Drilling in the Atlantic Ocean basin has revealed large quantities of organic matter throughout Cretaceous strata. The organic-rich deposits in the North Atlantic do not appear to be genetically related to those in the South Atlantic. There are clear differences in the character of the organic matter and its possible origins.

The contrast in type of organic matter preserved in Cretaceous strata from the North and South Atlantic can be explained by continental drainage patterns and evolutionary stages of ocean basin development. During the Early Cretaceous, a less evolved, much more restricted South Atlantic exhibited conditions favorable to production and preservation of marine organic matter. This is in contrast to the more evolved, more open North Atlantic throughout the Cretaceous, and the Late Cretaceous South Atlantic. This evolutionary development of Atlantic passive margins aids in explaining the observed distribution of oil and gas discoveries.