Seminar

The Cambrian ‘explosion’ and the Great Ordovician Biodiversification Event (GOBE) are separated by a period of environmental and biotic turmoil. This aptly named Cambrian “dead interval” spans one of the most severe greenhouse climates of the past ~600 million years and records anomalous seawater conditions. This interval encapsulates several mass extinctions events, notably those of trilobite fauna in North America that demarcate regional “biomeres”. These extinctions are known to correspond with ocean anoxia and carbon cycle perturbations. I will present new chemostratigraphic and compiled biostratigraphic data from Cambrian successions of the North China/Sino-Korean block (NCB). These data help identify newly recognized trilobite extinctions in NCB upper Cambrian carbonate platform deposits, thus expanding the global extent of these biospheric perturbations. Coupled carbon and sulfur isotopic data (13Ccarb and 34SCAS) provide information on oceanic anoxic conditions during these extinctions. The cessation of these repeated extinctions coincides with global reductions in CO2 outgassing and climatic cooling, implying a causal linkage between baseline climate conditions and this extensive interval of ecosystem crisis. Collectively, these data help further elucidate the harsh environmental conditions that hindered early animal evolution.