SEARCH · USGS Science

Results for “Open Quaternary”

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 271 records · Page 15Linked to original sources

USGS2006

Preliminary isostatic gravity map of the Sonoma volcanic field and vicinity, Sonoma and Napa Counties, California

This isostatic residual gravity map is part of a three-dimensional mapping effort focused on the subsurface distribution of rocks of the Sonoma volcanic field in Napa and Sonoma counties, northern California. This map will serve as a basis for modeling the shapes of basins beneath the Santa Rosa Plain and Napa and Sonoma Valleys, and for determining the location and geometry of faults within the area. Local spatial variations in the Earth's gravity field (after accounting for variations caused by elevation, terrain, and deep crustal structure explained below) reflect the distribution of densities in the mid to upper crust. Densities often can be related to rock type, and abrupt spatial changes in density commonly mark lithologic boundaries. High-density basement rocks exposed within the northern San Francisco Bay area include those of the Mesozoic Franciscan Complex and Great Valley Sequence present in the mountainous areas of the quadrangle. Alluvial sediment and Tertiary sedimentary rocks are characterized by low densities. However, with increasing depth of burial and age, the densities of these rocks may become indistinguishable from those of basement rocks. Tertiary volcanic rocks are characterized by a wide range in densities, but, on average, are less dense than the Mesozoic basement rocks. Isostatic residual gravity values within the map area range from about -41 mGal over San Pablo Bay to about 11 mGal near Greeg Mountain 10 km east of St. Helena. Steep linear gravity gradients are coincident with the traces of several Quaternary strike-slip faults, most notably along the West Napa fault bounding the west side of Napa Valley, the projection of the Hayward fault in San Pablo Bay, the Maacama Fault, and the Rodgers Creek fault in the vicinity of Santa Rosa. These gradients result from juxtaposing dense basement rocks against thick Tertiary volcanic and sedimentary rocks.

Open-File Report↗

USGS2006

Revised geologic cross sections of parts of the Colorado, White River, and Death Valley regional groundwater flow systems, Nevada, Utah, and Arizona

This report presents revisions to parts of seven of the ten cross sections originally published in U.S. Geological Survey Open-File Report 2006-1040. The revisions were necessary to correct errors in some of the original cross sections, and to show new parts of several sections that were extended and (or) appended to the original section profiles. Revisions were made to cross sections C-C', D-D', E-E', F-F', G-G', I-I', and J-J', and the parts of the sections revised or extended are highlighted below the sections on plate 1 by red brackets and the word "revised," or "extended." Sections not listed above, as well as the interpretive text and figures, are generally unchanged from the original report. Cross section C-C' includes revisions in the east Mormon Mountains in the east part of the section; D-D' includes revisions in the Mormon Mesa area in the east part of the section; E-E' includes revisions in the Muddy Mountains in the east part of the section; F-F' includes revisions from the Muddy Mountains to the south Virgin Mountains in the east part of the section; and J-J' includes some revisions from the east Mormon Mountains to the Virgin Mountains. The east end of G-G' was extended about 16 km from the Black Mountains to the southern Virgin Mountains, and the northern end of I-I' was extended about 45 km from the Muddy Mountains to the Mormon Mountains, and revisions were made in the Muddy Mountains part of the original section. This report contains 10 interpretive cross sections and an integrated text describing the geology of parts of the Colorado, White River, and Death Valley regional groundwater flow systems in Nevada, Utah, and Arizona. The primary purpose of the report is to provide geologic framework data for input into a numerical groundwater model. Therefore, the stratigraphic and structural summaries are written in a hydrogeologic context. The oldest rocks (basement) are Early Proterozoic metamorphic and intrusive crystalline rocks that are considered confining units because of their low permeability. Late Proterozoic to Lower Cambrian clastic units overlie the crystalline rocks and are also considered confining units within the regional flow systems. Above the clastic units are Middle Cambrian to Lower Permian carbonate rocks that are the primary aquifers in the flow systems. The Middle Cambrian to Lower Permian carbonate rocks are overlain by a sequence of mainly clastic rocks of late Paleozoic to Mesozoic age that are mostly considered confining units, but they may be permeable where faulted. Tertiary volcanic and plutonic rocks are exposed in the northern and southern parts of the study area. In the Clover and Delamar Mountains, these rocks are highly deformed by north- and northwest-striking normal and strike-slip faults that are probably important conduits in transmitting groundwater from the basins in the northern Colorado and White River flow systems to basins in the southern part of the flow systems. The youngest rocks in the region are Tertiary to Quaternary basin-fill deposits. These rocks consist of middle to late Tertiary sediments consisting of limestone, conglomerate, sandstone, tuff, and gypsum, and younger Quaternary surficial units consisting of alluvium, colluvium, playa deposits, and eolian deposits. Basin-fill deposits are both aquifers and aquitards. The rocks in the study area were complexly deformed by episodes of Mesozoic compression and Cenozoic extensional tectonism. Some Cretaceous thrust faults and folds of the Sevier orogenic belt form duplex zones and define areas of maximum thickness for the Paleozoic carbonate rocks. Cenozoic faults are important because they are the primary structures that control groundwater flow in the regional flow systems.

Arizona, Nevada, Utah↗

USGS1983

Hydrology of area 38, Western Region, Interior Coal Province, Iowa and Missouri

A nationwide need for information characterizing hydrologic conditions in mined and potential mine areas has become paramount with the enactment of the Surface Mining Control and Reclamation Act of 1977. This report is designed to be useful to the mine owners, operators, and others by presenting information about the existing hydrologic conditions and by identifying sources of hydrologic information. General hydrologic information is presented using a brief text with an accompanying map, chart, graph, or other illustration for each of a series of water-resources-related topics. The summation of the topical discussions provides a description of the hydrology of the area. Coal has been mined for 130 years in Area 38, but large reserves remain. Production peaked in 1917 when Iowa produced 9 million tons and Missouri produced 6 million tons. Underground mining has been replaced by surface mining in Area 38. Not all past surface-mined lands are subject to reclamation under recently enacted reclamation laws. The surface-water monitoring network in Area 38 consists of 183 stations. Streamflow varies seasonally and from year to year. Water-quality data are available for 49 stations in the study area. Measurements of specific conductance, dissolved solids, pH, alkalinity, sulfate, iron, manganese, trace metals and other constituents are available for 36 stations operated between 1978 and 1981 expressly for the collection of water-quality data within basins containing coal mines. A cumulative impact of coal mining on the mineralization of surface water is evident from specific-conductance data for stations downstream from mining activities. Alkalinity in streams in Area 38 averaged greater than 118 milligrams per liter, providing the capability to neutralize acid-mine drainage to some extent. Sulfate concentrations in streamflow averaged 88 milligrams per liter at stations upstream from coal mines and 269 milligrams per liter at stations downstream from coal mines. Significant relationships exist between totalrecoverable-iron concentrations and suspendedsediment concentrations. Manganese concentrations are larger in streams draining mined areas. Streamflow at 5 of the 36 coal-hydrology stations in Area 38, all located downstream from coal mines, exceeded acid-mine-drainage criteria at one time or another. In Area 38 dissolved-solids concentrations in water from the Cambrian-Ordovician aquifer range from 300 to 15,000 milligrams per liter; in southcentral Iowa and where the aquifer underlies the Missouri River alluvium, as in Boone County, Missouri, dissolved-solids concentrations are less than 1,000 milligrams per liter. In these areas the Cambrian-Ordovician aquifer is suitable for domestic and other uses. Chemical quality of water from Quaternary aquifers generally is suitable for domestic uses and other uses, dissolved-solids concentrations averaged less than 1,000 milligrams per liter. Iron, manganese and nitrate are excessive in some instances. Chemical quality of water from Mississippian and Pennsylvanian aquifers is unsuitable for domestic use and may be unsuitable for other uses. The Pennsylvanian and Misissippian aquifers have average sulfate concentrations in excess of 1,000 milligrams per liter.

Iowa, Missouri↗

USGS1995

Isopachs of Quaternary deposits, Fremont 1- by 2- degree Quadrangle and part of Omaha Quadrangle, Nebraska, digitized from a published 1:250,000-scale geologic map

A geologic map showing the isopachs of Quaternary deposits in the Fremont and part of the Omaha, Nebraska, 1- by 2-degree quadrangles was published at a scale of 1:250,000 in 1975 (Burchett and others, 1975). This report describes the conversion of Quaternary thickness data into a digital geographic data set. A film separation of the published isopachs was scan-digitized and processed to produce digital geographic data. Geographic feature attributes and data-set documentation also are included in the digital data set. The digital data set are formatted for distribution with accordance with the Spatial Data Transfer Standard approved by the U.S. National Institute of Standards and Technology.

Open-File Report↗

USGS2021

Paleoseismic trenching reveals late quaternary kinematics of the Leech River Fault: Implications for forearc strain accumulation in Northern Cascadia

New paleoseismic trenching indicates late Quaternary oblique right‐lateral slip on the Leech River fault, southern Vancouver Island, Canada, and constrains permanent forearc deformation in northern Cascadia. A south‐to‐north reduction in northward Global Navigation Satellite System velocities and seismicity across the Olympic Mountains, Strait of Juan de Fuca (JDF), and the southern Strait of Georgia, has been used as evidence for permanent north–south crustal shortening via thrust faulting between a northward migrating southern forearc and rigid northern backstop in southwestern Canada. However, previous paleoseismic studies indicating late Quaternary oblique right‐lateral slip on west‐northwest‐striking forearc faults north of the Olympic Mountains and in the southern Strait of Georgia are more consistent with forearc deformation models that invoke oroclinal bending and(or) westward extrusion of the Olympic Mountains. To help evaluate strain further north across the Strait of JDF, we present the results from two new paleoseismic trenches excavated across the Leech River fault. In the easternmost Good Hope trench, we document a vertical fault zone and a broad anticline deforming glacial till. Comparison of till clast orientations in faulted and undeformed glacial till shows evidence for postdeposition faulted till clast rotation, indicating strike‐slip shear. The orientation of opening mode fissuring during surface rupture is consistent with right‐lateral slip and the published regional S H max "> S H max SHmax directions. Vertical separation and the formation of scarp‐derived colluvium along one fault also indicate a dip‐slip component. Radiocarbon charcoal dating within offset glacial till and scarp‐derived colluvium suggest a single surface rupturing earthquake at 9.4 ± 3.4    ka "> 9.4 ± 3.4 ka 9.4±3.4 ka ⁠ . The oblique right‐lateral slip sense inferred in the Good Hope trench is consistent with slip kinematics observed on other regional west‐northwest‐striking faults and indicates that these structures do not accommodate significant north–south shortening via thrust faulting.

Washington↗

USGS1999

Geologic map of the East of Grotto Hills quadrangle, California: A digital database

The East of Grotto Hills 1:24,000-scale quadrangle of California lies west of the Colorado River about 30 km southwest of Searchlight, Nevada, near the boundary between the northern and southern parts of the Basin and Range Province. The quadrangle includes the eastern margin of Lanfair Valley, the southernmost part of the Castle Mountains, and part of the northwest Piute Range. The generally north-trending Piute Range aligns with the Piute and Dead Mountains of California and the Newberry and Eldorado Mountains and McCullough Range of Nevada. The southern part of the Piute Range adjoins Homer Mountain (Spencer and Turner, 1985) near Civil War-era Fort Piute. Adjacent 1:24,000-scale quadrangles include Castle Peaks, Homer Mountain, and Signal Hill, Calif.; also Hart Peak, Tenmile Well, and West of Juniper Mine, Calif. and Nev. The mapped area contains Tertiary (Miocene) volcanic and sedimentary rocks, interbedded with and overlain by Tertiary and Quaternary surficial deposits. Miocene intrusions mark conduits that served as feeders for the Miocene volcanic rocks, which also contain late magma pulses that cut the volcanic section. Upper Miocene conglomerate deposits interfinger with the uppermost volcanic flows. Canyons and intermontane valleys contain dissected Quaternary alluvial-fan deposits, mantled by active alluvial-fan deposits and detritus of active drainages. The alluvial materials were derived largely from Early Proterozoic granite and gneiss complexes, intruded by Mesozoic granite, dominate the heads of Lanfair Valley drainages in the New York Mountains and Mid Hills (fig. 1; Jennings, 1961). Similar rocks also underlie Tertiary deposits in the Castle Peaks, Castle Mountains, and eastern Piute Range.

California↗

USGS2025

Reconciliation of geochronology and paleozoogeography for Quaternary marine terraces, San Luis Obispo Bay area, California, USA

In the San Luis Obispo Bay area of central California, interpretations of marine terrace ages have been hampered by inconsistent results from geochronological indicators (U-series ages of corals and correlations using amino acid racemization of mollusks) and seemingly contradictory paleozoogeographic aspects of fossil faunal assemblages. New U-series ages of corals, amino acid data from mollusks, and detailed analyses of fossil mollusk assemblages are presented that reconcile many of the apparently discordant results from previous studies. The two lowest-elevation terraces are Q1 (lower) and Q2 (upper); both are thought to date from high-sea stands of marine isotope stage (MIS) 5, the last interglacial complex. A combination of U-series dating and amino acid racemization results indicates that the Q1 terrace probably dates to the ∼80 ka high-sea stand of MIS 5a. U-series analyses of corals from the Q2 terrace show open-system histories, but consideration of two alternative open-system histories indicates that this terrace likely hosts corals dating to the high-sea stands of MIS 5c (∼105–95 ka) and MIS 5e (∼130–115 ka). Amino acid ratios in the fossil bivalve Leukoma staminea (Conrad, 1837) support the age differences between the two terraces and the open-system models suggested by the U-series data. Alkenone studies along much of the coast of California have shown that sea surface temperatures (SSTs) of the eastern Pacific Ocean were warmer than present during MIS 5e. During MIS 5c, on the other hand, SSTs were either similar to the present or cooler, but in either case, much cooler than during MIS 5e. The paleozoogeographic aspects of the molluscan faunas from the Q2 terrace support an interpretation that these deposits contain a mixture of fossils from both the MIS 5c and 5e high-sea stands. Fossils from the Q2 terrace include southern or southward-ranging species (likely dating to MIS 5e) and northern or northward-ranging species (likely dating to MIS 5c). A mixture of MIS 5e and MIS 5c fossils on the Q2 terrace is consistent with similar data reported for other localities in California. This phenomenon is explained by glacial isostatic adjustment (GIA) processes, which brought about a higher-than-present sea level during MIS 5c. GIA processes, combined with a low uplift rate, allowed mixing of MIS 5e fossils during the MIS 5c high-sea stand through capture of an MIS 5e terrace that had experienced minimal uplift in ∼20,000 years. Terrace reoccupation and fossil mixing such as that in the San Luis Obispo Bay area can be expected along any part of the Pacific Coast of North America that was affected by GIA processes and where uplift rates are low.

California↗

USGS2017

Millennial-scale variability in the local radiocarbon reservoir age of south Florida during the Holocene

A growing body of research suggests that the marine environments of south Florida provide a critical link between the tropical and high-latitude Atlantic. Changes in the characteristics of water masses off south Florida may therefore have important implications for our understanding of climatic and oceanographic variability over a broad spatial scale; however, the sources of variability within this oceanic corridor remain poorly understood. Measurements of ΔR, the local offset of the radiocarbon reservoir age, from shallow-water marine environments can serve as a powerful tracer of water-mass sources that can be used to reconstruct variability in local-to regional-scale oceanography and hydrology. We combined radiocarbon and U-series measurements of Holocene-aged corals from the shallow-water environments of the Florida Keys reef tract (FKRT) with robust statistical modeling to quantify the millennial-scale variability in ΔR at locations with (“nearshore”) and without (“open ocean”) substantial terrestrial influence. Our reconstructions demonstrate that there was significant spatial and temporal variability in ΔR on the FKRT during the Holocene. Whereas ΔR was similar throughout the region after ∼4000 years ago, nearshore ΔR was significantly higher than in the open ocean during the middle Holocene. We suggest that the elevated nearshore ΔR from ∼8000 to 5000 years ago was most likely the result of greater groundwater influence associated with lower sea level at this time. In the open ocean, which would have been isolated from the influence of groundwater, ΔR was lowest ∼7000 years ago, and was highest ∼3000 years ago. We evaluated our open-ocean model of ΔR variability against records of local-to regional-scale oceanography and conclude that local upwelling was not a significant driver of open-ocean radiocarbon variability in this region. Instead, the millennial-scale trends in open-ocean ΔR were more likely a result of broader-scale changes in western Atlantic circulation associated with an increase in the supply of equatorial South Atlantic water to the Caribbean and shifts in the character of South Atlantic waters resulting from variation in the intensity of upwelling off the southwest coast of Africa. Because accurate estimates of ΔR are critical to precise calibrations of radiocarbon dates from marine samples, we also developed models of nearshore and open-ocean ΔR versus conventional 14 C ages that can be used for regional radiocarbon calibrations for the Holocene. Our study provides new insights into the patterns and drivers of oceanographic and hydrologic variability in the Straits of Florida and highlights the value of the paleoceanographic records from south Florida to our understanding of Holocene changes in climate and ocean circulation throughout the Atlantic.

Florida↗

USGS2000

Map and database of Quaternary faults and folds in Colombia and its offshore regions

As part of the International Lithosphere Program’s “World Map of Major Active Faults,” the U.S. Geological Survey (USGS) is assisting in the compilation of a series of digital maps of Quaternary faults and folds in Western Hemisphere countries. The maps show the locations, ages, and activity rates of major earthquake-related features such as faults and fault-related folds. They are accompanied by databases that describe these features and document current information on their activity in the Quaternary. Top date, the project has published fault and fold maps for Costa Rica (Montero and others, 1998), Panama (Cowan and others, 1998), Venezuela (Audemard and others, 2000), Bolovia/Chile (Lavenu, and others, 2000), and Argentina (Costa and others, 2000). The project is a key part of the Global Seismic Hazards Assessment Program (ILP Project II-0) for the International Decade for Natural Hazard Disaster Reduction.

Open-File Report↗

USGS2013

Generalized surficial geologic map of the Fort Irwin Area, San Bernardino County, California

The geology and landscape of the Fort Irwin area, typical of many parts of the Mojave Desert, consist of rugged mountains separated by broad alluviated valleys that form the main coarse-resolution features of the geologic map. Crystalline and sedimentary rocks, Mesozoic and older in age, form most of the mountains with lesser accumulations of Miocene sedimentary and volcanic rocks. In detail, the area exhibits a fairly complex distribution of surficial deposits resulting from diverse rock sources and geomorphology that has been driven by topographic changes caused by recent and active faulting. Depositional environments span those typical of the Mojave Desert: alluvial fans on broad piedmonts, major intermittent streams along valley floors, eolian sand dunes and sheets, and playas in closed valleys that lack through-going washes. Erosional environments include rocky mountains, smooth gently sloping pediments, and badlands in readily eroded sediment. All parts of the landscape, from regional distribution of mountains, valleys, and faults to details of degree of soil development in surface materials, are portrayed by the surficial geologic map. Many of these attributes govern infiltration and recharge, and the surface distribution of permeable rock units such as Miocene sedimentary and volcanic rocks provides a basis for evaluating potential groundwater storage. Quaternary faults are widespread in the Fort Irwin area and include sinistral, east-striking faults that characterize the central swath of the area and the contrasting dextral, northwest-striking faults that border the east and west margins. Bedrock distribution and thickness of valley-fill deposits are controlled by modern and past faulting, and faults on the map help to identify targets for groundwater exploration.

California↗

USGS1996

Sediment magnetic, paleomagnetic, and geochemical data from Quaternary lacustrine sediment in a core from Grass Lake, Siskiyou County, California

Sediment magnetic and geochemical results have been obtained from the top 60 meters of lacustrine sediments recovered in two cores from Tule Lake in northern California. The sediment magnetic and geochemical data, presented here in tabular form, complement studies of diatoms and pollen in the cores that are the bases for published paleoclimatic interpretations. This report also documents the methods used to obtain the magnetic properties and geochemical data.

Open-File Report↗

USGS1985

Reconnaissance geology of the Al Ba'ayith quadrangle, sheet 26/41 D, Kingdom of Saudi Arabia

The Al Ba'ayith quadrangle, located in the northeastern part of the Arabian Shield, is underlain by upper Proterozoic intrusive rocks and volcanogenic layered sequences bounded by unconformities. The oldest rocks are silicic volcanic rocks of the Banana formation that is tentatively assigned to the Hulayfah group. Successively younger layered rocks are the Maraghan formation of the Murdama group, consisting of lithic graywacke, siltstone, and shale; the Hibshi formation, coarse-grained lithic sandstone and conglomerate; the Sufran formation, dacitic and andesitic lava flows and ash-flow tuffs; the Jurdhawiyah formation, andesitic flows and agglomerate, and conglomeratic sandstone; and the Hadn formation, rhyolite flows and ash-flow tuffs, conglomerate, sandstone, and andesite flows. Plutonic rocks are of four main age groups: an early group consisting of orthogneiss of granodioritic and granitic composition, and metagabbro; a pre-Hibshi group consisting of the Murran complex (diorite and quartz diorite) and quartz monzodiorite; a post-Hibshi group, consisting of altered mafic plutonic rocks, granodiorite of the Idah suite, and monzogranite of the Shuwayman suite; and a latest Precambrian group of highly evolved granitic rocks, consisting of alkali-feldspar granite, granophyre, and syenogranite. Structures in the orthogneiss and metagabbro trend northeast to northwest, and in the Murran complex, generally east. The Maraghan formation was folded and thrust over the Hibshi formation along the northeast-trending Raha fault. The Jurdhawiyah formation is at the northern margin of the east-trending Shuqrah basin. Northwest-trending left-lateral faults probably belong to the Najd fault system. Quaternary surficial deposits mantle large areas of the quadrangle, and consist of sheet gravel, alluvial fan gravel, eolian and alluvial sand and silt, and sabkhah deposits. Gold-bearing quartz veins occur associated with small plutons of the Idah suite in the southeastern part of the quadrangle, and have been mined in the past. Ironstones, near Murran in the center of the quadrangle contain trace amounts of silver and gold.

Open-File Report↗

USGS1981

Composition of tidal flat sediments, Willapa Bay, Washington

The purpose of this study was to characterize the modern sediments of sandy tidal flats in Willapa Bay, Washington based on their composition. Generally, clay comprises less than five percent of the sediment. Clay content increases upslope and up-estuary. Principal clay minerals are montmorillanite, illite, and chlorite; two clay mineral suites are present: (1) muddy flat suite with clay containing 44% montmorillonite, and (2) sandy flat suite with clay composition of 88% montmorillonite. Heavy minerals make up approximately four percent of the tidal flat sediment. Distribution of heavy minerals reflect their source with (1) heavy minerals most abundant near the beach on flats to the north where they were eroded out of terrace deposits, and (2) relatively greater heavy mineral concentrations (supplied by the Naselle River) across the entire flat to the south. The composition of the heavy mineral suite is mainly clinopyroxene, orthopyroxene, hornblende, epidote, and opaque minerals. This mineral suite represents several sources including rivers, ocean and ocean beaches, and reworked local Tertiary and Quaternary deposits. Tidal flat sediments are approximately 90% light minerals, mostly quartz. The light fraction also contains small quantities of lithic fragments, pumice, vegetation, and biogenic shell fragments. Tertiary and Quaternary terrace deposits are the major source of most of the light material. Fossils make up less than one percent of the bottom sediment. Two foram assemblages are present: (1) a modern shallow-water assemblage characterized by Trochammina inflata, found mainly in muddy flats near rivers, and (2) a relic deep-water assemblage (Eocene to Cretaceous) characterized by such species as Bathysiphon and Cyclammina found predominantly on the sandy flats. Macrofossils consists of shells of the modern tidal flat mollusc assemblage. Organic sediments were mostly carbon (1%). The highest concentrations of organic carbon are associated with muddy sediments near the Palix River and Pickernell Creek; overall, organic carbon concentration increased up-estuary. C/N ratios are transitional between open marine environments and marsh deposits of estuaries.

Washington↗

USGS2009

Quaternary science reviews Pacific Basin tsunami hazards associated with mass flows in the Aleutian arc of Alaska

We analyze mass-flow tsunami generation for selected areas within the Aleutian arc of Alaska using results from numerical simulation of hypothetical but plausible mass-flow sources such as submarine landslides and volcanic debris avalanches. The Aleutian arc consists of a chain of volcanic mountains, volcanic islands, and submarine canyons, surrounded by a low-relief continental shelf above about 1000–2000 m water depth. Parts of the arc are fragmented into a series of fault-bounded blocks, tens to hundreds of kilometers in length, and separated from one another by distinctive fault-controlled canyons that are roughly normal to the arc axis. The canyons are natural regions for the accumulation and conveyance of sediment derived from glacial and volcanic processes. The volcanic islands in the region include a number of historically active volcanoes and some possess geological evidence for large-scale sector collapse into the sea. Large scale mass-flow deposits have not been mapped on the seafloor south of the Aleutian Islands, in part because most of the area has never been examined at the resolution required to identify such features, and in part because of the complex nature of erosional and depositional processes. Extensive submarine landslide deposits and debris flows are known on the north side of the arc and are common in similar settings elsewhere and thus they likely exist on the trench slope south of the Aleutian Islands. Because the Aleutian arc is surrounded by deep, open ocean, mass flows of unconsolidated debris that originate either as submarine landslides or as volcanic debris avalanches entering the sea may be potential tsunami sources. To test this hypothesis we present a series of numerical simulations of submarine mass-flow initiated tsunamis from eight different source areas. We consider four submarine mass flows originating in submarine canyons and four flows that evolve from submarine landslides on the trench slope. The flows have lengths that range from 40 to 80 km, maximum thicknesses of 400–800 m, and maximum widths of 10–40 km. We also evaluate tsunami generation by volcanic debris avalanches associated with flank collapse, at four locations (Makushin, Cleveland, Seguam and Yunaska SW volcanoes), which represent large to moderate sized events in this region. We calculate tsunami sources using the numerical model TOPICS and simulate wave propagation across the Pacific using a spherical Boussinesq model, which is a modified version of the public domain code FUNWAVE. Our numerical simulations indicate that geologically plausible mass flows originating in the North Pacific near the Aleutian Islands can indeed generate large local tsunamis as well as large transoceanic tsunamis. These waves may be several meters in elevation at distal locations, such as Japan, Hawaii, and along the North and South American coastlines where they would constitute significant hazards.

Alaska↗

USGS2002

Preliminary geologic map of the Santa Barbara coastal plain area, Santa Barbara County, California

This report presents a new geologic digital map of the Santa Barbara coastal plain area at a compilation scale of 1:24,000 (one inch on the map = 2,000 feet on the ground) and with a horizontal positional accuracy of at least 20 m. This preliminary map depicts the distribution of bedrock units and surficial deposits and associated deformation underlying and adjacent to the coastal plain within the contiguous Santa Barbara and Goleta 7.5' quadrangles. A planned second version will extend the mapping westward into the adjoining Dos Pueblos Canyon quadrangle and eastward into the Carpinteria quadrangle. The mapping presented here results from the collaborative efforts of geologists with the U.S. Geological Survey Southern California Areal Mapping Project (SCAMP) (Minor, Kellogg, Stanley, Stone, and Powell) and the tectonic geomorphology research group at the University of California at Santa Barbara (Gurrola and Selting). C.L. Powell, II, performed all new fossil identifications and interpretations reported herein. T.R. Brandt designed and edited the GIS database,performed GIS database integration and created the digital cartography for the map layout. The Santa Barbara coastal plain is located in the western Transverse Ranges physiographic province along a west-trending segment of the southern California coastline about 100 km (62 mi) northwest of Los Angeles. The coastal plain region, which extends from the Santa Ynez Mountains on the north to the Santa Barbara Channel on the south, is underlain by numerous active and potentially active folds and partly buried thrust faults of the Santa Barbara fold and fault belt. Strong earthquakes that occurred in the region in 1925 (6.8 magnitude) and 1978 (5.1 magnitude) are evidence that such structures pose a significant earthquake hazard to the approximately 200,000 people living within the major coastal population centers of Santa Barbara and Goleta. Also, young landslide deposits along the steep lower flank of the Santa Ynez Mountains indicate the potential for continued slope failures and mass movements that may threaten urbanized parts of the coastal plain. Deformed sedimentary rocks in the subsurface of the coastal plain and the adjacent Santa Barbara Channel contain deposits of oil and gas, some of which are currently being extracted. Shallow, localized sedimentary aquifers underlying the coastal plain provide limited amounts of water for the urban areas, but the quality of some of this groundwater is compromised by coastal salt-water contamination. The present map compilation provides a set of uniform geologic digital coverages that can be used for analysis and prediction of these and other geologic hazards and resources in the coastal plain region. In the map area the oldest stratigraphic units consist of resistant Eocene to Oligocene marine and terrestrial sedimentary rocks that form a mostly southward-dipping and laterally continuous sequence along the south flank of the Santa Ynez Mountains. Less resistant, but more variably deformed, Miocene, Pliocene, and Pleistocene marine sedimentary rocks and deposits are exposed in the lower Santa Ynez foothills and in the coastal hills and sea cliffs farther south. Pleistocene and Holocene surficial alluvial, colluvial, estuarine, and marine-terrace deposits directly underlie much of the low-lying coastal plain area, and similar-aged alluvial and landslide deposits locally mantle the lower flanks of the Santa Ynez Mountains. Structurally, the Santa Barbara coastal plain area is dominated by the Santa Barbara fold and fault belt, an east-west-trending zone of Quaternary, partly active folds and blind and exposed reverse and thrust faults. The dominant trend of individual structures within the belt is west-northwest -- slightly oblique to the overall trend of the fold and fault belt. A conspicuous exception, however, is the More Ranch fault system, which strikes east-northeast across the fold and f

Open-File Report↗

USGS1983

Reconnaissance geologic map of the Harrat Tuffil Quadrangle, sheet 20/39 B, Kingdom of Saudi Arabia

The Harrat Tuffil quadrangle, sheet 20/39 B, is located between lat 20°30’ and 21°00’ N. and long 39°30’ and 40°00’ E. about 50 km southeast of Jiddah. A western belt of Proterozoic metapelites and related rocks, defined as the Sa’diyah formation, structurally underlies and locally is interlayered with Proterozoic metabasaltic rocks of oceanic chemical affinity to the east. The Sa’diyah formation and the metabasaltic rocks are tentatively correlated with the Sabya formation and Baish group. These rocks may represent a miogeosynclinal tectonic setting in the 800 to 850 Ma period of development of the southwestern Arabian Shield. The presence of aluminous metasediments suggest a continental source area, probably west of oceanic and (or) immature island-arc rocks of the Baish(?) igneous suite. The Sa’diyah formation and metabasaltic rocks are intruded by a granite gneiss batholith, probably about 600 Ma old, and by small plutons of granodiorite and syenogranite. Peraluminous monzogranite occurs within the western part of the Sa’diyah formation belt and may provide an alternate source for the aluminous politic rocks. Tentative correlation of an isolated exposure of Jurassic(?) dolomite with the Hanifa Formation significantly extends the areal range of possible Jurassic sedimentary rocks in the Tihamat province. An intense dike swarm intrudes all of the pre-Miocene rocks in the quadrangle. This Damm dike complex is named for Wadi ad Damm. Dike chemistry shows both subalkaline and alkaline bimodal suites. The Sita formation is broadly coeval with the Damm Dike complex and contains volcanic rocks with similar bimodal chemistry. The Sita formation conformably overlies and is locally interbedded with the Sumaysi formation, which is palynologically dated in the Makkah quadrangle as Eocene (~50 Ma). Potassium-argon dating indicated intrusion and volcanism over the period ~50Ma to ~20 Ma ago. The Tertiary volcanic, hypabyssal, and plutonic rocks are all light rare-earth element enriched as would be expected in a rift-related tectonic setting. These rocks represent proto-Red Sea igneous activity and are correlated with the Jizan group. Shama rhyolite near Harrat Tuffil is unconformably overlain by a boulder conglomerate correlated with the Bathan formation. Miocene alkali basalt forms a large paleovalley-fill lava flow at Harrat ad Damm and small flow remnants north of Jabal Sita. Erosional downcutting at Harrat ad Damm averaged ~10 m per MA over the past 11 Ma. Pliocene alkali basalt unconformably overlies Bathan formation and Shama rhyolite at Harrat Tuffil. The uplift of Quaternary reef limestone along the Red Sea coast indicates recent faulting as shown in the adjoining Shu’ayba and Al Ghalah quadrangles. A perlite deposit at Jabal Shama may be suitable as light aggregate for concrete. Sparse barite veins were discovered in the lower Shumaysi formation. Relatively small deposits of Sa’diyah formation marble may be of interest for local use in building or cement. The Jurassic dolomite is locally quite pure and may have economic applications.

Open-File Report↗

USGS1993

A response to "Milankovitch theory viewed from Devils Hole" by J. Imbrie, A.C. Mix and D.G. Martinson

The detailed and well-dated 500,000-yr record of oxygen-18 variations found in vein calcite core DH-11 taken from Devils Hole in Nevada provides several challenges to the Milankovitch theory for the occurrence of Quaternary glaciations. A recent discussion paper (Imbrie and others, 1993) has dismissed the relevance of this well-dated core for determining the timing of global climatic fluctuations and, moreover, asserts that the Devils Hole record provides support for the Milankovitch theory. Upon analysis of the arguments found in this discussion, the authors found nothing to dissuade them from the original conclusion that the Devils Hole chronology does present a serious challenge to the Milankovitch theory.

Open-File Report↗

USGS1996

Sediment magnetic and geochemical data from Quaternary lacustine sediment in two cores from Tule Lake, Siskiyou County, California

Open-File Report↗