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At least 55 records · Page 3Linked to original sources
USGS1988

Sedimentology of the Argo and Gascoyne abyssal plains, NW Australia: Report on Ocean Drilling Program Leg 123 (Sept. 1–Nov. 1, 1988)

Ocean Drilling Program Leg 123 drilled two sites in the Indian Ocean in order to study the rifting and early spreading of one of the world’s oldest ocean basins. Site 765 was drilled in 5714 meters of water on the Argo Abyssal Plain northwest of Australia. The sedimentary succession records the opening of an ocean basin, from the first sediments deposited atop young oceanic crust, to the present day. The oldest sediments are microlaminated brown silty claystones, locally rich in calcareous bioclasts. Most of the sequence is dominated by turbidites (primarily calcareous) which probably originated within canyons cut into the margin of the drowned platform of the North West Shelf of Australia. Site 766 is located in 3998 meters of water, at the base of the steep western margin of the Exmouth Plateau. The oldest sediments penetrated are glauconitic, volcaniclastic, and bioclastic sandstones and siltstones, which are interbedded with inclined basaltic sills. These sediments were deposited by a prograding submarine fan system which shed shallow marine sediments westward or northwestward off of the western rim of the Exmouth Plateau. Sandstones are succeeded by silty claystones, recording gradual abandonment or redirection of the fan system. An overlying sequence of pelagic and hemipelagic clayey and zeolitic calcareous oozes and chalks is succeeded by featureless and homogeneous pelagic nannofossil oozes.

Argo abyssal plain, Gascoyne abyssal plain↗
USGS1995

Surface electromagnetic geophysical exploration of the ground-water resources of Isla de Mona, Puerto Rico, a caribbean carbonate island

Two electromagnetic surface geophysical techniques were used to explore the ground-water resources of Isla de Mona, Puerto Rico—a 55-square-kilometer island located between Puerto Rico and Hispañiola, Isla de Mona is a tectonically uplifted carbonate plateau of Neogene age that has an average elevation of about 50 meters above mean sea level. This plateau is bounded by vertical cliffs except on the southwest where there is a narrow, 3-square-kilometer coastal plain. The coastal plain is composed of Quaternary carbonate deposits, and has a maximum elevation of less than 10 meters above mean sea level. No large-scale surface-water features are found on the plateau or on the coastal plain. To better understand the aquifer characteristics of the island, terrain conductivity and transient electromagnetic data were collected on the coastal plain and on the plateau. Computer programs were used to analyze quantitatively the electromagnetic data. Geoelectric models were produced to approximate the depth below land surface of the saline-freshwater interface underlying both the coastal plain and the plateau. Because the geophysical methods could not discern the water-table, it was assumed that it was near sea level. The thickness of the freshwater lens was estimated by subtracting the elevation of the land surface above mean sea level from the depth to the saline-freshwater interface as determined from the geophysical data. Results from the geophysical methods and water-level observations indicate that a freshwater lens with a maximum thickness of about 10 meters exists under the coastal plain. This lens thins towards the ocean, and it also thins away from the ocean toward the plateau. The model produced from the transient electromagnetic data indicates that the freshwater lens under the plateau has a maximum thickness of about 14 meters, which is a much thinner lens than previously estimated. A freshwater lens thickness of 14 meters is similar to direct measurements by divers in Cueva de Agua at Punta los Ingleses (located on the southeast coast), and observations by divers of freshwater seeps into the ocean at depths of 8 to 10 meters along the north coast cliffs after a major rainstorm. Ground-water flow in the coastal plain appears to be radial from the center of the freshwater mound. At the intersection between the coastal plain and the plateau, the flow is parallel to the coastline. The direction of flow on the rest of the plateau could not be determined accurately with the available data.

Carbonates and Evaporites↗
USGS1998

Where's the reef: the role of framework in the Holocene

Holocene reef models generally emphasize the role of in-place and interlocking framework in the creation of a rigid structure that rises above its surroundings. By extension, a number of ancient biohermal deposits have been disqualified as “true reefs” owing to their lack of recognizable framework. Fifty-four cores from several eastern Caribbean sites (Fig. 1) clearly demonstrate that in-place and interlocking framework is not common in these reefs that are comprised of varying mixtures of recognizable coral (primary framework), loose sediment/rubble and secondary framework made up mostly of coralgal fragments bound together by submarine cementation and biological encrustation. Recovery of primary and secondary framework ranged from 22% (avg.) in branching-coral facies to 33% in intervals dominated by head corals. Accretion rate decreased as expected with water depth. However, the recovery of recognizable coral generally increased with water depth, inversely to presumed coral-growth rates. This pattern reflects a spectrum in the relative importance of coral growth (primary construction), bioerosion, hydromechanical breakdown and the transport of sediment and detritus. The relative importance of each is controlled by the physical-oceanographic conditions at the site of reef development and will dictate both the architecture of the reef and the character of its internal fabric. We do not propose that framework reefs do no exist, as they most assuredly do. However, the fact that so many modern reefs are not dominated by in-place and interlocking framework suggests that its use as the primary determinant of ancient reefs may be unreasonable. We, therefore, propose the abandonment of framework-based models in favor of those that treat framework generation, physical/biological degradation, sedimentation, and encrustation as equal partners in the development of modern and ancient reefs alike.

Carbonates and Evaporites↗
USGS2010

The Middle Jurassic basinal deposits of the Surmeh Formation in the Central Zagros Mountains, southwest Iran: Facies, sequence stratigraphy, and controls

The lower part of the Lower to Upper Jurassic Surmeh Formation consists of a succession of shallow marine carbonates (Toarcian-Aalenian) overlain by a deep marine basinal succession (Aalenian-Bajocian) that grades upward to Middle to Upper Jurassic platform carbonates. The termination of shallow marine carbonate deposition of the lower part of the Surmeh Formation and the establishment of deep marine sedimentation indicate a change in the style of sedimentation in the Neotethys passive margin of southwest Iran during the Middle Jurassic. To evaluate the reasons for this change and to assess the basin configuration during the Middle Jurassic, this study focuses on facies analysis and sequence stratigraphy of the basinal deposits (pelagic and calciturbidite facies) of the Surmeh Formation, referred here as 'lower shaley unit' in the Central Zagros region. The upper Aalenian-Bajocian 'lower shaley unit' overlies, with an abrupt contact, the Toarcian-lower Aalenian platform carbonates. It consists of pelagic (calcareous shale and limestone) and calciturbidite facies grading to upper Bajocian-Bathonian platform carbonates. Calciturbidite deposits in the 'lower shaley unit' consist of various graded grainstone to lime mudstone facies containing mixed deep marine fauna and platform-derived material. These facies include quartz-bearing lithoclast/intraclast grainstone to lime mudstone, bioclast/ooid/peloid intraclast grainstone, ooid grainstone to packstone, and lime wackestone to mudstone. The calciturbidite layers are erosive-based and commonly exhibit graded bedding, incomplete Bouma turbidite sequence, flute casts, and load casts. They consist chiefly of platform-derived materials including ooids, intraclasts/lithoclasts, peloids, echinoderms, brachiopods, bivalves, and open-ocean biota, such as planktonic bivalves, crinoids, coccoliths, foraminifers, and sponge spicules. The 'lower shaley unit' constitutes the late transgressive and the main part of the highstand systems tract of a depositional sequence and grades upward to platform margin and platform interior facies as a result of late highstand basinward progradation. The sedimentary record of the 'lower shaley unit' in the Central Zagros region reveals the existence of a northwest-southeast trending platform margin during the Middle Jurassic that faced a deep basin, the 'Pars intrashelf basin' in the northeast. The thinning of calciturbidite layers towards the northeast and the widespread Middle Jurassic platform carbonates in the southern Persian Gulf states and in the Persian Gulf area support the existence of a southwest platform margin and platform interior source area. The platform margin was formed as a result of tectonic activity along the preexisting Mountain Front fault associated with Cimmerian continental rifting in northeast Gondwana. Flooding of the southwest platform margin during early to middle Bajocian resulted in the reestablishment of the carbonate sediment factory and overproduction of shallow marine carbonates associated with sea-level highstand, which led to vertical and lateral expansion of the platform and gradual infilling of the Pars intrashelf basin by late Bajocian time. ?? 2010 Springer-Verlag.

Carbonates and Evaporites↗
USGS2010

Spring distribution in Winona County, Minnesota, USA and the relationship with geologic strata in a karst landscape

Karst aquifers are important groundwater resources, but are vulnerable to contamination due to relatively rapid subsurface transport. Springs, points where the landscape and water table intersect and cold groundwater discharges, link aquifer systems with land surfaces and water bodies. As such, in many regions, they are critical to the viability of lakes, streams and cold-water fish communities. An understanding of where springs are located is important to watershed, fishery and environmental management efforts in karst regions. To better understand spatial distribution of springs and as a potential method for identifying variables that characterize locations of springs for improved land and watershed management, a nearest-neighbor analysis and a discriminant function analysis (DFA) of springs were conducted in Winona County, Minnesota, USA, a karst landscape. Nearest-neighbor analysis examined the spatial spring distribution. Twenty-two variables describing the locations of springs were analyzed to ascertain their ability to discriminate correct aquifer unit or bedrock unit classification for each spring. Springs were clumped with the highest densities in the lowest elevations. Springs were correctly assigned to aquifer units and bedrock units with eight and 11 landscape variables, respectively. Forest land cover was the only land cover type contributing to spring discrimination. Consideration of upland human activities, particularly in forested areas, on spring discharge along with a better understanding of characteristics describing spring locations could lead to better management activities that locate and protect springs and their important contributions to regional ecohydrology.

Minnesota↗
USGS2012

Spatial analysis of geologic and hydrologic features relating to sinkhole occurrence in Jefferson County, West Virginia

In this study the influence of geologic features related to sinkhole susceptibility was analyzed and the results were mapped for the region of Jefferson County, West Virginia. A model of sinkhole density was constructed using Geographically Weighted Regression (GWR) that estimated the relations among discrete geologic or hydrologic features and sinkhole density at each sinkhole location. Nine conditioning factors on sinkhole occurrence were considered as independent variables: distance to faults, fold axes, fracture traces oriented along bedrock strike, fracture traces oriented across bedrock strike, ponds, streams, springs, quarries, and interpolated depth to groundwater. GWR model parameter estimates for each variable were evaluated for significance, and the results were mapped. The results provide visual insight into the influence of these variables on localized sinkhole density, and can be used to provide an objective means of weighting conditioning factors in models of sinkhole susceptibility or hazard risk.

West Virginia↗
USGS2014

Geochemistry of groundwater in the Beaver and Camas Creek drainage basins, eastern Idaho

The U.S. Geological Survey (USGS), in cooperation with the U.S. Department of Energy, is studying the fate and transport of waste solutes in the eastern Snake River Plain (ESRP) aquifer at the Idaho National Laboratory (INL) in eastern Idaho. This effort requires an understanding of the natural and anthropogenic geochemistry of groundwater at the INL and of the important physical and chemical processes controlling the geochemistry. In this study, the USGS applied geochemical modeling to investigate the geochemistry of groundwater in the Beaver and Camas Creek drainage basins, which provide groundwater recharge to the ESRP aquifer underlying the northeastern part of the INL. Data used in this study include petrology and mineralogy from 2 sediment and 3 rock samples, and water-quality analyses from 4 surface-water and 18 groundwater samples. The mineralogy of the sediment and rock samples was analyzed with X-ray diffraction, and the mineralogy and petrology of the rock samples were examined in thin sections. The water samples were analyzed for field parameters, major ions, silica, nutrients, dissolved organic carbon, trace elements, tritium, and the stable isotope ratios of hydrogen, oxygen, carbon, sulfur, and nitrogen. Groundwater geochemistry was influenced by reactions with rocks of the geologic terranes—carbonate rocks, rhyolite, basalt, evaporite deposits, and sediment comprised of all of these rocks. Agricultural practices near and south of Dubois and application of road anti-icing liquids on U.S. Interstate Highway 15 were likely sources of nitrate, chloride, calcium, and magnesium to groundwater. Groundwater geochemistry was successfully modeled in the alluvial aquifer in Camas Meadows and the ESRP fractured basalt aquifer using the geochemical modeling code PHREEQC. The primary geochemical processes appear to be precipitation or dissolution of calcite and dissolution of silicate minerals. Dissolution of evaporite minerals, associated with Pleistocene Lake Terreton, is an important contributor of solutes in the Mud Lake-Dubois area. Oxidation-reduction reactions are important influences on the chemistry of groundwater at Camas Meadows and the Camas National Wildlife Refuge. In addition, mixing of different groundwaters or surface water with groundwater appears to be an important physical process influencing groundwater geochemistry in much of the study area, and evaporation may be an important physical process influencing the groundwater geochemistry of the Camas National Wildlife Refuge. The mass-balance modeling results from this study provide an explanation of the natural geochemistry of groundwater in the ESRP aquifer northeast of the INL, and thus provide a starting point for evaluating the natural and anthropogenic geochemistry of groundwater at the INL.

Idaho↗
USGS2005

Paleokarst and reservoir porosity in the Ordovician Beekmantown Dolomite of the central Appalachian basin

A karst-unconformity play at the top of the Ordovician Beekmantown Dolomite is judged to have great petroleum potential in Ohio and adjacent states; wells have high ultimate reserves and large areas remain untested. To better understand the origin, development, and distribution of Beekmantown porosity, we conducted a petrologic-stratigraphic study of cores and thin sections from 15 oil and gas wells. The massive dolomite, characterized by a hypidiotopic-idiotopic texture, formed by the replacement of stacked peritidal carbonate cycles. Secondary porosity occurs at two scales: (1) mesoscopic - breccia porosity, solution-enlarged fractures, large vugs, and caverns, and (2) microscopic - intercrystalline, intracrystalline, molds, small vugs, and microfractures. Mesoscopic pores (providing the major storage capacity in this reservoir) were produced by intrastratal solution and collapse of carbonate layers, whereas microscopic pores (connecting the larger pores) generally formed by the leaching of individual carbonate grains and crystals. Most pore types developed during periods of subaerial exposure across the carbonate bank, tied to either the numerous, though brief falls of relative sea level during Beekmantown deposition or more importantly the prolonged Knox unconformity at the close of sedimentation. The distribution of reservoir-quality porosity is quite heterogeneous, being confined vertically to a zone immediately below the unconformity and best developed laterally beneath buried hills and noses of this erosion surface. The inferred, shallow flow of ground water in the Beekmantown karst, primarily below topographic highs and above a diagenetic base level close to the water table, led to this irregular distribution of porosity.

Carbonates and Evaporites↗
USGS1979

Selected bibliography on subsidence processes and related engineering problems in carbonate rocks

The Solution Subsidence and Collapse project is a U.S. Geological Survey research activity funded by the Reactor Hazards Research program. The objective of the study is to determine the geologic and hydrologic controls and mechanisms of ground subsidence in soluble rock terranes caused by natural processes and man's activities. The results of the research will be used for the general geologic characterization of proposed and existing nuclear reactor sites in regions underlain by soluble rocks. In addition, the knowledge gained from the study will be applied to defining potential geologic hazards in soluble rock areas where ground subsidence or collapse can occur. The Solution Subsidence and Collapse project is divided into two study units, one looking at subsidence in evaporitic terranes, the other in carbonate terranes. Each of the two geologic environments has its own unique set of conditions that lead to subsidence and, therefore, each warrants its own special study. As part of the subsidence study a selected bibliography covering various topics on ground subsidence in carbonate karst terranes was compiled and is presented here. The entries in the bibliography are placed in five categories: (1) General; (2) Geology, Geomorphology, Hydrology; (3) Caves, Solution Channels; (4) Subsidence, Sinkholes; and (5) Engineering, Land Use, Detection. A separate bibliography on ground subsidence caused by dissolution and removal of salt and other soluble evaporites has been published as a companion reference to this report (Ege, 1979).

Open-File Report↗
USGS1985

Petroleum geology and resources of northeastern Mexico

Petroleum deposits (primarily gas) in northeastern Mexico occur in two main basins, the Tertiary Burgos basin and the Mesozoic Sabinas basin. About 90 gas fields are present in the Burgos basin, which has undergone active exploration for the past 30-40 years. Production in this basin is from Oligocene and Eocene nearshore marine and deltaic sandstone reservoirs. Most of the fields are small to medium in size on faulted anticlinal or domal structures, some of which may be related to deep-seated salt intrusion. Cumulative production from these fields is about 4 trillion cubic feet gas and 100 million barrels condensate and oil. Since 1975, about 10 gas fields, some with large production rates, have been discovered in Cretaceous carbonate and Jurassic sandstone reservoirs in the Sabinas basin and adjacent Burro-Picachos platform areas. The Sabinas basin, which is in the early stages of exploration and development, may have potential for very large gas reserves. The Sabinas basin is oriented northwesterly with a large number of elongate northwest- or west-trending asymmetric and overturned Laramide anticlines, most of which-are faulted. Some of the structures may be related to movement of Jurassic salt or gypsum. Lower Cretaceous and in some cases Jurassic rocks are exposed in the centers of the larger anticlines, and Upper Cretaceous rocks are exposed in much of the remainder of the basin. A thick section of Upper Cretaceous clastic rocks is partly exposed in tightly folded and thrust-faulted structures of the west-east oriented, deeply subsided Parras basin, which lies south of the Sabinas basin and north of the Sierra Madre Oriental fold and thrust belt south and west of Monterrey. The sedimentary cover of Cretaceous and Jurassic rocks in the Sabinas and Parras basins ranges from about 1,550 m (5,000 ft) to 9,000 m (30,000 ft) in thickness. Upper Jurassic rocks are composed of carbonate and dark organic shaly or sandy beds underlain by an unknown thickness of Late Jurassic and older redbed clastics and evaporites, including halite. Lower Cretaceous rocks are mainly platform carbonate and fine clastic beds with some evaporites (gypsum or anhydrite) deposited in two main rudist reef-bearing carbonate cycles. Upper Cretaceous rocks are mainly continental and marine clastic beds related to early development of the Laramide orogeny. This Upper Cretaceous sequence contains a marine shale and deltaic clastic complex as much as 6,000 m (20,000 ft) or more thick in the Parras basin, which grades northward and eastward to open marine, fine clastic beds. The Burgos basin, which is an extension of the Rio Grande embayment of the western Gulf of Mexico basin province, contains an eastward-thickening wedge of Tertiary continental and marine clastics. These beds are about 1,550 to 3,000 m (5,000-10,000 ft) thick in the outcrop belt on the west side of the basin and thicken to more than 16,000 m (50,000 ft) near the Gulf Coast.

Circular↗
USGS1991

Geohydrology and quality of water in aquifers in Lucas, Sandusky, and Wood counties, northwestern Ohio

The hydrology and quality of ground water were evaluated for the surficial sand and carbonate aquifers in northwestern Ohio. A locally important surficial sand aquifer in western Lucas County was evaluated on the basis of data from 10 wells completed in undeveloped and developed areas. The carbonate aquifer in Silurian and Devonian bedrock at its northernmost extent on the Ohio mainland was evaluated on the basis of data from previous studies and data from 466 wells and 11 springs. Most data are for the period 1985-88. The unconfined surficial sand aquifer is less than 50 ft. (feet) thick. Clay-rich drift, which restricts vertical movement of water, underlines the aquifer. Recharge is from precipitation, and discharge is by evapotranspiration and by flow to local streams and drainage ditches. Water levels are generally 2 to 8 ft. below land surface and fluctuate a total of about 3.5 ft. seasonally in a forested area. Concentrations of iron and manganese in ground water are excessive in some areas. Waters from shallow drive-point wells in residential areas contained larger concentrations of dissolved solids, hardness, sodium, and chloride than did waters from identical wells in undeveloped areas. The presence of nitrate nitrogen an other selected constituents in ground water in residential areas, and the absence of these constituents in ground water in undeveloped areas, indicate that the surficial sand aquifer has been affected by development. In carbonate aquifer, fractures, bedding-plane joints, and other secondary openings are the principal water-bearing zones. These zones can be areally and stratigraphically separated by low-permeability rock. Leaky artesian or semiconfined conditions predominate beneath most of the 1,400-mi? study area. The aquifer is confined by relatively impermeable underlying shale of Silurian age and overlying clay-rich drift of Quaternary age. Unproductive strata, including evaporites, within the sequence of carbonate rocks also confine some water-bearing zones. The carbonate aquifer is part of a regional ground-water-flow system; however, subsystems such as the eastern karst and central outcrops are locally important. The potentiometric surface indicates that recharge from areas south and west of the study area flows toward discharge areas along major rivers (Maumee, Portage, and Sandusky) , to a buried bedrock valley in central Sandusky County, and to springs and flowing wells. The potentiometric surface flattens markedly near the southern shore of Lake Erie, where ground-water levels approximate those of the lake, indicating a hydraulic connection between the lake and the aquifer. Hydrogeologic characteristics and water-quality data indicate that Lake Erie is not a major source of recharge to the aquifer. Ground-water ages inferred from tritium concentrations and potentiometric-surface maps indicate that recharge from precipitation enters the aquifer by subsurface drainage in karstified strata in eastern Sandusky County and by infiltration in shallow bedrock areas where drift is less than 20 ft. thick. The quality of water in the carbonate aquifer is described with reference to 52 properties and constituents that characterize chemical, radiochemical, bacteriologic, and physical conditions. Ground-water samples from 135 wells and 11 springs are used in the characterization. On the basis of these data, water from the aquifer is generally suitable for drinking and for most domestic purposes. The most areally widespread aesthtic factors limiting the use of ground water are hardness, concentrations of dissolved solids, sulfate and iron, and the presence of hydrogen sulfide. Selected bacteria are commonly present and may compromise the potability of water from the aquifer. Coliform bacteria from surface sources were found in 47 of 143 water samples. Analyses for total coliform bacteria indicate that 36 of the 125 samples from wells maintained for potable supply have bacteria counts of 4

Water-Resources Investigations Report↗
USGS1993

Origin and significance of tourmaline-rich rocks in the Broken Hill district, Australia

Tourmaline-rich rocks are widespread minor lithologies within the Early Proterozoic Willyama Supergroup in the Broken Hill district, Australia. Tourmaline concentrations occur in strata-bound and local stratiform tourmalinites, clastic metasedimentary rocks, quartz-gahnite lode rocks, stratiform Pb-Zn-Ag sulfide ores, garnet quartzites, strata-bound scheelite deposits, quartz-tourmaline nodules, discordant quartz veins, and granitic pegmatites. Most of the tourmaline-rich rocks are within the Broken Hill Group that hosts the main Pb-Zn-Ag ores.At the Globe mine along the northeast end of the main lodes, tourmalinites are closely associated with Pb-Zn-Ag mineralization and in places are interbedded with Mn-rich garnet quartzites. Galena and other ore minerals occur locally in the cores of recrystallized tourmaline grains in these tourmalinites, indicating that tourmaline and sulfides were present together prior to deformation and high-grade metamorphism. Electron microprobe analyses of tourmalines intergrown with Fe sulfides at the Globe mine show Mg-rich compositions relative to tourmalines in sulfide-free assemblages from the same area, suggesting early (premetamorphic) introduction of boron and Mg enrichment of tourmaline by sulfide-silicate reactions during metamorphism.Combined field and geochemical data indicate that the district tourmalinites represent normal clastic sediments that were metasomatically altered by boron-rich hydrothermal fluids at or below the sediment-water interface. Whole-rock chemical analyses of 33 tourmaline-rich rocks show linear trends of data for major and trace elements that closely resemble the trends observed for unmineralized elastic metasedimentary rocks of the district. Average Fe/Al, Mg/Al, Na/Al, and Ti/Al molar ratios of the tourmaline-rich rocks and clastic metasediments are very similar; the average K/Al molar ratio of the tourmaline-rich rocks is significantly lower than that of the clastic metasediments, reflecting the loss of K during tourmalinite formation. Chondrite-normalized patterns of rare earth elements (REE) in the quartz-rich tourmalinites are generally similar to those of the clastic metasediments, except for minor depletions of light REE; local positive and negative Ce anomalies suggest tourmalinite formation in the presence of seawater or a seawater-derived pore fluid. The geochemical data imply relative immobility of Al, Ti, Cr, and heavy REE during hydrothermal alteration and later metamorphism. Boron isotope analyses of 52 tourmaline separates show a total range of delta 11 B values from -26.8 to -17.0 per mil. Fine-grained, euhedral, nonpoikilitic tourmalines from tourmalinites in the andalusite-muscovite zone in the northern part of the district (e.g., Black Prince mine) have delta 11 B values from -21 to -17 per mil, whereas coarse granoblastic and poikilo-blastic tourmalines from the sillimanite and two-pyroxene granulite zones in the southern part of the district (e.g., Globe mine) have delta 11 B values of-24 to -19 per mil. Tourmalines in strongly retrogressed tourmalinites have delta 11 B values from about -27 to -20 per mil. The observed variations in delta 11 B are consistent with prograde and retrograde metamorphic fractionation of boron isotopes, in which the fluid phase is preferentially enriched in the heavier isotope ( 11 B). Premetamorphic hydrothermal fluids that deposited the Black Prince tourmalinites had delta 11 B values of-8 to -5 per mil at 200 degrees to 300 degrees C, suggesting a boron source from nonmarine evaporite borates.Tourmalinites in the Broken Hill district apparently formed by the same submarine hydrothermal processes as the main Pb-Zn-Ag lodes and the siliceous ferromanganese protoliths of the garnet quartzites. In our model, the hydrothermal system(s) acquired abundant boron by leaching evaporitic borates within the Thackaringa Group, the stratigraphic sequence that underlies the Broken Hill Group and most of the tourmaline concentrations. We suggest that evaporites of the Thackaringa Group provided a source of readily extractable boron for formation of the tourmalinites and also the source of the fluoride, sulfur, and perhaps the carbonate in the main lodes; such evaporites may have been critical for increased metal chloride complexing and transport necessary for deposition of the high-grade Pb-Zn-Ag ores. The Broken Hill deposit may have formed contemporaneously with the Mount Isa and McArthur River Pb-Zn-Ag deposits in similar evaporite-bearing sequences during widespread Early Proterozoic continental rifting.

Economic Geology↗
USGS2020

Geology and assessment of undiscovered oil and gas resources of the Sverdrup Basin Province, Arctic Canada, 2008

The Sverdrup Basin Province, an area of 515,000 square kilometers on the northern margin of North America, extends 1,300 kilometers across the Canadian Arctic Islands from near the Mackenzie Delta to northern Ellesmere Island. It consists of an intracratonic late Paleozoic to early Cenozoic rift-sag basin and a Mesozoic rift shoulder that bounds it on the north. Basin inception was Mississippian, manifested by deposition of nonmarine strata in rift basins, followed by Pennyslvanian marine transgression, which began with evaporites and progressed to Permian carbonate and clastic deposition at basin fringes and organic-rich marine strata in the basin center. Sediment transport was both northward from North America and southward from a now-subsided or rifted-away landmass to the north. Mesozoic strata indicate continued marine deposition, including both organic-rich, fine-grained rocks deposited during highstands and progradational deltaic sequences. A new episode of rifting began in Middle Jurassic time and culminated in the opening of the Canada Basin by Early Cretaceous seafloor spreading. The Sverdrup Rim formed as the rift shoulder between North America and the thinned, subsided crust to the north. Widespread Upper Cretaceous organic-rich shales were deposited during the major transgression induced by Canada Basin opening, followed by an influx of coarser east-derived detritus. In Paleogene time, incipient North Atlantic seafloor spreading caused deformation in northeasternmost North America, producing uplifts that shed detritus westward across the Sverdrup Basin. Tight folding and thrusting resulting from the Eurekan orogeny took place in the eastern part of the basin during the Eocene, with decreasing intensity of deformation westward. Since deformation ended in late Eocene time, little significant tectonism or deposition has taken place. Two petroleum systems were defined in the Sverdrup Basin Province. Upper Paleozoic marine shale generated petroleum beginning in the Early Triassic, but this petroleum system was not quantitatively assessed because reservoir quality in adjacent strata is poor, the rocks are mostly overmature, and subsequent deformation likely affected trap integrity. The second petroleum system was sourced by Lower Triassic strata rich in oil-prone organic matter. Oil was generated during Paleogene burial synchronous with Eurekan deformation, and the oil migrated into Triassic and Jurassic deltaic, shallow marine and nonmarine strata. However, most of the oil may have escaped during deformation and subsequent uplift and erosion, which probably caused oil to be displaced from traps by gas expansion. The population of undiscovered accumulations was characterized as likely to include stratigraphically trapped and small, structurally trapped accumulations, with a median size of 80 million barrels of oil (MMBO); the number of undiscovered accumulations was estimated to be between 1 and 50, with the most likely number being 10. The resulting estimate of undiscovered, technically recoverable, conventional oil resources is 61 to 1,255 MMBO, with a mean of 427 MMBO. Undiscovered, technically recoverable, conventional gas resources are estimated at 4.95 trillion cubic feet (TCF), with slightly more than half of that in nonassociated gas accumulations. A third petroleum system in the adjacent Amerasia Basin Province to the north was considered somewhat likely to contain accumulations on the Sverdrup Rim. Deeply buried Upper Jurassic, Upper Cretaceous, and Eocene organic-rich strata probably generated oil that may have migrated up the continental slope into Triassic to Paleogene sandstones on the Sverdrup Rim. Based on analogy with the Barrow Arch in Alaska, a median of 20 accumulations was estimated, with accumulation volumes as much as 2,500 MMBO and a median of 100 MMBO. The probability of at least one accumulation of the minimum size assessed (50 MMBO) was estimated at 0.22. The resulting estimate of undiscovered, technically recoverable, conventional oil resources is 0 to 2,679 MMBO, with a mean of 424 MMBO. Mean estimates for associated and nonassociated gas are 1.3 and 2.3 TCF, respectively.

Sverdrup Basin↗
USGS1967

Devonian of the Northern Rocky Mountains and plains

The Devonian System, represented predominantly by shallow-water marine carbonate, is widespread in Montana, Wyoming, eastern Idaho, North Dakota, South Dakota, and northwestern Nebraska. It comprises cratonic rocks in the east and miogeosynclinal rocks in the west. The cratonic rocks thicken generally northward from their southern limit in Wyoming across a broad shelf that occupies most of Wyoming and Montana. In northern Montana, they are as much as 1,250 feet thick. Cratonic rocks also thicken eastward from areas of Early Mississippian erosional thinning in central and eastern Montana to as much as 2,000 feet in the intracratonic Williston basin centered in northwestern North Dakota. The miogeosynclinal rocks, which moved eastward on low-angle thrust faults, abut against cratonic rocks along a north-trending disturbed belt in western Wyoming, western Montana and eastern Idaho. The miogeosynclinal rocks thicken abruptly westward from 1,000 feet near this belt to about 3,000 feet near the east edge of the Idaho batholith. Farther west they have been buried beneath younger rocks, altered by the batholith, or eroded. Five subdivisions of the Devonian System are treated separately: 1. Upper Lower Devonian (Coblenzian) marginal and nearshore marine carbonate rocks and related continental and estuarine discontinuous sinkhole and channel-fill deposits. 2. Upper Middle Devonian (Givetian) carbonate rocks that contain a 525-foot-thick evaporitic sequence in the Williston basin. 3. Lower Upper Devonian (Frasnian, toI ) cyclically deposited carbonate rocks that include thick beds of dolarenite and dolomitized calcarenite on the west. 4. Upper Upper Devonian (Famennian, toII-IV ) evaporitic rocks overlain by fossilferous open-marine shale and limestone. 5. Undivided uppermost Devonian (Famennian, to V-VI ) and lowermost Mississippian (Tournaisian, cuI-lower cuII α ) carbonaceous and clastic rocks deposited in six shallow basins interspersed among areas uplifted during the penecontemporaneous Antler orogeny.

Idaho, Montana, Nebraska, North Dakota, South Dako↗
USGS1982

Radioactive mineral spring precipitates, their analytical and statistical data and the uranium connection

Major radioactive mineral springs are probably related to deep zones of active metamorphism in areas of orogenic tectonism. The most common precipitate is travertine, a chemically precipitated rock composed chiefly of calcium carbonate, but also containing other minerals. The mineral springs are surface manifestations of hydrothermal conduit systems which extend downward many kilometers to hot source rocks. Conduits are kept open by fluid pressure exerted by carbon dioxide-charged waters rising to the surface propelled by heat and gas (CO2 and steam) pressure. On reaching the surface, the dissolved carbon dioxide is released from solution, and calcium carbonate is precipitated. Springs also contain sulfur species (for example, H2S and HS-), and radon, helium and methane as entrained or dissolved gases. The HS- ion can react to form hydrogen sulfide gas, sulfate salts, and native sulfur. Chemical salts and native sulfur precipitate at the surface. The sulfur may partly oxidize to produce detectable sulfur dioxide gas. Radioactivity is due to the presence of radium-226, radon-222, radium-228, and radon-220, and other daughter products of uranium-238 and thorium-232. Uranium and thorium are not present in economically significant amounts in most radioactive spring precipitates. Most radium is coprecipitated at the surface with barite. Barite (barium sulfate) forms in the barium-containing spring water as a product of the oxidation of sulfur species to sulfate ions. The relatively insoluble barium sulfate precipitates and removes much of the radium from solution. Radium coprecipitates to a lesser extent with manganese-barium- and iron-oxy hydroxides. R-mode factor analysis of abundances of elements suggests that 65 percent of the variance of the different elements is affected by seven factors interpreted as follows: (1) Silica and silicate contamination and precipitation; (2) Carbonate travertine precipitation; (3) Radium coprecipitation; (4) Evaporite precipitation; (5) Hydrous limonite precipitation and coprecipitated elements including uranium; (6) Rare earth elements deposited with detrital contamination (?); (7) Metal carbonate adsorption and precipitation. Economically recoverable minerals occurring at some localities in spring precipitates are ores of iron, manganese, sulfur, tungsten and barium and ornamental travertine. Continental radioactive mineral springs occur in areas of crustal thickening caused by overthrusting of crustal plates, and intrusion and metamorphism. Sedimentary rocks on the lower plate are trapped between the plates and form a zone of metamorphism. Connate waters, carbonate rocks and organic-carbon-bearing rocks react to extreme pressure and temperature to produce carbon dioxide, and steam. Fractures are forced open by gas and fluid pressures. Deep-circulating meteoric waters then come in contact with the reactive products, and a hydrothermal cell forms. When hot mineral-charged waters reach the surface they form the familiar hot mineral springs. Hot springs also occur in relation to igneous intrusive action or volcanism both of which may be products of the crustal plate overthrusting. Uranium and thorium in the sedimentary rocks undergoing metamorphism are sometimes mobilized, but mobilization is generally restricted to an acid hydrothermal environment; much is redeposited in favorable environments in the metamorphosed sediments. Radium and radon, which are highly mobile in both acid and alkaline aqueous media move upward into the hydrothermal cell and to the surface.

Open-File Report↗
USGS2017

U.S. Geological Survey Karst Interest Group Proceedings, San Antonio, Texas, May 16–18, 2017

Introduction and Acknowledgments Karst aquifer systems are present throughout parts of the United States and some of its territories, and have developed in carbonate rocks (primarily limestone and dolomite) and evaporites (gypsum, anhydrite, and halite) that span an interval of time encompassing more than 550 million years. The depositional environments, diagenetic processes, post-depositional tectonic events, and geochemical weathering processes that form karst aquifers are varied and complex. These factors involve biological, chemical, and physical changes that when combined with the diverse climatic regimes in which karst development has taken place, result in the unique dual- or triple-porosity nature of karst aquifers. These complex hydrogeologic systems typically represent challenging and unique conditions to scientists attempting to study groundwater flow and contaminant transport in these terrains. The dissolution of carbonate rocks and the subsequent development of distinct and beautiful landscapes, caverns, and springs have resulted in the most exceptional karst areas being designated as national or state parks. Tens of thousands of similar areas in the United States have been developed into commercial caverns and known privately owned caves. Both public and private properties provide access for scientists to study the flow of groundwater in situ . Likewise, the range and complexity of landforms and groundwater flow systems associated with karst terrains are enormous, perhaps more than for any other aquifer type. Karst aquifers and landscapes that form in tropical areas, such as the cockpit karst along the north coast of Puerto Rico, differ greatly from karst landforms in more arid climates, such as the Edwards Plateau in west-central Texas or the Guadalupe Mountains near Carlsbad, New Mexico, where hypogenic processes have played a major role in speleogenesis. Many of these public and private lands also contain unique flora and fauna associated with these karst hydrogeologic systems. As a result, numerous federal, state, and local agencies have a strong interest in the study of karst terrains. Many of the major springs and aquifers in the United States have developed in carbonate rocks, such as the Floridan aquifer system in Florida and parts of Alabama, Georgia, and South Carolina; the Ozark Plateaus aquifer system in parts of Arkansas, Kansas, Missouri, and Oklahoma; and the Edwards-Trinity aquifer system in west-central Texas. These aquifers, and the springs that discharge from them, serve as major water-supply sources and form unique ecological habitats. Competition for the water resources of karst aquifers is common, and urban development and the lack of attenuation of contaminants in karst areas due to dissolution features that form direct pathways into karst aquifers can impact the ecosystem and water quality associated with these aquifers. The concept for developing a platform for interaction among scientists within the U.S. Geological Survey (USGS) working on karst-related studies evolved from the November 1999 National Groundwater Meeting of the USGS. As a result, the Karst Interest Group (KIG) was formed in 2000. The KIG is a loose-knit, grass-roots organization of USGS and non-USGS scientists and researchers devoted to fostering better communication among scientists working on, or interested in, karst science. The primary mission of the KIG is to encourage and support interdisciplinary collaboration and technology transfer among scientists working in karst areas. Additionally, the KIG encourages collaborative studies between the different mission areas of the USGS as well as with other federal and state agencies, and with researchers from academia and institutes. To accomplish its mission, the KIG has organized a series of workshops that have been held near nationally important karst areas. To date (2017) seven KIG workshops, including the workshop documented in this report, have been held. The workshops typically include oral and poster sessions on selected karst-related topics and research, as well as field trips to local karst areas. To increase non-USGS participation an effort was made for the workshops to be held at a university or institute beginning with the fourth workshop. Proceedings of the workshops are published by the USGS and are available online at the USGS publications warehouse https://pubs.er.usgs.gov/ by using the search term “karst interest group.” The first KIG workshop was held in St. Petersburg, Florida, in 2001, in the vicinity of the large springs and other karst features of the Floridan aquifer system. The second KIG workshop was held in 2002, in Shepherdstown, West Virginia, in proximity to the carbonate aquifers of the northern Shenandoah Valley, and highlighted an invited presentation on karst literature by the late Barry F. Beck of P.E. LaMoreaux and Associates. The third KIG workshop was held in 2005, in Rapid City, South Dakota, near evaporite karst features in limestones of the Madison Group in the Black Hills of South Dakota. The Rapid City KIG workshop included field trips to Wind Cave National Park and Jewel Cave National Monument, and featured a presentation by Thomas Casadevall, then USGS Central Region Director, on the status of Earth science at the USGS. The fourth KIG workshop in 2008 was hosted by the Hoffman Environmental Research Institute and Center for Cave and Karst Studies at Western Kentucky University in Bowling Green, Kentucky, near Mammoth Cave National Park and karst features of the Chester Upland and Pennyroyal Plateau. The workshop featured a late-night field trip into Mammoth Cave led by Rickard Toomey and Rick Olsen, National Park Service. The fifth KIG workshop in 2011 was a joint meeting of the USGS KIG and University of Arkansas HydroDays, hosted by the Department of Geosciences at the University of Arkansas in Fayetteville. The workshop featured an outstanding field trip to the unique karst terrain along the Buffalo National River in the southern Ozarks, and a keynote presentation on paleokarst in the United States was delivered by Art and Peggy Palmer. The sixth KIG workshop was hosted by the National Cave and Karst Research Institute (NCKRI) in 2014, in Carlsbad, New Mexico. George Veni, Director of the NCKRI, served as a co-chair of the workshop with Eve Kuniansky of the USGS. The workshop featured speaker Dr. Penelope Boston, Director of Cave and Karst Studies at New Mexico Tech, Socorro, and Academic Director at the NCKRI, who addressed the future of karst research. The field trip on evaporite karst of the lower Pecos Valley was led by Lewis Land (NCKRI karst hydrologist), and the field trip on the geology of Carlsbad Caverns National Park was led by George Veni. This current seventh KIG workshop is being held in San Antonio at the University of Texas at San Antonio (UTSA). This 2017 workshop is being hosted by the Department of Geological Sciences’ Student Geological Society (SGS), and student chapters of the American Association of Petroleum Geologists (AAPG) and Association of Engineering Geologists (AEG), with support by the UTSA Department of Geological Sciences and Center for Water Research. The UTSA student chapter presidents, Jose Silvestre (SGS), John Cooper (AAPG), and Tyler Mead (AEG) serve as co-chairs of the 2017 workshop with Eve Kuniansky of the USGS. The technical session committee is chaired by Eve Kuniansky, USGS, and includes Michael Bradley, Tom Byl, Rebecca Lambert, John Lane, and James Kaufmann, all USGS, and Patrick Tucci, retired USGS. The logistics committee includes Amy Clark, Yongli Gao, and Lance Lambert (Department Chair), UTSA Department of Geological Sciences; and Ryan Banta and Allan Clark, USGS, San Antonio, Texas. The field trip committee is chaired by Allan Clark and includes Amy Clark, Yongli Gao, and Keith Muehlestein, UTSA; Marcus Gary, Edwards Aquifer Authority and University of Texas at Austin; Ron Green, Southwest Research Institute; Geary Schindel, Edwards Aquifer Authority; and George Veni, NCKRI. Additionally, two organizations have assisted the UTSA student chapters in hosting the meeting by donating funds to the chapters: the Edwards Aquifer Authority, San Antonio, Texas, and the Barton Springs Edwards Aquifer Authority, Austin, Texas. Additionally, Yongli Gao, Center for Water Research and Department of Geological Sciences, UTSA, helped develop sessions on cave and karst research in China for this workshop. These proceedings could not have been accomplished without the assistance of Lawrence E. Spangler as co-editor who not only has subject matter expertise, but also serves as an editor with the USGS Science Publishing Network. We sincerely hope that this workshop continues to promote future collaboration among scientists of varied and diverse backgrounds, and improves our understanding of karst aquifer systems in the United States and its territories. The extended abstracts of USGS authors were peer reviewed and approved for publication by the USGS. Articles submitted by university researchers and other federal and state agencies did not go through the formal USGS peer review and approval process, and therefore may not adhere to USGS editorial standards or stratigraphic nomenclature. However, all articles had a minimum of two peer reviews and were edited for consistency of appearance in the proceedings. The use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. The USGS Water Availability and Use Science Program funded the publication costs of the proceedings.

Scientific Investigations Report↗
USGS2002

Fluid-rock reactions in an evaporitic melange, Permian Haselgebirge, Austrian Alps

Tectonically isolated blocks of carbonate rocks present within the anhydritic Haselgebirge melange of the Northern Calcareous Alps record a complex history of deformation and associated deep-burial diagenetic to very low-grade metamorphic reactions. Fluids were hot (up to ~ 250 ??C) and reducing brines charged with carbon dioxide. Individual carbonate outcrops within the melange record different regimes of brine-rock reactions, ranging from pervasive dolomite recrystallization to dedolomitization. Early diagenetic features in these carbonates were almost entirely obliterated. Matrix dolomite alteration was related to thermochemical sulphate reduction (TSR) recognized by the replacement of anhydrite by calcite + pyrite ?? native sulphur. Pyrite associated with TSR is coarsely crystalline and characterized by a small sulphur isotope fractionation relative to the precursor Permian anhydrite. Carbonates associated with TSR show low Fe/Mn ratios reflecting rapid reaction of ferrous iron during sulphide precipitation. As a result, TSR-related dolomite and calcite typically show bright Mn(II)-activated cathodoluminescence in contrast to the dull cathodoluminescence of many (ferroan) carbonate cements in other deep-burial settings. In addition to carbonates and sulphides, silicates formed closely related to TSR, including quartz, K-feldspar, albite and K-mica. 40Ar/39Ar analysis of authigenic K-feldspar yielded mostly disturbed step-heating spectra which suggest variable cooling through the argon retention interval for microcline during the Late Jurassic. This timing coincides with the recently recognized subduction and closure of the Meliata-Hallstatt ocean to the south of the Northern Calcareous Alps and strongly suggests that the observed deep-burial fluid-rock reactions were related to Jurassic deformation and melange formation of these Permian evaporites.

Sedimentology↗
USGS1989

Boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites

Boron isotope ratios (11B/10B) have been measured on 60 tourmaline separates from over 40 massive sulfide deposits and tourmalinites from a variety of geologic and tectonic settings. The coverage of these localities is global (5 continents) and includes the giant ore bodies at Kidd Creek and Sullivan (Canada), Broken Hill (Australia), and Ducktown (USA). Overall, the tourmalines display a wide range in ??11B values from -22.8 to +18.3??? Possible controls over the boron isotopic composition of the tourmalines include: 1) composition of the boron source, 2) regional metamorphism, 3) water/rock ratios, 4) seawater entrainment, 5) temperature of formation, and 6) secular variations in seawater ??11B. The most significant control appears to be the composition of the boron source, particularly the nature of footwall lithologies; variations in water/ rock ratios and seawater entrainment are of secondary importance. The boron isotope values seem especially sensitive to the presence of evaporites (marine and non-marine) and carbonates in source rocks to the massive sulfide deposits and tourmalinites. ?? 1989 Springer-Verlag.

Contributions to Mineralogy and Petrology↗