Palaeozoic glacial depositional environments of SW Saudi Arabia: process and product

Abstract

Saudi Arabia is one of the few places in Gondwana where deposits of two Palaeozoic glaciations are well preserved. They were formed under similar conditions in a tectonically stable shelf setting. We studied the sedimentary facies and architectural geometries of Upper Ordovician and Permo-Carboniferous glaciogenic deposits in the Wajid Sandstone and developed a genetic model for both units. Common features and of both glacial episodes are (a) incision of glacial (tunnel?) valleys, (b) subsequent valley fill by proglacial deposits in front of an oscillating, polythermal ice shield; (c) intra-formational erosional events through repeated ice advance, (d) widespread and large-scale soft deformation due to glacial surge during deglaciation, and (e) marine transgression most probably due to eustatic sea-level rise following deglaciation. The general patterns and observations fit well with recently published observations on Upper Ordovician deposits in northern Africa, pointing to closely coupled glaciological processes of the North African–Arabian ice shield. Although the same general patterns apply for the Permo-Carboniferous glaciation, sedimentary styles and petrographical properties differ, probably due to a more heterogeneous ice-flow pattern controlled by a more pronounced topography after the Hercynian tectonic event.

Petrography and geochemistry of Palaeozoic quartz-rich sandstones from Saudi Arabia: implications for provenance and chemostratigraphy

“…Yet, at least for the Wajid area, a homogenous northward transport direction cannot be inferred for the entire Palaeozoic succession. Opposing (northwest to southeast) transport directions in the glaciogenic units of the Sanamah and Juwayl formations have been interpreted in recent studies (Hinderer et al 2009;Keller et al 2011;Al-Ajmi et al 2015). They also indicated the Arabian-Nubian Shield (ANS) as a possible source area for the Juwayl Formation.…”

“…In the Late Ordovician, Gondwana had moved further south, moving the Arabian Plate into palaeo-latitudes of 40° S to 60° S (Sharland et al 2001). This brought Arabia into reach of the polar ice cap of the Hirnantian glaciation, causing sub-glacial erosion across the platform (Vaslet 1990;Keller et al 2011). Tunnel valleys, radiating away from the ANS, incised deeply into platform sediments (Sharland et al 2001;Le Heron et al 2009).…”

“…The CarboniferousPermian brought with it the second large Palaeozoic glaciation of Gondwana. Glacial and peri-glacial sediments were deposited on the Hercynian ('pre-Unayzah') unconformity (Le Heron et al 2009;Keller et al 2011). Glacial advance was towards the north and northwest in northern Arabia and to the south and southeast in southern Arabia, away from the main ice shield, as evidenced by direction of tunnel valleys and striated surfaces (Hinderer et al 2009;Khalifa 2015).…”

“…Lithology consists of mature, medium-to coarse-grained sandstone and pebbly conglomerates, with a few intercalations of finer siliciclastics (Keller et al 2011;AlAjmi et al 2015), deposited in a shallow marine environment (Al-Ajmi et al 2015). The Dibsiyah Formation is the lateral equivalent of the Saq Formation of central and northern Saudi Arabia.…”

Glaciogenic reservoirs and hydrocarbon systems: an introduction

“…The Hirnantian glaciation is clearly recorded in the stable isotope signature of low-latitude carbonates (HICE: Delabroye & Vecoli 2010). The glacial record of the Hirnantian maximum is well expressed in parts of the Gondwana supercontinent, particularly in North Africa, Arabia and South Africa, where extensive, laterally continuous outcrops in Saudi Arabia (Keller et al 2011), Jordan (Douillet et al 2012), Algeria (Girard et al 2012;Hirst 2012) and Libya Girard et al 2012) allow detailed investigation of the sedimentology and facies of the glacial succession. Boreholes drilled for petroleum exploration also provide high-quality subsurface data sets in these areas (e.g.…”