Results for “Southeastern Geology” — Page 67

USGS1992

A geochemical investigation of selected areas in Greenville and Laurens Counties, South Carolina: Implications for mineral resources

The purpose of this study is to geochemically evaluate three areas within the Greenville 1° x 2° quadrangle (see index map) that have been shown by previous studies to contain anomalously high amounts of tin. Jackson and Moore (1992) reported the presence of cassiterite (SnO 2 )-bearing heavy-mineral concentrates from stream sediment samples that were collected during a regional geochemical reconnaissance of the Greenville 1° x 2° quadrangle. The data reported here confirm identified in selected heavy-mineral concentrate samples. In addition, anomalously high concentrations of barium, beryllium, lanthanum, and thorium are also reported for parts of the same areas. No significant mineral deposits are known to occur in the study areas. There was, however, minor production of monazite from several nearby localities (Sloan, 1908), and gold was produced from deposits in the northeastern part of Greenville County and nearby Spartanburg County (McCauley and Butler, 1966). The three areas selected for resampling are located in the Inner Piedmont physiographic province of South Carolina (see index map). The generalized tectonic setting of the region and the locations of the study is just north of Greenville, S.C. Much of it is within the moderately to steeply sloped terrane of Paris Mountain State Park where elevations reach approximately 600 m. Simpsonville, S.C., is neat the center of the second study area, and the southernmost study area is near Hickory Tavern, S.C. Both the Simpsonville and Hickory Tavern study areas are in more gently rolling Piedmont terrane. Each of the sampled areas is drained by tributaries of the Enoree and Reedy Rivers. Parts of three different thrust sheets underlie the region covered by this study (fig. 1); in ascending structural position, they are the Six Mile, Paris Mountain, and Laurens thrust sheets (Nelson and others, 1987). Nelson (1988, p. 7) described the contacts between these sheets as being along unnamed faults. The rocks in and around the study areas have undergone sillimanite-muscovite-grade metamorphism (Nelson, 1988, p. 9). Nelson (1988, p. 13) reports that the Six Mile thrust sheet was metamorphosed about 344 Ma. The geology of these sheets as described in this study, including geologic contacts, rock descriptions, and unit names, generally follows that of Nelson and others (1987, 1989). Within the Paris Mountain study area, rocks of the Paris Mountain thrust sheet predominate (fig. 2) and consist of a biotite-muscovite-sillimanite schist (EZsp) that has extensive lenses of fine- to medium- grained biotite granite gneiss (Pzgp). Areas of biotite granite gneiss that occur in the southern part of the Paris Mountain study area contain extensive pegmatitic and leucogranitic phases. These pegmatitic zones consist mostly of coarse-grained microcline feldspar and quartz with minor amounts of muscovite, biotite, and garnet. Smaller pegmatite lenses (<0.5 m thick) that occur within the biotite-muscovite-sillimanite schist of the Paris Mountain study area are generally of similar mineralogy, although some contain tourmaline crystals up to 5 cm in length. The Six Mile thrust sheet underlies the northern edge of the Paris Mountain study area, where it is composed of gneissic biotitic granites of the Caesars Head Granite (figs. 1 and 2). The northwestern part of the Simpsonville study area (figs. 1 and 3), within the Paris Mountain thrust sheet, is underlain by a biotite-muscovite-sillimanite schist (EZsp) that contains lenses of biotite granite gneiss (Pzgp). In the southeastern part of the Simpsonville study area, within the Laurens thrust sheet, biotite gneiss (EZgl), biotite granite gneiss (Pzgf), and minor amphibolite (EZal) are interlayered biotite (EZgl), granite gneiss (Dgg), and amphibolite (EZal) of the Laurens thrust sheet (fig. 4).

South Carolina↗

USGS2001

Ground-Water Hydrology of the Upper Deschutes Basin, Oregon

The upper Deschutes Basin is among the fastest growing regions in Oregon. The rapid population growth has been accompanied by increased demand for water. Surface streams, however, have been administratively closed to additional appropriation for many years, and surface water is not generally available to support new development. Consequently, ground water is being relied upon to satisfy the growth in water demand. Oregon water law requires that the potential effects of ground-water development on streamflow be evaluated when considering applications for new ground-water rights. Prior to this study, hydrologic understanding has been insufficient to quantitatively evaluate the connection between ground water and streamflow, and the behavior of the regional ground-water flow system in general. This report describes the results of a hydrologic investigation undertaken to provide that understanding. The investigation encompasses about 4,500 square miles of the upper Deschutes River drainage basin.A large proportion of the precipitation in the upper Deschutes Basin falls in the Cascade Range, making it the principal ground-water recharge area for the basin. Water-balance calculations indicate that the average annual rate of ground- water recharge from precipitation is about 3,500 ft3/s (cubic feet per second). Water-budget calculations indicate that in addition to recharge from precipitation, water enters the ground-water system through interbasin flow. Approximately 800 ft3/s flows into the Metolius River drainage from the west and about 50 ft3/s flows into the southeastern part of the study area from the Fort Rock Basin. East of the Cascade Range, there is little or no ground-water recharge from precipitation, but leaking irrigation canals are a significant source of artificial recharge north of Bend. The average annual rate of canal leakage during 1994 was estimated to be about 490 ft3/s. Ground water flows from the Cascade Range through permeable volcanic rocks eastward out into the basin and then generally northward. About one-half the ground water flowing from the Cascade Range discharges to spring-fed streams along the margins of the range, including the upper Metolius River and its tributaries. The remaining ground water flows through the subsurface, primarily through rocks of the Deschutes Formation, and eventually discharges to streams near the confluence of the Deschutes, Crooked, and Metolius Rivers. Substantial ground-water discharge occurs along the lower 2 miles of Squaw Creek, the Deschutes River between Lower Bridge and Pelton Dam, the lower Crooked River between Osborne Canyon and the mouth, and in Lake Billy Chinook (a reservoir that inundates the confluence of the Deschutes, Crooked, and Metolius Rivers).The large amount of ground-water discharge in the confluence area is primarily caused by geologic factors. North (downstream) of the confluence area, the upper Deschutes Basin is transected by a broad region of low-permeability rock of the John Day Formation. The Deschutes River flows north across the low-permeability region, but the permeable Deschutes Formation, through which most of the regional ground water flows, ends against this rampart of low-permeability rock. The northward-flowing ground water discharges to the streams in this area because the permeable strata through which it flows terminate, forcing the water to discharge to the surface. Virtually all of the regional ground water in the upper Deschutes Basin discharges to surface streams south of the area where the Deschutes River enters this low-permeability terrane, at roughly the location of Pelton Dam.The effects of ground-water withdrawal on streamflow cannot presently be measured because of measurement error and the large amount of natural variability in ground-water discharge. The summer streamflow near Madras, which is made up largely of ground-water discharge, is approximately 4,000 ft3/s. Estimated consumptive ground-water use in the basin i

Water-Resources Investigations Report↗

USGS2005

Structural evolution of fault zones in sandstone by multiple deformation mechanisms: Moab fault, southeast Utah

Faults in sandstone are frequently composed of two classes of structures: (1) deformation bands and (2) joints and sheared joints. Whereas the former structures are associated with cataclastic deformation, the latter ones represent brittle fracturing, fragmentation, and brecciation. We investigated the distribution of these structures, their formation, and the underlying mechanical controls for their occurrence along the Moab normal fault in southeastern Utah through the use of structural mapping and numerical elastic boundary element modeling. We found that deformation bands occur everywhere along the fault, but with increased density in contractional relays. Joints and sheared joints only occur at intersections and extensional relays. In all locations , joints consistently overprint deformation bands. Localization of joints and sheared joints in extensional relays suggests that their distribution is controlled by local variations in stress state that are due to mechanical interaction between the fault segments. This interpretation is consistent with elastic boundary element models that predict a local reduction in mean stress and least compressive principal stress at intersections and extensional relays. The transition from deformation band to joint formation along these sections of the fault system likely resulted from the combined effects of changes in remote tectonic loading, burial depth, fluid pressure, and rock properties. In the case of the Moab fault, we conclude that the structural heterogeneity in the fault zone is systematically related to the geometric evolution of the fault, the local state of stress associated with fault slip , and the remote loading history. Because the type and distribution of structures affect fault permeability and strength, our results predict systematic variations in these parameters with fault evolution. ?? 2004 Geological Society of America.

Geological Society of America Bulletin↗

USGS2010

Bicentennial of the 1811–1812 New Madrid earthquake sequence, December 2011–2012

A series of earthquakes hit the New Madrid seismic zone of southeastern Missouri, northeastern Arkansas, and adjacent parts of Tennessee and Kentucky, in December 1811 to February 1812. Three earthquakes had a magnitude of 7.0 or greater. The first earthquake occurred December 16, 1811, at 2:15 a.m.; the second 9 a.m. on January 23, 1812; and the third on February 7, 1812, at 3:45 a.m. These three earthquakes were among the largest to strike North America since European settlement. The main shocks were followed by many hundreds of aftershocks that lasted for decades. Many of the aftershocks were major earthquakes themselves. The area that was strongly shaken by the three main shocks was 2-3 times as large as the strongly shaken area of the 1964 M9.2 Alaskan earthquake, and 10 times as large as that of the 1906 M7.8 San Francisco earthquake.

General Information Product↗

USGS2023

Bedrock-surface elevation and overburden thickness maps of the five boroughs, New York City, New York

Digital maps of bedrock elevation and overburden thickness (depth to bedrock) were constructed for the five boroughs of New York City by the U.S. Geological Survey, in cooperation with the New York City Department of Design and Construction, from a compilation of historical and newly acquired data. Raster surfaces were interpolated from a point database containing data from more than 14,000 locations collected from a variety of sources. These data were collected between 1905 and 2021. These maps were constructed to supplement existing tools for the evaluation of potential construction of geothermal heat pump technology for buildings in New York City. The bedrock underlying the study area ranges from easily weathered to very resistant to weathering. This differential susceptibility to erosion, along with numerous north-northwest-trending faults, is believed to control the shape of the bedrock surface. Glacial scouring of the bedrock during the Pleistocene Epoch is the most recent control on the topography of bedrock surfaces. Overburden thickness is an important consideration for evaluation and construction of geothermal systems. Bedrock-surface elevation ranges from about 360 feet above sea level (in central Staten Island and northern Bronx) to 1,200 feet below sea level (in southern Queens) (North American Vertical Datum of 1988). The overburden thickness ranges from 0 foot thick at surface outcrops on Staten Island, Manhattan, and the Bronx, to 1,280 feet thick in southeastern Queens.

Data Report↗

USGS1975

Radiometric age map of southeast Alaska

This map includes published, thesis, and open-file radiometric data available to us as of June, 1975. Some dates are not plotted because of inadequate location data in the original references. The map is divided into five sections, based on 1:1,000,000 scale enlargements of the National Atlas maps of Alaska. Within each section (e.g., southeastern Alaska), radiometric dates are plotted and keyed to 1:250,000 scale quadrangles. Accompanying each map section is table 1, listing map numbers and the sample identification numbers used in DGGS Special Report 10: Radiometric Dates from Alaska-A 1975 Compilation”. The reader is referred to Special Report 10 for more complete information on location, rock type, dating method, and literature references for each age entry. A listing of dates in Special Report lo which require correction or deletion is included S table 2. Corrected and additional entries are listed in table 3. The listings in tables 2 and 3 follow the format of Special Report 10. Table 4 is a glossary of abbreviations used for quadrangle name, rock type, mineral dated, and type of dating method used.

Alaska↗

USGS1975

Radiometric age map of Aleutian Islands

This map includes published, thesis, and open-file radiometric data available to us as of June, 1975. Some dates are not plotted because of inadequate location data in the original references. The map is divided into five sections, based on 1:1,000,000 scale enlargements of the National Atlas maps of Alaska. Within each section (e.g., southeastern Alaska), radiometric dates are plotted and keyed to 1:250,000 scale quadrangles. Accompanying each map section is table 1, listing map numbers and the sample identification numbers used in DGGS Special Report 10: Radiometric Dates from Alaska-A 1975 Compilation”. The reader is referred to Special Report 10 for more complete information on location, rock type, dating method, and literature references for each age entry. A listing of dates in Special Report lo which require correction or deletion is included S table 2. Corrected and additional entries are listed in table 3. The listings in tables 2 and 3 follow the format of Special Report 10. Table 4 is a glossary of abbreviations used for quadrangle name, rock type, mineral dated, and type of dating method used.

Alaska↗

USGS1975

Radiometric age map of southwest Alaska

This map includes published, thesis, and open-file radiometric data available to us as of June, 1975. Some dates are not plotted because of inadequate location data in the original references. The map is divided into five sections, based on 1:1,000,000 scale enlargements of the National Atlas maps of Alaska. Within each section (e.g., southeastern Alaska), radiometric dates are plotted and keyed to 1:250,000 scale quadrangles. Accompanying each map section is table 1, listing map numbers and the sample identification numbers used in DGGS Special Report 10: Radiometric Dates from Alaska-A 1975 Compilation”. The reader is referred to Special Report 10 for more complete information on location, rock type, dating method, and literature references for each age entry. A listing of dates in Special Report lo which require correction or deletion is included S table 2. Corrected and additional entries are listed in table 3. The listings in tables 2 and 3 follow the format of Special Report 10. Table 4 is a glossary of abbreviations used for quadrangle name, rock type, mineral dated, and type of dating method used.

Alaska↗

USGS1975

Radiometric age map of southcentral Alaska

This map includes published, thesis, and open-file radiometric data available to us as of June, 1975. Some dates are not plotted because of inadequate location data in the original references. The map is divided into five sections, based on 1:1,000,000 scale enlargements of the National Atlas maps of Alaska. Within each section (e.g., southeastern Alaska), radiometric dates are plotted and keyed to 1:250,000 scale quadrangles. Accompanying each map section is table 1, listing map numbers and the sample identification numbers used in DGGS Special Report 10: Radiometric Dates from Alaska-A 1975 Compilation”. The reader is referred to Special Report 10 for more complete information on location, rock type, dating method, and literature references for each age entry. A listing of dates in Special Report lo which require correction or deletion is included S table 2. Corrected and additional entries are listed in table 3. The listings in tables 2 and 3 follow the format of Special Report 10. Table 4 is a glossary of abbreviations used for quadrangle name, rock type, mineral dated, and type of dating method used.

Alaska↗

USGS1975

Radiometric age map of northern Alaska

This map includes published, thesis, and open-file radiometric data available to us as of June, 1975. Some dates are not plotted because of inadequate location data in the original references. The map is divided into five sections, based on 1:1,000,000 scale enlargements of the National Atlas maps of Alaska. Within each section (e.g., southeastern Alaska), radiometric dates are plotted and keyed to 1:250,000 scale quadrangles. Accompanying each map section is table 1, listing map numbers and the sample identification numbers used in DGGS Special Report 10: Radiometric Dates from Alaska-A 1975 Compilation”. The reader is referred to Special Report 10 for more complete information on location, rock type, dating method, and literature references for each age entry. A listing of dates in Special Report lo which require correction or deletion is included S table 2. Corrected and additional entries are listed in table 3. The listings in tables 2 and 3 follow the format of Special Report 10. Table 4 is a glossary of abbreviations used for quadrangle name, rock type, mineral dated, and type of dating method used.

Alaska↗

USGS2007

Magnetotelluric Data, Mid Valley, Nevada Test Site, Nevada

Introduction The United States Department of Energy (DOE) and the National Nuclear Security Administration (NNSA) at their Nevada Site Office (NSO) are addressing ground-water contamination resulting from historical underground nuclear testing through the Environmental Management (EM) program and, in particular, the Underground Test Area (UGTA) project. One issue of concern is the nature of the somewhat poorly constrained pre-Tertiary geology and its effects on ground-water flow. Ground-water modelers would like to know more about the hydrostratigraphy and geologic structure to support a hydrostratigraphic framework model that is under development for the Rainier Mesa/Shoshone Mountain Corrective Action Unit (CAU). During 2003, the U.S. Geological Survey (USGS), in cooperation with the DOE and NNSA-NSO, collected and processed data at the Nevada Test Site in and near Yucca Flat (YF) to help define the character, thickness, and lateral extent of the pre-Tertiary confining units. We collected 51 magnetotelluric (MT) and audio-magnetotelluric (AMT), stations for that research. In early 2005 we extended that research with 26 additional MT data stations, located on and near Rainier Mesa and Shoshone Mountain (RM-SM). The new stations extended the area of the hydrogeologic study previously conducted in Yucca Flat. This work was done to help refine what is known about the character, thickness, and lateral extent of pre-Tertiary confining units. In particular, a major goal was to define the upper clastic confining unit (UCCU). The UCCU is comprised of late Devonian to Mississippian siliciclastic rocks assigned to the Eleana Formation and Chainman Shale. The UCCU underlies the Yucca Flat area and extends westward towards Shoshone Mountain, southward to Buckboard Mesa, and northward to Rainier Mesa. Late in 2005 we collected another 14 MT stations in Mid Valley and in northern Yucca Flat basin. That work was done to better determine the extent and thickness of the UCCU near the southeastern RM-SM CAU boundary with the southwestern YF CAU, and also in the northern YF CAU. The purpose of this report is to release the MT data at those 14 stations. No interpretation of the data is included here.

Open-File Report↗

USGS1992

Jurassic ash-flow sheets, calderas, and related intrusions of the Cordilleran volcanic arc in southeastern Arizona: Implications for regional tectonics and ore deposits

Volcanologic, petrologic, and paleomagnetic studies of widespread Jurassic ash-flow sheets in the Huachuca-southern Dragoon Mountains area have led to identification of four large source calderas and associated comagmatic intracaldera intrusions. Stratigraphic, facies, and contact features of the caldera-related tuffs also provide constraints on the locations, lateral displacements, and very existence for some major northwest-trending faults and inferred regional thrusts in south-eastern Arizona. For example, the intricate Cochise thrust system, as mapped by others in the southern Dragoon Mountains, consists instead of primary depositional contacts within caldera-fill megabreccia, and the inferred regional thrusts do not exist, at least as previously interpreted. Silicic alkalic compositions of the Jurassic caldera-related, ash-flow tuffs; bimodal associated mafic magmatism; and interstratified coarse sedimentary deposits provide evidence for synvolcanic extension and rifting within the Cordilleran magmatic arc. Gold-copper mineralization is associated with subvolcanic intrusions at several of the Jurassic calderas.

Arizona↗

USGS1975

Silurian and Devonian miogeosynclinal and transitional rocks of the Fish Creek Reservoir window, central Idaho

Documentation of Devonian continental-shelf shallow-water carbonate rocks in the core of the Fish Creek Reservoir window shifts the known westernmost limit of the Devonian miogeosyncline 50 km (30 mi) southwest across the structural grain from the well-known miogeosynclinal sequence in the Lost River Range. The miogeosynclinal carbonate sequence in the window has a minimum thickness of 450 m (1,500 ft). It comprises the upper Lower Devonian (Emsian) and lower Middle Devonian (Eifelian) Carey Dolomite (new), the upper Middle Devonian (Givetian) and Upper Devonian Jefferson Formation, and the Upper Devonian Picabo Formation (new). Conodont faunas precisely date the Carey. The Picabo Formation, composed of interbedded sandy dolomite-pebble conglomerate and dolomitic quartzose sandstone, is unlike any previously described formation of Late Devonian or Early Mississippian age in central Idaho. It resembles parts of the Stansbury, Beirdneau, Leatham, and Victoria Formations, which reflect areas of local Late Devonian uplift and erosion of older shelf rocks in northern Utah and southeastern Idaho. Transitional (continental-slope) rocks of the Roberts Mountains Formation representing reef and offreef facies are thrust over the Devonian shelf sequence within the Fish Creek Reservoir window. The Roberts Mountains Formation here is precisely dated as latest Silurian (Pridolian, eosteinhornensis Zone) through earliest Devonian (Lochkovian) by a sequence of conodont faunas. The easternmost known exposures of possible Devonian siliceous facies rocks assigned to the Milligen(?) Formation are present less than 4.8 km (3 mi) southwest of the shelf sequence. Structural relations and paleotectonic reconstructions suggest that they have a minimum eastward translation of 32 km (20 mi). The Devonian continent-ocean basin interface, along which the Antler orogenic belt developed at this latitude, probably was located near the east edge of the present Idaho batholith.

Idaho↗

USGS2015

Groundwater availability of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho

The Columbia Plateau Regional Aquifer System (CPRAS) covers about 44,000 square miles of southeastern Washington, northeastern Oregon, and western Idaho. The area supports a $6-billion per year agricultural industry, leading the Nation in production of apples, hops, and eight other commodities. Groundwater pumpage and surface-water diversions supply water to croplands that account for about 5 percent of the Nation’s irrigated lands. Groundwater also is the primary source of drinking water for the more than 1.3 million people in the study area. Increasing competitive demands for water for municipal, fisheries/ecosystems, agricultural, domestic, hydropower, and recreational uses must be met by additional groundwater withdrawals and (or) by changes in the way water resources are allocated and used throughout the hydrologic system. As of 2014, most surface-water resources in the study area were either over allocated or fully appropriated, especially during the dry summer season. In response to continued competition for water, numerous water-management activities and concerns have gained prominence: water conservation, conjunctive use, artificial recharge, hydrologic implications of land-use change, pumpage effects on streamflow, and effects of climate variability and change. An integrated understanding of the hydrologic system is important in order to implement effective water-resource management strategies that address these concerns. To provide information to stakeholders involved in water-management activities, the U.S. Geological Survey (USGS) Groundwater Resources Program assessed the groundwater availability as part of a national study of regional systems (U.S. Geological Survey, 2008). The CPRAS assessment includes: The present status of groundwater resources, How these resources have changed over time, and Development and application of tools to estimate system responses to stresses from future uses and climate variability and change. This effort builds on previous investigations, especially the USGS Columbia Plateau Regional Aquifer-System Analysis study (CP-RASA). A major product of this new assessment is a numerical groundwater-flow model of the system. The model was used to estimate water-budget components of the hydrogeologic units composing the groundwater system, and to evaluate groundwater availability under existing land- and water-use conditions and a possible future climate scenario representing an increase in pumpage demand due to a warming climate. Information from this study also allowed for analysis of: The CPRAS for predevelopment times (pre-1920), Variations from 1920 through 2007, Conditions during 1985–2007 (referred to as “existing conditions”), and Changes in the system from predevelopment times. The model also is a useful tool for investigating water supply, water demand, management strategies, groundwater-surface water exchanges, and potential effects of changing climate on the hydrologic system.

Idaho, Oregon, Washington↗

USGS2024

Hydrogeologic framework and extent of saltwater intrusion in Kings, Queens, and Nassau Counties, Long Island, New York

In 2016, the U.S. Geological Survey began a multiyear cooperative study with the New York State Department of Environmental Conservation to evaluate the sustainability of Long Island’s sole-source aquifer system through hydrogeologic mapping, compilation of groundwater chloride concentrations, and groundwater flow modeling. In the initial phase of the islandwide study, the hydrogeologic framework and extent of saltwater intrusion in aquifers in Kings, Queens, and Nassau Counties on western Long Island, N.Y., were investigated. The aquifer system underlying western Long Island has been under stress from pumping of public, irrigation (golf course), and industrial supply wells. Saltwater intrusion has occurred from surrounding embayments (East River, Long Island Sound, Jamaica Bay, and the Atlantic Ocean) due to pumping. Eighteen boreholes were drilled and cores taken during 2019–21 to collect hydrogeologic, geochemical, and geophysical data to delineate the complex subsurface hydrogeology and extent of saltwater intrusion within the study area. Evaluation of the new cores, reexamination of legacy core descriptions, and analysis of borehole geophysical logs was used to refine the previously published hydrogeologic framework of Pleistocene and Cretaceous unconsolidated sediments in the area, including delineation of a previously undefined hydrogeologic unit between the Magothy aquifer and the Raritan confining unit, herein named the “upper Raritan aquifer.” The upper Raritan aquifer was first recognized in southeastern Nassau County from an analysis of about 50 closely spaced boreholes with high-resolution core descriptions and gamma-ray (gamma) logs. Further analysis of borehole logs across the study area indicated that the upper Raritan aquifer was also present in Kings and Queens Counties. Nuclear magnetic resonance (NMR) logging was used for the first time on Long Island to provide estimates of the hydraulic properties of the major aquifer and confining units. Unlike other geophysical logs that record responses to the rock matrix and fluid properties and are strongly dependent on mineralogy, NMR logs record responses to the presence of hydrogen protons in the formation fluid to determine water fraction and pore-size distribution. NMR log analysis provided estimates of the clay-bound, capillary-bound, and mobile water fractions and hydraulic conductivity of aquifers and confining units penetrated by five wells in Nassau County. Pumpage for public-supply and industrial wells on Long Island began in the 1870s with small, localized suppliers of populated areas in Kings and Queens Counties. By 1904–16, pumpage for public water supply in Kings County averaged 21 million gallons per day, and averaged 37 million gallons per day in Queens County, mostly from the upper glacial aquifer. Saltwater intrusion was reported as early as the beginning of the 20th century and included the upper glacial-Jameco-Magothy and Lloyd-North Shore aquifer systems. By 1936, pumping in central Kings County created a major cone of depression in the water table extending to the south shore of much of Kings County and into southwestern Queens County. Saltwater intrusion has caused the shutdown of public-supply wells in Kings, Queens, and Nassau Counties. A large saltwater intrusion wedge in the Lloyd aquifer was indicated in southern Queens County in the early part of the 20th century, and the saltwater interface may have been onshore predevelopment. Most of Kings and Queens Counties are intruded with saltwater in both the upper glacial-Jameco-Magothy and Lloyd-North Shore aquifers systems. Saltwater increased during the 20th century and continues to increase to the present (2023) in the Lloyd-North Shore aquifer system in Great Neck and Manhasset Neck in northern Nassau County. A major wedge of saltwater intrusion in the upper glacial-Jameco-Magothy aquifer in southwestern Nassau County appears to be increasing.

New York↗

USGS1994

Evolution of volcanic and tectonic features in caldera settings and their importance in the localization of ore deposits

Many calderas are located along regionally important fault zones that are intermittently active before and after the caldera cycle. In mineralized calderas, the ore deposits are controlled by structures developed during caldera formation and by regional faults which intersect and reactivate the caldera-related structures. In the earliest phase of the caldera cycle, tumescence occurs over the shallowly emplaced magma chamber and normal faults develop within the structural dome above the magma chamber. This early phase of faulting is disrupted by caldera formation but some of the faults are preserved outside the caldera margin and may become important ore-controlling structures such as the Ruja mercury deposit in the McDermitt caldera complex, Nevada, and the precious metal deposits in the Atlanta district, Nevada, outside the Indian Peak caldera. Caldera-related structures such as ring fracture faults are commonly the most important in controlling the emplacement of resurgent magma, as well as postcollapse intrusions and associated ore deposits. During the resurgence phase of the caldera, faults related to an apical graben, and radial and ring faults and fractures form and may extend outside the collapse structure. Radial and ring faults and fractures provided the structural control for gold alunite-type deposits in the Rodalquilar caldera complex, Spain.At the end of the caldera cycle, the area over the batholith related to the caldera-forming magma chambers is uplifted as isostatic compensation occurs, or subsides if the volcanic field is developed within a rapidly subsiding graben. Volume change resulting from crystallization will also contribute to subsidence. Regional subsidence of the Lake Owyhee volcanic field in southeastern Oregon at the end of the caldera cycle is reflected by arkosic sedimentation in the caldera basins and throughout the eastern part of the volcanic field. Crystallization of the underlying batholith permits the reestablishment of brittle deformation along the regional faults which initially may have controlled magma emplacement. This tectonic activity may reactivate caldera structures and these typically become important for localization of hydrothermal activity. Hot spring-type gold deposits in the Lake Owyhee volcanic field formed when a regional northwest-trending structure reactivated the caldera ring fracture fault zone of the Three Fingers caldera. The formation of hydrothermal ore deposits at the end of the caldera cycle is often related to tectonic reactivation of caldera structures by regional faults and emplacement of small volumes of magma as stocks and vent complexes along these structures.

Economic Geology↗

USGS2023

Status of water-level altitudes and long-term and short-term water-level changes in the Chicot and Evangeline (undifferentiated) and Jasper aquifers, greater Houston area, Texas, 2022

Since the early 1900s, groundwater withdrawn from the primary aquifers that compose the Gulf Coast aquifer system—the Chicot, Evangeline, and Jasper aquifers—has been an important source of water in the greater Houston area, Texas. This report, prepared by the U.S. Geological Survey in cooperation with the Harris-Galveston Subsidence District, City of Houston, Fort Bend Subsidence District, Lone Star Groundwater Conservation District, and Brazoria County Groundwater Conservation District, is one in an annual series of reports depicting the status of water-level altitudes and water-level changes in these aquifers in the greater Houston area. In this report, the Chicot and Evangeline aquifers are treated as a single hydrogeologic unit for the purposes of providing annual assessments of regional-scale water-level altitudes and changes over time. In 2022, shaded depictions of water-level altitudes for the Chicot and Evangeline aquifers (undifferentiated) ranged from about 270 feet (ft) below the North American Vertical Datum of 1988 (NAVD 88) to about 195 ft above NAVD 88. The largest decline in water-level altitudes indicated by the 1977–2022 long-term water-level-change map was southeast of The Woodlands. In comparison, the 1990–2022 long-term water-level-change map depicts declines in water-level altitudes in localized areas at or near certain wells in parts of northwestern Harris County and southern Montgomery County. The largest rise in water-level altitudes for 1977–2022 was observed in a relatively large area in southeastern Harris County, whereas the largest rise in water-level altitudes for 1990–2022 was observed in a relatively small area in central Harris County. The 5-year short-term water-level-change map depicts the largest declines at three wells in northern Fort Bend County and the largest rises at five wells in southwestern and central Harris County. The 1-year short-term water-level-change map depicts the largest decline at a well in north-central Harris County and the largest rises at a well in north-central Fort Bend County and a well in southwestern Harris County. In 2022, shaded depictions of water-level altitudes for the Jasper aquifer ranged from about 213 ft below NAVD 88 to about 285 ft above NAVD 88. The 2000–22 long-term water-level-change map depicts water-level declines throughout most of the study area where water-level-measurement data from the aquifer were collected, with the largest decline in north-central Harris County and south-central Montgomery County south of The Woodlands. The 5-year short-term water-level-change map depicts the largest decline at a well in Conroe and the largest rise at a well in south-central Montgomery County. The 1-year short-term water-level-change map depicts the largest decline at a well in south-central Montgomery County east of The Woodlands and the largest rise at a well in Conroe.

Texas↗

USGS2022

Status of water-level altitudes and long-term water-level changes in the Chicot and Evangeline (undifferentiated) and Jasper aquifers, greater Houston area, Texas, 2021

Since the early 1900s, groundwater withdrawn from the primary aquifers that compose the Gulf Coast aquifer system—the Chicot and Evangeline (undifferentiated) and Jasper aquifers—has been the primary source of water in the greater Houston area, Texas. This report, prepared by the U.S. Geological Survey in cooperation with the Harris-Galveston Subsidence District, City of Houston, Fort Bend Subsidence District, Lone Star Groundwater Conservation District, and Brazoria County Groundwater Conservation District, is one in an annual series of reports depicting the status of water-level altitudes and water-level changes in aquifers in the greater Houston area. In contrast to previous reports, the Chicot and Evangeline aquifers are treated as a single hydrogeologic unit in this report. In 2021, shaded depictions of water-level altitudes for the Chicot and Evangeline aquifers (undifferentiated) ranged from 300 feet (ft) below the North American Vertical Datum of 1988 (NAVD 88) to 300 ft above NAVD 88. The largest decline in water-level altitudes indicated by the 1977–2021 long-term water-level-change map for the Chicot and Evangeline aquifers (undifferentiated) was in the north-central part of The Woodlands, Tex., whereas the 1990–2021 long-term water-level-change map for the Chicot and Evangeline aquifers (undifferentiated) depicts a large area of decline in water-level altitudes in northwestern Harris County, northwest of Jersey Village, Tex. The largest rise in water-level altitudes in the Chicot and Evangeline aquifers (undifferentiated) was observed in a relatively large area in southeastern Harris County for 1977–2021, whereas the largest rise in water-level altitudes for 1990–2021 was in a relatively large area in central Harris County. In 2021, shaded depictions of water-level altitudes for the Jasper aquifer ranged from 250 ft below NAVD 88 to 300 ft above NAVD 88. The 2000–21 long-term water-level-change map for the Jasper aquifer depicts water-level declines throughout most of the study area where water-level-altitude data from the Jasper aquifer were collected, with the largest decline in northern Harris County southwest of The Woodlands.

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