New conodont faunas from the Late Ordovician of the Central Carnic Alps, Austria

Conodont faunas recovered from both the Uggwa and Wolayer limestones of the Central Carnic Alps, Austria documented unequivocally the Amorphognathus ordovicicus Zone. Hamarodus europaeus (Serpagli, 1967), Scabbardella altipes (Henningsmoen, 1948) and Walliserodus amplissimus (Serpagli, 1967) represent some of the characteristic species. The association closely matches in composition and age the conodont material described on the Italian side of the Alps. A younger fauna was recovered immediately above a well-known brachiopod Hirnantia Fauna in the Cellon section, a classic reference for Silurian conodont biostratigraphy. The association keeps a clear Ordovician aspect having its markers in A. cf. A. ordovicicus Branson and Mehl. 1933 and A. lindstroemi (Serpagli, 1967). Elements of "Dichodella-Birksfeldia", possibly corresponding to the distinctive North American Gamachian genus Gamachignathus, are well represented. Taxa previously common in colder regimes, such as Sagittodontina and Istorinus, are also present. The abundance and moderate diversity of this fauna, composed of about twenty species, allow a first significant definition of the Hirnantian conodont fauna from the Atlantic Faunal Region

Large environmental disturbances caused by magmatic activity during the Late Devonian Hangenberg Crisis

A wide range of various proxies (e.g., mineralogy, organic carbon, inorganic geochemistry, C and Mo isotopes, and framboidal pyrite) were applied for interpretation of changing oceanic redox conditions, bioproductivity, and the regional history of magmatic activity. This resulted in internally consistent interpretation of the late Famennian Hangenberg Crisis in subtropical deepest water sites of the epeiric Rhenohercynian and Saxo\u2013Thuringian basins, as well as more open sites of the Paleo-Tethys Ocean. High mercury concentrations were detected in all of the studied sections, with the highest values strata in the Carnic Alps (up to 20 ppm) and Thuringia (up to 1.5 ppm). The beginning of the Hg anomaly and the presence of pyroclastic material, indicate that local magmatic activity was initiated before the deposition of the Hangenberg Black Shale (HBS). The onset of the HBS deposition coincided with the expansion of phosphate-enriched, anoxic to euxinic waters during short-lived CO2-greenhouse spike of a warm\u2013humid climate. Intensive magmatic activity was a trigger for climatic changes, an excessive eutrophication, and an accelerated burial of organic carbon during the Hangenberg transgressive pulse. The injection of catastrophic amounts of CO2, toxic elements and acids from volcanic activity could have led to acidification, mutation of spores, and episodes of mass mortality of marine plankton

Silurian stratigraphy and paleogeography of north Gondwanan and Perunican Europe

74 páginas.-- En: Landing, E. , and M.E. Johnson, Editors.Peer reviewe