Factors controlling the Cenozoic sequence development in the eastern partsof the North Sea

The causal relationship between the Cenozoic sequence development in the so utheastern North Sea Basin and sea-level changes, climatic fluctuations and tectonic events is unravelled by relating variations in the relative sea l evel and base level, based on interpretations of seismic surveys, to publis hed delta(18)O variations and eustatic changes. The latter curve is based o n the Earth's orbital forcing, and here informally termed as the GSI curve. The analysis shows that the Cenozoic sequence development in the southeast ern North Sea was influenced by climatically and tectonically induced sea-l evel changes. The major Cenozoic sequence stratigraphic boundaries (lower o rder) are highly influenced by tectonic events, e.g. uplift of Fennoscandia and increased subsidence rates in the basin centre. Reactivation of Mesozo ic fault zones controlled the deposition of minor sand bodies transported t o the centre of the basin during the Late Palaeocene by mass hows. The loca tion of an Oligocene mound structure, which constitutes part of a sequence, is controlled by the overall palaeotopography of the basin and local fault -related depressions. Correlation between (i) the ages of our sequences and the delta(18)O variat ions in the Oligocene succession, and (ii) the GSI curve and the base-level fluctuations of the late Miocene and younger sequences, show that the gene ration of the higher order sequence boundaries were driven by glacio-eustat ic sea-level changes. A climatic control of the sequence formation due to g lacio-eustatic sea level changes is therefore suggested for the Oligocene a nd Pliocene sequences, and probably also for the Upper Miocene sequences.