Recognition of the depositional architecture of the Upper Cretaceous sedimentary basin in the central part of the Carpathian Foreland

 

The study area is situated in the central part of the Carpathian Foreland in Poland. The interpreted interval includes the uppermost part of the Upper Jurassic – Lower Cretaceous carbonate complex, as well as the mixed carbonate-clastic Upper Cretaceous series. The sedimentation of the studied formations during the Late Jurassic and Cretaceous took place in the shelf zone of the northern, passive margin of the Tethys Ocean, and the paleoenvironment of sedimentation was heterogeneous and evolving over time.

 

For the study, 3D seismic data and geophysical (well logs) and geological information obtained from wells were used. High resolution seismic data were great input for seismic sequence stratigraphy and analysis in the Wheeler domain and enabled us to obtain insightful attribute volumes (such as spectral decomposition, sweetness and relative acoustic impedance).

The seismostratigraphy interpretation of the Upper Cretaceous mixed carbonate-clastic formations was based on the sequence stratigraphy methodology, which enabled detailed identification of depositional systems tracts and depositional sequences within these formations. Based on the analysis of the chronostratigraphic image and the Wheeler diagram, the main directions of sedimentary material transport into the Upper Cretaceous sedimentary basin in the central part of the Carpathian Foreland in Poland were determined. Numerous discontinuities and hiatuses related to erosional events or periods of non-deposition were identified in the Wheeler diagram. Small local dislocations, in some cases not visible in the seismic image, were also interpreted based on the chronostratigraphic seismic image. The interpretation has greatly contributed to the reconstruction of the basin's depositional architecture.

Seismic attribute maps, calculated directly on the surface of the interpreted intra-Cretaceous chronostratigraphic seismic horizon, allowed for a detailed analysis of paleoenvironmental elements within Upper Cretaceous formations. This seismic horizon corresponds to the maximum flooding surface (mfs) and connects the sedimentary packages deposited in a transgressive systems tract within one of the identified depositional sequences, as interpreted from the chronostratigraphic image in the structural domain and the Wheeler diagram. Based on the interpretation of the maps obtained, several elements of depositional architecture were identified, i.e., barrier Island with washover, elongated tidal banks, crevasse splays, and bay-head deltas, which generally allow for the definition of two adjacent types of transgressive coast type, i.e. the barrier island coast dominated by waves and the open estuarine coast dominated by tides.

The work was funded by the National Science Center Poland (NCN); SONATA 17: Recognition of the depositional architecture of the Upper Cretaceous sedimentary basin in the central part of the Carpathian Foreland (2021/43/D/ST10/02728)