GEOLOGY AND GEOGRAPHY.
Vicechair: Ezat Heydari, Mississippi Office of Geology
8:30 Symposium: ACTIVE TECTONICS IN NORTHERN MISSISSIPPI
8:30 SOME COMMON TYPES OF GROUND FAILURE AND TESTS TO DETERMINE THEIR SEISMIC OR NON-SEISMIC ORIGIN
Stephen Obermeier, EqLiq Consulting, Rockport, IN 47635
Liquefaction-induced features are being used in widely differing seismotectonic settings to prove paleoseismic strong shaking, and to approximate epicentral locations and levels of shaking and magnitudes (e.g., Obermeier and Dickenson, 2000, BSSA, v. 90; Obermeier et al., in press, 2000, USGS Open-File Rept., Paleoliquefaction studies in continental settings: geologic and geotechnical factors in interpretations). Using liquefaction effects is a preferred method for paleoseismic interpretation in many places. In regions of nonliquefiable deposits, other ground-failure types have been used with limited success to evaluate paleoseismicity. Interpretations (and misinterpretations ) have been based on plastically deformed fine-grained sediment, clastic infillings from above, landslides, rockslides, precariously balanced rocks, weathering features, frost effects, plus others. Concepts and analysis procedures for their application commonly are only crudely developed or only crudely sensitive. But for some (man y?) of these types of features the question of seismic origin could be addressed better by using principles for proving the origin of liquefaction-induced features, with minor modifications. For suspected liquefaction-induced features, a seismic origin must accord with regional and local patterns, must have proper morphology and timing, and, additionally, the possibility of nonseismic mechanisms must be eliminated (Obermeier, 1996, Engr. Geol., v. 44). For assessing a seismic origin to other feature types (as above), the criteria would be essentially the same as for seismically induced liquefaction, and only the possible nonseismic triggering mechanisms would differ.
9:30 LIQUEFACTION IN MEMPHIS AND SHELBY COUNTY, TENNESSEE
Roy B. Van Arsdale, University of Memphis, Germantown, TN 38139
Reconnaissance along major streams in Shelby County, Tennessee, revealed earthquake-induced sand dikes in cut banks of the Wolf and Loosahatchie rivers. Most of the dikes are near the mouths of these rivers within the city limits of Memphis, but one dike occurs 36 km upstream in the bank of the Wolf River in Collierville. The dikes range in width from 1 to 50 cm and at some localities can be traced vertically as much as 4 m from their source bed to within 50 cm of the flood plain surface. The age of the dikes is unknown, but they are interpreted to be from the great 1811-1812 New Madrid earthquakes. The larger number of dikes and upstream extent of liquefaction along the Wolf River suggest that liquefaction susceptibility is greater in the Wolf River flood plain than in other flood plains in Shelby County. This greater liquefaction susceptibility of the Wolf River flood plain appears to be due to the abundance of sand in its basal point-bar sequence and a relatively thin overbank silt/clay cap. Channelizatio n of the Wolf River in 1964, and subsequent river entrenchment has reduced flooding along the lower reaches of the river thus permitting flood plain development. However, the channelization has also increased susceptibility for earthquake liquefaction and associated lateral spreading of the Wolf River flood plain and increased earthquake risk due to building development on the flood plain.
10:15 LIQUEFACTION AND OTHER POSSIBLE SEISMOGENIC FEATURES SOUTHWEST OF THE NEW MADRID SEISMIC ZONE IN EASTERN ARKANSAS
Robert E. [Lemmer.sup.*], Haydar J. Al-Shukri, Jeffrey B. Connelly, and Hanan H. Mahdi, University of Arkansas, Little Rock, AR 72204
Aerial and surface reconnaissance has discovered earthquake-related features approximately 44 to 100 km southwest of Marked Tree, Arkansas. A detailed subsurface investigation was conducted at three sites, two near Marianna, Arkansas and one near Parkin, Arkansas. Three trenches were excavated revealing three large ([greater than] 107 m X 55 m) elliptically-shaped liquefaction features resembling those within the NMSZ. Each of the excavations exposed a fine-medium grained sand blow deposit overlying a thick, plastic clay layer. The sand blows were fed by numerous vertical to shallow dipping sand dikes [less than]1 cm to 20 cm thick. Forty-five near vertical dikes were logged at one site whereas only 3-5 dikes were exposed at a second site. A 1.5 km long linear feature near Parkin was also investigated. The lineament trends N56[degrees]E and has a ground surface that is 2.75 meters higher to the southeast. No fault was seen in the trench, however, sand and clay layers tilted to the northwest were exposed sugg esting possible faulting farther to the east. A geophysical survey is planned to investigate this possibility. The size of the liquefaction features and the distance of 100 km from the active NMSZ require either a major New Madrid earthquake or another seismogenic source. In either case, the seismic hazard in the region south of the active NMSZ may be underestimated.
10:45 SHALLOW SEISMIC REFLECTION IMAGING OF THE BIG CREEK FAULT ZONE: IMPLICATIONS FOR SEISMIC HAZARD IN NORTHWEST MISSISSIPPI
James B. [Harris.sup.*] , Randel Tom Cox , Seth A. Berman , and Brant W. Cole , (1.) Millsaps College, Jackson, MS 39210; (2.) University of Memphis, Memphis, TN 38152; (3.) Fairfield Industries, Sugar Land, TX 77478; and (4.) New Mexico Tech, Socorro, NM 87801
Shallow seismic reflection imaging was used to identify, characterize, and evaluate the significance of near-surface (late Tertiary and Quatemary) tectonic deformation associated with the northeast-striking Big Creek fault zone (BCFZ) in the Lower Mississippi Valley (LMV). Shear-wave seismic reflection profiles were collected at two sites: (1) southwest of Helena, Arkansas, across the Big Creek escarpment; and (2) at Porter Gap, Tennessee, across the margin of the Chickasaw bluffs of the Mississippi River. The interpreted seismic profile across the Big Creek escarpment shows that the scarp is underlain by several high-angle faults, with a principal fault extending upward into Quaternary sediments (shallower that 45 m). Warping of shallow reflections indicates compression and suggests that the principal fault has been active as a reverse or transpressional fault in the LMV's contemporary (east-west compressional) stress field. The Porter Gap profile exhibits strong, continuous, reflections at depths of 50-75 m and 90-120 m. Both reflections are disrupted by a near-vertical fault coincident with the west-facing bluff margin. Separation on the fault is up-to-the-west, although structural relief along the line is higher on the east (consistent with topography). Therefore, the fault is interpreted to have been structurally inverted during late Tertiary or Quaternary time. This is similar to the deformational history suggested by the reflection profile across the Big Creek escarpment near Helena. Future seismic investigations are planned to evaluate the possible extension of the BCFZ into northwest Mississippi and the Memphis metropolitan area.
11:15 MISSISSIPPI EARTHQUAKES
Michael B.E. Bograd, Mississippi Office of Geology, Jackson, MS 39289
Mississippi's known earthquake history spans over 300 years. The greatest risk to the state from earthquakes is from the New Madrid Seismic Zone, but 42 events are known to have occurred within Mississippi, scattered throughout the state. There is a diffuse cluster of epicenters in the northwestern quadrant of the state, the quadrant closest to the NMSZ. There is a tight cluster in Clarke County, where a third of Mississippi's known earthquakes have occurred. The earliest known Mississippi earthquake was felt in Biloxi in 1853. The strongest earthquake within the state was the 1931 event in the Batesville-Charleston area; it was felt over 65,000 square miles in five states. The next strongest was the 1967 earthquake near Greenville; though only magnitude 3.8, it was felt over 25,000 square miles in four states. Southern Mississippi was shaken by a 1955 earthquake that was felt all along the Coast. There are few seismic instruments in and around Mississippi, so epicentral locations and depths are poorly const rained. Thus we have inadequate information to assign these earthquakes to specific structural features. It may be speculated that the earthquakes in northwestern Mississippi may be associated with features related to the Reelfoot Rift. The proximity of the Pickens-Gilbertown fault zone to the Clarke County earthquakes must be considered. Other features that have been suggested as causes of earthquakes in Mississippi include the southern Appalachians and the White River fault zone.
1:30 Divisional Poster Session
INVESTIGATION OF POSSIBLE PALEOLIQUEFACTION FEATURES IN MISSISSIPPI
Hanan H. [Mahdi.sup.*] , Haydar J. AI-Shukri , Robert E. Lemmer , Jeffrey B. Connelly , and Michael B.E. Bograd , (1.) University of Arkansas, Little Rock, AR 72204 and (2.) Mississippi Office of Geology, Jackson, MS 39289
Mississippi is in a mid-plate region of infrequent strong earthquakes. The active New Madrid Seismic Zone, close to northwestern Mississippi, poses the greatest risk to the state from earthquakes. In a region of infrequent earthquakes and a short historical record, we must resort to a search for physical evidence of past strong earthquakes. Investigation is under way in northwestern Mississippi of possible paleoliquefaction features (old sand blows resulting from earthquake-induced liquefaction). Sites in Tunica County, Mississippi, bear the same signature on satellite imagery as sites in Arkansas confirmed to be paleoliquefaction features. Agricultural fields on 1962 aerial photographs of Tunica County show circular patches of light color that could be more reflective sand surrounded by darker alluvial soils. Field investigations during the dry summer of 2000 screened sites worthy of further work. The next step will be profiling each feature with hand-auger and collecting ground-penetrating radar data. If t hese investigations indicate possible sand-blow features, the sites will be trenched, and attempts will be made to determine the age of the features. If these are indeed earthquake-induced sand blows, the implications for earthquake risk to Mississippi are significant. Perhaps the New Madrid earthquakes of 1811-1812 were stronger than now understood, or there was a strong earthquake farther south than any now known.
IDENTIFICATION OF SURFACE LINEAMENTS UTILIZING LANDSAT IMAGERY AND EVALUATION OF THEIR POTENTIAL ASSOCIATION WITH TECTONIC FEATURES IN NORTHWEST MISSISSIPPI
James Alan Barck, University of Mississippi, University, MS 38677
In 1811 and 1812 a series of violent earthquakes occurred near New Madrid, Missouri. These events were associated with tectonic activity along what has come to be known as the New Madrid Seismic Zone (NMSZ) which is currently one of the most seismically active regions in North America. Due to the size of the area affected by the 1811-1812 earthquakes, the presence of the NMSZ has become a major concern for the central continental region including northwest Mississippi. Through the use of remote sensing and geographical information systems (GIS) analysis, a number of linear surface features (lineaments) have been identified in northwest Mississippi which are believed to be related to buried faults within this region. Identification of these features has been performed primarily using Landsat 7 thematic mapper satellite imagery. Geologic evidence has been accumulated which supports a relationship between these observed lineaments and buried tectonic features. Of continuing concern is the intersection of a numb er of these lineaments with vital infrastructure features in northwest Mississippi.
NATURALLY OCCURRING RADIOACTIVE MATERIALS (NORM) IN PRODUCED WATER FROM MISSISSIPPI OIL WELLS: AN OVERVIEW
Julie [Kelley.sup.*] , John C. Matthews , Joel S. Kuszmaul , Charles T. Swann , and Rick L. Ericksen , (1.) University of Mississippi, University, MS 38677 and (2.) Mississippi State Board of Registered Professional Geologists, Jackson, MS 39225-2742
Large quantities of formation waters are co-produced with hydrocarbons. Formation waters, or brines, contain high concentrations of dissolved minerals and salts. Some of these brines contain significant concentrations of radionuclides especially radium and its decay products. The radioactive elements in the brines are commonly referred to as naturally occurring radioactive materials (NORM). This study involved the sampling of brines from 262 oil wells across Mississippi. The concentrations of radionuclides ([Ra.sup.228], [Ra.sup.226], and [Ac.sup.228]) were measured in each sample, where detectable concentrations were present, using methods that varied for each isotope. Additional measurements of the chemistry of each of the sampled brines were also made; these include pH, [Cl.sup.-], total dissolved solutes, and density. The data was integrated into a Geographic Information System (GIS) database. This database has been used to characterize the nature of the variation in NORM concentrati ons of each of the producing fields and basins as well as chemical trends across Mississippi. Important findings include that unlike studies of researchers in other areas, such as Fisher (1995, Texas Bureau of Economic Geology, Geological Circular 95-3) working with brines of Texas, there was not a strong correlation of NORM concentrations and Chloride ([Cl.sup.-]) concentrations. This relation was true within each production basin and across Mississippi as a whole. Another important finding has been that the differences in NORM concentrations within the brines are not as varied from one region to another as might be expected. While these results alone do not provide sufficient information for a complete analysis of the potential risks associated with these NORM, the characterization of the NORM concentrations across Mississippi will assist with such an analysis.
2:00 UNUSUAL ASPECTS OF THE HEADWATERS OF THE TOMBIGBEE AND HATCHIE RIVERS AND POSSIBLE NEOTECTONIC IMPLICATIONS
Randel Tom Cox, University of Memphis, Memphis, TN 38152
Regional analysis of transverse drainage-basin asymmetry of the northeastern Mississippi embayment reveals a region of pronounced asymmetry in northeastern Mississippi such that streams preferentially occupy the southeastern side of their basins. In this area of basin asymmetry (the headwaters of the Hatchie River) low order tributaries flow southeastward before making 180[degrees] bends to join northwestward-flowing higher order tributaries and the trunk channel of the Hatchie River. The anomalous flow direction of these low order streams is the same as the southeastward flow direction of the Tombigbee River and its tributaries immediately southeast of the Hatchie basin. One process that might give rise to this drainage pattern is capture of Tombigbee headwaters by the Hatchie River. However, comparison of the elevation of confluences of equivalent order streams in the headwaters of the Tombigbee and Hatchie Rivers shows the Tombighee River to be incised [sim]25 meters deeper than the Hatchie River. Thus, i t is implausible that the Hatchie River has captured Tombigbee tributaries. As an alternative hypothesis, southeastward Quaternary ground tilting may have shifted preexisting Hatchie headwater tributaries to the southeastern side of their basins and may have led to the development of new (lowest order) southeastward-flowing Hatchie tributaries. In addition, tilting would reduce original northwestward Hatchie basin stream gradients and thus reduce incision rate. In the Tombigbee basin, southeastward tilting would steepen gradients and increase incision rate. This episode of ground tilting also may have contributed to changes in the ancestral course of the Tennessee River.
2:30 PRELIMINARY EARTHQUAKE ANALYSIS OF MISSISSIPPI STATE UNIVERSITY
David H. Snodgrass and Darrel W. [Schmitz.sup.*], Mississippi State University, Mississippi State, MS 39762
Mississippi State University's main campus is located approximately 250 kilometers from the southern end of the New Madrid Seismic Zone. Given the history of the New Madrid Seismic Zone and the evidence of seismicity in the State of Mississippi, the risk for a potentially significant earthquake in the region that includes Mississippi State University (MSU) is perceivable. Although there had been no investigation on the MSU campus concerning the potential risk of seismic-induced ground motion, it was clear from other studies conducted in Mississippi that one was needed. A preliminary ground-surface response evaluation of three sites on the MSU campus was conducted using a response analysis software WESHAKE5. Dynamic soil models and acceleration data were determined for use in WESCHAKE5. Results of the analysis suggested spectral peak ground accelerations to range from 0.57 g to a 0.65 g generated from a 6.2 and a 8.25 magnitude earthquake event at an epicentral distance of approximately 250 kilometers. The hi ghest spectral amplifications were consistent at one of the sites for both the 6.2 and 8.25 magnitude events. Lowstrain values and the dynamic site periods were calculated which suggest possible damage to the MSU campus on the order of ten percent or less. It is believed that the stratigraphic units on campus are relatively homogeneous and that the other buildings on the campus would fall within the same general low-strain values and thus the same ten percent order of damage.
Divisional Lectures Begin
3:15 MISSISSIPPI'S CLOSED DEPRESSIONS REVISITED: THEIR RELATIONSHIP TO SIMILAR FEATURES ELSEWHERE ON THE COASTAL PLANS
David M. [Patrick.sup.*] and James H. May, University of Southern Mississippi, Hattiesburg, MS 39406 and U.S. Army Engineer Research and Development Center, Vicksburg, MS 39180
Reconnaissance-level digital elevation model studies of parts of southern Mississippi, Alabama, and the Florida Panhandle were conducted in order to document the occurrence and significance of depressions in areas beyond those previously described in George County. The depressions in George County are sinkhole-like, topographically closed, and occur on surfaces underlain by siliclastics currently mapped as the Citronelle Formation. Our studies indicated that, in Mississippi, these depressions are mainly limited to George and Greene counties where they occur at elevations which range from approximately 210 to 310 feet above sea level and their longest dimensions range from a few hundred feet to over 4000 feet. Isolated occurrences were found near Biloxi, Mendenhall, Ovette, and Wiggins. In southwestern Alabama, the depressions were similar to those in adjacent George County; however, their surface elevations ranged from 150 to 320 feet and they are smaller in size. Similar depressions may be seen in Santa Ros a, Okaloosa, and Walton counties in Florida where the depression occur at elevations between 100 and 150 feet and they are formed in Holocene sands overlying sands and gravels mapped as the Citronelle Formation. We speculate that these Gulf Coast depressions have resulted from localized volume reduction due to leaching and desilicification of coarse- and fine-grained clastics during periods of lowered groundwater level during the Pleistocene. As such, the origins of these depressions also bear some similarity to the Carolina Bays of the Atlantic Coastal Plain.
3:30 GEOLOGIC FACTORS USED IN HGM MODELS N WETLAND MITIGATION IN SOUTH MISSISSIPPI
Suzanne A. [Boyd.sup.*] and David M. Patrick, University of Southern Mississippi, Hattiesburg, MS 39406
Hydro-geomorphic models (HGM's) are tools being adopted for wetlands permitting, mitigation and banking. These models depend upon the identification of native plant populations upon specific geomorphic surfaces and hydrologic conditions. These models require understanding of local stratigraphy, geomorphology, hydrology and soils; particularly if the area has been modified. Pitcher plant areas at Camp Shelby provide an excellent example. We studied selected areas having reduced silt loams such as the Bibb or Trebloc soils developed upon the fine-grained Hattiesburg and Pascagoula formations, and characterized by flat to nearly flat topography and shallow ground water tables. These sites included areas cleared for training activities, and those areas that had naturally reverted to or been planted with pines. We found that areas that are cleared for line-of-site or other purposes, contain high numbers of pitcher plants and rare plant species, while geographically adjacent and geologically similar unmodified are as contained less biodiversity. The key to understanding and modeling these two conditions is stratigraphic; that is, the development of sufficiently high water tables after clearing in Hattiesburg or Pascagoula soils. Modified areas underlain by more permeable soils of the Citronelle Formation also have higher water tables than unmodified areas; but, these water levels generally are deeper than those of the Hattiesburg or Pascagoula formations and less amenable to pitcher plants except where water tables are perched.
3:45 A METHOD FOR QUANTITATIVE DETERMINATION OF [RA.sup.226] AND [RA.sup.228] IN PRODUCED FORMATION WATERS (BRINES) FROM OIL AND GAS WELLS
John C. [Matthews.sup.*] , Catrina Bogan , Charles T. Swann , and Rick L. Ericksen , (1.) University of Mississippi, University, MS 38677 and (2.) Mississippi State Board of Registered Professional Geologists, Jackson, MS 39225-2742
A method is described for quantifying [Ra.sup.226] and [Ra.sup.228], at levels down to 1 Bq/L, from produced formation waters (brines) from oil and gas wells. The method corrects for the high and variable solute concentrations and compositions encountered in brines, and for Ra that becomes insoluble during storage. The method employs isolation of Ra on Empore[TM] Ra Rad Disks, which selectively bind Ra and isolate it from its decay products. This allows quantification of freshly isolated [Ra.sup.226] by counting its 186-keV gamma emission. The Rad Disks are then aged to allow [Ac.sup.228], the first decay product of [Ra.sup.228], to grow in and equilibrate, followed by quantification of its 911-keV and 969-keV gamma emissions. Prior to the Rad Disk step, Ra along with other divalent and multivalent cations from the brines are collected by carbonate precipitation. These are redissolved in 2 N [HNO.sub.3] and passed through the Rad Disks. The carbonate precipitation step re moves K and other monovalent cations, which interfere with Ra adsorption by the Rad Disks. This method was developed as part of a project to survey the radioactivity of hydrocarbon-production byproducts from Mississippi. The samples have shown Ra ranging from 1.1 Bq/L (0.9 Bq/100g of solute) to 120 Bq/L (50.3 Bq/100g of solute). The isotope distribution in the high sample was 34.7 [+ or -] 0.6 Bq/L (8.50 [+ or -] 0.14 pmole/L) of [Ra.sup.226] and 85 [+ or -] 52 Bq/L (74 [+ or -] 45 fmole/L) of [Ra.sup.228]. The low sample was below the detection limit for [Ra.sup.226] and 1.1 [+ or -] 0.5 Bq/L (0.94 [+ or -] 0.39 fmole/L) for [Ra.sup.228]. The average values were 188.2 g/L solute, 12.6 Bq/L (3.1 pmole/L) of [Ra.sup.226], and 15.1 Bq/L (13.1 fmole/L) of [Ra.sup.228].
4:00 Divisional Business Meeting
8:30 FIRST ABSOLUTE DATES FROM PLEISTOCENE-HOLOCENE COASTAL PLAIN UNITS AND SURFACES IN MISSISSIPPI
Ervin G. Otvos, Gulf Coast Research Laboratory, Ocean Springs, MS 39566-7000
Optical and thermoluminescence (OSL and TL) are now being routinely used to date barrier, alluvial, and eolian deposits, some as old as 800 ka. These new methods succeed where other means of absolute dating often fail in nonfossiliferous sandy-silty deposits of poorly constrained relative ages; whether younger or older than the upper limit of the radiocarbon method. In recent years, for the very first time late Quaternary Mississippi coastal plain units have been dated by these methods. Remnants of the second oldest coastal terrace (the alluvial "Big Ridge" unit and surface), correlatable with the Montgomery in SW Louisiana and east Texas occur east and west of the Pascagoula River. Recently, the OSL and. TL methods produced consistent ages of 176.5-220 ka BP. They fits well within the global time frame of the penultimate interglacial stage, associated with high eustatic sea levels. In conformity with known Sangamon Interglacial ages worldwide, in particular Oxygen Isotope Substage 5e of a record-high sea le vel, most alluvial Prairie alluvial and Gulfport barrier samples were dated between 116.6-124.0 ka BP. Samples from intermediate Pearl River valley terraces, formed during Late Pleistocene Wisconsinan low sea level (glacial) substages, dated between 34.7 and 55.2 ka BP. Mississippi-Louisiana coastal dates contribute significantly to the chronostratigraphic reconstruction of Late Pleistocene and Holocene climatic episodes, sea level events, and terrace development episodes on the northern coastal plain of the Gulf of Mexico.
8:45 DETERMINING ARTIFICIAL VS NATURAL HOLOCENE SEDIMENTATION, HANCOCK COUNTY, MISSISSIPPI
Keil Schmid, Mississippi Office of Geology, Jackson, MS 39289
The recreational, esthetic, and cost benefits of sand beaches have made renourishment an attractive protection option in Mississippi Sound. Thus, nearshore sediment volumes and projected beach life spans are important information to local and state planners. Quantifying volumetric change and shoreline retreat values is an important first step; however, the unique aspects of fill deposition also provide an opportunity to clarify long-term sediment transport. Naturally, this is made easier by the use of "unique" fill sediment; or, alternately, with highly accurate bathymetry prior to and following renourishment. Unfortunately, use of both fill sediment and bathymetry in Hancock County were limited by sediment source and time, respectively. Although the fill sediments were not unique, trace fossils, the sediments filling them, changes in shell content, and faint contacts helped distinguish discreet sedimentary sequences. The differences were subtle enough, however, to raise questions as to their origins. To inc rease confidence in the elevation of Fill/Holocene contacts an 'if then' logic, using both profile and sediment data was employed. Short-term depositional patterns determined from profiles were used to validate or reject individual sedimentary sequence contacts as the Fill/Holocene boundary. The volume of the calculated fill thickness agrees well with historical fill additions and suggests that most of the sediment stays within the nearshore system. This technique, while taking some purity out of the interpretation, helped increase confidence and repeatability in determining the Fill/Holocene boundary.
9:00 STRATIGRAPHIC TEST HOLES ALONG HIGHWAY 6 IN NORTH MISSISSIPPI DIFFERENTIATE THE LOWER PALEOGENE SECTION
David E. Thompson, Mississippi Office of Geology, Jackson, MS 39289
The outcrop pattern in north Mississippi on the current Geologic Map of Mississippi (1969) displays an extensive Tallahatta Formation outline and a thin Wilcox Formation. The Naheola Formation is not represented. Numerous investigators, including Cleaves (1980), have recognized the sandy character of the upper Wilcox in north Mississippi; however, that interval has been included genetically with the overlying Meridian Sand. This assignment likely accounts for the widespread Tallahatta pattern on the 1969 map. Additionally, a convention chosen by most investigators in north Mississippi is to pick the base of the Wilcox at the lowest sand above typical Porters Creek shale. Previous and current mapping of the Midway-Wilcox outcrop belt from the Mississippi-Alabama state line into northern Mississippi indicates that certain "lower Wilcox" sands belong to the Naheola Formation. A series of test holes was drilled along Highway 6 from western Pontotoc County to eastern Panola County to differentiate Midway, Wilcox, and Claiborne units downdip. Lignite and clay units of the middle Wilcox were useful as control data in this correlation. Mapping units include, in ascending order, the Porters Creek Formation, the Oak Hill and Coal Bluff Members of the Naheola Formation, the Gravel Creek and Grampian Hills Members of the Nanafalia Formation, the Tuscahoma Formation, the Hatchetigbee Formation, the Meridian Sand, and the Tallahatta Formation.
9:15 GEOLOGY OF THE OXFORD SOUTH 7.5 MINUTE TOPOGRAPHIC QUADRANGLE LAFAYETTE COUNTY, MISSISSIPPI
Stephen L. Ingram, [Sr..sup.*] and Charles T. Swann, University of Mississippi, University, MS 38677-1848 and Mississippi Mineral Resources Institute, University, Mississippi 38677
Although Lafayette County and the Oxford area is undergoing rapid urbanization, the only existing geological maps consists of two fifteen minute quadrangles mapped in 1952. Reliable geological data are essential for well planned growth and industrial development. Review of the 1952 map identified the need for revision and updating of the lithostratigraphy, and the availability of 7.5 minute topographic maps allows the fine-tuning of outcrop belts based on the 1952 fifteen minute maps. The Oxford South quadrangle was chosen because revision of stratigraphy and geological needs due to urbanization could be met simultaneously. Lithostratigraphic units cropping out within the quadrangle include the Eocene Hatchetigbee Formation (Wilcox Group), the Meridian Sand (Claiborne Group), Tallahatta Formation (Claiborne Group), high elevation terraces deposits (Pleistocene (?)), minor loess deposits (Pleistocene), and modern flood plains. The Ackerman stratigraphic name has been dropped in favor of the standard Wilcox Gr oup nomenclature of Alabama. Outliers of Kosciusko Formation that were mapped in 1952 have also been reassigned to the Tallahatta Formation.
9:30 SEDIMENTOLOGIC CHARACTERISTICS AND CLIMATICALLY CONTROLLED REDOX CYCLES IN THE DEMOPOLIS AND MOOREVILLE FORMATIONS, MISSISSIPPI
Ezat Heydari, Mississippi Office of Geology, Jackson, MS 39298
The Mooreville Formation and the Lower Member of the Demopolis Chalk consist of numerous redox cycles, ranging in thickness from 0.3 to 5 m (1-15 feet). Each cycle is composed of a basal dark, laminated section, grading upward into a gray, wispy laminated interval, and capped by a white, bioturbated layer. The basal laminated section indicates sedimentation under anoxic bottom water conditions, hostile to burrowing organisms. The wispy laminated interval indicates that bottom waters became slightly oxygenated and organisms tolerant of low oxygen conditions were sparsely present. The bioturbated layer at the top of each cycle is indicative of deposition under fully oxygenated conditions. Wet climate initiated deposition of the laminated layer at the base of each cycle by delivering a large volume of siliciclastics and terrestrial organic matter to the basin, resulting in bottom water anoxia. The subsequent arid climate promoted precipitation of carbonate-rich, bioturbated strata capping each cycle. The middle member of the Demopolis Formation is a massive, highly bioturbated chalk. It contains abundant trace fossils including Thalassinoides, Planolites, Chondrites, Teichichnus, and Zoophycos. A very shallow burrowing event generated a background-mottled texture apparent in all samples. Thalassinoides was one of the earliest burrows to form, as evidenced by its reworking by other trace fossils. It was followed by Planolites, Teichichnus, and Zoophycos. Chondrites reworked all other trace fossils and was the last bioturbation episode to have influenced the chalk.
10:00 THE BASAL EOCENE SECTION AT THE SUPER WAL-MART CONSTRUCTION SITE IN MERIDIAN, MISSISSIPPI
David T. Dockery III, Mississippi Office of Geology, Jackson, MS 39289
Excavations and some 51 soil borings at the Super Wal-Mart construction site in Meridian, Mississippi, show the following sequence of sediments above the Paleocene-Eocene boundary at the Tuscahoma-Bashi Formation contact. Lowstand deposits (lacking fossil shells) in the lower Bashi Formation (exposed in a 100-foot-long by 20-foot-high, stepped cut at a bridge-site excavation leading to the I20 East Frontage Road) rest unconformably on dark-gray, clayey silts and sands of the Tuscahoma Formation and include in ascending order: (1) a 2-foot-thick, basal, white sand, (2) a 3.5-foot-thick, thinly-bedded, clayey silt containing plant fossils, and (3) a 5-foot-thick white sand with cross stratification and Ophiomorpha burrows. Lowstand deposits are overlain by a concretionary, 4-foot-thick, very fossiliferous, transgressive-marine, brown sand, in the upper Bashi Formation. Above the Bashi marine sand is a highstand-regressive, deltaic sequence in the Hatchetigbee Formation, including: (1) a 14-foot-thick, dark-gra y, thinly bedded, prodelta, clayey silt, (2) a 25- to 35-foot-thick, cross-bedded, distributary-channel sand, and (3) a 15-to 20-foot-thick (truncated at surface elevations), dark brownish-gray to light brown, delta-plain, clayey silt. Cross-bed sets in the distributary-channel sands of the Hatchetigbee Formation show a flow direction from north to south. Elevations taken from borings of the top of the prodelta shale show an abrupt 10-foot-drop in datum along the site's northwestern corner, an area that required a dewatering trench.
10:15 LINGUISTIC CURIOSITIES IN THE PUBLICATIONS OF THE MISSISSIPPI GEOLOGICAL SURVEY
Michael B.E. Bograd, Mississippi Office of Geology, Jackson, MS 39289
Scientists appreciate "elegant literature." They also make use of technical jargon in their writing, and that has its place. When geologists write for the public and specialists in other fields, as they often do, communication is enhanced when they write simply and clearly. The advice in Strunk and White's The Elements of Style is as useful to a geologist writing a professional paper as it is to a journalist. The publications of the Mississippi Geological Survey (now the Mississippi Office of Geology) are used by engineers, environmentalists, biologists, and hobbyists, as well as by geologists. The geological information they contain is important for a myriad of applications, including agriculture, road-building, water resources, and siting sanitary landfills. The first publications were printed in the 1850s, though most date from 1907 and later. The writing styles of the various authors run the gamut from formal to casual. Some of the text written in an "earlier time" sounds odd to readers today, but may reflect the times in which it was written, or perhaps the author's exuberance or frustration. Reading these publications provides interesting examples of effective, quaint, and sometimes amusing literature. One can learn which report was called "a literary, linguistic and scientific curiosity," or read a poem about the sand problem, or learn which now-endangered species was considered good eating. Studying examples of good, and bad, writing can serve to illustrate the importance of writing plainly and clearly.
10:30 MICROBIAL AND IODINE ANALYSIS OF SURFACE SOIL SAMPLES PREDICT OIL AND GAS FROM AN 18,000-FOOT RESERVOIR IN A WILDCAT WELL IN COVINGTON COUNTY, MISSISSIPPI
Jack S. [Moody.sup.*] and Robert Ervin, Mississippi Office of Geology, Jackson, MS 39289-1307
This study tests the ability of various surface sampling techniques and analyses to detect the presence of oil and gas reservoirs for wildcat wells. Surface samples were collected in a grid pattern using GPS. Samples were collected by Mississippi Office of Geology staff and sent to labs for analysis and interpretation; the labs had no well location information. Both iodine and microbial analyses predicted that hydrocarbons would be present. Sampling for this well was spread out over several months and surface conditions changed from very dry to wet. The time and condition change affected one of the two microbial methods. The Roundtree #1 Robertson 21-9 well was drilled to 18,725 feet. The well was completed from a Cotton Valley reservoir at 17,976 feet flowing 321 barrels of oil (BO) and 471,000 cubic feet (471 MCF) of gas per day. As of August, 2000, the well had flowed 26,948 BO and 22,570 MCF and no water. In August, the daily flow rate was 163 BO. The successful prediction by microbes and iodine of the r esulting production suggests their usefulness as another tool in oil and gas exploration.
10:45 THE MISSISSIPPI OFFICE OF GEOLOGY ENERGY INTERNET SITE: USING XML AND OTHER INTERNET STANDARDS FOR DATA PUBLISHING
Peter Hutchins, Mississippi Office of Geology, Jackson, MS 39289
The Mississippi Office of Geology (MOG) Energy Internet Site is a project funded through the Petroleum Technology Transfer Council and Mississippi Department of Economic and Community Development. Well listing and production data come from the Mississippi Oil and Gas Board. The site represents an attempt to bring availability, access and usefulness of energy data to its highest potential using the latest in computer and Internet technology. Using open standards and technologies such as eXtensible Markup Language (XML), the potential use of the data is not limited to a web page but can be used directly from any application capable of working with the Internet and/or XML, a combination that is catching on fast. The site provides a search engine to locate one or more wells or field names; from this a document can be provided containing all that is known on the well or field of interest. Various other data sources that MOG provides are listings from the core library and several scout card image collections scann ed in by the office staff. The scanning of logs and various other reports is in progress. Also provided are interactive maps and charts. This site was designed around the XML support provided in Microsoft Internet Explorer web browser, version 5, which is a free tool. Other browsers are supported with use of simple HTML. The site can be accessed at http://library.geology.deq.state.ms.us/energy.
11:00 THE USE OF DIGITAL INTERACTIVE COUNTY OIL AND GAS PRODUCTION INDEX MAPS ON THE MISSISSIPPI OFFICE OF GEOLOGY'S ENERGY LIBRARY WEB SITE
Stephen D. Champlin, Mississippi Office of Geology, Jackson, MS 39289
The Energy Section of the Mississippi Office of Geology has an ongoing project to create county oil and gas production index maps to show the location of oil and gas fields and, by the use of color coding, indicate the producing geologic formations for each field. Maps for 43 counties are planned. The software program used is AutoDesk's AutoCad 14 on a 450 MHZ Pentium III PC. As of October 2000, 15 county maps were completed and available as color plot hard copy. The digital maps are used on the Office of Geology Web site as an interactive link to online searchable oil and gas databases, which include field/well production and other well data the office may have such as cores, samples or images (scout information, logs, or mud logs). Using AutoCad, URL addresses are attached to the field outlines and names on each map. The digital maps are then exported as dwf files and incorporated into the Office of Geology's web site. To view the county maps the user must install the Autodesk WHIP! tool. This free downloa d tool allows real-time pan and zoom, printing from within your Web browser, and enables the embedded links to the searchable oil and gas databases. The planned final product of the project is a state oil and gas production map, which may also be available on the Internet. The site can be reached at http://library.geology.deq.state.ms.us/energy.
11:15 OBTAINING CLEAN SAMPLES OF PALYGORSKITE CLAY FOR MINERALOGICAL EVALUATIONS
Harold D. [Robinson.sup.*] and E. Schrader, University of Mississippi, University, MS 38677 and Shorter College, Rome, GA 30165
Palygorskite, also known as, attapulgite, is a clay mineral mined from Miocene strata north of Tallahassee, Florida. Used in various commercial applications ranging from suspension agents to adsorbents, the mineralogy of the mined clays often directly relates to the physical properties of the clay. As part of previous undergraduate work at Millsaps College, Jackson, MS, and a thesis project at the University of Mississippi, Oxford, MS, obtaining an ultra pure sample of clay was a necessary step in the process of describing the mineralogy of the various strata of clay mined in the region. As mined, the palygorskite always contains low levels of quartz, calcite, and dolomite. Various methods were researched for use in producing relatively pure samples of clay to be used in both XRD and whole rock analyses. When investigating the mineralogy of this clay mineral, exceptionally clean samples are required to compare the mineralogical properties of these samples with published descriptions. Preparation methods rese arched included gravity settling, centrifuging, dispersants, and acid washing. Utilizing a combination of the selected methods, a technique was developed to reduce or eliminate these contaminants from the clay samples. Results from both XRD and whole rock analyses indicate the effectiveness of process.
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|Publication:||Journal of the Mississippi Academy of Sciences|
|Date:||Jan 1, 2001|
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