Correlation of calcite-cemented layers in shallow-marine sandstones of the Fensfjord Formation in the Brage Field

摘要: Shallow-marine sandstones of the Fensfjord Formation in Brage Field contain numerous calcite-cemented layers with thicknesses up to 1.6 m. Most are located within bioturbated coarse silt fine-grained sandstone, and similar lateral extents greater than 3 km Bridport Sands Dorset. Less common horizontally or hummocky laminated intervals resemble concretions Bencliff Grit. The dominant source Ca2+ calcite cement three formations is probably biogenic carbonate. Isotopic analysis indicates that contains a mixture carbon from decomposition organic matter In predominantly derived carbonate, whereas Grit large proportion fermentation reactions. Wireline log correlation, supported by core description comparison studied outcrops, most extensive have at least 6 km. Geochemical closely spaced samples correlated four wells show isotopic signatures trace element contents widely different thought belong same layer. Samples along two vertical sections through layer also contents, even though separation between sample sets was only 30 cm. This suggests geochemical may be limited value for correlation layers.