Evidence of sea-level fall in sequence stratigraphy: Examples from the Jurassic

The inference of relative sea-level change is fundamental to sequence strat igraphy, but in many situations determination of sea-level rise, with assoc iated marine transgression, is more reliable than sea-level fall. This is e specially true of epicontinental marine successions characterized by low su bsidence and sedimentation rates and only limited influx of coarse silicicl astic sediments. In either the Exxon or Galloway schemes of sequence strati graphy, offshore condensed sections are taken as evidence of sea-level rise and are normally associated with maximum flooding surfaces. However, conde nsed sections may grade into stratigraphic hiatuses or disconformities of a very different character from what are interpreted as sequence-hounding un conformities in the Exxon scheme. There may also be evidence of the erosion of significant amounts of consolidated rock, which is more plausibly accou nted for by relative sea-level fall leading to emersion than to unusually i ntense storm or current activity in a submarine setting. Several examples f rom the European Jurassic are discussed here.