Changes in mineral composition and depositional environments recorded in the present and past basin-fill sediments of the Kathmandu Valley, central Nepal

Paudel, Mukunda Raj; Kuwahara, Yoshihiro; Sakai, Harutaka

doi:10.3126/hjs.v2i4.912

Cited by 8 publications

(8 citation statements)

References 2 publications

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“…The basement is formed by Precambrian to Devonian rock and then overlain by Quaternary fluviolacustrine deposit with the thickness of 550-600 m in the central part of the valley (Kharel et al 1998). The composition of mineral is dominated by quartz, K-feldspar, plagioclase, and mica with minor chlorite and calcite in the basin (Paudel et al 2004).…”

Section: Study Areamentioning

confidence: 99%

Assessment of Deep Groundwater Quality in Kathmandu Valley Using Multivariate Statistical Techniques

Chapagain

Pandey

Shrestha

et al. 2009

Water Air Soil Pollut

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This study was carried out to assess the overall water quality and identify major variables affecting the deep groundwater quality in Kathmandu Valley, Nepal. Forty-two deep wells were sampled during premonsoon and monsoon seasons in 2007 and analyzed for the major physicochemical variables. The water quality variables such as NH 4 + -N, Fe, Pb, As, and Cd at most of the sampling locations exceeded the World Health Organization guideline levels for drinking water. Multivariate statistical techniques such as factor analysis and cluster analysis were applied to identify the major factors (variables) corresponding to the different source of variation in deep groundwater quality. Factor analysis indentified six major factors explaining 74.77% of the total variance in water quality; and the major variations are related with the degree of groundwater mineralization, decomposition of organic matter, and reduction of groundwater environment. The water quality of deep groundwater is influenced by the natural hydrogeochemical environment. The wells are broadly divided into two major groups based on the similar groundwater characteristics using cluster analysis. Results show that water quality of deep groundwater does not vary significantly as a function of season.

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Section: Study Areamentioning

confidence: 99%

Assessment of Deep Groundwater Quality in Kathmandu Valley Using Multivariate Statistical Techniques

Chapagain

Pandey

Shrestha

et al. 2009

Water Air Soil Pollut

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“…5d). Besides the clay minerals, the sediments are composed of detrital and precipitated minerals (quartz, feldspars, micas, calcite) (Paudel et al, 2004), amorphous silica (diatom shell) (Hayashi, 2007;Hayashi et al, 2009), and organic materials (Mampuku et al, 2008).…”

Section: Resultsmentioning

confidence: 99%

“…In the clay-poor zones corresponding to weakened chemical weathering and erosion conditions (or dry climate), unique laminite beds with alternating very thin white calcite-rich and black carbonaceous clayey layers (20-30 pairs/cm), which are not contradictory to the low sedimentation rates in the clay-poor zones, are recognized (Sakai, 2001;Paudel et al, 2004;Kuwahara, 2006). Paudel et al (2004) and Kuwahara (2006) have reported that the calcite particles in the laminite beds are very fine (~50 µm), euhedral, and authigenic (precipitated in lake water).…”

Section: Weathering and Erosion Processes In The Kathmandu Basinmentioning

confidence: 97%

Controlling weathering and erosion intensity on the southern slope of the Central Himalaya by the Indian summer monsoon during the last glacial

Kuwahara

Masudome

Paudel

et al. 2010

Global and Planetary Change

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a b s t r a c tThis paper reports the results of clay mineral analysis (the amount of clay fraction, clay mineral assemblages, illite crystallinity) of samples collected from a drilled core (Rabibhawan (RB) core) located in the westcentral part of the Kathmandu Basin on the southern slope of the Central Himalaya. The amount of clay fraction in the core sediments between 12 m and 45 m depth (corresponding to ca. 17-76 ka), which belong to the Kalimati Formation, is variable and shows three clay-poor zones (19-31 ka, 44-51 ka, and 66-75 ka). The variations correspond with those of illite crystallinity index (Lanson index (LI) and modified Lanson index (MLI)) and kaolinite/illite ratio as well as the fossil pollen and diatom records reported by previous workers. These data reveal the following transformations occurring during the weathering process in this area: micas ðmainly muscoviteÞ→illiteð→illite−smectite mixed layer mineral ðR = 1ÞÞ→kaoliniteThe sedimentation rate (~50 cm/kyr) of clay-poor zones that correspond to dry climate intervals is only half that of clay-rich zones (~120 cm/kyr) that correspond to wet climate intervals, indicating weakened chemical weathering and erosion and low suspended discharge during dry climate intervals. The clay-poor zones commonly show unique laminite beds with very fine, authigenic calcite, which was probably precipitated under calm and high calcite concentration conditions caused by low precipitation and run-off. The variations between dry and wet conditions in this area as deduced from clay minerals appear to follow the Indian Summer Monsoon Index (ISMI) (30°N-30°S, 1 July) and northern hemisphere summer insolation (NHSI) signals (30°N) at 1 July, especially during the dry climate zones, whereas the wet maxima of the wet climate zones somewhat deviate from the strongest NHSI. On the other hand, the dry-wet records lead markedly the SPECMAP stack (by about 5000 years). These results suggest that the Indian summer monsoon precipitation was strongly controlled by the NHSI or summer insolation difference between the HimalayanTibetan Plateau and the subtropical Indian Ocean, showing a major fluctuation on the 23,000 years precessional cycle, and that it was not driven by changes in high-latitude ice volume, although the records of clay mineral indices during the wet intervals leave a question that other factors, in addition to insolation forcing, may play important roles in weathering, erosion, and sedimentation processes.

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“…The stratigraphy of the sediment deposits have been classified with different names by a number of authors as shown in Table 1. Sakai (2001) has proposed a new classification of sediment stratigraphy in ascending order as: Tarebhir, Lukundol and Itaiti Formations in the southern part; The aquifer material consists of lake deposits (gravel, sand, silt, clay, peat and lignite) and fluvial deposits (boulder, gravel, sand and silt) (Kharel et al 1998); and mineral composition of the aquifer material is dominated by quartz, K-feldspar, plagioclase and mica with minor chlorite and calcite (Paudel et al 2004).…”

Section: Geology and Hydrogeologic Unitsmentioning

confidence: 99%

Hydrogeologic characteristics of groundwater aquifers in Kathmandu Valley, Nepal

Pandey

Kazama

2010

Environ Earth Sci

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This paper reviews, compiles and comprehensively analyzes spatial variations in hydrogeologic characteristics of shallow and deep groundwater aquifers in Kathmandu Valley. To estimate transmissivity (T) (and then hydraulic conductivity) as a function of specific capacity (SC), an empirical relationship between T and SC is developed for shallow and deep aquifer. The results show that T and SC are log linearly related by an equation T = 0.8857(SC) 1.1624 [R 2 = 0.79] in shallow and T = 1.1402(SC) 1.0068 [R 2 = 0.85] in deep aquifer. The estimated T ranges from 163 to 1,056 m 2 /day in shallow aquifer and 22.5 to 737 m 2 /day in deep aquifer. Finally, mapping of spatial distribution in hydrogeologic characteristics (thickness, T, hydraulic conductivity and storage coefficient) in shallow and deep aquifers are accomplished using ArcGIS9.2 and such maps would be useful in delineating potential areas for groundwater development and simulating groundwater flow in the aquifer system.

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Changes in mineral composition and depositional environments recorded in the present and past basin-fill sediments of the Kathmandu Valley, central Nepal

Cited by 8 publications

References 2 publications

Assessment of Deep Groundwater Quality in Kathmandu Valley Using Multivariate Statistical Techniques

Assessment of Deep Groundwater Quality in Kathmandu Valley Using Multivariate Statistical Techniques

Controlling weathering and erosion intensity on the southern slope of the Central Himalaya by the Indian summer monsoon during the last glacial

Hydrogeologic characteristics of groundwater aquifers in Kathmandu Valley, Nepal

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