Glacial-Holocene climate-driven shifts in lacustrine and terrestrial environments: Rock magnetic and geochemical evidence from East Antarctic Mochou Lake

Noronha-D'Mello, Cheryl A and Nair, A and Mahesh, B S and Warrier, Anish Kumar and Mohan, Rahul and Kurian, Siby (2021) Glacial-Holocene climate-driven shifts in lacustrine and terrestrial environments: Rock magnetic and geochemical evidence from East Antarctic Mochou Lake. Palaeogeography, Palaeoclimatology, Palaeoecology, 576. ISSN 0031-0182

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Abstract

Geomorphic reconstructions of the East Antarctic Ice Sheet history across Antarctica suggest diachronous and varying retreat patterns with changing climate. However, little is known of how terrestrial environments responded to these climate changes because the continental ice sheet covered most Antarctic coastal oases during the Last Glacial Maximum (LGM), eliminating terrestrial records. In this study, the environmental history spanning the last 25,400 years was reconstructed using geochronology, lithology, rock magnetism and geochemistry to understand the effect of glacial–deglacial climate variations on surface processes and Mochou Lake ecology. During the last glacial period (25.4 to 18.8 cal. kyr BP), intensified winds and the freeze-thaw action of ice actively weathered the high elevation western catchment that was a dominant sediment source to the lake. The glacial environmental conditions induced a persistent perennial lake ice-cover resulting in anoxia, low sedimentation, primary production and weak brackish conditions. Progressively, as deglacial con�ditions augmented around 18.8 cal. kyr BP, increased catchment meltwater flow enhanced sediment transport and also transformed the lake into a freshwater basin, although perennial ice-cover still prevailed. Further, the biotic development of the lake began later in the Mid-Holocene as compared to other lakes in the region, wherein the seasonal lake ice cycle and/or ice moat developed. Weak chemical weathering and pedogenesis also commenced in the catchment in response to the warming climate trend. This delayed response to the Holocene warming was possibly due to the local cooling effect of the D¨ alk Glacier's discharge that also led to sea-ice persistence in the Prydz Bay. This study also provides further evidence that parts of the Larsemann Hills remained free of erosive grounded ice during the LGM and subsequent deglaciation. The Mirror Peninsula, specifically, escaped ice overriding despite being enclosed by the Dalk ¨ Glacier, Lake Nella ice lobe and Amery Ice Shelf.

Item Type: Article
Uncontrolled Keywords: Deglaciation Lake sedimentation Sediment provenance Weathering Paleoecology Paleolimnology
Subjects: Engineering > MIT Manipal > Civil Engineering
Depositing User: MIT Library
Date Deposited: 20 Sep 2021 04:52
Last Modified: 20 Sep 2021 04:52
URI: http://eprints.manipal.edu/id/eprint/157354

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