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

Abstract

Extreme wave events of 1000 and 1500 years (radiocarbon ages) have been recently reported in Mahabalipuram region, southeast coast of India. Subsequently, we carried out extensive sedimentological analysis in regions covering a total lateral coverage of 12 km with a new archeological site as the central portion of the study area. Twelve trenches in shore normal profiles exhibit landward thinning sequences as well as upward fining sequences confirming with the global signatures of extreme wave events. The sediment size ranges from fine-to-medium and moderately well sorted-to-well sorted, and exhibit positive skewness with platykurtic-to-leptokurtic nature. We now propose the abrupt winnowing or back and forth motion including unidirectional transport of these deposited sediments, which results in positive skewness. Textural analyses derived from scanning electron microscope studies (SEM) demonstrate the alteration produced, in the ilmenite mineral with vivid presence of pits and crescents with deformation observed on the surface due to extreme wave activities. This is further confirmed with the predominance of high-density mineral such as magnetite (5.2) and other heavy minerals in these deposits inferred the high-intensity of the reworking process of the beach shelf sediments.

Identification and characterization of tsunami deposits off southeast coast of India from the 2004 Indian Ocean tsunami: Rock magnetic and geochemical approach

“…The topography controls the sedimentation of tsunami deposits with the best preservation in depressions (Wassmer et al 2010). Various aspects of the 2004 IOT onshore deposits on the east and west coasts of India were reported by several researchers (Altaff et al 2005;Earnest et al 2005;Jayakumar et al 2005Jayakumar et al , 2008Kumaraguru et al 2005;Nagendra et al 2005;Neetu et al 2005;Narayan et al 2005;Srinivasalu et al 2009;Anilkumar et al 2006;Chaudhary et al 2006;Hussain et al 2006Hussain et al , 2010Mascarenhas 2006;Shanmugam 2006Shanmugam , 2012Yeh et al 2006;Babu et al 2007;Bahlburg and Weiss 2007;Mascarenhas and Jayakumar 2008;Pari et al 2008;Vijayalakshmi et al 2010;Jayakumar 2012). However, studies on offshore tsunami deposits in India are limited (Srinivasalu et al 2010;Jonathan et al 2012) and many case studies are necessary to develop a depositional model.…”

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

“…The recent paper , demonstrates the rich geological characteristics in the same area (granularity, texture and magnetic susceptibility variations) that is suggestive of the possibility of extreme wave events and is thus presently studied further to estimate whether high resolution subsurface signatures and timing of these deposits can be correlatable with reported diagnostic features in the same area reported by Vijayalakshmi et al (2010). Our study will test the interpretations of Vijayalakshmi et al (2010), who attributed textural and mineralogical properties of landward-fining sequences along this coastal region to extreme wave events.…”

“…Our study will test the interpretations of Vijayalakshmi et al (2010), who attributed textural and mineralogical properties of landward-fining sequences along this coastal region to extreme wave events.…”

“…A recent paper by Vijayalakshmi et al (2010) describes these transects, along with a detailed treatment of textural and mineralogical characteristics. This paper presents evidence for extreme wave events based on additional high-resolution geophysical images from adjacent sites, complemented with a new set of optical dates of subsurface event horizons.…”

Subsurface Images Shed Light on Past Tsunamis in India

“…Each disconformity coincides with a high concentration of heavy minerals in sediment cores Vijaya Lakshmi et al, 2010], the GPR response being due primarily to a high magnetite content (>10%) at these layers. These high heavy-mineral concentrations (HMCs) result from particles that marginally resist erosion because of their weight.…”