Benthic foraminifera living in Gulf of Mexico bathyal and abyssal sediments: Community analysis and comparison to metazoan meiofaunal biomass and density     

Joan M. Bernhard  Barun K. Sen Gupta  Jeffrey G. Baguley 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2617

Benthic foraminiferal biomass, density, and species composition were determined at 10 sites in the Gulf of Mexico. During June 2001 and 2002, sediment samples were collected with a GoMex box corer. A 7.5-cm diameter subcore was taken from a box core collected at each site and sliced into 1-cm or 2-cm sections to a depth of 2 or 3 cm; the >63-μm fraction was examined shipboard for benthic foraminifera. Individual foraminifers were extracted for adenosine triphosphate (ATP) using a luciferin–luciferase assay, which indicated the total ATP content per specimen; that data was converted to organic carbon. Foraminiferal biomass and density varied substantially (2–53 mg C m⁻²; 3600–44,500 individuals m⁻², respectively) and inconsistently with water depth: although two 1000-m deep sites were geographically separated by only 75 km, the foraminiferal biomass at one site was relatively low (9 mg C m⁻²) while the other site had the highest foraminiferal biomass (53 mg C m⁻²). Although most samples from Sigsbee Plain (>3000 m) had low biomass, one Sigsbee site had >20 mg foraminiferal C m⁻². The foraminiferal community from all sites (i.e. bathyal and abyssal locales) was dominated by agglutinated, rather than calcareous or tectinous, species. Foraminiferal density never exceeded that of metazoan meiofauna at any site. Foraminiferal biomass, however, exceeded metazoan meiofaunal biomass at 5 of the 10 sites, indicating that foraminifera constitute a major component of the Gulf's deep-water meiofaunal biomass.  相似文献   

Quantification and spatial distribution of pore-filling materials through constrained rock physics template and fluid response modelling in Paleogene clastic reservoir from Cauvery basin,India     

Prabal Shankar Das  Rima Chatterjee  Sumangal Dasgupta  Ranajit Das  Debjani Bakshi  Mukesh Gupta 《Geophysical Prospecting》2019,67(1):150-166

Sands belonging to Kamalapuram Formation of Paleocene-Eocene age are deposited in Cauvery basin as incised valley fill during a regressive cycle. Here we attempt to quantify the influence of diagenesis on pore-filling materials using rock physics template constrained by geohistory modelling. Primarily, porosity–velocity and acoustic impedance – the ratio of P-wave and S-wave velocity (V_P/V_s) cross-plots are used as rock physics templates. Rock physics template has efficiently quantified pore-filling materials namely; contact cement and non-contact cement. The estimated contact cement and non-contact cement are correlated with conventional petrophysical logs within the selected depth interval. Further, this correlation is used to interpret the composition of pore-filling materials. Shallower depth intervals (I and II) exhibit moderate non-contact cement (4–5%) and insignificant contact cement (1–2% approx.) depositions. However, deeper interval (III) records a significant amount of pore-filling materials amounting average of 12% non-contact cement and 4% contact cement. Pore-filling materials demonstrate a positive correlation with the depth of burial. The fluid response is substantially affected by the degree of diagenesis, composition and spatial distribution of pore-filling materials. Shallower depth intervals (1770–1786 m and 1858–1878 m) are relatively more sensitive to fluid changes as it is affected by insignificant contact cement. The depth interval 1770–1786 m shows class II (oil) and class III (gas) amplitude variation with offset anomalies. The sand occurring in depth interval 1858–1878 m demonstrates class IIP (oil) and II (gas) anomaly. The deeper interval (2118–2170 m) is comparatively stiffer and demonstrates class I amplitude variation with offset (oil and gas sand) anomaly.  相似文献   

International Association of Geomorphologists Newsletter No. 13 (2/1996)     

Avijit Gupta  Publication Secretary  IAG 《地球表面变化过程与地形》1997,22(5):507-509

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Dynamic soil–structure interaction effects on the seismic response of suspension bridges     

Manish Shrikhande  Vinay K. Gupta 《地震工程与结构动力学》1999,28(11):1383-1403

A stochastic approach has been formulated for the linear analysis of suspension bridges subjected to earthquake excitations. The transfer functions of various responses have been formulated while including the effects of dynamic Soil–Structure Interaction (SSI) via the use of the fixed-base modes of the structure. The excitation has been characterized by the ‘equivalent stationary’ processes corresponding to the free-field motions at each support and by an assumed coherency function between these motions. The proposed formulation considers the non-stationarity in the structural response due to sudden application of excitation by considering (i) the time-dependent frequency response functions, and (ii) the order statistics formulation for the peak factors in evolutionary response processes. The formulation has been illustrated by analysing the seismic response of the Golden Gate Bridge at San Francisco for two example excitations conforming to USNRC-specified design spectra. The significance of various governing parameters on the dynamic soil–structure interaction effects on the seismic response of suspension bridges has also been studied. It has been found that the contribution of the vertical component of ground motion to the bridge response increases with increasing soil compliance. Also, the extent to which the spatial variation of ground motion affects the bridge response depends on how significant the SSI effects are. Copyright © 1999 John Wiley & Sons Ltd.  相似文献   

Land use and land cover changes in Jahlma watershed of the Lahaul valley, cold desert region of the northwestern Himalaya, India   总被引：1，自引：1，他引：0  

Santaram S. OINAM Yashwant S. RAWAT R. S. KHOIYANGBAM KHWAI KPAM Gajananda Jagdish C. KUNIYAL S. C. R. VISHVAKARMA 《山地科学学报》2005,2(2):129-136

Land use and land cover changes that occurred during the period from 1991 to 2001 in the Jahlma watershed of the Lahaul valley, a cold desert region of the northwestern Himalaya, were evaluated using land use data and visual interpretation of IRS Satellite imageries. The results revealed that out of the six major land use forms within the watershed, land areas under agriculture, kitchen garden and settlement land were found increased, whereas a declining trend was recorded in areas under grassland, barren land and Salix plantation. The cultivated land within the watershed increased from 54.87 % （total of agriculture land, kitchen garden, grassland, barren land, Salix plantation and residential area） in 1991 to 56.89 % in 2OOl, corresponding to an expansion of 4.41 ha. On the other hand, the areas of grassland decreased from 31.41% in 1991 to 29.81% in 2001. Such a dramatic land use and land cover changes taking place within the 33 km^2 watershed area in a single decade deafly indicates the prevailing danger of land degradation and environmental deterioration in the region.  相似文献   

Intra-day variability of three Seyfert galaxies measured with XMM-Newton     

Ashutosh Tripathi  Paul Joseph Wiita  Alok Chandra Gupta  Min-Feng Gu  Mai Liao 《天文和天体物理学研究(英文版)》2019,(8)

We present and analyze the variability of three Seyfert galaxies on intra-day timescales. We have analyzed in a uniform manner the 38 longest( 30 ks) observations made for NGC 4051, MCG-06–30–15 and NGC 4151 by XMM-Newton between 2000 and 2015. The nuclei were quite active during essentially all of these observations and the overall X-ray fluxes(0.3–10 keV) varied by an order of magnitude. Most of the observations do appear to show characteristic timescales, estimated through their auto-correlation functions, ranging between ~2.9 ks and ~45.3 ks. The hard(2–10 keV) and soft(0.3–2.0 keV) bands are very well correlated but consideration of their hardness ratios shows that the sources typically soften during flares. We also provide new estimates of the central black hole masses for these three AGNs that support the hypothesis that Narrow Line Seyfert 1 galaxies have relatively small central black holes.  相似文献