Geol. Mag. 144 (3 ), 2007, pp. 417–448. c  2007 Cambridge University Press 417 doi:10.1017/S0016756807003330 First published online 23 March 2007 Printed in the United Kingdom A comparative analysis of some Late Carboniferous basins of Variscan Europe STANISLAV OPLU ˇ STIL ∗ & CHRISTOPHER J. CLEAL † ∗ Charles University in Prague, Faculty of Science, Albertov 6, 128 43 Praha 2, Czech Republic †Department of Biodiversity & Systematic Biology, National Museum Wales, Cathays Park, Cardiff CF10 3NP, UK (Received 6 February 2006; accepted 1 August 2006) Abstract – Vegetation diversity and pattern changes, and their relation to tectono-sedimentary histories are compared between selected Euramerican Late Palaeozoic coalfields, to understand better the controls on the dynamics of the Pennsylvanian terrestrial ecosystems and to demonstrate the problems with comparing data from various basins. The analysis is based on data from the following basins of different geotectonic and palaeogeographical positions: the cratonic Pennines Basin, the foreland South Wales and Upper Silesia basins, and the fault-related Intra Sudetic and Central and Western Bohemia basins. The analysis indicates that complex factors are responsible for changes in plant diversity and vegetation patterns. These are related to climate, tectonics, preservation potential, sampling biases and the current state of revision of the flora in each basin. Plant diversity patterns in the basins differ because of local controls and/or the character and detail of the available data. Maximum diversity varies among the basins within the Langsettian and Duckmantian substages. Two apparent step-like drops in diversity were detected within coal-bearing strata of most basins: at the Duckmantian/Bolsovian boundary and at the Bolsovian/Asturian boundary. Further and more prominent falls are related to transitions from coal-bearing to non-coal-bearing (mostly red bed) strata or vice versa during Stephanian times. Interpretation of climatic signals recorded in the sedimentary successions indicates that Westphalian and middle Stephanian times were wet intervals, whereas early and late Stephanian times were drier. Keywords: Pennsylvanian, palaeobotany, biodiversity, Variscan Foreland. 1. Introduction The Pennsylvanian Subperiod was one of the most important times of coal formation in Earth history. Extensive lowland areas of palaeotropical Euramerica and China were covered by extensive wetland forests dominated by arborescent lycopsids and sometimes marattialean tree ferns. For a combination of biological and taphonomic reasons, these forests resulted in the build-up of thick peat deposits which have since been converted into coal (Cleal & Thomas, 2005), hence these forests are often referred to as the coal forests. Our understanding of this general character of Pennsylvanian times has recently been improved by detailed palynological and floristic studies, which have revealed the existence of various environmentally or climatically controlled floral biomes, as well as biotic changes and extinctions through the time interval (e.g. Phillips, Peppers & DiMichele, 1985; DiMichele & Phillips, 1994; DiMichele, Pfefferkorn & Phillips, 1996; DiMichele, Pfefferkorn & Gastaldo, 2001; Falcon-Lang, 2003). Thus, we now know that the Euramerican coal forests were established to their maximum extent by the end of Early Pennsylvanian times, and began to disintegrate towards the end of †Author for correspondence: chris.cleal@museumwales.ac.uk Middle Pennsylvanian times, when most tree lycopsids were replaced by tree ferns. In Euramerica, the remains of coal forests had all but disappeared by the end of Late Pennsylvanian times, although extensive areas of forest persisted in China through into Permian times. This disintegration of the Euramerican coal forests was accompanied by global climatic warming (e.g. Cleal & Thomas, 2005; Gastaldo, DiMichele & Pfefferkorn, 1996) and in low palaeolatitudes by drying recorded by alternating coal-bearing and coal-barren red bed strata (e.g. Besly, 1987, 1988). Mechanisms responsible for these changes in the Pennsylvanian terrestrial ecosystems are frequently discussed (e.g. Phillips, Peppers & DiMichele, 1985; Rowley et al. 1985; Besly, 1987; Parrish, 1998; Cleal & Thomas, 1999; Scotese, Boucot & McKerrow, 1999; Falcon-Lang, 2004; Opluˇ stil, 2004). However, the importance of individual controls on the biotas still re- mains rather speculative, due to the general absence of broad comparative analyses of the tectono-sedimentary, climatic and fossil records between different basins. For example, Phillips, Peppers & DiMichele (1985) demonstrated an apparent change from arborescent- lycopsid to arborescent-fern vegetation around the Middle/Upper Pennsylvanian boundary, based on coal- ball and palynological analyses of mainly North American coals. However, it has since been shown that