Search USGS⌕ Search

SEARCH · Search USGS

Results for “Geological Journal”

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

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

At least 631 records · Page 35Linked to original sources
USGS2004

A simple autocorrelation algorithm for determining grain size from digital images of sediment

Autocorrelation between pixels in digital images of sediment can be used to measure average grain size of sediment on the bed, grain-size distribution of bed sediment, and vertical profiles in grain size in a cross-sectional image through a bed. The technique is less sensitive than traditional laboratory analyses to tails of a grain-size distribution, but it offers substantial other advantages: it is 100 times as fast; it is ideal for sampling surficial sediment (the part that interacts with a flow); it can determine vertical profiles in grain size on a scale finer than can be sampled physically; and it can be used in the field to provide almost real-time grain-size analysis. The technique can be applied to digital images obtained using any source with sufficient resolution, including digital cameras, digital video, or underwater digital microscopes (for real-time grain-size mapping of the bed). ?? 2004, SEPM (Society for Sedimentary Geology).

Journal of Sedimentary Research↗
USGS1986

Geologic studies in Alaska by the U.S. Geological Survey during 1985

This circular contains short reports about many of the geologic studies carried out in Alaska by the U.S. Geological Survey and cooperating agencies in 1985. The topics cover a wide range in scientific and economic interest. Separate bibliographic listings of published reports are included. These listings are: (1) data releases and folio components derived from the Alaska Mineral Resource Assessment Program, (2) reports on Alaska released in U.S. Geological Survey publications in 1985, and (3) reports about Alaska by U.S. Geological Survey authors in various scientific journals in 1985.

Alaska↗
USGS2011

Assessment of topographic and drainage network controls on debris-flow travel distance along the west coast of the United States

To better understand controls on debris-flow entrainment and travel distance, we examined topographic and drainage network characteristics of initiation locations in two separate debris-flow prone areas located 700 km apart along the west coast of the U.S. One area was located in northern California, the other in southern Oregon. In both areas, debris flows mobilized from slides during large storms, but, when stratified by number of contributing initiation locations, median debris-flow travel distances in Oregon were 5 to 8 times longer than median distances in California. Debris flows in Oregon readily entrained channel material; entrainment in California was minimal. To elucidate this difference, we registered initiation locations to high-resolution airborne LiDAR, and then examined travel distances with respect to values of slope, upslope contributing area, planform curvature, distance from initiation locations to the drainage network, and number of initiation areas that contributed to flows. Results show distinct differences in the topographic and drainage network characteristics of debris-flow initiation locations between the two study areas. Slope and planform curvature of initiation locations (landslide headscarps), commonly used to predict landslide-prone areas, were not useful for predicting debris-flow travel distances. However, a positive, power-law relation exists between median debris-flow travel distance and the number of contributing debris-flow initiation locations. Moreover, contributing area and the proximity of the initiation locations to the drainage network both influenced travel distances, but proximity to the drainage network was the better predictor of travel distance. In both study areas, flows that interacted with the drainage network flowed significantly farther than those that did not. In California, initiation sites within 60 m of the network were likely to reach the network and generate longtraveled flows; in Oregon, the threshold was 80 m.

California;Oregon;Washington↗
USGS2011

Hydrologic conditions and terrestrial laser scanning of post-firedebris flows in the San Gabriel Mountains, CA, U.S.A

To investigate rainfall-runoff conditions that generate post-wildfire debris flows, we instrumented and surveyed steep, small watersheds along the tectonically active front of the San Gabriel Mountains, California. Fortuitously, we recorded runoff-generated debris-flows triggered by one spatially restricted convective event with 28 mm of rainfall falling over 62 minutes. Our rain gages, nested hillslope overland-flow sensors and soil-moisture probes, as well as a time series of terrestrial laser scanning (TLS) revealed the effects of the storm. Hillslope overland-flow response, along two ~10-m long flow lines perpendicular to and originating from a drainage divide, displayed only a 10 to 20 minute delay from the onset of rainfall with accumulated totals of merely 5-10 mm. Depth-stratified soil-moisture probes displayed a greater time delay, roughly 20- 30 minutes, indicating that initial overland flow was Hortonian. Furthermore, a downstream channel-monitoring array recorded a pronounced discharge peak generated by the passage of a debris flow after 18 minutes of rainfall. At this time, only four of the eleven hillslope overland flow sensors confirmed the presence of surface-water flow. Repeat TLS and detailed field mapping using GPS document how patterns of rainsplash, overland-flow scour, and rilling contributed to the generation of metter-scale debris flows. In response to a single small storm, the debris flows deposited irregular levees and lobate terminal snouts on hillslopes and caused wide- spread erosion of the valley axis with ground surface lowering exceeding 1.5 m.

California↗
USGS2011

Observations of debris flows at Chalk Cliffs, Colorado, USA: Part 1, in-situ measurements of flow dynamics, tracer particle movement and video imagery from the summer of 2009

Debris flows initiated by surface-water runoff during short duration, moderate- to high-intensity rainfall are common in steep, rocky, and sparsely vegetated terrain. Yet large uncertainties remain about the potential for a flow to grow through entrainment of loose debris, which make formulation of accurate mechanical models of debris-flow routing difficult. Using a combination of in situ measurements of debris flow dynamics, video imagery, tracer rocks implanted with passive integrated transponders (PIT) and pre- and post-flow 2-cm resolution digital terrain models (terrain data presented in a companion paper by STALEY et alii, 2011), we investigated the entrainment and transport response of debris flows at Chalk Cliffs, CO, USA. Four monitored events during the summer of 2009 all initiated from surface-water runoff, generally less than an hour after the first measurable rain. Despite reach-scale morphology that remained relatively constant, the four flow events displayed a range of responses, from long-runout flows that entrained significant amounts of channel sediment and dammed the main-stem river, to smaller, short-runout flows that were primarily depositional in the upper basin. Tracer-rock travel-distance distributions for these events were bimodal; particles either remained immobile or they travelled the entire length of the catchment. The long-runout, large-entrainment flow differed from the other smaller flows by the following controlling factors: peak 10-minute rain intensity; duration of significant flow in the channel; and to a lesser extent, peak surge depth and velocity. Our growing database of natural debris-flow events can be used to develop linkages between observed debris-flow transport and entrainment responses and the controlling rainstorm characteristics and flow properties.

Colorado↗
USGS2011

Observations of debris flows at Chalk Cliffs, Colorado, USA: Part 2, changes in surface morphometry from terrestrial laser scanning in the summer of 2009

High resolution topographic data that quantify changes in channel form caused by sequential debris flows in natural channels are rare at the reach scale. Terrestrial laser scanning (TLS) techniques are utilized to capture morphological changes brought about by a high-frequency of debris-flow events at Chalk Cliffs, Colorado. The purpose of this paper is to compare and contrast the topographic response of a natural channel to the documented debris-flow events. TLS survey data allowed for the generation of high-resolution (2-cm) digital terrain models (DTM) of the channel. A robust network of twelve permanent control points permitted repeat scanning sessions that provided multiple DTM to evaluate fine-scale topographic change associated with three debris-flow events. Difference surfaces from the DTM permit the interpretations of spatial variations in channel morphometry and net volume of material deposited and eroded within and between a series of channel reaches. Each channel reach experienced erosion, deposition, and both net volumetric gains and losses were measured. Analysis of potential relationships between erosion and deposition magnitudes yielded no strong correlations with measures of channel-reach morphometry, suggesting that channel reach-specific predictions of potential erosion or deposition locations or rates cannot be adequately derived from statistical analyses of pre-event channel-reach morphometry.

Colorado↗
USGS2011

An empirical method to forecast the effect of storm intensity on shallow landslide abundance

We hypothesize that the number of shallow landslides a storm triggers in a landscape increases with rainfall intensity, duration and the number of unstable model cells for a given shallow landslide susceptibility model of that landscape. For selected areas in California, USA, we use digital maps of historic shallow landslides with adjacent rainfall records to construct a relation between rainfall intensity and the fraction of unstable model cells that actually failed in historic storms. We find that this fraction increases as a power law with the 6-hour rainfall intensity for sites in southern California. We use this relation to forecast shallow landslide abundance for a dynamic numerical simulation storm for California, representing the most extreme historic storms known to have impacted the state.

California↗
USGS2012

Paleoseismic and geomorphologic evidence of recent tectonic activity of the Pozohondo Fault (Betic Cordillera, SE Spain)

Instrumental and historical seismicity in the Albacete province (External Prebetic Zone) has been scarcely recorded. However, major strike-slip faults showing NW-SE trending provide geomorphologic and paleoseismic evidence of recent tectonic activity (Late Pleistocene to Present). Moreover, these faults are consistently well oriented under the present stress tensor and therefore, they can trigger earthquakes of magnitude greater than M6, according to the lengths of surface ruptures and active segments recognized in fieldwork. Present landscape nearby the village of Hellin (SE of Albacete) is determined by the recent activity of the Pozohondo Fault (FPH), a NW-SE right-lateral fault with 90 km in length. In this study, we have calculated the Late Quaternary tectonic sliprate of the FPH from geomorphological, sedimentological, archaeoseimological, and paleoseismological approaches. All of these data suggest that the FPH runs with a minimum slip-rate of 0.1 mm/yr during the last 100 kyrs (Upper Pleistocene-Holocene). In addition, we have recognized the last two major paleoearthquakes associated to this fault. Magnitudes of these paleoearthquakes were gretarer than M6 and their recurrence intervals ranged from 6600 to 8600 yrs for the seismic cycle of FPH. The last earthquake was dated between the 1st and 6th centuries, though two earthquakes could be interpreted in this wide time interval, one at the FPH and other from a far field source. Results obtained here, suggest an increasing of the tectonic activity of the Pozohondo Fault during the last 10,000 yrs.

Pozohondo Fault↗
USGS1987

Pure shear and simple shear calcite textures. Comparison of experimental, theoretical and natural data

The pattern of lattice preferred orientation (texture) in deformed rocks is an expression of the strain path and the acting deformation mechanisms. A first indication about the strain path is given by the symmetry of pole figures: coaxial deformation produces orthorhombic pole figures, while non-coaxial deformation yields monoclinic or triclinic pole figures. More quantitative information about the strain history can be obtained by comparing natural textures with experimental ones and with theoretical models. For this comparison, a representation in the sensitive three-dimensional orientation distribution space is extremely important and efforts are made to explain this concept. We have been investigating differences between pure shear and simple shear deformation incarbonate rocks and have found considerable agreement between textures produced in plane strain experiments and predictions based on the Taylor model. We were able to simulate the observed changes with strain history (coaxial vs non-coaxial) and the profound texture transition which occurs with increasing temperature. Two natural calcite textures were then selected which we interpreted by comparing them with the experimental and theoretical results. A marble from the Santa Rosa mylonite zone in southern California displays orthorhombic pole figures with patterns consistent with low temperature deformation in pure shear. A limestone from the Tanque Verde detachment fault in Arizona has a monoclinic fabric from which we can interpret that 60% of the deformation occurred by simple shear.

Journal of Structural Geology↗
USGS1989

New evidence for polyphase metamorphism of glaucophane schist and eclogite exotic blocks in the Franciscan Complex, California and Oregon

The early metamorphic history of high-grade exotic blocks in the Franciscan Complex may be more complicated than previously supposed. The different assemblages of high-grade glaucophane schists, eclogite, amphibolite and hornblende schist are commonly considered to have formed at the same time from essentially unmetamorphosed oceanic crust. However, new textural and mineralogical data presented here suggest that high-grade glaucophane schist and eclogite have replaced an earlier epidote-amphibolite facies assemblage that is identical to the primary assemblages in many of the hornblende-rich blocks. At least some of the hornblende-rich blocks may therefore be well-preserved remnants of the earlier metamorphism. Comparison of the mineral assemblages and element partititioning in the mixed-assemblage blocks suggests that the glaucophane schist and eclogite metamorphism took place at slightly lower temperatures but at the same or higher pressures than the earlier, hornblende-forming stage. -Authors

Journal of Metamorphic Geology↗
USGS2003

Structural framework of a major intracontinental orogenic termination zone: The easternmost Tien Shan, China

The Barkol Tagh and Karlik Tagh ranges of the easternmost Tien Shan are a natural laboratory for studying the fault architecture of an active termination zone of a major intracontinental mountain range. Barkol and Karlik Tagh and lesser ranges to the north are bounded by active thrust faults that locally deform Quaternary sediments. Major thrusts in Karlik Tagh connect along strike to the east with the left-lateral Gobi-Tien Shan Fault System in SW Mongolia. From a Mongolian perspective. Karlik Tagh represents a large restraining bend for this regional strike-slip fault system, and the entire system of thrusts and strike-slip faults in the Karlik Tagh region defines a horsetail splay fault geometry. Regionally, there appears to be a kinematic transition from thrust-dominated deformation in the central Tien Shan to left-lateral transpressional deformation in the easternmost Tien Shan. This transition correlates with a general eastward decrease in mountain belt width and average elevation and a change in the angular relationship between the NNE-directed maximum horizontal stress in the region and the pre-existing basement structural grain, which is northwesterly in the central Tien Shan (orthogonal to SHmax) but more east-west in the eastern Tien Shan (acute angular relationship with SHmax . Ar-Ar ages indicate that major range-bounding thrusts in Barkol and Karlik Tagh are latest Permian-Triassic ductile thrust zones that underwent brittle reactivation in the Late Cenozoic. It is estimated that the modern mountain ranges of the extreme easternmost Tien Shan could have been constructed by only 10-15 km of Late Cenozoic horizontal shortening.

Journal of the Geological Society↗
USGS2003

The Mw 7.7 Bhuj earthquake: Global lessons for earthquake hazard in intra-plate regions

The Mw 7.7 Bhuj earthquake occurred in the Kachchh District of the State of Gujarat, India on 26 January 2001, and was one of the most damaging intraplate earthquakes ever recorded. This earthquake is in many ways similar to the three great New Madrid earthquakes that occurred in the central United States in 1811-1812, An Indo-US team is studying the similarities and differences of these sequences in order to learn lessons for earthquake hazard in intraplate regions. Herein we present some preliminary conclusions from that study. Both the Kutch and New Madrid regions have rift type geotectonic setting. In both regions the strain rates are of the order of 10-9/yr and attenuation of seismic waves as inferred from observations of intensity and liquefaction are low. These strain rates predict recurrence intervals for Bhuj or New Madrid sized earthquakes of several thousand years or more. In contrast, intervals estimated from paleoseismic studies and from other independent data are significantly shorter, probably hundreds of years. All these observations together may suggest that earthquakes relax high ambient stresses that are locally concentrated by rheologic heterogeneities, rather than loading by plate-tectonic forces. The latter model generally underlies basic assumptions made in earthquake hazard assessment, that the long-term average rate of energy released by earthquakes is determined by the tectonic loading rate, which thus implies an inherent average periodicity of earthquake occurrence. Interpreting the observations in terms of the former model therefore may require re-examining the basic assumptions of hazard assessment.

Gujarat↗
USGS1973

A spectrochemical method for determining the composition of native gold

The spectrochemical method described herein for determining trace, minor, and major element distribution in native gold is applicable over a wide range of particle sizes and over a very large concentration range. The matrices of samples and standards are very closely matched. The method was tested on 100 nuggets from a gold sample collected in Alaska. The data show that the method is adequate for 30 of the 31 elements checked; only the mercury values are not acceptable. The data also show that more than one sample is necessary for a complete evaluation of all elements in one geologic location.

Alaska↗
USGS1978

Granite of Rosalie Peak, a phase of the 1700-million-year-old Mount Evans Pluton, Front Range, Colorado

The Rosalie Granite was a name applied by S. H. Ball in 1906 to a granite which forms a ridge between Mount Evans and Mount Rosalie (renamed Rosalie Peak). The type locality originally designated for the Rosalie Granite was in a pluton (later called the Rosalie lobe) 10 kilometers southeast of Rosalie Peak on Deer and Elk Creeks. The name "Rosalie Granite" was abandoned by T. S. Levering in 1929 because the granite of the Rosalie lobe is actually the distinctly younger Pikes Peak Granite, only 1,030 m.y. (million years) old, whereas the "Rosalie Granite" between Mount Evans and Rosalie Peak is a felsic phase of the l,700-m.y.-old Mount Evans pluton. In addition, the Rosalie Granite has more MgO and Sr and less Na 2 O, F, and Rb than the Pikes Peak Granite, and the two granites differ petrographically. In order to avoid confusion in correlation, the name Rosalie should not be applied to rocks in this area. Therefore, we propose that the Rosalie lobe be renamed Lone Rock pluton and that the "Rosalie Granite" be informally referred to as the granite of Rosalie Peak until it can be attached to a formal geologic rock unit.

Colorado↗
USGS1978

Pleistocene history of volcanism and the Owens River near Little Lake, California

During pluvial periods of the Pleistocene and Holocene, a large river flowed south from Owens Lake to China Lake between the Sierra Nevada and the Coso Range. The most recent channel, dry during historic time, is clearly marked by cliffs and falls. An older, now-abandoned part of the channel beneath Pleistocene lavas east of the present course is inferred from a meander-shaped ridge in Mesozoic basement rocks and a strong positive magnetic anomaly, presumably produced by a wedge of canyon-filling basalt. Three cycles of eruption and stream erosion have occurred along the present course. The first resulted when water impounded by damming of the now-abandoned eastern course found its way along the west margin of a basalt flow at the base of the Sierra Nevada escarpment, eventually carving a canyon at least 150 meters deep. Subsequently, two cycles, each consisting of an intracanyon basalt flow followed by major stream erosion, modified this canyon to its present configuration. A potassium-argon age of about 440000 years before present for the oldest of the three eroded lavas indicates that the river was not diverted from its easterly course until after that time. The age and character of lacustrine deposits in Searles Lake, a downstream part of the same drainage system, indicate that the greatest discharge of the river, and therefore, erosion of the two younger lavas since 440000 years B.P., probably occurred between 130000 and 10000 years B.P. An estimate of the rate of erosion during this period of time together with loosely constrained potassium-argon ages for the basalt of intermediate age suggests that the youngest lava is probably a few tens of thousands of years old and the intermediate lava somewhat less than 100000 years old. The youthfulness of the youngest basalt suggests that a fourth cycle of an intracanyon lava flow followed by stream erosion is a likely event for the near geologic future.

California↗
USGS1974

Thermal inertia mapping from satellite – Discrimination of geologic units in Oman

The Nimbus III and IV satellites provide reflectance and emittance data from the earth's surface at 8-km resolution. These data have been used to derive a physical property of geologic materials termed '"thermal inertia" which appears to have great promise for discriminating surficial units. A thermal inertia map of part of Oman was produced from the Nimbus satellite measurements. Correlation of this map with a reconnaissance geologic map showed gross agreement with the major units but also suggested the need for some modifications of the reconnaissance map. Some of the anomalies were verified by comparison with a later, more detailed map; others remain unexplained and may indicate previously undiscriminated geologic units.

Journal of Research of the U.S. Geological Survey↗
USGS2014

Comment on “The role of interbasin groundwater transfers in geologically complex terranes, demonstrated by the Great Basin in the western United States”: report published in Hydrogeology Journal (2014) 22:807–828, by Stephen T. Nelson and Alan L. Mayo

The subject article (Nelson and Mayo 2014) presents an overview of previous reports of interbasin flow in the Great Basin of the western United States. This Comment is presented by authors of a cited study (comprising chapters in one large report) on the Great Basin carbonate and alluvial aquifer system (GBCAAS; Heilweil and Brooks 2011; Masbruch et al. 2011; Sweetkind et al. 2011a, b), who agree that water budget imbalances alone are not enough to accurately quantify interbasin flow; however, it is proposed that statements made in the subject article about the GBCAAS report are inaccurate. The Comment authors appreciate the opportunity to clarify some statements made about the work.

Hydrogeology Journal↗