Stratigraphy of the Lower Pierre Shale (Campanian): Implications for the Tectonic and Eustatic Controls on Facies Distributions

Janet Bertog

doi:10.1155/2010/910243

Abstract

The lower Pierre Shale represents a time of significant changes in the Cretaceous Western Interior Seaway, resulting from complex interactions of tectonism and eustatic sea level changes. The recognition and redefinition of the units of the lower Pierre Shale has facilitated understanding of the dynamics of the basin. The Burning Brule Member of the Sharon Springs Formation is restricted to the northern part of the basin and represents tectonically influenced sequences. These sequences are a response to rapid subsidence of the axial basin and the Williston Basin corresponding to tectonic activity along the Absoroka Thrust in Wyoming. Unconformities associated with the Burning Brule Member record a migrating peripheral bulge in the Black Hills region corresponding to a single tectonic pulse on the Absoroka Thrust. Migration of deposition and unconformities supports an elastic model for the formation and migration of the peripheral bulge and its interaction with the Williston Basin.

Highlights

Timing of thrust activity in tectonically active thrust belts, such as the Cretaceous Sevier Orogenic belt in the western United States, is generally estimated by the recognition of synorogenic clastic sedimentation responding to the thrust activity
Detailed stratigraphic analysis of the lower Pierre Shale Group throughout the basin indicates a much more complex distribution of facies. The recognition of these facies changes was reported in Martin et al [9] and Bertog et al [10], where the Sharon Springs Formation was divided into three members in central South Dakota and these correlations were expanded to the Black Hills, Kansas and North Dakota (Figure 4)
During deposition of the Burning Brule Member of the Sharon Springs Formation, facies patterns indicate that a north-south partitioning of the basin was present

Summary

Introduction

Timing of thrust activity in tectonically active thrust belts, such as the Cretaceous Sevier Orogenic belt in the western United States, is generally estimated by the recognition of synorogenic clastic sedimentation responding to the thrust activity (see, e.g., [1,2,3,4]). Detailed stratigraphic analysis of the lower Pierre Shale Group throughout the basin indicates a much more complex distribution of facies The recognition of these facies changes was reported in Martin et al [9] and Bertog et al [10], where the Sharon Springs Formation was divided into three members in central South Dakota and these correlations were expanded to the Black Hills, Kansas and North Dakota (Figure 4). During the middle Campanian, the Zuni II second order eustatic sea level cycle reached its peak during deposition of the Niobrara Formation when overall sea-level highs and tectonic quiescence favored carbonate deposition [11] As this cycle began a regression that continued throughout the end of the Cretaceous, carbonate deposition gave way to clastic deposition, which dominated the seaway throughout the remainder of the Cretaceous.

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Discussion

Conclusion