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Tectonic forcing of delta progradation is increasingly being invoked to explain stratal stacking patterns in foreland basins. Nonetheless, the recognition of different types of tectonic forcing and their consequences for the spatial and temporal distribution of accommodation often rely on incomplete data sets and indirect sequence stratigraphic criteria. Previous work has concluded that the Cenomanian-Turonian Frontier Formation of northern Utah, north-west Colorado and south-west Wyoming ('Vernal Delta') owes its origin largely to tectonic overprinting of depositional patterns, although the lack of a comprehensive sequence stratigraphic framework for the unit has hampered evaluation of this claim. This study provides detailed facies and sequence stratigraphic analyses based on outcrop sections and wireline log suites from the Uinta, Piceance and Green River basins. Four genetically related intervals were defined and mapped by using regionally traceable stratigraphic horizons (flooding surfaces and sequence boundaries). Internally, intervals are composed of distal and proximal delta front lithologies, and coastal plain facies. Overall, Intervals 1 to 4 form a major basinward projection of coarse clastic strata generated in response to four separate, high-frequency regressions. Furthermore, a change through time from southward projection of elongate lobes (Intervals 1 and 2) to eastward dispersal and development of a broad, arcuate planform (Intervals 3 and 4) can be explained in terms of changes in prevailing tectonic forcing mechanisms. North-south trending Sevier Orogeny forebulge structures controlled Intervals 1 and 2. West-east progradation (Intervals 3 and 4) was probably controlled by Proterozoic basement lineament reactivation due to Laramide foreland uplifts. Therefore, this study provides direct geological evidence for the initiation of local Laramide deformation as early as 90 Ma. These findings contribute to a more complete understanding of tectonic forcing of coastal to shallow marine successions in foreland basins and the tectonic evolution of the western USA. [ABSTRACT FROM AUTHOR]

SUMMARY Within the Northern Basin and Range Province, USA, we estimate horizontal velocities for 405 sites using Global Positioning System (GPS) phase data collected from 1994 to 2010. The velocities, together with geologic, volcanic, and earthquake data, reveal a slowly deforming region within the Snake River Plain in Idaho and Owyhee-Oregon Plateau in Oregon separated from the actively extending adjacent Basin and Range regions by shear. Our results show a NE-oriented extensional strain rate of 5.6 ± 0.7 × 10−9 yr−1 in the Centennial Tectonic Belt and an ∼E-oriented extensional strain rate of 3.5 ± 0.2 × 10−9 yr−1 in the Great Basin. These extensional rates contrast with the very low strain rate within the 125 km × 650 km region of the Snake River Plain and Owyhee-Oregon Plateau, which is indistinguishable from zero (−0.1 ± 0.4 × 10−9 yr−1). Inversions of the velocities with dyke-opening models indicate that rapid extension by dyke intrusion in volcanic rift zones, as previously hypothesized, is not currently occurring in the Snake River Plain. This slow internal deformation, in contrast to the rapidly extending adjacent Basin and Range regions, indicates shear along the boundaries of the Snake River Plain. We estimate right-lateral shear with slip rates of 0.3-1.4 mm yr−1 along the northwestern boundary adjacent to the Centennial Tectonic Belt and left-lateral oblique extension with slip rates of 0.5-1.5 mm yr−1 along the southeastern boundary adjacent to the Intermountain Seismic Belt. The fastest lateral shearing evident in the GPS occurs near the Yellowstone Plateau where strike-slip focal mechanisms and faults with observed strike-slip components of motion are documented. The regional velocity gradients are best fit by nearby poles of rotation for the Centennial Tectonic Belt, Snake River Plain, Owyhee-Oregon Plateau, and eastern Oregon, indicating that clockwise rotation is not locally driven by Yellowstone hotspot volcanism, but instead by extension to the south across the Wasatch fault due to gravitational collapse and by shear in the Walker Lane belt resulting from Pacific-Northern America relative plate motion. [ABSTRACT FROM AUTHOR]

A study using multiple techniques provided insight into tectonic influences on ground water systems; the results can help to understand ground water systems in the tectonically active western United States and other parts of the world. Ground water in the San Bernardino Valley (Arizona, United States and Sonora, Mexico) is the main source of water for domestic use, cattle ranching (the primary industry), and the preservation of threatened and endangered species. To improve the understanding of ground water occurrence, movement, and sustainability, an investigation was conducted using a number of complementary methods, including major ion geochemistry, isotope hydrology, analysis of gases dissolved in ground water, aquifer testing, geophysics, and an examination of surface and subsurface geology. By combining information from multiple lines of investigation, a more complete picture of the basin hydrogeology was assembled than would have been possible using fewer methods. The results show that the hydrogeology of the San Bernardino Valley is markedly different than that of its four neighboring basins in the United States. The differences include water quality, chemical evolution, storage, and residence time. The differences result from the locally unique geology of the San Bernardino Valley, which is due to the presence of a magmatically active accommodation zone (a zone separating two regions of normal faults with opposite dips). The geological differences and the resultant hydrological differences between the San Bernardino Valley and its neighboring basins may serve as a model for the distinctive nature of chemical evolution of ground water in other basins with locally distinct tectonic histories. [ABSTRACT FROM AUTHOR]

The article focuses on a paper that presented at the American Water Resources Association (AWRA) conference and its topic was suggested by Charles T. DuMars, water rights attorneys in New Mexico. The paper was presented to respond the problem in Albuquerque-Belen Basin regarding the unusable volume of ground water. With the aid of mathematical groundwater models developed by the U.S. Geological Survey and the Office of the New Mexico State Engineer, hydrologists were able to plan solutions to obtain usable groundwater in the basin. In addition, veteran geologist Bob Grant estimated the volume of saturated valley fill in the Rio Grande trough in the basin.

Aim The biogeography of western North American freshwater molluscs has traditionally been attributed to vicariance associated with late Tertiary rearrangement of landscape based on distributional evidence and the putatively limited dispersal ability of these organisms. We examined the phylogeography of a widely ranging western springsnail ( Pyrgulopsis wongi Hershler, 1989) to test this hypothesis and evaluate the relative importance of vicariance and dispersal in structuring the distribution of this species. Location Southwestern Great Basin (California and Nevada), United States of America. Method Two mitochondrial genes (COI, NDI) were sequenced for 28 populations of P. wongi spanning its entire geographic range, which consists of 10 topographically closed drainage basins. We also sequenced eight closely related congeners, as well as the type species of the closely related eastern North American genus Floridobia Hershler & Thompson, 2002, which was used as the outgroup. Phylogenies based on the combined data set were obtained using several methods, and networks for each gene were generated as an additional means of examining relationships among haplotypes. Partitioning of haplotype variation was studied usingamova, migration between populations was estimated using a coalescent-based method (mdiv), and divergence times were inferred using a locally calibrated molecular clock andmdiv. Results Pyrgulopsis wongi is subdivided into narrowly localized and widely distributed lineages that diverged in the Pleistocene, well after the inception of the contemporary regional landscape. While large ΦST values and the localized geographic distributions of most haplotypes imply absence or negligible contemporary dispersal of this spring-dwelling snail, the pattern of phylogeographic structuring, presence of a few widespread haplotypes, and results of themdiv analyses suggest geologically recent dispersal across drainage divides. Main conclusions Phylogeography of P. wongi conflicts with the traditional vicariance model as it is not structured by the contemporary landscape and is instead indicative of geologically recent dispersal. In the absence of evidence that dispersal of this species occurred through surface water connections during the relevant (Quaternary) time frame, we conjecture that spread may have instead been mediated by transport on waterfowl or via upland stream capture. The non-concordance between phylogeography and landscape reported in this and other recent studies of Pyrgulopsis suggests that members of this diverse and imperiled genus should not be managed using an a priori, ‘watershed as conservation unit’ approach. [ABSTRACT FROM AUTHOR]

We use three large normal fault arrays in the northeastern Basin and Range Province, western United States, to document catchment development and relief production during fault growth. Fault slip and slip rates increase systematically along strike from zero at the fault tips. Catchment relief and across-strike range width both increase as slip accumulates but reach maximum values at a distance of ∼15 km from the fault tips and remain uniform along strike over much of the footwalls. Catchment outlet spacing also increases away from the fault tips but does not reach a uniform value and may vary by a factor of 5–6 along strike. We infer that catchments first elongate in the across-strike direction as slip accumulates and the range half-width increases. Once the half-width reaches its maximum value, continued catchment growth is possible only by along-strike capture, which increases outlet spacing but not relief. The close correspondence between catchment relief and range half-width suggests that geomorphically limited hillslope and channel gradients are achieved within the 15 km tip zone. Thus, the limiting factor in footwall development is the width of the range, which is controlled by two external agents: the geometry and spacing of the major faults, and the elevations of base level on both flanks. [ABSTRACT FROM AUTHOR]

The San Gabriel Basin is a Pliocene—Pieistocene Transverse Ranges structure bounded by the San Gabriel Mountains on the north, the San Jose and Puente Hills on the east, and the Repetto and Montebello Hills on the west. A basement boundary between gneissoid rocks of San Gabriel Mountains aspect and Peninsular Ranges rocks strikes east across the basin and connects with the San Jose fault. This boundary may represent the eastward continuation of the Canton fault, a middle Miocene precursor of the San Gabriel fault system with up to 30 km of right slip. Canton fault displacement is largely canceled by ∼22.5 km of left slip on a precursor to the Raymond fault such that an Oligocene dacite in the San Jose Hills and clasts derived from it show little evidence of large horizontal displacement between the San Gabriel Mountains and Puente Hills. Clockwise rotation in the middle Miocene probably influenced the distribution of lateral slip. The fill in the northeast-trending Pliocene—Pleistocene San Gabriel Basin is a basal shallow-marine sequence overlain by the nonmarine Duarte Conglomerate, in contrast to the deep-water Fernando Formation of the Los Angeles Basin. The paleoslope trends south in the direction of the Repetto and Puente Hills, evidence that uplift of these hills postdated deposition. The triangular San Gabriel Basin is currently a stable block bounded by the right-slip, northwest-striking East Montebello fault on the west and the left-slip(?), northeast-striking Walnut Creek fault on the east. Farther east, the San Jose and Puente Hills are underlain by an east-trending active fold belt, including the San Jose reverse fault and anticline, the Walnut anticline, and the Puente Hills anticline adjacent to the right-lateral Whittier fault. The East Montebello fault is bounded on the west by the Elysian Park anticlinorium, a fold belt in downtown Los Angeles. The left-slip Holocene Raymond fault joins the Sierra Madre reverse fault at its segment boundary marked by the Clamshell-Sawpit fault. The triangular stable block between east-trending fold belts is bounded on the south by the Puente Hills blind thrust and on the north by the Sierra Madre fault, documenting north-south Quaternary convergence. East-west extension is also indicated, although not confirmed by geodetic measurements. [ABSTRACT FROM AUTHOR]

Newly released reflection seismic and borehole data, combined with sedimentological, provenance, and biostratigraphic data from Upper Cretaceous—Paleocene strata in the proximal part of the Cordilleran foreland-basin system in Utah, establish the nature of tectonic controls on stratigraphic sequences in the proximal to distal foreland basin. During Campanian time, coarse-grained sand and gravel were derived from the internally shortening Charleston-Nebo salient of the Sevier thrust belt. A rapid, regional Campanian progradational event in the distal foreland basin (>200 km from the thrust belt in >8 m.y.) can be tied directly to active thrust-generated growth structures and an influx of quartzose detritus derived from the Charleston-Nebo salient. Eustatic sea-level variation exerted a minimal role in sequence progradation. [ABSTRACT FROM AUTHOR]

Clay mineral assemblages have been investigated in a sequence of Late Quaternary age sediments (160 ka) from the Santa Barbara Basin off California. These predominantly terrigenous sediments contain an assemblage of clay minerals dominated by smectite mostly derived from discharges of the Santa Clara River, together with illite and kaolinite from adjacent relief. Besides its characteristic clay mineral signature, the Santa Clara River has the largest drainage basin in this region and contributes most of the terrigenous load to the Santa Barbara Basin. Smectite contents of the sediments in the basin may therefore be used as a proxy for precipitation and run-off. Distinct changes in the relative abundance of smectite allow reconstruction of the pattern of precipitation, and its relations with regional environments and global climate. This showed that major intervals of precipitation coincide with local development of pine during glacials, and oak during terminations and interglacials; some expansion of mountain glaciers in the Sierra Nevada, especially when they occur during local minima of insolation; and lacustrine developments in the now arid continental interior of California. Major precipitation intervals started during glacials, and persisted during terminations and early interglacials, associated with a weak California Current and subsequent expansion of warm Pacific surface waters. In detail, major precipitation intervals consist of alternating episodes of higher and lower rainfall modulated by orbital precession, with a significant correlation between episodes of high rainfall and minima in precession, which were times of increased meridional gradients, enhanced poleward heat transfer and northward expansion of tropical waters. [Copyright &y& Elsevier]

Geochronological, structural, and sedimentological data provide the basis for a regional synthesis of the evolution of the Cordilleran retroarc thrust belt and foreland basin system in the western U.S.A. In this region, the Cordilleran orogenic belt became tectonically consolidated during Late Jurassic time (∼155 Ma) with the closure of marginal oceanic basins and accretion of fringing arcs along the western edge of the North American plate. Over the ensuing 100 Myr, contractile deformation propagated approximately 1000 kilometers eastward, culminating in the formation of the Laramide Rocky Mountain ranges. At the peak of its development, the retroarc side of the Cordillera was divided into five tectonomorphic zones, including from west to east the Luning-Fencemaker thrust belt; the central Nevada (or Eureka) thrust belt; a high-elevation plateau (the "Nevadaplano"); the topographically rugged Sevier fold-thrust belt; and the Laramide zone of intraforeland basement uplifts and basins. Mid-crustal rocks beneath the Nevadaplano experienced high-grade metamorphism and shortening during Late Jurassic and mid- to Late Cretaceous time, and the locus of major, upper crustal thrust faulting migrated sporadically eastward. By Late Cretaceous time, the middle crust beneath the Nevadaplano was experiencing decompression and cooling, perhaps in response to large-magnitude ductile extension and isostatic exhumation, concurrent with ongoing thrusting in the frontal Sevier belt. The tectonic history of the Sevier belt was remarkably consistent along strike of the orogenic belt, with emplacement of regional-scale Proterozoic and Paleozoic megathrust sheets during Early Cretaceous time and multiple, more closely spaced, Paleozoic and Mesozoic thrust sheets during Late Cretaceous-Paleocene time. Coeval with emplacement of the frontal thrust sheets, large structural culminations in ArcheanProterozoic crystalline basement developed along the basement step formed by Neoproterozoic rifting. A complex foreland basin system evolved in concert with the orogenic wedge. During its early and late history (∼155-110 Ma and ∼70-55 Ma) the basin was dominated by nonmarine deposition, whereas marine waters inundated the basin during its midlife (∼ 110-70 Ma). Late Jurassic basin development was controlled by both flexural and dynamic subsidence. From Early Cretaceous through early Late Cretaceous time the basin was dominated by flexural subsidence. From Late Cretaceous to mid-Cenozoic time the basin was increasingly partitioned by basement-involved Laramide structures. Linkages between Late Jurassic and Late Cretaceous Cordilleran arcmagmatism and westward underthrusting of North American continental lithosphere beneath the arc are not plainly demonstrable from the geological record in the Cordilleran thrust belt. A significant lag-time (∼20 Myr) between shortening and coeval underthrusting, on the one hand, and generation of arc melts, on the other, is required for any linkage to exist. However, inferred Late Jurassic lithospheric delamination may have provided a necessary precondition to allow relatively rapid Early Cretaceous continental underthrusting, which in turn could have catalyzed the Late Cretaceous arc flare-up. [ABSTRACT FROM AUTHOR]

As in many continental margins, Mesozoic rifting in the Gulf of Mexico trended subparallel to older tectonic structures created by opening and closure of a prior ocean basin. Unlike the situation in most other margins, however, extension in the Gulf of Mexico did not involve widespread reactivation of these older tectonic features. This difference may be related to the unusual facts that (1) the antecedent passive continental margin was a transform rather than a rift margin and (2) the prior orogeny did not substantially thicken the crust. In order to characterize the interaction between Mesozoic rifting and prior tectonic events, two geophysical transects were constructed across the central Gulf of Mexico coastal plain and continental shelf. The transects show that the early Paleozoic passive continental margin buried beneath the late Paleozoic Ouachita orogen was little affected by compressional tectonism or Mesozoic extension during opening of the Gulf of Mexico. The thickness of the crust on this ancient margin decreases from 35 km to 10 km over a distance of only 50 km, consistent with previous interpretations that this was a transform margin. The Ouachita fold-and-thrust belt is shown to be a thin-skinned doubly vergent orogen that formed above a well-preserved southward-dipping subduction system. Relict Cambrian oceanic crust may exist beneath the southern part of the orogen, but its presence is not required by the data. The thin crust and shallow mantle in the Ouachita suture created a zone of relatively high strength that acted as a barrier to Mesozoic extension, which is restricted to regions south of the orogen. Extension was initially distributed over a broad area that included the Mississippi Interior Salt Basin and regions south of the Wiggins Arch. Extension became progressively more focused south of the Wiggins Arch with time, culminating in the onset of seafloor spreading beneath the modern continental rise. Mesozoic extension factors are β = 1.4-1.9 beneath the Mississippi Interior Salt Basin, β ≈ 2.9 immediately south of the Wiggins Arch, and β ≈ 4 adjacent to the oldest oceanic crust in the central Gulf of Mexico. Keywords: Gulf of Mexico; North America; rifting; Ouachita orogeny; gravity profiles. [ABSTRACT FROM AUTHOR]

The full spectrum of basin modes in a tropical–extratropical basin is studied comprehensively in a linear shallow-water system. Two sets of least-damped basin modes are identified. At the low-frequency end is the planetary wave basin mode, whose period is determined by the cross-basin time of the planetary wave on the poleward boundary of the basin, consistent with recent theories. At the higher-frequency end is the Kelvin wave basin mode, whose period is determined by the around-basin traveling time of the Kelvin wave. Sensitivity experiments are also performed on the eigenvalue problem to study the dynamics of these basin modes. It is found that the period of the planetary wave basin mode is determined by an effective basin boundary that is always at a latitude no higher than the geometric basin boundary. The effective poleward boundary is located at the most poleward latitude where the planetary wave can cross the entire basin. It is also found that the Kelvin wave basin modes are vulnerable to boundary perturbations. If the coastal Kelvin wave propagation is suppressed along the basin boundary, the Kelvin wave basin mode would degenerate to the equatorial basin mode that has been obtained theoretically from the long-wave approximation. [ABSTRACT FROM AUTHOR]

Focuses on a study that presented bankfull hydraulic geometry relationships and recurrence intervals for the Southeastern Plain ecoregion and the flatwoods subtype of the Middle Atlantic Coastal Plain ecoregion found within North Carolina's Coastal Plain physiographic province. Methodology; Results of the study; Conclusions.

Examines the association of backarc and arc-related tectonic units in California. Influence of alkalic and arc-related magnetic processes to backarc basin; Initiation of the Franciscan subduction; Formation of the Round Mountain serpentine melange.

Studies the crustal structure and tectonics from the Los Angeles basin to the Mojave Desert, southern California. Maximum depth of the Los Angeles basin; Formation of north dipping buttress by the Duarte branch of the Sierra Madre fault zone; Dip and depth extension of the San Andreas fault line.

Presents the results of a study which examined the origin and age of the Manila high and associated sunklands in the Big Lake basin of northern Arkansas' New Madrid seismic zone. Stratigraphy; Topography; Deformation chronology of the Manila high and Big Lake basin; Position of the Little River.

Presents the results of a study on the distribution of fluid pressure, the origin of cement and vein minerals that inhibit fluid flow, and the mechanisms for fluid migration and fluid-pressure generation within the northeastern part of Cook Inlet basin in Alaska. Tectonics of upper Cook Inlet basin; Lithology of tertiary and upper mesozoic sedimentary rocks.

Proposes a model for progressive arcward contraction of the fore-arc basin in the Rumsey Hills region, southwestern Sacramento Valley, beginning in Cretaceous and continuing episodically through Cenozoic time. Seismic reflection data used to develop the forward model; Major tectonic and depositional events; Stratigraphic and structural relationships.