Rhynchopora geinitziana V e r n. z piaskowców permskich zapadliska północnosudeckiego i jej znaczenie dla stratygrafii permu w południowo-zachodniej Polsce

Abstract

Podano szczegółowy opis fauny morskiej znalezionej w utworach terygenicznych, które w stosowanym podziale litostratygraficznym permu zaliczane są do górnego czerwonego spągowca – saksonu. W konkluzji wyrażono pogląd, że wpływ morza górnopermskiego w omawianym regionie jest znacznie większy niż przyjmuje się obecnie. Konsekwentnie autor uważa, że utwory zaliczane do saksonu są utworami morza górnopermskiego, a utwory salinarne cechsztynu stanowią młodszy megacykl sedymentacji w tym zbiorniku.RHYNCHOPORA GEINITZIANA V ERN. FROM ·PERMIAN SANDSTONES OF THE NORTH-SUDETIC DEPRESSION AND ITS SIGNIFICANCE FOR STRATIGRAPHY OF THE PERMIAN OF SW POLANDThe paper presents descriptions of Rhynchopora geinitziam Ve r n. and other brachiopods found in white sandstones(Weissliegendes Locality C1 - Fig. 4) and mottled sandstones (Rotliegendes, Locality H1 - Fig. 3) underlaying Zechstein Basal Limestone horizon in the North-Sudetic Depression (SW Poland). The collection of 26 specimens is housed in the Museum of the Geological Institute in Warsaw (coIl. no. 1476.11.1-10). Besides Rhynchopora geinilziana, the collection comprises some much more worn-out specimens of brachiopods (Productus sp.) and bivales cr the genus Schizodus.The RotIiegendes section of that area, up to 2000 m in thickness, comprises clastic rocks varying in lithology, and subvolcanic and eruptive rocks and their tuft's in its middle part. The latter are overlain by Upper RotIiegendes (Saxonian) rocks which being with so called Main Conglomerate (J. Krason, 1964).Sandstones of the above complex are grey or almost white in large areas at the contact with clay-carbonate rocks of the Werra cyclothem (Zechstein). According to predominating point of view, grey sandstones (Grauliegendes) originated due to decolouring of underlaying mottled sandstones of the Rotliegendes, and the white ones (Weissliegendes) have also been redeposited in the Zechstein sea (H. Meinecke, 1910; J. Oberc, J. Tomaszewski, 1964; U. Kriebel 1967. and thers). Consequently, the white sandstones are assigned to the Zechstein. The boundaries between red, white and grey sandstones are, however, usually gradational and it is not possible to define them Up to the present, no features were found which would evidence redeposition of the white sandstones. All the sandstones are similar in mineralogical composition, petrography and lithological features, differing only in colour.The contact ofr sandstones and Zechstein rocks is relatively sharp. Sandstones are usually overlain by the BasaI Limestone or Copper-bearing Shale. Mottled sandstones of eastern part of the Depression (Leszczyna Syncline) yielded bivalve fauna (see E. Zimmermann and B. Kühn, 1918. 1936; T. Gunia, 1962).Rhynchopora geinitziana V e r n. was hitherto known from the Kazanian Stage a eastern part of the East-European Platform (A. W. Nieczajew, 1894, 1911) and the Weissliegendes of the Gera region in the GDR (R.B. Geinitz, 1848). The Permian brachiopod assemblage of Texas (O.A. Cooper, R.E. Grant, 1976, p. 2663, Table 695. Phota; 1-5) comprises Rhynchopora patuta C o o p e  et  G r a n t. identical as Rhynchopora geinilziana V e r n. presented here.In Poland, Rhynchopora geinitziana V e r n. was not found in overlaying links a the Zechstein Limestone. Sandstones of the same horizon occurring in other parts of the Fore-Sudetic Monocline yield inarticulate brachiopods and bivalves (J. Wyżykowski, 1964; G. Tokarski, 1966; S. Alexandrowicz, K. Słupczynski, 1970; S. Alexandrowicz, J. Jarosz, 1971; T.W Błaszczyk, W. Prymka, 1973) as well as foraminifers, chinoids, ostracodes and bryozoans (T.M. Peryt, 1976). It may be the assumed that areas situated closer to the shores were the most favourable environment for R. geinitziana V e r n. which has been forming some kind of biostromes there.The above data validate the assumption that Rhynchopora geinitziana V e r n. is the guide species of transgressive deposits m the Late Permian sea. In the area of the North-Sudetic Depression, marine sedimentation began with deposition of terrigenic rocks of the conglomeratic-sandy facies and the faunal assemblages were differentiated and selected in time of that transgression.In concluding, it is possible to repeat here an earlier statement (S. Lisiakiewicz, 1978) that the Main Conglomerate resting on volcanic rocks or siltstones of the Middle Rotliegendes should be treated as the basal (transgressive) conglomerate of the Upper Permian and the Saxonian rocks - as deposits of the Late Permian sea.Family Rhynchoporidae K ü h n, 1949Genus Rhynchopora K I n g, 1856Rhyhchopora geinitziana (V e r n e u i I) 1845(Table I, Figs. I - 5, 7)M ate r i a I: Twenty specimens differing in preservation (18 from the Locality 1\ and 2 from the Locality C1); 6 complete and excellently preserved and the remaining ones preserved as more or less damaged ventral or dorsal valves).D I m e n s o  I o n s of 1 specimen (in mm):Length 12.3Width 12.1Thickness 8.8D e s c r i p t I o n. Dorsal and ventral valves are ornamented with distinctly regular ribs. Ribs ovate in cross-section, radially spreading from apex, and varying from 20 to 22 in number on dorsal valve and from 22 to 24 on the ventral. Growth lines may be traced in marginal parts of some valves. Valve surface also displays micropores (about 40 in number per 1 cm2). Umbonal ange ranges from 105 to 120°, equalling 1100 for 70% of specimens. Lateral outline of valve is also highly characteristic (Table I, Figs. 1 - 3).The specimens of R. geinitziana V e r n. also display some stable characteristic features, traceable on outer side of both ventral and dorsal valves (Table II. Figs. 8, 9), i.e. dark, almost black inter-rib lines: two on ventral valve and one on the dorsal On ventral valve, the inter-rib lines converge in the apex at the angle of about 35°, comprising a bundle of 6 ribs; lateral bundles consist of 7 - 8 ribs. On dorsal valve, the inter-rib line passes through the middle and it bifurcates close to stylical opening. The length of these radial lines approaches one-third of valve length.In concluding it may be stated that all the figured specimens and those incompletely preservedbelong to the same species and surely to the same genus.C o m p a r i s o n s. The studied specimens are similar to those described as Rhynchopora geinitziana V e r n e u i l  by W. King (1856). The comparison showed that they differ from the E. de Verneuil's holotype and the neotypes figured by H.B. Geinitz, W. King, A.W. Nieczajew and E. Malzahn in the presence of characteristic inter-rib lines on outer side of valves. The comparative analysis of morphology of the studied specimens and that described by J. Kłapciński (1972, Table VIII, Fig. 1) showed distinct differences in ornamentation of valves and shape of their ribs.O c c u r r e n e c: Sudety Mts, North-Sudetic Depression, borehole no. 272 (Locality H1 and gallery 101 bis (Locality C1 in the Konrad mine. The specimens of Rhynchopora geinitziana are derived . from top part of Weissliegendes sandstone (C1 and mottles sandstones of the Rotliegendes (H1) according to the lithostratigraphic subdivision of the Pennian System The two sandstone types contact the Basal Limestone of the Zechstein.