Diagenetic rejuvenation of raised coral reefs and precision of dating. The contribution of the Red Sea reefs to the question of reliability of the Uranium-series datings of middle to late Pleistocene key reef-terraces of the world

Abstract

To cite this version:Jean-Claude Plaziat, J.L. Reyss, Abdelmajid Choukri, Charlotte Cazala. Diagenetic rejuvenation of raised coral reefs and precision of dating. The contribution of the Red Sea reefs to the question of reliability of the Uranium-series datings of middle to late Pleistocene key reef-terraces of the world. Carnets de Geologie, Carnets de Geologie, 2008, CG2008 (A04), pp.1-35. <hal-00266906> Abstract: This paper is a general review of the dating of reefs on the coasts of the Red Sea, including those of Egypt, Jordan, Sudan, Eritrea, Saudi Arabia and Djibouti. New methods of sampling and dating (U/Th) already tested on the reefs and associate deposits of the African coast of Egypt have demonstrated that processes of rejuvenation shown to exist in the best-preserved corals are probably attributable to the diagenesis of the organic material in their bio-minerals, thus justifying a revision of a great many datings of corals supposedly younger or older than the age assigned to the high-level isotopic substage (δ 18 O) MIS 5.5 (= 5e). During this late Pleistocene substage, a rapid lowering of sea level, short and limited to about ten meters, was detected and associated with a glacio-eustatic episode of global influence. A comparison of these Middle East reef chronologies with those of New Guinea, Australia and the western Atlantic that are referred only with difficulty to the δ 18 O global sea-level curves, casts doubt on the reliability of many regional reconstructions. Moreover the most "classic" reef chronologies, more or less out-of-phase with global isotopic records calls for a reexamination of the chronologic basis of the reference curves derived from marine isotopic data.Key Words: Th/U α dating; coral reef; Pleistocene; Red Sea; diagenesis; glaciation; sea-level change; rejuvenation hypothesis; Australia; Bahamas; Barbados; Bermudes; Djibouti; Egypt; Eritrea; Ethiopia; Jordan; Papua New Guinea; Sudan.

Sea-level rise due to polar ice-sheet mass loss during past warm periods

“…As yet, no consensus exists regarding this suite of scenarios, but robust sedimentary evidence from multiple coastal sites argues for at least one and possibly several meter-scale sea-level oscillations during the course of the highstand (e.g., 64,71,72,73,76). These data suggest dynamic behavior of polar ice sheets at a time when global mean temperature was similar to present.…”

Quantitative comparison of Pleistocene and Recent coral reef habitats in the northern Red Sea (El Quseir, Egypt)

“…It is therefore possible that the Porites-and merulinid-dominated coral communities of the fossil reef terraces were once situated in a lagoonal back-reef habitat. The idea of tectonic uplift in this area has been rejected in numerous publications (e.g., Hoang and Taviani 1991;Bosworth and Taviani 1996;Plaziat et al 1998Plaziat et al , 2008, which supports the interpretation of the fossil terraces as backreefs rather than reef slopes. However, in a study that takes glacio-hydro-isostatic processes into account, Lambeck et al (2011) conclude that long-term tectonic uplift along the northern and central sides of the Red Sea is more likely than tectonic stability.…”

“…However, in a study that takes glacio-hydro-isostatic processes into account, Lambeck et al (2011) conclude that long-term tectonic uplift along the northern and central sides of the Red Sea is more likely than tectonic stability. The uplift rate for Quseir el Qadim is stated as 0.057 mm per year and the observed Last Interglacial sea level as 7 m higher than today (Plaziat et al 2008;Lambeck et al 2011). Thus, the MIS 5e fossil reef terraces that are situated 3-5 m above sea level today could have been reef slopes at around 10-m depth or deeper.…”

“…3b-f). Corresponding to ages provided for nearby terraces, the reefs are tentatively assigned to MIS 5e (i.e., the Eemian stage) between 115 and 130 kyr before present (Plaziat et al 2008).…”

“…Pleistocene reef terraces of the Red Sea have been studied since the late 19th century (Walther 1888) and have been investigated over the past few decades with respect to sea level changes, microfacies, diagenesis, age, and faunal composition (Veeh and Giegengack 1970;Dullo 1986Dullo , 1990Andres et al 1988;Hoang and Taviani 1991;El Moursi et al 1994;Gvirtzman 1994;Bosworth and Taviani 1996;Strasser and Strohmenger 1997;Taviani 1998a, b;Plaziat et al 2008;Lambeck et al 2011;Parker et al 2012;Mewis and Kiessling 2013). To our knowledge, however, no study has quantitatively compared the faunal composition of modern and nearby fossil reefs in an attempt to define the original depositional water depth.…”