12-14 September, 2011, Lucknow - Earth Science India

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National Conference on Science of Climate Change and Earth’s Sustainability: Issues and Challenges ‘A Scientist-People Partnership’ 12-14 September, 2011, Lucknow HOLOCENE ENVIRONMENTAL MODIFICATIONS ALONG THE SOUTHWEST COAST OF INDIA: AS INFERRED FROM THE MULTI-PROXY ANALYSIS OF PALAEO-DEPOSITS OF MEENCHIL RIVER, KERALA, INDIA B. Ajay Kumar Department of Mining and Geology, Idukki District office, Thodupuzha, Kerala email: jemnair@gmail.com The morphology and behaviour of a large number of rivers completely changed during the climate changes of Quaternary times. The Quaternary sea-level changes caused for the channel shifting of many rivers. Neo-tectonism has also had its influence in the fluvial systems and this metamorphosis reflected great changes of discharge and sediment load. Earlier studies suggested that the sea level along the southwestern part of the coast stood around 60–100 m below the present msl during the last glacial maxima (around 20,000YBP) and the rivers flowing at that time incised their valleys to this base level. Later, during the Holocene, a prominent event of marine transgression (8000- 6000YBP) and another event of regression (5000-3000YBP) were occurred along Kerala coast. Geomorphological modifications were also recorded according to these sea level changes and contemporaneous tectonism. It was evident that the river systems of Kerala might have affected by these geological processes. The remarkable presence of palaeodeposits in the lower reaches of Meenachil River led to an investigation into the palaeoenvironmental conditions and nature of deposition of these deposits. The textural analysis showed that palaeo-deposits of sand characteristically exhibit different sets of depositional environment suggestive of marine transgression and regression episodes. It is also suggested that the region might have experienced structural disturbances leading to the phenomena like river avulsion and channel abandonment. The radiocarbon dating of the samples revealed that the age of the palaeo-deposits is fairly older than the age of formation of the Vembanad Lake. The evaluation of the organic carbon, nitrogen and the C/N ratio of the embedded carbonaceous clay suggested that the deposits were formed by terrestrial plants and the region had experienced high intensity rainfall during the earlier part of the Holocene. The evaluation also suggested a fairly relevant shift of the Meenachil main channel from south to north. The occurrence of Bombax ceiba, Terminalia sp, Bauhinia sp. pollens from the sedimentary layers showed the presence of nearby deciduous forest formed due to possible conversion from evergreen forests due to the changes in atmospheric and environmental conditions.The palaeo-palynological studies suggested a dry climate during the later part of the Holocene. On the other hand, the analysis of the embedded 14
National Conference on Science of Climate Change and Earth’s Sustainability: Issues and Challenges ‘A Scientist-People Partnership’ 12-14 September, 2011, Lucknow carbonized woods in palaeodeposits of sand suggested a highly productive environment during the early - middle Holocene. The assemblage of Artocarpus, Holigarna and Canarium indicated that the area was covered by dense forest and the area witnessed the high intensity rainfall. Later, the region experienced dry climate, as revealed from the later deposition of Spondias. However, occurrence of Sonneratia, specially indicated the proximity of sea in the area at the time of deposition. Obviously, the sea level was much higher at that time than at present and the sea had receded then. CLIMATE AND SEISMICITY IN THE LAHAUL AND SPITI, NW HIMALAYA DURING THE LAST 25 KA: EVIDENCES FROM YUNAM BASIN, INDIA Archna Bohra 1,2 and B.S. Kotlia 2 1 Department of Geology, Durham House, Kumaun University, Nainital 2 Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi email: archna.bohra@gmail.com, archnabohra@yahoo.com Two aspects make the area around the Baralacha La, H.P. (altitude 4,573m) significant from the viewpoint of tectonics and climate. Firstly, it is situated in the north of the Pir Panjal a domain which is considered to have undergone the active tectonic uplift from Miocene to the Late Cenozoic times. Further, it is positioned on the northern margin of the Intertropical Convergence Zone (ITCZ). Since the higher north-western Himalaya receives most of its moisture from the westerlies, it becomes climatically a sensitive area where changes in the strength of monsoonal circulation system and its influence on hillslope processes can be evaluated. Presently, the westerlies are responsible for dominant source of precipitation (about 75% of annual) at Baralacha Pass, the surroundings of which are characterized by sharp temperature contrasts between sunny and shady slopes, high diurnal temperature variability, temperature inversions and variability in rainfall. The Baralacha fault was responsible for damming the Yunam Tso due to the tectonic upliftment around >ca. 25.3 ka BP. Quaternary climate change of the region is summarized from proxy records. In order to reconstruct the possible monsoonal impact on the hydrological system of the Yunam lake basin during the last 25.3 ka BP, we studied the geomorphology of the basin and combined the results with multi-proxy records from Yunam varve sediments. Major analyses on the 7.56 m long varve palaeolake profile comprise geochemical data (multi-elements, high-resolution X-ray fluorescence, XRF), mineral composition (XRD), mineral magnetism (, S-ratio), soft sediments and carbon isotope (C 3 and C 4 vegetation). The results indicate the maximum glacier advance falls within the period between ca. 20.1-17.5 ka BP. The last glacial maximum was cool and dry. The climate 15
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12-14 September, 2011, Lucknow - Earth Science India

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