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1.
N. P. Sukumaran 《Journal of Earth System Science》1994,103(4):489-497
Examined in this paper is the tentative history of the depositional flux of230Thxs (the unsupported fraction of230Th scavenged from the overlying water column), for the Late Quaternary period from a sediment core of the Central Indian Basin
(CIB). The measured depositional flux of230Thxs is found substantially higher than that of the possible theoretical flux from the overlying water column. Historical records,
reconstructed from the230Thxs chronology suggests that the depositional flux has varied considerably with time, reflecting an enhanced scavenging during
the Holocene and the preceding interglacial periods whereas, comparatively lower flux than the predicted one occurred during
the Last Glacial Maximum (LGM) period. The average ratio of the measured depositional flux to that of the predicted flux from
the overlying water column, indicates that the core site acts as a sink for230Thxs and based on the existence of bottom current activity; the230Thxs could be the result of focusing of younger sediments. The depositional index (Di) has also been calculated to quantify the
extent of lateral supply throughout the core with time. The estimated (Di) suggests that bottom focusing and feeble deposition
and/or winnowing processes had occurred and that the former was most prevalent during the Holocene and the preceding interglacials,
whereas the latter was observed at the LGM period. 相似文献
2.
Prabhin Sukumaran Dhananjay A. Sant K. Krishnan Govindan Rangarajan 《Journal of the Geological Society of India》2012,79(1):41-52
A high resolution quantitative granulometric record for site Uchediya [21°43′2.22″ N, 73° 6′26.22″ E; 10 m a. s. l.] gives
understanding towards accretion history of the late Holocene flood plain in the lower reaches of Narmada River. Two sediment
facies (sandy and muddy) and seven subfacies (sandy subfacies: StMS+FS+CS, SmFS+MS, SlFS+VFS, and StMS + CS; muddy subfacies: FmSILT+VFS+FS, FmSILT+VFS (O) and FmSILT+VFS (T)) are identified based on cluster analysis supplemented with sedimentary structures observed in field and other laboratory
data. Changes in hydrodynamics are further deduced based on various sedimentological parameters and their ratios leading to
arrive at a depositional model. 相似文献
3.
Prabhin Sukumaran C. Rajshekhar Dhananjay A. Sant K. Krishnan 《Journal of the Geological Society of India》2012,80(3):403-408
Storms from the Arabian Sea are the most significant meteorological feature in western India that brings extreme rainy days together with catastrophic flooding. The present study reports two such palaeo-storm horizons at 1.16 m and 3.2 m above the present day water level in the Narmada channel, 56 km inland based on sedimentology and foraminiferal records. Both the horizons show similar sediment facies and foraminiferal assemblage. The present findings instigate to look for such new sites and build palaeo-storm records for western India. 相似文献
4.
Dhananjay A. Sant Sudesh K. Wadhawan Rajinder K. Ganjoo Nathani Basavaiah Prabhin Sukumaran Sourabh Bhattacharya 《Journal of the Geological Society of India》2011,78(2):147-156
The paraglacial sequence in the Leh valley, Ladakh Himalaya preserves imprints of various processes active during deglaciation
in the late phase of Last Glacial. In present work, a high resolution sedimentological record generated for Spituk is presented
identifying aeolian episodes, mudflow events from Ladakh Range and debris flows extending from Zanskar Range across present
Indus River. Two temporal phases of water ponding within Spituk Sequence are also identified. The seismites recorded at various
stratigraphic depths and their association with the sediment facies signifies gravity induced process besides possible seismic
activity as an added phenomena. Linkage between paraglacial processes since Last Glacial to Recent is tracked and evaluated. 相似文献
5.
Hari Om Vats M. R. Deshpande O. P. N. Calla N. M. Vadher B. M. Darji V. Sukumaran 《Earth, Moon, and Planets》1996,75(2):127-133
In this article we report the peculiar oscillations in the intensity of microwave (4.15 GHz) emission seen during the impact of K fragment of comet Shoemaker-Levy 9 on July 19, 1994. The oscillations begin at 10h 13m 25s UT suddenly with a frequency of ~0.3 Hz and gradually the frequency of these oscillations increases to ~ 1 Hz. The oscillations are not due to local atmosphere or the radio interference from signals of geostationary satellite. They are intrinsic to the microwave emission from Jupiter during the impact of K fragment. Peak-to-peak amplitude of the oscillations is about 34% of the total microwave emission from Jupiter. If we assume that only 50% of the microwave emission is non-thermal and only the non-thermal emission suffered oscillations, then the oscillations are about 68% of the non-thermal emission from Jupiter. The observations also indicate that there are three continuum enhancements during this event and periodic oscillations almost all through. The third enhancement was the largest and during this enhancement there were some additional aperiodic variations. The aperiodic variations were of the order of few minutes and were possibly generated by the gravity waves. The periodic oscillations could be synchrotron emission modulated by the plasma oscillation in the outer magnetosphere. kg]Key words 相似文献
6.
7.
Naduvilaveettil Sukumaran Kalesh Chenycherri House Sujatha S. Muraleedharan Nair 《Journal of Oceanography》2001,57(1):29-36
Information on the distribution of dissolved Folin phenol active substances (FPAS) such as tannin and lignin in the seawater along the west coast of India is provided. Notable amounts of FPAS (surface concentrations: 80 g/l to 147 g/l and bottom concentrations: 80 g/l to 116 g/l) were detected in the seawater along the coast. The distribution pattern brings about a general depth-wise decrease. A seaward decrease was observed in the southern stations whereas reverse was the case in northern stations. A significant negative correlation was observed between FPAS concentration and dissolved oxygen in sub-surface samples. The appreciable amounts of FPAS detected in the coastal waters indicate the presence of organic matter principally originating from terrestrial (upland and coastal marsh) ecosystems in the marine environment. In this context, they may be used as tracers to determine the fate of coastalborn dissolved organic matter in the ocean and to determine directly the relationship between allochthonous and autochthonous organic matter. 相似文献
8.
Intercalated volcanic ash layers in two deep-sea sediment cores from the Central Indian Basin (CIB) are examined for the possibility of an in situ source of suboceanic volcanism. An in situ source has been predicated based on the bottom morphological structures and activation of seamounts during the geological past. The tentative correlation between depositional ages of the ash layer horizons and the period of global climatic cooling events reinforces the hypothesis that the suboceanic volcanic episode might have been initiated during the onset of glaciation. 相似文献
9.
10.
Intercalated volcanic ash layers in two deep-sea sediment cores from the Central Indian Basin (CIB) are examined for the
possibility of an in situ source of suboceanic volcanism. An in situ source has been predicated based on the bottom morphological
structures and activation of seamounts during the geological past. The tentative correlation between depositional ages of
the ash layer horizons and the period of global climatic cooling events reinforces the hypothesis that the suboceanic volcanic
episode might have been initiated during the onset of glaciation.
Received: 20 June 1995 / Revision received: 11 May 1998 相似文献