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The kinematics of ancient tidewater ice margins: criteria for recognition from grounding-line moraines

By
Ida Lønne
Ida Lønne
Villaveien 21, N-1440 Drøbak, Norway
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W. Nemec
W. Nemec
Department of Earth Science, University of Bergen, N-5007 Bergen, Norway
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Published:
January 01, 2011

Abstract

Modern studies indicate that the kinematic behaviour of tidewater glaciers is a crucial part of ice-sheet dynamics. A similar relationship may be expected for ancient ice sheets, but can the kinematics of ancient tidewater ice margins be recognized? The paper addresses this methodological issue by pointing to the high-resolution stratigraphic record of marine moraines, thus far little explored. On the basis of a series of case studies, a range of field criteria are proposed for the recognition of short-term grounding-line movement and possible oscillations in moraine outcrop sections. The method combines allostratigraphic mapping and architectural facies analysis of the moraine sedimentary units formed during glacier advance, subaqueous stillstand and eventual subaerial stillstand, with recognition of the successive ice-contact surfaces. The stacking architecture of the sedimentary units and their ice-contact bounding surfaces reveal the time–distance trajectory of the grounding-line positions. It is also possible to recognize changes in the mode and rate of subglacial sediment delivery, as well as fluctuations in the ice flux and meltwater discharge. This methodology invites detailed studies of marine moraines. Systematic case studies on a regional scale may provide new information on the behaviour of tidewater ice margins and lead to unprecedented insights into the dynamics of ancient ice sheets.

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Contents

Geological Society Special Publication

Ice-Marginal and Periglacial Processes and Sediments

I. P. Martini
I. P. Martini
University of Guelph, Canada
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H. M. French
H. M. French
University of Guelph, Canada
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A. PéRez Alberti
A. PéRez Alberti
Universidade de Santiago de Compostela, Spain
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Geological Society of London
Volume
354
ISBN electronic:
9781862396029
Publication date:
January 01, 2011

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