Litostratygrafia i środowisko sedymentacji osadów górnego triasu w rejonie Chmielnika

Abstract

LITHOSTRATIGRAPHY AND SEDIMENTARY ENVIRONMENT OF UPPER TRIASSIC ROCKS FROM THE CHMIELNIK AREA Summary The paper presents results of studies on lithostratigraphy and sedimentology of the only complete sequence of the Upper Triassic so far known from the southern margin of the Holy Cross Mts (Fig. 1). Seven informal lithostratigraphic units were differentiated in that sequence (Fig. 2). The lower part of the sequence, corresponding to the German Lettenkohle horizon, is represented by sandy rocks with mudstone intercalations. The rocks pass upwards into mainly pelitic ones with subordinate intercalations of psammitic and psephitic material. The two uppermost units are built of sandstones and conglomerates with intercalations of pelitic rocks. The sedimentological analysis made possible differentiation of 14 lithofacies corresponding to individual types of sediments from modern neashore and continental sedimentary environments. The identified associations include those of nearshore zone (sediments of lagoon - A, and longshore - B - and mouth - B bars), coastal plain zone (sediments of mud flat - D, marshes - E, and mud tidal flat - F), and meandering river and delta (sediments of distributary channels - H, major channels - J, flood plain - N, channel bars - L, crevasse splays - M, torrential fans - K, and alluvial fans - G) as well as association of sediments of the lacustrine type (O). The sequence of the identified lithofacies and their associations indicates regressive character of the Upper Triassic section, with a continuous transition from sediments of the nearshore marine environment to those of fluvial-lacustrine ones.