A world-class example of a Late Palaeozoic glaciated landscape in Chad

Author(s): Christoph Kettler, Ricarda Wohlschlägl, Catherine Russell, Lars Scharfenberg, Jean François Ghienne, Daniel Paul Le Heron
Abstract: Continental glacial deposits are rarely preserved in nature. Recent studies of the LPIA reveal the presence of periglacial deposits in Northern Chad covering an area of 20,000 km². Using satellite maps, this project managed to examine the entirety of the Ennedi Plateau. 3D reconstructions of this mountain range reveal complex glacial morphological features. This paper presents large-scale subglacial features interbedded with proglacial fluvial features and discussed the variables at play during the progressive, repetitive, and perhaps cyclical nature of the Carboniferous glaciation. Using remote sensing techniques, this paper shows that there are three major ice advance–retreat cycles that led to the deposition of mega-scale glacial lineations with a complex fluvial channel belt. Palaeo-geomorphological mapping of satellite images in northern Chad reveals that the Late Carboniferous Chadian ice sheet covered at least 20,000 km², a much greater extent than previously thought (ca. 6000 km²). Glacial lineations (GLs) are dominant and extensive on the plateau. They are arranged in widespread ice stream networks and developed at multiple stratigraphic levels. This broadly indicates palaeo-ice flow to the north. We report a newly discovered pristine channel belt, covering at least 300 km² of a plateau in the Ennedi Plateau. A swarm of N–S trending channels, up to 250 m wide, is recognised. These are of both braided and meandering characters and are organised into channel belts of up to 500 m width. The mapped palaeo-morphology shows complex crosscutting relationships. The channel belt is intercalated with zones of GLs; hence, ice activity preceded and succeeded fluvial activity. Preserved planform sinuous channel geometries show distinctive point bar deposits and scroll bar geometries therein, which testify to a terrestrial, subaerial environment, rather than to their evolution in the subglacial realm, e.g. as eskers. Therefore, we find that cross-cutting, amalgamated channel systems record the complex phases of meltwater release during glacial retreat in the advance–retreat cycles of the Late Palaeozoic Ice Age in Chad.
Organisation(s): Department of Geology, Department of Lithospheric Research
External organisation(s): University of Leicester, Louisiana State University, Louisiana State University, Alexandria, University of New Orleans, Université de Strasbourg
Journal: Sedimentary Geology
Volume: 455
ISSN: 0037-0738
DOI: https://doi.org/10.1016/j.sedgeo.2023.106470
Publication date: 09-2023
Peer reviewed: Yes
Austrian Fields of Science 2012: 105404 Geomorphology, 105101 General geology
Keywords
ASJC Scopus subject areas: Geology, Stratigraphy
Sustainable Development Goals: SDG 15 - Life on Land
Portal url: https://ucrisportal.univie.ac.at/en/publications/2c3cc439-0c2f-47bf-8955-2e74ef961e19

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