Wykształcenie facjalne liasu wierchowego w otoczeniu Doliny Chochołowskiej w Tatrach

Abstract

FACIES DEVELOPMENT OF THE HIGH-TATRIC LIAS IN THE VICINITY OF THE CHOCHOŁOWSKA VALLEY (TATRA MTS) Summary The paper presents results of facies studies on high tatric Lias in the neighbourhood of the Chochołowska Valley, Tatra Mts. With reference to macroscopic observations and thin section analyses, 4 major facies and one microfacies of the Lias are differentiated and characterized. Deposits of sandy facies mainly consist of quartz grains of various types and grains of Triassic carbonate rocks (mainly Norian dolomicrites). Other terrigenous components here include K-feldspars, plagioclases, muscovite, zircon, rutile and tourmaline. Deposits of sandy-crinoidal facies consist of quartz grains and trochites as well as the same components as in the above facies. Quartz-crinoidal- pelloidal microfacies, differentiated within the sandy-crinoidal facies, consists of quartz grains, trochites and pelloides of the same fraction (0.1-0.4 mm) and present in similar quantities. Deposits of crinoidal facies yield mainly trochites and, as a rule, insignificant admixture of fine quartz grains. Deposits of spongiolite facies are characterized by the presence of chalcedony mass with embedded siliceous sponge spicules. Organic components other than trochites and sponge spicules, present in all the facies, especially the sandy-crinoidal, include foraminifers, detritus of bryozoan colonies, ostracods, echinoid spines, elements of ophiuroid skeletons, and holothurian sclerites. Macrofossils (terebratulids, pectens and belemnites) are innumerous and poorly preserved. The surveyed sections were correlated with reference to similarities in microfacies, which casts some light on spatial relations between the facies. The recorded time intervals of predominance of sandy sedimentation are explained in terms of block movements in source areas, which is connected with location of the studied zone at that time within an area of dissected intraoceanic ridge.