Mass Extinction In South China Research Articles

Survival strategies of brachiopod faunas from the end-Permian mass extinction

Global reviews reveal that 102 brachiopod species (including 40 indeterminate species) belonging to 43 genera within 27 families survived the end-Permian mass extinction in South China, the Himalayan regions (southern Tibet, Nepal, Salt Range and Kashmir), southern Alps (Italy), Arctic Canada, western USA and Western Australia. Of these, the surviving brachiopods are most abundant and widespread in South China where they occur in 32 of the 42 Permian–Triassic (P/T) boundary sections around the world. Brachiopod faunas are the most abundant and diverse post-extinction survivors, and their appearance above the end-Permian mass extinction horizon somewhat masks recognition of the end-Permian extinction. These surviving brachiopods occur in three stratal intervals corresponding to the “Mixed Fauna Beds” (MFB hereafter) 1–3 of the P/T boundary beds. A sharp drop in diversity of the brachiopod faunas coincides with the widely accepted end-Permian mass extinction horizon. The post-extinction brachiopods were also affected by a subsequent crisis corresponding to the boundary between MFB 2 and MFB 3 so that most survivors were extinct approximately 0.7 Ma after the end-Permian mass extinction. The surviving brachiopods were mainly Productida, followed by Spiriferida. In particular, small chonetids, chonetid-like productellids and smooth, thin-shelled ambocollid spiriferids are most abundant. Lingula is extraordinarily abundant and widespread approximately 0.7 Ma after the greatest extinction when many regions became devoid of articulate brachiopods. Widespread, broadly adapted and small-sized taxa preferentially survived. Frequent intrageneric speciation of widespread, widely adapted generalist genera enabled survival brachiopods to occupy rapidly and efficiently vacant ecospace in the aftermath of the end-Permian extinction. The ecological habitats of the post-extinction brachiopods are subdivided into nearshore, epeiric sea, restricted carbonate platform, open carbonate platform, ramp and outer shelf environments. Of these, the survival brachiopods are most diverse in the open platform environments. The nearshore zone provided ideal habitats for the nonarticulated brachiopods to occupy; whereas the survivors in the outer shelf are predominantly chonetids and chonetid-like productellids. The most successful survivors, the productid brachiopods, are widely distributed in six types of ecological habitats and thus have no apparent preference for specific environments. The end-Permian extinction resulted in the movement of biogeographical provinces towards the palaeo-equator. The brachiopods survived mostly in the palaeo-equatorial provinces and along the southern margins of the Palaeo-Tethys Ocean.

Calcimicrobialite after end-Permian mass extinction in South China and its pa-laeoenvironmental signifi-cance

Calcimicrobialites, which could be correlated to the layer 27 in Meishan section according to the Hindeodus parvus, occur abruptly on the end-Permian mass extinction boundary in South China. Microbialites mainly distribute on the top of reef facies or shallow carbonate platforms, thinning into deep facies. All the microbialites discovered are composed of micrite and coarse crystal digitate carbonate or patch carbonate. Microfossils usually dominate in the microbialites, and small gastropods, bivalves and ostracodes can also be found. This fossil assemblage represents a simple but particular remanent biota after the end-Permian mass extinction on the top of reefs or shallow carbonate platforms. Abrupt occurrence of microbialites above the mass extinction boundary is the ecological response to the end-Permian global event in reef or shallow carbonate facies. Many studies have been done on the Permian-Triassic boundary and event in deep water facies sections or middle to lower shelf facies sections. However, the calcimicrobialites in South China are mainly located above reef facies or shallow carbonate platform facies. It will surely be helpful for people to know more about the different responses in different depths of ancient marine environment during the transition between Permian and Triassic by the study of petrology, palaeontology and palaeoecology of the calcimicrobialites.