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.
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...
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...
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.
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.
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.
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.
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.
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...
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...
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.
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.
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.
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.
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