Date of Award

8-2023

Degree Name

Doctor of Philosophy

Department

Geological and Environmental Sciences

First Advisor

Mohamed Sultan, Ph.D.

Second Advisor

Alan E. Kehew, Ph.D.

Third Advisor

Peter J. Voice, Ph.D.

Fourth Advisor

Richard Becker, Ph.D.

Keywords

Glacial landforms, Hirnantian, ice stream, late Ordovician, megalineation, North Gondwana

Abstract

Mega-streamlined landforms on Earth and Mars have been attributed to aeolian, glaciogenic, fluvial, and tectonic processes. Identifying the forces that shaped these landforms is paramount for understanding landscape evolution and constraining paleo-climate models and ice sheet reconstructions. Exhumed Late Ordovician glacial deposits and landscape of the North Gondwana are reported here for the first time from SE Egypt. Using field and remote sensing (Advanced Land Observing Satellite [ALOS], Phased Array L-band Synthetic Aperture Radar (PALSAR) radar, multispectral Landsat TM datasets, and digital elevation models (DEMs) I mapped the distribution of the Late Ordovician glacial features (i.e. deposits and landforms) in the SE Egypt. I identified two main glaciogenic facies in three locations in the SED: (1) massive, poorly sorted, matrix-supported, boulder-rich diamictites in Wadi El-Naam and Korbiai, and (2) more sorted, occasionally bedded outwash deposits in Betan area. Inspection of radar, DEMs, and Landsat OLI images revealed previously unrecognized ENE-trending glacial megalineations (MLs) over the peneplained Neoproterozoic basement rocks in SE Egypt, whose trends align along their projected extension with those of glacial features (tunnel valleys and striation trends) reported from Saudi Arabia. These glaciogenic features are believed to be largely eroded during the uplift associated with the Red Sea opening, except for those preserved as basal units beneath the Nubia Sandstone Formation or as remnant isolated deposits within paleo-depressions on the basement complex. In the second part of this study, I present field and satellite-based evidence for a Late Ordovician glacial origin for the ENE-trending mega-streamlined landforms in Arabia, that were interpreted to have been formed by Quaternary aeolian erosion. These streamlined features were exhumed during the Red Sea–related uplift. Then I use Late Ordovician paleo-topographic data to reconstruct the Late Ordovician ice sheet using identified and previously reported glacial deposits and landforms. My reconstruction suggests these glacial features are part of a major, topographically controlled, marine-terminating ice stream, with a minimum length of 1000 km extending from SE Egypt to northern and central Arabia and possibly more than twice this length if the glaciomarine and iceberg deposits in the present-day western Iran are part of this system. These observations support the continuation of the Late Ordovician (Hirnantian) ice sheet from the Sahara into Arabia through SE Egypt, which reinforces models advocating for a single, major, and highly dynamic ice sheet. My results also provide new morphological-based constraints for Late Ordovician climate models.

Access Setting

Dissertation-Open Access

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