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Title: The timing, dynamics and palaeoclimatic significance of ice sheet deglaciation in central Patagonia, southern South America
Author: Bendle, Jacob
ISNI:       0000 0004 8500 1108
Awarding Body: Royal Holloway, University of London
Current Institution: Royal Holloway, University of London
Date of Award: 2018
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Robust reconstructions of glacial retreat are required to elucidate controls on ice-sheet deglaciation and (a)synchronicity in the climate system. Such reconstructions can be derived through detailed geological investigations of glacial landforms and sediments. Patagonia, in southern South America, contains a well-preserved glacial record and occupies an important location regarding major Southern Hemisphere climate systems. However, resolving the history of ice-sheet deglaciation has proven problematic, owing to generally low-resolution geomorphological mapping, and a paucity of high-precision dating control. This thesis explores the deglacial history of the Lago General Carrera-Buenos Aires (LGC-BA) and Lago Cochrane-Pueyrredón (LC-P) ice lobes (46-48°S) of the former Patagonian Ice Sheet (PIS). The region is chosen because there are uncertainties associated with: (i) the deglacial configuration and evolution of retreating ice lobes and proglacial lake systems; and (ii) the sub-millennial timing of deglacial events. A new glacial geomorphological map is produced to reconstruct the spatio-temporal evolution of ice lobes and proglacial lakes. The elevation(s) of relict lake shorelines are examined to quantify glacio-isostatic adjustment and accurately assign former lake levels, lake outflows, and ice-margin positions, through the last deglaciation. These new reconstructions are used to target sites for high-resolution dating. A ~1000-year varve chronology is developed at LGC-BA after examining the sedimentary properties of laminated glaciolacustrine sequences. Tephrochronology anchors this record to the calendar-year timescale. The chronology indicates that PIS retreat commenced at 18,086 ± 214 cal a BP, and accelerated from 5 to 18 m yr-1 over the next ~1000 years. The new timing for deglaciation at LGC-BA allows an exploration of climate forcing mechanisms. Comparisons with palaeoclimatic records reveal a hemisphere-wide warming influence on LGC-BA deglaciation. Moreover, spectral analyses of varve thickness time-series demonstrate a likely teleconnection with tropical Pacific climate oscillations, and PIS sensitivity to short-term variations in melt-season temperature.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Patagonia ; Ice sheet deglaciation ; Palaeoclimate ; Glacial lakes ; Glacial varves ; Tephrochronology ; Bayesian age-modelling