Papers by Sudarshan Bhandari
Japanese Journal of Palynology
Japanese Journal of Palynology
Evidence from various climate proxies provides us with increasingly reliable proof that only in t... more Evidence from various climate proxies provides us with increasingly reliable proof that only in the past 10 millennia were natural systems more or less as we see them at the present (without considering human impact). Prior to 10,000 years ago, natural systems repeatedly changed under the influence of an unstable climate. This is particularly true over the last one million years. During these times, terrestrial environments were populated by a diversity of large animals that did not survive either the last dramatic climate change or the increasing power of humans. The volume of continental ice covering the land and its impact on the planet’s physiography∗ and vegetation have varied consistently. We can try to imagine extreme conditions: the very cold springtimes of the full glacials∗, and the warm springtimes of the rapid deglaciation phases, with enormous volumes of water feeding terrifying rivers. Most of this story is frozen in the ice cover of Greenland and Antarctica, the deep ...
Bulletin of the Department of Geology, 2009
A 28-m thick exposure of the younger stage deposits of Kathmandu Valley fluvio-deltaic deposits a... more 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 (<0.02) restricted to quartz-rich coarse sand, whereas the uppermost 20-cm thick section affected by anthropogenic activity exhibits enhanced range (0.15-2). RM of specimens from some 80 levels reveals predominantly normal polarity except for a part of ca. 80cm thick sandy silt, located about 6-m above the base, yielding reverse polarity attributed to the Laschamp Reversal Event/Excursion (LRE) dated in literature at ca. 41 Ka. This inference, along with majority of other 14C data, lends further support to the affinity of Dhapasi section to the Gokarna Formation (ca. >...
Geophysical Journal International, 2012
A molasse sequence comprising 1.5-km-thick sediments of the Lower and Middle Siwaliks Group in th... more A molasse sequence comprising 1.5-km-thick sediments of the Lower and Middle Siwaliks Group in the sub-Himalayan North Belt along the Tinau Khola River in west-central Nepal was studied for the low-field magnetic susceptibility and anisotropy using single core specimens of siltstone/sandstone from 127 stratigraphic levels. The magnetic fabric comprises primary sedimentary-compactional and secondary tectonic components. It is characterized by (i) predominantly oblate magnetic susceptibility anisotropy ellipsoids, (ii) low anisotropy (P mostly <1.1) and low magnetic susceptibility (<ca. 10 −7 m 3 kg −1) contributed mainly by paramagnetic and diamagnetic minerals and (iii) WNW-ESE magnetic lineations subparallel to the fold axes/bedding strikes/thrust front, and hence normal to the direction of palaeotectonic compression. Thermal demagnetization of single core specimens from 103 levels across 1120 m of the lower part revealed a characteristic remanence of the high unblocking temperature (> 600 • C) in hematite. Remanence ratios derived from demagnetization data allowed the first-order estimation of remanence contributions from magnetic minerals (goethite, maghemite, magnetite and hematite), and discrimination of rockmagnetic zones correlatable with distinct lithofacies, which will facilitate objective mapping. We correlated a magnetic polarity sequence, constructed from normal and reverse polarity directions from 77 levels that passed the reversal test and represented primary remanences, with the standard geomagnetic polarity timescale to constrain the depositional age between ca. 13.2 Ma (base of Chron C5AAN, 13.015-13.183 Ma) and the middle of Chron C5n.2n (9.987-11.040 Ma). We calculated the sediment accumulation rate for polarity zones from the chronologically better constrained part below Chron C5n.2n (i.e. below 11.040 Ma) to be 25-61 cm kyr −1 (average, 39 cm kyr −1), which is consistent with the value of 32-50 cm kyr −1 reported from Siwaik sections in Nepal. The notable increase in accumulation rate after 12.1 Ma probably reflects the peak of the earlier phase of uplift and/or unroofing of the Himalayan source region followed by rapid accumulation in the foredeep, and a link to monsoon initiation/intensification. Compared to the expected remanence from the latest APWP for the Indian Plate 10-13 Ma, the best-defined mean (351.8 • /20.9 •) is rotated anticlockwise by 9.2 • and records an inclination shallowing of 25 •. Constraining the base of the Tinau Khola north section to 13.2 Ma (i.e. older than the Tinau Khola south by 1.7 Myr) should open up new horizons for multidisciplinary and multiproxy research targeting geotectonic/climatic/environmental palaeoreconsructions of Himalaya-wide events.
Magnetic susceptibility (MS), one of the physical properties used in mineral and oil exploration,... more Magnetic susceptibility (MS), one of the physical properties used in mineral and oil exploration, has been popular recently for rapid assessment of quality and quantity of material in land, water and air systems in natural media or even for assessment of pollution/contamination level, e.g., by heavy metals, due to anthropological activities. This has become possible due to portable MS-meters, which allow rapid differentiation of geological medium (rock formations and soils) at varying state of weathering and posing difficulty for accurate mapping in the natural outcrops. Variation in MS has been measured in roadside rock outcrops in Central Nepal along the Kathmandu-Mugling- Jugedi and Mugling-Pokhara-Ramdighat-Kerabari routes. A pocket–sized MS meter (SM-30 by ZH Instruments, Czech Republic) was used to measure MS in situ on the smooth surfaces of rocks that belong to the formations mapped as Nawakot Complex, Kathmandu Complex, Sirkot Group, Kaligandaki Supergroup and Tansen Group in the inner and outer parts of the Nepalese Lesser Himalaya. Site mean MS data (averages of 15 readings at each site) reveal: (i) a wide range of (-0.003 to 5.1) x 10-3 SI; (ii) Lowest MS (&lt;0.1 x 10-3 SI ), for quartzite, quartzose sandstone, limestone, dolomite, which are predominantly composed of diamagnetic minerals (quartz, calcite and dolomite); (iii) Intermediate range of (0.1-1.0) x 10- 3 SI for most shales, diamictites, slates, phyllites, sandstones, schists; and (iv) high values (1.0–5.1) x 10-3 SI for amphibolite schists, metasandstones, sandstones with volcanic detritus, hematite-rich sediments and trachytic volcanic rocks in increasing order. MS has good potential for fine-scale discrimination of formations characterized even by similar lithologies, composed of quartz or carbonate minerals, inability of whose objective identification has led to proliferation of formations, uncertainties in local and/or regional correlation and therefore confusions in their age assignment.
Bulletin of The Department of Geology, 2009
A 28-m thick exposure of the younger stage deposits of Kathmandu Valley fluvio-deltaic deposits a... more 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 (k; in 10 -3 SI) of the natural sediments ranges from 0.001 to 0.15, with lower range (<0.02) restricted to quartz-rich coarse sand, whereas the uppermost 20-cm thick section affected by anthropogenic activity exhibits enhanced range (0.15-2). RM of specimens from some 80 levels reveals predominantly normal polarity except for a part of ca. 80cm thick sandy silt, located about 6-m above the base, yielding reverse polarity attributed to the Laschamp Reversal Event/Excursion (LRE) dated in literature at ca. 41 Ka. This inference, along with majority of other 14 C data, lends further support to the affinity of Dhapasi section to the Gokarna Formation (ca. >45 to 34 Ka).
Review of Palaeobotany and Palynology, 2016
Journal of Nepal Geological Society
Plant macrofossil investigation was carried out on the Late Quaternary sediments of the Kathmandu... more Plant macrofossil investigation was carried out on the Late Quaternary sediments of the Kathmandu Valley, central Nepal. The fluvial-deltaic to fluvio-lacustrine deposits of the Kathmandu Basin are found to be rich in plant macrofossil assemblages. A total of 66 taxa from 38 families were identified to genus and some of them up to species level from five different macrofossil bearing layers (BG-1 to BG-5) from the 33 m thick Besigaon section belonging to the Gokarna Formation exposed at the northern part of the basin. The lower half of the exposed section is completely devoid of macrofossil horizons, however the upper half yielded a significant amount which could be used for climatic interpretation. The characteristic feature of the Besigaon section is the dominance of angiosperms in the lower and middle horizons (BG-1, BG-2, BG-3) but gymnosperms in the upper horizons (BG-4, BG-5). The dominance of angiosperms such as Carpinus, Alnus, Pyracantha, Quercus subgen. Cyclobalanopsis, Eu...
Journal of Nepal Geological Society
Variation in magnetic susceptibility (MS) along highways has been measured in rock outcrops withi... more Variation in magnetic susceptibility (MS) along highways has been measured in rock outcrops within the Nepalese Lesser Himalaya in the following road sectors: Kathmandu-Mugling-Jugedi along the road that joins Kathmandu and Narayanghat, and Mugling-Pokhara-Ramdighat-Kerabari sector along Prithvi and Siddhartha highways. A pocket susceptibility meter (ZH Instruments SM30) was used to measure MS in situ on the fl at surfaces at roadside or river/stream exposures of rocks that belong to Nawakot Complex, Kathmandu Complex, Sirkot Group, Kali Gandaki Super Group and Tansen Group in the inner and outer parts of the Lesser Himalaya. Site mean MS (average of 15 readings at each outcrop) data reveal the following characteristics: (i) A large range of average MS between (-0.003 to 5.1) x 10 -3 SI; (ii) Lowest MS magnitudes (<0.1 x 10 -3 SI ) for quartzite, quartzose sandstone, limestone, dolomite, which are predominantly composed of diamagnetic minerals (quartz, calcite and dolomite); (iii) Intermediate range of (0.1-1.0) x 10 -3 SI is found in most shales, diamictites, slates, phyllites, sandstones, schists; and (iv) High values (1.0-5.1) x 10 -3 SI for amphibolite schists, metasandstones, sandstones with volcanic detritus, hematite-rich sediments and trachytes or trachyandesites. MS has good potential for fi ner-scale discrimination of geological formations represented by macroscopically similar lithologies, especially those composed by predominantly quartz or carbonate minerals, inability of whose objective identifi cation has led to proliferation of formations in the geological literature.
Journal of Nepal Geological Society
The Late Pleistocene plant macrofossils from the Thimi Formation of the Kathmandu Valley have bee... more The Late Pleistocene plant macrofossils from the Thimi Formation of the Kathmandu Valley have been reported in this paper. On the basis of 71 taxa from 39 families, seven plant macrofossil assemblages T-1 to T-7 were described from 18.5 m thick section of the Thimi Formation exposed at Madhyapur Thimi, Bhaktapur. Pinus, Abies, Tsuga, Carpinus, Sambucus, Rubus, Eurya, Potentilla and Scirpus are the common elements in the Thimi Formation. It is found that the cool temperate elements (Abies, Pinus, Tsuga, Picea, Taxus) were dominated over warm climatic elements (Quercus, Eurya, Pyracantha, etc.) during the deposition of the Thimi Formation. The underlying Gokarna Formation exhibited subtropical to warm temperate vegetation with the dominance of subtropical elements such as Eurya, Ficus, Zizyphus, etc. over temperate elements like Betula, Tsuga and Abies. During the depositional period of the Thimi Formation, this subtropical to warm temperate type of vegetation shifted to warm to cold ...
Journal of Nepal Geological Society
The Lukundol Formation, a fluvio-lacustrine deposit, constituting the lowermost part of the sedim... more The Lukundol Formation, a fluvio-lacustrine deposit, constituting the lowermost part of the sedimentary sequence in the Kathmandu valley, is made up of conglomerates in its basal part; thick beds of carbonaceous clay, lignite, silt and sand in the middle part; interbedded clay and gravel in the upper part; and very thick beds of gravel in the uppermost part. Its exposure in the Khahare Khola, near the Lukundol village, is about 205 m thick. The palynostratigraphy of the Lukundol Formation revealed the dominance of gymnosperms over the angiosperms and herbaceous members. In the pollen diagram, Pinus and Quercus are the predominant taxa whereas Castanopsis and Oleaceae are the next dominant ones. Three fossil pollen zones were differentiated in the Lukundol Formation. Zone I indicates a subtropical climate, zone II belongs to a warm temperate climate, and zone III represents a subtropical to warm-temperate climate.
Bulletin of the Department of Geology, 2009
Rock Mechanics and Rock Engineering, 2007
Conventional blasting causes cracks and fractures in the rock. Controlled blasting techniques pro... more Conventional blasting causes cracks and fractures in the rock. Controlled blasting techniques produce the macrocrack in a desired direction and eliminate microcrack in the remaining rock. Macrocrack development in desired direction is required for extraction of dimensional stone and at the same time there is need to reduce microcrack development in the block and remaining rock. To achieve the objectives, experimental work in the quarries was carried out for separating marble block from the in situ strata as practiced in some of the Indian mines by using detonating cord of 30 to 50 g=m by varying hole spacing, hole diameter, air cushioning, water and sand filled blastholes. Blasthole notching was carried out. Further, tests were carried out by using various liners inside the blasthole to determine the damages in the extracted block and remaining rock. The designed experimental work was undertaken and rock samples were collected by coring before and after blasting for quantification of microcrack in the rock. P-wave velocity and microscopic studies were conducted for quantification of damages. Experiments were also conducted at laboratory scale for the quantification of damages in single circular and notched holes with variation of stemming and liners. The P-wave velocity close to hole always reduces after blast and in case of NG-based charge and detonating cord it decreases up to 1=3 rd . With PVC pipe and paper tube liners decrease is negligible. Thus, by using notched hole with paper tube, decrease in P-wave is minimum indicating least damage.
Quaternary Science Reviews, 2006
Field stratigraphy, sedimentology and luminescence dating of the exposed fluvial and aeolian sequ... more Field stratigraphy, sedimentology and luminescence dating of the exposed fluvial and aeolian sequences from the southern desert margin were used to discern the pattern of southwest monsoon variability during the last 130 ka. The sedimentary architecture and textural attributes of the sediments belonging to the period 130-120 ka suggests the existence of a meandering river system consequent to enhanced southwest monsoon conditions. A shift from a meandering to a braided pattern during 120-100 ka indicates a phase of reduced precipitation. Presence of flood plain fines and bedded calcretes during $100-70 ka suggest a period of enhanced monsoon with seasonality. Following this, a phase of weak monsoon activity was observed during 70-60 ka. Regional flood plain aggradation and pedogenesis during the period o60-30 ka indicated enhanced southwest monsoon condition. Onset of fluvio-aeolian sedimentation after 30 ka and initiation of a regionally extent aeolian sedimentation during 20-11 ka indicates overall dry climatic condition. These observations accord well with the total organic carbon (TOC) data and suggest a vegetation /moisture control on the aeolian sedimentation in the region.
Palaeogeography, Palaeoclimatology, Palaeoecology, 1997
A 52 m thick upper Pleistocene and Holocene terrestrial succession in the Bhimtal-Naukuchiatal ba... more A 52 m thick upper Pleistocene and Holocene terrestrial succession in the Bhimtal-Naukuchiatal basin, southcentral Kumaun Himalaya, India was studied using chronological, palaeontological, palynological and ~13C measurements. The section recorded evidence for climatic changes. At least two phases of arid climate and one phase of humid climate were recognised. Preliminary palaeomagnetic studies revealed a reversal of polarity, presumably correlatable with the Mono Lake excursion. Prior to this, no reversal event in the upper Pleistocene-Holocene terrestrial sediments of Indian subcontinent is known. A fossiliferous horizon, discovered in the lower part of the section, consisted of Sorex and Mus. This is the only report of a Late Pleistocene micromammalian assemblage in the Kumaun Himalaya.
Journal of Atmospheric and Oceanic Technology, 2009
Information on the spatial and temporal variability of rain rate is important not only for meteor... more Information on the spatial and temporal variability of rain rate is important not only for meteorology and hydrology but also for the design of remote sensing and in situ measuring or of millimeter wave communication systems. The Ocean Topography Experiment (TOPEX)/Jason Tandem Mission (TM) collocated rain dataset is used in this study to determine the small space-scale (5 km) and time-scale (70 s) rain variability. TOPEX and Jason dual-frequency (Ku and C bands) radar altimeter data have been extensively used during the past decade to detect and study oceanic precipitations. During the TM, designed to intercalibrate and validate the two altimeters, the two satellites were put on the same orbit with a 70-s time separation. With combined use of altimeter and passive microwave radiometers (also available on board altimeter missions), rain intensity, rain attenuation, rain layer height, rain event length, and surface winds can also be estimated and provide valuable coincident geophysical contextual information. The size of the TM collocated rain database (140 000 samples) is large enough to allow a meaningful statistical analysis of the time-space variability of rain over the World Ocean. The analysis of the different terms contributing to the variability of rain attenuation, from which rain rate is inferred, shows that the geophysical and/or instrumental noise is small enough to allow a meaningful estimation of the variability of the measured rain rate. The analysis of the time and space variabilities and their relation reveals two well-defined regimes. The first one, corresponding to convective rain cells (i.e., rain rate greater than 3-4 mm h 21 , length smaller than 50 km, and freezing level greater than 3.5 km), is characterized by high temporal and spatial variabilities (greater than 2-3 mm h 21 ) that increase with increasing rain intensity and decreasing cell length. Horizontal variability is significantly larger than the temporal one and surface wind has a very limited impact. The second regime corresponds to stratiform and/or weak rain cells. The temporal and spatial variabilities are relatively low (on the order of 1-2 mm h 21 ) and vary little with rain intensity and cell length. The temporal variability increases with surface wind and largely exceeds the spatial variability (ratio of 2 or more); the ratio strongly increases with increasing wind speed. * Current affiliation: Ahmedabad,
Journal of Asian Earth Sciences, 2005
Late Pleistocene fluvial sediments that were deposited in a slowly sinking basin are now exposed ... more Late Pleistocene fluvial sediments that were deposited in a slowly sinking basin are now exposed as 30 -50 m high incised vertical cliffs all along the Lower Narmada Valley in western India. The exposed fluvial deposits have been classified into two sediment packages, alluvial fan sediments overlain by alluvial plain sediments. The alluvial plain sequence has not been studied previously. It consists mainly of sands and silts and is dominated by overbank deposits. Occurrence of large scale bedforms in the alluvial plain sequence points to the existence of a large sand bed river in an alluvial plain setting. The major sedimentary facies in stratigraphic order include large channel fills, giant epsilon cross bedded strata, overbank fines occurring in horizontal, massive and undulatory stratified forms associated with crevasse splay and backswamp deposits, and a reddish brown palaeosol overlain by thinly stratified sands and silts at the top of the exposed sediment succession. Large sized channel fills occur at two stratigraphic levels, which are morphologically similar and are indicative of high rates of deposition and avulsion. The large channel fill structures and the giant epsilon cross bedded strata indicate a large single channel river that was consistently 10 -15 m deep and about 70 -80 m wide even during the dry seasons. These dimensions are larger than those of the present day Narmada River at low discharge levels. The overbank sediments indicate rapid deposition through frequent overbank floods and floodplain aggradation by a laterally shifting river. Available chronologic data suggests that the reddish brown palaeosol correlates with a regional phase of pedogenesis in the alluvial plain of Gujarat prior to the Last Glacial Maximum (LGM). The thinly stratified sands and silts overlying the palaeosol were deposited by a considerably depleted but perennial river during the arid phase of the Last Glacial Maximum. Overall, the alluvial plain sediments of the Lower Narmada valley, particularly those below the palaeosol, have been attributed to a hyper-avulsive large river with low sinuosity whose high discharge levels were determined primarily by a large catchment area further to the east and not by the semiarid climate prevailing in the Gujarat alluvial plain during the upper part of the Late Pleistocene. The study concludes that the Narmada River has maintained a large catchment at least since the last 100 ka, however, the river was characterised by a much bigger channel during much of the Late Pleistocene with discharge levels higher than the present day. q
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Papers by Sudarshan Bhandari