Does Glacial-Interglacial Transition Affect Sediment Accumulation in Monsoon-Dominated Regions?     

Dharmendra Pratap SINGH  Rajeev SARASWAT  Dinesh K. NAIK 《《地质学报》英文版》2017,91(3):1079-1094

The spatio-temporal changes in sedimentation rate along the continental margin of the monsoon-dominated eastern Arabian Sea during the last 24 kyr have been estimated from a compilation of 58 radiocarbon dated cores, in order to understand the effect of glacial-interglacial variation on sedimentation. The sedimentation rate has been computed for four-time slices, viz. the last glacial maximum, glacial-interglacial transition, early Holocene and late Holocene. We report that the average sedimentation rate in the slope to the abyssal region of the entire eastern Arabian Sea, although higher during the Holocene as compared with that during the last glacial maximum and glacial-interglacial transition, does not significantly vary during all four-time intervals. The sedimentation rate during any particular time interval, however, varies from core to core, thus indicating zonal changes. We report four zones of relatively high sedimentation rate, viz. the northeastern Arabian Sea, the region off the Gulf of Khambhat, the region off Goa and Mangalore, and off the southern tip of India. We suggest that a complex interaction of land-ocean-atmospheric processes controlled sedimentation rate in the eastern Arabian Sea during the last 24 kyr in such a way that the average sedimentation rate does not vary significantly, even during highly contrasting climatic conditions.  相似文献   

How will Benthic Foraminifera Respond to Warming and Changes in Productivity?: A Laboratory Culture Study on Cymbaloporetta plana     

KURTARKAR R. Sujat  SARASWAT Rajeev  KAITHWAR Amrat  NIGAM Rajiv 《《地质学报》英文版》2019,93(1):175-182

Anthropogenic activities are likely to cause global warming. Global warming will affect marine productivityand thus food availability for marine organisms. Both the seawater temperature and food availability affect benthicforaminifera, the most abundant marine calcareous microorganisms. Therefore, a laboratory culture experiment wasconducted on Cymbaloporetta plana to understand the coupled effect of temperature(25°C, 27°C, 30°C) and food(102±5,203±9, 305±14, 407±18, 508±23 diatom cells). At all temperatures, growth increased with increase in food. The specimenssubjected to 27°C temperature attained the maximum growth and those subjected to 25°C were the smallest. All specimensfed with 508±23 cells reproduced, 0 irrespective of temperature. Of all the specimens without food, 40% at 27°C and 20% at25°C reproduced, whereas specimens subjected to 30°C did not reproduce. The 100% rate of reproduction at 27°C suggeststhat it is the optimum temperature for growth and reproduction. All the specimens at 30°C and without additional food,died, whereas at 25°C and 27°C, the mortality rate was 80% and 60%, respectively. The limited growth and reproductionwith decreasing food clearly indicates that food availability also controls the growth and reproduction of shallow waterbenthic foraminifer C. plana. Therefore, warming coupled with decreasing productivity is likely to severely affect thegrowth and abundance of shallow water benthic foraminifera.  相似文献   

Soil—landscape relationship of Hissar District using aerial photo — interpretation technique     

R. L. Ahuja  V. N. Garalapuri  M. L. Manchanda  B. K. Suneja  B. S. Sangwan 《Journal of the Indian Society of Remote Sensing》1979,7(2):39-44

Soil survey of Hissar district (Haryana) covering total area of 6,331 sq. kms. was carried out using the aerial photographs of 1 : 25,000 scale. A detailed physiographic legend was prepared and boundaries were confirmed in relation to soil. Soil-landscape relationship was established during the course of study. Four major physiographic units were identified in the area : i. e. i) Aeolian plain, ii) Alluvial plain, iii) Drishdawati flood plain, iv) Ghaggar flood plain. Each of the major unit was sub-divided on the basis of photo elements, tone, texture, erosion, parcelling etc. The soils of the sand dunes/ Bars are classified as Typic Torripsamments/Ustipsamments; plain-Typic, Camborthids/Calciorthids/Ustrochrepts; basins-Aquic Ustochrepts and salt affected plain-Aquic Natrustalfs.  相似文献   

Horizontal soil-water intake through a thin zone of reduced permeability     

L.R. Ahuja  D. Swartzendruber 《Journal of Hydrology》1973,19(1):71-89

One-dimensional, horizontal soil-water absorption through a thin zone of constant nonzero hydraulic resistance is examined theoretically and experimentally. Mathematically, this involves a numerical solution, as well as a similarity reduction of the problem for early to intermediate times. The flow equations are transformed by introducing a dimensionless parameter, which enables the solution for any value of thin-zone resistance to be obtained from the solution for a given known thin-zone resistance. At the inlet boundary between the thin zone and the soil column, the soil-water content increases with time to approach the saturated value. The cumulative absorption of water by the soil column increases more than proportionally with the square root of time for early and intermediate times, and approaches a square-root-of-time proportionality at large times. For both the soil-water content at the inlet boundary and the cumulative water absorption by the soil column, simple expressions arise from the similarity-reduction analysis, which is based on specific functional forms of the soil-water diffusivity and suction head. For early to intermediate times of flow, the similarity-reduction analysis describes adequately the calculated numerical-solution flow data for Yolo soil, as well as the measurements obtained experimentally on Salkum silty clay loam.  相似文献   

A terrain evaluation using remote sensing and gis—case study of neyyar wild life sanctuary, Kerala     

D. S. Suresh Babu  B. K. Jaya Prasad  V. S. Rajeev 《Journal of the Indian Society of Remote Sensing》1999,27(4):253-267

A multi-thematic analysis based on different physical factors has been adopted to generate integrated maps on erosion proneness as well as on critical slope under a GIS platform for terrain evaluation. This spatial data on erosion proneness has demonstrated that 17.62 km² area, out of the 140 km² in the catchment zone, needs careful attention for ecorestoration. In the critical slope map four land stability classes have been demarcated. The area represented as Unstable and Moderately-stable is found to be important for slope stability problems. Temporal change in the drainage network over a period of four decades as well as the extent of loss in the perennial status of tributaries have been recorded to evaluate the landform changes. A catchment treatment plan has also been suggested.  相似文献   

Initial results of bio-potential signal (Seismic Electric Signal) related to seismic activities     

Vinod Kushwah  Rudraksh Tiwari  Mulayam S. Gaur  Rajeev K. Tiwari 《Acta Geophysica》2013,61(4):935-949

In recent year, there has been growing interest in the possible use of electromagnetic observations to study earthquakes and possible precursors prior to seismic activity, in response to the success in United States, Japan, Russia, China, and other countries using seismo-electromagnetic methods. We have established a new experimental setup (i.e., biopotential sensor) in Farah region (geographic coordinates: 27.17°N, 77.47°E), Mathura, India. The setup has started operating and analyzed the data since November 2011. The data have been tested by various methods and a good correlation with seismic events was found; thus, a real-time analysis from 21:00 p.m. through 8:00 a.m. every day was initiated. First, we recorded the amplitude enhancement in bio-potential and found positive correlation with seismic activities (near Delhi and Rajasthan) and analyzed the data with solar flares and magnetic storms during the same period, finding a negative correlation of these events. The studies of these events are in progress with statistical analysis of the data. We chose the observing site in Farah region because this region is well known for being a site of a conductive channel of seismic activity.  相似文献   

Developing Spectral Library of Major Plant Species of Western Himalayas Using Ground Observations     

K. R. Manjunath  Amit Kumar  Mehra Meenakshi  R. Renu  S. K. Uniyal  R. D. Singh  P. S. Ahuja  S. S. Ray  Sushma Panigrahy 《Journal of the Indian Society of Remote Sensing》2014,42(1):201-216

  相似文献   

Seasonal variation in the deformation rate in NW Himalayan region     

D. D. Khandelwal  Vineet Gahalaut  Naresh Kumar  Bhaskar Kundu  Rajeev Kumar Yadav 《Natural Hazards》2014,74(3):1853-1861

We report GPS measurements of continuous observations from the multi-parametric geophysical observatory (MPGO) at Ghuttu, Garhwal Lesser Himalaya. Other than the evidence of secular motion depicting strain accumulation due to locking of the underneath seismically active detachment, measurements at Ghuttu show annual variation of ±4 mm on horizontal component. Such variations are more prominent in the north coordinate and do not directly correlate with the meteorological parameters such as variations in rainfall, water table, and atmospheric pressure measured at the MPGO observatory. These variations are also not the artefact of data processing and network. They correlate with the water load storage in the Ganga plains, with minimum in displacement coinciding with the maximum storage of water in Ganga plains immediately after the monsoon and vice versa. Such variations also appear to cause annual variation in the low-magnitude earthquake frequency in the Himalayan region, being relatively more in the winter period.  相似文献   

Toward a greenhouse equivalence index: The total exposure analogy   总被引：1，自引：0，他引：1  

Kirk R. Smith  Dilip R. Ahuja 《Climatic change》1990,17(1):1-7

Work supported by Office of Policy Analysis, U.S.E.P.A.  相似文献   

Abundance and Ecology of Endemic Asterorotalia trispinosa from the Western Bay of Bengal: Implications for its Application as a Paleomonsoon Proxy     

Rajeev?SARASWAT  Manumalenki?MANASA  Thejasino?SUOKHRIE  Mohammad?Syed?SAALIM  Rajiv?NIGAM 《《地质学报》英文版》2017,91(6):2268-2282

A total of 97 surface sediment samples were collected from the continental shelf and slope of the western Bay of Bengal to assess the potential application of Asterorotalia trispinosa as a paleomonsoon proxy. The relative abundance of living as well as total (living and dead) A. trispinosa ranges from being absent to a maximum of ~31%. The highest abundance of A. trispinosa is close to the outfall region of the Ganga-Brahmaputra Rivers and decreases away from the river mouths. Contrary to that, A. trispinosa is rare in front of both the Cauvery and Pennar river outfall regions, in the central part of the western Bay of Bengal. The living A. trispinosa abundance is the lowest in between two major river systems, viz. Ganga-Brahmaputra-Mahanadi and Krishna-Godavari. The relative abundance of both the total and living A. trispinosa is strongly positively correlated with ambient seawater temperature, and negatively correlated with %Corg and salinity. Based on the spatial distribution, we conclude that A. trispinosa is stenohaline in nature, rather than euryhaline, and further that the increased relative abundance of A. trispinosa indicates warmer and only marginally hyposaline environment. Even though the ecological preference of A. trispinosa suggests it as a potential paleomonsoon proxy, the restricted distribution implies limited application.  相似文献