Mechanizm sedymentacji i pozycja facjalna wapienia węglowego w południowo-zachodniej części Gór Świętokrzyskich

Abstract

MECHANISM OF SEDIMENTATION AND FACIAL LOCATION OF THE COAL LIMESTONE IN SOUTHWESTERN HOLY CROSS MTS. Summary The Upper Visean limestone beds, exposed in the western part of Gałęzice syncline (Holy Cross Mts), are developed in the form of a few lenticular bodies, several hundred meters long and maximum 35 m thick. An extraordinary abundance of benthic fossils (rugose corals, brachiopods, crinoid debris) caused that the investigated limestones have hitherto been interpreted as in situ shelf carbonates. Within carbonate complex, seated in deep-water shaly sediments, it is possible to distinguish 3 basic lithological types: carbonate breccia, coarse-grained crinoid packstones and grainstones, and cephalopod wackstones. The complex starts with a breccia bed (0.5 to 5 m thick) that comprises clasts of various Devonian and Carboniferous limestones along with large colonies of corals, floating in coarse-grained skeletal debris. which is mixed with phosphatic nodules and clasts of radiolarian shales. The overlying interval is developed as medium and thick-bedded (up to 110 cm) bioclastic, mainly crinoid, limestones. Cephalopod wackstones appear only in 2 thin-bedded intercalations at the top of carbonate unit. Observations from the newly exposed section in the western part of Jaźwiny Hill, in Ostrówka quarry, allow to infer a deep-water sedimentary environment of the carbonate complex. This hipothesis is supported by: - location of the complex in the deep-water basinal sequence, - sedimentological features: graded-bedding in thin layers, poor sorting and random fabric in thick layers, the presence of allochthonous material derived from the bedrock, floating clasts in coarse-grained matrix, etc., - interfingering of pelagic limestones with crinoid calcirudites, - mixed fauna from different ecological niches, - lens-shaped geometry of limestone beds. The investigated carbonate unit represents submarine fans, deposited by sediment-gravity flows. The orientation of bioclasts, measured on the soles of layers, and the geometry of beds indicate the transport direction toward the north, from non-extant, hypothetical carbonate platform, located south of the Gałęzice area.