Evidence for a local reef eclipse in a shallow marine carbonate environment following the regional extinction of archaeocyaths in Laurentia (Stage 4, Cambrian)

摘要: Archaeocyathan sponges were the dominant metazoan framework builders during Series 2 of Cambrian. After their near extinction Toyonian stage (middle Stage 4), this important ecological role was eventually filled by robustly skeletonized lithistid sponges. However, exact timing restructuring is not well understood and likely contemporaneous across different paleocontinents. For example, reefs from Wuliuan China appear to show rapid replacement archaeocyaths with sponges, yet earliest occurrence lithistids in Laurentia until early Furongian. In study, we explore Mule Spring Limestone Nevada, which contains shallow water carbonate environments immediate aftermath regional archaeocyathan extinction, for signs reef-building activity. Within formation, find evidence sparse microbial-built leolites some potentially poorly preserved organisms. totality our field observations thin-section point counts suggest that there no substantial activity either microbial or organisms within study locality. Our data a local reef eclipse interval locality investigated. We also incorporate geochemical proxies determine paleoredox conditions, well-oxygenated marine conditions through period interest. Lack hardground substrate proposed as cause gap record. These results temporary loss framework-building occurred after demonstrates impact losing on environment.