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At least 1,495 records · Page 83Linked to original sources
USGS2018

Seafloor fluid seeps on Kimki Ridge, offshore southern California: Links to active strike-slip faulting

The Kimki Ridge fluid seeps are located in western Catalina Basin about 60 km southwest of the southern California mainland and at a water depth of approximately 1100 m. Multichannel seismic reflection profiles collected by the U.S. Geological Survey (USGS) in 2014 show acoustic transparency within the Kimki Ridge, suggesting the possibility of fluid seeps and possible sub-seafloor fluid pathways. Subsequent multibeam bathymetric and backscatter intensity data collected during a cooperative University of Washington/USGS cruise in early 2016 show subtle seafloor buildups with high acoustic backscatter (reflectivity) in three places along Kimki Ridge, supporting the existence of fluid seepage. A Remotely Operated Vehicle (ROV) dive, conducted as part of the Nautilus Exploration Program, took place in August 2016 to confirm the presence of these previously unknown seeps and document their characteristics as well as those of any associated biological communities. Two of the three seeps were explored by ROV, and showed abundant evidence of fluid seepage, including characteristic algal mats, chemosynthetic clams, and authigenic carbonate formation. The seeps are comprised of carbonate buildups 1–3 m thick and 300–500 m across. Within these areas, we interpret broad crater-like depressions 30–50 m across and 1–2 m deep to be individual seep vents. The seep areas appear to be broad zones of diffuse seepage that support chemosynthetic biologic communities; however, active venting was not observed. Geochemical analyses of rock samples collected from the seeps indicate microbially driven anaerobic oxidation of methane at or near the sediment water interface. Seismic-reflection profiles show chimney-like fluid pathways along the limbs and in the axis of the fold forming Kimki Ridge, and evidence of methane in shallow sediments can be traced into the adjacent Catalina Basin. A system of closely spaced faults located at the axis of the Kimki Ridge anticline may serve as pathways to allow fluid flow to the seafloor. Our data are consistent with other studies that suggest that transpression is an important component in the formation and localization of fluid seeps in a strike-slip setting, implying that seep formation may be a common occurrence at fault stepovers or transpressional bends in strike-slip systems.

California↗
USGS2019

Three-dimensional basin and fault structure from a detailed seismic velocity model of Coachella Valley, Southern California

The Coachella Valley in the northern Salton Trough is known to produce destructive earthquakes, making it a high seismic hazard area. Knowledge of the seismic velocity structure and geometry of the sedimentary basins and fault zones is required to improve earthquake hazard estimates in this region. We simultaneously inverted first P wave travel times from the Southern California Seismic Network (39,998 local earthquakes) and explosions (251 land/sea shots) from the 2011 Salton Seismic Imaging Project to obtain a 3-D seismic velocity model. Earthquakes with focal depths ≤10 km were selected to focus on the upper crustal structure. Strong lateral velocity contrasts in the top ~3 km correlate well with the surface geology, including the low-velocity (<5 km/s) sedimentary basin and the high-velocity crystalline basement rocks outside the valley. Sediment thickness is ~4 km in the southeastern valley near the Salton Sea and decreases to <2 km at the northwestern end of the valley. Eastward thickening of sediments toward the San Andreas fault within the valley defines Coachella Valley basin asymmetry. In the Peninsular Ranges, zones of relatively high seismic velocities (~6.4 km/s) between 2 to 4 km depth may be related to Late Cretaceous mylonite rocks or older inherited basement structures. Other high-velocity domains exist in the model down to 9 km depth and help define crustal heterogeneity. We identify a potential fault zone in Lost Horse Valley unassociated with mapped faults in Southern California from the combined interpretation of surface geology, seismicity, and lateral velocity changes in the model.

California↗
USGS2016

Processes of multibathyal aragonite undersaturation in the Arctic Ocean

During 3 years of study (2010–2012), the western Arctic Ocean was found to have unique aragonite saturation profiles with up to three distinct aragonite undersaturation zones. This complexity is produced as inflow of Atlantic-derived and Pacific-derived water masses mix with Arctic-derived waters, which are further modified by physiochemical and biological processes. The shallowest aragonite undersaturation zone, from the surface to ∼30 m depth is characterized by relatively low alkalinity and other dissolved ions. Besides local influence of biological processes on aragonite undersaturation of shallow coastal waters, the nature of this zone is consistent with dilution by sea-ice melt and invasion of anthropogenic CO 2 from the atmosphere. A second undersaturated zone at ∼90–220 m depth (salinity ∼31.8–35.4) occurs within the Arctic Halocline and is characterized by elevated p CO 2 and nutrients. The nature of this horizon is consistent with remineralization of organic matter on shallow continental shelves bordering the Canada Basin and the input of the nutrients and CO 2 entrained by currents from the Pacific Inlet. Finally, the deepest aragonite undersaturation zone is at greater than 2000 m depth and is controlled by similar processes as deep aragonite saturation horizons in the Atlantic and Pacific Oceans. The comparatively shallow depth of this deepest aragonite saturation horizon in the Arctic is maintained by relatively low temperatures, and stable chemical composition. Understanding the mechanisms controlling the distribution of these aragonite undersaturation zones, and the time scales over which they operate will be crucial to refine predictive models.

Journal of Geophysical Research: Oceans↗
USGS2018

Salt marsh loss affects tides and sediment budget in shallow bays

The current paradigm is that salt marshes and their important ecosystem services are threatened by global climate change; indeed, large marsh losses have been documented worldwide. Morphological changes associated with salt marsh erosion are expected to influence the hydrodynamics and sediment dynamics of coastal systems. Here the influence of salt marsh erosion on the tidal hydrodynamics and sediment storage capability of shallow bays is investigated. Hydrodynamics, sediment transport, and vegetation dynamics are simulated using the numerical framework Coupled Ocean‐Atmosphere‐Wave‐Sediment Transport in the Barnegat Bay‐Little Egg Harbor system, USA. We show that salt marsh erosion influences the propagation of tides into back‐barrier basins, reducing the periodic inundation and sediment delivery to marsh platforms. As salt marshes erode, the sediment trapping potential of marsh platforms decreases exponentially. In this test case, up to 50% of the sediment mass trapped by vegetation is lost once a quarter of the marsh area is eroded. Similarly, without salt marshes the sediment budget of the entire bay significantly declines. Therefore, a positive feedback might be triggered such that as the salt marsh retreats the sediment storage capacity of the system declines, which could in turn further exacerbate marsh degradation.

New Jersey↗
USGS2023

A framework for estimating global river discharge from the Surface Water and Ocean Topography satellite mission

The Surface Water and Ocean Topography (SWOT) mission will vastly expand measurements of global rivers, providing critical new data sets for both gaged and ungaged basins. SWOT discharge products (available approximately 1 year after launch) will provide discharge for all river that reaches wider than 100 m. In this paper, we describe how SWOT discharge produced and archived by the US and French space agencies will be computed from measurements of river water surface elevation, width, and slope and ancillary data, along with expected discharge accuracy. We present for the first time a complete estimate of the SWOT discharge uncertainty budget, with separate terms for random (standard error) and systematic (bias) uncertainty components in river discharge time series. We expect that discharge uncertainty will be less than 30% for two-thirds of global reaches and will be dominated by bias. Separate river discharge estimates will combine both SWOT and in situ data; these “gage-constrained” discharge estimates can be expected to have lower systematic uncertainty. Temporal variations in river discharge time series will be dominated by random error and are expected to be estimated within 15% for nearly all reaches, allowing accurate inference of event flow dynamics globally, including in ungaged basins. We believe this level of accuracy lays the groundwork for SWOT to enable breakthroughs in global hydrologic science.

Water Resources Research↗
USGS2007

Water use regimes: Characterizing direct human interaction with hydrologic systems

The sustainability of human water use practices is a rapidly growing concern in the United States and around the world. To better characterize direct human interaction with hydrologic systems (stream basins and aquifers), we introduce the concept of the water use regime. Unlike scalar indicators of anthropogenic hydrologic stress in the literature, the water use regime is a two‐dimensional, vector indicator that can be depicted on simple x‐y plots of normalized human withdrawals ( h out ) versus normalized human return flows ( h in ). Four end‐member regimes, natural‐flow‐dominated (undeveloped), human‐flow‐dominated (churned), withdrawal‐dominated (depleted), and return‐flow‐dominated (surcharged), are defined in relation to limiting values of h out and h in . For illustration, the water use regimes of 19 diverse hydrologic systems are plotted and interpreted. Several of these systems, including the Yellow River Basin, China, and the California Central Valley Aquifer, are shown to approach particular end‐member regimes. Spatial and temporal regime variations, both seasonal and long‐term, are depicted. Practical issues of data availability and regime uncertainty are addressed in relation to the statistical properties of the ratio estimators h out and h in . The water use regime is shown to be a useful tool for comparative water resources assessment and for describing both historic and alternative future pathways of water resource development at a range of scales.

Water Resources Research↗
USGS1997

Permian deposition in the north central Brooks Range, Alaska: Constraints for tectonic reconstructions

Two opposing tectonic models have been offered to explain the regional structural relations in the north central Brooks Range fold-thrust belt of northern Alaska. The first suggests that rocks of the northern Endicott Mountains were thrust from south to north over the area of the present Mount Doonerak high and are therefore highly allochthonous. The second implies that the rocks of the northern Endicott Mountains were deposited in a basin that lay north of the Mount Doonerak high and later were thrust a short distance southward onto the northern flank of the high and are thus parautochthonous. To provide stratigraphic constraints for these models, this study examines Permian facies of the north central Brooks Range. Permian rocks in the north central Brooks Range comprise a thin (40 to 160 m thick), fining-upward succession of clastic, storm-influenced shelf deposits. When the rocks of the northern Endicott Mountains are restored south of the Mount Doonerak area, a minimum distance of 80 km, the Permian deposits grade systematically from distal facies (Siksikpuk Formation) in the southwest to proximal facies (Echooka Formation) in the northeast. Facies trends in the reconstructed Permian basin include, from southwest to northeast, (1) an increase in carbonate content and corresponding decrease in silica content, (2) a general darkening and thickening of shaley intervals, (3) an increase in proximal features of storm beds, including coarser, thicker, more abundant, and more closely spaced beds, and (4) an increase in abundance and diversity of the faunal assemblage with a corresponding decrease in age. These stratigraphic relations imply that rocks of the northern Endicott Mountains are allochthonous and structurally overlie a proximal stratigraphie succession similar to that exposed in the Mount Doonerak area and northeastern Brooks Range.

Journal of Geophysical Research B: Solid Earth↗
USGS2008

Understanding contaminants associated with mineral deposits

Interdisciplinary studies by the U.S. Geological Survey (USGS) have resulted in substantial progress in understanding the processes that control the release of metals and acidic water from inactive mines and mineralized areas, the transport of metals and acidic water to streams, and the fate and effect of metals and acidity on downstream ecosystems. The potential environmental effects associated with abandoned and inactive mines, resulting from the complex interaction of a variety of chemical and physical processes, is an area of study that is important to the USGS Mineral Resources Program. Understanding the processes contributing to the environmental effects of abandoned and inactive mines is also of interest to a wide range of stakeholders, including both those responsible for managing lands with historically mined areas and those responsible for anticipating environmental consequences of future mining operations. The recently completed (2007) USGS project entitled 'Process Studies of Contaminants Associated with Mineral Deposits' focused on abandoned and inactive mines and mineralized areas in the Rocky Mountains of Montana, Colorado, New Mexico, Utah, and Arizona, where there are thousands of abandoned mines. Results from these studies provide new information that advances our understanding of the physical and biogeochemical processes causing the mobilization, transport, reaction, and fate of potentially toxic elements (including aluminum, arsenic, cadmium, copper, iron, lead, and zinc) in mineralized near-surface systems and their effects on aquatic and riparian habitat. These interdisciplinary studies provide the basis for scientific decisionmaking and remedial action by local, State, and Federal agencies charged with minimizing the effects of potentially toxic elements on the environment. Current (2007) USGS research highlights the need to understand (1) the geologic sources of metals and acidity and the geochemical reactions that release them from their sources, (2) the pathways that facilitate transport from those sources, and (3) the processes that control the fate of the elements once released from the sources. Experts in the fields of economic geology, structural geology, mineralogy, geophysics, geochemistry, hydrology, ground-water modeling, microbiology, and toxicology came together for a series of studies that address these relationships on scales ranging from the microscopic to the watershed. This Circular presents results and highlights from the detailed, interdisciplinary studies that include investigations in both mining-affected areas and mineralized but unmined areas. The first section of the Circular describes laboratory and site-scale field investigations that primarily focus on mineralogic and biologic controls on the source and release of metals and acidity from mine-waste rock and hydrothermally altered areas. The second section describes a set of basin- to watershed-scale studies that not only investigate the source and release of metals and acidity but also the transport of these constituents away from the source areas. The third section is a summary of results from postremediation ecosystem monitoring. For more information on these and other project-related studies, please visit the project Web site at http://minerals.cr.usgs.gov/projects/contaminants/index.html. The Web site includes a complete bibliography and detailed descriptions of each interdisciplinary study.

Circular↗
USGS2007

Infection by a black spot-causing species of Uvulifer and associated opercular alterations in fishes from a high-desert stream in Wyoming

Black spot is a common disease syndrome of freshwater fishes. This study provides information on the rank of density of the black spot agent and opercular bone alterations associated with at least one digenean, Uvulifer sp., infecting native and non-native catostomids and cyprinids of the Upper Colorado River Basin. We evaluated the density rank of pigmented metacercariae and associated alterations in the operculum of the bluehead sucker Catostomus discobolus, flannelmouth sucker C. latipinnis, white sucker C. commersoni, catostomid hybrids, roundtail chub Gila robusta, and creek chub Semotilus atromaculatus, sampled from Muddy Creek, Wyoming, USA in 2003 or 2004. All fish species contained individuals that exhibited gross signs of the black spot agent. Bluehead and flannelmouth suckers had 100% prevalence of infection. Although the other suckers and chubs contained encysted metacercariae in at least one individual, the presence of pigmented metacercariae was not apparent (i.e. based on gross observations) in many individuals. Catostomids had higher densities of metacercariae than cyprinids, as shown by frequency distributions of density ranks. Opercular holes (i.e. holes that completely penetrated the opercle and were in direct association with the pigment associated metacercariae) and pockets (depressions on the external surface of the opercle associated with metacercariae) were abundant among catostomids but rare among cyprinids. ?? Inter-Research 2007.

Diseases of Aquatic Organisms↗
USGS2024

Differentiating cheatgrass and medusahead phenological characteristics in western United States rangelands

Expansions in the extent and infestation levels of exotic annual grass (EAG) within the rangelands of the western United States are well documented. Land managers are tasked with developing plans to limit EAG spread and prevent irreversible ecosystem deterioration. The most common EAG species and the subject of extensive study is Bromus tectorum (cheatgrass). Cheatgrass has spread rapidly in western rangelands since its initial invasion more than 100 years ago. Another concerning aggressive EAG, Taeniatherum caput-medusae (medusahead), is also commonly found in some of these areas. To control the spread of EAGs, researchers have investigated applying several control methods during different developmental stages of cheatgrass and medusahead. These control strategies require accurate maps of the timing and spatial patterns of the developmental stages to apply mitigation strategies in the correct areas at the right time. In this study, we developed annual phenological datasets for cheatgrass and medusahead with two objectives. The first objective was to determine if cheatgrass and medusahead can be differentiated at 30 m resolution using their phenological differences. The second objective was to establish an annual phenology metric regression tree model used to map the growing seasons of cheatgrass and medusahead. Harmonized Landsat and Sentinel-2 (HLS)-derived predicted weekly cloud-free 30 m normalized difference vegetation index (NDVI) images were used to develop these metric maps. The result of this effort was maps that identify the start and end of sustained growing season time for cheatgrass and medusahead at 30 m for the Snake River Plain and Northern Basin and Range ecoregions. These phenological datasets also identify the start and end-of-season NDVI values, along with maximum NDVI throughout the study period. These metrics may be utilized to characterize annual growth patterns for cheatgrass and medusahead. This approach can be utilized to plan time-sensitive control measures such as herbicide applications or cattle grazing.

western United States↗
USGS1990

Geological interpretation of combined Seabeam, Gloria and seismic data from Anegada Passage (Virgin Islands, north Caribbean)

The Anegada Passage (sensu lato) includes several basins and ridges from Southeast of Puerto Rico to the corner of the Virgin Islands Platform. Seabeam (Seacarib I) and Gloria long-range sidescan sonar surveys were carried out in this area. These new data allow us to propose an interpretation of the Anegada Passage. Most of the features described are related to wrench faulting: (a) St Croix and Virgin Islands Basins are pull-apart basins created in a right-lateral strike-slip environment based on their rhomboidal shape and seismic data (e.g. the flower structure). These two pull-aparts are divided into two sub-basins by a curvilinear normal fault in the Virgin Islands Basin and a right-lateral strike-slip fault in the St Croix Basin. (b) Tortola Ridge and a 'dog's leg' shaped structure are inferred to be restraining bends between two right-lateral strike-slip faults. (c) We identified two ENE-WSW volcanic lineaments in the eastern area and one volcano lying between Virgin Islands and St Croix Basins. (d) As shown by the seismic activity main wrench motion occurs along the north slope of Virgin Islands Basin and through Anegada Passage. A branching of this main fault transmits the transtensional motion to St Croix Basin. A two-stage story is proposed for the creation of the basins. A first extensional event during Eocene(?)-Oligocene-lower Miocene time created Virgin Islands, St Croix Basins and the tilted blocks of St Croix Ridge. A second transtensional event from Pliocene to Recent gave the present day pattern to this area. However, the displacement along the strike-slip faults is no more than 15 km long. The proposed geodynamic model is based on the separation of the northeastern Caribbean boundary into two blocks. In the West, the indenter of Beata Ridge gives a northeastern motion to Hispaniola Block. In the East, as a result of Hispaniola Block's motion, the Puerto Rico-Virgin Islands Block could escape in an east-northeast direction.

Anegada Passage↗
USGS2002

Mexican native trouts: A review of their history and current systematic and conservation status

While biologists have been aware of the existence of native Mexican trouts for over a century, they have received little study. The few early studies that did much more than mention their existence began in the 1930s and continued into the early 1960s, focusing primarily on distributional surveys and taxonomic analyses. Starting in the 1980s the Baja California rainbow trout became the subject of more detailed studies, but very little remains known of mainland trouts of the Sierra Madre Occidental. We review earlier studies and report on our own collections and observations made between 1975 and 2000. We present newly discovered historical evidence that leads us to conclude that a "lost" cutthroat trout, a lineage not previously known from Mexico, was collected more than a century ago from headwaters of the Ri??o Conchos (a major tributary of the Rio Grande (= Ri??o Bravo)), a basin not previously considered to harbor a native trout. We review the last century of regional natural resource management and discuss our own observations of trout habitats. Impacts of logging, road building and overgrazing are widespread and expanding. Many streams suffer from heavy erosion, siltation and contamination, and though long-term hydrologic data are generally not available, there is evidence of decreased discharge in many streams. These problems appear related to region-wide land management practices as well as recent regional drought. Trout culture operations using exotic rainbow trout have rapidly proliferated throughout the region, threatening genetic introgression and/or competition with native forms and predation on them. Knowledge of distribution, abundance, relationships and taxonomy, not to mention ecology and population biology, of native trouts of the Sierra Madre Occidental remains inadequate. Vast areas of most mainland drainages are still unexplored by fish collectors, and even rudimentary information regarding basic biology, ecology and population structure of stocks remains lacking. Concentrated exploration, research and management of this long overlooked and undervalued resource are all urgently needed. The history of natural resources exploitation that placed so many native trouts of the western United States on threatened and endangered species lists is repeating itself in the Sierra Madre Occidental. Without concentrated action and development of region-wide socio-economic solutions for current, largely non-sustainable resource management practices, native Mexican trout gene pools will soon be in grave danger of extinction.

Reviews in Fish Biology and Fisheries↗
USGS2008

Infiltration from an impoundment for coal‐bed natural gas, Powder River Basin, Wyoming: Evolution of water and sediment chemistry

Development of coal‐bed natural gas (CBNG) in the Powder River Basin, Wyoming, has increased substantially in recent years. Among environmental concerns associated with this development is the fate of groundwater removed with the gas. A preferred water‐management option is storage in surface impoundments. As of January 2007, permits for more than 4000 impoundments had been issued within Wyoming. A study was conducted on changes in water and sediment chemistry as water from an impoundment infiltrated the subsurface. Sediment cores were collected prior to operation of the impoundment and after its closure and reclamation. Suction lysimeters were used to collect water samples from beneath the impoundment. Large amounts of chloride (12,300 kg) and nitrate (13,500 kg as N), most of which accumulated naturally in the sediments over thousands of years, were released into groundwater by infiltrating water. Nitrate was more readily flushed from the sediments than chloride. If sediments at other impoundment locations contain similar amounts of chloride and nitrate, impoundments already permitted could release over 48 × 10 6 kg of chloride and 52 × 10 6 kg of nitrate into groundwater in the basin. A solute plume with total dissolved solid (TDS) concentrations at times exceeding 100,000 mg/L was created in the subsurface. TDS concentrations in the plume were substantially greater than those in the CBNG water (about 2300 mg/L) and in the ambient shallow groundwater (about 8000 mg/L). Sulfate, sodium, and magnesium are the dominant ions in the plume. The elevated concentrations are attributed to cation‐exchange‐enhanced gypsum dissolution. As gypsum dissolves, calcium goes into solution and is exchanged for sodium and magnesium on clays. Removal of calcium from solution allows further gypsum dissolution.

Water Resources Research↗
USGS2020

"Modified Unified Method" of carp capture

Populations of Hypophthalmichthys molitrix (silver carp) and Hypophthalmichthys nobilis (bighead carp), (together referred to herein as “bigheaded carp”) have increased exponentially in the greater Mississippi River Basin. Detrimental effects on native fish and economically important fisheries have occurred where these invasive, filter-feeding fish are abundant. The Unified Method, a harvest technique developed in China for bigheaded carp in flood plain lakes, uses herding techniques and a variety of nets to drive bigheaded carp and concentrate them into an area where they can be easily harvested. The U.S. Geological Survey is adapting the Chinese Unified Method concepts to be consistent with North American financial, societal, and environmental conditions. We have modified these techniques and incorporated modern technology to reduce the time and expense of Unified Methods and to allow them to be used in public waters. Thus, the operations in North America are often described as the “Modified Unified Method.” The U.S. Geological Survey is studying and refining the Modified Unified Method to provide stakeholders with efficient, validated, and environmentally friendly methods for carp removal; however, this method is still new to the United States and additional research is needed to further increase the efficiency of Modified Unified Method operations.

Fact Sheet↗
USGS1994

Assessment of the hydrologic interaction between Imikpuk Lake and the adjacent airstrip site near Barrow, Alaska, 1993

Imikpuk Lake serves as the drinking water source for the Ukpeagvik Inupiat Corporation-National Arctic Research Laboratory (UIC-NARL), formerly known as the Naval Arctic Research Laboratory, near Barrow, Alaska. During the 1970's and 1980's, accidental releases of more than 1,300 cubic meters of various types of fuel occurred at the airstrip site adjacent to the lake. To aid an assessment of the potential risk 10 the quality of water in the lake posed by fuel remaining in the subsurface, the hydrologic interaction between the lake and ground water at the airstrip site was examined. The study area lies within the region of continuous permafrost where hydrologic processes are largely controlled by the short annual thaw season and the presence of near-surface permafrost. Runoff occurs for only a short period each year, typically from early or mid-June to late September, and a shallow ground- water system develops during approximately the same period as a result of shallow thawing of the subsurface. During the spring and summer of 1993, snowpack and surface-water data were collected throughout the Imikpuk Lake basin, and subsurface- flow-system data were collected at the airstrip site. The total annual inflow to the lake was estimated 10 be approximately 300,000 cubic meters per year, based on four methods of estimation. The ground-water flow system at the airstrip site is complex, primarily because of variations in local land-surface topography. Subsurface frost-elevation data indicate that a permafrost ridge exists beneath one of the elevated building pads at the site. Similar ridges beneath elevated roadways at the site may act as impediments to ground-water flow, reducing the flux of subsurface water to Imikpuk Lake. However, on the basis of the assumption that such impediments do not reduce flux substantially, the ground-water flux from the airstrip site was estimated to be approximately 173 cubic meters per year--less than 0.1 percent of the estimated annual inflow to Imikpuk Lake.

Open-File Report↗
USGS1973

Permian paleogeography of the Arctic

Three large land areas were dominant in the Arctic during the Permian: Fennoscandia, central and southern Siberia (Angara), and Canada. Smaller landmasses were in China, the Seward-Chukotskiy region, northern and eastern Siberia, and near Alaska. Coal deposits and strata bearing land plants covered a large area in central Siberia; saline basins containing red beds formed in the Zechstein, Perm, and West Texas basins as the seas withdrew, generally in the later Permian. Eugeosynclinal troughs, apparently limited to the Pacific border regions, were marked by volcanism and deposition of predominantly clastic sediments in many areas. Platform and miogeosynclinal deposits, dominated by carbonate rocks, preceded saline deposition in the basins and persisted on shallow shelves adjacent to the geosynclines. The Arctic Permian marine fauna evolved in middle Permian time because of partial isolation of the Arctic areas from the southern ocean. Endemism, latitudinal temperature controls, and the effect of ocean currents explain in large part the faunal patterns in Permian seas. Post-Permian tectonic movements account for anomalies in the present positions of some rock sequences and fossils. Northeasterly drift and counterclockwise rotation of the northern landmasses are suggested. Right-lateral shear along the southern edge of Asia is supported, followed by northward movement of peninsular India.

Journal of Research of the U.S. Geological Survey↗
USGS2022

Marine minerals in Alaska — A review of coastal and deep-ocean regions

Minerals occurring in marine environments span the globe and encompass a broad range of mineral categories, forming within varied geologic and oceanographic settings. They occur in coastal regions, either from the continuation or mechanical reworking of terrestrial mineralization, as well as in the deep ocean, from diagenetic, hydrogenetic, and hydrothermal processes. The oceans cover most of the Earth’s surface and as a result, any inventory of global resources is incomplete without the inclusion of marine minerals. This study by the U.S. Geological Survey reviews current knowledge regarding deep-ocean and coastal marine minerals within the marine areas surrounding Alaska, including the Alaska Outer Continental Shelf (OCS). For the purposes of this study, we have divided these areas in to eight regions: (1) Gulf of Alaska seamounts, (2) Chukchi Borderland, (3) Canada Basin, (4) Aleutian Arc, (5) Seward Peninsula, (6) Goodnews Bay, (7) Bristol Bay and Alaska Peninsula, and (8) southern and southeastern Alaska. The Alaska OCS encompasses several areas broadly conducive to marine mineral formation, including extensional basins resulting from an active subduction zone where massive sulfide deposits may form, deep abyssal plains with conditions that may lead to manganese nodule formation, seamounts that can provide substrate for the growth of ferromanganese crusts, and erosional settings and submerged continental crust where placer deposits are found. For deep-ocean hydrothermal minerals and manganese nodules, the Alaska OCS contains prospective regions, including the Canada Basin and the Aleutian Arc; however, no such minerals have yet been identified. We explore the probability that these minerals occur based on reviews of existing geologic and oceanographic data within the relevant sections. In regions far from shore data are limited. Deep-ocean ferromanganese crusts are known to occur in two regions: (1) the Gulf of Alaska seamounts and (2) the Chukchi Borderland in the Arctic Ocean. Limited sampling has occurred in both regions, and along the Chukchi Borderland the sampling was outside of the OCS and the U.S. Exclusive Economic Zone. Data relevant to coastal minerals is more extensive, and in some places fairly systematic sampling was conducted. Several nearshore placer deposits have been exploited for decades; however, the potential for nearshore extension of terrestrial ore deposits is less well considered. This contribution considers the state of knowledge regarding marine mineral occurrences within the Alaska regions and identifies the data gaps in order to help inform future marine mineral related research efforts around Alaska.

Alaska↗
USGS1974

Hydrogeologic aspects of structural deformation in the northern Gulf of Mexico Basin

The first Earth Resources Technology Satellite (ERTS-1), launched by the National Aeronautics and Space Administration in.July 1972, is providing valuable data for investigations of the most inaccessible and hostile regions of the Earth the Arctic and Antarctic. ERTS images and map products derived from them offer a whole new dimension in source material for multidiscipline investigations in the earth sciences. For the first time scientists can view synoptic, repetitive scenes of the polar regions in four spectral bands. Ongoing experiments funded by NASA and conducted in the U.S. Geological Survey have demonstrated the feasibility of revising coastlines on maps of Antarctica, detected gross changes in the northern limits of the three largest ice shelves in the world, and led to the discovery of uncharted mountain ranges.

Louisiana, Texas↗