Written history's limitation becomes apparent when attempting to document the predecessors of extreme coastal events in the Indian Ocean, from 550-700 years in Thailand and 1000 years in Indonesia. Detailed ground-penetrating radar (GPR) surveys in Mahabalipuram, southeast India, complemented with sedimentological analyses, magnetic susceptibility measurements, and optical dating provide strong evidence of extreme wave events during the past 3700 years. The diagnostic event signatures include the extent and elevation of the deposits, as well as morphologic similarity of buried erosional scarps to those reported in northern Sumatra region. Optical ages immediately overlying the imaged discontinuities that coincides with high concentration of heavy minerals date the erosional events to 340?35, 350?20, 490?30, 880?40, 1080?60, 1175?188, 2193?266, 2235?881, 2489?293, 2450?130, 2585?609, 3710 ± 200 years ago. These evidences are crucial in reconstructing paleo extreme wave events and will pave the way for regional correlation of erosional horizons along the northern margin of Indian Ocean. © Indian Academy of Sciences.

Rajesh R. Nair

Department of Ocean Engineering

MADHAV K MURARI

C S VIJAYA LAKSHMI

ILYA BUYNEVICH

RON J GOBLE

P SRINIVASAN

S G N MURTHY

DESHRAJ TRIVEDI

SURESH CHANDRA KANDPAL

S M HUSSAIN

Coastal erosion

correlation

extreme event

ground penetrating radar

HEAVY MINERAL

LUMINESCENCE DATING

Magnetic susceptibility

OCEAN WAVE

optical method

Sedimentology

India

Indian Ocean

INDIAN OCEAN (SOUTHEAST)

KANCHIPURAM

Tamil Nadu

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Journal of Earth System Science

The refraction of the 2004 Indian Ocean tsunami waves caused drastic devastation along East coast of India, mainly in the area of investigation. Here, we appraise and integrate the sedimentary characteristics and microfossil studies of the area. The gigantic tsunami waves caused the landward fining of sediments that were carried as suspended load. Tsunami sediments have distinctive characteristics, like fine-to-medium grained sand, moderately to poorly sorted sediments which indicating sudden winnowing followed by tranquil flood. Positively skewed grain size distribution indicating unidirectional transport, and mesokurtic to platykurtic character implying poorly sorted single source origin. The species of benthonic foraminifers and ostracods reside in marine environment indicating shallow water origin of sediments. The onshore deposits are vertically divided into three depositional units interpreted from Ground Penetrating Radar (GPR) signatures-Unit 1 is a relatively continuous parallel layer indicative of calm environment; Unit 2 has paleochannels and burial scarps, seen as oblique reflections that might be indicative of an intense erosional environment; Unit 3 is interpreted as 2004 tsunami layer, has three subunits. Each main units have been separated by Heavy Mineral Concentrated (HMC) layers, deposited by continuous wave action (~ 20 cm) and by the tsunami (&gt; 30 cm) activity, evidenced by low magnetic susceptibility values at the bottom compared to the top of the HMC layers. GPR has been effectively utilized in this paper as subsurface imaging tool for the interpretation and reconstruction of stratigraphy, and also helped to unearth the erosional and depositional environments. © 2012 Springer Science+Business Media Dordrecht.

Journal of Coastal Conservation

Integrated approach of assessing sedimentary characteristics of onshore sand deposits on the Velankanni coast, Tamil Nadu, India: Sheds light on extreme wave event signatures

The East coast of India is subject to continuous changes by high energy events. We sought to assess the depositional conditions along the coast from the geophysical and sedimentological character of the dune sands of the Gopalpur and Paradeep coast of Odisha, and the Sagarnagar coast of North Visakhapatnam. Quartz layers of the heavy mineral-rich zone collected at a depth of ~2 m from the landward foot of the dunes in the Visakhapatnam and Odisha coast, gave the OSL age estimates as 1,050±50 and 260±10 years respectively, revealing that the age of the dunes in Visakhapatnam are older than those on the Odisha coast. Episodic high energy events have affected the coast. Evidence from ground penetrating radar data consists of three stratigraphic units. The upper unit consists of vague reflections, parallel to the ground in continuous manner, most probably formed by wind action. On the other hand, the middle layer shows high amplitude reflections of heavy mineral-rich massive layers, possibly the result of tsunami activity. The lower massive layer parallel to the ground surface shows a low reflection pattern. The GPR studies showed that the thickness of the heavy mineral layers is greater on the landward foot of the dune as compared to that on the seaward side. According to the grain size analysis, the dune is composed of both wind generated and tsunamigenic sediments. The scanning electron microscope studies revealed that the heavy minerals present in the dunes are mainly sillimanite, ilmenite, garnet, pyroxene, rutile, sphene, biotite, hornblende, zircon, monazite and magnetite. The study demonstrates the origin of sand dunes in different ages along the East Coast of India by the effect of various natural phenomena. © Springer Science+Business Media Dordrecht 2013.

Assessment of coastal dune characteristics using georadar imaging and sedimentological analysis: Odisha and Visakhapatnam, India

The 2004 Indian Ocean tsunami caused massive devastation and left a lasting impact along many of the major coastal regions in South Asia, including the coast of Tamil Nadu, a state in the southeastern tip of India. Following the event, sand deposits draped the low-lying areas and buried the muddy sediments of the coastal plain [Babu et al., 2007; Srinivasalu et al., 2007]. In addition, erosional features related to the tsunami, such as channels and scarps, have been observed along many parts of the coast (Figure 1a). This tsunami, along with a recorded history of intense monsoons, has highlighted the need for focused research on the role of extreme events in shaping the geological character of India's coastal plains.

Subsurface images shed light on past tsunamis in India

Journal of the Geological Society of India

Report on glaciogenic Talchir deposits from Koradi area, Nagpur district, Central India: Lithofacies and petrography

Geoarchaeology

Geoarchaeological evidence of a Chola-period tsunami from an ancient port at Kaveripattinam on the southeastern coast of India

Res: Anthropology and aesthetics

Books received, July 2010—April 2011

Granularity and textural analysis as a proxy for extreme wave events in southeast coast of India

Subsurface signatures and timing of extreme wave events along the southeast Indian coast

Journal	Journal of Earth System Science
Publisher	Indian Academy of Sciences
Open Access	No