Kambr górny wschodniej części obniżenia perybałtyckiego

Abstract

W artykule przedstawiono wyniki badań piaskowcowo-węglanowych utworów kambru górnego wschodniej części obniżenia perybałtyckiego, które zostały stwierdzone w profilach otworów wiertniczych wykonanych w latach 1961-1973. Zamieszczono zwięzły opis ich litologii, podano typową sekwencję zespołów skalnych oraz przeprowadzono podział lito- i biofacjalny, wyróżniając na podstawie trylobitów i ramienionogów utwory poziomu Agnostus pisiformis, poziomu Homagnostus obesus i poziomu Parabolina spinulosa. Część końcowa artykułu zawiera omówienie problematyki facjalnej, zarys paleogeografii górnokambryjskiego basenu sedymentacyjnego oraz zestawienie korelacyjne z równowiekowymi utworami obszarów sąsiednich: zachodniej części obniżenia perybałtyckiego i wyniesienia Łeby.UPPER CAMBRIAN OF EASTERN PART OF THE PERIBALTIC DEPRESSIONIn eastern part of the Peritbaltic Depression the Upper Cambrian deposits were found for the first time in the borehole Pasłęk IG-1 in 1961 and subsequently in the borehole Olsztyn IG-2. In the years 1969-1973 the Upper Cambrian rocks occurring in situ were penetrated by several boreholes: Dębowiec Warmiński 2, Dębowiec Warmiński 3,. Żelazna Góra 1, Gładysze 2, Henrykowo 1, Młynary 1, Młynary 3 and Krynica Morska 2 (Fig. 1).The lithological assemblage of the Upper Cambrian from the eastern part of the Peribaltic Depression comprises monotonous packet of sandstone-carbonate rocks discordantly resting on sandstone-silts tone Middle Cambrian rocks (Fig. 2). The .packet of Upper Cambrian rocks is overlain by transgressive conglomeratic deposits of the Lower Tremadocian (Pakerortian) or, when Tremadocian deposits were completely removed by erosion, directly by a thin layer of glauconitic conglomerates of the Lower Arenigian (Latorpian). Sedimentary gaps and stratigraphical breaks are marked between the Middle and Upper Cambrian as well as the Upper Cambrian and Ordovician. The gaps are marked throughout the area but their stratigraphic range·appears variable (Fig. 3).Typically developed Upper Cambrian complex from the eastern part of the Peribaltic Depression consists of oligomictic, medium- or various-grained, calcareous quartz sandstones in the lower part, medium-grained calcareous quartz sandstones with sandy limestone intercalations in the middle and sandy and crystalline limestones in the upper part (B. Szymański, 1976). The sandstone-carbonate Cambrian deposits are thin, 0.7 to 1.1 m thick.The faunal content of sandstone-carbonate deposits of the Upper Cambrian of the eastern part of the Peribaltic Depressin made possible to differentiate time equivalents of three biostratigraphic zones: the Agnostus pisiformis, Homagnostus obesus and Parabolina spinulosa zones (Fig. 3). Because of the lack of continuity between the Middle and Upper Cambrian as well as between the Upper Cambrian and Tremadocian the complex of Upper Cambrian rocks should be treated as a naturally differentiated transgressive sedimentary cycle belonging to the Cambrian-Tremadocian macrocyle (B. Szymański, 1974).The sedimentary cover of the Upper Cambrian of the Peribaltic Depression displays a marked differentiation in lithological composition throughout the region. The differentiation makes it possible to distinguish two lithofacial zones: external, sandstone-carbonate, and internal, clay-carbonate zones (Fig. 4).The faunal content of the Upper Cambrian deposits of the eastern part of the Peribaltic Depression makes possible their biocorrelation with contemporaneous strata from neighbouring areas of the Łeba Elevation (K. Lendzion, 1970; W. Bednarczyk, 1972), western part of the Peribaltic Depression (K. Lendzion, oral inf.) and the Góry Świętokrzyskie (S. Orłowski, 1968b) in Poland, the Leningrad area in the USSR (A. A. Kaplan, O. N. Andrejeva, N. E. Tshernysheva et aI., 1973), Denmark (V. Poulsen, 1966), Sweden (A. B. Westerg¯rd, 1922) and Norway (G. Henningsmoen, 1957, 1958).