This study describes the biostratigrapaic distribution of Meramecian conodonts from three measured sections of the Greenbrier Limestone (Meramecian-Lower Chesterian), located in the Greendale and Hurricane Ridge Synclines of southwestern Virginia and southern West Virginia. The Little Valley Formation, Hillsdale Limestone and lower portions of the "Denmar-Gasper" and "Ste. Genevieve" Formations, consisting of rocks deposited in a variety of shallow carbonate-ramp environments, were investigated. Two new multielement conodont apparatuses were recognized: Kladognathus sp. A and Hindeognathus ("Apatognathus") laevipostica. Elements of Kladognathus sp. A are morphologically distinct from homologous elements of the K. levis-K. tenuis group. Evolutionary change from K. levis to K. tenuis is marked by slight Sa and Sb element changes, and the addition of an X element, DE Lambdagnathus fragilidens. Species of Kladognathus are promising Meramecian biostratigraphic markers. Also recognized in this study are species of: Cavusgqnathus, Gnathodus, Hindeodus, Idioprioniodus, Lochriea, Rhachistognathus, “Spathognathodus," Synprioniodina? and Taphrognathus. Meramecian formations in the study area can be correlated with the Mississippian stratotype (Illinois Basin) based on the following zones: Taphrognathus varians - "Apatognathus," "A." scalenus - Cavusgnathus aad Gnathodus bilineatus - Cavusgnathus charactus. Southward thickening of the "A." scalenus zone from the Hurricane Ridge Syncline (11 m) to the Greendale Syncline (180-200 m) reflects higher rates of sedimentation and subsidence in the depositional area of the latter. In addition, thinness of the zone in the Hurricane Ridge Syncline may be due to a hiatus between this zone and the younger G. bilineatus zone. This hiatus is not indicated by conodont faunas from the Greendale Syncline, which preserves a more complete Meramecian biostratigraphic record. Conodont and litahologic evidence for a coeval hiatus exists in other areas of eastern North America: the Illinois Basin stratotype, eastern Kentucky, Southern Ohio and eastern Tennessee. / Master of Science

Ph. D.

The Parsons Lineament (a major Appalachian Cross-strike Structural Discontinuity, CSD) extends from the Plateau of West Virginia into the Valley and Ridge Province in northern Rockingham County, Virginia. Regional and second—order folds change in strike from typical Central Appalachian trends (N30—35°E) to near due north within the CSD, regional anticlines plunge out, and major thrusts terminate within thisi zone. ln the Rockingham County portion of the Broadtop Synclinorium, the CSD is marked by an increase in intensity (ratio of surface area to volume) of systematic joints and second—order, sinistral strike-slip faults. Two sets of regional joints occur : J1, a pervasive east—west— trending, near vertical joint set, and J2 which varies with structural position. Peaks in J1 intensity coincide with known strike-slip faults and pronounced photolineaments. J2 is associated with closure on the Bergton anticline. Drilled depths to the Oréskany horizon, age relations and intensity of systematic joints suggest deformation associated with a northeast—facing lateral ramp is responsible for both the Parsons lineament and closure on the Bergton natural gas field. Within the North Mountain thrust sheet, the Parsons CSD consists of a linear zone of anomalously-trending, second-order folds and shears near the nose of the Linville anticline. Blind thrusts responsible for second-order folding are exposed in a quarry face and strain values (from pressure fringes adjacent to pyrite framboids in Martinsburg shales) suggest that the second-order folds adjacent to the Linville anticline are the result of movement on the Saumsville fault in the subsurface. Age relations of S1 and S2 cleavages and V2 calcite veins indicate an east-to-west order of thrusting for the Pulaski-Staunton and Saumsville faults. The linear disturbed zone results from displacement transfer at the termination of the Saumsville fault and, together with the structural anomalies in the Broadtop Synclinorium, constitutes the Valley and Ridge extension of the Parsons CSD. / Master of Science

Geologic mapping along the northeasternmost 25 miles of the St. Clair fault, which traverses the Central and Southern Appalachian juncture at about the middle of this segment, was accomplished to observe the changes in geologic style and structural trend that occur across the juncture in this northwesterly Valley and Ridge strike belt. The study area is an excellent smale scale area for observations on the nature of the juncture over the larger scale as it includes most of the features that characterize this juncture such as change of physiographic and structural trend and transition from thrust fault-dominated deformation to fold-dominated deformation. The juncture or recess is prominent in the study area as a sharp bend in Gap-Moss Mountains and is in fact one of the sharpest bends occurring at the junction. Southwest of this recess, the stratigraphic units on the northwest of the St. Clair fault are overturned and a broad syncline is formed on the northwest, known as the Hurricane Ridge. The axis of this fold closely parallels the strike of the St. Clair fault. As the junction is approached the Hurricane Ridge syncline changes axial strike to the north and passes northwest of the Browns Mountain anticlinorium which is plunging out into the junction. Just northeast of the recess the St. Clair fault bifurcates and its strike is slightly changed when the segments rejoin. Northeast of this point, the St. Clair fault loses stratigraphic displacement and instead of a single broad fold northwest of the fault and parallel to it, there are numerous small folds developed that strike 20-30° more northerly than the fault. The fault does not, however, truncate any of the folds. The St. Clair fault extends 13 miles into the Central Appalachians where it dies out down the plunge of an anticline at Morning Knob in Alleghany County, Virginia. A strong shear zone is evident in the core of the structure at Morning Knob but is lost as the competent Silurian units plunge under Devonian shales. Integrating this information with other recent work on the juncture it may be concluded that: 1. The change of topographic and structural trend across the Central and Southern Appalachian juncture does not require any significant difference in timing of deformation. 2. There is probably no significant difference in orientation of principal stress across the juncture but rather the change of trend and differences of geologic "style" reflect contrasts in thickness and facies within the sedimentary column and contrasts involving basement topography which indirectly influence cover structure. Thus the changes evident across the juncture are seen to be the result of differential physical response to the applied stress. / Master of Science