Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Coastal Sediments”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,729 records · Page 96Linked to original sources
USGS2014

Archive of single-beam bathymetry data collected from select areas in Weeks Bay and Weeks Bayou, southwest Louisiana, January 2013

A team of scientists from the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, collected 92 line-kilometers of dual-frequency single-beam bathymetry data in the tidal creeks, bayous, and coastal areas near Weeks Bay, southwest Louisiana. Limited bathymetry data exist for these tidally and meteorologically influenced shallow-water estuarine environments. In order to reduce the present knowledge gap, the objectives of this study were to (1) develop methods for regional inland bathymetry mapping and monitoring, (2) test inland bathymetry mapping system in pilot locations for integrating multiple elevation (aerial and terrestrial lidar) and bathymetry datasets, (3) implement inland bathymetry mapping and monitoring in highly focused sites, and (4) evaluate changes in bathymetry and channel-fill sediment storage using these methods. This report contains single-beam bathymetric data collected between January 14 and 18, 2013. Data were collected from the RV Mako (5-meter vessel) in water depths that ranged from <1 meter to 7.7 meters. Locations of data collection ranged from open-bay systems to narrow inland tidal creeks (U.S. Geological Survey Field Activity Number 13CCT01). This report serves as an archive of processed bathymetry data. Geographic information system data provided in this document include a 10-meter cell-size interpolated gridded bathymetry surface, and trackline maps. Additional files include error analysis maps, Field Activity Collection System logs, and formal Federal Geographic Data Committee metadata. Do not use these data for navigational purposes.

Louisiana↗
USGS1993

Geological and technological assessment of artificial reef sites, Louisiana outer continental shelf

This paper describes the general procedures used to select sites for obsolete oil and gas platforms as artificial reefs on the Louisiana outer continental shelf (OCS). The methods employed incorporate six basic steps designed to resolve multiple-use conflicts that might otherwise arise with daily industry and commercial fishery operations, and to identify and assess both geological and technological constraints that could affect placement of the structures. These steps include: (1) exclusion mapping; (2) establishment of artificial reef planning areas; (3) database compilation; (4) assessment and interpretation of database; (5) mapping of geological and man-made features within each proposed reef site; and (6) site selection. Nautical charts, bathymetric maps, and offshore oil and gas maps were used for exclusion mapping, and to select nine regional planning areas. Pipeline maps were acquired from federal agencies and private industry to determine their general locations within each planning area, and to establish exclusion fairways along each pipeline route. Approximately 1600 line kilometers of high-resolution geophysical data collected by federal agencies and private industry was acquired for the nine planning areas. These data were interpreted to determine the nature and extent of near-surface geologic features that could affect placement of the structures. Seismic reflection patterns were also characterized to evaluate near-bottom sedimentation processes in the vicinity of each reef site. Geotechnical borings were used to determine the lithological and physical properties of the sediment, and for correlation with the geophysical data. Since 1987, five sites containing 10 obsolete production platforms have been selected on the Louisiana OCS using these procedures. Industry participants have realized a total savings of approximately US $1 500 000 in salvaging costs by converting these structures into artificial reefs. ?? 1993.

Ocean and Coastal Management↗
USGS2017

Application of an unstructured 3D finite volume numerical model to flows and salinity dynamics in the San Francisco Bay-Delta

A linked modeling approach has been undertaken to understand the impacts of climate and infrastructure on aquatic ecology and water quality in the San Francisco Bay-Delta region. The Delft3D Flexible Mesh modeling suite is used in this effort for its 3D hydrodynamics, salinity, temperature and sediment dynamics, phytoplankton and water-quality coupling infrastructure, and linkage to a habitat suitability model. The hydrodynamic model component of the suite is D-Flow FM, a new 3D unstructured finite-volume model based on the Delft3D model. In this paper, D-Flow FM is applied to the San Francisco Bay-Delta to investigate tidal, seasonal and annual dynamics of water levels, river flows and salinity under historical environmental and infrastructural conditions. The model is driven by historical winds, tides, ocean salinity, and river flows, and includes federal, state, and local freshwater withdrawals, and regional gate and barrier operations. The model is calibrated over a 9-month period, and subsequently validated for water levels, flows, and 3D salinity dynamics over a 2 year period. Model performance was quantified using several model assessment metrics and visualized through target diagrams. These metrics indicate that the model accurately estimated water levels, flows, and salinity over wide-ranging tidal and fluvial conditions, and the model can be used to investigate detailed circulation and salinity patterns throughout the Bay-Delta. The hydrodynamics produced through this effort will be used to drive affiliated sediment, phytoplankton, and contaminant hindcast efforts and habitat suitability assessments for fish and bivalves. The modeling framework applied here will serve as a baseline to ultimately shed light on potential ecosystem change over the current century.

California↗
USGS2005

USGS scientists study sediment deposited by 2004 Indian Ocean tsunami

In January, U.S. Geological Survey (USGS) scientists traveled to countries on the Indian Ocean to study sediment deposited by the devastating tsunami of December 26, 2004. They hope to gain knowledge that will help them to identify ancient tsunami deposits in the geologic record—which extends much farther into the past than written records—and so compile a history of tsunamis that can be used to assess a region's future tsunami risk.

Sound Waves: Coastal science and research news fro↗
USGS2007

South San Francisco Bay, California

The U.S. Geological Survey, in cooperation with the California Coastal Conservancy and the National Oceanic and Atmospheric Administration, mapped the floor of south San Francisco Bay and adjoining land using single-beam sonar and airborne lidar (light detection and ranging). To learn more, visit http://pubs.usgs.gov/sim/2007/2987/. View eastward. Elevations in mapped area color coded: purple (approx 15 m below sea level) to red-orange (approx 90 m above sea level). South San Francisco Bay is very shallow, with a mean water depth of 2.7 m (8.9 ft). Trapezoidal depression near San Mateo Bridge is where sediment has been extracted for use in cement production and as bay fill. Land from USGS digital orthophotographs (DOQs) overlaid on USGS digital elevation models (DEMs). Distance across bottom of image approx 11 km (7 mi); vertical exaggeration 1.5X.

California↗
USGS2002

Historic bluff retreat and stabilization at Flag Harbor, Chesapeake Bay, Maryland

Studies of bluff erosion and slope stability along the western shore of Chesapeake Bay suggest relative evolution from steep, eroding coastal bluffs to stable slopes at angles of repose ca. 35 degrees over decades. Because of the dating methods in those studies, it was impossible to precisely define rates of change. The present study provides historic age control. A pair of small harbor structures were constructed in the early 1950's at Chesapeake Beach, MD to maintain a dredged channel to a small marina occupying a ravine in the Calvert Cliffs. Prior to construction, this section of shoreline was comprised of eroding steep bluffs cut into Miocene-age sediments. Downdrift erosion is now apparent south of the structures as is updrift deposition behind the northern jetty. Since construction the updrift sand body has prograded northward and progressively deposited protective beaches along the toes of the bluffs. Former eroding bluffs nearest the harbor are now stable, vegetated slopes at angles near 35 degrees. Slope angles widen to the north and to the northern limit of the sand body. Beyond this are eroding bluffs standing at angles of 70-80 degrees. The relative time required for eroding bluffs to reach stability is estimated by interpolating the distance and time for the sand body to prograde northward since harbor construction. We measured slope angles at intervals northward from the updrift structure for a distance of 2000 feet. A least squares regression of slope angle vs distance showed progressive decrease in angle from north to south. Actively eroding 70-80 degree bluffs gave way to vegetated, but slumping slopes, and finally to stable 35-degree slopes at the harbor. A relationship between time and distance along the shore allowed us to estimate a stabilization time for this location of 35-40 years. The shortness of this time scale allows us to suggest that attempts to artificially stabilize eroding bluffs along this coast is not a simple task of protecting the toes of slopes from wave action. Once shoreline retreat ends, sloughing of sediment from bluff faces gives way to longer-term landslide processes. The bluff top recedes until a stable 35-degree slope is attained. Thus, simple shoreline protection methods may not preserve property at the bluff edge.

Open-File Report↗
USGS1976

Progress report on geology of the Edwards aquifer, San Antonio area, Texas, and preliminary interpretation of borehole geophysical and laboratory data on carbonate rocks

This report describes the geology and porosity of the rocks of the Edwards aquifer, with particular attention to the eastern half of the San Antonio area. The data were obtained from geologic and geophysical studies of nine cored test holes, from laboratory analyses of samples of the aquifer materials, and from recent stratigraphic studies by other investigators. The Georgetown Formation and the Edwards Group or their equivalent stratigraphic units are extensively exposed in central Texas and they occur in the subsurface throughout southern Texas. They consist of a complex sequence of carbonate rocks deposited during Early Cretaceous time under different depositional conditions. Within the study area, the thickness of the carbonate rocks ranges from less than 400 feet (122 m) in the eastern part of the area to more than 600 feet (183 m) in the southwestern part. The depositional environments significantly affected the texture and the composition of the sediments. The Maverick Basin in the southwestern part of the study area was a euxinic basin surrounded by a barrier rudistid reef. Fine-grained carbonates and some associated evaporites occur within this basin. The San Marcos Platform in the eastern part of the study area was intermittently submerged by a transgressing continental sea. Much of the sediments are extensively reworked and burrowed by marine organisms. Several thick sequences of dolomites, evaporites, and associated collapsed deposits occur on the San Marcos Platform. The carbonates of the San Marcos Platform are extensively dissolved within the fresh-water zone. Much of the dissolution is selective of beds containing evaporites or porous dolomites. The dominant structural feature of the study area is a broad homocline that extends from nearly flat-lying beds on the Edwards Plateau to steeply dipping beds of the deep subsurface of the Gulf Coastal Plain. The homocline is interrupted by the Balcones Fault Zone, which is a zone of normal faults that extend across the study area. The intensity and complexity of faulting increases eastward as part of a progression from gentle flexures in the southwestern part of the study area to a complex pattern of tilted fault blocks on the San Marcos Platform.

Texas↗
USGS2022

Development and description of a composite hydrogeologic framework for inclusion in a geoenvironmental assessment of undiscovered uranium resources in Pliocene- to Pleistocene-age geologic units of the Texas Coastal Plain

A previously completed mineral resources assessment of the Texas Coastal Plain indicated the potential for the future discovery of uranium resources. Geoenvironmental assessments that include the hydrogeologic framework can be used as a tool to understand the potential effects of mining operations. The hydrogeologic framework for this study focused on the composite hydrogeologic unit of the tract permissive for the occurrence of uranium consisting of the upper part of the Miocene-age Fleming Formation/Lagarto Clay, Pliocene-age Goliad and Pleistocene-age Willis Sands, Pleistocene-age Lissie and Beaumont Formations, and Holocene-age alluvial sediments (fluvial alluvium and eolian sand deposits). This composite hydrogeologic unit, which contains the Chicot and Evangeline aquifers of the Gulf Coast aquifer system, is intended for inclusion in a regional-scale geoenvironmental assessment of as yet undiscovered uranium resources. This article provides (1) a brief literature review describing the geologic and hydrogeologic settings, (2) the methodology used to develop a composite hydrogeologic framework, and (3) descriptions and maps of the land-surface altitude, composite hydrogeologic unit base and midpoint depth, water-level altitude, depth of water, unsaturated and saturated zone thickness, and transmissivity and hydraulic conductivity. A composite hydrogeologic unit, created by combining geologic and hydrogeologic data and maps for individual geologic and hydrogeologic units, is intended for use as a tool in a geoenvironmental assessment to evaluate potential contaminant migration through various avenues. Potential applications include using the hydrogeologic framework as an input into a geoenvironmental assessment to help estimate the potential for (1) runoff of contaminants into surface water, (2) infiltration of contaminants into the groundwater (aquifers), or (3) movement of contaminants from the mining area through wind, groundwater-flow, or streamflow in a given permissive tract. The procedures outlined in this paper also provide a method for developing hydrogeologic frameworks that can be applied in other areas where mining may occur.

Texas↗
USGS2004

Archive of Digital Boomer Seismic Reflection Data Collected During USGS Field Activities 93LCA01 and 94LCA01 in Kingsley, Orange, and Lowry Lakes, Northeast Florida, 1993 and 1994

In August and September of 1993 and January of 1994, the U.S. Geological Survey, under a cooperative agreement with the St. Johns River Water Management District (SJRWMD), conducted geophysical surveys of Kingsley Lake, Orange Lake, and Lowry Lake in northeast Florida. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, GIS information, observer's logbook, Field Activity Collection System (FACS) logs, and formal FGDC metadata. A filtered and gained GIF image of each seismic profile is also provided. Refer to the Acronyms page for expansion of acronyms and abbreviations used in this report. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Examples of SU processing scripts and in-house (USGS) software for viewing SEG-Y files (Zihlman, 1992) are also provided. The data archived here were collected under a cooperative agreement with the St. Johns River Water Management District as part of the USGS Lakes and Coastal Aquifers (LCA) Project. For further information about this study, refer to http://coastal.er.usgs.gov/stjohns, Kindinger and others (1994), and Kindinger and others (2000). The USGS Florida Integrated Science Center (FISC) - Coastal and Watershed Studies in St. Petersburg, Florida, assigns a unique identifier to each cruise or field activity. For example, 93LCA01 tells us the data were collected in 1993 for the Lakes and Coastal Aquifers (LCA) Project and the data were collected during the first field activity for that project in that calendar year. For a detailed description of the method used to assign the field activity ID, see http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html. The boomer is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled at the sea surface and when discharged emits a short acoustic pulse, or shot, that propagates through the water and sediment column. The acoustic energy is reflected at density boundaries (such as the seafloor or sediment layers beneath the seafloor), detected by the receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (e.g., 0.5 s) and recorded for specific intervals of time (e.g., 100 ms). In this way, a two-dimensional vertical image of the shallow geologic structure beneath the ship track is produced. Acquisition geometery for 94LCA01 is recorded in the operations logbook. No logbook exists for 93LCA01. Table 1 displays acquisition parameters for both field activities. For more information about the acquisition equipment used, refer to the FACS equipment logs. The unprocessed seismic data are stored in SEG-Y format (Barry and others, 1975). For a detailed description of the data format, refer to the SEG-Y Format page. See the How To Download SEG-Y Data page for more information about these files. Processed profiles can be viewed as GIF images from the Profiles page. Refer to the Software page for details about the processing and examples of the processing scripts. Detailed information about the navigation systems used for each field activity can be found in Table 1 and the FACS equipment logs. To view the trackline maps and navigation files, and for more information about these items, see the Navigation page. The original trace files were recorded in nonstandard ELICS format and later converted to standard SEG-Y format. The original trace files for 94LCA01 lines ORJ127_1, ORJ127_3, and ORJ131_1 were divided into two or more trace files (e.g., ORJ127_1 became ORJ127_1a and ORJ127_1b) because the original total number of traces exceeded the maximum allowed by the processing system. Digital data were not recoverable for 93LCA

Data Series↗
USGS1975

Evaluation of reservoir sites in North Carolina: Regional relations for estimating the reservoir capacity needed for a dependable water supply

Draft-storage-frequency relations, which show the storage required for a reservoir to furnish a specified withdrawal or draft are regionalized for four zones in the State, using the mean annual flow of the streams as an index. The differences between the zones primarily reflect differences in the variability of stream flow. To assure the available draft will fall below 75 percent of the mean annual flow of a stream only once in 50 years on the average, a reservoir in the mountains would need a usable storage capacity of 45 percent of the mean annual runoff of the impounded stream. In comparison, reservoirs in parts of the Piedmont furnishing a draft of 75 percent of the mean annual flow must have usable storage equal to 60 percent of the mean annual runoff of the stream. In the inner Coastal Plain the storage required increases to 84 per-cent, and in the outer Coastal Plain to about 110 percent. These increases in storage necessary to furnish a certain draft are indicative of the general increase in streamflow variability, both seasonally and between years, that occurs from west to east in the State. Net evaporative draft, the evaporative loss from reservoirs when annual evaporation exceeds annual precipitation, also varies from west to east. For instance, a reservoir impounding a Piedmont stream, and designed with a 5 percent chance of deficiency, will have a net evaporative draft about twice as large as a similar sized reservoir in the Coastal Plain. In the mountains, annual precipitation always exceeds evaporation because of the cooler temperatures and higher rates of precipitation. Annual net evaporation is also proportionately smaller for large reser voirs than for small ones. On a Coastal Plain reservoir, with storage equivalent to the mean annual runoff of the stream and being drafted at 90 percent of the mean annual flow, the net evaporation for a stream with a mean annual runoff of only 500 acre-feet (0.62 cubic hectometres) is three times as great as for a stream with mean annual runoff of 100,000 acre-feet (123 cubic hectometres). Thus, one large reservoir has less evaporation loss than several small ones capable of furnishing, collectively, the same reliable draft. Under some circumstances, sedimentation can quickly reduce the available storage in a reservoir, thus decreasing the reliable draft. Estimated sedi-mentation rates in the Piedmont can range from 240 acre-feet per year (0.3 cubic hectometres per year) in a severely exposed drainage basin of 10 square miles (26 square kilometres) to 0.4 acre-feet per year (493 cubic metres per year) in a wooded basin of the same size. Seepage beneath and around a reservoir dam is normally not significant in the State. The usual engineering practices should be followed, however, to avoid locating the dam on an open or active fault, cavernous limestone, or continuous beds of sand or gravel.

North Carolina↗
USGS1997

Characteristics of and corrections for core shortening in unconsolidated sediments

Thinning, bypassing, and compaction of shallow unconsolidated sediments during manual coring or vibracoring operations probably cause more sediment deformation and greater stratigraphic displacement than is commonly reported in the wetland literature. We measured core shortening in open-barrel cores from fluvial wetlands, lagoonal flats, and marshes to document the magnitude and characteristics of shortening where sediments may be stiff and require extra mechanical effort to recover a sufficient length of sample for analysis. Results of those measurements indicate that thinning or non- recovery of discrete sediment intervals can range from 0 to 67 percent and cumulative core shortening can be as much as 30 percent even for cores less than one meter long. Detailed open-barrel measurements also show that core shortening is not uniformly distributed throughout the depth of penetration as is often assumed. Analytical data derived from shortened cores can only be properly interpreted if patterns of shortening are established and incorporated into the analysis. Minor artificial displacement of sediment depths can alter plots of physico-chemical parameters and can significantly influence calculated rates of sedimentation and other depth-dependent statistical relationships. This study (1) demonstrates how plots of interval shortening and cumulative shortening can be used to characterize the distribution of shortening at depth and (2) presents a simple equation for stratigraphic restoration so that core observations and analyses are corrected to their original depths.

Journal of Coastal Research↗
USGS1982

Upper Cretaceous subsurface stratigraphy and structure of coastal Georgia and South Carolina

Upper Cretaceous subsurface stratigraphy and structure of coastal Georgia and South Carolina is based on the study of 24 wells along two transects, one extending across the seaward-dipping sedimentary basin termed the 'Southeast Georgia Embayment' northeastward to the crest of the Cape Fear Arch, and the other alined east-west, parallel to the basin axis and including the COST GE-l well on the Outer Continental Shelf. A new biostratigraphic analysis, using calcareous nannofossils, of the Fripp Island, S.C., well and reinterpretations of the Clubhouse Crossroads corehole 1, South Carolina, and other wells in South Carolina, Georgia, and northernmost Florida have made possible the comparison and reevaluation of stratigraphic interpretations of the region made by G. S. Gohn and others in 1978 and 1980 and by P. M. Brown and others in 1979. The present study indicates that within the Upper Cretaceous section the stratigraphic units formerly assigned a Cenomanian (Eaglefordian and Woodbinian) age are Coniacian (Austinian) and Turonian (Eaglefordian) in age. A previously described hiatus encompassing Coniacian and Turonian time is not present. More likely, a hiatus is probably present in the upper Turonian, and major gaps in the record are present within the Cenomanian and between the Upper Cretaceous and the pre-Cretaceous basement. After an erosional episode in Cenomanian time that affected the section beneath eastern Georgia and South Carolina, Upper Cretaceous marine clastic and carbonate rocks were deposited on a regionally subsiding margin that extended to the present Blake Escarpment. In contrast, during Cenozoic time, especially in the Eocene, subsidence and sedimentation rates were uneven across the margin. A thick progradational sequence of carbonate rocks accumulated in the Southeast Georgia Embayment and also built the present Continental Shelf, whereas farther offshore a much thinner layer of sediments was deposited on the Blake Plateau. There is no general agreement on the exact placement of the Cenomanian-Turonian boundary in Europe or the United States Western Interior, and the widespread Sciponoceras gracile ammonite zone represents an interval of equivocal age between accepted Cenomanian and Turonian strata. The extinction of the foraminifer genus Rotalipora took place within the Sciporwceras gracile zone; it is used here to identify the Cenomanian-Turonian boundary. Pollen zone IV (Complexiopollis-Atlantopollis assemblage zone) is an important and widespread biostratigraphic unit characterized by a distinctive spore and pollen flora. It is consistently associated with lower Turonian calcareous nannofossils on the Atlantic continental margin; these nannofossil assemblages are also present in pollen zone IV, in strata that encompass the Sciponoceras gracile zone and the lower part of the Mytiloides labiatus zone in the Gulf Coastal Plain at Dallas, Tex.

Professional Paper↗
USGS2000

Strontium isotope geochemistry of groundwaters and streams affected by agriculture, Locust Grove, MD

The effects of agriculture on the isotope geochemistry of Sr were investigated in two small watersheds in the Atlantic coastal plain of Maryland. Stratified shallow oxic groundwaters in both watersheds contained a retrievable record of increasing recharge rates of chemicals including NO 3 − , Cl, Mg, Ca and Sr that were correlated with increasing fertilizer use between about 1940 and 1990. The component of Sr associated with recent agricultural recharge was relatively radiogenic ( 87 Sr/ 86 Sr=0.715) and it was overwhelming with respect to Sr acquired naturally by water–rock interactions in the oxidized, non-calcareous portion of the saturated zone. Agricultural groundwaters that penetrated relatively unoxidized calcareous glauconitic sediments at depth acquired an additional component of Sr from dissolution of early Tertiary marine CaCO 3 ( 87 Sr/ 86 Sr=0.708) while undergoing O 2 reduction and denitrification. Ground-water discharge contained mixtures of waters of various ages and redox states. Two streams draining the area are considered to have higher 87 Sr/ 86 Sr ratios and NO 3 − concentrations than they would in the absence of agriculture; however, the streams have consistently different 87 Sr/ 86 Sr ratios and NO 3 − concentrations because the average depth to calcareous reducing (denitrifying) sediments in the local groundwater flow system was different in the two watersheds. The results of this study indicate that agriculture can alter significantly the isotope geochemistry of Sr in aquifers and streams and that the effects could vary depending on the types, sources and amounts of fertilizers added, the history of fertilizer use and groundwater residence times.

Maryland↗
USGS1990

Salt-dome locations in the Gulf Coastal Plain, South-Central United States

Information on salt domes in Gulf of Mexico Coastal Plain, south-central United States and the adjacent Continental Shelf were compiled from major published sources, 1973-84. The location of 624 salt domes is shown on a map at a scale of 1:1 ,500,000. A color-coding system was used to show that the occurrence, size, shape, and location of these domes varies among sources. Two tables of additional data accompany the map and include other available information such as: identifying sources, depth to salt and caprock, diameter, volume, name, and uppermost zone of surrounding sediment that is penetrated, as well as the number of matches between sources. The locations of salt domes that penetrate specific zones within the gulf coast regional aquifer system are shown on maps. (USGS)

Water-Resources Investigations Report↗
USGS2017

Persistent shoreline shape induced from offshore geologic framework: Effects of shoreface connected ridges

Mechanisms relating offshore geologic framework to shoreline evolution are determined through geologic investigations, oceanographic deployments, and numerical modeling. Analysis of shoreline positions from the past 50 years along Fire Island, New York, a 50 km long barrier island, demonstrates a persistent undulating shape along the western half of the island. The shelf offshore of these persistent undulations is characterized with shoreface-connected sand ridges (SFCR) of a similar alongshore length scale, leading to a hypothesis that the ridges control the shoreline shape through the modification of flow. To evaluate this, a hydrodynamic model was configured to start with the US East Coast and scale down to resolve the Fire Island nearshore. The model was validated using observations along western Fire Island and buoy data, and used to compute waves, currents and sediment fluxes. To isolate the influence of the SFCR on the generation of the persistent shoreline shape, simulations were performed with a linearized nearshore bathymetry to remove alongshore transport gradients associated with shoreline shape. The model accurately predicts the scale and variation of the alongshore transport that would generate the persistent shoreline undulations. In one location, however, the ridge crest connects to the nearshore and leads to an offshore-directed transport that produces a difference in the shoreline shape. This qualitatively supports the hypothesized effect of cross-shore fluxes on coastal evolution. Alongshore flows in the nearshore during a representative storm are driven by wave breaking, vortex force, advection and pressure gradient, all of which are affected by the SFCR.

New York↗
USGS2008

Archive of digital boomer seismic reflection data collected during USGS field activity 02LCA02 in Lakes Ada, Crystal, Jennie, Mary, Rice, and Sylvan, Central Florida, July 2002

In July of 2002, the U.S. Geological Survey and St. Johns River Water Management District (SJRWMD) conducted geophysical surveys in Lakes Ada, Crystal, Jennie, Mary, Rice, and Sylvan, central Florida, as part of the USGS Lakes and Coastal Aquifers (LCA) study. This report serves as an archive of unprocessed digital boomer seismic reflection data, trackline maps, navigation files, Geographic Information System (GIS) files, and formal Federal Geographic Data Committee (FGDC) metadata. Filtered and gained (a relative increase in signal amplitude) digital images of the seismic profiles are also provided. Refer to the Acronyms page for expansions of acronyms and abbreviations used in this report. The archived trace data are in standard Society of Exploration Geophysicists (SEG) SEG-Y format (Barry and others, 1975) and may be downloaded and processed with commercial or public domain software such as Seismic Unix (SU). Example SU processing scripts and USGS software for viewing the SEG-Y files (Zihlman, 1992) are also provided. The USGS Florida Integrated Science Center (FISC) - St. Petersburg assigns a unique identifier to each cruise or field activity. For example, 02LCA02 tells us the data were collected in 2002 for the Lakes and Coastal Aquifers (LCA) study and the data were collected during the second field activity for that study in that calendar year. Refer to http://walrus.wr.usgs.gov/infobank/programs/html/definition/activity.html for a detailed description of the method used to assign the field activity ID. The boomer plate is an acoustic energy source that consists of capacitors charged to a high voltage and discharged through a transducer in the water. The transducer is towed on a sled floating on the water surface and when discharged emits a short acoustic pulse, or shot, which propagates through the water, sediment column, or rock beneath. The acoustic energy is reflected at density boundaries (such as the seafloor, sediment, or rock layers beneath the seafloor), detected by the receiver, and recorded by a PC-based seismic acquisition system. This process is repeated at timed intervals (for example, 0.5 s) and recorded for specific intervals of time (for example, 100 ms). In this way, a two-dimensional (2-D) vertical profile of the shallow geologic structure beneath the ship track is produced. Figure 1 displays the acquisition geometry. Refer to table 1 for a summary of acquisition parameters. Table 2 lists trackline statistics. The unprocessed seismic data are stored in SEG-Y format (Barry and others, 1975). For a detailed description of the data format, refer to the SEG-Y Format page. See the How To Download SEG-Y Data page for download instructions. The printable profiles provided here are GIF images that were filtered and gained using Seismic Unix software. Refer to the Software page for details about the processing and examples of the processing scripts. The processed SEG-Y data were exported to Chesapeake Technology, Inc. (CTI) SonarWeb software to produce an interactive Web page of the profile, which allows the user to obtain a geographic location and depth from the profile for a curser position. This information is displayed in the status bar of the browser.

Florida↗
USGS2003

Cruise report for A1-02-SC southern California CABRILLO project, Earthquake Hazards Task

A two-week marine geophysical survey obtained sidescan-sonar images and multiple sets of high-resolution seismic-reflection profiles in the southern California offshore area between Point Arguello and Point Dume. The data were obtained to support two project activities of the United States Geological Survey (USGS) Coastal and Marine Geology (CMG) Program: (1) the evaluation of the geologic hazards posed by earthquake faults and landslides in the offshore areas of Santa Barbara Channel and western Santa Monica Basin and (2) determine the location of active hydrocarbon seeps in the vicinity of Point Conception as part of a collaborative study with the Minerals Management Service (MMS). The 2002 cruise, A1-02- SC, is the fourth major data-collection effort in support of the first objective (Normark et al., 1999a, b; Gutmacher et al., 2000). A cruise to obtain sediment cores to constrain the timing of deformation interpreted from the geophysical records is planned for the summer of 2003.

California↗
USGS2011

Continuous resistivity profiling data from the Corsica River Estuary, Maryland

Submarine groundwater discharge (SGD) into Maryland's Corsica River Estuary was investigated as part of a larger study to determine its importance in nutrient delivery to the Chesapeake Bay. The Corsica River Estuary represents a coastal lowland setting typical of much of the eastern bay. An interdisciplinary U.S. Geological Survey (USGS) science team conducted field operations in the lower estuary in April and May 2007. Resource managers are concerned about nutrients that are entering the estuary via SGD that may be contributing to eutrophication, harmful algal blooms, and fish kills. Techniques employed in the study included continuous resistivity profiling (CRP), piezometer sampling of submarine groundwater, and collection of a time series of radon tracer activity in surface water. A CRP system measures electrical resistivity of saturated subestuarine sediments to distinguish those bearing fresh water (high resistivity) from those with saline or brackish pore water (low resistivity). This report describes the collection and processing of CRP data and summarizes the results. Based on a grid of 67.6 kilometers of CRP data, low-salinity (high-resistivity) groundwater extended approximately 50-400 meters offshore from estuary shorelines at depths of 5 to >12 meters below the sediment surface, likely beneath a confining unit. A band of low-resistivity sediment detected along the axis of the estuary indicated the presence of a filled paleochannel containing brackish groundwater. The meandering paleochannel likely incised through the confining unit during periods of lower sea level, allowing the low-salinity groundwater plumes originating from land to mix with brackish subestuarine groundwater along the channel margins and to discharge. A better understanding of the spatial variability and geological controls of submarine groundwater flow beneath the Corsica River Estuary could lead to improved models and mitigation strategies for nutrient over-enrichment in the estuary and in other similar settings.

Maryl↗