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At least 973 records · Page 54Linked to original sources
USGS1982

Evaulation of remote sensing, geological and geophysical data for south-central New York and northern Pennsylvania

A study was made of the relationship between lineaments observed on Landsat satellite images and the geologic framework of a portion of the Allegheny Plateau of south-central New York and northern Pennsylvania. The area is underlain by a relatively thick sequence of salt and other evaporites in the Silurian Salina Group and is a potential site for deep-storage of solid nuclear waste. A combination of remote sensing techniques, detailed geologic mapping and geophysical investigations were applied to the problem. Because of the premature termination of the Department of Energy contract, only a portion of the total work was completed. The completed portion of the project included 1) digital contrast enhancement of several Landsat multispectral scanner (MSS) images, 2) analysis of lineament patterns from a Landsat MSS-7 mosaic, 3) field mapping of bedrock joint patterns, 4) compilation and analysis of surface and subsurface structure and isopach maps, 5) collection and digital analysis of aeromagnetic data for southern New York, 6) compilation and analysis of aeromagnetic and gravity data for much of New York and Pennsylvania, and 7) analysis of seismic reflection survey lines for selected portions of New York and Pennsylvania. We identified eight major lineaments or lineament zones and studied them in detail. They typically represent linear alignments of the most conspicuous or prominent physiographic features observable on Landsat images. The Cortland-Ithaca, Watkins Glen-Tanghannock, Seneca Lake-Elmira, Painted Post-Blossburg and Endicott-Syracuse conspicuous lineaments include the Corning-Bath, Van Etten-Towanda, Van Etten-Candor and Van Etten-Odessa lineaments. In addition, a major fault system--the West Danby fault zone--was further defined by geologic and geophysical investigations during our study; the fault zone was not recognizable on satellite images. The lineaments and lineament zones were categorized by their azimuthal trends. Those with a northerly orientation (e.g. Van Etten-Towanda, Seneca Lake-Elmira, Painted Post-Blossburg and Endicott-Syracuse) are most common. Northeasterly lineaments (e.g. Cortland-Ithaca and Watkins Glen-Taughannock) also are common. The Corning-Bath and Van Etten-Odessa lineaments have a northwesterly orientation and the Van Etten-Candor lineament is the sole representative of the east-west direction. The West Danby fault system also trends east-west. All the lineaments or lineament zones studied appear to be related, in one fashion or another, to structural disturbances, because changes in the structural attitude of beds or thickness of rocks commonly occur along their extent. The changes in many instances occur on multiple stratigraphic horizons and in a manner suggestive of several different styles of tectonism, leading to the conclusion that the lineaments and lineament zones have been periodically reactivated during the Paleozoic and Mesozoic Eras. Aeromagnetic data commonly show a parallel alignment of contours juxtaposed or on line with lineaments and lineament zones, suggesting that these physiographic alignments owe their origin to features within the crystalline basement. Pre-Alleghanian faulting and depositional patterns show that the study area was affected by basement-controlled adjustments along and in the same direction as most of the lineaments and lineament zones. Actual displacements cannot be proven for all of the lineaments or lineament zones, but changes in dip of the rocks across these features suggest either basement hingelines or small displacement faulting which cannot be resolved by the present data. These displacements occurred in at least Middle-Late Ordovician, Middle-Late Silurian and the Early-Middle Devonian times. The major northeast trending lineament zones (Cortland-Ithaca and Watkins Glen-Taughannock) correspond in orientation and lie along the northeastward projection of the Rome Trough, a postulated Paleozoic aulacogen. Results of

Open-File Report↗
USGS2016

Flood-hazard analysis of four headwater streams draining the Argonne National Laboratory property, DuPage County, Illinois

Results of a flood-hazard analysis conducted by the U.S. Geological Survey, in cooperation with the Argonne National Laboratory, for four headwater streams within the Argonne National Laboratory property indicate that the 1-percent and 0.2-percent annual exceedance probability floods would cause multiple roads to be overtopped. Results indicate that most of the effects on the infrastructure would be from flooding of Freund Brook. Flooding on the Northeast and Southeast Drainage Ways would be limited to overtopping of one road crossing for each of those streams. The Northwest Drainage Way would be the least affected with flooding expected to occur in open grass or forested areas. The Argonne Site Sustainability Plan outlined the development of hydrologic and hydraulic models and the creation of flood-plain maps of the existing site conditions as a first step in addressing resiliency to possible climate change impacts as required by Executive Order 13653 “Preparing the United States for the Impacts of Climate Change.” The Hydrological Simulation Program-FORTRAN is the hydrologic model used in the study, and the Hydrologic Engineering Center‒River Analysis System (HEC–RAS) is the hydraulic model. The model results were verified by comparing simulated water-surface elevations to observed water-surface elevations measured at a network of five crest-stage gages on the four study streams. The comparison between crest-stage gage and simulated elevations resulted in an average absolute difference of 0.06 feet and a maximum difference of 0.19 feet. In addition to the flood-hazard model development and mapping, a qualitative stream assessment was conducted to evaluate stream channel and substrate conditions in the study reaches. This information can be used to evaluate erosion potential.

Illinois↗
USGS1975

Tectonics of the western Valley and Ridge foldbelt, Pendleton County, West Virginia - a summary report

A belt of high anticlines, the Nittany anticlinorium, occupies the western Valley and Ridge foldbelt in the central Appalachians. It extends southwestward from the Nittany arch of central Pennsylvania into the Virginias. An investigation of the tectonics of this anticlinorium in Pendleton County, W. Va., rules out active basement involvement in the deformation of the area. Cross-sectional models consistent with the accumulated data show that Middle Cambrian through Middle Ordovician carbonate rocks are technically stacked, shingle-fashion, from southeast to northwest below predominantly folded younger strata that have undergone less lateral shortening. Differential shortening in this area is of the proper order to balance cover deformation in the Allegheny synclinorium to the west. Field relations suggest a long period of abnormally high fluid pressures in Lower Devonian and older strata during deformation. At this time, the area was under sufficient northwest, near-horizontal compressive stress for abundant quartz deformation lamellae to form. Gravity sliding is ruled out as the deforming mechanism for this part of the Appalachian foldbelt. No significant tectonism appears to have occurred prior to Pennsylvanian time in this area.

West Virginia↗
USGS2013

Investigations of groundwater system and simulation of regional groundwater flow for North Penn Area 7 Superfund site, Montgomery County, Pennsylvania

Groundwater in the vicinity of several industrial facilities in Upper Gwynedd Township and vicinity, Montgomery County, in southeast Pennsylvania has been shown to be contaminated with volatile organic compounds (VOCs), the most common of which is the solvent trichloroethylene (TCE). The 2-square-mile area was placed on the National Priorities List as the North Penn Area 7 Superfund site by the U.S. Environmental Protection Agency (USEPA) in 1989. The U.S. Geological Survey (USGS) conducted geophysical logging, aquifer testing, and water-level monitoring, and measured streamflows in and near North Penn Area 7 from fall 2000 through fall 2006 in a technical assistance study for the USEPA to develop an understanding of the hydrogeologic framework in the area as part of the USEPA Remedial Investigation. In addition, the USGS developed a groundwater-flow computer model based on the hydrogeologic framework to simulate regional groundwater flow and to estimate directions of groundwater flow and pathways of groundwater contaminants. The study area is underlain by Triassic- and Jurassic-age sandstones and shales of the Lockatong Formation and Brunswick Group in the Mesozoic Newark Basin. Regionally, these rocks strike northeast and dip to the northwest. The sequence of rocks form a fractured-sedimentary-rock aquifer that acts as a set of confined to partially confined layers of differing permeabilities. Depth to competent bedrock typically is less than 20 ft below land surface. The aquifer layers are recharged locally by precipitation and discharge locally to streams. The general configuration of the potentiometric surface in the aquifer is similar to topography, except in areas affected by pumping. The headwaters of Wissahickon Creek are nearby, and the stream flows southwest, parallel to strike, to bisect North Penn Area 7. Groundwater is pumped in the vicinity of North Penn Area 7 for industrial use, public supply, and residential supply. Results of field investigations by USGS at the site and results from other studies support, and are consistent with, a conceptual model of a layered leaky aquifer where the dip of the beds has a strong control on hydraulic connections in the groundwater system. Connections within and (or) parallel to bedding tend to be greater than across bedding. Transmissivities of aquifer intervals isolated by packers ranged over three orders of magnitude [from about 2.8 to 2,290 square feet per day (ft 2 /d) or 0.26 to 213 square meters per day (m 2 /d)], did not appear to differ much by mapped geologic unit, but showed some relation to depth being relatively smaller in the shallowest and deepest intervals (0 to 50 ft and more than 250 ft below land surface, respectively) compared to the intermediate depth intervals (50 to 250 ft below land surface) tested. Transmissivities estimated from multiple-observation well aquifer tests ranged from about 700 to 2,300 ft 2 /d (65 to 214 m 2 /d). Results of chemical analyses of water from isolated intervals or monitoring wells open to short sections of the aquifer show vertical differences in concentrations; chloride and silica concentrations generally were greater in shallow intervals than in deeper intervals. Chloride concentrations greater than 100 milligrams per liter (mg/L), combined with distinctive chloride/bromide ratios, indicate a different source of chloride in the western part of North Penn Area 7 than elsewhere in the site. Groundwater flow at a regional scale under steady-state conditions was simulated by use of a numerical model (MODFLOW-2000) for North Penn Area 7 with different layers representing saprolite/highly weathered rock near the surface and unweathered competent bedrock. The sedimentary formations that underlie the study area were modeled using dipping model layers for intermediate and deep zones of unweathered, fractured rock. Horizontal cell model size was 100 meters (m) by 100 meters (328 ft by 328 ft), and model layer thickness ranged from 6 m (19.7 ft) representing shallow weathered rock and saprolite up to 200 m (656 ft) representing deeper dipping bedrock. The model did not include detailed structure to account for local-scale differences in hydraulic properties, with the result that local-scale groundwater flow may not be well simulated. Additional detailed multi-well aquifer tests would be needed to establish the extent of interconnection between intervals at the local scale to address remediation of contamination at each source area. This regional groundwater-flow model was calibrated against measured groundwater levels (1996, 2000, and 2005) and base flow estimated from selected streamflow measurements by use of nonlinear-regression parameter-estimation algorithms to determine hydraulic conductivity and anisotropy of hydraulic conductivity, streambed hydraulic conductivity, and recharge during calibration periods. Results of the simulation using the calibrated regional model indicate that the aquifer appears to be anisotropic where hydraulic conductivity is greatest parallel to the orientation of bedding of the formations underlying the area and least in the cross-bed direction. The maximum hydraulic conductivity is aligned with the average regional strike of the formations, which is “subhorizontal” in the model because the altitudes of the beds and model cells vary in the strike, as well as dip, direction. Estimated subhorizontal hydraulic conductivities (in strike direction parallel to dipping beds) range from 0.001 to 1.67 meters per day (0.0032 to 5.5 feet per day). The ratio of minimum (dip direction) to maximum (strike direction) subhorizontal hydraulic conductivity ranges from 1/3.1 to 1/8.6, and the ratio of vertical to horizontal hydraulic conductivity ranges from 1/1 to 1/478. However, limited available field data precluded rigorous calibration of vertical anisotropy in the model. Estimated recharge rates corresponding to calibration periods in 1996, 2000, and 2005 are 150, 109, and 124 millimeters per year (5.9, 4.3, and 4.9 inches per year), respectively. The calibrated groundwater-flow model was used to simulate groundwater flow under steady-state conditions during periods of relatively high withdrawals (pumpage) (1990) and relatively low withdrawals (2000 and 2005). Groundwater-flow paths originating from recharge areas near known areas of soil contamination (sources) were simulated. Pumped industrial and production wells captured more groundwater from several of these sources during 1990 than after 1990 when pumping declined or ceased and greater amounts of contaminated groundwater moved away from North Penn Area 7 Superfund site to surrounding areas. Uncertainty in simulated groundwater-flow paths from contaminant sources and contributing areas, resulting from uncertainty in estimated hydraulic properties of the model, was illustrated through Monte Carlo simulations. The effect of uncertainty in the vertical anisotropy was not included in the Monte Carlo simulations. Contributing areas indicating the general configuration of groundwater flow towards production well MG-202 (L-22) in the study area also were simulated for the different time periods; as simulated, the flow paths do not pass through any identified contaminant source in North Penn Area 7. However, contributing areas to wells, such as MG-202, located near many pumped wells are particularly complex and, in some cases, include areas that contribute flow to streams that subsequently recharge the aquifer through stream loss. In these cases, water-quality constituents, including contaminants that are present in surface water may be drawn into the aquifer to nearby pumped wells. Results of a simulated shutdown of well MG-202 under steady-state 2005 conditions showed that the area contributing recharge for nearby production well MG-76 (L-17), when MG-202 is not pumping, shifts downstream and is similar to the area contributing recharge for MG-202 when both wells are pumping. Concentrations of constituents in groundwater samples collected in fall 2005 or spring 2006 were compared to simulated groundwater-flow paths for the year 2005 to provide a qualitative assessment of model results. The observed spatial distribution of selected constituents, including TCE, CFC-11, and CFC-113 in groundwater in 2005 and the chloride/bromide mass ratios in 2006, generally were consistent with the model results of the simulated 2005 groundwater-flow paths at North Penn Area 7, indicating the presence of several separate sources of contaminants within North Penn Area 7.

Pennsylvania↗
USGS1941

Geologic structure and occurrence of gas in part of southwestern New York

The area covered by this report is in southwestern New York and includes a little more than 3,000 square miles in Steuben and Yates counties and parts of the six adjacent counties. This area has been mapped to determine the structural attitude of the exposed rocks, so as to aid those interested in prospecting for natural gas in the Oriskany sandstone of Lower Devonian age. Because of the gentle regional dip toward the southwest, the youngest beds are exposed in the southwest corner of the area, and progressively older beds crop out northeastward in successive bands that strike generally northwest. All the exposed rocks are of Upper Devonian age except those in a narrow belt at the extreme north edge of the area, where a small thickness of Middle Devonian rocks crops out. The maximum thickness of beds so exposed is nearly 4,000 feet, of which the lower part is predominantly soft dark shale and the upper part predominantly fine-grained sandstone and gray shale. All the beds are marine except a few tongues of continental deposits—red shale and sandstone and gray mudstone—in the youngest beds. All the beds thicken southeastward, so that there is a northwestward convergence between any two lithologic units in the series. More than 30 key horizons that are persistent and distinctive were mapped, and altitudes on these key horizons served as a basis for constructing the structure contour map. Many of the key horizons are formation or member boundaries, but others are the tops or bottoms of limestone or sandstone beds within formations. All the stratigraphic units mapped are purely lithologic. (See pl. 2.) The Tully limestone, which crops out along the northern border of the area, is an easily recognizable and therefore valuable key bed for subsurface correlations in this part of the State. Below the Tully limestone is a thick body of Middle Devonian shales of the Hamilton group which rests on another valuable key bed, the hard, cherty Onondaga limestone, also of Middle Devonian age. Below the Onondaga limestone is the Lower Devonian Oriskany sandstone, which is the gas-producing bed. Unlike the Onondaga, the Oriskany is locally thin or absent. The structure of most of the area is shown by contour lines at 25-foot intervals, but, where key horizons are lacking the structure is indicated by dip symbols. Upon the regional south and southwest dip are superposed numerous gentle folds whose axes trend approximately northeastward in the greater part of the area but more nearly eastward in the eastern part. The folds generally tend to become narrower and steeper, and therefore more closely spaced, southwestward. Many of the anticlines fork southwestward, whereas the synclines tend to fork northeastward. All the folds have a westward or southwestward plunge. Throughout the area the rocks are jointed in two dominant sets—one that trends northwest and the other east or northeast. No evident relation between these joints, which were measured only in the hard, relatively brittle beds, and the individual folds or domes was discernible. The faults are concentrated in the northeastern and southwestern parts of the area and trend either northeastward or northwestward. Some are nearly vertical normal faults ; others are steep reverse faults. Subsurface data show that most of the faults increase in throw downward and also that many subsurface faults do not reach the surface. A group of faults in the northwestern part of the Greenwood quadrangle and the southwestern part of the Hornell quadrangle were active during Upper Devonian time, while the Gowanda shale and overlying beds were being deposited. At this stratigraphic horizon the beds in a zone a few hundred feet thick are highly deformed in a wide belt on both sides of the faults. Sandstone layers are thinned out into long stringers or swollen into thick masses and in places are bent acutely without fracture. Thin layers of shale, coquina, and sand have flowed together into intricately plicated zones that lack cleavage and joints. These features show that the sediments were deformed while wet and plastic and buried only a little way below the sea floor. The beds that were laid down over these disturbed zones were not involved in this deformation. Many of the sharper flexures and most of the faults are not evident in the beds several hundred feet stratigraphically higher. Accordingly, broad, gentle folds in these higher beds in parts of the area south and west of the northwest corner of the Greenwood quadrangle may conceal, at considerable depths below them, narrow folds separated by abrupt flexures or faults. Several of the larger streams and rivers occupy strike valleys, and their courses swing to follow the changing strike of the rocks where they cross successive folds. But, with few exceptions, the small streams are not adjusted to the bedrock structure. Domes likely to serve as traps for natural gas are concentrated in the northeastern and southwestern parts of the area. The Wayne-Dundee gas field is in the northeastern part. All the other potentially valuable domes in this part of the area have been drilled and found valueless except one small structural feature in the southern part of the Ovid quadrangle, which, if the Oriskany is present, may trap a small quantity of gas. In the Greenwood quadrangle in the southwestern part of the area there is one gas field and four well-defined domes, all of which may be productive if the Oriskany sandstone is present. In the northwest corner of the quadrangle the dips indicate at least two domes that can be adequately defined and evaluated only by geophysical prospecting. The State Line gas field is in the Wellsville quadrangle. In the southeast corner of this quadrangle there are three other domes of comparable size that may also be productive if underlain by the Oriskany sandstone. At other places in the Wellsville quadrangle the dips suggest several anticlinal axes on which analogous productive domes may be found. The structural features in this quadrangle, however, are defined by contours only in the southeastern part. In the Woodhull quadrangle a large dome east of Jasper may be productive, and the western top of the large Wood-hull dome in the southwestern part of the quadrangle seems to warrant drilling, despite the absence of the Oriskany in a well on the eastern top. Two wells drilled in 1936 and 1937 a little northeast of a broad, nearly flat-topped dome in the Hornell quadrangle, a few miles east of Hornell, struck small flows of gas, suggesting that wells drilled higher on this dome may be productive. In much of the southwestern part of the area seismograph surveys should be of great value in determining the structure at the Tully and Onondaga horizons. Without abundant subsurface control of this sort, the danger of drilling into subsurface faults can hardly be overemphasized. Three closed or nearly closed synclines in the Greenwood and Wellsville quadrangles appear to be favorable places to drill for oil in the shallow sands— presumably parts of the Dunkirk sandstone.

New York↗
USGS1989

Preliminary geologic map of the Puu Anahulu quadrangle, Hawaii

Vent deposits and lava flows from Hualalai Volcano and lava flows from Mauna Loa and Mauna Kea Volcanoes cover the Puu Anahulu 7 1/2-minute quadrangle. Hualalai's diffuse north-trending rift zone, marked by the large trachyte cone of Puu Waawaa and several basaltic spatter cones, is located mainly in the southwestern part of the quadrangle. Several Hualalai flows originated in the Hualalai quadrangle, crossed the Puu Anahulu quadrangle, and terminated in the Kiholo quadrangle. Hualalai flows cover most of the western half of the quadrangle and are interlayered with Mauna Loa lavas along a 2-kilometer-wide strip from southeast to northwest across the middle of the Puu Anahulu quadrangle. Mauna Loa flows cover most of the eastern half. Mauna Kea flows are restricted to the northeastern corner, where they underlie Hualalai and Mauna Loa lavas. A few extensive and relatively young flows from Hualalai and Mauna Loa cover most of the quadrangle; thus, the older units are generally small in area. The oldest units in the quadrangle are the trachyte cone of Puu Waawaa and its flow, which includes Puu Anahulu, covers about 7 percent of the quadrangle. Basaltic lavas of Hualalai range in age from latest Pleistocene to less than 2,000 years. Pleistocene lavas cover about 5 percent of this quadrangle, lavas that are 5,000 - 10,000 years old cover about 5 percent, lavas that are 3,000 - 5,000 years old cover about 3 percent, and three extensive flows that are 1,500 - 3,000 years old cover about 25 percent. The oldest Mauna Loa flows, that are probably 5,000 - 10,000 years old, cover about 2 percent of this quadrangle, flows that are 3,000 - 5,000 years old cover about 18 percent, six extensive flows that are 1,500 - 3,000 years old cover about 23 percent, and the 1859 flow, that is the youngest volcanic unit, and covers about 10 percent of its area. Two hawaiite flows from Mauna Kea, that are late Pleistocene in age, cover about 2 percent of the quadrangle.

Hawaii↗
USGS2023

Geology of the Mount Rogers area, revisited: Evidence of Neoproterozoic continental rifting, glaciation, and the opening and closing of the Iapetus Ocean, Blue Ridge, VA–NC–TN

Recent field and geochronological studies in eight 7.5-minute quadrangles near Mount Rogers in Virginia, North Carolina and Tennessee recognize (1) important stratigraphic and structural relationships for the Neoproterozoic Mount Rogers and Konnarock Formations, and the northeast end of the Mountain City window; (2) the separation of Mesoproterozoic rocks of the Blue Ridge into three age groups; and (3) the timing and emplacement of the Blue Ridge thrust sheet. The study area includes folded and faulted Paleozoic strata of the Valley and Ridge in the northwest juxtaposed by metamorphic and igneous rocks of the Blue Ridge to the southeast. In the Valley and Ridge, Cambrian to Middle Ordovician carbonate and clastic rocks are exposed in a syncline in the Pulaski thrust sheet; these rocks are overridden by the Blue Ridge thrust sheet. The northeast end of the Mountain City window is interpreted as a simple window; the Stone Mountain fault is folded and continues as the Iron Mountain fault on the NW-side of the window. The Stone Mountain fault does not exist at the surface to the NE near the Razor Ridge volcanic center. Instead, a continuous section of Proterozoic gneisses, Mount Rogers Formation, Konnarock Formation and Chilhowee Group is now recognized. Rhyolites of the Mount Rogers Formation range from 760–749Ma, with detrital zircon age populations from associated volcaniclastic rocks indicating magmatism and rifting began by ~780 Ma. Rhyolite outliers in the Konnarock Formation and a change from rift-related clastic rocks of the Mount Rogers Formation transitioning to maroon laminites, mudstones and laminites with dropstones, suggest that the Konnarock Formation may be as old as ~751 Ma. Mesoproterozoic crystalline rocks of the Blue Ridge, previously referred to as the Cranberry Gneiss, are distinguished based on field relationships and SHRIMP U–Pb zircon geochronology: (1) ~1.33 Ga pre-Grenvillian crust; (2) 1190–1140 Ma granitoids (early magmatic suite); and (3) 1075–1030 Ma granitoids (late magmatic suite). Multiple greenschist-facies high-strain zones, including the 2–11 km wide Fries high-strain zone, occur in the Blue Ridge thrust sheet. Fabrics across the Fries and Gossan Lead faults have similar orientations and NW–directed contractional deformation. 40 Ar/ 39 Ar hornblende, muscovite, and K-feldspar ages indicate the western and eastern Blue Ridge had different thermal histories. The eastern Blue Ridge (Gossan Lead thrust sheet) experienced a 360–340 Ma amphibolite facies event prior to juxtaposition with the western Blue Ridge. 40 Ar/ 39 Ar muscovite ages in western Blue Ridge rocks document greenschist facies metamorphism and deformation and emplacement of the Blue Ridge thrust sheet at ~340 Ma; the Catface and Fries faults are tentatively interpreted to be contemporaneous. After initial emplacement of the Blue Ridge thrust sheet at ~340 Ma, shortening was accommodated by westward translation along the basal decollement, which carried the Blue Ridge thrust sheet to its current position.

North Carolina, Tennessee, Virginia↗
USGS2004

Hydrogeology, water quality, and distribution and sources of salinity in the Floridan aquifer system, Martin and St. Lucie Counties, Florida

The Floridan aquifer system is considered to be a valuable source for agricultural and municipal water supply in Martin and St. Lucie Counties, despite its brackish water. Increased withdrawals, however, could increase salinity and threaten the quality of withdrawn water. The Floridan aquifer system consists of limestone, dolomitic limestone, and dolomite and is divided into three hydrogeologic units: the Upper Floridan aquifer, a middle confining unit, and the Lower Floridan aquifer. An informal geologic unit at the top of the Upper Floridan aquifer, referred to as the basal Hawthorn/Suwannee unit, is bound above by a marker unit in the Hawthorn Group and at its base by the Ocala Limestone; a map of this unit shows an area where substantial eastward thickening begins near the coast. This change in thickness is used to divide the study area into inland and coastal areas. In the Upper Floridan aquifer, an area of elevated chloride concentration greater than 1,000 milligrams per liter and water temperature greater than 28 degrees Celsius exists in the inland area and trends northwest through north-central Martin County and western St. Lucie County. A structural feature coincides with this area of greater salinity and water temperature; this feature is marked by a previously mapped northwest-trending basement fault and, based on detailed mapping in this study of the structure at the top of the basal Hawthorn/Suwannee unit, an apparent southeast-trending trough. Higher hydraulic head also has been mapped in this northwest-trending area. Another area of high chloride concentration in the Upper Floridan aquifer occurs in the southern part of the coastal area (in eastern Martin County and northeastern Palm Beach County); chloride concentration in this area is more than 2,000 milligrams per liter and is as great as 8,000 milligrams per liter. A dissolved-solids concentration of less than 10,000 milligrams per liter defines the brackish-water zone in the Floridan aquifer system; the top and base of this zone are present at the top of the aquifer system and within the Lower Floridan aquifer, respectively. The base of the brackish-water zone, which can approximate a brackish-water/saltwater interface, was determined in 13 wells, mostly using resistivity geophysical logs. The depth to the saltwater interface was calculated using the Ghyben-Herzberg approximation and estimated predevelopment hydraulic heads in the Upper Floridan aquifer. In five of six inland area wells, the depth to the base of the brackish-water zone was substantially shallower than the estimated predevelopment interface (260 feet or greater), whereas in five of seven coastal area wells, the difference was not large (less than about 140 feet). Confining units in the inland area, such as dense dolomite, may prevent an interface from forming at its equilibrium position. Because of head decline, the calculated interface using recent (May 2001) water levels is as much as 640 ft above the base of the brackish water zone (in the northern part of the coastal area). Isotopic data collected during this study, including deuterium and oxygen-18 (18O/16O), the ratio of strontium-87 to strontium-86, and carbon-13 (13C/12C) and carbon-14, provide evidence for differences in the Floridan aquifer system ground-water geochemistry and its evolution between inland and coastal areas. Ground water from the inland area tends to be older than water from the coastal area, particularly where inland area water temperature is elevated. Isotopic data together with an anomalous vertical distribution of salinity in the coastal area indicate that the coastal area was invaded with seawater in relatively recent geologic time, and this water has not been completely flushed out by the modern-day flow system. Upward leakage from the Lower to Upper Floridan aquifer of high salinity water occurs through structural deformities, such as faults or fracture zones or associated dissolution features in the inland area. An upward trend in salinity is indicated in 16 monitoring wells in the inland area, and agricultural withdrawals are probably causing these increases. Most of these wells are located in areas of elevated Upper Floridan aquifer ground-water temperature. Areas of higher water temperature could represent areas of greater potential for increases in salinity. More detailed mapping of the structure of the uppermost geologic units in the aquifer system could better define areas of deformation. Additionally, high potential exists in much of the study area for upward or lateral movement of the saltwater interface because of large declines in hydraulic head since predevelopment. The northern part of the coastal area has the greatest potential for movement; however, upward movement of the interface in the coastal area could be retarded by low vertical permeability. The potential for upward or lateral movement of the interface in the southern part of the coastal area seems to be low, but structural deformation could be present in northeastern Palm Beach County, allowing for localized upward leakage of saltwater.

Florida↗
USGS2018

Bedrock geologic map of the Lisbon quadrangle, and parts of the Sugar Hill and East Haverhill quadrangles, Grafton County, New Hampshire

The bedrock geologic map of the Lisbon quadrangle, and parts of the Sugar Hill and East Haverhill quadrangles, Grafton County, New Hampshire, covers an area of approximately 73 square miles (189 square kilometers) in west-central New Hampshire. This map was created as part of a larger effort to produce a new bedrock geologic map of Vermont through the collection of field data at a scale of 1:24,000. A large part of the map area consists of the Bronson Hill anticlinorium, a post-Early Devonian structure that is cored by metamorphosed Cambrian to Devonian sedimentary, volcanic, and plutonic rocks. The Bronson Hill anticlinorium is the apex of the Middle Ordovician to earliest-Silurian Bronson Hill magmatic arc that contains the Ammonoosuc Volcanics, Partridge Formation, and Oliverian Plutonic Suite, and extends from Maine, through western New Hampshire (down the eastern side of the Connecticut River), through southern New England to Long Island Sound. The deformed and partially eroded arc is locally overlain by a relatively thin Silurian section of metasedimentary rocks (Clough Quartzite and Fitch Formation) that thickens to the east. The Silurian section near Littleton is disconformably overlain by a thicker, Lower Devonian section that includes mostly metasedimentary and minor metavolcanic rocks of the Littleton Formation. The Bronson Hill anticlinorium is bisected by a series of northeast-southwest trending Mesozoic normal faults. Primarily among them is the steeply northwest-dipping Ammonoosuc fault that divides older and younger units (lower and upper sections) of the Ammonoosuc Volcanics. The Ammonoosuc Volcanics are lithologically complex and predominantly include interlayered and interfingered rhyolitic to basaltic volcanic and volcaniclastic rocks, as well as lesser amounts of slate, phyllite, ironstone, chert, sandstone, and pelite. The Albee Formation underlies the Ammonoosuc Volcanics and is predominantly composed of interbedded metamorphosed sandstone, siltstone, and phyllite. During the Late Ordovician, a series of arc-related plutons intruded the Ammonoosuc Volcanics including the Moody Ledge pluton and the Scrag granite of Billings (1937). Subsequent plutonism related to the Acadian orogeny occurred after volcanism and deposition resulted in the Littleton Formation during the Late Devonian, including the intrusion of the Haverhill pluton and French Pond Granite found in the southern part of the map. This report consists of a geologic map and an online geographic information systems database that includes contacts of bedrock geologic units, faults, outcrops, and structural geologic information. The geologic map is intended to serve as a foundation for applying geologic information to problems involving land use decisions, groundwater availability and quality, earth resources such as natural aggregate for construction, assessment of natural hazards, and engineering and environmental studies for waste disposal sites and construction projects.

New Hampshire↗
USGS1973

Tertiary plate tectonics and high-pressure metamorphism in New Caledonia

The sialic basement of New Caledonia is a Permian-Jurassic greywacke sequence which was folded and metamorphosed to prehnite-pumpellyite or low-grade greenschist facies by the Late Jurassic. Succeeding Cretaceous-Eocene sediments unconformably overlie this basement and extend outwards onto oceanic crust. Tertiary tectonism occurred in three distinct phases. 1. During the Late Eocene a nappe of peridotite was obducted onto southern New Caledonia from northeast to southwest, but without causing significant metamorphism in the underlying sialic rocks. 2. Oligocene compressive thrust tectonics in the northern part of the island accompanied a major east-west subduction zone, at least 30 km wide, which is identified by an imbricate system of tectonically intruded melanges and by development of lawsonite-bearing assemblages in adjacent country rocks; this high-pressure mineralogy constituted a primary metamorphism for the Cretaceous-Eocene sedimentary pile, but was overprinted on the Mesozoic prehnite-pumpellyite metagreywackes. 3. Post-Oligocene transcurrent faulting along a northwest-southeast line (the sillon ) parallel to the west coast caused at least 150 km of dextral offset of the southwest frontal margin of the Eocene ultramafic nappe. At the present time, the tectonics of the southwest Pacific are related to a series of opposite facing subduction (Benioff) zones connected by transform faults extending from New Britain-Solomon Islands south through the New Hebrides to New Zealand and marking the boundary between the Australian and Pacific plates. Available geologic data from this region suggest that a similar geometry existed during the Tertiary and that the microcontinents of New Guinea, New Caledonia and New Zealand all lay along the former plate boundary which has since migrated north and east by a complex process of sea-floor spreading behind the active island arcs.

Tectonophysics↗
USGS1995

Geologic map of Arsia Mons Volcano, Mars

The geologic map shows the flanks and summit caldera of Arsia Mons, the southernmost of three large shield volcanoes ( Arsia , Pavonis, and Ascrae us Montes) that form the Tharsis Montes volcanic chain (fig. 1). The volcanoes lie along the cre st of a regional northeast-trending rise that extends more than 3,000 km along or near the planet-wide boundary that separates th e southern highlands from the northern lowlands. Previous geologic mapping of this region (Scott and others, 1981; Scott and Tanaka, 1986) shows six major lava flows that were extruded from the Tharsis volcanoes during the Early Hespe rian to Late Amazonian Epochs; the flows cover and area exceeding 7x10 6 km 2 around the volcanic centers. All of these flows – mapped as members of the Tharsis Montes Formation – are pre sent in the map area. Broad, fan-shaped surficial deposits that resemble landslides extend down the northwest sides of each volcano and of Olympus Mons, about 1,500 km northwest of Arsia Mons (fig. 1). The largest of these gently sloping, lobate deposits is on Arsia Mons, where ambiguous relations bet wee n one facies of the fan-shaped accumulations and underlying topographic features have provoked questions as to the origin of the deposits.

IMAP↗
USGS1974

Geology of quadrangles H-12, H-13, and parts of I-12 and I-13, (zone III) in northeastern Santander Department, Colombia

A program of geologic mapping and mineral investigation in Colombia was undertaken cooperatively by the Colombian Instituto Nacional de Investigaciones Geologico-Mineras (formerly known as the Inventario Minero Nacional), and the U. S. Geological Survey; by the Government of Colombia and the Agency for International Development, U. S. Department of State. The purpose was to study, and evaluate mineral resources (excluding of petroleum, coal, emeralds, and alluvial gold) of four selected areas, designated Zones I to IV, that total about 70,000 km2. The work in Zone III, in the Cordillera Oriental, was done from 1965 to 1968. The northeast trend of the Cordillera Oriental of Colombia swings abruptly to north-northwest in the area of this report, and divides around the southern end of the Maracaibo Basin. This section of the Cordillera Oriental is referred to as the Santander Massif. Radiometric age determinations indicate that the oldest rocks of the Santander massif are Precambrian and include high-grade gneiss, schist, and migmatite of the Bucaramanga Formation. These rocks were probably part of the Precambrian Guayana Shield. Low- to medium-grade metamorphic rocks of late Precambrian to Ordovician age .include phyllite, schist, metasiltstone, metasandstone, and marble of the Silgara Formation, a geosynclinal series of considerable extent in the Cordillera Oriental and possibly the Cordillera de Merida of Venezuela. Orthogneiss ranging from granite to tonalite is widely distributed in the high- and medium-grade metamorphic rocks of the central core of the massif and probably represents rocks of two ages, Precambrian and Ordovician to Early Devonian. Younger orthogneiss and the Silgara are overlain by Middle Devonian beds of the Floresta Formation which show a generally low but varying degree of metamorphism. Phyllite and argillite are common, and infrequent marble and other calcareous beds are fossiliferous. Except for recrystallization in limestones of !the Permian-Carboniferous Diamante Formation, sedimentary rocks younger than Devonian are unmetamorphosed. The effects of Precambrian regional dynamothermal metamorphism and plutonism on Precambrian geosynclinal deposits reached the upper amphibolite facies in the Bucaramanga Gneiss. The geosynclinal Silgara Formation was subjected to similar conditions in Late Ordovician and Early Silurian time but reached only the greenschist or lower amphibolite facies. Orthogneisses generally show a concordance of foliation and lineation with the neighboring Silgara Formation and the Bucaramanga Gneiss as well as similarities in grade of metamorphism. Regional dynamothermal metamorphism in Late Permian and Triassic time reached, low grade in the Floresta Formation and caused recrystallization of limestone of the Diamante Formation. The Bucaramanga and Silgara metamorphic rocks show evidence of metrogressive metamorphism accompanied by high activity or potassium and water, but whether this occurred at the time the Floresta was metamorphosed or later is not clear. Batholiths, plutons, and stocks of igneous rocks in the Santander massif range from diorite to granite. Radioactive age data indicate that most belong to a single plutonic interval. These are referred to as the Santander Plutoniq Group and are Jurassic and Jurassic-Triassic- Two suites of this group are pink granite and quartz monzonite, and gray quartz monzonite and granodiorite. Contact relations indicate that the pink and more granitic rocks are younger than the gray and more mafic rocks, but radioactive age data are in conflict with this. Undated plutonic rocks that are not clearly related to the group are assigned to relatively older or younger age positions. West of the Bucanamanga fault rhyolite makes up a small body at one locality and forms an intrusive sheet with granophyre and intrusive breccias in Triassic sedimentary rocks at another locality. Its age is unknown, but it probably is younger than the

Open-File Report↗
USGS1980

Water resources data for Florida, water year 1979; Volume 4, northwest Florida

Water resources data for the 1979 water year in Florida consists of continuous or daily discharge for 272 streams, periodic discharge for 86 streams, continuous or daily stage for 90 streams, periodic stage for 62 streams, peak discharge for 73 streams and peak stage for 14 streams; continuous or daily elevations for 113 lakes, periodic elevations for 106 lakes; continuous ground water levels for 504 wells and periodic ground water levels for 3528 wells; quality of water data for 359 surface water sites and 923 wells. The data for Northwest Florida includes continuous or daily discharge for 69 streams, periodic discharge for 28 streams, peak discharge for 23 streams and continuous or daily stage for 4 streams; continuous elevations for 4 lakes and periodic elevations for 30 lakes; continuous ground water levels for 41 wells and periodic ground water levels for 353 wells; quality of water for 37 surface water sites and for 95 wells. These data represent the National Water Data System records collected by the U.S. Geological Survey and cooperating local, state and federal agencies in Florida.

Florida↗
USGS1988

Teleseismic and near-field analysis of the Nahanni earthquakes in the Northwest Territories, Canada

The analysis of the Nahanni earthquakes of October 5, 1985 (MS 6.6), and December 23, 1985 (MS 6.9), will have important implications for the assessment of seismic hazards in intraplate environments. To maximize the information available to seismic engineers, broadband data recorded teleseismically are analyzed jointly with strong-motion data recorded in the near field. The time-domain analysis of teleseismic data yields the source mechanisms, depths, and complexities of rupture of each earthquake. Both earthquakes occurred as shallow thrusts with centroid depths (6 to 7 km) and shallowly dipping fault planes that correspond well with the aftershock distributions obtained from a local survey run by the Canadian Geological Survey. The shallow nodal plane for the October 5 earthquake dips 30° to the WSW, while the shallow nodal planes of the subevents for the December 23 earthquake dip an average of 23° to the WSW. The October 5 earthquake has an impulsive initial rupture, followed by a weak subevent of longer duration but smaller moment release. The December 23 earthquake exhibits more complexity, being comprised of three subevents of similar size. The subevent delays derived from the teleseismic analysis are used to help interpret arrivals in records of ground velocity recorded in the near field of the December 23 earthquake. The rupture geometries inferred from the joint near- and far-field analysis suggest that the rupture processes were unusually complicated and that the 2g peak that occurs late in one of the near-field records could be a localized phenomenon. Spectral analyses of the teleseismic P waves yield the following source parameters for the October 5 and December 23 earthquakes, respectively: the seismic moments are 1.2 and 1.8 × 1026 dyne-cm, the radiated energies are 1.8 and 2.8 × 1021 dyne-cm, and the dynamic stress drops are 65 and 50 bar. The acceleration source spectra of both earthquakes exhibit an intermediate slope (| üα(ω) | ∝ω) from 0.03 to 0.3 Hz, suggesting that the earthquakes represent the failure of asperities. Extrapolating the teleseismic P-wave spectra to estimate the near-field S-wave spectra yields good fits to the acceleration spectra from two strong motion records, but underestimates the spectra from a third strong motion record with the strongest, but possibly localized, accelerations.

Bulletin of the Seismological Society of America↗
USGS2016

Continental Shelf Morphology and Stratigraphy Offshore San Onofre, CA: The Interplay Between Rates of Eustatic Change and Sediment Supply

New high-resolution CHIRP seismic data acquired offshore San Onofre, southern California reveal that shelf sediment distribution and thickness are primarily controlled by eustatic sea level rise and sediment supply. Throughout the majority of the study region, a prominent abrasion platform and associated shoreline cutoff are observed in the subsurface from ~ 72 to 53 m below present sea level. These erosional features appear to have formed between Melt Water Pulse 1A and Melt Water Pulse 1B, when the rate of sea-level rise was lower. There are three distinct sedimentary units mapped above a regional angular unconformity interpreted to be the Holocene transgressive surface in the seismic data. Unit I, the deepest unit, is interpreted as a lag deposit that infills a topographic low associated with an abrasion platform. Unit I thins seaward by downlap and pinches out landward against the shoreline cutoff. Unit II is a mid-shelf lag deposit formed from shallower eroded material and thins seaward by downlap and landward by onlap. The youngest, Unit III, is interpreted to represent modern sediment deposition. Faults in the study area do not appear to offset the transgressive surface. The Newport Inglewood/Rose Canyon fault system is active in other regions to the south (e.g., La Jolla) where it offsets the transgressive surface and creates seafloor relief. Several shoals observed along the transgressive surface could record minor deformation due to fault activity in the study area. Nevertheless, our preferred interpretation is that the shoals are regions more resistant to erosion during marine transgression. The Cristianitos fault zone also causes a shoaling of the transgressive surface. This may be from resistant antecedent topography due to an early phase of compression on the fault. The Cristianitos fault zone was previously defined as a down-to-the-north normal fault, but the folding and faulting architecture imaged in the CHIRP data are more consistent with a strike-slip fault with a down-to-the-northwest dip-slip component. A third area of shoaling is observed off of San Mateo and San Onofre creeks. This shoaling has a constructional component and could be a relict delta or beach structure. (C) 2015 Elsevier B.V. All rights reserved.

California↗
USGS1977

Metamorphic rocks of the Yakutat-St. Elias area, south-central Alaska

Metamorphic rocks in the Yakutat-St. Elias area range in grade from zeolite to amphibolite facies. Radiometric age determinations on selected metamorphic rocks have helped to identify two major metamorphic events, one in Late Cretaceous time that was characterized by penetrative deformation, and one in the Miocene Epoch that resulted in widespread recrystallization and igneous intrusions. Mapped facies units show many discontinuities across major faults, and their distribution indicates major differential uplift between several structurally bound crustal blocks within a strongly deformed mobile belt west of the Art Lewis fault. Late Cretaceous metamorphic gradients indicate that the blocks have been tilted to the west or northwest parallel to their general structural grain. As mineral assemblages that were recrystallized during Miocene time occur on both sides of the Fairweather fault, large-scale, post-Miocene strike-slip movement along the fault is not indicated.

Alaska↗
USGS1975

Ground-water resources and geology of Waukesha County, Wisconsin

Good-quality water is available from the sand-and-gravel, Niagara, and sandstone aquifers in Waukesha County, Wis. As much as 15 gallons per minute (0.95 litres per second) can be obtained from wells almost everywhere in the county. Several hundred gallons per minute are available from aquifers in the glacial drift that fill bedrock valleys to thicknesses of 300 feet (91 metres) or more. Estimated well yields from much of the surficial outwash in western Waukesha County exceed 500 gallons per minute (31 litres per second). Estimated well yields from most of the Niagara aquifer, a dolomite as much as 325 feet (99 metres) thick in the eastern two-thirds of the county, exceed 50 gallons per minute (3.2 litres per second). The sandstone aquifer underlies the entire county and ranges in thickness from about 400 feet (120 metres) in the northwest corner to about 2,400 feet (730 metres) in the southeast corner. This aquifer yields more than 1,000 gallons per minute (63 litres per second) to wells over most of the county and is the principal source for municipal and subdivision water. Ground water in Waukesha County is of good quality and is suitable for most uses. Most of the water is a calcium magnesium bicarbonate type, is very hard [more than 180 mg/l (milligrams per litre) hardness], and requires softening for some uses. The ground water locally contains iron and manganese concentrations that exceed the limits (0.3 and 0.05 mg/l, respectively) recommended by the U.S. Public Health Service (1962, p. 7). Water high in sulfate and dissolved solids (saline water) is present locally in the Niagara and sandstone aquifers. Water from one well contained excessive nitrate (more than 45 mg/l). With one exception, wells sampled at irregular intervals indicated no significant changes in their chemical characteristics with time. About 24.3 million gallons per day (1.06 cubic metres per second) of ground water was pumped in the county in 1970. Sixty-two percent was withdrawn from the sandstone aquifer. More than one-half of the latter amount was for domestic use, and more than one-third was for industrial and commercial uses.

Wisconsin↗
USGS2005

Conceptual model of sediment processes in the upper Yuba River watershed, Sierra Nevada, CA

This study examines the development of a conceptual model of sediment processes in the upper Yuba River watershed; and we hypothesize how components of the conceptual model may be spatially distributed using a geographical information system (GIS). The conceptual model illustrates key processes controlling sediment dynamics in the upper Yuba River watershed and was tested and revised using field measurements, aerial photography, and low elevation videography. Field reconnaissance included mass wasting and channel storage inventories, assessment of annual channel change in upland tributaries, and evaluation of the relative importance of sediment sources and transport processes. Hillslope erosion rates throughout the study area are relatively low when compared to more rapidly eroding landscapes such as the Pacific Northwest and notable hillslope sediment sources include highly erodible andesitic mudflows, serpentinized ultramafics, and unvegetated hydraulic mine pits. Mass wasting dominates surface erosion on the hillslopes; however, erosion of stored channel sediment is the primary contributor to annual sediment yield. We used GIS to spatially distribute the components of the conceptual model and created hillslope erosion potential and channel storage models. The GIS models exemplify the conceptual model in that landscapes with low potential evapotranspiration, sparse vegetation, steep slopes, erodible geology and soils, and high road densities display the greatest hillslope erosion potential and channel storage increases with increasing stream order. In-channel storage in upland tributaries impacted by hydraulic mining is an exception. Reworking of stored hydraulic mining sediment in low-order tributaries continues to elevate upper Yuba River sediment yields. Finally, we propose that spatially distributing the components of a conceptual model in a GIS framework provides a guide for developing more detailed sediment budgets or numerical models making it an inexpensive way to develop a roadmap for understanding sediment dynamics at a watershed scale.

Geomorphology↗