Print this pagePredictive Diagenesis in a Sequence Stratigraphic Framework
TAYLOR, KEVIN, ROB GAWTHORPE, CHARLES CURTIS, SOPH FANNON, and JOHN VAN WAGONER
Excellent exposure within the Blackhawk and Castlegate Formations of Book Cliffs, Utah has allowed for predictive diagenetic models to be developed within a high resolution sequence stratigraphic framework.
Early carbonate cements (predominantly ferroan dolomite) are abundant within these successions. They occur as both large (up to 10 m thick and in excess of 100 m long) isolated concretions and as thin (<2 m thick) laterally extensive cement zones within shoreface and fluvial sandstones. There is no simple relationship between thickness and width of the cement bodies.
Sandstones containing the large isolated concretions occur down-dip of leached zones that are localised below coal horizons. In contrast, the laterally extensive cement zones only occur beneath marine flooding surfaces. Geochemical and stable isotope data suggest that the major source of carbonate for the large isolated concretions was remobilised marine carbonate, and that a significant meteoric water component was present. In contrast, data for the thin laterally extensive cements indicate a significant carbonate contribution from organic matter oxidation.
We propose that the large isolated concretions formed through meteoric remobilisation of detrital carbonate leached from beneath coals in updip locations. Laterally extensive cement zones formed as a consequence of breaks in sediment accumulation associated with marine flooding surfaces. This study places diagenetic processes within a sequence stratigraphic framework allowing better prediction of reservoir quality in the subsurface.