Clay Minerals Distribution of Beach Sediments of ...

International Journal of Earth Sciences and Engineering ISSN 0974-5904, Vol. 04, No. 05, October 2011, pp. 891-895

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Clay Minerals Distribution of Beach Sediments of Tirumalairajanar Coast, TamilNadu East Coast of India S. VENKATRAMANAN, T. RAMKUMAR and ANITHA MARY. I Dept of Earth Sciences, Annamalai University, Annamalainagar- 608002 Tamil Nadu, India Email: [email protected], [email protected], [email protected] Abstract: Spatial distribution of the clay minerals shows considerable variation along 11 km stretch of the beach sediments of Tirmalairajanar coast. The clay mineral assemblage consists mainly of chlorite, kaolinite, montmorillonite gibbsite and very scarce illite. The clay from the sediments has been separated and studied for mineral identification using X-ray diffraction (XRD) analysis. XRD analysis of the samples treated with Ca and K, glycolated, and heated at various temperatures shows well-developed peaks of chlorite, illite, kaolinite, montmorillonite and gibbsite. An attempt has been made to decipher the origin of clay minerals along the coast of Tirumalairajanar. Keywords: Clay minerals, XRD, Tirumalairajanar coast, east coast of India 1. Introduction:

3. Material and Methods:

Clay minerals of beach sediments have been used widely as a first order guide to the source, environment and the transport paths of fine grained sediments. (Grim, 1988, Biscay,1965, Griffin. et.al, 1968 and Hashimi and Nair, 1989). Variation in clay mineral abundance, therefore, is a tool for deciphering sediment sources and transport vectors to an area.In this study, the spatial distribution in the clay minerals within this area to determine the relative influence of adjacent land geology and climate on the dispersal and distribution of clay minerals, and to identify the sources of sediments in this region.

Beach sediment samples were collected during 2010 (September) using a plastic spatula from 8 stations. Clay mineral composition was determined by X-ray diffractometry using the so-called oriented clay slide method and an analytical protocol based on Holtzapffel (1985). For each sample, organic matter was removed by means of with H2O2 (20 volumes), followed by washing with distilled water and centrifugation. The samples were then decarbonated with HCl (10%), and washed with distilled water followed by several centrifugations until the pH was neutral. Clay particles were obtained according to Stokes’ law: each sample was stirred with distilled water in a bottle and then allowed to settle for 1 h 40 min. The top 2 cm of the suspension was then pipette off and centrifuged, and spread to make the oriented clay slide. Clay mineral samples were analysed under air-dried conditions, under ethylene glycol-solvated conditions, and after enough heating to collapse any expandable layers. The air dried oriented clay slide was immediately analysed using an X-ray diffractometer. The clay slide was then exposed to ethylene glycol vapour in a desiccator for 24 h, and subsequently reanalysed. Another slide was treated by heating at 540 C for 3 h 30 min and

2. Study Area: The study area (Fig.1) forms part of Tirumalairajanar coast. It falls between the latitude N 11°00’00’’ to 10°50’00’’and longitude E 79°40’00’’ to 79°50’00’’ and forms part of survey of India Toposheet No 58M/13 and 16 on 1:50,000 scale. The Cauvery, Arasalar, Tirmalarajanar, Vellar, Adappar, Vettar and Vedaranyam canals are the main rivers flowing in this area and debauches in to the Bay of Bengal. The study area is surrounded by Tanjore district in the west, Cuddalore district in the North, Palk straight in the South and Bay of Bengal in the east.

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S. VENKATRAMANAN, T. RAMKUMAR and ANITHA MARY. I

analysed. The X-ray diffractometer used was an PANalytical X’Pert MRD equipped with a Co target operating at 30 kV/40 mA. The relative abundance of major clay minerals was semi quantitatively determined by peak area on d001 reflections, on ethylene glycol diffractograms. This method was adapted

from Holtzapffel’s (1985) and took ground noise into account (Dunoyer de Segonzac, 1969). Test runs revealed an average error of _5%. Major clay minerals like kaolinite+chlorite, illite, montmorillonite and gibbsite were identified from reflection peaks.

Figure 1: Location Map of the Study Area 4. Results and Discussion: Clay minerals that are identified in this work are kaolinite, chlorite, montmorillonite, illite and gibbsite. As the diffractograms in Fig. 2 and 3(a, b, c & d) show, distribution of clay minerals in the Tirumalairajanar coast. There are no significant regional variations in the lithology or climate of the adjacent land mass and reported soil and estuarine clay mineralogy (Nair, 1976, Varghese and Aiyer, 1980) is markedly different from the clay minerals observed in the study area. The main clay minerals were chlorite and montmorillonite, this peak indicating its dominance and abundance over other minerals. It should be noted here that geologically the Tirumalairajanar coast

comprises of quaternary sedimentary formation of ferruginous laterite. A comparative study of the quantative values of clay minerals shows that chlorite is the dominant mineral in four stations (S5,S6,S7,S8) and followed by montmorillonite, illite, kaolinite and gibbsite. Chlorite concentration high in the southern part of the study area. In general chlorite is considered to be a common mineral of detrital origin and a product of intense weathering in dry conditions. As such, it is difficult to establish any trend or interrelationship of clay minerals in various units; however, their peak values show that chlorite and montmorillonite are the two most dominant of all the minerals, as well as


Clay Minerals Distribution of Beach Sediments of Tirumalairajanar Coast, TamilNadu East Coast of India for the entire area, whereas kaolinite, illite and gibbsite have almost uniform trends in all the stations. In general, illite is considered as a detrital clay and derivative of acidic crystalline and sedimentary rocks (Biscaye, 1965, Windom, 1976). It is common in marine environment; however, its in situ origin has no evidence. In the recent set-up, illite is noticed to be a characteristic mineral of all the stations. Similar evidence of the sediment source is also suggested by the presence of the laterite granules. (Thiagarajan, 1980, Dubrulle, et. al. 2007). It is clear from this study that small quantity of illte is being released from the catchment area to the Tirumalairajanar and Arasalar rivers. Illite therefore must have originated from the arigillaceous sedimentary rocks and also illite observed at station 4 and 5 it may be attributed to the formation of this mineral

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from montmorillonite. Montmorillonite converts to illite by absorbing more potassium ions from saline waters (Mohan and Damodaran, 1992). The kaolinite is distributed in all the stations from north to south. Basically, the kaolinite composition, i.e. Al2SiO5(OH)+ can be formed by any aluminium silicate by weathering, provided the K+, Na+, Ca++, Mg++ and Fe++ should easily leach from the parent rock. Feldspar, particularly rich in K+ and Na+, an abundant constituent of sedimentary rocks, apparently yields kaolinite after weathering and leaching away of K+ and Na+, mainly under the influence of groundwater (Keller, 1970). Therefore, it is possible that temperature variations within the limits of the prevailing climatic condition of the study area might have played a significant role in the formation of kaolinite through chemical weathering.

Figure 2: X-Ray Diffractograms of Representative Samples along the Length of the Coast (A, B, C and D)


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S. VENKATRAMANAN, T. RAMKUMAR and ANITHA MARY. I

Figure 3: X-Ray Diffractograms of Representative Samples along the Length of the Coast (A, B, C and D) 5. Conclusions: This survey has allowed us to determine clay minerals in beach sediments in Tirumalairajanar coast. The distribution patterns of kaolinite, chlorite, montmorillonite, illite and gibbsite, the clay minerals produced due to chemical weathering of the sedimentary rocks. The increased contents of chlorite and montmorillonite in the beach sediments are prostrated to mainly from a contribution of the Tirumalairajanar and Arasalar rivers via the Bay of Bengal. Acknowledgements: The authors acknowledge the valuable suggestions given by Dr. D.Venkat Reddy and Editor in- Chief which greatly helped in the final presentation of the paper. References: [1] Biscaye, P. E., 1965. Mineralogy and sedimentation of recent deep-sea clay in

Atlantic Ocean and adjacent seas and oceans. Geol. Soc. Am. Bull., 76, 803– 832. [2] Dubrulle. C., P. Lesueur, D. Boust, O. Dugue, N. Poupinet, and R. Lafite., 2007. Source discrimination of finegrained deposits occurring on marine beaches: The calvados beaches (eastern bay of the Seine, France). Estuarine, Coastal and Shelf Science, 72, 138-154. [3] Dunoyer de Segonzac, G., 1969. Les mine´raux argileux dans la diagene`se, passage au me´tamorphisme. Me´moires du service de la carte ge´ologique d’Alsace et de Lorraine 29, 320. [4] Griffin, J.J, Windom, H and Goldberg, E.D., 1968. Deep Sea Research, 23, 949. [5] Grim .R.E, 1988. Clay mineralogy, Mc Graw Hill Book Company, Newyork, .600. [6] Hashimi, N.H. and Nair, R.R, 1989. Indian Association Sedimentologist, 8, 17.


Clay Minerals Distribution of Beach Sediments of Tirumalairajanar Coast, TamilNadu East Coast of India [7] Holtzapffel, T., 1985. Les mine´raux argileux. Pre´paration, analyse diffractome ´trique et de´termination. Socie´te´ Ge´ologique du Nord, Publication no. 12, 136. [8] Keller, W. D., 1970. Environmental aspects of clay minerals. J. Sediment. Petrol., 40, 788–813. [9] Mohan, P.M and Damodaran, K.T, 1992. Indian Journal of Marine sciences, 21, 300. [10] Nair, R.R., 1976. Unique mud banks, Kerala, southwest India. Bulletin American Association of Petroleum geologist, 60, 616-620. [11] Thiagarajan, R. 1980. Geology and geomorphology of Kerala coast.

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Proceedings of the seminar in Geology and Geomorphology of Kerala, Geological survey of India special publication, 5, 55-66. [12] Varghese, T and R.S. Aiyer. 1980. Influence of geomorphological and climatic factors on the soil formation of Kerala. Geology and Geomorphology of Kerala, Geological survey of India special publication, 5, 69-72. [13] Windom, H. L., 1976. Lithogenous material in marine sediments. In Chemical Oceanography (eds Riley, J. P. and Chester, R.), Academic Press, New York, vol. 5, pp. 103–135.
