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At least 1,279 records · Page 71Linked to original sources

USGS1978

Correlations between seismic wave velocities and physical properties of near-surface geologic materials in the southern San Francisco Bay region, California

To identify geologic units with distinctly different seismic responses for the purposes of seismic zonation, compressional and shear wave velocities have been measured in boreholes at 59 sites in the San Francisco Bay region in a wide range of near-surface (0-30m) geologic materials. Several physical parameters, which can be readily determined in the field, were found to correlate with the shear wave velocities and were used to define seismically distinct groups. For the unconsolidated to semiconsolidated sediments, texture, standard penetration resistance and depth were used to define eight seismically distinct groups. For the bedrock materials, fracture spacing and hardness were used to differentiate ten distinct categories. The correlation obtained between shear wave velocity and the physical parameters were used to regroup the map units defined for the San Francisco Bay region into seismically distinct units. The map units for the younger unconsolidated sediments can be really differentiated seismically. In contrast, the older semiconsolidated sedimentary deposits and bedrock units, which have experienced significant variations in post-depositial changes, show wider and overlapping velocity ranges. The map units for the sedimentary deposits have been regrouped into eight seismically distinct geotechnical units. The bedrock map units have been broadly regrouped into five distinct categories. Compressional wave velocities were not found to be well correlated with the physical parameters dependent on the soil or rock structure. For materials above the water table, the wide velocity variations found for each geotechnical group can be attributed to differences in degree of saturation. The strong correlations observed between shear wave velocity and other readily determine physical properties suggest that geologic maps which incorporate these parameters are most useful for seismic zonation.

California↗

USGS1953

Rosamond Prospect, Kern county, California

Small quantities of autunite and gummite (?) occur in tuffaceous sedimentary rocks of the Rosamond formation of Miocene age at the Rosamond prospect. The property is about 10 miles south of Mojave, Jern County, California, in the western Mojave Desert. Examination of the propert in January 1952, by George W. Walker and Luther H. Baumgardner of the U.S. Geological Survey, indicates the the autunite occurs principally as coating on fracture and joint surfaces and, to a less extent, as disseminations in the tuffaceous rocks adjacent to faults. A waxy, reddish-brown, radioactive mineral, here called gummite (?), is found in small quantities on slickensided fault surfaces associated with iron oxides and chlorite (?). The uranium minerals are erratically distributed over an area of about 15 acres. Assay of 12 samples indicate a uranium content ranging from 0.002 to 0.59 percent and an average content of slightly less than 0.08 percent uranium.

California↗

USGS1973

Ground water in the Eugene-Springfield area, southern Willamette Valley, Oregon

The cities of Eugene and Springfield and their outlying suburban and rural districts constitute an area of rapid population growth where progressively greater volumes of ground water are being required for irrigation and industrial and public supplies. The area is also one of diverse geologic and hydrologic conditions. As used in this report, the Eugene-Springfield area covers about 450 square miles and includes a part of the lower foothills of the Coast and Cascade Ranges and a strip of the main valley plain of the southern Willamette Valley. Volcanic and sedimentary rock units exposed in the foothills range in age from Eocene to Miocene. In the main valley plain the older units are overlain by Pleistocene and Holocene alluvial deposits. Marine-deposited sandstone, siltstone, shale, and mudstone of the older sedimentary units are fine grained and poorly permeable and yield water slowly to wells. The volcanic rocks, primarily of dacitic and andesitic composition, yield small quantities of water that are generally adequate only for domestic use. The alluvial deposits (sand and gravel) of the valley plain (central lowland) contain the most productive aquifers in the area and are considered to be the only ground-water reservoir for which large-scale development of ground-water supplies is feasible. Aquifers in the area are recharged principally by direct infiltration of precipitation. Most of the precipitation, which averages about 4C inches per year, occurs during late autumn and winter. Minimum recharge by infiltration of precipitation to the alluvial aquifers beneath the valley plain is estimated to be about 100,000 acre-feet. Ground water is discharged naturally from the central lowland by seepage and spring flow to small streams, by subsurface outflow to adjacent areas, and by evapotranspiration. Storage capacity of the central lowland in the Eugene-Springfield area is estimated to be about 2.1 million acre-feet in the zone 10-150 feet below land surface. The quantity of ground water available annually from this area is far greater than the 23,000 acre-feet pumped for all uses in 1968. This pumpage was about 23 percent of the perennial yield (100,000 acre-ft), and about 77,000 acre-feet of water was left available for additional withdrawal. If annual withdrawals of water were increased to 100,000 acre-feet per year, the levels in the ground-water reservoir would be lowered. Once new equilibriums are established, increased withdrawals could be accommodated without progressive losses in aquifer storage or excessive losses in flow of the larger streams. Ground water from the alluvial deposits of the valley plain is chemically suitable for irrigation and other uses, as is most of the water obtained from perched-water bodies in the sedimentary and volcanic rocks. However, the mineral content of water from the older sedimentary rocks, particularly from deeper producing zones, is greater than the mineral content of water from the alluvial deposits. Locally, some of the water from the older rocks is too saline for most uses. Increased use of ground water may result in certain problems pertaining to waste-disposal practices, local overdraft of aquifers, well interference, and well construction. Present data are adequate to evaluate some of the factors relating to foreseeable problems but allow only tentative conclusions to be drawn about other factors, which include local direction of flow, rate of ground-water movement, and areas of possible ground-water contamination. Additional information obtained through systematic study will be needed to deal with these problems.

Oregon↗

USGS1975

K-Ar age of the Similkameen Batholith and Kruger Alkalic Complex, Washington and British Columbia

Twelve K-Ar age determinations from the Similkameen batholith and the contiguous Kruger Alkalic Complex, including seven newly reported here, range from 69.9 m.y. to 177.2 m.y. Ages of coexisting hornblende and biotite show discordancies ranging from about 72 m.y. to 106 m.y., with hornblende consistently showing the greater analytical age. The hornblendes, with one exception, show increasing analytical age with increasing potassium content and approximately fit a 191.0-m.y. 40 Ar (radiogenic )/K isochron. The isochron shows a negative intersection with the 40 Ar (radiogenic) axis, indicating partial argon loss. The large negative deviation from the isochron of one low-potassium sample suggests that the isochron is biased to older ages. If so, the Similkameen and Kruger rocks probably crystallized between roughly 177 m.y. and 191 m.y. ago. The discordancies between hornblende and coexisting biotite are attributed to argon loss during one or possibly more episodes of thermal metamorphism, the most recent of which was probably between about 50 and 70 m.y. ago. This bracket is based on the age of apparently unmetamorphosed sedimentary deposits containing detritus from the Similkameen and Kruger bodies and the analytical age of the youngest biotite.

British Columbia, Washington↗

USGS1952

Stratigraphy and paleontology of the Noatak and associated formations, Brooks Range, Alaska

A think complex sequence of olastic rocks, formerly named the Noatak formation, underlies the Lisburns formation (Mississippian) in the Brooks Range, northern Alaska. Five formations have been recognized as a result of of recent investigations by the author and other geologists of the Navy Oil Unit, U.S. Geological Survey. In the western Brooks Range, the three formations present below the Lisburns formation are: Utukok formation (Upper Touranisian to Lower Visean), Montak formation (restricted) (Upper Devonian to Lower Tournaisian (?)) and Hunt Fork (?) formation (Upper Devonian). In the central Brooks Range the Kayak formation (Lower to Upper Tournaisian), Kanayut formation (Upper Devonian to Lower Tournaisian (?)), and Hunt Fork formation (Upper Devonian) lie below the Lisburns formation. Lithologic and faunal characteristics of these sedimentary units reveal the regional pattern of sedimentation and suggest specific paleoecologic environments. The chart conglomerates in the Kanayut and Noatuk formations are thought to have formed in a belt characterized by fluctuating marine and nonmarine conditions, the chart source being a mid-Devonian ragolith. Analysis of formulas suggest certain correlations with the European, Siberian, and western Cordilleran sections. Described faunas of the Utukok and Kayak formations include 40 braciopod species and varieties, 9 echinodera species, 2 bryzoan species, 8 molluscan species, and 1 tribute species, of which 13 are new.

Alaska↗

USGS1990

Preliminary geologic map of the Thaniyat Turayf Quadrangle, sheet 29C, Kingdom of Saudi Arabia

The Thaniyat Turayf quadrangle, sheet 29C, lies in the northwestern part of Saudi Arabia near the border with Jordan. The quadrangle is located between lat 29°00'-30°00' N. and long 37°30'-39°00' E. It includes the southwestern rim of the Sirhan-Turayf Basin and is underlain by Silurian to Miocene- Pliocene sedimentary rocks that are partly covered by surficial duricrust, sand, and gravel. Most of the sedimentary rocks of the map area are of marine origin, varying from outer shelf to near-shore and coastal-lagoon environments. Episodes of fluvial-deltaic deposition reflecting marine regression occurred in the Devonian, and continental and lacustrine sedimentation are characteristic of the Miocene. Tensional structures, such as linear- joint fractures, grabens, and block faulting, probably resulted from rifting associated with the opening of the Red Sea. The map area contains the southern part of the Southwestern Area, an important phosphate-rock province that includes the Thaniyat Phosphorite member. Total estimated resources of phosphorite in three select areas of the Thaniyat Phosphorite member are 978,000,000 t with an average grade of 24 percent P 2 O 5 . A new structural concept introduced in this report extends the Wadi as Sirhan graben complex southeastward into the An Nafud. This concept increases the size of the potentially oil-and-gas-bearing Wadi as Sirhan region to include the An Nafud.

Open-File Report↗

USGS1969

Structural geologic interpretations from radar imagery

Certain structural geologic features may be more readily recognized on sidelooking airborne radar (SLAR) images than on conventional aerial photographs, other remote sensor imagery, or by ground observations. SLAR systems look obliquely to one or both sides and their images resemble aerial photographs taken at low sun angle with the sun directly behind the camera. They differ from air photos in geometry, resolution, and information content. Radar operates at much lower frequencies than the human eye, camera, or infrared sensors, and thus "sees" differently. The lower frequency enables it to penetrate most clouds and some precipitation, haze, dust, and some vegetation. Radar provides its own illumination, which can be closely controlled in intensity and frequency. It is narrow band, or essentially monochromatic. Low relief and subdued features are accentuated when viewed from the proper direction. Runs over the same area in significantly different directions (more than 45° from each other), show that images taken in one direction may emphasize features that are not emphasized on those taken in the other direction; optimum direction is determined by those features which need to be emphasized for study purposes. Lineaments interpreted as faults stand out on radar imagery of central and western Nevada; folded sedimentary rocks cut by faults can be clearly seen on radar imagery of northern Alabama. In these areas, certain structural and stratigraphic features are more pronounced on radar images than on conventional photographs; thus radar imagery materially aids structural interpretation.

Alabama;Nevada↗

USGS2004

Geohydrology of the French Creek Basin and simulated effects of drought and ground-water withdrawals, Chester County, Pennsylvania

This report describes the results of a study by the U.S. Geological Survey, in cooperation with the Delaware River Basin Commission, to develop a regional ground-water-flow model of the French Creek Basin in Chester County, Pa. The model was used to assist water-resource managers by illustrating the interconnection between ground-water and surface-water systems. The 70.7-square mile French Creek Basin is in the Piedmont Physiographic Province and is underlain by crystalline and sedimentary fractured-rock aquifers. Annual water budgets were calculated for 1969-2001 for the French Creek Basin upstream of streamflow-measurement station French Creek near Phoenixville (01472157). Average annual precipitation was 46.28 in. (inches), average annual streamflow was 20.29 in., average annual base flow determined by hydrograph separation was 12.42 in., and estimated average annual ET (evapotranspiration) was 26.10 in. Estimated average annual recharge was 14.32 in. and is equal to 31 percent of the average annual precipitation. Base flow made up an average of 61 percent of streamflow. Ground-water flow in the French Creek Basin was simulated using the finite-difference MODFLOW-96 computer program. The model structure is based on a simplified two-dimensional conceptualization of the ground-water-flow system. The modeled area was extended outside the French Creek Basin to natural hydrologic boundaries; the modeled area includes 40 square miles of adjacent areas outside the basin. The hydraulic conductivity for each geologic unit was calculated from reported specific-capacity data determined from aquifer tests and was adjusted during model calibration. The model was calibrated for above-average conditions by simulating base-flow and water-level measurements made on May 1, 2001, using a recharge rate of 20 in/yr (inches per year). The model was calibrated for below-average conditions by simulating base-flow and water-level measurements made on September 11 and 17, 2001, using a recharge rate of 6.2 in/yr. Average conditions were simulated by adjusting the recharge rate until simulated streamflow at streamflow-measurement station 01472157 matched the long-term (1968-2001) average base flow of 54.1 cubic feet per second. The recharge rate used for average conditions was 15.7 in/yr. The effect of drought in the French Creek Basin was simulated using a drought year recharge rate of 8 in/yr for 3 months. After 3 months of drought, the simulated streamflow of French Creek at streamflow-measurement station 01472157 decreased 34 percent. The simulations show that after 6 months of average recharge (15.7 in/yr) following drought, streamflow and water levels recovered almost to pre-drought conditions. The effect of increased ground-water withdrawals on stream base flow in the South Branch French Creek Subbasin was simulated under average and drought conditions with pumping rates equal to 50, 75, and 100 percent of the Delaware River Basin Commission Ground Water Protected Area (GWPA) withdrawal limit (1,393 million gallons per year) with all pumped water removed from the basin. For average recharge conditions, the simulated streamflow of South Branch French Creek at the mouth decreased 18, 28, and 37 percent at a withdrawal rate equal to 50, 75, and 100 percent of the GWPA limit, respectively. After 3 months of drought recharge conditions, the simulated streamflow of South Branch French Creek at the mouth decreased 27, 40, and 52 percent at a withdrawal rate equal to 50, 75, and 100 percent of the GWPA limit, respectively. The effect of well location on base flow, water levels, and the sources of water to the well was simulated by locating a hypothetical well pumping 200 gallons per minute in different places in the Beaver Run Subbasin with all pumped water removed from the basin. The smallest reduction in the base flow of Beaver Run was from a well on the drainage divide between the French Creek Basin and the Marsh Creek Basin to the south; the simulated base flow of Beaver Run at the mouth was reduced 1 percent. The greatest reduction in the base flow of Beaver Creek was from a well close to Beaver Run; the simulated base flow of Beaver Run at the mouth was reduced 8 percent. The simulations showed that (1) if the contributing area of a well is in a basin, pumping will affect stream base flow and water levels in that basin whether the well is inside or outside that basin; (2) wells in different areas of a basin away from a divide produce a similar reduction in base flow; (3) a well within a basin will derive more water from diverted base flow and less water from storage than a well on or near a basin divide; and (4) the reduction in base flow at the mouth of the stream is the same for a well in the headwaters and a well downstream near the confluence. Model simulations illustrate some of the typical analyses and results that can be produced. The model was calibrated using annual values for recharge and ground-water ET and then was run using the annual values in a seasonally independent transient mode to show changes with time. The timing and relative magnitude of some of the changes simulated with the model when viewed in terms of a normal climatic year may be subject to considerable uncertainty because of the variability in seasonal recharge and ground-water ET rates. Transient model simulations for short-term periods are indicative of possible hydrologic system response and are considered an approximation.

Pennsyvlania↗

USGS1960

Geology, water resources and usable ground-water storage capacity of part of Solano County, California

The area described is confined largely to the valley-floor and foothill lands of Solano County, which lies directly between Sacramento, the State capital, and San Francisco. The area is considered in two subareas: The Putah area, which extends from Putah Creek southward to the Montezuma Hills and from the foothills of the Coast Ranges eastward to the west edge of the Yolo Bypass; and the Suisun-Fairfield area, which is to the southwest in the notch in the Coast Ranges through which the waters of the Great Central Valley of California reach San Francisco Bay. There are no known hydrologic interconnections between the two subareas, through either surface streams or underground aquifers. The climate of the area is characterized by warm, rainless summers and by cool winters in which temperatures seldom drop much below freezing. The rainfall ranges from about 17 inches per year along the east side to perhaps 24 inches in the foothills to the west, and irrigation is necessary for all crops except dry-farmed grains, pastures, and some orchards. PUTAH AREA The Putah area occupies the southwestern corner of the Sacramento Valley, a topographic and structural basin underlain by a thick accumulation of sediments eroded from the surrounding hills and mountains by the Sacramento River and its tributaries. The eastern Coast Ranges and foothills lying west of the Sacramento Valley are a generally northward-trending belt of eastward-dipping sedimentary rocks that range in age from Cretaceous to Pleistocene. Successively younger strata are exposed eastward, and the essentially undeformed deposits of late Pleistocene and Recent age that immediately underlie the valley lap onto the tilted sediments of the foothills. Most of the streams of the Putah area rise east of the high ridge of Cretaceous rocks marking the western boundaries of Solano and Yolo Counties, but Putah Creek, the largest stream in the area, rises far west of that ridge and flows across it in a deep, narrow canyon. Putah Creek and the smaller streams have constructed an alluvial plain, herein designated the Putah plain, which slopes eastward and southeastward from the foothills toward the Sacramento River. A large part of the Putah plain is traversed by a branching set of distributary channel ridges or natural levees formed at times of overflow of Putah Creek. The rocks in the Putah area range in age from Cretaceous to Recent. For the purposes of this investigation they are divided into eight geologic or stratigraphic units, from youngest to oldest: (1) Stream-channel deposits, (2) younger alluvium, (3) older alluvium, (4) Tehama formation and related continental sediments, (5) volcanic sedimentary rocks, (6) basalt, (7) undifferentiated sedimentary rocks of Paleocene(?) and Eocene age, and (8) undifferentiated rocks of Cretaceous age. The stream-channel deposits are predominantly loose sand and gravel along the channel of Putah Creek. In part they are actively moving downstream and shifting. The younger alluvium, of Recent age, consists of flood-plain deposits underlying the Putah plain, Vaca Valley, Pleasants Valley, and the small valleys in the foothills north of Putah Creek and in the English Hills. Exposures of younger alluvium are characterized by soils lacking significant profile development and in many places by channel-ridge topography. The older alluvium occupies the stratigraphic interval between the younger alluvium and the Tehama formation and related continental sediments and is probably of late Pleistocene age. Its contact with the underlying Tehama formation and related continental sediments is unconformable near the foothills, but it may be gradational beneath much of the Putah plain. The base of the older alluvium is not well defined at many places but is inferred to be at the bottom of an irregular and ill-defined zone of coarse deposits, which ranges from about 50 feet to more than 150 feet below the land surface. Exposures of the older

Water Supply Paper↗

USGS1983

Stratigraphic framework and distribution of lignite on Crowleys Ridge, Arkansas

The purpose of this report is to establish a stratigraphic framework of lignite beds and associated strata of Crowleys Ridge, Arkansas. Drill hole data provided by the Arkansas Geological Commission is used in the synthesis and interpretation. Areas containing lignite of potential resource value are also delineated. To illustrate the regional stratigraphic framework of Crowleys Ridge, a cross section was constructed from logs of selected oil and gas test wells, along or adjacent to the north-south trending ridge over a distance of about 115 miles. This section reveals that lignite-bearing Tertiary formations dip gently southward along the ridge. The Paleocene-Eocene Wilcox Group forms the bedrock in the northern part of the ridge and successively younger bedrock of the Eocene Claiborne and Jackson Groups is identified in the central and southern part of the ridge. Crowleys Ridge is mantled with alluvium and loess of Quaternary age, and sand and gravel beds of the Lafayette Formation of Pliocene (?) age that unconformably overlie the Paleocene and Eocene rocks. The thickness of lignite-bearing sedimentary deposits ranges from 830 feet in the north to 2,480 feet in the south. The Wilcox, Claiborne, and Jackson Groups of Paleocene and Eocene age are believed to be fluvial-deltaic in origin. The detailed vertical and horizontal stratigraphic characteristics and distribution of lignite beds in the sediments were determined by constructing seven cross sections from lithologic and geophysical logs of the lignite investigations on Crowleys Ridge by the Arkansas Geological Commission and private companies. Correlation and interpretation of the lignite-bearing strata reveal ten lignite beds of resource potential. These lignite beds range from a few inches to 9.5 ft in thickness and are assigned to stratigraphic intervals that are designated as zone 1 through 7. Zone 1 is near the middle of the Wilcox Group and zone 7 is near the middle of the overlying Claiborne Group. Some of these lignite beds are correlated over distances as much as 30 miles. Other lignite beds thin to a few inches thick and disappear within short distances. Four areas are delineated on Crowleys Ridge that contain one or more lignite beds each 2.5 feet or more thick. Strippable lignite is limited to 300 feet in this area, therefore, all holes were drilled to 300 feet or less. Chemical analyses of eight lignite samples from Crowleys Ridge are on record with the U.S. Geological Survey's National Coal Resources Data System. Two of the samples are from the Wilcox Group, and six are from the Claiborne Group, but the lignite beds from which the samples were taken are unidentified. However, the analyses are believed to be representative of the lignite within the lignite-bearing sequence. The two Wilcox samples had moisture values of 36.3 and 40.1 percent; ash, 30.5 and 20.5 percent (U.S. Bureau of Mines); sulfur content, 0.3 and 1.0 percent; and Btu values, 3,910 and 4,590 on an as received basis. The six Claiborne samples had moisture values ranging from 34.7 to 43.7 percent; ash from 11.9-28.2 percent (USBM); sulfur content, 0.3-3 percent; and Btu values, 3,400 to 5,160. U.S. Geological Survey average ash content for the eight samples was 36.22 percent, and the major oxides are SiO2 (60.75 percent), Al2O3 (15.23 percent), CaO (6.96 percent), Fe2O3 (6.65 percent), and SO3 (5.64 percent). No anomalous values were recorded for the trace element content. Lignite is not currently mined on Crowleys Ridge. It has potential for use as a fuel for direct firing of boilers to generate electricity. It also has potential for gasification to produce pipeline gas, and for liquefaction to produce fuel oil. More drilling and analyses are needed to better define the quantity and quality of lignite beds within the four significant areas with resource potential and to determine the extent of lignite beds 2.5 ft or more thick that occur in several isolated areas.

Open-File Report↗

USGS2016

Trace elements at the intersection of marine biological and geochemical evolution

Life requires a wide variety of bioessential trace elements to act as structural components and reactive centers in metalloenzymes. These requirements differ between organisms and have evolved over geological time, likely guided in some part by environmental conditions. Until recently, most of what was understood regarding trace element concentrations in the Precambrian oceans was inferred by extrapolation, geochemical modeling, and/or genomic studies. However, in the past decade, the increasing availability of trace element and isotopic data for sedimentary rocks of all ages has yielded new, and potentially more direct, insights into secular changes in seawater composition – and ultimately the evolution of the marine biosphere. Compiled records of many bioessential trace elements (including Ni, Mo, P, Zn, Co, Cr, Se, and I) provide new insight into how trace element abundance in Earth's ancient oceans may have been linked to biological evolution. Several of these trace elements display redox-sensitive behavior, while others are redox-sensitive but not bioessential (e.g., Cr, U). Their temporal trends in sedimentary archives provide useful constraints on changes in atmosphere-ocean redox conditions that are linked to biological evolution, for example, the activity of oxygen-producing, photosynthetic cyanobacteria. In this review, we summarize available Precambrian trace element proxy data, and discuss how temporal trends in the seawater concentrations of specific trace elements may be linked to the evolution of both simple and complex life. We also examine several biologically relevant and/or redox-sensitive trace elements that have yet to be fully examined in the sedimentary rock record (e.g., Cu, Cd, W) and suggest several directions for future studies.

Earth-Science Reviews↗

USGS2007

Subsurface stratigraphic cross sections of cretaceous and lower tertiary rocks in the Wind River Basin, central Wyoming: Chapter 9 in Petroleum systems and geologic assessment of oil and gas resources in the Wind River Basin Province, Wyoming

The stratigraphic cross sections presented in this report were constructed as part of a project conducted by the U.S. Geological Survey to characterize and evaluate the undiscovered oil and gas resources of the Wind River Basin (WRB) in central Wyoming. The primary purpose of the cross sections is to show the stratigraphic framework and facies relations of Cretaceous and lower Tertiary rocks in this large, intermontane structural and sedimentary basin, which formed in the Rocky Mountain foreland during the Laramide orogeny (Late Cretaceous through early Eocene time). The WRB is nearly 200 miles (mi) long, 70 mi wide, and encompasses about 7,400 square miles (mi 2 ) (fig. 1). The basin is structurally bounded by the Owl Creek and Bighorn Mountains on the north, the Casper arch on the east, the Granite Mountains on the south, and the Wind River Range on the west.

Wyoming↗

USGS2008

Geologic Maps and Cross Sections of the Tuba City Open Dump Site and Vicinity, With Implications for the Occurrence and Flow of Ground Water

This report is designed to make available to interested parties geologic and limited hydrologic and geochemical information about the Tuba City Open Dump (TCOD) site. This information has been gathered during studies of the site from January to September 2008. Mapping by the authors and construction of cross sections show that a section of gently northeast-dipping Jurassic sedimentary rocks underlies the TCOD and vicinity. Low mesas in the area are capped by variably cemented gravels and siliceous limestones. Surficial sediments are composed of eolian sand and fluvially reworked eolian sand that overlie bedrock underneath the TCOD. Nearby Pasture Canyon is underlain by fluvial and floodplain sediment consisting of sand and silt. Shallow ground water of the water-table aquifer at the TCOD moves westward through the surficial sediment and the underlying weathered bedrock to Pasture Canyon then southward along the canyon. A fracture zone extends up the wash that passes just to the north of the TCOD and brings deeper ground water of the N-aquifer to the water-table aquifer. Bedrock consists of the Jurassic Navajo Sandstone composed of thick sections of eolian crossbedded sandstone with lesser laterally discontinuous layers of silty sandstone, siltstone, and limestone. Below the Navajo Sandstone is a section informally known as the Kayenta Formation-Navajo Sandstone transition zone. It is composed of calcareous sandstone, silty sandstone, siltstone, and limestone beds that intertongue with crossbedded sandstone. The finer grained rocks in both major bedrock units form aquitards that limit downward movement of ground water. The water-table aquifer is perched on these aquitards, which locally occurs beneath the two open dumps that form the TCOD site. A monocline occupies the position of Pasture Canyon west of the TCOD. Fractures likely related to the monocline are exposed in several localities. Deep ground waters consist of dilute calcium-bicarbonate waters low in all trace elements. Shallow ground water is variably affected by near-surface processes, which add varying amounts of sodium, chloride, sulfate, and trace elements. Locally, human influences, such as the TCOD, affect shallow ground-water chemistry.

Open-File Report↗

USGS2024

Short-term sediment dispersal on a large retreating coastal river delta via 234Th and 7Be sediment geochronology: The Mississippi River Delta Front

Many Mississippi River Delta studies have shown recent declines in fluvial sediment load from the river and associated land loss. In contrast, recent sedimentary processes on the subaqueous delta are less documented. To help address this knowledge gap, multicores were collected offshore from the three main river outlets at water depths of 25–280 m in June 2017 just after the peak river discharge period, with locations selected based on 2017 U.S. Geological Survey seabed mapping. The coring locations included the undisturbed upper foreset, mudflow lobes, gullies, and the undisturbed prodelta. Nine multicores were analyzed for Beryllium-7 activity, and four cores were analyzed for excess Thorium-234 activity via gamma spectrometry, granulometry and X-radiography. Our results indicate a general trend of declining 7 Be and 234 Th activities and inventories with increasing distance from sources and in deeper water. The core X-radiographs are graded from the predominantly physically stratified nearshore to the more bioturbated offshore, consistent with the sedimentation patterns. Sediment focusing assessed via the 7 Be and 234 Th sediment inventories shows preferential sedimentation in gully and lobe environments, whereas the upper foreset and prodelta focusing factors are relatively depleted. Overall, short-term sediment deposition from the main fluvial source remains active offshore from all three major river outlets, despite the overall declining river load.

Louisiana↗

USGS2002

Basis and methods of NASA airborne topographic mapper lidar surveys for coastal studies

This paper provides an overview of the basic principles of airborne laser altimetry for surveys of coastal topography, and describes the methods used in the acquisition and processing of NASA Airborne Topographic Mapper (ATM) surveys that cover much of the conterminous US coastline. This form of remote sensing, also known as "topographic lidar", has undergone extremely rapid development during the last two decades, and has the potential to contribute within a wide range of coastal scientific investigations. Various airborne laser surveying (ALS) applications that are relevant to coastal studies are being pursued by researchers in a range of Earth science disciplines. Examples include the mapping of "bald earth" land surfaces below even moderately dense vegetation in studies of geologic framework and hydrology, and determination of the vegetation canopy structure, a key variable in mapping wildlife habitats. ALS has also proven to be an excellent method for the regional mapping of geomorphic change along barrier island beaches and other sandy coasts due to storms or long-term sedimentary processes. Coastal scientists are adopting ALS as a basic method in the study of an array of additional coastal topics. ALS can provide useful information in the analysis of shoreline change, the prediction and assessment of landslides along seacliffs and headlands, examination of subsidence causing coastal land loss, and in predicting storm surge and tsunami inundation.

Journal of Coastal Research↗

USGS1982

Reconnaissance Geology of the Jabal as Sukkah Quadrangle, Sheet 21/43 B, Kingdom of Saudi Arabia

The Jabal as Sukkah quadrangle (21/43 B) lies in the southern Najd region within the Arabian Shield between lat 21°30' and 22°00' N. and long 43°30' and 44°00' E. The oldest rocks exposed are a very thick sequence of volcanic flow rocks of mostly felsic to intermediate composition interbedded with volcaniclastic and sedimentary rocks. The layered rocks reflect a less primitive state of crustal evolution than has generally been ascribed to this sequence. These rocks were deposited upon an emerging basement of mafic to intermediate composition, and the sedimentary materials reflect a source terrane of mostly intermediate to felsic character. The layered rocks were subjected to three separate episodes of compressional deformation, each followed by appreciable talc-alkalic plutonism. Each of the plutonic suites contains a differentiated series that began with the emplacement of mafic to intermediate rocks, progressed to talc-alkalic granites, and terminated with an end-member granite rich in silica and total alkalis. The petrography and rock chemistry indicate that the more alkalic members of the talc-alkalic granites were capable of generating ore-bearing fluids and perhaps ore deposits of large size in the region. However, subsequent erosion likely removed all but some of the deeper, smaller vestiges of such deposits from within the study area. No exploitable deposits were found during the course of this investigation.

Jabal as Sukkah Quadrangle↗

USGS2017

Geophysical characterization of seismic station sites in the United States – The importance of a flexible, multi-method approach

Noninvasive geophysical site characterization methods were used in two recent projects to obtain shear-wave velocity (VS) profiles to a minimum depth of 30 m and the time-averaged VS of the upper 30 meters (VS30) at seismic station sites. These projects include the 2009 American Recovery and Reinvestment Act (ARRA) funded U.S. Geological Survey site characterization project for 191 sites in California and the Central-eastern United States (CEUS), and the 2012 Electric Power Research Institute (EPRI) funded project for 33 additional CEUS sites. These sites are located in rural to urban settings with topographic conditions ranging from relatively flat sedimentary basins to mountaintop ridges. About 60 percent of the ARRA sites and 80 percent of the EPRI sites are located on rock or have thin sediment cover over rock, including Quaternary volcanic rock, Tertiary sediments and sedimentary rock, and Mesozoic (or older) crystalline or sedimentary rock. The remaining sites consist of thick sequences of Quaternary sediments overlying older sediments and rock. ARRA sites were characterized using non-invasive active and passive surface-wave methods, including the horizontal-tovertical spectral ratio (HVSR) method and one or more of the following: spectral analysis of surface waves (SASW), multichannel analysis of surface waves (MASW; Rayleigh and Love waves) and, occasionally, array microtremor (linear and 2-D arrays) methods. P-wave seismic refraction data were also acquired at rock and shallow-rock sites. S-wave seismic refraction and/or Love-wave MASW methods were applied at sites where characterization proved difficult with Rayleighwave methods. Based on our experience from the ARRA project, we acquired Rayleigh- and Love-wave based MASW and P- and S-wave refraction data for the EPRI project at CEUS sites. The HVSR method was found to be useful for identifying shallow-rock sites and for evaluating the relative variability of the depth-to-rock interface beneath the seismic station and the testing array(s). The fundamental mode modeling assumption was generally valid at most of these sites; nevertheless, multi-mode or effective-mode modeling routines were occasionally required, particularly in the case of shallow high-velocity layers. Deep sediment sites were characterized using active and, when appropriate, passive surface-wave based methods. Rock and shallow sediment sites were generally more challenging to characterize than deep sediment sites. About 10 percent of rock sites could not be characterized using surface wave methods, thus these sites were characterized using body-wave refraction methods. Love wave methods were found to be more effective than Rayleigh wave methods at some rock and shallow-rock sites (e.g., sites with shallow rock and sites with a thin low-velocity, highly attenuating surface layer). Lateral velocity variability was found to be very common at rock and shallow-rock sites, often causing significant scatter in the surface-wave dispersion data. Seismic refraction models have demonstrated that it may not be unusual for VS30 to vary by 20 percent, or more, over small distances (several tens of meters) at such sites. Based on these experiences, it is important to consider the application of combinations of methods when using noninvasive geophysical approaches to characterize seismic site conditions.

Conference Paper↗

USGS2012

Review and update of the applications of organic petrology: Part 1, geological applications

Organic petrology developed as coal petrology at the beginning of the 20th century dedicated mainly to the study of coals because of their utilization in industry. Coal petrology was then considered a branch of coal science. Later, with the development of specialized nomenclature, classification of coal components, and the standardization and improvement of analytical (microscopical) methods, this discipline expanded in interests and name, becoming organic petrology. Organic petrology carries a broader context, being as well a tool applied in the study of dispersed organic matter in sedimentary rocks due to its importance in exploration for fossil fuel resources. At present, organic petrology is a discipline widely recognized for its role in fundamental and applied research with respect to both coal utilization and in geosciences. Throughout the 20th century several important monographs have been published on the discipline of organic petrology, including “Stach's textbook of coal petrology” (1st edition 1935, 2nd 1975, 3rd 1982), updated as the more general “Organic petrology” by Taylor et al. (1998). More recently, the text “Applied coal petrology: the role of petrology in coal utilization” was published by Suárez-Ruiz and Crelling (2008). This review is the first in a two-part review series that describes and updates the role of organic petrology in geosciences. A second part complementing this one and focused on the applications of organic petrology to other scientific fields will follow.

International Journal of Coal Geology↗