Ichnology of the Ordovician Cruziana rugosa group in Western Europe and in the Near East and its palaeoecological potential for Mediterranean Gondwana

点击翻译按钮获取中文摘要

The Ordovician represents a period of dramatic changes in the biosphere. Initiated by fundamental climatic, oceanographic and transitions of exogenic material cycles, an unprecedented diversification of marine life led to palaeoecological differentiation and to changes in the organism-substrate interactions, which are important tools for numerous geological applications, such as biostratigraphy, palaeogeography, modelling of living and depositional environments and their regional and transregional correlation. Such transformations are documented from this period – when marine shelfs reached their widest extension in the entire Phanerozoic (Ordovician) – especially from the shallow marine realm. While different groups of marine invertebrates from the Ordovician period have been well studied with regard to their importance as biostratigraphic and palaeoecological tools, the usefulness of Ordovician ichnocoenoses, however, has so far only rarely been subject of in-depth studies. There is a distinct knowledge gap particularly for the widespread peri-Gondwanan deposits without any body fossil content – the closing of this gap must be classified as a major task of the international Ordovician research. The proposed project aims to investigate the „Mediterranean Province“ of the northern peri-Gondwanan shelf area in present-day NW France (Armorican Massif, Brittany) and in the Near/Middle East (SE Turkey and S Jordan, Arabian Plate) with respect to its Lower Ordovician ichnofauna, in particular to the characteristic Cruziana rugosa group. In preparation to the project, in the above-mentioned areas the project working group succeeded in the discovery of hitherto unknown spectacular trace fossil sites of Cruziana rugosa group assemblages. By an interdisciplinary approach, which combines palaeontological-palaeobiological and sedimentological-facies methods, it will be possible to capture spatiotemporal characteristics of the Cruziana rugosa group and to define their potential as a facies, a palaeoecological, a paleogeographic and a transregional correlation tool in geosciences. Modifying local factors will be identified along a palaeogeographic gradient, and will be result in the reconstruction of palaeo-latitudinal diversity shifts. Largely based on the high quality and the palaeogeographical position of the newly discovered fossil sites in Western Europe and the Near/Middle East a reliable tool for transregional correlation at the northern peri-Gondwanan rim will be developed by palaeontological and sedimentological studies as well as by palaeoecological, facies and palaeogeographical conclusions. The proposed project fills a critical gap in the current international efforts of investigation of the Lower/Middle Ordovician Biosphere and of the fundamental qualitative changes in the biosphere-geosphere interactions in the early Palaeozoic.