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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

Moment-radius-stress drop relations and composite focal mechanisms were determined for 33 small, shallow, strike slip earthquakes (1.7$MLS4.3) in the Matsushiro region of southwest Honshu, Japan during the period August 1971 through September 1974. Estimates of the scalar moment derived from deconvolved SH displacement amplitude spectra range from 1018 to 1022 dyne-cm. The apparent stress ranges from 0.001 to 3.00 bars and the relationship between apparent stress and moment is approximately linear with a slope of 1. Ph. D.

Few detailed facies analyses of rift to passive-margin transitions have been undertaken in exhumed orogenic belts. In the central Appalachians, the Chilhowee Group records such an evolution. The Unicoi and basal Hampton Formations record the transition from rifting to opening of the Iapetus Ocean. The majority of the Hampton Formation and the overlying Erwin Formation represent an overall regressive sequence punctuated by five progradational packages that accumulated along a passive margin. The rift to passive·margin phases of sedimentation in the central Appalachians reflect a continuum from fault·influenced to thermotectonic subsidence. Alluvial sediments and intercalated basalts of the lower Unicoi Formation developed in a rift setting. Paleontological data indicate that rifting continued into lower Cambrian time. The upper Unicoi Formation represents the incipient phase of passive-margin sedimentation related to a first-order, sea level rise. Differences in degree of crustal attenuation controlled the distribution of sedimentary environments during transgression. On the most attenuated crust to the east, initial transgressive facies consist of tidal sandwave and sandridge deposits intercalated with proximal and medial braid-pIain deposits. As transgression progressed cratonwards onto less attenuated crust, tidal sedimentation was supplanted by tide- and wave-influenced sedimentation characterized by sandwave complexes, tidal inlets and longshore bedforms. Drowning at the top of the Unicoi Formation is indicated by outer-shelf black mudstones. Deepening may have been enhanced by continued movement along listric faults throughout the incipient phase of passive-margin development. Examination of outcrops of the Hampton and Erwin Formations on different thrust sheets has permitted an across-strike reconstruction of the Early Cambrian Chilhowee shelf in space and time. Progradational packages developed under storm- and fair·weather wave conditions. Coarsening· and thickening-upward sequences on westerly thrust sheets were generated during progradation of shoreface, inner-shelf and outer-shelf environments. Outer-shelf facies predominate on easterly thrust sheets. Intertidal-flat deposits on the most westerly thrust sheet erosively overlie progradational shoreface sediments and developed during transgression in an embayment in which the tidal wave was amplified. More distal transgressive deposits consist of fining- and thinning·upward sequences with glauconitic horizons, and condensed sections in mudstones. Ph. D.

The Lucerne pluton intrudes rocks of the Penobscot formation Ordovician-Silurian (?)), a quartz-rich sulfidic pelite that contains muscovite, biotite, cordierite, andalusite, plagioclase, pyrrhotite and graphite outside the thermal aureole; and the Bucksport formation (=Vassalboro, Silvian-Devonian (?)), a calcareous, quartzofeldspathic pelite that contains chlorite, biotite, celadonitic muscovite, albite, and ilmenite outside the Lucerne aureole. Within the aureole, the Penobscot formation contains K-feldspar plus andalusite as the result of muscovite reaction with quartz. Corundum occurs at the immediate contact of the granite from the. reaction of the remaining muscovite. The Bucksport formation is recrystallized within the aureole to a purple and green gneiss. The gneissic banding is not present in the low grade calcareous rocks, and represents the segregation of biotite-rich and calc-silicate-rich bands. Vertical or sleepy dipping, the banding parallels both the regional strike and the intrusive contact, and is probably the result of both mechanical and chemical effects. The following sequence of assemblages (+ quartz) is found in the calcareous portions of the Bucksport formation as the Lucerne contact is approached: a) chl + bio + musc + cc + albite; b) bio + cc + plag (An₂₅₋₃₃); c) actinolite + cc + K-feldspar + plag (An₄₀); d) diopside + zoisite + sphene +cc+ plag (An₈₅₋₉₀). Interbedded pelites contain biotite + quartz + plagioclase + pyrite with corundum occurring at the igneous contact in quartz free beds. The mineral assemblages in the Lucerne aureole indicate a lithostatic pressure between 1000 and 3000 bars during metamorphism with temperatures between 700°C and 450°C. Isobaric univariant assemblages in the calc-silicate beds indicate buffering of H₂O/CO₂ fluids produced by prograde reactions. H₂O rich fluids that produced zoisite were probably associated with late stage crystallization of the Lucerne. Master of Science

The Altavista area lies at the north end of a large area of continuous detailed mapping in the proposed westward thrusted Smith River Allochthon of the Southwest Virginia Piedmont. It also lies at the south end of an area of continuous mapping in the central Virginia Piedmont. The stratigraphy of the Smith River Allochthon has not been related to any other in the Southern Appalachians. The units defined to the north of Altavista are Late Precambrian to Early Paleozoic in age and correlated to many other areas in the Central and Southern Applalchians. At Altavista the two stratigraphies merge and are correlatable. The Bowens Creek Fault, which bounds the west side of the Smith River Allochthon, separates blocks that contain the same stratigraphy. If allochthonous at all, the Smith River Allochthon has therefore not been thrusted any great distance. The rocks of the Smith River Allochthon have been metamorphosed to midde to upper amphibolite facies conditions during the Taconic Orogeny whereas those of Central Virginia only achieved upper greenschist conditions during this event. The Evington Group pelitic schists and gneisses in Altavista exhibit an inverted prograde metamorphism and subsequent retrogression. The Pressure·temperature path for these rocks forms the lower part of a loop from high pressure to lower pressure and higher temperature followed by a nearly isobaric retrogression. Paths of this type are characteristic of terranes that have experienced nappe emplacement. The Altavista area represents the footwall beneath a nappe that has been eroded away because the metamorphic gradient is inverted yet the stratigraphy is upright. Two phases of deformation in this event formed isoclinal folds and refolded isoclinal folds and a pervasive S2 foliation. The formation of large domes along the Bowens Creek Fault postdates the high grade metamorphism. The structures were formed in a three·stage dextral transpressional event. This Carboniferous dextral transcurrent event is Appalachian wide and well documented in the Brookneal zone to the east. The Bowens Creek Fault is therefore unrelated to the high grade metamorphism, further disproving the existence of the Smith River Allochthon. Ph. D.

The gneissic Port Deposit pluton and associated James Run metavolcanics bear a fault relation with the Wissahickon metasediments of the Glenarm terrane of the northeastern Maryland Piedmont, USA. Bulk chemical and mineralogical data classify the meta-igneous rocks as a bimodal tholeiite-dacite/tonalite suite with trondhjemitic affinities and indicate that subsolidus alteration during dynamic metamorphism was minor. Comparison of these data with other tectonic environments suggests their generation by partial fusion of amphibolitic basement. Previous studies have dated magmatic events in the Maryland Piedmont at 520 Ma, 420 Ma, and 300 Ma (Sinha et al., 1980). The U-Pb zircon upper intercept age for the Port Deposit is 525 ± 10 Ma, the Rb-Sr whole rock isochron age is 467 ± 21 Ma, and Rb-Sr model biotite ages are 400 and 300 Ma. Regional and theoretical considerations indicate the 525 zircon age may represent the time of igneous consolidation. Detailed petrographic observations in the Port Deposit indicate the Rb-Sr whole rock age represents the time of deformation and development of gneissic textures. The 467 Middle Ordovician age of deformation for the Port Deposit is interpreted as representative of the Taconic orogeny for the central Appalachian Piedmont; Rb-Sr whole rock systematics were upset, but concurrent anatexis of felsic basement is not locally evident. The fault contact between the Port Deposit and easternmost facies of the Wissahickon places an upper age limit of 467 Ma for that particular facies. Rb-Sr model biotite ages are interpreted as metamorphic cooling phenomenon and reflect the 420 and 300 Ma thermal highs. Master of Science

The Christiansburg map area consists of about 19 square miles in Montgomery County, Virginia, and is underlain by sedimentary rocks ranging in age from Middle Cambrian to Middle Ordovician. Post-Ordovician strata have been eliminated by thrusting and erosion. From south to north the rocks belong to five fault blocks: the Max Meadows, Pulaski, Saltville, Salem, and Catawba blocks. The Max Meadows block contains only the Middle Cambrian Rome Formation, the oldest rocks exposed within the area. The parautochthonous Saltville block includes rocks from Upper Cambrian to Middle Ordovician in age, which are exposed in windows of the Pulaski fault block. The Pulaski block contains highly fractured and brecciated Cambrian carbonates. The Salem block contains rocks ranging in age from Middle Cambrian to Lower Ordovician. The Salem fault terminates west of Christiansburg, Virginia. Rocks of the Catawba block range from Middle Cambrian to Mississippian in age, but only the section up to the Middle Ordovician is exposed in the map area. The windows through the Pulaski thrust sheet expose the large Christiansburg anticlinorium of the Saltville fault block. The size of each window is proportional to the size of the anticlinal fold developed on the crestal portion of the anticlinorium. The faulting may have occurred shortly after deposition of the Mississippian strata exposed in the Price Mountain window north of the area. The apparent parallelism of the thrust sheets and the overridden strata indicates that much of the present structural relief was formed after emplacement of the thrust sheets. Master of Science