Effects of Diagenesis on the Divalent Cation Proxies (Sr/Ca, Mg/Ca) and their Isotope Systems (delta 44/40Ca, delta 88/86Sr, delta 26/24Mg) on biogenic carbonate hardparts

Kurzbeschreibung

Previous research applying alkaline-earth element ratios (Sr/Ca, Mg/Ca, etc.) and their corresponding non-traditional isotope systems (δ44/40Ca, δ88/86Sr, δ24/26Mg) have focused on paleoceanographic or environmental signals. The effects of diagenetic alteration on these isotope systems have yet received little or no attention as well as the potential of these non-traditional isotopes to study and quantify diagenetic processes have also not been tested so far. However, both aspects are becoming increasingly important when attempting to reconstruct ambient changes in seawater geochemical composition and when robust absolute (e.g. U/Th-series) or stratigraphic ages (e.g. 87Sr/86Sr) are to be determined. In our study we will examine the dynamic changes of alkaline earth element ratios and their isotope systems as a function of the various diagenetic processes altering orginal signals. In this regards we will also focus on uranium (U) and the U/Ca ratio and corresponding isotope ratios (234U/238U, δ44/40Ca) in a suite of carbonate samples which span a range of pristine (‘closed’ system behaviour) to completely altered carbonate material (fully ‘open’ system). Aragonitic corals are selected because corals are one of the most important carbonate archives for the reconstruction of environmental parameters of the past (seawater temperatures, nutrient availability, sea-level change). However, aragonitic corals are also a prominent subject to diagenetic alteration because aragonite is thermodynamically unstable and will transform to high- and low-Mg calcite, respectively, in a time scale from a few years to many thousands of years.

Start

April 2013

Ende

März 2016

Bewilligungssumme (gesamt)

Bewilligungssumme (GEOMAR)

199000

Zuwendungsgeber / Programm

DFG / Research Unit (FOR)

Koordination

null

Kontakt

Anton Eisenhauer