L.S. Chamyal - Academia.edu (original) (raw)

Papers by L.S. Chamyal

lies very close to NG-R (Radhakrishna, 2005), and (4) the the traverse of the Indian plate over t... more lies very close to NG-R (Radhakrishna, 2005), and (4) the the traverse of the Indian plate over the Conrad hotspot. NG-R also falls within a narrow corridor across the Effect of these first order factors and other finer details intriguing 80°E, along which lie a number of significant need to be considered in modeling the damage along the tectonomagmatic features (eg. Jabalpur, Bhadrachalam, east coast particularly near the NG-R. Ongole, Nellore, Pondicher-ry, Panna, etc.,); it may be noted in this context that in the offshore region adjoining southern Natioiznl Geophysical Research U. RAVAL most Sri Lanka, major N-S trending fracture zones appear I~zstitute, Hyclerabadto enter in 80°E corridor and these have been attributed to Ernail:

Mobile colloidal particles are known to be ubiquitous in Quaternary fluvial sediments and subsurf... more Mobile colloidal particles are known to be ubiquitous in Quaternary fluvial sediments and subsurface environments which facilitate the transport of contaminants to the aquifer. Despite this harmful effect, very few efforts have been made to study the properties and transport of colloids in Quaternary sediments. In order to understand the properties of these colloids, samples were collected from the exposed late Quaternary sediment sequences dating back to 125 ka from the Mahi River basin. The isolated colloids from these sequences were characterized for their size distribution, electrical conductivity and concentration. The polydispersed colloidal particles occur in varying amounts at different depth intervals. The low electrical conductivity of colloids in the Rayka section could be related to the low concentration of colloids.

The area bound by the rivers Sabarmati and Luni forming a part of North Gujarat and Southwest Raj... more The area bound by the rivers Sabarmati and Luni forming a part of North Gujarat and Southwest Rajasthan alluvial plains has preserved in its sediments and landscape various changes which have occurred in the drainage systems during the Upper Quaternary times. The present day drainage mainly cuts across the material deposited by a set of older rivers which now stand disrupted. The present day rivers are observed to have been superimposed over older river channels and dominantly follow numerous tectonic lineaments and faults of a later date. The new channels reveal and have preserved relicts of the earlier fluvial system. Geomorphic and drainage studies reveal existence of two ancient major river systems, the remnants of which are now represented by the Banas and Rupen rivers. The Banas, along with its major tributary Sipu is the sole survivor of the older fluvial system. whereas Rupen has been partially destroyed.

... Titre du document / Document title. Significance of bank material at Tilakwada in lower Narma... more ... Titre du document / Document title. Significance of bank material at Tilakwada in lower Narmada Valley. Auteur(s) / Author(s). CHAMYAL LS ; BINDU SHARMA ; MERH SS ; HASSAN KARAMI ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). MS univ. Baroda, dep. ...

Indian Summer Monsoon (ISM) is the major climatic feature in the Indian sub continent. Since mari... more Indian Summer Monsoon (ISM) is the major climatic feature in the Indian sub continent. Since marine proxies used for monsoon reconstructions are the expressions of the wind strength that may or may not translate on land as rainfall, the continental records are the direct proxies of rainfall variability. We have made an attempt here to synthesize the available works aimed at past monsoon reconstruction using the chronologically constrained continental archives. The nature of geomorphic response of a fluvial system depends upon its environmental setting and the magnitude and duration of a climatic perturbation. In the present synthesis it was observed that events that lasted for ∼10 4 years could imprint its signature particularly in the fluvial systems irrespective of their geographical location. Except few examples, there is virtually no evidence of short term climatic fluctuations coming out from the available fluvrial records. Could it be due to the fact that short lived climate instability (10 2 to 10 3 years) are not sufficient enough to bring about major geomorphic changes in fluvial processes? Climatic inferences drawn so far using the fluvial and aeolian archives are largely based on the field stratigraphy, sedimentology and chronometric studies from limited geographical areas. There is a need for wider coverage pertaining to the fluvial systems particularly in the peninsular and southern Indian rivers. Further, unless, the clitmate proxies like stable isotopes, geochemistry, and environmental magnetism are used the monsoonal inferences would remain qualitative. Lacustrine sequences provide uninterrupted record of monsoonal variability. This important continental archive has not been exploited to its potential, except for the Thar Desert Renewed efforts should be made to explore other areas including the Himalaya.

The Depositional Record

Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is recons... more Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during t...

Atlas of Structural Geological and Geomorphological Interpretation of Remote Sensing Images

Current Science, Aug 25, 2014

We report the occurrence of large floods in the Sabarmati River Basin during cal AD 1400-1440. Sl... more We report the occurrence of large floods in the Sabarmati River Basin during cal AD 1400-1440. Slackwater palaeoflood deposits have been preserved in the highly dissected ravines along the middle reaches of the river, wherein 5-6 discrete flood events have been identified. The minimum discharge that emplaced the highest deposit has been estimated as ~15,680 m 3 s-1 and is higher than that recorded (3050 m 3 s-1) during the recent 2006 flood. The timing of these high-magnitude flood events in the Sabarmati and adjacent river basins suggests that extreme hydrological events have occurred in response to excess monsoon periods and are largely controlled by the regional climatic conditions. Moreover, these flood events are seen to be broadly synchronous in the alluvial river basins of Gujarat across climatic zones, but are at variance in pattern from the records of the bedrock peninsular rivers.

1st Indian Near Surface Geophysics Conference & Exhibition, 2019

AGU Fall Meeting Abstracts, Dec 1, 2017

The present study employs multisensor remote sensing approach for delineating the morphological i... more The present study employs multisensor remote sensing approach for delineating the morphological intricacies of the Banni plain, a hyper arid saline terrain, generally referred to as 'flat'. The Banni plain is a part of the Great Rann basin and is the culmination of shallow marine sedimentation during the Holocene. Owing to the variable submergence characteristics, the Banni plain displays geomorphological characteristics that are unique and distinctly different from the rest of the terrain of the Great Rann. The RISAT SAR data of the Banni plain used in the present study was acquired in the month of August, 2012, i.e. during the monsoon season when large parts of the Banni plain are normally submerged, waterlogged or saturated with rain water. The inundation is found to be a key factor, in the backscatter of radar waves in the available SAR data which is exploited in the present study to interpret landscape characteristics of the Banni plain. Backscatter from non-inundated s...

Quaternary International, 2021

Abstract Areas around Bhavnagar and Jamnagar in eastern and northern parts of Saurashtra respecti... more Abstract Areas around Bhavnagar and Jamnagar in eastern and northern parts of Saurashtra respectively, are identified previously as prone to recurrent earthquake swarm activity. Sparse seismotectonic studies so far have not revealed any linkage with known faults in Bhavnagar area while no structures are known to occur in the area around Jamnagar. We carried out detailed tectono-geomorphic studies with contrasting geomorphic settings with a view to provide an insight into the swarm activity from a geomorphological perspective. The study is based on extensive field studies and quantitative geomorphic analysis of landscape and drainage. The area around Bhavnagar is divisible into two tectono-geomorphic domains – the E-W trending Sihor Fault zone located to the west of Bhavnagar (domain-I) and the terrain to its south which shows undulating landscape controlled by N–S trending structural trends (domain-II). The quadrant in the SW between these two domains consists of southward titled trappean hills which form source area for drainages flowing northward through Sihor Fault zone and those flowing eastward through domain-II. Late Quaternary, possibly Holocene tectonic activity along the Sihor Fault is indicated by the northward tilt of alluvial plain surface, knickpoint in rivers and small scale minor faults along the fault zone, prominent decrease in depth of fluvial incision away from the fault zone and youthful landscape indicated by drainage basin analysis. Domain-II comprises the largely erosional pediplain developed over trappean and Tertiary rocks to the south of Bhavnagar. The drainages show an early stage of landscape development due to ongoing tectonic activity. The area around Jamnagar is dominantly a peneplain formed over subhorizontal trappean lava flows. The peneplain is a manifestation of the prolonged period of non-erosion and deposition during the Cenozoic. The rivers show youthful landscape in the central part of the peneplain which includes, large knickpoints, rapids, anomalous river bends, steepening of channel gradient and large potholes. This ENE-WSW trending zone of anomalous fluvial geomorphic anomalies points to the existence of a fault or fold in the subsurface. The structure appears to be active as indicated by the denser cluster of earthquake swarm along this zone. We infer that the generation of earthquake swarm activity comprising low to moderate magnitude shocks is caused by the sheared rocks along the Sihor Fault near Bhavnagar and the ENE-WSW trending subsurface structure near Lalpur which provide avenues for downward percolation of rainwater to deeper levels causing loss of frictional resistance along weak planes.

Springer Hydrogeology, 2018

The socio-economic development in Mainland Gujarat has been river centric. The physical environme... more The socio-economic development in Mainland Gujarat has been river centric. The physical environment of these rivers relates to the landscape response to climate change and tectonic forcing. There is a great diversity in the land and water resources of the region; on the one hand, where there is excess run-off in the rivers such as Narmada and Tapi, the population in the Sabarmati basin faces water scarcity. The agricultural growth in these basins has been exceptionally high; however, unplanned irrigation activities have put the surface as well as the groundwater resources under severe stress. The industrial effluents discharged into the main rivers or the tributaries further aggravate these problems. Soil and bank erosion though common are still up to a level where conservation methods can be applied. Thus, the socio-economic relevance of these river basins is very high and a large potential exists to further improve the conditions of water supply, agriculture, soil erosion and pollution. Each geomorphic unit has a unique resource potential, and a scientific evaluation of the potential is necessary for the socio-economic development of the region.

Journal of Mountain Science, 2021

The study deals with stream response to sustained tectonic during the Cenozoic and development of... more The study deals with stream response to sustained tectonic during the Cenozoic and development of two parallel scarps in the western Kachchh. The study encompasses fluvial networks developed over the Jara and Jumara domes, which are a part of the laterally extensive belt of flexures bounded by the Kachchh Mainland Fault (KMF) to their north and called as Northern Hill Range (NHR). Parameters such as longitudinal profile, Hack profile, stream length gradient index (SL), hypsometric curve, hypsometric integral (HI), valley floor width to height ratio (Vf), elongation ratio (Re) and escarpment sinuosity (ES) were analysed. Hack profiles of the major rivers draining through the area show similar convex up nature suggesting primary influence of the tectonics in controlling and shaping the landscape of the region. Elongation ratio <6 and undergone higher degree of fluvial erosion indicated by the low values of hypsometric integral suggest the tendency of river systems to increase the basin area longitudinally rather than laterally. The study suggests that higher net uplift in the eastern half (Jumara dome) caused the rivers to overcome the structural control and to carve out generally straight north oriented channels. The rivers of western part (Jara dome) show more prominent structural control of cuesta girdles formed in compact lithologies and attributed to the domal structure. The ~10 km long Jaramara scarp believed to the remnant of older KMF scarp, is a product of headward erosion of the fluvial channels through different hard and soft litho-units of the area. The similar orientation of Jaramara scarp and morphology of the Ukra intrusive body suggests that the Ukra intrusive played a significant role in controlling the formation and morphology of the Jaramara scarp.

Quaternary International, 2021

Abstract We carried out sedimentological and mineral magnetic studies on a ∼60 m long core recove... more Abstract We carried out sedimentological and mineral magnetic studies on a ∼60 m long core recovered from the central part of the Great Rann of Kachchh (GRK), a marginal marine basin, located on the western continental margin of India to understand the Holocene paleoenvironmental changes. We critically analysed the sedimentation pattern, sediment characteristics along with paleoclimatic signatures of global and regional relevance. In GRK basin, the sedimentation started in early Holocene (∼10.6–9.3 kyr BP) under rapidly rising post glacial sea level with very high sedimentation rate (8.71 cm/yr to 2.37 cm/yr) which is also seen in several marginal marine basins across the globe. The abundant laminations, coarse grained sediment flux and environmental magnetic parameters (χlf, S-ratio) suggests that the sedimentation occurred in developing monsoonal conditions under wetter yet fluctuating climate during this period. After ∼9 kyr BP, the environmental magnetic proxies show transition toward relatively wetter condition with peak at ∼6.5 kyr BP. This wetter climatic phase on the other hand corroborates with reduction of sedimentation rate to 0.46 cm/yr. This reduction in sedimentation rate under strengthening monsoonal conditions probably occurred due to rapid filling up of the basin on account of earlier high sedimentation in the basin. The sedimentation rate is reduced significantly after the onset of aridity at ∼4 kyr BP except a minor wet spell recorded during ∼1.5 to 1 kyr BP before drying of the GRK basin.

Journal of Structural Geology, 2020

The E-W striking Kachchh Rift Basin (KRB) at the western continental margin of Indian plate is lo... more The E-W striking Kachchh Rift Basin (KRB) at the western continental margin of Indian plate is located in the northern part of Gujarat state, India. KRB has undergone polyphase deformation owing to changing stress-field since Late Triassic. We establish the kinematic framework along the NW striking intra-uplift Vigodi-Gugriana-Khirasra-Netra Fault System (VGKNFS) located at the western part of the KRB. The VGKNFS consists of 0.25-50 km long, sub-parallel, striated, reactivated dip-slip faults. A total of 1150 fault-slip data consisting of fault planes and striations attitude were recorded from 66 sites (including a single site with systematic joints). Slip-sense of faults was determined by documenting kinematic indicators. Paleostress analysis was carried out using Win-Tensor, T-Tecto, FaultKin and SG2PS to compare and validate the results. The chi-square statistical analysis was undertaken to evaluate how relevant are paleostress analysis results to the present-day compressional stress field. Geophysical investigations were conducted at selected sites using Ground Penetrating Radar (GPR) to understand the shallow subsurface geometry and trace the continuity of faults buried below patchy alluvial cover. 15-17 m long, 2D GPR cross-sections were recorded across faults using monostatic antenna of 200 MHz frequency. Two major deformation events-D1 and D2 are determined in the present study. The extension event D1 shows W and NW-NNW extension during Late Triassic to Late Cretaceous. It occurred during the rift phase of KRB in response of the break-up of Gondwanaland. The latest event D2 shows NNE-NE compression from Late Cretaceous up to the present. It is interpreted to have developed during post-rift inversion phase, induced by collision of the Indian plate with the Eurasian plate at ~55 Ma.

Zeitschrift für Geomorphologie, 2018

Episodes, 2015

The present study is based on the field observations and geochemical analyses of flood sediments ... more The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013. The study suggests that the sediments were contributed from two major sources: the moraines and alluvial fans located in the Trans and Higher Himalaya; and the landslides in the Higher and Lesser Himalaya. Although the flood was the result of a high intensity rainfall event, the magnitude was increased due to the proliferation of settlements along the river and a series of partially constructed barrages on the river bed. Geochemical analyses of the flood sediments indicated that the contribution of power-project generated debris locally enhanced the flood magnitude. Further, the study argues that the terrain north of the Main Central Thrust (Higher Himalaya) should be kept free from major interventions, including hydropower projects, to reduce flood hazards. The study finally calls for a critical reevaluation of current development policy and the approach towards harnessing the enormous hydropower potential of the Himalayan rivers in general and in the Uttarakhand Himalaya in particular.

Geosciences Journal, 2018

The Kachchh palaeo-rift graben at the western continental margin of India is currently undergoing... more The Kachchh palaeo-rift graben at the western continental margin of India is currently undergoing active coseismic deformation in response to the periodic release of NE-SW oriented compressive stresses along the E-W trending intra-basinal faults. The seismically active Kachchh Mainland Fault (KMF) is the largest intra-basinal fault that is characterized by a narrow zone comprising a chain of domes and anticlines forming the rugged hilly topography of the Northern Hill Range (NHR) in the upthrown block. The present paper deals with the Jumara and Jara domes which have received considerable attention with respect to the Mesozoic biostratigraphy, however, no study has been carried out on geomorphological and neotectonic aspects. The major geomorphological units in the area include a low relief but rugged structurally controlled topography over the domes, the KMF scarp, the precipitous Jaramara scarp, the back slope over the Jaramara scarp and the rugged hilly topography over the large Ukra intrusive body that shows a complicated structural contact relation with the Mesozoic rocks ranging from concordant to discordant. Our detailed field studies supplemented by geomorphological analysis using DEM, topographical profiles, drainage characteristics and longitudinal profiles reveal the dominant control of sustained uplift along the KMF under compression in the development of the present youthful and structurally controlled landscape. Our study also suggests that the imposing E-W trending Jaramara scarp is formed due to the long-term retreat of the KMF scarp in response to uplift, while the present low relief scarp along the KMF is largely the result of post-Miocene uplift. The incision in Quaternary miliolite deposits in the Jara river gorge, deeply incising nature of the rivers, several large and small knickpoints and scanty occurrence of Quaternary miliolite deposits indicate an uplift of ~25 m during the Late Quaternary time.

lies very close to NG-R (Radhakrishna, 2005), and (4) the the traverse of the Indian plate over t... more lies very close to NG-R (Radhakrishna, 2005), and (4) the the traverse of the Indian plate over the Conrad hotspot. NG-R also falls within a narrow corridor across the Effect of these first order factors and other finer details intriguing 80°E, along which lie a number of significant need to be considered in modeling the damage along the tectonomagmatic features (eg. Jabalpur, Bhadrachalam, east coast particularly near the NG-R. Ongole, Nellore, Pondicher-ry, Panna, etc.,); it may be noted in this context that in the offshore region adjoining southern Natioiznl Geophysical Research U. RAVAL most Sri Lanka, major N-S trending fracture zones appear I~zstitute, Hyclerabadto enter in 80°E corridor and these have been attributed to Ernail:

Mobile colloidal particles are known to be ubiquitous in Quaternary fluvial sediments and subsurf... more Mobile colloidal particles are known to be ubiquitous in Quaternary fluvial sediments and subsurface environments which facilitate the transport of contaminants to the aquifer. Despite this harmful effect, very few efforts have been made to study the properties and transport of colloids in Quaternary sediments. In order to understand the properties of these colloids, samples were collected from the exposed late Quaternary sediment sequences dating back to 125 ka from the Mahi River basin. The isolated colloids from these sequences were characterized for their size distribution, electrical conductivity and concentration. The polydispersed colloidal particles occur in varying amounts at different depth intervals. The low electrical conductivity of colloids in the Rayka section could be related to the low concentration of colloids.

The area bound by the rivers Sabarmati and Luni forming a part of North Gujarat and Southwest Raj... more The area bound by the rivers Sabarmati and Luni forming a part of North Gujarat and Southwest Rajasthan alluvial plains has preserved in its sediments and landscape various changes which have occurred in the drainage systems during the Upper Quaternary times. The present day drainage mainly cuts across the material deposited by a set of older rivers which now stand disrupted. The present day rivers are observed to have been superimposed over older river channels and dominantly follow numerous tectonic lineaments and faults of a later date. The new channels reveal and have preserved relicts of the earlier fluvial system. Geomorphic and drainage studies reveal existence of two ancient major river systems, the remnants of which are now represented by the Banas and Rupen rivers. The Banas, along with its major tributary Sipu is the sole survivor of the older fluvial system. whereas Rupen has been partially destroyed.

... Titre du document / Document title. Significance of bank material at Tilakwada in lower Narma... more ... Titre du document / Document title. Significance of bank material at Tilakwada in lower Narmada Valley. Auteur(s) / Author(s). CHAMYAL LS ; BINDU SHARMA ; MERH SS ; HASSAN KARAMI ; Affiliation(s) du ou des auteurs / Author(s) Affiliation(s). MS univ. Baroda, dep. ...

Indian Summer Monsoon (ISM) is the major climatic feature in the Indian sub continent. Since mari... more Indian Summer Monsoon (ISM) is the major climatic feature in the Indian sub continent. Since marine proxies used for monsoon reconstructions are the expressions of the wind strength that may or may not translate on land as rainfall, the continental records are the direct proxies of rainfall variability. We have made an attempt here to synthesize the available works aimed at past monsoon reconstruction using the chronologically constrained continental archives. The nature of geomorphic response of a fluvial system depends upon its environmental setting and the magnitude and duration of a climatic perturbation. In the present synthesis it was observed that events that lasted for ∼10 4 years could imprint its signature particularly in the fluvial systems irrespective of their geographical location. Except few examples, there is virtually no evidence of short term climatic fluctuations coming out from the available fluvrial records. Could it be due to the fact that short lived climate instability (10 2 to 10 3 years) are not sufficient enough to bring about major geomorphic changes in fluvial processes? Climatic inferences drawn so far using the fluvial and aeolian archives are largely based on the field stratigraphy, sedimentology and chronometric studies from limited geographical areas. There is a need for wider coverage pertaining to the fluvial systems particularly in the peninsular and southern Indian rivers. Further, unless, the clitmate proxies like stable isotopes, geochemistry, and environmental magnetism are used the monsoonal inferences would remain qualitative. Lacustrine sequences provide uninterrupted record of monsoonal variability. This important continental archive has not been exploited to its potential, except for the Thar Desert Renewed efforts should be made to explore other areas including the Himalaya.

The Depositional Record

Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is recons... more Holocene evolutionary history of the Banni Plain in the Great Rann of the Kachchh Basin is reconstructed from a subsurface sediment core of ca 50 m. Detailed data on textural and lithofacies variations, grain‐size analysis, environmental magnetism and accelerator mass spectrometry 14C dates on seven samples were generated on the sediment core retrieved from the Banni Plain near Berada. A high‐resolution record extending back to 10 ka has been reconstructed from the top ca 40 m of the core section comprising shallow marine sediments. The core is divisible into five depositional units. The basal part is a fluvial depositional unit followed upward by estuarine, sub‐tidal, intertidal and supra‐tidal environments. The sediment accumulation rate is highest in the sub‐tidal to intertidal facies (1.9 cm year−1) and decreases towards the supra‐tidal facies to 0.09 cm year−1. Environmental magnetic analysis, χlf coupled with the S‐ratio, indicates high magnetic mineral concentrations during t...

Atlas of Structural Geological and Geomorphological Interpretation of Remote Sensing Images

Current Science, Aug 25, 2014

We report the occurrence of large floods in the Sabarmati River Basin during cal AD 1400-1440. Sl... more We report the occurrence of large floods in the Sabarmati River Basin during cal AD 1400-1440. Slackwater palaeoflood deposits have been preserved in the highly dissected ravines along the middle reaches of the river, wherein 5-6 discrete flood events have been identified. The minimum discharge that emplaced the highest deposit has been estimated as ~15,680 m 3 s-1 and is higher than that recorded (3050 m 3 s-1) during the recent 2006 flood. The timing of these high-magnitude flood events in the Sabarmati and adjacent river basins suggests that extreme hydrological events have occurred in response to excess monsoon periods and are largely controlled by the regional climatic conditions. Moreover, these flood events are seen to be broadly synchronous in the alluvial river basins of Gujarat across climatic zones, but are at variance in pattern from the records of the bedrock peninsular rivers.

1st Indian Near Surface Geophysics Conference & Exhibition, 2019

AGU Fall Meeting Abstracts, Dec 1, 2017

The present study employs multisensor remote sensing approach for delineating the morphological i... more The present study employs multisensor remote sensing approach for delineating the morphological intricacies of the Banni plain, a hyper arid saline terrain, generally referred to as 'flat'. The Banni plain is a part of the Great Rann basin and is the culmination of shallow marine sedimentation during the Holocene. Owing to the variable submergence characteristics, the Banni plain displays geomorphological characteristics that are unique and distinctly different from the rest of the terrain of the Great Rann. The RISAT SAR data of the Banni plain used in the present study was acquired in the month of August, 2012, i.e. during the monsoon season when large parts of the Banni plain are normally submerged, waterlogged or saturated with rain water. The inundation is found to be a key factor, in the backscatter of radar waves in the available SAR data which is exploited in the present study to interpret landscape characteristics of the Banni plain. Backscatter from non-inundated s...

Quaternary International, 2021

Abstract Areas around Bhavnagar and Jamnagar in eastern and northern parts of Saurashtra respecti... more Abstract Areas around Bhavnagar and Jamnagar in eastern and northern parts of Saurashtra respectively, are identified previously as prone to recurrent earthquake swarm activity. Sparse seismotectonic studies so far have not revealed any linkage with known faults in Bhavnagar area while no structures are known to occur in the area around Jamnagar. We carried out detailed tectono-geomorphic studies with contrasting geomorphic settings with a view to provide an insight into the swarm activity from a geomorphological perspective. The study is based on extensive field studies and quantitative geomorphic analysis of landscape and drainage. The area around Bhavnagar is divisible into two tectono-geomorphic domains – the E-W trending Sihor Fault zone located to the west of Bhavnagar (domain-I) and the terrain to its south which shows undulating landscape controlled by N–S trending structural trends (domain-II). The quadrant in the SW between these two domains consists of southward titled trappean hills which form source area for drainages flowing northward through Sihor Fault zone and those flowing eastward through domain-II. Late Quaternary, possibly Holocene tectonic activity along the Sihor Fault is indicated by the northward tilt of alluvial plain surface, knickpoint in rivers and small scale minor faults along the fault zone, prominent decrease in depth of fluvial incision away from the fault zone and youthful landscape indicated by drainage basin analysis. Domain-II comprises the largely erosional pediplain developed over trappean and Tertiary rocks to the south of Bhavnagar. The drainages show an early stage of landscape development due to ongoing tectonic activity. The area around Jamnagar is dominantly a peneplain formed over subhorizontal trappean lava flows. The peneplain is a manifestation of the prolonged period of non-erosion and deposition during the Cenozoic. The rivers show youthful landscape in the central part of the peneplain which includes, large knickpoints, rapids, anomalous river bends, steepening of channel gradient and large potholes. This ENE-WSW trending zone of anomalous fluvial geomorphic anomalies points to the existence of a fault or fold in the subsurface. The structure appears to be active as indicated by the denser cluster of earthquake swarm along this zone. We infer that the generation of earthquake swarm activity comprising low to moderate magnitude shocks is caused by the sheared rocks along the Sihor Fault near Bhavnagar and the ENE-WSW trending subsurface structure near Lalpur which provide avenues for downward percolation of rainwater to deeper levels causing loss of frictional resistance along weak planes.

Springer Hydrogeology, 2018

The socio-economic development in Mainland Gujarat has been river centric. The physical environme... more The socio-economic development in Mainland Gujarat has been river centric. The physical environment of these rivers relates to the landscape response to climate change and tectonic forcing. There is a great diversity in the land and water resources of the region; on the one hand, where there is excess run-off in the rivers such as Narmada and Tapi, the population in the Sabarmati basin faces water scarcity. The agricultural growth in these basins has been exceptionally high; however, unplanned irrigation activities have put the surface as well as the groundwater resources under severe stress. The industrial effluents discharged into the main rivers or the tributaries further aggravate these problems. Soil and bank erosion though common are still up to a level where conservation methods can be applied. Thus, the socio-economic relevance of these river basins is very high and a large potential exists to further improve the conditions of water supply, agriculture, soil erosion and pollution. Each geomorphic unit has a unique resource potential, and a scientific evaluation of the potential is necessary for the socio-economic development of the region.

Journal of Mountain Science, 2021

The study deals with stream response to sustained tectonic during the Cenozoic and development of... more The study deals with stream response to sustained tectonic during the Cenozoic and development of two parallel scarps in the western Kachchh. The study encompasses fluvial networks developed over the Jara and Jumara domes, which are a part of the laterally extensive belt of flexures bounded by the Kachchh Mainland Fault (KMF) to their north and called as Northern Hill Range (NHR). Parameters such as longitudinal profile, Hack profile, stream length gradient index (SL), hypsometric curve, hypsometric integral (HI), valley floor width to height ratio (Vf), elongation ratio (Re) and escarpment sinuosity (ES) were analysed. Hack profiles of the major rivers draining through the area show similar convex up nature suggesting primary influence of the tectonics in controlling and shaping the landscape of the region. Elongation ratio <6 and undergone higher degree of fluvial erosion indicated by the low values of hypsometric integral suggest the tendency of river systems to increase the basin area longitudinally rather than laterally. The study suggests that higher net uplift in the eastern half (Jumara dome) caused the rivers to overcome the structural control and to carve out generally straight north oriented channels. The rivers of western part (Jara dome) show more prominent structural control of cuesta girdles formed in compact lithologies and attributed to the domal structure. The ~10 km long Jaramara scarp believed to the remnant of older KMF scarp, is a product of headward erosion of the fluvial channels through different hard and soft litho-units of the area. The similar orientation of Jaramara scarp and morphology of the Ukra intrusive body suggests that the Ukra intrusive played a significant role in controlling the formation and morphology of the Jaramara scarp.

Quaternary International, 2021

Abstract We carried out sedimentological and mineral magnetic studies on a ∼60 m long core recove... more Abstract We carried out sedimentological and mineral magnetic studies on a ∼60 m long core recovered from the central part of the Great Rann of Kachchh (GRK), a marginal marine basin, located on the western continental margin of India to understand the Holocene paleoenvironmental changes. We critically analysed the sedimentation pattern, sediment characteristics along with paleoclimatic signatures of global and regional relevance. In GRK basin, the sedimentation started in early Holocene (∼10.6–9.3 kyr BP) under rapidly rising post glacial sea level with very high sedimentation rate (8.71 cm/yr to 2.37 cm/yr) which is also seen in several marginal marine basins across the globe. The abundant laminations, coarse grained sediment flux and environmental magnetic parameters (χlf, S-ratio) suggests that the sedimentation occurred in developing monsoonal conditions under wetter yet fluctuating climate during this period. After ∼9 kyr BP, the environmental magnetic proxies show transition toward relatively wetter condition with peak at ∼6.5 kyr BP. This wetter climatic phase on the other hand corroborates with reduction of sedimentation rate to 0.46 cm/yr. This reduction in sedimentation rate under strengthening monsoonal conditions probably occurred due to rapid filling up of the basin on account of earlier high sedimentation in the basin. The sedimentation rate is reduced significantly after the onset of aridity at ∼4 kyr BP except a minor wet spell recorded during ∼1.5 to 1 kyr BP before drying of the GRK basin.

Journal of Structural Geology, 2020

The E-W striking Kachchh Rift Basin (KRB) at the western continental margin of Indian plate is lo... more The E-W striking Kachchh Rift Basin (KRB) at the western continental margin of Indian plate is located in the northern part of Gujarat state, India. KRB has undergone polyphase deformation owing to changing stress-field since Late Triassic. We establish the kinematic framework along the NW striking intra-uplift Vigodi-Gugriana-Khirasra-Netra Fault System (VGKNFS) located at the western part of the KRB. The VGKNFS consists of 0.25-50 km long, sub-parallel, striated, reactivated dip-slip faults. A total of 1150 fault-slip data consisting of fault planes and striations attitude were recorded from 66 sites (including a single site with systematic joints). Slip-sense of faults was determined by documenting kinematic indicators. Paleostress analysis was carried out using Win-Tensor, T-Tecto, FaultKin and SG2PS to compare and validate the results. The chi-square statistical analysis was undertaken to evaluate how relevant are paleostress analysis results to the present-day compressional stress field. Geophysical investigations were conducted at selected sites using Ground Penetrating Radar (GPR) to understand the shallow subsurface geometry and trace the continuity of faults buried below patchy alluvial cover. 15-17 m long, 2D GPR cross-sections were recorded across faults using monostatic antenna of 200 MHz frequency. Two major deformation events-D1 and D2 are determined in the present study. The extension event D1 shows W and NW-NNW extension during Late Triassic to Late Cretaceous. It occurred during the rift phase of KRB in response of the break-up of Gondwanaland. The latest event D2 shows NNE-NE compression from Late Cretaceous up to the present. It is interpreted to have developed during post-rift inversion phase, induced by collision of the Indian plate with the Eurasian plate at ~55 Ma.

Zeitschrift für Geomorphologie, 2018

Episodes, 2015

The present study is based on the field observations and geochemical analyses of flood sediments ... more The present study is based on the field observations and geochemical analyses of flood sediments to ascertain the nature and causes of destruction in the Mandakini and Alaknanda river valleys during June 2013. The study suggests that the sediments were contributed from two major sources: the moraines and alluvial fans located in the Trans and Higher Himalaya; and the landslides in the Higher and Lesser Himalaya. Although the flood was the result of a high intensity rainfall event, the magnitude was increased due to the proliferation of settlements along the river and a series of partially constructed barrages on the river bed. Geochemical analyses of the flood sediments indicated that the contribution of power-project generated debris locally enhanced the flood magnitude. Further, the study argues that the terrain north of the Main Central Thrust (Higher Himalaya) should be kept free from major interventions, including hydropower projects, to reduce flood hazards. The study finally calls for a critical reevaluation of current development policy and the approach towards harnessing the enormous hydropower potential of the Himalayan rivers in general and in the Uttarakhand Himalaya in particular.

Geosciences Journal, 2018

The Kachchh palaeo-rift graben at the western continental margin of India is currently undergoing... more The Kachchh palaeo-rift graben at the western continental margin of India is currently undergoing active coseismic deformation in response to the periodic release of NE-SW oriented compressive stresses along the E-W trending intra-basinal faults. The seismically active Kachchh Mainland Fault (KMF) is the largest intra-basinal fault that is characterized by a narrow zone comprising a chain of domes and anticlines forming the rugged hilly topography of the Northern Hill Range (NHR) in the upthrown block. The present paper deals with the Jumara and Jara domes which have received considerable attention with respect to the Mesozoic biostratigraphy, however, no study has been carried out on geomorphological and neotectonic aspects. The major geomorphological units in the area include a low relief but rugged structurally controlled topography over the domes, the KMF scarp, the precipitous Jaramara scarp, the back slope over the Jaramara scarp and the rugged hilly topography over the large Ukra intrusive body that shows a complicated structural contact relation with the Mesozoic rocks ranging from concordant to discordant. Our detailed field studies supplemented by geomorphological analysis using DEM, topographical profiles, drainage characteristics and longitudinal profiles reveal the dominant control of sustained uplift along the KMF under compression in the development of the present youthful and structurally controlled landscape. Our study also suggests that the imposing E-W trending Jaramara scarp is formed due to the long-term retreat of the KMF scarp in response to uplift, while the present low relief scarp along the KMF is largely the result of post-Miocene uplift. The incision in Quaternary miliolite deposits in the Jara river gorge, deeply incising nature of the rivers, several large and small knickpoints and scanty occurrence of Quaternary miliolite deposits indicate an uplift of ~25 m during the Late Quaternary time.