A time-based approach to source rocks and associated fine-grained units employing a framework of large-scale stratigraphic sequences provides a high-level scoping tool to pinpoint the temporal position of potential organic-rich, core mudrock facies throughout Phanerozoic time. Utilizing a composite global eustacy curve taken from published sources, a total of 45 second-order flooding intervals are noted, 16 of which correspond to times of larger, more extensive, extrabasinal transgressions. Each of the 45 flooding events is associated with development of an organic-rich, core mudrock facies that has potential to serve as a local to interregional source kitchen for unconventional mudrock plays. Individual second-order core mudrock units may vary widely in terms of generative potential owing to differences in global to local geologic conditions at time of depositional and to differing post-depositional histories. Individual 2nd-order intervals must therefore be carefully assessed using a variety of geologic, geochemical, and petrophysical methods in order to define present-day resource potential.