Sedimentary environment of the condensed Ordovician limestones from Mójcza section (Holy Cross Mts.)

Abstract

The paper deals with sedimentary evolution of the condensed Ordovician sequence outcropping in Mójcza village, near Kielce (Central Poland), basing on microfacies analysis. The occurrence of fossils, their preservation and mineral composition enabled the author to distinguish five microfacies types. The Mójcza section is generally composed of grainstones and packstones which form the Mójcza Limestone Formation, and calcareous claystones intercalated with wackestones assigned to the Zalesie Formation. The deposition of limestones from the Mójcza section took place on the outer part of drowned isolated carbonate platform of temperate water setting in uniform sedimentary conditions with low accumulation rate. This environment, located in the upwelling currents activity area, was favourable for phosphatization of sediment. Abundance of ferruginous ooids in the upper Llanvirn, L1andeilo and upper Caradoc sediments suggests highstand sea-level conditions during Middle and Upper Ordovician.