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Stratigraphy and tectonic implications of late Pleistocene valley fill in the Hope Valley, Canterbury, South Island, New Zealand

By
Henrik Rother
Henrik Rother
Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
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Harry M. Jol
Harry M. Jol
Department of Geography and Anthropology, University of Wisconsin–Eau Claire, Eau Claire, Wisconsin, 54702, USA
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James Shulmeister
James Shulmeister
Department of Geological Sciences, University of Canterbury, Private Bag 4800, Christchurch, New Zealand
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Published:
January 01, 2007

A thick sequence (∼177 m) of aggradational deposits was studied in the lower Hope Valley. Valley fill is preserved in a tectonic depression, which is associated with a releasing bend on the active strike slip Hope Fault. Our results indicate that local basin subsidence since the last glacial maximum (LGM) occurred at a rate of 1.4–2.5 mm/yr, which roughly matches the regional tectonic uplift rate. The approximate balance between uplift and basin subsidence resulted in a local late Pleistocene sedimentary pattern that was primarily controlled by climate-induced processes of aggradation and degradation.

Here we describe deposits and subsurface sedimentary structures from an exposure located near Glynn Wye on the southern side of the Hope Valley. Sediments at the base of the studied sequence comprise 55 m of lacustrine/deltaic deposits that are overlain by thick fluvial and glaciofluvial gravels. Infrared stimulated luminescence (IRSL) dating on the lake beds yielded an age of 60.3 ∼5.6 ka BP, suggesting late OIS 4 (oxygen isotope stage) age for the lake. A subsequent phase of fluvial aggradation buried paleolake deposits under 65 m of glaciofluvial outwash. This was followed by the progression of a glacial advance which deposited a moraine over the top of the sequence. A luminescence age (IRSL) of 32.1 ∼2.6 ka BP from the outwash deposit below the moraine indicates that glaciofluvial aggradation prior to the ice incursion was well advanced during late OIS 3. Postglacial fluvial degradation caused 160 m of incision into the lower Hope Valley, thereby partially excavating the deeper basin fill.

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Contents

GSA Special Papers

Stratigraphic Analyses Using GPR

Gregory S. Baker
Gregory S. Baker
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Harry M. Jol
Harry M. Jol
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Geological Society of America
Volume
432
ISBN print:
9780813724324
Publication date:
January 01, 2007

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