SEARCH · USGS Science

Results for “The Depositional Record”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,171 records · Page 65Linked to original sources

USGS2012

Sequential development of platform to off-platform facies of the great American carbonate bank in the central Appalachians

In the central Appalachians, carbonate deposition of the great American carbonate bank began during the Early Cambrian with the creation of initial ramp facies of the Vintage Formation and lower members of the Tomstown Formation. Vertical stacking of bioturbated subtidal ramp deposits (Bolivar Heights Member) and dolomitized microbial boundtsone (Fort Duncan Member) preceded the initiation of platform sedimentation and creation of sand shoal facies (Benevola Member) that was followed by the development of peritidal cyclicity (Daragan Member). Initiation of peritidal deposition coincided with the development of a rimmed platform that would persist throughout much of the Cambrian and Early Odrovician. At the end of deposition of the Waynesboro Formation, the platform became subaerially exposed because of the Hawke Bay regression, bringing the Sauk I supersequence to and end. In the Conestoga Valley of eastern Pennsylvania, Early Cambrian ramp deposition was succeeded by deposition of platform-margin and periplatfrom facies of the Kinzers Formation. The basal Sauk II transgression during the early Middle Cambrian submerged the platform and reinitiated the pertidal cyclicity that had characterized the pre-Hawke Bay deposition, This thick stack of meter-scale cycles is preserved as the Pleasant Hill and Warrior Formations of the Nittany arch, the Elbrook Formation of the Great Valley, and the Zooks Corner Formations of the Conestoga Valley. Deposition of peritidal cycles was interrupted during deposition of the Glossopleura and Bathuriscus-Elrathina Biozones by third-order deepening episodes that submerged the platform with subtidal facies. Regressive facies of the Sauk II supersequence produced platform-wide restrictions and the deposition of the lower sandy member of the Gatesburg Formation, the Big Spring Station Member of the Conococheague Formation, and the Snitz Creek Formation. Submergence of the platform was initiated during the late Steptoean ( Elvinia Zone) with the epansion of extensive subtidal thrombotic boundstone facies. Vertical stacking of no fewer than four of these thrombolite-dominated intervals records third-order deepening episodes separated by intervening shallowing episodes that produced peritidal ribbony and laminated mudcracked dolostone. The maximum deepening of the Sauk III transgression produced the Stonehenge Formation in two separate and distinct third-order submergences. Circulation restriction during the Sauk III regression produced a thick stack of meter-scale cycles of the Rockdale Run Formation, and the lower Bellefonte Dolomite of the Nittany arch (central Pennsylvania). This regressive phase was interrupted by a third-order deepening event that produced the oolitic member of the lower Rockdale Run and the Woodsboro Member of the Grove Formation in the Frederick Valley. Restricted circulation continued into the Whiterockian, with deposition of the upper Rockdale Run and the Pinesberg Station Dolomite in the Great Valley and the missile and upper parts of the Bellefonte Dolomore and the Nittany Arch region. This deposition was continuous from the Ibexian into the Whiterockian; the succession lacks significant unconformities and there are no missing biozones through this interval, the top of which marks the end of the Sauk megasequence. During deposition of the Tippecanoe megasequence, the peritidal shelf cycles were reestablished during deposition of the St. Paul Group. The vertical stacking of lithologies in the Row Park and New Market Limestones represents transgressive and regressice facies of a third-order deepening event. This submergence reached its maximum deepening within the lower Row Park Limestone and extended with the Nittany arch region with deposition of equivalent Loysburg Formation.. Shallow tidal-flat deposits were bordered to the south and east by deep-water ramp deposits of the Lincolnshire Formation. The St. Paul Group is succeeded upsection by ramp facies of the Chamersberg and the Edinburg Formations in the Great Valley, whereas shallow-shelf sedimentation continued in the Nittany-arch area with the depostion of the Hatter Limestoen and the Snyder and Linden Hall Formations. Carbonate deposition on the great American carbonate bank was brought to an end when it was buried beneath clastic flysch deposits of the Martinsberg Formation. Foundering of the bamk was diachronus, and the flysch seidments prograded from east to west.

Maryland, Pennsylvania, Virginia, West Virginia↗

USGS2002

Hydrogeology and extent of saltwater intrusion on Manhasset Neck, Nassau County, New York

Manhasset Neck, a peninsula on the northern shore of Long Island, N.Y., is underlain by unconsolidated deposits that form a sequence of aquifers and confning units. Ground water at several public-supply wells has been affected by the intrusion of saltwater from the surrounding embayments (Manhasset Bay, Long Island Sound, Hempstead Harbor). Twenty-two boreholes were drilled during 1992-96 for the collection of hydrogeologic, geochemical, and geophysical data to delineate the subsurface geology and the extent of saltwater intrusion within the peninsula. A series of continuous high-resolution seismic- reflection surveys was completed in 1993 and 1994 to delineate the character and extent of the hydrogeologic deposits beneath the embayments surrounding Manhasset Neck. The new drill-core data indicate two hydrogeologic units--the North Shore aquifer and the North Shore confining unit--where the Lloyd aquifer, Raritan confining unit, and the Magothy aquifer have been completely removed by glacial erosion. Water levels at selected observation wells were measured quarterly throughout the study. These data, and continuous water-level records, indicate that (1) the upper glacial (water-table) and Magothy aquifers are hydraulically connected and that their water levels do not respond to tidal fluctuations, and (2) the Lloyd and North Shore aquifers also are hydraulically connected, but their water levels do respond to pumping and tidal fluctuations. Offshore seismic-reflection surveys in the surrounding embayments, and drill-core samples, indicate at least four glacially eroded buried valleys with subhorizontal, parallel reflectors indicative of draped bedding that is interpreted as infilling by silt and clay. The buried valleys (1) truncate the surrounding coarse-grained deposits, (2) are asymmetrical and steep sided, (3) trend northwest-southeast, (4) are 2 to 4 miles long and about 1 mile wide, and (5) extend to more than 400 feet below sea level. Water from 12 public-supply wells screened in the Magothy and upper glacial aquifers contained volatile organic compounds in concentrations above the New York State Department of Health Drinking Water maximum contaminant levels, as did water from one public- supply well screened in the Lloyd aquifer and from two observation wells screened in the upper glacial aquifer. Five distinct areas of saltwater intrusion have been delineated in Manhasset Neck; three extend into the Lloyd and North Shore aquifers, and two extend into the upper glacial and Magothy aquifers. Borehole-geophysical-logging data indicate that several of these saltwater wedges range from a few feet to more than 125 feet in thickness and have sharp freshwater-saltwater interfaces, and that chloride concentrations within these wedges in 1997 ranged from 102 to 9,750 milligrams per liter. Several public-supply wells have either been shut down or are currently being affected by these saltwater wedges. Data show active saltwater intrusion in at least two of the wedges.

New York↗

USGS2012

Short-term survival of ammonites in New Jersey after the end-Cretaceous bolide impact

A section containing the Cretaceous/Paleogene (= Cretaceous/Tertiary) boundary in Monmouth County, New Jersey, preserves a record of ammonites extending from the end of the Cretaceous into possibly the beginning of the Danian. The section includes the upper part of the Tinton Formation and lower part of the Hornerstown Formation. The top of the Tinton Formation is represented by a richly fossiliferous unit (the Pinna Layer) that contains many bivalves in life position as well as ammonite jaws preserved inside body chambers. Ammonites include Pachydiscus (Neodesmoceras) mokotibensis, Sphenodiscus lobatus, Eubaculites carinatus, E. latecarinatus; Discoscaphites iris, D. sphaeroidalis; D. minardi, and D. jerseyensis. The Pinna Layer probably represents a relatively short interval of time lasting tens to hundreds of years; it is conformably overlain by the Burrowed Unit, which contains a single fragment of Discoscaphites sp. and several fragments of E. latecarinatus, as well as several isolated specimens of ammonite jaws including two of Eubaculites. Examination of the mode of preservation of the ammonites and jaws suggests that they were fossilized during deposition of the Burrowed Unit and were not reworked from older deposits. Based on the ammonites and dinoflagellates in the Pinna Layer and the Burrowed Unit, these strata traditionally would be assigned to the uppermost Maastrichtian, corresponding to calcareous nannofossil Subzone CC26b. However, a weak iridium anomaly (500–600 pg/g) is present at the base of the Pinna Layer, which presumably represents the record of the bolide impact. Correlation with the iridium layer at the Global Stratotype Section and Point at El Kef, Tunisia, would, therefore, imply that these assemblages are actually Danian, provided that the iridium anomaly is in place and the ammonites and dinoflagellates are not reworked. If the iridium anomaly is in place, or even if it has migrated downward from the top of the Pinna Layer, the ammonites would have survived the impact at this site for a brief interval of time lasting from a few days to hundreds of years.

New Jersey↗

USGS1980

Possible fault detection in Cottonball Basin, California: an application of radar remote sensing.

An analysis of a 3-cm wavelength radar image of Cottonball Basin in Death Valley National Monument has revealed the existence of two suspect fault traces in evaporite deposits that are less than 2000-yr old. The traces are well defined on the image because the radar system was able to differentiate surface roughness variations at the centimeter scale. The features are not recognizable on data sets recorded in the visible and near-infrared spectral bands. - from Authors

Remote Sensing of Environment↗

USGS2005

Stable isotope ratios in swale sequences of Lake Superior as indicators of climate and lake level fluctuations during the Late Holocene

Beach ridges along the coastline of Lake Superior provide a long-term and detailed record of lake level fluctuations for the past 4000 cal BP. Although climate change has been invoked to explain these fluctuations, its role is still in debate. Here, we reconstruct water balance by employing peat samples collected from swale deposits present between beach ridge sequences at two locations along the coastline of Lake Superior. Carbon isotope ratios for Sphagnum remains from these peat deposits are used as a proxy for water balance because the presence or absence of water films on Sphagnum controls the overall isotope discrimination effects. Consequently, increased average water content in Sphagnum produces elevated ??13C values. Two maxima of Sphagnum ??13C values interpreted to reflect wetter conditions prevailed from 3400 to 2400 cal BP and from about 1900 to 1400 cal BP. There are two relatively short drier periods as inferred from low Sphagnum ??13C values: one is centered at about 2300 cal BP, and one begins at 1400 cal BP. A good covariance was found between Sphagnum ??13C values and reconstructed lake-levels for Lake Michigan in which elevated carbon isotope values correlate well with higher lake levels. Based on this covariance, we conclude that climate exerts a strong influence on lake levels in Lake Superior for the past 4000 cal BP. ?? 2005 Elsevier Ltd. All rights reserved.

Quaternary Science Reviews↗

USGS1978

VAMPs—Possible hydrocarbon-bearing structures in Bering Sea Basin: Geologic notes

Narrow (1 to 2 km) subsurface columns of concave reflection horizons are common time-base seismic profiles collected in the Bering Sea basin. The columns of recorded downflexures are thought to be velocity pulldowns and commonly are associated with one or more arched or gently domed high-amplitude reflection horizons about 100 m higher in the section. Inferred from this association is that subsurface deposits characterized by anomalously low acoustic velocity are present. We refer to the velocity-anomaly and reflection-amplitude association as a velocity-amplitude feature, or VAMP, and speculate that VAMPs are deep-seated “bright spots” underlain by a strong velocity pulldown possibly caused by gas-charged deposits.

AAPG Bulletin↗

USGS1974

Molybdenite in the Montezuma District of central Colorado

The Montezuma mining district, in the Colorado mineral belt, is defined by an assemblage of porphyry, ore, and altered rocks that originated in the venting of a Tertiary batholith through weak structures in Precambrian rocks. The ore consists of silver-lead-zinc veins clustered on the propylitic fringe of a geometrically complex system of altered rocks, which is centered on the intersection of the Oligocene Montezuma stock with the Montezuma shear zone of Precambrian ancestry. Alteration chemistry conforms to the standard porphyry-metal model but is developed around several small intrusives strung out along the shear zone and is expressed as a mottled pattern, rather than as the usual thick concentric zones centered on one large plug. The distribution of trace amounts of molybdenite is consistent with the postulate of molybdenite deposits in the district, but the mottled alteration pattern may signify small and scattered, possibly very deep, deposits. Disseminated molybdenite is essentially coextensive with altered rock and increases slightly in quantity toward the inner alteration zones. Two groups of molybdenite veins, associated with phyllic and potassic alteration, represent possible diffuse halos of molybdenite deposits. One group of veins resembles the Climax and Henderson deposits but was seen only in a small and isolated area of outcrops. The second group of molybdenite veins is in a bismuth-rich part of the Montezuma stock and underlies an area of bismuth veins; this group records the passage of contact metasomatic ore fluids. Another bismuth-rich area is in the southeast corner of the stock in a region of bismuth veins and may indicate a third group of molybdenite veins.

Circular↗

USGS1977

The geological investigation of the Taurus-Littrow Valley: Apollo 17 landing site

Astronauts Cernan and Schmitt, of Apollo 17, landed in the Taurus-Littrow valley of the Moon on December 11, 1972. Their major objectives were: (1) to sample very ancient lunar material such as might be found in pre-Imbrian highlands as distant as possible from the Imbrium basin, and (2) to sample pyroclastic materials that had been interpreted as significantly younger than the mare basalts returned from previous Apollo landing sites. The crew worked approximately 22 hours on the lunar surface; they traversed about 30 km, collected nearly 120 kg of samples, took more than 2,200 photographs, and recorded many direct geologic observations. The lunar surface data, sample results, and geologic interpretation of orbital photographs are the bases for this geologic synthesis. The Taurus-Littrow massifs are interpreted as the upper part of thick faulted ejecta deposited on the rim of the transient cavity of the large southern Serenitatis basin, which was formed by a meteor impact about 3.9 to 4.0 b.y. ago. The target rocks, predominantly of the dunite-anorthosite-norite-troctolite suite or its metamorphosed equivalents, were fractured, sheared, crushed, and melted by the impact. The resulting mixture of crushed rock and melt was transported up and out of the transient cavity and deposited on and beyond its rim. Hot fragmental to partly molten ejecta and relatively cool cataclasite and relict target rocks were intermixed in a melange of lenses, pods, and veins. Crystallization of melts and thermal metamorphism of fine-grained fragmental debris produced breccia composed of lithic and mineral fragments in a fine-grained, coherent, crystalline matrix. Such breccia dominates the massif samples. Faults that bound the massifs were activated during formation of the basin, so that structural relief of several kilometers, due to high-angle faulting, was imposed on the ejecta almost as soon as it was deposited. Massive slumping, that produced thick wedges of colluvium on the lower massif slopes, probably occurred nearly contemporaneously with the faulting. Sculptured Hills material, perhaps largely cataclasite excavated from the southern Serenitatis basin by the same impact, was then deposited on and around the faulted ejecta of the massifs. Subfloor basalt, estimated to be about 1,400 m thick in the landing site, flooded the Taurus-Littrow graben prior to approximately 3.7 b. y. ago. The basalt is part of a more extensive unit that was broadly warped and cut by extensional faults before the accumulation in Mare Serenitatis of younger, less deformed basalts that overlap it. A thin volcanic ash unit, probably about 3.5 b. y. old, mantled the subfloor basalt and the nearby highlands. It, too, was subsequently overlapped by the younger basalts of Mare Serenitatis. In the time since deposition of the volcanic ash, continued bombardment by meteors and secondary projectiles has produced regolith, a mechanical mixture of debris derived mainly from the subfloor basalt, the volcanic ash, and the rocks of the nearby massifs and Sculptured Hills. The regolith, in combination with the underlying volcanic ash, forms an unconsolidated surficial deposit with an average thickness of about 14 m, sufficiently thick to permit abnormally rapid degradation of the smaller craters, especially those less than 200 m in diameter, so as to create a surface that seems less cratered than do other mare surfaces. Admixture of volcanic ash gives the surface a distinctive dark color, which, in combination with the less cratered appearance, led to the pre-mission interpretation of a young dark mantling unit. The uppermost part of the regolith in the landing area is basalt rich ejecta from the clustered craters of the valley floor. Most of the craters are interpreted as part of a secondary cluster formed by projectiles of ejecta from Tycho. When they struck the face of the South Massif, the projectiles mobilized fine-grained regolith material that was redeposited on the valley floor as the light mantle. Exposure ages suggest that the swarm of secondary projectiles struck the Taurus-Littrow area about 100 m.y. ago. The Lee-Lincoln fault scarp is part of an extensive system of wrinkle ridges and scarps that transect both mare and highlands rocks. The scarp cuts the crater Lara, but the major part of the displacement occurred before deposition of the light mantle. Minor post-light mantle displacement is shown by small extensional faults that cut its surface west of the Lee-Lincoln scarp.

Open-File Report↗

USGS1983

Reconnaissance geology of the Jabal Saq Quadrangle, sheet 26/43 C, Kingdom of Saudi Arabia

The Jabal Saq quadrangle is located in the northeastern part of the Arabian Shield at the northern end of the Najd region between lat 26?00' and 26?30' N. and long 43?00' and 43?30' E. The northeastern two-thirds of the quadrangle is underlain by Paleozoic sedimentary rocks, the southwestern one-third by Proterozoic metamorphic and igneous rocks. The oldest rocks in the quadrangle are weakly metamorphosed immature sandstones that may correlate with the Murdama group. They have been intruded by several large plutons ranging in composition from mafic granodiorite to syenogranite. A densely developed fracture cleavage cuts the metamorphic rocks; otherwise, no structural features were recorded. The quadrangle has low mineral potential; no ancient mines were identified. The Dharaymeeah syenogranite forms a large pluton and bears some petrologic resemblance to alkali granites identified elsewhere in the Arabian Shield that have documented potential for containing deposits of lithophile rare metals. Analyses of wadi sediment samples collected in the quadrangle suggest that the syenogranite may also be enriched in some of these elements. The anomalously radioactive Usba monzogranite resembles highly evolved peraluminous granite plutons that elsewhere in the world are associated with deposits of tin and tungsten.

Open-File Report↗

USGS2002

Crustal structure of the coastal and marine San Francisco Bay region, California

As of the time of this writing, the San Francisco Bay region is home to about 6.8 million people, ranking fifth among population centers in the United States. Most of these people live on the coastal lands along San Francisco Bay, the Sacramento River delta, and the Pacific coast. The region straddles the tectonic boundary between the Pacific and North American Plates and is crossed by several strands of the San Andreas Fault system. These faults, which are stressed by about 4 cm of relative plate motion each year, pose an obvious seismic hazard. We have many ways to study earthquake faults. Where faults break the land surface, we may learn valuable information needed for hazard assessment, such as cumulative offset, slip rate, and earthquake history. However, many of the major faults in the region are partly submerged beneath San Francisco and Monterey Bays. Although this situation poses problems in gathering observational data for hazard assessment, bay-region waterways provide an opportunity to study faultzone structure by using marine subsurface-imaging techniques, which are easier and cheaper than equivalent studies on land. In 1993, the U.S. Geological Survey (USGS) launched a 5-year project aimed at unearthing the basic science of the submerged San Andreas strike-slip fault system in the San Francisco Bay region with its many interacting strands. Primary project goals were structural, such as to discover how the San Andreas and Hayward Faults are connected or related at depth, to learn how the complex of faults in the San Andreas stepover zone on the Golden Gate platform functions, and to locate previously unknown faults. This volume thus contains mostly structural information about the San Francisco Bay region, much of it gathered through exploratory geophysical experiments. The volume is organized “top down,” from studies in the shallowest crust to the base of the crust. The first three chapters are linked through their use of novel geophysical techniques to study earthquake effects, coseismic slip, and shallow stratigraphy. Kayen and others examine crustal structure at very high resolution and demonstrate the use of ground-penetrating-radar tomography to measure the liquefaction potential of coastal sedimentary deposits. McGann and others use microfossils from drill cores along the San Francisco-Oakland Bay Bridge to determine a more detailed late Pleistocene stratigraphy of San Francisco Bay than was previously available. Geist and Zoback use the historical record of a small local tsunami generated by the great 1906 San Francisco earthquake to model the rupture process of that earthquake. The last four chapters are dedicated to studies of fault related structure of the seismogenic crust in and around the San Andreas Fault system in the San Francisco Bay region. Jachens and others compile an aeromagnetic anomaly map from new high-resolution flights across the bay region. Some of these anomalies mark the positions of offshore faults, and others are offset by faults, providing constraints on cumulative slip. Hart and others concisely summarize the marine seismic data recorded in and around San Francisco Bay, map the coverage, and provide archival information for those interested in acquiring data. The last two chapters present the results of the seismic data that have been analyzed. Bruns and others present their analysis of high-quality intermediate-resolution (~5-km penetration) seismic-reflection data gathered over the complex San Andreas-San Gregorio Fault junction. This junction, which is thought to be where the 1906 San Francisco earthquake originated (see Geist and Zoback, this volume), contains an apparent extensional right stepover in the San Andreas Fault. Finally, Parsons and others review and summarize the results of deep-crustal seismic-reflection experiments and local-earthquake tomographic studies, including previously unpublished data, and provide additional support and discussion for already-published studies. In summary, these studies were carried out in an environment where background information on faults in the San Francisco Bay region was sought. Much of the structural information presented here comes from experiments of a style unlikely to be conducted by the USGS in the near future. Together, the chapters in this volume provide a structural framework for a major part of a complex strike-slip fault system.

California↗

USGS1981

Paleoclimatic implications of Late Pleistocene marine ostracodes from the St. Lawrence lowlands.

Using modern zoogeographic data and inferred temperature ranges for Champlain Sea ostracode species, bottom water paleotemperatures were estimated for three phases of deposition of this inland sea. The temporal distribution of these and other environmentally diagnostic species in Champlain Sea deposits reveals a significant local climatic change in the Champlain Valley from frigid/subfrigid to cold-temperate marine conditions about 11 000 to 10 600 yr BP. Oceanographic changes in the Champlain Sea are correlated with major deglaciation events recorded in the North Atlantic.-from Author

Micropaleontology↗

USGS2017

Stable C, O and clumped isotope systematics and 14C geochronology of carbonates from the Quaternary Chewaucan closed-basin lake system, Great Basin, USA: Implications for paleoenvironmental reconstructions using carbonates

Isotopic compositions of lacustrine carbonates are commonly used for dating and paleoenvironmental reconstructions. Here we use carbonate δ13C and δ18O, clumped (Δ47), and 14C compositions to better understand the carbonate isotope system in closed-basin lakes and trace the paleohydrologic and temperature evolution in the Chewaucan closed-basin lake system, northern Great Basin, USA, over the Last Glacial/Holocene transition. We focus on shorezone tufas to establish that they form in isotopic equilibrium with lake water and DIC, they can be dated reliably using 14C, and their clumped isotope composition can be used to reconstruct past lake temperature. Calculations of the DIC budget and reservoir age for the lake indicate residence time is short, and dominated by exchange with atmospheric CO2 at all past lake levels. Modern lake DIC and shorezone tufas yield δ13C and 14C values consistent with isotopic equilibrium with recent fossil fuel and bomb-influenced atmospheric CO2, supporting these calculations. δ13C values of fossil tufas are also consistent with isotopic equilibrium with pre-industrial atmospheric CO2 at all shoreline elevations. This indicates that the 14C reservoir effect for this material is negligible. Clumped isotope (Δ47) results indicate shorezone tufas record mean annual lake temperature. Modern (average 13 ± 2 °C) and 18 ka BP-age tufas (average 6 ± 2 °C) have significantly different temperatures consistent with mean annual temperature lowering of 7 ± 3 °C (1 SE) under full glacial conditions. For shorezone tufas and other lake carbonates, including spring mounds, mollusk shells, and ostracod tests, overall δ13C and δ18O values co-vary according to the relative contribution of spring and lacustrine end member DIC and water compositions in the drainage system, but specific isotope values depend strongly upon sample context and are not well correlated with past lake depth. This contrasts with the interpretation that carbonate isotopes in closed-basin lake systems reflect changes in DIC and water budgets connected to higher or lower lake volumes. Instead, a small overlapping range of isotope compositions characterize multiple lake levels, so that none can be identified uniquely by isotope composition alone. Relative to other lake carbonates, δ13C and δ18O values for ostracods in Ana River Canyon deposits are very strongly influenced by Ana River water, suggesting low lake level and volume characterized Summer Lake for most of the past 100,000 years. Coupled with sedimentologic observations, the Ana River deposits thus suggest dry conditions like today are close to the mean climate state in the northern Great Basin. By contrast, basin-integrating highstands such as that dating to ∼14 ka BP, during the last glacial termination, are hydrologically unique and short-lived. Overall, our results indicate carbonate isotope records must account for the specific geochemical and hydrologic characteristics of lake system in order to provide robust paleoenvironmental reconstructions.

Great Basin↗

USGS1992

Late Cenozoic lacustrine and climatic environments at Tule Lake, northern Great Basin, USA

Cores of lake sediment to a depth of 334 m in the town of Tulelake, Siskiyou County, northern California, document the late Cenozoic paleolimnologic and paleoclimatic history of the northwestern edge of the Great Basin. The cores have been dated by radiometric, tephrochronologic and paleomagnetic analyses. Lacustrine diatoms are abundant throughout the record and document a nearly continuous paleolimnologic history of the Tule Lake basin for the last 3 Myr. During most of this time, this basin (Tule Lake) was a relatively deep, extensive lake. Except for a drier (and cooler?) interval recorded by Fragilaria species about 2.4 Ma, the Pliocene is characterized by a dominance of planktonic Aulacoseira solida implying a warm monomictic lake under a climatic regime of low seasonality. Much of the Pleistocene is dominated by Stephanodiscus and Fragilaria species suggesting a cooler, often drier, and highly variable climate. Benthic diatoms typical of alkaline-enriched saline waters commonly appear after 1.0 Ma, and tephrochronology indicates slow deposition and possible hiatuses between about 0.6 and 0.2 Ma. The chronology of even-numbered oxygen isotope stages approximately matches fluctuations in the abundance of Fragilaria since 800 ka indicating that glacial periods were expressed as drier environments at Tule Lake. Glacial and interglacial environments since 150 ka were distinct from, and more variable than, those occurring earlier. The last full glacial period was very dry, but shortly thereafter Tule Lake became a deep, cool lacustrine system indicating a substantial increase in precipitation. Aulacoseira ambigua characterized the latest glacial and Holocene record of Tule Lake. Its distribution indicates that warmer and wetter climates began about 15 ka in this part of the Great Basin. Diatom concentration fluctuates at 41 000 year intervals between 3.0 and 2.5 Ma and at approximately 100 000 year intervals after 1.0 Ma. In the late Pliocene and early Pleistocene, Aulacoseira solida percentages wax and wane in an approximately 400 000 year cycle. The possible response of Tule Lake diatom communities to orbitally-induced insolation cycles underscores the importance of this record for the study of late Cenozoic paleoclimate change. ?? 1992 Springer-Verlag.

Climate Dynamics↗

USGS1902

Twenty-Second Annual Report of the Director of the United States Geological Survey, 1900-1901: Part I - Director's report and a paper on asphalt and bituminous rock deposits

The work of the Geological Survey during the fiscal year 1900-01 was mainly a continuation of that of previous years, described in former reports. The organization was changed somewhat (see p. 48), but in a general way similar results were reached, which added materially to the sum of geologic and geographic knowledge. The detailed record of accomplishment, both in field and in office, will be found on later pages, under the heading " Work of the year" (p. 53). In this introduction some subjects of special interest will receive consideration.

Annual Report↗

USGS1961

Geology and ground-water resources of Sumner County, Kansas

This report describes the geography, geology, and ground-water resources of Sumner County in south-central Kansas. The hydrologic and geologic data upon which this report is based were obtained in the field during the summers of 1955 and 1956. Records of 300 wells and 2 springs, chemical analyses of 219 water samples from wells and test holes and of 15 from streams, and logs of 362 wells and test holes are included in tables. Sumner County has an area of 1,183 square miles and lies in the Wellington Lowland and Arkansas River Lowlands of the Central Lowland physiographic province. It is drained by Arkansas River, Ninnescah River, and Chikaskia River and their tributaries. The land surface in general is a southeastward-sloping, gently rolling plain. The average annual precipitation at Wellington is about 31 inches. Wheat fanning is the principal industry of the county, and oil is the chief natural resource. The Wellington Formation, of Permian age, crops out in the eastern two-thirds of the county except where it is covered by Pleistocene deposits. The Ninnescah Shale (Permian) overlies the Wellington Formation and crops out in parts of the western third of the county. The Permian rocks yield small quantities of hard water to wells. Pleistocene sand and gravel deposits of Nebraskan age are present in the northwestern corner of the county and yield moderate quantities of good water to wells. Discontinuous deposits of Kansan or Illinoisan age, locally mantled by colluvium, forms terraces in southern and eastern Sumner County, and may yield moderate quantities of water. Wisconsinan terrace deposits and Recent alluvium along the major streams yield large quantities of water. Colluvium and dune sand are unimportant as sources of water but may facilitate recharge. Maps of Sumner County included in this report show the outcrop areas of the formations, geologic cross sections, the shape and slope of the water table, the locations of wells and test holes for which records are given, and the distribution of chloride in water samples. The ground-water reservoir is recharged principally from rain and snow that fall within the county, by percolation from streams and other surface bodies of water, and by underflow from adjacent areas. Water is discharged from the ground-water reservoir by seepage into streams, by transpiration and evaporation, by movement into adjacent areas, and by wells. Water is pumped from wells for domestic, stock, municipal, industrial, and irrigation use. Irrigation from wells is most extensive in the valley of Arkansas River, in which area further development is most probable. Chemical analyses of samples of water from Sumner County indicate that the quality varies greatly from place to place. Sulfate is common in water from the Wellington Formation and Ninnescah Shale. Water from Pleistocene deposits is generally suitable for most uses except in local areas where it contains excessive chloride.

Kansas Geological Survey Bulletin↗

USGS2013

U-Pb ages of detrital zircons from the Tertiary Mississippi River delta plain in central Louisiana: Insights into sediment provenance

The sources of the tremendous amount of Cenozoic siliciclastic sediment deposited in the Gulf of Mexico region remain debated because of a lack of definitive provenance-identifying characteristics. In an effort to build on prior provenance analysis, we present 101–160 single-grain detrital zircon U-Pb ages for each of 10 outcrop samples from Upper Paleocene to Upper Miocene sandstones from a ∼10,000 km2 swath of central Louisiana corresponding to the ancient Mississippi River Delta, the largest Cenozoic depocenter in the northern Gulf of Mexico region. Sample depositional age control is derived from biostratigraphy and/or regional lithostratigraphic correlation. U-Pb ages in each of the samples range from Cenozoic to Archean, and correspond to the ages of various geologic terranes that underlie the modern Mississippi River drainage basin. However, the prominence of various age distributions changes systematically through the Cenozoic stratigraphy, and pronounced shifts in the abundance of certain age distributions between stratal packages appear to be correlated to shifts in heavy mineral assemblages recorded across the northern Gulf of Mexico coastal plain. Comparison of coastal plain detrital zircon age distributions to age distributions from North American sedimentary cover and the ages of major North American crystalline basement rocks, aided by a sediment mixing model, illuminates the provenance of each of the stratal packages, and suggests that (1) the Mississippi River catchment has resembled its present configuration, at least in the east-west dimension, for much, if not all, of the Cenozoic, and (2) depositional episodes on the Louisiana coastal plain characterized by high sediment supply also corresponded to high proportions of sediment sourcing from the Sevier-Laramide region of the interior western United States. Sediment supply to the Louisiana coastal plain by the paleo–Mississippi River has generally been high during the Cenozoic, except for an anomalous low during the Middle Eocene, when the abundance of sediment derived from the Rocky Mountain region decreased dramatically relative to sediment derived from the Appalachian region.

Louisiana↗

USGS1976

Geology and ore deposits of the Mahd Adh Dhahab District, Kingdom of Saudi Arabia

Mahd adh Dhahab is the principal gold-silver mine in Saudi Arabia; it was productive during three principal periods, two during ancient times (about 950 B.C. and 750-1258 A.D.) and one in modern times (1939-54). The early production is not known, but the recorded production in 1939-54 is 765,768 fine ounces gold and 1,002,029 ounces silver. The district is underlain by a sequence of pyroclastic and clastic rocks which probably belong to the Murdama Group. From oldest to youngest the units are andesite, lower agglomerate, lower tuff, upper agglomerate, and upper tuff. These units have been tilted northerly, forming a homocline, and they are complexly broken by six sets of faults; three of these sets, which strike N.25°-30°W., N.10°W. to N.20°E., and N.30°-60'E., contain productive quartz veins. The principal ore minerals are pyrite, chalcopyrite, sphalerite, galena, and minor tetrahedrite, argentite, and native gold and silver. The gold and silver occurs finely disseminated in the veins and in the altered selvages of the veins. Widespread potassic and propylitic alteration accompanied the ore-forming processes. Potassium feldspar was introduced during an early stage of vein formation. Isotopic analyses of lead in vein potassium feldspar and galena yield a model age of about 900-1050 million years with the possibility of the original lead source having been remobilized about 600 million years ago. Chlorite and carbonate are also prominent vein minerals.

Open-File Report↗

USGS2007

'Snake River (SR)-type' volcanism at the Yellowstone hotspot track: Distinctive products from unusual, high-temperature silicic super-eruptions

A new category of large-scale volcanism, here termed Snake River (SR)-type volcanism, is defined with reference to a distinctive volcanic facies association displayed by Miocene rocks in the central Snake River Plain area of southern Idaho and northern Nevada, USA. The facies association contrasts with those typical of silicic volcanism elsewhere and records unusual, voluminous and particularly environmentally devastating styles of eruption that remain poorly understood. It includes: (1) large-volume, lithic-poor rhyolitic ignimbrites with scarce pumice lapilli; (2) extensive, parallel-laminated, medium to coarse-grained ashfall deposits with large cuspate shards, crystals and a paucity of pumice lapilli; many are fused to black vitrophyre; (3) unusually extensive, large-volume rhyolite lavas; (4) unusually intense welding, rheomorphism, and widespread development of lava-like facies in the ignimbrites; (5) extensive, fines-rich ash deposits with abundant ash aggregates (pellets and accretionary lapilli); (6) the ashfall layers and ignimbrites contain abundant clasts of dense obsidian and vitrophyre; (7) a bimodal association between the rhyolitic rocks and numerous, coalescing low-profile basalt lava shields; and (8) widespread evidence of emplacement in lacustrine-alluvial environments, as revealed by intercalated lake sediments, ignimbrite peperites, rhyolitic and basaltic hyaloclastites, basalt pillow-lava deltas, rhyolitic and basaltic phreatomagmatic tuffs, alluvial sands and palaeosols. Many rhyolitic eruptions were high mass-flux, large volume and explosive (VEI 6-8), and involved H2O-poor, low-??18O, metaluminous rhyolite magmas with unusually low viscosities, partly due to high magmatic temperatures (900-1,050??C). SR-type volcanism contrasts with silicic volcanism at many other volcanic fields, where the fall deposits are typically Plinian with pumice lapilli, the ignimbrites are low to medium grade (non-welded to eutaxitic) with abundant pumice lapilli or fiamme, and the rhyolite extrusions are small volume silicic domes and coule??es. SR-type volcanism seems to have occurred at numerous times in Earth history, because elements of the facies association occur within some other volcanic fields, including Trans-Pecos Texas, Etendeka-Paran, Lebombo, the English Lake District, the Proterozoic Keewanawan volcanics of Minnesota and the Yardea Dacite of Australia. ?? Springer-Verlag 2007.

Bulletin of Volcanology↗