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Geomorphology of the deglaciated Eglinton Valley, Fiordland : new insights into the origin of hummocky terrain : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Geography at Massey University, Manawatu, New Zealand
The distribution and types of landforms within deglaciated valleys provide information
on past processes and indicate the potential for future changes and associated
hazards. This study is the rst to characterise the landform assemblages within
Eglinton Valley, Fiordland, New Zealand, and develop a model for the post-glacial
evolution of the valley. In particular, it assesses the origins of hummocky topography
on the valley oor which, like in many other parts of the world, have previously been
interpreted to be glacial in origin.
Geomorphic eld mapping, GPR, sedimentology (clast and agglomerate identi
cation), and a novel terrestrial cosmogenic nuclide dating (TCND) method of
extracting meteoric 10Be from pyroxene minerals were utilised to reconstruct the
geomorphology of the valley during the Holocene.
Glacial deposits were con rmed at Knobs Flat and Eglinton Flat while RA deposits
were conclusively found at Knobs Flat, Deer Flat, and adjacent to Lake
Malvora. Eglinton Valley has been completely blocked on (a minimum of) three
separate occasions, forming a large lake each time, with only Lake Gunn and a few
minor swamps and lakes (e.g. Lake Malvora) remaining today. Relative age dating
evidence suggests the rst lake was formed by the large Deer Flat RA, the next
formed due to the extensiveWesney Creek alluvial fan, and the youngest, Lake Gunn,
as a result of the Lake Gunn Landslide ~7.6 kyrs BP. TCND was uncompleted due to
lab contamination at the nal step, however, the methods attempted here appeared
to yield promising results.
The Eglinton Valley has been sculpted by glacial, mass movement, and uvial processes.
This work advances the knowledge of the processes responsible for the hummocky
terrain found throughout Eglinton Valley, and adds to the currently limited
pool of research into the reinterpretation of hummocky deposits within deglaciated
valleys in a global and New Zealand context.