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At least 505 records · Page 28Linked to original sources
USGS2009

Potential environmental issues of CO 2 storage in deep saline aquifers: Geochemical results from the Frio-I Brine Pilot test, Texas, USA

Sedimentary basins in general, and deep saline aquifers in particular, are being investigated as possible repositories for large volumes of anthropogenic CO 2 that must be sequestered to mitigate global warming and related climate changes. To investigate the potential for the long-term storage of CO 2 in such aquifers, 1600 t of CO 2 were injected at 1500 m depth into a 24-m-thick "C" sandstone unit of the Frio Formation, a regional aquifer in the US Gulf Coast. Fluid samples obtained before CO 2 injection from the injection well and an observation well 30 m updip showed a Na–Ca–Cl type brine with ∼93,000 mg/L TDS at saturation with CH 4 at reservoir conditions; gas analyses showed that CH 4 comprised ∼95% of dissolved gas, but CO 2 was low at 0.3%. Following CO 2 breakthrough, 51 h after injection, samples showed sharp drops in pH (6.5–5.7), pronounced increases in alkalinity (100–3000 mg/L as HCO 3 ) and in Fe (30–1100 mg/L), a slug of very high DOC values, and significant shifts in the isotopic compositions of H 2 O, DIC, and CH 4 . These data, coupled with geochemical modeling, indicate corrosion of pipe and well casing as well as rapid dissolution of minerals, especially calcite and iron oxyhydroxides, both caused by lowered pH (initially ∼3.0 at subsurface conditions) of the brine in contact with supercritical CO 2 . These geochemical parameters, together with perfluorocarbon tracer gases (PFTs), were used to monitor migration of the injected CO 2 into the overlying Frio “B”, composed of a 4-m-thick sandstone and separated from the “C” by ∼15 m of shale and siltstone beds. Results obtained from the Frio “B” 6 months after injection gave chemical and isotopic markers that show significant CO 2 (2.9% compared with 0.3% CO 2 in dissolved gas) migration into the “B” sandstone. Results of samples collected 15 months after injection, however, are ambiguous, and can be interpreted to show no additional injected CO 2 in the “B” sandstone. The presence of injected CO 2 may indicate migration from “C” to “B” through the intervening beds or, more likely, a short-term leakage through the remedial cement around the casing of a 50-year old well. Results obtained to date from four shallow monitoring groundwater wells show no brine or CO 2 leakage through the Anahuac Formation, the regional cap rock.

Texas↗
USGS1984

Assessment of undiscovered conventionally recoverable petroleum resources of the Northwest European region

The estimates of undiscovered conventionally recoverable petroleum resources in the northwest European region at probability levels of 95 percent, 5 percent, statistical mean, and mode are for oil (in billions of barrels): 9, 34, 20, and 15; and for gas (in trillions of cubic feet): 92, 258, 167, and 162. The occurrence of petroleum can be accounted for in two distinct geological plays located in the various subbasins of the region. Play I is associated with the distribution of mature source rocks of Late Jurassic age relative to four distinct trapping conditions. The play has been demonstrated productive mostly in the Viking and Central Grabens of the North Sea, where the shale has been buried to optimum depths for the generation of both oil and gas. To the north of 62 ? N. latitude up to the Barents Sea, source rocks become increasingly deeply buried and are interpreted to be dominantly gas prone; a narrow band of potentially oil-prone shales tracks most of the coast of Norway, but water depths in favorable localities commonly range from 600 to 1,200 feet. To the south of the Central Graben, the Jurassic source rocks are either immature or minimally productive because of a change in facies. Undrilled traps remain within the favorable source-rock area, and exploration will continue to challenge the boundaries of conventional wisdom, especially on the Norwegian side where little has .been reported on the geology of the adjoining Bergen High or Horda Basin, though, reportedly, the Jurassic source rocks are missing on the high and are immature in the southern part of the basin. Play II is associated with the distribution of a coal facies of Carboniferous age that is mature for the generation of gas and locally underlies favorable reservoir and sealing rocks. The play is limited largely by facies development to the present area of discovery and production but is limited as well to the southeast into onshore Netherlands and Germany by the unfavorable economics of an increasing nitrogen content in the gas. This increase is apparently caused by excessive temperatures associated with increasing depth of burial of the source rock. The history of discovery in the North Sea would appear to deny the commonly held maxim that large fields are found first and early in the exploration process. However, if the discovery data are examined from the perspective of the award date of each exploration license, then it is clear that the largest fields and most of the reserves have indeed been found early in the exploration process of a particular license. Discoveries made within 1 year of granting the license are on average large giants, and they account for slightly less than two-thirds of the original reserves. Discoveries made within 2 to 5 years of the granting of the license are on average less than giant size and smaller than increment-l-year discoveries by a factor of 4; these fields account for a little less than one-third of the reserves. Those fields found 6 or more years after the granting of the license are relatively small and account for 20 percent of all discoveries but only 4 percent of total original reserves. These data suggest that a measure of an area's exploration maturity is the length of time elapsed since the award of the concession.

Circular↗
USGS1967

Mineral appraisal of the Flattery Rocks, Quillayute Needles, and Copalis National Wildlife Refuges, Washington

The Flattery Rocks, Quillayute Needles, and Copalis National Wildlife Refuges lie off the Pacific coast of the Olympic Peninsula between Cape Flattery and Grays Harbor. They have a total land area of 247 acres and consists of numerous small islands, sea stacks and rocks that rise above a wave-cut platform. The refuges are in a belt of intensely folded and faulted marine sedimentary and volcanic rocks of early Eocene to Pliocene age. Pleistocene glaciofluvial deposits blanket the Tertiary strata along this coastal belt. The disturbed belt borders the eastern margin of a depositional basin on the continental shelf that probably contains a thick sequence of late Tertiary rocks.

Washington↗
USGS1976

Geology of central Costa Rica and its implications in the geologic history of the region

The oldest rocks in Costa Rica, the Nicoya Complex, crop out in an arcuate belt along the Pacific coast and outside the mapped area. The complex is an ophiolite assemblage and indicates that a Late Cretaceous arc-trench system, probably a southerly extension of the Middle America Trench, lay along and west of the present Pacific coast. Polarity of the system is indicated by the presence of a volcanic olivine basalt arc east of the ophiolite belt and by a younger magmatic arc farther east. Relative lack of metamorphism of the ophiolite assemblage suggests that the rocks were obducted rather than subducted. Fossil evidence indicates that the complex was emplaced no later than the late Campanian. By the late Eocene both the ophiolite assemblage and the olivine basalt arc had been established as major sediment sources for basins that lay to the east, and they continued as such through the Oligocene and possibly into the middle Miocene. Widespread deposition of trachyandesite lava and volcaniclastic sediments, local marine planation, uplift, and renewed volcanism mark what is presumed to be the end of the Miocene. Extreme south-to-north coarsening of the unconformably superposed Doan Formation and the presence of corals in the shaly facies of the Doan in the southern part of the mapped areas suggest that marine sedimentation there was undisturbed by orogeny and that intrusion of the Talamancan magmatic rocks must have followed deposition of the Doan. Volcaniclastic block breccia, characteristic of northern exposures of the Doan, indicates that volcanism in the proto- Cordillera Central had begun by at least Doan time. Volcanism has been a dominant process in central Costa Rica since that time.

Journal of Research of the U.S. Geological Survey↗
USGS2013

Covariation of climate and long-term erosion rates acrossa steep rainfall gradient on the Hawaiian island of Kaua'i

Erosion of volcanic ocean islands creates dramatic landscapes, modulates Earth’s carbon cycle, and delivers sediment to coasts and reefs. Because many volcanic islands have large climate gradients and minimal variations in lithology and tectonic history, they are excellent natural laboratories for studying climatic effects on the evolution of topography. Despite concerns that modern sediment fluxes to island coasts may exceed long-term fluxes, little is known about how erosion rates and processes vary across island interiors, how erosion rates are influenced by the strong climate gradients on many islands, and how modern island erosion rates compare to long-term rates. Here, we present new measurements of erosion rates over 5 yr to 5 m.y. timescales on the Hawaiian island of Kaua‘i, across which mean annual precipitation ranges from 0.5 to 9.5 m/yr. Eroded rock volumes from basins across Kaua‘i indicate that million-year-scale erosion rates are correlated with modern mean annual precipitation and range from 8 to 335 t km –2 yr –1 . In Kaua‘i’s Hanalei River basin, 3 He concentrations in detrital olivines imply millennial-scale erosion rates of >126 to >390 t km –2 yr –1 from olivine-bearing hillslopes, while fluvial suspended sediment fluxes measured from 2004 to 2009 plus estimates of chemical and bed-load fluxes imply basin-averaged erosion rates of 545 ± 128 t km –2 yr –1 . Mapping of landslide scars in satellite imagery of the Hanalei basin from 2004 and 2010 implies landslide-driven erosion rates of 30–47 t km –2 yr –1 . These measurements imply that modern erosion rates in the Hanalei basin are no more than 2.3 ± 0.6 times faster than millennial-scale erosion rates, and, to the extent that modern precipitation patterns resemble long-term patterns, they are consistent with a link between precipitation rates and long-term erosion rates.

Hawai'i↗
USGS1982

Techniques for estimating magnitude and frequency of floods in South Carolina

Methods are provided for estimating flood magnitudes at recurrence intervals of 2, 5, 10, 25, 50, and 100 years, for unregulated rural streams in South Carolina with drainage areas greater than 1.0 square mile. Multiple regression analyses were used to define the relation between flood discharge and basin and climatic variables. The analyses indicated that flood discharge is related to the drainage area and physiographic location of the basin. Accordingly, equations were developed for the Lower Coastal Plain, Inner Coastal Plain, Piedmont, and Blue Ridge provinces. The standard errors of estimate range from 31 to 56 percent. Station data used in the analyses are listed in the report. Individual relations of flood discharge and frequency to drainage area are given for some of the regulated major streams, including the Pee Dee, Catawba, Wateree, Broad, Saluda, Congaree, Santee, and Savannah Rivers. Storm tide-recurrence interval relations along the South Carolina coast indicate that the 500-year tide height can exceed 19 feet, National Geodetic Vertical Datum of 1929, at some locations. A compilation of flood records for gaging stations is included as supplemental data.

South Carolina↗
USGS1967

Geologic framework and petroleum potential of the Atlantic Coastal Plain and continental shelf, with a section on stratigraphy

The Atlantic Coastal Plain and Continental Shelf of North America is represented by a belt of Mesozoic and Cenozoic rocks, 150 to 300 miles wide and 2,400 miles long, extending from southern Florida to the Grand Banks of Newfoundland. This belt of Mesozoic and Cenozoic rocks encompasses an area of about 400,000 to 450,000 square miles, more than three-fourths of which is covered by the Atlantic Ocean. The volume of Mesozoic and Cenozoic rocks beneath the Atlantic Coastal Plain and Continental Shelf exceeds 450,000 cubic miles, perhaps by a considerable amount. More than one-half of this is seaward far enough to contain marine source rocks in sufficient proportion to attract exploration for oil. A larger fraction, perhaps three-quarters of the volume, may be of interest in exploration for gas. The Coastal Plain consists of land between the crystalline piedmont of the Appalachian System and mean low-tide from southern Florida to the tip of Long Island plus a few small offshore islands and the Cape Cod Peninsula. This is an area of more than 100,000 square miles. The Continental Shelf extends from mean law-tide to the break marking the beginning of the continental rise, which is somewhat less than 600 feet in depth at most places. It is a gently sloping platform, about 350,000 square miles in area, that widens from less than 3 miles off southern Florida to about 285 miles off Newfoundland. The Blake Plateau occupies an area of about 70,000 square miles between the 500 and 5,000-foot bottom contours from the Cape Hatteras vicinity to the northernmost bank of the Bahamas. It has a gentle slope with only minor irregularities and scattered patches of Recent sediments. Both gravity and magnetic anomalies along the Atlantic Coast reflect primarily compositional differences at considerable depths in the earth's crust, but are related to some extent to the structure and composition of the Coastal Plain sedimentary rocks and shallow basement. Four alternating belts of predominantly positive and predominantly negative Bouguer gravity anomalies extend diagonally across the region from southwest to northeast. These correspond roughly with the continental rise and slope, the Continental Shelf and Coastal Plain, the Appalachian Mountain System front, and the Piedmont Plateau-Blue Ridge-Appalachian Basin region.

Atlantic Coastal Plain↗
USGS2003

The seagrasses of the Gulf of Mexico

The Gulf of Mexico is a vast basin of water, spanning 12° of latitude, from 18° to 30°N. and 17° of longitude, from 81° to 98°W. It is bisected by the Tropic of Cancer and is largely subtropical; however, along the northern edge, up to five days with freezing temperatures are probable on an annual basis. The coastal fringe is moist, with annual precipitation in excess of 1 000 mm, except for southern Texas and northern Mexico. Precipitation is concentrated in the summer period, most pronounced along the coast of Mexico and least pronounced along the coast of Louisiana. Most of the Gulf of Mexico is fringed by a broad coastal plain, except for northwestern Cuba and sections of the Mexican coast near Veracruz. The inner continental shelf to a depth of 20 m is broad off the western side of the Yucatan Peninsula, along the coast of Louisiana and along the western side of Florida, extending as much as 80 km offshore to the tip of Florida. Elsewhere, the inner shelf is relatively narrow. Most of the rivers draining into the Gulf of Mexico have restricted catchments, except along the north shore, most obviously the Mississippi River, and parts of the western gulf, including the Rios Bravo IGrandel, Panuco, Grijalva and Usumacinta. Barrier islands and spits are prominent features along much of the coast, and coral reefs shelter the large expanse of water off the southern tip of Florida and off the coasts of Veracruz, Campeche, Yucatan and northwestern Cuba. Lunar spring tides are less than 1 m throughout the region.

Book chapter↗
USGS2023

2023 Coastal master plan: ICM-wetlands – Submerged aquatic vegetation (SAV) updates

Submerged aquatic vegetation (SAV) provides critical structural habitat for valuable nekton and wildlife species across coastal ecosystems and can buffer the negative effects of land loss. Landscape change and restoration efforts across coastal Louisiana can impact the occurrence, coverage, and species assemblages of SAV, and changes to these foundational species can have cascading impacts across food webs. To support the 2023 Coastal Master Plan efforts, a unique SAV model was developed to assess coverage and occurrence of SAV across aquatic waterbodies in response to environmental variables evaluated. This effort created a spatial model describing the probability of presence of SAV across the study area in response to changing conditions over the modeled time period. To develop the initial coverage data layer, we used remotely sensed Normalized Difference Vegetation Index (NDVI) and modified Normalized Difference Water Index (mNDWI) data from 2015-2018 to identify areas containing variable vegetation and water spectral reflectance. Key environmental variables evaluated included total suspended sediments (TSS), salinity, and physical exposure. Seasonal estimates for TSS and salinity were used, as research indicates that seasonal environmental variability is a significant driver for SAV establishment. Seasonal salinity was derived from Coast-wide Reference Monitoring Station (CRMS) data, and seasonal TSS was estimated from hyperspectral imagery. Estimates of physical exposure have previously been provided by calculating fetch (the distance across water over which waves can propagate), but this proved to be too computationally intensive to be feasible, and we found distance to land to be a reasonable proxy for exposure. To represent geographic conditions and historical factors influences on SAV establishment and occurrence (e.g., variables too numerous and complex to model) we developed a basin variable that served as a proxy for complex historical, or prior, conditions, determined by the forested, fresh, intermediate, brackish, or saline (FFIBS) score. The final model included spring TSS, spring salinity, distance to land, and the basin prior. The model performed well for the area evaluated, correctly classifying SAV (as present or absent) 89% of the time (Kappa = 580). SAV probability of presence responded as expected to change in these environmental variables, with likelihood of occurrence decreasing in response to increasing spring TSS, spring salinity, and distance to land. However, the model was more accurate at predicting absence (true negative = 0.940) than predicting presence (true positive = 0.626), suggesting that the scale of the model may limit the ability to predict presence. Moreover, the simplicity of the model limited the accuracy in highly dynamic environments, for example near the outflow of diversions or areas of significant changes in salinity or TSS. Through incorporating underwater communities like SAV, this master plan provides a holistic view of coastal change and restoration. To create healthy ecological structure and function in wetland habitats, the submergent communities must be considered alongside the emergent habitats. As the benefits of SAV are increasingly recognized, both here in Louisiana and beyond, SAV restoration and the use of SAV communities in assessing and improving ecological condition are becoming more common.

Louisiana↗
USGS2026

Interplay between tectonics and submarine mass transport deposits in Cortes Basin: New high-resolution geophysics in the Outer California Borderland

The Outer California Borderland (OCB) is an active transform plate boundary offshore Southern California, where the relationship between faulting and submarine mass transport deposits (MTDs) remains poorly understood. Onshore paleoseismic data provide high-resolution earthquake records, whereas marine geophysical data capture longer-term histories. Offshore fault systems pose hazards to infrastructure and dense coastal populations, particularly when linked to submarine landslides. We present new high-resolution geophysical data set (cruise SR2303), including bathymetric and CHIRP sub-bottom data integrated with legacy seismic reflection data and chronostratigraphic constraints from ODP Site 1012 to examine Quaternary MTD recurrence and tectonic controls in the Cortes Basin, OCB. Bathymetry shows deformational features, including slide scarps and previously unmapped fault segments with evidence of Holocene activity. CHIRP profiles reveal 10 stacked MTDs in the East Cortes Basin and 8 in the West Cortes Basin, spanning ∼752 ka with an average recurrence of ∼83.6 ± 1 ka. Acoustic imaging shows 7 MTD intervals coinciding with fault offset increments and fault growth suggesting earthquake-triggered mass wasting. A strong association between MTD occurrences and sea-level extremes also supports glacio-eustatic contribution to slope failure. Stratigraphic correlations suggest quasi-synchronous MTDs across the eastern and western areas, likely triggered by larger eathquakes in the Quaternary. Although the identified MTDs occur relatively far from the Southern California coast, they still pose a potential tsunamigenic hazard requiring further assessment. Moreover, if linked to earthquakes along major strike-slip faults, for example, the Ferrelo fault, the MTDs may provide valuable proxies to constrain rupture scenarios and fault connectivity within the understudied OCB.

California↗
USGS1982

Digital model evaluation of the predevelopment flow system of the Tertiary limestone aquifer, Southeast Georgia, Northeast Florida, and South South Carolina

A computer model using finite-difference techniques was used successfully to simulate the predevelopment flow regime within the multilayered Tertiary limestone aquifer system in Southeastern Georgia, Northeastern Florida, and Southern South Carolina as part of the U.S. Geological Survey 's Tertiary Limestone Regional Aquifer System analysis. The aquifer, of early Eocene to Miocene age, ranges from thin interbedded clastics and marl in the updip area to massive limestone and dolomite 1,500 feet thick in the downdip area. The aquifer is confined above by Miocene clay beds, and terminates at depth in low-permeability rocks or the saltwater interface. Model-simulated transmissivity of the upper permeable zone ranged from about 1 x 10 super 3 foot squared per day in the updip area and within parts of the Gulf Trough (a series of alinement basins filled by fine clastic in material) to about 1 x 10 super 6 foot squared per day in South Georgia, and area having large secondarily developed solution channels. The model results indicate that only about 540 cubic feet per second of water flowed through the predeveloped system, from the updip highland area of high altitude and in the areas north of Valdosta and southwest of Jacksonville, to discharge along streams in the updip area and diffuse upward leakage in the downdip area near the coast and offshore. (USGS)

Florida, Georgia, South Carolina↗
USGS2019

Potential sea level rise for the Chitimacha Tribe of Louisiana

Situated in the Mississippi Alluvial Plain of the Gulf Coast Prairie Landscape Conservation Cooperative (GCP LCC), the Chitimacha Tribe is one of four federally recognized tribes in Louisiana. The Tribal seat, trust lands/ reservation, and adjacent Tribal owned lands are located near Charenton, Louisiana, totaling nearly 1,000 acres. The Chitimacha, with a population of approximately 1,400 people, are currently impacted by storm surge, which is expected to increase with climate change. The additional stress from storms will likewise increase the vulnerability to catastrophic impact in the event of a breach in the Atchafalaya Basin Spillway levee. A collaborative effort between the U.S. Geological Survey (USGS) and the Chitimacha Tribe has been initiated to provide resources and expertise to increase the Tribe’s ability to prevent, plan, and prepare for these environmental challenges. By enhancing technical skills, providing access to environmental data, and increasing awareness of environmental issues, the Chitimacha will be better prepared to plan and adapt to the environmental impacts facing their lands related to land use and climate change. For this project, USGS researchers asked how Chitimacha Tribal Lands might be impacted by future sea level rise scenario projections. These models illustrate some flooding within the northernmost boundary of Chitimacha Tribal Lands.

Louisiana↗
USGS2011

Zircon U-Pb age of the Pescadero felsite: A late Cretaceous igneous event in the forearc, west-central California Coast Ranges

Downstream grain-size fining in stratigraphy is driven primarily by selective deposition of sediment, and the long-term efficiency of this process is determined by: (1) the magnitude and characteristics of the input sediment supply; (2) the spatial distribution of subsidence rate, which creates accommodation for sediment preservation; and (3) the dynamics of sediment transport and deposition. A key challenge is to determine how these first two factors control the caliber and spatial distribution of deposits over time scales of 10 4 –10 6 yr without incorporating sediment transport details that are largely unknowable for time-averaged stratigraphy in the geological past. We address this using grain-size data collected from fluvial conglomerates in the Eocene Pobla Basin, Spanish Pyrenees, a synorogenic basin where the timing of sediment deposition is well-constrained; the sediment budget is closed; and good exposure enables time lines within stratigraphy to be picked out unambiguously. For successive stratigraphic horizons, downstream trends in grain size and composition are derived for basin-filling sediment-routing systems with length scales of 6 and 40 km, respectively. Our data show that the rate of grain-size fining varies over time and with system length and can be linked to changes in source area. These results are contrasted with grain-size data from the Antist Group, a 60-km-long Oligocene system that mantles the Southern Pyrenees, where very slow rates of grain-size fining on the wedge top of this fold-and-thrust belt are observed. We apply a self-similarity–based selective deposition model to quantify the competing controls of tectonic subsidence and sediment supply on derived grain-size trends, and model results are compared with independent constraints on the Eocene–Oligocene evolution of the Pyrenees. Our results suggest that it is now possible to invert time-averaged grain-size trends in stratigraphy to gain quantitative information on the geological boundary conditions governing the evolution of sedimentary basins.

Geological Society of America Bulletin↗
USGS2014

Gravity, aeromagnetic and rock-property data of the central California Coast Ranges

Gravity, aeromagnetic, and rock-property data were collected to support geologic-mapping, water-resource, and seismic-hazard studies for the central California Coast Ranges. These data are combined with existing data to provide gravity, aeromagnetic, and physical-property datasets for this region. The gravity dataset consists of approximately 18,000 measurements. The aeromagnetic dataset consists of total-field anomaly values from several detailed surveys that have been merged and gridded at an interval of 200 m. The physical property dataset consists of approximately 800 density measurements and 1,100 magnetic-susceptibility measurements from rock samples, in addition to previously published borehole gravity surveys from Santa Maria Basin, density logs from Salinas Valley, and intensities of natural remanent magnetization.

California↗
USGS2018

California State Waters Map Series — Offshore of Point Conception, 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 sonar 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 Point Conception map area is in the westernmost part of the Western Transverse Ranges geologic province, which is north of the California Continental Borderland. Significant clockwise rotation—at least 90°—since the early Miocene has been proposed for the Western Transverse Ranges province, and this region is presently undergoing north-south shortening. The offshore part of the map area lies south of the stee p south and west flanks of t he Santa Ynez Mountains . The crest of the range , which has a maximum elevation of about 340 m in the map area, lies about 5 km north and east of the arcuate shoreline. The onland part of the coastal zone is remote and sparsely populated. The road to Jalama Beach County Park provides the only public coastal access in the entire map area. North of this county park, the coastal zone is part of Vandenberg Air Force Base. South of Jalama Beach County Park, most of the coastal zone is part of the Cojo-Jalama Ranch, purchased by the Nature Conservancy in December 2017. A relatively small part of the coastal zone in the eastern part of the map area lies within the privately owned Hollister Ranch. The nearest significant commercial centers are Lompoc (population, about 42,000), about 10 km north of the map area, and Goleta (population, about 30,000), about 50 km east of the map area. The Union Pacific railroad tracks run west and northwest along the coast through the entire map area, within a few hundred meters of the shoreline. The map area has a long history of petroleum exploration, and the seafloor notably includes large asphalt mounds and pockmarks that result from petroleum seepage. Several offshore gas and oil fields were discovered, and some were developed, in and on the margin of California’s State Waters. Much of the shoreline in the Offshore of Point Conception map area is characterized by narrow beaches that have thin sediment cover above bedrock platforms, backed by low (10- to 20-m-high) cliffs that are capped by a coastal terrace. Beaches are subject to wave erosion during winter storms, followed by gradual sediment recovery or accretion in the late spring, summer, and fall months during the gentler wave climate. The map area lies in the west-central part of the Santa Barbara littoral cell, which is characterized by west-to-east transport of sediment from Point Arguello on the northwest to Hueneme and Mugu Canyons on the southeast. Sediment supply to the map area is mainly from relatively small coastal watersheds, including the Jalama Creek–Espada Creek drainage basin (about 63 km 2 ), as well as Cañada del Jolloru, Black Canyon, Wood Canyon, Cañada del Cojo, and Barranca Honda. Coastal-watershed discharge and sediment load are highly variable, characterized by brief large events during major winter storms and long periods of low (or no) flow and minimal sediment load between storms. In recent (recorded) history, the majority of high-discharge, high-sediment-flux events have been associated with El Niño phases of the El Niño–Southern Oscillation climatic pattern. Following the coastline, the shelf bends to the north and northwest around Point Conception, and the trend of the shelf break changes from about 298° to 241° azimuth. Shelf width ranges from about 5 km south of Point Conception to about 11 km northwest of it; the slope ranges from about 1.0° to 1.2° to about 0.7° south and northwest of Point Conception, respectively. Southwest of Point Conception, the shelf break and upper slope are incised by a 600-m-wide, 20- to 30-m-deep, south-facing trough, one of five heads of the informally named Arguello submarine canyon. The map area is located at a major biogeographic transition zone between the east-west-trending Santa Barbara Channel region of the Southern California Bight and the northwest-trending central California coast. North of Point Conception, the coast is subjected to high wave exposure from the north, west, and south, as well as consistently strong upwelling that brings cold, nutrient-rich waters to the surface. Southeast of Point Conception, the Santa Barbara Channel is largely protected from strong north swells by Point Conception and from south swells by the Channel Islands; surface waters are warmer, and upwelling is weak and seasonal. Seafloor habitats in the broad Santa Barbara Channel region consist of significant amounts of soft, unconsolidated sediment interspersed with isolated areas of rocky habitat that support kelp-forest communities in the nearshore and rocky-reef communities in deeper water. The potential marine benthic habitat types mapped in the Offshore of Point Conception map area are directly related to its Quaternary geologic history, geomorphology, and active sedimentary processes. These potential habitats lie primarily within the Shelf (continental shelf) but also partly within the Flank (basin flank or continental slope) megahabitats. The fairly homogeneous seafloor of sediment and low-relief bedrock provides characteristic habitat for rockfish, groundfish, crabs, shrimp, and other marine benthic organisms. Several areas of smooth sediment form nearshore terraces that have relatively steep, smooth fronts, which are attractive to groundfish. Below the steep shelf break, soft, unconsolidated sediment is interrupted by the heads of several submarine canyons, gullies, and rills, also good potential habitat for rockfish. The map area includes the large (58.3 km 2 ) Point Conception State Marine Reserve.

California↗
USGS2010

Coastal vulnerability assessment of the Northern Gulf of Mexico to sea-level rise and coastal change

A coastal vulnerability index (CVI) was used to map the relative vulnerability of the coast to future sea-level rise along the Northern Gulf of Mexico from Galveston, TX, to Panama City, FL. The CVI ranks the following in terms of their physical contribution to sea-level rise-related coastal change: geomorphology, regional coastal slope, rate of relative sea-level rise, historical shoreline change rate, mean tidal range, and mean significant wave height. The rankings for each variable are combined and an index value is calculated for 1-kilometer grid cells along the coast. The CVI highlights those regions where the physical effects of sea-level rise might be the greatest. The CVI assessment presented here builds on an earlier assessment conducted for the Gulf of Mexico. Recent higher resolution shoreline change, land loss, elevation, and subsidence data provide the foundation for a better assessment for the Northern Gulf of Mexico. The areas along the Northern Gulf of Mexico that are likely to be most vulnerable to sea-level rise are parts of the Louisiana Chenier Plain, Teche-Vermillion Basin, and the Mississippi barrier islands, as well as most of the Terrebonne and Barataria Bay region and the Chandeleur Islands. These very high vulnerability areas have the highest rates of relative sea-level rise and the highest rates of shoreline change or land area loss. The information provided by coastal vulnerability assessments can be used in long-term coastal management and policy decision making.

Open-File Report↗
USGS1989

Vertical surface displacements along a part of the Newport-Inglewood zone of folds and faults, Los Angeles and Orange Counties, California

During the past half century, the onshore section of the Newport- Inglewood zone of folds and faults between the Dominguez oil field and Corona del Mar (fig. 1) has been repeatedly leveled to geodetic standards. These essentially fortuitous surveys are unrelated to either the tectonic framework or the urbanization of the Los Angeles basin, but were established instead because the Newport-Inglewood zone southward from the Long Beach area is roughly coincident with the coastline--and, hence, is roughly coincident with a naturally defined leveling route. Although these have been several relevelings athwart this zone north of the long Beach area, notably in the Baldwin Hills area (Castle and Yerkes, 1976), about 25 km to the northwest, the survey density, in both space and time, diminishes markedly northward. Thus, the results of the indicated relevelings along the Los Angeles-Orange County coast have permitted the relatively detailed appraisal of historic vertical surface movements described in this report. The Newport-Inglewood zone of folds and faults forms the surface expression of a major crustal boundary separating the Peninsular Ranges province on the east from the Continental Borderland province on the west (Castle and others, 1984, p. 8-9, pl. 1). Transcurrent fault movement along this boundary has produced not only continuing seismic activity, for which this zone is justly famous, but also folds and other structural features within the sedimentary veneer that have entrapped the petroleum deposits for which the Newport-Inglewood zone is even more famous. Although the northeast boundary of the exceptionally prolific Wilmington oil field is roughly coincident with the southeast edge of the Newport-Inglewood zone, we have deliberately excluded this area from consideration--in other than a peripheral way--simply because compaction-induced subsidence centering on the Wilmington field is viewed as a singularly spectacular example of this phenomenon and, hence, has been the subject of a series of detailed investigation (Harris and Harlow, 1947; Gilluly and Grant, 1949; Hudson, 1956; Miller, 1966; Poland and Davis, 1969; Allen and Mayuga, 1970; Castle and Yerkes, 1976).

California↗
USGS2014

Using spatial resampling to assess redd count survey length requirements for Pacific Lamprey

Pacific Lamprey Entosphenus tridentatus has declined across its range along the West Coast of North America, and an understanding of all life history phases is needed to address population recovery. Spawning surveys (redd counts) are common tools currently used to monitor returning adult salmonids, but such methodologies are in their infancy for Pacific Lamprey. Our objective was to assess the minimum spawning survey distance required to detect the presence of Pacific Lamprey redds and obtain precise redd density estimates from these data. To do this, we statistically resampled existing spawning locations of Pacific Lamprey collected during spawning surveys in four streams of the Willamette River Basin, Oregon, during spring of 2013. We found that the minimum survey distance for Pacific Lamprey redd detection was inversely related to the observed redd density and was always less than 1.2 km. Survey distance requirements to obtain precise redd counts (±20% of observed redd densities) were also inversely related to redd density and habitat availability, and varied between 1.3 km and 13.7 km. Our results suggest that spawning surveys are a potential tool for monitoring adult Pacific Lamprey abundance, but the specific objectives of the monitoring programs and acknowledgment of unknowns must be considered prior to implementation into recovery plans.

Oregon↗