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 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 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 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 Study of regional geological structures in Ridi-Shantipur area of Gulmi district, Lesser Himalaya, west-central Nepal

2019 ◽  
Vol 58 ◽  
pp. 111-118
Author(s):  
Shrawan Shakya ◽  
Kabi Raj Paudyal
Keyword(s):  
Regional Scale ◽  
Lesser Himalaya ◽  
The North ◽  
Central Nepal ◽  
West Central ◽  
Continuous Shear ◽  
Deformation Event ◽  
Middle Member ◽  
Geological Units ◽  
The Himalaya

The study was carried out in the Lesser Himalaya between Ridi-Shantipur area of the Gulmi District, west-central Nepal. Two geological units: the Nourpul Formation and the Dhading Dolomite were mapped in the area. These units belong to the Nawakot Group as explained by several researchers in central Nepal. The Nourpul Formation can further be divided into three members based on distinct mappable lithology, which are named as the Lower Member, the Middle Member and the Upper Member, respectively. The area is highly folded with several local and regional anticlines and synclines; Ridi Khola Anticline, Ridi-Karikot Syncline, Ruru Anticline, Baletaksar-Gwadi Syncline, Huga-Bamgha Anticline, Rimuwa-Rudrabeni Syncline, Juhan-Eksing Anticline, Juniya-Limgha Syncline, Bharse-Thaple Anticline, and Chiureko Syncline, respectively from the south to the north. All the folds are trending along to the ESE-WNW direction. The origin of these folds can be linked with the thrust propagation in the Himalaya that can be explained with the deformation event D4. The Harewa Khola Thrust is the only one regional scale thrust mapped in the area. The thrust carries the older Nourpul Formation over the Dhading Dolomite with the indications of thrust related features like slickensides and fault-breccias. The thrust seems to propagate to the north. There is a continuous shear zone mapped in the outcrops from the Tal Khola-Aslewa-Eksingh-Gudrung-Juhang- Rupakot region as an indicator of the presence of the Badi Gad Fault in the region.

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 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 Neogene fluvial systems in the Siwalik Group along the Tinau Khola section, west central Nepal Himalaya

2001 ◽  
Vol 25 ◽  
Author(s):  
Prakash Das Ulak ◽  
Katsuhiro Nakayama
Keyword(s):  
System Development ◽  
Major Change ◽  
Fluvial System ◽  
Facies Association ◽  
The North ◽  
Central Nepal ◽  
Main Boundary Thrust ◽  
West Central ◽  
Facies Associations ◽  
Siwalik Group

Along the Tinau Khola section of west central Nepal, the Siwalik Group is a 4 km thick pile of fluvial sedimentary sequence of mudstone, sandstone and conglomerate. It is exposed between the Main Boundary Thrust (MBT) to the north and the Frontal Churia Thrust (FCT), also known as the Main Frontal Thrust (MFT), in the south. The Siwalik Group is lithologically divided into the Arung Khola, Binai Khola and Chitwan formations, in ascending order. Six facies associations (FA1 to FA6) are recognised within the group based on grain size distribution, nature of bedforms, and sandstone-mudstone ratio. The fine-grained sediments of the Lower and Middle members of the Arung Khola Formation belong to the FA1-facies association and were interpreted to have deposited by a low-discharge, low -relief meandering fluvial system. The multiple accumulated thin-layered muddy sandstone sequence in the Upper Member of the Arung Khola and the Lower Member of the Binai Khola formations belong to FA2 and FA3- facies associations and were deposited by a flood flow-dominated meandering fluvial system. The deep sandy braided facies association (FA4) and shallow sandy braided facies association (FA5) are well developed in the Middle and Upper members of the Binai Khola Formation, respectively. The gravelly braided facies association (FA6) is recognised in the Chitwan Formation. The palaeomagnetically well-studied section of the Tinau Khola allows precise dating of the major change of fluvial system during the deposition of the Siwalk Group. The environment of predominantly shallow meandering rivers with low­ relief and low-discharge during the time of deposition of the Arung Khola Formation changed at 9.9 Ma and flooding in the rivers dramatically increased due to the intensification of monsoon precipitation. This hydrographic change also brought the change in facies from the earlier FA1 facies to FA2 and FA3 facies. Change from meandering to braided system occurred at 8.2 Ma because of the obvious regional tectonic upliftment of the Higher Himalaya bringing into FA4 and FA5-facies associations. Finally the FA6-facies association was developed due to the large gravelly braided system development at 2.5 Ma as a result of the Main Boundary Thrust movement along the frontal part of the Himalaya.

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.

scholarly journals Petrography of the Neogene Siwalik Group sandstones, Khutia Khola section, Nepal Himalaya: implications for provenance, paleoclimate and tectonic setting

2017 ◽  
Vol 53 ◽  
pp. 17-30
Author(s):  
Swostik Kumar Adhikari ◽  
Tetsuya Sakai
Keyword(s):  
Tectonic Setting ◽  
Source Rocks ◽  
Humid Climate ◽  
Climate History ◽  
Petrographic Composition ◽  
Nepal Himalaya ◽  
Fluvial Sediment ◽  
Siwalik Group ◽  
The Himalaya

The Neogene fluvial sediment (Siwalik Group) forming the southernmost foothill in the Himalaya is one of the best archives of climate history and uplift of the Himalaya. The petrographic composition of these fluvial sandstones provides information on source rocks, depositional climate of the Siwalik sediments and tectonic setting of the Himalaya. This study presents the petrographical results of the Siwalik sandstones from the Khutia Khola section, Nepal Himalaya. Petrographically, these sandstones are lithic arenites (30%) to sub-litharenites (70%). Provenance analyses show that sediments were mainly derived from recycled orogenic and transitional recycled areas in the recycled orogen block provenances. The climatic indexes suggest the semi-humid to humid climate during sedimentation of the Khutia Khola sandstones. The stratigraphic trend of the lithic components show that metamorphic lithic grains are increasing and sedimentary lithic grains are decreasing in up section, and the Lesser and Higher Himalayas are the mixed source of these Siwalik sandstones.

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