T225 From Alpine Glaciers to Ice Sheets: Understanding Glacial Dynamics, Landscapes, and Environmental Change

Wednesday, 7 November 2018
8:00 AM - 12:00 PM
Room 136-137

ORDOVICIAN GLACIATION IN NE AFRICA: FIELD AND REMOTE SENSING-BASED EVIDENCES FROM THE SOUTH EASTERN DESERT OF EGYPT

Paper number: T225-15
Program: Technical Sessions
Time: 11:35 AM – 11:50 AM

Authors

Abstract

Late Ordovician ice sheet deposits were reported from North Africa (Mauritania, Morocco, Algeria, Libya, Chad and SW Egypt) and Arabia (Jordan and Saudi Arabia). We report field and satellite-based (ALOS radar PALSAR L1; ArcGIS 10.6 visible and near infrared [VNIR] map) observations indicative of presence of exhumed subglacial landforms and Ordovician glaciogenic sediments in the South Eastern Desert of Egypt. The glaciogenic Ordovician deposits unconformably overlie Precambrian basement rocks and are overlain by the Paleozoic Nubian Sandstone Formation. These glaciogenic Ordovician deposits were eroded away except for those preserved as basal conglomeratic units below the Nubia Formation and as remnant isolated paleo-valley filling diamictites within the basement complex. The Ordovician glacial diamictites are polymictic, poorly sorted, and boulder rich sediments with well-rounded clasts and in some cases, with clear long axes parallel to the bedding planes. Field and satellite-based observations were used to identify and map the Ordovician subglacial landforms and glacial till deposits in the study area. Radar data was used to map subglacial ice flow lines, and the high resolution ArcGIS 10.6 base map to identify various subglacial landforms (e.g., polished rock surfaces, whalebacks, Roche moutonnees or drumlins). A paleo ENE-WSW trending ice flow direction was inferred from the dominant subglacial mega scale lineation trends. All of these features are indicative of, and consistent with, a wet-based Ordovician ice sheet that transported significant volumes of glacial tills and debris in north Gondwana. Findings contribute to our understanding of the paleoglaciology of north Gondwana and mineralization within the Arabian-Nubian Shield. The direct contact between the Ordovician wet-based ice sheets and mineralized zones within the shield could potentially produce placer deposits as evidenced by the recently discovered historical pharaoh’s gold mines within the glacial diamictites of the south Eastern Desert.

Geological Society of America Abstracts with Programs. Vol. 50, No. 6

doi: 10.1130/abs/2018AM-320677

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