| Summary: | Lake sediment cores from proglacial lakes can provide a detailed if indirect record of past glacial history and therefore past climate variations. This study involves analysis of a core from Kongressvatnet, a small lake in Kongress Valley on the high-arctic archipelago of Svalbard. Multiple characteristics of the core are examined in order to reconstruct the glacial history of the valley. This study seeks to determine 1) whether during the Little Ice Age, a cold period between about the 14th and 19th centuries, the glacier that once inhabited Kongress Valley grew large enough to have contributed melt-water and sediment to Kongressvatnet, 2) what the timing and extent of the Little Ice Age in Kongressdalen was, and how this characterization compares to other locations on Svalbard and around the Northern Hemisphere, and 3) whether or not the core examined in this study records modern warming. Analyses of samples from the core and of samples from fans feeding Kongressvatnet include Cesium-137 and Lead-210 dating, Loss on Ignition, and X-ray Diffraction. These analyses provide for three main proxies of past glacial extent: 1) dating provides a measure of changes in sedimentation rate, as well as chronological control, 2) LOI provides a measure of the weight percent organic matter of samples, which is used as an indicator of clastic sedimentation rate and, indirectly, glacial extent, and 3) X-ray Diffraction provides a carbonate index for samples, which indicates sediment provenance and therefore provides a record of activity of the glacially-fedfan. Note Added in Proof: One sediment core (18-KON-01) and the fan samples described in this thesis were collected in August 2018 by myself with help from other UNIS students. In October 2018, I collected the X-ray diffraction and X-ray fluorescence data for 18-KON-01 and the fan samples at the Lamont-Doherty Earth Observatory, with help from lab technicians. In October 2018, I made thin sections of 18-KON-01; in addition, I collected loss on ignition data of 18-KON-01 and the fan samples at Bates College, under supervision of Mike Retelle. In August 2019, Jarkko Linnamaa collected another sediment core (KV6) from Kongressvatnet. Jarkko then radiometrically dated KV6 at the University of Turku in Finland. These data were shared with me, with permission of Jarkko. It should be noted that this thesis erroneously identifies KV6 as the single core of investigation, when, in fact, LOI and CI data are derived from 18-KON-01, and the radiometric dates are from KV6. This study assumes that any radiometric date offsets between KV6 and 18-KON-01 would not affect core interpretations, as this study focuses on the timescale of centuries. Furthermore, both of the cores were deliberately recovered from the deepest depth of the lake (54 m, see Figure 8) so as to maximize the amount of annual sediment deposition per vertical centimeter withinthecores. Therefore, it is assumed that sedimentation rates within the cores are the same.
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