The local signature of sea-level changes.

Black shales and iron-stones, often considered as the signatures of regressions and transgressions, are described by examples from the Devonian and the Jurassic. Sea level changes cause local changes in sedimentation rates -- an example is the South German Jurassic which indicates an average periodicity of 4 Myr; a periodicity which also appears likely for a Devonian example. There is no one-to-one correspondence between global sea-level changes and local transgressive-regressive cycles. -from Authors