Stratigraphic position and facies significance of the limestone bands in the subsurface Carboniferous succession of the Lublin Upland

Abstract

The Carboniferous paralic succession (late Viséan - Westphalian a) of the subsurface Lublin Basin in eastern Poland yields carbonate deposts, which dominate in the Viséan phae of sedimentation, and become more subordinate towards the younger units (Yoredate-type cyclothems). Numerous, prefectly preserved calcareous algae and microprobematics, as well as fairly frequent conodonts indicate an overlapping of the succeeding uppermost Viséan strata, and precise the position of the Viséan/Namurian and Namurian B / Namurian C boundaries.The fine conodont zones have been distinguished: the Lochriea nodosa, the Lochriea cruciformis, the Gnathodus bollandensis, the Idiognathoides sinuosus-Idiognathoides delicatus, and the Idiognathoides tuberculatus zones. The lower boundary of the cruciformis Zone is postulated to coincide with the Viséan/Namurian boundary. The presence of Idiognathoides tuberculatus Zone indicates a close relationship of the Lublin Basin with the upper Bashkirian basins of the East European Platform.A distinction of the five algal zones: the Konickopora, the Kulikia sphaerica, the Calciforlium punctatum, the Calcifolium okense, and the Masloviporidium-Anthracoporellopsis zones enables to correlate regional complexes as well as distant sections, ranging from northern England to the Ukrainian Lvov-Volhynian Basin, and farther east to the Mosco and Dneper-Donets Basins, in the interval corresponding to the lates Viséan - earliest Namurian.The microfacies spectrum of limestone complexes and bands, dominated by the lagoonal algal and spiculitic, and the more distal foraminiferal and cironoidal lithotypes, bears evidences of local and temporary shoalings marked by peloid microfacies suceesion in the Limestone Band C (random arrangement) and Limestone Band F (shallowing upward), and application of Leeder and Strudwick's sedimentary models indicate a transformation of sedimentary regime in the earliest Namurian. An autocyclic, deltaic pattern of the late Viséan changed into an allocyclic system in the Namurian A, with duration of particular cycles estimated as about 500 k.y. This sedimentary turnover is recognised to coincide with the beginning of the Gondwana glaciation, and thus it suggests an eustatic cause of the lower Namurain cyclicity in the Lublin Carboniferaous Basin.