The only oceanic anoxic event documented from the Jurassic took place during the early Toarcian (~183 Ma). Since no DSDP (Deep Sea Drilling Project) or ODP (Ocean Drilling Program) cores have recovered black shales of this age—there being little or no Toarcian ocean crust remaining—the samples of black shale primarily come from outcrops on land. These outcrops, together with material from some commercial oil wells, are found on all major continents and this event seems similar in kind to the two major Cretaceous examples.