Paper No. 2
Presentation Time: 9:15 AM
ENVIRONMENTAL CONTROLS ON MARINE BIOTIC RECOVERIES FOLLOWING MASS EXTINCTIONS, WITH AN EXAMPLE FROM THE EARLY TRIASSIC
End-Permian mass extinction is accepted to be the severest biotic loss in Phanerozoic eon. The following biotic recovery in Early Triassic was delayed for ~5 Myr, though there were several early phases of recovery in this period. However, the cause of this prolonged biotic recovery in Early Triassic is unclear. Here we present a data set of TOC, major, minor and trace elements to calculate raw and flux value of primary productivity, terrestrial input and redox condition from Permian-Triassic (P-T) boundary to Spathian substage in Early Triassic at Chaohu, Daxiakou, Zuodeng and Spiti sections in South China Block and northern India. Our results turn out that 1) high nutrient level, high terrestrial input and reduced condition occurred at P-T boundary; 2) transient low nutrient level, low terrestrial input and oxidating condition occurred in early-middle Griesbachian; 3) high nutrient level, higher terrestrial input and reduced condition occurred in middle-late Induan; and 4) persist low nutrient level, low terrestrial input and oxidating conditions interrupted by high nutrient, terrestrial and reduced condition occurred in Olenechian. High terrestrial and reduced conditions concomitant with high nutrient level at P-T boundary exacerbated end-Permian mass extinction. Transient low nutrient level, terrestrial input and oxidating condition represents transient waning of environmental deterioration in early-middle Griesbachian. High nutrient level, terrestrial input and reduced conditions in middle-late Induan favored pelagic recovery by offering adequate food source, and, in the meantime, hindered benthos recovery by turbidity of water mass and reducing condition. Low nutrient level, terrestrial input and oxidating condition intermitted by high nutrient, terrestrial input and reduced condition in Olenechian favored pelagic and benthic recovery, but not led to the full recovery probably because of these unstable environmental conditions.