The Silurian stratigraphy of the Zawiercie-Żarki area (NE margin of the Upper Silesian Coal Basin)

Abstract

Structural position, lithological character, major petrographical features and biostradgrnphy of Silurian deposits are discussed basing upon data from boreholes drilled between 1970 and 1989. Dingnostic studies of graptolite and conodont fragments have enabled the recognition of Wenlock, lower Ludlow (Gorsdan) and presumably locally the lowermost part of upper Ludlow (Ludfordian) deposits within the clastic part of Silurian sequence, whereas within its carbonate part - Llandovery and lowermost Wenlock sediments. The Lower Silurian carbonates pass down into the Ordovician ones probably with sedimentary continuity. This evidenced by conodont successions in the boreholes sections Ż-88 and Ż-89. Anchimetamorphic transformations (regional, dynamic and thermal-meta5somatic) of Silurian rocks and a high degree of tectonic differentiation between individual sections are common. The lack of stratigraphically complete Silurian sequences results mainly from their intensive tectonism and the pre-Devonian and pre-Triassic erosion.