Sekwencja procesów petrogenetycznych osadów grupy świętokrzyskiej na tle podziałów lito- i biostratygraficznych

Abstract

SEQUENCE OF PETROGENETIC PROCESSES WITHIN THE DEPOSITS OF THE HOLY CROSS GROUPSUMMARYRecent works on the lithology and stratigraphy of the oldest sedimentary strata in the Holy Cross Mts, Central Poland, resulted in the recognition of petrogenetic processes responsible for the development of the Holy Cross Group (youngest Precambrian through the lowermost Ordovician; cf. Orłowski 1975). The obtained data, both of biostratigraphic (S. Orłowski) and petrographic (K. Łydka) nature, evidence a sedimentary continuity of the Cambrian deposits. They also indicate that the Holy Cross Group represents one sedimentary cycle (cf. Text-fig. 1), whereas the differentiation in its mineralogical composition resulted from geotectonic evolution of neighboring alimentary areas.The appearance of higher concentrations of kaolinite in sandstones of the Cambrian units younger than the Holmia Zone may point to the origin of quartz cement in these rocks. Namely, during the kaolinization of feldspars large amounts of silica had been freed, and that silica filled the interspace in sandstones and siltstones. Kaolinite is thereby regarded as authochthonous in the investigated sequence, and the chemical weathering of detrital feldspars as being of Cambrian age. More intensive weathering was responsible for a stronger decrease in feldspar frequency within the younger Cambrian deposits.The analyses of fine-pelitic fractions in the investigated deposits show that all the formations, starting from the Czarna Shale Fm. Up to the Klonówka Shale Fm. (cf. Text-fig. 1) display the same degree of the diagenetic advance that corresponds to the katagenetic stage. The secondary processes resulted in the difference between the sedimentary strata of the Holy Cross Group, and the strata attributed to the Riphean and characterized by the features typical of the initial stages of regional metamorphism (cf. Łydka 1973a).