Sedimentology and paleoecology of the Zechstein limestone (upper Permian) in the fore-sudetic area (Western Poland)

Abstract

Five main microfacies types can be distinguished within the rocks of the Zechstein Limestone (Zechstein 1, Upper Permian) of western Poland: (1) micritic; (2) biomicritic; (3) biolithitic; (4) oncolitic; and (5) a microfacies type characterized by micrites interlaminated with terrigenous clay material. The spatial distribution of these micro facies types enables us to establish five paleogeographical zones: (1) a basinal zone, characterized by thin sequences (about 5 m) of argillaceous micrites and/or deeper-water oncolites; (2) a zone of submarine elevations within the basin, composed of either thick (up to 66 m) sequences terminated by shallow-water oncolites and stromatolites, or condensed sequences (less than 2 m) containing vadose marine deposits; (3) a fore-barrier zone (5–20 m thick), mainly micritic with rare interbeds of biomicrites and oncolites; (4) a barrier zone of highly variable thickness and microfacies composition, with carbonate buildups made up of algal and bryozoan biolithites; and (5) a lagoonal zone (20–60 m thick) having a lower micritic and an upper oncolitic (and oolitic) part, both micrites and oncolites being sandy and argillaceous. The regressive nature of the microfacies sequence is marked in all these zones, but it is particularly well expressed in the barrier zone. Whereas in the lower Zechstein Limestone subtidal deposits (mainly argillaceous micrites and micrites) occur, carbonate buildups of shallow subtidal and intertidal origins are found in the upper Zechstein Limestone, while the uppermost Zechstein Limestone originated in a sabkha environment. The sedimentation model of the Zechstein Limestone in western Poland can be compared with that of the Recent carbonate sedimentation in the Persian Gulf, whereas other areas of Zechstein sedimentation have rather different morphologies.