Areas Of High Relief Research Articles

Observed Correlation Between Local Topography and Passive Neutron Measurements From the Dynamic Albedo of Neutrons (DAN) Instrument on the Mars Science Laboratory (MSL) Rover

AbstractThe Dynamic Albedo of Neutrons (DAN) instrument on the Mars Science Laboratory Curiosity rover primarily measures neutrons that have undergone interactions with rocks and materials in the rover's local environment. As the rover ascends Aeolis Mons, it may encounter more extreme local topography (e.g., cliffs, gullies, canyons). We present three parts of the rover's traverse in which local topography, expressed as the average local relief relative to the rover, is moderately to strongly correlated with an increase in passive thermal neutron count rates. These increases in count rates are consistent with results from radiation transport models of the instrument's performance near simulated topographic features. Additional DAN measurements in areas of high average local relief (>0.25 m) within 5 m of the instrument could bolster this correlation. DAN's sensitivity to topography in its passive mode could be utilized as a new measurement capability and has implications for the operation of future landed missions carrying neutron spectrometers (e.g., VIPER, MoonRanger, Lunar‐VISE).

Mines to moana: Hydrochemical legacies in a historically mined watershed

This study investigates contemporary freshwater contamination originating from old mine workings in the Thames-Coromandel region of Te Ika-a-Māui (North Island), Aotearoa New Zealand. We employed a multi-method approach, including stable H and O isotope determinations of surface water, geochemical modelling, and diffusive gradients in thin films (DGT) deployments. Atypically, spring-summer (Sept–Nov) surface water stable oxygen isotope ratios (δ18O) were negatively displaced from meteoric values (ca. −0.28 ± 0.13 ‰), indicating a remarkable degree of low-temperature water-rock interaction, likely enhanced by dry antecedent conditions. Isotope ratios in tributaries showed less alteration than the main stem, suggesting greater meteoric inputs and shorter residence times in areas of high topographic relief. Conversely, in the main stem, isotope ratios revealed higher mineral weathering, accompanied by elevated dissolved metal concentrations, consistent with dominant inputs from shallow groundwater. Weathering of primary sulfides contributed pronounced acidity in one tributary (pH ca. 3.8), but overall, carbonate buffering ameliorated acid mine drainage across the catchment (pH ca. 7–8). Nevertheless, our results confirm exceedances of ecological guideline values (>80% protection threshold) for several toxic metals including Al, Zn, Cd and Pb; with implications for fresh and coastal water quality in Tikapa Moana-o-Hauraki, the Firth of Thames.

Refined InSAR Mapping Based on Improved Tropospheric Delay Correction Method for Automatic Identification of Wide-Area Potential Landslides

Slow-moving landslides often occur in areas of high relief, which are significantly affected by tropospheric delay. In general, tropospheric delay correction methods in the synthetic-aperture radar interferometry (InSAR) field can be broadly divided into those based on external auxiliary information and those based on traditional empirical models. External auxiliary information is hindered by the low spatial–temporal resolution. Traditional empirical models can be adaptable for the spatial heterogeneity of tropospheric delay, but are limited by preset window sizes and models. In this regard, this paper proposes an improved tropospheric delay correction method based on the multivariable move-window variation model (MMVM) to adaptively determine the window size and the empirical model. Considering topography and surface deformation, the MMVM uses multivariate variogram models with iterative weight to determine the window size and model, and uses the Levenberg–Marquardt (LM) algorithm to enhance convergence speed and robustness. The high-precision surface deformation is then derived. Combined with hotspot analysis (HSA), wide-area potential landslides can be automatically identified. The reservoir area of the Baihetan hydropower station in the lower reaches of the Jinsha River was selected as the study area, using 118 Sentinel-1A images to compare with four methods in three aspects: corrected interferograms, derived deformation rate, and stability of time-series deformation. In terms of mean standard deviation, the MMVM achieved the lowest value for the unwrapped phase in the non-deformed areas, representing a reduction of 56.4% compared to the original value. Finally, 32 landslides were identified, 16 of which posed a threat to nearby villages. The experimental results demonstrate the superiority of the proposed method and provide support to disaster investigation departments.

Tectonic analysis of the Mula River Basin, Kirthar fold belt, Pakistan, using hypsometric index

The Mula River Basin is in an active tectonic region of the Kirthar fold fault belt in the Western Himalayas. The presence of numerous major faults like Chaman Fault, Kirthar Frontal Fault, and Bannh Fault near the study suggests complex tectonic processes in the region. The seismic record of the study area also indicates that this area is tectonically active. This makes the study area an ideal site to measure tectonic activity through geomorphic indices like hypsometric integrals (HI). For tectonic analysis of the Mula River Basin, we divided the study area into 309 subbasins. The results obtained from the HI calculations for the subbasins led us to the classification of the study area into three classes, i.e., class 1 (0.51–0.78), class 2 (0.37–0.50), and class 3 ([Formula: see text]), where class 1 is for the highest tectonic activity, class 2 responds to moderate, and class 3 is for the lowest tectonic activity. We calculated the hypsometric curves to understand the geomorphological cycle of the Mula River Basin. We quantified the subbasins of the Mula River Basin inside the highly active tectonic zone of Kirthar fold and fault zone as per their tectonic activity and found that a major portion of the study area indicates low tectonic activity (44.33%), medium tectonically active, and high tectonically active subbasins are 37.86% and 17.79%, respectively. These findings are supported by the presence of high-relief areas and known faults in the study area.

Improved efficient physics-based computational modeling of regional wave-driven coastal flooding for reef-lined coastlines

Coastal flooding affects low-lying communities worldwide and is expected to increase with climate change, especially along reef-lined coasts, where wave-driven flooding is particularly prevalent. However, current regional modeling approaches are either insufficient or too computationally expensive to accurately assess risks in these complex environments. This study introduces and validates an improved computationally efficient and physics-based approach to compute dynamic wave-driven regional flooding on reef-lined coasts. We coupled a simplified-physics flood model (SFINCS) with a one-dimensional wave transformation model (XBeach-1D). To assess the performance of the proposed approach, we compared its results with results from a fully resolving two-dimensional wave transformation model (XBeach-2D). We applied this approach for a range of storms and sea-level rise scenarios for two contrasting reef-lined coastal geomorphologies: one low relief area and one high relief area. Our findings reveal that SFINCS coupled with XBeach-1D generates flood extents comparable to those produced by XBeach-2D, with a hit rate of 92%. However, this method tends to underpredict the flood extent of weaker, high-frequency storms and overpredict stronger, low-frequency storms. Across scenarios, our approach overpredicted the mean flood water depth, with a positive bias of 7 cm and root mean square difference of 15 cm. Offering approximately 100 times greater computational efficiency than its two-dimensional XBeach counterpart, this flood modeling technique is recommended for wave-driven flood modeling in scenarios with high computational demands, such as modeling numerous scenarios or undertaking detailed regional-scale modeling.

The importance of terrain factors in the spatial variability of plant cover diversity in a steppe gully

Information about the slope angle and its exposure is often given when describing plant communities. However, the slope angle should be noted to affect a complex of different phenomena and processes. The slope angle affects the albedo and thermal regime of the soil. The slope angle affects the redistribution of moisture and determines the moisture availability of a particular area. The slope angle also determines the risks of erosion processes. In turn, erosion processes determine the depth of the soil layer and the content of organic matter in it, which greatly affects the conditions for plant life and their dynamics. Therefore, the slope angle of the relief is a complex environmental indicator, which is its most important weakness. The information on the slope angle of the relief surface does not indicate which environmental factor is limiting and determines the characteristics of the vegetation cover. Similarly, the quantitative orientation of a slope using rhumb lines is a rather crude way to indicate the role of terrain in the redistribution of solar energy. With a certain degree of accuracy, rhumbs characterize incoming solar radiation, but are not sensitive to estimating the amount of diffuse radiation. Modern geoinformation technologies make it possible to determine the amount of solar radiation reaching the terrain surface using a digital elevation model. The aim of the article was to identify the role of relief factors in terms of topographic wetness index, erosion index, and solar radiation in the spatial variability of the vegetation diversity of a steppe gully. There was no linear correlation between the other predictors. Some correlations can be interpreted as the result of certain nonlinear patterns. In this sense, the geomorphological predictors are mostly linearly independent and thus each of them carries independent information for characterizing environmental conditions. The vegetation cover of the gully system was represented by 263 plant species. The analysis of the synoptic phytosociological table allowed us to find out that the vegetation cover of the studied gully system is represented by six classes of vegetation. The geomorphological predictors allowed for a classification of vegetation types with an accuracy of 23.8% to 100%. The topographic wetness index was the most important for classification. Altitude and insolation were also important for classification (94 and 95 respectively). The topographic wetness index provided an accurate identification of wetland vegetation of the Phragmito-Magnocaricetea class. Naturally, this type of vegetation preferred biotopes with the highest level of soil moisture. High insolation accurately labeled the locations where Festuco-Brometea steppe vegetation was most likely to be found. Some of the artificial tree plantations that occurred in the thalweg of the gully can be clearly identified by the high level of the topographic wetness index. Another group of artificial tree plantations is located on relatively high relief areas and should be differentiated from Galio-Urticetea communities, which prefer locations with higher light levels, and from Molinio-Arrhenatheretea, which prefer locations with a higher risk of erosion. The most arid locations are preferred by Agropyretalia intermedio-repentis vegetation. Steppe and meadow vegetation located at altitudes less than 116 meters also differ in their preferred height. Steppe vegetation is usually located at a level higher than 95 meters. Natural steppe and meadow vegetation at elevations below 116 meters differs from semi-natural Galio-Urticetea vegetation in that the latter usually prefers more well lit locations. Steppe communities are misclassified as meadow in 15.3% of cases, and meadow is misclassified as steppe in 18.5% of cases. Artificial tree plantations are misclassified as steppe in 42.9% of cases and 14.3% are misclassified as Agropyretalia intermedio-repentis. In its turn, Agropyretalia intermedio-repentis is misclassified as Festuco-Brometea in 6.7% of cases, as Molinio-Arrhenatheretea or Onopordetalia acanthii in 3.3% of cases, and as Galio-Urticetea in 10.0% of cases. The Onopordetalia acanthii community was misclassified as Festuco-Brometea, Molinio-Arrhenatheretea and Galio-Urticetea in 6.7% of cases, respectively.

Oceanic Crust Formation in the Mid-Atlantic Ridge Segment between Azores and Icelandic Plumes: Results of Geological and Petrogeochemical Studies

The structure of the ocean floor and the composition of basalts and dolerites of the MAR segment between the Maxwell and Charlie Gibbs FZs (North Atlantic) were studied based on the data of the 53rd cruise of the R/V “Akademik Nikolaj Strakhov”. It was found that in this segment, along the spreading axis, areas of greater and lesser magmatic productivity alternate, which correspond to higher and lower bottom relief. In areas of high relief, spreading cells form in the axial zone, and rises of various nature dominate in the ridge zone: from tectonic to volcanic. In areas of low relief, the rift valley consists of deep rift basins, and low ridges are developed on the flanks, separated by wide depressions. Oceanic tholeites N, T and E-MORB are distinguished among the studied volcanites. The first of them are ubiquitous and were melted from mainly depleted mantle (source DM). Basalts and dolerites of E-MORB are found in areas of high relief. Their mantle substrate is formed by a mixture of DM and EM-2 material with the subordinate role of HIMU. T-MORB volcanites are mainly localized on large volcanic rises in the southern part of the studied MAR segment and were melted from a substrate formed by a mixture of DM and HIMU material with the subordinate role of EM-2. Two types of mantle inhomogeneities involved in melting are reconstructed: passive and active. The former are represented by blocks of the transformed continental lithosphere that are similar in composition to the EM-2 mantle source. Active inhomogeneities associate with the uplift near Maxwell FZ of the microplume of the enriched mantle with a composition close to HIMU and with its subaxial flow in the north direction up to the Charlie Gibbs FZ.

High-temporal-resolution of lithium isotopes in Yangtze River headwater: Hydrological control on weathering in high-relief catchments

How climate change regulates silicate weathering in tectonically active areas remains clear. To evaluate the roles of temperature and hydrology in continental-scale silicate weathering in high-relief catchments, we applied a high temporal resolution of lithium isotopes in the Yalong River, which drains the high-relief borders of the eastern Tibetan Plateau. The dissolved δ7Li values range from +12.2‰ to +13.7‰ in the non-monsoon season and are higher and significantly vary from +13.5‰ to +19.4‰ in the monsoon season. The negative correlation between dissolved δ7Li and the Li/Na ratio is attributed to the formation of various proportions of δ7Li-low secondary minerals during weathering. From non-monsoon to monsoon season, the weathering intensity decreases with increasing secondary minerals formation and the weathering transforms from a supply limited to a kinetically limited weathering regime, indicated by a negative correlation between dissolved δ7Li value and SWR/D ratio (SWR = silicate weathering rate and D = total denudation rate). No correlations between temperature and dissolved δ7Li values were observed, and SWR suggested that temperature is not the direct control factor of silicate weathering in high-relief areas. The dissolved δ7Li values display positive correlations with discharge, physical erosion rates (PERs), and SWR. This positive correlations was attributed to an increase in the PER which caused the formation of more secondary minerals with increasing discharge. These results indicate the rapid temporal variability of riverine Li isotopes and chemical weathering process in response to changes in hydrology rather than temperature. Combined with the compiled PER, SWR, and Li isotopes at various altitudes, we further suggest that weathering in high-altitude catchments is more sensitive to hydrological changes than weathering in low-altitude catchments. These results highlight the key role of the hydrologic cycle (runoff and discharge) and the geomorphic regime in controlling global silicate weathering.

Detection of Signal and Ground Photons From ICESat-2 ATL03 Data

The Advanced Topographic Laser Altimeter System (ATLAS) laser altimeter aboard the Ice, Cloud, and Land Elevation Satellite (ICESat-2) can measure the elevation of the Earth’s surface with unprecedented spatial detail. However, the quality of the derived signal and ground photons depends on the signal-to-noise ratio and canopy coverage. Current algorithms underperform for data collected during daytime over mountain areas with dense canopy. We demonstrate a novel procedure for signal photon detection and subsequent ground photon detection from ICESat-2 ATL03 data. We first introduce a gravity-based density model to characterize the anisotropic properties of photon distribution. Through jointly using the photon densities from the weak–strong beam pair, we are able to find key photons that have high probability being signals. A directional regional growing approach then takes these key photons as seeds to label all remaining signal photons. Finally, we introduce a weighted iterative median filter (WIMF) algorithm to identify ground photons whose height is closest to the estimated ground surface. A total of 36 ATL03 beams of two entire counties in USA are used for test and evaluation. Compared to the ATL03 and ATL08 algorithms, our signal photon finding method is more robust to the variation of topography, canopy coverage, and data collection time. Remarkably, the mislabeling caused by the after-pulsing effect does not present in our detected signal photons. Comparing current ATL03 and ATL08 products, the detected ground photons from our method are more consistent with reference to the 3DEP DEM, especially for strong beam data collected during daytime in dense canopy, high relief areas.

Covariate construction of nonconvex windows for spatial point patterns

In some standard applications of spatial point pattern analysis, window selection for spatial point pattern data is complex. Often, the point pattern window is given a priori. Otherwise, the region is chosen using some objective means reflecting a view that the window may be representative of a larger region. The typical approaches used are the smallest rectangular bounding window and convex windows. The chosen window should however cover the true domain of the point process since it defines the domain for point pattern analysis and supports estimation and inference. Choosing too large a window results in spurious estimation and inference in regions of the window where points cannot occur. We propose a new algorithm for selecting the point pattern domain based on spatial covariate information and without the restriction of convexity, allowing for better estimation of the true domain. Amodified kernel smoothed intensity estimate that uses the Euclidean shortest path distance is proposed as validation of the algorithm. The proposed algorithm is applied in the setting of rural villages in Tanzania. As a spatial covariate, remotely sensed elevation data is used. The algorithm is able to detect and filter out high relief areas and steep slopes; observed characteristics that make the occurrence of a household in these regions improbable. Keywords: Covariate, Euclidean shortest path, Nonconvex, Spatial point pattern, Window selection

Century-long multi-source analyses highlight decreasing vulnerability for a small, debris-covered and avalanche-fed glacier in the eastern Italian Alps

Small, debris-covered and avalanche-fed glaciers are widespread in high-relief areas of the world. However, their climatic response is poorly known because they cannot be investigated with ‘traditional’ techniques, like the glaciological mass-balance method, and long-term observations series are very rare. This work documents changes in elevation, mass balance rate and surface cover in the last century (from 1920 to 2020) for the small, debris-covered and avalanche-fed Montasio Glacier, where recent investigations show unusual response to climatic changes, but it is unclear whether this response is a short- or a long-term characteristic. Glacier response is analysed primarily through Digital Elevation Models reconstructed from different types of data sources (maps, terrestrial and aerial images, point clouds). Glacier changes are analysed jointly with trends in the most relevant climatic variables. The glacier experienced phases of rapid mass loss between 1920 and 1948 (−0.49 m w.e. y-1) and between 1982 and 2006 (−0.36 m w.e. y-1). Smaller imbalance occurred between 1948 and 1982 (−0.14 m w.e. y-1) and, remarkably, between 2006 and 2020 (−0.03 m w.e. y-1). Whereas the 1948–1982 was a favourable time-window for most glaciers in the Alps, the last fifteen years were characterized by rapid warming and show a clear divergence between the behaviour of the Montasio Glacier and of the rest of Alpine glaciers. A century-long increase in debris cover, now 2–3 m thick in the lower half of the glacier, explains largely this divergence. Snow-rich winters in recent years also played a role, because the glacier reacts sensitively to changes in solid precipitation. Even in the case of possible decreased snowfalls and increased melt associated with warming temperatures during the next decades, the glacier is not expected to vanish soon, because it will likely survive under a thick layer of debris and shadowed by the north walls of the Mount Jôf di Montasio. On the other hand, the results of this study, paired with the current distribution of permafrost in the study area, suggest that the Montasio Glacier will unlikely evolve into a rock glacier or a glacial-permafrost composite landform.

Regional assessment of gravity‐driven deformation offshore Namibia (West Africa)—Styles, distribution and controlling factors

AbstractThis paper presents a semi‐quantitative analysis of gravity‐driven deformation along the Namibian margin using extensive 2D depth converted seismic data. The geometries, internal characters and distribution of gravity‐driven systems were investigated through regional and detailed seismic studies. The research shows that surficial slumps are typically ca. 50 m thick and are characterised by contorted seismic facies commonly occurring along the slopes of the margin. They commonly funnel and cluster within high relief areas such as canyons and pre‐existing landslide scars. These contrast with coherent slides that are up to 2 km thick which extend laterally along the margin for tens to hundreds of kilometres. Slides preferentially occur in the proximal part of the margin and are constrained within the main margin depocenters. Here, high sedimentation rates and loading promote the generation of distinct, weak, overpressured layers that favour initiation of sliding of relatively coherent sediment masses. This research also shows that one‐third of volume of the post‐rift sediments on the Namibian margin were affected by slides and slumps. This demonstrates that gravity‐driven deformation is a key geological process that can strongly modify the evolution of rifted passive margins.

Experimental study on displacement of CH4 by liquid CO2 in coal seam

ABSTRACT Mine gas drainage is an important work in high gas outburst coal mines. How to improve the gas drainage concentration and drainage volume has always been the direction of exploration by coal mine technicians. In this paper, the experiment and field test of displacing CH4 with liquid CO2 were carried out. In the process of low temperature liquid CO2 phase transformation, a low stress and high permeability pressure relief area is formed in the coal and rock mass, so as to accelerate the free state of primary gas in coal and realize the intensified gas extraction of low-permeability coal seams. The results show that CH4 concentration and displacement efficiency in the displacement flow decrease at a greater rate and then stabilize; the cumulative CH4 displacement volume increases rapidly and stabilizes after reaching the critical time; the average concentration of gas drainage from single hole increases from 27.2% to 53.2%, and the gas drainage purity increases 2.3 times from 0.018 m3/min to 0.041 m3/min. The technology is simple to operate, does not produce high temperature and open flame, has the advantages of economy, safety, high efficiency and so on, it can be popularized and applied in gas mines.

Snow water equivalent change mapping from slope-correlated synthetic aperture radar interferometry (InSAR) phase variations

Abstract. Area-based measurements of snow water equivalent (SWE) are important for understanding earth system processes such as glacier mass balance, winter hydrological storage in drainage basins, and ground thermal regimes. Remote sensing techniques are ideally suited for wide-scale area-based mapping with the most commonly used technique to measure SWE being passive microwave, which is limited to coarse spatial resolutions of 25 km or greater and to areas without significant topographic variation. Passive microwave also has a negative bias for large SWE. Another method is repeat-pass synthetic aperture radar interferometry (InSAR) that allows measurement of SWE change at much higher spatial resolution. However, it has not been widely adopted because (1) the phase unwrapping problem has not been robustly addressed, especially for interferograms with poor coherence, and (2) SWE change maps scaled directly from repeat-pass interferograms are not an absolute measurement but contain unknown offsets for each contiguous coherent area. We develop and test a novel method for repeat-pass InSAR-based dry-snow SWE estimation that exploits the sensitivity of the dry-snow refraction-induced InSAR phase to topographic variations. The method robustly estimates absolute SWE change at spatial resolutions of < 1 km without the need for phase unwrapping. We derive a quantitative signal model for this new SWE change estimator and identify the relevant sources of bias. The method is demonstrated using both simulated SWE distributions and a 9-year RADARSAT-2 (C-band, 5.405 GHz) spotlight-mode dataset near Inuvik, Northwest Territories (NWT), Canada. SWE results are compared to in situ snow survey measurements and estimates from ERA5 reanalysis. Our method performs well in high-relief areas, thus providing complementary coverage to passive-microwave-based SWE estimation. Further, our method has the advantage of requiring only a single wavelength band and thus can utilize existing spaceborne synthetic aperture radar systems.

Insights from the topographic characteristics of a large global catalog of rainfall-induced landslide event inventories

Abstract. Landslides are a key hazard in high-relief areas around the world and pose a risk to populations and infrastructure. It is important to understand where landslides are likely to occur in the landscape to inform local analyses of exposure and potential impacts. Large triggering events such as earthquakes or major rain storms often cause hundreds or thousands of landslides, and mapping the landslide populations generated by these events can provide extensive datasets of landslide locations. Previous work has explored the characteristic locations of landslides triggered by seismic shaking, but rainfall-induced landslides are likely to occur in different parts of a given landscape when compared to seismically induced failures. Here we show measurements of a range of topographic parameters associated with rainfall-induced landslides inventories, including a number of previously unpublished inventories which we also present here. We find that the average upstream angle and compound topographic index are strong predictors of landslide scar location, while the local relief and topographic position index provide a stronger sense of where landslide material may end up (and thus where hazard may be highest). By providing a large compilation of inventory data for open use by the landslide community, we suggest that this work could be useful for other regional and global landslide modeling studies and local calibration of landslide susceptibility assessment, as well as hazard mitigation studies.

The Statherian Natividade Basin evolution constrained by U–Pb geochronology, sedimentology, and paleogeography, central Brazil

The tectonostratigraphic evolution of the intracontinental Natividade Basin is evaluated by zircon U/Pb analysis of one sample of acidic metavolcanic rock observed at the bottom of the depositional succession and three samples of metasedimentary rocks collected at different stratigraphic levels. The metavolcanic sample yielded a 1824 Ma zircon U–Pb age, and the youngest detrital zircon grains from the metasedimentary sequence resulted in a maximum depositional age of 1776 Ma for the paleobasin. The isotopic data associated with the analysis of stratigraphy, paleogeography, and sedimentary environments converge to the interpretation that the Natividade Group evolved from the late Paleoproterozoic (Statherian), possibly entering the early Mesoproterozoic. The sedimentation is interpreted to have occurred between the deposition of the Araí and the Traíras/Serra da Mesa groups. This understanding is due to the absence of continental sediments in the Natividade Basin (which could corroborate the correlation with the Araí Basin) and the absence of detrital zircon grains younger than 1.5 Ga (which would support the correlation with the Traíras/Serra da Mesa groups). The metavolcanic rocks are observed only locally and are interpreted as the result of melting by crustal rifting that was greatest in the south, related to the Araí Group, and decreased northwards of the study region. The mechanical subsidence responsible for the deposition of the Araí Group continental sediments was not observed in the Natividade Basin. The thermo-flexural subsidence responsible for the Natividade Basin evolution allowed the deposition of complex sedimentary environments related to mixed siliciclastic platforms and shallow water turbidite facies. Based on bibliographic studies and fieldwork data, our geological model suggests that the Almas Block was possibly a high paleorelief area, separating the Araí Basin to the south and the Natividade Basin to the north. This assertion is based on the following facts for the study area: i) there is no occurrence of the Veadeiros Supergroup sediments; ii) Nowadays in the region, there are many high relief areas related to quartzite layers and several granitic units that are resistant to denudation processes; iii) deposition of the shallow water turbidite present at the Natividade Group needed elevated source areas to control the sedimentation; iv) The predominance of carbonates and mass flow deposits in the southern portion of Natividade Group, near to Almas Block, suggests a lower depth of the sea to the south of the basin. Further north, the predominance of fine-grained terrigenous deposits suggest a deeper basin; v) it is common in rift-sag environments the preservation of elevated blocks as an isostatic compensation mechanism. The integrated analysis conducted allowed the following conclusions: the Natividade Basin evolution is not coeval with the Araí or the Traíras/Serra da Mesa basins and is classified as a sag-type basin in which the sedimentary environments resulted in massive carbonate accumulation in a complex platform controlled by the basement paleorelief.

The impact of rainfall distribution methods on streamflow throughout multiple elevations in the Rocky Mountains using the APEX model-Price River watershed, Utah.

The hydrology of mountainous watersheds in the western United States is significantly influenced by snow year-round. It is widely known that topography affects precipitation; however, the knowledge of how watershed rainfall designation methods affect streamflow is not well understood for high-relief areas. The objectives of this study were to assess the predictive capability of the Agricultural Policy/Environmental eXtender (APEX) model to simulate streamflow in a snowmelt-dominated watershed with high spatial rainfall variability through (a) allocating weather stations to sub-basins based on a conventional Thiessen polygon method (CM) or a rainfall-elevation-based input (RE) and using an areal average Parameter-Elevation Regression on Independent Slopes Model (PRISM) rainfall designation and (b) improving the snowmelt processes in the Price River watershed, Utah. The updated APEX model with snowmelt parameters significantly improved spring flood simulation. The RE was the most robust method in snowmelt and seasonal streamflow simulations compared with the CM and PRISM rainfall designations. Adapting the APEX model to simulate snow-dominant complex terrains will provide crucial water quantity and quality predictions for reliable environmental and watershed management assessment.

Analysis of Hillslope Erosion Based on Excess Topography in Southeastern Tibet

The southeastern Tibetan Plateau has been deeply dissected by major rivers and their tributaries into high-relief topography with deep gorges. In this region, most hillslope gradients in the high-relief areas approach a threshold value, and landslides are the dominant surface erosion process. For this work, we analyzed the hillslope erosion process by determining the excess topography from the threshold hillslope. Slope analysis found a similar normal distribution of slope values for six large drainage basins with different lithology, precipitation, and tectonic settings. Overall, 82% of the slopes in our study area were 30 ± 5°, so this was taken as a reasonable range of threshold hillslope angles. We determined that the excess topography calculated for different threshold values all occur along major fluvial inner gorges. We found a linear relationship between excess topography and the mean erosion rate in drainage basins, which indicates that hillslope erosion, especially landslides, is the main erosion process. In contrast, the correlation between excess topography and the slope is only found for low-relief topography. This suggests that excess topography is a better metric than the slope to reflect the spatial distribution of erosion rates in the southeastern Tibetan Plateau. In addition, for a threshold value of 30°, we collected data from 4,430 landslides and found that 71% of these landslides had occurred in an area of excess topography. This implies that most recent landslides did not reduce the slope below the threshold value. As a result, the potential for future landslides remains high in areas where landslides have recently occurred.

Altitude isotope effects in Mediterranean high-relief terrains: a correction method to utilize stream water data

ABSTRACT Quantification of the isotope altitude effect from precipitation allows the identification of recharge altitudes in high-relief areas. However, steep terrains frequently limit the use of this precipitation-based approach. Perennial rivers often provide easy, year-round access for water sampling. However, in high-relief regions rivers may not adequately represent regional precipitation isotope patterns because they integrate isotope signals along their course. This prevents the calculation of an altitudinal isotope gradient from river water samples alone. We present a study that shows how a river-based sampling approach served to determine the altitude effect. Replacing the original sample site altitude with the mean upstream catchment elevation as calculated from a digital elevation model allowed us to establish a plausible altitude isotope effect from stream water. The correction approach was verified independently using precipitation isotope data. This approach can potentially be transferred to other regions where precipitation sampling at various elevations is difficult to determine.

Reconstructing the tectono-sedimentary evolution of the Early–Middle Jurassic Tlaxiaco Basin in southern Mexico: New insights into the crustal attenuation history of southern North America during Pangea breakup

Abstract During Pangea breakup, several Jurassic extensional to transtensional basins were developed all around the world. The boundaries of these basins are major structures that accommodated continental extension during Jurassic time. Therefore, reconstructing the geometry of Jurassic basins is a key factor in identifying the major faults that produced continental attenuation during Pangea breakup. We reconstruct the tectono-sedimentary evolution of the Jurassic Tlaxiaco Basin in southern Mexico using sedimentologic, petrographic, and U-Pb geochronologic data. We show that the northern boundary of the Tlaxiaco Basin was an area of high relief composed of the Paleozoic Acatlán Complex, which was drained to the south by a set of alluvial fans. The WNW-trending Salado River–Axutla fault is exposed directly to the north of the northernmost fan exposures, and it is interpreted as the Jurassic structure that controlled the tectono-sedimentary evolution of the Tlaxiaco Basin at its northern boundary. The eastern boundary is represented by a topographic high composed of the Proterozoic Oaxacan Complex, which was exhumed along the NNW-trending Caltepec fault and was drained to the west by a major meandering river called the Tlaxiaco River. Data presented in this work suggest that continental extension during Pangea breakup was accommodated in Mexico not only by NNW-trending faults associated with the development of the Tamaulipas–Chiapas transform and the opening of the Gulf of Mexico, but also by WNW-trending structures. Our work offers a new perspective for future studies that aim to reconstruct the breakup evolution of western equatorial Pangea.