Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

K. P. Thrivikramji ¹, Swapan K. Ghosh ¹

Affiliations
1 Centre for Earth Science Studies, Trivandrum, IN

Abstract

Pyrite and glauconite are the only lauthigenic iron minerals present in Quilon Limestone. Pyrite occurs as fossil infiIlings and as disseminated grains having shapes like cubes and framboids. Four morphologically distinct types of glauconite have been identified, viz., capsulated pellets, globular pellets, microfossil casts and moulds. Glauconite occurs as fine sand sized aggregate of clay particles. The colour varies between different shades of green to greyish green.

The XRD pattern of glauconite pellets shows the presence of a mixed layer clay mineral assemblage of chlorite and montrnorillonite. The pyrite-, glauconite- and micrite-fabrics of the limestone show evidence of their formation in early diagenetic stages. Pyrite has formed in a neutral to alkaline pH condition in a localised reducing condition; glauconite also formed in a similar environment. However, overall environment was oxidising in a shallow and quiet inner shelf area.

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K. P. Thrivikramji ¹, M. Ramasarma ²

Affiliations
1 Centre for Earth Science Studies, Trivandrum-695 010, IN
2 Government College, Kottayam, IN

Abstract

Two structural facies viz., an upper flat-bed facies and a lower cross-bed facies are recognised in the outcrops along the Arabian sea coast. The geometry of the sand- stone body, the association of structural facies find bioturbation features imply that this sandstone formed in a beach-nearshore milieu. A relative fall of 4 to 5m in sea level is also proposed.

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G. K. Suchindan ¹, M. Samsuddin ¹, K. P. Thrivikramji ¹

Affiliations
1 Marine Science Division, Centre for Earth Science Studies, Trivandrum 695010, IN

Abstract

The coastal Zone of Kerala is characterised by typical broad strand plains and cliffed shoreline with or without a beach. A facsimile of such coastal settings have been identified between Mahe and Talapadi in northern Kerala. The strand plain consists of a series of sub parallel ridges formed by successive accretion of low narrow beach ridges parallel to the shoreline. The erosional and accretional behaviour of the beaches were monitored during a programme of field observation and survey during November 1980 to November 1981. In addition to the beach profiling at 64 survey locations, the breaker parameters and longshore currents were also monitored. It is estimated that 96.84m³/ linear meter of the beach has been eroded during the survey period.

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K. P. Thrivikramji ¹

Affiliations
1 University of Kerala, Trivandrum 695581, IN

Abstract

Beach profiles were surveyed twice in the year 1979, along transects placed approximately 10 km apart on the Laccadive sea shoreline, from Kanyakumari (Tamil Nadu) to Thalappadi (Kerala) - a distance of about 650km. Profile changes are analysed in the light of geomorphology, shelf width and gradient, wind data and ship-reported wave data. Cumulative and catastrophic shift of beach sediment during the sw monsoon of 1979 has been calculated. An apparent dichotomy exists between the beaches of northern Kerala (Malabar) and southern and central Kerala in that the beaches of Malabar are less severely eroded than those of Southern and Central Kerala.

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