Slope Debris Research Articles

Hydrogeology and groundwater management in a coastal granitic area with steep slopes in Galicia (Spain)

Groundwater availability, management and protection are great challenges for the sustainability of groundwater resources in the scattered rural areas of the Atlantic regions of Europe where groundwater is the only option for water supply. This report presents a hydrogeological study of the coastal granitic area of Oia in northwestern Spain, which has unique geomorphological and hydrogeological features with steep slopes favoring the erosion of the weathered granite. The hydrogeological conceptual model of the study area includes: (1) the regolith layer, which is present only in the flat summit of the mountains; (2) the slope debris and the colluvial deposits, which are present in the intermediate and lowest parts of the hillside; (3) the marine terrace; and (4) the underlying fractured granite. Groundwater recharge from rainfall infiltration varies spatially due to variations in terrain slope, geology and land use. The mean annual recharge estimated with a hydrological water balance model ranges from 75 mm in the steepest zone to 135 mm in the lowest flat areas. Groundwater flows mostly through the regolith and the detrital formations, which have the largest hydraulic conductivities. Groundwater discharges in seepage areas, springs, along the main creeks and into the sea. The conceptual hydrogeological model has been implemented in a groundwater flow model, which later has been used to select the best pumping scenario. Model results show that the future water needs for domestic and tourist water supply can be safely provided with eight pumping wells with a maximum pumping rate of 700 m3/day.

Ecology of the cold-adapted species Nebria germari (Coleoptera: Carabidae): the role of supraglacial stony debris as refugium during the current interglacial period

In the current scenario of climate change, cold-adapted insects are among the most threatened organisms in high-altitude habitats of the Alps. Upslope shifts and changes in phenology are two of the most investigated responses to climate change, but there is an increasing interest in evaluating the presence of high-altitude landforms acting as refugia. Nebria germari Heer, 1837 (Coleoptera: Carabidae) is a hygrophilic and cold-adapted species that still exhibits large populations on supraglacial debris of the Eastern Alps. This work aims at describing the ecology and phenology of the populations living on supraglacial debris. To this end, we analysed the populations from three Dolomitic glaciers whose surfaces are partially covered by stony debris. We found that supraglacial debris is characterised by more stable colder and wetter conditions than the surrounding debris slopes and by a shorter snow-free period. The populations found on supraglacial debris were spring breeders, differently from those documented in the 1980s on Dolomitic high alpine grasslands, which were reported as autumn breeders. Currently, Nebria germari seems, therefore, to find a suitable habitat on supraglacial debris, where micrometeorological conditions are appropriate for its life-cycle and competition and predation are reduced.

Slope stability evaluation and monitoring of a landslide: a case study from NE Turkey

Landslides are quite common natural hazards in the eastern Black Sea region of NE Turkey. Following the heavy rainfall in the Koprulu (Rize) village settlement area, located in this region where the slope debris overlies the agglomerates, a failure occurred. Due to the developed tension cracks and deformations on the ground, houses, tea gardens, and roads were damaged completely. To figure out the causes and mechanism of the sliding and to suggest the precautions, a detailed geotechnical study was carried out. Along the five survey lines, twelve boreholes were drilled with a total depth of 300 meters. Also, the geophysical surveys on ten profiles were conducted and the inclinometer measurements were taken in five boreholes. Undisturbed and disturbed samples were collected and laboratory experiments were performed. Inclinometer measurements indicated that the sliding started in the slope debris and then spread to the agglomeratic bedrock. The slope stability was examined using the limit equilibrium (LE) and finite element (FEM) analysis methods. The results of the slope stability analyses showed that the failure mode is talus slide with composite shape and outputs coincide with the inclinometer monitoring results. Based on the collected data, it is determined that there will be unavoidable engineering problems if no precautions are taken. Because of the negative reasons which make the application of supporting methods meaningless in the study area, it is considered that transferring the residences to a safer place without risk of natural hazards will be economical and reliable.

Formation mechanism of a rainfall triggered complex landslide in southwest China

This case study is about a landslide that occurred after 4 days of heavy rainfall, in the morning of June 29, 2012, in Cengong County, Guizhou Province of China, geographical coordinated 108°20′-109°03′E, 27°09′-27°32′N, with an estimated volume of 3.3×106 m3. To fully investigate the landslide process and formation mechanism, detailed geotechnical and geophysical investigations were performed including borehole drilling, sampling, and laboratory tests coupled with monitoring of displacement. Also, a combined seepage-slope stability modeling was performed to study the behavior of the landslide. After the heavy rainfall event, the sliding process started in this area. The landslide development can be divided into different parts. The man-made fill area, spatially distributed in the south side of the landslide area with low elevations, slid first along the interface between the slope debris and the strongly weathered bedrock roughly in the EW direction. Consequently, due to severe lateral shear disturbance, the slope in the main sliding zone slid next towards the SW direction, along the sliding surface developed within the strongly weathered calcareous shale formation located at a depth of 25-35 m. This means it was a rainfall triggered deep-seated landslide. Finally, retrogressive failure of a number of upstream blocks occurred, which moved in more than one direction. The initial failure of the man-made fill area was the ‘engine’ of the whole instability framework. This artificial material with low permeability, piled up in the accumulation area of surface and sub-surface and destroyed the drainage capacity of the groundwater. The numerical modeling results agreed with the analysis results obtained from the laboratory and field investigations. A conceptual model is given to illustrate the formation mechanism and development process of the landslide.

DEBRIS FLOW CHECK CONSTRUCTIONS SITUATED NEAR THE MOUTH OF RIVERS OF THE SAKHALIN ISLAND

The significant part of roads and railways of the Sakhalin Island are located in the coastal zone of the sea, in the lower part of the debris flow transit zone. Debris flows cause blockages and damage to the roadways. In some areas of the island are sites where the number of debris flow basins is 30-40 per km. Basically, these are slope debris flows, which are formed annually during precipitation of liquid precipitation, and whose volume can reach 500 m3. At the same time, debris flows can play an important role in the formation of beaches and protection from abrasion due to the removal of material to the mouth of the rivers. Transport of debris flow material to the coastal zone on the Sakhalin Island is carried out on the coasts of the Gulf of Patience, the Gulf of Aniva, the Tatar Strait, etc. Beach savings are the best of its natural protection against destruction. Therefore, the need to build seepage facilities is due not only to the need to protect the roadway, but also the importance of transporting debris flow material to the beach area. Characteristics of debris flows in the coastal zone of the island differ in a number of parameters, such as the volume of debris slides, the frequency of formation of debris flows, the type of debris flows, the size of carried fragments of rocks; therefore, when choosing a debris flow protection facility, it is necessary to be guided both by the parameters of debris flows and by the role of debris flows in the formation of beaches. The paper examines the current state of water chute and debris flows chute under the roads in the near-mouth parts of debris flow rivers, as well as the expediency of selecting debris flow protection structures depending on the characteristics of debris flows.

Research on the ecological restoration method for highway debris slope: A case study of Guidu Highway in China

To clarify the superiority of slope ecological restoration technology in slope restoration, the artificial slope in the section of Guiyang-Duyun highway as the case study was analyzed in this paper. Plant sample collection experiments were carried out by sample method, and the evaluation indicators factors were plant distribution density, biomass and soil nutrients. The effect of slope restoration was evaluated by comparing with the ecological effect of traditional slope restoration measures. The results showed that for the slope ecological restoration sample, the average cumulative plant density was 187 plants per square meter, about 3.8 times of the comparison sample. The average biomass was 333.25g/m2 , which was about 6.4 times that of the comparison sample. Soil nutrients were also much higher than those in the comparison sample. The ecological restoration of the slope with ProGanics and Flexterra materials was superior to the traditional slope restoration measures. The oretical research results will have important theoretical and technical significance for the ecological restoration method for highway debris slope of Guidu highway.

Fusulinids from slope debris flow beds in the Word Formation (Guadalupian, Middle Permian), Gilleland Canyon, northwestern Glass Mountains, West Texas

Three Guadalupian allochthonous debris flow beds in a slope-to-basin facies succession in northern Gilleland Canyon of the northwest Glass Mountains were sampled for fusulinid biostratigraphic age-dating. The deeper water allochthonous debris flow beds underlie the shelf-margin packstone-grainstone facies of the Willis Ranch Member of the Word Formation (3rd Word Limestone Bed of King 1931) (middle Guadalupian, early Wordian), which forms a distinct bench all along the west wall of Gilleland Canyon (114–169m above base of measured section). The uppermost GV-RC1 sample, from 104 m in the measured section, contained the fusulinids Parafusulina sellardsi, P. antimonioensis, P. deliciasensis, P. rothi, P. trumpyi, and P. boesei. SampleGV-CM1, from 83min the section, contained P. sellardsi, P. deliciasensis, P. rothi, P. boesei, and P. lineata. The lowest sample GV-CM20, from 76 m in the section, contained only P. deliciasensis and P. wildei. According to previous studies, most of these species appear in Roadian-aged strata and range upward into early Wordian-aged strata, but the common occurrence of P. sellardsi in the upper two samples, and the occurrence of P. antimonioensis in the uppermost sample confirm an early Wordian age.

Effects of loose deposits on debris flow processes in the Aizi Valley, southwest China

Loose deposits, rainfall and topography are three key factors that triggering debris flows. However, few studies have investigated the effects of loose deposits on the whole debris flow process. On June 28, 2012, a catastrophic debris flow occurred in the Aizi Valley, resulting in 40 deaths. The Aizi Valley is located in the Lower Jinsha River, southwestern Sichuan Province, China. The Aizi Valley debris flow has been selected as a case for addressing loose deposits effects on the whole debris flow process through remote sensing, field investigation and field experiments. Remote sensing interpretation and laboratory experiments were used to obtain the distribution and characteristics of the loose deposits, respectively. A field experiment was conducted to explore the mechanics of slope debris flows, and another field investigation was conducted to obtain the processes of debris flow formation, movement and amplification. The results showed that loose deposits preparation, slope debris flow initiation, gully debris flow confluence and valley debris flow amplification were dominated by the loose deposits. Antecedent droughts and earthquake activities may have increased the potential for loose soil sources in the Aizi Valley, which laid the foundation for debris flow formation. Slope debris flow initiated under rainfall, and the increase in the water content as well as the pore water pressure of the loose deposits were the key factors affecting slope failure. The nine gully debris flows converged in the valley, and the peak discharge was amplified 3.3 times due to a blockage and outburst caused by a large boulder. The results may help in predicting and assessing regional debris flows in dry-hot and seismic-prone areas based on loose deposits, especially considering large boulders.

Waldentwicklung und flachgründige Rutschungen: eine grossflächige GIS-Analyse

Forest dynamics and shallow landslides: a large-scale GIS-analysis Through continuous and abrupt changes in the forest and particularly in its root area, the disposition for shallow landslides also changes. The aim of this article is to learn more about the relationships between long-term forest dynamics and the risk of landslides with the help of large spatial data sets. A total of 6670 shallow landslides were selected from the natural event register StorMe, the event register of the Canton of Obwalden and the WSL database for shallow landslides and slope debris flows and overlaid with GIS data on the current and former forest situation (Siegfried maps of approx. 1880) and with windthrow areas (Vivian and Lothar). Shallow landslides occurred less frequently in the forest than outside of it at inclinations of less than 35 degrees. Higher landslide densities occurred in coniferous and mixed forests (compared to deciduous forests) and in relatively young forests (ingrown after 1880). Landslides in younger forests occurred on slopes less steep than in older forests. More shallow landslides occurred on former windthrow areas during the first 3 to 17 years after the event, however these landslides occurred on comparatively steep slopes. The analyses show that the disposition towards shallow landslides defined by slope inclination and subsoil can change strongly due to reforestation processes and natural disturbances. Silvicultural interventions may contribute to an improvement of the protective effect in the long term if they are carried out carefully and if they contribute to an increased adaptability to natural disturbances.

Reactivation of temporarily stabilized ice-cored moraines in front of polythermal glaciers: Gravitational mass movements as the most important geomorphological agents for the redistribution of sediments (a case study from Ebbabreen and Ragnarbreen, Svalbard)

Ice-cored moraine complexes are prominent landforms characteristic of many polythermal glacial landsystems on Svalbard, usually marking their maximum Little Ice Age extent. Despite being often stable over a period ranging from several years to 50–60 years, the abundance of dead-ice makes them potentially unstable in the future. This study aims to: (1) recognize the different processes that contribute to ice-cored moraine degradation; (2) document the spatial distribution of mass wasting sites within ice-cored moraine complexes of Ebbabreen and Ragnarbreen, Svalbard; (3) investigate the relationship between the distribution of mass-movement sites and the topographic properties of the landscape; (4) develop a model of mass-wasting mechanism in a proglacial area. We performed field-based geomorphological mapping combined with the interpretation of aerial photographs (1960, 1990, 2009), high-resolution satellite imagery (2013), UAV-based images (2014), terrestrial photographs (2011–2014), hillshade models and digital elevation models.In 2013, frontal and lateral ice-cored landforms occupied 3.33 km2 of the forelands of Ebbabreen and Ragnarbreen. The total area with an unstable ice-cored moraine condition was 0.57 km2 (127 sites). Debris falls, slides, rolls and flows were the most important processes contributing to the reworking of glacigenic sediments and altering of their properties. Four different morphological site types were identified: (1) near vertical ice-cliffs covered with debris, transformed mainly by dead-ice backwasting as well as debris falls and slides, (2) steep debris slopes with exposed ice-cores dominated by debris slides, (3) gentle sediment-mantled slopes transformed by debris flows, and (4) non-active debris-mantled areas transformed by dead-ice downwasting alone. The spatial and temporal activation of moraines' reworking was for the most part related to local geomorphic conditions (e.g., slope gradient, occurrence of streams, and meltwater channels). Gravitational mass-movements were responsible for the redistribution of debris within the moraine-complex, whereas fluvial transport by meltwater exported sediments outside the Little Ice Age moraines.

Evidence of the formation of landslide-dammed lakes in the Zagros Mountains range, Iran

Alternation of high and low resistance sedimentary beds, active tectonics, large rivers, and slope erosion in valleys consequently resulted in landslide in dammed lakes within the Zagros range. This study presents the results in the analysis of geological and topographic data, satellite imageries, morphotectonics and hydrodynamics of drainage networks about the landslide dammed lakes. There are four landslides in central Zagros (Zagros Fold-Thrust Belt, ZFTB) which have formed five dammed lakes named, Seymareh, Jāidār, Shūr, Shīmbār, and Godār. According to the results, damming landslides occurred in the active-tectonic regions on the slopes of anticlines and in valleys with undercutting effects of rivers on their slopes consisting of alternations of loose and resistant beds. The studied landslide dams in narrow valleys are formed as a result of blocking river by sliding debris slopes and rock slides. This study also indicates the formation of Jāidār and Godār in one stage and the presence of Lake Terrace sequence in Seymareh, Shūr and Shīmbār lakes. The observed sequences of terrace formation in these lakes are caused by four Seymareh Landslides followed by the three-stage excavation of Shūr and Shīmbār lakes.

Long-term transient groundwater pressure and deep infiltration in Alpine mountain slopes (Poschiavo Valley, Switzerland)

Bedrock aquifers in alpine catchments are important regional sources of freshwater. Data regarding bedrock groundwater-recharge processes are scarce and governing dynamics are poorly understood. The main datasets used to constrain regional groundwater recharge and flow, so far, have been based on indirect methods (environmental isotopes, river discharge rates, tunnel inflows). Here, a unique dataset is presented of long-term pore-water-pressure measurements from five deep boreholes situated in the upper reaches of a mountain slope at 1,500–2,300 m above sea level. In addition to multilevel pore pressure records, a detailed analysis of the hydrogeological conditions in the Alpine catchment is provided, along with the results from investigations of groundwater recharge mechanisms in response to variations in climatic conditions and hydraulic rock-mass properties. The recorded pressure data show annual pressure variations with amplitudes of 5–45 m and responses within a few days to summer rainstorms in the available depth range of 45–277 m below ground surface. One-dimensional analytical pore-pressure diffusion models and numerical infiltration models were applied to investigate pore-pressure dynamics and water-table variations. The model results reproduced the following parameters for the uppermost 100-m-thick layer: the observed amplitudes, rates and delays of pressure increase with porosities of 0.05–0.1%, specific storage of 5E-5 to 5E-7 m-1, and hydraulic diffusivities of 1E-1 to 1E-3 m2/s. Boreholes located in high-diffusivity areas (strongly fractured bedrock below coarse slope debris) had the strongest pressure variations and were most sensitive to weather conditions.

From geological to soil parent material maps - A random forest-supported analysis of geological map units and topography to support soil survey in South Tyrol

Parent material is an important factor of soil formation and consequently plays a dominant role in both traditional field soil survey and digital soil mapping. The emergence of a new generation of detailed geological maps at high spatial resolution in South Tyrol raises the question of how to effectively incorporate these into soil mapping efforts. By comparing the units of these geological maps with the parent material description of soil pits, we evaluate to what extent these can be used as soil parent material maps. Random forest classification and feature selection are applied to highlight those terrain parameters that i) best distinguish between the different surficial geology units, ii) separate soil profile sites with different soil parent material, and iii) can be used together with the geologic map to train a classifier to model the distribution of soil parent material in the study area. The main issue detected by analyzing the differences between the geologic map units and the soil parent material information is the dominant role of till, which acts as soil parent material for a large number of soils located on different geological map units. While slope debris is another class on which geological map and soil pit descriptions often disagree, the issues concerning its misclassification are connected more to categorical transitions between soil parent material classes. Terrain parameters characterizing surface roughness, specifically a combination of vector ruggedness measure (VRM) and topographic roughness index (TRI), were identified as being best suited to join the geological map units in modeling soil parent material and indicate areas where till as soil parent material should be expected. By evaluating these results together with the distribution of soil types, a geologic-topographic characterization is performed for each geological map unit, with the aim of highlighting specific combinations of geological units and topographical situations which should be in the center of future detailed soil surveys, consequently facilitating the soil mapping procedure.

Soil-landscape interplays at Harmony Point, Nelson Island, Maritime Antarctica: Chemistry, mineralogy and classification

Soils and landforms of Nelson Island remain one of the least studied in the South Shetlands Archipelago, despite that it is one of the oldest ice-free areas and is strongly vegetated. In this paper, we examine the main processes and factors of soil formation at Harmony Point and the relation of soils to landforms, vegetation and lithology.To achieve the goals, 26 pedons were collected and studied from a 4 km2 ice-free area at Harmony Point (S62°18′; W059°10′) on the southern area of Nelson Island (Maritime Antarctica). The soils were sampled on all representative local landforms, including three levels of uplifted marine terraces up to cryoplanated plateau, waterlogged depressions, rock felsenmeer, debris slopes and patterned ground, and a paraglacial border of the ice cap (270 m a.s.l). Sampling along the cryoplanated plateau was carried out along a gradient extending inland from the margins of the Ice Cap; and sampling of the marine terraces was performed along a chronosequence under varying bird-nesting influence and age. The main pedogenetic processes observed in this area are marked phosphatization, melanization from the accumulation of organic matter, and cryoturbation. Soil development varies from weakly developed, shallow, stony and cryoturbated to well-developed and organic-rich, phosphate soils with colors ranging from grayish to brown. The mineralogical composition of the clay fraction contains secondary minerals, indicating the active role of chemical weathering. Ornithogenic soils have mature phosphate minerals such as vivianite and taranakite, as well as poorly crystalline leucophosphite. Intensively cryoturbated soils are underlain by permafrost and are classified as Typic Haploturbels; polygonal soils are widespread on the cryoplanated plateau. Areas without permafrost were classified as Typic Gelorthents. Phosphatization is a dominant soil-forming process in this area and is associated with past and present-day guano accumulation by bird nesting and has led to the the development of deeper Ornithogenic Haplorthels. The ornithogenic soils occur at different topographic levels on the cryplanated platform and marine terraces. High P concentrations can be used as a proxy of the past nesting birds' activities, with far-reaching implications, especially with regards to vegetation growth and microbial activity and diversity.

Deep Electrical Resistivity Tomography for the Hydrogeological Setting of Muro Lucano Mounts Aquifer (Basilicata, Southern Italy)

The proposed work concerns the application of a deep geoelectrical survey to a carbonate aquifer in order to define the best location for exploitation well drilling for increasing water supply. However, an optimal characterization of a groundwater resource is the necessary condition to reach the indicated aim. Therefore, the geoelectrical investigation was guided from the previous geological and hydrogeological characterization. Moreover, geophysical methods are good tools to improve the groundwater model when detailed information is necessary, such as the localization of a pumping well. The work summarizes the hydrogeological knowledge at the West of the Basilicata Region (Muro Lucano, Italy). The investigated area is characterized by the presence of a karst aquifer which is made up of a carbonate ridge (Castelgrande, Muro Lucano) that tectonically dips southward and is widely covered by Pliocene deposits (sands and conglomerates), by the Irpinian unit and Sicilide unit formations, and by debris slope and landslide deposits. The assessment of the complex hydrogeological framework of the area was detailed by the use of a new multichannel deep geoelectrical technique (DERT). In details, the proposed technique was able to successfully locate a less resistive zone connected to a more fractured limestone and then it was suitable for the localization of a groundwater exploitation well.

Surface movement and cascade processes on debris cones in temperate high mountain (Picos de Europa, northern Spain)

Debris talus is a very common landform in the temperate high mountain, so much so that it is the most representative of the periglacial and nival processes. This work studies debris cones in the Picos de Europa, an Atlantic mountain range in the north of the Iberian Peninsula. A detailed geomorphological map was prepared, fieldwork was carried out on the debris cone surface, the ground and air thermal regime was analyzed, and a five-year Terrestrial Laser Scan survey carried out. Annual volume changes on the surface of the debris cones were detected and related to active processes and sediment transfer. Two different behaviors were observed in each cone. Cone A is linear, with equilibrium between accumulation and sediment transfer, while Cone B is concave-convex denoting accumulation processes in the upper part deriving from the greater frequency of snow avalanches. Changes in morphology surpass 50 cm/year with most of the activity taking place in the highest and lowest areas. The presence and action of the ice on the debris slope are moderate or non-existent and freeze-thaw processes are only active on the walls at over 2000 m a.s.l. The main processes on debris cones are debris flow and creep related to snowcover, but sediment transfer on the slopes involves high intensity-low frequency (debris flow, avalanches) and high frequency-low intensity processes (creep, shift, solifluction and wasting).

Early warning model for slope debris flow initiation

Early warning model of debris flow is important for providing local residents with reliable and accurate warning information to escape from debris flow hazards. This research studied the debris flow initiation in the Yindongzi gully in Dujiangyan City, Sichuan province, China with scaled-down model experiments. We set rainfall intensity and slope angle as dominating parameters and carried out 20 scaled-down model tests under artificial rainfall conditions. The experiments set four slope angles (32A degrees, 34A degrees, 37A degrees, 42A degrees) and five rainfall intensities (60 mm/h, 90 mm/h, 120 mm/h, 150 mm/h, and 180 mm/h) treatments. The characteristic variables in the experiments, such as, rainfall duration, pore water pressure, moisture content, surface inclination, and volume were monitored. The experimental results revealed the failure mode of loose slope material and the process of slope debris flow initiation, as well as the relationship between the surface deformation and the physical parameters of experimental model. A traditional rainfall intensity-duration early warning model (I-D model) was firstly established by using a mathematical regression analysis, and it was then improved into ISD model and ISM model (Here, I is rainfall Intensity, S is Slope angle, D is rainfall Duration, and M is Moisture content). The warning model can provide reliable early warning of slope debris flow initiation.

Stability and sensitivity analysis of Himalayan road cut debris slopes: an investigation along NH-58, India

The complex geological environment due to active tectonics and varied lithology with multiple phases of deformation and metamorphism led to a rugged topography and large destabilization of slopes in the Himalayan region. However, the ever-rising activities due to various ongoing developmental and urbanization processes in the region are contributing to instability of slopes. The significant number of causalities and massive economic loss is deliberately endangering Himalayan ecosystem due to landslide-related phenomena. Transportation corridors within Himalayan terrain experience frequent landslides, particularly the sections manifested by debris slopes. From several decades, the national highway-58, in Uttarakhand, Himalayas, has been endangered due to diverse and incessant slope failures. The present investigation demonstrates the stability appraisal along the strategic transportation corridor. These studies incorporate the various issues and causes pertaining to debris slides from Rishikesh to Devprayag, Uttarakhand. The numerical simulation assessment was undertaken by deterministic and sensitivity analyses by conventional limit equilibrium methods which is being augmented by much advanced and robust finite element tool. Factor of safety for each slope was determined, and correspondingly, best efficient slope stabilization remedies were proposed to enhance the stability of slopes. It is recommended that such strategic slope stability assessment should be performed within different vulnerable sections of the Himalayas and likewise regions for fruitful and sustainable step toward disaster mitigation.

The origin and geochemical characteristics of rutile in eluvial and fluvial-alluvial placers and quartz veins of the Menderes Massif from the Neoproterozoic Pan-African Belt, Western Turkey

Rutile occur in important amounts within Quaternary detrital sediments, and quartz veins which cut down the Paleozoic aged Eşme formation in the Menderes Massif on the Neoproterozoic Pan-Afrikan Belt in the west of Turkey. As a result of erosion, transport and accumulation of rutile-bearing quartz veins in the mica schists of the Eşme formation outcropped between Eşme (Uşak) and Kula (Manisa), the placer rutile occurrences occur in terraces, fluvial-alluvial and eluvial deposits. This study investigates the element content of rutile, oxygen isotope ratios of rutile and quartz, and formation temperature of rutile related to titanium source rock.Field observations show that rutiles are located in quartz veins that cut the schists. After these veins were fragmented and eroded, blocks of quartz with rutile and rutile grains are transported into clastic sediments in slope debris (eluvial), terraces and recent fluvial-alluvial deposits. Whereas quartz, rutile, ilmenite, and albite are found in the paragenesis of the rutile-bearing quartz vein fragments, the placers forming the terraces and current fluvial-alluvial deposits contain quartz, albite, muscovite, orthoclase, kaolinite, rutile, dravite, ilmenite, and zircon. The rutile grains in the examined placers and quartz vein fragments have grain sizes ranging from mm fractions to 5–6 cm.The major oxide compositions of the rutile grains have average values of 94 wt.% TiO2, 1.5 wt.% Fe2O3, 0.5 wt.% SiO2, and 0.3 wt.% Al2O3. The rutile samples have average values Nb of 1424 ppm, V of 980 ppm, W of 192 ppm, Ta of 94 ppm, and Zr of 73 ppm. The rutiles in the study area are defined as iron-rich rutile “nigrine” due to high iron content. Quartz veins are host rocks of rutile grains in the terrace and fluvial-aluvial sediments.The rutile-bearing quartz veins may be sourced from the Lower-Middle Miocene aged granites which are intruded the rocks in the Menderes Massif. Based on the analysis results of the methods of Zr thermometer from Zr values containing rutile and quartz-rutile geothermometer from oxygen isotope results (13.5‰ and 6‰) of quartz and rutile samples, the formation temperature of the rutile-bearing quartz veins were found to be at temperatures of 537 °C and 561 °C, respectively. These temperatures indicate that the rutile-bearing quartz veins may be in a temperature range between pegmatitic and/or hydrothermal stages.

Warning model study of debris flow slope source starting based on experimental method

To further realize the correlation between rainfall and the starting mechanism of the slope debris flow in the source area of Yindongzi gully, a typical model was selected after a detailed fieldwork and engineering investigation. The rainfall intensity and gradient were set as control variables using 20 large artificial rainfall physical model tests under four gradients and five rainfall intensity conditions to research the instability mechanism and failure patterns of the slope debris flow. The experimental results revealed the starting and failure model of the source of the loose slope and the response relationship of the surface deformation and the underground physical mechanical parameters. Then, a traditional I-D (rainfall intensity-duration) early warning model was established. Next, reliable warning parameters (i. e. gradient and moisture content) were extracted and the exponential model and means of the mathematical regression analysis were used to determine the IGD and IGM multi-parameter forecast model, while the traditional model was effectively modified for dependability and practical utility.