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This present study describes the geochemistry of fluvial sediments of the Palar river (lower reaches), Southern Peninsular India, with an aim to evaluate their provenance, weathering and tectonic setting. The bulk sediment chemistry is influenced by grain size. The river sediments are enriched with SiO2 and depleted in Al2O3, K2O, CaO, Na2O, MgO, P2O5, MnO, Fe2O3 as compared with UCC values. Geochemical classification indicate that the sediments are mainly arkose, wacke and shale in composition. Discriminant diagrams together with immobile element ratio plots reveal that, the Palar river sediments are mostly derived from rocks formed in an active continental margin. Additionally, the rare earth element ratios as well as chondrite-normalized REE patterns with flat HREE, LREE enrichment, and negative Eu anomalies indicate felsic rock sources. The chemical indices of alteration suggest that Palar river sediments are chemically immature and have experienced low chemical weathering effects. This is further supported by the Th/U Rb/Sr ratio and A-CN-K ternary diagram, with most of the sample data points falling close to the plagioclase-smectite line. The bivariate plot of Th/Sc versus Zr/Sc suggest a moderate recycled origin of the sediments. [ABSTRACT FROM AUTHOR]

The present-day Palar River and its palaeochannel located in the Southern Peninsular India were investigated with a multidisciplinary approach. The main aim of the study was to reconstruct the palaeoenvironment history of the Palar River basin and to delineate the role of Holocene fluctuations that played a major role in the geomorphological evolution of the region since the Holocene period. The results obtained based on sedimentary facies analysis supported by elemental concentrations and optically stimulated luminescence (OSL) dates reveal distinct seven climatic phases since the past ~10 ka. Phase 1 signifies a very high precipitation as attested by the low CWI with high Rb/Sr ratio. Subsequent to Phase 1, a decreasing trend in the northeast monsoon rainfall (NEMR) is observed (Phase 2). Phase 3 (~4.83-3.59 ka) reflects a decrease in NEMR further supported by low Mn/Al, Mg/ Al and Chemical Index of Alteration (CIA) values. Phase 4 (~3.59 ka) is marked by high sand flux, higher K/Al, Ti/Al, Rb/Sr and Ba/Sr ratios coupled with lower values of CaO/MgO, Mn/Al and Fe/Al indicating wetter conditions in the catchment area resulting in the intense weathering of the bedrocks caused owing to the increase in NEMR precipitation. Phase 5 (3.26-2.42 ka) reveals a decline in NEMR precipitation coupled with rapid upstream avulsion because of neotectonic activity that occurred in an intense dry phase. Phase 6 (~1.88-1.44 ka) is marked by an augment NEMR causing higher K/Al, Mg/ Al, Ti/Al ratios, CIA and CWI values. Finally, Phase 7 (~1.44 ka-present) is marked by lowered elemental solubility and mobility reflecting short periods of weaker or deteriorated NEMR. The documented record of the Palar River and palaeochannels suggests Holocene NEMR variability in the study region and is synchronous with the various proxy records of NEMR-dominated regions, however, revealing an inverse coupling with southwest monsoon rainfall (SWMR) during the Holocene period. [ABSTRACT FROM AUTHOR]

The Vellayani lake, located on the west coast, Kerala, South India, is a natural fresh water lake. In order to understand the source and nature of the sediments; thirteen lake floor sediment samples were collected from the Vellayani lake at different intervals along the S-N transects covering the entire surface area of the lake. Textural studies indicate that lake floor sediments are dominant in sand (55.39%) followed by clay (30.57%) and silt (14.04%) fractions. Coarse components are dominant at the inlet ofthe stream into the lake. The geochemical content of the sediments reveals low SiO, MnO, CaO, MgO, NaO, KO, and PO content while TiO, FeO and AlO are high when compared with Post Archean Australian Shale (PAAS) and Upper Continental Crust (UCC) values. SiO is high in coarse fractions while AlO is strongly associated with fine sediments. Major oxide contents supported by Rare Earth Element (REE) data reveal a distinct negative Eu anomaly reflecting a dominant cratonic origin of the sediments. Detailed geochemical data indicate a mixed source, predominantly, the lateritic soils, sedimentary and metamorphic bedrocks exposed around the lake and in the catchment area. [ABSTRACT FROM AUTHOR]

In the present study, a 60 cm sediment gravity core collected off the Cuddalore shore (11°42.419 N, 79°57.993 E) from a water depth of 150 m was radiocarbon dated and analysed for major elements (Si, Al, Na, K, Ca, Mg and P), trace elements (Fe, Cr, Mn, Co, Ni, Cu, Zn and Pb), calcium carbonate, and organic matter content to understand their behavior and probable sources and also to understand the monsoon variability. The sediment core has been radiocarbon dated from around 4100 to 3100 BP. High sand around 4000, 3700, 1500 BP with low CaCO 3 content suggests high sediment flux coupled with higher precipitation corresponding to increased erosion during these periods, and more fresh water runoff from rivers in the late Holocene, thus reflecting intensification of the SW and NE monsoon. The results of the major elemental analyses show the fine-grained, detrital nature of sediments with high values of Si and lower values of Al and Fe. The present study clearly demarcates that the distribution patterns of Cr, Cu, Pb and Zn that are controlled by the distribution of the fine grained fractions. The increased Mn content towards the lower end of the sediment core denotes the allogenic supply of Mn from oxic to-sub-oxic recycling within the sediment column in fine grain sediments. The mean CIA values (56.47) reflect immature, moderately weathered sediments that are mostly derived from sandstone and clay. [ABSTRACT FROM AUTHOR]

Abstract: Pookode Lake, Kerala, South India, a fresh water lake situated at an altitude of ∼770 m.a.s.l., receives predominantly rains from the south-west monsoon. A sediment core 125 cm long was investigated for sediment texture, dating and geochemical composition. Radiocarbon dates obtained on the organic carbon rich sediments of the Pookode Lake range in age from the mid-Holocene to more recent (6240–565 14C BP; BC 4786 to AD 1434 cal.). Geochemical data of the sediment cores were corroborated with phytolith and pollen studies. Although phytoliths occur in the entire sediment core, pollen assemblages start occurring only since 1500 14C BP (∼AD 650 cal.). The sediments older than 1500 14C BP were not suitable for the preservation of the pollen assemblages. There is a major change in the lake hydrology, indicating lacustrine conditions subsequent to 1500 BP. Occurrence of diatoms in the upper sediment layers of the sediment core indicates shallowing of the lake. Both the Medieval Warm Period (MWP) and the Little Ice Age (LIA) are represented in the Pookode Lake sediment core. Sediment texture, chemical weathering intensity (CWI) values supported by phytolith and pollen assemblages, indicate that overall warm and dry conditions prevailed during 6200–420 14C BP (BC 4786–AD 1434 cal.) but this was interrupted by short, intense wet phases between ∼3900 and ∼1900 (∼BC 4000–∼AD 300 cal.), ∼1400–∼760 (∼AD 800–∼AD 1200 cal.), and ∼420–∼140 14C BP (∼AD 1570–∼ AD 1860 cal.). The wet events resulted from the strengthening of south-west monsoon (SWM) causing rising water levels and brief expansion of the Pookode Lake margin. [Copyright &y& Elsevier]

The present study was carried out to determine the characteristics, distribution, and abundance of plastic debris in 25 sediment samples collected from the Poompuhar beach, southeast coast of India. The result reveals that the mean plastic debris abundance was 42 ± 27 particles/m2 dry weight (dw) (1 SD, n = 25) with higher concentrations in the river mouth. The dominant shapes in the study area were fragment (70.7%), followed by fiber (20.7%), and pellet-shaped (8.6%). The dominant colors of the plastic debris were: white-colored (47%) followed by blue (28%) and green (14%). The study further reveals that the dominant polymer type was polyethylene (PE, 63.4%), followed by nylon (PA, 16.9), polyvinyl chloride (PVC, 15.5%), polypropylene (PP, 3.1%), and polystyrene (PS, 1.1%). In the study area, the main source of plastic debris was from land-based fishing and tourism activities, and rainwater runoff from the Cauvery River. [Display omitted] • Plastic pollution was addressed along Poompuhar Beach, south east coast of India. • Dominant plastic shape was fragment (70.7%) > fiber (20.7%) > pellet (8.6%). • Plastic debris sources mainly from the terrestrial and marine sources. • Polyethylene (PE, 63.4%) was the dominant polymer in the study area. • Dominant plastics size was meso (68.1%), and micro (25.2%). [ABSTRACT FROM AUTHOR]

This study reports the spatial distributions of diatom assemblages and potential relationships between diatom diversity and environmental variables (C/N ratio, CaCO3%, clay mineralogy) using multivariate analyses in surface sediments of the Akkulam-Veli Lake. Surface sediment samples were collected at 19 sites throughout the lake to analyse diatom distribution, TOC, N, CaCO3%, clay mineralogy and sediment texture. The results suggest that the clay fraction is predominant in the eastern flank, whereas sand fraction is more in the western flank. TOC% and CaCO3% in the lake floor sediments are attributed to high organic activity within the lake and contributions from the vegetation around the lake margins. The results suggest that N is being added to the lake from secondary sources from catchment area leading to eutrophication of the lake. Further, clay mineralogy of the sediment samples reveals that kaolinite mineralogy dominates in clay fractions. Diatom studies show rich diversity of freshwater, marine and brackish diatoms and abundance of pollution-reflecting species such as Cyclotella sp. and Navicula sp. [ABSTRACT FROM AUTHOR]

Anchar Lake, a mono-basined freshwater lake in Kashmir Valley, has experienced major sediment deterioration due to changes in the local catchment and anthropogenic inputs during the recent past. The present study was conducted to evaluate the major, trace element concentrations and environment risk assessment in the surface sediments of Anchar Lake. Spatial distribution of organic matter (OM), CaCO3, TOC, sand-silt-clay and C/N ratio was studied to understand their source and accumulation in recent surface sediments. Textural studies indicate that most of the sediment samples are clayey silt to silty clay except one sample being of sandy-clay-silt nature. OM, CaCO3 content and C/N ratio results reveal that the sediments are organically rich and the source of OM is controlled by both; autochthonous and terrestrial sources. The major oxide geochemistry reflects higher concentrations of CaO, MgO and TiO2 compared to the  UCC values and the possible dilution effect of CaO on other major oxides. Environmental risk assessment indices (Igeo and EF) reveal that the lake surface sediments are low to moderately enriched with Cu, Ni, Zn and Pb and thus are a direct threat to aquatic life. Pollution load index indicates higher contamination of the sediment samples collected along the agricultural and urban land-cover sites. In the absence of industries and metal mines in the catchment area, the agricultural inputs, domestic effluents and untreated sewage discharges are the probable source for the moderate increase in trace metals in the lake sediments. Based on geochemical and environmental parameters, an assessment of sediment contamination results revealed potential risks ranging from moderate to strong for the lake environment, particularly towards areas proximal to agricultural and land-use sites. The above results from this study thus add to the fundamental knowledge of the present lake processes occurring within the lake and its interactions with the surrounding catchment areas. [ABSTRACT FROM AUTHOR]

A correction to the article "Distribution of Sediments and Organic Matter Source: Berijam Lake, Tamil Nadu" that was published in the November 2015 issue is presented.

The Indian Peninsula is generally considered as a tectonically stable region, where ancient rocks, rivers and land surfaces predominate. In some parts of this ancient landscape, however, the role of tectonic landsculpting is strongly indicated by the presence of youthful topography and historical seismic activity. The present study is primarily focused on the middle domain of the Kaveri River, which displays such youthful features. The tectonic controls on this cratonic river were evaluated on the basis of the investigations of the longitudinal profiles, morphotectonic indices of active tectonics, and fluvial records. The presence of steep channel gradients, prominent knickpoints, hanging valleys, narrow bedrock gorges, and channel-in-channel morphology imply rapid erosion rates in the middle domain of the basin in response to active deformation, particularly in the reach defined by two major active faults — the Kollegal–Sivasamudram Fault and the Mekedatu Fault. Further, considering the remarkably low modern and long-term denudation rates and OSL ages of the alluvial deposits (30–40 ka), the tectonically-driven rejuvenation does not appear to be geologically recent as postulated by earlier workers. [ABSTRACT FROM AUTHOR]