Annals of Arid Zone-r6 (3), 331-431, 1977

Quaternary geology, aridity and desertificationin Rajasthan

SUBRATA SINHA

Geological Survey of India, Western Region, Jaipur.

ABSTRACT

The paper highlights tbe importance of Quaternary Geological studies andtbe methodology, employed by the Geological Survey to India, to decipher thebistory and environment of the quaternary era in Rajasthan. It brings out thesequence of events from the earliest humid cold phase, followed by the firstgeneration of more extensive aridity which was separated from the currentarid phase by a warm sub-unit phase. After describing these phases, tbe paperbrings out the various geological and geomorphological characteristics obtain-ing in Rajasthan area that have actively contributed to its arid conditions,besides the role of anthropocentric activities in intensifying the process ofdesertification in and outside the arid zone.

INTRODUCTION

The geological history of the Earth has been divided into several eras.Of these, the most recent-the Quaternary-is the one which covers the smallesttime span, but presents a vast array of geological features, with voluminousdeposits. Yet, for more than a century, this Era and its deposits received theleast attention from earth scientists, who were far more preoccupied withproblems of mineral exploration, discovery of other economic deposits and fuelsources and solving the intricacies of the geological record of more distant eras.of the past. It is only with the search for groundwater that the quaternary inIndia and abroad, assumed a certain status and stature.

This paper attempts to present a brief summary of surmises and interpre-tations on the geological conditions and environmental vicissitudes of theQuaternary era in Rajasthan, based on available information that is nowforthcoming on a fairly appreciable scale. Without delving into local details,the statements represent the concellSUS of interpretations.

METHODOLOGY

The attention of the Geological Survey of India was first drawn to the'Quaternary formations of Rajasthan through hydrogeological surveys from the

332 : SUBRATA SINHA

last fifties onwards. However, it was with the setting up of the Desert GeologyDivision in 1974, recently reconstituted as a Quaternary Geology, Geomorpho-logy and Environmental Geology Division of western Region, that the detailedstudies on the Quaternary of Rajasthan have really commenced. As a part ofthis programme, the G.S.I. has undertaken an extensive programme of photo-geomorphological mapping of the terrain, backed up by extensive field checks,with intensive sedimentological studies on the numerous ~amples collected fromsections, drill holes and pits. Initially, the terrain, on the basis of the mapping,is divided into various geomorphic units, each with different geological-cum-geomorphological attributes, while the detailed field studies and sampling ulti-mately reveal the nature and sequential history of the deposits in the thirddimension. The time connotation of the sequences adds the fourth dimension.These studies enable the Quaternary stratigraphic sequences to be worked outand then correlated from area to area. The nature of material and the geomor-phological setting at various stages enable the worker to draw conclusions onthe palaeo-environmental conditions including climate. drainage characteristicsand terrain conditions. These studies are, therefore, leading to a gradualunravelling on a very extensive scale, the Quaternary history and climaticfluctuations. The capabilities and carrying capacities of the various basicgeomorphic units mapped have a fundamental land use connotation. Thisaspect l~ads to the preparation of suggested land use m'lps that may give regionalplanning a firm foundation, in conformity with the natural conditions andthereby help in precluding major disasters like desertification, soil erosion, etc.

PREVIOUS WORK

Numerous workers from ~arious fields have attempted to interpret thegeological conditions and palaeoclimates of Rajasthan, while several workers,archaeologists and prehistorians have studied the records of human habitationin their region. This paper shall not attempt to present their findings or docu-ment their work. Mention is being made of a few workers whose studies areof significance to the present studies by the team of G. S. I. workers. Singh(1971), Singh et at. (1974), and others, on the basis of the classical palynologicaland field studies in Sambhar and adjoining areas helped in establishing a datedQuaternary sequence, as correlated with dated records of human habitation.Ghose (1964, 1965) and other workers from the Central Arid Zone ResearchInstitute, Jodhpur had carried out geomorphological studies in parts of Rajasthanarid zone. A few eminent scientists, from the field of Earth Sciences, viz. Auden(1952) and Ghosh (1952), Archaeology, viz. Goudie, Allchin and Hegde (1973)and Geomorphology, viz. Verstappen (1970) had also dealt on the various

GEOLOGY, ARIDITY AND DESERTIFICATION : 333

aspects of the desert tracts. Their surmises have provided very valuable guidingmaterial for the present generation of workers in these fields. It should also beacknowledged that Agrawal (1975) and his P.R.L. team, and Mishra andRajguru (1975) of Pune University are carrying out valuable geochronologicaland geo-arc:heological analysis on the samples from these tracts, providing thenecessary inputs into. the system. "

GEOLOGICAL SETTING

Pre-quaternary: Before considering the details of the Quaternary sequ-ence, it would be most pertinent to give a brief summary of the Pre-Quaternarygeological set up of Rajasthan. In this connection. the tabulated statement(Table]) is based on the Geological Atlas of Rajasthan issued by the G.S.I.during 1976. It is obvious from a perusal of the tabulated sequence (Table 1)that apart from occurrences of the Eocene formations in western Rajasthan andmore extensive deposits of Mesozoic age in the same tract, the salient features ofthe rest of Rajasthan's geological setting date back to the Vindhyan and Pre-Cambrian eras. This shows that the Aravallis were a dominant feature of Rajas-than area ever since the Pre-Cambrian era. According to Auden (1952), " .. , ... thenummulitic sea extended further eastwards, on tge northwest side of the Aravallirange, as far as around Bikaner. But this sea became progressively smallerthroughout the Tertiary, and must have regressed from just these higherelevations where the saIt lakes and gypsum of northern Rajasthan are nowfimnd. By the later Tertiary and Pleistocene the Manchars of the northern partof the Kirthar range in Sind. and the mammalian-bearing Siwalik rocks ofPiram island, off Saurashtra, had become fluviatile. The evidence fromthese Siwalik beds is that the region was land, and sedimentation from thePliocene onwards was from rivers. Consequently, considerable rainfall inthe highlands from which the sediments were derived and transported mustbe postulated ".

According to Ghosh (1952) - '· ... the sea regressed probably in theUpper Ranikot, returned again in the Laki to disappear finally fromRajp?tana close to the end of the Eocene, i.e. with the onset of the first stageof. Himalayan orogeny .... East of the Aravalli range. Heron (1938) hassuspected a Tertiary peneplain consisting of a series of planes, at- slightlydifferent levels acoording to their relative resistance to weathering, and fallingin steps from the centre of the Range to the plains bounding it "

The Quaternary: Clearly, the Qlaternary era commenced in Rajasthanunder strictly non-marine conditions, a fact that is most significant for theemergence and habitation of Man in the tract and the most of aridity.

L

I:I:ZU<CX:llJ«

.;-;.ell>"'Co"-Il>",CIl>08v:i:.='0c'OolCtIlOl

0.::loo•...,'0col.e

I%l

I I I I<1:<1:00"Q.....l\.l.lN::::

.e;::ol.,

~ZLI.IUoIf!

'0Col'"

'-ocS~'0u

u:.a0-~•...~•..~•..V)

334 SUBRA TA SINHA

GEOLOGY, ARIDITY AND DESERTIFICATION: 335

The broad findings presented in this paper are based on the field investi-gations by the G.S.!. workers of the Quaternary Geology Division.

The range of interest of this team has been very wide, from Quaternaryhistory and palaeoclimatic evaluation, to land use and desert control aspects.By collating the observations of this team and interpreting them to give thelirst base for the Quaternary history of this region is worked out. Attentionis drawn to Table 2 (prepared by R.N, Ghosh-1976) for the Upeer Luni basin,on the basis of his field observations. This sequence has been corroborated invarious other fields where the geologists are working. FUlthermore. there isa general collation with the findings of Sing (1971) and Singh et al. (1974)on the basis ~f his pollen studies and field observations in the Sambhar andother areas of the Eastern tract.

It should be clearly stated at this stage that these observations do notinclude any specific geochronological determinations but merely indicate asequential situation, with 'the date inferences drawn from Singh et al. (1974),Goudie, et al. (1973) and other workers.

Humid Cold Phase: Studies indicate the presence of a wide-spread fluvia-61e environment in the tract, marked by a widespread boulder conglomerate andsandstone as the earliest Quaternary phase. Typical alluvial seq'uence ofterrace and flood plain deposits have been located in the Luni river basinfi'om the earliest Ho·locene. Interestingly, Mukhopadhyay and Ghosh (1976)have attributed the glacial drift in the form of Bap Boulder Beds of Bap-Kolayat region of western Rajasthan to the Quaternary updating it from theircontemporaneity with the Talchirs of Permo-CarboniferJus age. Their fieldevidences include their occurrence directly above the Palaeocene 'and Eocene

\

rocks of the Palana, Mark, Marh and Jogira Formations. In fact, the com-position of the boulders and their local ions in the tract does not preclude theprobababilty of their provenanr-e being in the Aravallis. On the other hand,the V-shaped volleys of the Aravallis and the occurrence of erratic bouldersfa:r from these provenances are features that may be eXplained by glacialdrifting or periglacial conditions prevailing at that time. The question is yetopen, but warrants further field investigations and studies. The point that isclearly established from all these evidences is the prevalence of definite humidand probably cold conditions upto the beginning of the Holocene (about 10,000B.C.). Auden's conclusions mentioned earlier also corroborated this. Singh(1971, p. 183) states that " __.... there is evidence that the phase endedwith an increase of rainfall at about the beginning of the Holoceneperiod ... ".

,

336 SUBRA TA SINHA

..•.. '"•.•00.'- 0.

Ji ~Oi:!.- _ en'-

~E~~CiQ~Q

,n....00'"1=0.",0•...•...-~:::::l;:c:o

.i.:a'"~o~cCou.~'0

•..•..'0

s::;2-

c•..E•..'"'"a:I

s::;.2

c.2E•..s::;II)00

c•..uII)

~

~0.0..;::

c.~'0u<

,-..c•..8s::;o...;;s::;~

>.00ocII)

Q

u:a0.•...oEoo

GEOLOGY, ARIDITY AND DESERTIFICA nON : 337

A,id Phase (Fi,st Generation) : fn the tabulated sequence (Table I) theEarly and Middle Holocene (8000-3000 B.C.) were marked by evidences ofaridity and aeolian activity of a wider extent than tbe present phase. Stabledunes, with considerable palaeosoil development are found even in Alwar,Jaipur. Bharatpur and other districts of eastern Rajasthan. These evidence~,apart from the surficial dunes in these eastern!tracu, are clearly noticed insections of the Luni, Mendha and other streams, the Sambhar sequence of lakedeposits and even roadside sections on the Jaiplu-Delhi road. Tbis phase ofaridity is also marked by the presence of typical desert landforms, viz. dunes,pediplains, pediments and bornhardts. Singh attributes the formation of theSambhar lake by the choking of a river, at this period, by aeolian sa.nd~.lVhatever the origin of tbe Sambbar basin may be, tlte recent studies definitelyindicate an aggravation, if not initiation of saline conditions in tbis basin.

It ,;hould also be mentioned that the Luni and its tributaries manifestedconsiderable choking of courses and cut offs of older courses, caused by aridconditions and drifting sands.

Warm Sub Humid Phase :-The sub-recent to recent phase (3000.1000 B.C.)in these tracts were marked by accelerated Huvial activity with an ameliora-tion of the climate towards warm humidity. Thi£ is adduced from va.riou~ fieldrelationsh.ip, noted at various sites of the Luui, Mendha. and elsewhere. Thef.eatures include the cutting of the older dune sequences by the Luni, gullyingand entl"enchment of oldel" aeolian coal"ser variety, conglomeratic lenses .andclays. This humid, pha.se, with enhanced fluvial activities, led to the presentgeomorphological configuration of the Luni basin a.nd its surrounding areal,in so far as the riverine situation is concerned, with braids, flood plain and back-swamps. The overall extent of the t[(lees of ~he older Luni system, its presentmisfit nature to the broader valleys, abandoned channels and otber featuresbear eloquent testimony to its wider prowess and influen~ in this region at thatstage.

Reant A,id Semi-Arid Phase: The two last millenia have seen anotherg.radual change in the region; which has left the Luni and the other riversystems as relicts of an eadier humid phase. The geological evidences of drift-ing ~and.••abandoned chal\nel~, active dunes and sand sheets, cboking of streamcourses, development of wadis and playas and the natural vegetation of westernRajasthan, do indicate arid and semi-arid conditions and desert like manifeHa-ti,ans in a major portion of Rajasthan. It should be clarified at this stage thatthere are no tong term meteorological records that enable us to vouch safe thatthese manifestations of aridity, mobilisatioll of older dunes and sand .advance in

338 : SUBRATA SINHA

certain tracts are due solely to climatic changes. On the contrary, there areirrefutable evidences of biotic interference leading to manifestations of deserticconditions and aotivisation of earlier sand deposits even beyond the climaticbarrier of arid zone. Investigations are in progress, to apportion, quantitatively,the role of these two major factors in this region.

GEOLOGICAL/GEOMORPHOLOGICAL CONTRIBUTIONS TOARIDITY

After briefly narrating the various palaeoclimatic phases observed duringthe Quaternary in Rajasthan, it may be worth summarising the geologi-cal and geomorphological factors that have contributed to the present aridity of

this tract :

1. Recurrent aridity in the geological history of this tract, with a parti-cularly significant phase of wider extent in the early Quaternary as describedearlier, has not given the terrain time enough to recover.

2. The earlier geological eras (Pre-Cambrian, etc.) have records ofaridity in the presence of evaporite sequences at depth, the wide-spread buffto l'eddish sandstones of Vindhyan formations etc.

3. There is an indisputable record of an earlier, and more extensivephase of aridity during the early Quaternary era, described earlier and thecurrent phase, separated by a brief interlude of a humid period with greaterfluvial activities. However, this phase, during which the Ghl1ggar culture(Kalibangan, etc~) thrived, was not long enough to allow the terrain to recoverfrom the phase of earlier aridity. The second phase of aridity led to super-imposition of features typical of an arid regime. Obviously, there is a widertract, at present semi-arid, outside the eastern fringe of the arid zone, whichbelonged to the earlier arid tract. This zone is .also sensitive to humanactivities and changes, being basically devoid of any considerable pedogenesisand alluviation. In fact, irrational land use and other causes of desertificationin both the arid zone and its outer periphery, expose the featul'es of earlieraridity to their effects, aggravating the general situation.

4. The present configuration of the Aravalli ranges effectively preventsthe full effects of the monsoons to be felt in the arid zone to its west. This isone of the major contributory factors to the aridity of this terrain.

5. The geomorphological setting of the Aravallis show that there areseveral gaps, often with streams crossing the ranges transversely. These provide

GEOLOGY, ARIDITY AND DESERTIFICATION : 33!}

potential passageways for ~ind transported material into the outer fringe,areas,in the direction of the main wind pattern.

6. In the terrain with evaporation far in excess of precipitation, thepresence of inland basins and depressions with centripetal drainage and thelack of a flushing system, help in the accumulation of salinity in the catchmentsand also their concentration in those basins.

7. The hydrogeological situation in the tract revealed in the Geohydro-logical Map of India published by the Geological Survey of India in 1969,and the work of various agencies, is one of restricted acquifers, often withbrackish and saline waters, with boundary conditions, deep water tables.Recharge facilities are limited due to the low precipitation high evaporationand geological setting. Even the freshwater zones of the Lathi formations ofJaisalmer suffer from these limitations. All these severely restrict exploitationpossibilities. recuperation and'maintenance of the groundwater regime.

8. Due to a combination of climatic and geomorphic factors there ishardly any surface water system in the tract that,is integrated and organised,having appreciable discharge in this tract, for the greater part of the year.The only exception is the Luni and its tributaries, which too is a misfit systemdisorganised and without any sustained flow for most months of the year.

9. The Rann of Kutch, which forms the south-western fringe of thedesert. is a salt march, periodically and partially inundated by the sea. Thisis also a contributory natural factor of increased salinity and aridity of theRajasthan arid zone.

10. The geological, geomorphological and hydrogeological settings havecombined to favour the development of caliche (calcium carbona tic material)in the soils and aeolian/fluvial material, in the profile to variable depths, withconsiderable induration and pan 'formation, inhibiting normal root andvegetal growth.

II. In adequate organic accumulation in the soil, due to the prevalenceof a climate unfavourable to vegetal growth, not only during the current aridphase, but from the previous one. As a result, the soils, even in the easterntracts, normally semi-arid, manifest limited pedogenesis, often only on stablisheddune features.

12. Apart from these basic pedogenetic limitations, the intrinsic climaticconditions that promote erosion and wind transport, constantly remove thetopsoil, resulting in an impoverishment of the productive environment. The

340 : SURRA T A SINHA

mobiJisation .and movement of salinised waters in some areas, the deep Willer

tables in other tracts, are also deterrents to healthy wil growth and produc-tivity.

It is needless to emphasise the fact that the role of Man in bringing ab( utdesertification and deterioration of the desert and it" fringe, become all themore damaging in an environment which, as shown in the preceding statements,have the natural tendency to remain arid and barren.

ACKNOWLEDGEMENTS

The author f'(ratefully acknowledges the contribution of his colleagues,S/Shri R.N. Ghosh, R.K. Biswas, R.P. Verma, j.K. Basu, B. Sural, R.N. Sri-vastava and G.S. Chattopadhyay for providing the field information and basicmaterial for this paper. He also acknowledges the kind permission of the D.G.and D.D.G. (WR), GSI to present this paper.

REFERENCES

Agrawal, D.P. 1975. Palat::'oclimate and geochronology of the arid regions ofIndia. Proc. Problems of Deserts in India, Workshop, jaipur, Sept., 1975.Abstract P. I!.

Auden, j.B. 1952. Some geological and chemical aspects of the R:>jasthan saltproblems. Bull. Nat. Inst Sci. India No. l. pp. 53-ti7.

Ghose, Bimal 1964. Geomorphological aspec~s of the formation of salt basin9in western RaJasthan. Proe. UNESCO Symp. Ind Arid Zone, Jodhpur pp.79·83.

Gh::>se,Bimal 1965. The genesis-ofthe desert Plains in the Central Liwi Basinof western Rajasthan. Jour. indo Soc. Soil Sci. 13(2): 123-126.

Ghosh, P. K. 1952. Western Rajasthan - its Tectonics and Minerals, IncludingEvaporites. Bull. Nat. lnst. Sci. India. No.1. pp. 101-130.

-Ghosh, R. N. 1975. The Luni - a case history of application of photo-geomor-phological techniques. Problems of Deserts in India, Proceeding of the'Workshop' held at Jaipur (Sept., 1975) Abstract, p. l.

Ghosh, R.N. 1976. Photogeological studies on Ancient Water Regimes ofRajasthan Rivers. Proc. Workshop on Palaef}climate and Archaeology of Raj.and Gujarat, Ahmedabad, Feb., 1976 (in press).

GEOLOGY, ARIDITY AND DESERTIFICATION: 341

Goudie, A.S., Allchin, B. and Hegde, K.T.M. 1973. The former extensions of theGreat Indian Sand Desert: Geor. Jour. 139 (2): 243-257.

Heron. A.M. ]938. The Phyosigraphy ofRajputana. Presidential address. Sectionof Geography and Geodesy. 25th Indian Science Congress Session.Proc. pt. IISection IV pp. 119-132.

Mishra V.N. and Rajguru, S.N. 1975. Some Aspects of Quaternary Environ-ment and Early Man in Western India. Problems of Deserts in India,Proceedings of the Worhhop held at Jaipur Sept., ]975. Abst. pp. 11-12.

Mukhopadhyay, A K. and Ghosh. R.N. ] 976. The problems of the stratigraphicposition of the Bap Boulders, Raja~than. Ind J(!ur. Earth Sci. 3(2):220-228.

Singh, Gurdip ]971. The Indus Valley Culture: Seen in the context of post-glacial climatic and eco]ogical studies in nort h-west India. Archueo. Phy.Anthrf). Ocenia. IV (2): 177-189.

Singh, Gurdip, Joshi, R.D., Chopra, S.K. and Singh, A.B. 1974. Late Quaternaryhistory of vegetation and climate of the Rajasthan Desert, India. Phil.Tans. Royol. Soc. London. 267 B (889) : 467-501.

Verstappen, H. Th. ]970. Aeoli'\o geomorphology of the Thar desert andpalaeoclimates. Z. Geomorph., Suppl. 10. pp. 104-119.