Multiphase inversion in the Baltic sector of the North German Basin: Influence of Africa-Iberia-Europe convergence during the Late Cretaceous and Cenozoic

<p>Within the DFG project StrucFlow, we investigate the multiphase character of Late Cretaceous to Cenozoic inversion in the Baltic sector of the North German Basin based on seismic interpretation. Our analysis rests upon modern high-resolution seismic profiles in combination with data from older seismic surveys and borehole information. The resulting seismic database consists of a dense profile network with a total length of some 10.000 km. This unprecedented seismic grid allows for a detailed tectono-stratigraphic interpretation of Cretaceous and Paleogene deposits in the Baltic sector of the North German Basin. Here, basin inversion began in the Coniacian and Santonian with uplift of the Grimmen High and minor reactivation of Zechstein salt structures. Crestal faults were formed or reactivated above salt pillows in the Bays of Mecklenburg and Kiel. The onset of inversion was contemporaneous with other adjacent basins and is likewise associated with building up intraplate stress within the European foreland related to the beginning Africa-Iberia-Europe convergence. Time-isopach maps of Paleocene deposits in the study area show a slight decrease in thickness to the west. This contrasts the prevailing trend of increasing thickness towards the southwest directed basin center and indicates a changed depositional environment. In the outer eastern Gl&#252;ckstadt Graben, increased thicknesses and diverging strata of late Eocene and Oligocene units indicate significant remobilization of salt structures during this time. Preexisting Triassic faults above the salt pillows &#8220;Schleim&#252;nde&#8221; and &#8220;Kieler Bucht&#8221; at the eastern border of the Gl&#252;ckstadt Graben were reactivated and form a north-south trending crestal graben filled with Paleogene sediments. This phase of salt remobilization is contemporaneous with the reintroduction of intraplate stress triggered by the Alpine and Pyrenean orogenies in the late Eocene. In the eastern Bay of Kiel and in the Bay of Mecklenburg, Late Eocene and younger sediments are largely absent due to Neogene uplift and erosion. Deepening of rim-synclines and synchronous infill of Paleogene strata give evidence for commencing salt pillow growth. Crestal faults pierce the Paleocene and Eocene strata, indicating salt movement at least during the later Eocene. This phase of salt movement occurred contemporaneously with salt remobilization in the Gl&#252;ckstadt Graben, initiation of the European Cenozoic Rift System and increased activity in the Alpine realm in the Late Eocene to Oligocene. We conclude that the rise of salt pillows since the Eocene significantly exceeds the growth during late Cretaceous to Paleocene inversion phase at the northeastern North German Basin.</p>