Depositional Sequences on Upper Cambrian Carbonate Platforms: Variable Sedimentologic Responses to Allogenic Forcing

Abstract

Six third-order depositional sequences are documented for Late Cambrian time by interbasinal correlation of cyclic carbonates from tectonic settings in the Appalachian and Cordilleran passive margins, the Texas cratonic embayment, and the southern Oklahoma aulacogen. Paleobathymetric interpretation, integrated with graphic correlation, is used to establish the relative synchroneity of Upper Cambrian depositional sequences and is crosschecked with two quantitative techniques that provide an approximation of the accommodation history independent of fluctuations in carbonate sediment production. The first technique, Fischer plots, graphically illustrates systematic changes in the stacking patterns of meter-scale cycles that presumably reflect third-order changes in accommodation potential. The second technique, subsidence analysis, determines the accommodation remaining after the isostatic and thermo-tectonic components of total decompacted subsidence have been removed. Integrating the three methods enhances the interbasinal correlation of individual third-order depositional sequences and permits the construction of a robust relative sea-level curve for the Upper Cambrian of North America.Comparison of the relative sea-level curve determined in this study with published curves derived from different regions of North America suggests that all six sequences have correlatives in other areas of the continent, supporting an allogenic control on sequence development. Detailed inspection of individual sequences from separate basins illustrates the influence of intrinsic factors such as tectonic setting, platform morphology, subsidence history, paleotopography, and prevailing oceanographic conditions on the Stratigraphic record. Even though each section is composed of different types of meter-scale cycles and component lithofacies that reflect the environmental dynamics of their depositional setting, similarities in the overall internal architecture of individual sequences are clearly evident, and suggests that continent-wide depositional patterns were controlled by a single allogenic mechanism, most likely eustasy.KeywordsDepositional SequenceHighstand System TractTransgressive System TractCambrian StratumAccommodation ChangeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.