Rozwój sedymentacji cechsztyńskiego dolomitu płytowego (Ca3) w rejonie Zatoki Puckiej

Andrzej Gąsiewicz



In the Puck Bay area the Platy Dolomite series developed in arid climate and marine waters experienced schizohaline conditions but generally increased in salinity levels with the time. The Platy Dolomite sequence is dominated by various type of microbialites (sensu 3) deposited in peritidal zones of the sabkha system. They are subdivided in three subfacies characterized by variously developed organic lamination: biolaminoids, stromatolites and stromatolite-like deposits. Most characteristic sedimentary units of the microbialites are biolaminoids (poorly developed muddy stromatolitic subfacies) which predominate the Platy Dolomite facies composition. The microbialite complex is intercalated by thin allochthonous facies composed of mud stones, rudstones, biodetrites and lumachelles, pelolltes, and oolites. Environmental interpretation of the Platy Dolomite components indicates differentiation of the depositional environment into two units: (I) a carbonate platform attached to the land, and (II) marginal part of the central Zechstein basin. The carbonate platform was rimmed by a narrow arched margin zone composed mainly of peritidal oolite shoals and connected with small tidal flats. The carbonate platform inner shelf is composed of thick tidal complex. In vertical section, the Platy Dolomite rocks exhibit a distinct bipartition according to their macroscopic features, mineralogical; biofacies and lithofacies compositions. It reflects different sedimentary patterns developed due to a common effect of subsidence and eustasy acted during the deposition of the section. The Platy Dolomite peritidal complex prograded basinward. The lower Platy Dolomite part originated mainly in supratidal zone and was connected with shallowing-upwards depositional cycle of the Grey Pelite deposited on a gently seaward inclined carbonate ramp. The upper one was formed mostly in the intertidal zone and was connected with slightly deepening-upwards sedimentary cycle deposited on the rimmed carbonate platform. A cyclicity of carbonate sands is observed in carbonate platform margin zone which, however, is not reflected in the inner carbonate platform zone.

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