Bat Monitoring, Fort Leonard Wood, Missouri: Sound and Seismic Effects

The U.S. Army Maneuver Support Center of Excellence and U.S. Army Garrison Fort Leonard Wood (Installation) has prepared a Biological Assessment (BA) to evaluate effects of the construction and operation of a Mine Clearing Line Charge (MICLIC) range on threatened and endangered species at the Installation. A pilot monitoring plan will describe the process in which field data are to be gathered and timelines in which field data are processed and/or reported. The data collected during this pilot monitoring survey will be used to validate the noise and seismic estimations, as described in the BA, for MICLIC detonations and ensure that thresholds of sound and vibration have not been surpassed. If field data results surpass thresholds, the USFWS will be consulted and appropriate coordination will be conducted. Dr. Kevin Mickus, geophysicist and Distinguished Professor in the Department of Geography, Geology, and Planning at Missouri State University (MSU), was the lead scientist on the pilot monitoring survey to assess the noise and sound effects during MICLIC testing. He was assisted in the field by Paul Wilkerson, an undergraduate student in geology. The seismic and sound data were collected at King Cave which is the closest of the seven caves to the MICLIC Range

Applying DC resistivity imaging to investigating the relationship between water quality and transpiration beneath circular islands in the Okavango Delta, Botswana: a case study of Thata Island

An electrical resistivity survey was carried out on Thata Island, one of the numerous circular islands in the Okavango Delta, to investigate the mechanism governing interactions between surface water, vegetation and groundwater. Seven data profiles were collected across the island and modelling results indicated that the centre of the island had low resistivity values (less than 10 ohm-m), while resistivity values increased laterally outside the island. Such lateral resistivity zoning responded to variation in shallow groundwater chemistry below the islands having a high concentration of solutes inside and the presence of fresh water outside the islands. Borehole to surface resistivity imaging results for the island indicated a plume of saline water sinking to depths of 60 m. Groundwater salinity below the island ranged from 11.7 g/l from the margin of the island to 122 g/l at the centre of the island. Beyond the 60m depth, groundwater salinity dropped to about 0.33 g/l at the centre of the island. Lateral and down-hole imaging results, as well as water salinity values, showed a migrating plume of high salinity groundwater from the surface of the island invading a relatively deeper low-density fresh groundwater environment. Combining geochemical, isotopic and electrical resistivity data indicated that capillary evaporation may have been the most important mechanism in creating high saline water under the centre of the island; however, high transpiration rates along the edges of the island may have been important in producing salts which could migrate toward the island\u27s centre. The results of this study showed how high salinity levels may have formed in near surface aquifers in natural inland delta environments in semi-arid areas

The application of quantitative fluorescent dye tracing to evaluate karst hydrogeologic response to varying recharge conditions in an urban area

Quantitative dye-tracing methods were utilized in a portion of the greater Springfield, Missouri metropolitan area. These methods were used to evaluate factors influencing groundwater movement through the shallow karst system in the area. Fortuitous timing of these studies with a summer drought allowed for very low-flow conditions to be tested, and the results of these tests suggest that shallow groundwater in the study area occurs in fractures and along bedding planes, with a significant input component from flow along bedding planes or other sub-horizontal features. Based on one unique trace, it appears that recent dye traces may be affected by groundwater elevations, where crossover from one conduit system to another occurs under most water level conditions, but ceases under the lowest flow conditions

A joint geophysical analysis of the Coso Geothermal Field, south-eastern California

Three-dimensional density models derived from gravity data and two-dimensional resistivity models derived from magnetotelluric data collected in the vicinity of the Coso geothermal field are analyzed in order to determine the source region of the geothermal field. The derived models show zones of both low resistivity and low density at and below 6 km depth in the Devils Kitchen and the Coso Hot Springs areas. These zones agree with seismic reflection and tomography results which found a high amplitude reflector at 5 km and low velocities zones below 5 km. We interpret the density and resistivity zones to indicate the presence of cooling magmatic material that provides the heat for the shallower geothermal system in these regions. A zone marked by high resistivity and low density was found to lie directly above the interpreted partially melted region extending to within 1 km depth below the surface in the reservoir region where it is capped by a low resistivity clay zone. In addition, the density models indicate that the high density bodies occurring under volcanic outcrops may be mafic intrusions

Geochemical processes contributing to the contamination of soil and surface waters in the Rio Conchos basin, Mexico

A geochemical characterization of the middle Rio Conchos basin is presented based on two contaminants, salts (Ca and Na) and toxic metalloids (As and Sb). Their content in surface water and sediment samples was determined, and their spatial distribution was mapped to show the relationship to each other, to the geology and hydrology, and to other potential factors affecting their distribution (i.e., prevailing winds). Correlation analyses between salts, toxic metalloids, and associated elements, and their spatial distribution aided in determining their sources, which included mines, rock outcrops, urban centers, irrigation waste water, and agricultural runoff. The salinity of the Rio Conchos reached a critical level after receiving waters of its contaminated tributary Rio Chuviscar and irrigation drain returns from the Irrigation District 005, but further downstream the water quality improved when it mixed with Carich water, significantly reducing its Na concentration. Based on its spatial distribution, the content of As in alluvial material was found to be associated with the presence of Ag-Pb mines and to a lesser degree to Oligocene ignimbrites. A correlation of As with Sb, Cu, and Bi suggests that natural sources are the dominant contribution of As within the area, although concentrations above permissible level for water were found in river water samples at a few places where sewage was also present, suggesting an additional (anthropogenic) important source of As. A characterization of natural sources affecting the chemistry of surface waters is a first step toward understanding the natural processes taking place and for documenting natural background levels that are needed to predict the response of the environment to various human activities

Geodynamics of the Southern Tethyan Margin in Tunisia and Maghrebian domain: new constraints from integrated geophysical study

The geodynamic evolution of the Southern Tethyan Margin of Tunisia is investigated using geophysical studies. Analysis of gravity and seismic reflection data in the Maghrebian domain and Southern Tunisia reveals the geodynamic role played by the North Saharan Flexure (NSF) in the evolution of the Southern Tethyan Margin. The Saharan Atlas Mountains (Atlasic Basin) and the African Craton (Telemzan High) are separated by the NSF which is a regional-scale feature that may represent a significant basement discontinuity that has controlled the Paleozoic, Mesozoic, and Cenozoic evolution of the Tunisian and Maghrebian Tethyan Basin

Evidence for an east-west regional gravity trend in northern Tunisia: Insight into the structural evolution of northern Tunisian Atlas

The Atlas orogeny in northern Algeria and Tunisia led to the destruction of Tethys oceanic lithosphere and cumulated in a collision of microplates rifted off the European margin with the North African continental margin. The location of the boundary between African plate and Kabylian microplate is expressed in northern Algeria by a crustal wedge with double vergence of thrust sheets, whereas in northern Tunisia the geologic environment is more complex and the location of the plate boundary is ambiguous. In this study, we analyzed gravity data to constrain the crustal structure along the northern margin of Tunisia. The analysis includes a separation of regional and residual gravity anomalies and the application of gradient operators to locate density contrast boundaries. The horizontal gradient magnitude and directional gradient highlight a prominent regional E-W gravity gradient in the northern Tunisian Atlas interpreted as a deep fault (active since at least the Early Mesozoic) having a variable kinematic activity depending on the tectonic regime in the region. The main E-W gravity gradient separates two blocks having different gravitational and seismic responses. The southern block has numerous gravity lineaments trending in different directions implying several density variations within the crust, whereas the northern block shows a long-wavelength negative gravity anomaly with a few lineaments. Taking into account the geologic context of the Western Mediterranean region, we consider the E-W prominent feature as the boundary between African plate and Kabylian microplate in northern Tunisia that rifted off Europe. This hypothesis fits most previous geological and geophysical studies and has an important impact on the petroleum and mineral resource prospection as these two blocks were separated by an ocean and they did not belong to the same margin

Gravity and seismic reflection imaging of a deep aquifer in an arid region: Case history from the Jeffara basin, southeastern Tunisia

A detailed mapping of the lateral and the vertical extension of the Upper Cretaceous units which contains aquifer bearing lithologies and may be part of the Complexe Terminal aquifer in the Jeffara basin of southeastern Tunisia using land and satellite Bouguer gravity anomaly data, eight seismic reflection profiles and two deep wells was performed. Borehole data indicated that the Upper Cretaceous unit is thickest within the Jeffara basin and thins considerably in the Dahar High. Bouguer gravity data in general confirms this result but lacks the resolution to accurately determine the thickness of the Upper Cretaceous units. Eight seismic reflection profiles constrained by borehole data indicated that the Upper Cretaceous aquifer may be present at depths greater than 500 m and is up to 400 m thick. The seismic reflection analysis showed that the Upper Cretaceous units contain two distinct zones. Within the northeastern portions of the Jeffara basin, the Upper Cretaceous units are influenced by horsts, grabens and tilted blocks where the Upper Cretaceous units are deeper and thicker units occur within the grabens. A second zone exits toward the basin\u27s southwestern section where the Upper Cretaceous units are shallower and gradually thin against the Dahar High. Structural contour maps of the top and the base of the Upper Cretaceous aquifer constructed from the seismic reflection profiles reveal the presence of fractured depressions in the northeastern part of the Jeffara basin that are favourable to the hydrogeological exploitation

Deep structure and crustal configuration of the Jeffara basin (Southern Tunisia) based on regional gravity, seismic reflection and borehole data: How to explain a gravity maximum within a large sedimentary basin?

The Jeffara basin of southern Tunisia contains a thick sequence of mainly Triassic and Permian sediments that is characterized by a gravity maximum. To explain the positive gravity signature over the Jeffara sedimentary basin and to obtain a more quantitative representation of the subsurface structure, a regional 2.5D gravity model constrained by seismic reflection and borehole data was constructed along a NE-SW trending profile. The depth to the crust/mantle implies that the Jeffara basin is associated with crustal thinning. The gravity model also implies that subsidence is controlled by a basement stepped down by relatively low-displacement faulting. This sedimentary subsidence, as described by a listric-faulting model, is probably caused by a thinned crust