Brachiopod communities of the Early Cambrian Guanshan Lagerstätte of Yunnan Province, China, and their associated facies.
[sciencythoughts.blogspot.com]
Discoveries of spectacular soft-bodied animal assemblages from Cambrian Konservat-Lagerstätten around the world have provided incredible insights into the anatomy, behaviour, ecology and early evolution of complex Metazoans. Early Cambrian Konservat-Lagerstätten from China, such as the Niutitang Fauna, Chengjiang Biota, Guanshan Biota, Shipai Biota, Balang Fauna, Kaili Biota and the newly discovered Qingjiang Biota, span a wide range of geological time and provide a unique opportunity to map changes in Early Cambrian ecological communities over time. The Guanshan Biota (Cambrian Series 2, Stage 4), one of the oldest Konservat-Lagerstätten from South China, occurs in the Wulongqing Formation in eastern Yunnan. Younger than the famous Chengjiang and Malong biotas (Cambrian Series 2, Stage 3), but older than the Kaili and Burgess Shale biotas (Miaolingian Series, Wuliuan Stage), the Guanshan Biota is a significant evolutionary bridge in our understanding of the chronology of the Cambrian radiation and its aftermath. Recent intensive, although preliminary, excavations reveal that the Guanshan Biota is composed of 14 major animal groups and various ichnotaxa. Uniquely, the Guanshan Biota is dominated by Brachiopods, which serves to distinguish it from all other Cambrian Konservat-Lagerstätten, which are dominated (in terms of diversity and relative abundance) by Euarthropod groups. Faunal overturn between the Chengjiang, Malong and Guanshan biotas suggests that the sessile benthic members of the assemblages are affected by the same factors that affect mobile Trilobites. Furthermore, the Wulongqing Formation is characterized by bioturbated, thinly bedded sandstones, siltstones and mudstones, which crop out widely in eastern Yunnan, South China and represent a transgressive systems tract directly after the Hongjingshao Formation. Previous, very generalised, sedimentological work on the Wulongqing Formation suggests a relative shallow (shoreface to offshore transitional) depositional environment, which is distinct from the generally deeper water (in some cases slope to basin) setting of most other early Cambrian deposits that preserve soft tissues.