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At least 1,585 records · Page 88Linked to original sources

USGS1989

Preliminary geologic map of the Turayf Quadrangle, sheet 31C, and part of the An Nabk quadrangle, sheet 31B, Kingdom of Saudi Arabia

The An Nabk and Turayf quadrangles lie at the northern border of the Kingdom of Saudi Arabia. Middle and upper Cenozoic sedimentary and volcanic rocks form the surface of the quadrangles, and sedimentary rocks of the Paleozoic, Mesozoic, and lower Cenozoic are found in the subsurface. The Paleozoic and Mesozoic rocks, described from drill hole records, include the Tabuk, Upper Sudair, Lower Jilh and Aruma formations which are mostly of marine origin. The map area is part of the Sirhan-Turayf Basin and contains the Thaniyat, China, and Arqah Phosphorite members of the Upper Cretaceous-Tertiary Turayf group. Only the Arqah Phosphorite, the uppermost of the three members, crops out at the surface. From its outcrop along the east border of the area, the Arqah dips westward into the subsurface and passes into an argillaceous deeper water fades. The Thaniyat and China also dip westward in the subsurface and pinch out into a deeper water fades. Upper Eocene calcareous claystone and chalk mapped in the Wadi As Sirhan depression on the west side of the map area are named the Rashrashiyah formation, and may be partly equivalent to Eocene bioclastic, chert-bearing carbonate rocks of the Turayf group mapped to the east. The Sirhan formation is a new name for rocks of Miocene(?) age occurring in the Wadi As Sirhan area. These rocks are mostly sandstone of probable continental origin, and contain thin beds of fresh water limestone. However, marine limestone beds also occur, indicating periodic incursions by the sea. Al Harrah, a large Quaternary-Tertiary basalt field in the Sirhan-Turayf Basin, occupies the central part of the map area. The flows consist of silicic alkali olivine basalt, typical of the Cenozoic lava flows of Saudi Arabia. Volcanism appears to be of the continental rift-type and is related to Red Sea rifting. Quaternary calcareous and gypsiferous duricrust is found discontinuously throughout the western part of the map area. At one time it apparently formed a carapace-like cover over all surface rocks, and indicates a much wetter in northern Saudi Arabia than the present climate. The Arqah Phosphorite member is exposed in the northeast corner of the map area and contains thin beds of phosphorite grading from 18 to 30 percent P 2 O 5 - Oil shows have been reported in Cretaceous rocks of the Wadi As Sirhan depression, and oil has been discovered recently nearby in Jordan. Geologic and geophysical conditions are favorable for the entrapment of oil in the Wadi As Sirhan area and additional exploration is recommended.

Open-File Report↗

USGS2016

Potash—A vital agricultural nutrient sourced from geologic deposits

This report summarizes the primary sources of potash in the United States. Potash is an essential nutrient that, along with phosphorus and nitrogen, is used as fertilizer for growing crops. Plants require sufficient potash to activate enzymes, which in turn catalyze chemical reactions important for water uptake and photosynthesis. When potassium is available in quantities necessary for healthy plant growth, disease resistance and physical quality are improved and crop yield and shelf life are increased. Potash is a water-soluble compound of potassium formed by geologic and hydrologic processes. The principal potash sources discussed are the large, stratiform deposits that formed during retreat and evaporation of intracontinental seas. The Paradox, Delaware, Holbrook, Michigan, and Williston sedimentary basins in the United States are examples where extensive potash beds were deposited. Ancient marine-type potash deposits that are close to the surface can be mined using conventional underground mining methods. In situ solution mining can be used where beds are too deep, making underground mining cost-prohibitive, or where underground mines are converted to in situ solution mines. Quaternary brine is another source of potash that is recovered by solar evaporation in manmade ponds. Groundwater from Pleistocene Lake Bonneville (Wendover, Utah) and the present-day Great Salt Lake in Utah are sources of potashbearing brine. Brine from these sources pumped to solar ponds is evaporated and potash concentrated for harvesting, processing, and refinement. Although there is sufficient potash to meet near-term demand, the large marine-type deposits are either geographically restricted to a few areas or are too deep to easily mine. Other regions lack sources of potash brine from groundwater or surface water. Thus, some areas of the world rely heavily on potash imports. Political, economic, and global population pressures may limit the ability of some countries from securing potash resources in the future. In this context, a historical perspective on U.S. potash production in a global framework is discussed.

Open-File Report↗

USGS2017

Nearshore sediment thickness, Fire Island, New York

Investigations of coastal change at Fire Island, New York (N.Y.), sought to characterize sediment budgets and determine geologic framework controls on coastal processes. Nearshore sediment thickness is critical for assessing coastal system sediment availability, but it is largely unquantified due to the difficulty of conducting geological or geophysical surveys across the nearshore. This study used an amphibious vessel to acquire chirp subbottom profiles. These profiles were used to characterize nearshore geology and provide an assessment of nearshore sediment volume. Two resulting sediment-thickness maps are provided: total Holocene sediment thickness and the thickness of the active shoreface. The Holocene sediment section represents deposition above the maximum flooding surface that is related to the most recent marine transgression. The active shoreface section is the uppermost Holocene sediment, which is interpreted to represent the portion of the shoreface thought to contribute to present and future coastal behavior. The sediment distribution patterns correspond to previously defined zones of erosion, accretion, and stability along the island, demonstrating the importance of sediment availability in the coastal response to storms and seasonal variability. The eastern zone has a thin nearshore sediment thickness, except for an ebb-tidal deposit at the wilderness breach caused by Hurricane Sandy. Thicker sediment is found along a central zone that includes shoreface-attached sand ridges, which is consistent with a stable or accretional coastline in this area. The thickest overall Holocene section is found in the western zone of the study, where a thicker lower section of Holocene sediment appears related to the westward migration of Fire Island Inlet over several hundred years.

New York↗

USGS2017

Developing enterprise tools and capacities for large-scale natural resource monitoring: A visioning workshop

In October 2016, the U.S. Geological Survey (USGS), in collaboration with the Pacific Northwest Aquatic Monitoring Partnership (PNAMP, www.pnamp.org), convened a 30-person workshop, https://www.pnamp.org/event/5509, to identify and prioritize development of enterprise systems for programs that monitor the status and trends of species populations and their terrestrial, aquatic, and marine habitats. Participants included representatives from federal natural resource research and land management organizations and nongovernmental organizations that manage natural resource monitoring programs. Objectives of the workshop were: 1) identify resources that support natural resource monitoring programs working across the data life cycle; 2) prioritize desired capacities and tools to facilitate monitoring design and implementation; 3) identify standards and best practices that improve discovery, accessibility, and interoperability of data across programs and jurisdictions; and 4) contribute to an emerging community of practice focused on natural resource monitoring.

Report↗

USGS1994

Geologic framework and hydrogeologic characteristics of the Edwards Aquifer outcrop, Comal County, Texas

All of the hydrogeologic subdivisions within the Edwards aquifer outcrop in Comal County have some porosity and permeability. The most porous and permeable appear to be hydrogeologic subdivision VI, the Kirschberg evaporite member of the Kainer Formation; hydrogeologic subdivision III, the leached and collapsed members, undivided; and hydrogeologic subdivision II, the cyclic and marine members, undivided, of the Person Formation. The two types of porosity in the Edwards aquifer outcrop are fabric selective, which is related to depositional or diagenetic elements and typically exists in specific stratigraphic horizons; and not fabric selective, which can exist in any litho strati graphic horizon. Permeability, the capacity of porous rock to transmit water, depends on the physical properties of the rock such as pore size, shape, distribution, fissuring, and dissolution. Two faults, Comal Springs and Hueco Springs, completely, or almost completely, offset the Edwards aquifer along much of their respective traces across Comal County. Porous and permeable Edwards aquifer limestone is juxtaposed against impermeable upper confining units in these areas. These faults completely, or almost completely, offset the Edwards aquifer and are thought to be barriers or partial barriers to groundwater flow where the beds are juxtaposed. In Comal County, the Edwards aquifer is probably most vulnerable to surface contamination in the rapidly urbanizing areas on the Edwards aquifer outcrop. Possible contamination can result from spills, leakage of hazardous materials, or runoff onto the intensely faulted and fractured, karstic limestone outcrops characteristic of the recharge zone.

Texas↗

USGS1995

Geologic framework and hydrogeologic characteristics of the Edwards Aquifer outcrop, Hays County, Texas

All of the hydrogeologic subdivisions within the Edwards aquifer outcrop in Hays County have some porosity and permeability. The most porous and permeable appear to be hydrogeologic subdivision VI, the Kirschberg evaporite member of the Kainer Formation; hydrogeologic subdivision III, the leached and collapsed members, undivided; and hydrogeologic subdivision II, the cyclic and marine members, undivided, of the Person Formation. The two types of porosity in the Edwards aquifer outcrop are fabric selective, which is related to depositional or diagenetic elements and typically exists in specific stratigraphic horizons; and not fabric selective, which can exist in any lithostratigraphic horizon. Permeability, the capacity of porous rock to transmit water, depends on the physical properties of the rock such as size, shape, and distribution of pores, and fissuring and dissolution. Two faults, San Marcos Springs and Mustang Branch, completely, or almost completely, offset the Edwards aquifer by juxtaposing Edwards aquifer limestone against nearly impermeable upper confining units along parts of their traces across Hays County. These faults are thought to be barriers, or partial barriers, to groundwater flow where the beds are juxtaposed. In Hays County, the Edwards aquifer probably is most vulnerable to surface contamination in the rapidly urbanizing areas on the Edwards aquifer outcrop. Contamination can result from spills or leakage of hazardous materials; or runoff on the intensely faulted and fractured, karstic limestone outcrops characteristic of the recharge zone.

Texas↗

USGS1969

Glaciation on the continental margin off New England

The Pleistocene glacial limit in the marine environment off New England can be traced by plotting the seaward limit of abundant sandy gravel and the position of shoals. Maximum limit of the last glaciation was probably along an irregular line extending through Nantucket Shoals, across Great South Channel, northern Georges Bank, and at least to the edge of the Scotian Shelf. If, as we assume, glaciers lowered sea level approximately 130 m, the ice margin was probably a subaerial one on Nantucket Shoals and Georges Bank, and it was bordered by outwash and meltwater channels leading away from the ice front. On the Scotian Shelf, the margin may have bordered directly on the ocean, to judge by the lack of shoals and the widespread dispersion of gravel out to the shelf edge. The glaciofluvial nature of the original deposits and marine reworking during the eustatic rise in sea level have made it difficult to recognize ice-contact deposits near the limit of maximum glacial advance. The gravel on shallow banks and ledges is in a bimodal mixture with sand. Association of coarse gravel and sand suggests postdepositional reworking of till by marine processes and removal of silt and clay. Gravel in the Gulf of Maine is mixed with sand, silt, and clay, a mixture characteristic of till.

Connecticut, Maine, Massachusetts, New Hampshire, ↗

USGS2004

Changing Salinity Patterns in Biscayne Bay, Florida

Biscayne Bay, Fla., is a 428-square-mile (1,109-square-kilometer) subtropical estuarine ecosystem that includes Biscayne National Park, the largest marine park in the U.S. national park system (fig. 1). The bay began forming between 5,000 and 3,000 years ago as sea level rose and southern Florida was flooded. Throughout most of its history, the pristine waters of the bay supported abundant and diverse fauna and flora, and the bay was a nursery for the adjacent coral-reef and marine ecosystems. In the 20th century, urbanization of the Miami-Dade County area profoundly affected the environment of the bay. Construction of powerplants, water-treatment plants, and solid-waste sites and large-scale development along the shoreline stressed the ecosystem. Biscayne National Monument was established in 1968 to ?preserve and protect for the education, inspiration, recreation and enjoyment of present and future generations a rare combination of terrestrial, marine, and amphibious life in a tropical setting of great natural beauty? (Public Law 90?606). The monument was enlarged in 1980 and designated a national park.

Fact Sheet↗

USGS1981

Petrology and petrography for USGS test wells 1, 2, and 3 in the Madison Limestone in Montana and Wyoming

The need for large quantities of energy has created interest in the Fort Union coal region of the Northern Great Plains. Extensive development of this coal, which may include on-site steam-power generation, gasification, liquefaction, and slurry-pipeline transport of the coal out of the region, would place a heavy demand on the region's limited streamflow. Paleozoic rocks that underlie the Fort Union coal region might supply, at least on a temporary basis, a significant part of the water required for coal development. Paleozoic rocks in the Northern Great Plains are related to the geologic history of the western border of the stable interior of the continent. The central part of the continental interior (Paleozoic craton) was made up of a stable core, the Canadian shield. To the west of the Canadian shield, the broad western flank of the Paleozoic craton made up the Cordilleran shelf, which is the site of the shallow-water marine rocks described in this report. The area of study covers approximately 200,000 square miles, and includes eastern Montana, western North Dakota and South Dakota, northeastern Wyoming, and northwestern Nebraska. The Madison Limestone, or Group, where it is divided, consists of a lower argillaceous limestone (Lodgepole Limestone); a middle unit of fossiliferous carbonate rock (Mission Canyon Limestone); and an upper unit of anhydrite, halite, and interbedded carbonate rock and shale (Charles Formation). The total section is made up of numerous cyclic, marker-defined units. The Madison Limestone was subdivided into units bounded by "marker beds" that consist of thin and widespread shaly carbonate or dark shale recognizable in the subsurface on geophysical logs. The five marker beds used for regional correlation purposes are as follows: M-1 represents the base of the Madison Limestone; M-3 is near the Kinderhookian-Osagean boundary; M-7 and M-8.5 fall within the Osagean; and M-12 is near the Osagean-Meramecian boundary. The top of the Madison Limestone is the Mc marker. Petrology and petrography of the Madison Limestone and associated rocks were studied from cores taken in three test wells of the U.S. Geological Survey. Six major rock types are recognized within cored intervals of the three test wells. Dolomite forms two-thirds of the total and limestone about 20 percent. The remainder consists of anhydrite, carbonate breccia, carbonate mudstone, and chert. Crystalline dolomite is the only abundant rock type in wells 1, 2, and 3 that has high enough porosity and permeability to provide significant yields of water. Crystalline dolomites not associated with evaporites may have formed by some sort of meteoric water-sea water mixing process in the subsurface shoreline environment by recrystallization of mud-rich limestones. Porosity and permeability values of all cored intervals of the Madison Limestone were determined. Mean porosity for the Madison Limestone is 8.4 percent, and mean permeability is 15.8 millidarcies. Because the Madison Limestone is relatively heterogeneous, permeability has a wide range in value.

Montana, Wyoming↗

USGS2024

Using surficial geologic maps, vegetation, and monitoring to address erosion impacts from grazing in Channel Islands National Park, California

Employing a map-unit classification scheme based on geomorphic process and age, the U.S. Geological Survey (USGS) mapped Quaternary surficial deposits of the five islands comprising Channel Islands National Park (CHIS), California, as no such maps previously existed. Mapping was motivated through an agreement with the National Park Service (NPS) to aid natural resource assessments, including post-grazing disturbance recovery and identification of mass wasting and tectonic hazards. The resulting detailed (1:12,000 scale) maps portray areas of upland erosional transport processes and alluvial, fluvial, eolian, beach, marine terrace, mass wasting, and mixed depositional processes at a scale commensurate with the process signal on the landscape. Detailed, GPS-located observations of sedimentology, pedogenic development, landscape position, and geomorphology constrain map unit identification. In addition, map-unit boundary delineation was determined in a GIS using a variety of high-resolution (sub-meter) aerial imagery and lidar-based DEMs complemented by derivative raster products. The GIS geodatabase schema used is GeMS compliant. Resolvable map-unit widths are as small as 10-15 meter. Locational accuracy of unit boundaries is estimated to be as low as 10 m or better. Detailed mapping is at a scale allowing determination of geomorphic transport processes operating on the landscape and conveys geologic information to land managers at a resolution commensurate with park resources. Map unit ages are constrained by relative soil chronostratigraphy, vertebrate and invertebrate fossils, and materials collected for dating control using radiogenic, luminescence, and cosmogenic radionuclide techniques. Associated topical studies examined connections between geology, surface water, and vegetation distribution and restoration.

California↗

USGS2005

Interpretation of the Last Chance thrust, Death Valley region, California, as an Early Permian décollement in a previously undeformed shale basin

The Last Chance thrust, discontinuously exposed over an area of at least 2500 km 2 near the south end of the Cordilleran foreland thrust belt in the Death Valley region of east-central California, is controversial because of its poorly constrained age and its uncertain original geometry and extent. We interpret this thrust to be Early Permian in age, to extend throughout a sedimentary basin in which deep-water Mississippian shale overlain by Pennsylvanian and earliest Permian limestone turbidites accumulated, to represent about 30 km of eastward displacement, and to be related to convergence on a northeast-trending segment of the Early Permian continental margin. Last Chance deformation occurred between the times of the Antler and Sonoma orogenies of Late Devonian–Early Mississippian and Late Permian ages, respectively, and followed Early to Middle Pennsylvanian truncation of the continental margin by transform faulting. In the western part of the Mississippian shale basin in east-central California, the originally recognized exposures of the Last Chance thrust show Neoproterozoic and early Paleozoic strata above lower-plate Mississippian shale. Farther east, faults subparallel to bedding above, below, and within the Mississippian shale are interpreted to mark the thrust zone and to represent a regional décollement. At the eastern margin of the basin, upper-plate thrust slices of deep-water, late Paleozoic strata are interpreted to have piled up against the margin of the Mississippian carbonate shelf to form a large antiformal stack above the Lee Flat thrust, which we regard as the easternmost exposure of the Last Chance thrust. Thrust loading depressed the western part of the shelf, creating a new sedimentary basin in which about 3.5 km of younger Early Permian deep-water strata were deposited against the antiformal stack. Later, probably in the Late Permian, other thrusts, including the Inyo Crest thrust, which was subsequently overlapped by Early to Middle(?) Triassic marine strata, cut across the Last Chance thrust. We interpret the Last Chance thrust as similar in many ways to Appalachian-type décollements in which the zone of thrusting is localized along a shale interval. The Last Chance thrust, however, has been dismembered during later geologic events so that its original geometry has been obscured. Our model may have unrecognized analogs in other structurally complex shale basins in which the initial deformation was along a major shale unit.

Earth-Science Reviews↗

USGS1997

Comagmatic A-type granophyre and rhyolite from the Alid volcanic center, eritrea, northeast Africa

Granophyric blocks within late-Pleistocene pyroclastic flow ejecta from the Alid volcanic center, northeast Africa, are the rapidly crystallized, intrusive equivalent of pumice from the pyroclastic flow. Phenocryst compositions and geochemical characteristics of the pumice and granophyre are virtually identical. Silicate melt inclusions and other geochemical and geological constraints reveal those processes leading to development of the granophyric texture. Rhyolitic (A-type) magma with ∼2.6 wt % dissolved H 2 O and a temperature near 870°C was intruded to within 2–4 km of the surface, causing deformation and structural doming of shallow marine and subaerial strata. Eruptions of crystal-poor rhyolite from this shallow magma chamber caused degassing, which forced undercooling and consequent granophyric crystallization of some of the magma remaining in the intrusion. The most recent eruption from Alid excavated the crystallized granitic wall of the magma chamber, bringing the granophyric clasts to the surface.

Journal of Petrology↗

USGS1976

Obsidian hydration dating and correlation of Bull Lake and Pinedale Glaciations near West Yellowstone, Montana

The ages of the last two glaciations near West Yellowstone, Montana, can be calculated by obsidian hydration techniques that are calibrated by K-Ar dating of obsidian-bearing lava flows. The average age of glacial abrasion of obsidian in the Pinedale terminal moraines is about 30,000 yr, with most age measurements between 20,000 and 35,000 yr. For the Bull Lake moraines, it is about 140,000 yr, with most measurements between 130,000 and 155,000 yr. This age for the Bull Lake moraines is also supported by geologic relations that show that the moraines are older than a rhyolite flow dated by K-Ar as 114,500 ± 7,300 yr old (lσ). These obsidian hydration ages of the Pinedale and Bull Lake Glaciations correlate well with the last two cold intervals of the marine record. The age determined for the Bull Lake Glaciation near West Yellowstone antedates the last interglaciation of the marine record, which is commonly correlated with the Sangamon Interglaciation. Our results suggest correlation of the Pinedale Glaciation near West Yellowstone with much or all of the Wisconsin Glaciation and of the Bull Lake with the late Illinoian. This differs with the commonly accepted correlation of the Pinedale with the late (“classical”) Wisconsin and of the Bull Lake with the early Wisconsin. The correlation of Bull Lake with late Illinoian appears equally or more compatible with traditional criteria for correlation, namely comparative soil development and degree of preservation of morainal morphology.

Wyoming, Montana, Idaho↗

USGS2011

An evaluation of the science needs to inform decisions on Outer Continental Shelf energy development in the Chukchi and Beaufort Seas, Alaska

The U. S. Geological Survey (USGS) was asked to conduct an initial, independent evaluation of the science needs that would inform the Administration's consideration of the right places and the right ways in which to develop oil and gas resources in the Arctic Outer Continental Shelf (OCS), particularly focused on the Beaufort and Chukchi Seas. Oil and gas potential is significant in Arctic Alaska. Beyond petroleum potential, this region supports unique fish and wildlife resources and ecosystems, and indigenous people who rely on these resources for subsistence. This report summarizes key existing scientific information and provides initial guidance of what new and (or) continued research could inform decision making. This report is presented in a series of topical chapters and various appendixes each written by a subset of the USGS OCS Team based on their areas of expertise. Three chapters (Chapters 2, 3, and 4) provide foundational information on geology; ecology and subsistence; and climate settings important to understanding the conditions pertinent to development in the Arctic OCS. These chapters are followed by three chapters that examine the scientific understanding, science gaps, and science sufficiency questions regarding oil-spill risk, response, and impact (Chapter 5), marine mammals and anthropogenic noise (Chapter 6), and cumulative impacts (Chapter 7). Lessons learned from the 1989 Exxon Valdez Oil Spill are included to identify valuable "pre-positioned" science and scientific approaches to improved response and reduced uncertainty in damage assessment and restoration efforts (appendix D). An appendix on Structured Decision Making (appendix C) is included to illustrate the value of such tools that go beyond, but incorporate, science in looking at what can/should be done about policy and implementation of Arctic development. The report provides a series of findings and recommendations for consideration developed during the independent examination of science gaps and sufficiency. These recommendations are important for understanding what the USGS discovered in the course of this study and to help inform and improve decision making.

Circular↗

USGS2001

Geologic map of the Arctic Quadrangle, Alaska

Introduction The Arctic quadrangle is well located to shed light on the basic geologic relations of northern Alaska. The rocks represent all of the stratigraphic systems from Cambrian to Cretaceous and all but one of the tectono-stratigraphic subterranes of the Brooks Range, from the autochthonous subterrane in the north to the allochthonous subterranes farther south. Among the distinctive geologic features displayed in the Arctic quadrangle are voluminous volcanic rocks of probable Devonian age, a wide array of Carboniferous carbonate facies in the Lisburne Group (which here extends up into the Middle Pennsylvanian), the southward transition of Upper Devonian (Famennian) clastic facies from fluvial conglomerate to marine sandstone, a full display of Upper Devonian (Frasnian) reef-related strata, and fossiliferous Ordovician rocks in both carbonate and chert terranes. Most of the quadrangle is in the Arctic National Wildlife Refuge (ANWR) and Arctic Wildlife Refuge Wilderness. The quadrangle also includes Arctic Village, the only village in the region and a potential destination or transfer point for visitors to the wildlife refuge.

Alaska↗

USGS2012

Simulated effects of dam removal on water temperatures along the Klamath River, Oregon and California, using 2010 Biological Opinion flow requirements

Computer model simulations were run to determine the effects of dam removal on water temperatures along the Klamath River, located in south-central Oregon and northern California, using flow requirements defined in the 2010 Biological Opinion of the National Marine Fisheries Service. A one-dimensional, daily averaged water temperature model (River Basin Model-10) developed by the U.S. Environmental Protection Agency Region 10, Seattle, Washington, was used in the analysis. This model had earlier been configured and calibrated for the Klamath River by the U.S. Geological Survey for the U.S. Department of the Interior, Klamath Secretarial Determination to simulate the effects of dam removal on water temperatures for current (2011) and future climate change scenarios. The analysis for this report was performed outside of the scope of the Klamath Secretarial Determination process at the request of the Bureau of Reclamation Technical Services Office, Denver, Colorado.  For this analysis, two dam scenarios were simulated: “dams in” and “dams out.” In the “dams in” scenario, existing dams in the Klamath River were kept in place. In the “dams out” scenario, the river was modeled as a natural stream, without the J.C. Boyle, Copco1, Copco2, and Iron Gate Dams, for the entire simulation period. Output from the two dam scenario simulations included daily water temperatures simulated at 29 locations for a 50-year period along the Klamath River between river mile 253 (downstream of Link River Dam) and the Pacific Ocean. Both simulations used identical flow requirements, formulated in the 2010 Biological Opinion, and identical climate conditions based on the period 1961–2009.  Simulated water temperatures from January through June at almost all locations between J.C. Boyle Reservoir and the Pacific Ocean were higher for the “dams out” scenario than for the “dams in” scenario. The simulated mean monthly water temperature increase was highest [1.7–2.2 degrees Celsius (°C)] in May downstream of Iron Gate Dam. However, from August to December, dam removal generally cooled water temperatures. During these months, water temperatures decreased 1°C or more between Copco Lake and locations 50 miles or more downstream. The greatest mean monthly temperature decrease was 4°C in October just downstream of Iron Gate Dam. Near the ocean, the effects of dam removal were small (less than 0.2°C) for most months. However, the mean November temperature near the ocean was almost 0.5°C cooler with dam removal.

Open-File Report↗

USGS2011

Undiscovered hydrocarbon resources in the U.S. Gulf Coast Jurassic Norphlet and Smackover Formations

The U.S. Geological Survey has completed assessments of undiscovered technically recoverable oil and gas resources in the Jurassic Norphlet and Smackover formations of the onshore coastal plain and State waters of the U.S. Gulf Coast. The Norphlet Formation consists of sandstones and interbedded shales and siltstones deposited during a marine transgression. Along its northeast margin, deposition of the Norphlet was in alluvial fans, fluvial systems, and dune and clastic sabkha environments. Mudstones of the underlying Smackover Formation act as source rocks for Norphlet reservoirs. The Norphlet was divided into the following three assessment units (AUs): the Norphlet Salt Basins and Updip AU, the Norphlet Mobile Bay Deep Gas AU, and the Norphlet South Texas Gas AU. The lower part of the Smackover consists primarily of dark carbonate mudstone and argillaceous limestone deposited in low-energy environments, and is one of the Gulf of Mexico Basin’s major source rocks. The upper part of the Smackover is comprised primarily of grain-supported carbonates deposited in high-energy environments. The Smackover was divided into the following four AUs: the Smackover Updip and Peripheral Fault Zone AU, the Smackover Salt Basin AU, the Smackover South Texas AU, and the Smackover Downdip Continuous Gas AU. Although the Norphlet and Smackover formations have been the focus of extensive exploration and production, they probably still contain significant undiscovered oil and gas resources.

Alabama, Louisiana, Mississippi, Texas↗

USGS1976

The Viking landing sites: Selection and certification

During the past several years the Viking project developed plans to use Viking orbiter instruments and Earth-based radar to certify the suitability of the landing sites selected as the safest and most scientifically rewarding using Mariner 9 data. During June and July 1976, the Earth-based radar and orbital spacecraft observations of some of the prime and backup sites were completed. The results of these combined observations indicated that the Viking 1 prime landing area in the Chryse region of Mars is geologically varied and possibly more hazardous than expected, and was not certifiable as a site for the Viking 1 landing. Consequently, the site certification effort had to be drastically modified and lengthened to search for a site that might be safe enough to attempt to land. The selected site considered at 47.5°W, 22.4°N represented a compromise between desirable characteristics observed with visual images and those inferred from Earth-based radar. It lies in the Chryse region about 900 kilometers northwest of the original site. Viking 1 landed successfully at this site on 20 July 1976.

Science↗