Magnetostratigraphy and sedimentary evolution of the late Miocene to early Pleistocene sediments, Quseir region, Egyptian Red Sea

Lean, CB and Hounslow, MW and Vine, FJ and Harwood, GM and Elvidge, L and Fisk, K and Kendall, AC and Montgomery, P (1998) Magnetostratigraphy and sedimentary evolution of the late Miocene to early Pleistocene sediments, Quseir region, Egyptian Red Sea. Geophysical Journal International, 133 (2). pp. 435-450. ISSN 0956-540X

Abstract

An integrated sedimentological and magnetostratigraphic study has allowed a detailed understanding of the late Miocene to early Pleistocene evolution of the sediments in the Quseir region of the Egyptian Red Sea coast. Palaeomagnetic samples were collected from sections in six wadis, covering the Shagara Formation, the Gabir and Samh members of the Wardan Formation, and the Abu Dabbab Formation evaporites. Remanence properties are carried by magnetite, haematite and goethite. The characteristic remanence is typically carried by detrital magnetite and haematite, with more recent overprints predominantly associated with haematite and goethite, produced by the weathering of diagenetic pyrite. The magnetostratigraphy has allowed the following detailed age assignments for the lithostratigraphic units. The Shagara Formation ranges in age from late Pliocene (late Piacenzian) to middle Pleistocene (0.6–2.5Ma). The Gabir Member is latest Messinian to earliest Piacenzian in age (≈3.5–5.5Ma) and the Samh Member, late Tortonian to mid-Messinian (≈6.0–7.5Ma). The age of the top of the Abu Dabbab Formation is probably mid-Tortonian (≈8Ma). Disconformities occur between all the lithostratigraphic units, with a local angular unconformity between the Shagara and Wardan Formations. Lowstands in global sea level appear to have a strong influence on the timing of these disconformities. Characteristic mixed alluvial and reef facies of the Shagara formation are a response to the ephemeral wetter climate following the initiation of northern hemisphere glaciation at ≈2.4Ma, enhanced by rift-margin uplift of basement complexes to the west. This tectonic activity was concentrated in the early Piacenzian. The marine Gabir Member was deposited during the early Pliocene and latest Messinian high-sea-level stands. The late Tortonian/early Messinian age and sedimentological character of the Samh Member indicates this unit was affected by marine flooding events, which ultimately produced, during drawdown phases, the off-shore Zeit Formation evaporites in half-graben depocentres.