Gebel Duwi Research Articles

A synthesis of biotic and stratigraphic data from the Middle East on late Paleocene global change

Lower Paleogene marine deposits cover extensive areas of Egypt and Israel, usually in a sub-horizontal or slightly tilted position. In combination with a near absence of vegetation, this setting provides unique opportunities to study upper Paleocene stratigraphy and events basin-wide and in great detail. We studied five upper Paleocene successions, focusing on planktic and benthic foraminifera, and stable isotopes. The sections are arranged on a generally NW-dipping slope of an epicontinental basin, which in its northern part was interrupted by ‐ predominantly submarine ‐ highs and lows of the Syrian Arc. Benthic foraminifera assemblages indicate overall deposition at c. 500 m at Ben Gurion and Wadi Nukhl, c. 200 m at Gebel Aweina and Gebel Qreiya, and c. 75 m at Gebel Duwi (Fig. 1). Lithology. ‐ Monotonous gray to brown marls prevail within the studied interval (Biozones P4‐P6a). The short stratigraphic interval of global biotic and environmental change, however, is marked by a foraminifera-rich calcarenitic bed, overlying ‐ in the more complete sections ‐ a 20‐50-cm thick fissile (Duwi) or TOCrich laminated (Nukhl and Qreiya) marl bed. The Aweina and Ben Gurion sections do not show the latter bed, but instead a discontinuity (omission surface) at the base of the calcarenitic bed. δ 13 C isotopes. ‐ The global negative carbon-isotope trend and the superimposed negative δ 13 C excursion (CIE) have been recorded in whole-rock samples from all sections within Zone P5 (sensu Berggren et al. 1995). The CIE coincides with the anomalous beds and terminates above the calcarenitic bed. In Aweina and Ben Gurion, the base of the CIE coincides with the discontinuity, indicating that in these sections at least the lower part of the shift is truncated (Fig. 2). Whereas whole-rock isotopic records from this region are suitable for stratigraphic purposes, specimenbased paleoenvironmental studies are generally not reliable. Thin-shelled fora

The impact of Paleocene/Eocene boundary events on middle neritic benthic foraminiferal assemblages from Egypt

A 25 m upper Paleocene to lower Eocene marly sequence exposed at Gebel Duwi, (Quseir, Red Sea coast of Egypt) provides a good opportunity for studying Paleocene/Eocene (P/E) boundary stratigraphy and events. Various bio-, eco-, and isotope stratigraphic correlations accurately delineate the position of the P/E boundary (i.e. the level of stable isotopic excursions and deep-sea benthic extinctions) in the middle part of this section, within Zones P5 and NP9. In this paper the impact of P/E boundary environmental perturbations on benthic foraminiferal communities of the shallow Tethyan shelf is examined. Benthic foraminiferal assemblages from Gebel Duwi, characterized by large Frondicularia phosphatica and F. nakkadyi in addition to a number of other neritic taxa, but without any typical outer neritic-bathyal taxa, suggest middle neritic (75–100 m) deposition throughout the studied interval and only minor relative sea-level variations (perhaps some 10–20 m). Across the boundary sea-level appears to have been stable. Yet, a distinct faunal turnover marks the P/E boundary of this shallow site, which, in contrast to deep-sea records, is less abrupt, being preceded by a gradual diversity decrease starting some four meters below the boundary. Moreover, most exits are either local or just temporary and thus not true extinctions: many (Lazarus) taxa reappear at some point above the boundary, while all but one of the disappearing taxa are known from other lower Eocene neritic deposits in Egypt. In general, benthic foraminiferal assemblages display low diversities and high dominance values (notably Anomalinoides aegyptiacus: up to 74%), suggesting high levels of environmental stress at the sea-floor. In combination with occasionally very high P B ratio's (up to 98%P), and generally laminated sediments, the character of the benthic assemblage points to a strong influence of recurrent dysoxia and/or anoxia. We suggest that these resulted from surface eutrophication by (intermittent) coastal upwelling and reduced ventilation of the bottom environment. Although these conditions prevailed during most of the time-interval studied, they were most severe during the latest Paleocene and early Eocene when eutrophication intensified, and the organic carbon flux to the sea-floor increased. Enhanced atmospheric contrasts between the Tethys seaway and the African continent, resulting in intensified longshore tradewinds, may have controlled these changes. At the P/E boundary the bottom environment became minimally ventilated, perhaps due to reduced oxygen advection from deeper waters. Three meters above the boundary a succession of increasingly diverse assemblages indicate a gradual decrease of environmental stress and a return to more normal conditions, although the organic carbon flux to the sea-floor remained high.

Comment on “Extension of the Najd Shear System from Saudi Arabia to the central eastern Desert of Egypt based on integrated field and LANDSAT observations” by M. Sultan, R.E. Arvidson, I. J. Duncan, R. J. Stern, and B. El Kaliouby

Comment on “Extension of the Najd Shear System from Saudi Arabia to the central eastern Desert of Egypt based on integrated field and LANDSAT observations” by M. Sultan, R.E. Arvidson, I. J. Duncan, R. J. Stern, and B. El Kaliouby

On the age of the Thebes Formation of Gebel Duwi, Quseir Area, Egypt abb:

On the age of the Thebes Formation of Gebel Duwi, Quseir Area, Egypt abb: