Luminescence dating of fluvial and coastal red sediments in the SE Coast, India, and implications for paleoenvironmental changes and dune reddening

Abstract

The Holocene and late Pleistocene environmental history of the teri ('sandy waste' in local parlance) red sands in the southeast coastal Tamil Nadu was examined using remote sensing, stratigraphy, and optically stimulated luminescence (OSL) dating. Geomorphological surveys enabled the classification of the teri red sands as, 1) inland fluvial teri, 2) coastal teri and 3) near-coastal teri dunes. The inland teri sediments have higher clay and silty-sand component than the coastal and near-coastal teri, suggesting that these sediments were deposited by the fluvial process during a stronger winter monsoon around ≫ 15 ka. The coastal teri dunes were deposited prior to 11.4 ± 0.9 ka, and the near-coastal dunes aggraded at around 5.6 ± 0.4 ka. We; interpret that the coastal dunes were formed during a period of lower relative sea level and the near-coastal dunes formed during a period of higher sea level. Dune reddening is post deposition occurred after 11.4 ± 0.9 ka for the coastal teri dunes and after 5.6 ± 0.4 ka for the near-coastal teri dunes. Presence of microlithic sites associated with the coastal dunes suggest that the cultures existed in the region during 11.4 ± 0.9 ka and 5.6 ± 0.4 ka.

Chronology of red dune aggradations of South India and its Palaeo-environmental significance

“…Given that the lower part of the dune in this section (MT-III) could not be sampled, it is implicit that >10 m of underlying sand was deposited earlier. Radiocarbon ages of two aragonite land snail shells (Gardner, 1981) collected below the red sands in the east coast had given calibrated ages (Jayangondaperumal et al, 2012) between 31,244-28,694 cal yr BP and 26,162-24,081 cal yr BP, which provides an estimate of their antiquity to >30-9 ka. Loose sand from the upper part of section MT-III accreted during the last 500 a.…”

“…Two sections were sampled at the coastal dunes in the east coast. The eastern section at Neduvankurichi (SK-1) is equivalent to TT1 of Jayangondaperumal et al (2012), in which they obtained 11.4 ka for a sample at 2 m depth. This together with results from present study (9-6 ka; SK-1 in Fig.…”

“…1) have been studied for their colour, sedimentology, geochemistry, palaeoclimate, archaeology and economic significance (Chandrasekharan and Murugan, 2001;Gardner and Martingell, 1990;Gardner, 1981;Jayangondaperumal et al, 2012;Joseph et al, 1999;Joseph et al, 2002;Thrivikramji, 2005 andThrivikramji et al, 2008). The red coating of these sands is due to iron oxides formed by in-situ weathering of garnet (Gardner and Pye, 1981).…”

“…Though the environmental conditions for dune aggradation are understood, their chronometry remained unresolved, the exception being the recent work by Jayangondaperumal et al (2012). Earlier studies on absolute dating of red sands using luminescence dating (e.g., Singhvi et al, 1986 andZhang et al, 2008) have shown that this method provides robust ages.…”

“…Most coastal dunes in east and west coast show middle to late Holocene age (Alappat et al, 2011;Kunz et al, 2010), while the red dune sands are dated to Late Pleistocene (Jayangondaperumal et al, 2012). In the east coast, Jayangondaperumal et al (2012) reported that inland dunes of ages > 11 ka, are associated with lower sea level and the near coastal red sands were deposited during the high sea level at ~6 ka. The present study had the objectives to develop a chronology for these dunes using OSL dating along with an assessment of effects of reddening on bleaching and radiation dosimetry.…”