The Bishnumati River, a major tributary of the Bagmati River in the Kathmandu Basin, is a low-gradient, low-sinuosity river with a short high-gradient head. The tributaries contributing the Bishnumati River supply sediments from granite-gneiss sources located towards the north of the river area, and from sedimentary rocks of the Phulchoki Group from the northwest and the west of the Bishnumati watershed. Four representative segments each from third, fourth, fifth and sixth order stretches were sampled and analysed for riverbed-material size, and gravel shape and composition, to characterise riverbed materials, to understand downstream distribution of shape, size and composition of sediments, and to understand provenance of riverbed materials. The D 50 of the segments 1, 2, 3 and 4 are 25.11 mm, 0.871 mm, 3.75 mm and 27.86 mm, respectively. The riverbed materials are classified as Gravel, muddy sandy Gravel and muddy Gravel, which are very poorly sorted indicating textural immaturity. Gravels are compact bladed in form. Oblate prolate index (OPI) shows more oblate nature of gravels from downstream segments (sixth order stream). Gravels have high settling sphericity (0.6-0.8) and slightly higher flatness index (0.51-0.54). They are subrounded to rounded although there exist some angular to well rounded gravels. Downstream changes in shape parameters are not remarkable perhaps because of short distance of transport, insufficient abrasion, or durability of gneissic and granitic clasts, or quick transport of gravels during floods. Shape also seems to be influenced more by inherited properties of parent rocks. The gravels from sedimentary rocks increase from the upstream to downstream sites of the river at the expense of reduction of gneissic and granitic gravels. Existence of siltstone and sandstone gravels in the fifth (Segment 2) and forth order (Segment 3) mainstreams is remarkable as there is no primary parent source upstream of these segments. Existence of sedimentary gravels shows local provenance (fluvio-deltaic terrace deposits) and perhaps suggests existence of paleodrainage system different from the present doi: 10.3126/bdg.v12i0.2250 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 55-62
{"title":"Riverbed-material texture and composition of Bishnumati River, Kathmandu, Nepal; implications in provenance analysis.","authors":"N. Tamrakar","doi":"10.3126/BDG.V12I0.2250","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2250","url":null,"abstract":"The Bishnumati River, a major tributary of the Bagmati River in the Kathmandu Basin, is a low-gradient, low-sinuosity river with a short high-gradient head. The tributaries contributing the Bishnumati River supply sediments from granite-gneiss sources located towards the north of the river area, and from sedimentary rocks of the Phulchoki Group from the northwest and the west of the Bishnumati watershed. Four representative segments each from third, fourth, fifth and sixth order stretches were sampled and analysed for riverbed-material size, and gravel shape and composition, to characterise riverbed materials, to understand downstream distribution of shape, size and composition of sediments, and to understand provenance of riverbed materials. The D 50 of the segments 1, 2, 3 and 4 are 25.11 mm, 0.871 mm, 3.75 mm and 27.86 mm, respectively. The riverbed materials are classified as Gravel, muddy sandy Gravel and muddy Gravel, which are very poorly sorted indicating textural immaturity. Gravels are compact bladed in form. Oblate prolate index (OPI) shows more oblate nature of gravels from downstream segments (sixth order stream). Gravels have high settling sphericity (0.6-0.8) and slightly higher flatness index (0.51-0.54). They are subrounded to rounded although there exist some angular to well rounded gravels. Downstream changes in shape parameters are not remarkable perhaps because of short distance of transport, insufficient abrasion, or durability of gneissic and granitic clasts, or quick transport of gravels during floods. Shape also seems to be influenced more by inherited properties of parent rocks. The gravels from sedimentary rocks increase from the upstream to downstream sites of the river at the expense of reduction of gneissic and granitic gravels. Existence of siltstone and sandstone gravels in the fifth (Segment 2) and forth order (Segment 3) mainstreams is remarkable as there is no primary parent source upstream of these segments. Existence of sedimentary gravels shows local provenance (fluvio-deltaic terrace deposits) and perhaps suggests existence of paleodrainage system different from the present doi: 10.3126/bdg.v12i0.2250 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 55-62","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"139 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127461560","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper describes on lithostratigraphy as well as evolution of the fluvial styles in late Cenozoic Siwalik Group along the Kankai River section of east Nepal Himalaya. The Siwalik Group lies on the southern flank of the Himalaya, is composed of molasse sediments, which were derived from the rising Himalaya in the north. The group along the Kankai River section is lithologically divided into the Lower, Middle and Upper Siwaliks, in ascending order based on increasing grain size and lithology. The Lower Siwaliks is subdivided into the lower and upper members, whereas the Middle Siwaliks is subdivided into the lower, middle and upper members on the basis of the relative thickness of the sandstone and mudstone beds, frequency of occurrence of these beds, and grain size of sandstone. The Upper Siwaliks is subdivided into the lower and upper members based on the clast size in conglomerate and constituent of the Siwalik sandstone boulders in conglomerate. Based on the lithology, assemblages of sedimentary structure and sediment body architectures, seven facies associations (FA1 to FA7) are recognised. These facies associations are closely related to each lithostratigraphic units of the area. The sediments of the lower and upper members of the Lower Siwaliks are products of the fine-grained meandering and flood flow-dominated meandering systems, respectively. The lower, middle and upper members of the Middle Siwaliks are interpreted as the deposits by sandy meandering, deep sandy braided and shallow braided systems, respectively whereas the lower and upper members of the Upper Siwaliks are the products of gravelly braided to debris flow-dominated braided systems, respectively.
{"title":"Lithostratigraphy and late Cenozoic fluvial styles of Siwalik Group along Kankai River section, East Nepal Himalaya","authors":"P. D. Ulak","doi":"10.3126/BDG.V12I0.2251","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2251","url":null,"abstract":"This paper describes on lithostratigraphy as well as evolution of the fluvial styles in late Cenozoic Siwalik Group along the Kankai River section of east Nepal Himalaya. The Siwalik Group lies on the southern flank of the Himalaya, is composed of molasse sediments, which were derived from the rising Himalaya in the north. The group along the Kankai River section is lithologically divided into the Lower, Middle and Upper Siwaliks, in ascending order based on increasing grain size and lithology. The Lower Siwaliks is subdivided into the lower and upper members, whereas the Middle Siwaliks is subdivided into the lower, middle and upper members on the basis of the relative thickness of the sandstone and mudstone beds, frequency of occurrence of these beds, and grain size of sandstone. The Upper Siwaliks is subdivided into the lower and upper members based on the clast size in conglomerate and constituent of the Siwalik sandstone boulders in conglomerate. Based on the lithology, assemblages of sedimentary structure and sediment body architectures, seven facies associations (FA1 to FA7) are recognised. These facies associations are closely related to each lithostratigraphic units of the area. The sediments of the lower and upper members of the Lower Siwaliks are products of the fine-grained meandering and flood flow-dominated meandering systems, respectively. The lower, middle and upper members of the Middle Siwaliks are interpreted as the deposits by sandy meandering, deep sandy braided and shallow braided systems, respectively whereas the lower and upper members of the Upper Siwaliks are the products of gravelly braided to debris flow-dominated braided systems, respectively.","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"257 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133340069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The finite difference program FLAC is used for dynamic modelling of slopes whereby the relationship of the slope geometry, earthquake input signals (mainly frequency of the wave) and the material properties with amplification of vibration on the surface are investigated. At the same time, the influence of varying input frequencies is also investigated. The higher slopes were amplified most by the lower input frequency whereas the reverse was true for the smaller slopes. The overall magnitude of the amplification was maximum with input signals of higher frequency and lower slope heights. The horizontal amplification as much as 17 (horizontal acceleration in the order of 1.7g) was obtained for the normal limestone slope with 20 m height when an input signal of 15 Hz frequency was applied. This experiment revealed that for extremely lower values of shear modulus, there was mostly attenuation instead of amplification and for extremely high values of shear modulus, amplification was negligible as compared to the certain range of intermediate shear modulus. Maximum amplification in the order of 6.5 (horizontal acceleration of 0.66g) was achieved for the shear modulus of 3000 MPa where slope height was of 40 m. doi: 10.3126/bdg.v12i0.2253 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 88-94
{"title":"Dynamic modelling in slopes using finite difference program","authors":"S. Dhakal","doi":"10.3126/BDG.V12I0.2253","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2253","url":null,"abstract":"The finite difference program FLAC is used for dynamic modelling of slopes whereby the relationship of the slope geometry, earthquake input signals (mainly frequency of the wave) and the material properties with amplification of vibration on the surface are investigated. At the same time, the influence of varying input frequencies is also investigated. The higher slopes were amplified most by the lower input frequency whereas the reverse was true for the smaller slopes. The overall magnitude of the amplification was maximum with input signals of higher frequency and lower slope heights. The horizontal amplification as much as 17 (horizontal acceleration in the order of 1.7g) was obtained for the normal limestone slope with 20 m height when an input signal of 15 Hz frequency was applied. This experiment revealed that for extremely lower values of shear modulus, there was mostly attenuation instead of amplification and for extremely high values of shear modulus, amplification was negligible as compared to the certain range of intermediate shear modulus. Maximum amplification in the order of 6.5 (horizontal acceleration of 0.66g) was achieved for the shear modulus of 3000 MPa where slope height was of 40 m. doi: 10.3126/bdg.v12i0.2253 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 88-94","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"29 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134226848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Manandhar, Uttam B. Shrestha, N. Yasufuku, K. Omine, Taizou Kobayashi
The research work was carried out at the proposed bridge site along Syafrubesi-Rasuwagadhi Road, Central Nepal. The study was based on field SPT/DCPT and laboratory tests. N values were determined from SPT/DCPT test. The index and mechanical properties of granular soils were computed in laboratory. Then, ultimate and allowable bearing capacities with safety factor 3 for maximum tolerable limit of 40 mm settlement was estimated by empirical equations provided by Teng (1988) and Terzaghi and Peck (1978). It is recommended that safe bearing capacity for 6 m size open square foundation at left and right abutments are suitable within 4.5 to 6 m depth. doi: 10.3126/bdg.v12i0.2254 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 95-100
{"title":"Safe bearing capacity evaluation of the bridge site along Syafrubesi-Rasuwagadhi road, Central Nepal","authors":"S. Manandhar, Uttam B. Shrestha, N. Yasufuku, K. Omine, Taizou Kobayashi","doi":"10.3126/BDG.V12I0.2254","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2254","url":null,"abstract":"The research work was carried out at the proposed bridge site along Syafrubesi-Rasuwagadhi Road, Central Nepal. The study was based on field SPT/DCPT and laboratory tests. N values were determined from SPT/DCPT test. The index and mechanical properties of granular soils were computed in laboratory. Then, ultimate and allowable bearing capacities with safety factor 3 for maximum tolerable limit of 40 mm settlement was estimated by empirical equations provided by Teng (1988) and Terzaghi and Peck (1978). It is recommended that safe bearing capacity for 6 m size open square foundation at left and right abutments are suitable within 4.5 to 6 m depth. doi: 10.3126/bdg.v12i0.2254 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 95-100","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"120993306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Kathmandu Valley offers the best archive to study the Late Pleistocene climate in Nepal. The Gokarna Formation, constituting the middle part of the sedimentary sequence of the Kathmandu Valley comprises alternating layers of carbonaceous clay, silt, massive to parallel and large scale cross stratified, fine to coarse grained sands and occasional gravel layers, deposited at fluvio-deltaic and lacustrine environment. The organic rich layers of clay, silt, silty-sand and micaceous fine sand consists of abundant plant macro-fossils (fruit, seed and leaves). Plant macrofossils assemblage from the Gokarna Formation (thickness 28.5 m, Dhapasi section) in the northern part of the valley consists of 56 taxa from 35 families. Depending upon the available plant, seven macrofossil assemblages, DS-I to DS-VII in ascending order were established. The common tree and shrubs discovered from this section were Eurya, Ficus, Carpinus, Quercus, Alnus, Rubus, Pyracantha, Zizyphus, Carpinus, Boehmeria etc. Carex, Scirpus triqueter, Scirpus, Polygonum, Euphorbia, Oxalis, Mosla, Viola etc. were the common herbaceous taxa. The constant occurrence of subtropical and warm temperate taxa including Eurya, Ficus, Pyracantha and Zizyphus indicated that subtropical and warm temperate climate continued during the deposition of those macrofossil assemblages. However change in the constituents of those taxa and occurrence of taxa indicating cooler climatic condition like conifers and Betula may indicate minor fluctuation of climate during the deposition of the Gokarna Formation.
{"title":"Late Pleistocene plant macro-fossils from the Gokarna Formation of the Kathmandu Valley, Central Nepal","authors":"S. Bhandari, A. Momohara, K. Paudayal","doi":"10.3126/BDG.V12I0.2252","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2252","url":null,"abstract":"The Kathmandu Valley offers the best archive to study the Late Pleistocene climate in Nepal. The Gokarna Formation, constituting the middle part of the sedimentary sequence of the Kathmandu Valley comprises alternating layers of carbonaceous clay, silt, massive to parallel and large scale cross stratified, fine to coarse grained sands and occasional gravel layers, deposited at fluvio-deltaic and lacustrine environment. The organic rich layers of clay, silt, silty-sand and micaceous fine sand consists of abundant plant macro-fossils (fruit, seed and leaves). Plant macrofossils assemblage from the Gokarna Formation (thickness 28.5 m, Dhapasi section) in the northern part of the valley consists of 56 taxa from 35 families. Depending upon the available plant, seven macrofossil assemblages, DS-I to DS-VII in ascending order were established. The common tree and shrubs discovered from this section were Eurya, Ficus, Carpinus, Quercus, Alnus, Rubus, Pyracantha, Zizyphus, Carpinus, Boehmeria etc. Carex, Scirpus triqueter, Scirpus, Polygonum, Euphorbia, Oxalis, Mosla, Viola etc. were the common herbaceous taxa. The constant occurrence of subtropical and warm temperate taxa including Eurya, Ficus, Pyracantha and Zizyphus indicated that subtropical and warm temperate climate continued during the deposition of those macrofossil assemblages. However change in the constituents of those taxa and occurrence of taxa indicating cooler climatic condition like conifers and Betula may indicate minor fluctuation of climate during the deposition of the Gokarna Formation.","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117127673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pitambar Gautam, T. Sakai, K. Paudayal, S. Bhandari, B. Gyawali, C. Gautam, M. Rijal
A 28-m thick exposure of the younger stage deposits of Kathmandu Valley fluvio-deltaic deposits at Dhapasi has been studied for magnetic susceptibility (MS), remanent magnetization (RM), grain size characteristics of fine-grained sediments, and sedimentary fabric by anisotropy of magnetic susceptibility (AMS) . In situ volume MS (κ; in 10 -3 SI) of the natural sediments ranges from 0.001 to 0.15, with lower range ( 45 to 34 Ka). Laser granulometry of fine-grained sediments from 76 levels reveals polymodal (2-4 modes) nature. With two prominent modes corresponding at 7.3 and 57.5 μm, these sediments plot into sandy silt, silt, and silty sand regions. MS correlates positively among broad grain size classes (i.e., increasing trend from sand through silt to clay). Mainly oblate susceptibility ellipsoids and low anisotropy degree shown by AMS data suggest a depositional fabric contributed by mainly paramagnetic minerals (e.g., phyllosilicates) responsible to low magnitudes of mass-specific MS (5-15 × 10 -8 m 3 kg -1 ). Magnetic lineations or maximum susceptibility axes (k max ) are inferred to be predominantly NNW to SSE below ca. 18-m level, but NNE to SSW above. Such difference points to shift of paleoflow during the sediment deposition, and together with slight differences in grain-size parameters, in two prominent intervals of prodelta deposits, suggests significant changes in the paleodrainage configuration and source-sink relationship. doi: 10.3126/bdg.v12i0.2247 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 17-28
{"title":"Magnetism and granulometry of Pleistocene sediments of Dhapasi section, Kathmandu (Nepal) : implications for depositional age and paleoenvironment","authors":"Pitambar Gautam, T. Sakai, K. Paudayal, S. Bhandari, B. Gyawali, C. Gautam, M. Rijal","doi":"10.3126/BDG.V12I0.2247","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2247","url":null,"abstract":"A 28-m thick exposure of the younger stage deposits of Kathmandu Valley fluvio-deltaic deposits at Dhapasi has been studied for magnetic susceptibility (MS), remanent magnetization (RM), grain size characteristics of fine-grained sediments, and sedimentary fabric by anisotropy of magnetic susceptibility (AMS) . In situ volume MS (κ; in 10 -3 SI) of the natural sediments ranges from 0.001 to 0.15, with lower range ( 45 to 34 Ka). Laser granulometry of fine-grained sediments from 76 levels reveals polymodal (2-4 modes) nature. With two prominent modes corresponding at 7.3 and 57.5 μm, these sediments plot into sandy silt, silt, and silty sand regions. MS correlates positively among broad grain size classes (i.e., increasing trend from sand through silt to clay). Mainly oblate susceptibility ellipsoids and low anisotropy degree shown by AMS data suggest a depositional fabric contributed by mainly paramagnetic minerals (e.g., phyllosilicates) responsible to low magnitudes of mass-specific MS (5-15 × 10 -8 m 3 kg -1 ). Magnetic lineations or maximum susceptibility axes (k max ) are inferred to be predominantly NNW to SSE below ca. 18-m level, but NNE to SSW above. Such difference points to shift of paleoflow during the sediment deposition, and together with slight differences in grain-size parameters, in two prominent intervals of prodelta deposits, suggests significant changes in the paleodrainage configuration and source-sink relationship. doi: 10.3126/bdg.v12i0.2247 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 17-28","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133539800","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Lake marginal sedimentation prevailed around the Paleo-Kathmandu Lake. Owing to the difference in local basin conditions; tectonics, source rock types and river systems therein, the lake marginal environments and sedimentary facies associations differ around the Paleo-Kathmandu Lake. In this study, the basin-fill sediments of southwestern margin of the Kathmandu Basin were studied for the sediments recorded in vertical sequences at various localities and facies analysis was made. Mainly eight facies were recognised. They were matrix-supported massive gravel (Gmm), matrix-supported graded gravel (Gmg), gravelly fine or mud (GF), massive silt (Fsm), massive mud (Fm), ripple-laminated silt or laminated silt/mud/clay (Fl), carbonaceous clay (C), and incipient soil with roots (Fr). Four facies associations that were identified were proximal fan-delta facies association (FA1), mid fan-delta facies associaiton (FA2), distal fan-delta facies association (FA3), and gravelly sinuous river facies association (FA4). Remarkably, these facies associations do not contain any sandy facies and foreset bedding of Gilbert-type. The fan-delta region was characterised by flood-dominated flows and vertical accretion of fines in the flood basins, and vegetated swamps rich in organic sediments. The distribution of facies associations suggests extensive lake transgression followed by rapid lake regression. The recent river system then incised the valley against local upliftment due to faulting or lowering of base level of the main river in the Kathmandu Basin probably related to draining out of the lake water. doi: Bulletin of the Department of Geology , Vol. 12, 2009, pp. 1-16
{"title":"Facies association and depositional environment of fan-delta sequence in southwest Kathmandu Basin, Nepal","authors":"N. Tamrakar, P. Shrestha, S. Maharjan","doi":"10.3126/BDG.V12I0.2246","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2246","url":null,"abstract":"Lake marginal sedimentation prevailed around the Paleo-Kathmandu Lake. Owing to the difference in local basin conditions; tectonics, source rock types and river systems therein, the lake marginal environments and sedimentary facies associations differ around the Paleo-Kathmandu Lake. In this study, the basin-fill sediments of southwestern margin of the Kathmandu Basin were studied for the sediments recorded in vertical sequences at various localities and facies analysis was made. Mainly eight facies were recognised. They were matrix-supported massive gravel (Gmm), matrix-supported graded gravel (Gmg), gravelly fine or mud (GF), massive silt (Fsm), massive mud (Fm), ripple-laminated silt or laminated silt/mud/clay (Fl), carbonaceous clay (C), and incipient soil with roots (Fr). Four facies associations that were identified were proximal fan-delta facies association (FA1), mid fan-delta facies associaiton (FA2), distal fan-delta facies association (FA3), and gravelly sinuous river facies association (FA4). Remarkably, these facies associations do not contain any sandy facies and foreset bedding of Gilbert-type. The fan-delta region was characterised by flood-dominated flows and vertical accretion of fines in the flood basins, and vegetated swamps rich in organic sediments. The distribution of facies associations suggests extensive lake transgression followed by rapid lake regression. The recent river system then incised the valley against local upliftment due to faulting or lowering of base level of the main river in the Kathmandu Basin probably related to draining out of the lake water. doi: Bulletin of the Department of Geology , Vol. 12, 2009, pp. 1-16","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"104 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132197551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aggregates are important constituents of pavement structures. Performance of aggregate layers depends on particle shape, grading and composition and their physical, mechanical and chemical properties. Careful study of these properties allows evaluation of aggregates according to the international norms. There are huge rock outcrops surrounding the Kathmandu Valley. With growing construction in and around the Kathmandu Valley, demand of aggregates has become so high that limited quarry sites within the valley are not sufficient to meet the requirements. Therefore, search of rock outcrops from which suitable aggregates may be quarried is sought to meet the current and future demands of aggregates suitable not only for the building and infrastructures but also for the roads or transport networks in the country. This study aims in exploring and evaluating suitability of natural crushedrock aggregates in western Kathmandu, Nepal for unbound pavement structures. Mainly three kinds of rocks were identified from the outcrops of the study area; siliceous limestone, crystalline limestone and calcareous siltstone. Shape factor (F) ranges from 0.99 to 1.40 in most of the samples indicating their cubic to disc shape. Aggregates have high roughness indices and moderate roundness indices. Flakiness indices of the test samples vary from 14% to 25% and elongation indices from 75.49 to 90.79% indicating that the crushed samples yield very little flat and elongated particles, and huge equant particles, which is very desirable for aggregates. Dry density of samples ranges from 2495 to 2658 kg/m 3 . WAV varies from 0.20 to 0.67%. ACV ranges from 22-26% and aggregates are strong enough to resist against compressive load. LAA varies from 27 to 30 % and AIV ranges from 10 to 14% showing that the aggregates have good hardness. The average CBR value is 61.12%. SSV ranges from 4.37 to 11.64%. All these indices meet the BS standard, American standard and Nepal standard, and are acceptable for road base and sub base courses of unbound pavement in roads. doi: 10.3126/bdg.v12i0.2248 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 29-42
{"title":"Evaluation of quality of crushed-limestone and -siltstone for road aggregates","authors":"Shrawan Khanal, N. Tamrakar","doi":"10.3126/BDG.V12I0.2248","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2248","url":null,"abstract":"Aggregates are important constituents of pavement structures. Performance of aggregate layers depends on particle shape, grading and composition and their physical, mechanical and chemical properties. Careful study of these properties allows evaluation of aggregates according to the international norms. There are huge rock outcrops surrounding the Kathmandu Valley. With growing construction in and around the Kathmandu Valley, demand of aggregates has become so high that limited quarry sites within the valley are not sufficient to meet the requirements. Therefore, search of rock outcrops from which suitable aggregates may be quarried is sought to meet the current and future demands of aggregates suitable not only for the building and infrastructures but also for the roads or transport networks in the country. This study aims in exploring and evaluating suitability of natural crushedrock aggregates in western Kathmandu, Nepal for unbound pavement structures. Mainly three kinds of rocks were identified from the outcrops of the study area; siliceous limestone, crystalline limestone and calcareous siltstone. Shape factor (F) ranges from 0.99 to 1.40 in most of the samples indicating their cubic to disc shape. Aggregates have high roughness indices and moderate roundness indices. Flakiness indices of the test samples vary from 14% to 25% and elongation indices from 75.49 to 90.79% indicating that the crushed samples yield very little flat and elongated particles, and huge equant particles, which is very desirable for aggregates. Dry density of samples ranges from 2495 to 2658 kg/m 3 . WAV varies from 0.20 to 0.67%. ACV ranges from 22-26% and aggregates are strong enough to resist against compressive load. LAA varies from 27 to 30 % and AIV ranges from 10 to 14% showing that the aggregates have good hardness. The average CBR value is 61.12%. SSV ranges from 4.37 to 11.64%. All these indices meet the BS standard, American standard and Nepal standard, and are acceptable for road base and sub base courses of unbound pavement in roads. doi: 10.3126/bdg.v12i0.2248 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 29-42","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"78 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124811646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Chitwan Valley is one of the largest Dun Valleys in the Himalayan foothills of Nepal. Dun gravels perhaps deposited in the late Pleistocene to very early Holocene about 22,000-7000 yr. B.P. Chitwan Dun Valley is underlain by Dun fan gravels or Dun gravels which form unconfined to semiconfined or leaky confined aquifers. The study area, situated in the NW part of the valley occupies an area of 70.8 km 2 .The hydrogeological situation in the study area is inferred from drilling data of Ground Water Resources Development Board (GWRDB), Agriculture Development Project Janakpur (ADPJ) and several private drilling companies .The Chitwan Dun Valley constitutes a closed groundwater system in the Siwalik Zone of Nepal Himalaya. The study area reveals the existence of two definite groundwater sub-basin each having its own hydraulic system and is a part of single large regional groundwater basin. Annual potential evapotranspiration (PET) calculated at Rampur (station no 0902) for five-year period (1990-1995) is 1.68 mm/day. Annual precipitation data recorded at Rampur is 2214 mm. Area of recharge is 70.8 km 2 and estimation of total groundwater storage(reserve) is 87.31 MCM per year, and dynamic reserve or annual potential recharge is estimated as 48.60 MCM per year. doi: 10.3126/bdg.v12i0.2249 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 43-54
{"title":"Hydrogeologic assessment and groundwater reserve evaluation in northwestern parts of Dun valley aquifers of Chitwan, inner Terai","authors":"Rajendra Neupane, S. Shrestha","doi":"10.3126/BDG.V12I0.2249","DOIUrl":"https://doi.org/10.3126/BDG.V12I0.2249","url":null,"abstract":"The Chitwan Valley is one of the largest Dun Valleys in the Himalayan foothills of Nepal. Dun gravels perhaps deposited in the late Pleistocene to very early Holocene about 22,000-7000 yr. B.P. Chitwan Dun Valley is underlain by Dun fan gravels or Dun gravels which form unconfined to semiconfined or leaky confined aquifers. The study area, situated in the NW part of the valley occupies an area of 70.8 km 2 .The hydrogeological situation in the study area is inferred from drilling data of Ground Water Resources Development Board (GWRDB), Agriculture Development Project Janakpur (ADPJ) and several private drilling companies .The Chitwan Dun Valley constitutes a closed groundwater system in the Siwalik Zone of Nepal Himalaya. The study area reveals the existence of two definite groundwater sub-basin each having its own hydraulic system and is a part of single large regional groundwater basin. Annual potential evapotranspiration (PET) calculated at Rampur (station no 0902) for five-year period (1990-1995) is 1.68 mm/day. Annual precipitation data recorded at Rampur is 2214 mm. Area of recharge is 70.8 km 2 and estimation of total groundwater storage(reserve) is 87.31 MCM per year, and dynamic reserve or annual potential recharge is estimated as 48.60 MCM per year. doi: 10.3126/bdg.v12i0.2249 Bulletin of the Department of Geology, Vol. 12, 2009, pp. 43-54","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128071678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Metabasites of the Lesser Himalaya along the Modi Khola valley in central Nepal are the supracrustal dikes and sills of basic igneous rocks emplaced in the clastic sediments and later metamorphosed together with the host rocks. They contain almost a constant metamorphic mineral assemblage of Ca-amphiboles+plagioclase+biotite+quartz±epidote±chlorite+(Fe-Ti oxides). Amphiboles occur in the form of porphyroblast and recrystallized matrix. The porphyroblasts are zoned with actinolitic cores and hornblende rims. The recrystallized matrix ranges in composition from actinolite in chlorite zone to hornblende in biotite and garnet zones. The cores of porphyroblasts are pre-kinematic and were probably formed prior to the Tertiary Himalayan orogeny. The rims of porphyroblasts and matrix amphiboles are syn-kynematic and were formed during the Upper Main Central Thrust activity in the Tertiary. The systematic changes in amphibole compositions as well as textural characteristics of metabasites are in good agreement with the classical concept of increasing metamorphic grade and intensity of deformation structurally upwards towards the Upper Main Central Thrust in the Lesser Himalaya.
{"title":"Petrographic records of two metamorphic events in the Lesser Himalayan metabasites, Modi Khola section, central Nepal","authors":"L. Paudel","doi":"10.3126/BDG.V11I0.1428","DOIUrl":"https://doi.org/10.3126/BDG.V11I0.1428","url":null,"abstract":"Metabasites of the Lesser Himalaya along the Modi Khola valley in central Nepal are the supracrustal dikes and sills of basic igneous rocks emplaced in the clastic sediments and later metamorphosed together with the host rocks. They contain almost a constant metamorphic mineral assemblage of Ca-amphiboles+plagioclase+biotite+quartz±epidote±chlorite+(Fe-Ti oxides). Amphiboles occur in the form of porphyroblast and recrystallized matrix. The porphyroblasts are zoned with actinolitic cores and hornblende rims. The recrystallized matrix ranges in composition from actinolite in chlorite zone to hornblende in biotite and garnet zones. The cores of porphyroblasts are pre-kinematic and were probably formed prior to the Tertiary Himalayan orogeny. The rims of porphyroblasts and matrix amphiboles are syn-kynematic and were formed during the Upper Main Central Thrust activity in the Tertiary. The systematic changes in amphibole compositions as well as textural characteristics of metabasites are in good agreement with the classical concept of increasing metamorphic grade and intensity of deformation structurally upwards towards the Upper Main Central Thrust in the Lesser Himalaya.","PeriodicalId":356325,"journal":{"name":"Bulletin of The Department of Geology","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131019180","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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