Abstract

A methodology for the correlation of offshore Silesian (Upper Carboniferous) sequences is developed using an integrative approach based upon biostratigraphy, downhole logging and geochemistry. We develop the combined use of miospore zonation, gamma ray spectrometry, formation velocities and carbon/sulphur ratios to determine the location of marine horizons and other lithofacies in a thick (>1 km) largely uncored Silesian sequence in the Southern North Sea Gas Basin. At least nine major marine horizons are recognized within a basin-fill sequence of Marsdenian, Yeadonian and Langsettian ages (Namurian B/C and Westphalian A) in the well. These horizons help to provide a detailed subdivision of the offshore sequence, although the correlations must remain tentative until further deep wells are drilled in the area. The implications of the correlations for offshore palaeogeography are that the area of northern Quadrant 48 was a deep, periodically anoxic basin until infill by successive submarine fan lobes in late Marsdenian times. Yeadonian delta front and coastal plain deposits pass upwards into fluvio-deltaic/wetland facies of the Langsettian.

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