Broad Valley Research Articles

Regional Structural Analysis and Reinterpretation in the Bonai-Keonjhar Belt, Singhbhum Craton: Implication for Revision of the Lithostratigraphic Succession

Abstract: The Mesoarchaean Iron Ore Group (IOG) of rocks in Bonai-Keonjhar belt is disposed in a horseshoe shaped synclinorium structure in the western part of the Singhbhum Craton. Morphology of this synclinorium is expressed by a near continuous western ridge and dissected eastern highlands with the broad Jamda-Koira valley at the centre. Detailed structural analysis in the northern part of the belt suggests that the synclinorium is in fact a series of NE-SW to NNESSW trending shallow plunging, second generation (D2) syncline and anticline which have overturned, inclined, relatively tight geometry in the western part and upright, open to gentle in the eastern part. This structure is clearly manifested by synclinal ridges and anticlinal valleys. Evidence of an early deformational event (D1) manifested by the presence of isoclinal folds on outcrop scale has been recorded. D1 and D2 are near co-axial. The last deformational event (D3) has led to dome and basin interference pattern due to cross folding along NW-SE striking axial planes. The volcano-sedimentary package in the belt commenced with platformal package represented by basic volcanic-quartzite association. The Bonai range volcanic, Nuakot volcanic and the Jagannathpur volcanic occurring in the western, southern and eastern parts of the belt has been interpreted to be correlatable representing the basal volcanic suite. The linear body of basic volcanic occurring at the central part of the belt is found to be occupying the core part of a shallow plunging anticlinal axial trace and thus has also been equated with the basal volcanic suite. There is but only one major BIF horizon in the Bonai-Keonjhar belt which has been structurally repeated across the belt, BIF occurring as NNE-SSW trending synclinal ridges flanked on either side by the older phyllitic sequences.

Post-fire response of riparian vegetation in a heavily browsed environment

Severe wildfires infrequently occur in large heterogeneous riparian valleys. Riparian areas may affect fire behavior and the pattern of burning due to saturated soils and patchy fuels that may have high moisture content in live and dead stems. We examined the effects of a severe fire on the dominant riparian vegetation: thin-leaf alder, river birch and willow, in a broad riparian valley in Rocky Mountain National Park, CO, USA. We mapped the canopy stem mortality and basal resprouting of 4507 first year post fire and 643 second year post fire individuals that had been the dominant woody canopy. To examine the effect of herbivory on resprouting willow stems, we established a paired experiment with 22 willows exclosed in cages to prevent browsing and 22 uncaged control plants. Aerial seed rain sticky traps were established on transects throughout the study area and pre-fire seed rain density was compared with post-fire seed rain densities.Fire effects on willow were severe, with 91% of individuals having complete canopy loss. Fifty-one percent of thin-leaf alder individuals and 71% of river birch individuals also had complete canopy loss. Seventy-four percent of river birch, 45% of willow and 35% of thin-leaf alder resprouted from the base in the first summer post fire. In the second year post fire, 84% of river birch, 62% of thin-leaf alder and 55% of willow had resprouted. Willows inside exclosures had greater biomass at the end of the growing season compared with willows outside exclosures. Summer browsing resulted in significantly lower willow biomass compared with exclosed plants and the additive effect of summer and winter browsing resulted in control plants having 64% reduction in biomass. Post-fire aerial seed rain was 90% lower than pre-fire densities.Fire dramatically altered the riparian vegetation. Willow seed rain was nearly eliminated because most stems were killed by fire. Resprouting woody riparian vegetation was prevalent however, ungulate browsing of the resprouting willow stems could limit the regrowth of a tall willow riparian overstory.

The Use of GIS for Evaluating Areas From Someş Mic Meadow Affected by Excess Moisture

The area taken into study is located in the Transylvanian-SomeAŸ depression which is individualized compared to the surrounding regions from the morphological point of view, with hills and broad valleys accompanied by terraces. In lithological terms, there are present the sedimentary rocks, especially clays, marls, sands, sandstones and limestones. The area has a relatively dense population and has many settlements, roads, crops, etc. The main objective of this work is the use of geographic information systems to obtain a comprehensive database to assist in the creation of thematic maps of the SomeAŸ Mic floodplain (drainage direction map, soil map etc.), maps that are useful in agriculture and can be continually updated to reflect the current situation in the field. In order to obtain these thematic maps was necessary to create the primary database by entering the data into the computer from existing cartographic products. These data were entered in numerical form by scanning them at the specific scale. The data necessary for creating these thematic maps were collected from topographic maps, soil maps and the geological map containing the area of interest. For achieveing the objectives of this paper were conducted the following steps: making the spatial support through scanning, georeferencing spatial support, vectorization of the spatial support, creating the alphanumeric database and at the end elaborating thematic maps for the area thaken into study.

PLEISTOCENE HUMAN OCCUPATION AT BEGINNERS LUCK CAVE, FLORENTINE VALLEY, TASMANIA

EVIDENCE of human occupation dated at approximately 20,000 years BP is recorded from a cave site in the Florentine Valley in south central Tasmania. The artifact assemblage and faunal content are described and the factors giving rise to bone accumulation are examined. Occupation has been dated by 14C analysis of associated charcoal and aspartic acid racemization dating of bone with close agreement between the two methods. The interior river valleys of southern Tasmania were being utilized by hunter-gatherers when the Last Glacial was reaching its climax and Tasmania was a peninsula of the Australian mainland. Suggestions by recent authors that late Pleistocene occupation was tightly coastal and that the interior was uninhabited are refuted. Under the open vegetation conditions prevailing during the late Pleistocene the broad river valleys of southern Tasmania provided easy routes for population movement and a suitable environment for game. In contrast dense wet forest was the dominant vegetation throughout the Holocene making these areas less attractive for both human occupation and the larger elements of the fauna.

Pseudovertical Temperature Profiles in a Broad Valley from Lines of Temperature Sensors on Sidewalls

AbstractPseudovertical temperature “soundings” from lines of inexpensive temperature sensors on the sidewalls of Utah’s Salt Lake valley are compared with contemporaneous radiosonde soundings from the north, open end of the valley. Morning [0415 mountain standard time (MST)] soundings are colder, and afternoon (1615 MST) soundings are warmer than radiosonde soundings because of warm and cold boundary layers that form over the slopes. Cross-valley temperature differences occur between east- and west-facing sidewalls because of differing insolation. Differences in vertically averaged pseudovertical and radiosonde temperatures are generally within 1°C, with a standard deviation of 2°–3°C. The pseudovertical soundings are especially good proxies for radiosondes in winter. The sounding comparisons identified along-valley differences in temperature, inversion depth, and lapse rate that have led to hypotheses concerning their causes, to be evaluated with future research. The low cost and much better time resolution of the pseudovertical soundings suggest that such lines will be a useful supplement to valley radiosondes and will have significant operational advantages if available in real time. Lines of surface-based sensors will prove useful in identifying intravalley meteorological differences and may be used to estimate free-air temperature structure in other valleys where radiosondes are unavailable.

Detection of hail signatures from single-polarization C-band radar reflectivity

Five different criteria that estimate hail signatures from single-polarization radar data are statistically evaluated over a 15-year period by categorical verification against loss data provided by a building insurance company. The criteria consider different levels or thresholds of radar reflectivity, some of them complemented by estimates of the 0°C level or cloud top temperature. Applied to reflectivity data from a single C-band radar in southwest Germany, it is found that all criteria are able to reproduce most of the past damage-causing hail events. However, the criteria substantially overestimate hail occurrence by up to 80%, mainly due to the verification process using damage data. Best results in terms of highest Heidke Skill Score HSS or Critical Success Index CSI are obtained for the Hail Detection Algorithm (HDA) and the Probability of Severe Hail (POSH). Radar-derived hail probability shows a high spatial variability with a maximum on the lee side of the Black Forest mountains and a minimum in the broad Rhine valley.

Temperature dependence of Young׳s modulus of silica refractories

The temperature dependence of Young׳s modulus of silica refractories exhibiting pore volume fractions in the range 18.6–20.9% is investigated via impulse excitation up to 800–1000°C and four-point bending up to 500°C. This temperature dependence exhibits a broad valley approximately below 200°C, where Young׳s modulus values decrease to 55–62% of their room temperature magnitude. Upon further heating, Young׳s modulus increases steeply within a few degrees around 230°C, followed by an S-shaped increase to maximum values corresponding to 174–282% of the room temperature values. Cooling branches are different from heating branches and do not form closed loops, indicating damage accumulation. Dilatation measurements, polarization microscopy, micromechanical calculations and X-ray phase analysis are used to underpin the conclusion that the observed elastic effects are not caused by phase transitions alone, but are combined effects of phase transitions and microcrack opening and partial closure.

Controls on Temperature in Salmonid‐Bearing Headwater Streams in Two Common Hydrogeologic Settings, Kenai Peninsula, Alaska

AbstractHeadwater streams are the most numerous in terms of both number and length in the conterminous United States and play important roles as spawning and rearing grounds for numerous species of anadromous fish. Stream temperature is a controlling variable for many physical, chemical, and biological processes and plays a critical role in the overall health and integrity of a stream. We investigated the controls on stream temperature in salmon‐bearing headwater streams in two common hydrogeologic settings on the Kenai Peninsula, Alaska: (1) drainage‐ways, which are low‐gradient streams that flow through broad valleys; and (2) discharge‐slopes, which are high gradient streams that flow through narrow valleys. We hypothesize local geomorphology strongly influences surface‐water and groundwater interactions, which control streamflow at the network scale and stream temperatures at the reach scale. The results of this study showed significant differences in stream temperatures between the two hydrogeologic settings. Observed stream temperatures were higher in drainage‐way sites than in discharge‐slope sites, and showed strong correlations as a continuous function with the calculated topographic metric flow‐weighted slope. Additionally, modeling results indicated the potential for groundwater discharge to moderate stream temperature is not equal between the two hydrogeologic settings, with groundwater having a greater moderating effect on stream temperature at the drainage‐way sites.

Mission and Modern Citrus Species Diversity of Baja California Peninsula Oases

The spring-fed mission oases of the Baja California peninsula, Mexico, hold several species, varieties and unique hybrids of heritage citrus, which may represent valuable genetic resources. Citrus species first arrived to the peninsula with the Jesuit missionaries (1697-1768), and new varieties were introduced during the colonial and rancho periods following the mission era. These heritage trees are grown in field and house gardens as ornamental, fruit and shade trees. Commercial citrus varieties introduced from the United States have become a strong source of economic revenue for peninsula agriculturalists. A few of the peninsula oases support commercial citrus groves, though these are primarily found in the broader valleys of the peninsula where groundwater is tapped for irrigation. The isolated environments of the mission oases and surrounding ranches have facilitated propagation of unique citrus types, and these have stabilized through integration into the cultural practices of the region. We identify and document citrus of the peninsula oases to serve as a baseline for those interested in the cultural ecology of citrus and citrus genetic resources.

Nocturnal wind‐directional shear in complex terrain

In the weak‐wind nocturnal boundary layer, the wind direction near the surface may vary substantially with height. The directional shear is caused by transient modes and shallow, terrain‐induced motions. This study examines the large directional shear for nocturnal data collected in the lowest 10 m from three field programs. The directional shear in two broad valleys with high sidewalls is dominated by transient motions within the valley cold pool. In contrast, the directional shear within a shallow narrow valley is dominated by terrain‐induced down‐valley drainage flows, in spite of the fact that the magnitude and height of the valley sidewalls are much smaller than the other two valleys. The relative contribution of the directional shear to the total vector shear is examined as a function of wind speed and stability.

Sample Skewness as a Statistical Measurement of Neuronal Tuning Sharpness

We propose using the statistical measurement of the sample skewness of the distribution of mean firing rates of a tuning curve to quantify sharpness of tuning. For some features, like binocular disparity, tuning curves are best described by relatively complex and sometimes diverse functions, making it difficult to quantify sharpness with a single function and parameter. Skewness provides a robust nonparametric measure of tuning curve sharpness that is invariant with respect to the mean and variance of the tuning curve and is straightforward to apply to a wide range of tuning, including simple orientation tuning curves and complex object tuning curves that often cannot even be described parametrically. Because skewness does not depend on a specific model or function of tuning, it is especially appealing to cases of sharpening where recurrent interactions among neurons produce sharper tuning curves that deviate in a complex manner from the feedforward function of tuning. Since tuning curves for all neurons are not typically well described by a single parametric function, this model independence additionally allows skewness to be applied to all recorded neurons, maximizing the statistical power of a set of data. We also compare skewness with other nonparametric measures of tuning curve sharpness and selectivity. Compared to these other nonparametric measures tested, skewness is best used for capturing the sharpness of multimodal tuning curves defined by narrow peaks (maximum) and broad valleys (minima). Finally, we provide a more formal definition of sharpness using a shape-based information gain measure and derive and show that skewness is correlated with this definition.

Relaciones suelo-vegetación en una toposecuencia del Escudo Guayanés, Venezuela

The Guayana Shield is one of the oldest territories in the planet and has millions of years subjected to leaching and erosion processes that produce oligotrophic soils. This scarcity of nutrients has not avoided the development of high, diverse and magnificent forests, where plants have adaptations to survive these difficult conditions. The aim of this work was to characterize the physical and chemical parameters of the soils in different forest communities of the Imataca Forest Reserve (IFR), to establish some interpretations on their origin, and some relationships between the edaphic components and the inhabitant species. Terrestrial journeys were carried out and two pathways were traced for the interpretation of forest communities. In each community, three plots (100m x 100m) for the ecological survey were established. In each plot, all trees, palms, and lianas were measured (dbh> or =10cm; dbh: diameter at breast height); four 10m x 10m understory sub-plots were evaluated, and a census of all the spermatophyta species (dbh< 10cm) was made. Soils were evaluated by means of a trial pit in each community, and a bore in each one understory sub-plot. The obtained data were analyzed by both a detrended and a canonical correspondence analysis. Results from a total of 15 plots allowed us to identify three communities: a forest dominated by Mora excelsa located in a narrow valley with high content of silt; a swamp forest dominated by Catostemma commune in a sandy broad valley, and a forest in clay hills dominated by Alexa imperatricis. Most of the soils had a pH between 3.1 and 4.5. Nutrients were in very low concentrations (N: 0-0.2%; P: 0-14ppm; K: 0-0.3 Cmol/kg) and A1 in toxicity quantities. We observed that Ca/A1 relationship greater than 1 meant a neutralization of the toxic effect of Al. Besides, basal area ranged from 20.4 to 32.3m2/ha; the highest level (top local forest development) corresponded with the C. commune community with a Ca/A1 value of 2.5. This research found an adequate relationship between soil and vegetation, as it was able to identify three communities into three distinct soil conditions. Nevertheless, edaphic constraints indicated that high forest cover must be maintained as an essential element for the conservation of these communities.

Late Quaternary deformation features along the Anninghe Fault on the eastern margin of the Tibetan Plateau

On the eastern margin of the Tibetan Plateau, the Anninghe, Zemuhe and Xiaojiang faults comprise a N–S-trending active left-lateral fault system extending more than 700km. The northernmost Anninghe Fault extends for ∼200km, consisting of two sub-parallel N–S trending strands. Along the western strand, the fault traces occur almost strictly along the broad and flat Anninghe valley, displacing high terraces, alluvial fans and tributary channels of the Anninghe River. The eastern strand, on the other hand, cuts through the steep mountain slopes, with prominent rectilinear upslope-facing scarps and shutter ridges against pounded fluvial sediments from the east. The displacements along the eastern strand are much larger than that along the western strand, indicating the eastern strand is the major fault absorbing the E–W shortening. This study demonstrates that the Anninghe Fault is now acting as a relief-building boundary fault and absorbing the E–W compression under the eastwards motion of the Tibetan Plateau. Accordingly, the Anninghe region is a topographic transition area from steep relief to low gradient topography. The variation in topographic gradient is consistent with the differing tectonic regime between southern and northern parts of the Tibetan Plateau.

Isotopes as Tracers of Water Origin in and Near a Regional Carbonate Aquifer: The Southern Sacramento Mountains, New Mexico

High-elevation groundwater sampled in 2003 in the Sacramento Mountains defines a line resembling an evaporation trend in δD-δ18O space. The trend results from recharge of winter precipitation into fractured limestone, with evaporation prior to recharge in broad mountain valleys. The same trend occurs in basin groundwater east and west of the range, indicating the high Sacramento Mountains as the principal regional water source, either direct from the limestone aquifers or from mountain-derived surface water. Tritium and carbon-14 indicate bulk residence times of a few decades in the high Sacramento Mountains and at Alamogordo, and of thousands of years south of Alamogordo and in the artesian aquifer near Artesia. Stable O, H isotope data fail to demonstrate the presence of Sacramento Mountains water in a saline aquifer of the Hueco Bolson (Texas).

Landscapes of Santa Rosa Island, Channel Islands National Park, California

Abstract. Santa Rosa Island (SRI) is the second-largest of the California Channel Islands. It is one of 4 east—west aligned islands forming the northern Channel Islands chain, and one of the 5 islands in Channel Islands National Park. The landforms, and collections of landforms called landscapes, of Santa Rosa Island have been created by tectonic uplift and faulting, rising and falling sea level, landslides, erosion and deposition, floods, and droughts. Landscape features, and areas delineating groups of related features on Santa Rosa Island, are mapped, classified, and described in this paper. Notable landscapes on the island include beaches, coastal plains formed on marine terraces, sand dunes, and sand sheets. In this study, the inland physiography has been classified into 4 areas based on relief and degree of fluvial dissection. Most of the larger streams on the island occupy broad valleys that have been filled with alluvium and later incised to form steep- to vertical-walled arroyos, or barrancas, le...

Landscape evolution during the late Quaternary at the Doce River mouth, Espírito Santo State, Southeastern Brazil

The sedimentary deposits of the deltaic plain of the Doce and Barra Seca rivers, Southeastern Brazil, were studied by facies analysis, pollen records, δ13C, C/N analysis and AMS 14C-dating. Today, this deltaic plain is dominated by beach ridges and sandy terraces occupied by arboreal and herbaceous vegetation. Between ~47,500 and ~29,400calyrB.P., a deltaic system was developed in response mainly to eustatic sea-level fall. Although the studied stratigraphic succession is compatible with the trend of global sea-level fall, the earlier sea-level suggested by the topographic position of these deltaic deposits was above the one expected during the MIS3 stage. A tectonic uplift likely occurred during the late Quaternary and raised these deposits. The post-glacial sea-level rise caused a marine incursion with invasion of embayments and broad valleys, and it favored the evolution of an estuary with wide tidal mud flats occupied by mangroves between ~7400 and ~5100calyrB.P. The high river sand supply and/or the relative sea-level fall in the late Holocene led to seaward and downward translation of the shoreline during normal/forced regression, producing progradational deposits with shrinkage of mangrove stands and expansion of marshes colonized by herbaceous vegetation. Therefore, the stratigraphic architecture and evolution of the Doce River deltaic plain suggest that fluvial sediment supply and relative sea-level fluctuations related to Quaternary global climatic changes and local tectonism exerted major controls on sedimentation through the variation of accommodation space and base-level changes.

Hydrochemistry and sediment characteristics of polar periglacial lacustrine environments on Fisher Island and Broknes Peninsula, East Antarctica

Fisher Island and Broknes Peninsula in the Larsemann Hills constitute part of a polar lowland periglacial environment between marine and glacial ecosystems. The landscape is characterized by gently rolling hills and broad valleys interspersed with lakes formed in glacially scoured basins. We analyzed the physicochemical parameters and the ionic constituents of water samples from 10 lakes in each of these two locations. Our results showed considerable differences between the two regions and demonstrated the influence of lithology and processes including weathering, evaporation, and atmospheric precipitation. All major cations and anions in the lake waters showed positive correlations indicating balanced ionic concentrations. Unconsolidated sediments were sparsely distributed and scattered over glacial deposits, valley fills, and occasional moraine ridges. The type and rate of sedimentation was mainly controlled by surface run-off and aeolian influx. The sediment samples from lake beds and the catchment area on Fisher Island were immature and poorly to very poorly sorted, consisting of gravelly sand with negligible silt and finer fractions. Sediments had a polymodal grain size distribution with the two major populations lying between -2 and -1 phi and between 0 and 1.5 phi. The sediments were lithic arenite to arkosic in composition and the microtextures imprinted over quartz grains were dominated by mechanical textures resulting from several stages of glacial crushing and grinding. The presence of deep dissolution cavities, cryptocrystalline precipitation, and euhedral crystal growth signified the effect of chemical activity after the deposition of grains in the lacustrine environment.

Using river long profiles and geomorphic indices to evaluate the geomorphological signature of continental scale drainage capture, Duero basin (NW Iberia)

Well-constrained case studies of transient landscape responses are needed to improve our understanding of erosion processes associated with drainage captures. The Duero basin is an excellent location for such a study because the landscape is currently undergoing pronounced geomorphological changes resulting from the opening of a former closed drainage. The present-day continental interior basin (>50,000km2) drains to the Atlantic Ocean via the Duero River, but during the Cenozoic the basin experienced a long endorheic period marked by the formation of evaporites. Currently, the entire continental interior is an area of relative tectonic quiescence, characterised by a relict low-relief upland topography (Meseta). Systematic variations in lithology and a well-constrained tectonic setting throughout the basin and adjacent areas allow for the comparison of channel morphology between the Cenozoic Duero basin and its western fringe. To explore the signal of transient geomorphic response to capture and opening of the former endorheic basin, the main channel and 24 tributaries were analysed in terms of their longitudinal profiles and the application of geomorphic indices (concavity index [Ci], valley floor width-to-height ratio [Vf], and stream-length gradient index [SL]). The analysis reveals two zones with distinctive morphologies: (1) an upper reach domain consisting of broad flat valleys and low-gradient streams where concave longitudinal profiles dominate and (2) a middle reach domain characterised by steep, deeply incised canyons where a convex long profile dominates marking a major kinckzone. The quantitative information on channel shapes and long profile geometries allows the interpretation of these patterns in terms of driving forces for fluvial landscape development. Large-scale morphometric analysis highlights the transient response of the entire basin to a capture-related base level lowering and illustrates the importance of drainage captures as potential internal drivers of landscape modification and topographic adjustments. Furthermore, the Duero basin case study also emphasises that well-constrained bedrock geology and tectonic patterns are essential to avoid misinterpretation of geomorphic indexes.

The Two Approaches of Surface-Texture Optimization in Thin-Film Silicon Solar Cells

Textured interfaces in thin-film silicon solar cells can increase the photocurrent of the devices. However, the challenge is how to design textures (periodic or random) that could outperform the state-of-the-art random ones. Moreover, the textures should enable defect-less semiconductor layer growth, which has often been neglected in the past, resulting in the low open-circuit voltage and fill factor of the devices. In this paper, we present two approaches for the systematic optimization of surface-textures: bottom-up and top-down. Fully 3-D optical simulations, including calibrated nonconformal layer growth model were employed to predict gains in short-circuit current densities in a micromorph solar cell (bottom-up approach) and a single-junction amorphous silicon solar cell (top-down approach). In the bottom-up approach, we start with a simple sinusoidal component and change its shape systematically in the direction of broader valleys, also resulting in better conditions for the layer growth. In the top-down approach, we start from a random texture (morphology fingerprint taken from Asahi U type substrate) and modify it in a spatial frequency domain. We show the role of the presence/absence of different frequency regions as well as the important role of the phase spectrum on the optical characteristics of the device. In both approaches, improved textures have the potential to outperform state-of-the-art random ones, not only from optical point of view but in terms of conversion efficiency as well.

Ultra high energy neutrinos: absorption, thermal effects and signatures

We study absorption of ultra high energy neutrinos by the cosmic neutrino background, with full inclusion of the effect of the thermal distribution of the background on the resonant annihilation channel. For a hierarchical neutrino mass spectrum (with at least one neutrino with mass below ∼ 10−2 eV), thermal effects are important for ultra high energy neutrino sources at z≳16. The neutrino transmission probability shows no more than two separate suppression dips since the two lightest mass eigenstates contribute as a single species when thermal effects are included. Results are applied to a number of models of ultra high energy neutrino emission. Suppression effects are strong for sources that extend beyond z ∼ 10, which can be realized for certain top down scenarios, such as superheavy dark matter decays, cosmic strings and cosmic necklaces. For these, a broad suppression valley should affect the neutrino spectrum at least in the energy interval 1012−1013 GeV — which therefore is disfavored for ultra high energy neutrino searches — with only a mild dependence on the neutrino mass spectrum and hierarchy. The observation of absorption effects would indicate a population of sources beyond z ∼ 10, and favor top-down mechanisms; it would also be an interesting probe of the physics of the relic neutrino background in the unexplored redshift interval z ∼ 10–100.