Constraining the Triassic to Early Cretaceous structural and sedimentary evolution of the northern Dutch Central Graben; a seismic and well log data analysis.

Abstract

The structural evolution of the present-day Dutch offshore has been influenced by tectonic events coupled with halokinesis, eustatic changes and modifications in the rate of sediment supply. The research aims to disentangle the effects of these controlling factors in the Upper Jurassic – Early Cretaceous sediments of the Dutch Central Graben, by studying the tectonic-induced sedimentation at high resolution. It accounts for local tectonic and regional salt re-distribution features. The results show a better quantification of tectonic pulses that increases the resolution of the current broader tectonostratigraphic framework. Reconstruction involves first-order restorations based on local kinematics and available 3D-seismics. The syn-rift sedimentation of the Upper Jurassic Schieland Group marks the onset of basin development, followed by Scruff Group sedimentation encompassing basin margins and subsequent basin center uplift into turtle anticlines. The well log control enabled a facies model and a quantification in tectonic successions, resulting in a higher order subdivision of the tectono-stratigraphic framework of the Late Callovian – Late Oxfordian deformation into five higher resolution tectonic pulses. These pulses are reflected in terms of increased tectonic activity followed by its subsequent decrease, while the correlation with available sea-level curves shows that they are not influenced by eustatic changes. Furthermore, our research also shows that the successions observed in the earlier Scruff Group are controlled dominantly by eustasy, as 3rd order sea-level fluctuations coincide with the lower order sedimentary cycles observed in well log data and are not linked to rifting mechanics. Differences in local basin development of the two studied transects show that local factors influence the tectonostratigraphic evolution significantly. These main controlling factors are linked with the interplay between fault activation and salt-re-distribution, resulting in a clear correlation of tectonic-induced sequences.