Abstract
James Hutton (1726-1797) realised that earth history could be deduced from the unconformities found at outcrop. One hundred years later unconformities were used to propose that the Earth deformed in short-lived tectonic episodes of global extent. This arose, and is perpetuated, by describing the geological histories deduced from outcrop of unconformities as a sequence of distinct events: deposition, deformation, uplift, denudation and so-forth. Punctuated catastrophic tectonism was refuted as plate tectonic concepts were established. However, echoes remain in regional geological studies of these, otherwise abandoned episodic tectonic models. This personal review draws lessons from seismic stratigraphy that are applied to two case studies, one from the external French Alps, the other from the Messinian of Sicily. These examine the tectonic significance, or lack thereof, of two well-documented unconformities to challenge interpretations of a distinct “pre-Nummulitic” deformation episode in the western Alps and that the Mediterranean region experienced an “intra-Messinian tectonic paroxysm. The key lies in seeking out and interpreting growth strata – those successions deposited during active deformation. Historically, away from seismic reflection imagery, growth strata are under-recorded in the geological record and may have gone un-noticed when regional geology is described without reference to accurate, scaled cross-sections.