Steep Escarpment Research Articles

Comprehensive Analysis of Landform and Land Use/ Land Cover Mapping of Waghora Watershed Using Sentinal-2B and SRTM-DEM Data

This paper aims to integrate the use of high spectral resolution a remote sensing data of Sentinel-2B imagery along with the Digital Elevation Model (DEM) derived from the SRTM stereo data to delineate the landforms and analyze the land use and land cover in Waghora watershed, Sausar tehsil, Chhindwara district, situated on basaltic terrain in northern Deccan plateau. A 30 m resolution DEM of the study area was generated, capturing terrain parameters like elevation, slope, aspect, hillshade, and drainage. Sentinel-2B (10 m) images from two seasons were collected FCC (false colour composite) and were prepared by ARCGIS software. combination of Sentinel-2B imagery, SRTM-DEM data, and ground truth verifications to delineate eight major landforms in the studied area. Slope information, extracted from high-resolution DEMs, reveals 4 distinct slope classes. The landforms, including Plateau, Escarpment, Foot Slope, Upper Pediment, Lower Pediment, Valley, Interfluve, and Mound, are characterized based on visual interpretation and geological context. Each landform exhibits unique features, elevation ranges, and dominant land use/cover types, such as single crop cultivation, forest, or degraded land. This detailed terrain analysis aids in land-use planning and environmental management initiatives. The land use/land cover analysis utilizes Sentinel-2B data to identify five classes: degraded forest, double crop, single crop, orchard, and land with and without scrubs. Dense forest dominates 24.2% of the watershed, while double crop and single crop lands cover 36.7% and 24.2% respectively. Orchards occupy a minimal 0.8% of the area, and wastelands account for 5.7%. The relationship between landforms, slope, and land use/cover reveals dominant forestation on steep escarpments, while valleys and interfluves support double cropping due to gentle slopes and depositional processesThe study elucidated connections to examine diverse biophysical phenomena. It highlights the effectiveness of employing SRTM-DEM and Sentinel-2B imagery for analyzing geomorphic characteristics and mapping land use/land cover, offering significant perspectives for land management and planning approaches.

Terrain analysis and hydrogeomorphic investigation of the Sita-Swarna river basin, Udupi, SW India: Insights from remote sensing methods

Hydrogeomorphic characteristics of the Sita-Swarna river basin, Western Ghats, India, are investigated to understand the influence of lithology, structure and geological control on the channel morphology. For preliminary investigation, remote sensing, geomorphic and morphometric analysis was carried out, producing slope, aspect and lineament maps from a 30 m resolution Digital Elevation Model (DEM) with the help of GIS. Remote sensing analysis inferred a steep south-to-southwest slope with dominant lineaments trending NW and ENE to E in the middle reaches of the Sita-Swarna river basin. These lineaments are deduced to have possibly been instigated by faults, shear zones, dyke ridges, or subsurface structures that influence the surficial topography. Upland and pediment geomorphic zone were identified, inferring Western Ghats Escarpment (WGE) and gently coastward W-sloping dissected pediment surface. A comprehensive morphometric analysis is performed using various linear, areal, and relief parameters for basin characterization. The linear parameters infer that the basin is structurally controlled and shows moderate to high permeability and flood susceptible areas downstream. The calculated morphometric parameters for basin characterization reveals that the Sita-Swarna river basin is at the mature stage of development and highly asymmetrical with the westward tilt, which indicates a possible influence of paleo tectonism. Rapid runoff is observed due to the steep escarpment leading to less infiltration and flash flood possibility during heavy rainfall. The present study mainly establishes the potential application of remote sensing methods to quantify the hydrogeological aspects, basin morphometry and landscape evaluation in the tropical climatic zone.

A review of Cuvier’s beaked whale strandings in the Mediterranean Sea

Cuvier’s beaked whale (Ziphius cavirostris) is the only species of beaked whale commonly found in the Mediterranean Sea, a deep, semienclosed basin. Beaked whales are generally an offshore family often found in association with the canyons and steep escarpments common to the area. Much of the current knowledge of this species has been derived from strandings data. Historically, strandings data for the Mediterranean Sea has been collected by individual researchers and more recently, over the last two decades, by national strandings networks. We reviewed strandings data collected by strandings networks from Italy, Greece, Spain and France. Additionally, we compiled strandings information gleaned from the literature, personal communications, regional newspapers and the world wide web from countries that border the Mediterranean Sea. While this review is certainly not exhaustive, it has allowed the creation of an extensive geo-referenced basin wide database using a geographic information system (GIS) of over 300 stranding events. The acquired data permit documentation of the number of mass stranding events, allow general observations about distribution and chronology of stranding events dating back to 1803 and enables evaluation of strandings based on several different criteria. The first recorded mass stranding event was in 1963 off Genova, Italy. Analysis shows that specific geographic stranding areas can be identified, even though the level of effort undertaken in the different countries may vary.

Frost-weathering control on the rate of late Quaternary landscape evolution, western flank of the Taebaek Mountain Range, Korea: a case of passive margin landscape evolution

ABSTRACT Passive continental margins can show anomalously high topography and exhibit a discrete steep escarpment, divide, and gentle slope from the exterior to the interior of the margin. Compared with active (i.e. convergent and strike-slip) tectonic regions, the processes and rates of change of high-altitude landscapes driven by tectonics and/or climate in tectonically inactive (passive) continental margins are poorly understood. We used 10Be catchment-wide denudation rates of fluvial sands (n = 29) collected in 17 catchments and 12 sub-catchments, as well as topographic analysis, to quantify the rate of landscape change along the western flank of the Taebaek Mountain Range (TMR). The denudation rates range from ∼20 to ∼70 mm/ka. These rates show no significant difference between upstream and downstream areas, implying that denudation is not (or is only negligibly) affected by deep-seated mass wasting processes and human impact. 10Be denudation rates in the northern TMR are 1.6 times higher than in the south. In addition, the relationship between denudation rates and geomorphic parameter values also differs from north to south. These observed spatial differences in the rate of denudation and geomorphic response can be explained by intense frost weathering rather than lithological control. Our quantitative analysis of denudation rates and topography suggests that southwest-directed migration of the range’s main divide occurs and that the range's western flank (low relief) is likely to be in a geomorphic state of quasi-equilibrium whereas the eastern flank (steep) still remains transient.

Insights into the subsurface structure of wrinkle ridges on Mars

Wrinkle ridges are important landforms on Mars and other planetary bodies and result from horizontal tectonic shortening. This study provides insights into the subsurface of selected wrinkle ridge sites, based on exposures provided by steep escarpments and crater slopes that crosscut wrinkle ridges. We mapped the complex fold and fault patterns and measured fault dips, where faults appear planar. The fault pattern underneath wrinkle ridges is diverse and is dominated by reverse faults and thrusts. The predominance of one fault system leads to morphological asymmetries of many wrinkle ridges. The upper tip of the dominant thrust fault is commonly situated beneath the steeper wrinkle ridge slope and may outcrop at its base. Polarity changes of wrinkle ridges along strike go along with a change of the dominant thrust direction. Symmetric wrinkle ridges are formed when a conjugate system of thrusts exists in the subsurface. Several wrinkle ridges display a main thrust fault whose dip angle bends over to a shallower dip at depth. The measurements of average dip for primary thrust and backthrust faults are 37° ± 2° and 28 ± 2°, respectively. In general, most of the examined wrinkle ridges are characterized by a multitude of subsidiary and backthrust faults. With the limitation that the uppermost 500-1000 m of the wrinkle ridges subsurface are accessible in this study and despite the large morphological and structural variability of wrinkle ridges, the kinematics of fault-propagation folds models seem to show a large match to our observations and measurements. Likewise, continuum mechanics models show a good fit to the obtained structural data. Fault-bend fold models and simple buckle folding models seem less compatible with observations.

Alcoves as Havens From a Harsh Martian Environment

AbstractFuture missions to Mars will undoubtedly be directed toward sedimentary terrains in search for evidence of past life and geologic history. Astronauts will need to find shelter from harsh surface conditions. Natural underground voids provide a readily adaptable habitat for crews to shelter from radiation. Naturally formed caves would be desirable habitat sites, but thick deposits of limestone or other soluble rocks in which karst topography would form have not been identified by current observations. Alcoves, arched recess in steep escarpments, should be widely distributed across the planet and provide an adaptable shelter for astronauts operating on the surface of Mars. Alcoves provide a more stable thermal environment, a reduced radiation environment, shielding from macro‐ and micro‐meteorite impacts, and protection from atmospheric disturbances.

Late Holocene peatland palm swamp (aguajal) development, carbon deposition and environment changes in the Madre de Dios region, southeastern Peru

Tropical peatlands are an important carbon reservoir; however, they are vulnerable to climate change, fire events, and human disturbances, and may become a significant carbon source if degraded. In this paper, we investigated the late Holocene record of vegetation change, peatland evolution, and C accumulation based on analysis of a sediment core through a Mauritia-flexuosa palm dominated swamp (locally called “ aguajal ”) in the Madre de Dios region in southern Peru to better understand tropical peatland dynamics. Sedimentation commenced within shallow water, ponded on an impervious substrate, perhaps within an abandoned river channel or oxbow lake (1380–820 cal yr BP) located adjacent to a steep escarpment with terra firme (upland) rainforest above and lateral to floodplain forests. This was followed by the development of marsh (820–640 cal yr BP). A closed-canopy Mauritia flexuosa -dominated palm swamp was subsequently established (640300calyr BP) which later changed into an open canopy and mixed Mauritia - Hedyosmum palm swamp (300 cal yr BP to present). Two major changes in peat and C accumulation rates were observed: (1) onset of peat and C accumulation at 820 cal yr BP and (2) decrease of peat and C accumulation after 520 cal yr BP. Comparisons of our results with palaeoecological records from aguajales in northern Peru suggest that the dynamics were different in this region. The peat and C accumulation rates in our study core in southern Peru were ca. 4 mm yr −1 and ca. 200 g m −2 yr −1 faster, similar to a few sites in northern Peru. Aguajales in Madre de Dios region in southern Peru are an important carbon sink. Analyzing the dynamics of aguajales which are a kind of typical peatlands in Amazonia and comparing among different sites allows exploration and prediction of regional peatlands' development under the potential future impact of natural changes. • First study of a palm peatland ( aguajal ) development in Madre de Dios region, southern Peru • This study includes late Holocene vegetation dynamics, peat and C accumulation of the aguajal • Controlling factors in the dynamics are fluvial changes and climate • Comparisons with northern Peru suggest different vegetation succession • Peat and C accumulation rates in Madre de Dios were faster, similar to a few sites in northern Peru

Turbulent flow characterization near the edge of a steep escarpment

Characteristics of turbulent flow over a steep escarpment were studied using a 1:25 scale model of the Bolund hill in a wind tunnel under neutral atmospheric stability conditions. The influence of Reynolds number, inflow shear profile, and escarpment geometry were investigated in relation to flow behavior including separation and reattachment, Reynolds stresses, vorticity, Turbulent Kinetic Energy (TKE) production, and Gaussianity. Multi-camera Particle Image Velocimetry (PIV) was used to examine the flow in the vicinity of the escarpment leading edge. Four test cases were studied across a Reynolds number range of 1 × 10 5 < R e h < 5 × 10 5 . Two different inflow profiles were evaluated, as well as two different leading edge geometries – a round edge with non-dimensional radius of curvature a η ≈ 0.2 and a sharp edge with η ≈ 0 . A sharp leading edge was found to produce a well-defined separation bubble, yielding distributions and magnitudes of Reynolds stress, vorticity and TKE production closely resembling those of flow over an idealized forward facing step, as well as full-scale measurements of TKE. Gaussianity of the flow was significantly modified by the escarpment, with high skewness and kurtosis occurring in the sharp edge case along the boundary of the separation bubble. • Small changes in escarpment leading edge sharpness greatly influence turbulent flow behavior. • Sharp edge caused relocation of area of peak turbulent kinetic energy. • Turbulent flow of sharp edge case better approximated full-scale measurements. • Turbulent flow of sharp edge case similar to canonical forward-facing step. • Gaussianity modified along separation bubble boundary.

The development of Kangiqsualujjuaq and the threat of snow avalanches in a permafrost degradation context, Nunavik, Canada

Slope processes are active in the rolling plateau landscapes of Nunavik, Northern Québec, Canada. There are a few short but very steep escarpments in this region. On January 1st, 1999 a powerful snow avalanche struck Kangiqsualujjuaq, one of the 14 Inuit villages in Nunavik. Nine people died and 25 were injured. This village and its surrounding are located within a glacial valley, in a periglacial environment. There is significant population growth, as well as in the other villages in Nunavik. As early as 1999-2000, there was a significant spatial reorganization of the village's infrastructures to avoid the impact of other snow-avalanche events. The main objective of this paper is to examine the village expansion in response to snow-avalanche process and population growth, within an area constrained with permafrost thawing and steep slopes. From naturalist geomorphologic methods, written sources such as archive documents and aerial photographs, the results show that slopes above Kangiqsualujjuaq are prone to release snow avalanches during blizzards from uncommon directions, and that the newly built housing may be at risk in some places, due to the conjunction of snow avalanches and permafrost thawing.

Influence of flow hydraulic characteristics on the ridge lower escarpment angle

In the riverbeds and canals that run on non-cohesive grounds, bedload sediments move in the ridges form. Ridge forms determine the flow rate of bedload sediments, hydraulic resistances, the types and rates of deformations in alluvial channels. The main elements of ridge formations are height, gentle and steep length with corresponding escarpments. The ridge's steep length and this corresponding escarpment change with changes in the flow hydraulic characteristics. With a change in the ridge's steep length and its steep escarpment, the hydraulic resistance of the channel, the flow rate of bedload sediments, the types, and the channel deformation rates change. In the laboratory, a series of experiments with different sediments compositions and diameters were carried out on the hydraulic tray to determine the main elements (total, gentle and steep length, and the ridge height) and the dynamic characteristics of the ridge formations and the flow hydraulic characteristics. Calculation formulas for determining the coefficient of the ridge lower escarpments with and without taking into account the angle of the natural ground escarpment under water and in the dry state, and the dependence of the steepness of the relative ridge on the relative flow velocity, are obtained. The obtained dependencies allow to accurately determine the geometric and dynamic characteristics of bedload ridges and the corresponding hydraulic characteristics that may define the view ridge formations, ridges resistance of the channel, and the flow rate of bedload sediments, and to design sustainable escarpments large channels.

Ecological studies of Commiphora genus (myrrha) in Makkah region, Saudi Arabia

Commiphora, myrrha, is a pantropical genus and perform well in arid and semi-arid environments. This genus has economic importance. Distribution of Commiphora species and their associated species in Saudi Arabia has not been studied to date. The current study report on (a) characterization and distribution of plant communities including Commiphora species and (b) assessment of factors influencing ecological preferences of these species. Five species of Commiphora are recorded inhabiting mountain slopes, steep escarpments or hills consisting of igneous rocks, either granites or basalt with drought prone shallow soil. One hundred and twenty-six plant species belonging to 95 genera and 35 families were found associated with different Commiphora species. Therophytes showed the most frequent life form class and Sudanian region elements recorded the highest phytogeographical units (28%) followed by Tropical elements. Field study showed that Commiphora gileadensis and C. quadricincta preferred granite and basalt rocks exposed to erosion, while C. myrrah, C. kataf and C. habessinica grow on resistant coarse pink granite. The analysis of 240 sampling stands with TWINSPAN revealed the vegetation of Commiphora habitats into eight vegetation groups; each group represented a distinct microhabitat. Dendrogram obtained from a hierarchical classification showed that habitats of C. gileadinsis and C. quadricincta are more similar than those of other species. This similarity was confirmed by Jaccard and Sorenson similarity indices and by Pearson correlation coefficient. This investigation compiled the information/data to facilitate future range management of Commiphora species.

Connectivity patterns in contrasting types of tableland sandstone relief revealed by Topographic Wetness Index

Recognition of structural connectivity is particularly challenging in terrains lacking a hierarchical fluvial system, but typified by strong bedrock control, extreme ruggedness of relief, the presence of sinks (closed depressions) as in karst, or considerably modified by anthropogenic interventions. In this paper, the issue of connectivity mapping in such a very rugged terrain – a sedimentary tableland underlain by sandstones, mudstones and marls – is addressed. Three specific geomorphic contexts were selected for detailed study. These are steep escarpments, canyon-riddled cuesta backslopes, and residual tabular hills (mesas), with relative relief of 100–300 m. This work is primarily based on geomorphometric approach, with the Topographic Wetness Index used as a tool to recognize pathways of water and possible sediment transfer across the sandstone tableland. In addition, maps of distribution of closed depressions were generated. High resolution (1 m) digital terrain models provided input topographical data. The results of desk research were verified by the results of field work aimed at recognition of visible signatures of geomorphological connectivity in the physical landscape. Specific connectivity patterns were identified for each setting, with two common features being strong structural control due to regular joint pattern and the presence of numerous sinks, resulting in widespread surface disconnectivity. Furthermore, differences between structural and functional connectivity emerge. The latter occurs very rarely, during rather infrequent extreme precipitation events, and there are only a few evident, permanent sediment transfer pathways in the areas subject to analysis. The presence of well-jointed and porous sandstones accounts for drainage diversion underground and restricted surface runoff from the tableland and hence, for an underdeveloped network of perennial streams and clearly identifiable valley morphology.

Slope failure and mass transport processes along the Queen Charlotte Fault, southeastern Alaska

Abstract The Queen Charlotte Fault defines the Pacific–North America transform plate boundary in western Canada and southeastern Alaska for c. 900 km. The entire length of the fault is submerged along a continental margin dominated by Quaternary glacial processes, yet the geomorphology along the margin has never been systematically examined due to the absence of high-resolution seafloor mapping data. Hence the geological processes that influence the distribution, character and timing of mass transport events and their associated hazards remain poorly understood. Here we develop a classification of the first-order shape of the continental shelf, slope and rise to examine potential relationships between form and process dominance. We found that the margin can be split into six geomorphic groups that vary smoothly from north to south between two basic end-members. The northernmost group (west of Chichagof Island, Alaska) is characterized by concave-upwards slope profiles, gentle slope gradients (&lt;6°) and relatively low along-strike variance, all features characteristic of sediment-dominated siliciclastic margins. Dendritic submarine canyon/channel networks and retrogressive failure complexes along relatively gentle slope gradients are observed throughout the region, suggesting that high rates of Quaternary sediment delivery and accumulation played a fundamental part in mass transport processes. Individual failures range in area from 0.02 to 70 km 2 and display scarp heights between 10 and 250 m. Transpression along the Queen Charlotte Fault increases southwards and the slope physiography is thus progressively more influenced by regional-scale tectonic deformation. The southernmost group (west of Haida Gwaii, British Columbia) defines the tectonically dominated end-member: the continental slope is characterized by steep gradients (&gt;20°) along the flanks of broad, margin-parallel ridges and valleys. Mass transport features in the tectonically dominated areas are mostly observed along steep escarpments and the larger slides (up to 10 km 2 ) appear to be failures of consolidated material along the flanks of tectonic features. Overall, these observations highlight the role of first-order margin physiography on the distribution and type of submarine landslides expected to occur in particular morphological settings. The sediment-dominated end-member allows for the accumulation of under-consolidated Quaternary sediments and shows larger, more frequent slides; the rugged physiography of the tectonically dominated end-member leads to sediment bypass and the collapse of uplifted tectonic features. The maximum and average dimensions of slides are an order of magnitude smaller than those of slides observed along other (passive) glaciated margins. We propose that the general patterns observed in slide distribution are caused by the interplay between tectonic activity (long- and short-term) and sediment delivery. The recurrence (&lt;100 years) of M &gt; 7 earthquakes along the Queen Charlotte Fault may generate small, but frequent, failures of under-consolidated Quaternary sediments within the sediment-dominated regions. By contrast, the tectonically dominated regions are characterized by the bypass of Quaternary sediments to the continental rise and the less frequent collapse of steep, uplifted and consolidated sediments.

The pre-breakup stratigraphy and petroleum system of the Southern Jan Mayen Ridge revealed by seafloor sampling

The Jan Mayen Microplate Complex (JMMC) in the NE Atlantic is interpreted to mostly consist of continental fragments with possible interstitial embryonic oceanic crust. A complex Cenozoic rifting history accompanied by extensive extrusive and intrusive volcanism have made the geological characterization of the JMMC challenging especially due to poor seismic imaging beneath the breakup basalt succession. The presence of continental crust in the JMMC is inferred by seismic and magnetic data, but ground truthing evidence have yet to be provided. Here, we present the results from a seafloor sampling campaign undertaken in 2011 on the Southern Jan Mayen Ridge complex. Seabed samples were recovered using a gravity corer and a dredge along a 1000 m high escarpment with a 19° slope. Sampling locations were selected based on the interpretation of seismic profiles that suggest the presence of possible pre-breakup successions outcropping along this steep escarpment. Results include a sequence of samples with age diagnostic palynomorph assemblages ranging from Permian/Triassic to Eocene, and including igneous samples related to the Early Eocene breakup volcanism. Importantly, the samples were retrieved from hard substrate in an erosional gully lacking overburden sediments and have ages arranged in younging upward sequential order, supporting their near in-situ position. The sampling results were integrated into a lithostratigraphic pseudo-well that can be used to constrain the evolution and breakup of the JMMC. Additionally, evidence for active migration of Jurassic sourced hydrocarbons comprise the first indication of a working hydrocarbon system, with important implications for the petroleum prospectivity of the Dreki area. Finally, these results confirm that the Southern Jan Mayen Ridge is indeed a sliver of continental crust.

A numerical model in predicting the initial karst development in porous limestone

The numerical model proposed in this paper represents a new method in predicting initial karst spatial distribution of carbonate aquifers. Karstification Index, \( \varPhi_{\text{K}} \), is a measure of the possible largest amount of calcite that can be dissolved from a unit area of rock and transported by groundwater flow during a unit length of time. Mathematically, it is defined as \( \varPhi_{\text{K}} = q \cdot s \), where q is the flux of groundwater and s is the rock solubility; and Karstification Index, \( \varPhi_{\text{K}} \), is the function of flow, heat, and calcium concentration. The numerical model simulates the time- and space-dependent susceptibility to, and process of, karstification by iterative calculations between \( \varPhi_{\text{K}} \) and hydraulic conductivity. A sample calculation is presented on a hypothetical limestone plateau with steep escarpment, a spring, and a river on one side, a vertical no flow boundary on the other side, and a horizontal impermeable base. The rock has an equivalent porous-medium hydraulic conductivity of K = 5E−8 ms−1, which is characteristic to non-karstified limestone. Initially, the spring is located at the intersection of the water table and the escarpment’s face some distance above the river. The simulation result showed that the water table is lowered in 2325 years across the plateau, but the spring’s drop is stopped after 65 years. Karstification is most intensive along the water table due to the higher value of Karstification Index which resulted from the intensive flux of the water. The continual decline of the water table results in a laterally elongated and progressively expanding body of karstified rock and finally as a horizontal conduit at river level. The concentration of Ca2+ and conduit diameter decrease from the spring toward the impermeable vertical wall on the opposite side and downward to the base of the plateau. The results are consistent with general theories and empirical observations of karst and cave evolution.

Morphometric analysis of plunge pools and sediment wave fields along western Great Bahama Bank

A systematic assessment of morphometric parameters of over 200 plunge pools along the steep escarpment base of western Great Bahama Bank and ~2000km2 of sediment wave fields of upslope migrating cyclic steps documents the importance of cascading density currents for sedimentation on the slope. The abrupt downslope termination of the Holocene mud wedge with the cyclic steps shows that strike parallel bottom currents interacting with the off-bank currents are responsible for slope sediment distribution. The plunge pools and sediment waves were generated by density-cascading and both are related to a hydraulic jump caused by two gradient changes along the slope profile. The bedforms highlight both the erosional and depositional nature of this current regime, which is controlled by slope gradient and the directional confinement by either grooves on the steep escarpment or gullies on the middle to lower slope. The >20m deep plunge pools are ellipsoidal, with an average width of 211m and length of 283m, but variations between 80–360m and 100–650m for width and length occur. They are caused by an average gradient break of 16° on the cemented upper slope. Gradient breaks of as low as 2° are reported to be sufficient to scour a plunge pool like the ones in the study area, but higher gradient breaks between 10 and 20° are quite common for consistent plunge pool development. A second gradient break further down slope changes flow conditions for the generation of cyclic steps, with asymmetric waveforms of 4m high (average) in large wave fields in the entire the study area. Orientation is mainly orthogonal to the main slope direction but wave lengths and sinuosity vary, depending on the morphologic location of the wave field. The comparison with sediment wave fields with similar geometries or in similar environments shows that flow reconstruction based on the wave height and wave length alone along with a characterization of sediment grain size, however, yields non-unique results and is site specific.

Tectonic Geomorphology in Parts of Koyna Region, Maharashtra

ABSTRACT Geomorphic signatures in parts of Koyna region were analysed using satellite images and morphometric indices (stream length gradient index and valley width to height ratio) with limited field checks in key areas for understanding the role of tectonics in this seismically active zone. The Koyna River zone, particularly downstream of Koyna dam wall up to Kajali Nadi, is characterised by incised narrow valleys, steep escarpments and structurally controlled drainage. Presence of knick points at consistent elevations between 825 m to 675 m, steep gradients in an otherwise gradual longitudinal profile and valley width to height ratio less than 1.0 suggest readjustment of the streams along NW-SE and N-S directions. The escarpment slopes in general have en echelon arcuate ridge pattern ∼ N45°-N 225° in the western part, and then becomes ∼N 10°-N 190° near Donachiwadi, almost orthogonal to the E-W Koyna River. The Donachiwadi fault runs parallel to the escarpment slopes observed near Kodoli. The fluvial system in Koyna thus indicates rejuvenation controlled by basement propagated structures.

Heterozoan carbonate deposition on a steep basement escarpment (Late Miocene, Almería, south‐east Spain)

AbstractHeterozoan temperate‐water carbonates mixed with varying amounts of terrigenous grains and muddy matrix (Azagador limestone) accumulated on and at the toe of an inherited escarpment during the late Tortonian–early Messinian (late Miocene) at the western margin of the Almería–Níjar Basin in south‐east Spain. The escarpment was the eastern end of an uplifting antiform created by compressive folding of Triassic rocks of the Betic basement. Channelized coralline‐algal/bryozoan rudstone to coarse‐grained packstone, together with matrix‐supported conglomerate, are the dominant lithofacies in the higher outcrops, comprising the deposits on the slope. These sediments mainly fill small canyon‐shaped, half‐graben depressions formed by normal faults active before, during and after carbonate sedimentation. Roughly bedded and roughly laminated coralline‐algal/bryozoan rudstone to coarse‐grained packstone are the main lithofacies forming an apron of four small (kilometre‐scale) lobes at the toe of the south‐eastern side of the escarpment (Almería area). Channelized and roughly bedded coralline‐algal/bryozoan rudstone to coarse‐grained packstone, conglomerates, packstone and sandy silt accumulated in a small channel‐lobe system at the toe of the north‐eastern side of the escarpment (Las Balsas area). Carbonate particles and terrigenous grains were sourced from shallow‐water settings and displaced downslope by sediment density flows that preferentially followed the canyon‐shaped depressions. Roughly laminated rudstone to packstone formed by grain flows on the initially very steep slope, whereas the rest of the carbonate lithofacies were deposited by high‐density turbidite currents. The steep escarpment and related break‐in‐slope at the toe favoured hydraulic jumps and the subsequent deposition of coarse‐grained, low‐transport efficiency skeletal‐dominated sediment in the apron lobes. Accelerated uplift of the basement caused a relative sea‐level fall resulting in the formation of outer‐ramp carbonates on the apron lobes, which were in turn overlain by lower Messinian coral reefs. The Almería example is the first known ‘base of slope’ apron within temperate‐water carbonate systems.

Post-rift influence of small-scale convection on the landscape evolution at divergent continental margins

After decades of geological and geophysical data acquisition along with quantitative modeling of the long-term evolution of the landscape at divergent continental margins, the search for an explanation for the formation and evolution of steep escarpments bordering the coast is still a challenging task. One difficult aspect to explain about the evolution of these escarpments is the expressive variability of denudation rate through the post-rift phase observed in many margins. Here I propose that the interaction of small-scale convection in the asthenosphere with the base of the continental lithosphere can create intermittent vertical displacements of the surface with magnitude of a few hundreds of meters at the continental margin. These topographic perturbations are sufficient to produce an expressive variability in the rate of erosion of the landscape through the post-rift phase similar to the exhumation history observed along old divergent margins. I show that the vertical motion of the surface is amplified when a mobile belt is present at the continental margin, with lithospheric mantle less viscous than the cratonic lithosphere and, consequently, more prone to be partially eroded by the convective asthenosphere. I conclude that the influence of small-scale convection is not the primary explanation for the formation of high topographic features at divergent continental margins, but can be an important component contributing to sustain a preexistent escarpment. The present results are based on numerical simulations that combine thermochemical convection in the mantle, flexure of the lithosphere and surface processes of erosion and sedimentation.

ANALYSIS ON THE ROAD TRANSPORTATION NETWORKS OF THE AMHARA REGION, ETHIOPIA

The Amhara National Regional State is lying between the Abay and Tekeze rivers with vast territory, endowed with varied climatic regions and different kinds of natural recourses. It is one of the areas of earliest settlement in Ethiopia as a result of which has been experiencing high deterioration of natural resources. The rugged and steep escarpments and the frequently incised topography are making the construction of road transportation very difficult and expensive in financial terms. Moreover, landslides and severely eroded gullies in regions of heavy precipitations have exacerbated the problems to enhance the road network of the area as a result of which it remained far from adequacy for the population of the region. Even today the transport map of the region is most impressive by it bareness. Generally, the overall results of this study indicate that the road network in the Amhara National Regional State is with single connection tree like shape with few extended arms, with the value of Beta index less than 1, Cyclomatic number equals 0, Gamma index between 0-0.42, Alpha index ranging between 0-0.6. These results show that most of the areas in Amhara region are inaccessible and need a long distance travel to access the nearest road. Based on these empirical findings and the reviewed literature, the researcher would like to recommend that the construction of more road networks is imperative in Amhara region taking into account the socio-economic importance of the areas to be connected to the main road system of the country.