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USGS1969

Geology, hydrology, and water quality in the Fresno area, California

The Fresno area comprises about 1.400 square miles lying west of the foothills of the Sierra Nevada and east of the trough of the San Joaquin Valley. The rainfall averages less than 10 inches per year causing agricultural development to depend mainly on surface-water deliveries and ground-water pumpage. Surface-water deliveries and ground-water pumpage, however, vary considerably from year to year. For example, in agricultural year 1958 (April 1, 1958-March 31, 1959) surface-water deliveries were about 1,340,000 acre-feet and agricultural ground-water pumpage was about 1,740,000 acre-feet, but in agricultural year 1960 deliveries were only about 560,000 acre-feet and pumpage was about 2,520,000 acre-feet. Alluvial fans are the dominant geomorphic features in the area. Small alluvial fans have been formed near the foothills by the deposits from the numerous intermittent streams that lie both north and south of the Kings River. Thicker and much more extensive alluvial fans have been formed under most of the area by deposits from the San Joaquin and Kings Rivers. Geologic units in the area consist of consolidated rocks and unconsolidated deposits. In turn, consolidated rocks consist of basement complex of pre-Tertiary age and marine and continental sedimentary rocks of Cretaceous and Tertiary age. Unconsolidated deposits are of both Tertiary and Quaternary age. Most of the geologic units dip gently southwestward approximately paralleling the back slope of the Sierra Nevada. Although some of these geologic units are faulted, especially in the deep subsurface, faulting has not affected the occurrence and movement of fresh ground water. The basement complex crops out along the eastern border of the area and yields only small amounts of water to wells; the marine and continental sedimentary rocks do not crop out in the area and do not yield any water to wells. The unconsolidated deposits are divided into an older series of Tertiary and Quaternary age, and a younger series of Quaternary age. The continental deposits of Tertiary and Quaternary age crop out beneath the extreme southeastern part of the area and yield small amounts of water to wells, and the deposits of Quaternary age crop out over most of the area and yield more than 90 percent of the water pumped from wells. The deposits of Quaternary age in turn are divided into older alluvium, lacustrine and marsh deposits, younger alluvium, flood-basin deposits. and sand dunes. The older alluvium is by far the most important aquifer in the Fresno area. It consists of intercalated lenses of clay, silt, silty and sandy clay, clayey and silty sand, sand, gravel, cobbles, and boulders, and in general it is fine grained near the trough of the valley and beneath the alluvial fans of intermittent streams. In the older alluvium, yields to wells range from less than 20 gpm (gallons per minute) to more than 3,000 gpm. The lacustrine and marsh deposits occur only in the subsurface in the western part of the area. Consisting mostly of silt and clay, they are virtually impermeable and thus restrict the vertical movement of water. These deposits from oldest to youngest are designated the E-clay, the C-clay, and the A-clay. The E-clay is the thickest and most extensive of all the lacustrine and marsh deposits. Because the clays tend to confine ground water in the Fresno area, five water bodies are recognized. These are the unconfined water body, the shallow water body, the confined water body below the A-clay, the confined water body below the C-clay, and the confined water body below the E-clay. The unconfined water body underlies most of the Fresno area. The shallow and confined water bodies underlie parts of the extreme western part of the area. There, heads in successively underlying water bodies are less than those in overlying water bodies, indicating that some ground water moves slowly downward through the clays. From agricultural years 1957 to 1962, outflow in the area exceeded inflow. As a result, for this period, the Fresno area had a net deficit of about 2,890,000 acre-feet. This deficit was made up for mostly by a decline in ground water stored. Water levels in all water bodies have been declining over the years, yet when streamflow and canal deliveries are large they show a general rise. The general movement of ground water in the Fresno area is toward the southwest, although pumping depressions near Fresno and near the western part of the area, cause ground water to move northward, southward, and westward toward them.

California↗

USGS2008

Surficial Geologic Map of the Worcester North-Oxford- Wrentham-Attleboro Nine-Quadrangle Area in South- Central Massachusetts

The surficial geologic map layer shows the distribution of nonlithified earth materials at land surface in an area of nine 7.5-minute quadrangles (417 mi2 total) in south-central Massachusetts (fig. 1). Across Massachusetts, these materials range from a few feet to more than 500 ft in thickness. They overlie bedrock, which crops out in upland hills and in resistant ledges in valley areas. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (such as grain size and sedimentary structures), constructional geomorphic features, stratigraphic relationships, and age. Surficial materials also are known in engineering classifications as unconsolidated soils, which include coarse-grained soils, fine-grained soils, or organic fine-grained soils. Surficial materials underlie and are the parent materials of modern pedogenic soils, which have developed in them at the land surface. Surficial earth materials significantly affect human use of the land, and an accurate description of their distribution is particularly important for water resources, construction aggregate resources, earth-surface hazards assessments, and land-use decisions. The mapped distribution of surficial materials that lie between the land surface and the bedrock surface is based on detailed geologic mapping of 7.5-minute topographic quadrangles, produced as part of an earlier (1938-1982) cooperative statewide mapping program between the U.S. Geological Survey and the Massachusetts Department of Public Works (now Massachusetts Highway Department) (Page, 1967; Stone, 1982). Each published geologic map presents a detailed description of local geologic map units, the genesis of the deposits, and age correlations among units. Previously unpublished field compilation maps exist on paper or mylar sheets and these have been digitally rendered for the present map compilation. Regional summaries based on the Massachusetts surficial geologic mapping studies discuss the ages of multiple glaciations, the nature of glaciofluvial, glaciolacustrine, and glaciomarine deposits, and the processes of ice advance and retreat across Massachusetts (Koteff and Pessl, 1981; papers in Larson and Stone, 1982; Oldale and Barlow, 1986; Stone and Borns, 1986; Warren and Stone, 1986). This compilation of surficial geologic materials is an interim product that defines the areas of exposed bedrock and the boundaries between glacial till, glacial stratified deposits, and overlying postglacial deposits. This work is part of a comprehensive study to produce a statewide digital map of the surficial geology at a 1:24,000-scale level of accuracy. This surficial geologic map layer covering nine quadrangles revises previous digital surficial geologic maps (Stone and others, 1993; MassGIS, 1999) that were compiled on base maps at regional scales of 1:125,000 and 1:250,000. The purpose of this study is to provide fundamental geologic data for the evaluation of natural resources, hazards, and land information within the Commonwealth of Massachusetts.

Open-File Report↗

USGS1999

Seismic and tsunami hazard in Puerto Rico and the Virgin Islands

Executive Summary Puerto Rico and the Virgin Islands are located at an active plate boundary between the North American plate and the northeast corner of the Caribbean plate. The region was subject in historical times to large magnitude earthquakes and devastating tsunamis. A major downward tilt of the sea floor north of Puerto Rico and the Virgin Islands, large submarine rockslides, and an unusually large negative gravity anomaly are also indicative of a tectonically active region. Scientists have so far failed to explain the deformation of this region in a coherent and predictable picture, such as in California, and this has hampered their ability to assess seismic and tsunami hazards in the region. The NE corner of the Caribbean is unique among the seismically-active regions of the United States in that it is mostly covered by water. This fact presents an additional challenge for seismic and tsunami hazard assessment and mitigation. The workshop, convened in San Juan on March 23-24, 1999, was "historic" in that it brought together for the first time a broad spectrum of scientists, engineers, and public and private sector officials who deal with such diverse questions as tectonic models, probabilistic assessment of seismic hazard, prediction of tsunami runup, strong ground motion, building codes, stability of man-made structures, and the public’s preparedness for natural disasters. It was an opportunity for all the participants to find out how their own activity fit into the broad picture of science and how it aids society in hazard assessment and mitigation. In addition, the workshop was offered as a continuing education course at the Colegio de Ingenieros y Agrimensores de Puerto Rico, which assured a rapid dissemination of the results to the local community. A news conference which took place during the workshop alerted the public to the efforts of the USGS, other Federal agencies, the Commonwealth of Puerto Rico, universities and the private sector. During the first day of the workshop, participants from universities, federal institutions, and consulting firms in Puerto Rico, the Virgin Islands, the continental U.S., Dominican Republic, and Europe reviewed the present state of knowledge including a review and discussion of present plate models, recent GPS and seismic reflection data, seismicity, paleoseismology, and tsunamis. The state of earthquake/tsunami studies in Puerto Rico was presented by several faculty members from the University of Puerto Rico at Mayaguez. A preliminary seismic hazard map was presented by the USGS and previous hazard maps and economic loss assessments were considered. During the second day, the participants divided into working groups and prepared specific recommendations for future activities in the region along the six following topics below. Highlights of these recommended activities are: Marine geology and geophysics – Acquire deep-penetration seismic reflection and refraction data, deploy temporary ocean bottom seismometer arrays to record earthquakes, collect high-resolution multibeam bathymetry and side scan sonar data of the region, and in particular, the near shore region, and conduct focussed high-resolution seismic studies around faults. Determine slip rates of specific offshore faults. Assemble a GIS database for available marine geological and geophysical data. Paleoseismology and active faults - Field reconnaissance aimed at identifying Quaternary faults and determining their paleoseismic chronology and slip rates, as well as identifying and dating paleoliquefaction features from large earthquakes. Quaternary mapping of marine terraces, fluvial terraces and basins, beach ridges, etc., to establish framework for understanding neotectonic deformation of the island. Interpretation of aerial photography to identify possible Quaternary faults. Earthquake seismology – Determine an empirical seismic attenuation function using observations from local seismic networks and recently-installed broad-band stations. Evaluate existing earthquake catalogs from local networks and regional stations, complete the catalogs. Transcribe the pre-1991 network data from 9-track tape onto more stable archival media. Calibrate instruments of local networks. Use GPS measurement to constrain deformation rates used in seismic-hazard maps. Engineering – Prepare liquefaction susceptibility maps for the urban areas. Update and improve databases for types of site conditions. Collect site effect observations and near-surface geophysical measurements for future local (urban-area) hazard maps. Expand the number of instruments in the strong motion program. Develop fragility curves for Puerto Rico construction types and details, and carry out laboratory testing on selected types of mass-produced construction. Consider tsunami design in shoreline construction projects. Tsunami hazard - Extract tsunami observations from archives and develop a Caribbean historical tsunami database. Analyze prehistoric tsunami deposits. Collect accurate, up-to-date, near-shore topography and bathymetry for accurate inundation models. Prepare tsunami flooding and evacuation maps. Establish a Caribbean Tsunami Warning System for Puerto Rico and the Virgin Islands. Evaluate local, regional, national, and global seismic networks and equipment, and their role in a tsunami warning system. Societal concerns – Prepare warning messages, protocols, and evacuation routes for earthquake, tsunami, and landslide hazards for Puerto Rico and the U.S. Virgin Islands. Advocate enforcement of existing building codes. Prepare non-technical hazard assessment maps for political and educational uses. Raise the awareness of potentially affected populations by presentations at elementary schools, by the production of a tsunami video, and by distribution of earthquake preparedness manuals in newspaper supplements. Promote partnerships at state and federal level for long-term earthquake and tsunami hazard mitigation. This partnership should also include the private sector such as the insurance industry, telecommunication companies, and the engineering community. The following reports of the various working groups are the cumulative recommendations of the community of scientists, engineers, and public officials, who participated in the workshop. The list of participants and the workshop’s agenda are given in the appendix. Marine and Geology and Geophysics Working Group Paleoseismology and Active Faults Working Group Joint Working Group for Earthquake Seismology and Engineering Tsunami Working Group Societal Concerns Working Group

Puerto Rico and the Virgin Islands↗

USGS2001

Geologic map and digital database of the Conejo Well 7.5 minute quadrangle, Riverside County, southern California

This data set maps and describes the geology of the Conejo Well 7.5 minute quadrangle, Riverside County, southern California. The quadrangle, situated in Joshua Tree National Park in the eastern Transverse Ranges physiographic and structural province, encompasses part of the northern Eagle Mountains and part of the south flank of Pinto Basin. It is underlain by a basement terrane comprising Proterozoic metamorphic rocks, Mesozoic plutonic rocks, and Mesozoic and Mesozoic or Cenozoic hypabyssal dikes. The basement terrane is capped by a widespread Tertiary erosion surface preserved in remnants in the Eagle Mountains and buried beneath Cenozoic deposits in Pinto Basin. Locally, Miocene basalt overlies the erosion surface. A sequence of at least three Quaternary pediments is planed into the north piedmont of the Eagle Mountains, each in turn overlain by successively younger residual and alluvial deposits. The Tertiary erosion surface is deformed and broken by north-northwest-trending, high-angle, dip-slip faults in the Eagle Mountains and an east-west trending system of high-angle dip- and left-slip faults. In and adjacent to the Conejo Well quadrangle, faults of the northwest-trending set displace Miocene sedimentary rocks and basalt deposited on the Tertiary erosion surface and Pliocene and (or) Pleistocene deposits that accumulated on the oldest pediment. Faults of this system appear to be overlain by Pleistocene deposits that accumulated on younger pediments. East-west trending faults are younger than and perhaps in part coeval with faults of the northwest-trending set. The Conejo Well database was created using ARCVIEW and ARC/INFO, which are geographical information system (GIS) software products of Envronmental Systems Research Institute (ESRI). The database consists of the following items: (1) a map coverage showing faults and geologic contacts and units, (2) a separate coverage showing dikes, (3) a coverage showing structural data, (4) a point coverage containing line ornamentation, and (5) a scanned topographic base at a scale of 1:24,000. The coverages include attribute tables for geologic units (polygons and regions), contacts (arcs), and site-specific data (points). The database, accompanied by a pamphlet file and this metadata file, also includes the following graphic and text products: (1) A portable document file (.pdf) containing a navigable graphic of the geologic map on a 1:24,000 topographic base. The map is accompanied by a marginal explanation consisting of a Description of Map and Database Units (DMU), a Correlation of Map and Database Units (CMU), and a key to point-and line-symbols. (2) Separate .pdf files of the DMU and CMU, individually. (3) A PostScript graphic-file containing the geologic map on a 1:24,000 topographic base accompanied by the marginal explanation. (4) A pamphlet that describes the database and how to access it. Within the database, geologic contacts , faults, and dikes are represented as lines (arcs), geologic units as polygons and regions, and site-specific data as points. Polygon, arc, and point attribute tables (.pat, .aat, and .pat, respectively) uniquely identify each geologic datum and link it to other tables (.rel) that provide more detailed geologic information.

California↗

USGS1980

Quaternary stratigraphic sections with radiocarbon dates, Chandler Lake Quadrangle, Alaska

Twenty-eight organic samples from 17 localities in the Anaktuvuk, Tulunga, and Itkillik Valleys and at Shainin Lake range in age from more than 40,000 to about 1000 14C yr B.P. These dates, combined with fossil identifications and measured stratigraphic sections, provide significant insights into the history of glaciation, climatic change, and related events of late Quaternary time in the north-central Brooks Range. Two dates from Tulunga Valley show that peat-forming intervals during the middle Wisconsin and during an earlier period were terminated by episodes of loess accretion that probably correspond to glaciations in the Brooks Range. The Anayaknaurak Bluff exposure in Anaktuvuk Valley contains a weathered till of the Banded Mountain (Itkillik I) glaciation overlain by unweathered outwash gravel of Antler Valley (Itkillik II) age. Radiocarbon dates from finer alluvium above the outwash indicate that a subsequent glacial readvance north of the range front occurred shortly after 13,000 yr B.P. This event was synchronous with a major glacial readvance that culminated between about 12,900 and 12,700 yr B.P. farther east in the Atigun and Sagavanirktok Valleys. Additional dates from Anaktuvuk Valley show that glacier ice had retreated from the Antler Valley end-moraine complex by 10,600 yr B.P. The elongate basin that formed behind the moraine dam was being filled by alluvium at this time, and filling continued as late as 6200 yr B.P. near the range front. A possible climatic reversal during this interval is suggested by dates from Anaktuvuk Valley and from Toolik Valley farther east, which show peat formation between about 9500 and 8200 yr B.P. followed by solifluction and fan-building. Soil test pits and other excavations near Anaktuvuk Pass show that the pass was deglaciated some time prior to 7250 yr B.P., and was suitable for human habitation by at least 6500 yr B.P. Dated buried peat suggests a change to more severe frost climate sometime after about 4750 yr B.P. Other dates from the Chandler Lake quadrangle bear mainly on formation of low (generally 2.5 to 6 m) river terraces during intervals of renewed glaciation at valley heads during the late Holocene. Neoglaciation in the north-central Brooks Range evidently began about 3500 yr B.P., or at least was perceptible by this time as increased loess influx to sites north of the range front. Stream alluviation was in progress 2800-2700 yr B.P. at sites near Anaktuvuk Pass, and continued until sometime after 2000 yr B.P. Final phases of alluviation began about 1200 and 450 yr B.P. Independent dating of cirque-glacier advances by lichenometry supports the alluvial chronology and suggests that alluviation was controlled largely by increased sediment yield to streams during times of cirque-glacier expansion and increased rock-glacier activity.

Alaska↗

USGS2007

Stratigraphy, structure, and geologic and coastal hazards in the Penuelas to Salinas area, southern Puerto Rico: A compendium of published literature

The Puerto Rico Electrical Power Authority has proposed construction of a pipeline to convey natural gas from the municipio of Peñuelas to the Aguirre thermoelectric power plant in the municipio of Salinas in southern Puerto Rico. To ensure that the geologic conditions along the possible routes do not represent a threat to the physical integrity of the natural gas pipeline, and thus comply with State and Federal regulations, the Puerto Rico Electrical Power Authority requested the U.S. Geological Survey to provide a synthesis of published literature of the geology of the coastal plain in the Peñuelas to Salinas area. The study area is located in part of the Southern Coastal Plain of Puerto Rico. In the area that extends from the municipio of Peñuelas eastward to the Laguna de las Salinas at Ponce, a distance of about 5 miles, the study area is underlain by middle Tertiary carbonate units. Eastward from the Laguna de las Salinas to the pipeline terminus at the Aguirre power plant in Salinas, a distance of about 30 miles, the terrain is underlain by fan-delta deposits of Quaternary age. The carbonate units and the fan-delta deposits are underlain by early Tertiary and older-age volcaniclastics with subordinate sedimentary rocks and lavas. The Great Southern Puerto Rico Fault Zone is the principal geologic structural feature in southern Puerto Rico. At present, the Great Southern Puerto Rico Fault Zone is considered largely quiescent, although it apparently is associated with minor earthquakes. There is no evidence of terrestrial, late Quaternary faulting within the Peñuelas to Salinas area. Seismic activity in this area mostly originates from extension zones of more distal shallow sources such as Mona Canyon to the northwest and the Anegada Trough northeast of the island of Puerto Rico. The magnitude of completeness of earthquakes in the study area ranges from 2.0 to 2.5. The seismic density for the southern coast including the study area is about 0.128 earthquakes per square mile, which is close to the average for southwestern Puerto Rico. The estimated maximum peak ground acceleration most likely to occur in the study area, due to shallow depth seismicity with 2 percent probability of exceedance in 50 years, is 9 feet per second squared, as obtained by modeling results. The estimated peak ground acceleration with 2 percent probability of exceedance in 50 years, due to deep seismicity is 7 feet per second squared. In Ponce, the probability of exceedance per year is higher than 0.1 for the peak ground acceleration values less than 1 that result from shallow depth seismicity sources such as the Mona Passage extension zone. The potential for liquefaction due to seismic activity may exist in areas near the coastline that have loosely to poorly consolidated sedimentary deposits and a water table close to or at the land surface. Slope failure susceptibility within the study area, due to rainfall and seismic activity, may be limited to the area that extends westward from Laguna de las Salinas to Peñuelas. In this area, foothills with slopes exceeding 10 degrees are close to the coastline and are underlain by clayey limestone and marls. In the remaining part of the study area, eastward from Laguna de las Salinas to Salinas, the land is either nearly flat or has a slope of less than 10 degrees; consequently, the susceptibility to landsliding (slope failure) caused by seismic activity and rainfall is considered to be minimal or nonexistent. Based on modeling results from a previous study, the estimated maximum inland extent of tsunami-induced flooding is 2,600 feet in the Laguna de las Salinas and Boca Chica, located in Ponce and Juana Díaz, respectively. Flooding about 3,000 and 2,800 feet from the coastline are estimated for areas near Punta Cabullón and Jobos areas, respectively. According to the modeling results, the estimated maximum runup of the tsunami-induced flooding ranges from 9 to 14 feet for the Boca Chica and Punta Cabullón areas, respectively.

Puerto Rico↗

USGS1997

Ground-water resources of the Alabama River Basin in Alabama; Subarea 8 of the Apalachicola-Chattahoochee-Flint and Alabama-Coosa-Tallapoosa River Basins

Drought conditions in the 1980's focused attention on the multiple uses of the surface- and ground-water resources in the Apalachicola-Chattahoochee-Flint (ACF) and Alabama-Coosa-Tallapoosa (ACT) River basins in Georgia, Alabama, and Florida. State and Federal agencies also have proposed projects that would require additional water resources and revise operating practices within the river basins. The existing and proposed water projects create conflicting demands for water by the States and emphasize the problem of water-resource allocation. This study was initiated to describe ground-water availability in the Alabama River basin of Alabama, Subarea 8 of the ACF and ACT River basins, and to estimate the possible effects of increased ground-water use within the basin. Subarea 8 encompasses about 6,750 square miles in the Coastal Plain physiographic province in central and southwestern Alabama. The Alabama River extends from the juncture of the Coosa and Tallapoosa Rivers near the city of Montgomery, to its juncture with the Tombigbee River, near the town of Calvert in Washington County. Subarea 8 includes the Cahaba River basin from the physiographic 'Fall Line' at the city of Centreville in Bibb County, to its mouth in Dallas County; and the Alabama River basin from near Montgomery to the Alabama River cutoff, about 6 miles northeast of its juncture with the Tombigbee River. The study area is underlain by sedimentary deposits of Cretaceous, Tertiary, and Quaternary ages. Major aquifers underlying Subarea 8 are, from shallowest to deepest, the Coastal lowlands aquifer system, the Floridan aquifer system, the Lisbon aquifer, The Nanafalia-Clayton aquifer, the Ripley aquifer, the Eutaw aquifer, and the Tuscaloosa aquifer. The conceptual model described for this study qualitatively subdivides the ground-water flow system into local (shallow), intermediate, and regional (deep) flow regimes. Ground-water discharge to tributaries mainly is from local and intermediate flow regimes and varies seasonally. The regional flow regime probably approximates steady- state conditions and discharges chiefly to major drains such as the Alabama River, and in upstream areas, to the Cahaba River. Ground-water discharge to major drains originates from all flow regimes. Mean-annual ground-water discharge to streams (baseflow) is considered to approximate the long-term, average recharge to ground water. The mean-annual baseflow was estimated using an automated hydrograph- separation method, and represents discharge from the local, intermediate, and regional flow regimes of the ground-water flow system. Mean-annual baseflow discharging from Subarea 8 was estimated to be 20,300 cubic feet per second. Mean-annual baseflow represented about 61 percent of total mean-annual stream discharge for the period of record. Estimated and measured stream discharge for selected sites on the Alabama River and its tributaries were compiled for the years 1941, 1954, and 1986, during which sustained droughts occurred throughout most of the ACF-ACT area. Stream discharges were assumed to be sustained entirely by baseflow during the latter periods of these droughts. Estimated baseflow near the end of the individual drought years was about 17 percent of the estimated mean-annual baseflow at the Alabama River cutoff, the most downstream point of Subarea 8. The potential exists for the development of ground-water resources on a regional scale throughout Subarea 8. Estimated ground-water use in 1990 was less than 1 percent of the estimated mean-annual baseflow, and about 2.4 percent of baseflow during the droughts of 1941, 1954, and 1986. Because ground-water use in Subareas 5 and 6 represents a relatively minor percentage of ground-water recharge, even a large increase in ground-water use in Subareas 5 and 6 in Georgia probably would have little effect on the quantity of ground water and surface water in Alabama. In addition, ground-water use in Subarea 3 in Georgia probably h

Open-File Report↗

USGS2014

Seismicity of the Earth 1900-2012 Java and vicinity

The Sunda convergent margin extends for 5,600 km from the Bay of Bengal and the Andaman Sea, both located northwest of the map area, towards the island of Sumba in the southeast, and then continues eastward as the Banda arc system. This tectonically active margin is a result of the India and Australia plates converging with and subducting beneath the Sunda plate at a rate of approximately 50 to 70 mm/yr. The main physiographic feature associated with this convergent margin is the Sunda-Java Trench, which stretches for 3,000 km parallel to the Java and Sumatra land masses and terminates at 120° E. The convergence of the Indo-Australia and Sunda plates produces two active volcanic arcs: Sunda, which extends from 105 to 122° E and Banda, which extends from 122 to 128° E. The Sunda arc results solely from relatively simple oceanic plate subduction, while the Banda arc represents the transition from oceanic subduction to continental collision, where a complex, broad deforming zone is found. Based on modern activity, the Banda arc can be divided into three distinct zones: an inactive section, the Wetar Zone, bound by two active segments, the Flores Zone in the west and the Damar Zone in the east. The lack of volcanism in the Wetar Zone is attributed to the collision of Australia with the Sunda plate. The absence of gap in volcanic activity is underlain by a gap in intermediate depth seismicity, which is in contrast to nearly continuous, deep seismicity below all three sections of the arc. The Flores Zone is characterized by down-dip compression in the subducted slab at intermediate depths and late Quaternary uplift of the forearc. These unusual features, along with GPS data interpretations indicate that the Flores Zone marks the transition between subduction of oceanic crust in the west and the collision of continental crust in the east. The Java section of the Sunda arc is considered relatively aseismic historically when compared to the highly seismically active Sumatra section, despite both areas being located along the same active subduction margin. Shallow (0–20 km) events have occurred historically in the overlying Sunda plate, causing damage to local and regional communities. A recent example was the May 26, 2006 M6.3 left-lateral strike-slip event that occurred at a depth of 10 km in central Java, and caused over 5,700 fatalities. Intermediate depth (70–300 km) earthquakes frequently occur beneath Java as a result of intraplate faulting within the Australia slab. Deep (300–650 km) earthquakes occur beneath the Java Sea and the back-arc region to the north of Java. Similar to other intermediate depth events, these earthquakes are also associated with intraslab faulting. However, this subduction zone exhibits a gap in seismicity from 250 to 400 km, interpreted as the transition between extensional and compressional slab stresses. Historical examples of large intraplate events include: the 1903 M8.1 event, 1921 M7.5 event, 1977 M8.3 event, and August 2007 M7.5 event. Large thrust earthquakes close to the Java trench are typically interplate faulting events along the slab interface between the Australia and Sunda plates. These earthquakes also generally have high tsunamigenic potential due to their shallow hypocentral depths. In some cases, these events have demonstrated slow moment-release and have been defined as ‘tsunami’ earthquakes, where rupture is large in the weak crustal layers very close to the seafloor. These events are categorized by tsunamis that are significantly larger than predicted by the earthquake’s magnitude. The most notable tsunami earthquakes in the Java region occurred on June 2, 1994 (M7.8) and July 17, 2006 (M7.7). The 1994 event produced a tsunami with wave runup heights of 13 m, killing over 200 people. The 2006 event produced a tsunami of up to 15 m, and killed 730 people. Although both of these tsunami earthquakes were characterized by rupture along thrust faults, they were followed by an abundance of normal faulting aftershocks. These aftershocks are interpreted to result from extension within the subducting Australia plate, whereas the mainshocks represented interplate faulting between the Australia and Sunda plates.

Open-File Report↗

USGS2011

Review and interpretation of previous work and new data on the hydrogeology of the Schwartzwalder Uranium Mine and vicinity, Jefferson County, Colorado

The Schwartzwalder deposit is the largest known vein type uranium deposit in the United States. Located about eight miles northwest of Golden, Colorado it occurs in Proterozoic metamorphic rocks and was formed by hydrothermal fluid flow, mineralization, and deformation during the Laramide Orogeny. A complex brittle fault zone hosts the deposit comprising locally brecciated carbonate, oxide, and sulfide minerals. Mining of pitchblende, the primary ore mineral, began in 1953 and an extensive network of underground workings was developed. Mine dewatering, treatment of the effluent and its discharge into the adjacent Ralston Creek was done under State permit from about 1990 through about 2008. Mining and dewatering ceased in 2000 and natural groundwater rebound has filled the mine workings to a current elevation that is above Ralston Creek but that is still below the lowest ground level adit. Water in the 'mine pool' has concentrations of dissolved uranium in excess of 1,000 times the U.S. Environmental Protection Agency drinking-water standard of 30 milligrams per liter. Other dissolved constituents such as molybdenum, radium, and sulfate are also present in anomalously high concentrations. Ralston Creek flows in a narrow valley containing Quaternary alluvium predominantly derived from weathering of crystalline bedrock including local mineralized rock. Just upstream of the mine site, two capped and unsaturated waste rock piles with high radioactivity sit on an alluvial terrace. As Ralston Creek flows past the mine site, a host of dissolved metal concentrations increase. Ralston Creek eventually discharges into Ralston Reservoir about 2.5 miles downstream. Because of highly elevated uranium concentrations, the State of Colorado issued an enforcement action against the mine permit holder requiring renewed collection and treatment of alluvial groundwater. As part of planned mine reclamation, abundant data were collected and compiled into a report by Wyman and Effner (2007), which was to be used as a basis for eventual mine site closure. In 2010 the U.S. Geological Survey was asked by the State of Colorado to provide an objective and independent review of the Wyman and Effner (2007) report and to identify gaps in knowledge regarding the hydrogeology of the mine site. Key findings from the U.S. Geological Survey assessment include geological structural analysis indicating that although the primary uranium-hosting fault likely does not cross under Ralston Creek, many complex subsidiary faults do cross under Ralston Creek. It is unknown if any of these faults act as conduits for mine pool water to enter Ralston Creek. Reported bedrock permeabilities are low, but local hydraulic gradients are sufficient to potentially drive groundwater flow from the mine pool to the creek. Estimated average linear velocities for the full range of reported hydraulic conductivities indicate groundwater transit times from the mine pool to the creek on the order of a few months to about 3,800 years or 11 to 65 years using mean reported input values. These estimates do not account for geochemical reactions along any given flow path that may differentially enhance or retard movement of individual dissolved constituents. New reconnaissance data including 34S isotope and 234U/238U isotopic activity ratios show potentially distinctive signatures for the mine pool compared to local groundwater and Ralston Creek water above the mine site. Although the mine pool may be near an equilibrium elevation, evidence for groundwater recharge transients indicates inflow to the workings that are greater than outflow. There is not enough hydraulic head data adjacent to the mine workings to adequately constrain a final equilibrium elevation or to predict how several wet years in succession might affect variations in mine pool elevation. Although ground level adits are sealed with bulkheads, if the mine pool elevation were to rise slightly to the elevation of or abo

Open-File Report↗

USGS2018

Geologic framework for the national assessment of carbon dioxide storage resources—Atlantic Coastal Plain and Eastern Mesozoic Rift Basins

This chapter presents information pertinent to the geologic carbon dioxide (CO 2 ) sequestration potential within saline aquifers located in the Atlantic Coastal Plain and Eastern Mesozoic Rift Basins of the Eastern United States. The Atlantic Coastal Plain is underlain by a Jurassic to Quaternary succession of sedimentary strata that onlap westward onto strata of the Appalachian Piedmont physiographic province and generally thicken eastward toward the present-day Atlantic coastline and onto the present-day continental shelf. Although no significant petroleum discoveries have been made on the coastal plain, the deep saline aquifers of the region appear to contain porous strata (potential reservoirs, or “storage formations”) that are overlain by fine-grained, laterally continuous strata (potential seals), which are prospective CO 2 sequestration targets. For the Atlantic Coastal Plain, we identify two storage assessment units (SAUs), both of which consist of Cretaceous strata. The two SAUs are the Lower Cretaceous Composite SAU C50700101 and the Upper Cretaceous Composite SAU C50700102. The Eastern Mesozoic Rift Basins are a chain of generally southwest- to northeast-trending, elongate sedimentary basins that either underlie the Atlantic Coastal Plain or crop out within adjacent geologic provinces to the west. Similar to the Atlantic Coastal Plain, there has been no significant oil and gas production from any of the basins, although there is a proven petroleum system in several of them. At least three of these basins appear to contain potential storage formations overlain by potential seal units. Most of the other basins were not assessed because a storage and (or) seal formation could not be established in the timeframe of the assessment, often because of the paucity of subsurface data for these basins in comparison to other petroliferous basins of the United States. Thus, we present information supporting one quantitative assessment in the Newark basin, as well as information supporting two nonquantitative assessments, one for strata in the Gettysburg basin and the other for strata in the Culpeper basin. We briefly discuss six other basins within the Eastern Mesozoic Rift Basins that were not assessed. For all SAUs, we discuss the areal distribution of suitable CO 2 reservoir rock. We also describe the overlying sealing unit and the geologic characteristics that influence the potential CO 2 storage volume and reservoir characteristics. These characteristics include storage formation depth, gross thickness, net thickness, porosity, permeability, and groundwater salinity. Case-by-case strategies for estimating the pore volume existing within structurally and (or) stratigraphically closed traps are presented. Although assessment results are not contained in this chapter, the geologic information included herein was used to calculate the potential storage space in the SAUs.

Atlantic Coastal Plain and Eastern Mesozoic Rift B↗

USGS1969

Seismic environment of the Burro Flats site, Ventura County, California: a brief, limited literature review

A limited review of available literature suggests that the maximum horizontal ground acceleration at the Burro Flats site from earthquakes in the region could range from less than 0.1 to 0.49 g. A magnitude 8 earthquake on the nearby San Andreas fault could produce ground acceleration in the range 0.18 to 0.31 g, and an expectable larger earthquake on that fault could produce larger accelerations. Ground motion from possible smaller but closer earthquakes ranges up to 0.49 g for an earthquake of magnitude 6.5 on the adjacent "Burro Flats fault". Estimation of these accelerations is dependent on determining the geologic environment of the site, the appropriate earthquake magnitudes to be assigned significant faults in that environment, and the attenuation of shaking between the earthquake epicenters and the site. The site lies within a tectonically active region--the historically active San Andreas fault is only 34 miles to the northeast, and lesser faults showing evidence of late Quaternary displacement are located closer to the site. Evidence for youthfulness of these lesser faults varies, and except for the active Newport-Inglewood zone and the Santa Ynez fault, they qualify as possible but as yet-unproven active faults. All known faults with appropriate length to site-distance ratios that are reasonably classed as late Quaternary faults are discussed, and are included as potential earthquake generators. Earthquakes of appropriate magnitude to be assigned to each fault are determined by assuming rupture in one event of half the map length of the fault, and applying relations (determined by several authors) between earthquake magnitude and rupture length in historic events to determine magnitudes. These magnitudes are, for the purposes of this brief review, probably reasonable estimates of the capabilities of each fault, although earthquakes of larger magnitude are possible. Accelerations are then determined by assuming earthquakes of the above determined magnitude placed at the closest point to the site on the fault trace, and applying attenuation curves of three different authors. Considerable uncertainty is inherent in the rough estimates of seismic accelerations made herein, for they are dependent on a chain of judgments, each of which, in itself, is uncertain. Present knowledge of the geology of the region is incomplete, so that geometry and structural relations of the faults are in part uncertain, and much evidence bearing on the youth of the faults has yet to be gathered and evaluated. Estimation of earthquake magnitude is also uncertain, and even assuming that approximate magnitude is known rather than estimated from fault length, estimates of maximum ground acceleration may differ greatly depending on the authority used. Further consideration of ground acceleration at the site might refine the estimates made herein and resolve the apparent contradictions between the authorities cited. Attention to frequency and duration of strong shaking would also be appropriate. This study was undertaken at the request of A. J. Pressesky, Assistant Director for Nuclear Safety, Division of Reactor-Development and Technology, U.S. Atomic Energy Commission, in March, 1969. It is based on a brief review of pertinent literature to which the authors had immediate access during the few weeks (April-May, 1969) available for report preparation. Because the report is limited both in scope and thoroughness, it must be considered no more than a first estimate of the tectonic and seismic environment of the Burro Flats site, and should not be considered sufficient, in itself, as a basis for design. The report is intended, however, to indicate the breadth of inquiry that is necessary in the consideration of ground acceleration at sites in California, and to indicate the incomplete status of geologic mapping and other geologic studies in the region. The report describes the tectonic environment of the Burro Flats site, discusses 10 pertinent faults individually, and presents possible earthquake magnitudes for those faults and resultant potential ground accelerations at the site.

California↗

USGS2017

Estimation of the groundwater resources of the bedrock aquifers at the Kettle Moraine Springs State Fish Hatchery, Sheboygan County, Wisconsin

Groundwater resources information was needed to understand regional aquifer systems and water available to wells and springs for rearing important Lake Michigan fish species at the Kettle Moraine Springs State Fish Hatchery in Sheboygan County, Wisconsin. As a basis for estimating the groundwater resources available, an existing groundwater-flow model was refined, and new groundwater-flow models were developed for the Kettle Moraine Springs State Fish Hatchery area using the U.S. Geological Survey (USGS) finite-difference code MODFLOW. This report describes the origin and construction of these groundwater-flow models and their use in testing conceptual models and simulating the hydrogeologic system. The study area is in the Eastern Ridges and Lowlands geographical province of Wisconsin, and the hatchery property is situated on the southeastern edge of the Kettle Moraine, a north-south trending topographic high of glacial origin. The bedrock units underlying the study area consist of Cambrian, Ordovician, and Silurian units of carbonate and siliciclastic lithology. In the Sheboygan County area, the sedimentary bedrock sequence reaches a thickness of as much as about 1,600 feet (ft). Two aquifer systems are present at the Kettle Moraine Springs State Fish Hatchery. A shallow system is made up of Silurian bedrock, consisting chiefly of dolomite, overlain by unconsolidated Quaternary-age glacial deposits. The glacial deposits of this aquifer system are the typical source of water to local springs, including the springs that have historically supplied the hatchery. The shallow aquifer system, therefore, consists of the unconsolidated glacial aquifer and the underlying bedrock Silurian aquifer. Most residential wells in the area draw from the Silurian aquifer. A deeper confined aquifer system is made up of Cambrian- and Ordovician-age bedrock units including sandstone formations. Because of its depth, very few wells are completed in the Cambrian-Ordovician aquifer system (COAS) near the Kettle Moraine Springs State Fish Hatchery. Three groundwater-flow models were used to estimate the water resources available to the hatchery from bedrock aquifers under selected scenarios of well placement and seasonal water requirements and subject to constraints on the effects of pumping on neighboring wells, local springs, and creeks. Model input data (recharge, water withdrawal, and boundary conditions) for these models were compiled from a number of data and information sources. The first model, named the “KMS model,” (KMS stands for Kettle Moraine Springs) is an inset model derived from a published USGS regional Lake Michigan Basin model and was constructed to simulate groundwater pumping from the semiconfined Silurian aquifer. The second model, named the “Pumping Test model,” was constructed to evaluate an aquifer pumping test conducted in the COAS as part of this project. The Pumping Test model was also used to simulate the local effects of 20 years of groundwater pumping from this deep bedrock aquifer for future hatchery operations. The third model, named the “LMB modified model,” is a version of the published Lake Michigan Basin (LMB) model that was modified with aquifer parameters refined in an area around the hatchery (approximately a 5-mile radius circle, corresponding to the area stressed by the aquifer pumping test). This LMB modified model was applied to evaluate regional effects of pumping from the confined COAS. The available Silurian aquifer groundwater resource was estimated using the KMS model with three scenarios—named “AllConstraints,” “Constraints2,” and “Constraints3”—that specified local water-level and flow constraints such as drawdown at nearby household wells, water levels inside pumping well boreholes, and flow in local streams and springs. Each scenario utilized the MODFLOW Groundwater Management Process (GWM) to select three locations from six candidate locations that provided the greatest combined flow while satisfying the constraints. The three constraint scenarios provided estimates of 430 gallons per minute (gal/min), 480 gal/min, and 520 gal/min pumping from three wells—AllConstraints, Constraints2, and Constraints3, respectively. The same three wells were selected for the scenarios that estimated 480 gal/min and 520 gal/min; the scenario that estimated 430 gal/min shared two of these same wells, but the third selected well was different. The available COAS groundwater resource was estimated by two scenarios with each conducted over a period of 20 years with the Pumping Test model and the LMB modified model . The Pumping Test model was used to simulate local effects of pumping, and the LMB modified model was used to simulate regional effects of pumping. The scenarios simulate a range of total and seasonal pumping rates potentially linked to site activities. Scenario 1 simulates two wells completed in the Cambrian-Ordovician aquifer system, each pumping for 8 months at 300 gal/min, followed by pumping for 4 months at 600 gal/min. The average yearly pumping rate of Scenario 1 is 800 gal/min. Scenario 2 simulates three wells completed in the Cambrian-Ordovician aquifer system pumping for 8 months at 200 gal/min, followed by pumping for 4 months at 500 gal/min. The average yearly pumping rate of Scenario 2 is 900 gal/min. The Pumping Test model simulations confirmed that drawdown in the boreholes of the pumping wells at the selected 2-well or 3-well rates will meet the desired condition that the pumping water level remains at least 100 ft above the highest Cambrian-Ordovician unit open to the well. The LMB modified model was used to evaluate the regional drawdown of the pumping from the confined COAS under the same 2-well and 3-well scenarios. At the nearest known existing COAS well, Campbellsport production well #4, the simulated drawdown for Scenario 1 after 20 years of cyclical pumping with two pumping wells averaging a total of 800 gal/min is 16.9 ft, whereas the simulated drawdown for Scenario 2 after 20 years of pumping with three pumping wells averaging a total of 900 gal/min is 19.0 ft. The total deep aquifer thickness at the Campbellsport location is on the order of 620 ft, meaning that the simulated drawdown for either scenario is about 3 percent of the confined aquifer thickness. The models developed as part of this project are archived in the project data release. The archive includes the model input and output files as well as MODFLOW source code and executables. ( Haserodt and others, 2017 ).

Wisconsin↗

USGS1989

Geology and water resources of Owens Valley, California

Owens Valley, a long, narrow valley located along the east flank of the Sierra Nevada in east-central California, is the main source of water for the city of Los Angeles. The city diverts most of the surface water in the valley into the Owens River-Los Angeles Aqueduct system, which transports the water more than 200 miles south to areas of distribution and use. Additionally, ground water is pumped or flows from wells to supplement the surface-water diversions to the river-aqueduct system. Pumpage from wells needed to supplement water export has increased since 1970, when a second aqueduct was put into service, and local concerns have been expressed that the increased pumpage may have had a detrimental effect on the environment and the indigenous alkaline scrub and meadow plant communities in the valley. The scrub and meadow communities depend on soil moisture derived from precipitation and the unconfined part of a multilayered aquifer system. This report, which describes the hydrogeology of the aquifer system and the water resources of the valley, is one in a series designed to (1) evaluate the effects that ground-water pumping has on scrub and meadow communities and (2) appraise alternative strategies to mitigate any adverse effects caused by pumping. Two principal topographic features are the surface expression of the geologic framework--the high, prominent mountains on the east and west sides of the valley and the long, narrow intermountain valley floor. The mountains are composed of sedimentary, granitic, and metamorphic rocks, mantled in part by volcanic rocks as well as by glacial, talus, and fluvial deposits. The valley floor is underlain by valley fill that consists of unconsolidated to moderately consolidated alluvial fan, glacial and talus, and fluvial and lacustrine deposits. The valley fill also includes interlayered recent volcanic flows and pyroclastic rocks. The bedrock surface beneath the valley fill is a narrow, steep-sided graben that is structurally separated into the Bishop Basin to the north and the Owens Lake Basin to the south. These two structural basins are separated by (1) a bedrock high that is the upper bedrock block of an east-west normal fault, (2) a horst block of bedrock (the Poverty Hills), and (3) Quaternary basalt flows and cinder cones that intercalate and intrude the sedimentary deposits of the valley fill. The resulting structural separation of the basins allowed separate development of fluvial and lacustrine depositional systems in each basin. Nearly all the ground water in Owens Valley flows through and is stored in the saturated valley fill. The bedrock, which surrounds and underlies the valley fill, is virtually impermeable. Three hydrogeologic units compose the valley-fill aquifer system, a defined subdivision of the ground-water system, and a fourth represents the valley fill below the aquifer system and above the bedrock. The aquifer system is divided into horizontal hydrogeologic units on the basis of either (1) uniform hydrologic characteristics of a specific lithologic layer or (2) distribution of the vertical hydraulic head. Hydrogeologic unit 1 is the upper unit and represents the unconfined part of the system, hydrogeologic unit 2 represents the confining unit (or units), and hydrogeologic unit 3 represents the confined part of the aquifer system. Hydrogeologic unit 4 represents the deep part of the ground-water system and lies below the aquifer system. Hydrogeologic unit 4 transmits or stores much less water than hydrogeologic unit 3 and represents either a moderately consolidated valley fill or a geologic unit in the valley fill defined on the basis of geophysical data. Nearly all the recharge to the aquifer system is from infiltration of runoff from snowmelt and rainfall on the Sierra Nevada. In contrast, little recharge occurs to the system by runoff from the White and Inyo Mountains or from direct precipitation on the valley floor. Ground water flows from the margins of the valley towards the center of the valley; the ground water then flows south to the terminus of the system at Owens (dry) Lake. Ground water flows south from Bishop Basin to Owens Lake Basin through the narrows that constrict the flow opposite Poverty Hills. The aquifer system in the northern half of Owens Lake Basin is divided into east and west halves by the barrier effect caused by the Owens Valley fault. Discharge from the aquifer system is primarily by pumpage and evapotranspiration, and to a lesser extent by flowing wells, springs, underflow, and leakage to the Owens River-Los Angeles aqueduct system. Withdrawals from pumped or flowing wells is the largest component of discharge and accounts for about 50 percent of the outflow from the system. Transpiration by scrub and meadow plant communities, and to a lesser extent by irrigated alfalfa pasture, accounts for about 40 percent of the system's discharge. Natural hydraulic conductivity ranges from less than 400 to about 12,000 feet per day in the basalt flows, the more permeable material in the aquifer system. Where the basalts are fractured by explosives and drilling techniques, actual transmissivities can be greater than 1,000,000 feet squared per day. Hydraulic conductivities in sedimentary deposits of the aquifer system range from less than a few feet per day in lacustrine clays to more than 300 feet per day in gravel stringers and beach deposits in the transition zone between alluvial fan deposits and fluvial and lacustrine deposits. Degree of confinement in the aquifer system generally increases to the south and east in both the Bishop and Owens Lake Basins. The vertical hydraulic gradient across hydrogeologic unit 2 and confining beds in hydrogeologic units 1 and 3 is a function of (1) the asymmetric recharge and hydraulic head created by the dominant recharge from Sierra Nevada runoff and (2) the areal extent and thickness of the confining beds. Although most of the pumpage is from hydrogeologic unit 3, some coincident drawdown has been recorded in nonpumped wells that tap unit 1. Drawdown in hydrogeologic unit 1 is a function of changes in (1) lateral flow through hydrogeologic unit 1, (2) upward flow of ground water through the confining beds, (3) downward leakage of water from hydrogeologic unit 1 to unit 3 through wells, (4) direct withdrawal from well intervals open to hydrogeologic unit 1, and (5) increased evapotranspiration. The water in the aquifer system is generally of excellent quality for public supply and irrigation, with the exception of water stored in thick sequences of lacustrine silts and clays near Owens Lake. The water is principally a calcium bicarbonate type and dissolved-solids concentrations range from approximately 104 to 325 milligrams per liter. Water in the lacustrine sediments of Owens (dry) Lake is a sodium bicarbonate type and dissolved-solids concentrations are about 5,400 milligrams per liter.

California↗

USGS2015

Groundwater/surface-water interactions in the Bad River Watershed, Wisconsin

A groundwater-flow model was developed for the Bad River Watershed and surrounding area by using the U.S. Geological Survey (USGS) finite-difference code MODFLOW-NWT. The model simulates steady-state groundwater-flow and base flow in streams by using the streamflow routing (SFR) package. The objectives of this study were to: (1) develop an improved understanding of the groundwater-flow system in the Bad River Watershed at the regional scale, including the sources of water to the Bad River Band of Lake Superior Chippewa Reservation (Reservation) and groundwater/surface-water interactions; (2) provide a quantitative platform for evaluating future impacts to the watershed, which can be used as a starting point for more detailed investigations at the local scale; and (3) identify areas where more data are needed. This report describes the construction and calibration of the groundwater-flow model that was subsequently used for analyzing potential locations for the collection of additional field data, including new observations of water-table elevation for refining the conceptualization and corresponding numerical model of the hydrogeologic system. The study area can be conceptually divided into three primary hydrogeologic environments. The first encompasses the southern uplands with relatively low topographic relief, where groundwater-flow is unconfined and occurs primarily in sandy till and glacial outwash overlying Archean-aged crystalline bedrock. The second includes a transitional area of higher topographic relief and shallow depth to bedrock, in the vicinity of ridges formed by steeply dipping, early-Proterozoic aged metasedimentary units of the Marquette Range Supergroup (including the Ironwood Formation), and late-Proterozoic igneous units associated with the Midcontinent Rift System (MRS). Groundwater-flow in this area likely occurs primarily through connected networks of bedrock fractures that are not well characterized, and also in isolated pockets of Quaternary deposits. The third and last hydrogeologic environment includes lowlands along Lake Superior where a deep sandstone aquifer is confined by thick deposits of clay-rich till. Model input was compiled by using both published and unpublished data. Constant flux boundary conditions for the model perimeter were developed from a regional analytic element model described in appendix 1 of this report. Pumping from 26 high-capacity wells within the model area was included. The SFR stream network was developed from the National Hydrography Dataset (NHDPlus Version 2) and hydrography from the Wisconsin Department of Natural Resources (WDNR). Hydraulic conductivity values were determined for each model cell by interpolation from a network of pilot points, within zones representing major hydrogeologic units. Recharge to the groundwater system was estimated on a cell-by-cell basis by using the Soil Water Balance code (SWB), with gridded daily temperature and precipitation data for the period 1980–2011, and GIS coverages of soil and land-surface conditions. Estimated recharge varies considerably, following spatial patterns in the precipitation and soil hydrologic group inputs. The lowest recharge values occur in the Superior lowlands, whereas the highest values occur in the upland areas, especially those underlain by sandy soils, and in the vicinity of bedrock hills. The model was calibrated to groundwater-levels and base flows obtained from the USGS National Water Information System (NWIS) database, and groundwater-levels obtained from the WDNR and Band River Band well-construction databases. Calibration was performed via nonlinear regression by using the parameter-estimation software suite PEST. Groundwater levels and base-flow observations in the calibration dataset were well simulated by the calibrated model, with reasonable values of hydraulic conductivity. The pilot-point parameters that were most constrained by observations during model calibration coincided with the locations containing the most wells (head observations)—especially the population centers of Ashland, Mellen, and other communities along the major highway corridors. Results from the calibrated model illustrate differences in the nature of groundwater-ﬂow within the watershed. In the southern part of the watershed, where bedrock is shallow, groundwater ﬂow paths are relatively short, extending from local recharge areas to adjacent ﬁrst and second-order streams. In contrast, laterally continuous deposits of clay-rich till covering the Superior Lowlands isolate most smaller streams from the sandstone aquifer, allowing for longer ﬂow paths toward larger streams such as the Bad, Marengo, and White Rivers. Approximately three-quarters of all ﬁrst-order stream cells were dry in the Superior Lowlands, compared to only half of ﬁrst-order stream cells in the southern bedrock uplands. The model was used to delineate the groundwatershed for the Bad and Kakagon Rivers. “Groundwatershed” is deﬁned as the area contributing groundwater discharge to one of these streams and their tributaries. The groundwatershed was found to align closely with the surface-watershed, with the most notable exception occurring along the southwestern half of Birch Hill, where surface water drains southwest towards the Potato River, and groundwater ﬂows north and east towards Lake Superior. Similarly, the contributing area of groundwater-ﬂow to the Reservation was delineated. Results indicate the off-Reservation groundwater contributing area to be limited in comparison to the extent of the watershed, extending southward into the highlands underlain by MRS igneous rock units, but not further into the area underlain by the Marquette Range Supergroup. Stable isotope samples were collected from 54 wells within the watershed, to investigate sources of groundwater. Oxygen-18 (δ 18 O) values lower than -13.0 per mil were documented in the sampling, and likely indicate the presence of recharge water from the last glacial period (>9,500 years old) beneath the northern portion of the Reservation, in the vicinity of Odanah, Wisconsin. Finally, a new data-worth analysis of potential new monitoring-well locations was performed by using the model. The relative worth of new measurements was evaluated based on their ability to increase conﬁdence in model predictions of groundwater levels and base ﬂows at 35 locations, under the condition of a proposed open-pit iron mine. Results of the new data-worth analysis, and other inputs and outputs from the Bad River model, are available through an online dynamic web mapping service at ( http://wim.usgs.gov/badriver/ ).

Wisconsin↗

USGS1997

Preliminary geologic map of the San Fernando 7.5' quadrangle, southern California: A digital database

The city of San Fernando sits atop a structurally complex, sedimentologically diverse, and tectonically evolving late Tertiary-Quaternary basin situated within the Transverse Ranges of southern California. The surrounding San Fernando Valley (SFV) contains the headwaters of the Los Angeles River and its tributaries. Prior to the advent of flood control, the valley floor was composed of active alluvial fans and floodplains. Seasonal streams emanating from Pacoima and Big Tujunga Canyons drain the complex western San Gabriel Mountains and deposit coarse, highly permeable alluvium that contains generally high-quality ground water. The more shallow western part derives mainly from Tertiary and pre-Tertiary sedimentary rocks, and is underlain by less permeable, fine-grained deposits containing persistent shallow ground water and poorer water quality. Home of the 1971 San Fernando and the 1994 Northridge earthquakes, the SFV experienced near-record levels of strong ground motion in 1994 that caused widespread damage from strong shaking and ground failure. A new map of late Quaternary deposits of the San Fernando area shows that the SFV is a structural trough that has been filled from the sides, with the major source of sediment being large drainages in the San Gabriel Mountains. Deposition on the major alluvial fan of Tujunga Wash and Pacoima Wash, which issues from the San Gabriel Mountains, and on smaller fans, has been influenced by ongoing compressional tectonics in the valley. Late Pleistocene deposits have been cut by active faults and warped over growing folds. Holocene alluvial fans are locally ponded behind active uplifts. The resulting complex pattern of deposits has a major effect on liquefaction hazards. Young sandy sediments generally are highly susceptible to liquefaction where they are saturated, but the distribution of young deposits, their grain size characteristics, and the level of ground water all are complexly dependent on the tectonics of the valley. The San Fernando area lies on the southern slopes of the San Gabriel Mountains. The basement rocks here include high-grade metamorphic rocks of Precambrian age. The mountains are largely composed of crystalline basement that includes the Pelona Scist of probable Mesozoic age that has been overthrust by Precambrian gneisses; the gneisses were subsequently intruded by Mesozoic plutons prior to overthrusting along the latest Cretaceous Vincent thrust. Gneisses of somewhat variable composition and possibly varying ages are found in four terranes, but not all are in contact with Pelona Schist. Large tracts of Precambrian (1.2 billion years old) andesine anorthosite are intrusive into 1.7 billion year-old Mendenhall gneiss, and are found in the western part of the San Gabriels. Mixed with these are younger marble, limestone, and schist of possible Paleozoic age found in association with plutons along the southern margin of the range. The older rocks are intruded by diorite, quartz diorite, and granodiorite of Jurassic age. Also present are siliceous sedimentary rocks of Jurassic age. A thick section of Tertiary sedimentary and volcanic rocks overlie these units. The sediments located south of the San Gabriel Fault are totally different in character from those on the northern range flank, and mostly resemble the western Transverse Ranges due to their deposition in the southeastern Ventura basin; approximately 3,000 m of these sediments are exposed north and west of the city of San Fernando in the Tujunga syncline. Some of the Tertiary rocks are Paleocene and Eocene in age, but the bulk of these rocks are Oligocene and Miocene in age. The Vasquez and Sespe Formations of basal basaltic volcanic and sandstone are Oligocene and lower Miocene in age. These are overlain by clastic rocks of Tick Canyon and Mint Canyon Formations of middle to late Miocene age. Above these rocks are the Castaic, Modelo, and Santa Margarita Formations of fossiliferous marine shale, sand

California↗

USGS1975

Preliminary hydrogeologic appraisal of selected hydrothermal systems in northern and central Nevada

Several hydrothermal systems in northern and central Nevada were explored in a hydrogeologic reconnaissance. The systems studied comprise those at Stillwater and Soda Lakes-Upsal Hogback in the Carson Desert, Gerlach, Fly Ranch-Granite Range, and Double Hot Springs in the Black Rock Desert, Brady's Hot Springs, Leach Hot Springs in Grass Valley, Buffalo Valley Hot Springs, and Sulphur Hot Springs in Ruby Valley. The investigation focused on (1) delineating of areas of high heat flow associated with rising thermal ground water, (2) determining the nature of the discharge parts of the hydrothermal systems, (3) estimating heat discharge from the systems, (4) estimating water discharge from the systems, (5) obtaining rough estimates of, conductive heat flow outside areas of hydrothermal discharge, and (6) evaluating several investigative techniques that would yield the required information quickly and at relatively low cost. The most useful techniques were shallow test drilling to obtain geologic, hydraulic, and thermal data and hydrogeologic mapping of the discharge areas. The systems studied are in the north-central part of the Basin and Range province. Exposed volcanic rocks of latest Tertiary and Quaternary age are chiefly basaltic. Basaltic terranes are generally regarded as less favorable for geothermal resources than terranes that contain large volumes of young volcanic mocks of felsic to intermediate composition. Most of the known hydrothermal systems are associated with Basin and Range faults which are caused by crustal extension across the province. An area of high heat flow centered at Battle Mountain and possibly other areas of high heat flow may be related to crustal heat sources. However, some of the hydrothermal systems studied appear to be related to deep circulation of meteoric water in areas of 'normal' regional heat flow rather than to shallow-crustal heat sources. Discharge temperatures of thermal springs in the region range from slightly above mean annual air temperature (8?-12?C at most places) to boiling or slightly hotter. Geochemical data indicate that, in the major systems, subsurface temperatures at which thermal waters equilibrate with reservoir rocks range from 150? to more than 200?C. These data also indicate that the major systems are of the hot-water type rather than the vapor-dominated type. Depths of thermal-water circulation probably range from 2 to 6 kilometres in areas of 'normal' regional heat flow (~2 heatflow units) and from 1 to 3 kilometres in areas of high heat flow (~3-4 heat-flow units) such as near Battle Mountain. Most of the heat is discharged from the hydrothermal systems studied by (1) conduction through near-surface materials heated as a consequence of thermal-water convection, (2) convection as springflow, and (3) convection as steam discharge from spring pools, vents, fumaroles, and cracks. The mate of heat discharge by radiation from warm ground and by convection as lateral ground-water outflow is believed to be small in most systems and is not estimated. Estimates of net heat discharge from the systems studied range from about 0.8 x 106 calories per second at Buffalo Valley Hot Springs to about 14 x 106 calories per second at Stillwater. These estimates represent the approximate magnitude of the excess heat discharge from the thermal areas that results from the upward convection of hot water from deep sources. Water discharges from the hydrothermal systems by springflow, evapotranspiration, steam discharge, and lateral ground-water outflow. Estimated discharges range from about 0.2 x 106cubic metres per year from the Buffalo Valley Hot Springs system to about 3 x 106 cubic metres per year from the Stillwater system. In most of the hydrothermal systems studied and, by inference, in other similar systems in northern and central Nevada, the scale for potential .commercial development for production of electricity or for other uses may be constrained by the

Open-File Report↗

USGS1984

Hydrogeologic framework of the New Jersey coastal plain

Results are presented of a water-resources-oriented subsurface mapping program within the Coastal Plain of New Jersey. The occurrence and configuration of 15 regional hydrogeologic units are defined based primarily on the interpretation of borehole geophysical data. The nine aquifers and six confining beds are composed of unconsolidated clay, silt, sand, and gravel and range in age from Cretaceous to Quaternary. Electric and gamma-ray logs from more than 1,000 Coastal Plain wells were examined. Of these, interpretive data for 302 sites, selected for log depth, quality, and distribution, were used to prepare structure contour and thickness maps for each aquifer, and a thickness map for each confining bed. These maps, along with 14 hydrogeologic sections, show the geometry, lateral extent, and vertical and horizontal relationships among the 15 hydrogeologic units. The hydrogeologic maps and sections show that distinct lower, middle, and upper aquifers are present within the Potomac- Raritan-Magothy aquifer system near the Delaware River from Burlington County to Salem County. Although the lower aquifer is recognized only in this area, the middle aquifer extends into the northeastern Coastal Plain of New Jersey where it is stratigraph ically equivalent to the Farrington aquifer. The upper aquifer extends throughout most of the New Jersey Coastal Plain and is stratigraphically equivalent to the Old Bridge aquifer in the northeastern Coastal Plain. The overlying Merchantville-Woodbury confining bed is the most regionally extensive confining bed within the Coastal Plain of New Jersey. Its thickness ranges from less than 100 feet near the outcrop to more than 450 feet along the coast. The Englishtown aquifer system acts as a single aquifer throughout most of its subsurface extent, but contains two water-bearing sands in parts of Monmouth and Ocean Counties. The overlying Marshalltown-Wenonah confining bed is a thin, leaky unit ranging in thickness from approximately 20 to 80 feet. The Wenonah-Mount Laurel aquifer is identified in the subsurface throughout the New Jersey Coastal Plain southeast of its outcrop area. Sediments that overlie the Wenonah-Mount Laurel aquifer and that are subjacent to the major aquifers within the Kirkwood Formation and Cohansey Sand are described hydrologically as a composite confining bed. These include the Navesink Formation, Red Bank Sand, Tinton Sand, Hornerstown Sand, Vincentown Forma- tion, Manasquan Formation, Shark River Formation, Piney Point Formation, and the basal clay of the Kirkwood Formation. The Vincentown Formation functions as an aquifer within 3 to 10 miles downdip of its outcrop area. In areas farther downdip the Vincentown Formation functions as a confining bed. The Piney Point aquifer is laterally persistent from the southern New Jersey Coastal Plain northward into parts of Burlington and Ocean Counties. The Atlantic City 800-foot sand of the Kirkwood Formation can be recognized in the subsurface along coastal areas of Cape May, Atlantic, and southern Ocean Counties, but inland only as far west as the extent of the overlying confining bed. In areas west of the extent of the overlying confining bed, the Kirkwood Formation is in hydraulic connection with the overlying Cohansey Sand and younger surficial deposits and functions as an unconfined aquifer. (USGS)

New Jersey↗

USGS1981

Gold placer and Quaternary stratigraphy of the Jabal Mokhyat area, southern Najd Province, Kingdom of Saudi Arabia

An ancient gold placer at Jabal Mokhyat (lat 20?12.2'N., long 43?28'E.), about 90 km east of Qalat Bishah in the southern Najd Province, Kingdom of Saudi Arabia, was studied in 1973. Seven hundred and twenty-eight samples in 25 measured sections were collected along trenches and pits 2.5 m in depth and 2,600 m in total length. Alluvium was thicker than the excavation depth along about 50 percent of the trench length. The average gold content was 4.4 mg per m3, and the highest grade trench contained 40 mg gold per m 3. Because fine particulate gold is rare in the alluvium, a few large particles, 1 to 5 mm in diameter, greatly affected the sampling results. The ancient placer diggings are in small headwater wadis distributed over a 30-km 2 area, and the total dug area is about 1.2 km2. The placer produced an estimated 50 kg of gold and was worked about 2,600 + 250 years ago. The potential for a present-day placer operation is small. The gold is sparsely distributed in locally derived, flood-deposited, immature gravels throughout a stratigraphic section that consists of 1) calichified, saprolitic bedrock of Precambrian age; 2) basal, intensely calichified, saprolitic gravel (0-3 m thick) of Pleistocene age; 3) disconformable, slightly consolidated gravel and sand (0-1 m thick) of late Pleistocene age containing sparse, disseminated caliche; 4) firm loessic silt (0-1 m thick) of early Holocene age; and 5) loose sand and gravel (0.3-1 m thick) of late Holocene age. The loessic silt accumulated during the Holocene pluvial. The top of the loessic silt unit is dated at about 6,000 years B.P. by using charcoal from hearths of ancient man. Following the Holocene pluvial, the climate became arid, and extreme desiccation resulted in abundant eolian sand that progressively diluted the late Holocene gravels. The remnants of the pre-Holocene stratigraphy suggest similar climatic cycles during the Pleistocene. Abundant, sparsely mineralized, gold-bearing quartz veins (0-1 m wide) were the source of the placer gold. These late Proterozoic veins have hydrothermally altered wall-rock zones (1-5 m wide). The veins are dispersed over an area of 50 km 2. Though many veins were prospected in ancient times and some were slightly worked, only the Mokhyat ancient mine, located on a quartz-vein zone 30 m wide by 200 m long, was extensively worked. The quartz contains chalcopyrite, galena, sphalerite, tetrahedrite, an unidentified bismuth mineral, and small amounts of dispersed gold. The fissure quartz veins lie at the complexly splayed, terminal end of a small northwest-trending Najd fault that elsewhere along strike has ii km of left-lateral displacement. Most large veins are in north-trending vertical fractures where the stresses were distributed along an older, north-trending structural grain in andesitic greenstone terrane. Subhorizontal fracture sets contain conspicuous, well-developed gold-bearing quartz veins and associated alteration zones. These attest to the shallowness and youthfulness of mineralization during latest Precambrian time. Late Precambrian granitic plutons (625-600 m.y. old) had been deeply eroded before the gold minerals were emplaced; hence, the gold is not related to granitic plutonism. Abundant, widely distributed diabasic dikes associated with the Najd faulting event of latest Precambrian age were probably the heat source for the hydrothermal convection system and possibly the source of the gold.

Open-File Report↗