Spring 2006 Meeting Abstracts

Geology and Geography faculty and students will be presenting papers and posters this spring semester at the national AAG, regional Geological Society of America, and other meetings. Read their abstracts by clicking on the links below...

Alexander, C, clark@skio.peachnet.edu, Skidaway Institute of Oceanography, 10 Ocean Science Circle, Savannah, GA 31411 United States

Walsh, J, walshj@mail.ecu.edu, East Carolina University, Department of Geology and Coastal Resources Management, Greenville, NC 27858 United States

Orpin, A, a.orpin@niwa.co.nz, National Institute for Water and Atmospheric Research, NIWA Greta Point, Wellington, New Zealand

Sumners, B, bws0107@mail.ecu.edu, East Carolina University, Department of Geology and Coastal Resources Management, Greenville, NC 27858 United States

Kuehl, S, kuehl@vims.edu, Virginia Institute of Marine Sciences, P.O. Box 1346, Glouchester Point, VA 23062 United States

Pratson, L , Lincoln.Pratson@duke.edu, Duke University, Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708 United States

Gerber, T , tpg@duke.edu, Duke University, Division of Earth and Ocean Sciences, Duke University, Durham, NC 27708 United States

Carter, L. , l.carter@niwa.cri.nz, National Institute for Water and Atmospheric Research, NIWA Greta Point, Wellington, New Zealand

The development of dispersal systems on tectonically active margins is determined not only by the processes of fluvial discharge, oceanic sediment redistribution and sediment accumulation, but by structural elements as well (e.g., folding, faulting, submarine failures). The Waipaoa dispersal system exhibits a number of features that reflect the presence of tectonic elements that are affecting the development of the shelf and slope, including: uplifted anticlines; truncated anticlinal structures on some parts of the shelf edge; a large failure on the midslope blocking seaward sediment transport; clogged submarine canyons; and fault-derived accommodation space on the outer shelf. This study, a part of the NSF Margins Source-to-Sink initiative, is examining grain-size distributions, radionuclide activities (Th-234, Be-7, Pb-210, C-137, C-14) and tephrachronology to determine the influence of tectonic factors on the distribution of slope sedimentary processes in space and time. Be-7 activities suggest that fluvial sediment is rapidly reaching the shelfbreak, whereas Pb-210 accumulation rates suggest that sediment accumulation is actively being directed by tectonic elements. The distribution of rates demonstrates that significant material is accumulating on the outermost shelf at rates approaching 1 cm/y, is transported off-shelf to accumulate in the upper portions of submarine canyons along much of the margin at rates up to 2.5 cm/y and decreases below 1200 m water depth to approximately 0.2 cm/y in canyon and intercanyon sites. Farther seaward, rates are uniformly low, 0.05-0.1 cm/y, as significant quantities of sediment are blocked from further seaward transport by a large failure deposit. However, using high-resolution seismic data, the pattern of sedimentation appears to be broadly similar through time, suggesting the dominant drivers for sediment accumulation (e.g., tectonism, sediment supply and removal) have consistently varied through the Holocene.

Real-time kinematic global positioning systems (RTK-GPS) have been widely adopted by coastal researchers for the purpose of monitoring coastal change, but survey design is not standardized and the technology's potential has been underutilized in the investigation of questions requiring 3-dimensional topographic information. Most researchers use the equipment to measure widely-spaced profile lines and/or some proxy of the "shoreline" for comparison with older maps and aerial photos. Not only is the selection of this datum prone to error, but the limited spatial coverage of these methods severely restricts the range of applications for which the data can be used.

Detailed beach topography can be measured efficiently and accurately with the adoption of a survey design and data collection strategy similar to what was used for monthly beach surveys over a 2-year period on Shackleford Banks, NC. With a Trimble 4700 system mounted on an all-terrain vehicle (ATV), 6-11 alongshore lines were measured at breaks in slope on a complex beach while cross-shore tie-in lines measured in areas selected for their morphological representativeness further increased data density. This resulted in the collection of 30,000 to 80,000 data points on the beach of this 15-km long island during each typical 4-day survey period. RTK-GPS was also used to establish survey control point coordinates and frequent tests ensured the accuracy and precision of surveyed measurements. Kriging in ESRI's ArcMap produced detailed, accurate and flexible maps that were used to calculate and visualize changes in morphology and volume, as well as to derive and compare any desired datum or profile. LIDAR data were processed in the same way and analyzed in conjunction with the GPS data.

RTK-GPS is becoming increasingly user-friendly and widespread in its use, while scientists, government agencies, and the public are increasingly concerned with better understanding the ways in which our coastlines are changing. Carefully designing surveys will allow these data to be more useful for a multitude of applications.

North of Asheville, NC, the western Blue Ridge thrust complex consists of a series of thrust sheets that lie NW of the Burnsville fault. These thrust sheets are separated by thick greenschist-facies Alleghanian shear zones. Trupe et al. (2004) suggested that the Sams Gap-Pigeonroost (SGPR) fault, exposed near the TN-NC border, splays off the Fries fault west of the Grandfather Mountain window, and that the Fries fault therefore lies between the Burnsville fault and the SGPR fault. Near the Grandfather Mountain window, the Fries fault is a thick greenschist-facies mylonite zone. Our previous mapping suggests that the Fries fault should extend to into the Sams Gap and Mars Hill quadrangles. Merschat (1977) mapped a stratigraphic discontinuity in the Mars Hill quadrangle, and suggested that it is either a fault or an unconformity. This study was undertaken to locate the Fries fault in the Bald Creek, Sams Gap, and Mars Hill quadrangles, and to determine if Merschat's stratigraphic discontinuity is equivalent to the Fries fault. Basement rocks between the Burnsville fault and the SGPR fault consist of intensely folded, locally migmatitic biotite-hornblende gneiss, biotite gneiss, amphibolite, and calc-silicate rock, intruded by mafic rocks of the Bakersville Intrusive Suite. These mafic rocks contain amphibolite-facies assemblages, with local occurrences of granulite-facies assemblages near the Burnsville fault. Mafic dikes below the SGPR fault are slightly lower grade. We have found no evidence of a greenschist-facies shear zone coincident with the mapped stratigraphic discontinuity in the Mars Hill quadrangle. However, a thick greenschist-facies shear zone occurs ~10 km NW of this contact, in the SE corner of the White Rock quadrangle. This shear zone strikes NE, dips moderately to steeply SE and contains mylonite and ultramylonite with abundant SE-trending lineations. Outcrop-scale kinematic indicators show top-to-NW sense of shear. Mafic dikes within the shear zone have been retrograded to greenschist-facies assemblages and rotated to near concordance with mylonitic foliation. At present, it is unclear whether this shear zone represents the SGPR fault or the Fries fault. Further mapping is in progress to resolve this question.

In this paper we will discuss recent progress on constraining genetic relationships between asteroids in dynamical clusters or families. The presence and nature of collisionally-produced asteroid families provide important constraints on the processes involved in the disruptions of large (~100-1000 km diameter) planetesimals, on the collisional lifetime of asteroids as a function of size and composition, on the thermal history and internal compositional structure of their parent bodies, and on the rate of orbital diffusion in the asteroid belt.

A dynamical asteroid family is a group of asteroids that follow similar orbits about the Sun. There are disagreements on both the total number of dynamical families and their memberships. In addition, physical studies of asteroids and meteorites suggest that there is a problem with both the number of families identified to date and the inferred homogeneity within these families.

A genetic asteroid family is one in which the members were derived from a common parent body. Genetic families provide glimpses of the interiors of small planetary objects whose compositions, thermal evolutions, and geochemical processes were established by the ambient conditions present during the formation epoch of the solar system. Thus asteroids provide the only in situ record from the earliest part of solar system history for the mainbelt region.

The most reliable way of testing the reality of asteroid families is by deriving the mineralogy of individual members by remote sensing techniques. However, significant progress can be made by using meteorites as validity checks on asteroid compositional interpretations derived from remote sensing data. That is a primary goal of the Family Asteroid Compositional Evaluation Survey, which was established to fill gaps in existing family asteroid spectroscopic databases and to obtain new data on additional family members.

In order to accurately derive the mineralogy of asteroid from ground-based, remotely-sensed data, it is essential to remove atmospheric contamination effects from the spectra as completely as possible. This is particularly important with respect to near-infrared data (~7.2-2.5 microns) because absorption features due to atmospheric water vapor occur in mineralogically critical portions of this spectral region.

Abstract:
Colonial development in German East Africa was explicitly designed to eliminate Zanzibar's economic and cultural influence on the mainland. Labor, educational, transportation, and security policies were targeted at Islam as a main source and reflection of Zanzibar's power. This paper demonstrates both the anti-Islamic animus behind these policies and the Christian basis of German nationalism. Nationalism existed through the relationship of nation to patriarchy and racism, as well as religious prejudice. This paper, based on archival research in the German and Tanzanian National archives, explores these connections.

Neogene sedimentary rocks in the vicinity of Statesboro, GA consist of clastic rocks of the Miocene Coosawhatchie Formation. The rocks of the study area are weakly consolidated fine to coarse, locally conglomeratic, clayey sandstones with interbedded mudstone and siltstone. The presence of ghost shrimp burrows (Ophiomorpha nodosa) indicates that at least some of the Coosawhatchie Formation was deposited in an intertidal or shallow marine environment. Outcrops throughout the study area contain ubiquitous systematic joint sets. This study was undertaken to record fracture morphology, lithology, and the relative ages of the fracture sets found in the rocks of the Coosawhatchie Formation. A data set of 785 joint measurements was analyzed using stereonets and rose diagrams. Two joint set orientations were found to be dominant; I) 000°-180° +/- 20° and II) 070°-250° +/-20°. Three minor joint set orientations are III) 035°-215° +/- 15°, IV) 105°-285° +/- 15°, and V) 140° -320° +/- 15°. Dips of joints range from 75° to 90°. Relative age relationships, determined from joint terminations, indicate that set II is older than set I. Age relationships among the minor sets showed that set V is younger than the other two minor sets (III and IV). Age relationships between minor sets III and IV have not been determined. A strong relationship between lithology and fracture propagation exists. Fractures are better developed in sandstone layers than in clay-rich units. With increasing percentage of clay in sandstones, fractures are poorly developed and are typically non-linear. In outcrops with interbedded sandstone and mudstone, fractures in sandstone layers die out or terminate abruptly at contacts with mudstone layers. The joint orientations in this study are consistent with orientations and deformation sequences noted by previous workers in the Coastal Plain of GA (Bartholomew et al. 2000; Davis and Rich, 2005). The presence of systematic joint sets throughout sedimentary rocks of the GA Coastal Plain suggests fracturing in response to regional tectonic stresses, rather than localized deformation associated with discrete structures.

North of Millstone Landing near Hardeeville, Jasper County, South Carolina, the Savannah River has exposed an approximately 70 to 80 meter long cut bank, resulting in a 5 to 6 meter vertical bluff of complex undifferentiated fluvial terrace deposits. The site is within the Southeast Georgia Embayment, where relief is <30 meters. The cut bank reveals an atypical stratum of poorly sorted, well-rounded, and low sphericity (prolate/oblate) clastic and bioclastic materials ranging from very fine sand (.0625mm) to boulders (>256mm), with one bioclast having a length and width of 76cm and 28cm, respectively, and weighing 15kg. The stratum varies in thickness from 4cm to 4.6meters and dominant rock types include polycyclic quartz clasts, many showing signs of prior metamorphism, interspersed with highly weathered friable microcline. There is also an abundance of silicified fossiliferous cobbles and boulders. The clasts are located at the base of the subject stratum with their long axes generally oriented at right angles to the bluff's north-south trend, indicating probable paleocurrent directions. Silicified wood bioclasts represent angiosperms and gymnosperms; thin section analysis reveals Betula and Palmoxylon (Division Magnoliophyta), as well as Metasequoia (Division Pinophyta). Silicified cobbles of homogeneous masses of Turritella contain whole and fragmented shells, and silicified cobbles with Bryozoan colonies were also recovered. The most difficult part of this project has been determining how this unique material arrived at its current location. Considering the mass and size of the material, a significant fluvial event or events must have occurred to provide the critical velocity necessary for entrainment and rounding. Times of glaciation, with increased gradients of the Savannah River caused by significantly lowered sea level could have lead to such high flow velocity events. More research is necessary to determine if this site is unique within the coastal plain environment.

Deformation in Alleghanian shear zones in northwestern North Carolina and northeastern Tennessee is generally characterized by ductile deformation, locally overprinted by cataclastic features. Past workers have recognized the cataclastic overprint primarily in the westernmost shear zones (i.e., toward the foreland) and have suggested this as a manifestation of the faults bringing mylonitic rocks to shallower crustal levels and into a more brittle deformation regime. Our more recent work suggests a more complicated deformation history for these rocks. Cataclastic deformation occurs at least locally in all of the shear zones between the Grandfather Mountain and Mountain City windows. Additionally, rocks from several locations show evidence of a sequence of ductile-brittle-ductile-brittle deformation. Outcrop-scale features include veinlets of ultracataclasite (or pseudotachylite?) that were subsequently transposed into a mylonitic fabric. This mylonitic fabric shows later brittle fracturing. Thin sections of mylonitic granitic rocks show ribbons of dynamically recrystallized quartz that have been broken and displaced by cataclastic processes. The broken clasts of quartz ribbons show evidence of a subsequent rotation in a ductile matrix that is further overprinted by fracturing. We suggest that the multiple episodes of contrasting deformation styles occurred at equivalent structural positions, but resulted from variations in other conditions such as strain rates, fluid pressures, and/or strain hardening.

Wei Tu, Department of Geology and Geography, Georgia Southern University, Statesboro, GA 30460-8149

Daniel Sui, Department of Geography, Texas A&M University, College Station, TX 77845

Abstract: Setting in the context of current discussions on the digital city, this paper presents an empirical analysis on the transformation of economic structure and examines its environmental implications for Austin, Texas. This paper traces the evolution of Austin from a college town to a technopolis specializing in information and communication technology (ICT), and the concomitant environmental implications. The authors urge policymakers and urban managers to pay more attentions to three types of environmental problems in Austin in particular and other rising digital cities in general: 1) environmental impacts of the ICT sectors; 2) indirect impacts of non-manufacturing economic sectors such as information and service sectors; and 3) the consumption side of the economy. The authors argue that it is high time to examine new policy initiatives to harness the power of the new economy to achieve the goals of sustainable development in the information age.

Wei Tu
Department of Geology and Geography,
Georgia Southern University
Statesboro 30460-8149, USA
Email: wtu@georgiasouthern.edu

Abstract
It is hypothesized that intangible information is gradually substituting tangible energy/material in the emerging digital economy and the information age, which bears interesting social, economic and environmental implications. This research attempts to test the above hypothesis by studying the structural change of regional economic activities in the United States from 1990 to 2000 due to the difficulties in directly quantifying information. 20-sector (Two-digit 2002 NAICS) IO models are constructed for the eight regions of the United States in the years of 1990, 1995, and 2000. By incorporating the Input-Output (IO) analysis, the trends based on the direct, indirect effects of the IO models and the inter-sectoral transactions are assessed. The employment of Geographic Information Systems (GIS) also enhances the visualization of the analytic results. The findings of this study will also shed some light on the questions related to the environmental consequences of the digital economy, such as will the information (bit)-based new economy be more environmentally friendly than the energy/material (atoms)-based industrial economy?

Neoproterozoic to Cambrian greenschist facies rocks of the Persimmon Fork and Richtex Formations along the northwest side of the Little River valley consist of intermediate to felsic subaqueous tuffs and coarse volcaniclastics interlayered with increasing proportions of greenstone, greywacke and mudstone toward the southeast. The succession represents a transition from a proximal volcanic facies dominated by pyroclastic flows and coarse volcaniclastic rocks to an inner distal facies dominated by mudstones and fine tuffaceous rocks. Samples (52) of metavolcanics and associated intrusive rocks were analyzed for major and trace elements by ICP and ICP-MS respectively, using Li-metaborate fusion sample preparation. Classification of metavolcanic rocks using a Zr/Ti-Nb/Y plot indicates the major pyroclastic units are andesites and dacites. Greenstones plot as tholeiitic basalt and basaltic andesite. Tectonic discrimination of the basaltic rocks based on Ti-Zr-Y variation favors arc tholeiite; however, Th-Hf-Ta discrimination suggests calc-alkaline basalts, source enrichment or crustal contamination. Application of granitoid tectonic discrimiantion (Ta-Yb, Nb-Y) schemes to samples of variably foliated quartz diorite, biotite granite and granophyre show a clear volcanic arc affinity suggesting the plutons were essentially coeval with arc volcanism.

The Department of Geology and Geography at Georgia Southern University (GS)maintains a history of teaching pre-service and in-service teachers basic science concepts in classroom, lab and field settings. The authors began teacher education classes in 1988 with federal funding of summer courses through the Eisenhower Higher Education Act, now known as Improving Teacher Quality (ITQ). The Eisenhower/ITQ-funded St. Catherines Island Sea Turtle Conservation Program has provided fundamental science training as a field laboratory for coastal geology studies and served critical conservation needs for fifteen years. The NSF-funded Partnership for Reform in Science and Math currently provides essential funds to prepare teachers delivering earth science to 6th graders. The growth of earth science learning communities promotes continuing earth science education and dissemination of resources to active teachers. Industrial minerals have been a focal point for classes as both teachers and students appreciate the value of minerals in computers, CD players, and cars, making the subject both practical and fascinating. Field trips to mines and quarries allow teachers to build individual collections of samples and images as a base for lesson/project plans. Undergraduate students at GS are introduced to mineral resources in the Environmental Geology Laboratory Course. An NSF grant (DUE 0311730) allowed the purchase of a Rigaku Mini-Flex XRD unit and JADE search-match software, allowing students to investigate mineral components in household products and construction materials. The labs fufill part of the core-curriculum lab-science requirements exposing a large, diverse cross-section of students to mineral science using current technology. Emphasizing mineral science in both the undergraduate curriculum and graduate/enrichment courses for teachers is essential to improve public understanding of our industrial mineral requirements.

Examination of slopes in the Tandayapa Valley, Ecuador and surrounding Cordillera Occidental suggests that the initiation of contemporary natural landsliding is typically restricted to the convex ridgetop crest of very steep main valley slopes and to upper parts of slopes that descend into 1st and 2nd order tributary valleys. Typically, ridgetop crests exhibit several well-developed soil horizons within the upper 2-2.5 m separated by layers of sand from volcanic ash and/or pyroclastic flow deposits. Whereas, thin regolith profiles usually consisting of less than a meter of soils and volcanic sands overly deeply weathered but in-situ andesite bedrock were observed in other upper and midslope locations. The limited evidence available so far suggests that natural landslide occurrences are associated with those parts of the slope where there is sufficient thickness of soils and sediments to be able to fail but which is effectively unsupported from below ­ we term this soil cornice development. We argue that volcanic deposits accumulate on ridgetops and on any low gradient slopes, but accumulation on the upper valley slopes are limited by very high gradients, with most airfall materials sliding downslope as it accumulates. The midslope and lower slopes of the main valley and tributary valleys are thickly mantled with volcanic sediments, palaeosols and colluvial materials composed of airfall sediments that failed to accumulate on the steepest slopes. Their high frictional strength and good drainage enable them to remain. Natural failures of these slopes appear unlikely.

Xingyou Zhang and Wei Tu, Department of Geology and Geography, Georgia Southern University, Statesboro, GA 30460-8149

This study investigates the spatial and temporal clusters of narcotics activities in Chicago neighborhoods and their ecological association with the characteristics of neighborhood social and built environments. The primary neighborhood unit of this study is defined as Chicago police beat, the basic geographic unit for routine Chicago patrol activities and law-enforcement. The narcotics activity data are collected from Citizen Information Collection for Automated Mapping (ICAM) system developed by the Chicago Police Department. The neighborhood-level data are integrated within Geographic Information Systems (GIS) environment from multiple sources such as U.S. Census Bureau and Metro Chicago Information Center (MCIC). An empirical Bayesian spatial cluster analysis is applied to identify the neighborhood clusters of narcotics activities in Chicago.

The exploratory data analysis based on a three-month (July to September, 2005) period data shows that narcotics activities are concentrated more in western and southern Chicago. A spatial cluster analysis further identifies: 1) a significant high level cluster of narcotics activities in the police beats within four Chicago community areas: Austin, East and West Garfield, North Lawndale, 2) a few significant low level clusters of narcotics activities in northern Chicago, and 3) some spatial outliers of narcotics activities across Chicago.

The relationship between narcotics activities and neighborhood social and built environments will be evaluated to identify the risk and protective factors at the neighborhood level using Bayesian spatial Poisson regression models. Spatiotemporal cluster analysis will be adopted to identify the appropriate time for interventions. The above methods will be applied on a longer time series of narcotics activities data.

This study shows that the state-of-the-art geospatial analytical techniques will allow law-enforcement agencies and policymakers to more effectively and efficiently identify the spatiotemporal clusters of increasing narcotics activities and to more strategically target the narcotics-fighting efforts at desirable neighborhood levels. GIS is able to objectively quantify neighborhood social and built environments, while spatial statistical methods provide powerful tools to evaluate neighborhood narcotics activities, to detect their relationship with neighborhood contexts, and more importantly, to facilitate the implementation of preventive interventions of narcotics activities.