The Ciezkowice Sandstone is a lithostratigraphic term used to define a sand-prone succession of late Paleocene–middle Eocene age and is one of the main producing petroleum reservoirs in the Silesian unit of the central and eastern Polish Outer Carpathians. The excellent reservoir potential of these sandstones and their widespread occurrence make them a key objective for future exploration. In this study, the Ciezkowice Sandstone was analyzed using geophysical logs and nearby exposures in the Silesian unit between the towns of Ciezkowice and Krosno.

The analysis presented in this chapter has identified as much as four laterally persistent, sand-prone units in the Ciezkowice Sandstone. The dominant lithology of these units is coarse-grained, thick-bedded sandstones interbedded with fine-grained turbidites. The thickness of individual sandstone bodies ranges from 20 to more than 50 m (66 to more than 160 ft) within a gross sand-prone interval of as much as 350 m (1100 ft), in which sand/shale ratios can be as much as 9:1. Sandstone beds are mostly massive to normally graded and commonly display shale clasts, horizontal planar stratification, and water escape structures. The thickest beds are commonly amalgamated and locally display very large-scale trough cross-bedding. These sandstones are interpreted as high-density turbidites.

The Ciezkowice Sandstone units are interbedded with pelagic mudstone-dominated tongues, lithostratigraphically termed the “Variegated shales.” Sedimentological features of the sandiest units in the Ciezkowice Sandstone indicate that they were deposited in basin-plain settings during lowstand phases of basin evolution.

The Ciezkowice Sandstone represents a second-order lowstand sequence set (basin-floor fan equivalent). The Variegated shales were deposited during transgressive and highstand systems tracts, when sand supply to the basin was reduced significantly. Each Ciezkowice Sandstone–Variegated shale cycle is interpreted to represent a third-order depositional sequence in a lowstand sequence set of latest Paleocene to middle Eocene age. Several subunits of the Ciezkowice Sandstone provide good examples of basin-floor fan-stacking patterns characteristic for deposition in lowstand basin conditions.