M. S.

Folding prior to thrust-sheet emplacement is proposed to explain presence of overturned synclines in the footwalls of many thrust-faults in the Appalachian foreland fold- and thrust-belt of southwest Virginia. Investigation of relations in the footwalls of the Saltville and St. Clair thrust-sheets near the Southern-Central Appalachian juncture indicates presence of at least two distinct types of footwall structures: 1)isolated forelimbs of thrust-truncated asymmetric ramp-generated anticlines, and 2)areally extensive overturned subthrust synclines. Mesoscopic fabric data and strain states indicate rotation of bedding by folding prior to thrust-sheet emplacement rather than drag folding during thrusting. Low angles between bedding and cleavage planes and low strain values on the back limbs of folds at thrust terminations (Sinking Creek anticline) and in hangingwall strata seems to indicate folding was largely accomplished by flexural flow in units of relatively low mechanical strength. / M.S.

M.S.

Broken-formations (Hsu, 1974; Harris and Milici, 1977) occur in the lower part of the Pulaski thrust sheet and contain some of the most strongly deformed sedimentary rocks in the Valley and Ridge province of the southern Appalachians. Deformation in this zone ranges from grain-scale cataclasis to regional-scale faulting. The broken-formations are distinguished from rocks structurally higher on the sheet and from rocks of the underlying Saltville sheet by (1) a sharp increase in the variability of fold and fault styles, (2) greater ranges in fold plunges and dips of axial surfaces, (3) a low degree of preferred orientation of folds and faults, (4) an increase in the frequency of mesoscopic structures, and (5) the presence of Max Meadows tectonic breccia. Structural analyses indicate that deformation in the broken-formations is Alleghanian in age and that the deformed zone formed under elastico-frictional conditions, possibly under elevated fluid pressures with temporally variant stresses and that lithology may have played an important role in localizing the broken-formations along the base of the Pulaski sheet. / Ph. D.