Devonian Eustatic Events in the Western United States and Their Biostratigraphic Responses

Abstract

Abstract Sixteen deepening events, of which 11 were eustatic, and six regressive episodes, of which 3 were eustatic, acted as primary controls on Devonian sedimentation and biotic changes in the Western United States. Many stratigraphic unit boundaries, especially within limestone sequences, resulted from the eustatic rises, and widespread unconformities were produced by eustatic falls. Eustatic efficacy evidently was a highly significant control on bio-events and caused diversity changes, macrofaunal biofacies shifts, and local and worldwide extinctions. An Early Devonian (pesavis Zone) regression, which is here considered as the first intra-Devonian eustatic fall, dramatically changed brachiopod biofacies (also called faunal realms). Late Devonian eustatic falls just before the close of the Frasnian and Famennian Stages presaged worldwide extinctions in conodonts and macrofaunas.