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Natural and anthropogenic influences on the development of mud depocenters in the southwestern Baltic Sea

100%

Porz L. , Zhang W. , Schrum C.

Oceanologia

2023

tom No. 65 (1)

182--193

The morphological evolution of two mud depocenters in the southwestern Baltic Sea is investigated by comparison of numerical model results to geological and oceanographic data. The pathways of dense currents during episodic dense-water inflows from the North Sea are shown to correspond to current pathways inferred from contouritic depositional geometries in the flow-confining channels within the study area. A favorable comparison of model results to published current speed observations shows that the mesoscale dynamics of individual inflow events are reproduced by the model, indicating that external forcing and basin geometry rather than internal dynamics control the mesoscale dynamics of inflow events. The bottom current directions during inflows show high stability in the flow-confining channels and explain the contouritic depositional geometries. Asymmetric depositional features in the channels are qualitatively reproduced in the model. Bottom currents are less stable in areas without contouritic features, possibly resulting in an overall diffusive effect on sediment distribution in those areas. In a simulation of resuspension by bottom-contacting fishing gear, inter-basin sediment transport is increased by 4–30%, depending on the area, compared to the case of natural hydrodynamic resuspension. The model predicts an increased winnowing of the finest sediment fraction due to bottom trawling, leading to an overall coarsening-to-fining trend in the direction of net sediment transport. The results show that rather than hemi-pelagic background sedimentation, episodic events with high bottom current velocities as well as bottom-trawling induced resuspension are responsible for the present-day and future morphological configuration of the mud depocenters in the southwestern Baltic Sea.

Późnokredowa tektoniczno-sedymentacyjna ewolucja północnej Polski : opracowanie na podstawie regionalnych danych sejsmicznych

67%

Stachowska A. , Krzywiec P.

Przegląd Geologiczny

2024

tom Vol. 72, nr 6

270--279

Seismostratigraphic interpretation of the Cretaceous succession of northern Poland was based on regional geo-seismic transects, consisting, mostly, of unique, high-resolution, regional seismic profiles of the Poland SPANTMseismic survey, calibrated by geophysical, stratigraphic and lithological data from several deep boreholes. The upper Albian - Upper Cretaceous succession was divided into 5 seismostratigraphic units. The seismic facies have also been characterized. So far, the interpretation ofthe regional architecture ofthe Upper Cretaceous sedimentary cover of the East European Craton was commonly based on the classic, layer-cake model, assuming simple correlations of stratigraphic units between boreholes. The regional geophysical profiles from the Poland SPANTMsurvey revealed, however, a more complex picture. Within the upper Albian - Upper Cretaceous succession, two major units have been identified that are divided by regional mid-Upper Cretaceous unconformity. Within this succession, numerous clinoforms and erosional incisions have been recognized that are incompatible with the formerly applied layer-cake model. Two systems of contour currents (N-S and NW-SE) were identified as active during the deposition of mostly syn-inversion Upper Cretaceous succession. A new tectono-sedimentary model of the Late Cretaceous evolution of the shelf basin of northern Poland has been proposed that, which tentatively, linked depositional processes with the progressive lithospheric buckling during mid-Late Cretaceous sub-Hercynian tectonic movements.