Proglacial lakes during the Last Glacial Maximum in New Zealand

Ice-contact proglacial lakes form an important component of glacial systems. They influence the stability of mountain glaciers and can control ice sheet margin behaviour. Nevertheless, the effects of proglacial lakes on the rate of deglaciation and their importance in influencing ice dynamics remain relatively unquantified, especially in palaeo-studies of the Southern Hemisphere. Landforms and sediments in New Zealand preserve a remarkable footprint of Quaternary glaciation that can be exploited to fill this gap in the Southern Hemisphere glacial record. One of the most striking features of South Island, New Zealand, is the sequence of glacial lakes that occupy mountain valleys along the Southern Alps. The presence of these inland water masses is likely to have had an impact on ice-marginal dynamics of their adjacent glaciers. This thesis examines the nature of ice-marginal recession associated with proglacial lakes during the Last Glacial Maximum (LGM) across New Zealand. It is composed of four main results chapters: (i) documentation of the spatial distribution of glaciolacustrine landforms and sediments pertaining to the LGM across South Island; (ii) characterisation of the nature of glacier behaviour and the resultant LGM landsystem via detailed geomorphological mapping; (iii) assessment of the origin and evolution of sediments related to recession into a proglacial lake via detailed sedimentology; and (iv) the first application of numerical modelling to simulate the effect of an ice-contact proglacial lake on glacier geometry, behaviour, and style of recession. Overall, this thesis highlights that interpreting the glacial landform record as directly related to climatic perturbations may mask catchment or glacier-scale variability on sub-millennial timescales, especially when associated with a proglacial lake. Quantifying the magnitude and spatio-temporal variation of a lacustrine-terminating glacier emphasises the need to incorporate proglacial lakes into palaeo-reconstructions and projections of future glacier evolution.