Chad's cabinet of icy curiosities: Sharpening the interpretation of subglacial and ice marginal environments during the LPIA glaciation of the Ennedi Plateau

Ricarda Wohlschlägl; Christoph Kettler; Daniel Paul Le Heron; András Zboray

doi:10.1016/j.sedgeo.2023.106483

Titel

Chad's cabinet of icy curiosities: Sharpening the interpretation of subglacial and ice marginal environments during the LPIA glaciation of the Ennedi Plateau

Autor*in

Ricarda Wohlschlägl

Institut für Geologie, Fakultät für Geowissenschaften, Geographie und Astronomie, Universität Wien

Christoph Kettler

Department of Sedimentary Geology, Geosphere Austria

Daniel Paul Le Heron

Institut für Geologie, Fakultät für Geowissenschaften, Geographie und Astronomie, Universität Wien

... show all

Abstract

The Ennedi Plateau in Chad in north-central Africa exposes an outstanding example of a palaeo-ice stream glacial landsystem of late Palaeozoic age, with an assemblage of geomorphological structures of comparable preservation quality to those found in Quaternary deglaciated landscapes. Satellite images and various methods to combine acquired satellite data (e.g. band-ratio technique) have been used to interpret proglacial, ice-marginal and subglacial structures. The main goal of the study is to produce a detailed and more in-depth analysis of newly found structures that enhance our understanding of ice sheet behaviour in the Ennedi Plateau during the LPIA. We report the first known evidence of soft-sediment striated surfaces from outcrop, testifying to the existence of a soft-deformable bed. This deformable bed interpretation can probably be upscaled to explain the extensive swarms of mega-scale glacial lineations mapped previously across the plateau. Furthermore, we identify the first known fully preserved grounding zone wedge (GZW), replete with three-dimensional geometry, in the rock record. This unique structure exhibits a well pronounced slope and a convex topography. Its presence allows the position of the former coastline to be reconstructed as it is assumed that ice streams terminated into a former ocean basin. Building on the studies by Le Heron (2018) and Kettler et al. (this issue), our analyses permit unprecedented insights into the behaviour of a significant, mid-latitude, marine-terminating ice sheet during the LPIA.

Stichwort

Late Palaeozoic Ice AgeChadEnnediIce streamsMarine-terminating ice sheetGrounding zone wedgeSoft-sediment striated surfaces

Objekt-Typ

journal article

Sprache

Englisch [eng]

Persistent identifier

phaidra.univie.ac.at/o:2040019

DOI

10.1016/j.sedgeo.2023.106483

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