Trending Lineaments Research Articles

Morphotectonic evolution of the Quaternary landforms in the Yangui River basin in the Indo-Myanmar Range

The present study is an attempt to gain insight of the geodynamic implications on the evolution of Quaternary landforms in the Yangui River basin in the Indo-Myanmar Range (IMR), taking a multi-disciplinary approach. Originating at an elevation of ~2568 m asl, the Yangui River flows almost parallel to the regional strike of the IMR and drains into the Imphal valley at Yaripok and exhibits varied valley floor morphology. The valley floors are narrowest in the transverse valley sections. The fluvial landforms are represented by fill terraces, strath terraces and paleochannels. The chronologically constrained ages from fluvial stratigraphy suggests that the oldest phase of aggradation in the area began much before 8 ka. A total of 1164 lineaments were mapped, most trending NE-SW, which is slightly oblique to the regional strike of the IMR. East of the study area, the most prominent lineaments are those trending NE-SW. Lineament analysis suggests that the NNE-SSW trending lineaments are the first generation; followed by the ENE-SWS, while the youngest are the NW-SE trending lineaments. Quaternary landforms related to tectonic activity are observed in the Ringui area, where the morphology suggests transpressional tectonics. Cross-cutting relationships amongst faults suggest multiple phases of tectonic activity; linear valleys are observed along the fault planes. The cross conjugate faults and NW-SW lineaments of the area confirm tectonic activity in the area, which corroborates well with the seismogenic potential and oblique geometry of the Churachandpur-Mao Fault (CMF). Morphometric data also suggest ongoing tectonic activity in the area.

Mineralisation potential assessment using analytical hierarchy process (AHP) modeling technique: A case study of Ilesha schist belt, southwestern Nigeria

A mineralisation potential assessment in part of Ilesha Schist belt of southwestern Nigeria was carried out using multi criteria decision analysis (MCDA) in the context of analytical hierarchy process (AHP). Three parameters sourced from aeromagnetic, electrical resistivity and geological data were identified to favour gold mineralisation in the study area. These parameters include lineament density (Ld), lithology (Lt), and electrically derived coefficient of anisotropy (An). The application of data enhancement techniques such as total horizontal derivative, 3-D Euler deconvolution and source edge detection were employed in the production of lineament map of the study area. Two hundred and sixty-five (265) vertical electrical sounding (VES) points were investigated using Schlumberger configuration. Coefficient of anisotropy derived from the Dar-Zarouk parameters was obtained from the synthesized VES data. The lithologic information was obtained from the existing geological map of the area. The orientations of lineaments displayed on the aeromagnetic results suggest predominantly NE-SW trending structures, which are characteristic of the Pan African orogenic events in the area. However, few of the E-W trending lineaments are imprints of secondary structural alteration. Furthermore, the Euler deconvolution solutions revealed that the area is characterised by geological contacts with estimated depth of 94–600 m. The coefficient of anisotropy results obtained from the geo-electric parameters vary from 1.00–2.87. AHP weighting and ranking technique was used to develop a reliable mineralisation potential model (MPM). In line with the recommended lower limit of 10 %, the consistency ratio of the developed model is 9.61 %. The produced MPM was classified into low, moderate and high mineralisation potential zones. Preliminary validation of the MPM using the existing pits in the area showed 79 % success rate. The validation of the model using the existing geochemical information from the previous studies indicated 85 % agreement with the conceptual model; thus, confirming the reliability of the produced MPM. The developed model is therefore believed to serve as a future reference in the resource management of the study area.

Gravity Analysis for Subsurface Characterization and Depth Estimation of Muda River Basin, Kedah, Peninsular Malaysia

Gravity survey is one of the passive geophysical techniques commonly used to delineate geological formations, especially in determining basement rock and the overlying deposit. Geologically, the study area is made up of thick quaternary alluvium deposited on top of the older basement rock. The Muda River basin constitutes, approximately, of more than 300 m of thick quaternary alluvium overlying the unknown basement rock type. Previous studies, including drilling and geo-electrical resistivity surveys, were conducted in the area but none of them managed to conclusively determine the basement rock type and depth precisely. Hence, a regional gravity survey was conducted to determine the thickness of the quaternary sediments prior to assessing the sustainability of the Muda River basin. Gravity readings were made at 347 gravity stations spaced at 3–5 km intervals using Scintrex CG-3 covering an area and a perimeter of 9000 km2 and 730 km, respectively. The gravity data were then conventionally reduced for drift, free air, latitude, Bouguer, and terrain corrections. These data were then consequently analyzed to generate Bouguer, regional and total horizontal derivative (THD) anomaly maps for qualitative and quantitative interpretations. The Bouguer gravity anomaly map shows low gravity values in the north-eastern part of the study area interpreted as representing the Main Range granitic body, while relatively higher gravity values observed in the south-western part are interpreted as representing sedimentary rocks of Semanggol and Mahang formations. Patterns observed in the THD anomaly and Euler deconvolution maps closely resembled the presence of structural features such as fault lineaments dominantly trending along NW-SE and NE-SW like the trends of topographic lineaments in the study area. Based on power spectral analysis of the gravity data, the average depth of shallow body, representing alluvium, and deep body, representing underlying rock formations, are 0.5 km and 1.2 km, respectively. The thickness of Quaternary sediment and the depth of sedimentary formation can be more precisely estimated by other geophysical techniques such as the seismic reflection survey.

Analysis and Interpretation of Lineaments for Evaluation of Groundwater Potential in Shendam and Environs, North Central Nigeria

This study was done to evaluate the groundwater potentials of Shendam and environs using lineaments analysis. The trends of field joints were measured during mapping and using satellite remote sensing to generate lineament. The area is underlain by crystalline basement rocks of biotite granite, medium grain granite, and syenite. Assessment was carried out to depict the possibility of groundwater occurrence in the area. LANDSAT ETM+ imagery was used, together with the geological map to investigate areas favorable for groundwater development. This was achieved by plotting the lineament trends, superimposing the lineament on the geological map, superimposing the lineament on the drainage map, furthermore by plotting density map to know the groundwater potentials of the area. Lineament was used in drawing the respective rose diagrams for each rock type. Structurally, the area is characterized by a predominant NE to SW trend which also affects or controls drainage and groundwater occurrence with major groundwater recharge areas trending NE- SW of the study area. Analyses have shown that the study area has numerous fractures whose major trends are mainly in NE-SW directions. Lineament density maps shows the cross-cutting lineaments to be relatively high in the areas around the northeastern to southwestern parts of the study area but low in the other areas. Zones of high lineament intersection density are feasible zones for groundwater prospecting.

Identification of Deep Tectonic Structures of the Pho Lu area, northwestern Vietnam using Digital Elevation Model and Earth focal mechanism

The digital elevation model and the earthquake focal mechanism are utilized to define the geological structure of the Pho Lu area, northwestern Vietnam. The results allow the identification of lineaments and recognition of the correlation between the lineaments and geological structures directed in the study area. The digital elevation model (DEM) was used in the methodology of interpretation trends of lineaments derived from various enhancing techniques to show that the most lineament trend in the NW‒ SE direction. Further more, the interpreted lineament map demonstrates the NW‒SE system is correlated with the Red River fault zone, which is interpreted as a positive flower structure combined with the focal mechanism of earthquake. The results also demonstrate the capacity to used the digital elevation model and focal mechanism of the earthquake to identify deep geological structures.

Hydrological subsurface investigation using geophysical electrical and magnetic methods in and around Valliyar river basin, India

The focus of the present study is to identify potential groundwater zones using resistivity Schlumberger array and magnetic method for mapping hidden lineaments in and around the Valliyar river basin situated in the tail of Southern India. Estimation by 2-D radial power spectrum indicates that the maximum depth at which the magnetic source is present is about 700 m to 800 m. In case of shallow depth magnetic source rock, it is about 40 m to 45 m. The results of magnetic data have revealed the presence of a major magnetic lineament trending in NW to SE direction. The electrical resistivity survey in our study area gives information on sub-surface layers like the weathered zone, aquifer resistivity and aquifer thickness. The locations corresponding to ves-35, ves-40, and ves-47 have weathered and fracture layers having a thickness greater than 20 m, situated in the magnetic major lineament trend. Regarding master curves for layer analysis, H and HA type curves are generally observed in the hard rock region. The interpretation of results from the present study endorses that the coastal region of the study area has good groundwater potential.

Morphotectonic Analysis of Mboula Area in Relation with Central Cameroon Shear Zone (CCSZ) and Lithology Using Remote Sensing and Field Data

The field studies, the Landsat 8 OLI/TIRS processing and the digital elevation model of the Alos Palsar images enabled us to map the lineaments of the Mboula area, in the Adamawa-Yadé domain of the Central Pan-African Fold Belt. The use of the OLI 8 band on Landsat 7 × 7 window made it possible to highlight these lineaments. The result depicted in more than 12,417 segments of lines and curves corresponding to potential fractures and geological contacts. Note that the maximum number of main lineaments after treatment (3,274 lineaments) are oriented NE-SW. The second lineament trend in the study area is NNE-SSW and NNW-SSE respectively. The DEM of the Alos Palsar sensor made it possible to establish four geomorphological units in the study area: hilltop, mountain, plateau and alluvial plain. By superimposing these on the lithological map and tectonic, the coincidence is quite obvious. Thus, field and remote sensing analysis reveal that lithology and the CCSZ have influenced significantly the geomorphological evolution of the Mboula area. These results also illustrate the interest of remote sensing analysis in mapping tectonic structures, with benefit of time saving and precision.

Carbon dioxide diffuse emission at the Tolhuaca hydrothermal system (Chile) controlled by tectonics and topography

The Tolhuaca hydrothermal system is one of the few attested geothermal resources in Chile. While recent investigations provided some insights into the depth and temperature of the geothermal reservoirs and the chemical and mineralogical evolution of the hydrothermal system, little is still known about the CO2 degassing of the system and the local and shallow control of fluid pathways. Here, we document the soil CO2 degassing and soil temperature distributions in the southern part of the Tolhuaca hydrothermal system and at one of its northern fumaroles, and provide a first estimate of its total CO2 release. The surveyed area is responsible for a total CO2 emission of up to 30 t d−1. Hydrothermal CO2 emissions (~ 4–27 t d−1) are mostly restricted to the thermal manifestations or generally distributed along NNW trending lineaments, sharing the same orientation as the volcanic vents and thermal springs and fumaroles. Hydrothermal CO2 fluxes, fumaroles and thermal springs are generally encountered in topographic lows, in close vicinity of streams and often in clay-rich pyroclastic units, highlighting a relation between landscape evolution and the activity of the hydrothermal system. We suggest that glacial unloading and incision of the stream inside the clay-rich units have likely enhanced locally the permeability, creating a preferential pathway for the migration of deeper fluid to the surface. As several hydrothermal systems in the Andes are found on the flank of volcanoes hosting glaciers, we propose that they could have had a similar development to that of the Tolhuaca hydrothermal system.

INTERPRETATION OF AEROMAGNETIC DATA AND LANDSAT IMAGERY OVER THE NIGERIAN YOUNGER GRANITES IN AND AROUND KAFANCHAN AREA, NORTH-CENTRAL NIGERIA

In this research the lineaments of the Kafanchan area in North-central Nigeria were investigated in order to explore the mineralization zones of the area. Aeromagnetic data over Kafanchan and environs within the Younger Granite Province, in the North-Central Nigeria were collated and analyzed. The aeromagnetic map of the area was interpreted both qualitatively and quantitatively so as to identify the nature of the magnetic sources and the trends direction in the study area. The trend of the Total Magnetic Intensity (TMI) map is predominantly in NE-SW. The First Vertical Derivative (FVD) Lineaments Map was also correlated with LADSAT lineaments map and both maps agreed in most areas. The study area is characterized by predominant magnetic lineament trend in NE-SW direction and subordinate E-W direction. The result also shows that the most significant structural trends affecting the distribution of these magnetic anomalies in the study area is in NE-SW direction. The TMI map indicates that there are three major mineralization zones in the study area. The high magnetization contrast in the NE and SE parts of the study area correlates with the migmatite-gneiss, biotite-granites, granites and basalts which are associated with high magnetic contrasts. Also, the high magnetization contrast in the NW part of the area correlates with basalt and the biotite-granite. However, the predominant low magnetization contrast observed in the western half does not correlate with the basic igneous rock

Delineating and Interpreting the Gold Veins Within Bida and Zungeru Area, Niger State Nigeria, Using Aeromagnetic and Radiometric Data

Abstract Both Airborne Magnetic and Radiometric datasets were employed to interpret the geology and geological structures that serve as host to gold and associated minerals within the Bida and Zungeru, Niger State, Nigeria. An area of 55 by 110km2, contained within the cretaceous sediments of Bida Basin and the meta-sediments of Zungeru-sarkin-pawa schist belt. Data interpretation involve the application of a mathematical algorithm for data enhancing such as, Reduce to the Equator, Analytical signal, First Vertical Derivative, and Centre for Exploration Targeting (CET) to the magnetic data, and Ternary imaging to the radiometric data, with a sole aim of mapping geological structures such as faults fracture folds joints and geological boundaries and possible gold mineralization veins that arise from hydrothermally altered zones. Two major geological units inhibit the study area, the cretaceous sediment, and the meta-sediments, major feature identifies within the Cretaceous sediment are the folds majority of which are located within the contacts. The result of the 1VD display is the vivid picture of the observed structural features such as faults fractures folds’ contacts labeled F1 to F8 both within the high region of magnetic susceptibility (in red) and low regions (in blue) geology contacts (yellow), folds (bold yellow) all across the field. Prominently at the North-Western corner of the study area are sets of linear structure that trend NE-SW, located within the contacts between the mylonites and the amphibolites and the belt-type meta-sediments located around Katakwo, Gindei, Kwange, Gabas and Akusu villages. Equallyworth mentioning are sets of lineament (in blue) trend E-W all across the mid-region of the study area, precisely at the Eastern corner within and below the Federal University of Technology Minna around Kata-eregi, Sabon-Dagan, Kakaki down Minkwoigi, Sunbwagi, Kakagi, Sabon dagga, and Bobo-shiri towns, where the majority of volcanic activities must have been recorded. The airborne radiometric show mobilization of the immobile thorium Th, concentration, and this also indicated hydrothermally altered zones. The increase in potassium concentration and decrease in K/Th relation observed from radiometric interpretation are very pinpointing of hydrothermal activities within the study area. The gold mineralisations are found within this vein and in the adjacent, highly deformed host rock located below the Federal University of Technology Minna Campus. The deformation seems to comprise principally of pebbly schist, amphibolites along fine-grained and magnetite.

Influence of Pan-African tectonics on older Precambrian basement structural fabrics as revealed from the interpretation of aeromagnetic and remote sensing data of Ikole/Kabba region, southwestern Nigeria

Reliance on structural data from geological mapping will be grossly inadequate to establish an informative regional tectonogenic interpretation in southwestern Nigeria mainly because of poor exposure of outcrops due to severe weathering in the tropical region. Therefore high resolution aeromagnetic anomaly and Landsat-8 OLI/TIRS data were adopted for tectonic analysis of Ikole/Kabba area where qualitative analysis of Landsat-8 imagery provides surface lineaments with major E − W and N–S trends. Processing of the aeromagnetic anomaly data utilizing the horizontal gradient magnitude and total gradient methods indicated various E − W, NW - SE, N–S and NE - SW structural features in agreement with the surface lineaments; lending credence to the existing geologic structural interpretation. The resulting synoptic structural interpretation suggests the preservation of two major successive events; an earlier prominent E-W trending lineaments resulting from a N–S compressional deformation, succeeded by a brittle deformational event characterized by NW-SE and NE-SW trending lineaments. Additionally, the magnetic basement depth map deduced from the source parameter imaging technique shows depth values between 50 m and 650 m, which represent depths to the top of structural features within the basement rocks of the region. The collective interpretation of high resolution aeromagnetic anomaly and Landsat-8 data provides significant information about regional tectonics and structures that are good conduits for mineral deposits within the study area.

Recent faulting along Gorontalo fault based on seismicity data analysis and lineament mapping

We focused our study to characterize the geometry and activity of Gorontalo fault. We analysed reviewed the ISC seismic catalogue and the BMKG relocated earthquake events available for the time period of 1960 to 2021, located along the expected location of this fault. In addition, we analysed continuous record from local seismic observatory available for the same period. Further, we mapped the lineaments using 8.3-m resolution DEMNAS data. Tens on shallow earthquakes occurred in the vicinity of this fault with a range magnitude of M 2 to 3. Our lineament analysis however does not reveal distinctive pattern that may indicate the fault manifestation at the surface. The NW-SE trending lineaments are coincidence with the mapped trace of Gorontalo Fault. The weak surface manifestation of the fault scarp may be related to the tropical climatic condition of the area which may obliterate the faulting topography. However, we observed alignment of the seismicity distribution with the mapped NW-SE lineament, indicating that the lineament is likely representing active fault and these earthquakes are associated with faulting along this fault. Our study provide indication that the Gorontalo Fault is active and further study is necessary to investigate subsurface geometry and mitigate its seismic hazards.

FIELD, PETROGRAPHIC AND STRUCTURAL CHARACTERIZATION OF MADA BASEMENT ROCKS, WONAKA SCHIST BELT, NORTHWESTERN NIGERIA

Geological mapping and petrological studies were carried out within the placer gold (Au) mineralized zones in the Wonaka Schist Belt in order to establish detailed petrographic and structural features. Thin sections were produced for petrographic and microstructural studies and lineament analysis was coupled with field structural observations for interpretation. The study area comprises of quartz-mica-schist, phyllite, metasandstone, medium to coarse grained porphyritic granite, granitic gneiss, and diorite as the five major rock types with aplite, quartz and quartzo-feldspathic veins representing minor rock occurrences. The structural pattern is dominated by regional scale, NE striking foliation, and N striking brittle lineament. However, the dominant tectonic fabric within the metasediments and the granite gneiss are the steeply dipping, N, NW and NE-trending phyllitic cleavage, schistose foliations (S1) and gneissocity respectively, formed from first phase of deformation (D1). The emplacement of brittle tectonic features, undulose extinction observed in the quartz crystals, inter- and intra-granular microfractures are evidences of the late stage deformation that occur toward the end of the Pan African. Similarities with other mineralized belts in term of structures provide weight to the possibility of the NW-SE, N-S and NE-SW trending lineaments and specifically the NW-SE quartz and quartz ± feldspar ± hematite ± mica ± sulphide veins to host Au within the study area.

Structural interpretation of magnetic and satellite remotely sensed data of Osun State, Southwestern, Nigeria

ABSTRACT This study delineates surface and subsurface structural features in the hard rock terrain of Osun State using magnetic data and satellite remote sensing imageries. To achieve this aim, several image enhancement methods were applied to the magnetic data and satellite remotely sensed imageries to improve visualization and interpretation. The subsurface lineaments were detected and traced out from the maxima of Horizontal Gradient Magnitude, peaks of Analytical Signal Magnitude, and an Euler solution of Osun state. The magnetic lineament map reveals that the structural trend in the area is dominant by NE-SW and NNE-SSW. These structural trends were found to be consistent with the regional tectonics of the Southwest Basement of Nigeria. The NE-SW is the most conspicuous structural trend in the study area. The satellite imageries depict a characteristics feature of the occurrence of underlying structures in the basement complex of Osun State. The major lineament trends delineated in the composite surface lineament map are the NE-SW, NNE-SSW, and ENE-WSW directions. The 2.5 D model across the unmapped lineaments confirmed the existence of a thin dyke’s characteristic of fracture/fault in a typical basement complex terrain. The derived lineaments may serve as a reference for future geological and structural mapping.

Interpretation of Aeromagnetic Data over the Nigerian Sector of the Mamfe Basin

Four Aeromagnetic data over a part of the Nigerian Sector of the Mamfa Basin have been analyzed using qualitative approach and spectral analysis. The aeromagnetic maps, its analytic signal amplitude and geological modelling sketch helped in identifying the nature and depth of the magnetic sources in the study region. The qualitative interpretation reveals that the study area is characterized by magnetic lineament trend in NE-SW direction and subordinate E-W direction. The results obtained are in line with the trend of the Benue Trough. The aeromagnetic maps reveal that the sedimentary thickness increases towards the northern parts of the study area. The results also reveal that the total magnetic field intensity range from 7800 to 8290 nanotesla (nT) in the study area. The residual anomaly map reveals that the maximum anomaly value is 160nT which is found around Bansara and Ugep environs while the minimum magnetic value is -140nT towards the Abakiliki and Ikom areas. Results from spectral analysis indicated two magnetic source depths, which account for deeper and shallower sources. The deeper magnetic sources vary from 2.76 km near Abakiliki to 5.37 km near Bansara, whereas the shallow magnetic sources vary from 0.58 km near Ikom to 1.76 km near Ugep. The depth to basement map reveals that the sediment thickness increases towards the northern parts of the study area. The depths to basement are deeper in the northern and central parts trending northwest-southeast direction and shallower in the eastern and southern parts of the study area. The result also shows a linear depression with sedimentary accumulation trending northwest-southeast. The temperatures at depth for each anomaly block were estimated to range between 48.46 and 225.69°C with an average of 117.04°C. Based on the computed sedimentary thickness (2.76-5.37km) and temperature at depth (62-220°C), the possibility of hydrocarbon generation in the northern and central parts of the study area is realistic

Arcabouço magnetométrico-geológico do setor sudeste do Cinturão Dom Feliciano, Rio Grande do Sul, Brasil

No setor sudeste do Cinturão Dom Feliciano, Rio Grande do Sul, está localizado o limite entre os Terrenos Pelotas e Punta del Este, região que contém diversos granitoides e rochas metamórficas neoproterozoicas e vulcânicas mesozoicas. Três domínios magnéticos foram individualizados com base em diferentes orientações dos lineamentos observados: Domínio I, II e III, com lineamentos dominantes, respectivamente, N040–90ºE, N060–90ºE, e N070–90ºE. Modelagens magnéticas 2.5D foram realizadas em dois perfis geológico-geofísicos orientados N-S, com 6 km de extensão, distantes 3 km entre si. O perfil A-A’ secciona o Terreno Pelotas até a porção Norte do Terreno Punta del Este, enquanto o perfil B-B’ secciona apenas esse último terreno. No perfil A-A’, em uma análise qualitativa do modelo, observam-se três patamares de susceptibilidade que refletem o contraste litológico da região: rochas básicas aflorantes (Gabro Desvio Herval); granitoides associados a estruturas tardias (Suíte Dom Feliciano); e rochas granitoides/metamórficas associadas ao Complexo Pinheiro Machado e Gnaisse Arroio Pedrado. No perfil B-B’, também se observa três patamares de susceptibilidade que refletem as diferenteslitologias da região: corpos básicos tabulares anastomosados não aflorantes; granitoides associados a estruturas de cisalhamento (Granitos Chasqueiro e Três Figueiras), granitoides associados a estruturas tardias (Granito Bretanha) e rochas metamórficas associadas aos Complexos Arroio Telho e Arroio Grande. A caracterização magnetométrica das rochas da região, em conjunto com os dados geológicos disponíveis, possibilitam um avanço no entendimento do setor sudeste do Cinturão Dom Feliciano. Sugere-se, assim, como limite entre os Terrenos Pelotas e Punta del Este a Zona de Cisalhamento Ayrosa Galvão, bem como a identificação de corpos em profundidades e não aflorantes, sincinemáticos às zonas de cisalhamento e rochas magmáticas básicas

Orientation and Frequency Analysis of Topographic Lineaments in the Miringa Volcanic Zone of the Biu Plateau Region, Borno State, Nigeria

The aim of present study is to spatially analyze the topographic lineaments of tectonic origin in the Miringa Volcanic Zone located in the northwestern part of the Biu Plateau. To achieve such aim, SRTM of spatial resolution 12.5 m was utilized. The lineaments were automatically extracted by using PCI GEOMARTICA software version 10. This was followed by field work for ground thruting and to establish field relationships. ArcGis 10.5 software version was used for spatial analysis of lineaments while Rockworks version 16 was used in creating the Rossace used in lineament trend analysis and other related statistical variables associated with the lineaments of the study area. 2036 linear structures were identified in the area with a total length of 30,193.85 m. The maximum length of lineament recorded in the study area is 150 m while the minimum is 3.68 m. Field work revealed that most of the lineaments in the area developed from the weathering of contacts between successive volcanic beds in areas overlaid by the highly dissected plateaus, escarpment slopes and denudation hills. Trend analysis of lineaments of the study area indicates that the direction of lineaments tend to lie in the North-east to southwest direction (Azimuth 45°-225°) which has same direction with major drainage system and most of the volcanoes of the area. This signifies the presence of a major fissure trending in the north-east to south-west direction as the primary tectonic structure of the area. Subsequent exogenic processes exploited this structure leading to the formation of other micro-lineaments that trend along the same direction.

Quantitative Morphometric and Morphotectonic Analysis of Pahuj Catchment Basin, Central India

Abstract In the present work, the morphometric and morphotectonic analysis of the Pahuj basin catchment of the Bundelkhand region of Central India was carried by using remote sensing and GIS techniques. The drainage map, Digital Elevation Model (DEM), density, contour, aspect, and other thematic maps were extracted from ASTER-DEM (30m resolution) data by using geographical information system (GIS) tool. Five order streams have been validated in the study area and an inverse relationship between the stream order and stream number has been established. The high mean bifurcation ratio (Rb=5.12) indicates that the drainage pattern is controlled by geological structures in the impermeable granitic terrain. The stream frequency (2.69) is indicative of the increment of stream population for drainage density. Contrary to this the drainage density (2.08) is suggestive of low to moderate infiltration rate and is showing the thin vegetal cover on the impermeable rocky terrain. The elongation ratio (0.61) and form factor (0.29) infer that the catchment basin is elongated and shows low peak flows. The value of ruggedness and Melton ruggedness number implies that the basin is moderately rugged and debris watershed and is less susceptible to soil erosion. The drainage pattern of basin catchment flowing in diverse lithological and structural terrain (Archean and Palaeoproterozoic age) is exhibiting less influence of active tectonics. The NW-SE, E-W and NNE-SSW trending lineaments resembling the orientation of lower-order streams are suggestive of structural control. The NE-SW trending high order streams flowing in an elongated Pahuj basin catchment and coinciding with the orientation of major NE-SW lineaments are indicative of major tectonic control.

Geomorphic assessment of the factors contributing to the evolution of landforms in Ukhaldhunga area, Kosi River valley, Kumaun Himalaya, Uttarakhand

This paper documents the various factors contributing to the evolution of landforms in the Kosi River valley, Ukhaldhunga area of the Kumaun Himalaya, Uttarakhand. The area falls in the major tectonic boundary between the Lesser Himalaya and the sub-Himalaya. Passing through the Parewa-Ukhaldhunga-Dabara area, this tectonic contact is known as the Main Boundary Thrust (MBT), which is characterized by presence of varied landforms. Study of the development of geomorphology, particularly those evolved in the MBT zone, suggests that the morphological features are intimately associated with the tectonic activities related to the movement of rocks along the MBT and the surface processes such as fluvial and mass movement. The various landforms observed in the MBT zone include strath terraces, fill terraces, paleochannels and V-shaped valley that pertain to fluvial genesis; gravity induced landforms such as landslide debris and colluvial fans; and tectonic landforms such as linear fault traces, swerving/swing of river course and linear depressions. Signature of recent tectonic activity along the MBT is observed between Dabara and Khakrakot. The activity is evident in the form of 8-km-long active fault trace trending NW-SE. Normal fault related landforms are observed in the hanging wall block of the MBT. Neotectonic strath terraces and fill terraces are well developed in the MBT zone. Multiple events of recurrence of landslides are evident from exposed section of landslide debris fans. The bedrocks are highly sheared, suggesting successive tectonic movements along the MBT. As a consequence, tectonic wedges have developed in the bedrocks. These wedges have facilitated for the recurrence of a number of landslides. The anthropogenic activities have also aggravated the slope stability. Truncation of older debris fan surfaces by an erosional/fault scarp is observed and the scarp separates the older fans from the youngest debris fan deposit. The scarp runs parallel to the MBT and Kosi River. Swerving of the Kosi River is as a result of the tectonic forcing along active lineaments/faults. The trend of lineaments of the maximum and high density is NE-SW, which is transverse to the trend of the NW-SE trending Himalayan fold-thrust belt.

Genesis and structural arrangement of the collapsed Oued Gueniche plain and the surrounding folds (Neogene molassic basin of Bizerte, northeastern Tunisia): Insights from gravity data

The Oued Gueniche plain is located in the northeastern Tunisia. It is a part of the Bizerte Neogene molassic basin, developed at the front of the Alpine chain (The Maghrebides). The subsurface structure of this area is not enough explored and was subject of controversial interpretations. Gravity and seismic data acquired in the northeast of Tunisia were used to specify the subsurface structural configuration and the formation mechanism of the Oued Gueniche plain, as well as, its relationship with the surrounding folds. A total number of 664 gravity measurements were used to define the density distributions below the surface in the study area. The complete Bouguer gravity anomaly was performed with a reduction density of 2.4 g/cm3. Bouguer anomalies range from 9.5 to 34.8 mGal, high anomalies coincide with the Oued Gueniche plain in the northwest while weak anomalies are located on the southern part of the study area. The main NE-SW anomalies are superposed to the geological structures.The power spectrum of gravity data shows that the calculated average depth to the top of regional gravity sources is approximately 4 km while that of local (or residual) sources is approximately 0.6 km. The techniques for locating the limits of anomalous structures and estimating their depths (tilt derivative (TDR), Euler deconvolution (ED) and analytical signal (AS)) were applied to the Bouguer anomaly map to further specify the underground geological characteristics. The maxima of the horizontal gradient magnitudes (MGH) of Bouguer anomalies, upward continuated at different altitudes, revealed several NE-SW and E-W trending lineaments. A three-dimensional (3D) inversion model of gravity data has been developed for the Oued Gueniche plain in order to follow the distribution of densities.In addition, the interpretation of seismic profiles indicates that the central part of this plain is marked by the diapirism of Triassic rocks.The combination of these results with those of the surface (geological map and shallow hydrogeological boreholes) has led us to propose a kinematic model of the Bizerte region since the Middle Miocene and to update the structural scheme. Then, the NE-SW major faults (e.g. the newly defined Sfaia-Metline fault) and the NW-SE secondary ones have controlled the paleogeography and the structuration of the study area.