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Chronology of red dune aggradations of South India and its Palaeo-environmental significance

100%

Alappat L. , Seralathan P. , Shukla A. D. , Thrivikramji K. P. , Singhvi A. K.

Geochronometria

2013

tom Vol. 40, no. 4

274--282

Red sand dunes occur in the coastal plains of south east and west of Tamil Nadu, India be-tween the co-ordinates of 8°00’ to 9°30’ N; 77°18’ to 79° 00’ E. OSL dating of these sands indicated aggradations between ~16-9 ka and ~9-3 ka in the west and east coasts respectively. Dating results from inland red dunes at the foothills of Western Ghats show a break in deposition at ~6 ka and ag-gradation since ~2 ka. The sand aggradations in the west coast occurred during the transition period when SW monsoon in the area was re-establishing. The dunes attained their stability by 9 ka. In the coastal region, the aggradations were controlled by sea level changes and a local recycling of earlier dunes (in the east coast). In the inland areas, the dune building was controlled by sand supply from fluvial sources.

Chronology of Cauvery delta sediments from shallow subsurface cores using elevated-temperature post-IR IRSL dating of feldspar

86%

Alappat L. , Tsukamoto S. , Singh P. , Srikanth D. , Ramesh R. , Frechen M.

Geochronometria

2010

tom Vol. 37

37-47

We present the results of luminescence dating of sediments from two cores from the Cauvery Delta in south-east India. Since all natural quartz OSL signals except one sample were in saturation, the elevated temperature post-IR IRSL protocol for K-feldspar was applied to establish a chronology. Internal dose rates of K-feldspar grains were calculated from the measured internal content of potassium, uranium, thorium and rubidium in the bulk of K-feldspar grains using solution ICP-OES and ICP-MS analysis. A substantial scatter in single-aliquot De values was observed which is most probably due to the effect of incomplete bleaching of fluvial sediments before burial. A minimum age model was applied to extract possible depositional ages. The study revealed that except an upper layer of Holocene sediments (< 5m), the majority of the upper ~50m of Cauvery delta sediments were deposited between marine isotope stage MIS-5 and MIS-10 or older. The feldspar luminescence ages also indicate the existence of a period of non deposition or erosion in the upper part of the cores.