Geology Department, Pomona College, 185 E. Sixth St., Claremont, CA 91711, USA.
School of Biological Sciences & Environment Institute, University of Adelaide, Adelaide, SA 5005, Australia.
Sci Adv. 2024 Jul 26;10(30):eadp2650. doi: 10.1126/sciadv.adp2650.
The Emu Bay Shale (EBS) of South Australia is anomalous among Cambrian Lagerstätten because it captures anatomical information that is rare in Burgess Shale-type fossils, and because of its inferred nearshore setting, the nature of which has remained controversial. Intensive study, combining outcrop and borehole data with a compilation of >25,000 fossil specimens, reveals that the EBS biota inhabited a fan delta complex within a tectonically active basin. Preservation of soft-bodied organisms in this setting is unexpected and further underscores differences between the EBS and other Cambrian Lagerstätten. Environmental conditions, including oxygen fluctuations, slope instability, high suspended sediment concentrations, and episodic high-energy events, inhibited colonization of the lower prodelta by all but a few specialist species but favored downslope transportation and preservation of other largely endemic, shallow-water benthos. The EBS provides extraordinary insight into early Cambrian animal diversity from Gondwana. These results demonstrate how environmental factors determined community composition and provide a framework for understanding this unique Konservat-Lagerstätte.
南澳大利亚的鸸鹋湾页岩（EBS）在寒武纪特异埋藏化石中较为独特，因为它捕捉到了在布尔吉斯页岩型化石中罕见的解剖学信息，而且由于其推测的近岸环境，其性质一直存在争议。通过对露头和钻孔数据的综合研究，以及对超过 25000 个化石标本的汇编，揭示了 EBS 生物群栖息在构造活跃盆地内的扇三角洲复合体中。在这种环境中保存软体生物是出乎意料的，这进一步强调了 EBS 与其他寒武纪特异埋藏化石的不同之处。环境条件，包括氧气波动、边坡不稳定、高悬浮物浓度和间歇性高能事件，抑制了除少数专门物种以外的所有物种在下部前三角洲的定殖，但有利于下坡运输和保存其他主要为地方性的浅水底栖生物。EBS 为冈瓦纳大陆的早期寒武纪动物多样性提供了非凡的见解。这些结果表明环境因素如何决定群落组成，并为理解这种独特的保存化石提供了框架。
