Podział utworów górnej kredy i paleocenu centralnej części fałdu Brzanka-Liwocz (jednostka śląska)

Abstract

 Przedstawiono propozycję nowego podziału górnej kredy i paleocenu centralnej części fałdu Brzanka-Liwocz.Zwraca uwagę wysokie położenie stratygraficzrie pstrych łupków i warstw godulskich górnych.Z dolnych warstw istebniańskich opisano cztery poziomy utworów facji inoceramowej. Porównanie ich litologii i wieku z podobnymi utworami nasunięcia czarnorzeckiego pozwoliło na stwierdzenie analogii w rozwoju warstw istebniańskich w fałdzie Brzanka-Liwocz i nasunięciu czarnorzeckim. Fałd wykazuje również podobieństwo z wewnętrzną strefą jednostki śląskiej, o czym świadczy brak margli Rydeckich i węglowieckich, znanych z brzeżnej strefy tej jednostki (m. in. ze wspomnianego nasunięcia). SUBDIVISION OF THE UPPER CRETACEOUS AND PALEOCENE IN CENTRAL PARTOF THE BRZANKA - LIWOCZ FOLD (SILESIAN UNIT) Stratigraphy and lithology of the Upper Cretaceous and Paleocene in central part of the Brzanka- Liwocz fold (inner zone of the Silesian unit) are discussed. The field studies and micropaleontologicalanalyses gave the basis for differentiation of several members in the succession (Figs. 1, 2). The presented subdivision differs from that of K. Skoczylas-Ciszewska (1951, 1955) as it was made with reference to the work of H. Świdziński (1971), especially the subdivision proposed by him for successions of the Beskid Śląski Range. It should be also noted that the members differentiated here resemble in several aspects of lithological development those of the Czarnorzecze fold (northern, marginal part of the Silesian overthrust).The members identified in the Upper Cretaceous-Paleocene succession of central part of the Brzanka-Liwocz fold may be characterized as follows:Variegated Godula Shales (Upper Cenomanian? - Turonian - Lower Senonian), 100 m thick, represent a facies equivalent of flysch Godula Beds, including the uppermost part of upper member of the latter. This is in agreement with a trend to replacement of individual members by the Mottled Godula Shales towards northern margin of the Silesian unit.Upper Godula Beds, 390 m thick, represent the uppermost part of the Lower Senonian (Table 1) and, at the same time, a time equivalent of passage beds of the Godula and Istebna Beds from the Beskid Śląski Range.Lower Istebna Beds (Upper Senonian - Table 1), 600 m thick, comprise four horizons of rocks developed in the Inoceramian facies. Horizons analogous in lithology and age are also known from the Czarnorzecze overthrust (F. Szymakowska, J. Morgiel, 1964; F. Mitura, T. Birecki, 1966).The use of the strata as correlative horizons made it possible to find analogies in development of the Brzanka - Liwocz fold and Czarnorzecze overthrust (Table 2). The Brzanka - Liwocz succession differs from that of the latter locality in the lack of marls of the Frydek or Węglowiec type, which gives support for the hypothesis of marginal extent of these rocks in the Silesian unit. This difference makes the Inoceramian facies horizons (and, therefore, the Istebna Beds) similar to those known from a more internal zone of the Silesian unit, e.g. in the Pogórze Wiśnicko-Rożnowskie area.Upper Istebna Beds (Paleocene), 680 m thick, begin with a shaly series of the uppermost Maastrichtian-Paleocene (Table 1). The shales are overlain by thick-bedded sandstones (400 m thick)and the sequence ends with two complexes of brownish shales, separated by sandstones and attaining 280 m in thickness. The strata were not studied in detail.The above presented subdivision is consistent with the current views on stratigraphy of the Silesian unit in the Carpathians. The obtained results indicate that Upper Cretaceous-Paleocene members of the Brzanka-Liwocz fold display features common with both the inner and marginal zones of the Silesian unit. Thus it follows that they are developed in a facies "intermediate" between those typical of the two regions.