The end-Permian mass extinction (EPME) and the Early Triassic biotic recovery in the western Dolomites (Italy): state of the art

The Dolomites (Southern Alps, Italy) represent a key-area to study the biotic and environmental events connected to the end-Permian mass extinction (EPME) and the Early Triassic biotic recovery of shallow-marine ecosystems. Geological and palaeontological researches on these events began since in the early 19th century. The contributions of these studies to the stratigraphic setting, dating, intensity, pattern and causes of the EPME and Early Triassic biotic recovery are outlined herein. After almost two centuries of research, our present undestanding suggests the following multi-steps scenario. The EPME occurred during a short extinction interval, which started at the base of transgressive oolitic beds of the Tesero Member (Werfen Formation, latest Changhsingian). The early phase lasted only a few millennia. It caused a dramatic drop of fossil abundance and diversity and the extinction of about 65% of existing genera, including the large-sized brachiopods and molluscs. The second phase affected the sparse stenotopic marine organisms, most had survived within microbial communities, and finished just above the Permian/ Triassic boundary a few thousand years after the first phase. Stressed environmental conditions, recorded by low diversified benthic assemblages dominated by disaster taxa, lasted up to the lower Olenekian Campil Member (Werfen Fm.). The early biotic recovery phase, recorded by the reappearance of stenotopic organisms and an increase in biodiversity occurred about 1.3 Myr after the EPME witnessed in the Tirolites cassianus beds of the Val Badia Member.