• Carbon Dynamics in Vertisols as Revealed by High-Resolution Sampling

      Becker, Heidmann Peter; Andresen, Olaf; Kalmar, Dov; Scharpenseel, Hans Wilhelm; Yaalon, Dan H. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Two Vertisol soil profiles under xeric soil moisture regimes, located at Qedma and Akko, Israel, were investigated and compared to a profile under ustic moisture regime, located in Hyderabad, India. Samples were taken in complete successive 2 cm thin layers down to about 180 cm depth or more. Organic and inorganic carbon were analyzed with regard to 13C and 14C concentrations. While all soils have radiocarbon ages of several thousand years BP, the depth distributions reveal substantial differences between the soil carbon dynamics. 14C and, less pronounced, delta-13C clearly reflect the pedoturbation process. Further, its strength is found to be related to mainly soil moisture regime, then clay content and land use. In one soil, a change of growing from C4 to C3 crops in the past can be concluded from the delta-13C depth distribution.
    • Coastal Response to Changes in Sea Level since the Last 4500 BP on the East Coast of Tamil Nadu, India

      Achyuthan, Hema; Baker, V. R. (Department of Geosciences, The University of Arizona, 2002-01-01)
      Geomorphology, clay mineral composition, and radiocarbon dates from Muttukadu to Marakkanam estuaries and the tidal zone along the east coast of Tamil Nadu, India, have been used to reconstruct coastal evolution between approximately 4500 and 1100 BP. Formation of alternate oyster beds with intervening tidal clay units indicate fluctuation in the sea level may be a consequence of changes in the Mid-Holocene sedimentation pattern and coastal configuration. 14C dates from Muttukadu indicate a rapid relative sea-level rise (RSL) subsequent to 3500 BP and tidal flat sedimentation between 3475 and 3145 BP. Marine conditions along the east coast area returned around 1900 BP. Comparison of dates with other sites, e.g. Muttukadu, Mammallapuram, and Marakkanam, points toward short removal of marine conditions, ample sediment supplies in the tidal zones, and neotectonic activity. Reactivation of the north-south trending fault line occurred not earlier than approximately 1050 BP. Our study indicates that Middle to Late Holocene coastal sedimentation and the chronology of the tidal zone formation have been strongly influenced by local factors. These have provided considerable scope for internal reorganization with changing coastal processes.