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USGS1981

Reconnaissance investigation of brine in the eastern Rub al Khali, Kingdom of Saudi Arabia

Al Uruq al Mu'taridah-Umm as Samim area is located in a large topographic depression in the eastern Rub al Khali desert where playas several thousand square kilometers in area are exposedo A crust of eolian sand cemented with gypsum and halite has formed on many playa surfaces. Anhydrite nodules are common in the sampled area, where the depth to ground water generally exceeds 172 Cmo The chemistry of the three ground-water samples collected near the water well Ramallah-1 (lat 22?10'20'' N., long 54?20'37'' E.) is similar to that of sabkhah-related brines on the coast of the United Arab Emirates. Although there is no indication of economic quantities of evaporite minerals in the sampled area, the extent of the depression and its unique geologic environment recommend it for resource-evaluation studies.

Open-File Report↗

USGS1981

Chemical composition of sedimentary rocks in California and Hawaii

A compilation of published chemical analyses of sedimentary rocks of the United States was undertaken by the U.S. Geological Survey in 1952 to make available scattered data that are needed for a wide range of economic and scientific uses. About 20,000-25,000 chemical analyses of sedimentary rocks in the United States have been published. This report brings together 2,312 of these analyses from California and Hawaii. The samples are arranged by general lithologic characteristics and locality. Indexes of stratigraphy, rock name, commercial uses, and minor elements are provided. The sedimentary rocks are classified into groups and into categories according to the chemical analyses. The groups (A through F2) are defined by a system similar to that proposed by Brian Mason in 1952, in which the main parameters are the three major components of sedimentary rocks: (1) uncombined silica, (2) clay (R203 ? 3Si02 ? nH20), and (3) calcium-magnesium carbonate. The categories are based on the degree of admixture of these three major components with other components, such as sulfate, phos- phate, and iron oxide. Common-rock, mixed-rock, and special-rock categories apply to rocks consisting of 85 percent or more, 50-84 percent, and less than 49 percent, respectively, of the three major components combined. Maps show distribution of sample localities by States; triangular diagrams show the lithologic characteristics and classification groups. Cumulative-frequency curves of each constituent in each classification group of the common-rock and mixed-rock categories are also included. The numerous analyses may not adequately represent the geochemical nature of the rock types and formations of the region because of sampling bias. Maps showing distribution of sample localities indicate that many of the localities are in areas where, for economic or other reasons, special problems attracted interest. Most of the analyzed rocks tended to be fairly simple in composition - mainly mixtures of just two of the three major components or a mixture of these and a fourth component such as phosphate, gypsum, or iron oxide.

Professional Paper↗

USGS1978

Gilbert White talks about natural hazards

Dr. Gilbert White is Director of the Institute of Behavioral Science at the University of Colorado, Boulder, where he is responsible for natural Hazards Research and Applications Information Center supported by the National Science Foundation. He served in the Executive Office of the president in 1941-42, on the Federal Flood Control Policy Task Force in 1964-65, and on the U.S Geological Survey Advisory Panel on Earthquake Studies. Dr. White has authored five books on the social and economic aspects of natural resources, including water supply and river development, and on floods and other natural hazards.

Earthquake Information Bulletin (USGS)↗

USGS1990

Overview of the effects and influence of the activity of Mount St. Helens in the 1980s

The cataclysmic eruption of Mount St. Helens on May 18, 1980, made an enormous impact on the science of volcanology. The eruption was in daylight in clear weather, which provided an unprecedented opportunity to investigate relations among observations, products, and effects of a large explosive eruption. The May 18 events and subsequent activity stimulated perhaps the most intensive studies ever made at an active composite volcano, leading to greatly enhanced insights into both geologic and hydrologic processes operative in explosive volcanism. The eruption also disrupted much of the social and economic fabric of the Pacific Northwest. Volcanologists were called upon to explain the activity, in layman's terms, to government and corporate officials, the news media, schools, and the public at large. People eventually learned to live with the volcano and its uncertainties, and volcanologists better learned their role in helping society deal with a major natural disaster. Difficulties encountered at volcanic crises elsewhere in the world in the 1980s demonstrate that these are hard lessons. In future years, a paramount challenge for scientists will be to help society apply what has been learned at Mount St. Helens to crises both nearby and far away.

Washington↗

USGS2005

Geochemistry of sulfate minerals in high- and low-temperature environments: A tribute to Robert O. Rye

This special issue is a tribute to Robert O. Rye, known as "Bob" to most, in light of his highly productive and ongoing career. Almost all of the papers in this issue are derived from topical sessions on sulfate minerals in hydrothermal and low-temperature environments. The sessions, held at the 2000 Geological Society of America meeting in Reno, NV, and sponsored jointly by the Mineralogical Society of America, the Society of Economic Geologists and the Geochemical Society, included 29 oral and 9 poster presentations. The sessions complemented a short course on the crystallography, geochemistry and environmental significance of sulfate minerals, sponsored by the Mineralogical Society of America and the Geochemical Society, which immediately preceded the meeting (Alpers et al., 2000). The 23 papers in this special issue typify the breadth of Bob Rye’s research in this important area of geochemistry.

Chemical Geology↗

USGS1976

An environmental assessment of impacts of coal development on the water resources of the Yampa River basin, Colorado and Wyoming; Phase I work plan

Coal resources of the western United States are being developed at ever-increasing rates, causing concerns of the effects of mining and associated activities on the environment. The Yampa River basin in northwestern Colorado and south-central Wyoming is undergoing economic development of its coal, oil and gas, and uranium resources. The Yampa River basin assessment is a 21-year program of the U.S. Geological Survey. It is designed primarily to assess the availability and quality of the basin's water resources. The basin assessment also will evaluate potential environmental and selected socioeconomic impacts of energy-resource development plans proposed by mining and power companies. This report serves as a project work plan for the basin assessment's first-phase work activities. Economic development in the Yampa River basin will result in higher levels of residuals (noneconomic byproducts) being discharged into the environment. Residuals-management encompasses the technological and economic interrelationships that should be considered in order to comply with Federal and State environmental-control regulations regarding air quality, water quality, and disposal of solid wastes. The basin assessment, the first phase that is described by this report, is designed to provide Federal, State, and local decision-makers with the basic environmental information needed to formulate and to evaluate policies for the development of energy resources. The techniques applied and conclusions reached in the Yampa River basin assessment should aid similar studies of other energy-rich basins in the western United States.

Colorado, Wyoming↗

USGS1983

Trace-element geochemistry of postorogenic granites from the northeastern Arabian Shield, Kingdom of Saudi Arabia

Concentrations determined for all of the trace elements included in this study of postorogenic granites from the northeastern Arabian Shield are best described by log-normal distributions. The trace elements are divided into two groups: (1) compatible lithophile and siderophile elements (strontium, cobalt, scandium, manganese, europium, and titanium) and (2) incompatible lithophile elements (uranium, thorium, tantalum, rubidium, and rare-earth elements, except europium). The compatible elements exhibit greatest concentrations in the metaluminous postorogenic granites, and concentrations decrease with increasing degree of magma evolution. Economic potential for these elements and other geochemically similar elements is considered to be low. The concentrations of the incompatible elements increase with increasing degree of magma evolution and are greatest in the peralkaline and peraluminous granites. There is some geologic evidence that pegmatite and vein-forming processes were operative toward the end stage of postorogenic magmatism in the northeastern Arabian Shield, and therefore there is some probability for economic potential for these elements. It is suggested that such potential is greatest where highly evolved postorogenic granites intruded volatile (generally water )-rich country rocks.

Open-File Report↗

USGS2005

Role of ground water in geomorphology, geology, and paleoclimate of the southern High Plains, USA

Study of ground water in the Southern High Plains is central to an understanding of the geomorphology, deposition of economic minerals, and climate change record in the area. Ground water has controlled the course of the Canadian and Pecos rivers that isolated the Southern High Plains from the Great Plains and has contributed significantly to the continuing retreat of the westward escarpment. Evaporative and dissolution processes are responsible for current plateau topography and the development of the signature 20,000 small playa basins and 40 to 50 large saline lake basins in the area. In conjunction with eolian processes, ground water transport controls the mineralogy of commercially valuable mineral deposits and sets up the distribution of fine efflorescent salts that adversely affect water quality. As the water table rises and retreats, lunette and tufa formation provides valuable paleoclimate data for the Southern High Plains. In all these cases, an understanding of ground water processes contributes valuable information to a broad range of geological topics, well beyond traditional interest in water supply and environmental issues.

Colorado, Kansas, New Mexico, Texas↗

USGS1981

Map showing mineral-resource potential of the King Range and Chemise Mountain Instant Study Areas, Humboldt and Mendocino counties, California

The potential for economic development of energy-related or metallic mineral resources in the King Range and Chemise Mountain Instant Study Areas is low to moderate as indicated by geologic, geophysical, and geochemical investigations. No oil or gas seeps or coal seams were detected within the King Range or Chemise Mountain Study Area. The low porosity and permeability of the Franciscan sandstones that underlie these areas indicate a very low potential for oil or gas. The geothermal resource potential of these areas also is low. Minor manganese resources occur adjacent to the southeast corner of the King Range Instant Study Area near Queen Peak. The manganese forms small stratabound deposits associated with radiolarian chert and pillow basalt. The known deposits are too small and the manganese too low in concentration for further economic exploitation. Similar manganese mineralization may be within the belt of melange in the southeast corner of the King Range area and within the Chemise Mountain Instant Study Area, but economic deposits are unlikely. Although there has been historical base- and precious-metal exploration activity north of the King Range in the Mattole River drainage, our geologic and geochemical field data indicate almost no gold potential and low potentials for lead, zinc, copper, and silver. During this investigation, one high-grade vein and several minor veins containing lead, zinc, copper, and silver were discovered at Point Delgada immediately south of the King Range Instant Study Area. The vein mineralization is Miocene and cuts Cretaceous basalt flows, dikes, flow breccia, and younger overlying sedimentary rocks of the King Range. The vein mineralization at Point Delgada could be remobilized from more extensive unexposed stratabound base-metal mineralization at depth. Traces of lead and zinc detected within the King Range Instant Study Area may have similar stratabound or vein origins, but no resource potential is indicated. Minor copper mineralization with associated lead, zinc, and manganese anomalies within the Chemise Mountain Instant Study Area is of low economic potential because of the shearing, isolation, and lenticularity of the basaltic and cherty rocks within the melange mineralization.

California↗

USGS2010

Fluorine, fluorite, and fluorspar in central Colorado

Fluorine (F) is a widespread element that was deposited in a variety of rocks, minerals, and geologic environments in central Colorado. It occurs as a trace element, as a major component of the mineral fluorite (CaFs), and as a major economic source of fluorine in fluorspar deposits, which are massive concentrations of fluorite. This study has compiled available geochemical analyses of rocks, both unmineralized and mineralized, to determine the distribution of fluorine in specific age-lithologic categories, ranging from 1.8-giga-annum (Ga) metamorphic rocks to modern soils, throughout central Colorado. It also draws upon field studies of fluorine-rich mineral deposits, including fluorspar deposits, to decipher the nearly two-billion-year-long geologic history of fluorine in the study area, with implications for mineral-resource evaluations and exploration. The resulting compilation provides an important inventory of the naturally occurring levels and sources of fluorine that ultimately weather, erode, and become part of surface waters that are used for domestic water supplies in densely populated areas along the Colorado Front Range. Most commonly, fluorine is a trace element in virtually all rocks in the region. In the 3,798 unmineralized rocks that were analyzed for fluorine in the study area, the average fluorine content was 1,550 parts per million (ppm). The median was 640 ppm, nearly identical to the average crustal abundance of 650 ppm, and some high-fluorine rocks in the Pikes Peak area skewed the average to a value much greater than the median. Most unmineralized age-lithologic rock suites, including Proterozoic metamorphic rocks, 1.7- and 1.4-Ga granitic batholiths, Cambrian igneous rocks, Phanerozoic sedimentary rocks, and Laramide and Tertiary igneous rocks, had median fluorine values of 400 to 740 ppm fluorine. In all suites, however, a small number of analyzed samples contained more than 1 percent (10,000 ppm) fluorine. The 1.1-Ga plutonic rocks related to the Pikes Peak batholith had a mean fluorine content of 1,700 ppm, and primary magmatic fluorite and fluorite-bearing pegmatites are common throughout that igneous mass. Fluorine was deposited in many types of economic mineral deposits in central Colorado, and it currently is a significant trace element in some thermal springs. In the fluorspar deposits, fluorine contents were as high as 37 percent. Some fluorine-rich porphyry systems, such as Jamestown, had fluorine values that ranged from 200 ppm to nearly 37 percent fluorine, and veins in other deposits contained hydrothermal fluorite, although it was not ubiquitous. For the 495 samples from non-fluorspar mining districts (and excluding Jamestown), however, the median fluorine content was 990 ppm. This is above the crustal average but still relatively modest compared to the fluorspar deposits, and it indicates that the majority of the mineralizing systems in central Colorado did not deposit large amounts of fluorine. Nevertheless, the fluorine- and fluorite-rich mineral deposits could be used as guides for the evaluation and discovery of related but concealed porphyry and epithermal base- and precious-metal deposits. The Cenozoic geologic history of central Colorado included multiple periods during which fluorine-bearing rocks and mineral deposits were exposed, weathered, and eroded. This protracted history has released fluorine into soils and regoliths, and modern rainfall and snowmelt interact with these substrates to add fluorine to the hydrosphere. This study did not evaluate the fluorine contents of water or make any predictions about what areas might be major sources for dissolved fluorine. However, the abundant data that are available on fluorine in surface water and ground water can be coupled with the results of this study to provide additional insight into natural sources of fluorine in domestic drinking water.

Scientific Investigations Report↗

USGS2000

Late-kinematic timing of orogenic gold deposits and significance for computer-based exploration techniques with emphasis on the Yilgarn Block, Western Australia

Orogenic gold deposits are a widespread coherent group of epigenetic ore deposits that are sited in accretionary or collisional orogens. They formed over a large crustal-depth range from deep-seated low-salinity H 2 O–CO 2 ±CH 4 ±N 2 ore fluids and with Au transported as thio-complexes. Regional structures provide the main control on deposit distribution. In many terranes, first-order faults or shear zones appear to have controlled regional fluid flow, with greatest ore-fluid fluxes in, and adjacent to, lower-order faults, shear zones and/or large folds. Highly competent and/or chemically reactive rocks are the most common hosts to the larger deposits. Focusing of supralithostatic ore fluids into dilatant zones appears to occur late during the evolutionary history of the host terranes, normally within D 3 or D 4 in a D 1 –D 4 deformation sequence. Reactivation of suitably oriented pre-existing structures during a change in far-field stress orientation is a factor common to many deposits, and repeated reactivation may account for multiple mineralization episodes in some larger deposits. Absolute robust ages of mineralization support their late-kinematic timing, and, in general, suggest that deposits formed diachronously towards the end of the 100 to 200 m.y. long evolutionary history of hosting orogens. For example, in the Yilgarn Block, a region specifically emphasised in this study, orogenic gold deposits formed in the time interval between 40 and 90 m.y., with most about 60 to 70 m.y., after the youngest widespread basic-ultrabasic volcanism and towards the end of felsic magmatism. The late timing of orogenic gold deposits is pivotal to geologically-based exploration methodologies. This is because the present structural geometries of: (i) the deposits, (ii) the hosting goldfields, and (iii) the enclosing terranes are all essentially similar to those during gold mineralization, at least in their relative position to each other. Thus, interpretation of geological maps and cross-sections and three-dimensional models can be used to accurately simulate the physical conditions that existed at the time of ore deposition. It is particularly significant that the deposits are commonly related to repetitive and predictable geometries, such as structural heterogeneities within or adjacent to first-order structures, around rigid granitoid bodies, or in specific “locked-up” fold-thrust structures. Importantly, the two giant greenstone-hosted goldfields, Kalgoorlie and Timmins, show a remarkably similar geometry at the regional scale. Computer-based stress mapping and GIS-based prospectivity mapping are two computer-based quantitative methodologies that can utilize and take advantage of the late timing aspect of this deposit type to provide important geological aids in exploration, both in broad regions and more localized goldfields. Both require an accurate and consistent solid geology map, stress mapping requires knowledge of the far-field stresses during mineralization, and the empirical prospectivity mapping requires data from a significant number of known deposits in the terrane. The Kalgoorlie Terrane, in the Yilgarn Block, meets these criteria, and illustrates the potential of these methodologies in the exploration for orogenic gold deposits. Low minimum stress anomalies, interpreted to represent dilational zones during gold-related deformation, coincide well with the positions of known goldfields rather than individual gold deposits in the terrane, and there are additional as-yet unexplained anomalies. The prospectivity analysis confirms that predictable and repetitive factors controlling the siting of deposits are: (i) proximity to, and orientation and curvature of, granitoid-greenstone contacts, (ii) proximity to segments of crustal faults which strike in a preferred direction, (iii) proximity to specific lithological contacts which have similar preferred strike, (iv) proximity to anticlinal structures, and (v) the presence of preferred reactive host rocks (e.g., dolerite). The prospectivity map defines a series of anomalous areas, which broadly conform to those of the stress map (>78% correspondence). The most prospective category on this map covers less than 0.3% of the greenstone belts and yet hosts 16% of the known deposits, which have produced>80% of known gold. Thus, it discriminates in favour of the larger economically more-attractive deposits in the terrane. The successful application of stress mapping and prospectivity mapping to geology-based exploration for orogenic gold deposits indicates that more quantitative analysis of geological map data is a profitable line of research. The computer-based nature of these methodologies is ideal for the production of an ultimate, integrated, deposit target map, which can be compared to other, more conventional, targeting parameters such as geophysical and geochemical anomalies. Such an integrated strategy appears the way forward in the increasingly difficult task of cost-effective global exploration for orogenic gold deposits in poorly exposed terranes.

Western Australia↗

USGS2014

Crustal permeability: Introduction to the special issue

The topic of crustal permeability is of broad interest in light of the controlling effect of permeability on diverse geologic processes and also timely in light of the practical challenges associated with emerging technologies such as hydraulic fracturing for oil and gas production (‘fracking’), enhanced geothermal systems, and geologic carbon sequestration. This special issue of Geofluids is also motivated by the historical dichotomy between the hydrogeologic concept of permeability as a static material property that exerts control on fluid flow and the perspective of economic geologists, geophysicists, and crustal petrologists who have long recognized permeability as a dynamic parameter that changes in response to tectonism, fluid production, and geochemical reactions. Issues associated with fracking, enhanced geothermal systems, and geologic carbon sequestration have already begun to promote a constructive dialog between the static and dynamic views of permeability, and here we have made a conscious effort to include both viewpoints. This special issue also focuses on the quantification of permeability, encompassing both direct measurement of permeability in the uppermost crust and inferential permeability estimates, mainly for the deeper crust.

Geofluids↗

USGS2013

Historical methane hydrate project review

In 1995, U.S. Geological Survey made the first systematic assessment of the volume of natural gas stored in the hydrate accumulations of the United States. That study, along with numerous other studies, has shown that the amount of gas stored as methane hydrates in the world greatly exceeds the volume of known conventional gas resources. However, gas hydrates represent both a scientific and technical challenge and much remains to be learned about their characteristics and occurrence in nature. Methane hydrate research in recent years has mostly focused on: (1) documenting the geologic parameters that control the occurrence and stability of gas hydrates in nature, (2) assessing the volume of natural gas stored within various gas hydrate accumulations, (3) analyzing the production response and characteristics of methane hydrates, (4) identifying and predicting natural and induced environmental and climate impacts of natural gas hydrates, and (5) analyzing the effects of methane hydrate on drilling safety. Methane hydrates are naturally occurring crystalline substances composed of water and gas, in which a solid water-‐lattice holds gas molecules in a cage-‐like structure. The gas and water becomes a solid under specific temperature and pressure conditions within the Earth, called the hydrate stability zone. Other factors that control the presence of methane hydrate in nature include the source of the gas included within the hydrates, the physical and chemical controls on the migration of gas with a sedimentary basin containing methane hydrates, the availability of the water also included in the hydrate structure, and the presence of a suitable host sediment or “reservoir”. The geologic controls on the occurrence of gas hydrates have become collectively known as the “methane hydrate petroleum system”, which has become the focus of numerous hydrate research programs. Recognizing the importance of methane hydrate research and the need for a coordinated effort, the U.S. Congress enacted Public Law 106-‐193, the Methane Hydrate Research and Development Act of 2000. This Act called for the Secretary of Energy to begin a methane hydrate research and development program in consultation with other U.S. federal agencies. At the same time a new methane hydrate research program had been launched in Japan by the Ministry of International Trade and Industry to develop plans for a methane hydrate exploratory drilling project in the Nankai Trough. Since this early start we have seen other countries including India, China, Canada, and the Republic of Korea establish large gas hydrate research and development programs. These national led efforts have also included the investment in a long list of important scientific research drilling expeditions and production test studies that have provided a wealth of information on the occurrence of methane hydrate in nature. The most notable expeditions and projects have including the following: -‐Ocean Drilling Program Leg 164 (1995) -‐Japan Nankai Trough Project (1999-‐2000) -‐Ocean Drilling Program Leg 204 (2004) -‐Japan Tokai-‐oki to Kumano-‐nada Project (2004) -‐Gulf of Mexico JIP Leg I (2005) -‐Integrated Ocean Drilling Program Expedition 311 (2005) -‐Malaysia Gumusut-‐Kakap Project (2006) -‐India NGHP Expedition 01 (2006) -‐China GMGS Expedition 01 (2007) -‐Republic of Korea UBGH Expedition 01 (2007) -‐Gulf of Mexico JIP Leg II (2009) -‐Republic of Korea UBGH Expedition 02 (2010) -‐MH-‐21 Nankai Trough Pre-‐Production Expedition (2012-‐2013) -‐Mallik Gas Hydrate Testing Projects (1998/2002/2007-‐2008) -‐Alaska Mount Elbert Stratigraphic Test Well (2007) -‐Alaska Iġnik Sikumi Methane Hydrate Production Test Well (2011-‐2012) Research coring and seismic programs carried out by the Ocean Drilling Program (ODP) and Integrated Ocean Drilling Program (IODP), starting with the ODP Leg 164 drilling of the Blake Ridge in the Atlantic Ocean in 1995, have also contributed greatly to our understanding of the geologic controls on the formation, occurrence, and stability of gas hydrates in marine environments. For the most part methane hydrate research expeditions carried out by the ODP and IODP provided the foundation for our scientific understanding of gas hydrates. The methane hydrate research efforts under ODP-‐IODP have mostly dealt with the assessment of the geologic controls on the occurrence of gas hydrate, with a specific goal to study the role methane hydrates may play in the global carbon cycle. Over the last 10 years, national led methane hydrate research programs, along with industry interest have led to the development and execution of major methane hydrate production field test programs. Two of the most important production field testing programs have been conducted at the Mallik site in the Mackenzie River Delta of Canada and in the Eileen methane hydrate accumulation on the North Slope of Alaska. Most recently we have also seen the completion of the world’s first marine methane hydrate production test in the Nankai Trough in the offshore of Japan. Industry interest in gas hydrates has also included important projects that have dealt with the assessment of geologic hazards associated with the presence of hydrates. The scientific drilling and associated coring, logging, and borehole monitoring technologies developed in the long list of methane hydrate related field studies are one of the most important developments and contributions associated with methane hydrate research and development activities. Methane hydrate drilling has been conducted from advanced scientific drilling platforms like the JOIDES Resolution and the D/V Chikyu, which feature highly advanced integrated core laboratories and borehole logging capabilities. Hydrate research drilling has also included the use of a wide array of industry, geotechnical and multi-‐service ships. All of which have been effectively used to collect invaluable geologic and engineering data on the occurrence of methane hydrates throughout the world. Technologies designed specifically for the collection and analysis of undisturbed methane hydrate samples have included the development of a host of pressure core systems and associated specialty laboratory apparatus. The study and use of both wireline conveyed and logging-‐while-‐drilling technologies have also contributed greatly to our understanding of the in-‐situ nature of hydrate-‐bearing sediments. Recent developments in borehole instrumentation specifically designed to monitor changes associated with hydrates in nature through time or to evaluate the response of hydrate accumulations to production have also contributed greatly to our understanding of the complex nature and evolution of methane hydrate systems. Our understanding of how methane hydrates occur and behave in nature is still growing and evolving – we do not yet know if methane hydrates can be economically produced, nor do we know fully the role of hydrates as an agent of climate change or as a geologic hazard. But it is known for certain that scientific drilling has contributed greatly to our understanding of hydrates in nature and will continue to be a critical source of the information to advance our understanding of methane hydrates.

Report↗

USGS2014

Geologic framework for the national assessment of carbon dioxide storage resources: Williston Basin, Central Montana Basins, and Montana Thrust Belt study areas

The 2007 Energy Independence and Security Act directs the U.S. Geological Survey (USGS) to conduct a national assessment of potential geologic storage resources for carbon dioxide (CO 2 ). The methodology used by the USGS for the national CO 2 assessment follows that of previous USGS work. This methodology is non-economic and is intended to be used at regional to sub-basinal scales. The Williston Basin of North Dakota, South Dakota, and Montana, along with the Central Montana Basins and Montana Thrust Belt study areas are adjacent and share similar geologic units. In general, the Williston Basin study area is a wide sedimentary basin, whereas the Central Montana Basins study area contains sedimentary rocks along topographic highs and flat plains, and the Montana Thrust Belt study area is more structurally complex. This report identifies and contains geologic descriptions of nine storage assessment units (SAUs) in Cambrian to Upper Cretaceous sedimentary rocks within the Williston Basin study area. The Central Montana Basins and Montana Thrust Belt study areas were also investigated for this report. Nevertheless, no SAUs in these study areas were assessed because they contained potential sources of underground drinking water; although sufficient geologic data were available, and suitable storage formations meeting our size, depth, reservoir quality, and regional seal guidelines were found. Ultimately, the report focuses on the characteristics, specified in the methodology, that influence the potential CO 2 storage resource in the SAUs. Specific descriptions of the SAU boundaries as well as their sealing and reservoir units are included. Properties for each SAU, such as depth to top, gross thickness, porosity, permeability, groundwater quality, and structural reservoir traps, are usually provided to illustrate geologic factors critical to the assessment. The geologic information herein was employed, as specified in the USGS methodology, to calculate a probabilistic distribution of potential storage resources in each SAU with these assessment outputs contained in a companion results report. Figures in this report show the study area boundaries along with the SAU extent and cell maps of well penetrations through sealing units into the top of the storage formations. The USGS does not necessarily know the location of all wells and cannot guarantee the full extent of drilling through specific formations in any given cell shown on the cell maps.

Montana, North Dakota, South Dakota↗

USGS1999

Ten years of studies on Maryland's inner Continental Margin and coastal bays

During the past ten years of the Association of American State Geologists-Mineral Management Service Continental Margins Program, the Maryland Geological Survey investigated the sedimentological, paleontological, stratigraphical and geophysical character of Maryland's inner continental shelf. Based on seismic records and sedimentological analyses completed during the first four years, a late Quaternary stratigraphic model was developed. Five distinct stratigraphic units were identified and described on the Maryland inner shelf. These units represent late Pleistocene interglacial deposits, the oldest of which corresponds to pre-Illinoian (oxygen-isotope stages 7 and/or 9) transgressive shelf sands. Overlying the Q1 unit, the Q2 unit is a 6-meter thick mud sequence of oxygen-isotope stage 5 (128-75 ka) age. Units Q3 and Q4 representing fluvial and leading edge estuarine deposits (oxygen-isotope stages 4, 3 and 2) filled numerous paleochannels that were incised into units Q2 and Q1. Modern trailing-edge transgressive shelf shoals (Unit Q5) discontinuously cap the sequence. The 5th and 6th years studies reported on the economic minerals of surficial and cored sediments. Vibracores collected off the Maryland's shelf during previous studies were analyzed for mineral types and abundances, weight percent of general size fractions, and heavy mineral (HM) content. Mineralogic maturity indices were compiled to correlate the THM and economic heavy minerals (EHM) abundances with position offshore, sediment type, and the indices themselves. For the 7th year, the Maryland Geological Survey re-examined geophysical records and lithological data originally collected by the Army Corps of Engineers to locate and assess beach fill borrow areas for the Ocean City Beach Replenishment Project. Data from 163 vibracores and over 300 kilometers of high-resolution seismic profile records collected off Ocean City, Maryland, supported the stratigraphic model developed by MGS during the first four years of the AASG-MMS program. The Maryland coastal bays became the focus of study during the 8th and 9th years during which seismic records, cores and surficial sediment were collected in Isle of Wight and Assawoman Bays. Shallow pretransgression surface was mapped, relating the existing streams to offshore paleochannels. The tenth year study focused on developing a repository for vibracores collected on Maryland's inner continental shelf.During the past ten years of the Association of American State Geologists-Mineral Management Service Continental Margins Program, the Maryland Geological Survey investigated the sedimentological, paleontological, stratigraphical and geophysical character of Maryland's inner continental shelf. Based on seismic records and sedimentological analysis completed during the first four years, a late quaternary stratigraphic model was developed. Five distinct stratigraphic units were identified and described on the Maryland inner shelf. These units represent late Pleistocene interglacial deposits, the oldest of which corresponds to pre-Illinoian transgressive shelf sands.

Marine Georesources and Geotechnology↗

USGS2000

Puerto Rico: Marine sediments, terrestrial and seafloor imagery, and tectonic interpretations

Introduction: Puerto Rico is an island situated in the plate boundary zone between the Caribbean and the North American Plates. This is a geologically fascinating, tectonically active region, where the Caribbean Plate has over-ridden the North American Plate and is now sliding past it with strike-slip motion. The details of this tectonic interaction are poorly understood, largely because much of the region lies under water, making it difficult to study. The geologic setting of Puerto Rico has created or contributed to several pressing societal issues, related to human safety, environmental health, and economic development. Because the island lies on an active plate boundary, earthquakes are a constant threat and the densely populated coastal areas are vulnerable to tsunamis. Coastal erosion is a concern in many coastal areas, but is particularly serious to an island economy which relies heavily on a thriving tourist industry. In Puerto Rico, illegal mining of beach sands for use as aggregate has exacerbated coastal erosion and left coastal communities more exposed to the ravages of storms and tsunamis. The serious need for an affordable local source of aggregate to use in the growing construction industry on the island has created a strong interest in locating and evaluating offshore sand and gravel deposits. During the last 20 years the U.S. Geological Survey, often in cooperation with the Puerto Rico Department of Natural Resources and/or the University of Puerto Rico, has conducted a variety of projects to address the geologic aspects of these pressing societal issues. The papers and data presented here are the results of these projects. Some have been previously published elsewhere; others, such as the database of surficial sediments of the Puerto Rico insular shelf, interpretation of side-looking airborne radar imagery of the island, and the GIS data, are presented here for the first time. The purpose of this CD is to make the results of these diverse studies available in a readily accessible digital form, so that managers, planners, and other researchers can utilize the results.

Puerto Rico↗

USGS2023

Assessment and characterization of ephemeral stream channel stability in the Grand Valley, Colorado, 2018-22

The purpose of this study is to provide information regarding the stability of ephemeral streams on the north side of the Grand Valley, Colorado. The ungaged ephemeral streams in this semiarid region are of particular interest because (1) the underlying bedrock geology, Mancos Shale, is a sedimentary rock deposit that has been identified as a major contributor of salinity to the Colorado River and (2) despite infrequent flows of short duration, monsoon derived floods in these ephemeral streams can carry substantial amounts of sediment downstream, affecting up and downstream banks and channel cross sections. The study area is of interest as salinity, or the total dissolved solids concentration, in the Colorado River causes an estimated $300 to $400 million per year in economic damages in the United States and it is estimated that 62% of Upper Colorado River Basin dissolved-solid loads originate from geologic sources. In an effort to minimize salt contributions to the Colorado River from public lands administered by the Bureau of Land Management (BLM) a comprehensive three-pronged salinity control approach is being used which incorporates (1) controlling point sources of salinity; (2) controlling nonpoint sources of salinity; and (3) preventing nonpoint sources of salinity from persisting. In 2018, the U.S. Geological Survey, in cooperation with BLM, began an assessment of ephemeral streams located in the north side of the Grand Valley, Colorado, to characterize stream channel stability. The USGS developed a method for automatically extracting channel cross-section geometry from existing remotely sensed terrain models. Based on estimated flood stage and surrogate streamflows, hydraulic characteristics were calculated. Furthermore, the channel geometries and hydraulic characteristics were used to estimate channel stability utilizing a statistical model. In this ongoing study, cross-section stabilities were determined from a stream channel stability assessment for a subset of 1,406 visited locations out of a desired 13,415 cross sections which were delineated from remotely sensed terrain models. The application of Manning’s resistance equation in combination with multiple Logistic Regression models demonstrated that channel stability can be estimated with an 0.85 goodness of fit for a validation dataset when using a combination of drainage area, width to depth ratio, sinuosity, and shear stress as the explanatory variables. Stream channel stability was extrapolated for the remaining 13,415 unvisited cross sections using the multiple Logistic Regression model and defined explanatory variables. Mapping the ephemeral streams and their associated stabilities could be used to prioritize areas for BLM remediation or changes in management strategies to reduce sediment and salinity loading to the Colorado River.

Colorado↗

USGS2013

A framework for quantitative assessment of impacts related to energy and mineral resource development

Natural resource planning at all scales demands methods for assessing the impacts of resource development and use, and in particular it requires standardized methods that yield robust and unbiased results. Building from existing probabilistic methods for assessing the volumes of energy and mineral resources, we provide an algorithm for consistent, reproducible, quantitative assessment of resource development impacts. The approach combines probabilistic input data with Monte Carlo statistical methods to determine probabilistic outputs that convey the uncertainties inherent in the data. For example, one can utilize our algorithm to combine data from a natural gas resource assessment with maps of sage grouse leks and piñon-juniper woodlands in the same area to estimate possible future habitat impacts due to possible future gas development. As another example: one could combine geochemical data and maps of lynx habitat with data from a mineral deposit assessment in the same area to determine possible future mining impacts on water resources and lynx habitat. The approach can be applied to a broad range of positive and negative resource development impacts, such as water quantity or quality, economic benefits, or air quality, limited only by the availability of necessary input data and quantified relationships among geologic resources, development alternatives, and impacts. The framework enables quantitative evaluation of the trade-offs inherent in resource management decision-making, including cumulative impacts, to address societal concerns and policy aspects of resource development.

Natural Resources Research↗