Carbon, oxygen, and sulfur isotope compositions and model of the Silurian rock formation in northwestern Belarus

Resumo

The paper describes the results of study of the Silurian clayey–carbonate rocks ranging from the Telychian Stage (Llandovery) to the Gorstian Stage (Ludlow) recovered by the Borehole Davtyuny 3k in northwestern Belarus. Rocks of the Sheinwoodian Stage demonstrate a positive excursion of δ¹³C with amplitude of 4.7‰, marking the Ireviken biotic event recorded in the global chemostratigraphic curve. Values of δ¹⁸O for the carbonate material in the studied section (25.5–29.2‰ SMOW) are close to those for Silurian rocks from the Baltic region, Scandinavia, Ukraine, Poland, and Canada. The whole section contains postsedimentary gypsum as nodules and the infilling of fissures and fenestrae. Values of δ³⁴S in gypsum (21.3–26.7‰ CDT) are close to those for the Silurian rocks on the Phanerozoic isotope plot. The formation of gypsum was related to a partial development of the supralittoral environment over the sublittoral and littoral clayey–carbonate substrate. The seawater accumulated in lowlands of the supralittoral plain after storms was intensely concentrated during arid conditions and accumulated in the clayey–carbonate sediment. The subsequent underground evaporation promoted the formation of gypsum as nodules in the unlithified sediments and the infilling of fissures and fenestrae in the lithified rocks.