--> ABSTRACT: Distribution of Lower Cambrian Fluvial and Progradational Marine Facies Along Frontal Blue Ridge: Chilhowee Group of East Tennessee, by Dan Walker and Steven G. Driese; #91022 (1989)

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Distribution of Lower Cambrian Fluvial and Progradational Marine Facies Along Frontal Blue Ridge: Chilhowee Group of East Tennessee

Dan Walker, Steven G. Driese

The Chilhowee Group (upper Proterozoic-Lower Cambrian) of eastern Tennessee represents a fluvial-to-marine transition that accompanied the stabilization on the eastern North American continental margin formed by the inception of the Iapetos Ocean. Variability along strike in Chilhowee facies has been recognized within the confines of the fluvial-to-marine transition. Facies, identified across eastern Tennessee study localities, cross formational boundaries; thus, a facies analysis provides a practical basis for studying patterns of Chilhowee sedimentation.

Throughout eastern Tennessee, five facies were recognized: conglomerate, sandstone, siltstone-mudstone, hummocky, and quartz-arenite. The fluvially dominated conglomerate facies represents deposition within a braided-stream system and is typical of the basal Chilhowee Group throughout the outcrop belt. Above the fluvially dominated basal Chilhowee, variability along strike increases in the marine-dominated facies. The hummocky, sandstone, quartzarenite, and siltstone-mudstone facies consist of interbedded sandstone, siltstone, and mudstone exhibiting fairweather-and storm wave-produced sedimentary structures. Sedimentation occurred on a storm-dominated shelf that received progradational pulses of shoreface sand (quartzarenite facies) from a cratonward source.

Variations in the relative abundance and stratigraphic position of shelf facies (hummocky and mudstone-siltstone facies), grain size, and bed thickness within the Chilhowee Group represent variations in coeval Chilhowee paleoenvironments along strike, attributable to differences in progradation vs. transgression at the continental margin. Examination of the Chilhowee Group within two major segments of the Great Smoky thrust complex indicates that the current relative distribution of facies differs from that inferred for the original depositional system. This difference may reflect (1) variation in the amount of tectonic transport experienced by the various segments of the thrust complex, (2) divergence between structural strike and depositional strike, or (3) the effect of local promo tories and embayments within the North American-Iapetos continental margin.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.