Mechanisms for the formation of cratonic stratigraphic sequences

Abstract

North American Phanerozoic cratonic strata comprise six transgressive/regressive sequences separated by interregional unconformities. The mechanism of formation of the sequences and their bounding unconformities remain uncertain. Although eustasy probably contributed, it cannot have acted alone in their formation, as testified by syn-depositional faulting and post-depositional tilting of strata. We have developed a three-dimensional stratigraphic model which incorporates vertical motions from dynamic topography, background cratonic subsidence, eustasy, denudation, mixed carbonate and elastic deposition, Airy isostasy in response to loading and unloading, and mechanical compaction. The model has been used to test possible contributions of eustasy, epeirogeny and background subsidence to patterns of cratonic strata. The results demonstrate the potential of dynamic topography to account for observed long-wavelength tilting. They also demonstrate the importance of background subsidence on the craton in providing accommodation space to accumulate and preserve the observed thicknesses of stratigraphic sequences.

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