Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Complexity”

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

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

At least 1,099 records · Page 61Linked to original sources
USGS1983

Petroleum geology and resources of southeastern Mexico, northern Guatemala, and Belize

Petroleum deposits in southeastern Mexico and Guatemala occur in two main basinal provinces, the Gulf Coast Tertiary basin area, which includes the Reforma and offshore Campeche Mesozoic fields, and the Peten basin of eastern Chiapas State (Mexico) and Guatemala. Gas production is mainly from Tertiary sandstone reservoirs of Miocene age. Major oil production, in order of importance, is from Cretaceous, Paleocene, and Jurassic carbonate reservoirs in the Reforma and offshore Campeche areas. Several small oil fields have been discovered in Cretaceous carbonate reservoirs in west-central Guatemala, and one major discovery has been reported in northwestern Guatemala. Small- to medium-sized oil accumulations also occur in Miocene sandstone reservoirs on salt structures in the Isthmus Saline basin of western Tabasco State, Mexico. Almost all important production is in salt structure traps or on domes and anticlines that may be related to deep-seated salt structures. Some minor oil production has occurred in Cretaceous carbonate reservoirs in a buried overthrust belt along the west flank of the Veracruz basin. The sedimentary cover of Paleozoic through Tertiary rocks ranges in thickness from about 6,000 m (20,000 ft) to as much as 12,000 m (40,000 ft) or more in most of the region. Paleozoic marine carbonate and clastic rocks 1,000 to 2,000 m (3,300 to 6,500 ft) thick overlie the metamorphic and igneous basement in part of the region; Triassic through Middle Jurassic red beds and evaporite deposits, including halite, apparently are present throughout the region, deposited in part in a Triassic graben system. Upper Jurassic (Oxfordian) through Cretaceous rocks make up the bulk of the Mesozoic regional carbonate bank complex, which dominates most of the area. Tertiary marine and continental clastic rocks, some of deep water origin, 3,000 to 10,000 m (10,000 to 35,000 ft) thick, are present in the coastal plain Tertiary basins. These beds grade eastward into a carbonate sequence that overlies the Mesozoic carbonate complex on the Yucatan platform. During the past 10 years, about 50 large oil fields were discovered in the Reforma and offshore Campeche areas. Oil is produced from intensely microfractured Cretaceous, Paleocene, and Upper Jurassic dolomite reservoirs on blockfaulted salt swells or domes. Most fields are located in the Mesozoic carbonate-bank margin and forebank talus (Tamabra) facies, which passes through the offshore Campeche and onshore Reforma areas. Oil source rocks are believed to be organic-rich shales and shaly carbonate rocks of latest Jurassic and possibly Early Cretaceous age. At least six of the Mesozoic discoveries are giant or supergiant fields. The largest is the Cantarell complex (about 8 billion to 10 billion barrels (BB)) in the offshore Campeche area and the Bermudez complex (about 8 BB) in the Reforma onshore area. Oil columns are unusually large (from 50 m to as much as 1,000 m, or 160 ft to 3,300 ft). Production rates are extremely high, averaging at least 3,000 to 5,000 barrels of oil per day (bo/d); some wells produce more than 20,000 bo/d, particularly in the offshore Campeche area, where 30,000- to 60,000-bo/d wells are reported. Tertiary basin fields produce primarily from Miocene sandstone reservoirs. About 50 of these are oil fields ranging from 1 million barrels (MMB) to 200 MMB in size, located on faulted salt structures in the Isthmus Saline basin. Another 30 are gas or gas-condensate fields of a few billion cubic feet to 3 trillion to 4 trillion cubic feet (Tcf) located on salt structures or probable salt structures in the Macuspana, Comalcalco, Isthmus Saline, and Veracruz basins. Source rocks for the gas are believed to be carbonaceous shales interbedded with the sandstone reservoir bodies. Identified reserves in the southeastern Mexico-Guatemala area, almost all in the Mesozoic fields, are about 53 BB of oil, 3 BB of natural gas liquids, and 65 Tcf of gas. The estimat

Circular↗
USGS2009

Fort Collins Science Center Ecosystem Dynamics Branch

Complex natural resource issues require understanding a web of interactions among ecosystem components that are (1) interdisciplinary, encompassing physical, chemical, and biological processes; (2) spatially complex, involving movements of animals, water, and airborne materials across a range of landscapes and jurisdictions; and (3) temporally complex, occurring over days, weeks, or years, sometimes involving response lags to alteration or exhibiting large natural variation. Scientists in the Ecosystem Dynamics Branch of the U.S. Geological Survey, Fort Collins Science Center, investigate a diversity of these complex natural resource questions at the landscape and systems levels. This Fact Sheet describes the work of the Ecosystems Dynamics Branch, which is focused on energy and land use, climate change and long-term integrated assessments, herbivore-ecosystem interactions, fire and post-fire restoration, and environmental flows and river restoration.

Fact Sheet↗
USGS2001

Geologic Map of the Thaumasia Region, Mars

The geology of the Thaumasia region (fig. 1, sheet 3) includes a wide array of rock materials, depositional and erosional landforms, and tectonic structures. The region is dominated by the Thaumasia plateau, which includes central high lava plains ringed by highly deformed highlands; the plateau may comprise the ancestral center of Tharsis tectonism (Frey, 1979; Plescia and Saunders, 1982). The extensive structural deformation of the map region, which is without parallel on Mars in both complexity and diversity, occurred largely throughout the Noachian and Hesperian periods (Tanaka and Davis, 1988; Scott and Dohm, 1990a). The deformation produced small and large extensional and contractional structures (fig. 2, sheet 3) that resulted from stresses related to the formation of Tharsis (Frey, 1979; Wise and others, 1979; Plescia and Saunders, 1982; Banerdt and others, 1982, 1992; Watters and Maxwell, 1986; Tanaka and Davis, 1988; Francis, 1988; Watters, 1993; Schultz and Tanaka, 1994), from magmatic-driven uplifts, such as at Syria Planum (Tanaka and Davis, 1988; Dohm and others, 1998; Dohm and Tanaka, 1999) and central Valles Marineris (Dohm and others, 1998, Dohm and Tanaka, 1999), and from the Argyre impact (Wilhelms, 1973; Scott and Tanaka, 1986). In addition, volcanic, eolian, and fluvial processes have highly modified older surfaces in the map region. Local volcanic and tectonic activity often accompanied episodes of valley formation. Our mapping depicts and describes the diverse terrains and complex geologic history of this unique ancient tectonic region of Mars. The geologic (sheet 1), paleotectonic (sheet 2), and paleoerosional (sheet 3) maps of the Thaumasia region were compiled on a Viking 1:5,000,000-scale digital photomosaic base. The base is a combination of four quadrangles: the southeast part of Phoenicis Lacus (MC–17), most of the southern half of Coprates (MC–18), a large part of Thaumasia (MC–25), and the northwest margin of Argyre (MC–26). The medium-resolution Viking images used for mapping and base preparation also formed the basis of the 1:2,000,000 scale subquadrangle series. Earlier geologic maps of all or parts of the region include: (1) maps of the Phoenicis Lacus, Coprates, Thaumasia, and Argyre quadrangles at 1:5,000,000 scale based mainly on Mariner 9 images (respectively, Masursky and others, 1978; McCauley, 1978; McGill, 1978; and Hodges, 1980), (2) the global map of Mars at 1:25,000,000 (Scott and Carr, 1978) compiled largely from the 1:5,000,000 scale geologic maps, (3) maps showing lava flows in the Tharsis region at 1:2,000,000 scale compiled from Viking and Mariner 9 images (Scott, 1981; Scott and Tanaka, 1981a, b; Scott and others, 1981), (4) the map of the western equatorial region of Mars at 1:15,000,000 scale based on Viking images (Scott and Tanaka, 1986), and (5) the map of the Valles Marineris region at 1:2,000,000 scale compiled from Viking images (Witbeck and others, 1991). The previous maps have described the overall geology and geomorphology of the region but have not unraveled the detailed stratigraphy and complex evolution of this unique and geologically diverse martian province. The main purpose of this comprehensive mapping project is to reconstruct the stratigraphic, structural, and erosional histories of the Thaumasia region. The region is the last major province of the Tharsis region to undergo detailed structural mapping using Viking images; its history is essential to documenting the overall tectonic history of Tharsis. Other provinces of Tharsis that have been structurally mapped include Syria Planum (Tanaka and Davis, 1988), Tempe Terra and Ulysses Patera (Scott and Dohm, 1990b), and Alba Patera (Tanaka, 1990). Another primary mapping objective is to determine the region's volcanic history and assess the relations among fault systems and volcanoes (Wise and others, 1979; Scott and Tanaka, 1980; Whitford-Stark, 1982; Scott and Dohm, 1990a). A secondary mapping objective is to determine the distribution and ages of valleys. In our study, we incorporated detailed photogeologic mapping, comprehensive crater statistics (table 1), and geologic, paleotectonic, and paleoerosional Geographic Information System (GIS) databases. Sheets 1–3 show geologic units, faults and other significant structures, and valleys, respectively. To help unravel the complex geologic history of the Thaumasia region, we transferred the highly detailed geologic unit, paleotectonic, and paleoerosional information of sheets 1–3 into a multilayered GIS database for comparative analysis. The geologic information was transferred from hard copy into a digital format by scanning at 25 micron resolution on a drum scanner. The 2-bit scanned image was then converted to an x,y coordinate system using ARC/INFO's vectorization routine. The geologic unit, structural, and erosional data were transformed into the original map projection, Lambert Conformal. The average transformation root mean square error was 0.25 km (acceptable for the Thaumasia map base at 1:5,000,000 scale). After transformation, the features were properly attributed and tediously checked. Once digitized, the map data can be transformed into any map projection depending on the type of data analysis. For example, the equal-area sinusoidal projection was used for determining the precise area of geologic units (table 1). In addition to the geologic map and its attendant stratigraphic section, correlation chart, and description of map units, we include text sections that clarify the histories and temporal, spatial, and causal relations of the various geologic units and landforms of the Thaumasia region. The geologic summary section defines the sequence of major geologic events.

IMAP↗
USGS2000

Geologic map of the Wildcat Lake 7.5' quadrangle, Kitsap and Mason Counties, Washington

The Wildcat Lake quadrangle lies in the forearc of the Cascadia subduction zone, about 20-km east of the Cascadia accretionary complex exposed in the Olympic Mountains (Tabor and Cady, 1978),and about 100-km west of the axis of the Cascades volcanic arc. The quadrangle lies near the middle of the Puget Lowland, which typically has elevations less than 600 feet (183 m), but on Gold Mountain, in the center of the quadrangle, the elevation rises to 1761 feet (537 m). This anomalously high topography also provides a glimpse of the deeper crust beneath the Lowland. Exposed on Green and Gold Mountains are rocks related to the Coast Range basalt terrane. This terrane consists of Eocene submarine and subaerial tholeiitic basalt of the Crescent Formation, which probably accreted to the continental margin in Eocene time (Snavely and others, 1968). The Coast Range basalt terrane may have originated as an oceanic plateau or by oblique marginal rifting (Babcock and others, 1992), but its subsequent emplacement history is complex (Wells and others, 1984). In southern Oregon, onlapping strata constrain the suturing to have occurred by 50 Ma; but on southern Vancouver Island where the terrane-bounding Leech River fault is exposed, Brandon and Vance (1992) concluded suturing to North America occurred in the broad interval between 42 and 24 Ma. After emplacement of the Coast Range basalt terrane, the Cascadia accretionary complex,exposed in the Olympic Mountains west of the quadrangle,developed by frontal accretion and underplating (e.g., Clowes and others, 1987). The Seattle basin, part of which lies to the north of Green Mountain, also began to develop in late Eocene time due to forced flexural subsidence along the Seattle fault zone (Johnson and others, 1994). Domal uplift of the accretionary complex beneath the Olympic Mountains occurred after approximately 18 million years ago (Brandon and others, 1998). Ice-sheet glaciation during Quaternary time reshaped the topography of the quadrangle, and approximately two-thirds of the map area is covered with Quaternary deposits related to the last glaciation. Geophysical studies and regional mapping indicate the Seattle fault lies north of Green Mountain. This fault produced a large earthquake about 1000 years ago and may pose a significant earthquake hazard (Bucknam and others, 1992; Atwater and Moore, 1992; Karlin and Abella,1992; Schuster and others, 1992; Jacoby and others, 1992). We found no evidence of Holocene faulting in the Wildcat Lake quadrangle. Geologic mapping within and marginal to the quadrangle began with Willis (1898), who described glacial deposits in Puget Sound. Weaver (1937) correlated volcanic rocks in the quadrangle to the Eocene Metchosin Volcanics on Vancouver Island. Sceva (1957), Garling and Moleenar (1965), and Deeter (1978) all focused on mapping and understanding the Quaternary stratigraphy of the Kitsap Peninsula, but they also examined bedrock in the quadrangle. Reeve (1979) was the first to examine the igneous rocks on Green and Gold Mountains in some detail, and Clark (1989) significantly improved Reeve's (1979) mapping. Clark's (1989) mapping was conducted soon after extensive logging on the mountains. A surficial geologic map of the Seattle 1:100,000-scale quadrangle, which includes the Wildcat Lake 1:24,000-scale quadrangle, was published by Yount and others (1993). Yount and Gower (1991) also published a bedrock geologic map of the Seattle quadrangle. Geologic mapping for this report was conducted by Haeussler in the spring and summer of 1998 and in the winter of 1999. We could not substantially improve upon the bedrock mapping of Clark (1989) and thus it is incorporated into this map. Well data in the southeastern corner of the map area also helped to constrain the surficial mapping (Geomatrix Consultants, 1997). In addition, 1995 vintage 1:12,000-scale aerial photographs were used in mapping Quaternary deposits. Geologic time scale is that of Berggeren and others (1995).

Washington↗
USGS2004

Lahar Hazards at Casita and San Cristóbal Volcanoes, Nicaragua

Casita and San Cristóbal volcanoes are part of a volcano complex situated at the eastern end of the Cordillera de los Maribios. Other centers of volcanism in the complex include El Chonco, Cerro Moyotepe, and La Pelona. At 1745 m, San Cristóbal is the highest and only historically active volcano of the complex. The volcano’s crater is 500 to 600 m across and elongate east to west; its western rim is more than 100 m higher than its eastern rim. The conical volcano is both steep and symmetrical. El Chonco, which lies west of San Cristóbal, is crudely conical but has been deeply dissected by streams. Cerro Moyotepe to the northeast of San Cristóbal is even more deeply incised by erosion than El Chonco, and its crater is breached by erosion. Casita volcano, about 5 km east of San Cristóbal volcano, comprises a broad ridge like form, elongate along an eastwest axis, that is deeply dissected. Nested along the ridge are two craters. The younger one, La Ollada crater, truncates an older smaller crater to the east near Casita’s summit (1430 m). La Ollada crater is about 1 km across and 100 m deep. Numerous small fumarole fields occur near the summit of Casita and on nearby slopes outside of the craters. Casita volcano overlaps the 3-km-wide crater of La Pelona to the east. Stream erosion has deeply incised the slopes of La Pelona, and it is likely the oldest center of the Casita-San Cristóbal volcano complex. In late October and early November 1998, torrential rains of Hurricane Mitch caused numerous slope failures in Central America. The most catastrophic occurred at Casita volcano, on October 30, 1998. At Casita, five days of heavy rain triggered a 1.6-million-cubic-meter rock and debris avalanche that generated an 2- to 4- million-cubic-meter debris flow that swept down the steep slopes of the volcano. The debris flow spread out across the volcano’s apron, destroyed two towns, and killed more than 2500 people. In prehistoric time, Casita erupted explosively to form ash-fall deposits (tephra), debris avalanches, lava flows, and hot flowing mixtures of ash and rock (called pyroclastic flows). The chronology of activity at Casita is rather poorly known. Its last documented eruption occurred 8300 years ago, and included a pyroclastic flow. Tephra deposits exposed in the east crater suggest the possibility of subsequent eruptions. Work prior to Hurricane Mitch suggested that a part of the volcano’s apron that included the area inundated during the 1998 event south of Casita was a lahar pathway. Erosion during Hurricane Mitch revealed that at least three large lahars descended this pathway to distances of up to 10 km. This report describes the hazards of landslides and lahars in general, and discusses potential hazards from future landslides and lahars at San Cristóbal and Casita volcanoes in particular. The report also shows, in the accompanying lahar hazard-zonation maps, which areas are likely to be at risk from future landslides and lahars at Casita and San Cristóbal.

Open-File Report↗
USGS2005

Evaluation of unsaturated-zone solute-transport models for studies of agricultural chemicals

Seven unsaturated-zone solute-transport models were tested with two data sets to select models for use by the Agricultural Chemical Team of the U.S. Geological Survey's National Water-Quality Assessment Program. The data sets were from a bromide tracer test near Merced, California, and an atrazine study in the White River Basin, Indiana. In this study the models are designated either as complex or simple based on the water flux algorithm. The complex models, HYDRUS2D, LEACHP, RZWQM, and VS2DT, use Richards' equation to simulate water flux and are well suited to process understanding. The simple models, CALF, GLEAMS, and PRZM, use a tipping-bucket algorithm and are more amenable to extrapolation because they require fewer input parameters. The purpose of this report is not to endorse a particular model, but to describe useful features, potential capabilities, and possible limitations that emerged from working with the model input data sets. More rigorous assessment of model applicability involves proper calibration, which was beyond the scope of this study. Uncalibrated ("cold") simulations were run using all seven models to predict the transport of bromide (Merced) and the transport and fate of atrazine and three of its transformation products (White River Basin). Among the complex models, HYDRUS2D successfully predicted both the surface retention and accumulation of bromide at depth at the Merced site, whereas RZWQM and VS2DT predicted only the latter. RZWQM predictions of atrazine were closest to observed values at the White River Basin site, where preferential flow has been observed. LEACHP predicted smaller solute concentrations than observed at both the Merced and White River Basin sites. Among the simple models, CALF predicted the highest values of atrazine and deethylatrazine at the measurement depth of 1.5 meters. CALF includes the Addiscott flow option for preferential flow, and also accepts user-specified dispersivity. PRZM underpredicted solute concentrations, probably because control of dispersion is a problem with this model. GLEAMS has a maximum simulation depth of 1.5 meters, which is limiting for mass-balance purposes because it creates a potential disconnect between unsaturated-zone transport and the water table. Of the models tested, RZWQM, HYDRUS2D, VS2DT, GLEAMS and PRZM had graphical user interfaces. Extensive documentation was available for RZWQM, HYDRUS2D, and VS2DT. RZWQM can explicitly simulate water and solute flux in macropores, and both HYDRUS2D and VS2DT can simulate water and solute flux in two dimensions. The version of RZWQM tested had a maximum simulation depth of 3 meters. The complex models simulate the formation, transport, and fate of degradates of up to three to five compounds including the parent, with the exception of VS2DT, which simulates the transport and fate of a single compound.

California, Indiana↗
USGS2006

Surficial sediment character of the Louisiana offshore continental shelf region: A GIS compilation

The Louisiana coastal zone, comprising the Mississippi River delta plain stretching nearly 400 km from Sabine Pass at the Texas border east to the Chandeleur Islands at the Mississippi border, represents one of North America’s most important coastal ecosystems in terms of natural resources, human infrastructure, and cultural heritage. At the same time, this region has the highest rates of coastal erosion and wetland loss in the Nation due to a complex combination of natural processes and anthropogenic actions over the past century. Comparison of historical maps dating back to 1855 and recent aerial photography show the Louisiana coast undergoing net erosion at highly variable rates. Rates have increased significantly during the past several decades. Earlier published statewide average shoreline erosion rates were >6 m/yr; rates have increased recently to >10 m/yr. The increase is attributable to collective action of storms, rapid subsidence, and pervasive man-made alterations of the rivers and the coast. In response to the dramatic landloss, regional-scale restoration plans are being developed by a partnership of federal and state agencies for the delta plain that have the objectives of maintaining the barrier islands, reducing wetland loss, and enhancing the natural sediment delivery processes. There is growing awareness that the sustainability of coastal Louisiana's natural resources and human infrastructure depends on the successful restoration of natural geologic processes. Critical to the long term success of restoration is scientific understanding of the geologic history and processes of the coastal zone region, including interactions between the rivers, wetlands, coast, and inner shelf. A variety of geophysical studies and mapping of Late Quaternary sedimentary framework and coastal processes by U.S. Geological Survey and other scientists during the past 50 years document that the Louisiana delta plain is the product of a complex history of cyclic delta switching by the Mississippi River and its distributaries over the past ~10,000 years that resulted in laterally overlapping deltaic depocenters. The interactions among riverine, coastal, and inner shelf processes have been superimposed on the Holocene transgression resulting in distinctive landforms and sedimentary sequences. Four Holocene shelf-phase delta complexes have been identified using seismic reflection data and vibracores. Each delta complex is bounded by transgressive surfaces. Following each cycle of deposition and abandonment, the delta lobes undergo regional subsidence and marine reworking that forms transgressive coastal systems and barrier islands. Ultimately, the distal end of each of the abandoned delta lobes is marked by submerged marine sand bodies representing drowned barriers. These sand bodies (e.g. Ship Shoal, Outer Shoal, Trinity Shoal, Tiger Shoal, St. Bernard Shoal) offer the largest volumes and highest quality sand for beach nourishment and shoreline and wetlands restoration. These four large sand shoals on inner continental shelf, representing the reworked remnants of former prograded deltaic headlands that existed on the continental shelf at lower sea level, were generated in the retreat path of the Mississippi River delta plain during the Holocene transgression. Penland and others (1989) have shown these sand bodies represent former shoreline positions associated with lower still stands in sea level. Short periods of rapid relative sea-level rise led to the transgressive submergence of the shorelines which today can be recognized at the -10 m to -20 m isobaths on the Louisiana continental shelf. Trinity Shoal and Ship Shoal represent the -10 m middle-to-late Holocene shoreline trend, whereas Outer Shoal and the St. Bernard Shoals define the -20 m early Holocene shoreline trend (Penland and others, 1989). Collectively, these sand shoals constitute a large volume of high quality sandy sediment potentially suitable for barrier island nourishment and coastal restoration. The USGS has actively supported coastal and wetlands geologic research for the past two decades in partnership with universities (e.g., Louisiana State University, University of New Orleans), state agencies (e.g. Louisiana Geological Survey, Louisiana Department of Natural Resources), and private organizations (Williams and others, 1992a,b; Williams and Cichon, 1993; List and others, 1994). These studies have focused on regional-scale mapping of coastal and wetland change and developing a better understanding of the processes that cause coastal erosion and wetlands loss, particularly the rapid deterioration of Louisiana's barrier islands, estuaries, and wetlands environments. With a better understanding of these processes, the ability to model and predict erosion and wetlands loss will improve. More accurate predictions will, in turn, allow for proper management of coastal resources. Improved predictions will also allow for better assessments of the utility of different restoration alternatives.

Louisiana↗
USGS2012

Magmatic ore deposits in layered intrusions - Descriptive model for reef-type PGE and contact-type Cu-Ni-PGE deposits

Layered, ultramafic to mafic intrusions are uncommon in the geologic record, but host magmatic ore deposits containing most of the world's economic concentrations of platinum-group elements (PGE) (figs. 1 and 2). These deposits are mined primarily for their platinum, palladium, and rhodium contents (table 1). Magmatic ore deposits are derived from accumulations of crystals of metallic oxides, or immiscible sulfide, or oxide liquids that formed during the cooling and crystallization of magma, typically with mafic to ultramafic compositions. "PGE reefs" are stratabound PGE-enriched lode mineralization in mafic to ultramafic layered intrusions. The term "reef" is derived from Australian and South African literature for this style of mineralization and used to refer to (1) the rock layer that is mineralized and has distinctive texture or mineralogy (Naldrett, 2004), or (2) the PGE-enriched sulfide mineralization that occurs within the rock layer. For example, Viljoen (1999) broadly defined the Merensky Reef as "a mineralized zone within or closely associated with an unconformity surface in the ultramafic cumulate at the base of the Merensky Cyclic Unit." In this report, we will use the term PGE reef to refer to the PGE-enriched mineralization, not the host rock layer. Within a layered igneous intrusion, reef-type mineralization is laterally persistent along strike, extending for the length of the intrusion, typically tens to hundreds of kilometers. However, the mineralized interval is thin, generally centimeters to meters thick, relative to the stratigraphic thickness of layers in an intrusion that vary from hundreds to thousands of meters. PGE-enriched sulfide mineralization is also found near the contacts or margins of layered mafic to ultramafic intrusions (Iljina and Lee, 2005). This contact-type mineralization consists of disseminated to massive concentrations of iron-copper-nickel-PGE-enriched sulfide mineral concentrations in zones that can be tens to hundreds of meters thick. The modes and textures of the igneous rocks hosting the mineralization vary irregularly on the scale of centimeters to meters; autoliths and xenoliths are common. Mineralization occurs in the igneous intrusion and in the surrounding country rocks. Mineralization can be preferentially localized along contact with country rocks that are enriched in sulfur-, iron-, or CO2-bearing lithologies. Reef-type and contact-type deposits, in particular those in the Bushveld Complex, South Africa, are the world's primary source of platinum and rhodium (tables 2 and 3; fig. 2). Reef-type PGE deposits are mined only in the Bushveld Complex (Merensky Reef and UG2), the Stillwater Complex (J-M Reef), and the Great Dyke (Main Sulphide Layer). PGE-enriched contact-type deposits are only mined in the Bushveld Complex. The other deposits in tables 2 and 3 are undeveloped; some are still under exploration.

Open-File Report↗
USGS2015

Algoma-, Superior-, and oolitic-type iron deposits of the Islamic Republic of Mauritania (phase V, deliverable 83)

High-grade hematitic iron ores (or HIF, containing 60–65 percent Fe) have been mined in Mauritania from Superior-type iron deposits since 1952. Depletion of the high grade ores in recent years has resulted in a number of new projects focused on lower grade magnetite ores in Algoma-type banded iron formation (or BIF, containing approximately 35 percent Fe). Large deposits of oolitic-type iron ores are also present in Phanerozoic sedimentary rocks in Mauritania. According to recent U.S. Geological Survey figures, Mauritania is the fifteenth largest iron producer in the World and currently has about 1.1 billion tonnes of crude iron ore reserves (USGS, 2012). The main hosts for Algoma-type iron ore are BIF in: (1) the Mesoarchean rocks of the Tiris Complex and (2) Amsaga Complex, (3) the Mesoarchean Lebzenia Group in the greenstone belts of the Tasiast-Tijirit terrane, and (4) the Saouda Group of the Inchiri district. Neoarchean Algoma-type BIF is present in the (5) Eizzene and Oumachouema Groups of the Inchiri district, (6) the Ijibbitene Group of the Ijibbitene massif, and (7) the Guenieba and Gadel Groups of the Gorgol Noir Complex in the southern Mauritanides. Superior-type iron ores are restricted to the allochthonous Paleoproterozoic sequences of the Kediat Ijil and Guelb El Mhaoudat, which overlie the Tiris Complex. Paleoproterozoic BIF are present in the Sfariat belt, which hosts at least three known occurrences, and at Guelb Zednes, all of which are interpreted as fragments of Superior-type iron formation that have been either imbricated with or allochthonously deposited on the Mesoarchean-Paleoproterozoic suture zone during the Birimian orogeny. Phanerozoic oolitic ironstones are hosted in the upper Silurian and lower Devonian rocks of the Gara Bouya Ali Group and the Zemmour Group in the Tindouf Basin in northern Mauritania and in the end Ordovician Tichit Group, the Silurian Oued Chig Group, and the lower Devonian Tenemouj Group in the Taoudeni Basin near Tidjikja. These rock groups define 11 permissive tracts for Algoma-, Superior-, and oolitic-type iron deposits in Mauritania.

Open-File Report↗
USGS2014

Waterbird egg mercury concentrations in response to wetland restoration in south San Francisco Bay, California

The conversion of 50–90 percent of 15,100 acres of former salt evaporation ponds to tidal marsh habitat in the south San Francisco Bay, California, is planned as part of the South Bay Salt Pond Restoration Project. This large-scale habitat restoration may change the bioavailability of methylmercury. The South Bay already is known to have high methylmercury concentrations, with methylmercury concentrations in several waterbirds species more than known toxicity thresholds where avian reproduction is impaired. In this 2013 study, we continued monitoring bird egg mercury concentrations in response to the restoration of the Pond A8/A7/A5 Complex to a potential tidal marsh in the future. The restoration of the Pond A8/A7/A5 Complex began in autumn 2010, and the Pond A8 Notch was opened 5 feet (one of eight gates) to muted tidal action on June 1, 2011, and then closed in the winter. In autumn 2010, internal levees between Ponds A8, A7, and A5 were breached and water depths were substantially increased by flooding the Pond A8/A7/A5 Complex in February 2011. In June 2012, 15 feet (three of eight gates) of the Pond A8 Notch was opened, and then closed in December 2012. In June 2013, 15 feet of the Pond A8 Notch again was opened, and the Pond A8/A7/A5 Complex was a relatively deep and large pond with muted tidal action in the summer. This report synthesizes waterbird data from the 2013 breeding season, and combines it with our prior study’s data from 2010 and 2011.

California↗
USGS2018

Bedrock geologic map of the Miles Pond and Concord quadrangles, Essex and Caledonia Counties, Vermont, and Grafton County, New Hampshire

The bedrock geologic map of the Miles Pond and Concord quadrangles covers an area of approximately 107 square miles (276 square kilometers) in east-central Vermont and adjacent New Hampshire, north of and along the Connecticut River. This map was created as part of a larger effort to produce a new bedrock geologic map of Vermont through the collection of field data at a scale of 1:24,000. The majority of the map area consists of the Bronson Hill anticlinorium, a post-Early Devonian structure that is cored by metamorphosed Cambrian to Silurian sedimentary, volcanic, and plutonic rocks. A major feature on the map is the Monroe fault, interpreted to be a west-directed, steeply dipping Late Devonian (Acadian) thrust fault. To the west of the Monroe fault, rocks of the Connecticut Valley-Gaspé trough dominate and consist primarily of metamorphosed Silurian and Devonian sedimentary rocks. To the north, the Victory pluton intrudes the Bronson Hill anticlinorium. The Bronson Hill anticlinorium consists of the metamorphosed Albee Formation, the Ammonoosuc Volcanics, the Comerford Intrusive Complex, the Highlandcroft Granodiorite, and the Joselin Turn tonalite. The Albee Formation is an interlayered, feldspathic metasandstone and pelite that is locally sulfidic. Much of the deformed metasandstone is tectonically pinstriped. In places, one can see compositional layering that was transposed by a steeply southeast-dipping foliation. The Ammonoosuc Volcanics are lithologically complex and predominantly include interlayered and interfingered rhyolitic to basaltic volcanic and volcaniclastic rocks, as well as lesser amounts of siltstone, phyllite, graywacke, and grit. The Comerford Intrusive Complex crops out east of the Monroe fault and consists of metamorphosed gabbro, diorite, tonalite, aplitic tonalite, and crosscutting diabase dikes. Abundant mafic dikes from the Comerford Intrusive Complex intruded the Albee Formation and Ammonoosuc Volcanics east of the Monroe fault. The Highlandcroft Granodiorite and Joslin Turn tonalite plutons intruded during the Middle to Late Ordovician. West of the Monroe fault, the Connecticut Valley-Gaspé trough consists of the Silurian and Devonian Waits River and Gile Mountain Formations. The Waits River Formation is a carbonaceous muscovite-biotite-quartz (±garnet) phyllite containing abundant beds of micaceous quartz-rich limestone. The Gile Mountain Formation consists of interlayered metasandstone and graphitic (and commonly sulfidic) slate, along with minor calcareous metasandstone and ironstone. Graded bedding is common in the Gile Mountain Formation. Rocks of the Devonian New Hampshire Plutonic Suite intruded as plutons, dikes, and sills. The largest of these is the Victory pluton, which consists of weakly foliated, biotite granite and granodiorite. The Victory pluton also intruded a large part of the Albee Formation to the north. This report consists of a geologic map and an online geographic information systems database that includes contacts of bedrock geologic units, faults, outcrops, and structural geologic information. The geologic map is intended to serve as a foundation for applying geologic information to problems involving land use decisions, groundwater availability and quality, earth resources such as natural aggregate for construction, assessment of natural hazards, and engineering and environmental studies for waste disposal sites and construction projects.

New Hampshire, Vermont↗
USGS2018

Adaptive management in native grasslands managed by the U.S. Fish and Wildlife Service—Implications for grassland birds

Burning and grazing are natural processes in native prairies that also serve as important tools in grassland management to conserve plant diversity, to limit encroachment of woody and invasive plants, and to maintain or improve prairies. Native prairies managed by the U.S. Fish and Wildlife Service (FWS) in the Prairie Pothole Region of the northern Great Plains have been extensively invaded by nonnative, cool-season species of grasses. These invasions were believed to reflect a common management history of long-term rest and little or no defoliation by natural processes (burning and grazing). To address the challenges associated with these invasive species, the FWS embraced a collaborative approach in 2008, in partnership with U.S. Geological Survey, to restore native prairies on lands managed by FWS. This approach is known as the Native Prairie Adaptive Management (NPAM) initiative and was based on the application of an adaptive decision-support framework to assist managers in selecting management actions despite uncertainty and in maximizing learning from management outcomes. The primary objective of this approach was to increase the composition of native grasses and forbs on native, unbroken sod while minimizing costs. The alternative management actions that were used to meet this objective include grazing, burning, burning and grazing, and rest (no action). A major challenge for FWS resource managers participating in the NPAM initiative was the recognition that other taxa, besides native grasses and forbs, may be affected by the alternative management practices, thus complicating the adaptive-management cycle and deepening the uncertainty. Specifically, many grassland birds are sensitive to changes in vegetation composition and structure, and thus management that alters vegetation also may affect bird populations. The primary objectives of this study were to assess the effects of alternative management actions on grassland birds on FWS-owned grasslands that are managed under the adaptive-management framework, and to assess the association of vegetation structure and composition as mechanisms for triggering grassland bird responses to management. We surveyed breeding birds and sampled vegetation on 89 native prairie NPAM units managed by the FWS during 2011–13, including 55 units in 2011, 87 units in 2012, and 87 units in 2013. The NPAM units were in 19 FWS refuge complexes and wetland management districts, including 14 complexes in FWS Region 6 (North Dakota, South Dakota, and Montana) and 5 complexes in FWS Region 3 (Minnesota). Generalized linear mixed models were used to evaluate the effects of management actions on vegetation structure, vegetation composition, and densities of common bird species. Vegetation structure and composition varied among study units and years, and many of these differences were linked to specific management activities or to the recency of those activities. We recorded 110 bird species in the 89 adaptive-management units. Models of bird abundance reflected not only disturbance-derived changes in vegetation structure and species-specific vegetation preferences but also the influence of defoliation treatments. Vegetation composition was less important to grassland birds than vegetation structure; in particular, mean vertical obstruction (vegetation height-density), bare-ground cover, and litter depth positively or negatively influenced densities of some grassland bird species. The diversity of bird responses to management in this study underscores the complexity of natural grassland systems and the need for heterogeneity management in grasslands in this region.

Minnesota, Montana, North Dakota, South Dakota↗
USGS2021

Synthesis of geochronologic research on Late Pliocene to Holocene emergent shorelines in the lower Savannah River area of southeastern Georgia, USA

Emergent late Pliocene and Pleistocene shoreline deposits, morphologically identifiable Pleistocene shoreline units, and seaward-facing scarps characterize the easternmost Atlantic Coastal Plain (ACP) of the United States of America. In some areas of the ACP, these deposits, units, and scarps have been studied in detail. Within these areas, temporal and spatial data are sufficient for time-depositional frameworks for shoreline-evolution to have been developed and published. For other areas, such as the southeastern Atlantic Coastal Plain (SEACP), available data are conflicting and (or) insufficient to develop such a framework, or to make shoreline correlations. Differential epeirogenic uplift and shoreline deformation, resulting from mantle-flow and climate-induced isostatic adjustments, complicate regional shoreline correlations. In the SEACP, the topographically prominent Orangeburg Scarp (hereafter, the Scarp) rises tens of meters in elevation from southeastern Georgia to southeastern North Carolina. The degree to which the Scarp and shoreline units seaward of the Scarp are deformed continues to be debated, but there is general agreement that the lower Savannah River area (LSRA) of Georgia and South Carolina is the least deformed area of the SEACP. This paper synthesizes published and previously unpublished numerical age and stratigraphic data for emergent Pliocene and younger shoreline deposits in the LSRA in Georgia. Age data are applied to these shoreline deposits as they are delineated (map units) on the 1976 geologic map of Georgia by Lawton and others. Age assignments are based on stratigraphic position, fossil content, soil and weathering diagnostic properties, and numerical ages as determined by meteoric Beryllium‑10 paleosol residence time ( 10 BePRT), optically stimulated luminescence (OSL), uranium disequilibrium series (U-series), amino acid racemization (AAR), and radiocarbon ( 14 C) analyses. These data provide a preliminary Pliocene-Pleistocene geochronology for the Orangeburg Scarp and shoreline deposits seaward of the Scarp in the LSRA of Georgia. Minimum ages and age ranges indicate the following: the Orangeburg Scarp formed sometime in the late Pliocene and early Pleistocene, between 3 Ma and 1 Ma; three, and possibly four, shoreline complexes were deposited in the middle Pleistocene; two shoreline complexes were deposited in the late middle and the late Pleistocene; deposition of the youngest shoreline complex began in the late Pleistocene and continues to the present; each shoreline complex was modified by multiple sea level highstands over time periods that lasted tens of thousands to hundreds of thousands of years; and Pleistocene shoreline chronology differs in part from modeled global sea level highstands.

Georgia, South Carolina↗
USGS2021

Cape Romain partnership for coastal protection

This final report summarizes activities, outcomes, and lessons learned from a 3-year project titled “Climate Change Adaptation for Coastal National Wildlife Refuges” with the Cape Romain National Wildlife Refuge (NWR) and local partners in the surrounding South Carolina Lowcountry. The Lowcountry is classified as the 10-county area encompassing the coastal plain of South Carolina (this report specifically focuses on Berkeley, Charleston, and Georgetown Counties). The goals of this work, sponsored by the U.S. Geological Survey’s Southeast Climate Adaptation Science Center (SECASC), were to foster active engagement with stakeholders; to develop a comprehensive definition of adaptation problems faced by agencies, organizations, and individuals near the Cape Romain NWR that accounts for global change, local values, knowledge and perceptions; and to encourage social learning and building of effective networks and trust across South Carolina Lowcountry organizations and individuals. Although project scoping began at the scale of the Atlantic seaboard, by engaging with NWRs from Massachusetts to Florida, participating refuge personnel eventually selected the Cape Romain NWR to serve as a case study for testing our goals. The Cape Romain Partnership for Coastal Conservation was established to address global change impacts at a regional level and includes representation from Federal and State resource agencies, local conservation nongovernmental organizations, and organizations representing underserved community interests. Research topics, originating from discussions with Cape Romain Partnership for Coastal Conservation members, focused on quantifying key drivers of change including localized sea-level rise (SLR) predictions, estimates of coastal hurricane inundation as amplified by SLR, and urban growth trends and forecasts. These key drivers provided a foundation to engage stakeholders in planning exercises to begin a process of collective understanding and collaborative decision making. The goal of this process was to develop collective strategies of adaptation to enhance community and ecosystem resilience in the South Carolina Lowcountry. South Carolina’s Lowcountry is experiencing rapid environmental and social transformation because of SLR rates approaching twice the global average, chronic tidal flooding and catastrophic storm surges, erosion and loss of habitats that provide essential services to wildlife and humans, and increasing social polarization fueled by aggressive low-density urban growth and other forms of land conversion. To support characterizations of plausible future scenarios, we used available or, in some cases, developed new models to project future conditions of key environmental and social-economic drivers. Because of the imprecision of mean global SLR projections, the SECASC commissioned a climatological study to account for local conditions and multiple representative concentration pathways to project a tailored distribution of future sea levels. These projections were matched to SLR scenarios provided by existing models to anticipate the range of future coastal habitat changes in the South Carolina Lowcountry. SLR scenarios were also incorporated into existing storm-surge models, which do not account for alternate baseline sea levels, to project the local effects of future hurricanes. To evaluate the extent and effects of population growth and urban expansion, we relied on an existing urban-growth model to map the spatial distribution of land-conversion probabilities, the total area of which is predicted to increase twofold to threefold over the next 60 years. In addition to this simplified model, an econometric model is in development to account for nonlinear feedback dynamics in land value, land use, and ecosystem service production. Although not yet completed, the goals of this model are to produce more-detailed projections of growth dynamics and to allow predictions of development patterns resulting from alternate land-use planning policies and incentives. Collaborative planning for an uncertain future requires more than providing decision makers with information on future physical and ecological conditions; developing effective and consensual strategies must also integrate sociological values, multiple cultural perspectives, and an understanding of human behavior. To support broad stakeholder engagement in integrative approaches to adaptation planning, emphasis was placed on the importance of considering differences in how individuals perceive their environment and create meaning. Because cultural frameworks form the basis for perceptions and, ultimately, the behaviors of individuals and institutions, we describe a model of human behavior and how it can be used to understand the effect of cultural complexity and variation in perception on choices, behavioral change, and long-term maintenance of behaviors. We consider a model commonly used in the field of behavioral health that accommodates variation in human perception when describing stages of behavior and the dynamics of behavioral change. Tailoring communication and engagement activities to targeted stakeholders is likely to benefit from increased understanding of behavioral change processes. The complex nature of this problem limited the usefulness of a traditional decision-analytic approach, we explored alternative methods for engagement, collaborative learning and decision making. Recognizing that project partners and Lowcountry stakeholders may be at different stages of preparedness and interest level for modifying behavior as a function of global change, we facilitated a scenario-planning exercise to familiarize partners with this well-established approach for communicating the opportunities and threats arising under alternative, plausible futures. We developed narratives for four alternative South Carolina Lowcountry scenarios to be used in later strategic planning that focus on quantitative trends for three primary drivers with high impact and high uncertainty: manifestations of climate change, social-political shifts at a global level, and forces of local value and power structures. This scenario-planning exercise underscored the complex relation between the temporospatial scale of the production of ecological goods and services and the institutional scale at which they are managed. We then guided the partners through an assessment of the relevant strengths and weaknesses of the Cape Romain Partnership for Coastal Protection, using the threats and opportunities characterized by each scenario to understand how the partnership might respond when attempting to meet conservation and societal objectives. The partnership identified key strengths including partnership experience, outreach and technical capacities, a substantial conservation land base, and high social cohesion in the South Carolina Lowcountry. Limited communication expertise, institutional inertia, and insufficient staffing and funding were recognized as important weaknesses across the partnership. By examining and scoring combinations of internal strengths and weaknesses and external threats and opportunities, the partnership developed sets of prioritized strategies to consider in the context of a given scenario. Although we had insufficient time to examine all scenarios in detail, the intent was to identify a portfolio of strategic actions to address threats and opportunities represented in multiple plausible futures. Top-ranking strategies encompassed a range of actions that focused on strengthening the conservation community and communicating the benefits of nature (that is, ecosystem services) to leveraging partnerships to expand land protection. This report also details the methods and preliminary results of several models developed or applied in support of this project. Two parcel-selection algorithms were used to evaluate anticipated habitat changes and patterns of urban growth to guide decisions on optimal conservation reserve design to protect habitat communities. One approach used a widely available planning software (MARXAN) to maximize conservation benefits near the Cape Romain NWR, whereas the other approach was a novel application of economic theory to account for uncertainty in future conditions and for the risks of unanticipated habitat loss. This latter model applies modern portfolio theory to estimate the risk of investing in any portfolio of land parcels (that is, candidate “reserves”) under climate-change uncertainty by quantifying the variation and spatial correlation of conservation benefits derived from each portfolio. We expanded the range of actions beyond simply whether or not to invest in a set of land parcels, an approach commonly used in spatial conservation planning, to also include consideration of divestment from currently protected lands. Such refinements allow for better accounting of system dynamics and can evaluate the benefits of flexible conservation tools such as rolling easements. Model results were conditional on a decision maker’s risk tolerance but highlighted general strategies of land conservation to increase future habitat representation beyond what is expected under the current protected land base. We built models that may help inform coastal planning by estimating salinity dynamics and the performance of oyster reef restoration efforts to predict the combined effects of global change and management of freshwater flows on coastal habitats and the processes that contribute to their resilience. These models can support restoration decisions by evaluating the expected benefits of site locations for shoreline protection and fisheries production. Lastly, we developed a spatially explicit economic model that predicts feedback dynamics among land value, land-use change, and effects on ecosystem service provision to explore zoning policies and incentives on urban growth and ecosystem services. We summarize these efforts with insights and considerations for the Cape Romain Partnership for Coastal Protection to continue to engage stakeholders in effective adaptation planning. First, notions of place attachment (referred to as sense of place), and the role of culture in social discourse are increasingly being used to understand the complex interactions between society and the environment and how societies respond and adapt to climate change. Sense of place was a unifying theme whenever the future of the South Carolina Lowcountry was discussed. The contribution of the South Carolina Lowcountry’s environmental wealth, rich cultural heritage, and quality of life to sense of place has important implications for how adaptation planning might best be pursued. More community-based governance of the commons (in other words, natural and cultural resources held in common), in which broad stakeholder participation and power sharing are key elements, is considered important. This devolution of governance is characterized by polycentric institutions and self-organizing social networks that promote a local culture of knowledge sharing, problem solving, and learning. These so-called bridging organizations (or individuals) often provide the leadership necessary to bring together potentially disparate Government agencies and institutions, private organizations, and individuals in a collective process of problem solving. Our observations also suggest that the conservation community in the South Carolina Lowcountry views its activities as integral to the broader governance of social-ecological systems, in which responses to the forces of global change are mediated through culture, economics, and politics. Rather than directly competing with other interests, the South Carolina Lowcountry conservation community seems to embrace an interpretation of conservation in which the fundamental objective is the quality of human life rather than environmental protection. Fundamental to the types of governance reforms described above is the notion of coproduction, in which experts and users collaborate to develop a shared body of knowledge. In this approach, scientists work with stakeholders to help frame questions, design research, and collect and analyze data. Such sustained collaborations are increasingly believed to be an effective way to produce useable (or actionable) science. The emphasis on social learning, leveraging strong social networks, coordinating and deliberating among diverse stakeholders, and applying principles of adaptive management is an essential contribution to adaptive capacity. The diverse and robust set of scientific approaches, methods to help stakeholders collaborate in effective and goal-driven planning processes, and decision tools resulting from this project hopefully will assist Cape Romain NWR and its partners prepare for climatic, ecological, and social changes over the coming decades.

South Carolina↗
USGS1953

Niobium (columbium) and titanium at Magnet Cove and Potash Sulphur Springs, Arkansas

This work was done because niobium (columbium) has been found in several of the minerals and rocks of the Magnet Cove and Potash Sulphur Springs areas. Niobium is in demand for use in high-temperature and non-creep steels. The Magnet Cove and Potash Sulphur Springs areas are in central Arkansas between Malvern and Hot Springs. They are underlain by similar alkaline igneous complexes consisting of nepheline syenite, more basic alkaline rocks, and calcite rock or carbonatite. The igneous rocks intrude Paleozoic sedimentary rocks and are truncated by a Late Cretaceous erosion surface. At Magnet Cove deposits of rutile (TiO 2) occur within the igneous complex; two deposits of brookite (TiO 2 ) occur in quartzite of the Arkansas novaculite formation of probable Devonian and Mississippian age, near the margin of the complex. Perovskite (calcium titanate) occurs in several places in the igneous complex. Niobium is present in rutile, brookite, and perovskite, and also probably in other minerals not yet analyzed. In order to determine the distribution and average content of niobium in the larger titanium deposits, drill core and channel samples were analyzed for niobium, titanium, and other elements; and average figures were calculated. Concentrates and single crystals were also analyzed. Material from drill cores of perovskite-bearing magnetite-pyroxene rock on the Mo-Ti Corporation property was studied and analyzed. The Kimsey calcite quarry area was mapped, and channel samples and single crystals were analyzed. Channel samples from trenches on the Wilson prospect at Potash Sulphur Springs were analyzed. The areas studied contain large resources of titanium and niobium, of low grade. The major results of the analytical work are summarized in the following table.

Arkansas↗
USGS1957

Geology of possible petroleum provinces in Alaska

The history of petroleum exploration in Alaska and the geology of possible petroleum provinces in Alaska are reviewed. Maps showing Alaska's major Mesozoic and Tertiary tectonic elements, possible petroleum provinces, and indications of petrol, are included in this report. Annotated references in Geological Survey publications relating to petroleum and oil shale in Alaska are given at the end of the report. For the purpose of appraising its petroleum possibilities, Alaska is divided into the southern, central, and northern major geologic-physiographic regions. Southern Alaska includes the arcuate mountain chain formed by the Alaska and Aleutian Ranges and the Mentasta- Nutzotin Mountains, the coastal range and valley area to the south, and the southeastern Alaska "panhandle" -- an area of 185,000 square miles. Oil seeps on the west shore of Cook Inlet in southern Alaska were known as early as 1853, and claims were staked in this region in 1882. Drilling began near the oil seeps in the Katalla district about 1901, and this started Alaska's first period of oil activity. From 1902 to 1933 the Katalla field produced 154,000 barrels of oil from fractured shale and sandstone of Tertiary age the- first and only commercial production in Alaska. On the basis of geology, surficial indications of petroleum, and test wells drilled, six possible petroleum provinces are indicated in southern Alaska. They are Heceta Island area, Keku Islands area, Cook Inlet Mesozoic province, Gulf of Alaska Tertiary province, Cook Inlet Tertiary province, and Copper River basin. The exposed rocks in the Heceta Island area include lower Paleozoic graywacke-type sandstone, sandstone, conglomerate, and massive limestones with reeflike structures; igneous rocks are rare or lacking in much of the area. The Kosciusko-Tuxekan-Heceta synclinorium, the main structural feature, is modified by minor folds and faults. Some of the minor folds are reported to be broad and open, with flanks dipping 20°-145°. As far as known, the Heceta Island area has not heretofore been seriously considered as a possible petroleum province. Rocks of Silurian to Cretaceous age are exposed in the Keku Island area and include moderately folded and relatively unaltered limestone and other marine sedimentary rocks. The Cook Inlet Mesozoic province, a land area of approximately 18,500 square miles, includes a great thickness of unmetamorphosed marine sedimentary rocks of Jurassic and Cretaceous age. At least 23 test wells were drilled or started in this province by the end of 1955. Shows of oil and gas were encountered in many of these wells. During 1955 at least ten oil companies were active in this area and by the end of 1955 about 1 1/2 million acres were included in oil and gas leases applied for or granted. The Gulf of Alaska Tertiary province includes about 5,200 square miles in which rocks of Tertiary age are exposed or are believed to underlie Quaternary deposits. Between 1901 and the end of 1955 about 47 wells were drilled or started in this province. The Cook Inlet Tertiary province embraces an area of about 9,500 square miles, of which about 4,100 is covered by the shallow waters of Cook Inlet. Petroleum exploration has been in that part of the area which overlaps the Cook Inlet Mesozoic province. Eocene or younger Tertiary nonmarine sedimentary rocks are believed to underlie much of the province, and marine rocks of Tertiary age may also be present. The Copper River basin is a topographic basin underlain by unconsolidated deposits of Quaternary age. Tertiary rocks favorable for the accumulation of petroleum may underlie part of the basin but this is not believed likely. Except for some leasing activity no petroleum exploration has been recorded in the Copper River Basin to the end of 1955. Central Alaska is a region of about 275,000 square miles and consists of an irregular assemblage of intricately dissected uplands and alluvium-floored lowland basins. Scattered peaks of resistant intrusive igneous rocks surmount most of the upland areas. In the vast region of central Alaska only six test wells are known to have been drilled for the purpose of finding oil and gas. The maximum depth reached was 350 feet and the holes were mostly or entirely in Quaternary deposits. In recent years several oil companies have investigated some parts of the region and large areas in the Yukon-Koyukuk province are now under lease. Oil seeps, gas seeps, and other indications of petroleum have been reported from many localities; samples from two localities have been analyzed and reported to be petroleum. The geology of central Alaska is similar in a general way to that of the area between the Rocky Mountains and Sierra-Cascade belts of the United States. Sedimentary rocks, probably equivalent to the Precambrian Belt series, and rocks of the Cambrian and all younger geologic systems have been recognized in central Alaska. The structure of the region is known to be complex, but except in local mineral districts, it has not been mapped in detail. Based on the limited amount of available information, the region cannot be regarded as distinctly favorable for significant accumulations of petroleum. However, three pre-Cenozoic provinces, the Yukon-Koyukuk, the Kobuk, and the Kandik, and several large Cenozoic basin provinces may be worthy of further investigation. Northern Alaska includes the Brooks Range and all the treeless tundra north to the Arctic Coast, an area of about 125,000 square miles. The presence of oil seeps along the Arctic Coast has been known at least since 1900 and a description of the Cape Simpson oil seeps vas published in 1909. Since then oil and gas seeps have been described from nine localities, and oil shales and oil-bearing sandstones are known from many localities in the Arctic Foothills province. Oil and gas deposits have been discovered and geologic conditions are favorable for oil and gas accumulations in approximately half of the region. In 1923 approximately 37,000 square miles in northern Alaska was reserved by Executive order as Naval Petroleum Reserve No. 4. In 1944 the U. S. Navy began a vast petroleum exploration program which was suspended in 1953. In the years 1945 through 1955, 37 test wells and 45 core tests were drilled on 18 structures. Three oil fields, Umiat, Simpson, and Fish Creek, and two gas fields, South Barrow and Gubik, were discovered. Total reserve estimates for all discoveries of oil to 1955 range from 30 to 100 million barrels, and for gas, from 370 billion to 900 billion cubic feet. All northern Alaska, with the exception of the Brooks Range, can be considered a possible petroleum province, but the region can be subdivided into provinces of somewhat different potentialities. These subdivisions roughly correspond with the geomorphic provinces and sections, which in turn reflect differences in geology. The known oil-bearing beds are of Mesozoic age, primarily Cretaceous, and thus the possible petroleum provinces could be designated as Mesozoic. However, Paleozoic and Cenozoic rocks with favorable reservoir characteristics are exposed in the region and possibly underlie, in favorable structural situations, some of the areas as yet not tested. The Arctic Coastal Plain province includes gently folded and flat-lying Mesozoic beds that overlie a basement complex of Paleozoic and early Mesozoic age. Near the southern edge of this province the basement rocks are at depths of at least 20,000 feet, and to the north these rocks rise to within 2,500 feet of the surface. The Teshukpuk Lake section of the Arctic Coastal plain includes many of the known oil seeps; it is the most accessible to sea transportation, and lies almost completely within NPR 4. Thirteen test wells and 35 core tests have been drilled here; one gas field and two (at present, noncommercial) oil fields have been discovered. The possibility of further discoveries may depend largely on locating porous sandstones in stratigraphic rather than anticlinal traps. The White Hills section is distinguished topographically from the Teshukpruk section by its white-gravel-covered hills and fever lakes, and geologically by the presence of Tertiary rocks, including 2,000 feet of nonmarine beds in the west and at least 7,000 feet of marine beds to the east, in the vicinity of Carter Creek. This section appears to be more complex structurally. No test wells have been drilled in the White Hills section. The Northern Foothills section includes many closed anticlines. Twenty-four test wells and ten core tests have been drilled on 11 structures and two discoveries have been made -the Umiat oil field and the Gubik gas field. All these tests have been drilled in Cretaceous rocks. The Southern Foothills section is structurally similar to the Alberta Foothills and to the northern part of the Brooks Range. Great thicknesses of marine shale of Lover Cretaceous, Jurassic, and Triassic age are exposed. The outcropping Mesozoic sandstones are generally poorly sorted, nonporous, and impermeable. To the south the section is bordered by mountainous exposures of Mississippian limestone, which probably underlie at least part of this section. The rocks that underlie the deeply eroded complex structures of the Brooks Range include schist, slate, argillite, and limestone. Some exposed limestones have a strong petroleum-like odor and contain traces of petroleum residues.

Alaska↗
USGS1961

Geologic summary of the Appalachian Basin, with reference to the subsurface disposal of radioactive waste solutions

The Appalachian basin is an elongate depression in the crystalline basement complex which contains a great volume of predominantly sedimentary stratified rocks. As defined in this paper it extends from the Adirondack Mountains in New York to central Alabama. From east to west it extends from the west flank of the Blue Ridge Mountains to the crest of the Findlay and Cincinnati arches and the Nashville dome. It encompasses an area of about 207,000 square miles, including all of West Virginia and parts of New York, New Jersey, Pennsylvania, Ohio, Maryland, Virginia, Kentucky, Tennessee, North Carolina, Georgia, and Alabama. The stratified rocks that occupy the basin constitute a wedge-shaped mass whose axis of greatest thickness lies close to and parallel to the east edge of the basin. The maximum thickness of stratified rocks preserved in any one part of the basin today is between 35,000 and 40,000 feet. The volume of the sedimentary rocks is approximately 510,000 cubic miles and of volcanic rocks is a few thousand cubic miles. The sedimentary rocks are predominantly Paleozoic in age, whereas the volcanic rocks are predominantly Late Precambrian. On the basis of gross lithology the stratified rocks overlying the crystalline basement complex can be divided into nine vertically sequential units, which are designated "sequences" in this report. The boundaries between contiguous sequences do not necessarily coincide with the commonly recognized boundaries between systems or series. All sequences are grossly wedge shaped, being thickest along the eastern margin of the basin and thinnest along the western margin. The lowermost unit the Late Precambrian stratified sequence is present only along part of the eastern margin of the basin, where it lies unconformably on the basement complex. It consists largely of volcanic tuffs and flows but contains some interbedded sedimentary rocks. The Late Precambrian sequence is overlain by the Early Cambrian clastic sequence. Where the older sequence is absent, the Early Cambrian sequence rests on the basement complex. Interbedded fine- to coarse-grained noncarbonate detrital rocks comprise the bulk of the sequence, but some volcanic and carbonate rocks are included. Next above is the Cambrian-Ordovician carbonate sequence which consists largely of limestone and dolomite. Some quartzose sandstone is present in the lower part in the western half of the basin, and much shale is present in the upper part in the southeast part of the basin. The next higher sequence is the Late Ordovician clastic sequence, which consists largely of shale, siltstone, and sandstone. Coarse-grained light-gray to red rocks are common in the sequence along the eastern side of the basin, whereas fine-grained dark-gray to black calcareous rocks are common along the west side. The Late Ordovician clastic sequence is overlain unconformably in many places by the Early Silurian clastic sequence. The latter comprises a relatively thin wedge of coarse-grained clastic rocks. Some of the most prolific oil- and gas-producing sandstones in the Appalachian basin are included. Among these are the "Clinton" sands of Ohio, the Medina Sandstones of New York and Pennsylvania, and the Keefer or "Big Six" Sandstone of West Virginia and Kentucky. Conformably overlying the Early Silurian clastic sequence is the Silurian-Devonian carbonate sequence, which consists predominantly of limestone and dolomite. It also contains a salt-bearing unit in the north-central part of the basin and a thick wedge of coarse-grained red beds in the northeastern part. The sequence is absent in much of the southern part of the basin. Large volumes of gas and much oil are obtained from some of its rocks, especially from the Oriskany Sandstone and the Huntersville Ghert. The Silurian-Devonian carbonate sequence is abruptly overlain by the Devonian clastic sequence a thick succession of interbedded shale, mudrock, siltstone, and sandstone. Colors range from predominantly purple and red in the northeastern part of the basin to predominantly dark gray and black in the southwestern part. Many rocks in the upper part contain hydrocarbons in commercial quantities. The next higher sequence is a heterogeneous succession that comprises most rocks of Mississippian age in the basin. It is composed largely of fine-grained to very coarse-grained noncalcareous clastic rocks in the northern half of the basin, and largely of carbonate rocks in the southern part. Large quantities of oil and gas are produced from the sequence. The youngest sequence consists of coarse-grained clastic rocks largely of Pennsylvanian age. In the center of the basin a relatively small volume of lithologically similar rocks of Permian age are included. The sequence has been intensively mined for coal throughout most of its extent. The waste-disposal possibilities of the stratified rocks in the Appalachian basin are considered in terms of the following: 1) gross lithology of the sequences; 2) general lithology of the rock units composing the sequences; and 3) the structural attitudes of the sequences in different parts of the basin. The degree of exploitation of economically significant mineral* resources is considered briefly where such exploitation may affect waste-disposal possibilities. Hydrologic aspects are not in general considered. Based largely on consideration of the above geologic factors the following types of reservoirs associated with particular geologic environments offer some prospects for the disposal of radioactive waste solutions. They are: 1) artificially created cavities in thick salt beds; 2) artificially fractured thin lenticular sandstone bodies isolated in shale or mudrock sequences; 3) portions of thick noncarbonate clastic sequences possessing appreciable natural porosity and permeability; 4) thin clastic units (with natural or artificially created openings) in the plate of a thrust fault overlain by impermeable strata. Considered in its entirety the Late Ordovician clastic sequence appears to have a greater number of favorable geologic factors for waste-disposal purposes than the others. The Early Silurian clastic sequence, the Silurian-Devonian carbonate sequence, and the Devonian clastic sequence offer fewer possibilities. The Late Precambrian stratified sequence, Early Cambrian, and the Cambrian-Ordovician carbonate sequence offer few possibilities. The Mississippian and Pennsylvanian sequences appear to be generally unsuitable.

Appalachian Basin↗
USGS1972

Reconnaissance geology of the Jabal Bitran quadrangle, Kingdom of Saudi Arabia

The Jabal Bitten quadrangle covers an area of 2833 sq km in the eastern part of the Precambrian Shield in Saudi Arabia. The rocks in the quadrangle are divided geographically alone arcuate north-trending lines into an eastern area of granite intruded by a swarm of dikes of rhyolite and andesite, and a western area of dominantly pelitic chlorite-sericite schist, separated by the narrow central complex of the Idsas Range. This complex is composed of pyroclastic rocks, lava, conglomerate, marble, and plutonic mafic rocks that have been intricately modified by episodes of metamorphism, igneous intrusion, and faulting. The Idsas Range contains ancient gold and copper mines, and deposits of magnetite, copper, asbestos, and chromite. The rocks in the Jabal Bitten quadrangle are here interpreted to consist of three major sedimentary and volcanic groups, the lowermost of which was deposited unconformably on hornblende-biotite granite gneiss, and all of which are intruded by granite dikes and plutons. From oldest to youngest the layered rocks are called Halaban Group, Bi'r Khountina Group, and Murdama Group, A biotite-hornblende granite is older than uppermost Bi'r Khountina, and peralkalic granite is younger than Murdama. The layered rocks of these groups are generally metamorphosed to the greenschist facies. The metamorphic grade rises abruptly at the Idsas Range to the albite-epidote-amphibolite facies and lower subfacies of the amphibolite facies in parts of the Halaban Group; some skarn east of the range may be in the upper part of the amphibolite facies. Characteristically, the Halaban Group has the highest grade and the greatest range in metamorphic grade, and the Murdama Group has the lowest but most uniformly developed metamorphic grade. The metamorphism of the rocks was caused by three successive pulses of regional dynamothermal metamorphism plus contact metamorphism around the younger bodies of plutonic igneous rocks. Four major structural elements of the quadrangle are reflected in the geography and geologic units. These are a mantled gneiss dome on the east separated from a north-plunging synclinorium in rocks of the Murdama and Bi?r Khountina Groups on the west by a narrow dejective zone of the Halaban and lower Bi?r Khountina. The dejective zone is much modified by impricate overthrusts and accompanying tear faults. These major faults have pushed elements of the Halaban and Bi?r Khountina westward over Bi?r Khountina and Murdama, with the result that very complex fault patterns have evolved. Open geochemical reconnaissance of the area disclosed one positive anomaly for nickel and 40 threshold indications of several elements, principally nickel, chromium, copper, and tungsten. Heavy-mineral and radiometric reconnaissance showed 18 areas containing scheelite and/or powellite and four areas of anomalous radioactivity. Most of these features are in the dejective zone, as are five of the nine ancient workings, the massive and disseminated magnetite, most of the secondary copper minerals, and the traces of asbestos, magnesite, and chromite known in the quadrangle. The mantled gneiss dome and a complex of gabbro and amphibolite on its southwestern flank are the next most mineralized areas. Scant evidence of mineralization is present in the Murdama Group west of the dejective zone. Magnetite deposits at Jabal Idsas have the greatest potential of the mineral deposits in the Jabal Bitran quadrangle. Further study of gold at Fawara and Selib mines is recommended, as is investigation of a positive nickel anomaly that shows threshold cobalt and above background radioactivity. The garnetiferous skarn in the east-central part of the quadrangle should be examined for composition and abrasive character of the garnet and for the remote possibility of tungsten in scheelite and beryllium in helvite.

Open-File Report↗