Geomorphic Surfaces Research Articles

3D mapping efficacy of a drone and terrestrial laser scanner over a temperate beach-dune zone

Understanding dynamic earth surface processes requires various spatial and temporal information to help produce patterns of landform change. Recent developments in sensor technology such as Structure from Motion (SfM), camera-mounted airborne Unmanned Aerial Vehicles (UAVs) and Terrestrial Laser Scanning (TLS) have provided a means of acquiring high-resolution spatial data on land surface topography. Through repeat surveys, these techniques enable much better understanding of what is termed ‘geomorphometry’, where we can examine a geomorphic surface for change over space and time. In coastal environments, change can involve significant alteration and generation of landforms over relatively short periods and, therefore, we require a means of measuring surface morphology quickly and over large areas. Here, we examine a section of a beach-dune system in NW Ireland using SfM-UAV and TLS plus baseline dGPS data points to assess the value of these techniques and to understand their effectiveness (and limitations). Issues such as accuracy, resolution and differences of Digital Elevation Models (DEMs) are assessed for their efficiency, associated challenges and relative performance over variations in terrain types and analytical approaches. We also examine the implications for differences in areal and volume calculations of the coastal landforms using both approaches. We find that sensor performance is highly dependent on the terrain being measured, with undulations, slope, vegetation cover, acquisition resolution (point density) and interpolation issues all having pronounced impacts on effectiveness and data quality. In general, the TLS performed better over flatter, low-angled topography containing sparse/non-vegetated areas than in areas with complex landforms where survey shadows appear to compromise final DEMs. The SfM-UAV shows good performance over different terrains with the exception of relatively flat, featureless areas such as sandy beaches and densely-vegetated surfaces where differences between techniques are >1 m. Data acquisition however is much (×30) faster using a SfM-UAV with more extensive survey areas covered than using a TLS.

How maintenance and restoration measures mediate the response of riparian plant functional composition to environmental gradients on channel margins: Insights from a highly degraded large river

Riparian habitats are transitional zones where strong environmental gradients shape community. To prevent flood risks and channel migration on managed rivers, civil engineering techniques have been widely used. Recently, ecological restoration of rivers has become a major issue. However, given the alteration of natural disturbance regimes induced by human infrastructures, the real added-value of these restoration actions is questionable. Thus, a major challenge is to better understand whether changes in abiotic conditions induced by human activity influence the response of plant communities to environmental gradients. Studying a highly degraded large river, we evaluated the effect of the elevation and soil texture gradients on plant functional composition and assessed whether human-mediated environment gradients, achieved through maintenance and restoration measures, shape community structure. In the summer of 2017, we sampled 17 geomorphic surfaces, mostly gravel bars, along the Rhône River and its tributaries that were either repeatedly cleared (brush clearing vs plowing), newly reprofiled or naturally rejuvenated by high flows. The results show shifts in trait values with elevation and convergence in plant traits with increasing proportion of fine sediments. The co-occurrence of species with contrasting traits was higher in highly disturbed environments, revealing the importance of rejuvenation processes. However, the influence of both environmental gradients was mediated by human activity. For maintenance measures, plowing was better able to promote species diversity and limited biotic homogenization along environmental gradients. Among the three geomorphic surfaces, naturally rejuvenated bars were the most stressful environments, hosting distinct functional assemblages, while communities on newly reprofiled banks were in the same ecological trajectories as repeatedly cleared bars. To promote an effective ecological restoration of riparian zones, (i) a greater variability of the minimum flow is needed, (ii) bedload transport restoration should be a priority and (iii) reprofiled banks should better mimic the landforms of natural river margins.

Characterisation of faults as earthquake sources from geomorphic data in the Tongariro Volcanic Complex, New Zealand

ABSTRACTAt the southern Taupo Rift, tectonic faults and volcanic edifices have interacted during the last 350 kyr. The NNE-striking Tongariro Volcanic Complex is bounded and displaced by four parallel normal faults: National Park, Waihi, Poutu and Upper Waikato Stream, which collectively define the Tongariro Graben. Offsets of geomorphic surfaces of known age and fault trace geometry were used to characterise the seismic parameters of these faults. Along-strike distribution of fault displacement suggests that these faults could rupture as a whole. However, geomorphic data and geometrical characteristics of surface ruptures suggest that they could also rupture in shorter segments. This study calculates higher slip-rates (∼2.6 ± 0.8 and 2.2 ± 1.9 mm/yr for Waihi and Poutu fault zones, respectively) and greater earthquake magnitudes (up to MW 7.2 ± 0.1 and 6.9 ± 0.1, respectively) than previous studies, suggesting an important seismic hazard for the Tongariro area.

Analysis of the Potential Soil Parent rock Resources and Ecological Footprint in Jadaka, Kandahar, Kargo, Makada and Sarki Aska Villages of Dutse, Nigeria

A study of the parent materials and ecological analysis, covering five sites of Dutse area in Jigawa State, Nigeria was undertaken; applying the concepts of visual assessment and ecological footprint to describe the biophysical condition of the rock particles and human economy. The objectives of the study were to classify the basic parent rocks and ecological footprints around them and to draw conclusions regarding the proper utilization of rocks and sustainable economic development in the area. Assessment activities were carried out based on four concepts, which are a description of the underlying parent rocks, geomorphic surface soil characteristics, measurement of the rock size and ecological footprint by human demand on rocks. Factors recounting the true nature and condition of parent rocks such as classes, type, texture, col- our, and pedogenesis were evaluated to guide biophysical characteristics of the rocks. The major surface features were recorded as anthropogenic-related to heating and breaking of rocks, cirque land, gullied land, and rock-outcrop. Data from the typical rock sizes in term of length and height were used for describing and contrasting the dimension of rock's formation and fragmentation in each site. This dimension was measured on average as 12.7 m Kargo, 10.8m Kandahar, 9.0 m Jadaka, 7.6 m Makada and 3.7m Sarkin Aska. Ecological footprint indicated that about 2.4 ha to 3.7 ha of the total rock areas are required to support the population of these villages. Proper utilization and management of the parent rocks can be used as a means of improving the sustainable livelihood of the population in the study sites.

Role of geomorphic surface on the above-ground biomass and soil organic carbon storage in a semi-arid region of Iranian loess plateau

The so-called Iranian loess plateau is a unique landscape with a complex topography and steppe vegetation developed under semi-arid climate. We studied the relationships between geomorphic features, soils, biomass of above-ground vegetation (biomass) and soil organic carbon storage (SOCS) to further enhance our understanding of geomorphological processes, soil formation and evaluating SOCS in this strongly dissected landscape. Based on the previous knowledge, the effect of slope aspect on differentiation of soils is considerable in the studied area. Therefore, slope aspect was included as a phase of the geomorphic surface (PGS) in the geomorphic hierarchy to better analyze and understand the soil variation and development. A total of 220 soil samples were taken in different PGS from three depths 0–20, 20–40 and 40–60 cm. For additional details, biomass sampling was collected on 1 m2 quadrat in every location where the soil samples were taken. Results showed that the 0–20 cm layer with 2.13 kg m−2 had the maximum amount of SOC density (SOCD). Among studied units, moderately flat plain (VA111), loess tableland (TB111) and middle hill with north aspect (Hi211_2) had the highest SOCD compared to other units in the three studied depths. The results also indicated that PGS Hi211_2 had a significantly higher SOCD and biomass than PGS middle hill with south aspect (Hi211_1) in three soil layers. The highest values of SOCS were similarly found in the surface soil layer of PGS Hi211_2 accounting for 42816.55 Mg equal to 36.84% of total SOCS. In all PGSs, there were a positive significant correlations between biomass and SOCD (r2 = 0.62, p = 0.01, n = 80). Therefore, the present study revealed that the variation of SOCD is mainly controlled by the PGS in hillslope landscape. Findings of SOCS denoted the importance of protecting surface and subsurface soil layers in hillslope to store SOC. In general, an accurate understanding of geomorphic surface is needed to accurately estimate SOCS, biomass and to evaluate soil and ecosystem related effects on global warming of ecologically sensitive semi-arid areas.

Assessment of sudden sediment source areas incurred by extreme rainfall in a mountainous environment: Approach using a subsurface hydrologic concept

In mechanism studies on sudden sediment source areas (SSAs), such as those of shallow landslides, area-specific soil strength information at the soil layer between saturated and unsaturated soil is an important factor. Although various soil-testing methods have been developed, it is difficult to measure soil strength directly due to local variation. Therefore, the purpose of this study is to estimate SSAs of shallow landslides by considering the soil strength attributes reflected in a simple subsurface hydrologic concept (SHC). The selected study area is a granitic region in Jinbu, eastern South Korea, where shallow landslides occurred at more than 1200 locations in 2006. To estimate SSAs, soil strength was generated using several methods (i.e., direct shear tests [DSTs], Monte Carlo-simulated direct shear tests [MSDTs], and triaxial compression test [TCTs]). In addition, to investigate the effects of soil attributes in saturated/unsaturated soil on the SHC, soil depth was surveyed at a small hillslope site within the large study area. A topographically driven physical shallow landslide stability model (SHALSTAB) was utilized to investigate the performance based on the various soil strength attributes, and the results were analyzed using receiver operating characteristic (ROC) analyses. In the evaluation using the three soil strength measures (Case I), the accuracy assessment of the estimated SSAs was relatively low (range of 0.45–0.71). Using the soil strength attribute reflecting SHC (Case II), the results showed a reasonable range of accuracy (0.84–0.85). In addition, using the effects of soil strength reflected by SHC and average soil depth (Case III) also showed good predictive accuracy (0.81–0.82), but it was lower than that of Case II. This indicates that combining the hydraulic properties related to soil strength facilitates more accurate identification of SSAs causing geomorphic surface changes.

Enhanced zoogeomorphological processes in North Africa in thehuman-impacted landscapes of the Anthropocene

New zoogeomorphological features discovered in dryland landscapes of Northern Africa reflect human-animal agency since prehistory, and attest to complex, networked activities over great distances. We discuss the role of zoogeomorphology in shaping Earth's surface since the beginning of the Anthropocene, the timeframe when natural processes shifted and landscape evolution became more human-dominated. We focus on contexts in arid and semiarid lands of Northern Africa, which are metastable, sensitive ecosystems that are prone to modifications triggered by climatic and anthropogenically forced factors. Studying the geoarchaeological record in context of landscape impact and animal procurement by people throughout Antiquity is important for reconstructing domestication and husbandry of cattle, sheep, and goats in this region. Among the features we recognize in association with transhumance, pastoralism, and herding are trails, trackways, footholds, animal daybeds, stables, animal dwellings, rockshelters, game blinds, and monuments, to name a few. Related activities with landscape-scale impacts include herding, transport, corralling and browsing of cattle (Bos sp.), goats, and sheep (ovicaprines) as well as pasturage activities like cropping, fire-setting, and manuring. These activities were disturbances that affected surface processes like erosion and dust mobilization, as well as reduced vegetation and ecosystems productivity. In dryland Africa, and especially in the Sahara, intensive herding led to the alteration of the pristine aspects of bare rock surfaces and of the stone desert pavement (i.e., the hamada); many regions preserved evidence of middle-late Holocene animal daybeds, trampled areas, and barren tracks and trails. We suggest that human and herd animal activities affected geomorphic surfaces that affected slope stability, intensified erosion and dust mobilization, and enhanced dust export from the African continent offshore. We reinterpret the increased dust emission from North Africa during the mid-Holocene at the end of the African Humid Period, as has been interpreted from ocean cores; aridification of the Green Sahara followed the insolation-forced monsoonal maximum, and was exacerbated by human-animal activities across the Sahara and the Sahel. We argue that the spread of human activities and intensive husbandry of cattle, and caprines (goat and sheep) in this region significantly influenced the geomorphic stability, ecosystem and landscape sustainability in a comparable manner of overuse observed in present-day arid and marginal environments, where pastoral overgrazing pressure increases erosion processes and enhances dust mobilization. We suggest that human-animal activities have amplified dust generation from the North African continental interior since ~7 ka BP. This evidence of prehistoric human impacts on surface processes in North Africa supports arguments for an early beginning of the Anthropocene.

The Potential Relationship Between Archaeological Artifact Exposure and Surface Geomorphic Processes: Northeastern Peloponnese, Greece

ABSTRACTComplex interactions between topography, near-surface geology, active tectonics, climate, and human activity shape a landscape, conditioning archaeological deposits and making sediment deposits from surface erosion important archives. There is a potential relationship between the intensity of geomorphic processes and surface artifact distribution. This study assesses the potential relationship between soil erosion by water and the spatial distribution of archaeological surface artifacts in the Inachos River watershed, Greece. The mountainous, semi-arid Mediterranean region is particularly vulnerable to soil loss. Soil erosion is quantified by applying the Revised Universal Soil Loss Equation in a GIS framework. Estimates of soil loss vary spatially compared to surface artifact finds of the pedestrian survey of the Western Argolid Regional Project. A statistically significant relationship is identified between surface erosion rates and artifact density. Preferential topography for occupation suggests this is an associative rather than causative relationship. Knowledgeable interpretation of artifact distribution enables accurate reconstruction of human settlement history.

Active tectonics in 4D high-resolution

With a little more than 100 years since the publication of seminal and field-defining investigations, active tectonics is still a relatively young sub-discipline of structural geology. This research field addresses the accumulation of strain due to plate tectonic motion and more importantly release thereof through the occurrence of earthquakes (or other strain-releasing events). In that regard, active tectonics aims to characterize the incremental steps of plate tectonics. Determining earthquake chronologies, fault slip rates, and other common objectives importantly feed into our understanding of, for example, fault mechanics and crustal rheology. Characterizing the recurrence of large and potentially devastating earthquakes, is further motivated by seismic hazard assessment and risk mitigation.The primary data source in active tectonics is surface and shallow subsurface evidence of faulting –presenting itself in topographic and stratigraphic data sets respectively. Field observations and air photo interpretation of displaced stratigraphic and geomorphic markers were used almost 40 years ago to formulate end-member models of earthquake recurrence. Technological developments since then –especially within the last two decades– have dramatically increased the abundance and resolution of topographic data sets and the ability to date stratigraphic units and geomorphic surfaces, enabling the formulation of better-informed conceptual models of earthquake recurrence. Here, we provide an overview of the high-resolution topographic data sets and dating methods that enabled the recent advances of active tectonics.

Pedogenic evidence of Urmia Lake's maximum expansion in the late Quaternary

The Urmia Lake recession, and the resulting increase in vast barren area around it, has been rapid in recent decades and thus has attracted attention of environmentalists and geoscientists alike. However, evidence for its different strandlines and the largest extension of the lake during the late Quaternary has not been reported yet. The principal goals of the current research were to figure out pedological evidence of its maximum expansion during the late Quaternary and mapping out the different strandlines along the western shores of Urmia Lake over time. Thirty-two soil pedons at different landscape positions, geomorphic surfaces and distances from Urmia Lake were studied during autumn in 2013 and 2014. Micromorphological and mineralogical studies were performed for some diagnostic horizons. Results showed along the transect under study three different entities diagnostic of the lake's history (1) lithological discontinuities, (2) saline lacustrine sediments, (3) buried soils. However, almost 2 km from the closest pedon to the lake, no evidence of saline playa sediments were detected. Based on previous chronology results from Urmia Lake, which indicated high lake levels with very low salinity since about 180 ky BP, the sediments of this part of the study area were considered to have been deposited at the same period of time, indicating a maximum expansion of Urmia Lake during the late Quaternary. The current results demonstrate that soil pedons which were situated at various distances from Urmia Lake denote different stages of the lacustrine evolution. Along with the distance from the lake the development of soils increases. Due to a longer and more intensive impact of pedogenic processes on the topstratum the overall soil system becomes more “mature”. The study of buried soils and their comparison to upper non-buried soils revealed that in some cases, the buried soils were more evolved than their upper soils or vice versa. Through these observations, the periods of exposure to soil-forming processes after each sedimentation period was detected and schematic diagrams illustrating periods of highstands and lowstands (recessions) of Urmia Lake were reconstructed. This study demonstrates that even though multiple episodes of lake recession were apparent, the level of Urmia Lake increased during hydroclimatic events conducive to lake expansion, which affected the soil evolution due to several fluctuations during the late Quaternary.

Relationship of Landscape Positions with Soil Properties on Maize Yield in Ultisol

Relationship of landscape position and soil properties to maize (Zea mays L.) yield was studied in coastal plain soils of Akwa Ibom state. The study aimed at assessing the physico-chemical soil attributes down the geomorphic surface as well as assessing the yield of maize in the respective landscape positions. A total of 3600 plant population (hybrid maize) were planted on 0.072ha in a Randomized complete block design. The traditional land preparation technique was employed with slashing of regrowth vegetation with cutlass. The trashes was left on the sites and allowed to dry for three weeks. Preburn soil samples were taken before burning the trashes at the end of three weeks after slashing. The samples collected were analyzed in the laboratory for physico-chemical properties using standard methods. Collected data were statistically analyzed and means of statistically significant parameters were separated using LSD (0.05). The results showed that sand particle of burnt and un-burnt soils were significantly different at 0-15cm of Upper slope (US) but not significantly different in other landscape positions (p<0.05). Soil pH in burnt soil was significantly different from the un-burnt soil (both at surface and sub surface) in the three landscape positions. Mean maize yields (with husk) was 0.09 and 0.11kg/ha before and after burning plots of US ; 0.12 and 0.16kg/ha in before and after burning plot of the middle Slope (MS) while the Bottom valley (BV) had 0.14 and 0.16kg/ha in before and after burning plots. Altogether, both husked and de-husked yields were higher in burnt plots than unburnt plots. Along the slope, husked yield followed the order: BV (0.15kg/ha) > MS (0.14kg/ha) > UP (0.10kg/ha)) while de-husked yield also followed similar pattern but different magnitude.

Predicting potentially toxic elements in tropical soils from iron oxides, magnetic susceptibility and diffuse reflectance spectra

Environmental impacts can be more accurately assessed with the aid of spatial characterization of potentially toxic elements (PTEs). In fact, developing cost-effective, environmentally friendly spatial characterization methods for PTEs can facilitate the expeditious, accurate, detailed diagnosis of soil in large areas. In this study, we used three geomorphic surfaces of Oxisols to assess the ability of chemical and X-ray diffraction analyses of iron oxides, diffuse reflectance spectroscopy (DRS) and magnetic susceptibility (MS) measurements to predict the contents in PTEs (Ba, Co, Cr, Cu, Mn, Mo, Ni, Pb and Zn) and their spatial variability. Magnetic susceptibility and diffuse reflectance spectroscopy allowed well-calibrated prediction models for Ba, Co, Cu, Mn and Ni to be developed, whereas DRS-calibrated methods afforded more accurate prediction of Ba and Mn contents, and magnetic susceptibility-calibrated methods of Co and Ni contents. The correlation between PTEs and free iron contents, and their spatial pattern, testifies to the goodness of the proposed methods for predicting the contents of potentially toxic elements in soils.

Soils Developed on Geomorphic Surfaces in the Mountain Region of the State of Rio de Janeiro

ABSTRACT: The evaluation of soils in representative landscapes constitutes an opportunity to evaluate spatial distribution, discuss formation processes, and apply this knowledge to land use and management. In this sense, from the perspective of an environmentally diversified region, the aim of the present study is to evaluate the occurrence and understand the formation of soils in different geomorphic surfaces of a landscape from a mountain region in the state of Rio de Janeiro. The study was developed in the Pito [...]

Calcic soils as indicators of profound Quaternary climate change in eastern Isfahan, Iran

In the high plateau region of central Iran, there is both a lack of information on calcic soil processes and aspects of Quaternary paleoclimate. Thus, the research discussed here was undertaken as a first step to assess the utility of calcic soil research in the region. The properties and isotope composition of calcic soils was studied on a complex of alluvial fans, located about 50km SE of the city of Isfahan. At least three geomorphic surfaces have formed during an interval from the middle Pleistocene to the Holocene. These geomorphic surfaces contain calcareous soils and paleosols. Interpretation of the pedogenic evidence indicates that there have been multiple periods of clay formation and carbonate accumulation over time, with an overall trend of increasing environmental aridity. Microscopy shows that overprinting is a major factor responsible for the accumulation of calcrete, suggesting the impacts of climate oscillations on the calcrete formation. Stable isotope composition of pedogenic carbonates in soils of differing ages is suggestive of a decrease in plant density and an increase in evaporation as soils become younger. This research highlights the utility of the morphology and isotope chemistry of calcic soils for constraining environmental change during the Quaternary.

The modeling of archaeological and geomorphic surfaces in a multistratified urban site in Padua, Italy

AbstractMultistratified archaeological sites are important archives of past human activities, recording the superposition of anthropogenic deposits over centuries and millennia. We attempted the reconstruction of buried geomorphic and archaeological surfaces in the 1.55 km2, 7 m thick, multistratified urban site of Padua in northern Italy, through the spatial interpolation of 117 elevation points relative to unique archaeological features. Key data were the elevations above sea level of ancient surfaces and features, such as the presettlement alluvial plain, roads, floors, and hearths dating from Bronze to Imperial Roman ages. Present surface elevations were provided by a Light Detection and Ranging (LiDAR) digital elevation model. Spline interpolation produced general‐trend surfaces of the buried alluvial plain, Iron Age (13th–10th and 6th centuries B.C.), and Roman (first century B.C. and first to second centuries A.D.) levels. Validation of the later Roman surface indicates a decimeter accuracy of interpolation. Geographic information system overlay operations resulted in quantitative estimates of the vertical growth of the site, the volumes of archaeological deposits, and the depth of burial of the different levels. This research provided new insights on the development of the ancient city and its relations with paleohydrography, representing a starting point for the assessment of buried archaeological heritage.

RELATIONSHIP OF LANDSCAPE POSITIONS WITH SOIL PROPERTIES ON MAIZE YIELD IN ULTISOL

Relationship of landscape position and soil properties to maize (Zea mays L.) yield was studied incoastal plain soils of Akwa Ibom state. The study aimed at assessing the physico-chemical soil attributesdown the geomorphic surface as well as assessing the yield of maize in the respective landscapepositions. A total of 3600 plant population (hybrid maize) were planted on 0.072ha in a Randomizedcomplete block design. The traditional land preparation technique was employed with slashing of regrowth vegetation with cutlass. The trashes was left on the sites and allowed to dry for three weeks. Preburn soil samples were taken before burning the trashes at the end of three weeks after slashing. Thesamples collected were analyzed in the laboratory for physico-chemical properties using standardmethods. Collected data were statistically analyzed and means of statistically significant parameters wereseparated using LSD (0.05). The results showed that sand particle of burnt and un-burnt soils weresignificantly different at 0-15cm of Upper slope (US) but not significantly different in other landscapepositions (p<0.05). Soil pH in burnt soil was significantly different from the un-burnt soil (both atsurface and sub surface) in the three landscape positions. Mean maize yields (with husk) was 0.09 and0.11kg/ha ‘before’ and ‘after’ burning plots of US ; 0.12 and 0.16kg/ha in ‘before’ and ‘after’ burningplot of the middle Slope (MS) while the Bottom valley (BV) had 0.14 and 0.16kg/ha in ‘before’ and‘after’ burning plots. Altogether, both husked and de-husked yields were higher in burnt plots than unburnt plots. Along the slope, husked yield followed the order: BV (0.15kg/ha) > MS (0.14kg/ha) > UP(0.10kg/ha)) while de-husked yield also followed similar pattern but different magnitude.

The long‐term legacy of geomorphic and riparian vegetation feedbacks on the dammed Bill Williams River, Arizona, USA

AbstractOn alluvial rivers, fluvial landforms and riparian vegetation communities codevelop as a result of feedbacks between plants and abiotic processes. The influence of vegetation on river channel and floodplain geomorphology can be particularly strong on dammed rivers with altered hydrology and reduced flood disturbance. We used a 56‐year series of aerial photos on the dammed Bill Williams River (Arizona, USA) to investigate how (a) different woody riparian vegetation types influence river channel planform and (b) how different fluvial landforms drive the composition of riparian plant communities over time. We mapped vegetation types and geomorphic surfaces and quantified how relations between fluvial and biotic processes covaried over time using linear mixed models. In the decades after the dam was built, woody plant cover within the river's bottomland nearly doubled, narrowing the active channel by 60% and transforming its planform from wide and braided to a single thread and more sinuous channel. Compared with native cottonwood–willow vegetation, nonnative tamarisk locally induced a twofold greater reduction in channel braiding. Vegetation expanded at different rates depending on the type of landform, with tamarisk cover on former high‐flow channels increasing 17% faster than cottonwood–willow. Former low‐flow channels with frequent inundation supported a greater increase in cottonwood–willow relative to tamarisk. These findings give insight into how feedbacks between abiotic and biotic processes in river channels accelerate and fortify changes triggered by dam construction, creating river systems increasingly distinct from predam ecological communities and landforms, and progressively more resistant to restoration of predam forms and processes.

Paleoenvironment of geomorphic surfaces of an alluvial fan in the eastern Isfahan, Iran, in the light of micromorphology and clay mineralogy

Alluvial fans are one of the most important landforms in geomorphological and paloenvironmental studies. The objective of this study was the application of clay mineral assemblages and micromorphological properties of the studied paleosols in the geomorphic surfaces of an alluvial fan in the eastern Isfahan as proxies for paleoenvironmental and paleoclimatic changes. Micromorphology, X-ray diffraction, and scanning electron microscopy approaches were used to study the representative pedons. The results indicated that the illuviation process in the calcareous soils of the arid regions of the eastern Isfahan was probably in response to Quaternary moist conditions. There was no significant difference between clay coating properties of the studied relict and buried paleosols. Clay mineralogical study suggested that kaolinite and illite were inherited from the parent materials, while smectite and palygorskite were formed in the soil environment. Paleoargillic horizon was characterized by smectite and calcic (especially the calcrete) horizons were dominated by palygorskite. Palygorskite was accumulated by both neoformation and illuviation processes. High clay content, high intensity of smectite peak, and activity of the illuviation process in paleoargillic horizon demonstrated the seasonality of climate (rainfall) even in the moist periods of Quaternary in Central Iran. Clay mineralogical assemblages suggested a trend of increasing environmental aridity in the study area. This study, therefore, highlighted the role of clay mineralogical investigations in arid lands’ geomorphological and paleoenvironmental researches.

反射法地震探査および重力探査から明らかになった仙台平野南部の伏在活断層

The southern part of the Sendai Plain is located between the Futaba active fault zone and the Nagamachi-Rifu active fault zone. In the existing research, only 6.5km long of the active fault trace was estimated along the eastern foot of Medeshima Hills because the geomorphic surface of the Medeshima Hills is warping toward east. Besides the above, no other active fault trace had been clearly identified in this area. To reveal the subsurface structure, we conducted 5.3-km-long of seismic reflection survey across the southern part of the Sendai Plain, near the mouth of the Abukuma river, which is the northern extension of Futaba active fault zone. The result of seismic profile analyzed with a standard CMP method shows the existence of concealed active fault beneath the Sendai Plain and 30-40m of dislocations in seismic reflectors from Miocene to Quaternary layer. The activity of the concealed fault is estimated as a C-class (Long-term rate of faulting, 0.01-0.1mm/yr). The survey of relative gravity measurement at intervals of 200 m was also conducted, including the seismic reflection survey line. Steep gradient of the Bouguer gravity anomaly were observed in the vicinity of the concealed active fault that is revealed from the seismic reflection survey. Analysis with the 2-D density structure analysis demonstrates that steep gradient of Bouguer gravity anomaly was responsible for large deformation of pre-Miocene basement rocks by repeated faulting of the concealed active fault. In addition, to discuss a tectonic evolution of the Sendai Plain, we made topographic profiles, using 1m-DEM and 2m-DEM data across the plain. Topographies of these profiles show that discontinuity of 1.5-2.2m on both sides of the westernmost beach ridge in the southern part of the Sendai Plain. Active faulting of the concealed fault has possibly contributed to these topographic discontinuities.

Influence of Different Geomorphic Surfaces and Profile Modification on the Growth of <i>Maesopsis eminni</i> (Engl) at the Yongka Western Highlands Research Garden Park Nkwen-Bamenda, North West Cameroon

The growth of Maesopsis under the influence of various geomorphic surfaces was followed within a period of 70 months. Young plants of two months old were transplanted into 70 × 70 × 70 cm holes under natural conditions (no inputs such as manure and other amendments). A randomized complete block design was set up for the experiment, alongside a control, and growth parameters followed (height and collar circumference). Three blocks with different geomorphic surfaces were put in place for the experiment (upper slope or block 1, middle slope or block 2 and foot slope or block 3). Results of the experiment indicated that geomorphic surface had a significant effect on height but not on collar circumference. Plant height increased progressively from upper slope to foot slope; less tall trees were found at the upper slope, while the tallest trees were found at the foot slope. After 70 months, maximum average height attained by plants for the experiment was 1228.3 cm, observed in block 3 (foot slope), significant at 0.05 confidence level with respect to geomorphic surface. In blocks 1 and 2 (upper slope and middle slope), maximum average heights attained were 798.5 and 937.5 cm, respectively and were shown to be statistically equal at 0.05 confidence level. Geomorphic surface had no effect on collar circumference. Maximum average collar circumferences attained after 70 months were 62.8 cm (observed at the upper slope), 61.3 cm (observed at the middle slope) and 76.3 cm (observed at the foot slope) and the various collar circumferences were shown to be statistically the same at 0.05 confidence level. For the control, maximum height attained after 70 months was 1240 cm (observed at the foot slope). At the upper slope and middle slope, maximum average heights were respectively, 800 cm and 905 cm, and were statistically equal at the 0.05 confidence level but different from the foot slope value of 1240 cm. Maximum average collar circumference was observed at the foot slope (76.3 cm), while circumferences of 62.8 cm and 61.3 cm were respectively observed at the upper and middle slopes. In the control, collar circumference was shown to be statistically equal at the upper and middle slopes but different from that at the foot slope at 0.05 confidence level. Correlations between growth parameters were more explained for the control than for the experiment. Increasing plant height was associated with decreasing percent slope (at a p-value of 0.05) corresponding to increasing soil depth favoring root exploration and soil and water retention. Profile modification enhanced plant growth and enabled the cultivation of trees on all geomorphic surfaces.