INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, 2011

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1 INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCES Volume 1, No 7, Vijayakumar.V et al., licensee IPA- Open access - Distributed under Creative Commons Attribution License 2.0 Research article ISSN Sedimentological characteristics of Perumal lake Cuddalore District, Tamilnadu, South India Vijayakumar.V, Vasudevan.S, Pruthiviraj.T Department of Earth Sciences, Annamalai University, Annamalai Nagar vijaykumar.geo@gmail.com doi: /ijessi ABSTRACT A thorough knowledge of sedimentary processes that cause the production, transportation and deposition in varied hydrodynamic conditions, is most important in environmental reconstruction. Size analysis of sediment is an essential requirement to understand their mechanism of transportion and deposition. Textural parameters are primarily related to made of transportation and energy condition of the transporting medium in this study it is focused on classification of grain size certain measures (Mean, Sorting, Skewnees and kurtosis) of special relevance in lake sedimentological contexts and some applications related to sediment types and bottom dynamics. Lakes provide a multitude of uses and are prime regions for human settlement and habitation. It is important to approach the grain size study of the sediments and geochemical study of the Lake sediment for planning and management of Lacustrine environment. Keywords: Textural parameters, Skewnees and kurtosis, grain size, Lacustrine environment. 1. Introduction Several studies had been done in order to understand the various Lacustrine sediment environments and related processes in the fresh water lakes worldwide. In the early nineteenth century, pioneering works have been undertaken on grain size characteristics of sediments. These include Udden (1914), Krumbein (1936), Otto (1939), Folk and Ward (1957) and Kolvan (1966). On the basis of shape of size frequency curves Keller (1945) has shown that dune sediments can be distinguished from beach sands. Inman (1949) has established a relationship between the dynamics involved during sedimentation and the resulting textural characteristics of the sedimentary rocks. Various authors have attempted to discriminate the varying environments like river, beach and dune by using textural parameters (Mason and Folk, 1958: Friedman 1961 and 1967). Grain size measures for demarcating the subtle differences in depositional environments are brought out by Folk (1966). The textural parameters are utilized to identify depositional environment of relict as well as recent sediments (Moiola and Weiser, 1968). 2. Study Area The area chosen for study is Lake Veeranam and Perumal, which are located in Cuddalore district of Tamilnadu. The Perumal lake is falls between north latitudes to N and east longitudes to E. It falls in the survey of India toposheet no. 58 M/10. The study area is bounded by Gadilam river in the north and Coleroon river in the south (Fig.1). It has good network of roads and railways. Received on December, 2010 Published on August

2 INDIA TAMILNADU Figure 1: Map showing in Location map of the study area. 3. Methodology Thirty surficial sediment samples were colleted by using Van veen. Roughly 1 2 Kg (wet weight) of sediments was collected at its site; samples were stored in sealed Ziploc- bags with lake water. Sub-samples were placed into beaker. The sample locations were identified and recorded with help of GPS (Garmin). The sediment samples were dried for at least 24 hours in an oven at 60 0 C to remove the moisture before analysis. From the dried samples, 100gm was taken by the conning and quartering method. The 100 gm of sample is then subjected to sieve analysis in ASTM sieves at half phi intervals for about 30 minutes in Ro-top sieve shaker. The sieved material in each fraction were collected and weighed. The weights of the individual fractions were tabulated for granulometric analysis. It is an essential part to understand the mode of transportation and depositional environment of sediments. Using graphic (Folk and Ward, 1957) and moment methods (Friedman, 1961, 1967 and 1979), the weight percentage of data of samples were processed by using modified programme of Schlee and Webster (1967) procedure. From the statistical parameters, frequency curves, bivariant plots, log probability curves and CM diagrams were drawn. 2013

3 Frequency in % 4. Results and discussion 4.1 Frequency Curves Frequency curves exhibit the pictorial representation of weight percentage of different fractions of sediments. The peakedness of fraction and uniformity of the sediments are inferred from it in the study area. Coleroon anicut are the important river system in Paravanar River and important supply to Perumal Lake. The sediments they carry along are debouched into the lake Perumal and to Bay of Bengal. In order to decipher the role of different transporting agents are the regulating nature of different sub-populations, size frequency curves have been drawn (B) Perumal Lake Grain Size (phi) Figure 2: Frequency curves The assemblages of frequency curve from different parts of the lake Perumal are shown in Fig.2.The frequency curves of the sediments from Lake Perumal are mostly polymodel character. Polymodality of the curves may be due to extreme variation in the velocity of the depositioning agent on lake of certain grain size in the source material (Sahu, 1964). According to Sahu (1964) polymodulity may also arise due to diversity in the size range of source material and due to derivation of sediments from two (or) more source (Pettijohn, 2014

4 1984). The polymodel nature of the sediments also implies that transportation by rolling, sliding, saltation and suspension processes in the both Lakes Grain size The grain size parameters viz., Mean size (M Z ) standard deviation (бi), Skewness (S ki ) and kurtosis (K G ) of percentile values derived from the cumulative curves following Folk and Ward (1957) and the moment technique based upon grouped data (Friedman, 1967) are most widely used. The grain size results are spatially given to the most of the samples are very fine sand (Fig.3.). The textural parameters of the Lake Perumal sediments were shown in table Mean size: (M Z ) Figure 3: Grain size analysis of Lake Perumal Sediments Mean size is the average size of the sediments represented by ф mean size and mainly an index of energy conditions. In the Lake Perumal, the mean size varies from1.99 ф to 5.72 ф with an average of 3.85 ф and thus falls in the Fine Sand to Medium Silt category (figure 4). 2015

5 Figure 4: Variogram for Textural Parameter - Mean In the Lake Perumal 20% represents Fine sand, 46.66% represents Very fine sand, 16.66% represents Coarse Silt and 16.66% Medium silt. The mean grain size is important tool for interpretations of sediment data in relation to bottom dynamics Standared deviation (бi) The standard deviation is the measure of sorting sediments and indicates the fluctuations in kinetic energy of the depositioning agent about its average velocity. Standard deviation indicates the difference in kinetic energy associated with these modes of deposition. Sorting has an inverse relation with standard deviation. In the lake Perumal, the minimum and maximum values of the standard deviation are 1.73 ф and 4.09 ф respectively with the average of 2.78 ф. The Lake Perumal it is observed that all the samples were falls in the poorly sorted to very poorly sorted nature (figure 5). Figure 5: Variogram for Textural Parameter- Standard Deviation 2016

6 Skewness (Ski) Skewness measures asymmetry of frequency distribution and marks the position of mean with respect to median. In a material sufficient quantity of different sizes, a coarsely skewed sample implies that the velocity of the deposition agent operated at a higher value than the average velocity for a greater length of time. In the present study, In the lake Perumal minimum and maximum Skewness values are 0.08 and 0.76 respectively with an average value of 0.39 with the representation of percent in strongly fine skewed, percent fine skewed, and 3.33 present nearly symmetrical nature. The lake Perumal sediment samples were falls in the near symmetrical to strongly fine skewed nature (Fig 4.3). The fine skewed nature of the sediments clearly exhibits sediment input from various sources of tributaries. The finely skewed nature is also implies a low velocity than normal. This skewness data indicate that in the sediments finer than the median class of the sediments dominate almost throughout their distribution Kurtosis (k G ) Figure 6: Variogram for Textural Parameter-Skewness Kurtosis is a quantitative measure used to describe the departure from normality of distribution. Many curves designated as normal by the skewness measure turns out to markedly non-normal when the kurtosis is computed. It is the ratio between the sorting in tails of the curve to that of the central portion. The minimum and maximum values of kurtosis of Lake Perumal are 0.51 and 4.07 respectively with an average value of 1.01; of the total samples analyzed percent represent Very platykurtic, percent platykurtic, 6.66 percent mesokurtic, 10 percent Leptokurtic and percent Very Leptokurtic. The lake Perumal samples fall within Very platykurtic to Very Leptokurtic nature (Fig.4.4). The dominance of platykurtic nature of the both lake sediments exhibits mixing two populations in sub-equal amount. The polymodal characteristic of sediment frequency is responsible for the platykurtic values C-M- Pattern The CM pattern is an important plot used in sedimentology for the analysis of sedimentary environment (Passega, 1957). The CM Pattern of the sedimentary environment are means of 2017

7 analyzing transportation mechanism, depositional environment with respect to size, range and energy level of transpiration and also is determining the processes and characteristic agents that are responsible for the formation of clastic deposits. It is also observed that in several environments the coarse fraction of sediment almost invariably is more representative of the depositional agent than the fine fraction. The two parameters used in the plot from the grainsize distribution are of particular significant C, the one percentile value represents the maximum grain size and indicates the competency of the transporting agent and the medium diameter M, expressed median grain-size of sediment transported. Figure 7: Variogram for Textural Parameter-Kurtosis The sediments are generally considered as mixture of two to three log-normal subpopulation produced chiefly by three modes of transportation: rolling, saltation and suspension. The suspension may be uniform type (or) graded type. According a single sample may contain all the three sub-population related to the three modes of transport. The coarser particles are transported by rolling, grain size of lower range are carried by jumping and sliding while the finest particles are carried in suspension. The particles carried in saltation are generally considered to be the product of graded suspension (Passega, 1964). Suspension may also be uniform (or) pelagic type. Two types of bottom currents namely tractive current and turbidity current are capable of transporting sediments. Traction currents are capable of transporting their load either by rolling ion in suspension and turbidity current, which is a rapid process, carries the entire load in suspension. In the present study, CM pattern was made following Passega (1957, 1964), and Passega and Byramjee (1969). The phi values of 1 st and 50 th percentile were converted to microns to plot on CM diagram (Fig.5). The CM plot at the present study shows that most of the sediment samples falls in the intermediate position between S and Q. This SQ segment exhibits that the Perumal lake sediments were underwent the Rolling and suspension current, which are the prime factors for transportation. Most of the plots of the Lake Perumal sediments occupy VII segment, which is denoted by C < 1 mm. mainly suspension sediments, rolled sediments <1mm may be incorporated. Thus the study shows that the sediments are mainly transported through traction along with heterogenous suspension. Rolling sediment is negligible. The plots occupy the zone of tractive current deposits. Finally, it may be summarized that the sediments were deposited by tractive current, the sediments were being carried in varying suspension. 2018

8 Figure 8: CM Pattern 5. Conclusion The grain size parameters viz., Mean size (M Z ) standard deviation (бi), Skewness (S ki ) and kurtosis (K G ) of percentile values derived from the cumulative curves following Folk and Ward (1957) and the moment technique based upon grouped data (Friedman, 1967) are most widely used. Mean size is the average size of the sediments represented by ф mean size and mainly an index of energy conditions. The mean grain size is important tool for interpretations of sediment data in relation to bottom dynamics. The grain size diagram to spatially highly distribute in the very fine sand. The standard deviation is the measure of sorting sediments and indicates the fluctuations in kinetic energy of the depositioning agent about its average velocity. The Lake Perumal it is observed that all the samples were falls in the poorly sorted to very poorly sorted nature.skewness measures asymmetry of frequency distribution and marks the position of mean with respect to median. The fine skewed nature of the sediments clearly exhibits sediment input from various sources of tributaries. The finely skewed nature is also implies a low velocity than normal. This skewness data indicate that in the sediments finer than the median class of the sediments dominate almost throughout their distribution. Kurtosis is a quantitative measure used to describe the departure from normality of distribution. Many curves designated as normal by the skewness measure turns out to markedly non-normal when the kurtosis is computed. It is the ratio between the sorting 2019

9 in tails of the curve to that of the central portion. The dominance of platykurtic nature of the both lake sediments exhibits mixing two populations in sub-equal amount. The polymodal characteristic of sediment frequency is responsible for the platykurtic values. The CM Pattern of the sedimentary environment are means of analyzing transportation mechanism, depositional environment with respect to size, range and energy level of transpiration and also is determining the processes and characteristic agents that are responsible for the formation of clastic deposits. Acknowledgement Authors would like to acknowledge the University Grant Commission (U.G.C), for providing the funds for this project. 6. References 1. Folk R.L, (1954), The distinction between grain size and mineral composition in sedimentary rock nomenclature, Journal of Geology, 62, pp Folk RL and Ward MC (1957), Brazos river bars; a study in the significance of grain size parameters, Journal of Sedimentary petrology, 27, pp Friedman G.M., Sanders J.E., (1978), Principles of Sedimentology, Wiley New york, pp Friedman GM, (1961), Distiction between Dune, Beach and river sands from textural characteristics, Journal of Sedimentary petrology, 31, pp Friedman GM (1967) Dynamic processes and statistical parameter compared for size frequency distribution of beach and river sands. Journal of Sedimentary petrology, 37 pp Friedman GM (1979) Differences in size distribution of population of particles among sands of various origins. Journal of Sedimentolgy, 8, pp Keller,W.D, (1945), size distribution of sand in some dunes, beaches and sand stones. Bulletin of American Association of Petroleum geologist, 29, pp Kolvan, J.E., (1966), The use of factor analysis in the determining depositional environments from grain size distributions. Jour. Sed. Petro. V.36, pp Krumbien WC, (1938), Application of logarithimic moments to size frequency distribution of sediments, Journal of Sedimentary petrology, 6, pp Otto, (1939), A modified logarithmic probability graph for the interpretation of mechanical analyses of sediments. Journal of Sedimentary petrology, 9, pp Passega, (1957), Texture as characteristic of clastic deposition, Bulletin of American Association of Petroleum geologist, 41 (9), pp

10 12. Pettijohn FJ, (1984), Sedimentary rocks 3rd Ed.CBS publ. and distributors Delhi, pp Sahu B.K (1964) Depositional mechanism from the size analysis of clastic sediments. Journal of Sedimentary petrology, 34, pp Schindler, D. W A hypothesis to explain differences and similarities among lakes in the Experimental Lakes Area, northwestern Ontario. Journal of Fish Research Board of Canada, 28, pp Udden (1914), Mechanical composition of clastic sediments, Geological society of America Bulletin, 25, pp