School Of Environment And Earth Sciences
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Item Luminescence chronology of Late Quaternary palaeo-lake deposits from the Upper Alaknanda Basin, Uttarakhand, India: Implication to palaeoclimate and depositional settings(Elsevier Ltd, 2022-01-06T00:00:00) Pattanaik, Jitendra Kumar; Singh, Atul; Kumar, Haldhar; Singh Shah, Sunil; Semwal, Prabhat; Sujith Naik, M.; Nayak, Kalyani; Jaiswal, Manoj K.; Banerjee, Argha; Nainwal, Harish Chandra; Shankar, RamachandranLakes downstream of the glaciers receive glacial meltwater and sediment supply resulting in formation of thick succession of lacustrine deposits. In this work, we have identified one such palaeo-lake deposit in the Upper Alaknanda Basin, close to Badrinath town. The sediments are of lacustrine origin; however the continuity is broken by intermittent fluvial deposits, which indicate changes in the depositional environment. We used Optically Stimulated Luminescence (OSL) dating to develop a robust chronology of the palaeo-lake deposit. Grain size analyses of sediments were carried out to understand the depositional environment, and morphometric analysis of the valley was conducted to obtained clues about the neotectonic activities in the region. The OSL ages show that the deposition of the lake sediments occurred between 21.6 � 4.7 ka to 10.5 � 1.4 ka. Two phases of paleo-lake deposit and subsequent outburst is established from the OSL age, grain size distribution and on the basis of field observations. The high sedimentation rate in the upper part of the deposit indicates an increase in the monsoonal rainfall and glacial retreat post Younger Dryas event. The colder periods are represented by varves and rhythmites, while the warmer periods are represented by thick laminated sand. This study indicates that the glaciers in the Upper Alakanada Basin responded to the fluctuations in the palaeo-climate. � 2022 Elsevier LtdItem Hydroclimate and vegetation changes in southeastern Amazonia over the past ?25,000 years(Elsevier Ltd, 2022-04-07T00:00:00) Reis, Luiza Santos; Bouloubassi, Ioanna; Mendez-Millan, Mercedes; Guimar�es, Jos� Tasso Felix; de Ara�jo Romeiro, Luiza; Sahoo, Prafulla Kumar; Pessenda, Luiz Carlos RuizStable isotope analysis of plant waxes (?13Cwax and ?Dwax) along with detailed pollen data provide a new perspective on vegetation and precipitation variability in Serra Sul de Caraj�s, southeastern (SE) Amazonia, over the past ?25 cal kyr BP. The ?Dwax record indicates drier conditions during the Last Glacial Maximum (LGM) and a transition to wetter conditions into the Holocene, while the ?13Cwax data reveal that vegetation did not experienced C3/C4 shifts and remained dominated by C3-plant communities. Under glacial conditions C3-savanna was prominent on the Serra Sul plateau with tropical forest areas limited to the lower slopes. Tropical forests expanded upslope and forest patches developed on the plateau as a response to more humid and warmer conditions during the Holocene. Pollen data indicate a shift towards more open landscape of savanna, woodlands, and open forests during the mid-Holocene. The ?Dwax record exhibits a distinct moisture variability during the Holocene, not always coherent with the vegetation data (pollen), especially during the mid-Holocene interval. Our study confirms the complexity and the overall lack of coherence among Holocene moisture proxy records throughout the monsoon domain in South America and suggest that Holocene local moisture conditions might not follow the regional monsoonal variability. Our data further stress the need for more multi-proxy reconstructions of hydroclimate patterns in SE Amazonia. � 2022 Elsevier LtdItem Paleoclimatic and Environmental Interpretation using Clay Mineralogy and Surface Textural Analysis of Quartz Grains from Miocene deposits of Tapar, Kutch, Gujarat(Central University of Punjab, 2018) Mahmud, Hassan; Sharma, MilankumarThe Tapar area situated in Kutch district of Gujarat is exposed of the miocene deposit. Extensive work has been done on Kutch basin on paleontological aspects but very less on sedimentological aspect. Clay assemblages is a great tool to understand the paleoclimate and environment of deposition. The study of the clay assemblages in the area show a higher amount of kaolinite and very less amount of dickite assemblages with negligible amount of Vermiculite and clinochlore indicating a tropical climate. Quartz being highly resistive mineral can withstand normal chemical weathering and physical weathering. Surface textural study of quartz grains indicates towards fluvial conditionItem Paleoclimate And Paleoenvironment Analysis Of Panchet Formation Of Damodar Basin, India Using Xrd Analysis(Central University of Punjab, 2018) Boral, Nandan; Sharma, K MilankumarThe bulk rock geochemistry of 14 samples collected from the Asansol district, West Bengal, India, from the Northern bank of the river Damodar were analysed using XRD. The studied area belongs to the Panchet Formation of Lower Triassic age of Lower Gondwana group of rocks. The major analysis has been done using the clay mineralogy. These data enables to reconstruct the ancient environmental and climatic condition during the deposition. Samples were dried in an oven up to 65°c temperature for a week and grinded to finest level in Retch RS200.Raw XRD data receive were analysed in X'Pert high software. SEM samples were prepared by disintegrating sandstone with Hydrogen peroxide. Equal sized quartz grains were analyzed under Carl Zeiss Merlin Compact 6073 Field Emission Scanning Electron Microscope and their surface textures observed. Three major clays (Smectite, Illite and Kaolinite) have been identified for the correlation with different sections. The percentage of these three clays calculated manually. Presence of high Smectite with Kaolinite indicates warm humid environment of formation, with rainfall ranging from 50-150 cm, higher amount of Smectite over Kaolinite indicates variation in seasonality during the deposition.