Recurrent and Long-Term Oceanic Anoxia Contributed to Aborted Biotic Recovery Following the Permian-Triassic Crisis

Area of Science:

• Paleoceanography
• Marine geochemistry
• Paleontology

Background:

• The Early Triassic biotic recovery following the Permian-Triassic crisis is poorly understood.
• Ocean chemistry significantly influences marine ecosystem recovery.
• The Chaohu Area provides a critical site for studying this period.

Purpose of the Study:

• To evaluate the influence of ocean chemistry on Early Triassic biotic recovery in the Chaohu Area.
• To reconstruct the paleoceanographic conditions during the Early Triassic.
• To identify the environmental factors driving or inhibiting marine life recovery.

Main Methods:

• Analysis of pyrite content, δ¹³C_org, and S isotopic composition of pyrite.
• Reconstruction of ocean anoxia and oxic conditions using geochemical proxies.
• Correlation of geochemical data with biotic recovery events.

Main Results:

• Recurrent and long-term ocean anoxia characterized the Early Triassic in the Chaohu Area.
• Two distinct episodes of oxic conditions occurred in the earliest and late early Spathian.
• A positive δ¹³C_org shift and δ³⁴S excursion at the Smithian/Spathian boundary coincided with biotic recovery and oxic conditions.

Conclusions:

• Oxic conditions, potentially enhanced by global ocean circulation during climate cooling, contributed to biotic recovery.
• Frequent environmental perturbations and persistent ocean anoxia ultimately prevented sustained biotic recovery in the Early Triassic.