SEARCH · USGS Science

Results for “Marine Structures”

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

SourceResearch connectionFrom yearThrough year

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

At least 793 records · Page 44Linked to original sources

USGS2016

California State Waters Map Series — Offshore of Monterey, California

Introduction In 2007, the California Ocean Protection Council initiated the California Seafloor Mapping Program (CSMP), designed to create a comprehensive seafloor map of high-resolution bathymetry, marine benthic habitats, and geology within the 3-nautical-mile limit of California’s State Waters. The CSMP approach is to create highly detailed seafloor maps through collection, integration, interpretation, and visualization of swath bathymetry data, acoustic backscatter, seafloor video, seafloor photography, high-resolution seismic-reflection profiles, and bottom-sediment sampling data. The map products display seafloor morphology and character, identify potential marine benthic habitats, and illustrate both the surficial seafloor geology and shallow subsurface geology. The Offshore of Monterey map area in central California is located on the Pacific Coast, about 120 km south of San Francisco. Incorporated cities in the map area include Seaside, Monterey, Marina, Pacific Grove, Carmel-by-the-Sea, and Sand City. The local economy receives significant resources from tourism, as well as from the Federal Government. Tourist attractions include the Monterey Bay Aquarium, Cannery Row, Fisherman’s Wharf, and the many golf courses near Pebble Beach, and the area serves as a gateway to the spectacular scenery and outdoor activities along the Big Sur coast to the south. Federal facilities include the Army’s Defense Language Institute, the Naval Postgraduate School, and the Fleet Numerical Meteorology and Oceanography Center (operated by the Navy). In 1994, Fort Ord army base, located between Seaside and Marina, was closed; much of former army base land now makes up the Fort Ord National Monument, managed by the U.S. Bureau of Land Management as part of the National Landscape Conservation System. In addition, part of the old Fort Ord is now occupied by California State University, Monterey Bay. The offshore part of the map area lies entirely within the Monterey Bay National Marine Sanctuary, one of the nation’s largest marine sanctuaries. State beaches and parks within the map area include Fort Ord Dunes State Park and the Marina, Monterey, and Asilomar State Beaches, as well as Carmel River State Beach, which includes the Carmel River Lagoon and Wetland Natural Preserve. The map area also includes all or part of several State Marine Protected Areas, including the Carmel Pinnacles, Asilomar, and Lovers Point–Julia Platt State Marine Reserves, as well as the Carmel Bay, Pacific Grove Marine Gardens, Edward F. Ricketts, and Portuguese Ledge State Marine Conservation Areas. The coastal zone in the map area is characterized by two distinct physiographies. From Marina to Monterey, sandy beaches are backed by a belt of sand dunes, as much as 30 to 40 m high and as wide as 8 km. The Salinas River supplies the sand for the beaches and dunes. Nearshore sediment transport is primarily to the south, in the southern Monterey littoral cell. Along the Monterey peninsula, which lies at the north end of the rugged Santa Lucia Range, coastal relief is very different. The peninsula is characterized largely by low marine terraces that formed mostly on hard and relatively stable granitic bedrock. Carmel Beach in Carmel-by-the-Sea is the longest continuous beach in this area; bedrock points and small pocket beaches characterize most of the rest of the peninsula. The Carmel River littoral cell extends along the coast from Point Pinos to Point Lobos (just south of the map area), including Carmel Beach; sediment transport is primarily to the south. The granitic rocks that crop out so prominently along the Monterey peninsula make up part of the Salinian block, a crustal terrane that in this area lies west of the San Andreas Fault and east of the San Gregorio Fault. The strike-slip San Andreas Fault Zone, which lies just 26 km east of the map area, is the most important structure within the Pacific–North American transform plate boundary. The San Gregorio Fault, a secondary fault within the distributed plate boundary, cuts through (and is roughly aligned with) Carmel Canyon, a submarine canyon in the southwest corner of the map area that is part of the Monterey Canyon system. The San Gregorio Fault Zone is part of a fault system that is present predominantly in the offshore for about 400 km, from Point Conception in the south (where it is known as the Hosgri Fault) to Bolinas and Point Reyes in the north. The offshore part of the map area primarily consists of relatively flat continental shelf, bounded on the west by the steep flanks of Carmel Canyon. Shelf width varies from 2 to 3 km in the southern part of the map area, near the mouth of Carmel Canyon, to 14 km in Monterey Bay. Bedrock beneath the shelf is overlain in many areas by variable amounts (0 to 16 m) of upper Quaternary shelf and nearshore sediments deposited as sea level fluctuated in the late Pleistocene. “Soft-induration,” unconsolidated sediment is the dominant (about 63 percent) habitat type on the continental shelf, followed by “hard-induration” rock and boulders (about 34 percent) and “mixed-induration” substrate (about 3 percent). At water depths of about 100 to 130 m, the shelf break approximates the shoreline during the sea-level lowstand of the Last Glacial Maximum, about 21,000 years ago. Carmel Canyon and other parts of the Monterey Canyon system in the map area extend from the shelf break to water depths that reach 1,600 m. Most of the extensive incision of the shelf break and canyon flanks probably occurred during repeated Quaternary sea-level lowstands. The relatively straight floor of Carmel Canyon notably is aligned with the San Gregorio Fault Zone. Mixed hard-soft substrate is the most common (about 51 percent) habitat type in Carmel Canyon; hard bedrock and soft, unconsolidated sediment cover about 40 percent and 9 percent of canyon habitat, respectively. This part of the central California coast is exposed to large North Pacific swells from the northwest throughout the year. Wave heights range from 2 to 10 m, the larger swells occurring from October to May. During El Niño–Southern Oscillation (ENSO) events, winter storms track farther south than they do in normal (non-ENSO) years, thereby impacting the map area more frequently and with waves of larger heights. Benthic species observed in the map area are natives of the cold-temperate biogeographic zone that is called either the “Oregonian province” or the “northern California ecoregion.” This biogeographic province is maintained by the long-term stability of the southward-flowing California Current, the eastern limb of the North Pacific subtropical gyre that flows from southern British Columbia to Baja California. Biological productivity resulting from coastal upwelling supports populations of Sooty Shearwater, Western Gull, Common Murre, Cassin’s Auklet, and many other less populous bird species. An observable recovery of Humpback and Blue Whales has occurred in the area; both species are dependent on coastal upwelling to provide nutrients. The large extent of exposed inner shelf bedrock supports large forests of “bull kelp,” which is well adapted for high-wave-energy environments. The kelp beds are well-known habitat for the population of southern sea otters. Common fish species found in the kelp beds and rocky reefs include lingcod and various species of rockfish and greenling.

California↗

USGS2021

Novel insights into the genetic population connectivity of transient whale sharks (Rhincodon typus) in Pacific Panama provide crucial data for conservation efforts

The whale shark ( Rhincodon typus ) is an endangered and highly migratory species, of which solitary individuals or aggregations are observed in oceans worldwide and for which conservation efforts are hindered by a lack of comprehensive data on genetic population connectivity. Tissue samples were collected from wandering whale sharks in Pacific Panama to determine genetic diversity, phylogeographic origin, and possible global and local connectivity patterns using a 700–800 bp fragment of the mitochondrial control region gene. Genetic diversity among samples was high, with five new haplotypes and nine polymorphic sites identified among the 15 sequences. Haplotype diversity ( H d = 0.83) and nucleotide diversity (π = 0.00516) were similar to those reported in other studies. Our sequences, in particular haplotypes PTY1 and PTY2 , were similar to those previously reported in the Arabian Gulf and the Western Indian Ocean populations (a novel occurrence in the latter case). Haplotypes PTY3 , PTY4 , and PTY5 were similar to populations in Mexico and the Gulf of California. In contrast, the only populations to which our Panamanian sequences were genetically dissimilar were those from the Atlantic Ocean. The absence of reference sequences in GenBank from southern sites in the Eastern Tropical Pacific, such as Galapagos (Ecuador), Gorgona and Malpelo Islands (Colombia), and Coco Island (Costa Rica), reduced our capacity to genetically define regional patterns. Genetic differentiation and connectivity were also assessed using an analysis of molecular variance (AMOVA), which showed a similar population structure (five groups) to the neighbor-joining tree. Other population features based on neutrality tests, such as Tajima’s D and Fu’s Fs statistics, showed positive values for Panama of 0.79 and 1.61, respectively. Positive values of these statistics indicate a lack of evidence for population expansion among the sampled individuals. Our results agree with previous reports suggesting that whale sharks can travel over long distances and that transboundary conservation measures may be effective for species protection.

Gulf of Chiriqu↗

USGS2012

The shallow-water fish assemblage of Isla del Coco National Park, Costa Rica: Structure and patterns in an isolated, predator-dominated ecosystem

Fishes at Isla del Coco National Park, Costa Rica, were surveyed as part of a larger scientific expedition to the area in September 2009. The average total biomass of nearshore fishes was 7.8 tonnes per ha, among the largest observed in the tropics, with apex predators such as sharks, jacks, and groupers accounting for nearly 40% of the total biomass. The abundance of reef and pelagic sharks, particularly large aggregations of threatened species such as the scalloped hammerhead shark (up to 42 hammerheads ha-1) and large schools of jacks and snappers show the capacity for high biomass in unfished ecosystems in the Eastern Tropical Pacific. However, the abundance of hammerhead and reef whitetip sharks appears to have been declining since the late 1990s, and likely causes may include increasing fishing pressure on sharks in the region and illegal fishing inside the Park. One Galapagos shark tagged on September 20, 2009 in the Isla del Coco National Park moved 255km southeast towards Malpelo Island in Colombia, when it stopped transmitting. These results contribute to the evidence that sharks conduct large-scale movements between marine protected areas (Isla del Coco, Malpelo, Galápagos) in the Eastern tropical Pacific and emphasize the need for regional-scale management. More than half of the species and 90% of the individuals observed were endemic to the tropical eastern Pacific. These high biomass and endemicity values highlight the uniqueness of the fish assemblage at Isla del Coco and its importance as a global biodiversity hotspot.

Cocos Island, Isla Del Coco↗

USGS2021

A socio-ecological imperative for broadening participation in coastal and estuarine research and management

For most of the scientific disciplines associated with coastal and estuarine research, workforce representation does not match the demographics of communities we serve, especially for Black, Hispanic or Latino, and Indigenous peoples. This essay provides an overview of this inequity and identifies how a scientific society can catalyze representational, structural, and interactional diversity to achieve greater inclusion. Needed changes go beyond representational diversity and require an intentional commitment to build capacity through inclusivity and community engagement by supporting anti-racist policies and actions. We want to realize a sense of belonging on the part of scientists in society at large and enable research pursuits through a lens of social justice in service of coastal communities. Minimally, this framework offers an avenue for increased recruitment of individuals from more diverse racial and ethnic identities. More broadly, the mechanisms described here aim to create a culture in scientific societies in which social justice, driven by anti-racist actions, produces systemic change in how members of scientific societies approach, discuss, and address issues of inequity. We have written this essay for members of the coastal and marine science community who are interested in change. We aim to call in new voices, allies, and champions to this work.

Estuaries and Coasts↗

USGS2004

Integrating digital information for coastal and marine sciences

A pilot distributed geolibrary, the Marine Realms Information Bank (MRIB), was developed by the U.S. Geological Survey Coastal and Marine Geology Program and the Woods Hole Oceanographic Institution, to classify, integrate, and facilitate access to scientific information about oceans, coasts, and lakes. The MRIB is composed of a categorization scheme, a metadata database, and a specialized software backend, capable of drawing together information from remote sources without modifying their original format or content. Twelve facets are used to classify information: location, geologic time, feature type, biota, discipline, research method, hot topics, project, agency, author, content type, and file type. The MRIB approach allows easy and flexible organization of large or growing document collections for which centralized repositories would be impractical. Geographic searching based on the gazetteer and map interface is the centerpiece of the MRIB distributed geolibrary. The MRIB is one of a very few digital libraries that employ georeferencing -- a fundamentally different way to structure information from the traditional author/title/subject/keyword approach employed by most digital libraries. Lessons learned in developing the MRIB will be useful as other digital libraries confront the challenges of georeferencing.

Journal of Digital Information Management↗

USGS2000

Protection of fish spawning habitat for the conservation of warm-temperature reef-fish fisheries of shelf-edge reefs of Florida

We mapped and briefly describe the surficial geology of selected examples of shelf-edge reefs (50–120 m deep) of the southeastern United States, which are apparently derived from ancient Pleistocene shorelines and are intermittently distributed throughout the region. These reefs are ecologically significant because they support a diverse array of fish and invertebrate species, and they are the only aggregation spawning sites of gag ( Mycteroperca microlepis ), scamp ( M. phenax ), and other economically important reef fish. Our studies on the east Florida shelf in the Experimental Oculina Research Reserve show that extensive damage to the habitat-structuring coral Oculina varicosa has occurred in the past, apparently from trawling and dredging activities of the 1970s and later. On damaged or destroyed Oculina habitat, reef-fish abundance and diversity are low, whereas on intact habitat, reef-fish diversity is relatively high compared to historical diversity on the same site. The abundance and biomass of the economically important reef fish was much higher in the past than it is now, and spawning aggregations of gag and scamp have been lost or greatly reduced in size. On the west Florida shelf, fishers have concentrated on shelf-edge habitats for over 100 yrs, but fishing intensity increased dramatically in the 1980s. Those reefs are characterized by low abundance of economically important species. The degree and extent of habitat damage there is unknown. We recommend marine fishery reserves to protect habitat and for use in experimentally examining the potential production of unfished communities.

Florida↗

USGS2000

Protection of fish spawning habitat for the conservation of warm temperate reef fish fisheries of shelf-edge reefs of Florida

Florida↗

USGS2011

The characteristics of gas hydrates recovered from the Mount Elbert Gas Hydrate Stratigraphic Test Well, Alaska North Slope

Systematic analyses have been carried out on two gas hydrate-bearing sediment core samples, HYPV4, which was preserved by CH 4 gas pressurization, and HYLN7, which was preserved in liquid-nitrogen, recovered from the BPXA-DOE-USGS Mount Elbert Stratigraphic Test Well. Gas hydrate in the studied core samples was found by observation to have developed in sediment pores, and the distribution of hydrate saturation in the cores imply that gas hydrate had experienced stepwise dissociation before it was stabilized by either liquid nitrogen or pressurizing gas. The gas hydrates were determined to be structure Type I hydrate with hydration numbers of approximately 6.1 by instrumentation methods such as powder X-ray diffraction, Raman spectroscopy and solid state 13 C NMR. The hydrate gas composition was predominantly methane, and isotopic analysis showed that the methane was of thermogenic origin (mean δ 13 C = −48.6‰ and δ D = −248‰ for sample HYLN7). Isotopic analysis of methane from sample HYPV4 revealed secondary hydrate formation from the pressurizing methane gas during storage.

Alaska↗

USGS2009

Investigation into the Origin and Character of Surficial Sedimentary Deposits at the Midshore Regional Solid Waste Facility near Easton, Maryland

A temporary exposure at the Midshore Regional Solid Waste Facility near Easton, MD, provided an opportunity to document the characteristics of the complex assemblage of surficial facies in that area. This unusually large cross section allowed interpretation of the changing processes that shaped the landscape in response to climate change through the late Pleistocene. Eight stratigraphic units were recognized: (1) gray, fossiliferous, muddy silt of the marine Miocene Choptank Formation; (2) coarse, crossbedded conglomerate of the late Miocene to Pliocene fluvial Pensauken Formation; (3) bioturbated muddy conglomerate interpreted as deposits of small colluvial fans; (4) pebbly, quartzose sand overlying a planar erosional surface reflecting a marine transgression; (5) irregular pods and lenses of sand and gravel deformed into bowl-shaped folds and faulted, which are interpreted as wind deposits over a semipermanent snow cover (niveo-aeolian deposits); (6) crossbedded sand and conglomerate with abundant mud partings indicating tidal influences on sinuous stream channels; (7) heavily bioturbated silt and sand with abundant root casts and flattened vesicles interpreted as aeolian loess deposits in marshy fens; and (8) pebbly sand and mud with scattered boulders and cobbles that reflect modern infill of the excavation by the operators. Soils formed on units 3, 4, and 7. Superimposed on units 4, 5, and 7 is evidence of deep freezing and permafrost development and subsequent thermokarst development after thawing, which includes large, complexly filled wedge-shaped cracks, deformed bedding and faults, fluid-injection structures, and spherical blobs of sand and mud. Each of the stratigraphic units has irregular distributions and lateral changes. The results of this study provide a unique insight into the geometry of surficial deposits that will help facilitate mapping of units, interpretation of cored intervals, and understanding of ground-penetrating radar profiles. The study also documents the widespread effects of permafrost during the last glacial episode well south of the maximum advance of ice sheets.

Open-File Report↗

USGS2013

Impact of Late Holocene climate variability and anthropogenic activities on Biscayne Bay (Florida, U.S.A.): Evidence from diatoms

Shallow marine ecosystems are experiencing significant environmental alterations as a result of changing climate and increasing human activities along coasts. Intensive urbanization of the southeast Florida coast and intensification of climate change over the last few centuries changed the character of coastal ecosystems in the semi-enclosed Biscayne Bay, Florida. In order to develop management policies for the Bay, it is vital to obtain reliable scientific evidence of past ecological conditions. The long-term records of subfossil diatoms obtained from No Name Bank and Featherbed Bank in the Central Biscayne Bay, and from the Card Sound Bank in the neighboring Card Sound, were used to study the magnitude of the environmental change caused by climate variability and water management over the last ~ 600 yr. Analyses of these records revealed that the major shifts in the diatom assemblage structures at No Name Bank occurred in 1956, at Featherbed Bank in 1966, and at Card Sound Bank in 1957. Smaller magnitude shifts were also recorded at Featherbed Bank in 1893, 1942, 1974 and 1983. Most of these changes coincided with severe drought periods that developed during the cold phases of El Niño Southern Oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO), or when AMO was in warm phase and PDO was in the cold phase. Only the 1983 change coincided with an unusually wet period that developed during the warm phases of ENSO and PDO. Quantitative reconstructions of salinity using the weighted averaging partial least squares (WA-PLS) diatom-based salinity model revealed a gradual increase in salinity at the three coring locations over the last ~ 600 yr, which was primarily caused by continuously rising sea level and in the last several decades also by the reduction of the amount of freshwater inflow from the mainland. Concentration of sediment total nitrogen (TN), total phosphorus (TP) and total organic carbon (TOC) increased in the second half of the 20th century, which coincided with the construction of canals, landfills, marinas and water treatment plants along the western margin of Biscayne Bay. Increased magnitude and rate of the diatom assemblage restructuring in the mid- and late-1900s, suggest that large environmental changes are occurring more rapidly now than in the past.

Florida↗

USGS2010

EAARL coastal topography-Cape Hatteras National Seashore, North Carolina, post-Nor'Ida, 2009: first surface

These remotely sensed, geographically referenced elevation measurements of lidar-derived first-surface (FS) topography datasets were produced collaboratively by the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL, and the National Park Service (NPS), Northeast Coastal and Barrier Network, Kingston, RI. This project provides highly detailed and accurate datasets of a portion of the National Park Service Southeast Coast Network's Cape Hatteras National Seashore in North Carolina, acquired post-Nor'Ida (November 2009 nor'easter) on November 27 and 29 and December 1, 2009. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative airborne lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine aircraft, but the instrument was deployed on a Pilatus PC-6. A single pilot, a lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations. For more information about similar projects, please visit the Decision Support for Coastal Science and Management website.

Data Series↗

USGS2011

EAARL Coastal Topography-Cape Hatteras National Seashore, North Carolina, Post-Nor'Ida, 2009: Bare Earth

These remotely sensed, geographically referenced elevation measurements of lidar-derived bare-earth (BE) topography datasets were produced collaboratively by the U.S. Geological Survey (USGS), St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL, and the National Park Service (NPS), Northeast Coastal and Barrier Network, Kingston, RI. This project provides highly detailed and accurate datasets of a portion of the National Park Service Southeast Coast Network's Cape Hatteras National Seashore in North Carolina, acquired post-Nor'Ida (November 2009 nor'easter) on November 27 and 29 and December 1, 2009. The datasets are made available for use as a management tool to research scientists and natural-resource managers. An innovative airborne lidar instrument originally developed at the NASA Wallops Flight Facility, and known as the Experimental Advanced Airborne Research Lidar (EAARL), was used during data acquisition. The EAARL system is a raster-scanning, waveform-resolving, green-wavelength (532-nanometer) lidar designed to map near-shore bathymetry, topography, and vegetation structure simultaneously. The EAARL sensor suite includes the raster-scanning, water-penetrating full-waveform adaptive lidar, a down-looking red-green-blue (RGB) digital camera, a high-resolution multispectral color-infrared (CIR) camera, two precision dual-frequency kinematic carrier-phase GPS receivers, and an integrated miniature digital inertial measurement unit, which provide for sub-meter georeferencing of each laser sample. The nominal EAARL platform is a twin-engine aircraft, but the instrument was deployed on a Pilatus PC-6. A single pilot, a lidar operator, and a data analyst constitute the crew for most survey operations. This sensor has the potential to make significant contributions in measuring sub-aerial and submarine coastal topography within cross-environmental surveys. Elevation measurements were collected over the survey area using the EAARL system, and the resulting data were then processed using the Airborne Lidar Processing System (ALPS), a custom-built processing system developed in a NASA-USGS collaboration. ALPS supports the exploration and processing of lidar data in an interactive or batch mode. Modules for presurvey flight-line definition, flight-path plotting, lidar raster and waveform investigation, and digital camera image playback have been developed. Processing algorithms have been developed to extract the range to the first and last significant return within each waveform. ALPS is used routinely to create maps that represent submerged or sub-aerial topography. Specialized filtering algorithms have been implemented to determine the 'bare earth' under vegetation from a point cloud of last return elevations.

Data Series↗

USGS2019

Structure contour and overburden maps of the Niobrara interval of the Upper Cretaceous Cody Shale in the Wind River Basin, Wyoming

The Wind River Basin in central Wyoming is one of many structural and sedimentary basins that formed in the Rocky Mountain foreland during the Laramide orogeny. The basin is bounded by the Washakie, Owl Creek, and southern Bighorn uplifts on the north, the Casper arch on the east, the Granite Mountains uplift on the south, and Wind River uplift on the west. The first commercial oil well in Wyoming was drilled at Dallas dome near an oil seep along the southwestern edge of the Wind River Basin in 1884. Since then, many important conventional oil and gas fields, that produce from reservoirs ranging in age from Mississippian through Tertiary, have been discovered in this basin. In addition, an extensive unconventional (continuous) overpressured basin-centered gas accumulation has been identified in Cretaceous and Tertiary strata in the deeper parts of the basin. It has been suggested that various Upper Cretaceous marine shales, including the Cody Shale, are the principal hydrocarbon source rocks for many of these accumulations. With recent advances in horizontal drilling and multistage fracture stimulation, there has been an increase in exploration and completion of wells in equivalent marine shales in other Rocky Mountain Laramide basins that were traditionally thought of only as hydrocarbon source rocks. The maps presented in this report were constructed as part of a project carried out by the U.S. Geological Survey to characterize the geologic framework of potential undiscovered continuous (unconventional) oil and gas resources of the Niobrara interval of the Upper Cretaceous Cody Shale in the Wind River Basin in central Wyoming.

Wyoming↗

USGS1984

Ferromanganese micronodules from the surficial sediments of Georges Bank

Ferromanganese micronodules have been found on Georges Bank, off the U.S. northeast coast, distributed throughout the surficial sediments within an area about 125 km long and at least 12 km wide. These coarse, sand-sized concretions have precipitated from metal-rich interstitial waters and contain many of the textural and structural features common to other neritic nodules. Most of the nodules have accreted around detrital grains, and X-ray powder diffraction analyses indicate the presence of geothite and vernadite (  -MnO 2 ) in the ferromanganese layers. Chemical analyses of the micronodules, when compared with similar data on deep-sea manganese nodules, reveal lower Mn/Fe ratios, significantly higher concentrations of V and As, comparable values of Mo, and an order of magnitude less of Co, Ni, Ce and most other metals.

Georges Bank↗

USGS2010

Three-dimensional geologic modeling of the Santa Rosa Plain, California

New three-dimensional (3D) lithologic and stratigraphic models of the Santa Rosa Plain (California, USA) delineate the thickness, extent, and distribution of subsurface geologic units and allow integration of diverse data sets to produce a lithologic, stratigraphic, and structural architecture for the region. This framework can be used to predict pathways of groundwater flow beneath the Santa Rosa Plain and potential areas of enhanced or focused seismic shaking. Lithologic descriptions from 2683 wells were simplified to 19 internally consistent lithologic classes. These distinctive lithologic classes were used to construct a 3D model of lithologic variations within the basin by extrapolating data away from drill holes using a nearest-neighbor approach. Subsurface stratigraphy was defined through the identification of distinctive lithologic packages tied, where possible, to high-quality well control and to surface exposures. The 3D stratigraphic model consists of three bounding components: fault surfaces, stratigraphic surfaces, and a surface representing the top of pre-Cenozoic basement, derived from inversion of regional gravity data. The 3D lithologic model displays a west to east transition from dominantly marine sands to heterogeneous continental sediments. In contrast to previous stratigraphic studies, the new models emphasize the prevalence of the clay-rich Petaluma Formation and its heterogeneous nature. Isopach maps of the Glen Ellen Formation and the 3D stratigraphic model show the influence of the Trenton Ridge, a concealed basement ridge that bisects the plain, on sedimentation; the thickest deposits of the Glen Ellen Formation are confined to north of the Trenton Ridge.

California↗

USGS2016

Shallower structure and geomorphology of the southern Puerto Rico offshore margin

Oblique convergence between the North American and Caribbean plates along the eastern Greater Antilles island arc has yielded the compressive Muertos margin in the backarc region. The Muertos margin is characterized by an asymmetric thrust belt with overall opposite vergence to the subduction system in the forearc region. Offshore south of Puerto Rico, this thrust belt disappears and is replaced by a succession of NE─SW- and E─W-trending deep basins and steep ridges that characterize the western Anegada passage, resulting in a complex deformation pattern. Using new high-resolution multibeam bathymetry and a dense data set of mostly new seismic reflection profiles, we studied the along- and across-strike variations of the geomorphology and shallower structure of the southern Puerto Rico offshore margin. We have identified four morphotectonic provinces: the Puerto Rican sub-basin and Muertos trough, the Muertos margin, the insular shelf and the western Anegada passage. The Muertos margin province shows two distinct slope sub-provinces: the active Muertos thrust belt formed by N─S-compression between the island arc and the Caribbean plate’s interior ─which includes lower and upper thrust belts with distinct deformational styles and lateral continuity─ and the shelf slope covered by a thick package of layered sediments highly-incised by a dense canyon network. This network is disrupted by the Investigator fault zone consisting of a 130 km-long E─W-trending band of active extensional deformation. The Investigator fault zone shows differential surface expression caused by along-strike changes in the magnitude and distribution of the deformation, though this deformation is driven by a N─S-oriented extension, and if there is any amount of strike-slip it is insignificant. In the western Anegada passage province, the Whiting basin and Whiting and Grappler ridges are formed by large dipslip normal faults driven by a NW─SE-oriented extensional regime. The western St. Croix rise shows a complex structure as attested by the existence of NE─SW- and E─W-oriented normal faults. The NE─SW-trending NW-dipping normal faults observed at the summit of the rise predate the E─W-bounding faults that could accommodate the extensional deformation at the Present. This study provides detailed observations on the active tectonic and sedimentary processes to help future studies assessing the natural resources and the seismic and tsunamigenic hazard in the Puerto Rico region.

Marine and Petroleum Geology↗

USGS2016

Seasonal sediment dynamics shape temperate bedrock reef communities

Mobilized seafloor sediment can impact benthic reef communities through burial, scour, and turbidity. These processes are ubiquitous in coastal oceans and, through their influence on the survival, fitness, and interactions of species, can alter the structure and function of benthic communities. In northern Monterey Bay, California, USA, as much as 30% of the seafloor is buried or exposed seasonally, making this an ideal location to test how subtidal temperate rocky reef communities vary in the presence and absence of chronic sediment-based disturbances. Designated dynamic plots were naturally inundated by sediment in summer (50 to 100% cover) and swept clean in winter, whereas designated stable plots remained free of sediment during our study. Multivariate analyses indicated significant differences in the structure of sessile and mobile communities between dynamic and stable reef habitats. For sessile species, community structure in disturbed plots was less variable in space and time than in stable plots due to the maintenance of an early successional state. In contrast, community structure of mobile species varied more in disturbed plots than in stable plots, reflecting how mobile species distribute in response to sediment dynamics. Some species were found only in these disturbed areas, suggesting that the spatial mosaic of disturbance could increase regional diversity. We discuss how the relative ability of species to tolerate disturbance at different life history stages and their ability to colonize habitat translate into community-level differences among habitats, and how this response varies between mobile and sessile communities.

California↗

USGS1999

Recent advances in life history of Gulf of Mexico sturgeon, Acipenser oxyrinchus desotoi, in the Suwannee River, Florida, USA: A synopsis

Gulf sturgeon spawn on portions of three sites in the upper Suwannee River, which may appropriately be described as spawning reefs. The same areas are utilized from year to year. Habitat factors important in spawning site determination include gravel/cobble substrate, the presence of eddy fields, a neutral to slightly alkaline pH, and an empirically observed range in calcium ion content (6-18 mg/L Ca++, corresponding to a conductivity range of 40-110??S). Eggs are deposited contagiously within a small area (< 10,000 m2) with very little scatter, suggesting little if any current drift. They are not found from samplers on immediately adjacent sand substrate. The broadcast spawner model does not seem to fit the Gulf sturgeon. Spawning begins 4-7 days after the March new moon, with water temperature above 17.0 oC, and extends for 9-23 days as discrete events involving individual females. Spawning may continue, if water temperature remains below 21-22oC. The total annual pool of spawning females in the Suwannee population is estimated at 80 individuals. Young of the year utilize open sand habitat away from shoreline and vegetated habitat. They disperse widely, and occur over freshwater reaches from rkm 10-237; no particular affinity with spring water habitat is evident. Larger Gulf sturgeon tend to congregate in deep holes serving as summer-fall holding areas. They fast and lose weight while remaining in freshwater, but more than compensate this loss during winter feeding in marine waters. The major downriver migration to the estuary takes place in October-November. After a period of river mouth staging, subadults and adults migrate into Gulf of Mexico nearshore mesohaline waters. They move further out and into deeper water (> 3 m) when water temperatures drop in mid-December, but final destinations in mid-winter remain unknown. Age-2 through 6 juveniles remain in the river mouth estuary over winter. In late January through early February YOY migrate downriver for the first time, joining larger juveniles to overwinter and feed. Tag and recapture data yield a Suwannee River population of Gulf sturgeon estimated at 7,650 individuals, with an annual turnover rate of 16%. Based on stability in cumulative recapture rates from 1991-1998, population size is stable with an effective balance between recruitment and mortality. However, population structure is dynamic, controlled by the juxtaposition, conjunction, and summation of successive strong and weak year classes. Length/age frequency distributions for 1995 and 1998 populations censuses are very different. The 1995 distribution is bimodal with a dominant mode of 9-14 year old subadults/adults, and a sub-dominant of mode of 2-4 year old juveniles. The 1998 distribution is trimodal, but overwhelmingly dominated by 6-9 year old subadults. Erosion by 1998 of the major subadult/adult mode from the 1995 census illustrates that large adults encounter the same high mortality as smaller fish. Ultimate adult size in the population has remained constant at 2.2 cm TL over 13 years, indicating a maximum life expectancy of 25 years for Suwannee River Gulf sturgeon.

Conference Paper↗