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At least 253 records · Page 14Linked to original sources
USGS2009

Geophysical data from offshore of the Chandeleur Islands, eastern Mississippi Delta

This report contains the geophysical and geospatial data that were collected during two cruises on the R/V Acadiana along the eastern, offshore side of the Chandeleur Islands in 2006 and 2007. Data were acquired with the following equipment: a Systems Engineering and Assessment, Ltd., SwathPlus interferometric sonar; a Klein 3000 dual-frequency sidescan sonar; and an EdgeTech 512i chirp sub-bottom profiling system. The long-term goal of this mapping effort is to produce high-quality, high-resolution geologic maps and geophysical interpretations that can be utilized to investigate the impact of Hurricane Katrina, identify sand resources within the region, and make predictions regarding the future evolution of this coastal system.

Louisiana↗
USGS2008

Enhanced Sidescan-Sonar Imagery Offshore of Southeastern Massachusetts

The U.S. Geological Survey (USGS), National Oceanic and Atmospheric Administration (NOAA), and Massachusetts Office of Coastal Zone Management (CZM) have been working cooperatively to map and study the coastal sea floor. The sidescan-sonar imagery collected during NOAA hydrographic surveys has been included as part of these studies. However, the original sonar imagery contains tonal artifacts from environmental noise (for example, sea state), equipment settings (for example, power and gain changes), and processing (for example, inaccurate cross-track and line-to-line normalization), which impart a quilt-like patchwork appearance to the mosaics. These artifacts can obscure the normalized backscatter properties of the sea floor. To address this issue, sidescan-sonar imagery from surveys H11076 and H11079 offshore of southeastern Massachusetts was enhanced by matching backscatter tones of adjacent sidescan-sonar lines. These mosaics provide continuous grayscale perspectives of the backscatter, more accurately reveal the sea-floor geologic trends, and minimize the environment-, acquisition-, and processing-related noise.

Open-File Report↗
USGS2011

Surficial geology of the sea floor in Long Island Sound offshore of Orient Point, New York

The U.S. Geological Survey (USGS), the National Oceanic and Atmospheric Administration (NOAA), and the Connecticut Department of Environmental Protection (CT DEP) are working cooperatively to map and interpret features of the sea floor along the northeastern coast of the United States. This report presents multibeam bathymetry and sidescan-sonar data obtained during NOAA survey H11446, which was conducted in a 12-km2 area in Long Island Sound offshore of Orient Point, NY. In addition, sediment and photographic data from 26 stations obtained during a USGS verification cruise are presented. Overall, the sea floor slopes gently seaward, but topography is more complex in sand-wave and boulder areas, which are evident in the multibeam and sidescan-sonar data from the study area. Sand waves generally have north-south-oriented crests with 10- to 20-m wavelengths. Sand-wave asymmetry indicates eastward net sediment transport in the east and westward net sediment transport in the northern and western parts of the study area. Areas with boulders on the sea floor are typically hummocky and are part of a glacial moraine system. Boulders are typically encrusted with seaweed, sponges, and anemones as shown in the bottom photography.

Open-File Report↗
USGS2010

High-resolution seismic-reflection data offshore of Dana Point, southern California borderland

The U.S. Geological Survey collected high-resolution shallow seismic-reflection profiles in September 2006 in the offshore area between Dana Point and San Mateo Point in southern Orange and northern San Diego Counties, California. Reflection profiles were located to image folds and reverse faults associated with the San Mateo fault zone and high-angle strike-slip faults near the shelf break (the Newport-Inglewood fault zone) and at the base of the slope. Interpretations of these data were used to update the USGS Quaternary fault database and in shaking hazard models for the State of California developed by the Working Group for California Earthquake Probabilities. This cruise was funded by the U.S. Geological Survey Coastal and Marine Catastrophic Hazards project. Seismic-reflection data were acquired aboard the R/V Sea Explorer, which is operated by the Ocean Institute at Dana Point. A SIG ELC820 minisparker seismic source and a SIG single-channel streamer were used. More than 420 km of seismic-reflection data were collected. This report includes maps of the seismic-survey sections, linked to Google Earth? software, and digital data files showing images of each transect in SEG-Y, JPEG, and TIFF formats.

Open-File Report↗
USGS2011

Sea-floor geology and topography offshore in Eastern Long Island Sound

A gridded multibeam bathymetric dataset covers approximately 133.7 square kilometers of sea floor offshore in eastern Long Island Sound. Although originally collected for charting purposes during National Oceanic and Atmospheric Administration hydrographic survey H11997, these acoustic data, and the sea-floor sampling and photography stations subsequently occupied to verify them during USGS cruise 2010-015-FA, are part of an expanding series of studies that provide a fundamental framework for research and resource management (for example, cables, pipelines, and dredging) activities in this major East Coast estuary. Results show the composition and terrain of the seabed and provide information on sediment transport and benthic habitat. Bedrock outcrops, erosional outliers, lag deposits of boulders, scour depressions, and extensive gravel pavements are common in the eastern part of the study area. These features, which result from the near-constant exposure to strong tidal currents, indicate sedimentary environments dominated by processes associated with erosion. Large fields of transverse and barchanoid sand waves in the western part of the study area reflect slightly lower energy levels and sedimentary environments where processes associated with coarse bedload transport prevail.

Open-File Report↗
USGS2011

Geophysical data from offshore of the Gulf Islands National Seashore, Cat Island to Western Horn Island, Mississippi

This report contains the geophysical and geospatial data that were collected along the western offshore side of the Gulf Islands of Mississippi on the research vessel Tommy Munro during two cruises in 2010. Geophysical data were collected by the U.S. Geological Survey in Woods Hole, Massachusetts, and St. Petersburg, Forida, in cooperation with the U.S. Army Corps of Engineers Mobile District. Bathymetric-sonar, sidescan-sonar, and Chirp seismic-reflection data were acquired with the following equipment, respectively: Systems Engineering and Assessment, Ltd., SwathPlus interferometric sonars; Klein 3000 and 3900 dual-frequency sidescan sonars; and an EdgeTech 512i Chirp sub-bottom profiling system. The long-term goals of this mapping effort are to produce high-quality, high-resolution geologic maps and interpretations that can be utilized to identify sand resources within the region, to better understand the Holocene evolution, and to anticipate future changes in this coastal system. Processed geospatial data files and the geophysical data provided in this report help attain these goals.

Mississippi↗
USGS2012

Comparison of concentrations and profiles of polycyclic aromatic hydrocarbon metabolites in bile of fishes from offshore oil platforms and natural reefs along the California coast

To determine the environmental consequences of decommissioning offshore oil platforms on local and regional fish populations, contaminant loads in reproducing adults were investigated at seven platform sites and adjacent, natural sites. Specimens of three species (Pacific sanddab, Citharichthys sordidus ; kelp rockfish, Sebastes atrovirens ; and kelp bass, Paralabrax clathratus ) residing at platforms and representing the regional background within the Santa Barbara Channel and within the San Pedro Basin were collected. Some of the most important contaminant classes related to oil operations are polycyclic aromatic hydrocarbons (PAHs) because of their potential toxicity and carcinogenicity. However, acute exposure cannot be related directly to PAH tissue concentrations because of rapid metabolism of the parent chemicals in fish; therefore, PAH metabolites in bile were measured, targeting free hydroxylated PAHs (OH-PAHs) liberated by enzymatic hydrolysis of the bound PAH glucuronides and sulfates. An ion-pairing method was developed for confirmatory analysis that targeted PAH glucuronides and sulfates. Concentrations of hydroxylated PAHs in all samples (76 fish from platforms and 64 fish from natural sites) were low, ranging from less than the limits of detection (5 to 120 nanograms per milliliter bile; 0.03 to 42 nanograms per milligram protein) to a maximum of 320 nanograms per milliliter bile (32 nanograms per milligram protein). A previously proposed dosimeter of PAH exposure in fish, 1-hydroxypyrene, was not detected at any platform site. Low concentrations of 1-hydroxypyrene were detected in 3 of 12 kelp rockfish collected from a natural reef site off Santa Barbara. The most prevalent OH-PAH, 2-hydroxyfluorene, was detected at low concentrations in seven fish of various species; of these, four were from two of the seven platform sites. The greatest concentrations of 2-hydroxyfluorene were found in three fish of various species from Platform Holly and were only about threefold above low, yet quantifiable, concentrations found in three fish from Horseshoe Reef, East Anacapa Island, and Coche Point natural sites; the mean concentrations among all sampling sites were not measurably different.

California↗
USGS2013

Regional maps of subsurface geopressure gradients of the onshore and offshore Gulf of Mexico basin

The U.S. Geological Survey created a comprehensive geopressure-gradient model of the regional pressure system spanning the onshore and offshore Gulf of Mexico basin, USA. This model was used to generate ten maps that included (1) five contour maps characterizing the depth to the surface defined by the first occurrence of isopressure gradients ranging from 0.60 psi/ft to 1.00 psi/ft, in 0.10-psi/ft increments; and (2) five supporting maps illustrating the spatial density of the data used to construct the contour maps. These contour maps of isopressure-gradients at various increments enable the identification and quantification of the occurrence, magnitude, location, and depth of the subsurface pressure system, which allows for the broad characterization of regions exhibiting overpressured, underpressured, and normally pressured strata. Identification of overpressured regions is critical for exploration and evaluation of potential undiscovered hydrocarbon accumulations based on petroleum-generation pressure signatures and pressure-retention properties of reservoir seals. Characterization of normally pressured regions is essential for field development decisions such as determining the dominant production drive mechanisms, evaluating well placement and drainage patterns, and deciding on well stimulation methods such as hydraulic fracturing. Identification of underpressured regions is essential for evaluating the feasibility of geological sequestration and long-term containment of fluids such as supercritical carbon dioxide for alternative disposal methods of greenhouse gases. This study is the first, quantitative investigation of the regional pressure systems of one of the most important petroleum provinces in the United States. Although this methodology was developed for pressure studies in the Gulf of Mexico basin, it is applicable to any basin worldwide.

Open-File Report↗
USGS2013

High-resolution seismic-reflection and marine-magnetic data from offshore central California--San Gregorio to Point Sur

The U.S. Geological Survey collected high-resolution seismic-reflection data on four surveys (S-N1-09-MB, S-15-10-NC, S-06-11-MB, and S-04-12-MB) and marine-magnetic data on one survey (S-06-11-MB) between 2009 and 2012, offshore of central California between San Gregorio and Point Sur. This work was supported in part by the California Seafloor Mapping Program. The survey areas span about 120 km of California's coast (including Monterey Bay). Most data were collected aboard the U.S. Geological Survey R/V Parke Snavely. Cumulatively, approximately 1,410 km of single-channel seismic-reflection data were acquired, mainly using a SIG 2mille minisparker. About 44 km of data were collected simultaneously using an EdgeTech Chirp 512. Subbottom acoustic penetration spanned tens to several hundreds of meters, variable by location. Marine magnetic data were collected on approximately 460 km of track lines (mainly in southern Monterey Bay) using a Geometrics G882 cesium-vapor marine magnetometer. This report includes maps and navigation files of the surveyed transects, linked to Google Earth™ software, as well as digital data files showing images of each transect in SEG-Y and JPEG formats. The images of bedrock, sediment deposits, and tectonic structure provide geologic information that is essential to hazard assessment, regional sediment management, and coastal and marine spatial planning at Federal, State and local levels, as well as to future research on the geomorphic, sedimentary, tectonic, and climatic record of central California.

California↗
USGS2014

Maps showing bathymetry and modern sediment thickness on the inner continental shelf offshore of Fire Island, New York, pre-Hurricane Sandy

The U.S. Geological Survey mapped approximately 336 square kilometers of the lower shoreface and inner continental shelf offshore of Fire Island, New York, in 2011 by using interferometric sonar and high-resolution chirp seismic-reflection systems. This report presents maps of bathymetry, acoustic backscatter, the coastal plain unconformity, the Holocene marine transgressive surface, and modern sediment thickness. These spatial data support research on the Quaternary evolution of the Fire Island coastal system and provide baseline information for research on coastal processes along southern Long Island.

New York↗
USGS2015

Sea-floor morphology and sedimentary environments in western Block Island Sound, offshore of Fishers Island, New York

Multibeam-bathymetric and sidescan-sonar data, collected by the National Oceanic and Atmospheric Administration in a 114-square-kilometer area of Block Island Sound, southeast of Fishers Island, New York, are combined with sediment samples and bottom photography collected by the U.S. Geological Survey from 36 stations in this area in order to interpret sea-floor features and sedimentary environments. These interpretations and datasets provide base maps for studies on benthic ecology and resource management. The geologic features and sedimentary environments on the sea floor are products of the area’s glacial history and modern processes. These features include bedrock, drumlins, boulders, cobbles, large current-scoured bathymetric depressions, obstacle marks, and glaciolacustrine sediments found in high-energy sedimentary environments of erosion or nondeposition; and sand waves and megaripples in sedimentary environments characterized by coarse-grained bedload transport. Trawl marks are preserved in lower energy environments of sorting and reworking. This report releases the multibeam-bathymetric, sidescan-sonar, sediment, and photographic data and interpretations of the features and sedimentary environments in Block Island Sound, offshore Fishers Island.

New York↗
USGS2015

Maps showing the change in modern sediment thickness on the Inner Continental Shelf offshore of Fire Island, New York, between 1996-97 and 2011

The U.S. Geological Survey mapped approximately 336 square kilometers of the lower shoreface and inner continental shelf offshore of Fire Island, New York, in 1996 and 1997, using high-resolution sidescan-sonar and seismic-reflection systems, and again in 2011, using interferometric sonar and high-resolution chirp seismic-reflection systems. This report presents a comparison of sediment thickness and distribution as mapped during these two investigations. These spatial data support research on the Quaternary evolution of the Fire Island coastal system and provide baseline information for research on coastal processes along southern Long Island.

New York↗
USGS2015

Depth-to-basement, sediment-thickness, and bathymetry data for the deep-sea basins offshore of Washington, Oregon, and California

Contours and derivative raster files of depth-to-basement, sediment-thickness, and bathymetry data for the area offshore of Washington, Oregon, and California are provided here as GIS-ready shapefiles and GeoTIFF files. The data were used to generate paper maps in 1992 and 1993 from 1984 surveys of the U.S. Exclusive Economic Zone by the U.S. Geological Survey for depth to basement and sediment thickness, and from older data for the bathymetry.

California, Oregon, Washington↗
USGS2016

High-resolution seismic-reflection data from offshore northern California — Bolinas to Sea Ranch

The U.S. Geological Survey collected high-resolution seismic-reflection data in September 2009, on survey S-8-09-NC, offshore of northern California between Bolinas and Sea Ranch. The survey area spans about 125 km of California’s coast and extends around Point Reyes. Data were collected aboard the U.S. Geological Survey R/V Parke Snavely . Cumulatively, ~1,150 km of seismic-reflection data were acquired using a SIG 2mille minisparker. Subbottom acoustic depth of penetration spanned tens to several hundred meters and varied by location and underlying sediments and rock types. This report includes maps and a navigation file of the surveyed transects, utilizing Google Earth™ software, as well as digital data files showing images of each transect in SEG-Y and JPEG formats. The images of bedrock, sediment deposits, and tectonic structure provide geologic information that is essential to hazard assessment, regional sediment management, and coastal and marine spatial planning at Federal, State and local levels. This information is also valuable for future research on the geomorphic, sedimentary, tectonic, and climatic record of central California.

California↗
USGS2021

Summary of oceanographic and water-quality measurements offshore of Matanzas Inlet, Florida, 2018

U.S. Geological Survey (USGS) scientists and technical staff deployed instrumented underwater platforms and buoys to collect oceanographic and atmospheric data at two sites near Matanzas Inlet, Florida, on January 24, 2018, and recovered them on April 13, 2018. Matanzas Inlet is a natural, unmaintained inlet on the Florida Atlantic coast that is well suited to study inlet and cross-shore processes. The two study sites were located offshore of the surf zone, in 9 and 15 meters of water depth, in a line perpendicular to the coast. A sea-floor platform was deployed at each site to measure ocean currents, wave motions, acoustic and optical backscatter, temperature, salinity, and pressure. The objective was to quantify the hydrodynamic forcing for sediment transport and the response to such forcing near the seabed in the vicinity of an unmaintained inlet.

Florida↗
USGS1978

Statistical analysis of re-bid federal offshore Gulf of Mexico oil and gas leases

Through 1977, there were 178 cases where exactly the same Federal offshore oil and gas bonus bid lease was offered and received bids in 2 sales. (In addition, there were 131 cases where there was an overlap of acreage between a lease offered and receiving bids in 2 sales.) Table 1 summarizes these exact re-bid leases which are in 2 categories: (1) Leases re-bid after rejection of any and all bids received as a result of a prior offering, and (2) Leases re-bid after prior offering, issue, and relinquishment of a lease. We will call the former category rejected re-bid leases, the latter relinquished re-bid leases. Table 1 shows there were 120 of the former and 58 of the latter. The purpose of this study was simply development and analysis of the statistics of re-bid leases. The reasons why the data behave as they do are subjective and unavoidably involve nontechnical value judgments. Therefore, we do not speculate on the reasons in this report. The data source for this study was the LPR-5/-10 data base maintained by the General Services Administration, Fort Worth, Texas.

Gulf of Mexico↗
USGS1979

Location and hydrocarbon content of a gravity core from the offshore Eel River basin, northern California

The core was collected from ponded sediment near the crest of a diapir-like feature on the Eel Plateau. The measured hydrocarbons are likely to have been derived from deep in the Neogene sedimentary section of the Eel River Basin. Their presence at the surface may indicate migration along fractures in or bordering the diapiric feature and seepage into unconsolidated sediments that are ponded locally within structural and bathymetric depressions. The extent of low molecular weight hydrocarbons at or near the-surface elsewhere in the basin is unknown, but the information based on hydrocarbon composition obtained at this site indicates the possibility that thermogenically-derived hydrocarbons have formed and accumulated in the sedimentary rocks of the offshore Eel River Basin.

California↗
USGS1980

A summary report of the regional geology, petroleum potential, environmental geology, and operational considerations in the area of proposed lease sale No. 68, offshore southern California

This report reviews geological, geophysical and technological data that are pertinent to proposed OCS Lease Sale 68. Under consideration are 26,000 mi 2 (67,400 km 2 ) of the California Continental Borderland north of the U.S.-Mexico boundary. The area includes both leased and unleased tracts and lies adjacent to the highly productive coastal basins of southern California. Factors that have contributed to petroleum generation in the onshore basins, such as thickness, burial depth and hydrocarbon content, are less favorable in parts of the offshore region. Nevertheless, regional geologic and geophysical mapping together with data from stratigraphic test wells and bottom samples suggest that source beds, reservoir rocks and traps are present beneath the borderland. Strata of Miocene age are widespread within the area of proposed OCS Lease Sale 68 and contain fair to excellent potential source rocks. Eocene and early Miocene sandstone beds in the Cortes Bank test well and late Miocene and Pliocene rocks in the Point Conception test well have porosities that are within the range of good reservoir rocks. Late middle Miocene through Pliocene sandy turbidites of reservoir quality possibly occur in some outer borderland basins. Additional prospective targets are fractured Miocene shale beds that may be present in the deeper basins and on the down-flank margins of major uplifts. Numerous structural and stratigraphic traps, which formed in response to late Cenozoic wrench tectonics, are distributed throughout the borderland.

California↗