"DISASTER OOLITES" IN THE PERMIAN-TRIASSIC BOUNDARY INTERVAL, TAURIDE MOUNTAINS (TURKEY)

The Permian-Triassic boundary in the Aladag and Antalya nappes (Tauride Mountains, Turkey) occurs immediately above a thin (~60 cm) oolite. In both areas the oolite is overlain by 16-18 m of stromatolites, which in turn are succeeded by another 9-29 m of mostly oolite. Whereas the basal Triassic stromatolites and oolites are nearly devoid of bioclasts, Upper Permian carbonates beneath the boundary oolite are wackestones and packstones with diverse invertebrates, dasycladacean and gymnocodiacean algae, and smaller foraminifers.

Basal Triassic stromatolites and other microbialites occur at many localities ranging from Mexico and Nevada through the Paleotethys region to South China. They have been interpreted as "disaster forms" that accumulated in the aftermath of the end-Permian mass extinction. According to this interpretation, stromatolites developed in shallow shelf and platform settings in the absence of grazing pressure and(or) competition from marine invertebrates.

The intimate facies association of oolites and stromatolites in widely separated Turkish sections leads us to speculate that deposition of oolites may also have been a response to the end-Permian mass extinction. We suggest that "disaster ooids" precipitated from marine water, which, in the near absence of shelly invertebrates, had become oversaturated with respect to calcium carbonate. By analogy, so-called "default" precitation of ooids has been documented in the western interior of the modern Caicos Platform, where nutrient-poor water limits the abundance of skeletonized organisms.