School Of Environment And Earth Sciences

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    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, Ramachandran
    Lakes 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 Ltd
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    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 Ruiz
    Stable 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 Ltd