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21.
L. MallikR. Mazumder B.S. MazumderM. Arima P. Chatterjee 《Marine and Petroleum Geology》2012,30(1):43-49
Tidal rhythmites have been documented from modern continental shelves and distal offshore settings. In significant contrast to their modern counterparts, sedimentological studies of ancient tidal rhythmites formed in distal offshore settings and quantification of tidal rhythms encoded therein are, however, scarce. This paper presents sedimentological analysis of vertically accreted tidal rhythmites from the Palaeoproterozoic Chaibasa shale facies in India, and quantification of their tidal rhythms. The facies characteristics of the Chaibasa Shale coupled with harmonic analysis of the laminae thicknesses of the sandstone inter-layers corroborate a distal shelf palaeogeography for the generation of the vertically accreted tidal rhythmites. The latter are the distal counterparts of laterally accreted, tidal “bundle” deposits, well preserved within the shallow marine Chaibasa sandstones. The number of lunar days in a synodic month (∼23) estimated from the Chaibasa shale facies is, however, considerably lower than that estimated from the Chaibasa sandstone facies (∼32) suggesting that the tidal record encoded from the Chaibasa shale facies is incomplete. 相似文献
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A total of 25 surface sediment samples, collected along a North-South transect (from 9.69° N to 55.01° S and from 80° E and 40° E) in the south western Indian Ocean, were used to study the coiling direction patterns in foraminifera planktonic species Neogloboquadrina pachyderma, Globigerinita glutinata and Globigerina bulloides. Comparison between the coiling direction and mean proloculus size (MPS) revealed that all these profiles along N-S transect were not in tandem and thus indicated non-existence of any relationship between the coiling direction and reproductive modes expressed in terms of mean proloculus size. 相似文献
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N. Khare A. Mazumder P. Govil V. P. Singh 《Journal of the Geological Society of India》2009,73(3):379-385
Morphological variations with respect to the number of chambers in Neogloboquadrina pachyderma (Ehrenberg) were investigated in 25 surficial sediments of Indian Ocean taken along the N-S transect between 9.69° N and
55.01° S latitude and 80° E and 40° E longitude. The number of chamber was counted for at least 40 specimens picked for each
sample. The average number of chamber was correlated with the average temperature and salinity along the changing latitude.
The results showed a high correlation between the number of chambers and temperature and salinity. It was noted that number
of chambers decreases from equatorial to polar region. The carbonate saturation and nutrient availability could possibly be
other causes for the change in number of chambers. The results of this study, if applied on the subsurface marine sediments,
will bear implications on paleoclimatic condition in the Indian Ocean region. 相似文献
24.
S. Mazumder P. van Hemert A. Busch K-H.A.A. Wolf P. Tejera-Cuesta 《International Journal of Coal Geology》2006,67(4):267-279
Presently many research projects focus on the reduction of anthropogenic CO2 emissions. It is intended to apply underground storage techniques such as flue gas injection in unminable coal seams. In this context, an experimental study has been performed on the adsorption of pure CO2 and preferential sorption behavior of flue gas. A coal sample from the Silesian Basin in Poland (0.68% V Rr), measured in the dry and wet state at 353 K has been chosen for this approach. The flue gas used was a custom class industrial flue gas with 10.9% of CO2, 0.01% of CO, 9% of H2, 3.01% of CH4, 3.0% of O2, 0.106% of SO2 and nitrogen as balance.Adsorption isotherms of CO2 and flue gas were measured upto a maximum of 11 MPa using a volumetric method. Total excess sorption capacities for CO2 on dry and wet Silesia coal ranged between 1.9 and 1.3 mmol/g, respectively. Flue gas sorption capacities on dry and wet Silesia coal were much lower and ranged between 0.45 and 0.2 mmol/g, respectively, at pressures of 8 MPa. The low sorption capacity of wet coal has resulted from water occupying some of the more active adsorption sites and hence reducing the heterogeneity of adsorption sites relative to that of dry coal. Desorption tests with flue gas were conducted to study the degree of preferential sorption of the individual components. These experiments indicate that CO2 is by far the prefered sorbing component under both wet and dry conditions. This is followed by CH4. N2 adsorbs very little on the coal in the presence of CO2 and CH4. It is also observed that the adsorption of CO2 onto coal is not significantly hindered by the addition of other gases, other than dilution effect of the pressure.In addition to the sorption experiments, the density of the flue gas mixture has been determined up to 18 MPa at 318 K. A very good precision of these measurements were documented by volumetric methods. 相似文献
25.
Biplob Das Anita Narwani Blake Matthews Rick Nordin Asit Mazumder 《Journal of Paleolimnology》2009,42(2):167-181
We investigated how the history of local disturbances in a watershed can influence the regional coherence of ecosystem properties
in lakes that have similar morphometry and climatic conditions. We measured sedimentary δ13C, δ15N, C:N and %BSiO2 in Sooke Lake Reservoir (SOL) and Shawnigan Lake (SHL), which are located within 4 km of each other on Vancouver Island,
Canada. SOL is an impounded lake whose watershed has been fully protected over the last century, although the lake level has
been raised 3 times via impoundment during this period. SHL has a similar limnological regime, but the surrounding watershed
has been developed extensively for residential uses. We investigated how a pulse disturbance regime in SOL (i.e. repeated
dam raising) and a press disturbance regime in SHL (i.e. persistent development) influenced the variability of paleoindicators
in each system over time. We found that these contrasting disturbance regimes reduced the regional temporal coherence of aquatic
productivity between the two lakes (indicated by %BSiO2), but did not influence the regional coherence of nutrient status or the main carbon sources of the lakes (indicated by %C,
%N and δ13C). In contrast, an indicator of the sources and cycling of nitrogen (δ15N) showed increased coherence. Local disturbances also affected the variability of the paleoindicators within each system
over time. In SOL, impoundments led to both declines (%N, δ15N) and increases (δ13C) in the variability of paleoindicators. In SHL, persistent watershed development led to lower variability of two paleoindicators
(%N, %BSiO2). Overall, our data suggest that local disturbances can influence the %BSiO2 and C:N ratio of lake sediments, but are less likely to alter the regional coherence of %C, %N and δ13C between lakes.
Biplob Das and Anita Narwani contributed equally to this work. 相似文献
26.
Experiments are conducted in a laboratory flume on the propagation of a surface wave against unidirectional flow with a sediment bed. This article presents the spatial variation of bedforms induced by the wave-blocking phenomenon by a suitably tuned uniform fluid flow and a counter-propagating wave. The occurrence of wave-blocking is confirmed by finding a critical wave frequency in a particular flow discharge in which the waves are effectively blocked and is established using the linear dispersion relation. The purpose of this work is to identify wave-blocking and its influence on the development of bedforms over the sediment bed. Interestingly bedform signatures are observed at a transition of bedforms in three zones, with asymmetric ripples having a steeper slope downstream face induced by the incoming current, followed by flat sand bars beneath the wave-blocking zone and more symmetric ripples below the wave-dominated region at the downstream. This phenomenon suggests that the sediment bed is segmented into three different regions of bed geometry along the flow. The deviations of mean flows, Reynolds stresses, turbulent kinetic energy, and power spectral density due to the wave-blocking phenomenon are presented along the non-uniform flow over sediment bed. The bottom shear stress, bed roughness and stochastic nature of the bedform features are also discussed. The results are of relevance to engineers and geoscientists concerned with contemporary process as well as those interested in the interpretation of palaeoenvironmental conditions from fossil bedforms. © 2019 John Wiley & Sons, Ltd. 相似文献
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Khan Nafis Sadik Roy Sujit Kumar Mazumder Md. Touhidur Rahman Talukdar Swapan Mallick Javed 《Natural Hazards》2022,114(1):883-906
Natural Hazards - The confluence of the Ganges, Jamuna, and Padma rivers is one of the most dynamic in the world, an internationally important research area because of the confluence of two of the... 相似文献
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ATM Sakiur Rahman Md. Kamruzzama Chowdhury Sarwar Jahan Quamrul Hasan Mazumder 《Journal of the Geological Society of India》2016,87(2):179-193
In Bangladesh, agriculture plays a major role in the national economy. In the drought prone Barind area in NW Bangladesh, cropping intensity has increased almost double since late eighties of last century (from 1985) because of the introduction of groundwater irrigation. Long-term behavior of groundwater table (GWT) in the drought prone Barind area has been studied using MAKESENS model in the wake of massive installation of tube-wells. The study reveals that the maximum and minimum depths to GWT during 1991-2010 show on average declining trend of 4.51 m and 4.73 m. The long-term prediction for the period of 2020-50 assuming the current rate of groundwater withdrawal is that the declining trend will be 1.16 to 1.59 and 1.07 to 1.82 times more for maximum and minimum groundwater depths respectively in comparison to the present. The rigorous exploitation of groundwater for irrigation, decreasing rainfall and surface geological attributes lead towards declining trend of GWT. This will hamper the country’s food security and ultimately threaten its socio-economic sustainability. So the appropriate strategies for the management of groundwater resource on a sustainable basis should be the priority for maintaining agricultural productivity. 相似文献