Paleozoic glaciation in NE Africa: field and remote sensing-based evidence from the South Eastern Desert of Egypt

Abstract

Exhumed Paleozoic glacial deposits and landforms of the North Gondwana are reported here for the first time from the South Eastern Desert (SED) of Egypt. Using field observations and remote sensing datasets (Advanced Land Observing Satellite [ALOS], Phased Array L-band Synthetic Aperture Radar [PALSAR] radar, multispectral Landsat TM datasets, and digital elevation models [DEMs]), we mapped the distribution of Paleozoic glacial features (i.e. deposits and landforms) in the SED. Two main glaciogenic facies were identified in three locations in the SED: (1) massive, poorly sorted, matrix supported, boulder-rich diamictites in Wadi El-Naam and Korbiai, and (2) moderately-sorted, occasionally bedded outwash deposits in Betan area. Inspection of radar, DEMs, and Landsat Operational Land Imager (OLI) images revealed previously unrecognized ENE-WSW trending glacial megalineations (MLs) over the peneplained Neoproterozoic basement rocks in the central sections of the SED, whose trends align along their projected extension with those of glacial features (tunnel valleys and striation trends) reported from Saudi Arabia. The glaciogenic features in the SED 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 within the basement complex. The apparent spatial correlation of the SED glacial features with well-defined Late Ordovician deposits in North Africa and in Saudi Arabia, and the reported thermochronometric analyses and fossil records are consistent with a Late Ordovician age for the SED glaciogenic features and support models that call on the continuation of the Late Ordovician (Hirnantian) ice sheet from the Sahara into Arabia through the SED of Egypt.

Red Sea tectonics unveil the largest known terrestrial ice stream: New constraints on Late Ordovician ice sheet dynamics

“…Two models were proposed for the distribution of the Ordovician ice sheet(s): (1) a single, major ice sheet over Gondwanaland extending across North Africa, Arabia, South Africa, and South America 5,8,9 , or (2) small ice caps in South Africa and South America separated from the northern ice sheet in North Africa and Arabia 10,11 . Late Ordovician glacial deposits and landforms are well reported from North Africa, Arabia, southern Europe, South Africa, and South America [10][11][12][13] . However, their localized and dispersed nature 5 hindered proper reconstruction of the ice sheet extent and the development of a comprehensive understanding of the Late Ordovician glaciation and ocean dynamics.…”

“…The ice sheet retreated, sea levels rose, and Early Silurian shale was deposited over glacial sequences; together, they formed a glaciogenic petroleum system 15,33 . The Gondwana continent witnessed a second, longer (>70 My), Permo-Carboniferous glacial event, that was reported in southern, but not northern Arabia 12 . The south pole migrated in a southwest direction across Gondwana from northwest Africa in the Late Ordovician to central Antarctica during the Permo-Carboniferous 9,34 .…”

“…Northwest Arabia was then uplifted and the depositional processes were interrupted during the Middle to Late Ordovician in response to far-field effects of the Taconic orogeny, which incised valleys and canyons (paleo-valleys) within the Qasim Formation and exposed the underlying Saq Sandstone and basement complex 32 . Following the Taconic orogeny, the LOIS extended across North Gondwana, including the study area 12,25 , and eroded and polished the exposures of the Neoproterozoic basement and the Saq sandstone, forming subglacial streamlined landforms, tunnel valleys and filled the paleo-valleys and canyons. The ice sheet retreated, sea levels rose, and Early Silurian shale was deposited over glacial sequences; together, they formed a glaciogenic petroleum system 15,33 .…”

“…Despite the early discoveries of the Late Ordovician glacial deposits in Arabia 24,25 , no ice streams have been identified. Recently, Late Ordovician glacial deposits and exhumed subglacial mega-lineations (MLs) and landforms were reported from southeast Egypt over the Neoproterozoic basement rocks of the Arabian Nubian Shield 12 . On the other side of the Red Sea, and along the postulated extension of the newly reported glacial MLs, similar eastnortheast-trending streamlined ridges were recognized in northwest Arabia over the Neoproterozoic basement of the Arabian Nubian Shield and the Cambro-Ordovician Saq Sandstone and were widely interpreted as mega-yardangs [26][27][28] .…”

A conceptual model for glaciogenic reservoirs: From landsystems to reservoir architecture

“…Recent studies indicate that ice streaming in ancient deposits is more common than previously thought and can be recognized from glaciogenic successions of Ordovician and Late Palaeozoic age (Andrews et al, 2019;Assine et al, 2018;Elhebiry et al, 2019;. Identification of such features in the subsurface can aid understanding sediment transport mechanisms, mode of deposition, resulting reservoir distribution and fluid migration pathways.…”