Mountain Block Research Articles

Sensitivity of Simulated Mountain Block Hydrology to Subsurface Conceptualization

AbstractMountain block systems are critical to water resources and have been heavily studied and modeled in recent decades. However, due to lack of field data, there is little consistency in how models represent the mountain block subsurface. While there is a large body of research on subsurface heterogeneity, few studies have evaluated the effect that common conceptual choices modelers make in mountainous systems have on simulated hydrology. Here we simulate the hydrology of a semi‐idealized headwater catchment using six common conceptual models of the mountain block subsurface. These scenarios include multiple representations of hydraulic conductivity decaying with depth, changes in soil depth with topography, and anisotropy. We evaluate flow paths, discharge, and water tables to quantify the impact of subsurface conceptualization on hydrologic behavior in three dimensions. Our results show that adding higher conductivity layers in the shallow subsurface concentrates flow paths near the surface and increases average saturated flow path velocities. Increasing heterogeneity by adding additional layers or introducing anisotropy increases the variance in the relationship between the age and length of saturated flow paths. Discharge behavior is most sensitive to heterogeneity in the shallow subsurface layers. Water tables are less sensitive to layering than they are to the overall conductivity in the domain. Anisotropy restricts flow path depths and controls discharge from storage but has little effect on governing runoff. Differences in the response of discharge, water table depth, and residence time distribution to subsurface representation highlight the need to consider model applications when determining the level of complexity that is needed.

Habitat requirements affect genetic variation in three species of mayfly (Ephemeroptera, Baetidae) from South Africa.

This study investigates genetic diversity in three species of Ephemeroptera, one eurytopic and therefore widespread (Afroptilum sudafricanum) and two stenotopic and thus endemic (Demoreptus natalensis and Demoreptus capensis) species, all of which co-occur in the southern Great Escarpment, South Africa. Mitochondrial DNA was analysed to compare the genetic diversity between the habitat generalist and the two habitat specialists. Afroptilum sudafricanum showed no indication of population genetic structure due to geographic location, while both Demoreptus species revealed clear genetic differentiation between geographic localities and catchments, evident from phylogenetic analyses and high FST values from AMOVA. In addition, the phylogenetic analyses indicate some deeper haplotype divergences within A. sudafricanum and Demoreptus that merit taxonomic attention. These results give important insight into evolutionary processes occurring through habitat specialisation and population isolation. Further research and sampling across a wider geographic setting that includes both major mountain blocks of the Escarpment and lowland non-Escarpment sites will allow for refined understanding of biodiversity and associated habitat preferences, and illuminate comparative inferences into gene flow and cryptic speciation.

Morphological comparison of blocks in chaos terrains on Pluto, Europa, and Mars

Chaotic terrains are characterized by disruption of preexisting surfaces into irregularly arranged mountain blocks with a “chaotic” appearance. Several models for chaos formation have been proposed, but the formation and evolution of this enigmatic terrain type has not yet been fully constrained. We provide extensive mapping of the individual blocks that make up different chaos landscapes, and present a morphological comparison of chaotic terrains found on Pluto, Jupiter's Moon Europa, and Mars, using measurements of diameter, height, and axial ratio of chaotic mountain blocks. Additionally, we compare mountain blocks in chaotic terrain and fretted terrain on Mars. We find a positive linear relationship between the size and height of chaos blocks on Pluto and Mars, whereas blocks on Europa exhibit a flat trend as block height does not generally increase with increasing block size. Block heights on Pluto are used to estimate the block root depths if they were floating icebergs. Block heights on Europa are used to infer the total thickness of the icy layer from which the blocks formed. Finally, block heights on Mars are compared to potential layer thicknesses of near-surface material. We propose that the heights of chaotic mountain blocks on Pluto, Europa, and Mars can be used to infer information about crustal lithology and surface layer thickness.

Downhill sledding at 40 AU: Mobilizing Pluto's chaotic mountain blocks

We present a force-balance analysis of the mobilization and emplacement of the large mountain block chains observed on the western rim of Pluto's Sputnik Planitia basin. These mountain blocks are likely disrupted pieces of Pluto's water ice crust that are grounded in the nitrogen ice that fills the basin. After fracturing from the basin rim, they could have slid downslope into the basin under their own weight on timescales as short as hundreds to thousands of years, collecting into the observed ranges where the basin slope shallows below a critical value. This movement would require a lubricating fluid, most likely nitrogen, to be present at the base of the blocks.Traction from flowing nitrogen glaciers could have initiated or aided transport for blocks that are small enough to be at least halfway immersed by the nitrogen. Lateral convective forces within the nitrogen ice sheet did not play a significant role in the mobilization of all but the smallest of the observed blocks that likely float buoyantly in the nitrogen ice.If the blocks did emplace by basal sliding, the requirement that liquid nitrogen be present to provide lubrication provides a key to Pluto's past climate history. This work adds to the body of evidence that erosional features and other surface modification could have been driven by the surface or near-surface flow of liquid nitrogen resulting from global climate change on Pluto.

Mapping Natural Forest Remnants with Multi-Source and Multi-Temporal Remote Sensing Data for More Informed Management of Global Biodiversity Hotspots

Global terrestrial biodiversity hotspots (GBH) represent areas featuring exceptional concentrations of endemism and habitat loss in the world. Unfortunately, geospatial data of natural habitats of the GBHs are often outdated, imprecise, and coarse, and need updating for improved management and protection actions. Recent developments in satellite image availability, combined with enhanced machine learning algorithms and computing capacity, enable cost-efficient updating of geospatial information of these already severely fragmented habitats. This study aimed to develop a more accurate method for mapping closed canopy evergreen natural forest (CCEF) of the Eastern Arc Mountains (EAM) ecoregion in Tanzania and Kenya, and to update the knowledge on its spatial extent, level of fragmentation, and conservation status. We tested 1023 model possibilities stemming from a combination of Sentinel-1 (S1) and Sentinel-2 (S2) satellite imagery, spatial texture of S1 and S2, seasonality derived from Landsat-8 time series, and topographic information, using random forest modelling approach. We compared the best CCEF model with existing spatial forest products from the EAM through independent accuracy assessment. Finally, the CCEF model was used to estimate the fragmentation and conservation coverage of the EAM. The CCEF model has moderate accuracy measured in True Skill Statistic (0.57), and it clearly outperforms other similar products from the region. Based on this model, there are about 296,000 ha of Eastern Arc Forests (EAF) left. Furthermore, acknowledging small forest fragments (1–10 ha) implies that the EAFs are more fragmented than previously considered. Currently, the official protection of EAFs is disproportionally targeting well-studied mountain blocks, while less known areas and small fragments are underrepresented in the protected area network. Thus, the generated CCEF model should be used to design updates and more informed and detailed conservation allocation plans to balance this situation. The results highlight that spatial texture of S2, seasonality, and topography are the most important variables describing the EAFs, while spatial texture of S1 increases the model performance slightly. All in all, our work demonstrates that recent developments in Earth observation allows significant enhancements in mapping, which should be utilized in areas with outstanding biodiversity values for better forest and conservation planning.

Climatic dynamics and topography control genetic variation in Atlantic Forest montane birds

Montane organisms responded to Quaternary climate change by tracking suitable habitat along elevational gradients. However, it is unclear whether these past climatic dynamics generated predictable patterns of genetic diversity in co-occurring montane taxa. To test if the genetic variation is associated with historical changes in the elevational distribution of montane habitats, we integrated paleoclimatic data and a model selection approach for testing the demographic history of five co-distributed bird species occurring in the southern Atlantic Forest sky islands. We found that changes in historical population sizes and current genetic diversity are attributable to habitat dynamics among time periods and the current elevational distribution of populations. Taxa with populations restricted to the more climatically dynamic southern mountain block (SMB) had, on average, a six-fold demographic expansion, whereas the populations from the northern mountain block (NMB) remained constant. In the current configuration of the southern Atlantic Forest montane habitats, populations in the SMB have more widespread elevational distributions, occur at lower elevations, and harbor higher levels of genetic diversity than NMB populations. Despite the apparent coupling of demographic and climatic oscillations, our data rejected simultaneous population structuring due to historical habitat fragmentation. Demographic modeling indicated that the species had different modes of differentiation, and varied in the timing of divergence and the degree of gene flow across mountain blocks. Our results suggest that the heterogeneous distribution of genetic variation in birds of the Atlantic Forest sky islands is associated with the interplay between topography and climate of distinct mountains, leading to predictable patterns of genetic diversity.

Groundwater recharge sources in semiarid irrigated mountain fronts

AbstractHigh‐elevation mountains often constitute for basins important groundwater recharge sources through mountain‐front recharge processes. These processes include streamflow losses and subsurface inflow from the mountain block. However, another key recharge process is from irrigation practices, where mountain streamflow is distributed across the irrigated piedmont. In this study, coupled groundwater fluctuation measurements and environmental tracers (18O, 2H, and major ions) were used to identify and compare the natural mountain‐front recharge to the anthropogenically induced irrigation recharge. Within the High Atlas mountain front of the Ourika Basin, Central Morocco, the groundwater fluctuation mapping from the dry to wet season showed that recharge beneath the irrigated area was higher than the recharge along the streambed. Irrigation practices in the region divert more than 65% of the stream water, thereby reducing the potential for in‐stream groundwater recharge. In addition, the irrigation areas close to the mountain front had greater water table increases (up to 3.5 m) compared with the downstream irrigation areas (<1 m increase). Upstream crops have priority to irrigation with stream water over downstream areas. The latter are only irrigated via stream water during large flood events and are otherwise supplemented by groundwater resources. These changes in water resources used for irrigation practices between upstream and downstream areas are reflected in the spatiotemporal evolution of the stable isotopes of groundwater. In the upstream irrigation area, the groundwater stable isotope values (δ18O: −8.4‰ to −7.4‰) reflect recharge by the diverted stream water. In the downstream irrigation area, the groundwater isotope values are lower (δ18O: −8.1‰ to −8.4‰) due to recharge via the flood water. In the nonirrigation area, the groundwater has the highest stable isotope values (δ18O: −6.8‰ to −4.8‰). This might be due to recharge via subsurface inflow from the mountain block to the mountain front and/or recharge via local low altitude rainfall. These findings highlight that irrigation practices can result in the dominant mountain‐front recharge process for groundwater.

The endemic plants of Mozambique: diversity and conservation status.

An annotated checklist of the 271 strict-endemic taxa (235 species) and 387 near-endemic taxa (337 species) of vascular plants in Mozambique is provided. Together, these taxa constitute c. 9.3% of the total currently known flora of Mozambique and include five strict-endemic genera (Baptorhachis, Emicocarpus, Gyrodoma, Icuria and Micklethwaitia) and two near-endemic genera (Triceratella and Oligophyton). The mean year of first publication of these taxa is 1959, with a marked increase in description noted following the onset of the two major regional floristic programmes, the “Flora of Tropical East Africa” and “Flora Zambesiaca”, and an associated increase in botanical collecting effort. New taxa from Mozambique continue to be described at a significant rate, with 20 novelties described in 2018. Important plant families for endemic and near-endemic taxa include Fabaceae, Rubiaceae and Euphorbiaceae s.s. There is a high congruence between species-rich plant families and endemism with the notable exceptions of the Poaceae, which is the second-most species rich plant family, but outside of the top ten families in terms of endemism, and the Euphorbiaceae, which is the seventh-most species rich plant family, but third in terms of endemism. A wide range of life-forms are represented in the endemic and near-endemic flora, with 49% being herbaceous or having herbaceous forms and 55% being woody or having woody forms. Manica Province is by far the richest locality for near-endemic taxa, highlighting the importance of the cross-border Chimanimani-Nyanga (Manica) Highlands shared with Zimbabwe. A total of 69% of taxa can be assigned to one of four cross-border Centres of Endemism: the Rovuma Centre, the Maputaland Centre sensu lato, and the two mountain blocks, Chimanimani-Nyanga and Mulanje-Namuli-Ribaue. Approximately 50% of taxa have been assessed for their extinction risk and, of these, just over half are globally threatened (57% for strict-endemics), with a further 10% (17% for strict-endemics) currently considered to be Data Deficient, highlighting the urgent need for targeted conservation of Mozambique’s unique flora. This dataset will be a key resource for ongoing efforts to identify “Important Plant Areas – IPAs” in Mozambique, and to promote the conservation and sustainable management of these critical sites and species, thus enabling Mozambique to meet its commitments under the Convention on Biological Diversity (CBD).

Evidence for groundwater mixing at Freeling Spring Group, South Australia

Water sampling at springs that are a part of the Freeling Spring Group, South Australia, was used along with electrical resistivity imaging (ERI) data to evaluate the sources and pathways for groundwater to the springs and to find evidence of mixing between the Great Artesian Basin (GAB) aquifer system (Algebuckina Sandstone, Cadna-owie Formation and lateral equivalents) and waters from the adjacent mountain block basement (MB) aquifer. Five springs and a well were used to evaluate spring chemistry; multi-electrode resistivity data were collected along three orientations over the Freeling Spring site. The resistivity data indicate three independent electrically conductive curvilinear features connected to the spring. These features are evidence of mixing at the spring vent similar to what would be predicted from traditional hydraulic flownets. The chemistry of the spring water samples indicates that the water emanating from the Freeling Spring Group is a mixture of waters from both the GAB and the MB aquifers, supporting the geophysical evidence. The data suggest mixing occurs along a fracture in the body of the MB and porous media flow in the GAB beds, but the system is dominated by the GAB flow, which provides approximately 90% of the discharge.

Characterisation of Sand Accumulations in Wadi Fatmah and Wadi Ash Shumaysi, KSA, Using Multi-Source Remote Sensing Imagery

The study area has three sand accumulations: Two in Wadi Fatmah and one in Wadi Ash Shumaysi, midwest of Saudi Arabia. The spatial extents of these sand accumulations have significantly increased over the last few decades. Multi-source satellite imagery, such as CORONA (1967, 1972), SPOT 5 (2013), LandSat TM (1986), and LandSat 8 OLI (2013), enabled monitoring and analysis of the interplay between the changes in the anthropogenic activities and spatial expansion of the areas of sand accumulation. The main driving force of the spatial expansion could be strongly linked to extensive changes in the anthropogenic regimes in the middle zone of Wadi Fatmah and its surrounding landforms and mountain masses. In this context, the once dominant agricultural lands of the middle zone of Wadi Fatmah have been transformed into abandoned agricultural areas. Extensive off-road driving has resulted in soil degradation. Excavation and mining activities for urban spatial expansion are widespread over the valley floor, the adjacent bajada, and the mountain blocks. These anthropogenic activities have remarkably induced strong wind erosion of the soil in severe arid conditions in the middle zone of Wadi Fatmah and Wadi Ash Shumaysi. Wind erosion has eventually produced a sufficient sand budget to be transported into the areas of sand accumulation. The primary consequence of the excess sand budget has been an increase in the spatial extents and dune migration rates of sand accumulations in the study area. However, this increase varies from one sand accumulation to another. In this study, we used multi-source remote sensing imagery and the state-of-the-art COSI-Corr technology to characterize sand accumulations in the study area and to determine the spatio-temporal changes in both the spatial extents and the dune migration rates. The mean annual migration rates of sand dunes in the three sand accumulations ranged from 5.5 and 7.2 to 8.6 m/yr. Analysis of the spatial extent and migration rates of sand accumulations indicates that the study area may have experienced desertification in response to changes in the anthropogenic regimes through the last few decades.

Mountain‐Block Recharge: A Review of Current Understanding

AbstractMountain‐block recharge (MBR) is the subsurface inflow of groundwater to lowland aquifers from adjacent mountains. MBR can be a major component of recharge but remains difficult to characterize and quantify due to limited hydrogeologic, climatic, and other data in the mountain block and at the mountain front. The number of MBR‐related studies has increased dramatically in the 15 years since the last review of the topic was conducted by Wilson and Guan (2004), generating important advancements. We review this recent body of literature, summarize current understanding of factors controlling MBR, and provide recommendations for future research priorities. Prior to 2004, most MBR studies were performed in the southwestern United States. Since then, numerous studies have detected and quantified MBR in basins around the world, typically estimating MBR to be 5–50% of basin‐fill aquifer recharge. Theoretical studies using generic numerical modeling domains have revealed fundamental hydrogeologic and topographic controls on the amount of MBR and where it originates within the mountain block. Several mountain‐focused hydrogeologic studies have confirmed the widespread existence of mountain bedrock aquifers hosting considerable groundwater flow and, in some cases, identified the occurrence of interbasin flow leaving headwater catchments in the subsurface—both of which are required for MBR to occur. Future MBR research should focus on the collection of high‐priority data (e.g., subsurface data near the mountain front and within the mountain block) and the development of sophisticated coupled models calibrated to multiple data types to best constrain MBR and predict how it may change in response to climate warming.

Mapping Crustal Shear Wave Velocity Structure and Radial Anisotropy Beneath West Antarctica Using Seismic Ambient Noise

AbstractUsing 8‐ to 25‐s‐period Rayleigh and Love wave phase velocity dispersion data extracted from seismic ambient noise, we (i) model the 3‐D shear wave velocity structure of the West Antarctic crust and (ii) map variations in crustal radial anisotropy. Enhanced regional resolution is offered by the UK Antarctic Seismic Network. In the West Antarctic Rift System (WARS), a ridge of crust ∼26–30 km thick extending south from Marie Byrd Land separates domains of more extended crust (∼22 km thick) in the Ross and Amundsen Sea Embayments, suggesting along‐strike variability in the Cenozoic evolution of the WARS. The southern margin of the WARS is defined along the southern Transantarctic Mountains and Haag‐Ellsworth Whitmore Mountains (HEW) block by a sharp crustal thickness gradient. Crust ∼35–40 km is modeled beneath the Haag Nunataks‐Ellsworth Mountains, decreasing to ∼30–32 km thick beneath the Whitmore Mountains, reflecting distinct structural domains within the composite HEW block. Our analysis suggests that the lower crust and potentially the middle crust is positively radially anisotropic (VSH>VSV) across West Antarctica. The strongest anisotropic signature is observed in the HEW block, emphasizing its unique provenance among West Antarctica's crustal units, and conceivably reflects a ∼13‐km‐thick metasedimentary succession atop Precambrian metamorphic basement. Positive radial anisotropy in the WARS crust is consistent with observations in extensional settings and likely reflects the lattice‐preferred orientation of minerals such as mica and amphibole by extensional deformation. Our observations support a contention that anisotropy may be ubiquitous in the continental crust.

Hydrology of Mountain Blocks in Arizona and New Mexico as Revealed by Isotopes in Groundwater and Precipitation

Mountain-block groundwater in the Southern Basin-and-Range Province shows a variety of patterns of δ18O and δ2H that indicate multiple recharge mechanisms. At 2420 m above sea level (masl) in Tucson Basin, seasonal amount-weighted means of δ18O and δ2H for summer are −8.3, −53‰, and for winter, −10.8 and −70‰, respectively. Elevation-effect coefficients for δ18O and δ2H are as follows: summer, −1.6 and −7.7 ‰ per km and winter, −1.1 and −8.9 ‰ per km. Little altitude effect exists in 25% of seasons studied. At 2420 masl, amount-weighted monthly averages of δ18O and δ2H decrease in summer but increase in winter as precipitation intensity increases. In snow-banks, δ18O and δ2H commonly plots close to the winter local meteoric water line (LMWL). Four principal patterns of (δ18O, δ2H) data have been identified: (1) data plotting along LMWLs for all precipitation at >1800 masl; (2) data plotting along modified LMWLs for the wettest 30% of months at <1700 masl; (3) evaporation trends at all elevations; (4) other patterns, including those affected by ancient groundwater. Young, tritiated groundwater predominates in studied mountain blocks. Ancient groundwater forms separate systems and mixes with young groundwater. Recharge mechanisms reflect a complex interplay of precipitation season, altitude, precipitation intensity, groundwater age and geology. Tucson Basin alluvium receives mountain-front recharge containing 50%–90% winter precipitation.

An Integrated Novel Approach to Understand the Process of Groundwater Recharge in Mountain and Riparian Zone Aquifer System of Tamil Nadu, India

The nature of groundwater recharge along the mountain front (MF) and riparian zone (RZ) was discerned by multiple tools involving rain/water level relationship, geophysical of subsurface, seasonal hydrochemistry and environmental isotopic signatures. The proposed study has been carried out in Courtallam Hills, the north-western part of Tirunelveli District, South India. The study area is a hilly terrain with narrow valleys endowed with steep slopes. The relationship between water-level fluctuation and precipitation were evaluated by observing daily water level in 8-h interval at three piezometer zones and regular rainfall data. It was inferred that the RZ played a role in storage zone and gets recharged from mountain block (MB) and lateral flow. The seasonal geochemistry of the groundwater was studied to determine the sources of recharge in MF and RZ. Geostatistical treatment of factor analysis revealed that weathering was the dominant recharge process along the foothill. The geophysical studies reveal good quality of groundwater observed in the northern part along with low conductance and high resistivity. The increased level of groundwater conductivity and lower resistivity was noted in southern part of the study area due to the irrigation activities. The isotopic tracers range from − 2.5 to − 12.6‰ for δ18O and from − 91.2 to − 15.5‰ for δ2H. Moreover, the groundwater recharge was evaluated by source of rainfall moisture. High-altitude recharge from MB along the MF was clearly indicated by depleted isotopic content of the water samples. It was also supported by hydrogeochemical and statistical evidences, showing that rainfall over both MB and MF zones provided the recharge to foothill aquifers, while the RZ zone was mainly recharged by local precipitation with less contribution from regional flows.

Assessment of groundwater depletion caused by excessive extraction through groundwater flow modeling: the Celaya aquifer in central Mexico

A numerical groundwater flow model was developed for the Celaya aquifer in central Mexico to assess the potential impacts of excessive groundwater use in the region. The numerical simulations were made with the program FEFLOW, which allowed the use of an irregular mesh that was adjusted to boundaries with irregular geometries and refined in wells and streams. Considering mountain block hydrology, both diffuse and stream-focused recharges were simulated. Hydraulic properties were assigned according to the three-dimensional distribution of lithologic units, which were estimated using geological information from the region. The model was calibrated using static water level measurements in wells and qualitative information of some hydrological processes. Some of the trends observed in the residuals were related to time-constant boundary conditions which can only be solved by developing a regional groundwater flow model. The simulations were undertaken for predevelopment, present, and future scenarios, up to the year 2030. The future simulations considered two possible scenarios: (1) future extractions are equal to current extractions; and (2) future extractions increase gradually in time. The results show that current groundwater extractions are not sustainable in the long term and decreases in extraction rates are required to achieve sustainable groundwater use in the region.

Fault Geometries and Structures Associated With the Rupture Endpoints of the 2008Mw7.9 Wenchuan Earthquake, Eastern Tibet Plateau, China

AbstractThe 2008 Wenchuan earthquake (Mw7.9) initiated at the southern part of the Yingxiu‐Beichuan fault of the Longmen Shan fault zone, eastern Tibet Plateau. The earthquake rupture propagated northeast for ~300 km, producing dextral‐thrust slip along the fault zone. Numerous studies have documented the characteristics of the rupture zone; however, the exact endpoints and the termination structures at both ends remain poorly constrained. On the northeasternmost rupture section, the aftershock distribution extends ~50 km along strike past the end of the observed surface rupture, suggesting that the rupture may extend northeastward at depth. Our field observations show that the aftershock zone follows a NE‐trending linear trace indicative of an active fault at the surface and confirm that the Qingchuan fault, which is one of the faults of the northeastern Longmen Shan fault zone and is reported to have ruptured during the 2008 earthquake by some studies, did not rupture during the Wenchuan earthquake. Detailed investigations show that the rupture terminated at an area between the Qingchuan and the Bahai‐Yuquanba faults where these two faults bound a 10‐ to 20‐km wide mountain block. To the southwest, the southwesternmost end of the Wenchuan earthquake rupture zone terminated south of Sanjiang, where a NE‐trending 50‐cm high fault scarp marks the endpoint of the surface rupture. Our study suggests that fault step overs at the northeastern and southwestern segments may have acted as a barrier to rupture propagation and thus play an important role in controlling the rupture propagation but were not critical in terminating the rupture, whereas the cross structures and/or stratigraphy (complex or massifs) in the northeastern and southwestern rupture endpoints area appear to have controlled the rupture termination.

A joint study in geomorphology, pedology and sedimentology of a Mesoeuropean landscape in the Meseta and Atlas Foreland (NW Morocco). A function of parent lithology, geodynamics and climate

The origin of the landscape spreading across NW Morocco (Meseta, Atlas Mts. Foreland) is geodynamically controlled by two collisional and one extensional regime, while climate changes had only a minor impact on the shaping the landscape. The existing landscape pertains to the series characterized by highly to partially eroded mountain blocks of Paleozoic and Early Mesozoic age which is represented at its best by the relics of the Variscan orogeny resultant in what is called “Mesoeurope”. The Mesoeuropean landscape in Morocco is described by four morphodynamic units.MD 1 (0.4–1.8 Ma/generation 3) has brought about landforms in a fluvial (-alluvial) depositional environment with a strong aeolian influence at its margins. Its drainage patterns feature a moderate to gentle dip of the palaeo-current with a predominantly meandering depositional regime. The major minerals are quartz, calcite, smectite, and smectite-illite mixed-layers (submature landscape).MD 2 (2.0–3.0 Ma/generation 2) involves coastal-marine processes of a microtidal environment. Only quartz warrants mentioning as major constituent (supermature landscape).MD 3 (Neogene/generation 1) is the core zone with extensive planation and chemical weathering which gave rise to amorphous silica and smectite-group minerals (mature landscape).MD 4 (Quaternary/generation 4) encompasses landforms typical of alluvial-fluvial environments evolving under a moderate to strong palaeo-current in the foothills of the Atlas Mts. Aside of quartz, calcite, chlorite, muscovite, illite, and feldspar, labile heavy minerals are as widespread as the calcitic carbocretes. Modern structural disturbances are accountable for the immature landforms and high preservation potential of labile mineral constituents.A morphodynamic comparison between the reference type of “Mesoeurope” and the current morphodynamic type under study in Morocco results into a binary classification scheme encompassing two phases, an older one called phase of planation and a younger one called phase of dissection, a sequence which reflects quiescence and relative stable geodynamic conditions succeeded by a period of tectonic mobility. There is one striking difference between the Moroccan landscape and the reference type in Mid-Europe; the reference type has no equivalent morphodynamic unit which was triggered by the opening of the Atlantic Ocean denoted by the lack of U/Pb data of supergene alteration minerals in the reference log. The most widespread soil types encountered in the Moroccan study sites are vertisols (MD 1, MD3), luvisols (MD 1, MD 2, MD 4) and cambisols. Second in abundance are planosols, which are confined to MD 2 and, locally, arenosol associated with plinthite (MD 1); kastanozem and chernozem (MD 3) are rare members of the topsoil. While the log activity of SiO2 varies in a narrow range, the pH of the meteoric water is considerable wide, from 4.2 to 9.4. The physical-chemical regime suggests a binary subdivision into a more acidic regime (MD1, MD2) in the N and an alkaline one (MD 3, MD4) in the S which goes along with the change in the redox ratios of organic matter (LER/HER) and the climate-zonation.

LANDSLIDES AND THE INCORRECT INTERPRETATION OF GEOLOGICAL STRUCTURE – EXAMPLES FROM THE SUDETY MOUNTAINS

Despite the relatively large number of individual landslides recognized and described over the last several years from the Sudety (Sudetes) Mountains (Lower Silesia, SW Poland), most of the papers focused on the geomorphological characterisation of these forms. This paper presents the results of geological and geomorphological mapping of individual landslides, recognized within three geological units: the Wleń Graben (Northsudetic Synclinorium), the Łączna Elevation (Intrasudetic Synclinorium) and the Glinno Graben (Sowie Mountains Block). Particular attention has been paid to the role of the geological structure in the initiation and development of mass movements as well as the degree of transformation of the planar, structural elements (bedding planes, joints, faults) of the landslide bedrock. The results of geological mapping and geomorphometric analysis with a basis in Light Detection and Ranging (LiDAR) show that the structural measurements carried out in the past within previously unrecognized landslides were probably the main reason for incorrect interpretations of the geology of the areas investigated.

Variations in Soil Water Content, Infiltration and Potential Recharge at Three Sites in a Mediterranean Mountainous Region of Baja California, Mexico

In this research, we examined temporal variations in soil water content (θ), infiltration patterns, and potential recharge at three sites with different mountain block positions in a semiarid Mediterranean climate in Baja California, Mexico: two located on opposing aspects (south- (SFS) and north-facing slopes (NFS)) and one located in a flat valley. At each site, we measured daily θ between 0.1 and 1 m depths from May 2014 to September 2016 in four hydrological seasons: wet season (winter), dry season (summer) and two transition seasons. The temporal evolution of θ and soil water storage (SWS) shows a strong variability that is associated mainly with high precipitation (P) pulses and soil profile depth at hillslope sites. Results shows that during high-intensity P events sites with opposing aspects reveal an increase of θ at the soil–bedrock interface suggesting lateral subsurface fluxes, while vertical soil infiltration decreases noticeably, signifying the production of surface runoff. We found that the dry soil conditions are reset annually at hillslope sites, and water is not available until the next wet season. Potential recharge occurred only in the winter season with P events greater than 50 mm/month at the SFS site and greater than 120 mm/month at the NFS site, indicating that soil depth and lack of vegetation cover play a critical role in the transport water towards the soil–bedrock interface. We also calculate that, on average, around 9.5% (~34.5 mm) of the accumulated precipitation may contribute to the recharge of the aquifer at the hillslope sites. Information about θ in a mountain block is essential for describing the dynamics and movement of water into the thin soil profile and its relation to potential groundwater recharge.

Taxonomic and genetic diversity of rodents from the Arsi Mountains (Ethiopia)

Abstract The Arsi Mountains (Southeastern Ethiopian mountain block) are a unique region comprising a range of habitats, including natural montane forest, extensive ericaceous scrub and small, restricted patches of Afroalpine ecosystem. During 3 years of sampling small mammals, 13 rodent species were recorded, including the extremely rare Mus imberbis and Dendromus nikolausi. Genetic analysis was used to shed light on the taxonomic diversity of rodents in the Arsi Mountains and their evolutionary associations with populations from other Ethiopian montane massifs (including the neighbouring Bale Mountains). All species recorded are endemic to the Ethiopian highlands. The results of this study provide the first genetically confirmed data on the occurrence of such endemic species as Lophuromys melanonyx, L. chrysopus and a yet undescribed Dendromus species in the Arsi Mountains. The genetic affinities of some Arsi rodents with their conspecifics in the neighbouring Bale Mountains were also explored. The results suggest the Arsi Mountains as one of the most important hotspots of unique Ethiopian mammal diversity.