
Dimensions-Vesicle diameter 102-120 11m.Occurrence-This species appears in the Nagod
Limestone within the Bhander Group and ranges upto the SirbuShale. Ffavosum is recorded from the Late Neoproterozoic toTerminal Proterozoic sediments ofSweden and Norway (Vidal& Knoll, 1983).
Genus-LOPHOPSPHAERlDTIJM Timofeev, 1959 exDownie, 1963
Type specjes-LOPHOSPHAERIDIUM RARUMTimofeev,1959
LOPHOPSPHAERlDTIJM RARUM Timofeev, 1959
(PI. 10.9, 10)
Description-Vesicle subspherical to subtriangular,thick-walled; vesicle surface ornamented by the closely placedsmall solid tubercles and spines with pointed ends.
Dimensions-Vesicle diameter 40-44 11m, tubercles 211mlong.
Occurrence-L. rarum appears rarely in the NagodLimestone and persists in the Sirbu Shale. This taxon is verycommon in the Early and Middle Cambrian sediments withearliest records from the latest Ediacaran-Early Cambrian(Volkova, 1968; Downie, 1974).
LOPHOPSPHAERIDTIJM sp. cf. L. TRUNCATUM Volkova,1969
(pI. 10.8, 14)
Description-Vesicle spherical, thick-walled, becomesubtiangular to quadrangular due to compressions; surface
ornamented by sparsely distributed well-developed small solidtubercles.
Dimensions-Vesicle diameter 42-46 11m, tubercles 2-3 11mlong.
Remarks-The Vindhyan specimens are larger in size,and tubercles are sparsely distributed. So, these specimensare compared with the L. lruncalum, and not assigned to it.
Occurrence-This species appears rarely in the NagodLimestone and persists in the overlying Sirbu Shale within theBhander Group. L. /runcalum is a common element ofCambrianacritarch assemblages with its earliest records from the EarlyCambrian (Volkova el al., 1979; Knoll & Swett, 1987;Moczydlowska, 1991).
Subgroup--NETROMORPHlTAE Downie, Evitt & Sarjeant,1963
Gen us-NAVIFUSA Combaz, Lange & Pansart, 1967
Type species-NAVIFUSANAVIS Eisenack, 1938.
NAVIFUSAMAJENSIS Pyatiletov, 1980
(PI.3.10;PI.5.15;PI.7.1,8)
Description-Cylindrical, nonseptate, longitudinallyelongate (naviform) vesicle, tapers at both the longitudinal
ends with rounded tips. Vesicle-wall smooth, often associated
with thin folds, folds generally running parallel to the long
axis of the vesicle.
Dimensions-Vesicle 50-225 11m (length) x 27-40 11m(breadth).
Occurrence-In Vindhyan basin, N. majensis shows the
restricted occurrence within the Kheinjua Subgroup with its
appearance in the Koldaha Shale and disappearance in theupper part of the Rampur Formation. Elsewhere, its earliest
records are known from the Middle to Late Mesoproterozoic
"PLATES /'
Organic-walled microfossils from the Salkhan Limestone (Kheinjua Subgroup). Illustrated specimens from the Jhal-Bihara outcrop section, and theDMH-A well (940-780 m depth interval), representing the Salkhan Limestone_ Scale bar = 10 ).1m.
I, 2. Sa/ka squamifera Pyaliletov. I. 1I/55-G \0; EFR T 37/1. 2. III 10,55-GI0; EFR L 48.
3 Symplassosphaeridium /umidulum Timofeev. 11/55-G 10; EFR 12.F 31.
4. Eomicrocys/is elegalls Golovenok & Belova. DM H-A, 930- 13
35m/I; EFR F 61/1.5. Eomicrocys/is malgica Golovenok & Be\ova. DMH-A, 930- 14,
35m/I; EFR P 28.6 Eoelllophysalis belcherellsis Hofmann. 11/55-G 10 ; EFR H 341 15.
3. .7. Te/raphycus gregalis Oehler. 11/55-G10 ; EFR U 57/2. 16.
8 Leiosphaeridia asperara (Naumova) Lindgren. 1I/55-GI0; EFRK 47/1.
J7.
9. Simia allllulare (Timofeev) Mikhailova & Jankauskas 11/55- 18.GIO; EFR R 42.
II. Tappania plana Yin. 10. DMH-A, 930-35m/l; EFR N 43/4.11. 11/55-G 10; EFR 029/3.Siphollophycus robuslum (Schopf) Knoll, Swett & Mark. DM HA, 930-35m/1; EFR R 32/3.Slic/osphaeridi"", sinapliculullt Timofeev. 11/55-G 10; EFR K40.
19. Leiosphaeridia kulgullica Jankauskas. 14. 11/55-GI0; EFR R32/3. 19. 1I/55-G I 0; EFR D 62NaVIfusa majensis Pyatiletov. DMH-A, 870-75m/l; EFR N35/1.Navifusa segmen/a/a Prasad & Asher. DM H-A, 800-05m/l;EFR G 37.P/erospermopsimorpha insoli/a Timofeev. DMH-A, 855-60m:EFR 047.Leiosphaeridia crassa (Naumova) Jankauskas. 11/55-GJO; EFRL 34/2
PRASAD el or.-ORGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 41
-""
..,-~
:i;... - . :
. ~.~. .' .
., ~.~_I. ~." .~t;
~D
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9
8
17
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".....;
PLATE 5
42 THE PALAEOBOTANIST
sediments (Hofmann & Jackson, 1994; Prasad & Asher, 200 I)and range upto the Early Neoproterozoic (Jankauskas, 1980b).
NAVIFUSA SEGMENTATA Prasad & Asher, 200 I
(P1.3.6; PI. 5.16; P1.7.IO, 16)
Description-Cylindrical, septate, longitudinallyelongate (naviform) vesicle, tapers at both the longitudinalends with rounded tips. Vesicle-wall smooth to scabrate,divided into a number of rectangular chambers or segmentsby the transeverse striations or grooves, vesicle oftenassociated with irregular thin folds.
Dimensions-Vesicle 66-150 11m (length) x 11-36 11m(breadth).
Occurrence-In Vindhyan basin, N. segmentata showsthe restricted occurrence within the Kheinjua Subgroup. Itappears in the Koldaha Shale and disappears at the upperboundary ofthe Rampur Formation. This species was originallyrecorded from the Middle Mesoproterozoic (ca. 1350 Ma)sediments (Bahraich Group) ofGanga Basin (Prasad & Asher,200 I). Later on, Yin and Yuan (2002) recorded this speciesfrom the Late Mesoproterozoic (ca. 1200-1100 Ma) BeidajianFormation (Ruyang Group), Shanxi, China and cosidered it asMiddle to Late Mesoproterozoic age-potential taxa.
Subgroup--ACANTHOMORPHlTAE Downie et af., 1963
Genus--TAPPANlAYin, 1997
Typespecies-TAPPANIAPLANA Yin, 1997.
TAPPANlAPLANA Yin, 1997
(PI. 2.6; PI. 3.2, 5; PI. 5.10, II; PI. 6.11)
Description-Acanthomorph acritarch, vesiclesubspherical, oval to broadly elliptic, with a prominent, necklike trapezoid extension (projection) on one side of the vesicle,having a fimbriate distal margin. Vesicle bears irregularlydistributed, hollow, heteromorphic, conical to tubularprocesses; processes distally tapering as accumulate, truncateto furcate ends.
Dimensions-Vesicle diameter 50-90 11m.Occurrence-In the Vindhyan basin, T plana appears in
the Deonar Formation and persists in the overlying KoldahaShale, Fawn Limestone and disappears in the RampurFormation. The earliest record ofT plana is from the late EarlyMesoproterozoic (ca. 1450 Ma) sediments ofcentral Australia(Zang & Walter, 1989), and abundantly occurs in Middle andLate Mesoproterozoic sediments ofChina and India (Yrn, 1997;Prasad & Asher, 200 I).
TAPPANlATUBATA Yin, 1997
(PI.2.5; P1.3.I, 3,4; PI. 6.12, 13)
Description-Acanthomorph acritarch, vesiclesubspherical to oval, with a prominent, apically neck-liketubular projection lextention. Surface bears well developed,irregularly distributed hollow, often long, heteromorphic,conical to tubular processes that distally taper as accumulate,truncate to furcate ends with often darkened mass.
Remarks-The apically neck-like projection/extensionon one side of the vesicle in T tubata is elongate tubular,whereas trapezoid in T plana.
Dimensions-Vesicle diameter 40-80 11m.Occurrence-T tubala appears in the Deonar FOimation
and persists in the overlying Koldaha Shale, Fawn Limestoneand disappears in the upper parts of Rampur Formation. Itsoldest record is from the late Early Mesoproterozoic (ca, 1450Ma) sediments of central Australia (Zang & Walter, 1989), andoccurs quite abundantly in Middle to Late Mesoproterozoic(ca. 1350-1050 Ma) sediments ofChina and India (Yin, 1997;Prasad & Asher, 200 I).
Genus--VANDALOSPHAERIDIUM Vidal, 1981
1'ypespecies-VANDALOSPHAERIDIUMRETICULATUM(Vidal) Vidal, 1981.
VANDALOSPHAERIDIUM RETICUlATUM (Vidal) Vidal,1981
(PI. 6.5, 6; PI. 9.23; PI. 11.12,13)
Description-Vesicle large, spherical to subspherical.Vesicle surface ornamented with numerous regularly arranged,short processes; processes support outer membrane of thevesicle.
......PLATE 6 ,/
Organic-walled microfossils from the Rampur Formation (Kheinjua Subgroup). Illustrated specimens from the Jhal-Bihara outcrop section, and theDMH-A well (780-620 m depth interval), representing the Rampur Formation. Scale bar = 10 11m.
I. Trachysphaeridium laminarilum (Timofeev) Vidal. 11/168/1;EFR.G 66/3.
2. Leiosphaeridia asperala (Naumova) Lindgren. 11/168/2; EFRV 69/2.
3. Trachyhyslrichosphaera Iruncaia German & Jankauskas inJankauskas. 11/168/2; EFR W 57/1.
4. Gangasphaera bulbousus Prasad & Asher. 11/168/1; EFR P 48/3.
5, 6. Vandalosphaeridium reliculalUm (Vidal) Vidal. 5. 11/168/1; EFR
T 66/2. 6. 111168/1; EFR D 51.7. Vandalosphaeridium varangeri (Vidal) Vidal. 11/168/1; EFR 0
4713.8, 9, 10.MelanocyrilIium sp. 8. 11/168/1; EFR J 57. 9. 11/168/2; EFR K
71/4. 10.11/168/1; EFR H 62/1.I I. Tappania plana Yin. 111168/1; EFR L 48/4.12. Tappania sp. cf. T. IUbaia Yin. 111168/2; EFR J 66/4.13. Tappania lubala Yin. 11/168/1; EFR J 34.
PRASAD el al..-0RGANIC·WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 43
, -.,I.
~·'" ~-.
"'. ~','I ~TJ
~ ":~~,.~. -
PLATE 6
44 THE PALAEOBOTANIST
Dimensions-Vesicle diameter 51-70 /lm, processes 3-5/lm long.
Occurrence-This species appears in the RampurFormation and occurs rarely upto the Sirbu Shale. The earliestrecord of this species is from the Middle Neoproterozoicsediments ofSweden and Norway (Vidal & Knoll, 1983), and isan important element of the Late Neoproterozoic assemblages(Knoll, 1996).
Genus-GERMINOSPHAERA Mikhailova, 1986
emend. Butterfield in Butterfield et aI., 1994
Type species---GERMINOSPHAERABISPINOSAJankauskas,1989.
GERMINOSPHAERA UNISPINOSA Jankauskas, 1989
(PI. 10.3;PI.II.I,2)
Genus-TRACHYHYSTRICHOSPHAERA Gennan inTimofeev et aI., 1976 emend. German & Jankauskas in
Jankauskas,1989
Type species-TRACHYHYSTRICHOSPHAERAAIMIKAGerman in Timofeev et aI., 1976.
TRACHYHYSTRICHOSPHAERATRUNCATAGennan&JankauskasinJankauskas,1989
(PI. 6.3)
Description-Vesicle spherical and thick, single layeredwith chagrinate surface. Vesicle bears sparsely distributedshort, spine-like processes that communicate with the vesicle.
Dimensions-Vesicle diameter 30-35 /lm, processes 2-3/lmlong.
Occurrence-This species occurs rarely in the RampurFormation of the Sernri Group. This species is originallyrecorded from the Early Neoproterozoic (ca. 1000-900 Ma)Lakhanda Formation of eastern Siberia (German in Timofeevet aI., 1976). This species is also known to occur in the LateNeoproterozoic and Tenninal Proterozoic sediments ofSiberia(Jankauskas, 1989) and India (Prasad & Asher, 200 I).
Remarks-Butterfield et al. (1994), in their emendation,suggested that the T truncata is an entirely a distinct taxon,and does not fit into the circumscription ofTrachyhystrichosphaera. However, at present, this specimenis placed under the T truncata German and Jankauskas.
Description-Vesicle spherical to subspherical, singlelayered. Vesicle wall scabrate to granulate, often with irregularfolds. A long single prominent process emerges from one endof the vesicle; process broad at base, distally tapers into apointed end, process not communicating with the vesicle.
Dimensions-Vesicle diameter 30-36/lm, process 9-65 /lmlong.
Occurrence-G. unispinosa appears in the NagodLimestone and become common in the overlying Sirbu Shale.Although the earliest records of this species are from the EarlyNeoproterozoic sediments in eastern Officer Basin, Australia(Zang, 1995), it is quite common in the latest Neoproterozoicand Terminal Proterozoic sediments ofSvalbard (Butterfield etaI., 1994), China (Yin & Wang, 1990) and India (Prasad & Asher,200 I).
GERMINOSPHAERA BISPINOSA Jankauskas, 1989
(PI. 11.3)
Description-Vesicle spherical, thin, single layered;vesicle surface psi late to scabrate, with numerous irregularfolds. A single long process emerges from one end of thevesicle, witout communicating with the vesicle; process broadat base, distally bifurcates into the two 6-9/lm long proccesses,each processes distally pointed with closed ends.
Dimensions-Vesicle diameter 30-36/lm, processes 1015/lm long.
Occurrence-In the Vindhyan Basin, this species rarely
'-PLATE 7 /
Organic-walled microfossils from the Rampur Formation (Kheinjua Subgroup). Illustrated specimens from the Jhal-Bihara section, and the DMHA well (780-620m depth interval), representing the Rampur Formation. Scale bar ~ IO~m.
I, 8. Navifusa majensis Pyatiletov. Fig. 1, [1/168/1; EFR N 58/ I. 10, 16. Navifusa segmenlala Prasad & Ashaer. 10. DM H-A, 640-45m/
Fig. 8, DMH-A, 680-85m/l; EFR V 56/4. 2; EFR U 33/3. 16. DMH-A, 680-85m/2; EFR H 28/2.
2, 3, 5. Budding leiosphaerids. 2. [[/168/2; EFR L 31. 3. [[/168/2; EFR 12. Satka sfJlIalllifera Pyatiletov. [1/168/2; EFR 0 72/1.
W 43/3.5. [[/168/2; EFR T 60/1. 13. Tmchysphaeridilllll sp. cf. T lallfeldi Vidal. [[1168/2; EFR V 50.
4. EOlllicrocystis rnalgica Golovenok & Belova. 111168/2; EFR P14. Stictosphaeridiulll implexllm Timofeev. 11/168/2; EFR S 35.
31.,15. Arctacellularia tetrngonala (Maithy) Hofmann & Jackson.
DMH-A, 690 -95m/J; EFR W54.6, II. Satka colonialica Jankauskas. 6. 111168/2; EFR B 60/2. II. III 17. Sipho/lophyclls rugosum (Maithy) Hofmann & Jackson. III
168/2; EFR D 52/1. 168/1; EFR F69/4.7. Chlorogloeaopsis ka/lshiensis (Maithy) Hofmann & Jackson. 18. Kildinosphaem granulara Vidal in Vidal & Siedlecka. 111168/2;
[1I16811; EFR N 63/2. EFR M47/3.9 Ch/orogloeaopsis conlexla (German) Hofmann & Jackson. 19. Kildinosphaera verrucata Vidal in Vidal & Siedlecka. [[1168/1;
DMH-A, 690-95m/l; EFR V 54/3. EFR S 29/4
PRASAD el ai-ORGANIC-WALLED M1CROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 45
12
7
•
6
.-
- •• -.:!
" ... • '0#"; ~.~. ~ ~.,.. Mo~. ~~
-' t" ."".,... •
.t "'e '(.J.1£\~'. -\ of"~
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1"6
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~ 10
8
9
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..:.:--.~
-~
PLATE 7
46 THE PALAEOBOTANIST
occurs in the uppermost lithounit of the Vindhyan Supergroupwithin the Sirbu Shale. Although, its earliest records are fromthe Early Neoproterozoic (Jankauskas, 1989), it is quite commonin the Late Neoproterozoic and Terminal Proterozoic sediments(Butterfield et aI., 1994).
Subgroup-PTEROMORPlllTAE Downie et aI., 1963
Genus-SIMlA Mikhailova & lankauskas in lankauskas,1989
Type species---SIMIAANNULARE (Timofeev, 1969)Mikhailova & lankauskas in lankauskas, 1989.
SIMIAANNULARE (Timofeev, 1969) Mikhailova &lankauskas in lankauskas, 1989
(PI. 3.8; PI. 5.9)
Description-Vesicle small, spherical to subsphaerical,double-walled; inner part comparatively dark and thickened,appears enveloped by a thin outer transparent layer; outerlayer slightly extends beyond the vesicle periphery, showinga narrow peripheral transparent rim.
Dimensions-Vesicle diameter 30-36 11m.Discussion-Simia and Pterospermopsimorpha are
similar in morphology. However, the outer transparent layer inSimia completely envelops the vesicle; whereas, a narrowtransparent zone is formed around the vesicle peripheralmargins in Pterospennopsimorpha.
Occurrence-In the Vindhyan basin, Simia annulareappears in the Koldaha Shale and persists in the overlyingFawn Limestone and Rampur Formation. It disappears in theupper parts of the Rohtas Subgroup. Its oldest record is fromthe Middle Mesoproterozoic (ca, 1350 Ma) sediments of India(Prasad & Asher, 200 I), and very common in the LateMesoproterozoic to Late Neoproterozoic sediments(Samuelsson et aI., 1999; Yin & Guan, 1999).
Subgroup-HERKOMORPlllTAE Downie, Evitt & SaIjeant,1963
Genus--DlCTYOTIDIUM Eisenack 1955 emend. Staplin,1961
Type species--DlCTYOTIDIUM DlCTYOTUM Eisenack,1938.
DlCTYOTIDIUM sp.
(PI. 11.4-7)
Description-Spharical to subspherical globular vesicle,single layered; vesicle surface divided into a number ofirregular reticulate campi, ridges thin and low, lacunal areaspolygonal.
Dimensions-Vesicle diameter 27-57 11m.Comparison-The Vindhyan specimens ofDictyotidium
differ from the known species of this genus in being smaller insize and having low ridges. So, these specimens are identifiedas the Dictyotidium sp., rather assign it to the species.
Occurrence-This form is recorded rarely in the SirbuShale. The earliest records ofDictyotidium are from the EarlyCambrian sediments (Volkova et al., 1979; Moczydlowska,1991), and common constituents of the Middle and LateCambrian assemblages.
Genus--CYMATIOSPHAERA Wetzel, 1933
Type species--CYMATIOSPHAERA RADIATA Wetzel,1933.
CYMATIOSPHAERAsp.
(PI. 10.17; PI. 11.18)
Description-Vesicle subspherical with polygonaloutline; central body indiscernible, a relatively darkenedpolygonal area present at the center of the vesicle. Vesicle
.......PLATES ,/
Organic-walled microfossils from the Rohtas Subgroup. Illustrated specimens from the Jhal-Bihara outcrop section, and the OMH-A well (625-575m depth interval), representing the Rohtas Subgroup. Scale bar = 10 11m.
I. Oscillatoriopsis sp. OM H-A, 625·30mll; EFR J 63/3. 9.2. Bavlinella faveo/ala emend. Schepeleva Vidal. 11/388/1; EFR F
45. 10.3. Symp/assosphaeridium lumidu/ulII Timofeev. 11/388/2; EFR II.
L 43/44 Sliclosphaeridiul11 sinaplieu/ulII Timofeev. 11/388/1; EFR X 12
55/45 Sliclosphaeridiul11 imp/exum Timofeev. 11/388/1; EFR G 49. 13.
6 Salka squallllfera Pyatiletov. OM H-A, 565- 570m/l; EFR P 14.
67/3.7 Salka c%nialiea Jankauskas. 11/388/2; EFR P 70. 15.
8 Lophosphaeridilllll jansoniusii Salujha, Rehman & Arora. OM H-16, 17.
A, 565- 570mll; EFR T 57/2.
Leiosphaeridia asperala (Naumova) Lindgren. 11/388/2; EFRN 56.Ki/dinosphaera granu/ata Vidal. 11/388/2; EFR U 60/1.Traehysphaeridiul11 /aminarilulll (Timofeev) Vidal. 11/388/1,EFR S 32/1.Ki/dinosphaera verrueala Vidal in Vidal & Siedlecka. 11/388/2;EFR G 48/2.Plerospermopsimorpha saecala Yin 11/388/1; EFR M 32/1Karalllia segmenlala Jankauskas, Mikhailova & German. OMHA, 650-55I2m; EFR W 46.Oscillalor/opsis psi/olo Maithy. OM \-I-A, 625- 30m/I; EFR J38/2Leiosphaeridia lenuissima Eisenack. 16. 11/388/1; EFR V 23/2.17. 11/388/2; EFR V 24/2.
PRASAD el al..--0RGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INOlA 47
.
13
•~
.~ ... , ..... «co,
~.
.. i,~
10
....& '..... .
~
. " J '.•& Jr,. . tl'.', ..'" . -we- ~"
~
..
.~~.....·11
[]
In
14 15
PLATE 8
48 THE PALAEOBOTANIST
surface divided into a number of distinct well-developedpolygonal chambers (campi); campi separated by raisedthickened, and granulated muri (ridges).
Dimensions-Vesicle diameter 78-84 ~m.
Comparison-The Vindhyan specimens ofCymatiosphaera differ from the known species of this genusin being the bigger in size and having very thick ridges. Thesespecimens are identified as the Cymatiosphaera sp. ratherassign it to the species level.
Occurrence-This species appears in the NagodLimestone, and continues to occur in the Sirbu Shale. Theearliest records of Cymatiosphaera are from the EarlyCambrian (Volkova et aI., 1979; Moczydlowska, 1991).
Occurrence-This species appears in the Sirbu Shaleand rarely occurs in this formation. The earliest records ofCristallinium camabriense are from the Early Cambriansediments and forms important constituents of the early andmiddle Cambrian assemblages (Volkova et al., 1979;Moczydlowska, 1991).
Subgroup---POLYGONOMORPHlTAE Downie etal., 1963
Genus--OCTOEDRYXIUM Rudavskaia, 1973 emend. Vidal,I976a
Type species-OCTOEDRYXIUMTRUNCATUMRudavskaia, 1973 emend. Rudavskaia in Jankauskas, 1989.
Genus---CRISTALLINIUM Vanguestaine, 1978
Type species---CRISTALLINIUM CAMBRIENSE(Slavikova, 1968) Vanguestaine, 1978.
CRISTALLINIUM sp. cf. C. CAMBRIENSE (Slavikora)Vanguestaine, 1978
(PI. 1l.17)
Description-Vesicle polyhedral with polygonal outline.Vesicle surface divided into a number of polygonal chambers(campi) by thin and slightly raised muri (ridges); ridges adornby small coni and cristae.
Dimensions-Vesicle diameter 63-78 ~m.
Comparison-The Vindhyan specimens of Cristalliniumcomparable with the C. cambriense (Slavikora) Vanguestaine(1978) in its morphology and ornamentation. However, thecampi are not distinct as in the case of C. cambbriense.
OCTOEDRYXIUM YlNDHYANENSE sp. nov.
(P1.2.1-4)
Holotype-Pl. 2, fig. I ; slide no. II/48C/5B II; T67/3(England Finder); size 24 x 24 ~m.
Locus typicus-Jhal- Bihara section, Son valley (easternMadhya Pradesh), India.
Stratum rypicum-Deonar Formation, Semri Group (LowerVindhyan).
Age-Early to Middle Mesoproterozoic.Erymology-Vindhyan, refers to the hill ranges in the
Northern India, on which the name "Vindhyan Basin" isderived.
Diagnosis and description-Vesicles octahedral, sidemargins straight to convex, often undulated (due topresevational compression); longitudinal width 17-24 mm,transeverse width 17-34mm; holotype (PI. 2. I) measures 24 x
'-PLATE 9 ,/
Organic-walled microfossils from the Kaimur and Rewa groups. Taxa in figs. 1-17 the from the Kaimur Group ( DMH-A, 575- 480 m depthinterval); Taxa in figs.18-26 from the Rewa Group of the Barhi-Badanpur-Maihar section, and the DMH-A well (480-320 m depthinterval). Scale bar = 10 I'm.
Kaimur Group:I, 3. Leiosphaeridia minulissima (Naumova) Jankauskas. Fig.l,
DMH-A, 520-25m/2; EFR V 44/3. Fig. 3, DMH-A, 520-25m/2; EFR J 26.
2. Leiosphaeridia asperata (Naumova) Lindgren. DMH-A, 52025m/I; EFR Q 45.
4, 5. Symplassosphaeridium lumidulum Timofeev. Fig. 4, DMH-A,520-25mll; EFR N 36. Fig. 5, DMH-A, 570-75m/2; EFR M57.
6, 7. Bavlinella faveolala emend. Schcpeleva Vidal. 6. DMH-A, 52025m/I; EFR U 37.
8, 9. Synsphaeridium sorediforme (Timofcev) Eisenack. 8. DMHA, 520- 25mll; EFR P 52/2. 9. DMH-A, 515-20m/2; EFR E58/3.
10, II. Leiosphaeridia crassa (Naumova) Jankauskas. 10. DMH-A,533- 40m/l; EFR R 51/4.11. DMH·A, 520-25m/1; EFR F 27/2.
12. Kildinosphaera chagrinnta Vidal in Vidal & Siedlecka. DMHA, 535-40m; EFR K 48.
13, 14. Synsphaeridium gOllandicum Eisenack. 13. DMH-A, 520-25m/2; EFR T 63/3. 14. DMH- A, 520-25m/2; EFR U 48.
15. Synsphaeridium sp. DMH-A, 535-40m/2; EFR U 41.
16. P/erospermopsimorpha sacenla Yin. DMH-A, 520-25m/1; EFR
G 35.
17. Kildinosphaera granulala Vidal in Vidal & Siedlecka.DMH·A,
500-505m;EFR P44.
Rewa Group:
18, 22. Synsphaeridi/lm sored/forme (Timofeev) Eisenack 18. RP-I/
I; EFR U 55/2. 22. RP-I II; EFR S 681119. Leiosphaeridia asperala (Naumova) Lindgren. RP-I/2; EFR Q
40.
20. OCloedryxium (runCalum RlIdavaskaia emend. RlIdavaskaia in
Jankauskas. RP-I II; EFR W 40.
21. Synsphaeridi/lm gOllandicum Eisenack. RP-III; EFR N 33.
23. Vandalosphaeridium reliculalum (Vidal) Vidal. RP-I/2; EFR K
64/1.
24. Bavlinella faveolala Schepeleva emend. Vidal. RP-I/2; EFR X
59/2.
25. Leiosphaeridia jacl/lien (Timofeev) Mikhailova & Jankauskas.
RP-III; EFR U 29.
26. Plerospermopsimorpha saccnta Yin. DMH-A, 325-330m; EFR
o 55/2.
PRASAD el al.-0RGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 49
. ..... ..~..:tr,".".1-~,. '~.;.il. ~:~,,~..J. ... I
"'.' '.:-rio;" ,. . -Jf',',• ..··,fItc.;r ~ : .•" ....; ••- . . I
-' .. :' .~~*\, .., .. ~""'" .•~l : ...~~~
,.... " . .:..-9
7
5
",
~ ·f ., "",,. ..<': "'k',
..'•
, :
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22
21
19
PLATE 9
50 THE PALAEOBOTANIST
24 rum. Vesicle surface granulate; joints of the faces raised,developed into swollen ridges or protuberances,protuberances often projected beyond the vesicle margins,showing processes.
Comparison-Ocloedryxium vindhyanense sp. nov.differs from the type species a. lruncalum Rudavskaia, 1973emend. Rudavskaia, 1989 (in Jankauskas, 1989), in havinggranulate vesicles and being relatively smal1er in size.
Occurrence-This species occurs abundantly in theDeonar Formation and within Kheinjua Subgroup, continuesto occur rarely in the overlying Koldaha Shale and disappearsin the upper part ofKoldaha Shale.
Phylum----CYANOPHYTA Stainer el al., 1978
Class--<...:OCCOGONEAE Thuret, 1875
0, tier - CHR("l )COCCALES Wettstein, 1924
Family---{.:HkOOCOCCALES Nageli, 1849
Genus-EOMICROCYSTIS Golovenok & Belova, 1984
Type species-EOMICROCYSTIS ELEGANS Golovenok &Belova, 1984.
EOMICROCYSTIS ELEGANS Golovenok & Belova, 1984
(PI. 2.9; PI. 4.5; PI. 5.4)
OCTOEDRYXIUMTRUNCATUMRudavskaia,1973emend.
Rudavskaia in Jankauskas, 1989
(pI. 9.20)
Descriplion-Vesicles octahedral, sides straight toconvex; longitudinal width 35-37 nun, transeverse width 24-2711m. Vesicle surface granulate; joints of the faces raised,developed into poorly defined swol1en ridges orprotuberances.
Comparison-The present specimen closely compareswith a. lruncalum emend. Rudavskaia, 1973 Rudavskaia (inJankauskas, 1989). The other species of this genus, viz. a.vindhyanense, recovered from the Semri Group in VindhyanBasin, differs in having granulate vesicles and being relativelysmal1er in size.
Occurrence-a. lruncalum appears in the Panna Shale(Rewa Group) and rarely occurs in the overlying GanugarhShale and Nagod Limestone units of the Bhander Group. Theearliest records of O. lruncalum are from the LateNeoproterozoic Middle Visingkso Beds, Sweden (Vidal, 1976a;Vidal & Knoll, 1983), and ranges upto Terminal Proterozoic(Knol1, 1996).
Descriplion-Spherical to subspherical colony,consisting 16 to 35 numbers of loosely packed, smal1, roundedto sphaeroidal cel1s with 3-6.5 11m diameter.
Dimensions-Colony diameter 28-56 J.lm.Occurrence-In Vindhyan Basin, E. elegans appears in
the Deonar Formation, become abundant in the KheinjuaSubgroup and disappears in the upper part of the RohtasSubgroup. Its earliest records are from the EarlyMesoproterozoic sediments (Peat el al., 1978; Horodyski, 1980),and abundant in the Middle to Late Mesoproterozoic and EarlyNeoproterozoic sediments (Hofmann & Jackson, 1994;Jankauskas, 1989).
EOMICROCYSTIS MALGICA Golovenok & Belova, 1986
(PI. 4.6; PI. 5.5; PI. 7.4)
Descr(otion-Spherical to subspherical colony, with 16to 45 numbers of tightly packed smal1 globoidal cel1s of2-4 J.lmdiameter. Cel1s appear embedded in the thin mucilaginousmatrix.
Dimensions-Colony diameter 28-56 11m.Occurrence-In Vindhyan Basin, E. malgica appears in
the Deonar Formation, become abundant in the sediments of
......PLATE 10 /"
Organic-walled microfossils from the Ganurgarh Shale and the Nagod Limestone (Bhander Group). Illustrated specimens from the Barhi-BadanpurMaihar section, and the DMH-A well (depth interval 320-165m -Ganurgarh Shale; 165-105 m-Nagod Limestone). Scale bar = 10 11m.
Ganurgarh Shale:I. Oscillaforiopsis psi/ala Maithy & Shukla. DMH-A, 215-20m/
2; EFR G 61114. Obruchevella par va Reitlinger DMH-A, 165-70m/1; EFR T
34/3.5. Obrllchevella valdaica (Shepeleva ex Aseeva) Jankauskas,
Mikhailova & German. DMH-A, I 65-70m/2; EFR 0 37/3.15. Leiosphaeridia asperafa (Naumova) Lindgren. DMH-A, 215
20m/I; EFR J 43.
Nagod Limestone:2. Chlorog/oeaopsis kanshiensis (Mailhy) Hofmann & Jackson.
DMH-A, 150-55m/2; EFR T 33/3.3. Germinosphaera unispinosrr Jankauskas. DM H-A, 115-20m/
I; EFR S 56/46. Obruchevella valdaica (Shepeleva ex Aseeva) Jankauskas,
Mikhailova & German DMH-A, 150-55m/2; EFR T 407, II. Obrtlchevella delicata Reitlinger 7. DMH-A, 150-55m/1; EFR
K 27. II. DMH-A, 150-55m/2; EFR M 69.8, 14. Lophosphaeridillm sp. cr. L. trllncatllm Volkova. 8. IV/625B;
EFR 0 55/4. 14. IV/ 613/1; EFR T 50/4.9, 10. Lophosphaeridium rarum Timofeev. 9. IV/625B; EFR S 68.
10. DMH-A, 150 -55m/1; EFR R 38.12. Obruchevella parva Reillinger DMH-A, 150-55m!l; EFR K
42.13. Ki/dinosphaera chagrinata Vidal in Vidal & Siedlecka. IV/625B;
EFR 0 6816. Leiosphaeridi jacufica (Timofeev) Mikhaylova & Jankauskas.
DMH-A, 110-15m/l; EFR L 44.17. Cymatiosphaera sp. DMH-A, 150-55m/2; EFR K 51.18. Favososphaeridium favosum Timofeev. DMH-A, 115-20m/l,
EFR 0 64.
PRASAD el al..--DRGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 51
;J:...
5
)-.....r
"'.l
'~";'~'~,. ".. -..' :\.~"t"- .... ' ·(......... .., .
..._~'.j I ~~.
.. , 'II. , ... '"".
, J .... .t, I
" 2
..L· "., ,~. ,
8
(I~ .._-
i .~?i -...,;r' I ~f':J.';l .. ;,' f,.~1," ...~.. '\
',;)6 ....t~ "!T 00Il J '",,", '
PLATE 10
52 THE PALAEOBOTANIST
Kheinjua Group and disappears in the upper part of the RohtasSubgroup. Its earliest records are from the EarlyMesoproterozoic sediments (Peat et al.. 1978; Horodyski, 1980)and very common in the Middle to late Mesoproterozoic andEarly Neoproterozoic sediments (Hofmann & Jackson, 1994;]ankauskas, 1989).
Genus-BAVLL'JELLA Schepeleva, 1962 emend. Vidal,1976a
Type species---BAVLlNELLA FAVEOLATA Schepeleva,1962 emend. Vidal, 1976a.
BAVLINELLAFAVEOLATA Schepeleva, 1962 emend. Vidal,1976a
(PL 8.2; PL 96, 7,24)
Description-Spherical to subspherical colonies, clusterof 3-4 colonies very common; each colony consisting ofnumerous, generally 16-40 in number, closely packed cell-likepolygonal to subpolygonal units of 4 to 6 ~m diameter.
Dimensions-Colony diameter 32-56 ~m.
Occurrence-In Vindhyan Basin, S colonialica appearsin the Deonar Formation, become abundant in the sedimentsof Kheinjua Group and disappears in the upper part of theRohtas Subgroup Its earliest records are from the EarlyMesoproterozoic (ca. 1450-1400 Ma) sedU11ents of Roper Group,central Australia (Peat el aI, 1978) and lower Belt Supergroup,Montana (Horodyski, 1980). This species is very common inthe late Mesoproterozoic sediments (Hofmann & Jackson,1994) and become rare in Early to Middle Neoproterozoic (ca.900-750 Ma) sediments (Knoll & Swelt, 1985).
Description-Spherical to sub;pherical globular colony,consisting of large number of tightly to packed, very smallglobfJidal cells of 1.5 to 25 ~m diameter. Cells appear embeddedin the thin mucilaginous matrix.
Dimensions-Colony diameter 32-40 ~mOcclilTence-B javeoloto appears in the Rampul
Formation in Kheinjua Subgroup and occurs rarely in all theoverlying formations of the Vindhyan Supergroup. Its earliestrecord is from the Early Neoproterozoic (ca. 900-800 Ma)Veteranen Group, Spitsbergen (Knoll & Swelt, 1985) and isvery conunon elements of late Neoproterozoic and TerminalProterozoic organic-walled microfossil assemblages (Vidal &Knoll, 1983).
Genus-SATKA ]ankauskas, 1979b
Type species-SATKAFAVOSAJankauskas, 1979b.
SATKA COLONIALICA ]ankauskas, 1979b
(PL 4.11, 15; PL 76,11; PL 87)
SATKASQUAM1FERAPyatiletov,1980
(PL 27; PL 410, 13: PL 5.1,2; PL 7.12; PL 86)
Description-Colonies oval to elliptic, flattened. mosllyelongate; cluster of 2-3 colonies very common; each colonyconsisting of numerous closely packed cell-like subpolygonalunits of 4 to 6 ~m size. Individual unit packaged in a distinctbelt-like rows transeverse to the longer axis of the colony.
Dimensions-Colony diameter 35-65 ~mOCClirrencc-S sqlloll1i!cra appears in the Deonar
Formation, become abundant in the Kheinjua Subgroup anddisappears in upper part of the Robtas Subgroup Its earl iestrecords are from the Early Mesoproterozoic (ca. 1450-1400 Ma)sediments of Roper Group, central Australia (Peat et aI, 1978)and lower Belt Supergroup, Montana (Horodyski, 1980). Thisspecies is very common in the late Mesoproterozoic sediments(Jankaukas, 1979a, 1980a; Hofm3lill & Jackson, 1994; Prasad& Asher, 2001) and shows rare occurrence in the Early andMiddle Neoproterozoic (ca. 900-750 Ma) sediments (Knoll &Swelt, 1985)
'-..PLATE 11 /'
Organic-walled mIcrofossils from {he Sirbu Shale (13hander Group) IlIuSlratcd specimens from {he Barhi- Badanpur -Maihar section. and the DMIIA well (105-00 01 dep{h in{erval), represcnting {he SlTbu Shale successIon. Scale bar = 10 11m
I. 2. Gerlllillosphaera uilispillosa Jankauskas. I DM H-A. 15-2001/I, EFR N 43. 2. DMH-A, 75-8001/1, EFR Q 37/2Germillosphaera bispil10sa Jan kauskas. DM I-I-A, 15-2001/1;EFR R 52/2
4,5,6,7 DiclyOtidium sp. 4. V-413. EFR 0 67/3. 5 V-63/1, EFR V 64/36. V-4/3, EFR N 72/3 7 DMH-A. 150-5501/1, EFR K 31/3
8. Trachysphaeridium laufeldi Vidal. DM H-A. 75-80111/1. EFR P70/4 .•
9. Obruchevella parva Reillinger. DMH-A, 75-80mf2; EFR Q 6510. Obruchevella parvissima Song. DMH-A, 15-20mfl; EFR R 51/
2I I Obruchevella delicata Reillinger. DMH-A, 20-2501/1, EFR Q
29/2.
12. 13. Val1dalosplwerldium reliculal/(m (Vidal)Vidal. 12. DMII-A, 15
2001/1; EFR 060. 13. DMH-A, IS-20m/I, EFR D 51/4
14. Chlorogloeaopsis C0l11eXla (German) Hofmann & Jackson.
DMH-A, 100-105mfl; EFR W 49.
15. Kildil10sphnera verruca/a Vidal in Vidal & Siedlccka. DMH-A,
75-8001/1, EFR H 43/4.
16 Leiosphaeridia asperata (Naumova) Lindgren. DMH-A. 75
800112; EFR P 64.
17. CrislOllil1ium sp. cf. C. cambriel1se (Slavikova) Vangueslaine.V/
4; EFR Q 62/2
18. Cymatiosphaera sp. V-4/3; EFR V 67/4.
PRASAD el al.. ---DRGANIC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, [NOlA 53
15
.' .
.~;;.,:". ~.t. .e~'"...... It p
\. ~ h........~_. -...
• •c.. ; .~'~ . ---• ~.'p'•. -"':.'.'
.. #i~--'1i1:. ' .....,."'1 ,-. -.. -
..," .
<...
PLATE 11
54 THE PALAEOBOTANIST
Class-HORMOGONEAE Thuret, 1875Order-OSCILLATORIALES Elenkin, 1949
Family-OSCILLATORlACEAE DmTIortier ex Kirchner,1900
Genus-OBRUCHEVELLAReitlinger, 1948
Typespecies-OBRUCHEVELLADELICATAReitlinger,1948.
OBRUCHEVELLAVALDAlCA(Shepeleva,1974exAseeva,1974) Jankauskas, Mikhailova & Gennan, 1989 in
Jankauskas, 1989
(pI. 10.5,6)
Description-Helically coiled, long, aseptate filamentousmicrofossils, compressed, with subcircular to oval outline;comprising tightly wound coils (helices) of almost unifonndiameter. Helices (spiral coils) tightly concentric, compressed,without any gaps between the successive helics; centralportions of the coiled mass generally missing.
Dimensions-Coil (helix) diameter 42-60 ~lm, filamentdiameter 5-9 11m.
Remarks-o. valdaica is distinguished from otherspecies of Obruchevella by its compressed and tightlyconcentric coils (helices) without any gaps between thesuccessive whorls.
Occurrence-In Vindhyan Basin, 0. valdaica appears inthe basal part ofBhander Group within the Ganurgarh Shale,and shows common occurrence in the overlying NagodLimestone and the Sirbu Shale. This species is abundantlyrecorded from the Ediacaran (Vendian) sediments of RussianPlatfonn (Aseeva, 1974; Gennan et aI., 1989) and elsewhere(for details Mankiewicz, 1992). Although, this species is alsorecorded from Late Mesoproterozoic sediments (Hofmann &Jackson, 1994; Samuelsson et aI., 1999; Prasad &Asher, 2001),but its abundance in Tenninal Proterozoic is well established.
OBRUCHEVELLAPARVAReitlinger, 1959
(PI. lOA, 12; PI. 11.9)
Description-Helically coiled, long filamentousmicrofossils, with subcircular to oval helices (spiral coils).Whorls with tightly to loosely wound helices (coils) ofunifonnhalix diameter, 7-10 helices very common; filament with crosspartitions, dividing the filaments in a number of smallrectangular compartments ..
Dimensions-Helix diameter 45-60 11m, filament diameter5-lOllffi
Remarks-O parva is distinguishable from the otherspecies of the Obruchevella in having little loosely woundhelices (coils) than the 0 valdaica, and comparatively tighthelices than the 0 delicara. Filament bears cross-partitions,and diameter varies between 5-I 0 11m.
Occurrence-In Vindhyan Basin, 0. parva appears in
the Ganurgarh Shale within the Bhander Group, showsabundance in the Nagod Limestone and the Sirbu Shale. 0parva is regarded as the Ediacaran (Vendian)-Early Cambrianmarker microfossil. It is abundantly recorded in the Ediacaran(Vendian) sediments from a number oflocalities, and observedto appear in the Early Ediacaran and disappears in EarlyCambrian (for details Mankiewicz, 1992).
OBRUCHEVELLADELICATAReitlinger, 1948
(PI. 10.7, II;PI.11.11)
Description-Hilically coiled, long filamentousmicrofossils, with broad filament diameter (12-16 11m);comprising well defined, subcircular to oval, loosely woundhelices (coils). Helices ofunifonn helical diameter, successivehelices widely separated; 5-7 whorls very common.
Dimensions-Helix diameter 45-66 11m, filament diameterl2- 16 1lm
Remarks-O. delicata is distinguishable from otherspecies ofObruchevella in having loose wounds, well defmedand widely separated successive whorls and filament diametervaries between 12-16 11m.
Occurrence-O. delicata appears abundantly in theNagod Limestone within the Bhander Group and very commonin the overlying Sirbu Shale. This species is abundantlyrecorded from the Late Ediacaran (Vendian) and Early Cambriansediments, and observed to appear in the Late Ediacaran andranges upto Early Ordovician (for details Mankiewicz, 1992).
OBRUCHEVELLAPARVlSSIMASong, 1984
(PI. 1UO)
Description-Helically coiled, filamentous microfossils,with very naLTOW filament; comprising a number of looselywound helices of varying diameter; successive heices closelycoiled.
Dimensions-Coil (helix) diameter 35-52 11m; filamentdiameter 3-5 11m.
Remarks-O parvissima is distinguishable from the otherspecies of Obruchevella in having loosely wound, closelyplaced successive whorls and very narrow filament diameterbetween 3-5 ~lm.
Occurrence-In Vindhyan Basin, 0. parvissima occursrarely in the Sirbu Shale within the Bhander Group. It isoriginally recorded from the Early Cambrian (Meishucunian)sediments ofYunnan, China (Song, 1984).
Genus-POLYTHRICHOIDES Gennan, 1974
Type species-POLYTIffiICHOIDES LINEATUS German,1974 emend. Knoll et aI., 1991
POLYTHRICHOIDESLINEATUSGerman, 1974 emend.Knoll et aI., 1991
(PI.1.13;P1.2.12)
Description-Elongate fragments of tubular filamentous
PRASAD el o/.-ORGANiC-WALLED MICROFOSSILS FROM SON VALLEY, MADHYA PRADESH, INDIA 55
aggregates, comprising a number of longitudinally aligned,closely placed, non-septate, narrow filaments, showing atwisted rope-like feature; individual filaments parallelorientation, showing a longitudinally striated aspect;aggregates without sheath
Dimensions-Fragment length 180-385 flm, filamentdiameter 1- 2 flm.
Occurrence-In Vindhyan Basin, P Iineatus occurabundantly in Kajrahat Limestone and rarely present in theDeonar Formation. This form is very common in theMesoproterozoic sediments of China (Yin & Yuan, 2002),Canada (Hofmann & Jackson, 1994) and Zaire (Maithy, 1975)and also very frequent in the Neoproterozoic sediments ofSiberia (German, 1974) and Svalbard (Knoll et aI., 1991).
Genus--KARAMlA Kolosov, 1984
Type species-KARA.tVllA SEGMENTATA Jankauskas,Mikhailova & Gennan, 1989.
KARAM.IA SEGMENTATA Jankauskas, Mikhailova &Gelman, 1989
(PI. 1.14)
Description-Elongate, ? non-septate filament,composed of a number of transverse to slightly obliquegrooves or striations, that divide the filament into a number ofsegments. Apparently looks like a narrow, non-septatefilament, with tight coiling.
Dimensions-Filament length 180-230 flm, filamentdiameter 66 flm.
Occurrence-In Vindhyan Basin, K. segmentata is verycommon in the Kajrahat Limestone and rarely present in theDeonar Formation. This fonn is rarely recorded from the Middleto Late Mesoproterozoic sediments of Canada (Hofmarul &Jackson, 1994) and Early Neoproterozoic sediments ofRussianPlatfOim (Jankauskas et aI., 1989).
Vase-shaped Microfossils
Genus---MELANOCYRILLfiJM Bloeser, 1979 ex Bloeser,1985
Typespecies--MELANOCYRILLnJM HEXODIADEMABloeser, 1979.
MELANOCYRILLruM sp.
(PI. 6.8-10)
Description-Vesicle flask-shaped, oval to elliptic inoutline; vesicle surface dark and thickened, with granulate toechinate omamentation. One side of the vesicle abruptly tapersto fOrol a neck-like narrow tubular extention; extension with adistinct opening at distal end.
Dimensions-Vesicle length 38-55 flm, width 36-52 flm;neck-like extension length 7-12 flm.
Occurrence-The recovered specimens broadlycomparable with the vase-shaped microfossils referable toMelanocyrillium B10eser (1985). However, these specimensdiffer with typical Melanocyrillium in having narrow tubularneck and much smaller in size with irregular shape; whereas inMelanocyrillium neck is wide. So, the Vindhyan specimens ofthe vase-shaped microfossils are provisionally referred to asthe Melanocyrilliwn sp.
REPOSITORY
The slides, examined for organic-walled microfossils fromoutcrop as well as subsurface (DMH-A well) sections of theVindhyan Basin from Madhya Pradesh, are preserved in theRepository Section of the Palynology Laboratory (GeologyDivision) at the KDM Institute of Petroleum Exploration,ONGC, Dehradun (India) with registration No. KDMIPE/ PALYI20041 BPI VINDHYAN-M.P. The desired outcrop slides can beretrieved by traverse name and sample nos. (like Jhal-BiharaTr., II/5-D), and the subsurface slides by the well name (DMHA) with respective depth intervals (like 450-455m). Theillustrated taxa are located by England Finder References (EFRJ50/2), mentioned against each fonns.
Ackllowledgements-The authors are grateful to Shri YB. Sinha,Director (Exploration), Oil and natural gas Corporation Ltd., forkind permission to publish tllis papa Dr D. Ray, Executive DirectorHead, KDMIPE, Mrs NJ. Thomas, Gen. Manager (GRG) SlIri JamesPeters, Dy. Gen. Manager (Geology) and Dr NC. Mehrotra, Dy.Gen. Manager (Palynology) gave valuable suggestions during thecourse ofthis work,for which authors are indebted to them. Thanksare also due to Dr S.N Swamy, Chief Palynologist, for fruitfuldiscussions, crllical comments and reviewing the manuscript. Authorsare also indebted to Dr H. J. Hofmann, Department ofEarth andPlanetQ/)' Sciences, McGill University, Canadafor critically reviewingthe IIwnuscript and offering the valuable suggestions.
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