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Sachin Kumar Tripathi
Geological Survey of India
Earth & Planetary Sciences

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Channel Controlled Foraminiferal Distribution off Bakkhali, West Bengal, India Sachin Kumar Tripathi; Resmi S.; Satyendra Baraik; Debasis Sengupta; Amitava Lahiri
BULLETIN OF THE MARINE GEOLOGY Vol 33, No 2 (2018)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (4941.68 KB) | DOI: 10.32693/bomg.33.2.2018.557

Abstract

Study area is situated 8 km south of the Bakkhali Island, West Bengal of India and its subaqueous environment influenced by the fluvial processes such as Hooghly River in west and its distributary like Muri Ganga in the centre and Saptamukhi River in the east. To understand the submarine behavior of these channels and associated meiobenthos, total of 28 sediment samples have been studied in detail. The study reveal that a total of fifteen species of recent benthic foraminifera belonging to 13 genera under 11 families were present and their distribution mainly controlled by channel morphology and sediment character. Based on the distribution of these benthic foraminiferal species, two assemblages have been identified. First assemblage, observed within the Hooghly and Muri Ganga channel, where salinity is comparatively low and sediment is mainly dominated by silt and clay. The most dominating benthic foraminifers of this assemblage are Ammobaculites agglutinans, Cribrostomoides jeffreysii and Asterorotalia trispinosa. Whereas, second assemblage mainly comprise of A. trispinosa, Ammonia beccarii, Asterorotalia spp., Elphidium excavatum, Elphidium crispum and Ammonia tepida noticed over the sand bars and adjoining shallow area. Keywords: channel morphology, Muri Ganga, Hooghly, sand bar
Genesis and Morphotectonic Characterisation of Crescent- Shaped feature from Alcock Rise, Andaman Sea Sachin Kumar Tripathi; Resmi Sathikumar; Jishnu Balagangadharan Kaustubhakumari; Priyanka Dey Guha; Soibam Ishwarchandra Meitei
BULLETIN OF THE MARINE GEOLOGY Vol 34, No 2 (2019)
Publisher : Marine Geological Institute of Indonesia

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (9302.597 KB) | DOI: 10.32693/bomg.34.2.2019.626

Abstract

Study of 98 crescent shape depressions over Alcock Rise, Andaman Sea were reported for the first time in between water depth -500 and -2000 m using multibeam swath bathymetry data. These gigantic depressions have crescent length (CL) varies from 600 to 3800 m and width (CW) varies from 200 to 2500 m with an average central depression of 500 m. Detailed parametric characterization reveals that slope and axial ratio of these crescentic structures have no direct relationship with general shape and steepness of their escarpment. Moreover, spatial distribution of these structures show a clustering of elongated crescent with higher crescent length to width ratio in NW margin of Alcock Rise compare to centre. This change in shape from open elliptical to semicircular depression probably suggests that earlier formed open crescents were modified at later stage to semicircular depressions. As observed in the seismic data, the formation of the crescentic depressions were initiated by the normal fault in-association with major dextral transform fault and subsequently its geometry was modified by local transpression along with seismicity induced slumping and bottom current scouring from the weaker zones. So, tectonics and bottom current activity provides simpler explanation for the formation of crescentic structure over Alcock Rise.Keywords: Crescentic depression, Alcock Rise, Swath bathymetry, Bottom current, Normal fault.
Co-Authors Amitava Lahiri Debasis Sengupta Jishnu Balagangadharan Kaustubhakumari Priyanka Dey Guha Resmi S. Resmi Sathikumar Satyendra Baraik Soibam Ishwarchandra Meitei