1991-92 - Birbal Sahni Institute of Palaeobotany

1991-92Objective: To date Quaternary sediment profiles, ocean sedimentcores, coastal deposits and shell depositsand Kankar horizons in the Ganga plain: To establish the Liquid Scintillation Countingmethod for C-14 datingEighty two samples were processed for radiocarbon dating which included 14background and three stan~ard preparations. For twenty one samples benzene wassynthcsized for C-14 determination using liquid scintillation counting method.Fifty samples have been dated using both the methods (viz. gas counting and liquidscintillation counting) C-14 age determination.A fifty two metre thick Quaternary sediment profile from BHaspur, Nainitalwas dated for a collaborative programme with the Kumaon University on neotectonicactivity of the region. The top 20 metres is within the C-14 age range and onlytwo samples could be dated in this interval. The sedimentation rate is highlyvariable. A core of lake deposit from Orissa relating to the study on the evolutionof mangrove vegetation was dated to 3,470 ± 170 yrs at a depth of 3.5 m. Acarbonaceous ocean-sediment core from Andaman Sea was dated using the organicfraction of the sediment. In this core the calcareous part was almost negligible.The C-14 age at a depth of 33 cm is 11,850 yrs and at 1.0 m it is 21,000 yrs. Thecalculated sedimentation rate is 0.73 cml1,OOO yrs which is lower than that of thepredominantly calcareous core obtained from near Narcondam Island. A profile ofshell deposit from the shelf region in the East Coast was dated for coastal studies.The shells at a depth of 2.1 m give an age of 33,000 ± 1,200 yrs. In addition C-14age determinations on lake sediment profiles from Darjeeling, Garhwal andNilgiris were carried out for palynological and palaeoclimatic studies. Four charcoalsamples relating to archaeological studies from Nepal and Mesolithic cultureof Kerala were dated. The Mesolithic culture of Kerala has been dated for the firsttime at 2,850 ± 80 yrs B.P.The liquid scintillation method for C-14 dating has been established. 1\velvesamples have been dated using this method. For six samples both the gas countingand liquid scintillation counting methods were employed. The C-14 ages in boththe cases are in very good agreement.Programme 8.2G. Rajagopalan: Fission- Track dating of minerals and fossilmaterialsObjective: To carry out Fission·Track dating of glauconitefrom Vindhyan Supergroup and other equivalentformations: To attempt Fission-Track dating of petrified woodfrom the Deccan Intertrappean beds: To carry out Fission- Track dating of check samplesand International standard samples47