TERRESTRIAL ECOSYSTEM STABILITY IN THE SEPURKOVIAN (NAMURIAN) TO BASHKIRIAN (LANGSETTIAN) OF THE SILESIAN BASIN, CZECH REPUBLIC

The Silesian Basin, Czech Republic, and coeval basins in Poland and Ukraine, record Late Mississippian and Early Pennsylvanian marine and continental cyclothemic deposits that accumulated within braidplain, coastal plain, and marginal-to-marine settings. Stratigraphic thickness exceeds 5200 m and encompasses the Sepurkovian-Bashkirian, Mid-Carboniferous boundary as identified by the classic Floral Gap of Gothan. The Ostrava Fm. is Mississippian and consists of the Petřovice, Hrušov, Jaklovec, and Poruba Mbrs., whereas the Karvina Fm. is Pennsylvanian in age and consists of the Saddle, Sucha, and Doubrava Mbrs. A change from paralic to limnic deposits occurs across the boundary.

The cyclothemic stratigraphy is interpreted within sequence stratigraphic context, with TSTs identified on the presence of marine invertebrate assemblages overlying LST coal-bearing intervals. Eighty marine zones are known and are grouped into 21 horizons, all of which are considered to represent HSTs above an MFS. The Mississippian Ostrava Fm. contains 55 of these cycles, several of which have stacked marine horizons separating coal-bearing intervals.

Peat mire and extrabasinal isotaphonomic assemblages occur within each coal-bearing interval, and provide a comprehensive data set on terrestrial ecosystem dynamics during the buildup of Gondwanan glaciation. Results of UPGMA cluster analysis and Bayesian data mining demonstrate similar trends of assemblage stasis throughout the Ostrava Fm. Clusters consist of assemblages from the Petřovice and lower Hrušov Mbrs., the Upper Hrušov and lowermost cycle in the Jaklovec Mbr., and the remainder of the Jaklovec and Poruba Mbrs. The Gaebler Horizon clusters independently, whereas the Pennsylvanian assemblages cluster separately. The vegetation persists within each Mississippian cluster for an average of 18 depositional cycles. Results from Bayesian statistical analysis are similar; distinct assemblages occur within the Petřovice and Hrušov Mbrs., whereas assemblages within the Jaklovec and Poruba Mbrs. are indistinguishable. Terrestrial ecosystems persist in the Late Mississippian for several million years before systematic changes in assemblages occur. These changes come at threshold stratigraphic horizons that may be related to missing continental lithologies.