Charakterystyka petrograficzna ordowiku z Mójczy koło Kielc i porównanie z równowiekowymi osadami innych obszarów Polski

Abstract

PETROGRAPHIC CHARACTERISTIC OF THE ORDOVICIAN FROM MÓJCZA IN THE ŚWIĘTY KRZYŻ MOUNTAINS COMPARED WITH DEPOSITS OF IDENTICAL AGE FROM OTHER REGIONS OF POLAND

The Ordovician sediments of Mójcza in the Święty Krzyż Mountains are of interest due to the occurrence of chamosite oolites in the bioclastic limestones of the Caradocian. Here and there, these oolites show peculiar forms, similar to H. E. Kalkovsky's (1909) “conical oolites" and. A. V. Carozzi's (1960) "cerebroid oolites". The author assumes these forms to have been genetically connected with stromatoliths.

On the basis of petrographic analyses of sampIes of Ordovician sediments, collected from outcrops and bore-holes situated in different parts of Poland, the author presents some preliminary sedimentological and palaeogeographical conclusions. The sediments of the glauconitic facies occurring in the Lower Ordovician pass upwards gradually into oolitic chamosite marls. The reason for this change of facies the author considers to be a change in supply of potassium from the continent. During sedimentation of the glauconite series the excess of potassium became exhausted and silcates devoid of this element developed. Subsequently the author discusses in her conclusions the differences in content of terrigenic material and in iron concentration, determined in the Ordovician sediments on Polish territory. In her opinion these differences are not connected with the position of the shore line, but with dissimilar conditions of intraformational reworking of deposits accumulated in the sedimentation basin.