- © 2002 AAPG/DEG
Biota living in lakes and their watersheds are the sources of organic compounds for lake sediments. Much of the organic matter contained in sediments has undergone microbial reprocessing. Nevertheless, organic matter in lake sediments can retain source information and thereby contribute to the paleolimnological record. In sediment cores from Mansar and Surinsar lakes of Lesser Himalaya, Jammu, C/N ratios and δ13C values suggest that the primary source of organic carbon was vascular land plants. Low total nitrogen contents, low amino acid/amino sugar ratios, low amino acid carbon and nitrogen contents, and low δ15N values, the latter in Mansar lake, suggest terrigenous organic matter higher in lignin or carbohydrate contents and biodegradation in bottom sediments. The higher δ15N values in Surinsar lake indicates more autochthonous contribution of organic content. Variations in the organic carbon and total nitrogen contents in the cores are related to grain size, inorganic carbonate, and degradation at the bottom levels. The 210Pb data of the core fractions of these lakes show variation in the rate of sedimentation in Mansar lake, that is, 8.2 mm/yr in the northern and 4.5 mm/yr in the southern flank, whereas in Surinsar lake, it is 7.2 mm/yr, which indicates variation in sedimentation/erosion in the lake basins.
Brijraj K. Das has previously been on the teaching faculty of Banaras Hindu University. He has been deeply involved in environmental and geochemical studies of lakes in Chnadigarh, India, particularly those in the Himalayas, and in investigating the continental records of Holocene palaeoclimatic change and its comparison with deep sea climatic data. His investigations are related to sediment chemistry, biogeochemistry, and stable isotope chemistry on surface and deep core sediments from the foreland basin. He has contributed a number of papers on these lakes and is a pioneering worker on the lakes of India. He was awarded the British Council fellowship to the UK and the Alexander Von Humboldt senior fellowship to Germany, and some of his papers have received awards in India as well. He is writing a book on the environmental geochemistry of the lakes of India.