POLLEN ANALYSIS OF FOSSIL SOILS ALONG THE BANK OF GHOD RIVER, INAMGAON, MAHARASHTRA*
VISHNU-MITTRE & H. P. GUPTA Birbal Sahni Institute of Palaeobotany, Lucknow-226007
ABSTRACT sonal nullahs. It is largely black cotton Pollen analysis of fossil soils along the bank of soil though sandy deposits are nQt infre• Ghod Rivet, Inamgaon, Maharashtra, suggests the quent. former occurrence of a dry deciduous forest domi• Thi.s pa.!t of district Pune is highly arid. nated by Holoptelea integrijolia. The annual pre• No clImatIc data are available for Inamgaon cipitation then was not higher than now and an environment of unstability of soil concentration or for any station in the immediate vicinity. along the banks had prevailed. The subfossil soils Pune has mean annual rainfall around 600 were formed by ponding of flood waters when the mm with only 47 rair,y da.ys in a year and water level in the river had risen much higher 58 per cent humidity. The mean annual than at the present caused probably by tectonic movement in the catchment area. temperature ranges frem 18°C to 32°C with The percentage distribution of pore apertures on th~ highe"t recorded around 43°C. Being subfossil pollen grains of Holoptelea integ,'ijoha has d.ner than Pune, the mean anual precipita• been found to differ considerably from the modern tIon at Inamgaon and vicinity is less than plants of this species suggesting a physiological change in the modern plants. 500 mm (pers. information Mr. Kajale of D.eccan ~ollege, Poona) and temperatures slightly hIgher than obtained at Pune. INTRODUCTION
STRATIGRAPHY OF FOSSIL SOILS the occurrenceright Ibankof offo~silGhodsoilsriver,alonga THEtributary of the Bhima RiYer was The fossil soils occur along the right bank first discovered l.y Lala Aditya Narayan, of Ghod river in the form of bands of dark an archaeologist attached to ,the team of black clay extending over a short distance Prof. H. D. Sankalia excavating a Central of about It m. There are three prominent Indian Chalcolithic site, Inamgaon, about bands measuring about 7-21 Cmin thiCkness 1·60 km distant and upstream from the·right alternating with thin bands of sand or silt bank of the tributary. The attention of in between. The section comprising the the senior author to these fossil soils was ~ands of clay~ intercalated with sand layers drawn kindly by Prof. H. D. Sankalia during hes over a thm layer of brown sand resting his visit to Ir.amgaon in Feb. 1969. The on highly ferruginous boulder gravel about site is about 90 km di~,tant from Pune, 21 cm of which is exposed, and is overlain district Pune, Maharashtra. by about 1'20-1'50 m sand making the top Inamgaon lies in the dry arid region bear• of the bark. The boulder gravel i~ about ing patches of the Southern Tropical Thorn J ·50-~·50 m high from the river bed. Forest cO'mprising open low communities The top layer of black clay, about J 5-20 in which Acacia, Prosopis spp. and the other cm in thickne"s, was highly weathered and thorny hard wood species predomina·te. penetrated by rootlets of vegetation' growing Trees of ZizyPhus and Anogeiss1,f,s latifolia, over the bank. The middle laver telow Soymida febrifttga and shrubs of Capparis ab.out 20-~5 cm of sand layer, consisted of spp .. occur scattered in various preportions. thm bands of black clay alternating with Fleshy Euphorbias are not very infrequent. fine banes of silt or sand. The bottommost The trees are stunted with short boles and layer of black clay resting on a thin layer low crowns. Species of Aristida and Hete• of brown sand of about 3-6 cm in thickness ropogon contortus are the prominent grasses. was about 7-10 Cm thick. The brown sand Clumps of Typha occur in and around sea- overlay the boulder gravel.
*Pollen analyses by H. P. Gupta; text and interpretation by Vishnu-Mittre. 72 Pages 73-7"-
M 0 POLLEN ANALYSIS OF' BLACK CLAY EXPOSED IN A SECTION • • • • • ALONG RIGHT BANK OF GHOD RIVER, INAMGAON, • • MAHARASHT RA . • • • • • POONA" • • • • •• • • • • • • • • • SAND • • • • • • • • • • • • •• • • • • • • • • •
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TEXT-FIG. 1 VISHNU-MITTRE & GUPTA - POLLEN ANALYSIS OF FOSSIL SOILS 75
A thorough search was made both up and discovered in every house excavated (Indian downstream along both the banks of the Archaeology-A Review, 1969-70). river to discover similar exposures of fossil soils, but the search proved fruit• less. POLLEN ANALYSIS The black clay bands in the section appear Text-fig. 1 to have been formed by ponding of water after an intermittent flooding episode causing No samples for analysis were collected the deposition of silt and clay repeatedly from the top layer of the fossil soils. for it over one another when the water level in was found much weathered and penetrated the river must have risen about 3·50 m above by rootle1s. The middle layer was com• the present river level. The overlying thick pe.ratively less weathered ar:d the bottom deposit of sand must have depo8ited by layer the le;:,st. Two to three samples each another flooding episode of more severe in vertical series were collected from the nature than the one preceding it. *A C14 middle and the bottom layers. date (TF-1003, 21725 ± m i.e. 19775 B.C) The samples were subjected to usual of shells from a pebble conglomerate oc• chemical treatment involving the use of curring about 2 m above the modern bed HF and suhsequently acetolY8is after Erdt• of the Ghod river reveals that the formation man (1943). All the samples from the of these black clay layers is subsequent to middle layer and the One from the bottom 20,000 years B.C. layer did not yield sufficient pollen for the The ferruginous boulder gravel appe8.rs construction of pollen spectra. The details to be the top of the pebble conglomerate (based upon percentages of each individual and both the gravel and the conglomerate calculated on the number of pollen grains are highly suggestive of the first major flood• of all land plants) of the two pollen spectra ing phase here. The last flooding phase from sample nos. 4 and 5 belonging to the which tended to deposit the top sand de• bottom layer are set agair:st stratigraphical posit may be of early historical times 2.S profile in text-fig. 1. evidenced by the embankment remains of Pollen Spectra - The two spectra are boulders set in hard mortar towards the dominated by pollen of Holoptelea integri• west of the Chalcolithic site, Inamgaon. folia, of which the pollen grains are 3-5 porate These flooding episodes resulted in alteration as contrasted from 4-6 porate in modern of the river course as is evidenced by the plants of this sepcies reported by Rhandelwal occurrence of a river channel running close and Vishnu-Mittre (1974). The percentage to the embankment which diverted the distribution of pores on pollen of modern and floodwaters in a NfS direction. From the subfos8il H oloptelea integrifolia also differs above it would appear that the formation considerably as shown in table-l below. of the black layers took place during the receding phase of the last Pluvial or sub• sequent to it. TABLE 1- PERCENTAGE DISTRIBUTION OF PORES ON POLLEN GRAINS OF Early Stone Age man was witness to the MODERN AND SUBFOSSIL HOLOPTELEA major flooding episode as stone tools of this INTEGRIFOLIA age have been recovered from the gravel deposits opposite Inamgaon together with NUMBER OF69'8%24'2%22'6%Sample74'6%6'0%No.SUBFOSSILPOLLEN542'6%40'8%16'6%MODERNPOLLEN2'8% remains of Bos4-poratt'6-porate5-poratenamadicus. PORESThe regionNo.has4 Sample been inhabited 3-porateby man since then as evi• denced by the large factory site probably of Late Stone Age near Inamgaon and by the Malwa and the Jorwe cultures dated from 1600 to 1000 B.c. Deer was the most hunted animal here during the central Indian Chalcolithic Culture as its bones have been
*The other date for shells from Middle Stone Pollen erains of Syzygium vary from 0·48• Age tools bearing sandy pebbles 2m above the river bed is TF-ll77, 19290 ± 360 i.e. 17340 B.C. to 2·75 per cent indicating long distar.ce (Agrawal & Kusumagar, 1975, p. 150) transport. A single polyad of Acacia has 76 THE PALAEOBOTANIST
been met with only in sample no. 4 indicat• in the very moist Teak forest (rainfall ing its loc3.1origin. Pollen grains referred over 2500 mm). to Leguminosae-Papilionaceae are also Elsewhere it occurs in the dry deciduous recognised. They are all finely reticul",te, forests, viz., Dry Teak forest in Madras and wlporate or colporoidate, 20-28 X 15-23 tJ. in as Holoptelea forest in Western Ganges Khola size, and could as well belong to gel;era in Uttar Pradesh under a rainfall regime cutside this natural order. Pollen grair:s of 900-1500 mm. Dalbergia sissoo and Sa1• referred to jasminum (0'75% to 3·3%) may rnalia mn.labarica are cor,spicuous associates as well belong to other members of Oleaceae. in the Holoptelea forest in U.P. Pollen of aquatics is singularly absent. Formir,g n2.rrow strips along streams The ground vegetation is poorly represented it occurs along Mahi river in Banswara by small percentage of pollen grains of Division in Rajasthan; on sandy alluvium Caryophyllaceae, Cheno-amaranths (referred in the Kher-Sissoo (Acacia catechu and to as Chenopodiaceae in text-fig. 1), Dalbergia sissoo) forest all along rivers in Composit2.e, Solanaceae, Liliaceae, Gra• Haldwani division, U.P. It also occurs mineae and Urticaceae. A single grass in the Northern Tropical Thorn forest under pollen of 75 [J. has been observed in sample a rainfall regime of 250-670 mm on flat no. 5. A wild grass producing large-sized alluvial soils in the Desert Thorn forest pollen can only be inferred. Two p )llen with me2,n annual temperature being 25°C• grains of Cyperaceae have been ob8erved 31°C; in the Desert Thorn forest in Bassi, in only sample no. 4 wherein a single pollen Jaipur division and in the Ravine Thorn of Polygonum has also been encounterer1. forest in Etawah together with Acacia. Interpretation - In the absence of data Although this deciduous plant species is concerning pollen preservation phenomena distributed in a variety of climatic regimes, and the comparable modern pollen spectra, yet it is of more common occurrence in the a tentative interpretation of the pollen dry deciduous forest on flat alluvial soils spectra can only be attempted here. The along the streams. It is a member of the predominance of arboreal pollen particu• primary series with the second arrivals larly of H oloptelea integri/olia over that of to the original colonists, Acacia catechu a..nd NAP is highly suggesti ve of a forest of H olo• Dalbergia of the riverain type. Along WIth ptelea with Acacia in the vicinity. Syzygium its associates such as Adina cordi/olia, Lager• of which small percentage of pollen grains stroemia, Albizzia, Salmalia, Terminalia, etc. has been recovered, is a high pollen pro• it occurs on immature riverain sandy or ducer. Its pollen obviously has been trans• gravelly soils liable to frequent flooding. ported from 10:Jg dista.nce. It also occurs on consolidated sand dunes From an account of the ecology and as at Bassi in the ]aipur Forest Division in distribution of H oloptelea integri/olia given Rajasthan. Passing through a dry deciduous by Champion and Seth (1968) one finds it phase, this primary succession leads to the a deciduous tree, widely distributed in India climatic climax vegetation of the area. and ascending to 700 m in the hills. It is The influence of the soil exceeds that of a light demander and not frost re~istant. climate as is apparent from the similarity It occurs as a primary sere in new reverine of the riverain seres from D.P. to Kerala soils throughout drier deciduous forest to and from Punjab to Assam. Its occurrence semievergreen post climax. Secondary seres therefore reflects unstability of soil concen• are more xerophytic tending to resemble tration in various stages of consolidation and dry deciduous forest. On deep and porous its distribution is governed and controlled soils it is capable of thriving without much moisture in soil. It occurs on lateritic and by edaphic factor rather than by climate. black cotton wi Is and Dalbe1'gia lati/olia With the progressive development of mature is one of its close associates. soils the divergence in succession takes place Under the moist climate it is known to leading to climax vegetation in equilibrium occur in Kerala in the Tropical West Coast with the climate of the region. The suc• Evergreen Forest under a rainfall regime cession is quicker under better d!strib~ted of 2000-~500 mm. Here it usually ferms rainfall and milder winter than III regIOns a narrow strip between the wet evergreer. where such favourable conditions do not and moist deciduous forests. It also occurs exist (Champion & Seth 1968a, 1968b). ViSHNU-MiTTRE & GUPTA - POLLEN ANALYSIS OF FossiL SOiLS
Abundant occurrence of Holoptelea pollen suggests a distinot change in the physiology in the fossil soils discovered along the bank of H oloptelea integrifolia since the late of Ghod River strongly suggests the former Pluvial times. local occurrence of H oloptelea forest fringing the banks of the river. That the forest CONCLUSION was of a deciduous type is also suggested by the identification of polyads of Acacia. The fossil soils along the right bank of An environment of unstability of soil con• Ghod River were formed through ponding centration in various stages of consolidation of flood waters during a flooding episode flooded periodically had prevailed when the subsequent to 20,000 years ago. The ab• soils now burried had been laid. A dry sence of pollen in all the fossil soils has climate with precipitation from 250 to 760 limited our inference of past vegetation and mm can only be surmised. The formation climate to only two pollen spectra from the of the subfossil soils is the result of ponding bottom layer. The abundance of Holoptelea of flood waters when the water level of the pollen in tbe pollen spectra suggests the river had risen much higher than at the occurrence of a dense Holoptelea forest along present. Pollen data do not suggest that the banks of the river during the later part the floods were caused by high precipitation. of the last pluvial. No trees of Holoptelea Tectonic factor in the catchment area can not were observed at Inamgaon and in the be overlooked. vicinity during the senior author's visit to Holoptelea integrifolia is a very high pollen the area. Very likely the trees were missed producer. A t'wig of 150 flowers produces since they were leaflets at the time of visit as much as 6, 62, 350 to 16, 264, 500 pollen in Mid-February and flowering had not grains (Khandelwal & Vislmu-Mittre, 1974). commenced yet. The amount of pollen preserved in local The climate when the black clay layers sediments at Lucknow ranges from 1'5% were deposited was probably arid as at to 43'7% whereas the atmosphere during present with an environment of unstability its flowering period has up to 42'5% pollen of soil concentration along the banks of the (Khandelwal, 1974). At Lucknow itself river. its plants occur from scattered trees to It is hoped that the investigation of more groves including the planted ones. The such fossil seils in this area would certainly recovery of 65-70% pollen therefore in the throw decisive information on past vegeta• fossil soils is not surprising and it indeed tion and climate than inferred here from suggests the occurrence of a dense Holoptelea two pollen spectra only. forest provided such high percentage of its The senior author records his thanks to pollen is not due to differential preservation. Prefessor H. D. ~;ankalia for drawing bis The sub fossil pollen being 3-5 porate in attention to the site and for the facilities contrast to 4-6 porate in modern plants to visit it and to collect samples for analysis.
REFERENCES
Agrawal D. P. & KUSUMAGAR, SHEELA (1975). Analysis. Waltham, Mass. U.S.A. Radiocarbon dates of some Late Quaternary Indian Archaeology - A Review, 1969-70. samples. Curr.Sci. 44 (5): 149-151. KHANDELWAL, ASHA (1974). Studies in atmo• CHAMPION, SIR HARRY, G. & SETH, S. K. (1968a). spheric pollen grains and fungal spores at Luck• A revised survey of the Forest Types of India. now. Ph.D. Thesis. Lucknow University. Delhi. KHANDELWAL, ASHA & VISHNU-MITTRE (1975). IDEM (1968b) General silviculture for India. Delhi. Palynology of Holoptelea integrifolia Planch. ERDTMAN, G. (1943). An Introduction to Pollen Palaeobotanist.22 (2): 127-132.