The origin and depositional architecture of Paleogene quartz-glauconite sands in the Lubartów area, eastern Poland

Abstract

The study uses quantitative methods to analyse the latest Bartonian to Early Rupelian sedimentary succession at the SE outskirts of the Polish Lowland Paleogene Basin, in the back-bulge zone of the Carpathian orogenorebulge. The vertical lithotype proportion diagrams from a large number of well logs are compiled to reveal the area’s sequence stratigraphy. Six sequences are recognized and correlated with 3rd-order eustatic sea level cycles. The basal sequence of type 1 is overlain by three sequences of type 2 and followed by a fifth sequence of type 1, whose depositional forced-regressive and lowstand systems tracts brought the main volume of quartz-glauconite sand to the study area. The study focuses further on the deposits of this fifth sequence, exposed and surveyed with GPR in the Nowodwór-Piaski sand pit. Their sedimentary facies analysis reveals the local spatial pattern of a wave-dominated and tidally-influenced sedimentation, supporting the earlier notions of a southern palaeoshoreline and a tectonically-controlled sedimentation.The analysis, aided by multidimensional GPR survey, indicates syndepositional development of a tectonic graben filled laterally by fault scarp-attached large sand bars and an axial action of tidal ebb currents. The bars were formed of shore-derived sand swept by littoral waves from the graben footwall areas. As the graben’s tectonic activity ceased, it became buried by the lowstand regressive sands overlain by gravelly foreshore deposits, most of which were later removed by the Pleistocene glacial erosion. A 3D model of the deposits in the Nowodwór-Piaski area is constructed on the basis of outcrop and GPR data with the use of multiple-point statistical methodology to depict the internal architecture, heterogeneity and spatial relationships of main sedimentary facies. The model can serve as a guide for the future exploration and exploitation of the quartz-glauconite sands in the area and as instructive example of how a petroleum reservoir model of a complex sedimentary succession can be constructed with the use of modern statistical methods.