Environmental and evolutionary controls on Triassic reef recovery Case studies from isolated and attached carbonate platforms in South China Jonathan L. Payne, Department of Geological & Environmental Sciences, Stanford University The re-establishment of platform-margin reef complexes during the Middle Triassic, nearly 5 million years after end-Permian mass extinction (252.6 Ma), has been viewed as an important sign of biotic recovery from the end-Permian event. However, the timing of reef initiation of carbonate platform margins and its relationship to coeval environmental amelioration remain poorly constrained. We have used an exceptionally-exposed reef in south China to obtained detailed information on the timing and environmental context of reef initiation and on the spatial and temporal distribution of reef builders within a Middle Triassic reef complex. Our research shows: Reef recovery began in early Anisian time, as indicated by heavy carbon isotope values in the stratigraphically lowest parts of the reef. 2. Reef recovery coincided with a reduction in the carbon isotope gradient from shallow to deep water, suggesting shallow-marine anoxia and its associated effects on the composition of primary producers may have inhibited recovery prior to Middle Triassic time. 3. Following reef initiation, the diversity and abundance of framework-building organisms increased gradually. However, Tubiphytes and early marine cements continued to form the vast majority of the reef framework throughout the Middle Triassic.