Wapienie glonowe i rodolity z piaskowców ciężkowickich jednostki śląskiej w Karpatach

Stanisław Leszczyński


Algal limestones and rhodolites from Ciężkowice sandstones of the Silesian Unit (Polish Carpathians)

Much of the Carpathian flysch was deposited in internal parts of sedimentary basins. The record of previous marginal sediments of -the flysch basins have been preserved as clastic fragments which are penecontemporaneous with deposition of flysch. Such clasts provide informations concerning the composition of shorelines of flysch seas. Especially interesting in this aspect are limestone clasts. Commonly they ere rich in organic remains which point to a differentiated character of biocoenoses of the shores. This work deals with clastic fragments of algal limestones and rhodolites from the Ciężkowice sandstones. The Ciężkowice sandstones of the Silesian Unit represent a coarse grained lithofacies of Paleocene and Lower Eocene (Fig. 1). These sandstones occur as lenslike bodies superimposed one upon another within variegated shales. In geologic literature such bodies are called “horizons”. A considerable part of sandstones is made up of microconglomerates (the diameters of pebbles range from 2—50 mm). The conglomerates are chiefly oligomictic (quartz conglomerates). Polymictic conglomerates and pebbly mudstones are not so abundant. The sandstones have mainly a character of fluxoturbidites (sensu Carter, 1975, p. 172). The clastic material was derived from various parts of the silesian cordillera. The algal limestones and rhodoli They are found in the III and II horizons of the Ciężkowice sandstones (Fig. 1). The places in which the algal limestones and individual rhodolites occur are shown in Fiig. 2. The algal limestones are represented by the biosparites and biomicrites. The biosparites occur chiefly as well rounded pebbles. They consist mainly of coralline algae. They also contain foraminifers, echinoid spines, echinodermal plates, fragments of bryozoan colonies, molluscan fragments, worm tubes, and unidentified organic remains (Pl. I, Fig. 4, 5). The following algal genera have been identified: Lithothamnium, Mesophyllum. (Pl. II, Fig. 3, 4), Lithophyllum, and rarely Archaeolithothamnium. The forainifers are belonging to suborders: Rotaliina (among them there are — Discocyclina, and Asterocyclina), Textuilariina, and rarely Miliolina. In the biosparites the detrital fragments are well sorted. Among such fragments there are the rhodolites up to 5 cm diameter. These rhodolites have mainly ellipsoidal shape. Discoidal, and spheroidal rhodolites are rare. In cross section the rhodolites show columnar and laminar structure (Pl. I, Fig. 3). The majority of rhodolites belong to the group eipiphyte (Maslov, 1962). All rhodolites show bores of lithophages. The rhodolites are made up chiefly of the following algal genera: Archaeolithothamnium (Pl. II, Fig. 2), Lithothamnium (Pl. I, Fig. 2), and Mesophyllum. Lithophyllum is very rare (Bl. II, Fig. 1). Among encrusting organisms there are algae of the family Squamariaceae (Pl. I, fig. 1), foraminifers, serpulid worms, and bryozoans. Biomicrites contain the detritus similar to that of the biosparites. This detritus is chaotically distributed in the micrite mass (Pl. Ill, Fig. 1, 2, 3, 4). The rhodolites are here very rare. These biomicrites correspond to wackstones of Dunham (1962). They contain a group of algae similar to those from biosparites. Among the foraminifers Paleogene Globigerinidae are very numerous. Individual rhodolites occurring in the Ciężkowice sandstones have a size range of 0,5 to 10 cm, whereby the spheroidal and ellipsoidal forms are dominant (Pl. IV, Fig. 5, 6). The individual rhodolites have chiefly laminar and columnar internal structures (Pl. IV, Fig. 3, 4). There are epiphytic anjd hermophytic rhodolites (Maslov, 1962). Such rhodolites are formed by coralline algae of the genera: Archaeolithothamnium, Lithothamnium (Pl. IV, Fig. 1, 2), and Mesophyllum. Among encrusting organisms there are algae of the family Squamariaceae, foraminifers, bryozoans and serpulids. Some of the rhodolites show borings of lithophages. The material filling these borings contain abundant Globigerina which are similar to those occurring in the biomicrites discussed. The algal limestones as well as the rhodolites are of Middle Paleocene — Lower Eocene age. Individual rhodolites appear to be contemporaneous with deposition of the Ciężkowice sandstones. The algail limestones may be slightly Older. The assemblage of organisms which occur in the algal limestones and in the individual rhodolites was a part of the biocoenoses of the marginal zones of the Silesian trough. The algae which made up the rhodolites in biosparites are characteristic of the neritic zones. High degree of sorting of the bisparites and the predominance of rhodolites showing spheroidal and ellipsoidal shapes indicate a high energy environment (cf. Bosence, 1976; Bosellini, Ginsburg, 1971). The presence of Globigerina suggest that the biomicrites were derived from areas situated further off the shores. The texture of biomicrites point to low energy environment. The mode of occurrences of individual rhodolites in the Ciężkowice sandstones indicates that these rhodolites have been redeposited from the shoreis of the Silesian trough. The occurence of well rounded pebbles of ailgal limestones in Ciężkowice sandstones points to positive tectonic movement of the shores bordering the silesian basin, whereby the nearshore sediments were rised above the sea level and subject to erosion. These tectonic movements and erosion took place during Uppermost Paleocence and Lower Eocene.

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