Over 700 km of industry seismic reflection data in the central Appalachians were reprocessed using both conventional and newly developed processing schemes. A new processing sequence, called dip projection, is introduced. The technique projects crooked-line processed CMPs onto a straight line oriented in the general dip direction for the area. The new stacked sections more closely approximate a dip line and hence are more migration-friendly and interpretable than the crooked-line stacks. Methods of determining the lateral continuity of subsurface density contrasts were also applied to gravity data from the study area. Known collectively as potential field attributes, the analytic signal, the tilt angle, and the gradient of the tilt angle (the potential field wavenumber ) proved valuable in the analysis of the gravity data. Comparison of reflection seismic data from the southern and central Appalachians revealed a dichotomy of seismic reflectivity from east to west. A highly reflective crust beneath the Piedmont in both the central and southern Appalachians contrasts with a general lack of reflectivity beneath the Blue Ridge and Valley and Ridge provinces where coherent reflections are restricted to the upper 3-4 seconds of the data. This difference in reflectivity is interpreted as a fundamental difference in the location and orientation of preexisting zones of weakness between the different crustal regions with respect to the tectonic events affecting the Appalachians since the early Paleozoic. The combination of the results of new methods of seismic and potential fields processing with deep well and geologic information allowed the lateral continuity of two major structures in the central Appalachians to be examined. The Blue Ridge in Virginia was found to overly a duplex of Cambrian-Ordovician carbonates formed in response to stresses during the Alleghanian Orogeny. A large thrust sheet of similar carbonate rocks was interpreted beneath the Nittany Anticlinorium in West Virginia. To the south in Virginia, this thrust sheet is replaced by imbrication of the carbonate package. The change in structural style may be related to the existence of a lateral ramp or it may reflect the overall change in structural style from the central to southern Appalachians. / Ph. D.

Geomorphologists have long observed the influence of lithology on landscape form and evolution. However, the specific mechanisms by which this is accomplished are not well characterized. Here, I investigate the role of lithology in landscape evolution processes across spatial and temporal scales and geomorphic domains, to progress our understanding of the basic controls on the processes which shape Earth's surface. These investigations were carried out within the Valley and Ridge province of the Appalachian Mountains, where contrasts in strength of underlying lithologies (juxtaposed by Alleghanian deformation) exert a clear, dominant control on the fabric of the landscape, providing an excellent opportunity to study the influence of lithology on a variety of landscape evolution processes. First, I assess the geomorphic function of boulders found on hillslopes and channels in the Valley and Ridge province of the Appalachians, which are sourced from resistant lithologies capping ridgelines. High-resolution UAV surveys and field mapping of boulder distributions and characteristics reveal that boulders are abundant on hillslopes and highly concentrated in channels, often trap sediment upslope, and appear to be long-lived. These observations suggest that boulders act as armor for hillslopes and channels, shielding weaker underlying units from erosion and inhibiting fluvial incision, and therefore play an important role in preserving topography in the Valley and Ridge landscape, highlighting a specific mechanism by which lithology exerts an influence on topography in this setting. Second, I investigate the relative importance of rock strength and discontinuity spacing in setting fluvial bedrock erodibility by comparing knickpoint and non-knickpoint bedrock, which correspond to end-member erodibility cases, and assess how lithology impacts knickpoint expression. Detailed field surveys of 21 lithologic knickpoints, surrounding non-knickpoint reaches, and corresponding bedrock properties reveal three key outcomes: 1) discontinuity spacing is a stronger predictor of knickpoint occurrence, and therefore more significant in setting bedrock erodibility in this setting, confirming quantitatively the hypothesis that discontinuities exert a dominant control on fluvial erodibility, 2) knickpoint expression is a function of the unique combination of characteristics within a given stratigraphic interval, and therefore highly complex and specific to local conditions, implying that knickpoint morphology should be interpreted with extreme caution, and 3) because all 21 study knickpoints occur within the same unit, inter-unit heterogeneity must be accounted for before lithologic influence on channel profile convexities can be ruled out, rather than comparing to geologic map contacts. These findings represent an important contribution towards a more functional understanding of the influence of lithology on fluvial bedrock incision processes. / Doctor of Philosophy / It has long been observed that underlying geology has a strong impact on the shape of the surrounding landscape and influences the erosional processes that act within that landscape. However, though the importance of rock type in shaping landscapes is recognized, the specific mechanisms by which this is accomplished are not well understood. The work presented here investigates the role of rock type and rock properties in landscape evolution processes in both hillslope and river environments within the Valley and Ridge Province of the Appalachian Mountains. This setting is ideally suited for investigating the role of rock type on landscape evolution processes because of the wide variation in rock types present in this setting, which exert a strong influence on local topography (e.g., strong rocks form ridges while weak rocks underlie valleys). First, I mapped the distribution of large boulders on local Valley and Ridge slopes and mountain streams to assess the potential for these boulders to play a role in preserving local topography. Results show that boulders are sourced from resistant rock types found along ridgelines, and are abundant on hillslopes and highly concentrated in channels. Boulders also trap sediment upslope and appear to remain in place for long periods of time. These observations suggest boulders play an important role in slowing erosion of weaker rock types underlying hillslopes and channels, and therefore aid in preserving topography in this setting. Second, I conducted detailed surveys of local small-scale waterfalls and surrounding flat river reaches and compared properties of the bedrock between these locations to better understand how bedrock properties influence erodibility. In this setting, waterfalls often signify strong underlying bedrock relative to the rock beneath flat river reaches, so comparing bedrock properties between these areas should give insight into how properties like rock strength and bed thickness impact how erodible the bedrock is. Results show that bed thickness is the most important variable impacting bedrock erodibility in this setting, and that waterfall appearance is a product of the unique combination of bedrock properties within a given area. These results are important for improving our ability to model natural landscapes and erosional processes, and for developing a more complete understanding for the relationships between rock type and river morphology.

Eight study sites were established in mid-elevation, south aspect, mixed-oak forests in the Ridge and Valley and Allegheny Mountain physiographic provinces of Southwestern Virginia and West Virginia to address questions concerning the variability in species composition, richness, and relative abundance of vascular plant species in those communities. All forest strata were sampled using a nested plot design. Variability in species richness and species composition was found to be high. Total species richness values ranged from 84 to 273, and Sorrenson's Coefficient of Similarity index values indicated that approximately 46, 38, and 51 percent of the species in the overstory, mid-story, and herb stratum were the same among sites, respectively. However, despite differences in composition and richness, K-S tests revealed significant differences in the distribution of ranked relative abundance only in the mid-story at two sites. Differences did occur in the relative abundance of twelve growth form categories. While tree seedlings and perennial herbs dominated, on average, woody vines and fern species represented substantial coverage on sites in the Allegheny Mountains. Correlations among forest strata were weak. The greatest amount of variation in species richness was attributiable to the standard deviation of a forest site quality index (FSQI), which was thought to represent the variation in microtopography across each site. The lack of correlation and high variability in plant species richness and composition, despite similarities in topographic characteristics, reinforce the inherent weaknesses involved with using the chronosequence approach to studying ecological responses in the Southern Appalachian mixed-oak region. Future remeasurement and long term monitoring of these study sites, following the implementation of silvicultural manipulations, will provide the information needed to make inference on the effects of forest management practices on Southern Appalachian mixed-oak forests. / Master of Science

Thesis (D.P. Th.)--Bob Jones University, 2002. / Includes bibliographical references (leaves 322-338).

Thesis (D.P. Th.)--Bob Jones University, 2002. / Includes bibliographical references (leaves 322-338).

Thesis (D.P. Th.)--Bob Jones University, 2002. / Includes bibliographical references (leaves 322-338).

Thesis advisor: J. Christopher Hepburn / The Nashoba terrane of SE New England is one of three peri-Gondwanan tectonic blocks caught between Laurentia and Gondwana during the closure of the Iapetus Ocean in the early to mid- Paleozoic. U-Pb analyses (LA-ICP-MS) were carried out on zircon suites from the meta-sedimentary rocks of the Nashoba terrane. The youngest detrital zircons in the meta-sedimentary rocks of the Nashoba terrane are Ordovician in age. There is no significant difference in age between meta-sedimentary units of the Nashoba terrane across the Assabet River Fault Zone, a major fault zone that bisects the NT in a SE and a NW par. Zircon in meta-sedimentary rocks in the Marlboro Fm., the oldest unit of the Nashoba terrane, is rare, which may reflect the basaltic nature of the source material, and is commonly metamict. The Marlboro Fm. contained the oldest detrital grain of all the analyzed samples, with a core of ~3.3 Ga and rim of ~2.6 Ga indicating that it was sourced from Archaen crustal material. Detrital zircons from the Nashoba terrane show a complete age record between the Paleoproterozoic and Paleozoic that strongly supports a provenance from the Oaxiqua margin of Amazonia. The detrital zircon suite of the Nashoba terrane is distinct from both Avalonia and the Merrimack belt; however, they resemble zircon suites from Ganderia. This study proposes that the Nashoba terrane of Massachusetts correlates with the passive trailing edge of Ganderia. Finally, metamorphic zircon analyses of the terrane show that the Nashoba terrane experienced a peak in hydrothermal fluid infiltration during the Neoacadian orogeny. / Thesis (MS) — Boston College, 2011. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Thesis advisor: Yvette Kuiper / 40Ar/39Ar single-grain total-fusion ages of muscovite and biotite and one 40Ar/39Ar furnace step-heating age of hornblende from the Tadmuck Brook Schist, Nashoba Formation, and Ball Hill mylonite zone are used to reconstruct the late tectonic and metamorphic history of the Nashoba terrane in eastern Massachusetts. The data fall into three age populations. Age population I (~376-330 Ma) is interpreted as cooling after a migmatization event in the Nashoba terrane, population II (~300 Ma) may be associated with normal movement on the Clinton-Newbury fault, and population III (~267 Ma) is possibly related to cooling of the Rocky Pond Granite. No younger Alleghanian overprint was observed. / Thesis (MS) — Boston College, 2012. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

The Tugaloo terrane in the eastern Blue Ridge, located in the high-grade southern Appalachian crystalline core,contains small internal basement massifs, the Neoproterozoic Tallulah Falls Formation, and Paleozoic granitoid plutons. Detailed geologic mapping in the Lake Toxaway and eastern Big Ridge quadrangles was done to better understand the regional tectonic history. Whole-rock geochemistry was used to determine similarities between the augen phase of the 1.15 Ga Toxaway Gneiss and the 1.15 Ga Wiley Gneiss of northeastern Georgia. The study found that all eastern Blue Ridge orthogneisses are similar and probably share a source. The previously identified Whiteside, Looking Glass, and Pink Beds plutons, and the newly identified Horseshoe Rock and Round Mountain plutons were also characterized. All plutons are low-K, catazonal granodiorites and trondhjemites that plot as volcanic arc or syncollisional granites on tectonic discrimination diagrams. The Looking Glass, Pink Beds, and Round Mountain plutons were dated using U-Pb SHRIMP zircon geochronology, and their ages are 333 + 16 Ma, 371.3 + 4.2 Ma, and 342.5 + 2.4 Ma, respectively. Zircon saturation temperature estimates for these plutons, and a Whitney and Stormer two-feldspar estimate for the Round Mountain pluton, indicate that they intruded at 700-800° C. Whole-rock geochemistry was used to constrain the origin of amphibolites and hornblende gneisses around the Toxaway dome. One sample was a metabasalt with MORB composition, like other eastern Blue Ridge samples. Two other samples have a metasedimentary protolith . Migmatitic aureoles found in the amphibolite facies rocks around the Whiteside, Looking Glass, and Horseshoe Rock plutons are syn-intrusional and represent a zone of contact metasomatism. The new pluton ages constrain the regional deformation history. At least 6 deformations are recognized in the eastern Blue Ridge. Dominant regional foliation is traditionally attributed to the second event (~466 Ma). However, foliations measured within all plutons are identical to foliations measured in the surrounding rock, indicating that foliations had to form after the youngest pluton intruded (~333 Ma), and that Alleghanian deformation was dominant in this region. These observations do not explain cross-cutting relationships observed around older plutons and raise new questions about southern Appalachian tectonics.

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains x, 113 p. Includes abstract and vita. Advisor: Patricia Reagan, Dept. of Economics. Includes bibliographical references (p. 105-108).