West Extension Research Articles

Influence of inherited Indian basement faults on the evolution of the Himalayan Orogen

Abstract Indian basement faults, which bound three orogen-perpendicular palaeotopographic ridges of Precambrian Indian basement south of the Himalaya, extend to the base of the Indian lithosphere and to the northern extent of the Indian lithosphere underneath Tibet. In the eastern Himalaya, the active orogen-perpendicular Yadong–Gulu graben is aligned with an earthquake-generating strike-slip fault in the high Himalaya. We argue that the graben results from crustal necking during reactivation of the underplated basement fault. In the central Himalaya, along-strike diachronous deformation and metamorphism within the Himalayan metamorphic core, as well as lateral ramps in the foreland thrust belt, spatially correspond to the Lucknow and Pokhara lineaments that bound the subsurface Faizabad Ridge in the Indian basement. Analogue centrifuge modelling confirms that offset along such deep-seated basement faults can affect the location, orientation and type of structures developed at various stages of orogenesis and suggests that it is mechanically feasible for strain to propagate through a melt-weakened mid-crust. We suggest that inherited Indian basement faults affect the ramp-flat geometry of the basal Main Himalayan Thrust, partition the Himalayan range into distinct zones, localize east–west extension resulting in the Tibetan graben and, ultimately, contribute to lateral variability in tectonic evolution along the orogen's strike.

Stepwise basin evolution of the Middle Jurassic–Early Cretaceous rift phase in the Central Graben area of Denmark, Germany and The Netherlands

Abstract This paper presents the results of a cross-border study of the Middle Jurassic–Early Cretaceous rift phase in the Danish–German–Dutch Central Graben area. Based on long-distance correlations of palynologically interpreted wells, a stepwise basin evolution pattern was determined. Four phases are defined and described as tectonostratigraphic mega-sequences (TMS). The TMS are governed by changes in the tectonic regime. TMS-1 reflects the onset of rifting, triggered by regional east–west extension. Rift climax was reached during TMS-1, reflected by thick mudstone accumulations. TMS-2 reflects a change in the tectonic regime from east–west to NE–SW extension. NW–SE-trending normal faults became active during this phase, switching the depocentres from the graben axis into adjacent basins. TMS-3 displays divergent basin development. In the Dutch Central Graben area, it is characterized by a basal unconformity and widespread sandstone deposition, indicating continued salt and fault activity. Organic-rich mudstone deposition prevails in the Danish and German Central Graben area, indicating sediment starvation and water-mass stratification. With TMS-4 the rift phase ended, reflected by regionally uniform mudstone deposition. The basin evolution model presented here coherently places the lithostratigraphic units occurring in a stratigraphic framework and provides a valuable basis for hydrocarbon exploration activities in the region.

Mesozoic structural evolution of the New Siberian Islands

Abstract The New Siberian Islands are affected by a number of Mesozoic tectonic events. The oldest event (D1a) is characterized by NW-directed thrusting within the South Anyui Suture Zone combined with north–south-trending sinistral strike-slip in the foreland during the Early Cretaceous. This compressional deformation was followed by dextral transpression along north–south-trending faults, which resulted in NE–SW shortening in the Kotelny Fold Zone (D1b). The dextral deformation can be related to a north–south-trending boundary fault zone west of the New Siberian Islands, which probably represented the Laptev Sea segment of the Amerasia Basin Transform Fault in pre-Aptian–Albian times. The presence of a transform fault west of the islands may be an explanation for the long and narrow sliver of continental lithosphere of the Lomonosov Ridge and the sudden termination of the South Anyui Suture Zone against the present Laptev Sea Rift System. The intrusion of magmatic rocks 114 myr ago was followed by NW–SE-trending sinistral strike-slip faults of unknown origin (D2). In the Late Cretaceous–Paleocene, east–west extension (D3) west of the New Siberian Islands initiated the development of the Laptev Sea Rift System, which continues until today and is largely related to the development of the Eurasian Basin.

Compact Resolved Ejecta in the Nearest Tidal Disruption Event

Abstract Tidal disruption events (TDEs) occur when a star or substellar object passes close enough to a galaxy’s supermassive black hole to be disrupted by tidal forces. NGC 4845 (d = 17 Mpc) was host to a TDE, IGR J12580+0134, detected in 2010 November. Its proximity offers us a unique close-up of the TDE and its aftermath. We discuss new Very Long Baseline Array (VLBA) and Karl G. Jansky Very Large Array observations, which show that the radio flux from the active nucleus created by the TDE has decayed in a manner consistent with predictions from a jet-circumnuclear medium interaction model. This model explains the source’s broadband spectral evolution, which shows a spectral peak that has moved from the submillimeter (at the end of 2010) to GHz radio frequencies (in 2011–2013) to in 2015. The milliarcsecond-scale core is circularly polarized at 1.5 GHz but not at 5 GHz, consistent with the model. The VLBA images show a complex structure at 1.5 GHz that includes an east–west extension that is ∼40 mas (3 pc) long, as well as a resolved component that is 52 mas (4.1 pc) northwest of the flat-spectrum core, which is all that can be seen at 5 GHz. If ejected in 2010, the northwest component must have had over five years. However, this is unlikely, as our model suggests strong deceleration to speeds within months and a much smaller, sub-parsec size. In this interpretation, the northwest component could have either a non-nuclear origin or be from an earlier event.

Project Spotlight: Heldenfels opens third Texas plant to supply beams for 21-bridge highway project

Heldenfels Enterprises Inc. opened a new prestressed concrete plant in El Paso, Tex., to help supply beams for the Loop 375 Border Highway West extension project, which includes 21 bridges.

NEW CONSTRAINTS ON THE MOLECULAR GAS IN THE PROTOTYPICAL HyLIRGs BRI 1202–0725 AND BRI 1335–0417

ABSTRACT We present Karl G Jansky Very Large Array observations of CO( ) line emission and rest-frame 250 GHz continuum emission of the Hyper-Luminous IR Galaxies (HyLIRGs) BRI 1202–0725 (z = 4.69) and BRI 1335–0417 (z = 4.41), with an angular resolution as high as 0.″15. Our low-order CO observations delineate the cool molecular gas, the fuel for star formation in the systems, in unprecedented detail. For BRI 1202–0725, line emission is seen from both extreme starburst galaxies: the quasar host and the optically obscured submm galaxy (SMG), in addition to one of the Lyα emitting galaxies in the group. Line emission from the SMG shows an east–west extension of about 0.″6. For Lyα-2, the CO emission is detected at the same velocity as [C ii] and [N ii], indicating a total gas mass ∼4.0 × 1010 M ⊙. The CO emission from BRI 1335–0417 peaks at the nominal quasar position, with a prominent northern extension (∼1″, a possible tidal feature). The gas depletion timescales are ∼107 years for the three HyLIRGs, consistent with extreme starbursts, while that of Lyα-2 may be consistent with main sequence galaxies. We interpret these sources as major star formation episodes in the formation of massive galaxies and supermassive black holes via gas-rich mergers in the early universe.

Activation of a Minor Graben and Pull‐Apart Basin Just East of Bukadaban during the 2001 Kunlun Earthquake (Mw 7.8)

Abstract Surface ruptures found east of the high peak of Bukadaban that formed during the 2001 Kunlun earthquake reveal a minor northeast–southwest‐trending graben, across which oblique approximately east–west extension occurred. Scarps along the southeast flank of the graben indicate vertical components of slip of 3–4 m, and left steps in the trace suggest a component of left‐lateral slip. Scarps on the northwest flank show vertical components of only ∼1.5 m; east–west‐trending ridges in the flanking footwall and hanging wall imply north–south shortening and therefore also a component of left‐lateral slip. These observations corroborate the inference made by others that Bukadaban, though >6000 m high, lies within or adjacent to an active pull‐apart basin between two major strike‐slip segments oriented ∼N100°E.

Fall-breeding beef females failing to conceive during spring breeding

ABSTRACT A study was conducted to evaluate the economics of retaining ownership and rebreeding nonpregnant spring-calving cows to be sold as pregnant fall-calving cows. Spring-born crossbred females diagnosed as nonpregnant after the regular spring breeding season were used over a 2-yr period at 2 locations, Gudmundsen Sandhills Laboratory (GSL) and West Central Research and Extension Center (WCREC). A partial budget analysis was performed to evaluate the economic aspects of this strategy; total cost was calculated by adding the purchase price, feeding and management cost, breeding expenses, and 6% annual interest rate on the purchase price. The net cost of one pregnant cow was calculated as the difference between total cost and cull value, divided by the number of pregnant cows. A sensitivity analysis evaluated the economics of retaining and rebreeding for market scenarios for the last 5 yr at different pregnancy rates. The overall rebreeding pregnancy rate was 86.1% at GSL and 80.0% at WCREC; the percentage of the pregnant cows that conceived in the first 21 d of the breeding season was 84.4% at GSL and 66.6% at WCREC. The increasing cow prices from November to April and a greater market price for pregnant females resulted in a net gain of $520.29 and $616.81 per pregnant female for GSL and WCREC, respectively. Simulation performed using market prices for the last 5 yr demonstrated the strategy is cost effective in different market scenarios, excluding 2012/2013 because of drought—feed prices were the highest and cow prices the lowest of the 5 yr analyzed. Other than atypical scenarios like drought, positive economic results may be possible even at low pregnancy rates, but as the pregnancy rate increases, net proceeds also increase.

Structural inversion of the Tamworth Belt: Insights into the development of orogenic curvature in the southern New England Orogen, Australia

The middle to late Permian Hunter Bowen Event is credited with the development of orogenic curvature in the southern New England Orogen, yet contention surrounds the structural dynamics responsible for the development of this curvature. Debate is largely centred on the roles of orogen parallel strike-slip and orogen normal extension and contraction to explain the development of curvature. To evaluate the dynamic history of the Hunter Bowen Event, we present new kinematic reconstructions of the Tamworth Belt. The Tamworth Belt formed as a Carboniferous forearc basin and was subsequently inverted during the Hunter Bowen Event. Kinematic reconstructions of the Tamworth Belt are based on new maps and cross-sections built from a synthesis of best-available mapping, chronostratigraphic data and new interpretations of depth-converted seismic data. The following conclusions are made from our study: (i) the Hunter Bowen Event was dominantly driven by margin normal contraction (east–west shortening; present-day coordinates), and; (ii) variations in structural style along the strike of the Tamworth Belt can be explained by orthogonal vs. oblique inversion, which reflects the angular relationship between the principal shortening vector and continental-arc margin. Given these conclusions, we suggest that curvature around the controversial Manning Bend was influenced by the presence of primary curvature in the continental margin, and that the Hastings Block was translated along a sinistral strike-slip fault system that formed along this oblique (with respect to the regional east–west extension and convergence direction) part of the margin. Given the available temporal data, the translation of the Hastings Block took place in the Early Permian (Asselian) and therefore preceded the Hunter Bowen Event. Accordingly, we suggest that the Hunter Bowen Event was dominantly associated with enhancing curvature that was either primary in origin, or associated with fault block translation during the Early Permian. This model differs to previously proposed reconstructions where curvature largely formed by orogen parallel strike-slip transportation during the Hunter Bowen Event.

Differential Settlement and Induced Structural Damage in a Cut-and-Cover Subway Tunnel in a Soft Deposit

AbstractThis study investigated the differential settlement and induced structural damage in the west extension of Nanjing Metro Line 1. The minimum and maximum cumulative settlements measured over the course of four years of operation were 1 mm and 122 mm, respectively. Four settlement troughs in the longitudinal direction of the line, as well as a periodic variation of differential settlement between the stations and the tunnel, were observed. Approximately 10% of the vertical radius of curvature of the line violates the safety limit of 15,000 m, and three typical kinds of cracks (i.e., transverse cracks in the tunnel roof and in the track bed, and inclined cracks in the outer wall) and leakage have occurred. The differential settlement of the line was mainly caused by the nonuniform distribution of underlying soft soil. The periodic variation of differential settlement between the stations and tunnel was attributed to the structural characteristics and the seasonal variation in the groundwater level. T...

Stream profile analysis, tectonic geomorphology and neotectonic activity of the Damxung‐Yangbajain rift in the south Tibetan Plateau

AbstractThe Damxung‐Yangbajain rift is one of the most active north–south trending rifts in the south Tibetan Plateau, and it has been playing an important role in accommodating the east–west extension of the Tibetan Plateau. Both stream profiles on the Nyainqentanglha Range adjacent to the northwest part of the Damxung‐Yangbajain rift and tectonic geomorphology in the north of the rift are analyzed to assess the spatial pattern and intensity of rock uplift which is related to neotectonic activity. A total of 85 stream profiles across the Nyainqentanglha Range are analyzed, and 111 knickpoints are interpreted. Most of these stream profiles are characterized by prominent convexities with two or more knickpoints, many of which are formed due to the strong rock uplift evidenced by abnormal concavity and extremely high steepness indices during the Quaternary. Neotectonic activity in this region is well replicated in the stream profile indices and offset landforms. Tectono‐geomorphic analysis shows that the concavity and steepness indices correlate with the fault movements at many places. The Damxung‐Yangbajain rift is characterized by left‐lateral strike‐slip in the north of Damxung and by normal movement in middle and southern parts. The middle and southern parts have been undergoing higher uplift than has the northern area. It is most likely that the strong uplift is related to the heat flow under the crust. Earthquakes occurring in the Damxung‐Yangbajain rift, including a M8 in 1411 and M6.6 in 2008, are thought to be related to heat flow activity. All of the stream profile indices and tectonic geomorphology show that the Damxung‐Yangbajain rift is not in a stable state. Copyright © 2016 John Wiley & Sons, Ltd.

Post-Caledonian extension in the West Norway–northern North Sea region: the role of structural inheritance

Abstract The northern North Sea region has experienced repeated phases of post-Caledonian extension, starting with extensional reactivation of the low-angle basal Caledonian thrust zone, then the formation of Devonian extensional shear zones with 10–100 km-scale displacements, followed by brittle reactivation and the creation of a plethora of extensional faults. The North Sea Rift-related approximately east–west extension created a new set of rift-parallel faults that cut across less favourably orientated pre-rift structures. Nevertheless, fault rock dating shows that onshore faults and shear zones of different orientations were active throughout the history of rifting. Several of the reactivated major Devonian extensional structures can be extrapolated offshore into the rift, where they appear as bands of dipping reflectors. They coincide with large-scale boundaries separating 50–100 km-wide rift domains of internally uniform fault patterns. Major north–south-trending rift faults, such as the Øygarden Fault System, bend or terminate against these boundaries, clearly influenced by their presence during rifting. Hence, the North Sea is one of several examples where pre-rift basement structures oblique to the rift extension direction can significantly influence rift architecture, even if most of the rift faults are newly-formed structures.

Evaluating the West Virginia Interpretive Guide Heritage Steward Program

West Virginia University's Extension Service partnered with the Recreation, Parks, and Tourism Resources Program to offer an entry level certification opportunity to interpretive guides in West Virginia. The result of this partnership is the West Virginia Interpretive Guide Heritage Steward Program aimed at providing low-cost, widely available training course to guides throughout the state. The course is divided into two components—a set of online modules and an in-person skill assessment workshop. This exploratory study used a retrospective post-then-pre survey design to assess the course impact on participants’ beliefs related to the effectiveness of the course, as well as self-reported changes in interpretive competency. Results indicated the course was successful in increasing participant competence related to developing and delivering interpretive talks. This effective regionally based certification course is potentially a model that could be used to expand personal interpretive certification opportunities for guides.

Partial melting in amphibolites in a deep section of the Sveconorwegian Orogen, SW Sweden

Garnet amphibolite metataxites at the Steningekusten Nature Reserve in southwestern Sweden contain tonalitic patches and veins. Whole rock chemistry suggests that the protoliths were mafic igneous rocks with alkaline affinities. Orthopyroxene megacrysts are present in leucosome in parts of these garnet amphibolites but absent in others. Orthopyroxene megacrysts were formed by vapor-absent melting initiated by incongruent melting of biotite followed by the breakdown of hornblende. The net reaction was Bt+Hbl+Pl+/−Qtz↔Opx+Melt+Cpx+Gt. Melting occurred at pressures of approximately 1GPa and temperatures which probably exceeded 800°C. Pyroxenes are surrounded by hornblende–quartz symplectites, and hornblende in these coronas has distinctly lower concentrations of (Na+K) and Ti than that in adjacent mesosome. The hornblende rims formed upon cooling and reaction with crystallizing melt. This created a barrier to further reaction thus preserving the orthopyroxene megacrysts. Garnet amphibolite metatexites lacking pyroxene megacrysts have features characteristic of vapor-present melting including lack of peritectic phases predicted by vapor-absent melting reactions, larger amounts of leucosome (14 versus 7%), and less distinct melanosomes. The variation in these migmatites reflects open system behavior, either on a regional scale with the migration of aqueous fluids into the amphibolites or on a local scale with the migration of melt within the amphibolites. Zircons from all units have CL-dark core domains that are dated at 1415–1390Ma. The core zones are cut and overgrown by CL-dark and CL-bright rims that are dated at 975–965Ma. The zircon rims are thin in the mesosome but are thicker in the leucosome suggesting that they formed during migmatization. New growth of zircon associated with migmatization at ca. 970Ma corresponds to the timing of crustal scale partial melting in the deep regions of the Sveconorwegian orogen, synchronous with east–west extension and the intrusion of mafic dykes. If partial melting was driven by an influx of aqueous fluids, they were probably derived from a relatively cool source region, which would indicate tectonic juxtaposition of hotter and cooler terranes.

FIELD BINDWEED MANAGEMENT IN DRIP IRRIGATED PROCESSING TOMATOES

Subsurface drip irrigation in processing tomatoes (Solanum lycopersicum) has been rapidly adopted in California over the past decade, and is now used on approximately 90% of the production area. The economic necessity of maintaining the beds and replanting with only minimal tillage for multiple seasons has created a system where field bindweed (Convulvulus arvensis) has become more prevalent. Beginning in 2011, field studies were conducted at University of California Davis campus to evaluate the efficacy of registered herbicide combinations in controlling established field bindweed in processing tomatoes; parallel studies were conducted at the UC West Side Research and Extension Center using drip irrigation. The treatment design was a randomized block split-plot with four replications. Main plots consisted of pre-emergent and pre-plant incorporated (PPI) applications of pendimethalin, trifluralin, sulfentrazone, and rimsulfuron at label rates. Split-plot treatments were post-emergent applications of rimsulfuron or carfentrazone, applied after transplanting to emerged bindweed. Concurrently, additional herbicide treatment combinations included sequential post applications of rimsulfuron, carfentrazone, or carfentrazone + glyphosate; trifluralin applied PPI and again at lay-by, sulfentrazone + S-metalochlor PPI, trifluralin + S-metalochlor + rimsulfuron combination, as well as untreated and hand weeded controls. Overall, trifluralin was the most effective pre-emergence treatment for suppressing established field bindweed, however, this effect was not significantly different than the other treatments or the untreated control by the end of the season. Post-emergent applications of rimsulfuron and carfentrazone significantly improved bindweed control about 21% in most instances. The combination of trifluralin PPI and either rimsulfuron or carfentrazone applied post emergence, or applying trifluralin both pre and at layby, have been the best treatments for controlling field bindweed in these trials, with bindweed control of 50-80% compared to the untreated control. No significant differences were noted for tomato crop growth or yield; however, concerns remain about this herbicide program for its potential crop phytotoxicity and plant-back restrictions.

Predicting subseismic fracture density and orientation in the Gorm Field, Danish North Sea

Abstract The chalk reservoir of the Gorm Field, southern North Sea is dome-shaped and faulted owing to a combination of salt diapirism and regional east–west extension. Fractures developed in the structure considerably enhance permeability. The dataset discussed here records fractures in horizontal wells from more than 10 km of image logs and provides a special opportunity to test theoretical models of fracture development with quantitative observations. In an effort to forecast fracture density and fracture orientation, we have estimated the strains in the structure using an elastic dislocation model that incorporates mechanical boundaries in the form of the tectono-stratigraphic interface with salt and tectonic faults. More than 50% of the angular differences between poles to the planes of simulated and observed fractures are less than 30°; 75% are less than 45°. Relative strain magnitude appears to be a useful indicator of fracture density. At the field scale, small strain magnitudes correspond with small non-zero fracture densities and relatively large strain magnitudes correspond with high fracture densities.

The Feasibility Study of Distributed Photovoltaic Power Generation System in Western Region of China

Due to the natural environment, geographic location, the technical conditions and restrictions of many factors, centralized parallel operation of power grid the west extension and popularization in our country with high difficulty and feasibility. The distributed photovoltaic power generation possesses the following advantages: less investment, flexibility and compatibility. The joint operation of DG with power grid brings tremendous variation in control and operation for modern power system, ultimately the stability of power supply is enhanced and the life quality of residents is improved in western region of China. This paper explores the operation mode of distributed photovoltaic power generation in remote areas, and introduces the concrete operation mode of the project, analyzes the adaptability of distributed photovoltaic mode. Finally, the feasibility of the application of the distributed photovoltaic power generation in the western region of China is analyzed in this paper.

Present day crustal vertical movement inferred from precise leveling data in eastern margin of Tibetan Plateau

We collect precise leveling data observed in the period of 1970 to 2012 around the eastern margin of the Tibetan Plateau, and process the data to acquire present day crustal vertical velocity field. Vertical rates of 9 GPS sites are employed as a priori constraints to define the reference frame. The velocity field shows that most of the regions in the eastern margin of the Tibetan Plateau are undergoing uplift. The Gongga Shan and West Qinling are uplifting at maximum rates of 5.8±1.0mm/a and 6.0±1.3mm/a, respectively. A 2-D buried dislocation model is used to infer normal or reverse dip-slip rates. The result indicates that the reverse slip rate along the Longmen Shan fault is 4.2±0.5mm/a, followed by the Daliangshan and Longriba faults with the rates of 3.7±0.5 mm/a and 2.8±0.3mm/a respectively. TheZemuhe and northern section of the Xiaojiang fault have the normal slip rates of 2.3±1.0mm/a and 2.9±0.4mm/a respectively. Combining vertical velocity field with GPS derived horizontal velocity field, we investigate the characteristics of crustal movement and dynamic mechanism. The 3D velocity field indicates that the Helan Shan is uplifting and the Yinchuan graben is subsiding. The 3D crustal movement of the Liupan Shan region is segmented, with the area in the vicinity of the northern Liupan Shan fault uplifting and the area in the vicinity of southern Liupan Shan fault subsiding respectively. The subsidence of the central and southern Sichuan–Yunnan terrain is caused by the near east–west extension. The budget of horizontal material influx suggests that movements of the upper and lower crust are rather different in most of the region, excessive material influx into the lower crust/upper mantle underneath most of the sub-blocks seems required to maintain the uplift rates inferred from leveling, providing evidence for the existence of lower crustal flow in this region.

End of the Line: The Overseas Railway

The Florida East Coast Railway’s Key West Extension enabled the remote island to become a key port for goods shipped to and from Central America.

Numerical Simulation of Ground Surface Settlement Induced by Open-Cut Subway Station

Ground surface settlement induced by open-cut subway station has important implications for construction safety. Based on a subway station background of the line 3 west extension engineering of kunming metro line co.LTD. On the basis of geological survey results and indoor geotechnical mechanics experiment, the 3D geological model was established by three-dimensional finite difference method FLAC3D. Ground surface settlement Law and Retaining structure stability induced by subway station construction was analyzed. The analysis results provides a reference for structure optimization design and scientific construction of similar deep foundation pit engineering.