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11.
Muhammad Hassaan Swapan Kumar Bhattacharya Manoj Joseph Mathew Numair Ahmed Siddiqui 《Arabian Journal of Geosciences》2017,10(8):192
Subsidence and thermal history analysis are carried out in order to investigate the Cenozoic basin development of the southwestern (Tenggol Arch and basinal side) part of the Malay basin. Structurally, the southwestern part consists of normal faults and horst and graben geometry. Tectonic subsidence curves show that the basinal side is more active than the Tenggol Arch due to movement along normal faults. Cenozoic development initiated with the deposition of sedimentary Units M & L (Oligocene) and the activation of the Tenggol fault on the basinal side. Several periods of accelerated and slow subsidence are observed during the Oligocene to Middle Miocene that could be associated with changes in regional stresses caused by pulsating plate movement. The Malay Basin experienced inversion throughout the Middle to Late Miocene related to mantle induced slab avalanche effect, causing relatively higher tectonic subsidence rates on the Tenggol Arch compared to the basinal side, suggesting that the Tenggol Arch is less affected by inversion than the basinal side. After a period (Late Miocene) of non-deposition, the basin was reactivated (Pliocene to recent) due to thermal relaxation with thick sedimentation. Paleo heat flows estimated utilizing a novel technique introduced in this study and present day heat flow calibrated using BHT data further supports our results, in that increase in heat flow is related to rapid tectonic subsidence. An anomalously high heat pulse affected the basin during inversion and could be the cause of meta-sediment formation whereas present heat flows, although high compared to average basins, shows decreasing trend from the inversion period. 相似文献
12.
Early Cenozoic rapid flight enigma of the Indian subcontinent resolved: Roles of topographic top loading and subcrustal erosion 总被引：1，自引：1，他引：0
Muthuvairavasamy Ramkumar David Menier Manoj Mathew M. Santosh Numair A. Siddiqui 《地学前缘(英文版)》2017,8(1):15-23
Intrinsic magmatic processes are considered as critical operators of plate movements. Here we demonstrate the role of extrinsic processes consequent to intrinsic processes as a catalyst for anomalous rapid plate movement. The rapid and accelerated flight of the Indian subcontinent since Deccan volcanism until its collision with Eurasia remains as one of the geological conundrums. Data on seismic tomography, peninsular geomorphology and inferences on continuum of subcrustal structures are utilized to address this enigma. We propose geomorphic isostasy as the mechanism that has driven this fastest drift ever recorded in geological history. It was initiated by sudden instability after the Deccan volcanism and resultant extensive accumulation of lava pile over continental lithosphere of northern India, northern-eastern tilt due to crustal thickness heterogeneity and subcrustal thermal stratification. The drift was sustained by Carlsberg and Central Indian ridge-push until collision and sediment top loading at northeast thenceforth. These inferences and geomorphic isostasy as a catalytic mechanism necessitate variability of drift rates as integral inputs for any continental scale modeling. 相似文献
13.
Amjad Ali Pirzada Jamal A. Siddiqui Kate Bromfield Athar Ali Khan Pervaiz Iqbal 《Arabian Journal of Geosciences》2017,10(23):520
Uplifted reefs due to being important palaeoclimate archives and a rich source of information on past physical and geochemical changes globally have become the centre of marine research. The uplifted fossil Quaternary coral communities of Jiwani and Gwadar are perfect places to study the palaeoclimatic and geological changes that have shaped the Balochistan coast. Studies on the palaeodiversity of corals along the Makran coast of Pakistan are lacking. In the present study, the samples collected using line intercept method from four uplifted sites (Balochistan coast: one at Gwadar and three at Jiwani) were analysed. The relative distribution and diversity of scleractinian fossil corals was determined, and the factors responsible for coral decline along Pakistan coast were compared with modern coral distribution and diversity. A total of 48 fossil coral species were recorded in nine families and 22 genera. High coral diversity was recorded in the uplifted landward sites of Jiwani and Gwadar headland. Terraces close to the shore at Jiwani had lower diversity. The corals seem to be Quaternary: most likely Pleistocene to Holocene. The modern fauna lacks many species recorded in the fossil community, thus suggesting a faunal turnover in diversity and redistribution of coral fauna which may be linked with past geological events and increasing anthropogenic pressure. 相似文献
14.
15.
A self-consistent method has been evolved to infer physical parameters like density, radiation field and abundances using
line and continuum radiations as diagnostics. For that purpose, we first calculate the temperatures of graphite and silicate
grains using the model of Li and Draine (Astrophys. J. 554:778, 2001) by solving self-consistently the energy balance for G
0 (1–104) times the radiation field following Weingartner and Draine (Astrophys. J. Suppl. Ser. 134:263, 2001). Consequently, infrared emission fluxes are also obtained. To keep it simple, this is presented in the empirical form of
parameters T
D
and wavelength. The same model of the grain is adopted for photoelectric heating of gas using the formalism of Weingartner
and Draine (Astrophys. J. Suppl. Ser. 134:263, 2001) (hereafter referred to as WD) and Bakes and Tielens (Astrophys. J. 427:822, 1994) (hereafter referred to as BT) for radiation field cited above in the range (6<hν≤13.6 eV). Temperature and abundances are determined using our own code for PDR very similar to cloudy code. All the possible
sources of heating and cooling are considered for setting up the thermal balance. For the gas phase abundances that vary with
depth in the cloud due to dust, self- and mutual shielding, chemical balance is solved. Most of the photoionization, photodissociation
or chemical reaction rates are taken from UMIST database. We present an analysis of the cooling lines of singly ionized carbon
[CII] at 158 μm and neutral oxygen [OI], at 63 μm and far infrared (FIR) continuum for a variety of star forming galaxies.
Method of analysis of observational data is different from that of Malhotra et al. (Astrophys. J. 561:766, 2001). The radiation field G
0, density N
h
and abundance of carbon are obtained through best fit of observed and calculated intensities for lines and continuum radiations. 相似文献
16.
ABSTRACTThe major flood of 2014 in the two eastern, transboundary rivers, the Jhelum and Chenab in Punjab, Pakistan, was simulated using the two-dimensional rainfall–runoff model. The simulated hydrograph showed good agreement with the observed discharge at the model outlet and intervening barrages, with a Nash-Sutcliffe efficiency of 0.86 at the basin outlet. Further, simulated flood inundation extent showed good agreement with the MODIS imagery with a fit (%) of 0.87. For some affected areas that experienced short-duration flooding, local housing damage data confirmed the simulated results. Besides the rainfall–runoff and flood inundation modelling, parameter sensitivity analysis was undertaken to identify the influence of various river and floodplain parameters. The analysis showed that the river channel geometric parameters and the roughness coefficients exerted the primary influence over flood extent and peak flow. 相似文献
17.
Using surplus production model packages of ASPIC(a stock-production model incorporating covariates) and CEDA(Catch effort data analysis),we analyzed the catch and effort data of Sillago sihama fishery in Pakistan.ASPIC estimates the pa-rameters of MSY(maximum sustainable yield),Fmsy(fishing mortality),q(catchability coefficient),K(carrying capacity or unexploited biomass) and B1/K(maximum sustainable yield over initial biomass).The estimated non-bootstrapped value of MSY based on logistic was 598 t and that based on the Fox model was 415 t,which showed that the Fox model estimation was more conservative than that with the logistic model.The R2 with the logistic model(0.702) is larger than that with the Fox model(0.541),which indicates a better fit.The coefficient of variation(cv) of the estimated MSY was about 0.3,except for a larger value 88.87 and a smaller value of 0.173.In contrast to the ASPIC results,the R2 with the Fox model(0.651-0.692) was larger than that with the Schaefer model(0.435-0.567),indicating a better fit.The key parameters of CEDA are:MSY,K,q,and r(intrinsic growth),and the three error assumptions in using the models are normal,log normal and gamma.Parameter estimates from the Schaefer and Pella-Tomlinson models were similar.The MSY estimations from the above two models were 398 t,549 t and 398 t for normal,log-normal and gamma error distributions,re-spectively.The MSY estimates from the Fox model were 381 t,366 t and 366 t for the above three error assumptions,respectively.The Fox model estimates were smaller than those for the Schaefer and the Pella-Tomlinson models.In the light of the MSY estimations of 415 t from ASPIC for the Fox model and 381 t from CEDA for the Fox model,MSY for S.sihama is about 400 t.As the catch in 2003 was 401 t,we would suggest the fishery should be kept at the current level.Production models used here depend on the assumption that CPUE(catch per unit effort) data used in the study can reliably quantify temporal variability in population abundance,hence the mod-eling results would be wrong if such an assumption is not met.Because the reliability of this CPUE data in indexing fish population abundance is unknown,we should be cautious with the interpretation and use of the derived population and management parameters. 相似文献
18.
A. Siddiqui 《Astrophysics and Space Science》1990,167(2):263-269
In the present paper, we have given a generalization of a unified study of the Voigt functionsK(x, y) andL(x, y) obtained by Srivastava and Miller (1987; Vol. 135, pp. 111–118) which play an important role in several diverse fields of physics-such as astrophysical spectroscopy and the theory of neutron reactions. Explicit expressions for these functions are given in terms of relatively more familiar special functions of one and two variables; indeed, each of these representations will naturally lead to various other needed properties of the Voigt functions. 相似文献
19.
A dynamic theory of hydrocarbon migration 总被引：1，自引：0，他引：1
This paper presents a new analysis of secondary migration of hydrocarbon that does not require capillary forces for trapping, but instead uses the method of characteristics and wave theory. The waves change speed and either reflect or refract (or partially reflect and partially refract) as they contact with layers of different flow capacities. Reflection of a certain wave from a boundary starts hydrocarbon accumulation below that boundary. The method is easy to use and conforms readily to graphical solution. For the sake of simplicity there is only two-phase flow. The application of this method gives new insights into the physics of migration and entrapment of oil. The method gives realistic times for oil accumulation and points to oil generation rate as the most sensitive variable. Oil and water densities, viscosities, and permeability are also important. We find that at the very small generation rates usually assumed the time required to develop a given column thickness is insensitive to the distance from the source rock. In general, the method also predicts a non-uniform saturation in the oil column caused by an interaction between buoyancy and viscous forces. Being based on the dynamic interactions of viscous and buoyancy forces, our theory is considerably at odds with hydrostatic approaches. We assume no capillary pressure, one-dimensional flow, and no regional groundwater flow, conditions which are not realized in actual migration. The theory should be viewed therefore as an end member of a more general theory; nevertheless, the largely graphical solutions give fundamental insights that are difficult to obtain by other techniques. 相似文献
20.
The effects of exposure to LC50 (10.5 mg/l) for 96 h and to a sublethal concentration (1.05 mg/l) of Sevin for 120 days have been observed on some haematological, biochemical and enzymatic parameters of Channa punctatus. The fish were hyperglycemic and hyperlactemic and the glycogen content of the liver and muscles decreased, but the lactic acid content of two tissues increased. The activity of hexokinase increased in the kidney, intestine, liver and muscles but decreased in the gills and brain. The activity of lactate dehydrogenase decreased in the kidney and intestine, and increased in the liver, muscles, brain and gills. The pyruvate dehydrogenase activity decreased in all the six tissues. Both the exposures produced a decrease in the succinate dehydrogenase activity of the liver. The enzyme activity decreased in the brain, gills and muscles after chronic exposure, whereas the kidney and intestine showed an elevation in enzyme activity. 相似文献