Poziom Goniatites granosus (wizen górny) w zachodniej części Gór Świętokrzyskich

Abstract

 Omówiono litologię, struktury sedymentacyjne, szczątki organiczne i stratygrafię utworów karbonu dolnego z głębokiego otworu wiertniczego Radwanów IG 1 oraz z trzech znacznie płytszych w synklinie piekoszowskiej. Otwory położone są w zachodnim przedłużeniu centralnego obszaru wychodni paleozoiku świętokrzyskiego, w obrębie mezozoicznego obrzeżenia. Przewodnie goniatyty umożliwiają zaliczenie niektórych odcinków profilów do najwyższego poziomu goniatytowego w wizenie górnym (Gog) oraz podpoziomu (Gog1). Porównanie profilów z utworami poziomu Goniatites granosus synkliny gałęzicko-bolechowskiej i otw. Łopuszno IG 1 dowodzi analogii litostratygraficznych, litofacjalnych i środowiskowych. Badania wskazują na znaczny, u schyłku wizenu, zasięg zalewu morskiego w zachodniej części Gór Świętokrzyskich ze strefą zwiększonej subsydencji osadów i obszarem źródłowym dla utworów szarogłazowych okolic Radwanowa. THE GONIATITES GRANOSUS ZONE (UPPER VISEAN) IN WESTERN PART OF THE GÓRY ŚWIĘTOKRZYSKIE MTS Four drillings made at western extension of Paleozoic outcrops of the Góry Swiętokrzyskie Mts, within the area of their Mesozoic margin (Figs. 1, 2) in the years 1972–1975, encountered Lower Carboniferous sequences varying in thickness. Deep borehole Radwanów IG 1 is situated in axial part of a Mesozoic structure known as the Radwanów anticline, and the remaining ones – within the area of other Mesozoic structure, the Piekoszów syncline. Devonian-Carboniferous basement of the latter, relatively shallow-seated, represents an extension of Devonian and Carboniferous rocks of the Kielce syncline, directly adjoining the Piekoszów syncline in the east. In the Kielce syncline, these rocks crop out at the surface. In the studied borehole sections, Carboniferous rocks were found to be directly overlain by the Upper Permian with sedimentary discontinuity or tectonic contact. The rocks encountered by the boreholes are characterized in detail, discussing their lithology and preliminary results of petrographic studies, sedimentary structures of both erosional and deformational types, organic remains and stratigraphy. Tables I–VIII show selected core samples, sedimentary structures and faunal and floral remains, and Table I – quantitative and qualitative comparisons of the organic material. Carboniferous rocks are everywhere dark-gray in colour, fractured and cut by calcite veinlets, displaying fairly intense tectonic disturbances. Pyrite ingrowths are fairly common. There were differentiated some types of rocks, generally occurring in the form of thin intercalating layers. Faunal remains are usually poorly preserved and the floral – generally carbonized, and either dispersed or concentrated in the form of layers. There were also recorded miospores, the studies of which are in progress.The record of guide species of goniatitids makes possible assignation of some intervals of borehole sections to the uppermost goniatitid zone of the Upper Visean (Goniatites granosus Zone) and, in the case of the borehole Piekoszów IG 1, also the Gog1 Subzone. Faunal remains are most numerous and their systematic differentiation the highest in the latter column. Correlations of lithological development and the lack of any clear indices for the Upper Carboniferous age suggest that rocks encountered in the 1674.5–2243.5 m interval in the borehole column Radwanów IG 1 belong to the Go g Zone. Real thickness of that is here close to 330 m, i.e. almost twice as high as in neighbouring borehole Łopuszno IG 1 and the Gałęzice syncline (H. Żakowa, 1969, 1971). This suggests presence of a zone of increased seafloor subsidence in the Radwanów area. The origin of such zone in Late Visean times was already indicated by the Carboniferous column of the borehole Radoszyce 3, the thickness of which was estimated at about 625 m (H. Żakowa, 1980, Fig. 6). Real thickness of the    Gog  Zone in boreholes in the Piekoszów syncline ranges from 12 to 96 m.The presence of graywacke sandstones with relatively well preserved feldspars in the column Radwanów IG 1 suggests proximity of alimentary areas in which disintegration also involved ingeous rocks. Comparisons of rocks described here and those from the borehole Łopuszno IG 1 and theGałęzice–Bolechowice syncline show fairly large similarities in lithofacies and sedimentary environment. The studies indicate large extent of sea in western part of the Góry Świętokrzyskie Mts at the end of the Visean.