A detailed statistical study was performed on molluscan fossil assemblages collected from the Pliocene Morgarts Beach Member of the Yorktown Formation, located in Isle of Wight County, southeast Virginia. The principal objectives of this study were to examine potential sampling problems and biases inherent in paleontological research. This has been accomplished by statistically testing for the homogeneity, or lack thereof, in species assemblages obtained from samples collected from three localities within the Morgarts Beach Member. Multivariate analysis of variance, two-way analysis of variance, multiple comparison tests and cluster analysis were performed on data collected from a five horizon by five section sampling grid (18 feet [5.5 meters] high, 21 feet [6.4 meters] long) located at Morgarts Beach, Virginia. The results of this analysis demonstrate that the relative abundances of species present in the five horizons are significantly different, whereas the relative abundances of species present in the five sections are not significantly different. Results from cluster analysis show that species assemblages contained in samples collected from the Morgarts Beach Member located at Rushmere are substantially different from the Morgarts Beach type area assemblages, in terms of relative abundances of species. The reason for the lack of faunal similarity relates to the documented facies change between the two localities. The results demonstrate that there is no reliable method to obtain accurate census data (frequency abundance curves) from biostratigraphic or lithostratigraphic units deposited during anything but a restricted time interval. In addition, replicate sampling was found to be unnecessary when attempting to determine the relative abundances of species contained in closely spaced sections within the Morgarts Beach Member. Species accumulation curves were constructed from the data collected from the Morgarts Beach Member. Examination of these curves demonstrate that many rare species will not be found unless extensive collecting is undertaken. / Master of Science

M.S.

The Elbrook-Conococheage Formations (Middle to Upper Cambrian) are a kilometer-thick sequence of cyclic, peritidal carbonates that formed an aggraded, rimmed shelf on a mature, passive continental margin. Sedimentation rates for peri tidal carbonate environments far exceeded long term subsidence of the platform (3 to 5 cm/1000 yrs.); thus, the shelf stayed filled to sea level (i.e., was aggraded). Relative sea level rise did exceed sedimentation for brief periods, causing cyclic transgressions (max. 3 m initial submergence). Average cycle duration was 60,000 years. Cycles (1-7 m thick) are composed of basal subtidal/intertidal limestone consisting of bioherms, grainstone and ribbon carbonate; and dolomitic laminite caps containing minor quartz arenite, shale and breccia. Cycle development was controlled by initial submergence increment and position relative to shelf edge. Large initial submergence produced thick subtidal-based cycles representing shelf lagoon and shoal conditions. Small events resulted in submergence within the intertidal zone, which deposited thick, mudcracked intertidal limestones in outerplatform settings, and thick sequences of laminite in inner platform settings. Slopes on the platform were low (less than 3 cm/km); thus, subtidal facies developed in a mosaic pattern of lagoons and shoals, rather than in shore-parallel belts. When low areas filled, tidal flat laminites prograded seaward over subtidal units. Cyclicity may reflect spasmodic subsidence of the shelf, or uniform subsidence overprinted by small-scale glacio-eustatic sea level changes related to shifting patterns of mountain glaciation. Interior areas of Quaternary carbonate shelves are characterized by incipiently drowned facies and are punctuated by soil/caliche horizons and karst surfaces, that reflect 100 rn glacio-eustatic sea 'level fluctuations. In contrast, many ancient shelves, including the Cambre-Ordovician shelf of the Appalachians, were dominated by cyclic peritidal sequences lacking evidence of major sea level events. Aggraded shelves may represent the typical state of mature carbonate continental shelves in the absence of large-scale sea level fluctuations. / M.S.

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.

Middle Ordovician ramp carbonates were deposited in a rapidly subsiding foreland basin bordered on the southeast by tectonic highlands. Marine, turbid cements include neospar, bladed and turbid rim cements; they are associated with synsedimentary hardgrounds and erosional surfaces. Neospar cement is isopachous and locally botryoidal, and is neomorphic after acicular and botryoid aragonite. Bladed cement has a well-defined crystal morphology, and has non-recrystallized fabrics that suggest a high-Mg calcite precursor. Turbid rim cement syntaxially coats pelmatozoans; its substrate specificity suggests a high-Mg calcite precursor. Marine cements occur throughout the sequence but are abundant in nonreefal buildups, where syndepositional lithification was important in stabilizing buildups. The bulk of the later, non-marine cements are nonferroan, clear rim and equant cements. Zoned (defined by cathodoluminescence) clear cements consist of nonluminescent (oldest), bright and dull (youngest) cements; the sequence relates to increasingly reducing conditions of pore waters. Zoned peritidal cements are best developed in southeastern belts and have complex zonations, pendant to pore rimming fabrics, and are associated with crystal silt (which abuts all cement zones), solutional cavities and erosional surfaces (which locally truncates dull cement). These cements are meteoric vadose to shallow phreatic in origin. Cements in northwestern exposures of peritidal beds are dominated by nonzoned, dull cements which lack abundant evidence of early cementation. Major cementation of subtidal facies occurred under burial conditions. Burial cements in southeastern belts have a simple zonation reflecting progressive burial (up to 3000 m) of the carbonates. Shallow burial, non-luminescent cement in southeastern belts formed from oxidizing waters which expelled anoxic, connate marine waters, and meteoric waters were carried by aquifers from tectonic upland recharge areas on the southeastern basin margin. Burial cements in northwestern belts are dominated by dull cement, initial generations of which precipitated from downdip portions of aquifers. Deeper burial, bright and dull calcite and ferroan dolomite cements formed at burial depths (2000 to 3000 m) and temperatures (75 to 135°C or more) associated with hydrocarbon formation - emplacement. Final clear dull cement fills tectonic fractures and was emplaced during Late Paleozoic deformation. Deeper burial diagenesis appears to be genetically linked to Late Paleozoic, Mississippi Valley-type mineralization. Zoned peritidal and burial cements are mainly confined to southeastern portions of the ramp where cementation was influenced by meteoric waters from tectonic uplands and was carried northwest by paleoaquifers. Northwestern portions of the ramp were little influenced by these meteoric waters, and nonzoned dull cements precipitated from relatively reducing waters. The close association of zoned cements and regional uplands in the Middle Ordovician sequence indicates the importance of assessing regional geologic relationships, geologic history and tectonics in understanding regional cementation patterns and cementation processes of ancient carbonate platforms. / Ph. D.

Mapping of a 190 square km area along the western flank of the Blue Ridge anticlinorium in central Virginia has defined three major rock groups: (1) the earlier Precambrian Virginia Blue Ridge Complex; (2) the Late Precambrian Catoctin Group; and (3) the Early Cambrian Chilhowee Group. The Virginia Blue Ridge Complex is subdivided from oldest to youngest into the Pedlar, Marshall and Levingston formations. The Pedlar and Marshall formations, partially of metasedimentary origin, were metamorphosed to the granulite facies, retrograded to as low as the greenschist facies, and deformed into a series of east-trending folds prior to Late Precambrian. The relationships between the two metamorphic events and structural deformation was not determined. An angular unconformity separates the Catoctin Group from the Virginia Blue Ridge Complex upon which 300 m of topographic relief was developed. The Catoctin Group is subdivided from oldest to youngest into the Swift Run, Catoctin and Loudoun formations which are subdivided into phyllitic units of both sedimentary and pyroclastic origin separated by sequences of greenstone flows. Early Catoctin Group volcanism, originating in situ from northeast-trending dike complexes, was accompanied by normal faulting along the northwest-trending Stony Creek fault. Swift Run and lower Catoctin Formation sediments were transported principally from the southeast quadrant or were derived in situ from saprolite and colluvial deposits. Loudoun and upper Catoctin Formation arkosic sediments were derived from localized sources, west of the Blue Ridge, and transported in a southwesterly direction parallel to the Appalachian structural trend. Pyroclastics of the Catoctin Group probably were derived from a northwest source. The upper Catoctin Formation is older than 700 my. Paleozoic metamorphism of the Catoctin Group altered the lava flows toward the following greenschist assemblages of high oxidation state: quartz and albite plus (1) epidote, penninite and magnetite; or (2) penninite, magnetite and calcite. Subsequently, metamorphism indicative of a lower oxidation state altered the lavas toward the greenschist assemblage of: quartz, albite, epidote and actinolite. Actinolite content increases with depth at the expense of relict pyroxene, penninite and magnetite. Metamorphosed pyroclastics are characterized by sericite, quartz, magnetite and/or hematite. The Chilhowee Group is subdivided, from oldest to youngest, into the Weverton, Harpers and Antietam formations. A thrust fault zone separates metamorphosed Weverton and Harpers elastics from unmetamorphosed Antietam elastics. Metamorphosed Chilhowee and Catoctin sediments are characterized by formation of the following metamorphic minerals: epidote, penninite, sericite, and microcrystalline quartz. Chilhowee detritus was derived from the west-northwest and transported eastward and/or parallel to the Appalachian structural grain. Post-Precambrian deformation includes folding about northeast and north-trending axes followed by development of southeast-dipping cleavage during Paleozoic metamorphism. Cleavage development preceded northwestward thrusting of metamorphosed rocks of the Blue Ridge over unmetamorphosed Paleozoic rocks of the Valley and Ridge. Subsequently the principal joint trends were established followed by normal and strike-slip movement along northeast-trending high-angle faults. Intrusion of Mesozoic dikes post-dates high-angle faulting. / Ph. D.

The Spruce Run Mountain area embraces about 45 square miles in the south-central portion of Giles County. It lies wholly within the Appalachian Valley and Ridge Province. The rocks exposed in the Spruce Run Mountain area range in age from Middle Cambrian to Lower Devonian. All the rocks are sedimentary rocks deposited in a marine environment and have an aggregate thickness of approximately 6,500 feet. An important disconformity separates rocks of Lower Ordovician age from those of Middle Ordovician age. The Saltville thrust, a southeast dipping thrust fault, crosses the Spruce Run Mountain area trending northeast. The thrust separates Middle Cambrian dolomite from Ordovician formations on the southeast flank of the Spruce Run Mountain syncline. The Spruce Run Mountain syncline is a northeast trending overturned syncline with a southeast dipping axial surface. The Clover Hollow anticline and the Bane anticline border the northwest flank of the Spruce Run Mountain syncline. The geomorphology and geologic history of the area are briefly discussed. / Master of Science

Along the southeast flank of the Flattop Mountain anticline in Washington, Smyth, and Tazewell counties, Virginia from Tumbling Creek, Washington County, northeast to and beyond Tannersville, Tazewell County, the Silurian Tonoloway limestone is intercalated within a succession of otherwise impervious strata. Groundwater circulation is localized within the Tonoloway in which large groundwater conduits have been created by dissolution. The area studied contains sedimentary rocks that range in age from Upper Silurian to Upper Devonian, inclusive. This report describes the lithology and terrain distribution of these formations and discusses their effect on the groundwater circulation in the area. The Tonoloway limestone serves a special function in controlling the infiltration and direction of movement of subsurface waters. The locally reversed hydraulic gradients of groundwater infiltrating the Tonoloway in various portions of the area along Poor Valley between Tumbling Creek and Tannersville are largely determined by streams, tributary to the North Fork of the Holston River, which have eaten headward through Brushy Mountain to become extended subsequent streams draining segments of Poor Valley. Subsurface conditions are favorable for recovering large quantities of groundwater for industrial use from the cavernous Tonoloway during the warm months of the year with subsequent recharge during the colder months when cool groundwater is not needed by nearby industries. Recharge could be substantially increased by installation of infiltration wells which would convey a larger quantity of surface water leaving such remote valleys as Redrock Cove directly into the cavernous Tonoloway. The advantage of infiltration conduits would be to effect some semblance of continuous recharge and thus increase the quantity of water that could be withdrawn during the summer periods when demand for industrial water is particularly great. / Master of Science

Detailed mapping along the northern terminus of the Carolina slate belt in the area of Meherrin, Virginia extends the previously known limits of the Hyco and Aaron Formations from the greenschist metamorphic facies Carolina slate belt northward across a staurolite isograd into the amphibolite metamorphic facies Charlotte belt. The Hyco formation is subdivided into four facies: a crystal tuff facies, a felsic tuff facies, an interlayered mafic and felsic volcanic facies, and a feldspathic wacke facies. The Aaron formation is dominantly a pelitic schist. Three deformational events are identified. F₁ produced the initial foliation. F₂ produced the dominant penetatrive foliation, isoclinally folding the earlier foliation. F₃ produced a crenulation cleavage. The Hyco and Aaron formations are folded into a tight, steeply southeastward dipping, and slightly refolded syncline. The undifferentiated Charlotte belt rocks form a doublely plunging antiform of refolded F₂ folds. The syncline formed by the Hyco and Aaron formations is northeastward along strike from the type location of the Virgilina synclinorium. Glover and Sinha (1973) attribute the formation of the Virgilina synclinorium to a late Precambrian and (or) early Cambrian orogenic event, and Glover and others (1983) attribute late folding and metamorphism to the Taconic orogeny. F₁ is attributed to the Virgilina deformation. F₂ and F₃ are attributed to the Taconic and/or Acadian orogenies. / Master of Science

The Blacksburg Area as herein described is that portion of Montgomery County, Virginia, which comprises the north third of the Blacksburg Quadrangle. This Quadrangle is the southwest quarter of the Christiansburg topographic sheet published by the United States Geological Survey in 1890. The region is in the heart of the Allegheny Mountains. It is bounded by latitudes N. 37° 15' and N. 37° 10' and by longitudes W. 80° 30' and W. 80° 15', an area of approximately seventy-eight square miles. The east-west dimension is 13.8 miles and the north-south dimension is 5.7 miles. The town of Blacksburg, which is the location or the Virginia Polytechnic Institute, is within this area and is at longitude W. 80° 30' near the northern boundary of the area. The region is traversed in a north-south direction by state highway number 8 connecting the Lee Highway, U.S. 11, at Christiansburg, with Princeton, West Virginia, and main U.S. Highways to the west. A spur of the Norfolk am Western Railway connects Blacksburg with the main line at Christiansburg. The town of Shawsville is located in the extreme southeastern corner of the area. The main line of the Norfolk and Western Railway as well as U.S. Highway 11 pass through this town. They both connect that portion of the area with Roanoke, Virginia, and the eastern seaboard, with East Radford, Virginia, the Pocahontas Coal Fields and other points west to the Mississippi Valley. The main line at the Virginian Railway traverses the entire region from east to west, following the North Fork of the Roanoke River from Ironto to Ellett and from there westward by way of Merrimac. This railway, like the Norfolk and Western, is a connecting link between the Atlantic Seaboard at Norfolk, and the West Virginia Coal Fields by way of Roanoke. The Blacksburg Area is consequently readily accessible from most any direction by rail or by road, although within the area it is quite rugged and a few localities are none too easily reached. / Master of Science