Our understanding of how and where the ancestors of modern life evolved has been the question of many paleontologists for a long time. Recently, an international team of sedimentologists and paleontologists, including Dr. Luis Buatois, Dr. Gabriela Mángano, and Dr. Maximiliano Paz, demonstrated that a world-famous Cambrian soft-bodied fossil assemblage in Yunnan province, China, lived and died in a delta front environment affected by storms. The Chengjiang Biota records the exquisite preservation of soft-bodied marine invertebrates, including worms, early arthropods, and early vertebrates. This assemblage is around 518 million years old, around the time of the famous Cambrian explosion, where modern communities of animals first started to truly diversify. The Chenjiang biota has a similar faunal makeup to the Burgess Shale biota from British Columbia, Canada. The team analyzed a core taken from Cambrian outcrops in Yunnan, China, and discovered that the sequence of strata was formed in a shallow marine, deltaic environment. High rates of sedimentation and indications of high salinity point to this deltaic environment being dominated by storms and river floods. These kinds of sediments help us to understand the exceptional taphonomy of fossils from these Cambrian assemblages.

Figure. Block diagram showing the storm-flood-dominated delta and associated cores showing depositional sequences. (From F. Saleh et al., 2022)

The full article can be accessed in Nature Communications.

Written by Jack Milligan