Continental Ecosystems at high palaeolatitude before and after the Devonian-Carboniferous boundary: two examples from South Africa and Argentina

PRESTIANNI, C.; GESS, R.; RUSTÁN, J. J.; BALSEIRO, D.; VACCARI, N. E.; STERREN. A.

Bruselas

Simposio; IGCP596?SDS Symposium; 2015

Institut Royal des Sciences naturelles de Belgique

The terrestrialization of living forms is by far one of the most important process that took place during the Palaeozoic. It deeply modified all ecosystems, both marine and continental. Characterized by an unprecedented increase of the biodiversity and of the biomass on emerged lands, it is also marked, at the end of the Devonian period by severe crisis in marine ecosystems as well as by climatic instability. We here report two assemblages situated at both sides of the Devonian/Carboniferous boundary. The first has been collected by R.G. in the Waterloo Farm locality (South Africa) and is latest Famennian in age. The second comes from the Tournaisian part of the Sierra de las Minitas (Argentina). The purpose of this communication is to compare two particularly different environmental settings documenting the changes that occurred globally at the Devonian/Carboniferous boundary. The Waterloo Farm locality represents a lagoonal system partially separated from the Agulhas Sea by a barrier island complex (Gess and Hiller, 1995). Fine black anaerobic muds deposited in still portions of the lagoon accumulated a huge mixed assemblage representing the life of marine and fresh water influenced parts of the lagoonal system, as well as that of adjacent terrestrial environments. Terrestrial remains largely consist of plant material comprising a minimum of fifteen taxa. These represent most major Late Devonian groups including zosterophyllopsids, trimerophytes, sphenophytes, herbaceous and arborescent lycopdsids, iridopterids and progymnosperms. This locality provides a unique holistic picture of high latitude continental life in Gondwana immediately predating the End Devonian Extinction event.The here reported Sierra de la Minitas deposits consist in fine to medium grained fossiliferous sandstones deposited in a marine environment (Prestianni et al., 2015). Fossils from this interval include brachiopods, bivalves, crinoids, orthoconic nautiloids, gastropods, scarce fish remains and plants. The plant assemblage reveal a low diversity flora dominated by herbaceous lycopsids but also present traces of ferns and seed plants. Tournaisian Gondwanan plant communities from high latitudes are interpreted as being more complex than previously thought. Their discovery in a sedimentary environment associated with glacigenic deposits, shows that this new record might be linked to the coeval glacial age widely recorded elsewhere in Gondwana.enviar mensaje