Marine- and Lacustrine Deposition of Eskers

Abstract

The future stability of modern marine-terminating ice sheets is of great concern as an increased rate of retreat might mark the onset of their collapse. An increased rate of retreat is accompanied by an increase in meltwater and sediment discharge at the ice margin which has prompted research to focus on the drainage system of marine-terminating ice sheets. Recent discoveries of eskers at water-terminating margins of the Eurasian Ice Sheet Complex provide a premise for the study of the palaeo-drainage system during the retreat of the ice margin following the Last Glacial Maximum. This study explores two areas that were covered by water-terminating sectors of the Eurasian Ice Sheet Complex, Hopendjupet in the Barents Sea and Hoburgs Bank in the Baltic Sea, both of which exhibit palaeo-drainage landforms, tunnel valleys, and eskers. A special focus is placed on the study of eskers as they have rarely been described from marine-terminating ice sheets.

A new approach to mapping eskers on digital elevation models is presented that allows for a more detailed morphological analysis and statistical description than the traditional method of mapping eskers with lines. The new approach to mapping eskers uses polygons to map the extent of the landforms and a program written in Python is used to extract the length, height, width, and sinuosity of eskers as well as height and width changes along their length. Between Hopendjupet and Hoburgs Bank, a variety of esker types are found (beaded eskers, esker enlargements, esker corridors, complex eskers, and till eskers) representing esker deposition in subglacial and deltaic settings, time-transgressive and synchronous esker formation, and deposition in en- and subglacial channels. Eskers in Hopendjupet exclusively occur in connection to erosional Nye-channels suggestive of a generally erosive drainage system. Till eskers and crevasse-fill ridges on Hoburgs Bank form a geometric and sinuous ridge network that potentially represents the hydro-fracturing of a cold-based polythermal ice margin.