Late Carboniferous tectono-sedimentary evolution and related terrestrial biotic changes on the North Variscan and Appalachian forelands, and adjacent paralic and continental basins

Abstract

The general characteristics of the Pennsylvanian climate, palaeogeograrhy, tectonic processes and changes of terrestrial biotas are analysed based on an extensive set of published data. Data are also presented on the geotectonic and ralaeogeographical position, as well as the tectono-sedimentary evolution of the main basins across the Euramerican coal province, and the character of the strata around the Westphalian – Stephanian boundary in these basins. Controls potentially responsible for floristic changes and the decline of the coal measures forests are discussed. Among those which have appeared in the literature, the most important are global climate change, tectonism related to the Variscan Orogeny resulting in a decrease of subsidence rate and onset of basin inversion, palaeogeographical changes related to the formation of Pangea producing orographic barriers that affected precipitation-distribution and continental drift through the latitudinal climate belts. Since all these processes operated simultaneously, the final effect on terrestrial biotas is most probably the result of an interplay of all these controls. In the North America, the most important basins with a more or less complete sedimentary record across the Westphalian – Stephanian boundary are the Western and Eastern Interior Basins, the Appalachian Basin and the Canadian Maritimes Basin, which have been interpreted as cratonic, foreland and strike-slip basins respectively. In Europe, this boundary is recorded from the South Wales and the Upper Silesian Coal Basins in the North Variscan foreland and from adjacent continental basins (Saar-Lorraine, basins of the Bohemian Massif and South Carpathian area, and the Dobrudzha Basin located on the Moesian Platform). Different palaeogeographical and geotectonic positions of the basins provide an excellent platform for comparison of common and specific features in sedimentary and palaeontological records, and consequently the identification of the most important controls operating in each basin. Finally, it may allow us to identify the main mechanism responsible for the decline of tropical mires and the accompanying floristic changes.