Relationship between heavy mineral placer deposits and hinterland rocks of southern Kerala: A new approach for source-to-sink link from the chemistry

Authors and Affiliation: G.R. Ravindra Kumar & C. Sreejith, Centre for Earth Science Studies, Thuruvaikkal P.O., Thiruvananthapuram 695031, Kerala, India

Journal: Indian Journal of Geo-Marine Sciences, Vol. 39 (4), December 2010, pp. 562-571

Abstract: Beach sediments of the Kerala coast contain rich economically important heavy mineral deposits. Most previous studies have traced the source of heavy minerals to the Precambrian crystalline formations in the hinterland based on comparative mineral occurrences. No previous study has attempted to utilize petrological and geochemical characteristics and mineral chemistry of source rocks to effectively compare and determine sediment provenance. A clear knowledge on the composition of minerals from source and sink is important in precise recognition of source rock. Present study consists the geological, geomorphologic setting and mineralogical characteristics of hinterland rocks to trace their connection to placer deposits. It is recognized that garnet as the abundant heavy mineral in the placer sediments and in source rocks of different ages and petrogenetic affinity. Garnet composition varies between different source rock types due to its strong dependency on the bulk rock composition. In order to decipher the provenance we have compared major element composition of garnet in the source rocks and placer deposits. Compelling similarities in mineralogical and mineral chemical characteristics of garnets (Alm68Prp28Grs3Sps1) is noted between khondalites and placer sediments suggesting latter as major source rock for placer deposits of southern Kerala. The study demonstrates excellent potential of garnets in identifying placer mineral source.

Environmental Impact Assessment of sand mining from the small catchment river in the southwestern coast of India. Environmental Management

Authors and Affiliation: Sreedharan Sreebha and Damodaran Padmalal, Centre for Earth Science Studies, Thuruvaikkal P.O., Thiruvananthapuram 695031, Kerala, India

Journal: Environmental Management (2011), Vol. 47, pp.130-140.

Abstract: In the past few decades, the demand for construction grade sand is increasing in many parts of the world due to rapid economic development and subsequent growth of building activities. This, in many of the occasions, has resulted in indiscriminate mining of sand from in-stream and floodplain areas leading to severe damages to the river basin environment. The case is rather alarming in the small catchment rivers like those draining the southwestern coast of India due to limited sand resources in their alluvial reaches. Moreover, lack of adequate information on the environmental impact of river sand mining is a major lacuna challenging regulatory efforts in many developing countries. Therefore, a scientific assessment is a pre-requisite in formulating management strategies in the sand mining-hit areas. In this context, a study has been made as a case to address the environmental impact of sand mining from the in-stream and floodplain areas of three important rivers in the southwestern coast of India namely the Chalakudy, Periyar and Muvattupuzha rivers, whose lowlands host one of the fast developing urban-cum-industrial centre, the Kochi city. The study reveals that an amount of 11.527 million ty(-1) of sand (8.764 million ty(-1) of in-stream sand and 2.763 million ty(-1) of floodplain sand) is being mined from the midland and lowland reaches of these rivers for construction of buildings and other infrastructural facilities in Kochi city and its satellite townships. Environmental Impact Assessment (EIA) carried out as a part of this investigation shows that the activities associated with mining and processing of sands have not only affected the health of the river ecosystems but also degraded its overbank areas to a large extent. Considering the degree of degradation caused by sand mining from these rivers, no mining scenario may be opted in the deeper zones of the river channels. Also, a set of suggestions are made for the overall improvement of the rivers and its biophysical environment.

Evolution of the coastal wetland systems of SW India during the Holocene: Evidence from marine and terrestrial archives of Kollam coast, Kerala

Authors and Affiliation : D. Padmalal, K.P.N. Kumaran, K.M. Nair, B. Baijulal, Ruta B. Limaye, S. Vishnu Mohan, Centre for Earth Science Studies, Thuruvaikkal P.O., Thiruvananthapuram 695031, Kerala, India

Journal: Quaternary International, Volume 237, Issues 1-2, 15 May 2011, Pages 123-139

Abstract: Kerala coast in southwest India is endowed with an interlacing network of wetlands evolved during the Late Quaternary. The wetlands in the southern part of Kerala, especially around Kollam district, show antecedent characteristics and are incised on the Neogene sediments. These wetlands include 20.0–35.0 m thick deposits of Holocene sediments containing good archives of landform evolution and climate changes. Holocene sedimentation was initiated at about 8920 ± 110 BP and is represented mainly by sub-fossil wood/peat or carbonaceous clays. Subsequent deposition of brackish water to marine sediments occurred in the Middle Holocene. The proposed evolutionary model reveals that many wetland bodies including Sasthamkotta Lake, Chelupola Lake, Chittumalachira Lake and Kotta Lake were evolved from the proto-estuarine basins. The upper arms of the pre-Holocene Ashtamudi and Paravur estuaries were cut off due to progradation of alluvial sediments during the Holocene Climatic Optimum.