Cretaceous Research (2002) 23, 65–76doi:10.1006/cres.2002.0298, available online at http://www.idealibrary.com on

Lower Maastrichtian dinoflagellates from theViano Clay Formation at Viano, northernApennines, Italy

L. Roncaglia

Geological Survey of Denmark and Greenland (GEUS), Thoravej 8, DK-2400 NV Copenhagen, Denmark;e-mail: LR@geus.dk

Revised manuscript accepted 7 January 2002

The Viano Clay Formation, exposed in the northern Apennines, Italy, is a 360-m-thick, calcareous to siliciclastic turbiditethat was deposited in a deep, open-marine environment. This paper focuses on the organic-walled dinoflagellate assemblagesin the basal 253.3 m of the Viano Clay Formation in the type locality at Viano, Reggio Emilia. Key events are the highestoccurrence datums of Cannosphaeropsis utinensis, Hystrichodinium pulchrum, Isabelidinium cooksoniae and Odontochitinaoperculata, and the lowest occurrence datums of Cerodinium diebelii and Palaeocystodinium golzowense, which correlate with thelower Maastrichtian dinoflagellate Cerodinium diebelii Interval Zone. Upper Cretaceous foraminifera and nannoplanktonoccur in the Viano Clay Formation at Viano, together with rare Lower Paleocene species. Reworking of Upper Cretaceousnannofossils and foraminifera has been suggested in the literature but could not be confirmed in the present study. At Viano,the Viano Clay Formation is of early Maastrichtian age and conformably overlies the upper Campanian–lower MaastrichtianMonte Cassio Formation. � 2002 Elsevier Science Ltd. All rights reserved.

K W: Italy; northern Apennines; Upper Cretaceous; Maastrichtian; dinoflagellates; palynofacies; reworking;turbidite.

1. Introduction

The Viano Clay Formation is a fine-grainedcalcareous-siliciclastic turbidite intercalated with darkgrey, soft, jarositic, hemipelagic, very fine-grainedmudstones to silty sandstones. The formation, whichextends throughout the northern Apennines region,was described by Papani & Zanzucchi (1970) from thetype section located along the Tresinaro river, in theViano area, Reggio Emilia, Italy. It crops out on boththe southern and northern side of a syncline with aWNW–ESE trending axis (Figure 1). In the type area,the Viano Clay Formation is 360 m thick (Bonazziet al., 1982), overlies the upper Campanian–lowerMaastrichtian Monte Cassio Formation, and is over-lain by the Eocene Monte Piano Marls Formation(Iaccarino & Rio, 1972). According to the geologicalliterature, the Viano Clay Formation was deposited ina lower slope to bathyal environment (Mutti & RicciLucchi, 1972). The present paper focuses on theViano Clay Formation at its type locality.

Iaccarino & Rio (1972) suggested an Early Paleo-cene age for the formation, based on the recovery ofnannoplankton and planktonic foraminifera. These

0195–6671/02/$35.00/0

authors reported ‘‘a large number of well preservedmid to Upper Cretaceous forms and a few Tertiaryforms’’ (translated from Iaccarino & Rio, 1972,p. 649). They documented the occurrence of fiveLower Paleocene planktonic foraminifera: Globanoma-lina compressa, Globoconusa daubjergensis, Parasubbotinapseudobulloides, Praemurica inconstans and Subbotinatriloculinoides; and six Lower Paleocene nannoplank-ton species in the lowermost 253.3 m of the VianoClay Formation at Viano. According to Olsson et al.(1999), the planktonic foraminifera listed aboveindicate an Early Paleocene age.

The present paper aims to document the dinoflag-ellate assemblages, evaluate the extent of reworking,and assess the age of the Viano Clay Formation in thetype area.

2. Geological background

During the Late Cretaceous–Early Paleocene, severalepisodes of turbidite deposition occurred in the west-ern Tethys. These were triggered by a compressiveregime, resulting from the opening of the northern

� 2002 Elsevier Science Ltd. All rights reserved.

66 L. Roncaglia

Figure 1. Location map of the section studied at Viano, Reggio Emilia, Italy. The area covered by the large map is shownas a small rectangle on the insert map. The dashed line from A to B on the large map indicates the location of the section.The large map is based on Istituto Geografico Militare 25/V Series topographical map sheet 86 IV SE, Viano (1:25,000).

Figure 2. Schematic diagram of the Iberian, Adriatic andEuropean plates during the Late Cretaceous, with theAdriatic Margin and Ligurian basins indicated. The thickarrows show the kinematics during the Late Cretaceous.

Atlantic Ocean. In the Cenozoic, this compressiveregime led to the permanent closing of the westernTethys, and the development of the Apenninemountain chain.

In northern Italy, the Apennines consist of over-thrusted, tectonised, lithological units derived fromtwo major depositional basins: the Adriatic MarginBasin and the Ligurian Basin (Figure 2). The sedi-ments deposited in the Adriatic Margin Basin consistof Upper Jurassic–Cretaceous, fine- to coarse-grainedsiltstones, overlain by uppermost Upper Cretaceousto Paleogene, calcareous to siliciclastic turbiditesequences. These sediments were deposited in a con-tinental to marginal marine nearshore environment,and were overthrust later by sequences of the LigurianBasin. The Ligurian Basin sequences consist generallyof Upper Jurassic ophiolites overlain by Cretaceous–Eocene, thick, calcareous to siliciclastic turbidites(Abbate & Sagri, 1982; Marroni et al., 1992). Theseturbidites were deposited in deep, open-marine waters(Sestini et al., 1986). The Viano Clay Formationrepresents one of the turbidites of the Ligurian Basin.

3. Material and methods

Twenty-two samples were collected from the typesection of the Viano Clay Formation located on the

left bank of the Tresinaro River, 3 km south-west ofViano, Reggio Emilia, Italy (Figure 1). The samplingbegan at the base of a limestone layer 70 cm thick,which represents the basal unit of the formation

Dinoflagellates from the Viano Clay Formation, Italy 67

4. Results

4.1. Palynofacies

All residues from the Viano Clay samples containlarge amounts of phytoclasts, such as brown wood andleaf and cortex tissue, and AOM (Figure 4). The

phytoclast content ranges from 51 to 90% (average73%) of the total kerogen residue. Leaf and cortextissue occur in only ten samples from the section, andconstitute less than 1% (average 0.67%) of the totalkerogen residue. The AOM ranges from 8 to 43%(average 23%) of the total kerogen residue. Theremaining material is palynomorphs.

The palynomorph assemblage consists of dinoflag-ellates, acritarchs, other marine algae (mainly Palam-bages), foraminiferal linings and spores and pollen(Figure 4). Scolecodonts have also been observed;however, their occurrence is sparse and they were notcounted. The dinoflagellates, which are usually notwell preserved, range from 0.3 to 11% (average 2.3%)of the total kerogen residue, and dominate the paly-nomorph assemblages from most samples. Dinoflag-ellate diversity ranges from 1 to 31 species (average8.3) per sample (Figure 4). Other marine algae,acritarchs, and foraminiferal linings occur in lowpercentages (<1%). Sporomorphs are rare; bisaccatepollen are absent. Samples from the upper 49 m of theViano section (VI18–VI22, Figure 4) yielded fewerpalynomorphs than the samples below. The palyno-morph analysis in this paper deals only with organic-walled dinoflagellates.

Based on the dominance of brown wood, theabundance of AOM and dinoflagellates, and thevery low percentage of sporomorphs and leaf tissue,the palynofacies from the Viano Clay Formation atViano indicate deposition in an offshore marineenvironment, but under the influence of terrestrial/fluvial input. However, the abundance of phytoclastsin the formation may suggest the presence of alloch-thonous nearshore material. A decrease in thepercentage of dinoflagellates in the upper 106 m(from VI15 to VI22) and the relative increase inthe abundance of sporomorphs in the same intervalmay indicate a sea-level fall or a river delta in thevicinity.

4.2. Dinoflagellate biostratigraphy

In Figures 3 and 5, the dinoflagellate assemblagesfrom the Viano section have been correlated with theUpper Cretaceous dinoflagellate zonation scheme ofRoncaglia & Corradini (1997a). The dinoflagellatetaxa listed in the present paper and described before1998 are fully referenced in Williams et al. (1998);other taxa are referenced in the text. The HO ofCannosphaeropsis utinensis, Hystrichodinium pulchrum,Isabelidinium cooksoniae and Odontochitina operculata,and the LO of Cerodinium diebelii and Palaeocystodin-ium golzowense have been used herein to correlate thesection studied with previously established Upper

(Papani & Zanzucchi, 1970; Iaccarino & Rio, 1972).The sample positions are shown in Figure 3 (as‘heights’ in metres).

Standard palynological techniques, involving HCland HF (40%), were used on all palynologicalsamples. The residues were sieved through a 15-�mfilter cloth and the coarse fraction was given heavyliquid separation (using sodium polytungstate). Oxi-dation treatment was avoided. The residue wasmounted in Canada balsam on microscope slides andstudied under transmitted light. The study material ishoused in the palynological collection of the Depart-ment of Earth Sciences, University of Modena andReggio Emilia, Italy.

At least 250 kerogen particles were counted fromeach sample. They were grouped into the followingcategories: spores and pollen, foraminiferal linings,acritarchs, dinoflagellates, other marine algae, leafand cortex tissue, brown wood and amorphous or-ganic material (AOM, i.e., organic aggregates, faecalpellets and bacteria). Opaque matter was notcounted as this group may include inorganic mineralgrains. Using 15-�m filters, some of the smalleracritarchs and sporomorphs, as well as fine-grainedAOM were probably lost. A minimum operationaldiameter of 15 �m was established for countingAOM and phytoclast particles. The relative distri-bution of the kerogen categories expressed as apercentage of the total kerogen assemblage is shownin Figure 4.

A separate quantitative analysis was undertaken forthe dinoflagellates which were identified to specieslevel. Broken remains were counted as 0.25, 0.5 and0.75 of a specimen and added up to entire specimens.Single opercula were not counted. The dinoflagellatetaxa recorded are listed in the Appendix, and theirstratigraphic distribution is shown in Figure 3. Thelowest occurrence (LO) or highest occurrence (HO)of key dinoflagellates have been used for correlation ofthe Viano section with a previously defined biostrati-graphic zonation scheme in northern Italy (Roncaglia& Corradini, 1997a) (Figures 3, 5). The specimensphotographed are from strew mounts and are ident-ified with England Finder coordinates (Figure 6). Thegeochronologic scale adopted is that of Gradstein et al.(1995).

68 L. Roncaglia

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Dinoflagellates from the Viano Clay Formation, Italy 69

Figure 4. Relative abundance of major kerogen groups and dinoflagellate species diversity in the Viano Clay Formation atViano. The groups plotted are given as percentages of the total kerogen assemblage. The diversity is expressed as numberof species per sample and is based on the counts listed in Figure 3.

70 L. Roncaglia

Cretaceous dinoflagellate zonation schemes in theNorthern Hemisphere (Schrank & Perch-Nielsen,1985, Egypt; Kirsch, 1991, southern Germany;Marheinecke, 1992, north-west Germany; Costa &Davey, 1992, North Sea; Schiøler & Wilson, 1993,Danish North Sea; Hoek et al., 1996, Israel; Nøhr-Hansen, 1996, West Greenland; Siegl-Farkas, 1997,Hungary; Roncaglia & Corradini, 1997a, Italy). Acomparison with Upper Cretaceous assemblages inthe Southern Hemisphere is possible because of thestudies in Australia by Marshall (1985), Helby et al.(1987), McMinn (1988); in Antarctica by Askin(1988) and Pirrie et al. (1997); in the Southern Oceanby Mohr & Mao (1997); and in New Zealand byWilson (1984) and Roncaglia et al. (1999). The sixdinoflagellate events listed below in stratigraphicorder, are considered important in the Viano section(Figures 3 and 5).

1. Cerodinium diebelii (Figure 6.13), the index speciesfor the lower–middle Maastrichtian Interval Zone ofRoncaglia & Corradini (1997a), has an LO in thelowermost sample, VI01, at 0.5 m in the Viano section(Figure 3). Cerodinium diebelii occurs in the lowermostMaastrichtian in southern and central Europe(Kirsch, 1991; Marheinecke, 1992; Smelror et al.,1995; Roncaglia & Corradini, 1997a). It was recordedfrom the uppermost Upper Cretaceous in France(Foucher, 1979; Schiøler & Wilson, 2001), and in theNorth Sea area (Costa & Davey, 1992). The LO of C.diebelii occurs in the lowermost Maastrichtian in Israel(Hoek et al., 1996), North America (Bujak &Williams, 1977; May, 1980; Tocher, 1987), and WestGreenland (Nøhr-Hansen, 1996). In the SouthernHemisphere, the species was recorded from upper-most Campanian sediments in Antarctica (Pirrie et al.,1997) and in the Southern Ocean (Mohr & Mao,1997); it has an LO in the middle Campanian–lowerMaastrichtian interval in Australia (Helby et al., 1987;McMinn, 1988).2. The index species for the Palaeocystodinium golzo-wense Interval Subzone of Roncaglia & Corradini(1997a), P. golzowense has its LO at 54.55 m in theViano Clay Formation at Viano (Figure 3). The LO ofP. golzowense is recorded from the upper Campanianin Israel (Hoek et al., 1996), the lower Maastrichtianin Italy (Roncaglia & Corradini, 1997a, b), Germany(Kirsch, 1991; Marheinecke, 1992), Egypt (Schrank& Perch-Nielsen, 1985; El-Beialy, 1995), WestGreenland (Nøhr-Hansen, 1996), and Canada(Ioannides, 1986). These data point to a lateCampanian oldest age for the strata above the LOs ofC. diebelii and P. golzowense in the Viano section(Figure 3).

3. The HO of C. utinensis (Figure 6.10) in the Vianosection is at 93.9 m within the P. golzowense Subzoneof Roncaglia & Corradini (1997a) (Figure 3). InIsrael, the HO of C. utinensis defines the top of the CutInterval Zone of Hoek et al. (1996). Based on calibra-tion against calcareous nannoplankton and planktonicforaminiferal datums, the latter zone is dated as earlylate Maastrichtian. The HO of C. utinensis was re-corded from the upper Campanian in Hungary (Siegl-Farkas & Wagreich, 1996; Siegl-Farkas, 1997); thelower Maastrichtian in southern Germany (Kirsch,1991); and the upper Maastrichtian in the DanishNorth Sea area (Schiøler & Wilson, 1993). This‘event’ was reported from around the lower–upperMaastrichtian boundary by Williams et al. (1993).On present evidence, the strata above the HO ofC. utinensis at Viano are of Maastrichtian age.4. The HO of H. pulchrum (Figure 6.4) is at 110.6 min the Viano section (Figure 3). Wilson (1974)recorded the HO of this species in the lowerMaastrichtian in Denmark and The Netherlands.Costa & Davey (1992) and Schiøler et al. (1997) havereported this ‘event’ from the lowermost upperMaastrichtian in the North Sea and in the typesuccession of the Maastrichtian Stage, in TheNetherlands, respectively. The HO of H. pulchrumoccurs at the base of the Hemmoor section,north-west Germany, which is early Maastrichtian(Marheinecke, 1992). It has also been reported fromthe lower–middle Maastrichtian interval in southernGermany (Kirsch, 1991), and from the middle–upperMaastrichtian interval in northern Italy (Roncaglia &Corradini, 1997b). Therefore, as H. pulchrumis not generally considered to occur in the upperMaastrichtian (Williams & Bujak, 1985; Williamset al., 1993), I consider the HO of this species to be ofearly Maastrichtian age.5. Odontochitina operculata (Figure 6.11) and Isabelid-inium cooksoniae (Figure 6.9) have concurrent HOs at178 m at Viano (Figure 3), where the HO of O.operculata represents the HO of the genus Odontochi-tina. The HO of Odontochitina is a cosmopolitan‘event’, which has often been reported in the proxim-ity of the Campanian/Maastrichtian boundary in theNorthern Hemisphere (Wilson, 1971; May, 1980;Kirsch, 1991; Schiøler & Wilson, 2001). However,some observations point to the presence of Odontochi-tina spp. in the lower Maastrichtian (Williams &Bujak, 1985; Costa & Davey, 1992; Williams et al.,1993; Schrank & Ibrahim, 1995). The HO of Odon-tochitina has been recorded from the uppermostCampanian in Israel (Hoek et al., 1996) and atTercis Quarry, France (Schiøler & Wilson, 2001). Inthe Southern Hemisphere, the HO is generally

Dinoflagellates from the Viano Clay Formation, Italy 71

Figure 5. Correlation between the Viano section and the Upper Cretaceous dinoflagellate zonation of Roncaglia andCorradini (1997a). The ranges of six key dinoflagellates are also indicated. The highlighted area shows the stratigraphicinterval spanned by the Viano Clay Formation in the zonation scheme. The sample record numbers and their locationsin the log are indicated.

72 L. Roncaglia

considered to be a lowermost Maastrichtian ‘event’(Helby et al., 1987, Australia; Riding et al., 1992,Antarctica; Mohr & Mao, 1997, Southern Ocean;Roncaglia et al., 1999, New Zealand). Thus, theoldest age for strata above the HO of O. operculata inthe Viano section is early Maastrichtian. The HOof I. cooksoniae has been reported from the upperMaastrichtian in the North Sea (Costa & Davey,1992; Schiøler & Wilson, 1993) and Italy (Roncaglia& Corradini, 1997a).

In addition to the key ‘events’ discussed above,there are two other notable occurrences:

1. A single specimen of Alisocysta circumtabulata(Figure 6.2–3) was found at 5.5 m. Alisocysta occursacross the Cretaceous/Paleogene boundary; however,there are previous recordings of the genus from theMaastrichtian in the North Sea (Costa & Davey,1992; P. Schiøler, pers. comm. 2001). In the North-ern Hemisphere, A. circumtabulata has been reportedfrom the upper Campanian by Williams et al. (1993).2. The HO of Apteodinium deflandrei (Figure 6.7) wasrecorded at 64.55 m in the Viano section. Accordingto Williams et al. (1993), this ‘event’ occurs in theupper Campanian in the Northern Hemisphere. Thisdatum has been substantiated by the results obtainedby Schiøler & Wilson (2001) from the Tercis Quarry,France.

4.3. Foraminifera and calcareous nannoplankton

As part of the present study, the 22 samples from theViano Clay Formation at Viano were investigated forforaminifera and calcareous nannoplankton. Exceptfor the long-ranging agglutinated benthic Rhizamminaspp. and Rhabdammina spp., foraminifera were notencountered (R. Coccioni, pers. comm. 1999).Rhizammina and Rhabdammina occur together insamples VI5, VI7, VI10, VI11, VI13, and VI16 (seeFigures 3, 5 for sample locations) and indicate a LateCretaceous age.

The nannoplankton assemblages recovered arediverse, well-preserved and indicate an earlyMaastrichtian age (C. Fioroni, pers. comm. 1999;details to be published elsewhere). Nannoplanktonspecies younger than early Maastrichtian do not occurin the samples studied.

5. Reworking and contamination

Iaccarino & Rio (1972) recorded calcareous nanno-plankton and planktonic foraminifera from the Vianosection, with abundant, well-preserved and strati-

graphically ordered middle–Upper Cretaceous assem-blages, and a few, poorly preserved Lower Paleocenetaxa. These authors considered the Cretaceous taxa tobe reworked, and dated the Viano Clay Formation asEarly Paleocene. However, Iaccarino & Rio (1972,p. 649) stated: ‘‘Given the abundance and good pres-ervation of the Cretaceous forms, it is difficult toregard them all as reworked. It cannot be excludedthat the range of some species currently restricted tothe Upper Cretaceous may extend into the LowerPaleocene’’ (translated from Italian). Mai (1999) sug-gested that certain Paleocene nannofossils commonlyused as index fossils must have originated in the LateCretaceous. This possibility would explain the sparseoccurrence of Early Paleocene nannoplankton speciesin the Viano section and invalidate the idea ofreworked Upper Cretaceous nannoplankton in theformation.

Reworking is common in turbidites. The domi-nance of terrestrial organic material in the residuesstudied indicates the presence of nearshore material inthe Viano section, and suggests lateral transport fromthe shelf into deep water. The occurrence of alloch-thonous terrestrial material, however, does not neces-sarily indicate reworking. Based on the dinoflagellateand microfossil results from the present study, re-working of Upper Cretaceous assemblages in theViano section cannot be confirmed.

Post-depositional contamination from above, bywater circulation and burrowing, cannot be excluded.Intense episodes of bioturbation are inferred from theViano section within the �20-cm-thick mudstonelevels at 170–180 m above the base of the section.Therefore, the poor preservation and low numbers ofthe Early Paleocene nannoplankton and planktonicforaminifera recorded by Iaccarino & Rio (1972)may indicate transport and be the result of post-depositional contamination.

6. Conclusions

A detailed palynological study of 22 samples from thebasal 253.3 m of the Viano Clay Formation in the typearea documents the kerogen assemblage and dinoflag-ellate distribution within the formation. The formerindicates deposition in an offshore marine environ-ment subjected to influxes of terrestrial material.Abundant, stratigraphically ordered, lower Maastrich-tian dinoflagellates occur in the section. The HOs ofCannosphaeropsis utinensis, Hystrichodinium pulchrum,Isabelidinium cooksoniae and Odontochitina operculata,and the LOs of Cerodinium diebelii and Palaeocystodin-ium golzowense, allow correlation with the lowerMaastrichtian dinoflagellate C. diebelii Interval Zone

Dinoflagellates from the Viano Clay Formation, Italy 73

Figure 6. Selected dinoflagellate cysts from the Viano Clay Formation at Viano, Reggio Emilia, Italy. Specimens 1–9 are atthe same scale; specimens 10–13 are at the same scale. Scale bars in 3 and 12 represent 25 �m. 1, Pervosphaeridiummonasteriense, VI3b (England Finder coordinates F50-1), sectional focus, dorsal surface up. 2, Alisocysta circumtabulata,VI3b (E59), high focus, ventral surface up. 3, same specimen as 2, low focus, ventral surface up. 4, Hystrichodiniumpulchrum, VI3b (T54-2), sectional focus, dorsal surface up. 5, Litosphaeridinium cf. fenestreconum, VI3b (D59), low focus,dorsal surface up. 6, same specimen as 5, high focus, dorsal surface up. 7, Apteodinium deflandrei, VI3b (T62), high focus,dorsal surface up. 8, Isabelidinium sp., VI3b (H41), high focus, dorsal surface. 9, Isabelidinium cooksoniae, VI3b (H47),high focus, ventral surface up. 10, Cannosphaeropsis utinensis, VI7c (S7), sectional focus, ventral surface up. 11,Odontochitina operculata, VI3b (F55-4), sectional focus, dorsal surface up. 12, Corradinisphaeridinium personatum, VI3b(N50-3), sectional focus, dorsal surface up. 13, Cerodinium diebelii, VI17b (C13-3), sectional focus, ventral surface up.

74 L. Roncaglia

of Roncaglia & Corradini 1997a (Figure 5). Post-earlyMaastrichtian dinoflagellates are absent. In addition,lower Maastrichtian calcareous nannoplanktonassemblages and Upper Cretaceous agglutinated ben-thic foraminifera are present. Species of nannoplank-ton and foraminifera younger than early Maastrichtianhave not been recorded (C. Fioroni and R. Coccioni,respectively; both pers. comm. 1999). Thus, the dino-flagellate, nannoplankton and foraminiferal data re-corded point to an early Maastrichtian age for thebasal 253.3 m of the Viano Clay Formation at the typelocality, and indicate that the formation conformablyoverlies the upper Campanian–lower MaastrichtianMonte Cassio Formation. Dinoflagellate taxa denot-ing a late Maastrichtian–early Paleocene age were notobserved. The few early Paleocene foraminifera andnannoplankton species documented by Iaccarino &Rio (1972) are probably the result of post-depositional contamination by water circulationwithin the sediments and burrowing.

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Acknowledgements

This study was supported by grants from the ItalianMinistry of Universities (MURST, Rome) andthe Carlsberg Foundation (Copenhagen). FilippoPanini, Chiara Fioroni (Modena University, Italy)and Rodolfo Coccioni (Urbino University, Italy) arethanked for providing unpublished information onthe biostratigraphy of the section studied. FlemmingG. Christiansen, Richard Bradshaw (GEUS,Copenhagen) and Domenico Corradini (ModenaUniversity) are thanked for providing work-space andfacilities during the study period. Graham L. Williams(Bedford Institute of Oceanography, Dartmouth,Canada), David J. Batten (Institute of Geography andEarth Sciences, University of Wales, Aberystwyth,UK) and one anonymous referee are thanked forimproving the initial manuscript.

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Appendix

Dinoflagellates and an acritarch from the Viano Clay Formation atViano, Reggio Emilia, Italy, listed alphabetically by genus. Illus-trated taxa are followed by figure references. The numbers inbrackets refer to the taxa in Figure 3. The generic allocation followsWilliams et al. (1998). Dinoflagellate taxa not listed by the latter arereferenced in the text.

Achomosphaera sagena Davey and Williams, 1966 (11)Achomosphaera spp. (12)Alisocysta circumtabulata (Drugg, 1967) Stover and Evitt, 1978

(Figure 6.2–3) (13)Alterbidinium minus (Alberti, 1959) Lentin and Williams, 1985 (10)Apteodinum deflandrei (Clarke and Verdier, 1967) Lucas-Clark,

1987 (Figure 6.7) (14)Areoligera coronata (O. Wetzel, 1933) Lejeune-Carpentier, 1938

(15)Batiacasphaera sp. 1 (43)Caligodinium aceras (Manum and Cookson, 1964) Lentin and

Williams, 1973 (1)Cannosphaeropsis utinensis O. Wetzel, 1933 emend. Sarjeant, 1985

(Figure 6.10) (16)Cerodinium diebelii (Alberti, 1959) Lentin and Williams, 1987

(Figure 6.13) (2)Cerodinium subquadrum (Corradini, 1973) Lentin and Williams,

1987 (41)Chatangiella packhamii Marshall, 1990 (17)Cleistosphaeridium spp. (18)Cordosphaeridium fibrospinosum Davey and Williams, 1966 (40)Cordosphaeridium varians May, 1980 (19)Corradinisphaeridiniun personatum (Corradini, 1973) Masure, 1986

(Figure 6.12) (3)Cribroperidinium graemei (Slimani, 1994) Williams, Lentin and

Fensome, 1998 (20)Cyclonephelium castelcasiense Corradini, 1973 (35)Dinogymnium acuminatum Evitt, 1967 (44)Exochosphaeridium phragmites Davey, Downie, Sarjeant and

Williams, 1966 (21)Fromea fragilis (Cookson & Eisenack, 1962) Stover and Evitt, 1978

(22)Hystrichodinium pulchrum Deflandre, 1935 (Figure 6.4) (23)Hystrichosphaeridium salpingophorum Deflandre, 1935 (24)Hystrichosphaeridium tubiferum (Ehrenberg, 1838) Deflandre, 1937

(25)H. tubiferum brevispinum (Davey and Williams, 1966) Lentin and

Williams, 1973 (36)Isabelidinium cf. korojonense (Cookson and Eisenack, 1958) Lentin

and Williams, 1977 (45)Isabelidinium cooksoniae (Alberti, 1959) Lentin and Williams, 1977

(Figure 6.9) (26)Leberidocysta chlamydata (Cookson and Eisenack, 1962) Stover and

Evitt, 1978 (27)Litosphaeridium fenestreconum (May, 1980) Lucas-Clark, 1984 (28)Membranilarnacia sp. of Kirsch 1991 (29)

76 L. Roncaglia

Odontochitina operculata (O. Wetzel, 1933) Deflandre and Cookson,1955 (Figure 6.11) (4)

Oligosphaeridium complex (White, 1842) Davey and Williams, 1966(6)

Palaeocystodinium cf. australinum of Roncaglia and Corradini, 1997a(42)

Palaeocystodinium golzowense Alberti, 1961 (37)Palaeoperidinium pyrophorum (Ehrenberg, 1938) Sarjeant, 1967 (30)Palaeotetradinium silicorum Deflandre, 1936 (38)Paralecaniella indentata (Deflandre and Cookson, 1955) Cookson

and Eisenack, 1970 (7)

Pervosphaeridium intervelum Kirsch, 1991 (8)Pervosphaeridium monasteriense Yun, 1981 (Figure 6.1) (31)Phelodinium tricuspe (O. Wetzel, 1933) Stover and Evitt, 1978 (39)Pterodinium/Impagidinium group (32)Rottnestia wetzelii (Deflandre, 1937) Slimani, 1994 (33)Spiniferella cornuta (Gerlach, 1961) Stover and Hardenbol, 1994

(46)Spiniferites ramosus ramosus (Ehrenberg, 1838) Loeblich and

Loeblich, 1966 (9)Wilsonisphaera petila (Corradini, 1973) Slimani, 1994 (34)