Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

D. M. Maurya ¹, R. Rachna ¹, L. S. Chamyal ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Baroda - 390 002, IN

Abstract

Seismically induced deformational structures from the lower Mahi valley are reported. These include injected liquefied sand, contorted laminations, load structures, overturned small-scale folds and convolutions. syn-sedimentary microfaults and pseudonodules. The structures are similar to the seismically-induced deformation structures reported elsewhere and conform to the criteria for reiating them to seismic events. Radiocarbon dating of the two organic rich clay layers suggest the deformation is related to a Late Holocene seismic event that took place between 3320±90 and 2850±90 yrs. B.P.

Keywords

Seismology, Seismites, Holocene, Mahi Valley, Gujarat.

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Rachna Raj ¹, D. M. Maurya ¹, L. S. Chamyal ¹

Affiliations
1 Department of Geology, M.S.University of Baroda,Vadodara-390002, IN

Abstract

All along the Lower Mahi Valley, ravines form an important geomorphic unit. These have developed extensively in the Late Pleistocene continental sediments delimited by flat alluvial plains on one side and river channel on the other. The ravines are confined to all the three pediment, alluvial and estuarine zones. The intensity of these is more on the left bank compared to the right and suggest a differential uplift of the horst block dong basement faults. Morphologically, the ravines are divisible into two types: sharp crested, steep, deeply entrenched and gently sloping, with shallower depth and comparatively smaller in length. The directional analysis of ravine orientations show that the higher order ravines trending NE-SW and NNE-SSW are related to neotectonic activity along older structural trends during Early Holocene. The smaller and gently sloping ravines showing varying trends are attributed to semi-arid and humid climate.

Keywords

Geomorphology, Neotectonics, Pleistocene, Ravines, Mahi Valley, Gujarat.

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A. S. Khadkikar ¹, L. S. Chamyal ¹, J. N. Malik ¹, D. M. Maurya ¹, S. S. Merh ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara - 390 002, IN

Abstract

A more or less complete conformable succession of sediments of Quaternary age is documented from the Mahl river basin. A description of the lithostratigraphy is accompanied by the palaeoclimatic inferences drawn on the basis of deduced depositional environments, which shows a remarkable broad correspondance with global climatic fluctuations.

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Rachna Raj ¹, D. M. Maurya ¹, L. S. Chamyal ¹

Affiliations
1 Department of Geology, M.S. University of Baroda, Vadodara- 390 002, IN

Abstract

Neotectonic activity along pre-Quaternary tectonic trends has played a major role in the evolution of Mahi drainage basin. The Mahi basin is controlled by NE-SW and WNW-ESE Aravalli trend in the uplands and by NNW-SSE Tertiary basement faults in the distal part. Lineament analysis shows three structural trends in the area which are related to major regional tectonic trends. Stream orientations indicate that the NNE-SSW and NNW-SSE trends represent lineaments which were active during the youngest tectonic phase. The NE-SW and WNW-ESE trends are slightly older. The evolution of overall configuration of the basin is attributable to neotectonic activity along WNW-ESE and NESW trends which have been modified by a later phase of tectonic activity along NNW-SSE trend. Morphotectonic analysis has been helpful in assessing the relative degree of tectonic activity in the different geomorphic zones of the Mahi river basin. An increasing degree of tectonic activity towards the NE conforming to the northeastward extension of the Aravalli range where the central axis of the range lies, has been indicated.

Keywords

Neotectonics, Geomorphology, Morphometric Analysis, Mahi River, Western India.

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N. Juyal ¹, L. S. Chamyal ², S. Bhandari ², D. M. Maurya ², A. K. Singhvi ¹

Affiliations
1 Physical Research Laboratory, Navrangpura, Ahmedabad - 380 009, IN
2 Department of Geology, M S University of Baroda, Vadodara - 390 002, IN

Abstract

Chronometric and sedimentological data generated from the exposed Quaternary sequences of the Orsang River basin indicate close correspondence between the environmental changes and fluvial aggradation. The oldest and regionally extensive fine Silty-Clay occurring at the base of the successions is dated to >97 ka suggesting prevalence of high sinuosity suspended load fluvial regime. Its stratigraphics portion suggests that the deposition occurred during the enhanced southwest monsoon corresponding to the Marine isotopic Stage-5 (MIS-5). The gravel deposits that overlie provide an age of -60 ka indicating dominance of braided system (MIS-4) during the reduced southwest monsoon. The pluvial interstadial (MIS-3) is represented by flood plain facies that was deposited under the persistent fluvial system strengthened by enhanced southwest monsoon and assigned ages ranging between 50 and 30 ka. An extensive aeolian sand sheet that blankets the topography, is luminescence dated to 21 ka suggesting the onset of Last Glacial Maximum in the Orsang River basin.

Keywords

Late Pleistocene, Fluvial Aggradation, Environmental Change, Orsang River Basin, Western India.

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Rachna Raj ¹, subhash Bhandari ¹, D. M. Maurya ¹, L. S. Chamyal ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

The Karjan basin is one of the largest tributary basins of the Lower Narmada Valley. A major part of the basin comprises southward dipping basaltic flows of the Deccan Volcanic Group (DVG) delimited to the north by the Narmada- Son Fault. The lineaments indicate a strong control of the ENE-WSW and NNW-SSE trends on the geomorphology and drainage architecture. The ENE-WSW trending ridges with southern slopes and north facing escarpments including the Narmada-Son Fault (NSF) and ENE-WSW trending narrow intramontane valleys evidence the dominant control of ENE-WSW trend. Three tilt blocks have been delineated within a major tilt block formed due to differential uplifts along the NSF and two other sympathetic faults. A gradual decrease in the ruggedness of the topography towards south, preferential locations of river pondings, gorges and increased fluvial incision suggest continued southward tilting of the fault blocks due to differential uplift along ENE-WSW trending faults. The alluvial zone to the north of the Narmada- Son Fault is made up of Late Pleistocene to Holocene sediments and indicates two phases of river incision in the Karjan river basin, which are attributed to uplifts during Early and Late Holocene. Morphometric analyses of parameters sensitive to tectonics substantiate the field observations on active tectonics. The field evidence from the upland and alluvial zone and the morphometric analyses point to differential uplift of the Karjan basin along ENE-WSW trending faults during Holocene.

Keywords

Geomorphology, Active Tectonics, Karjan Basin, Western India.

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Utpal Chakrabarti ¹, Abhinaba Roy ¹, Subhash Bhandari ², Rachna Raj ², D. M. Maurya ², L. S. Chamyal ²

Affiliations
1 Geological Survey of India, Central Region, Nagpur, IN
2 Department of Geology, M. S. University of Baroda, Vadodara-390002, IN

Abstract

No Abstract.

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Subhash Bhandari ¹, Rachna Raj ¹, D. M. Maurya ¹, L. S. Chamyal ¹

Affiliations
1 Department of Geology, M.S.University of Baroda, Vadodara-390 002, Gujarat, IN

Abstract

Five alluvial fans have been recognised along the Narmada-Son Fault near Rajpipla in the Lower Narmada basin. These have been studied in their proximal, medial and distal parts. Lithofacies characteristics and facies associations indicate debris flows and sheet flood flows as the major processes responsible for aggradation of these fans. The fans have coalesced and formed a fault-bound geomorphic surface during Early Holocene. Sedimentation in an alluvial fan environment during the Early Holocene is not yet known from this part of Western India. Prolonged subsidence along Narmada-Son Fault and two other faults along the Narmada river and its tributary Karjan, have provided ideal site for the accumulation of fan deposits. These alluvial fans suggest differential movement along the Narmada-Son Fault and a humid climate during Early Holocene.

Keywords

Alluvial Fans, Holocene, Narmada-Son Fault, Western India.

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D. M. Maurya ¹, Rachna Raj ¹, L. S. Chamyal ¹

Affiliations
1 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

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.

Keywords

Quaternary Tectonism, Geomorphology, Basin Evolution, Fluvial System, Gujarat Alluvial Plains.

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M. G. Thakkar ¹, Bhanu Goyal ¹, D. M. Maurya ², L. S. Chamyal ²

Affiliations
1 Department of Earth and Environmental Science, KSKV Kachchh University, Bhuj, Kachchh - 370 001, IN
2 Department of Geology, M. S. University of Baroda, Vadodara - 390 002, IN

Abstract

The liquefaction attributes and crater geometry related to 2001 Bhuj earthquake has been reconstructed by trenching along large known craters formed near Umedpar in Kachchh. The study characterises the liquefied sediments in a large reactivated crater and distinguishes it from a non-reactivated crater located nearby. These characteristics can help in the interpretation of large paleocraters formed as a result of earthquake induced liquefaction.

Keywords

Liquefaction, Crater Geometry, Intra-Plate Seismicity, Kachchh.

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