Depositional architecture of the Upper Cretaceous succession in central Poland (Grudziądz-Polik area) based on regional seismic data

Abstract

Interpretation of the regional high-resolution seismic data of the PolandSPANTM survey in the Grudziądz-Polik area revealed a new depositional architecture of the Upper Cretaceous succession that differs substantially from the previously assumed layer-cake model, commonly applied to Permian-Mesozoic sequences. A previously unrecognized regional unconformity, dividing the Upper Cretaceous succession into two units characterized by very different internal geometries, was identified and mapped. The lower unit, with a generally layer-cake internal pattern, is overlain by an upper unit composed of a regionally low-angle succession that pinches out toward the south. This newly revealed regional pattern remained unrecognized in previous regional compilations based on borehole data, which suggested that a layer-cake depositional architecture prevailed throughout the entire Upper Cretaceous. This new image of Upper Cretaceous depositional patterns has far-reaching consequences for understanding of the evolution of the Polish Basin in the Late Cretaceous, including its subsidence and burial history, deposition, and tectonic development. A re-evaluation of the chronostratigraphy of the Upper Cretaceous of the Polish Basin is needed to temporally constrain the succession of sedimentary and tectonic events revealed here.