Carbon isotope stratigraphy of the basal Zechstein (Lopingian) strata in Northern Poland and its global correlation

Abstract

 The Kupferschiefer (T1) records a period of basin-wide euxinic conditions, and is thus considered an excellent time-marker in the Zechstein (Lopingian) basin. Previous studies indicated that both the Kupferschiefer and Marl Slate and the overlying Zechstein Limestone (Magnesian Limestone) show remarkable changes in carbon isotopic composition towards higher 13Ccarb values. We have examined the Kupferschiefer of the Zdrada IG 8 borehole that has recently been studied in detail by Pašava et al. (2010) aiming to use the carbon isotope data from the basal Zechstein for stratigraphic correlation of the Zechstein basin with the global isotopic curve for Late Permian. The δ13C values in the Zdrada IG 8 change from +0.7‰ at the Kupferschiefer base to +5.4‰ in its middle part, then decrease to +1.7‰ at the Kupferschiefer top and next rapidly increase to +3.5‰ (in the lowest part of the Zechstein Limestone) and finally to +5.1‰ (0.5 m above). This increasing trend continues into the Zechstein Limestone; all subsequent Zechstein marine carbonates show highly positive d13C values. The δ13C curve that best shows the Zechstein base may lie near a sequence boundary in the upper Guadalupian of South China that postdates the mid-Guadalupian extinction, but the early Wuchiapingian conodonts reported from the basal Zechstein deposits elsewhere exclude such an interpretation. The increase recorded in the interval from the Kupferschiefer to the Main Dolomite fits well the increase of the δ13C values observed after Isotope Event 0 (some 258 Ma) of the isotopic curve for the Late Permian, although the increase in the Zdrada IG 8 is clearly more significant than that of the global δ13C curve. In turn, the subsequent slight fall that accelerated after Isotope Event 1 fits the more significant fall in the Platy Dolomite.