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Mascarenhas, Antonio
- Granulometric Analyses of Pelites Using a Sedigraph: Examples from a Volcano-Sedimentary Environment
Abstract Views :189 |
PDF Views:1
Authors
Affiliations
1 National Institute of Oceanography, Dona Paula, 403 004 Goa, IN
1 National Institute of Oceanography, Dona Paula, 403 004 Goa, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 42, No 4 (1993), Pagination: 392-404Abstract
This article presents granulometric data of pelites (less than 40 microns) of mixed composition from a volcano-sedimentary environment. The Sedigraph serves as an useful tool in the analyses of silt-clay fraction of marine sediments. A cumulative curve from 40 to 1 micron can be obtained in 20 minutes. Pelites analysed show wide variations in grain size characteristics with the median value oscillating between 22 and 3 microns. In general, two fine grain size facies, each showing significant variations, are deciphered. Parabolic facies represents coarse silts whereas logarithmic facies comprise medium to fine silts. The type of grain size curves largely depends on the abundance of carbonate and pyroclastic mineral content of individual pelites. As compared to total pelites, their decalcified fractions sometimes show a significant shift of the grain median towards finer sizes. The intricacies of grain size studies of pelites of mixed composition are described in this paper.Keywords
Sedigraph, Sedimentology, Pelites.- Significance of Peat on the Western Continental Shelf of India
Abstract Views :177 |
PDF Views:2
Authors
Affiliations
1 National Institute of Oceanography, Dona Paula-403004, Goa, IN
1 National Institute of Oceanography, Dona Paula-403004, Goa, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 49, No 2 (1997), Pagination: 145-152Abstract
Peat layers 2 to 30 cm in thickness, 22 to 46 m below present sea level, are found along the inner shelf of India, up to 27 km from the coast. They are rich in plant debris, organic carbon and sulfur. These organic-rich layers are not sedimentary deposits. Lack of favourable substrates, absence of sheltered habitats, high energy physical environments, and a very rapid sea level rise during early Holocene indicate an unfavourable paleogeography and adverse oceanographic conditions for mangrove development and in situ peat formation. On the contrary, significant siliciclastic minerals, lithogenous elements and type III kerogen suggest a continental origin of peat. Restricted thickness, limited lateral distribution, absence of matted structures and laminated deposition imply transport of organics. Anomalous ages of wood with respect to present sea level are evidences of sediment reworking. Hence, peats on the continental shelf are not transgressive deposits.Keywords
Economic Geology, Peat, Western Continental Shelf, India.- Sand Fences: An Environment-Friendly Technique to Restore Degraded Coastal Dunes
Abstract Views :184 |
PDF Views:2
Authors
Affiliations
1 National Institute of Oceanography, Dona Paula - 403 004, IN
1 National Institute of Oceanography, Dona Paula - 403 004, IN
Source
Journal of Geological Society of India (Online archive from Vol 1 to Vol 78), Vol 71, No 6 (2008), Pagination: 868-870Abstract
An experiment to rebuild a dune field is attempted at Miramar beach, Goa. Installation of sand fences, a simple, cheap and environment friendly method of inducing accretion of sand is proposed as a remedial management option.Keywords
Sand Fences, Coastal Dunes, Environment, Goa.- Technology Demonstration of a Novel Seabed Resident Event-Driven Profiling System
Abstract Views :241 |
PDF Views:79
Authors
Antonio Mascarenhas
1,
Nitin Dabholkar
1,
Jayu Narvekar
1,
Shivanand Prabhudesai
1,
Siddharth Ghatkar
1,
Sadaf Ansari
1,
Pramod Maurya
1,
Elgar Desa
1,
Anand Lokapure
1,
Surekha Nagvekar
1,
Gajanan Navelkar
1,
R. Madhan
1,
Fernando Vijayan
1,
Vidish Shetye
1,
Llewellyn Fernandes
1,
Sanjeev Afzulpurkar
1,
T. Suresh
1
Affiliations
1 National Institute of Oceanography, Dona Paula, Goa 403 004, IN
1 National Institute of Oceanography, Dona Paula, Goa 403 004, IN
Source
Current Science, Vol 120, No 4 (2021), Pagination: 622-627Abstract
The seabed resident event-driven profiling system (SREP) was deployed in the northeastern Arabian Sea for winter convention studies. SREP is an autonomous profiling system consisting of two parts: a stationary seabed unit and a positively buoyant tethered profiling unit (profiler). It offers a novel and optimized approach to profiling in coastal waters from close to seabed (14.63 m above seabed) to the sea surface. The seabed unit houses an underwater winch system, underwater acoustic modem, pressure sensor, low-power electronics, batteries and divinylcell hydraulic crush point foam for subsea applications. The profiler houses a suite of oceanographic sensors: conductivity– temperature–depth, DO, chlorophyll, PAR, underwater acoustic modem, low-power electronics, batteries and divinylcell hydraulic crush point foam for subsea applications. The underwater winch system on the seabed unit spools out and spools in the profiler throughout the water column. Data acquisition on the profiler is done during ascending. The profiler ascends gradually in the water column at an average velocity of 20 cm/s. The seabed unit and the profiling unit communicate using a pair of underwater acoustic modems operating at 18–34 kHz. SREP was developed to obtain time-series water column measurements of coastal waters during the summer monsoon season (June–September) when the sea wave and wind conditions are extreme, thus making it difficult to deploy profiling packages from the ship. A description of SREP and observations made during the field deployment are presented in this article.Keywords
Coastal Waters, Profiling System, Seabed Unit, Technology Demonstration, Winter Convention Studies.References
- Mascarenhas, A. et al., A seabed resident event driven profiling system for use in coastal waters. Indian patent filed on 19 January 2015 (application No. 158/DEL/2015).
- Inall, M., Meldrum, D., Provost, P. G., Mercer, D. J. L., Griffiths, C., Peppe, O. C. and Vassie, I., HOMER: early results from a novel seabed-resident water column profiler. In OCEANS’05, IEEE Oceanic Engineering Society. Conference Proceedings, 2005, vols 1 and 2, pp. 1252–1255.
- Barnard, A. H. et al., The coastal autonomous profiler and boundary layer system (CAPABLE). In OCEANS’10, IEEE Marine Technology Society, Conference Proceedings, 2010, pp. 1–7.
- Send, U. et al., SeaCycler: a moored open-ocean profiling system for the upper ocean in extended self-contained deployments. J. Atmos. Ocean. Technol., 2013, 30(7), 1555–1565.
- Prandke, H. and Stips, A., Microstructure profiler to study mixing and turbulent transport processes. In OCEANS’98, IEEE Oceanic Engineering Society. Conference Proceedings (Cat. No. 98CH36259), 1998, vol. 1, pp. 179–183.
- Pinkel, R. et al., The wirewalker: a vertically profiling instrument carrier powered by ocean waves. J. Atmosp. Ocean. Technol., 2011, 28(3), 426–435.
- Prasanna Kumar, S. and Prasad, T. G., Winter cooling in the northern Arabian Sea. Curr. Sci., 1996, 71, 834–841.