GEOLOGIC MAP OF THE ROCKMART SOUTH, GEORGIA, 7.5-MINUTE QUADRANGLE: ILLUSTRATING THE NATURE OF THE SUB-ROCKMART CONTACT AND IMBRICATE SLICES OF CHILHOWEE AND NEWALA FORMATIONS

The response of the Foreland Basin to the changing orientations of orogenic stresses is preserved in the Cambrian through Mississippian rocks of the Valley and Ridge province. Detailed mapping of the sub-Rockmart contact shows a discordant relationship between the Rockmart Slate and the underlying folded Longview, Newala (Kingsport) and/or Lenoir Limestones. The angle of discordance ranges from a minimum of 14 to as much as 53 degrees. This varied discordance resulted from thrust faulting or detachment faulting which caused the Rockmart to override the underlying folded strata.

The nature of the sub-Rockmart contact is very complex and has undergone at least two periods of deformation. The earlier structures were formed by a nearly east-west-directed principal stress, an orientation coincident with the stresses that formed the Great Smoky Fault zone. Later deformation was by maximum principal stresses oriented in a northwest-southeast direction nearly normal to the trace of the Emerson-Talladega Fault Zone.

Areas along Simpson Creek and Hutchins Creek were previously mapped as a fault slice of the Shady Formation. Based on similarities of lithology in the district and preliminary identification of gastropod molds (middle Ordovician) preserved in bedded chert, we interpret this rock unit to be the Newala (Kingsport) Formation. The Newala is locally pyritic, thin to thick bedded, and contains thin-bedded nodular chert. Silicification of the bedding and joint surfaces is common along the Emerson-Talladega Fault Zone. Exposures along the creeks represent a structural window below the sub-Rockmart fault.

Some areas previously mapped as Fort Payne Chert and Floyd Shale have been remapped and interpreted as Weisner and Wilson Ridge Formations (Chilhowee). The Chilhowee is best exposed along and east of the Springdale Church Fault. The western trace of the Springdale Church Fault is marked by a quartzite and quartzite breccia (Weisner). Rocks exposed in the footwall are highly recrystallized and mylonitic. The large area east of the Springdale Church Fault is mostly underlain by phyllite and graphitic phyllite of the Wilson Ridge Formation. The complex repetition of the Weisner and Wilson Ridge is due to imbricate faulting associated with the Springdale Church Fault Zone.