scholarly journals Petrography of the Siwalik sandstones, Amlekhganj-Suparitar area, central Nepal Himalaya

2003 ◽  
Vol 28 ◽  
Author(s):  
Naresh Kazi Tamrakar ◽  
Shuichiro Yokota ◽  
Suresh Das Shrestha
Keyword(s):  
Middle Miocene ◽  
Foreland Basin ◽  
Early Pleistocene ◽  
Nepal Himalaya ◽  
Central Nepal ◽  
Present Study Area ◽  
Mean Grain Size ◽  
Siwalik Group ◽  
Variation Trends ◽  
The Himalaya

Middle Miocene to early Pleistocene sedimentary sequence deposited in the foreland basin of the Himalaya is represented by the Siwalik Group. In the present study area the Siwalik Group extends in a NW-SE direction and well-exposed. Forty­four sandstone samples were studied for texture, fabric and composition in order to assess their petrographic properties and variation trends of these properties in stratigraphic levels. Sandstones were classified into sublitharenite, subarkose, lithic arenite, arkosic arenite and feldspathic graywacke and further thirteen sub-clans. Mean grain size (M) and Trask sorting coefficient (So) increase up-section. Recalculated quartz, matrix, modified maturity index (MMI), total cement (Ct), cement versus matrix index (CMI) and ratio of strong cement over total cement ((Cfc/Cs)/Ct) also increase, whilst packing proximity (PP), packing density (PD) and consolidation factor (Pcc) decrease up-section showing distinct trends, and therefore, these properties are promising in recognizing the older sandstones from the younger ones.

scholarly journals Palaeohydrology of the Siwalik Group along the Bakiya Khola section, central Nepal Himalaya

2002 ◽  
Vol 26 ◽  
Author(s):  
Prakash Das Ulak
Keyword(s):  
Grain Size ◽  
Middle Miocene ◽  
Foreland Basin ◽  
Early Pleistocene ◽  
Fluvial Sediments ◽  
Nepal Himalaya ◽  
Sedimentary Structures ◽  
Central Nepal ◽  
Depositional System ◽  
Siwalik Group

Middle Miocene to Early Pleistocene fluvial sediments of the Siwalik Group comprises many fining-upward cycles from several to tens of metres thick. It is a foreland basin sediment with a coarsening-upward succession as a whole. The palaeohydrology and evolution of the fluvial depositional system of the group in the Bakiya Khola section of central Nepal was established using the grain size analyses, sedimentary structures and thickness of fining-upward cycles. Stratigraphically from older to younger sequence, the velocity and channel gradient of the palaeofluvial system varies from 0.28 m/s to 3.3 m/s and 2.9x10-5 to 3.4x10-4 m/m, respectively. The progressive changes in palaeovelocity and palaeochannel gradient reflect the southward propagation of thrust activities in the Himalayan front.

scholarly journals Lithofacies and depositional environment of the Siwalik Group in Samari-Sukaura River area, Central Nepal

2013 ◽  
Vol 16 ◽  
pp. 53-64 ◽  
Author(s):  
Dev Kumar Syangbo ◽  
Naresh Kazi Tamrakar
Keyword(s):  
Depositional Environment ◽  
Foreland Basin ◽  
River System ◽  
Nepal Himalaya ◽  
Meandering River ◽  
Fine Grained ◽  
Architectural Elements ◽  
Central Nepal ◽  
Eastern Zone ◽  
Siwalik Group

Thick sedimentary sequence deposited in the foreland basin of the Nepal Himalaya is represented by the Siwalik Group. The Siwalik Group is well exposed in the Samari-Sukaura River area. The present study is focused in southern portion of the MBT around the Samari-Sukaura area for its depositional environment. The Middle Siwaliks of the Sukaura Road sections is overlained by the Lower Siwaliks which is separated by the Karki Khola Thrust. Extension of the Lower Siwaliks in the Jyamire Khola and the Bundal Khola becomes wider in the eastern Zone. Repetition of the Lower Siwaliks along the southern margin of the MBT is recognized. Depending on lithofacies assemblage and facies analysis, the two broad facies assemblages FA1 and FA2 have been distinguished. FA1 shows SB, FF, LA, LS and CH architectural elements and is interpreted as a product of the fine-grained meandering river system. FA2 shows SB, FF, LA, DA and CH architectural elements and is interpreted as a product of sandy mixed-load meandering river system. DOI: http://dx.doi.org/10.3126/bdg.v16i0.8884   Bulletin of the Department of Geology Vol. 16, 2013, pp. 53-64

scholarly journals Paleohydrological reconstruction of the Siwalik Group along the Tinau Khola section, west-central Nepal Himalaya

2009 ◽  
Vol 39 ◽  
Author(s):  
Prakash Das Ulak
Keyword(s):  
Slope Gradient ◽  
Nepal Himalaya ◽  
Sedimentary Sequences ◽  
Central Nepal ◽  
Frontal Part ◽  
West Central ◽  
Channel Slope ◽  
Siwalik Group ◽  
The Himalaya ◽  
Velocity Channel

Neogene fluvial sedimentary sequences of the Siwalik Group are extensively accumulated in the southern frontal part of the Himalaya and well exposed in the Tinau Khola section of the west-central Nepal Himalaya. The group reveals a coarsening­ upwards succession in general but many fining-upwards fluvial successions on a scale from several to tens of metres is established in each lithological unit. The paleohydrological characteristics have been estimated using thickness of fining upwards fluvial successions, their grain diameters, and bedforms. The paleohydrology suggests an increase in flow velocity, channel slope gradient, and discharge of the fluvial system. Paleovelocity varies from 0.17 to 5.31 m/s, paleochannel gradient and paleodischarge change from l.13x10-5 to 7.33x10-4 m/m and 101 to 104 m3/s, respectively towards the stratigraphic top. These progressively changing paleohydrological characteristics reflect the southward propagation of thrusts caused by the upheaval of the Himalaya.

scholarly journals Thin-Skinned Tectonics of the Tansen-Pokhara Section, Central Nepal Himalaya

2015 ◽  
Vol 26 ◽  
pp. 15-28 ◽  
Author(s):  
Lalu Prasad Paudel
Keyword(s):  
Middle Miocene ◽  
Field Survey ◽  
Early Pleistocene ◽  
Tectonic Unit ◽  
Lesser Himalaya ◽  
Duplex Structure ◽  
Main Central Thrust ◽  
Nepal Himalaya ◽  
Central Nepal ◽  
Main Boundary Thrust

Geological field survey and structural analysis were carried out in the Tansen-Pokhara section of central Nepal in an attempt to unravel the thin-skinned tectonic geometry of the Lesser Himalaya. The Lesser Himalaya in the area forms a foreland-propagating duplex structure, each tectonic unit being a horse bounded by imbricate faults. The Upper Main Central Thrust and the Main Boundary Thrust are the roof and floor thrusts, respectively. The Bari Gad-Kali Gandaki Fault is an out-of-sequence fault. The Pindi Khola Fault is an antithetic back-thrust developed on the hangingwall of the Bari Gad-Kali Gandaki Fault, and the Kusma Fault is a splay-off of the Phalebas Thrust. Deformation of the Lesser Himalaya occurred in distinct three phases namely pre-Himalayan, Eohimalayan and Neohimalayan. The duplex structure was formed in the Neohimlayan stage in the period between Middle Miocene and Early Pleistocene. J. Nat. Hist. Mus. Vol. 26, 2012: 15-28

scholarly journals Neogene Vertebrate Paleontology and Stratigraphy of Nepal

1981 ◽  
Vol 1 (1) ◽  
Author(s):  
Robert M. West ◽  
Jens Munthe
Keyword(s):  
Radiometric Dating ◽  
Early Pleistocene ◽  
Vertebrate Paleontology ◽  
Kathmandu Valley ◽  
Late Pliocene ◽  
The Past ◽  
Group A ◽  
Physical Stratigraphy ◽  
Siwalik Group ◽  
The Himalaya

ABSTRACT For the past 150 years, the Siwalik Group, a Miocene through Pleistocene molasse along the flank of the Himalaya has been studied intensively stratigraphically and paleontologically in both India and Pakistan. This work recently has been extended into Nepal, where a presumably complete Siwalik section is present, and a modest number of vertebrate fossils have been found. All but one of Nepalese Siwalik vertebrates hare been collected along the southern edge of the Dang Valley in western Nepal. Two assemblages are now known. The older is of presumed Miocene age and likely equivalent to the fauna of the Chinji Formation in Pakistan. The other is of late Pliocene to early Pleistocene age and similar to the Indian Pinjor fauna. In addition, Plio-Pleistocene vertebrates have been reported from fluvial intermontane deposits in the Kathmandu Valley. As studies of radiometric dating, magnetostratigraphy, physical stratigraphy and fossil distributions are extended into Nepal, the place of the Nepalese Siwaliks and basin deposits will become increasingly clear.

scholarly journals Evolution of fluvial system and reconstruction of paleohydrology of late Cenozoic Siwalik Group, related to tectonic uplift of Himalaya and climatic change, Kankai River section, east Nepal Himalaya

2016 ◽  
Vol 51 ◽  
pp. 59-72
Author(s):  
Prakash Das Ulak
Keyword(s):  
River Section ◽  
Fluvial System ◽  
Late Cenozoic ◽  
Nepal Himalaya ◽  
Fine Grained ◽  
Lithostratigraphic Units ◽  
Facies Associations ◽  
Channel Slope ◽  
Siwalik Group ◽  
The Himalaya

This paper focuses on evolution of the fluvial system in the late Cenozoic Siwalik Group along the Kankai River section of East Nepal. The Siwalik Group lies on the southern flank of the Himalaya and composed of molasse sediments, which were derived from upheaval of the Himalaya. On the basis of lithology, assemblage of sedimentary structures and sediment body architectures, seven facies associations (FA1 to FA7) are recognized in the Kankai River section, East Nepal Himalaya. These recognized facies associations are closely related to each lithostratigraphic units of the area (Ulak 2009). The lower and upper members of the Lower Siwaliks are the 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 of the sandy meandering, deep sandy braided and shallow braided systems, respectively whereas the lower and upper members of the Upper Siwaliks are the products of the gravelly braided and debris flow-dominated braided systems, respectively. Paleohydrological characteristics and its evolutional changes of the group have been estimated by using grain diameter and thickness of fining upward fluvial successions. The paleohydrology suggests an increase in of flow velocity, channel slope gradient, and discharge of the fluvial system. Paleovelocity varies from 0.19 m/s to 5.31 m/s paleochannel gradient and paleodischarge changes from 6.67x10-5 to 2.97x10-4 m/m and 101 to 104 m3/s, respectively in stratigraphic upward. The progressively changes in the paleohydrology reflect the southward propagation of thrust activities, caused upheaval of the Himalaya.

scholarly journals Physical and geomechanical properties of the Siwalik sandstones, Amlekhganj-Suparitar area, central Nepal Himalaya

2002 ◽  
Vol 26 ◽  
Author(s):  
Naresh Kazi Tamrakar ◽  
Shuichiro Yokota ◽  
Suresh Das Shrestha
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Point Load ◽  
Early Pleistocene ◽  
Dry Density ◽  
Modulus Ratio ◽  
Deep Basin ◽  
Geomechanical Properties ◽  
Central Nepal ◽  
Siwalik Group

The Siwalik Group, one of the world's largest fluvial deposits, distributed in the fore deep basin of the rising Himalayas, crops out well in Central Nepal. The group comprises of mudstones, sandstones and conglomerates ranging in age from middle-Miocene to early Pleistocene. Sandstones form the major lithology in the Siwalik Group and distributed pervasively. Forty-four samples of sandstones were tested for physical and geomechanical properties in order to create a database on Siwalik sandstones and to know the variability of these properties with respect to their stratigraphic levels.  Dry density and saturated density of sandstones are 2.10-2.63 g/cm3 and 2.22-2.66 g/cm3, respectively. Porosity is found to vary between 1.93 and 15.2%.They bear weak to strong uniaxial compressive strength (1.29-51.6 MPa), very low to high point­ load strength (0.05-4.53 MPa, measured across bedding), high deformability (secant modulus =0.03-0.98 GPa and tangent modulus = 0.06-1.09)and low modulus ratio (17.8-86.6). The Schmidt hammer hardness in sandstones ranges from 12 to 52. Variation of these properties is independent of stratigraphic level. Dry density and porosity correlate well with uniaxial compressive strength, point-load strength and modulus ratio, and bear highly significant relationships. Hence, dry density and porosity can be used for predicting strength measures for the Siwalik sandstones.

scholarly journals Palaeolclimatic significance of palynological assemblages from the Siwalik sediments in the Dudhaura Khola section, central Nepal

2013 ◽  
Vol 46 ◽  
Author(s):  
Khum N. Paudayal
Keyword(s):  
Temperate Forest ◽  
Vegetation Pattern ◽  
Bottom Part ◽  
Nepal Himalaya ◽  
The Past ◽  
Central Nepal ◽  
Palynological Assemblages ◽  
Palynological Study ◽  
Siwalik Group ◽  
Vegetation And Climate

The palynological study of the Rapti Formation and Amlekhganj Formation from the Siwalik Group in the Dudhaura Khola section revealed plethora of information to interpret the past vegetation and climate existed during Late Miocene in the southern margin of the Nepal Himalaya. Altogether 30 samples were collected from Rapti Formation and Amlekhganj Formations exposed in the Dudhaura Khola section for the palynological study. Palynological assemblages recovered from the upper part of Rapti Formation and lower part of Amlekhganj Formation consist of 5 families and 10 genera from monocotyledon, 8 families and 14 genera from dicotyledon, 1 family and 4 genera from Gymnosperm and 5 families from Pteridophytes. High presence of Palm pollen and Ceratopteris spores in the Rapti Formation and Amlekhganj Formation suggests that the climate was warm and humid. The riverine vegetation is documented by the presence of Alnus, Typha, Potamogeton, Liliaceae and Poaceae.The frequency of zygnemataceous spores is common in the Rapti Formation while it is decreases towards the bottom part of the Amlekhganj Formation. There is little gymnosperm pollen in the Amlekhganj Formation but their frequency and distribution is very less. This suggests change of vegetation pattern from tropical-subtropical forest to lower temperate forest during the deposition of Amlekhganj Formation and after wards.

scholarly journals Sedimentary facies analysis of the fluvial environment in the Siwalik Group of eastern Nepal: deciphering its relation to contemporary Himalayan tectonics, climate and sea-level change

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Lalit Kumar Rai ◽  
Kohki Yoshida
Keyword(s):  
Sea Level ◽  
Foreland Basin ◽  
Sea Level Change ◽  
Sedimentary Facies ◽  
Nepal Himalaya ◽  
Meandering River ◽  
Level Change ◽  
Siwalik Group ◽  
Himalayan Tectonics ◽  
And Sea Level

AbstractThe Siwalik Group, ranging from the Early Miocene to Pleistocene, is believed to be deposited in the fluvial environment and controlled by contemporary Himalayan tectonics and climate. In this study, we established the fluvial environment and its controlling factors responsible for the deposition of the Siwalik succession along the Muksar Khola section in the eastern Nepal Himalaya. Five sedimentary facies associations are identified; these are interpreted as the deposits of flood plain-dominated fine-grained meandering river (FA1), flood-dominated overbank environment (FA2), sandy meandering river (FA3), anastomosing river (FA4), and debris flow-dominated gravelly braided river (FA5). These changes in the fluvial system occurred around 10.5 Ma, 10.0 Ma, 5.9 Ma and 3.5 Ma, defined by existing magnetostratigraphy constraints, due to the effects of hinterland tectonics, climate and sea-level change and continuous drifting of the foreland basin towards the hinterland concerning depositional age. The thick succession of an intraformational conglomerate reveals intensification of the monsoon started around 10.5 Ma in the eastern Nepal Himalaya. The present study also shows asynchronous exhumation of the Himalaya from east to west brought a significant difference in the fluvial environment of the Neogene foreland basin.

scholarly journals Lithostratigraphy of the Siwalik Group, Khutia Khola section, Far Western Nepal Himalaya

2015 ◽  
Vol 49 (1) ◽  
pp. 29-39
Author(s):  
Swostik Kumar Adhikari ◽  
Tetsuya Sakai
Keyword(s):  
Grain Size ◽  
River System ◽  
Coarse Grained ◽  
Nepal Himalaya ◽  
Gravel Size ◽  
Major River ◽  
Middle Siwalik ◽  
Siwalik Group ◽  
Salt And Pepper ◽  
The Himalaya

The Neogene fluival sediments (Siwalik Group) forming the southernmost hills in the Himalaya is well exposed along the Khutia Khola in the Far Western Nepal. The newly established lithostratigraphy is subdivided into the Jagati Formation (2110 m, equivalent to the Lower Siwalik) and the Kala Formation (2050 m, equivalent to the Middle Siwalik) in ascending order. Each formation is further divided into three members; the lower, middle and upper, based on the ratio of mudstone vs. sandstone beds as well as color and grain size of sandstone. The Jagati Formation is characterized by reddish-brown mudstones interbedded with very fine- to coarse-grained sandstones. Paleosols characterized with burrows, rhizoliths, desiccation cracks, concretions and nodules are present in higher proportion than thinly laminated or massive mudstone beds. The Kala Formation comprises thin- to thick-bedded, very fine- to very coarse-grained sandstones and pebbly sandstones interbedded with reddishbrown, greenish-grey to dark-grey mudstones. Sandstone beds exhibit "salt and pepper" appearance. In the lower part of the upper member sub-rounded to rounded pebbles are scattered along with trough and planar cross-laminations in sandstone beds, whereas the gravel size tends to be larger and few cobble size gravels also appear in the upper part. Thinly laminated or massive mudstones are common and paleosols are less frequent. The age of the boundary between the Jagati and Kala Formations (Lower-Middle Siwaliks) is around 11.05 Ma. The boundaries age between the middle and upper members of the Jagati Formation is around 12.7 Ma and between the lower and middle members of the Kala Formation is around 9.0 Ma. The dominance of finer sediments and thinner sandstone units than that of neighboring Siwalik successions indicate the fluvial fancies of the Khutia Khola section is deposited by a small river system and may represent the inter fluve setting of major river systems.

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