• A Comparative Study of Monsoonal and Non-Monsoonal Himalayan Lakes, India

      Kusumgar, Sheela; Agrawal, D. P.; Deshpande, R. D.; Ramesh, Rengaswamy; Sharma, C.; Yadava, M. G. (Department of Geosciences, The University of Arizona, 1995-01-01)
      Sedimentological, mineral magnetic and carbon isotopic studies on cores from Mansar Lake in the Jammu area provide paleomonsoonal history dating back to 580 BC. From ca. 580 BC to AD 300, the region experienced precipitation similar to the present, whereas from AD 300 to 1400, the monsoon was relatively subdued. A small excursion ca. AD 1100 suggests an effect of medieval warming. Studies in the Kumaon region did not provide a proper precipitation record, as anthropogenic activity interfered with sedimentation. Manasbal Lake in Kashmir gave an inversion of 14C chronology due to younger paleosols in the drainage basin. Further, the episodic nature of sedimentation in Manasbal Lake hampered the reconstruction of precipitation history in the area.
    • Lake Sediments from the Kashmir Himalayas: Inverted 14C Chronology and Its Implications

      Kusumgar, Sheela; Agrawal, D. P.; Bhandari, Narendra; Deshpande, R. D.; Raina, Alok; Sharma, Chhemendra; Yadava, M. G. (Department of Geosciences, The University of Arizona, 1992-01-01)
      We have measured 14C, 210Pb and 137Cs profiles in two representative cores from Manasbal Lake, Kashmir, India. The sedimentation rate derived from 210Pb and 137Cs in the upper part of the core is in the range of 3.4 to 5.5 mm yr-1. In contrast, 14C ages show an inversion at depths >20 cm. These results are attributed to the erosion of the ubiquitous 10-20-m-thick loess mantle, based on the similarity of 14C ages of the inversion layer in the sediments and the paleosols present in the catchment area. Frequency-dependent mineral magnetic susceptibility (Xfd), carbon to nitrogen ratios and pigment concentrations in the profile show a significant amount of allochthonous component in the lake deposits and support the conclusion that the 14C dates do not reflect the chronology of the in-situ lake sedimentation but episodic deposition of the surrounding loess. Thus, 14C serves as a useful tracer to understand source components of the sediments.
    • Physical Research Laboratory Radiocarbon Dates VI

      Agraival, D. P.; Kusurngar, Sheela; Yadava, M. G. (Department of Geosciences, The University of Arizona, 1991-01-01)
    • Radiocarbon and Stable Carbon Isotopes in Two Soil Profiles from Northeast India

      Laskar, Amzad H.; Yadava, M. G.; Ramesh, R. (Department of Geosciences, The University of Arizona, 2012-05-04)
      Two soil profiles from northeast India, one from Bakrihawar, an agricultural land, and the other from Chandipur, a virgin hilly area from Assam, are investigated to understand the organic carbon dynamics of the area. Due to frequent flooding, the Bakrihawar soil has accumulated a higher clay content than that of Chandipur. The carbon content is less than 1% by weight in both the sites. The higher clay content is responsible for relatively more soil organic carbon at Bakrihawar. The mean δ13C values at both sites reflect the values of the overlying vegetation. At Bakrihawar, both rice cultivation (C3) and natural C4 grasses contribute to higher mean enriched values of 13C relative to Chandipur, where the surface vegetation is mostly of C3 type. The turnover time of organic carbon, estimated using the residual radiocarbon content, depends strongly on the soil particle size distribution, especially the clay content (i.e. it increases with clay content). To the best of our knowledge, this is the first soil carbon dynamics study of its kind from northeast India.