Formation of sequences in the cratonic interior of North America by interaction between mantle, eustatic, and stratigraphic processes

Abstract

Models integrating geodynamic and stratigraphic processes show that some gross features of Phanerozoic North American cratonic strata can be explained with dynamic topographies generated by subduction and cycles of supercontinent aggregation and dispersal. A three-dimensional finite-element model is used to calculate mantle flow beneath North America during Phanerozoic time in response to episodes of subduction at cratonic margins and two cycles of supercontinent formation and breakup. Dynamic topographies calculated by the flow models are used as input to a stratigraphic model that also includes background subsidence, eustasy, denudation, clastic and carbonate deposition, compaction, and isostasy. These models successfully reproduce aspects of the Sloss sequences; the best matches were obtained by combining two wavelengths of dynamic topography with second-order eustasy. Long-wavelength dynamic topography generates first-order stratal cyclicity. Periods of erosion were shorter when North America was over a dynamic topography low than when it was over a high. Long-wavelength dynamic topography also explains the absence of Mesozoic strata on the eastern portion of the craton. Characteristic stratal patterns are shown to result from subduction-related dynamic topography, although sensitive to sediment supply and other subsidence mechanisms. Aspects of Upper Cretaceous stratal patterns may be explained by the effects of Farallon plate subduction. Generally, strata deposited in a dynamic topography depression have low preservation potential because the topography is reversible. Thus, ancient subduction-related dynamic topography is most likely to be represented by unconformities.