Sulphate reduction associated with hardgrounds: Lithification afterburn!

Dickson, J. A. D. and Wood, R. A. and Rougha, H. Bu Al and Shebl, H. (2008) Sulphate reduction associated with hardgrounds: Lithification afterburn! Sedimentary Geology, 205 (1-2). pp. 34-39. DOI 10.1016/j.sedgeo.2008.01.005

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Abstract

Negative excursions in δ13C profiles from platform carbonates that coincide with pyritised hardgrounds are commonly linked to subaerial exposure events, but we show here that they can also result from subsurface bacterially-mediated early cementation in addition to the precipitation of syndepositional marine cements. A non-soil-derived origin for δ13C-depleted micrites offers an alternative origin and bathymetric interpretation for these surfaces. The Lower Cretaceous Lekhwair Formation platform carbonate successions from offshore Abu Dhabi contain abundant hardgrounds that are important for both regional correlation and control of subsurface flow. The micrite from these hardgrounds have average δ13C values of + 0.7‰; 1.5‰ lower than non-hardground micrites that are similar to contemporary open ocean values. Hardground δ13C values are due to the addition of 13C-depleted carbonate, generated as a by-product of sulphate reduction, to the ‘normal’ marine calcite that caused hardground lithification. Pyritisation of the hardgrounds occurred before, during and after ‘normal’ calcite precipitation. The persistence of sulphate reduction after hardground lithification is shown by the presence of pyrite and low δ13C micrite in sediment up to a few mm above the hardgrounds.

Item Type:	Article
Uncontrolled Keywords:	08AREP IA55 ZADCO Sclumberger; cml
Subjects:	02 - Geodynamics, Geophysics and Tectonics
Divisions:	02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title:	Sedimentary Geology
Volume:	205
Page Range:	pp. 34-39
Identification Number:	10.1016/j.sedgeo.2008.01.005
Depositing User:	Sarah Humbert
Date Deposited:	16 Feb 2009 13:02
Last Modified:	23 Jul 2013 10:06
URI:	http://eprints.esc.cam.ac.uk/id/eprint/245

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