The McMullin syncline is located in Smyth County within the Valley and Ridge Province of southwestern Virginia. The syncline lies in a recess along the northern periphery of the Seven Springs-Pulaski thrust and consists of seven small fault blocks which are complicated by three generations of folding, the the F2 and F3 folds trending oblique to nearly perpendicular to regional Appalachian trends. Two components of stress operated on the local area, a major one directed from the southeast and a lesser one from the southwest. The latter component resulted from rotation of the Seven Springs-Pulaski thrust. The Marion, Virginia area where the McMullin syncline occurs developed up-plunge from the Tennessee basin depocenter. The McMullin syncline includes the Middle Ordovician cartonate onlap package which was deposited over the lower Ordovician upper Knox Group during a major transgression. Altogether, 3519 conodonts representing 48 monoelement or multielement apparatuses and 19 form species were recovered. Biostratigraphically important conodonts recovered from this ramp to basin sequence include: Polyplacognathus friendsvillensis, Polyplacognathus sweeti, Eoplacognatus lindstroemi, Pygodus serrus, and Pygodus anserinus. The Polyplacognathus friendsvillensis-P. Sweeti evolutionary lineage is a valuable datum on which to base correlations in the Southern Appalachians. The datum in this study confirms that the transgression moved northwestward. The Lenoir and Arline Formations correlate with the Pygodus serrus Zone of Eergström’s (1971a) North Atlantic zonation and the Effna Formation with the lowermost Pygodus anserinus Zone. / Master of Science

The Saltville-Broadford area is largely on the northwestern limb of the Greendale syncline in the Valley and Ridge Province of Virginia. The area mapped covers 12 square miles of the northwest corner of Smyth County, Virginia. The rocks in the area ranging in age from Cambrian to Mississippian are found in three different structural settings, the hanging wall and footwall of the Saltville fault, and in two thrust slices located along the trace of the Saltville fault. The hanging wall consists of the Honaker Dolomite of Cambrian age and younger rocks outside the map area. The footwall consists of the Price Sandstone, Maccrady Shale and Little Valley Limestone all of Mississippian age and older rocks outside the map area. The larger of the two slices consists of an overturned sequence of the Juniata Sandstone of Ordovician age to the Brallier Formation of Devonian age. The smaller slice consists of undifferentiated Devonian shale. The Saltville fault, a low-angle thrust, has overturned and cut off the southeastern limb of the Greendale syncline. During thrusting, two slices, at least one of which is overturned, were carried with the overriding block to their present positions. A total of 12,500 feet of movement was measured where the Cambrian, Honaker Dolomite is in fault contact with the Mississippian Little Valley Limestone. Total movement of the fault is believed to be of the order of 4 miles. The upper part of the Mississippian Maccrady Formation is a sequence of evaporites. Halite and gypsum constitute the chief economy of the Saltville area. / M.S.

The Adwolf-Thomas.Bridge area of Smyth County, Virginia is underlain by Paleozoic rocks that crop out in northwest-trending belts. The formations that are considered in this study include in ascending stratigraphic order, the Erwin Formation, Shady Dolomite, Rome Formation, Elbrook Formation and Conococheague of Cambrian age and the uppermost Knox Dolomite, Tumbez Formation, Mosheim Formation, Giesler Limestone, Arline Limestone and Rich Valley Formation of Ordovician age. The area is structurally complex. The southeast dipping Seven Springs thrust brings Late Cambrian rocks of the hanging wall into contact with rocks as young as Middle Ordovician age in the Saltville thrust block. The Holston River syncline and the Glade-Pond Mountain anticlinorium form the area southeast of the Seven Springs fault. The Holston River syncline is an asymmetrical, southweat-plunging syncline in rocks of Cambrian age. The Glade-Pond Mountain anticlinorium is also confined to rocks of Cambrian age and is complicated by a series of small anticlines which have been broken on their northeast limbs by southeast dipping reverse faults. Sands and carbonates were the predominant sediments deposited in Cambrian and Early Ordovician time. In Middle Ordovician time, both carbonates and clayey muds were deposited. As no Silurian or younger Pal~ozoic sediments are present, it is not known when sedimentation ended. Deformation, perhaps in part contemporaneous with sedimentation, appears to have been' climaxed in Mississippian time after sediments of this age were deposited in the area considerably to the north of the area discussed in this report (Butts 1940). / Master of Science