Abstract

A comprehensive data base for the Conasauga Group (Middle and Late Cambrian) throughout the Valley and Ridge province in east Tennessee was compiled from published and unpublished sources. Lithofacies and isopach maps and stratigraphic cross sections were constructed from this data base on both present-day and palinspastic bases to define regional depositional patterns of the Conasauga Group.

Isopach and lithofacies trends recognized on present-day base maps are generally consistent with those previously recognized. Lithofacies data are consistent with a shelf-intrashelf-basin-carbonate-ramp model proposed by other investigators for the Nolichucky Shale. Our study suggests that the southern edge of an intrashelf basin recognized within the Conasauga Group in southwest Virginia was 20 to 50 km southwest of present-day Knoxville.

Palinspastic-base lithofacies and isopach patterns for the Conasauga Group in east Tennessee suggest (1) the existence of a generally elliptical intrashelf basin that closes to the southwest and the north east; (2) that the eastern margin of the intrashelf basin consists of shaly limestone and dolostone, the dolostone being dominant eastward; (3) that basin sediments are limestone, shale, and shaly limestone (40%-80% limestone); and (4) that the western basin margin sediments are mostly calcareous shale and siltstone (20%-60% limestone) that become terrigenous west of the basin.

A sub-basin within the regional intrashelf basin has been identified. The axis of this sub-basin is oriented northwest, perpendicular to the regional trend of the shelf and Appalachian structure. Approximately 2,900 ft (883 m) of Conasauga strata accumulated in the subbasin, which first appeared during Pumpkin Valley Shale deposition and persisted through Maynardville Limestone deposition. We interpret the abrupt thickening at the margin of this basin to result from basement faulting, which produced a graben that subsided intermittently during basin filling. This structure may have economic significance in that there is an apparent correlation between the margin of this second-order basin and zinc mineralization in overlying carbonates of the Knox Group.

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