Stratigraphic Completeness of Carbonate-Dominated Records From Continental Interiors Versus Continental Margins: Stratigraphic Thinning Occurs Via Condensation and Omission At Multiple Scales

Abstract

Abstract Over Phanerozoic time scales, stratigraphic records from continental interiors, or cratons, are dramatically thinner and are generally assumed to be relatively incomplete, with more numerous and longer-duration hiatuses, compared to records from more rapidly subsiding continental margins. However, this assumption need not be true for the shorter time scales (i.e., several 106 years and shorter) over which accumulation of the preserved stratigraphic record on the continental interior actually takes place. This study compares carbonate-dominated sedimentary records from the Devonian continental interior (Iowa) and continental margin (Nevada) to evaluate whether the continental-interior record is (1) miniaturized, i.e., thinner, but equally complete; (2) comparable in thickness and quality where the sedimentary record is preserved, but certain portions of the record are notably absent, i.e., omitted or truncated; or (3) so invariably preserved that equivalent stratigraphic packages cannot be recognized compared to the continental-margin record. This study finds that fourth- to fifth-order cycles in Iowa are, on average, approximately half as thick and half as numerous compared to the continental margin of Nevada. Moreover, the stratigraphic record on the continental margin of Nevada is dominated by cycles that are composed of tidal-flat and shallow subtidal lithofacies, capped by simple flooding surfaces, and exhibit catch-up or keep-up depositional styles. The continental-interior record in Iowa is dominated by cycles that are composed of subtidal lithofacies, capped by a range of bounding surfaces, and exhibit catch-down or give-up depositional styles. These findings suggest that the thin record in Iowa is largely a result of low sedimentation rates associated with suppressed carbonate production in this epeiric-sea setting, rather than minimal subsidence rates and an increased potential for subaerial exposure and associated loss of record.