Ichnology, palaeoenvironment, and ecosystem dynamics of the Early Cambrian (Stage 4, Series 2) Guanshan Biota, South China

Abstract

The Guanshan Biota of the Wulongqing Formation (Cambrian Series 2, Stage 4) is a typical Burgess Shale‐type Lagerstätte, containing not only a diverse assemblage of exceptionally preserved body fossils but also abundant, sophisticated trace fossils. Detailed ichnological study of the lower part of the Wulongqing Formation from the Longbaoshan and Xinglongcun sections in the Kunming area, Yunnan, South China, reveals the presence of 17 ichnospecies, including Aggregatella isp., Cruziana isp., Didymaulichnus lyelli, Diplichnites isp., Guanshanichnus glockerichnoides, Monomorphichnus isp., Palaeophycus isp., Planolites beverleyensis, Planolites montanus, Planolites isp., Psammichnites isp., Phycodes isp., Skolithos verticalis, Thalassinoides isp., Treptichnus pedum, and two types of non‐specific coprolites. These trace fossils represent burrowing or locomotion behaviours of arthropods and vermes, and belong to the Cruziana and Skolithos ichnofacies. As the outcrop at the Xinglongcun section is not well exposed, a systematic sedimentary study was conducted at the Longbaoshan section. The Guanshan ichnofauna in the lower Wulongqing Formation at the Longbaoshan section occur in fine‐grained siliciclastic rocks with wavy bedding, lenticular bedding, and wrinkle structures, reflecting a tidal flat environment. The abundance of diverse trace fossils in the tidal flat facies indicate that many taxa, mostly arthropods, were able to colonize the very shallow marine environments, supporting the landward expansion of the Early Cambrian ecosystems.