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Analysis of plant‐wax biomarkers from sedimentary sequences can enable past environmental and hydrological reconstruction and provide insights into past hominin adaptations. However, biomarker preservation in desert contexts has been considered unlikely given the sparse nature of the vegetation within the landscape. Here we evaluate the preservation of n‐alkanes and fatty acids collected from four depositional sequences associated with archaeological contexts in the Nefud Desert, Saudi Arabia, and the Thar Desert, India. Pleistocene and Holocene samples were selected to understand the effects of age on preservation. The results of molecular distribution patterns and indices, particularly the high carbon preference index and average chain length, show the preservation of plant‐wax biomarkers in both the Holocene and Pleistocene desert sequences, while δ13C values and organic content provide insights into the vegetation contributing to the plant‐wax organic pool. This study provides a baseline for understanding human–environment interactions and for reconstructing changes in arid land habitats of relevance to hominins during the Quaternary. [ABSTRACT FROM AUTHOR]

The giant clam shells are considered excellent marine bioarchives and have been used in studying current and past climate variabilities. Here, we present the microstructure and growth rate variability of a giant clam shell (T. maxima) collected from the Minicoy Island Lakshadweep, India. We employed FE-SEM, EDX, Raman spectroscopy and petrographic analysis to identify coherent records of the past marine environmental settings and factors controlling growth rates in T. maxima. A consistent growth rate was observed throughout the shell ontology, except for the year 2010, when a relatively slow growth rate was observed due to exceptionally warm water temperatures. Slower microstructural growth is confirmed by an anomalously negative excursion in δ18O values caused by an anomalous sea surface warming event. Such kind of warming was previously documented for the region in 2010 that caused widespread coral bleaching throughout the Lakshadweep Archipelago. Interestingly, our results do not reveal any major growth hiatus in the T. maxima even after experiencing this anomalous thermal stress event, demonstrating the ability of these bivalve shells to reliably reconstruct past environments. These findings advance the potential of combining data from shell microstructure, petrographic, and isotope (δ18Oshell) analyses, to reconstruct the past extreme events preserved in giant clam shells from the Lakshadweep Archipelago. [ABSTRACT FROM AUTHOR]

The region around the coastal Chennai area, India, is drained by three major rivers that rise from the remnants of the Eastern Ghats and receive dominantly the northeast rains. These rivers meander short distances, deposit sediments into the Bay of Bengal and preserve signatures of past phases of sedimentation and incision. In this study, detailed mapping using satellite imageries and extensive field work, logging of the river cliff bank sections was supported by sediment texture and structure and optically stimulated luminescence (OSL) dates. The main objective of this study was to infer the major periods of aggradation and incision in coastal drainage basins receiving dominantly the northeast rains. Integration of all the earlier available dated alluvial sequences (14C ages) and the present study OSL dates reveal that a major period of sedimentation occurred during the early Holocene (9 to 8.3 ka), mid Holocene (7.6–5.5 ka) and late Holocene to recent (2.4 and 1.6 ka, 0.9–0.6 ka and around 0.2 ka) periods. The Koratallaiyar river has preserved older middle Holocene terraces. Younger ages of the south easterly and east flowing rivers such as the Palar and the Coovum signify that they have incised and eroded to the present riverbed levels by catastrophic floods during the late Holocene period. This has resulted in an imbalance between sediment supply and sediment transporting power thus laterally stacking sediments rather than vertically. [ABSTRACT FROM AUTHOR]

The Holocene arid events and related societal responses are important scientific inquiries due to concerns about their reoccurrences in the future. In the Indian subcontinent, significant number of studies have focussed on understanding the Holocene aridification events at 8.2 and 4.2 ka. Despite these studies, high resolution palaeoclimatic records from the eastern India during Holocene, particularly around the above-mentioned aridification events are lacking. In this study, we present high resolution Holocene palaeoclimate records reconstructed based on geochemical and isotopic data from the Chilika Lagoon located in the east coast of India. A 130 cm long sediment core, retrieved from the southern end of the lagoon, revealed a continuous sedimentation history between 8.49 and 0.99 ka. The variations in organic carbon isotopic compositions, total organic carbon contents, along with major and trace element abundances suggested a strong effect of 8.2 dry event and a shift in chemical weathering at around 4.2 ka in the eastern coast of India. Additionally, a strong warm climate anomaly was observed at 1.2 ka. Interestingly, higher sedimentation rates were observed post 4.2 ka, which potentially indicated a significant change in settlement dynamics and human interventions. It appears that the eastern coast of India experienced human migration and surge in agricultural practices similar to that in northwest India after the 4.2 ka climatic event. It is likely that people relocated themselves, which eventually increased the pastoral activities in newly occupied lands. Consequently, enhanced land use and land cover changes accelerated soil erosion in the region leading to higher sedimentation rate in the lagoon. [ABSTRACT FROM AUTHOR]

A giant clam shell (Tridacna maxima) collected from the lagoon of Minicoy Island in the southern Lakshadweep Archipelago, India, was used for a high-resolution stable isotope (δ18O, δ13C) analysis. The results reveal a cyclic pattern in δ18Oshell values, interpreted as combined signatures of seasonal temperature and δ18Osw fluctuations over the period from 2004 to 2014. These δ18Oshell cycles are characterized by a slight background scatter governed by rainfall events leading to short-term and limited freshening of the water in the partly restricted lagoon. The most striking features of the isotope data are exceptionally negative outliers in δ18Oshell values beginning in mid-2010. This first anomalous isotope excursion is followed by a phase of lowered growth rates lasting until the beginning of 2011. It is observed that this sudden change in oxygen isotope composition and shell precipitation was caused by anomalous sea surface warming, which was previously documented for the region in 2010 and caused widespread coral bleaching throughout the Lakshadweep Archipelago. Even though several other negative excursions in δ18Oshell values follow, the cyclicity in the isotope signal and the growth rates become again more regular in the distal part of the shell, indicating a gradual recovery of the bivalve after the initial thermal stress event. The results reveal that even short high-temperature events can significantly perturb the biology of giant clams and require long recovery phases. This information is particularly significant for conservation efforts for this endangered bivalve group in a world with ongoing global warming. [ABSTRACT FROM AUTHOR]

Freshwater lakes and sediments need to be monitored continuously for environmental assessment and geochemical explorations. Lake sediments are major sinks for organic matter and for all geochemical elements. In the present study, total organic matter (TOC), nitrogen (TN), and geochemical analysis of major oxides was carried out on Yercaud Lake surface sediments, located at a higher elevation in South India to infer sediment distribution pattern and source for organic matter. Particle size distribution of lake surface sediments suggests that the sediments are predominantly silty sand and sandy silt, poorly to very poorly sorted and symmetrically skewed. TOC/TN ratio (6.54–12.65) reveal that the organic matter (OM) is derived from the in situ lake sources particularly from the vascular plants and lake biota accumulation. Weathering indices that fall from [chemical index of alteration (CIA)] 88.59–93.08 values and A‐CN‐K plot reflects intense chemical weathering of the bedrock exposures in the source area, which was accelerated under warmer and humid climate conditions in the sub‐tropical regions. Al2O3/TiO2 ratio (6.94–26.62) indicates weathering particularly of the exposed charnockite rocks around the lake basin. [ABSTRACT FROM AUTHOR]

This study examines the catchment and source morphodynamics of the Palar River, Southern Peninsular India. Here, we applied a multidisciplinary approach (Remote sensing Techniques, Lineament Analysis, Geochemistry and Ground Penetration Radar) for a better understanding of its evolution during Holocene times. The lineaments present in the Palar River basin are showing dominantly NE-SW trend. There are five major faults identified in the Palar River basin. Fault F1 (strike slip fault) occurs in the upper part of the Palar River following the NE-SW trend. Other major faults F2 and F3 occurs in the middle reaches with a transition zone where frequent smaller magnitude earthquake occured and fault F4 traverses in parallel to the Cheyyar River. Fault F-5 nearer to the east coast indicates a passive tectonic activity regime. The after-effects of tectonic activity in the basin is further implicit from the GPR Profile. The sediments of active Palar River are dominantly litharenite, arkose, wacke; while, the paleochannels are shale in composition. Weathering proxies such as CIA, PIA, elemental ratios along with A–CN–K plot indicate a post-depositional intense weathering due to climatic variability for paleochannel sediments. Due to ongoing tectonic activity in the sources region along with subsequent aggradation and degradation in fluvial regimes, the sediments of active Palar River shows low to moderate weathering. Moreover, the geochemical data also reveals that the sediments from the Palar River and paleochannels are predominately from active continental and passive continental margins respectively. Moreover, the Major Oxide, Trace Elements and REE elements data indicate that Palar River sediments are from a felsic source while paleochannels are from mafic source. Hence, our study suggests that the catchment area of the Palar River has been shifted to the southward during the Holocene period due to tectonic uplift. Subsequently, the sediments of the paleochannels have undergone post-depositional weathering. Due to ongoing tectonic activity and intense precipitation in the region, enhances rapid erosion in the catchment area results in the deposition of the huge thickness of sediments from the middle to lower reaches of active Palar River. [ABSTRACT FROM AUTHOR]

Multi-proxy analysis of lake sediments provides high-resolution and reliable palaeoclimate records. The present study aims to investigate the palaeoenvironmental changes and eutrophic evolution of the Wular Lake, Kashmir Valley spanning the last ~ 500 years. Based on the multi-proxy analysis and supported by radiocarbon chronology, two prominent environmental phases were identified. From 74 to 45 cm, the sedimentation corresponds to the late 15th to early sixteenth century suggests the influence of cold, Little Ice Age (LIA) with nutrient-poor lacustrine environmental conditions. The following climate phase (28–9 cm) reflects the 19th and early twentieth century warmer and wetter environmental conditions. Enhanced TOC and N nutrient inputs in the lake sediments observed during the top 25 cm are likely contributed by anthropogenic sources owing to rapid and sustained anthropogenic land-use of watershed environments. This increase in the lake nutrients has been caused due to intense agriculture and horticulture practices leading to the lake eutrophication. [ABSTRACT FROM AUTHOR]

We present a comprehensive record of Holocene (11,590–628 cal. yr BP) climate and hydrographic changes around the Wular Lake located in Kashmir Valley, India. Based on the multi-proxy investigations, we have identified three phases of wet climate conditions that prevailed from the commencement of the Holocene Epoch – 9000 cal. yr BP, 8100–6650 cal. yr BP and 6350–5000 cal. yr BP, whereas periods of dry climate were observed during 9000–8100 cal. yr BP, 6650–6350 cal. yr BP and ~5000 to 4000 cal. yr BP. The results also suggested that the lake widened and deepened significantly around 6350–5000 cal. yr BP. The results indicated desiccation and the exposure of the lake margin around 5000–4500 cal. yr BP. The sedimentation rate since 4500–628 cal. yr BP was quite low for detailed paleoclimate interpretations. Oscillations in lake extension and deepening appear to be due to changing intensity of westerly moisture in the region, and we correlate several of the low lake-level phases to the Bond events caused by North Atlantic ice rafting events. [ABSTRACT FROM AUTHOR]

Loess paleosols have been often studied to reconstruct late Quaternary past climate changes. In the present study, textural analysis, TOC, CaCO3 content, micromorphology and clay mineralogy of the three loess paleosol profiles from three sites (Choori, Alochibagh and Burzahama), from Kashmir valley are presented. Based on the dates of Burzahama section, the exposed loess paleosols are approximately dated to 45ka. Textural analyses suggest that the sediments are largely fine silt followed by silty loam and silty clay loam. The fine sand component in the loess and paleosols indicate that winds in the valley were strong, but in phases the wind velocity was low. The paleosols are much thicker than loess layers and form several horizons within the lithosections. The increase of CaCO3 content indicates that it has leached in phases and along with total organic carbon (TOC) resulted in mild pedogenesis with variations in the rate of pedogenesis within the paleosols and forming pedocomplexes. Micromorphology of the loess-paleosols indicates the presence of calcite nodules with iron oxide coating indicating sub-aerial weathering and pedogenesis. The presence of channel structures in loess paleosols formed due to root traces and pores probably during the warmer periods. The replacement of chlorite by smectite clays in loess paleosols suggests that the alteration of clay minerals probably took place in cold, dry, warmer climatic conditions in low wind regime. [ABSTRACT FROM AUTHOR]

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]

A study involving grain size analysis was carried out from the Parsons valley lake deposit, Nilgiris, India to determine the depositional environments and paleoflood events since late Pleistocene period (∼29,838 cal yr BP). A 72 cm lacustrine core was collected from the lake and eight organic rich sediment samples were AMS radiocarbon dated. The study reveals variations in the grain size distribution chiefly influenced by regional climatic conditions. Paleoflood events have been identified by the individual sedimentary flood signatures of varying changes in the magnitude of sediment supply from the background silty sediment matrix around ∼29,838 and ∼8405 cal yr BP. [ABSTRACT FROM AUTHOR]

In this review, the shifts in organic matter (OM) accumulation and C:N ratios in lake sediments to reconstruct paleoclimate and paleo-environmental changes since the early Holocene period are presented. The C:N proxy data of total OM reflect wet climatic conditions during early Holocene (10 to 8.2 kyrs BP) due to enhanced southwest monsoon. This was followed by intermittent arid conditions during the mid and late Holocene period (8.2 to 2.8 kyr BP). Enhanced values of C:N ratio during middle to late Holocene (7.8-2.3 kyrs B.P) indicate periods with lower lake levels and minimum precipitation, while decreased C:N ratio point to stronger SW monsoon and expansion of the lakes. Further, C:N and δ13C results from the lake sediments reveal a detailed and continuous paleo-environmental changes in the relative sources of OM (allochthonous vs autochthonous). Proxy records using such natural archives have also been utilized to reconstruct past extreme events and environmental changes around the lake systems, such as causes for lake desiccation, hydrographic changes, alternations between C3 and C4 vegetation and historical disturbances in the catchment area since the early-late Holocene period coupled with the Indian summer monsoon. [ABSTRACT FROM AUTHOR]

Lakes and wetlands are dynamic geomorphic units of a landscape that hold geochemical signatures of sediment provenance and paleo-environmental shifts and are major sinks for organic matter accumulation. The source of organic matter is diverse in lake sediments and varies widely with the type and size of the lake and hence it is important to understand the source of organic carbon (terrestrial or in situ) in lake systems in order to monitor the health of the lake. Wular lake, located in north Kashmir, is one of the largest fresh water lake in India, situated at an average elevation of 1580m ASL. The lake is fed by a number of watersheds that bring a diverse type of sediments and organic matter and thus deposit them into the Wular lake basin. In order to understand sediment distribution pattern, content and source of organic matter, sediment provenance and the persisting environment in the Wular lake, 32 lake floor sediment samples covering the entire lake were collected and analyzed for organic element analysis, CaCO3, organic matter, sediment texture and diatom analysis. The results indicated that sediments in the lake are dominated by silt and silty clay. The organic carbon in the lake ranged from 0.83%-4.52% and nitrogen varied from 0.06%-0.5%. The Carbon to Nitrogen (C/N) ratios (9.04 to 22.03) indicate a mixed source of organic carbon but dominated by in situ lake sources from the vascular and lake biota accumulation. The diatom analysis revealed the occurrence of a diverse type of species along the sampling sites present within the lake. The wide distribution of the diatom species such as Cymbella, Cyclotella and Tabularia etc. in the lake indicate high organic pollution and alkaline fresh water environment prevailing in the lake. [ABSTRACT FROM AUTHOR]

The Kukkal basin, Tamil Nadu, India, receives most of its rain from the southwest monsoon (SWM). A sediment core from Kukkal Lake preserves a continuous sediment record from the early-Holocene to present (9000 yr BP to present). The present lake is situated at an elevation of ~1887 m a.s.l., in a small basin that appears to have alternated between a and wetland depositional environment. Climate proxies, including sediment texture, total organic carbon (TOC), total nitrogen (TN), C/N, pollen and geochemical composition indicate a steady progression to wetter conditions, with two stepwise changes at about 8000, and between 3200 and 1800 yr BP. The change at 8000 yr BP appears to correspond to a brief (100–150 years) dry spell recorded elsewhere in India. The change at 3200–1800 yr BP consisted in a rapid intensification of the SWM, and may correlate with the initiation of the ‘Roman Warm Period’. There is no clear evidence of changes at the times of the ‘Medieval Warm Period’ (‘MWP’) and the ‘Little Ice Age’ (‘LIA’). The C/N ratio of the sediments ranges from 14.02 to 8.31, indicating that the organic matter originated from a mixture of lacustrine algae, vascular and terrestrial plants. Chemical weathering indices (Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA)) are consistent with extreme silicate weathering. Pollen data show a development from savanna vegetation prior to about 8000 yr BP, followed by grassland with palms, the appearance of ferns just prior to 3200 yr BP and the establishment of the tropical humid forest between 3200 and about 1800 yr BP. [ABSTRACT FROM AUTHOR]

Late Pleistocene palaeoenvironments in the Thar Desert (India), located at the eastern extent of the Saharo-Arabian desert belt, have fluctuated considerably as a result of the varying range and intensity of the Indian summer monsoon. Phases of widespread Pleistocene aridity are well documented in the Thar Desert, but research focusing on humid proxies is critical to examine how the region may have facilitated population expansions across southern Asia. At Katoati, located on the northeast margin of the Thar Desert, the combination of field recording of sediment sections with detailed analyses (micromorphology, stable isotope, loss on ignition, magnetic susceptibility, and X-ray fluorescence) from an archaeological site identify a series of hominin occupations during phases of enhanced humidity between ~96 and 60 ka. A gradient of humidity on the eastern margin of the Thar Desert during the late Pleistocene is identified, with the periodic humidity evident at Katoati occurring more frequently and with longer duration towards the southern margin. This uneven distribution of humidity in the Thar Desert is likely to have strongly influenced when and where hominin populations could expand into and across the region. [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]

Concentrations of eight bisphenol analogues (BPs) including BPA, BPS, and BPF were determined in surface waters collected from select rivers in Japan, Korea, China, and India. BPA was found at a concentration in the range of several tens to several hundreds of nanograms per liter in most of the rivers surveyed and some of the highest concentrations (54–1950 ng/L) were found in rivers in Chennai, India. Concentrations of BPF were one to two orders of magnitude higher than those of BPA in river and sea waters collected from Japan, Korea and China, which suggested that BPF is a major contaminant in surface waters in several Southeast Asian countries. BPF concentrations as high as 2850 ng/L were found in the Tamagawa River in Japan. The flux of BPs through riverine discharges into Tokyo Bay was calculated to be approximately 5.5 t per year. Based on the flux estimates and the mass of BPF found in water column and sediment in Tokyo Bay, it was found that BPF degrades faster than BPA in the environment. Elevated concentrations of BPF found in surface waters suggest the need for further studies to determine the fate and toxicity of this compound. [ABSTRACT FROM AUTHOR]

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]

Abstract: There is no major chemical variation in the late Quaternary calcic nodules formed within vertisols in the foot-hill regions, and hardpan calcretes (greater than 200 ka) formed over the Precambrian substrate that occur as duricrust horizons in the plains around Coimbatore region, Tamil Nadu, India. The bulk chemistry of calcic nodules and the hardpan calcretes show very little variability in CaO, SiO2, Al2O3 and Fe2O3 content. The trend of trace metal content in calcic nodules and in the hardpan calcrete is Mn > Zn > Ni > Cr > Pb > Co > Cu and Zn > Mn > Ni > Co > Pb > Cu > Cr respectively. PAAS-normalised REE data of the calcretes (calcic nodules and the hardpan) demonstrate a positive Euanomaly. This could be attributed to feldspar, apatite mineral alteration and soil digenetic processes, differential weathering leaving behind plagioclase phenocrysts and apatite grains which are enriched in Eu. The stable isotope values of the calcic nodules do not exhibit a wide range (δ18O −3.39 to −5.84‰ and δ13C −3.01 to −6.64‰), compared to the hardpan calcretes (δ18O −2.91 to −12.98‰) and δ13C (−0.05 to −7.4‰). The palaeoenvironment during the formation of the calcretes nodules was dominated by the C4 plants with sparse vegetation cover and that the parent material/bedrock supported a thin veneer of soil column with sparse vegetation cover as present day. Calcic nodule accumulations in the soils has resulted from differential weathering and chemical histories within the soil profiles while the hardpan calcretes formed by complex pedogenic and chemical – groundwater processes in arid – semi-arid conditions over along geological period. During the late MIS3 to the LGM period the south west monsoon was weak with mean annual rainfall (MAR) between 300 and 500 mm/yr, the sea level was low and the rainfall at the time of carbonate formation would have remained damp enough to allow silicate weathering of the soil sediments. [Copyright &y& Elsevier]

Abstract: Pedogenic carbonates in a 19m-thick dune section (16R) at Didwana, and several shorter profiles from the eastern margin of the Thar Desert, Rajasthan, were studied for their stable isotope composition. Carbon isotope results show the C4 biomass (grasses?) has dominated local vegetation for most of the 250,000years represented by the 16R section. Our results display a decrease in δ 18O and δ 13C values during the last interglacial and early glacial periods. The higher δ 13C values in our dune records correlate to episodes in the strong upwelling and decreased sedimentation rates in Indian Ocean cores, probably the result of a strong Asian Monsoon. The high δ 13C values may, therefore, denote the expansion of C4 vegetation in response to warm, wetter monsoon circulation. Conversely, low δ 18O and δ 13C values mark the expansion of C3 vegetation, probably caused by enhanced winter rains and lower temperatures. [Copyright &y& Elsevier]

Five sediment cores from the tidal flats and estuaries between Cuddalore and Odinur, Tamil Nadu at ∼50-70 cm water depth were collected to study the down core variations in organic matter, calcium carbonate content and sediment texture. Quartz, feldspar and moderately rounded to well-round, garnet-rich sand were present in all cores except core IV collected from Marakkanam. Cuddalore (cores I-III) sediments were coarse-grained and those from Odinur (core V) varied from sand to silty sand to clay. Smectite, kaolinite, illite and vermiculite occurred as clay minerals. High content of organic matter was observed in cores from Marakkanam and Odinur. Radiocarbon dates on shell, organic carbon at the base and at intervals of the cores from Marakkanam (core IV) and Odinur (core V) are 8200 ± 230, 9170 ± 290, 5540 ± 430, 2700 ± 140 yrs BP respectively. The sea-level curve presented for the Marakkanam site indicates a gradual and slow sea-level rise since 9000 to 1800 yrs BP. Data on sediment texture, mineralogy, organic matter content supplemented by radiocarbon dates indicate that the deposition of these sediments has taken place in phases since the early Holocene. Reworking of the inner shelf sediments as a result of the dropping sea-level provided the ultimate sediment source for the progradation of the present coastline. [ABSTRACT FROM AUTHOR]

The State of Tamil Nadu was the most affected region in India during the tsunami of December 26, 2004, in the Indian Ocean, in terms of loss of life and damage. Numerical simulation was made for three tsunamis, the December 26, 2004, event, the Sumatra tsunami of 1833, and a hypothetical tsunami originating in the Andaman-Nicobar region. Since inundation is not included in these simulations, the tsunami amplitudes were deduced at the 10m depth contour in the ocean, off several locations on the coast of Tamil Nadu. The computed amplitudes appear reasonable as compared to known tsunami amplitudes from past events. [ABSTRACT FROM AUTHOR]

The article offers information on the 8th International Earth Science Olympiad that was held at the Palaceo de Magdalena, Santander, Spain from September 22-29, 2014, and mentions that it is one of the important programmes of the International Geoscience Education Organisation. It also discusses the selection procedure for high school students from India that represented their country in the olympiad, and mentions that professor Juan D. Centeno and his colleagues organized the event.

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]

Inevitable use of plastic materials in our day-to-day life has led to the entry of microplastic into aquatic environments, which are plastics less that than 5 mm. Microplastic is of great concern in recent years due to its impact on humans and aquatic organisms since they absorb organic contaminants and pathogens from the surrounding media due to higher surface and volume ratio. This is the first study attempted to study the distribution and source of microplastic contamination in Red Hills Lake which is one of the freshwater systems supplying water to the North of Chennai city. Thirty-two sediment samples and six water samples were collected covering an area 18.21 km 2 . The presence of microplastic was analyzed in water and sediment as per the National Oceanic and Atmospheric Administration (NOAA) protocol. The mean concentration of microplastic in water samples was 5.9 particles/L and 27 particles/kg in sediment. In both sediments and water, the most commonly found microplastic types are as follows: fibers (37.9%), fragments (27%), films (24%), and pellets (11.1%). Based on the FTIR, the common types of microplastic were of high-density polyethylene, low-density polyethylene, polypropylene, and polystyrene. Further samples were evaluated for surface elemental composition in order to understand whether heavy metals get adhered to the surface of microplastic using energy-dispersive X-ray. Our results indicated the presence of microplastic in water and sediments which will lead to further study of microplastic presence in biota and microplastic pollution in freshwater systems.

Heavy metals disposed through anthropogenic activities find their way into the oceans and seas through the rivers or through direct fall out from factory effluents. These heavy metals resuspend back into the water column along with the sediments and are known to affect the marine animals. Marine animals like fish, prawn, crab and mussel were collected along the East Coast (off Pulicat lake to Chennai Harbour) to evaluate trace metal concentrations in various tissues. The above specimens accumulated heavy metals such as Zn, Pb, Cu, Co, Cr, Ni and Cd. Fish, prawn, crab and mussel revealed higher concentration of heavy metals such as Zn, Pb, Cr Co, Cu and Ni and Cd in low levels. The results revealed that the heavy metal concentrations in the marine animals are below the threshold levels associated with the toxicological effects and the regulatory limits. The bioconcentration factors revealed that the animals have accumulated heavy metals along the food chain rather than from the water column and sediment.