Evidence of reworking and resuspension of carbonates during last glacial maximum and early deglacial period along the southwest coast of India

Abstract

A gravity core collected from the upper slope of southwest of Quilon at a water depth of 776 m (Lat: 8 • 12 263 N, Long: 76 • 28 281 E) was analysed for texture (carbonate free), calcium carbonate and organic carbon. Variation in silicic fraction seems to be controlled by silt, i.e., enrichment from 15 ka BP to 10 ka BP and then constant in Holocene. Below 15 ka BP, the silicic fraction gets depleted compared to the Holocene section with a minimum around 21 ka BP. Clay content remains nearly constant except in the Holocene where it shows an enrichment. Carbonate content of less than 63 micron when computed by subtracting coarse fraction content from the total carbonate suggests that the total carbonates are mainly concentrated in the finer fraction. All these carbonate phases show an inverse relationship with silicic fraction except in Holocene. Below 15 ka BP, CaCO 3 dominates in sediments comprising more than 65%, such an increase is also seen in the coarse fraction. Coarse fraction from these sections contains abundant nodular type aggregates encrusting small forams. This period is marked by a high sedimentation rate comparable to Holocene. These parameters suggest that the productivity and precipitation have increased in the Holocene due to the intensification of the southwest monsoon. During the last glacial maximum and early deglacial period the high sedimentation rate indicates redeposition of the carbonates from the existing carbonate lithofacies situated between Quilon and Cape Comorin probably due to the slope instability.

Glacial-interglacial productivity contrasts along the eastern Arabian Sea: Dominance of convective mixing over upwelling

“…This interpretation is also in consensus with the geochemical and isotopic study carried out near the area of investigation (Sarkar et al, 1993). In contrast, the considerable increase in the sedimentation rate along with the higher content of organic carbon and the increased silicic fraction in sediment deposited along the southwestern continental margin of India is attributed to the intense southwest monsoon during the Holocene (Verma and Sudhakar, 2006). Similarly, a significant increase in the clay mineral content in the southeastern continental margin sediment is explained by the increase in fluvial activity in the hinterland of the study area as a result of the intensification of southwest monsoon during the Holocene (Das et al, 2013).…”

“…In addition, information available from microfauna, stable isotopes of oxygen and nitrogen, and computation of paleoproductivity from modelling and application of transfer function have been discussed along with the impact of the Atlantic overturning circulation to understand the regional variations in paleoproductivity. The details of these investigations are given below (Sarkar et al, 1993(Sarkar et al, , 2000Cayre and Bard, 1999;Thamban et al, 2001;Pattan et al, 2001Pattan et al, , 2003Pattan et al, , 2005Pattan et al, , 2009Ivanova et al, 2003;Banakar et al, 2005;Guptha et al, 2005;Verma and Sudhakar, 2006;Singh et al, 2006Singh et al, , 2011Kessarkar and Rao, 2007;Schmittner et al, 2007;Narayana et al, 2009;Kessarkar et al, 2010;Das et al, 2013;Ishfaq et al, 2013;Naidu et al, 2014).…”

“…In contrast, the paleoproductivity scenario was found to have been different in the southeastern continental margin during the late Quaternary as there is fragmented and conflicting information (Sarkar et al, 1993(Sarkar et al, , 2000Pattan et al, 2001Pattan et al, , 2003Pattan et al, , 2005Verma and Sudhakar, 2006;Narayana et al, 2009;Das et al, 2013). For instance, Pattan et al (2001) traced the occurrence of the youngest Toba volcanic ash layer in a sediment core collected from the southwestern continental margin of India at 2300 m water depth.…”

Geomorphic response to sea level and climate changes during Late Quaternary in a humid tropical coastline: Terrain evolution model from Southwest India

“…Although many attempts have been made while addressing these changes [ 9 , 28 , 36 – 40 ], no systematic effort has been made in the sedimentary archives of southwest coast of India, especially in the northwestern part of the Trivandrum block between Achankovil and Thenmala lineaments/shear zones [ 41 ]. This section presents the results of the investigations carried out in the subsurface and surface sediments of the coastal lands between the Achankovil and Thenmala lineaments drained by the Pallikkal River.…”