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At least 1,099 records · Page 61Linked to original sources
USGS2008

Geologic and Geophysical Framework of the Santa Rosa 7.5' Quadrangle, Sonoma County, California

The geologic and geophysical maps of Santa Rosa 7.5? quadrangle and accompanying structure sections portray the sedimentary and volcanic stratigraphy and crustal structure of the Santa Rosa 7.5? quadrangle and provide a context for interpreting the evolution of volcanism and active faulting in this region. The quadrangle is located in the California Coast Ranges north of San Francisco Bay and is traversed by the active Rodgers Creek, Healdsburg and Maacama Fault Zones. The geologic and geophysical data presented in this report, are substantial improvements over previous geologic and geophysical maps of the Santa Rosa area, allowing us to address important geologic issues. First, the geologic mapping is integrated with gravity and magnetic data, allowing us to depict the thicknesses of Cenozoic deposits, the depth and configuration of the Mesozoic basement surface, and the geometry of fault structures beneath this region to depths of several kilometers. This information has important implications for constraining the geometries of major active faults and for understanding and predicting the distribution and intensity of damage from ground shaking during earthquakes. Secondly, the geologic map and the accompanying description of the area describe in detail the distribution, geometry and complexity of faulting associated with the Rodgers Creek, Healdsburg and Bennett Valley Fault Zones and associated faults in the Santa Rosa quadrangle. The timing of fault movements is constrained by new 40Ar/39Ar ages and tephrochronologic correlations. These new data provide a better understanding of the stratigraphy of the extensive sedimentary and volcanic cover in the area and, in particular, clarify the formational affinities of Pliocene and Pleistocene nonmarine sedimentary units in the map area. Thirdly, the geophysics, particularly gravity data, indicate the locations of thick sections of sedimentary and volcanic fill within ground water basins of the Santa Rosa plain and Rincon, Bennett, and northwestern Sonoma Valleys, providing geohydrologists a more realistic framework for groundwater flow models.

Open-File Report↗
USGS2012

Paleontology and geochronology of the Long Beach core sites and monitoring wells, Long Beach, California

The U.S. Geological Survey's Focus on Quaternary Stratigraphy in Los Angeles (FOQUS-LA) project was a cooperative coring program between Federal, State, and local agencies. It was designed to provide a better understanding of earthquake potentials and to develop a stratigraphic model of the western Los Angeles Basin in California. The biostratigraphic, geochronologic, and paleoecologic analyses of eight wells drilled during the FOQUS-LA project are presented. These analyses are based on microfossils (benthic and planktic foraminifers), macrofossils, paleomagnetic stratigraphy, optically stimulated luminescence, thermoluminescence, radiocarbon dating, and tephrochronology. A geochronologic framework (incorporating paleomagnetism, luminescence, and tephrochronology) was used to calibrate the sequence stratigraphic units in the FOQUS-LA wells and also was used to calibrate the ages of the microfossil stage and zonal boundaries. The results of this study show that (1) the offshore California margin zones can be used in a nearshore setting, and (2) the California margin zonal scheme refines the chronostratigraphic resolution of the benthic foraminiferal biostratigraphic framework for the Pacific Coast. Benthic foraminiferal stages are modified by the recognition of an early Hallian substage, which is a faunal change recognized throughout the Los Angeles Basin. Although no detailed macrofossil zonations exist for the Quaternary of southern California, several species, whose distribution is regulated by the climatic conditions, are useful as secondary marker species in the shallower water deposits of the Los Angeles Basin.

California↗
USGS2011

Geophysical, stratigraphic, and flow-zone logs of selected wells in Cayuga County, New York, 2001–2011

Geophysical logs were collected and analyzed along with bedrock core samples and bedrock outcrops to define the bedrock stratigraphy and flow zones penetrated by 93 monitor and water-supply wells in Cayuga County, New York. The work was completed from 2001 through 2011 as part of an investigation of volatile-organic compound contamination in the carbonate-bedrock aquifer system between Auburn and Union Springs. The borehole logs included gamma, caliper, wellbore image, fluid property, and flow logs. The log information was used with bedrock core samples to define the regional stratigraphy, evaluate flow zones within the bedrock aquifers, and develop and implement a multilevel monitoring design for groundwater levels and water quality within the study area.

New York↗
USGS2012

Evidence for mid-Holocene shift in depositional style in Mobile Bay, Alabama

The Holocene stratigraphy of Mobile Bay, Alabama, was mapped using a combination of high-resolution seismic data and sediment cores to refine changes in the bay's evolution during this time. The base of the Holocene-era stratigraphy is an erosional surface formed during the last glacial maximum. Overlying Holocene deposits are primarily estuarine mud that has a finely laminated weak acoustic signature. One exception is a thin unit, R1, with varying reflection amplitude that can be traced throughout the southern part of the bay. The continuity of the unit throughout the southern part of the bay suggests a baywide change in sedimentation that was perhaps driven by rapid retreat of the bay-head delta in response to a sudden rise in sea level or an abrupt change in accommodation space due to basin geometry. Along the southern edge of the bay, the R1 unit increases in thickness and reflector amplitude towards Morgan Peninsula. The peninsula itself underwent a period of erosion and narrowing between 4,300 to 3,000 years before present, and the variation in reflector amplitude and the geometry of this part of the R1 unit appear to reflect a period of increased overwashing of the peninsula during this period. Average estuarine sedimentation rates decreased after the formation of the R1 unit, and the decrease coincides with a decline in the rate of sea-level rise. A similar change in depositional style at approximately the same time in neighboring Apalachicola Bay suggests a change that affected the northeastern Gulf of Mexico region and not just Mobile Bay.

Alabama↗
USGS2014

Surface wave site characterization at 27 locations near Boston, Massachusetts, including 2 strong-motion stations

The geotechnical properties of the soils in and around Boston, Massachusetts, have been extensively studied. This is partly due to the importance of the Boston Blue Clay and the extent of landfill in the Boston area. Although New England is not a region that is typically associated with seismic hazards, there have been several historical earthquakes that have caused significant ground shaking (for example, see Street and Lacroix, 1979; Ebel, 1996; Ebel, 2006). The possibility of strong ground shaking, along with heightened vulnerability from unreinforced masonry buildings, motivates further investigation of seismic hazards throughout New England. Important studies that are pertinent to seismic hazards in New England include source-parameter studies (Somerville and others, 1987; Boore and others, 2010), wave-propagation studies (Frankel, 1991; Viegas and others, 2010), empirical ground-motion prediction equations (GMPE) for computing ground-motion intensity (Tavakoli and Pezeshk, 2005; Atkinson and Boore, 2006), site-response studies (Hayles and others, 2001; Ebel and Kim, 2006), and liquefaction studies (Brankman and Baise, 2008). The shear-wave velocity (VS) profiles collected for this report are pertinent to the GMPE, site response, and liquefaction aspects of seismic hazards in the greater Boston area. Besides the application of these data for the Boston region, the data may be applicable throughout New England, through correlations with geologic units (similar to Ebel and Kim, 2006) or correlations with topographic slope (Wald and Allen, 2007), because few VS measurements are available in stable tectonic regions. Ebel and Hart (2001) used felt earthquake reports to infer amplification patterns throughout the greater Boston region and noted spatial correspondence with the dominant period and amplification factors obtained from ambient noise (horizontal-to-vertical ratios) by Kummer (1998). Britton (2003) compiled geotechnical borings in the area and produced a microzonation map based on generalized velocity profiles, where the amplifications were computed using Shake (Schnable and others, 1972), along with an assumed input ground motion. The velocities were constrained by only a few local measurements associated with the Central Artery/Tunnel project. The additional VS measurements presented in this report provide a number of benefits. First, these measurements provide improved spatial coverage. Second, the larger sample size provides better constraints on the mean and variance of the VS distribution for each layer, which may be paired with a three-dimensional (3D) model of the stratigraphy to generate one-dimensional (1D) profiles for use in a standard site-response analysis (for example, Britton, 2003). Third, the velocity profiles may also be used, along with a 3D model of the stratigraphy, as input into a 3D simulation of the ground motion to investigate the effects of basin-generated surface waves and the potential focusing of seismic waves. This report begins with a short review of the geology of the study area and the field methods that we used to estimate the velocity profiles. The raw data, processed data, and the interpreted VS profiles are given in appendix 1. Photographs and descriptions of the sites are provided in appendix 2.

Massachusetts↗
USGS2016

Geologic and geochemical results from boreholes drilled in Yellowstone National Park, Wyoming, 2007 and 2008

Between 2007 and 2008, seven Earthscope Plate Boundary Observatory (PBO) boreholes ranging in depth from about 200 to 800 feet deep were drilled in and adjacent to the Yellowstone caldera in Yellowstone National Park, for the purpose of installing volcano monitoring instrumentation. Five of the seven boreholes were equipped with strainmeters, downhole seismometers, and tiltmeters. Data collected during drilling included field observations of drill cuttings, stratigraphy within the boreholes, water temperature, and water and drill cuttings samples from selected depths. Six of the seven boreholes encountered rhyolite lavas and tuffs. The rhyolite lavas compose the Canyon flow, the Gardner River flow, the Gibbon River flow, the Hayden Valley flow, the Nez Perce Creek flow, and the West Thumb flow. Boreholes also penetrated a vertical sequence through the Lava Creek Tuff and the Tuff of Bluff Point. In addition, one borehole drilled through a Swan Lake Flat Basalt sequence and terminated in a rhyolite lava flow. After drilling the seven PBO boreholes, cuttings were examined and selected for preparation of grain mounts, thin sections, and geochemical analysis. Major ions and trace elements (including rare earth elements) of selected cuttings were determined by x-ray fluorescence (XRF) and inductively coupled plasma-mass spectrometry (ICP-MS); the ICP-MS provided more precise trace-element analysis than XRF. A preliminary interpretation of the results of geochemical analyses generally shows a correlation between borehole cuttings and previously mapped geology. The geochemical data and borehole stratigraphy presented in this report provide a foundation for future petrologic, geochemical, and geophysical studies.

Wyoming↗
USGS2017

Lithofacies and sequence stratigraphic description of the upper part of the Avon Park Formation and the Arcadia Formation in U.S. Geological Survey G–2984 test corehole, Broward County, Florida

Rock core and sediment from U.S. Geological Survey test corehole G–2984 completed in 2011 in Broward County, Florida, provide an opportunity to improve the understanding of the lithostratigraphic, sequence stratigraphic, and hydrogeologic framework of the intermediate confining unit and Floridan aquifer system in southeastern Florida. A multidisciplinary approach including characterization of sequence stratigraphy, lithofacies, ichnology, foraminiferal paleontology, depositional environments, porosity, and permeability was used to describe the geologic samples from this test corehole. This information has produced a detailed characterization of the lithofacies and sequence stratigraphy of the upper part of the middle Eocene Avon Park Formation and Oligocene to middle Miocene Arcadia Formation. This enhancement of the knowledge of the sequence stratigraphic framework is especially important, because subaerial karst unconformities at the upper boundary of depositional cycles at various hierarchical scales are commonly associated with secondary porosity and enhanced permeability in the Floridan aquifer system.

Florida↗
USGS2026

Preliminary bedrock geologic map of the Port Henry quadrangle, Essex County, New York, and Addison County, Vermont

Introduction The bedrock geology of the 7.5-minute Port Henry quadrangle consists of deformed and metamorphosed Mesoproterozoic gneisses of the Adirondack Highlands unconformably overlain by weakly deformed lower Paleozoic sedimentary rocks of the Champlain Valley. The Mesoproterozoic rocks occur on the eastern edge of the Adirondack Highlands and represent an extension of the Grenville Province of Laurentia. Mesoproterozoic paragneiss, marble, and amphibolite hosted the emplacement of an anorthosite-mangerite-charnockite-granite (AMCG) suite, now exposed mostly as orthogneiss, at approximately 1.18–1.15 Ga (giga-annum). In the Port Henry quadrangle, the AMCG metaigneous rocks (Yhg, Ygb, Yanw) intruded older, mostly metasedimentary rocks of the Grenville Complex during the middle to late Shawinigan orogeny (~1,160–1,150 Ma [mega-annum]). All rocks were subsequently metamorphosed to upper amphibolite to granulite facies conditions during the 1,080–1,050 Ma Ottawan orogeny. New mapping reveals four periods of deformation: (1) D1 produced rarely preserved isoclinal folds in the paragneiss and marble and predates AMCG magmatism. (2) Subsequent D2 deformation produced the dominant gneissic fabric preserved in the rock, recumbent folding, and deformed all the Proterozoic units in the map area. Syn- to late-D2 felsic magmatism resulted in the regionally extensive Lyon Mountain Granite Gneiss, which hosts numerous magnetite ore bodies. (3) Mylonitic extensional shear zones and core complex formation marked the beginning of D3 deformation. Protracted D3 deformation resulted in F3 upright folding, dome and basin formation, pegmatite intrusion, reactivation of the S2 foliation, partial melting, metamorphism, metasomatism, iron-ore remobilization, and intrusion of magnetite-bearing pegmatite both as layer-parallel sills and crosscutting dikes. (4) D4 created northeast- and northwest-trending local high-grade ductile shear zones and boudinage, northwest-trending regional kilometer (km)-wide ductile shear zones, and crosscutting granitic pegmatite dikes. The development of the late-stage regional shear zones (D4) was likely due to the continuation of extensional doming and uplift from upper amphibolite facies conditions at the end of the Ottawan orogeny. The majority of iron-ore deposits in the Port Henry and adjacent Witherbee quadrangles are in the hanging wall of these extensional shear zones. In the Port Henry quadrangle, the km-wide Cheney Mountain shear zone is the result of D4 deformation. Kilometer-scale lineaments readily observed in lidar data are Ediacaran mafic dikes and Phanerozoic brittle faults. The Paleozoic rocks are part of the Early Cambrian to Late Ordovician carbonate bank on the ancient margin of Laurentia. The approximately 1-km-thick Cambrian to Ordovician stratigraphy records a transition from synrift clastics to passive-margin peritidal carbonate buildups to gradually deeper-water subtidal- to shelf-carbonates during foreland basin development associated with the Taconic orogeny. The Paleozoic rocks are weakly folded and block faulted. Large areas of the Champlain Valley are covered by undifferentiated glacial deposits, some of which contain mapped landslides. The map also shows waste rock piles and tailings from historical mining operations. This study was undertaken to improve our understanding of the bedrock geology in the Adirondack Highlands, establish a modern framework for 1:24,000-scale bedrock geologic mapping in the Adirondacks, provide a context for historical iron mines in the eastern Adirondacks, and update the stratigraphy of the Champlain Valley in New York and Vermont. This Open-File Report includes a bedrock geologic map; a description of map units; a correlation of map units; and a geographic information system database that includes bedrock geologic units, faults, outcrops, and structural geologic information.

New York, Vermont↗
USGS1962

Astrogeologic studies, semiannual progress report, February 26, 1961 to August 24, 1961

This report is the second semiannual report on a geological program of research conducted by the Geological Survey on behalf of the National Aeronautics and Space Administration. This research is being carried out under the Branch of Astrogeology. The long-range objectives of this program are to determine and map the stratigraphy and structure of the Moon's crust, to develop basic information on processes that have led to the present condition of the Moon's surface, and to work out the sequence of events in the geologic history recorded in the Moon's stratigraphy and structure. The work includes three closely interrelated areas of study: (1) investigation of the chemistry, petrography, and physical properties of extraterrestrial materials that may have been derived from the Moon, such as tektites, certain types of meteorites, and extraterrestrial dust; (2) experimental and field investigations of the mechanics and phenomena of impact of high-speed objects and of cratering; and (3) geologic mapping of the Moon. Immediate objectives for the fiscal year 1961 have included the preparation of geologic maps for the nominal target area for the Ranger Project of the National Aeronautics and Space Administration. Field and laboratory work on craters was directed toward developing data and an adequate theory for the integrated effect of meteoroid bombardment of the lunar surface. Special attention has been given to phase changes and solid state changes produced in rock by meteorite impact. American and Philippine tektites were the principal materials of possible lunar origin to receive detailed petrographic and chemical analysis.

Open-File Report↗
USGS1965

Plant and miscellaneous microfossils of the Pierre Shale

This preliminary report summarizes part of a Survey program to study, in detail, the stratigraphy and paleontology of a nearly complete sequence of Pierre Shale near Redbird, Wyoming. The physical stratigraphy and correlations are being analyzed by James Gill and W. A. Cobban. Various groups of invertebrate fossils are under study by Mr. Cobban, N. F. Sohl, and James Mello. Plant microfossils are the responsibility of Estella Leopold, assisted by Bernadine Tschudy.

Open-File Report↗
USGS1978

The marine geology of the eastern Santa Barbara Channel, with particular emphasis on the ground water basins offshore from the Oxnard Plain, Southern California

Marine geophysical investigations provide new data concerning the stratigraphy, tectonic and sedimentary history, and the ground water geology of the southeastern Santa Barbara Channel region. The offshore stratigraphy identified in seismic reflection profiles includes a succession of Neogene to Quaternary strata. The middle Miocene Conejo volcanics form an acoustical basement and the overlying late Cenozoic sedimentary rocks attain a thickness greater than 2,500 m. These sedimentary deposits fill a structurally controlled, physiographic and depositional depression called the Ventura Basin. Structure consists generally of a gently folded, east-trending Tertiary synclinorium bordered on the north by a regional thrust fault and on the south by a steep asymmetrical anticlinal ridge. Most structures show evidence of north-south compression that occurred during early Pleistocene time. Three well-defined unconformities represent widespread erosion in late Miocene, early to middle Pleistocene, and late Pleistocene time. The boundaries of Miocene, Pliocene, and lower Pleistocene strata continue uninterrupted eastward along the southern part of Santa Barbara basin to Hueneme Canyon, where they turn northeast and can be traced to the coast near Port Hueneme. These limits probably represent the south edge of the Santa Barbara basin during Pliocene and Pleistocene time. Fresh water-bearing materials of the Oxnard plain are unconsolidated Quaternary sediment laid down on more consolidated Tertiary rocks. Offshore, the total fresh water-bearing materials distinguished in the seismic reflection profiles attain a thickness of about 356 m and have an areal extent of over 760 km2. Strata that contain the offshore continuation of the five major on-land aquifers (Grimes Canyon, Fox Canyon, Hueneme, Mugu, and Oxnard aquifers) are identified in the seismic reflection profiles. These strata make up the two offshore ground-water basins, the Mound and Oxnard plain ground-water basins, which are separated by the east-west trending Oak Ridge fault. Possible entrance areas for salt water intrusion into fresh water aquifers are found along the walls of the submarine canyons and along the northern slopes of Santa Barbara and Santa Monica basins. Hueneme and Mugu aquifers are probably exposed locally in all five submarine canyons of the Oxnard offshore area and may also crop out along the upper northern slope of Santa Monica basin. In all of these areas, salt water readily intrudes the aquifers. A salinity-temperature-depth study made in April, 1971, does not indicate any great dilution of surface ocean water by fresh water that could be 'leaking' from the exposed aquifers along the walls of Hueneme Canyon and the landward slope of Santa Barbara Channel. Earthquakes in the vicinity of the Oxnard plain suggest that the region is seismically active. Epicenters are widely dispersed over the region. No distinct trend or alignment of earthquake epicenters occurs near the trace of any of the faults, although many epicenters are scattered around the Oak Ridge zone of deformation in the northern part of the region. The largest magnitude earthquake recorded in the area was a magnitude 5.7 that occurred on February 21, 1973, offshore of Point Mugu, south of the Oxnard plain.

California↗
USGS1979

The subsurface geology of the Florida-Hatteras shelf, slope, and inner Blake Plateau

The structure and stratigraphy of the Florida-Hatteras Slope and inner Blake Plateau was studied by means of 4,780 km of single-channel air gun seismic reflection profiles. Control for the seismic stratigraphy is provided by correlating reflecting units and paleontologically dated stratigraphic units identified in offshore wells and dredge hauls. Many Tertiary unconformities exist, and major regional unconformities at the end of the Oligocene and in the late Paleocene are mapped. Reflecting surfaces believed to represent the tops of the Cretaceous, Paleocene, and Oligocene extend throughout the region. Upper Cretaceous (pre-Maastrichtian) rocks on the southeastern side of the Carolina Platform form a large seaward-facing progradational wedge. The Upper Cretaceous rocks in the Southeast Georgia Embayment, are seismically transparent and on the inner Blake Plateau are cut by numerous small faults, perhaps due to compaction. Within the survey area relatively flat-lying Maastrichtian and Paleocene strata show no evidence that a feature similar to the present Florida-Hatteras Slope existed at the beginning of the Tertiary. Late Paleocene erosion, related to the initiation of the Gulf Stream flow, probably developed this regional unconformity. Eocene and Oligocene sediments landward of the present Gulf Stream form a thick sequence of seaward-dipping progradational beds. A seaward progradational wedge of Miocene to Holocene age covers a regionally traceable unconformity, which separates the Oligocene from the Miocene sediments. Under and seaward of the present Gulf Stream, the Eocene and younger sediment supply was much smaller and the buildup is comparatively insignificant. The difference in accumulation rates in the Eocene and younger sediments, landward and seaward of the Gulf Stream, is responsible for the Florida-Hatteras Slope. Tertiary isopach maps suggest that there is a well developed triangular depocenter under the shelf. The edges of the depocenter correspond with magnetic anomalies and it is suggested that the depocenter is related to differential subsidence during the Tertiary across older crustal structures. The Eocene and Oligocene units contain the aquifer onshore, and the aquifer probably remains in these units offshore. With this assumption the potential aquifer has been identified and traced under the shelf and slope.

Florida-Hatteras shelf, slope, and inner Blake Pla↗
USGS1980

Seismic hazard study of the western portion of the Garlock fault [California]

Investigations of the western segment of the Garlock fault were conducted at Castac Lake, Twin Lakes and Oak Creek Canyon. Studies were concentrated on the youngest fault trace as delineated by Clark (1973). Seismic refraction surveys, topographic surveys and geologic mapping provided positive evidence for fault offsets in Quaternary deposits at Twin Lakes and Oak Creek Canyon. Investigations at Castac Lake were concentrated on the fault segment north of the lake. Previous investigations south of the lake and across the dry lake bottom exposed unbroken strata dating back 8050 +300 years B.P. No evidence of offset of young deposits was found north of the lake from surface investigations or seismic refraction data. Trenching of sag pond deposits at Twin Lakes revealed fault traces representing 2 events confined to a zone 3 meters wide. The stratigraphy at Twin Lakes consists of alternating units of clay and sand allowing measurements of vertical offsets. Based on radiocarbon dates of detrital charcoal, the most recent movement occurred less than 890 +195 years B.P. and the proceeding event occurred greater than 2,800 +165 years B.P. Total vertical offset was 80 to 100 cm for the most recent movement and 55-60 cm for the proceeding event. Geomorphic analysis of offset alluvial stream channels at Oak Creek Canyon provided an estimate of 1.6 to 3.3 mm per year of left lateral movement during Holocene and late Pleistocene times. This estimate is based on correlation of soil profile development with dated soil stratigraphy in the San Joaquin Valley. Scarp heights and lack of definitive evidence for recent left-lateral offset in Oak Creek Canyon indicates a significant and perhaps predominant vertical component of movement with: 1) a comparatively long recurrence interval and/or 2) a small component of left-lateral movement. Arching of late Pleistocene deposits in Oak Creek Canyon is consistent with right-lateral rather than left-lateral wrench faulting, suggesting a fluctuation in stresses along this part of the fault since late Pleistocene time.

Open-File Report↗
USGS1980

The microzonation of the Memphis, Tennessee area

Although the probability of a major earthquake in the central U.S. is only one-tenth of the Californian events, any such event is expected to result in damage ten times greater than that anticipated in California. The city of Memphis, which is situated very close to the inferred epicenter of one of the three major 1811-1812 earthquakes, is in a potentially hazardous zone which will be susceptible to the usual seismic hazards. By recognizing the high level of seismicity in the New Madrid area, this study attempts to microzone the potential hazards in the city of Memphis. This study examines the pertinent criteria necessary for any microzonation study. The subjects considered include: (i) The seismicity of the central United States, (ii) Design earthquakes, (iii) Response analysis which allows us to construct the necessary microzonation maps. The seismicity of the region is evaluated according to the state-of-the-art literature available as there is no recorded strong motion data available for the central U.S. The maximum credible earthquakes which are likely to affect Memphis are evaluated as the one in a thousand year occurrence. However, earthquakes of a lower intensity (and lower recurrence rates) are selected as design earthquakes to permit a more realistic microzonation to be performed. For the response analysis, these earthquakes are simulated using synthetically generated accelerograms which exhibit the relevant parameters. These accelerograms displaying the significant characteristics of amplitude, predominant frequency and duration were selected to display, as accurately as possible, the anticipated nature of the horizontal bedrock-motions at Memphis. The horizontal motions (SH-waves) were applied at a depth of 45m below ground surface at numerous sites in the city of Memphis, where the soil stratigraphy had been conceptualized from borehole data. The soils data made available by local sources was the only information used for this study as any laboratory testing was outside the scope of this study. The dynamic soil properties were thus established from the available Standard Penetration Resistances and soil classifications. The results of the response analysis were transformed into microzonation maps depicting (i) zones showing qualitative estimates of ground response, (ii) zones showing the natural frequency of the soils, (iii) zones showing the peak spectral acceleration for 2% damping ratio, (iv) zones of liquefaction potential. These maps are essentially useful for preliminary investigation and we do not expect them to be used on a quantitative basis. However, further investigation is necessary in determining the stratigraphy and soil properties to a more accurate level if an earthquake hazard is anticipated.

Tennessee↗
USGS1982

High-resolution seismic-reflection profiles collected aboard R/V James M. Gilliss Cruise GS-7903-3, over the Atlantic Continental Slope and Rise off New England

During June 1979, the U.S. Geological Survey (USGS) collected 4,032 km of single-channel seismic-reflection data from the Atlantic Continental Slope and Rise off New England. The work was conducted aboard R/V JAMES M. GILLISS (cruise GS-7903-3). The purpose of the cruise was to determine the characteristics of mass sediment movement on the Continental Slope, and to study and correlate the stratigraphy of the Jurassic and Cretaceous strata lying north and south of the New England seamount chain. Seismic instrumentation included 40-in 3 , 160-in 3 , and 500-in 3 airguns; a Teledyne 800-joule minisparker system; a 3-5-kHz to 7-kHz, hull-mounted tunable transducer; and a 7-channel analog tape recorder. Navigation control during the cruise was provided by a Western Integrated Navigation System capable of integrating satellite, rho-rho Loran-C, hyperbolic Loran-C, gyro compass, and doppler speed-log position data. The prime navigation sensor was the rho-rho Loran-C automatically recorded at 20-second intervals and manually plotted every 15 minutes, backed up by hyperbolic Loran-C fixes automatically recorded every 5 minutes. Of the 4,032 km of data collected, 3,257 km of 3-5-kHz, minisparker and 40-in 3 airgun were for the sediment-slump studand the other 775 km of 3-5-kHz, minis parker, 160-in 3 air gun and 500-in 3 airgun were for the deep stratigraphy study. Overall, the quality of the data is excellent with good resolution and penetration. The original data may be examined at the U.S. Geological Survey, Woods Hole, MA 02543. Copies of the data can be purchased only from the National Geophysical and Solar-Terrestrial Data Center, NOAA/EDIS/NGSDC, Code D621, 325 Broadway, Boulder, CO 80303 (303-497-6338).

Open-File Report↗
USGS1988

Geologic map of the northwestern Caliente Range, San Luis Obispo County, California

The map area lies in the southern Coast Ranges of California, north of the Transverse Ranges and west of the southern San Joaquin Valley. This region is part of the Salinia-Tujunga composite terrane that is bounded on the northeast by the San Andreas fault (fig. 1) and on the southwest by the Nacimiento fault zone (Vedder and others, 1983). The Chimineas fault of this map is inferred to be the boundary between the Salinia and the Tujunga terranes (Ross, 1972; Vedder and others, 1983). Geologic mapping in the region of the California Coast Ranges that includes the area of this map has been largely the work of T.W. Dibblee, Jr. Compilations of geologic mapping at a scale of 1:125,000 (Dibblee, 1962, 1973a) provide the regional setting for this map, the northeast border of which lies about 6 to 7 km southwest of the San Andreas fault. Ross (1972) mapped the crystalline basement rocks in the vicinity of Barrett Creek, along the northeast side of the Chimineas fault ("Barrett Ridge" of Ross, 1972). Recent 1:24,000-scale mapping in the La Panza Range (fig. 1) (Vedder and others 1986a,b) overlaps onto the southwest edge of this map and provides useful information about the older rocks, mostly southwest of San Juan Creek. Stratigraphic knowledge of the area, which lies in the northern part of the middle Tertiary Cuyama basin, has evolved over a period of years beginning with the molluscan biostratigraphic work of Anderson and Martin (1914) and Loel and Corey (1932). Hill and others (1958) described the Tertiary stratigraphy of the region and proposed stratigraphic names. This stratigraphy was discussed further by Dibblee (1973b), and his revised nomenclature is used here. Stratigraphic studies in the southeastern Caliente Range (fig. 1) (Repenning and Vedder, 1961; Vedder, 1973) provided valuable information on the interrelations of continental, shallow-marine, and deeper marine facies in the southern part of the Cuyama basin, which have basinwide application. More recent stratigraphic studies by Lagoe (1984, 1985, 1987, 1988) further elaborate on aspects of Miocene basin history and paleogeography. Contributions to the tectonic history of the area have been made by Schwade and others (1958), on the basis of oil exploration in the Cuyama Valley area (fig. 1) in the 1940's and 1950's; by Bartow (1974), as part of a regional stratigraphic study; by Ballance and others (1983), on the basis of a study of Oligocene and early Miocene sedimentation; and most recently by Davis and others (1988) and Yeats and others (1988), who utilized a variety of new data from seismic reflection and from stratigraphic and structural studies. Field work for this map was done mostly in 1969-73 as part of a regional study of the Simmler and Vaqueros Formations (Bartow, 1974). Detailed field mapping was, therefore, concentrated on those units; other parts of the area were mapped by geologic reconnaissance and air-photo interpretation that were supplemented by data from published maps (Dibblee, 1973a; Vedder and others, 1986a,h). Mapping of the crystalline basement rocks at "Barrett Ridge" is from Ross (1972, plate 1). The structural style depicted in the accompanying cross sections favors the thrust belt concepts of Davis and others (1988) over the older interpretations of Dibblee (1962) or Cross (1962).

California↗
USGS1999

Proceedings of Conference on Status of Geologic Research and Mapping, Death Valley National Park

Welcome to this conference on the “Status of Geologic Research and Mapping in Death Valley National Park.” We organized this conference in an effort to foster communication and increase awareness among parties conducting geologic research in and around the park. Additionally, we hope to assess the status of geologic mapping efforts within the park boundaries in an effort to provide a framework for future discussions regarding the impact and merits of the development of a park-wide geologic map. The topics presented at this meeting reflect the breadth of recent and ongoing geologic research in and near Death Valley National Park. Sessions include (1) regional structure, tectonics, and bedrock geology; (2) Neogene basin stratigraphy, geophysics, and hydrology; (3) posters on mapping in the Death Valley region and topical ones on Death Valley National Park; (4) imagery, Quaternary stratigraphy and geomorphology, and Quaternary geochronology; and (5) paleoclimate and active tectonics. On a one-day field trip to Death Valley, we will visit areas of “type locality” status as well as areas of new research.

Open-File Report↗
USGS1992

Revised nomenclature, definitions, and correlations for the Cretaceous formations in USGS-Clubhouse Crossroads #1, Dorchester County, South Carolina

The stratigraphy of the Cretaceous section in a continuously cored stratigraphic test hole, USGS-Clubhouse Crossroads #1, is reviewed and amended herein. Located in southern Dorchester County, S.C., the Clubhouse Crossroads #1 core is one of the principal stratigraphic reference sections in the southern Atlantic Coastal Plain. Traditional and revised systems of stratigraphic nomenclature for the outcropping Cretaceous formations of the Carolinas are reviewed for their applicability in defining subsurface Cretaceous formations at Clubhouse Crossroads. The revised nomenclature, exemplified by the formations proposed by J. P. Owens in 1989 and by N. F. Sohl and Owens in 1991, is preferred for this purpose over the traditional nomenclature established by D.J.P. Swift and S.D. Heron, Jr., in 1969. The revised nomenclature is selected because of its greater emphasis on the historical succession of entire sedimentary systems (timeparallel formations), in contrast to the emphasis placed on the physical continuity of individual facies through time (time-transgressive formations) in the traditional nomenclature. Physical relationships between the two types of formations are discerned by using K.E. Caster's 1934 facies model, in which the time-transgressive units of the traditional model are his magnafacies and the time-parallel units of the revised model are sets of his laterally contiguous parvafacies. In 1977, G.S. Gohn and others and J.E. Hazel and others provisionally delineated Cretaceous formations in the Clubhouse Crossroads #1 core by using Swift and Heron's traditional units. The publication of additional lithologic and paleontologic data since 1977 for Cretaceous units in the core and for Cretaceous units throughout the Carolinas provides a basis for reviewing and amending the original definitions of the Cretaceous formations at Clubhouse Crossroads. Ages assigned to the Cretaceous units at Clubhouse Crossroads by Hazel and others are also reviewed. The boundaries and definitions of the Cape Fear, Middendorf, Black Creek, and Peedee Formations originally used for the core by Gohn and others and Hazel and others are substantially changed herein. In addition, the Black Creek Formation of the core is raised in rank to become the Black Creek Group, which consists of two newly defined formations (Cane Acre and Coachman) and two newly recognized formations previously described in outcrop (Bladen and Donoho Creek). Four subsurface formations that are not known in outcrop are newly defined in the core (Beech Hill, Clubhouse, Shepherd Grove, and Caddin). The revised stratigraphy of the Cretaceous section in the Clubhouse Crossroads #1 core, from base to top, is as follows: Beech Hill Formation (Cenomanian?), Clubhouse Formation (late Cenomanian? and Turonian), Cape Fear Formation (late Turonian? to early Santonian), Middendorf Formation (middle Santonian), Shepherd Grove Formation (late Santonian and early Campanian), Caddin Formation (early Campanian), Cane Acre Formation (middle Campanian, Black Creek Group), Coachman Formation (middle to late Campanian, Black Creek Group), Bladen Formation (late Campanian, Black Creek Group), Donoho Creek Formation (early Maastrichtian, Black Creek Group), and Peedee Formation (late early Maastrichtian to middle or late Maastrichtian).

Professional Paper↗