Late Quaternary Halimeda bioherms and aragonitic faecal pellet-dominated sediments on the carbonate platform of the western continental shelf of India

Millennial/centennial-scale thermocline ventilation changes in the Indian Ocean as reflected by aragonite preservation and geochemical variations in Arabian Sea sediments

“…It is noteworthy that the majority of the needle clusters of this type are observed in the HE1 interval of MD76. Hence, they appear to resemble aragonitic fecal pellets as observed by Rao et al (1994) on the West-Indian shelf.…”

“…The needles of the aggregates or clusters closely resemble material described in various environments, including the Persian Gulf (Fü tterer, 2000), the deposits of a vast relict carbonate platform on the Western India shelf (Rao et al, 1994), sediments from the Bahamas (Macintyre and Reid, 1992) and deep-sea sediments from the Eastern Mediterranean Sea (Thomson et al, 2004;Reitz and de Lange, 2006). Most of the needle aggregates in HE1 sediments of MD76 show a combination of loose aragonite 1-3 lm needles and clusters of <2 lm diameter consisting of needles of 0.1-0.5 lm (Fig.…”

Bathymetric Techniques and Indian Ocean Applications

“…The average slope of the study area is 0.90 0 , whereas the slope towards the shallower depth is 0.61 0 , and towards the deeper side this slope changes over to 1.68 0 . Rao et al, (1994) have reported that the recent clay-rich mud overlies the inner part of this slope area while relict sand is abundant in the outer slope area. In this work, using multibeam data, set of pockmarks were observed close to NNW-SSE trending fault zone.…”

An insight into the “Fifty-Fathom-Flat” off India's west coast

“…Further west, the seafloor falls to about 100 m. The transition area between 60 m (inner shelf) and 100 m (outer shelf) water depth is very narrow and often occupied by limestone, coral fragments and coarse sands (Wagle and Veerayya, 1996). Wagle and Veerayya (1996) and Rao et al (1994) have also reported massive mound structures and several pinnacles of 1 to 6 m high (up to 14 m high in places) comprising algal Halimeda bioherms along a series of NNW-SSE ridges in the SE quadrant of the FFF. The non-skeletal (non-Halimeda) grains on the FFF are largely aragonitic in composition, having smooth and shiny surfaces, rounded to ellipsoidal in shape and are described as oolitic sand (Nair, 1970) or fecal pellets (Rao et al, 1994).…”

“…1a). The FFF, located roughly between 90 and 260 km from the coast, covers an area of more than 28,000 km 2 and comprises almost wholly of carbonate oolite and sand formed between the Eocene and early Holocene (Rao et al, 1994). Representing the outer shelf, the FFF (1 fathom=6 ft =1.83 m) seems to be receiving sediment from large rivers like the Narmada and Tapti, while the silt and clay carried by these rivers are arrested on the inner shelf.…”