Geology and Geography.

Chair: Keil Schmid, Mississippi Office of Geology Vicechair: Jack Moody, Mississippi Office of Geology

FRIDAY MORNING

Lamar I

9:30 PLANS FOR AN ENTERPRISE GEOGRAPHIC INFORMATION SYSTEM FOR MISSISSIPPI

Michael B.E. Bograd, Mississippi Office of Geology, Jackson, MS 39289

The State of Mississippi is planning an enterprise geographic information system (GIS) to include an enhanced clearinghouse of public remote sensing (RS) data and a computer model of the state. The goals are to provide accurate, high-resolution, accessible data for all users via the Internet and support more efficient, less costly government services. In June 2002 Governor Musgrove established the Advisory Commission on Remote Sensing Technologies to make recommendations concerning a vision for coordination of RS/GIS activities in the state. One recommendation will be to establish a policy board with the authority to make the vision become a reality. The Legislature has charged the Mississippi Department of Environmental Quality with (1) developing a digital model of the state and (2) coordinating RS/GIS activities in the state. The Mississippi Digital Earth Model (MDEM) will consist of the seven framework layers (geodetic control, elevation, orthoimagery, hydrography, transportation, political boundaries, an d cadastral). Funding for acquiring the high-resolution data (estimated $75 million) will involve federal, state, and local entities over the next few years. The other components of the project--to coordinate GIS activities, design the architecture of the Web portal, and establish standards--should have little cost. Mississippi has the potential to become a leader in RS/GIS through coordination of the resources at all levels of government and by taking advantage of the research and education capabilities of its colleges, the existing communication network, and the facilities at the Stennis Space Center.

9:45 STATUS OF GEOLOGICMAPPING IN MISSISSIPPI: A PROPOSAL TO ESTABLISH A STATEWIDE GEOLOGIC MAP MODEL

Stephen L. Ingram, Sr. (1)*, Fazlay S. Faruque (2), and Charles T. Swann (3), (1,3) Mississippi Mineral Resources Institute, University, MS 38677, and (2) University of Mississippi, University, MS 38677

During the past decade, geologic mapping activities in Mississippi have been conducted at 1:24,000 scale by the Mississippi Mineral Resources Institute, Mississippi Office of Geology, Mississippi State University, University of Mississippi, and the University of Southern Mississippi. Coordination between these entities is important to ensure continuity in statewide map products. To aid coordination, an ad hoc stratigraphic committee composed of representatives from these organizations began meeting annually in 1998 to provide continuity and guidance on mapping issues for the state. To date, no "standard" has been established and the ad hoc oversight committee has not resolved current stratigraphic mapping problems; albeit, the committee has attempted to address these issues. We propose that a renewed effort be made by the oversight committee to develop a statewide geologic map model to: establish a comprehensive map standard for the state that complements the USGS national mapping initiative; address GIS form at and metadata issues; specify minimum map components to be included in published geologic maps to ensure product utility for the public domain; include "scientific peer review," when needed, to address continuity issues. Statewide implementation of these elements should result in best-quality, defensible map products for the "public domain" that maintain the highest scientific standards, ensuring credibility and utility of the product.

10:00 FIRST LOOK AT MERGED 7.5-MINUTE GEOLOGIC QUADRANGLES IN MISSISSIPPI, A REGIONAL VIEW

David E. Thompson *, Daniel W. Morse, Peter S. Hutchins, and Jeremy L. Hurley, Mississippi Office of Geology, Jackson, MS 39289

The Mississippi Office of Geology has been mapping the surface geology of 7.5-minute quadrangles since the early 1990s, predominantly in association with STATEMAP activities. Surface geologic mapping was initiated along the Mississippi/Alabama state line and concentrated on differentiation of the Upper Midway and Lower Wilcox Groups. The previously undifferentiated lower Wilcox Group was separated into the Tuscahoma and Nanafalia Formations. The Nanafalia Formation was further divided into the Grampian Hills and Gravel Creek Sand Members. The Naheola Formation of the Midway Group was found to be continuous and unbroken along its outcrop and was separated into the Coal Bluff and Oak Hill Members. By 2001, surface mapping was largely completed along the outcrop belt northward to the Mississippi/Tennessee state line. A number of 7.5-minute geologic quadrangle maps were developed with Arc/Info and published as individual paper Open-File Reports. A primary focus of the surface mapping project is, ultimately, to up date the 1:500,000-scale 1969 Geologic Map of Mississippi. Recently, the individual 7.5-minute quadrangle geology coverages were merged utilizing ArcMap GIS software, creating a seamless compilation of what were previously solitary geologic map products. This compilation of surface geologic maps provides a regional representation of updated surface geologic mapping, a medium for comparison with older large-scale geologic maps, and a vehicle for updating the 1969 Geologic Map of Mississippi.

10:15 GIS AND REMOTE SENSING TECHNIQUES AUGMENT SURFACE MAPPING IN NORTH MISSISSIPPI

Stephen L. Ingram, Sr. (1) *, Greg Easson (2), and Khaled Hasan (2), (1) Mississippi Mineral Resources Institute, University, MS 38677, and (2) University of Mississippi, University, MS 38677

GIS and remote sensing techniques were used to develop a surface mapping method to augment geologic field mapping in a portion of the heavily vegetated terrain of north Mississippi. Four lithologic intervals were targeted: Loess; Preloess; Memphis Sand; and lower Wilcox. Lithologic variation was assessed using Landsat imagery, National Elevation Dataset, and conventional field data. Land use information was extracted from satellite imagery, topographic parameters were derived from elevation data, and textural characteristics were generated from these datasets to provide a basis for surface mapping. Lithologic boundaries were then digitized and check against available digital geologic maps, and a field check was conducted to determine continuity between spatial mapping and conventional field data. Results show that the following relationships exist between lithology, topography, and land use in north Mississippi: Correlation exists between the highly dissected outcrops of the Memphis Sand and forested areas du e to the steep slopes which develop on these consolidated fine- to coarse-grained sediments; correlation also exists between Loess and highly developed agriculture because of the gradual slopes which characterize these younger, indurated fine-grained sediments; the unconsolidated Preloess deposits are regionally extensive, have variable slopes that appear hummocky in texture, and form a geomorphic terrace above the underlying Memphis Sand. This investigation shows that an integrated GIS-remote sensing technique can be used effectively to develop a more comprehensive geologic database to augment conventional geologic field studies conducted in the heavily vegetated terrain of north Mississippi.

10:30 GEOGRAPHIC DISTRIBUTION OF MISSISSIPPI'S PRE-SUBTITLED LANDFILLS: A GIS APPLICATION FOR ENVIRONMENTAL AWARENESS

Ross D. Williams * and Fazlay S. Faruque, Mississippi Office of Pollution Control, Jackson, MS 39289, and University of Mississippi Medical Center, Jackson, MS 39216

Pre-subtitle D Landfills are serious concerns for potential groundwater pollution in the State of Mississippi. These landfills were operable before federal regulations were enacted in 1994 and were to close in response to Subtitle D. Siting of these landfills in Mississippi was performed without a thorough understanding of site-specific geology and hydrogeology. Many of these sites were operated without engineering controls to mitigate the release of contaminants into the subsurface. In addition, groundwater resources within the proximity of the vast majority of these sites are not monitored. The objectives of this project are: (1) to develop a GIS database to identify the location of these landfills, (2) to identify local water wells and groundwater resources that may be or have been impacted, and (3) to implement a risk-ranking system for these abandoned facilities based on available knowledge of the groundwater resources of the area. These landfill sites are visited, and location coordinates for each are o btained using GPS. Each facility was walked and anomalies noted. This is an ongoing project and will address the findings of the first phase of the investigation, landfills south of Interstate 20.

11:00 Break

11:15 A LARGELY COMPLETE BASILOSAURUS FIND IN THE UPPER YAZOO CLAY IN SCOTT COUNTY, MISSISSIPPI 

David T. Dockery III (1) *, James E. Starnes (1), and Scott Peyton (2), (1) Mississippi Office of Geology, Jackson, MS 39289, and (2) Mississippi Museum of Natural Science, Jackson, MS 39202

In August-September 2002, a largely complete skeleton of the archaeocete whale Basilosaurus cetoides was excavated from the Yazoo Clay in the Clearview Landfill in the SW/4, Sec. 34, 5 N., 9 E., Scott County, Mississippi. The bones rested on an ancient, shell-littered, iron-stained, sea-floor surface (SFS1) that separated as a bedding plane some 27 feet below the Yazoo/Froest Hill contact as exposed 800 feet north-northwest of the site. SFS1 was also marked by several flat-lying, ossified, vertebral disks. Correcting for regional dip, SFS1 was about 22 feet below the top of the Yazoo Clay, which has a total thickness at the site of about 320 feet. One measurement found a second seafloor surface (SFS2) to overlie the bones and enclosing clay at 0.68 foot above SFS1. These surfaces rested some several feet above a foot-thick lime bed, probably the upper of two lime units seen in the upper Yazoo Clay on regional geophysical logs. The bones rested in an arc that stretched 64.3 feet from the left jaw and 4.5-foot- long skull at the east end to the last vertebra at the west end; the straight-line distance was 61.4 feet. The rarity of encrusting organisms, such as oysters, on bone surfaces indicated rapid burial.

11:30 PRELIMINARY OSTEOLOGY OF A BASILOSAURUS CETOIDES FROM THE UPPER YAZOO CLAY IN SCOTT COUNTY, MISSISSIPPI

James E. Stames * and Scott Peyton, Mississippi Office of Geology, Jackson, MS 39289, and Mississippi Museum of Natural Science, Jackson, MS 39202

The nearly complete skeletal remains of an archaeocete whale Basilosaurus cetiodes were excavated from the late Eocene sediments of the Yazoo Clay in the Clear-view Landfill in southern Scott County. The delicate bone material was documented and removed in August and September 2002 under the direction of the Mississippi Office of Geology and the Mississippi Museum of Natural Science (MMNS). The bones were largely in place where the animal came to rest upside down on the sea floor some 34 million years ago. The skull and right jaw were present. All seven cervical vertebrae and 34 other vertebrae were recovered, though some tail vertebrae were missing. The largest lumbar vertebra measured 17 3/4 inches in length; the shortest tail vertebra found was 4 1/2 inches in length. Several boney disks were preserved. Ossified rugose masses were paired to the five sternal segments, including a well preserved manubrium and xiphisternum. Other large bones included 34 ribs, both scapulae, both humeri, and parts of the radii and ulnae. The carpal elements and phalangeal bones were scattered, and it is not yet known how complete these are at present. No vestigial pelvic or hind limb bones were recovered. Preparation of the skeleton is ongoing at the MMNS.

11:45 GEOLOGIC LICENSURE--A STATUS REPORT OF LICENSURE

Rick L. Ericksen, Mississippi State Board of Registered Professional Geologists, Jackson, MS 39225

Currently there are 28 states and 1 US territory with geologic licensure laws. States which have recently enacted licensure laws include Texas and Utah--both of which are currently in their "grandfathering" phase. Licensure initiatives are ongoing in New York State and activity for geologic licensure has been initiated in both Louisiana and Oklahoma. Initiatives in Canada defining professional practice and "qualified persons" has led to an increasing emphasis of the importance of licensure in the US. In Mississippi, the RPG Act of 1997 will shortly be entering into its 6th year of operation. The Mississippi State Board of Registered Professional Geologists (MSBRPG) has seen an increase in the number of formal complaints filed related to issues concerning the unlicensed practice of geology and as a result been more involved in enforcement issues. The MSBRPG has also been involved in other areas related to geologic practice including increased dialogue with other state regulatory agencies which require geologic input in compliance with their regulatory functions. The MSBRPG also continues with its Voluntary Continuing Education program which provides no cost to low cost continuing education opportunities for those desiring to further their geological careers and knowledge of geologic and regulatory information, concepts, and practices and it also continues with another important part of its regulatory function in its administration of geologic, qualifying exams on a semiannual basis.

12:00 Divisional Poster Session

GEOLOGIC INTERPRETATION OF HIGH-RESOLUTION SEISMIC DATA WITH SUPPORTING CORE DATA FROM MISSISSIPPI CANYON 798

Carol B. Lutken (1) *, Erika Geresi (2), Charles T. Swann (1), Andy Gossett (1), and Thomas M. McGee (1), (1) Mississippi Mineral Resources Institute and Center for Marine Resources and Environmental Technology, University, MS 38677, and (2) Stanford University, Stanford, CA 94305

Prior to the summer 2002 cruise of the R.V. "Marion Dufresne" in the Gulf of Mexico, the USGS solicited a request from the Center for Marine Resources and Environmental Technology (CMRET) for a core-site that would augment ongoing work in support of the establishment of a permanent sea floor monitoring station. During July, the R.V. "Marion Dufresne" collected a 28-meter core at the requested site in Mississippi Canyon. Density and P-wave velocity logs were acquired onboard. After the Exact location of the core was known, the CMRET included the core-site as a target during their August 2002 geophysical cruise. Two orthogonal, 6-kilometer seismic profiles were run across the core-site using a surface source (80 [in.sup.3] watergun) and deep-towed receiver. The seismic profiles contain a section of uniformly bedded sediments, and apparently deep seated diapiric features. Detailed time-stratigraphic analysis of the core is pending. These new data provide an improved interpretation--including subdecimeter stratal resolution--of the geology of this area of the Gulf from which no prior shallow subsurface information had been available.

FRIDAY AFTERNOON

Lamar I

1:15 HURRICANE SEASON 2002-HANCOCK COUNTY BEACHES

Jack S. Moody (*), Keil Schmid, and Stephen Champlin, Mississippi Office of Geology, Jackson, MS 39289

The 2002 hurricane season resulted in back-to-back events on the Hancock County, Mississippi, beach. This artificial beach furnishes infrastructure protection and recreational opportunities. Due to the extensive data set gathered and maintained by the Mississippi Office of Geology, reliable storm damage to the costly county beach can be assessed. Sediment movement and volumes can be analyzed with an eye toward future damage prediction and engineered replenishment design. Isidore was the first of these storms to impact the beach. Early estimates suggest a median of 1.6 m (5 ft.) of shoreline retreat or 41,000 cubic yards of sand moved offshore. That is roughly twice the average annual rate. One week later Lili's storm surge flooded low portions of the beach and beach roads. With Lili's eye landing in western Louisiana, it was possible to observe the storm surge mechanics on the Hancock County beach in relative safety. The 2 to 3 foot wave heights and 3 to 4 second wave periods were not unlike those generated f rom non-hurricane events. The difference was that the storm surge wave energies (1700 #/cu.yd. of water) were expended inland of the submerged beach. The peak of the surge event was documented on video and still photography by filming every hour from common observation points.

1:30 DEER ISLAND, COASTAL MISSISSIPPI-A GEOLOGICAL AND HISTORICAL STORY

Keil Schmid and Ervin G. Otvos (*), Mississippi Office of Geology, Jackson, MS 39289, and, University of Southern Mississippi, Ocean Springs, MS 39566

Deer Island is a spindle-shaped, 5.7 km long island off Biloxi and Ocean Springs that was recently added to the Coastal Preserves Program. Prior to being utilized by European settlers, it was inhabited by Indians for possibly more than four thousand years. The island has one of the few remaining natural sandy shores on the Mississippi coast. Since 1850, rapid erosion has reduced the island area by about one-third. Vibracores and auger samples taken for a renourishment study revealed that the island, like the coastlines in Harrison County and part of Jackson County, is cored by late Pleistocene beach ridges. The Gulfport Formation ridges, in combination with estuarine Biloxi Formation and alluvial Prairie Formation deposits, form the islands geological framework. During the Wisconsin glacial lowstand these deposits formed bluffs on the incised Biloxi River valley. Overlying them, a series of Holocene fresh and brackish water sediments were deposited before and during the submergence of the river valley under s teadily rising estuarine waters. Age dates suggest that sea-level rise slowed shortly after ca. 4650 14C yr B.P. The buried Pleistocene land surface slopes southeastward under the island and at lower elevations mud, sand, and intertidal marsh peat cover the Pleistocene units. Small textural changes in the surface deposits have a strong influence on shore retreat rates. Understanding how local geology impacts erosion rates is essential in designing beach renourishment and marsh reclamation projects.

1:45 DEER ISLAND: EVOLUTION AND MORPHOLOGY

Steven D. Sloan (*) and Keil Schmid, Millsaps College, Jackson, MS 39210, and Mississippi Office of Geology, Jackson, MS 39289

Deer Island was acquired in May 2002 by the State of Mississippi and incorporated into the Mississippi Coastal Preserves Program. The 5.7 km long island is located just offshore of the entrance to Biloxi Bay in Harrison County, Mississippi. Since the 1850s the island has lost nearly one third of its area to erosion and is now being considered for beach renourishment and marsh restoration projects. Deer Island consists of Holocene sediments overlying a core of the Pleistocene Gulfport formation. In general, the Pleistocene outcrops in the west and Holocene surficial sediments are dominant to the east, which is the most severely eroded portion of the island. In an effort to determine the island's future retreat patterns the present beach morphology and historical shoreline change rates were used to model the island's evolution. The island's morphology was mapped in the field using eight different morphology components and then grouped into six different shoreline classifications. The highest change rates occurr ed along shorelines with relict beach (Type 6) morphology classification; the lowest change rates occurred along shorelines with wooded beach (Type 5) morphology classification. An extrapolated shoreline has been created for the year 2050 by measuring and averaging the rates of change for both long (decades) and short-term (years) periods along the shoreline at the different morphology types and projecting that into the future. Based on this analysis, another 20-25% of the island may be lost in the next 50 years.

2:00 AN INVESTIGATION OF THE ORIGIN AND EXTENT OF A PERCHED WETLAND, MILLSAPS COLLEGE, JACKSON, MISSISSIPPI

Jeannie R. Bryson * and Stan Galicki, Millsaps College, Jackson, MS 39210

The origin and extent of a perched wetland has been investigated using historical topographic maps, hydrologic data, and dendrochronological techniques. It has been previously determined that the area of study supports hydrophytic vegetation and has developed hydric soils; however, no investigations to date have determined the aerial extent or origin of the wetland area. A network of shallow piezometers and a central well were installed to monitor the water table in the wetland area. Daily measurements were made over several intervals throughout a 12-month period. The analysis of annual ring increments from post and red oak trees in the area were done to determine if there is a link between the death of several trees as a result of increased soil moisture related to the wetland. Based on successive topographic surveys conducted over the past 44 years the perched condition originated as result of the construction of a baseball field on campus. It is likely that groundwater flow from terrace deposits above the Yazoo Clay is localized in a former topographic depression that was filled during construction.

2:15 STEADY-STATE EVALUATIONS Of RECHARGE TRENCHES, ROCKY MOUNTAIN ARSENAL (RMA), COLORADO

Maureen K. Corcoran (1) *, James H. May (1), David M. Patrick (2), and Neville Gaggiani (3), (1) Engineer Research and Development Center, Vicksburg, MS39180; (2) University of Southern Mississippi, Hattiesburg, MS 39406; and (3) U.S. Geological Survey, Denver, CO 80225

At RMA, the original recharge wells down-gradient of the 6740-ft long North Boundary Containment-Treatment System became unusable by microbial fouling after several years of service and were subsequently replaced by fifteen recharge trenches. The 160 to 400-ft long trenches have been in service for over ten years and are periodically evaluated in terms of their performance in delivering clean water back to the shallow alluvial aquifer underlying the installation. Various methods have been used to evaluate trench performance; however, during the last seven years constant head, steady-state hydraulic conductivity testing has been used. The basis for such testing is that significant trench fouling would be evident from decreased hydraulic conductivity values. The tests are conducted after recharge is maintained at a constant, known rate over a period of several hours to assure steady-state conditions are met. Water levels are then measured in monitoring wells within and down-gradient of the trenches. From the mo nitoring well data, the hydraulic gradient and thickness (depth) of water in the trench-aquifer system can be calculated. Knowing these parameters plus trench-water area and recharge, the hydraulic conductivity may be calculated from Darcy's law. These hydraulic conductivity values are based upon several assumptions relative to aquifer thickness and flow direction and represent conditions of the aquifer as well as the trench. Periodic testing has yielded hydraulic conductivity values representative of well-sorted sand or gravel, indicating satisfactory trench-aquifer performance, and they have been found to deliver reliable, cost-effective information without interfering with recharge.

2:30 OVERVIEW OF THE MERG-MMRI-UNIVERSITIES RESEARCH INITIATIVE

Stephen L. Ingram, Sr., Mississippi Mineral Resources Institute, University, MS 38677

The Mississippi Energy Research Group (MERG), Mississippi Mineral Resources Institute (MMRI), and the state's four research universities (JSU, MSU, UM, and USM) have formed a coalition to conduct focused energy research for the state. This joint research initiative was undertaken because applied research essentially has been abandoned by the energy industry. Over the past decade federal funding has been sharply curtailed and deep state budget cuts spanning the past three years have seriously impacted all state agencies. The result is the elimination of upstream energy research in all but MMRI and the state's four research universities. The academic-industry partnership provides a bridge to address these funding difficulties by pooling resources. MERG, as the industry coalition partner, provides guidance on energy research needed to the support the natural resource industry. In keeping with its mission, MMRI coordinates energy resource research conducted by the state's universities. Both MMRI and the universit ies supply staff expertise and research facilities toward projects endorsed by MERG. This partnership represents the first concerted effort in more than twenty years to bring Mississippi's natural resource industry and academic communities together to focus on energy research within the state. Together, the coalition is addressing critical issues facing our state's energy supply and has begun to focus on potential "new plays" that could have high economic impact for all stakeholders--public and private.

2:45 Break

3:00 RAYLEIGH WAVE MEASUREMENT OF THE SOIL PROFILE

Wheeler Howard *, Craig J. Hickey, and James M. Sabatier, University of Mississippi, University, MS 38677

Rayleigh waves are seismic waves that propagate at the boundary of an elastic solid and a free surface. These waves account for approximately 67% of the energy created by a point source mechanical disturbance of an elastic medium. The air-soil interface is an approximate free surface boundary due to the impedance mismatch between air and soil. Another characteristic of Rayleigh waves is their exponential decay of amplitude in the elastic medium as distance from the free surface increases. This attribute is used in the spectral analysis of surface waves (SASW) to study material properties and structures as a function of wavelength. The depth at which the Rayleigh wave samples the soil is approximately one-fifth of the wavelength, therefore; knowledge of the dispersion curve allows for measurements of soil properties as a function of depth. This work will present calculations of Rayleigh wave dispersion curves for depth dependent soils. Data from a Rayleigh wave survey conducted in North Mississippi will be com pared with model calculations.

3:15 SEISMIC INVESTIGATION OF SURFACE DEFORMATION ASSOCIATED WITH THE KILMICHAEL DOME, MONTGOMERY COUNTY, MISSISSIPPI 

Steven D. Sloan * and James B. Harris, Millsaps College, Jackson, MS 39210

The Kilmichael Dome, first identified 70 years ago, is a circular feature exposed in unconsolidated Paleocene and Eocene sediments of north-central Mississippi. The structural complexity of the area, including zones of intense faulting and uplifted strata, has led to several suggested origins for the formation of Kilmichael Dome, including meteorite impact and regional tectonics. A shallow shear-wave seismic reflection profile was collected over a complex zone of surface faults, the Salem Church Fault Zone (SCFZ) on the northern flank of the Kilmichael Dome, with the goal of imaging the subsurface expression of deformation associated with the SCFZ. Further research will explore the relationship between shear-wave anisotropy and near-surface structural deformation utilizing multicomponent reflection and downhole seismic data to investigate shallow deformation associated with the Kilmichael Dome. This data set will allow us to more accurately assess the seismic velocities of the shallow sediments and constrain any identifiable shear-wave anisotropy. Recent field studies have identified surface deformation in the Kilmichael area that suggests high fluid pressures and sediment flow. If these features have a preferred alignment, our intent is to determine their orientations using multicomponent seismic methods. In addition to increased seismic resolution gained by using shear-waves in unconsolidated, water-saturated sediments, measurement of near-surface directional polarizations may provide valuable information for identifying neotectonic deformation, evaluating associated earthquake hazards, and guiding future paleoseismologic investigations.

3:30 THE COURTLAND AND CURTIS STATION EARTHQUAKES OF PANOLA COUNTY, MISSISSIPPI-A COMPARISON OF SIMILAR SEISMIC EVENTS

Charles T. Swann * and Terry L. Panhorst, University of Mississippi, University, MS 38677

The Courtland and Curtis Station earthquakes occurred in Panola County, Mississippi, in 1999 and 2002, respectively. Both events had hypocentral depths of approximately three miles, similar magnitudes (a duration magnitude 2.7 for the Curtis Station event and 2.8 for the Courtland event), and epicenters less than 20 miles apart. Both of these earthquakes are assigned to the White River Fault Zone which trends northwesterly through Panola County and into Arkansas. With so many similarities, similar intensities and felt areas would also be expected. These characteristics are, however, markedly different. The Courtland event had an associated felt area of approximately 100 square miles while the Curtis Station event was felt over an area of only approximately four square miles. Intensities also differed with a maximum intensity value of IV in the Courtland event and an intensity value of only II associated with the Curtis Station event. As the Curtis Station epicenter was located within the Mississippi River flo od plain, and the Courtland epicenter on the Tertiary highlands, we suggest these local differences are related to the differences in soil response to seismically-induced vibrations.

3:45 THE WHITE RIVER FAULT ZONE: A SOURCE OF SEISMIC CONCERN IN NORTHWEST MISSISSIPPI

Terry L. Panhorst * and Charles T. Swarm, University of Mississippi, University, MS 38677

The White River Fault Zone was first recognized by Fisk (1944) based upon topographic alignments and soil tonal changes visible on aerial photography. This feature extends from near Newport, Arkansas on the northwest end to about Grenada, Mississippi on the southeast end, a distance of 280 kilometers. In Arkansas this structural zone coincides with the orientation of the White River and the southern terminus of Crowley's Ridge. The Mississippi River bluff line in Panola County, Mississippi has the common N4OW orientation found elsewhere along the White River Fault Zone. Although lacking exact boundaries, this zone has generally been represented as about 15 kilometers wide. Geomorphic analyses of stream drainages along the White River Fault Zone fail to show preferred alignment or channel displacements indicative of active surficial faulting or regional tilting. In the past 25 years, however, at least 15 earthquakes have been recorded within the White River Fault Zone, most in the range of magnitude 1 to 3. Th e largest earthquake in the state of Mississippi, which occurred December 1931 with an estimated magnitude of 5, was along the White River Fault Zone near Charleston in Tallahatchie County. Although outside of the traditional limits of the New Madrid Seismic Zone, the White River Fault Zone appears to be a seismically active area that warrants serious seismic hazard assessment. Mitigation measures should be formulated for critical facilities such as hospitals, police and fire stations, and schools.

4:00 Divisional Business Meeting