Conference program and abstracts - Coastal-Change.Org

High Resoluation Holocene Climatic Registers from the
Red Sands of South Coast of India
A.Vidyasakar ,S. Srinivasalu, Linto Alappat, P.Morthekai
ABSTRACT
The ubiquitous Teri deposits or red sands of semiarid-southern-coastal-
Tamil Nadu, chiefly noticed to occur from Tirunelveli to Kanyakumari ,
show unique shades of red ranging from yellowish red (5YR4.5/6) to dark
reddish brown (2.5YR ¾) and dark red (10R 3/6). The autochthonouscalcareous-rhizoliths,
chiefly noticed in Sattankulam, Eluvilai, Sayarpuram
and muttom teris, dominantly show a discordant relationship with primary
sedimentary structures and morphologies (size, shape and sense of
branching) reminiscent of calcified-roots, need a much warmer climate
(like the current climate) for their formation. Red sands were closely
examined using remote sensing, stratigraphy, Geochemistry,
sedimentology, optically stimulated luminescence (OSL) dating, and
magnetic susceptibility. Besides, teris can grouped into ITDs (inland teri
deposits, area= 33.0 km2) and CTDs (coastal teri deposits, area = 437.0
km2). 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
The red colour and matrix of authigenic clays (viz., kaolinite and illite in the
fine fraction), products of pedogenic weathering, do strongly point to a
wetter or
humid climate which enables release of red pigment (or now hematite)
by the chemical alteration (intrastratal solution) of iron bearing heavy
minerals like the opaque ilmenite, red almandine-garnet and pyroxenes
of the heavy fraction as well as authigenic formation of clays from
feldspar in the frame work grains and matrix. Five different Samples
location of samples were collected by trench sampling at highest of 12m
depth in muttom ,6.6m at servaikaranmadam, 7.4 m at thoopu villa, 3.5 m
at Katchanavilai, and 4.5 m at Idachivilai at 10cm interval the samples
have collected and have worked on it. Onset of sand aggradation as
early as ~25ka on the east and west coast and dune reddening was
favored by stability dune to humid climate at ~9ka and after ~4ka. The
sand aggradation in the west coast which is controlled by sand
availability from the on shore during late Pleistocene to early Holocene
was seized during transgression at ~8ka. The upper part of the section
shows two distinct intervals of humid events between 17 and 14ka, as
evidence from the enhanced MS values, OM and clay content in the soil.
The Fourth IGCP 588: PREPARING FOR COASTAL CHANGE 35