SKELETAL ABUNDANCE AND EARLY ANIMAL REEFS: HOW REEF OCCURRENCES INFLUENCED SKELETONS IN EARLY PALEOZOIC SEAS (Invited Presentation)

The expansion of early skeletal organisms began in late Ediacaran time, with the appearance of cloudinids, Namacalathus, Sinotubulites, among other organisms. Skeletal organisms increased in diversity and abundance during the Cambrian, but it was not until the Great Ordovician Biodiversification Event that skeletons contributed significantly to carbonate production in the shallow marine realm. While this broad pattern has been recognized, what has been less well studied is the nature and distribution of skeletal organisms across environments throughout the Cambrian, particularly during the rise and fall of early Cambrian animal reefs. Recent analysis of skeletal abundance in archeaocyathan reefs and adjacent settings in the western United States shows that reefs influenced skeletal carbonate production, both within and outside of reef settings. Reef and non-reef samples from the Wood Canyon, Campito, Poleta, Harkless, Mule Springs and Carrara formations reveal shifts in diversity and abundance of carbonate skeleton producers throughout this interval. Skeletal animal diversity and abundance show a peak in the mid to late early Cambrian that coincides with abundant archaeocyathan reef development. In the aftermath of their extinction, common carbonate skeleton producers are limited to trilobites and echinoderms, and the number of clades contributing to carbonate skeletal production is low. These results suggest that the appearance and expansion of carbonate skeletal producers in the early Paleozoic is linked to animal reef development and likely influenced by hospitable environments.