Comparison of facies and petrography of Permian-Triassic boundary sections of Turkey, China and Japan: implications for causes and environments of the end-Permian mass extinction
Abstract
The causes of the end-Permian mass extinction (251 Ma), the most severe catastrophe in Earth's history, remain controversial. We present a global comparison of the facies succession across the Permian Triassic boundary (PTB) in Turkey, China and Japan and discuss implications for causes of extinction. In Turkey, microbialite framestone overlies the PTB, which is exhibited by a sharp truncation surface in oolite. This surface is encrusted with aragonite fans and contains no evidence of subaerial exposure. The upper half of the microbial unit is composed of wavy-bedded microbial laminae exhibiting evidence of soft sediment deformation. The PTB in China occurs at a sharp truncation surface lacking evidence of subaerial exposure similar to that found in Turkey. However, the surface occurs at the base of the microbialite and no oolite is present. Here, aragonite fans are more abundant in the basal part of the microbialite and soft sediment deformation is lacking. The PTB boundary section in Japan consists of dolomitized skeletal packstone overlain by dolomitized microbialite, and coquina limestone. Unlike China and Turkey, a truncation surface is not apparent in outcrop. However, petrography of the oldest microbialite sample reveals a truncation surface at the base of the microbialite. Aragonite fans are abundant throughout the microbialite and exhibit distinct morphologies. In some cases they nucleate on the microbial framework and radiate out into internal cavities; in other cases, they grow into the sediment. One sample contained small rounded grains that resembled ooids but the grains were entirely composed of radial aragonite crystal aggregates. The truncation surface, microbialites, and aragonite crystal fans formed in marine deposits synchronously across the global tropics during and following the end-Permian mass extinction. The global formation of a truncation surface in the marine environment is consistent with a rapid delivery of CO2 and a resulting decrease in pH and carbonate saturation of seawater that caused dissolution of carbonate sediments on the seafloor. The global precipitation of calcified microbialites and aragonite fans can be explained by subsequently increased carbonate and silicate weathering on the continents and delivery of carbonate alkalinity to the oceans by river systems. Rapid and massive delivery of CO2 to the oceans and atmosphere is most plausibly explained by interactions between Siberian Traps lavas and carbon-rich sedimentary strata of the Siberian craton.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2006
- Bibcode:
- 2006AGUFMPP23B1755S
- Keywords:
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- 4999 General or miscellaneous