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

P. Seralathan ¹, D. Padmalal ¹

Affiliations
1 Marine Geology Division, School of Marine Sciences, Cochin University of Science and Technology, Cochin 682 016, IN

Abstract

The Tertiary sequence begins with fossiliferous marl and is overlain by carbonaceous clay, china clay and laterite. The thin (3 cm thick), hard, compact duricrust layer, which is found interbedded within the carbonaceous clays, shows abnormal geochemical anomalies. Major elements such as Fe, Mn and Ca and the trace element Co show about 2-3 fold and 1-2 fold increase respectively in the duricrust than the upper and lower sections. However, the content of Na, K, Ni, Cu and organic carbon show an opposite trend. Cd does not show any marked variation along the profile. The CaCO₃ content is remarkably high in the duricrust and marl than the other layers. Fe and Mn contents are much higher in the laterite than china clay, other parameters do not show much variation. The high content of Fe, Mn, Ca and CaCO₃ and low Ni/Co ratio and organic carbon content in the duricrust layer indicate an oxidizing environmental condition which existed at the time of the formation of this layer, while the converse trend of these parameters in the carbonaceous clays indicate the prevalence of a reducing condition.

Keywords

Geochemistry, Pozhikkara Tertiary, Kerala Environment.

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D. Padmalal ¹, P. Seralathan ¹

Affiliations
1 Marine Geology Division, School of Marine Sciences, Cochin University of Science and Technology, Kochi 682 016, IN

Abstract

The tropical perennial muvattupuzha river and adjoining Vembanad estuary, Central Kerala, were surveyed for texture, organic carbon and heavy metals (Fe, Mn, Cu, Ni, Zn, and Cr) in suspended particulates and bed sediments. Sand is the dominant textural class in river, whereas mud, muddy sand and sand floor the estuarine substratum. Particulate organic carbon varies from 2.04-3.44% with a slight increase towards estuarine mouth. River sediments show low range of organic carbon (0.35 - 1.03%) while the estuarine sediments show 3-4 fold increase than that in the river. The concentration of Fe, Mn and Zn are in general higher in bed sediments than in suspended particulales. But Cu, Ni and Zn enrich in particulate phase. The overall variation of geochemical parameters is in general controlled by particle size as well as chemical desorption during estuarine mixing.

Keywords

Marine Geology, Muvattupuzha River, Vembanad Estuary, Kerala.

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P. Seralathan ¹, D. Padmalal ¹

Affiliations
1 Marine Geology Division, School of Marine Sciences, Cochin University of Science and Technology, Kochi - 682 016, IN

Abstract

The Muvattupuzha river and the Central Vembanad estuary have been studied mainly for grain size spectrum and textural parameters such as phi mean, standard deviation, skewness and kurtosis. In general, the grain size spectrum shows a marked gradation downstream. The observed variation is in consonance with the energy conditions controlled by the profile of the river as wellas the natural and man-made obstacles encountered in the river channel. In the estuary, the textural pattern is highly complicated owing to the fluctuation in the physico-chemical conditions prevailing in the system. Further, seasonal maintenance dredging activities by the Port authorities also have a considerable bearing on the sediment dispersal pattern of the estuary. The CM model worked out for the fluvial system perfectly agrees with the transportational and depositional regimes of the river and the estuary.

Keywords

Sedimentology, Muvattupuzha River, Vembanad Estuaty, Kerala.

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S. Rajendran ¹, P. Karthikeyan ¹, P. Seralathan ¹

Affiliations
1 Marine Geology Division, School of Marine Sciences, Cochin University of Science and Technology, Kochi - 682 016, IN

Abstract

Size specific abundance of heavy minerals (HM) in sediments of lower Bharathapuzha indicates an increase towards finer sizes, with the average maxima at ASTM +170. HM content in the bulk sample is similar to that of ASTM +60. Opaques, hornblende and pyroxenes are responsible for more than 90% variability. Garnet, monazite, zircon and sillimanite are least abundant. Hornblende, pyroxene and garnet are enriched in ASTM +60 but depleted in ASTM +230, whereas opaques show a reverse trend. HM content of bulk is similar to that of ASTM +60 and +120.

Heavy metal distribution has also been examined and the order of abundance is Fe>Mn>Ni>Cr>Zn>Pb>Cu>Cd. Bulk samples show the lowest content. Mud fraction is emiched in metals, i.e., more than five fold for Zn, Cu and around three fold for Ni, Cr, Mn and Fe. The difference of metal abundance between HM and mud fraction is only marginal for Ni and Pb. In HM, Cd, Cu and Zn content are very low whereas Cr, Mn and Fe are enriched. EF (Enrichment Factor) values of Cu, Zn, Cr and Mn are close to crustal abundance whereas Cd and to a small extent Pb show relatively high values possibly resulting from anthropogenic contributions.

Keywords

Geochemistry, Heavy Minerals, Bharathapuzha, Kerala.

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P. Seralathan ¹, M. S. Rajkumar ¹, V. Sunil Kumar ¹, N. Anandaraj ¹

Affiliations
1 Department of Marine Geology and Geophysics, Cochin University of Science and Technology, Kochi - 682 016, IN

Abstract

Vertical concentrations of salinity, Eh, pH, total alkalinlty, NO₂^-, NO₃^-,NH₄⁺, PO₄^3-,SiO₂, Fe, Mn, Na and K in interstitial water as well as sediment organic carbon and CaCO₃, from three different mangrove areas, bordering the Vembanad estuary, the largest backwater system along the southwest coast of India have been studied The selected three mangrove locations are not only kilometers a part but also differ vastly m physico-chemical environment themselves - namely a fresh water one (cores I and 2) a brackish (core 3) and a saline mangrove area (core 4) Relatively, lower Eh values are measured in fresh water mangrove sediments than the brackish/saline cores pH and K show a decreaseing trend with depth whereas alkalinity, NH₄⁺,PO₄^3-, Si0₂, Fe, Mn and Na ~ncreases ysternatlcally donward The lower limit of oxic zone in fresh water enviroment is very much compressed than in the brackish and saline regions, where a larger oxic zones preval NO₂^- and NO₃^- concentrations after an lnitial Increase (up to approximately 10 cm in cores 1 and 2) and (1 8 crn in core 3 and 4) decrease sharply lndicating nitrificatoon fo llVertical concentrations of salinity, Eh, pH, total alkalinlty, NO₂^-, NO₃^-,NH₄⁺, PO₄^3-,SiO₂, Fe, Mn, Na and K in interstitial water as well as sediment organic carbon and CaCO₃, from three different mangrove areas, bordering the Vembanad estuary, the largest backwater system along the southwest coast of India have been studied The selected three mangrove locations are not only kilometers a part but also differ vastly m physico-chemical environment themselves - namely a fresh water one (cores I and 2) a brackish (core 3) and a saline mangrove area (core 4) Relatively, lower Eh values are measured in fresh water mangrove sediments than the brackish/saline cores pH and K show a decreaseing trend with depth whereas alkalinity, NH₄⁺,PO₄^3-, Si0₂, Fe, Mn and Na increases systematically donward The lower limit of oxic zone in fresh water enviroment is very much compressed than in the brackish and saline regions, where a larger oxic zones preval NO₂^- and NO₃^- concentrations after an lnitial Increase (up to approximately 10 cm in cores 1 and 2) and (1 8 crn in core 3 and 4) decrease sharply lndicating nitrificatoon fo owed by denitnficatio PO₄^3-, Fe, Mn, NH₄⁺, K and alkalinity production are more in fresh water mangroves than brackish/ saline mangroves indicating gatherd degradation of organic matter under higher anoxic condition.

Keywords

Interstitial Water, Hydrochemistry, Mangroves, Vembanad estuary, Kerala.

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Girish Gopinath ¹, P. Seralathan ¹

Affiliations
1 Department of Marine Geology and Geophysics Cochin University of Science and Technology, Cochin- 682 016, IN

Abstract

The geochemical characteristics of groundwater in phreatic aquifer zone of laterites in the Muvattupuzha river basin, Kerala were evaluated during Pre-and Post-Monsoon seasons to assess its suitability for domestic and irrigation purposes Fifty-five water samples from dug wells in lateritic terrain were collected and analysed for pH, EC TDS, total iron, major cations and major anions. The results indicate that the groundwater except In zones having high content of total iron and low pH condition is fit for domestic usage. The hydrochemical facies diagram has revealed that the groundwaters of the basin have not much residential time within the country rock and hence not dynamic. The sodium adsorption ratio (SAR), residual sodium carbonate (RSC) and sodium percentage indicate heat the groundwater In general is good for irrigation purposes.

Keywords

Hydrochemistry, Phreatic Aquifer, Lateritic Terrain, Muvattupuzha River Basin, Kerala.

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