Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Rajiv Nigam ¹, Afimjit Mazumder ¹, Pravin J. Henriques ², Rajeev Saraswat ¹

Affiliations
1 Geological Oceanography Division, National Institute of Oceanography, Dona Paula - 403 004, IN
2 Geology Department, St. Xaviers College, Mumbai- 400 001, IN

Abstract

In order to study the response of benthic foraminifera, especially the rectilinear bi- and Tri-Serial benthic foraminifera (RBF) to oxygen-Depleted conditions from the Arabian Sea off central west coast of India, 103 surface sediment samples collected from a water depth of 15m to 3300m were studied for the benthic foramini feral content. A total of 383 recent benthic foraminiferal species were identified. Out of the total 383 benthic foraminiferal species identified in the study area, 65 species belong to 18 rectilinear bi- and tri-serial benthic foraminifer genera. The RBF abundance remains consistently high (>40%) between 90 m to ∼1200 m water depth. The intermediate depth zone of increased abundance of RBFs coincides with the prominent intermediate water oxygen minimum zone of the Arabian Sea (upper boundary ∼100 m and lower boundary ∼1000 to 1250 m). The other significant abundance (>40%) of rectilinear benthic foraminiferal forms is reported from the water depth range &#∼60 m with the maximum abundance reaching ˜78% at the water depth of 56 m. This zone has also been reported to be affected by seasonal severe Oxygen-Depleted conditions. Therefore, we propose that the increased abundance of RBF may be used as an indicator of Oxygen-Depleted conditions in the Arabian Sea. This benthic foraminiferal response to oxygen-depleted conditions, especially from the shallow water depths is significant as it can be applied to document the geologic extent of shallow water Oxygen-Depleted conditions that have been suggested as a consequence of spurt in the anthropogenic activities in the coastal regions.

Keywords

Oxygen Minima Zone, Rectilinear Benthic Foraminifera, Deep And Shallow Water OMZ, Central West Coast Of India.

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