Sponge Takeover from End-Permian Mass Extinction to Early Induan Time: Records in Central Iran Microbial Buildups

The end-Permian mass extinction was the most severe biotic crisis in Earth’s history. In its direct aftermath, microbial communities were abundant on shallow-marine shelves around Tethys. They colonized space left vacant after dramatic decline of skeletal metazoans. presence sponges and sponge bioherms has largely gone unnoticed due to sponges’ size cryptic method preservation. addition dominated facies recently described South Armenia Northwestern Iran, we describe here sponge-microbial cropping out two well-known Permian-Triassic boundary localities: Kuh-e Hambast section, south-east Abadeh city more distal Shahreza near Isfahan. both sections, horizon is located at top an upper Changhsingian ammonoid-rich nodular limestone, called Paratirolites limestone. At Hambast, overlying decimetric thick shale deposit “boundary clay,” latest Permian age, conformably overlain by well-dated transgressive basal Triassic platy limestone containing four successive levels decimeter meter scale, elongated form cup-shaped mounds made branching columnar stromatolites. Sponge fibers from possibly keratose demosponge, are widely present lime mudstone matrix. above level, clay much thicker (3 m), with thin intervals, contains main scale digitate microbialite crossing similar fibers. Three rich thrombolite domes can be seen 20 m earliest age. rare spicules their micritic These which post-extinction clay, followed buildups during Griesbachian time.