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Regional Studies: Stratigraphy, Tectonics and Volcanism |
Rice University, Department of Geology & Geophysics, PO Box 1892, Houston, TX 77251, USA
Exxon Production Research Co., PO Box 2189, Houston, TX 77252, USA
Sequence stratigraphic analysis of Paleogene central North Sea well-log, seismic and biostratigraphic data recognizes patterns of cyclic sedimentation seen in the physical stratigraphy and biostratigraphy. Numerous authors have documented cyclic sedimentation resulting from relative changes in sea level in northwest Europe, but interregional integration of these observations with North Sea subsurface data is lacking in the literature. Presented here is a chronostratigraphic correlation framework for the Paleogene of northwest Europe, built by integrating subsurface and outcrop data using sequence stratigraphic first principles. Biostratigraphic data from many sources is ordered with the composite standard method. Graphic correlation of this data documents certain correlations and helps suggest previously unrecognized ties.
Paleogene North Sea sediments record five major regressions and their intervening major transgressions. Overprinting this low frequency signal are 19 higher frequency sequence cycles that control lithofacies distribution. In northwest Europe, western basins (London-Hampshire, Paris and Belgian) have shallow marine to non-marine settings which reveal basinward and landward facies shifts that indicate sea level changes. The biostratigraphy of these shallow water deposits is linked to deep water central North Sea biostratigraphy by correlating through deeper water deposits outcropping in Denmark that have been tied to western basin stratigraphy. Using this biostratigraphic framework, key bounding surfaces are correlated between basins using sequence stratigraphic principles. Depositional sequences are recognized onshore that are completely sediment starved in the North Sea. The mixing of low and high frequency sea level signals requires that all of northwest Europe be studied to recognize the ‘true’ signal. Final correlations resolve 30 depositional sequences with five long-term sea-level changes that can vary from one sub-basin to another.
