A geological 3D model of the so-called Gorzów Block, located in the Gorzów Wielkopolski area in western Poland, presents the sedimentary-tectonic architecture of the depositional basin, including the deposit succession from Carboniferous rocks at the bottom (depth 2 .5–4 .5 km b .s .l .; Variscan basement) to Cenozoic sediments at the top . The model has been developed using a database of 23 3D and over a thousand of 2D seismic sections, as well as of 300 deep (>500 m) boreholes.
Upper Permian (Zechstein) evaporites (sulphates and salts) constituted c.a. 1/3 to 1/4 of the whole basin infill in zones of their thickness maxima. They were drilled in 280 boreholes and represent 10 sulphate (anhydrite) and 9 salt lithostratigraphic units (including two K–Mg salts units), corresponding to the Zechstein cyclothems from PZ1 to PZ4 . Core description of 58 boreholes allowed distinguishing several lithofacies attributed to various evaporate depositional environments, such as: open sulphate or salt basin (including deeper parts), sulphate platform, sulphate lagoon (including shallower parts), salt-sulphate lagoon and pan, and sulphate sabkha, salina and seaside lake, transforming into an inland one of playa type.
Thickness and lithofacies distribution of following evaporite lithostratigraphic units of four Zechstein cyclothems is illustrated by geological cross-sections and the thickness-palaeofacies maps of corresponding evaporate depositional basins . These maps present supposed location of palaeomorphological structures as shoals, platforms, islands, evaporitic (sulphate and salt) pans, lagoons and basins with their deeper and shallower parts . Also the lists of commented parameters of evaporite units (top and bottom depth, thickness and their statistics such as minimum, maximum and average values) are provided.
The thickness ratio value of sulphates to chlorides in following cyclothem successions enabled to define the type of evaporate depositional basin . Most of studied Zechstein evaporitic basins represented the “fluctuating” basin type (low negative and positive ratio values), in which the local subsidence and the changing precipitation and accumulation rate were dominant factors with a minor role of basin palaeobathymetry . Only the sedimentary basins of Oldest Halite (Na1, PZ1 cyclothem) and Top Anhydrite (A3r, PZ3 cyclothem) were classified as the “infill” evaporate basin type (high negative ratio value), where the precipitated evaporites adapted to the inherited former basin bottom morphology producing thicker sulphates on basin shoals and thicker salts in its depressions . Thickness differences indicated also the role of post- and synsedimentary tectonics, active especially during deposition of PZ2 and PZ3 evaporites .