Aptian Oceanic Anoxia: The shallow marine perspective

Pls join us for the following special lecture next week:

Thurs Oct 24 at 9:00 am in Biol 106

Dr. Adrian Immenhauser – Ruhr University Bochum, Germany - 14th IAS Special Lecture Tour (2019/2020)

Aptian Oceanic Anoxia: The shallow marine perspective

In 1976, Jackson and Slanger propose the term “Oceanic Anoxic Event” (OAE). This term describes a widespread, in part perhaps worldwide, phenomenon characterized by poor oceanic mixing leading to oxygen-depleted (hypoxic to anoxic) bottom water masses usually recorded in organic-rich basinal sediments (“black shales”). In the years to follow, very significant research has focussed on various OAE’s mainly in Jurassic and Cretaceous strata. Here, I approach this topic from the shallow marine perspective discussing the significance of recent, oxygen depleted coasts and their bearing on intervals of platform water anoxia in the Aptian of the southern and central Tethys Ocean. The potential and problems of redox proxies applied to fossil platform carbonates is evaluated and geochemical tools tested against paleoecological evidence. Arguments are brought forward to demonstrate that seawater anoxia during OAE’s is not an exclusively basinal phenomenon but may, depending on the system studied, explain abrupt reefal biota turnover in platform settings. The perhaps best way to at least approach the plethora of processes and products involved is the application of optimum curves and threshold limits combining the different data sets available at present. Sedimentologists and palaeoceanographers should consider to interact more actively with marine biologists and ecologists studying recent marine biotic response to environmental stressors.