24th April 2017

Paper published in Sedimentary Geology


Working alongside colleagues from the Université de Bourgogne and Total, Badley Ashton's Dr. Matthieu Devilled de Periere has had a paper published in volume 353 (May 2017) of the journal 'Sedimentary Geology'. Entitled "Influence of a major exposure surface on the development of microporous micritic limestones - Example of the Upper Mishrif Formation (Cenomanian) of the Middle East". The study examines the Microporous platform top limestones of the Cenomanian Mishrif Formation in Qatar to investigate the diagenetic processes associated with the top-Mishrif subaerial unconformity and its influence on the development of microporosity in underlying carbonates.

The full abstract is given below.

If you would like more information about either this paper or the entire volume, you can find more information here. If you are interested in seeing some of the other papers and presentations that Badley Ashton staff have produced, please take a look at the staff publications page.

Microporous platform top limestones of the Cenomanian Mishrif Formation (offshore Qatar) were studied in order to investigate the diagenetic processes associated with the top-Mishrif subaerial unconformity and its influence on the development of microporosity in underlying carbonates. Petrographical and stable isotope results indicate that complex diagenetic changes occurred during subaerial exposure of the Mishrif Formation, including pervasive dissolution and meteoric cementation, as well as neomorphism of the micritic matrix. Micrites at the top of the Mishrif Formation are coarse (i.e. > 2 μm), sub-rounded and very dull luminescent under cathodoluminescence. In this uppermost part of the studied interval, the limestone matrix first underwent dissolution of unstable grains in the vadose zone, with subsequent precipitation of low-magnesium calcite (LMC) overgrowths within an oxidising phreatic setting. This process explains the poor luminescence of the micrite crystals and their relatively coarse crystallometry which results in the present day in relatively good reservoir properties. δ13C ratios within the microporous limestones are negative (up to − 4‰ V-PDB) due to the incorporation of isotopically light carbon derived from palaeosols which developed during exposure. By contrast, fine (i.e. < 2 μm), polyhedral and bright luminescent micritic matrix with higher δ13C values (up to + 4‰ V-PDB) and lower permeability are dominant within the underlying carbonate interval. These fine micrites are likely to be the product of early neomorphic recrystallisation in the lowermost part of the palaeo-aquifer associated with the Top-Mishrif Unconformity, and were precipitated from meteoric or mixed dysoxic waters which were slightly supersaturated with respect to calcite.

diagenetic phases

Staining (A–B), cathodoluminescence (C–D), and unstained (E–F) photomicrographs illustrating various diagenetic phaseswithin the lower and upper intervals of the Guiriel Field.


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