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... 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.
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... 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)... 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. ...
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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... 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.
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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... 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...
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Research Interests: Geology, Monsoon, Current Science, Floodplain, Bedrock, and 3 morealluvium, Flood Myth, and Drainage basin
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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... 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...
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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... 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.
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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... 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.
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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... 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.
Research Interests: Geology, Geomorphology, Tectonics, RIFT, Fluvial, and 3 moreEscarpment, Mountain Science, and Sinuosity
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... 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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Abstract The present study uses clay mineralogy to delineate a ∼17 ka record of palaeoenvironmental/palaeoclimatic changes in the recently uplifted palaeogulf of Arabian Sea i.e. Great Rann of Kachchh (GRK). Situated on continental margin... more
Abstract The present study uses clay mineralogy to delineate a ∼17 ka record of palaeoenvironmental/palaeoclimatic changes in the recently uplifted palaeogulf of Arabian Sea i.e. Great Rann of Kachchh (GRK). Situated on continental margin of Indian subcontinent and flanked by Indus delta, the GRK basin has preserved continuous record of post glacial sedimentation. Clay mineral studies on two long cores (∼60 m and 50 m long) show more abundance of physical weathering products (illite and chlorite) over the chemical weathering products (smectite and kaolinite). We show that the GRK sediments depict multiple sources of sediment input. Dominance of illite-chlorite suggests GRK received sediments dominantly from the Himalayan terrain with minor contribution from adjacent regions. We present the oldest clay mineralogical signature of an interval of intensified monsoon conditions during the late Pleistocene (∼17.7–16.3 cal ka B.P.). Monsoon became stronger before ∼8.4 cal ka B.P., and whereas the mid Holocene weakening of monsoon occurred after ∼7 cal ka B.P. Despite the differences in source region and composition of clay mineral records from the GRK with northeastern and southeastern Arabian Sea, the sedimentation responded to major climatic shifts that have occurred since the LGM.
Research Interests: Archaeology, Geology, Geochemistry, Pleistocene, Quaternary, and 3 moreHolocene, Sediment, and Heavy mineral
Evidence of paleoenvironmental changes during the Holocene from the Lower Mahi basin of Western India have been documented. The unpaired S2surface all along the estuarine zone of the Mahi basin has been identified as an uplifted marine... more
Evidence of paleoenvironmental changes during the Holocene from the Lower Mahi basin of Western India have been documented. The unpaired S2surface all along the estuarine zone of the Mahi basin has been identified as an uplifted marine terrace. The terraces have preserved in their lithosections fairly distinct horizons of grayish brown clays rich in marine microfauna. The intervening silty-sand horizons are indicative of freshwater origin. The sedimentary structure and faunal assemblage indicate that these units have been deposited in a marginal marine environment. The14C ages obtained on these marine mud horizons show that between 3600 and 1700 bp the sea level was higher than at present. The geomorphic evidence suggests that a late Holocene uplift has played a significant role in lowering the relative sea level to its present position.
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Based on geomorphological characteristics, the vast, flat saline tract of the Great Rann of Kachchh is considered as a raised floor of a former gulf that was connected to the Arabian Sea in the west. In general, the Rann exhibits a unique... more
Based on geomorphological characteristics, the vast, flat saline tract of the Great Rann of Kachchh is considered as a raised floor of a former gulf that was connected to the Arabian Sea in the west. In general, the Rann exhibits a unique supratidal environment complicated by alternating periods of marine and freshwater inundation and extreme dryness. The Great Rann is divisible into four distinct geomorphic domains - the Banni plain, the Linear trench zone, the Great barren zone and the Bet zone. Contrary to the rest of the Great Rann, the Bet zone shows distinct variations in elevation due to the presence of bets (islands) and is dotted by several vegetated elevated areas, seasonal short distance channels and local depressions. The present study attempts to characterize the environmental conditions of the Bet zone comprising the northwestern part of the Great Rann. Surface sediment samples were collected by digging small pits in the Rann surface at several locations along ESE-WNW and roughly N-S oriented transects (transect 1 and 2). The samples were subjected to detailed grain size analysis and micropalaeontological analysis for determining foraminiferal assemblage. Overall, the sediments of the Bet zone are of sandysilty to clayey-silty in nature. The grain size was found to vary in accordance with the microgeomorphic setting of the stations. The foraminiferal assemblages recorded along the two transects belong to twelve genera ( Ammonia, Elphidium, Bolivina, Nonian, Bulimina, Cibicides, Helenina, Brizalina, Globigerinella, Globigerina, Globorotaloides Gallitellia ). Presence of some reworked foraminiferal tests suggests the transport of foraminifera from the Arabian Sea water surges under the influence of strong SW monsoon winds. However, the relatively higher diversity near the open ocean gets reduced in the Great Rann due to the typical hypersaline conditions, submergence patterns, mixing by fresh water (runoff, fresh water influx), and the microenvironments created by variations in the elevation of the Rann surface. The diversity is limited to the few tolerant taxa which can survive through such large scale changes in the environmental parameters.
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River meandering is an inherent characteristic of drain-ages in an alluvial plain. However, the style and degree of meandering depends on a number of geological factors, including tectonics. Here, we have investigated theVishwamitri... more
River meandering is an inherent characteristic of drain-ages in an alluvial plain. However, the style and degree of meandering depends on a number of geological factors, including tectonics. Here, we have investigated theVishwamitri river, a tributary of Dhadhar river flowing through Gujarat alluvial plain. The river follows a slope deviatory course and exhibits a narrow, highly sinuous and deeply incised meandering channel. Several lines of evidence, including satellite and topographic data, stratigraphic and sedimentological data and subsurface structural data have helped in understanding the controls on the channel morphology of the Vishwamitri river. The study has also revealed that the course of the Vishwamitri river has shifted towards east in the last 35 years, in response to neotectonic activity.
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The lineaments recognised in the Gujarat alluvial plains correspond to major structural and basement fault trends. The geomorphic and drainage anomalies in the plains are in conformity with the subsurface structural features. The variable... more
The lineaments recognised in the Gujarat alluvial plains correspond to major structural and basement fault trends. The geomorphic and drainage anomalies in the plains are in conformity with the subsurface structural features. The variable thickness of the Quaternary sediment cover suggests sedimentation in fault-bounded sub-basins within a larger basin. The exposed sediment column of 40-50 m dates back to ∼125 ka. The Quaternary evolutionary history of the Gujarat alluvial plains has been divided into three stages marked by distinct tectonic changes. Four phases of tectonic activity during the Quaternary have played a significant role in the evolution of these plains. The first two are associated with the deposition of a large volume of sediments. The last two comprise tectonic uplifts which have shaped the present landscape of Gujarat alluvial plains. Extensive ravines, valley fill terraces, asymmetric drainage, deeply incised fluvial valleys and entknched meanders are manifestations of tectonic uplift during the Holocene. The seismic record of the last few hundred years suggests continued tectonic instability of the area in and around Gujarat alluvial plains.
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Research Interests: Geology, Oceanography, Climate Change, Paleoclimatology, Paleoceanography, and 15 moreSomalia, Climate modeling, Monsoon, India, Indian Ocean, Holocene, Indian summer monsoon, Marine sediments, Upwelling, Biogenic silica, Indian monsoon, Intertropical Convergence Zone, Somali, Arabian Sea, and Southwest Monsoon
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The lost Saraswati River mentioned in the ancient Indian tradition is postulated to have flown independently of the Indus River into the Arabian Sea, perhaps along courses of now defunct rivers such as Ghaggar, Hakra and Nara. The... more
The lost Saraswati River mentioned in the ancient Indian tradition is postulated to have flown independently of the Indus River into the Arabian Sea, perhaps along courses of now defunct rivers such as Ghaggar, Hakra and Nara. The persistence of such a river during the Harappan Bronze Age and the Iron Age Vedic period is strongly debated. We drilled in the Great Rann of Kachchh (Kutch), an infilled gulf of the Arabian Sea, which must have received input from the Saraswati, if active. Nd and Sr isotopic measurements suggest that a distinct source may have been present before 10 ka. Later in Holocene, under a drying climate, sediments from the Thar Desert probably choked the signature of an independent Saraswati-like river. Alternatively, without excluding a Saraswati-like secondary source, the Indus and the Thar were the dominant sources throughout the post-glacial history of the GRK. Indus-derived sediment accelerated the infilling of GRK after ~6 ka when the Indus delta started to ...
The Kachchh Basin, located in Gujarat (India) at the western trailing edge of the Indian plate, comprises several east–west trending seismically active faults. The Kachchh Basin evolved in two major stages. The first is the rift stage,... more
The Kachchh Basin, located in Gujarat (India) at the western trailing edge of the Indian plate, comprises several east–west trending seismically active faults. The Kachchh Basin evolved in two major stages. The first is the rift stage, which correlates with the break-up and separation of the Indian plate in the Late Triassic–Early Cretaceous and synrift sedimentation. The second is the post-Deccan Trap inversion stage, when the basin was periodically uplifted along the existing east–west trending intrabasinal master faults: the Katrol Hill Fault, the Kachchh Mainland Fault, the South Wagad Fault, the Gedi Fault and the Island Belt Fault. The inversion of basin was initiated by the onset of a compressive stress regime in response to the collision of the Indian plate with the Eurasian plate in the far north during the Early Eocene. This is shown by the tilting of the Deccan Trap lava flows along with the underlying Mesozoic sequence and the associated intrusive bodies that occupy the ...
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Pachham Island is the westernmost island in a chain of four rocky islands within the Great Rann of Kachchh that are bounded in the north by the Island Belt Fault (IBF). The island is characterized by two parallel and structurally... more
Pachham Island is the westernmost island in a chain of four rocky islands within the Great Rann of Kachchh that are bounded in the north by the Island Belt Fault (IBF). The island is characterized by two parallel and structurally controlled Kaladungar hill range and Goradungar hill range separated by a synclinal central valley. The central valley has acted as a sink for the Quaternary sediments. The island is transversely traversed by a N-S trending basement high termed as Median high that shows pronounced geomorphic and drainage anomaly. The Quaternary sediments comprise coarse-grained colluvio-fluvial deposits, miliolite, and sandy alluvium. The coarse-grained Quaternary deposits were primarily derived from the colluvium generated due to the uplift of the Kaladungar hill range and Goradungar hill range along the IBF and Goradunagar Fault, respectively. The colluvial debris were subsequently reworked, transported down slope and deposited in the central valley. The presence of the deeply incised valleys in Quaternary sediments, two levels of terrace surfaces over the Median high, and the raised Rann floor surrounding the island suggest a dominant role of neotectonics in the landscape evolution and Quaternary sedimentation.
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ABSTRACT We present the results of our GPR and field based studies along the E-W trending Kachchh Mainland Fault (KMF), South Wagad Fault (SWF) and Gedi Fault (GF) that have prominent control on the landscape and ongoing seismic activity... more
ABSTRACT We present the results of our GPR and field based studies along the E-W trending Kachchh Mainland Fault (KMF), South Wagad Fault (SWF) and Gedi Fault (GF) that have prominent control on the landscape and ongoing seismic activity of the Kachchh palaeo-rift basin. The Subsurface Interface Radar-20 (SIR-20) GPR system of GSSI, USA alongwith 200 MHz, 100MHz and 80 MHz antenna was used to laterally map the near surface trace and the shallow subsurface nature of the faults. The KMF is found to be a steep northward dipping normal fault that becomes reverse in two segments. The SWF is revealed as a south dipping normal fault. The GF is largely a steep dipping reverse to vertical fault. The GPR data along with field evidences of neotectonic activity that include stratigraphie development of Quaternary sediments, variable incision and sediment deformation, suggest a dominantly N-S oriented compressional stress environment along the active faults of Kachchh basin. However, the distribution, accommodation and release of stresses are not uniform along the faults as they are cut across by oblique slip transverse faults. We infer that the understanding of ongoing seismic activity in the region is complicated by the multiple seismic sources and the segmented nature of the faults.
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The 2001 Bhuj earthquake (Mw 7.7) formed several medium to large sand blow craters due to extensive liq-uefaction of the sediments in the clay sediments of the Banni plain and Great Rann of Kachchh. We investigated three large sand blow... more
The 2001 Bhuj earthquake (Mw 7.7) formed several medium to large sand blow craters due to extensive liq-uefaction of the sediments in the clay sediments of the Banni plain and Great Rann of Kachchh. We investigated three large sand blow craters using Ground Penetrating Radar (GPR) with a view to understand the subsurface deformation , identify the vents and source of the vented sediments. The GPR was able to provide good resolution on stratigraphy and deformation upto a depth of 6.5 m. The GPR successfully imaged the subsurface characteristics of the craters based on the contrasting lithologies of the host sediments and the sediments emplaced in the craters. The GPR also detected vents continuing throughout the profile which are reflected as high amplitude vertical events. We conclude that the large sand blows during the 2001 Bhuj earthquake were produced due to liquefaction of sediments in the subsurface at >6.5 m depth. The study provides a modern analogue for comparing the liq...
ABSTRACT The traces of cutoff meander loops, swamps or shallow lakes provide ideal sites for understanding sedimentation pattern and depositional environment and also provide clues for the reconstruction of the past landscape. It is... more
ABSTRACT The traces of cutoff meander loops, swamps or shallow lakes provide ideal sites for understanding sedimentation pattern and depositional environment and also provide clues for the reconstruction of the past landscape. It is intriguing to analyze the process of present day meander cutoff for a better correlation with the processes of palaeomeander formation. In the north Gujarat alluvial plains, within the largely internally draining Vatrak river basin, one of its major tributary, Meshwa River, shows fluvial landscape with palaeochannels, meander scar and meander cutoffs features resulting from channel shifting processes. Data has been generated from abandoned channel fill to understand the fluvial dynamics and depositional environment. The river exhibits prominent changes in its course from the year 1971 to 2012 spreading over time span of 41 years. The point bars associated with the meanders have been abandoned and further incised providing scope for facies analysis and depositional environment interpretations. Five episodes of repeated submergence and emergence have been inferred probably related to levee deposits suggesting minor variations in the streamflow conditions. Based on the channel planform analysis and discharge estimations also it can be concluded that the rate of channel migration has varied over the last 40 years. The discharge estimations suggest that the major shift has however been related to a high magnitude flood event in the year 2009 that led to the channel meander cutoff. Variations in the index of channel migration also points towards higher channel migration rate and suggests that the river was in a highly erosive phase cutting its own channel and reworking the floodplain deposits.
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ABSTRACT A sediment core from Pariyaj Lake, from the Vatrak River basin, located at the desert margin in the Gujarat Alluvial Plains of western India, was investigated in a multidisciplinary aspect. The goal was to reconstruct the... more
ABSTRACT A sediment core from Pariyaj Lake, from the Vatrak River basin, located at the desert margin in the Gujarat Alluvial Plains of western India, was investigated in a multidisciplinary aspect. The goal was to reconstruct the palaeoclimate, palaeoenvironment and tectonic history and to understand the role these factors played in the geomorphological evolution of the area during the Holocene. Palaeoclimatic interpretations also shed light on the factors responsible for the rise and fall of the Harappan civilisation. The results obtained based on multiproxy studies show five climatic phases during the last 11,000 yr BP. Phase 1 (~ 11,000 cal yr BP) represents a very humid climate and high precipitation/discharge leading to high lake stand as attested by the high pollen concentration of semi-evergreen tree taxa, phytoliths belonging to cool and moist grasses, and large proportion of algae, marking the onset of Holocene. In phase 2 (~ 8000 to 9000 cal yr BP) a significantly reduced yield of pollen, phytoliths and aquatic algae indicates shrinkage of the lake. Phase 3 (~ 7630 cal yr BP) shows moderate yield of pollen and phytolith pointing towards fluctuating precipitation conditions. Phase 4 (~ 5864 to 4680 cal yr BP) shows very low pollen and phytolith counts, indicating a very dry spell. Finally, phase 5 (~ 4680 to 3500 cal yr BP) shows a good density and diversity of flora. The wet climate and high lake stand ~ 11,000 cal yr BP, 7630 cal yr BP and after ~ 4680 cal yr BP are synchronous with the lacustrine, marine and aeolian records of western India. The contribution of winter precipitation at 7630 cal yr BP and after ~ 4680 cal yr BP can be correlated with similar records from Rajasthan Lake. Decrease in the precipitation activity, the low lake stand and the onset of dry climatic condition between 8000 and 9000 cal yr BP corresponds to a near global anomaly of this period. Another dry event between ~ 5864 and 4680 cal yr BP documented in Pariyaj Lake record is synchronous with various proxy records of the mid–late Holocene Afro-Asiatic monsoonal belt.
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ABSTRACT A multi-proxy study on the sediments from lower Narmada valley, western India records large flooding events and high sediment influx linked to southwest monsoon variations during late Holocene. On the basis of proxy data and... more
ABSTRACT A multi-proxy study on the sediments from lower Narmada valley, western India records large flooding events and high sediment influx linked to southwest monsoon variations during late Holocene. On the basis of proxy data and chronology of preserved sediments, three major environmental perturbations at 1809, 1487, and 1187 cal BP have been identified that corroborate well with the regional fluctuations in southwest monsoon variability. A phase of dominant marine influence (between 2185 and 1809 cal BP) is inferred based on the presence of marine palynomorphs, mangrove pollen, and amorphous organic matter and is coincident with the phase of weak monsoon in the region. A transition from marine marsh environment to a phase of high fluvial influx occurred around 1809 cal BP. The fluvial influence is inferred based on the replacement of amorphous organic matter with structured organic matter, presence of fresh water algae, decrease in the δ13C values and dominance of kaolinite clay. The fluvial regime stabilized between 1487 and 1187 cal BP as recorded in the overbank sediments, palynomorphs, and geochemical indices, and sedimentation occurred under a highly oxidizing and high energy condition with long distance transport of sediments. The later incision of the sediment sequence, which post-dates 1187 cal BP, can be attributed to enhanced precipitation. The response of the lower Narmada valley to short term southwest monsoon fluctuations is manifest in the shifting deposition environments and a major role of terrestrial sediment influx variability is surmised, leading to relative sea level variations in this part of the Indian subcontinent. A temporal and process-based interplay between flooding periods and sediment discharge in river systems and tidal conditions is suggested for the tropical estuarine environments.
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... The northern margins of the islands is, DM Maurya et al. 74 Fig. 3. Morphostructural map of the Little Rann as worked out in the present study. Note the two fault bound linear island belts dividing it into three distinct subbasins.... more
... The northern margins of the islands is, DM Maurya et al. 74 Fig. 3. Morphostructural map of the Little Rann as worked out in the present study. Note the two fault bound linear island belts dividing it into three distinct subbasins. The subbasins are shown with different shades. ...