The glacial sedimentology and geomorphological evolution of an outwash head/moraine-dammed lake, South Island, New Zealand

Evans, David J. A., Rother, Henrik, Hyatt, Olivia M. and Shulmeister, James (2013) The glacial sedimentology and geomorphological evolution of an outwash head/moraine-dammed lake, South Island, New Zealand. Sedimentary Geology, 284-285 45-75. doi:10.1016/j.sedgeo.2012.11.005

Author Evans, David J. A.
Rother, Henrik
Hyatt, Olivia M.
Shulmeister, James
Title The glacial sedimentology and geomorphological evolution of an outwash head/moraine-dammed lake, South Island, New Zealand
Journal name Sedimentary Geology   Check publisher's open access policy
ISSN 0037-0738
Publication date 2013-02-15
Year available 2012
Sub-type Article (original research)
DOI 10.1016/j.sedgeo.2012.11.005
Open Access Status Not yet assessed
Volume 284-285
Start page 45
End page 75
Total pages 31
Place of publication Amsterdam, Netherlands
Publisher Elsevier
Language eng
Subject 1907 Geology
1913 Stratigraphy
Abstract Extensive exposures through the glacial landforms around southern Lake Pukaki, New Zealand, comprise seven lithofacies (LFs 1–7). LFs 1–3 are grouped together as LFA 1 (Pukaki Member) and record pulsed subaqueous grounding line fan progradation, cohesionless debris flows, underflow activity and rhythmite deposition by suspension settling, iceberg rafting of dropstones, and pulsed traction current activity. Localized disturbance of these deposits by glacitectonic deformation and multi-generational hydrofracture fills records minor readvances by the glacier snout and the emplacement of a glacitectonite (LF 4) derived from cannibalization of glacilacustrine sediments. LFs 4–6 are grouped together as LFA 2 (Twizel Member) and record direct glacigenic deposition of glacitectonite (LF 4), subglacial traction till (LF 5) and supraglacially dumped boulder rubble (LF 6). Stratigraphic relationships between LFA 1 with LFA 2 record the oscillatory behaviour of the former Tasman Glacier snout when it formed a calving margin in a proglacial and locally supraglacial lake dammed by a glacitectonically disturbed outwash head and lateral moraine ridges. This is entirely consistent with the landform–sediment record of its coeval terrestrial margins, where flutings and push moraines are diagnostic of active temperate glacier recession from a glacially overridden outwash head, the latter being recorded by the vertically stacked sub-horizontally bedded and coarse-grained gravels of LF 7 (Waitaki Member). Previous proposals that late Pleistocene lake damming was initiated by an ice-cored moraine arc appear unfounded, because the glacilacustrine deposits only lie above the altitude of the outwash head/lateral moraine arc in locations where they have been glacitectonically compressed. Alternatively, it is proposed that the overdeepened subglacial topography was produced by the construction of an outwash head, leading to a glacilacustrine sediment sink which operates at times when the expanded Tasman Glacier actively retreats from the outwash head apex. The changing landsystem imprint related to the shrinkage of the Tasman Glacier records spatio-temporal landsystem change, involving evolution from a coupled landsystem to a moraine-dammed to an uncoupled landsystem.
Keyword Glacial sedimentology
Moraine-dammed lake
Grounding-line fan
Glacitectonic deformation
Glacial landsystem change
Q-Index Code C1
Q-Index Status Confirmed Code
Grant ID 2006/R4
Institutional Status UQ
Additional Notes Available online 27 November 2012

Document type: Journal Article
Sub-type: Article (original research)
Collections: School of Geography, Planning and Environmental Management Publications
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