Abstract

This study documents a link between sea-level fall and basin-scale dolomite cementation of shoreface sandstones in the Upper Cretaceous Desert Member, Book Cliffs, Utah, by integrating sedimentology, sequence stratigraphy, and sedimentary geochemistry. Within the Desert Member shoreface sandstones, a number of high- frequency sequence boundaries formed as a result of relative sea-level falls that led to localized incised valley formation, subaerial exposure, and meteoric leaching of upper shoreface sandstones. Shoreface sandstones up to 10 km downdip from these subaerial exposure surfaces contain ferroan dolomite concretion bodies as much as 8 m thick. Basinward of this smaller (as much as 1 m in size), less abundant dolomite, concretions can be traced at the same horizons. Some δ18O data suggest that cement precipitated from porewater with a significant meteoric component, although reequilibration and recyrstallization cannot be eliminated. Some δ13C data suggest carbonate derivation from detrital dolomite leached from beneath organic-rich coastal plain strata deposited during high-frequency sequence boundary development. We propose that during high-frequency sequence boundary formation, meteoric fluids migrated basinward into shoreface sandstones as a result of the relative fall in sea level. The precipitation of dolomite cement in the shoreface sandstones was promoted by the updip dissolution and remobilization of detrital dolomite by the meteroic fluids, mixing with marine pore fluids, and the presence of detrital dolomite in the shoreface sandstones, which acted as nucleation sites for dolomite precipitation. This study illustrates the impact of stratigraphic development upon basin-scale early diagenetic cementation of siliciclastic succcesions.

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