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The mineralogy, bulk sediment geochemical composition, and U–Pb ages of detrital zircons retrieved from the Barra del Tordo (Tordo) and Tesoro beach sediments in the northwestern Gulf of Mexico were analyzed to determine their provenance. The beach sediments are mainly composed of quartz, ilmenite, magnetite, titanite, zircon, and anorthite. The weathering proxies such as the Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA), reveal a moderate-to-high intensity of weathering in the source area. The chondrite-normalized rare earth element (REE) patterns are similar to felsic igneous rocks, with large negative europium anomaly (Eu/Eu* = ~ 0.47–0.80 and ~ 0.57–0.67 in the Tordo and Tesoro beach sediments, respectively).Three major zircon U–Pb age groups are identified in the Tordo and Tesoro beach sediments, i.e., Proterozoic (~ 2039–595 Ma), Mesozoic (~ 244–70.3 Ma), and Cenozoic (~ 65.9–1.2 Ma). The differences of the zircon age spectrum between the Tordo and Tesoro beach sediments are not significant. The comparison of zircon U–Pb ages in this study with ages of potential source terranes suggests that the Mesozoic and Cenozoic zircons of the studied Tordo and Tesoro beach sediments were derived from the Eastern Alkaline Province (EAP) and Mesa Central Province (MCP). Similarly, the likely sources for the Proterozoic zircons were the Sierra Madre Oriental (SMOr) and Oaxaquia in the northwestern Gulf of Mexico. The results of this study further indicate that the sediments delivered to the beaches by rivers and redistributed by longshore currents were crucial in determining the sediment provenance.

The present investigation is focused on the forecasting visual observation of the impact of anthropogenic activity on the pilgrimage places located along the coastal environments in Tamil Nadu, India. Devotees performing the unregulated ritual ceremonies, open defecation, waste materials dumping and local municipality discharging wastewater contamination levels were assessed from direct visual surveillance, and by taking photographs and baseline information collected from five different pilgrimage sites. Results showed that ritual ceremonies, wastewater discharges and debris highly contaminated site-III, and found open defecation at site-I. The lack of coastal regulation, pollution awareness, insufficient sanitation facilities and failure to control the commercial and recreational activities have major deleterious effects on the present and future environments of the coastal areas. This is the first attempt conducted by visual assessment of the coastal pollution in pilgrimage places. The results immensely support the recommendation for proper regulation of ritual activities, arrangement of basic sanitation facilities and prohibition of wastewater discharges to prevent waterborne diseases as well as to strictly follow the regional and national level of coastal regulation policy to protect the biological resources of the Gulf of Mannar marine ecosystems.

This study examines textural characteristics, carbonate, organic carbon and chemical composition of sediment samples recovered in the nearshore region (~3–19 m water depth) at the Grijalva River mouth, southern Gulf of Mexico. The aim of this study is to assess the heavy metal contamination and provenance variations in sediments between the dry and northers (rainy) seasons. The proportion of sand, carbonate, and organic carbon contents were abundant at sites located near to the Grijalva River mouth, principally in northers season. Silt content is dominant in the dry season, especially in the sites located away from the Grijalva River mouth. The Chemical Index (CIX) values obtained for the dry (~76–84) and northers (~75–87) seasons indicated a moderate to high intensity of weathering and a humid climate in the source area. The low K2O/Al2O3 ratio values (

Microtextures of quartz and zircon grains from the Bosque and Paseo del Mar beaches in the Gulf of Mexico were examined using a Scanning Electron Microscopy (SEM), to infer their provenance and palaeoenvironment. A total of 16 microtextures from 200 grains were identified and were grouped into mechanical, chemical, and mechanical/chemical origin. Microtextures of mechanical origin represent parallel striations (ps), cracks due to collision (ck), conchoidal fractures (cf), v-shaped marks (vs), abrasion fatigue (af), meandering ridges (mr), chattermarks (ch), curved (cg) and straight grooves (sg), which are attributed to a high-energy fluvial and sub-aqueous marine environment. Solution pits (sp), crystal overgrowth (cro), and silica globules (sgl) of chemical origin indicated precipitation and dissolution in a silica saturated marine environment. Adhered particles (ap), elongated depressions (dp), and relief are grouped as mechanical/chemical origin, suggested a sub-aqueous nearshore marine environment. Although zircon is considered as a resistant mineral, the frequency of microtextures observed was higher in zircon than in quartz. The results of this study revealed that the Los Tuxtlas volcanic field, Chiapas Massif and Oaxacan Complexes in the SW Gulf of Mexico are the potential source areas, which supplied sediments to the Paseo del Mar and Bosque beach areas.

We applied both the ordinary linear regression (OLR) and the new uncertainty weighted linear regression (UWLR) models for the calibration and comparison of a XRF machine through 59 geochemical reference materials (GRMs) and a procedure blank sample. The mean concentration and uncertainty data for the GRMs used for the calibrations (Supplementary Materials) (available here) filewere achieved from an up-to-date compilation of chemical data and their processing from well-known discordancy and significance tests. The drift-corrected XRF intensity and its uncertainty were determined from mostly duplicate pressed powder pellets. The comparison of the OLR (linear correlation coefficient r∼0.9523–0.9964 and 0.9771–0.9999, respectively, for before and after matrix correction) and UWLR models (r∼0.9772–0.9976 and 0.9970–0.9999, respectively) clearly showed that the latter with generally higher values of r is preferable for routine calibrations of analytical procedures. Both calibrations were successfully applied to rock matrices, and the results were generally consistent with those obtained in other laboratories although the UWLR model showed mostly narrower confidence limits of the mean (slope and intercept) or lower uncertainties than the OLR. Similar sensitivity (∼2.69–46.17 kc·s−1·%−1 for the OLR and ∼2.78–59.69 kc·s−1·%−1 for the UWLR) also indicated that the UWLR could advantageously replace the OLR model. Another novel aspect is that the total uncertainty can be reported for individual chemical data. If the analytical instruments were routinely calibrated from the UWLR model, this action would make the science of geochemistry more quantitative than at present.

An online computer program called APMdisc (Active and Passive Margin discrimination) for the discrimination of siliciclastic sediments from active and passive margin settings was written in Java along with the ZK framework. APMdisc calculates four complex discriminant functions (DFilr(A-P)M and DFmlr(A-P)M; DFilr(A-P)MT and DFmlr(A-P)MT), which represent linear combinations of log-ratios of all ten major elements (M) and ten major and six trace elements (MT), respectively. In these equations, ilr and mlr stand for isometric log-ratio and modified log-ratio transformations of the chemical composition of active and passive margin sediments, respectively. The ilr transformation provided the same results as the mlr as documented for five case studies of Quaternary sediments from California, Antarctica, Nigeria, India, and Japan. We also present 9 other case studies (for Neogene to Quaternary sediments from known tectonic settings) and 11 application studies (Tertiary to Neoproterozoic sediments and sedimentary rocks) to show the functioning of the multidimensional discrimination proposed in this paper. In most cases, the results from the APMdisc were consistent with the literature conclusions inferred from different geological and geochemical techniques. Nevertheless, APMdisc provides probability estimates for both tectonic settings, which allows the decision to be made based on the probability concept. We also added a new Robustness module to APMdisc, which allows the user to test the robustness of a sample against field changes, such as weathering and diagenesis, and laboratory analytical errors or uncertainties. This program can therefore be recommended for deciphering the margin type of older terrains. The APMdisc program can be used online by researchers for tectonic discrimination based on sediment composition. The users can process the data file at our web portal http://tlaloc.ier.unam.mx.

Thirty-five near-surface sediment samples were recovered from the continental shelf and upper slope regions of the northwestern (NW) Gulf of Mexico. The geochemical data of the sediments recovered were examined to investigate the weathering intensity, provenance, palaeo-oxygenation condition, and level of heavy metal contamination. The sediments analysed showed a moderate to high intensity of chemical weathering. Major and trace element concentrations indicated a terrigenous origin, closely related to the weathering of rocks rich in aluminosilicates. The results of this study further revealed that major rivers, the Bravo and Soto La Marina, played an important role in delivering sediments to the study area. The concentration of transition trace elements such as Cr, Cu, Ni, and V revealed that the sediments were derived from intermediate rocks such as andesite. The V/Cr, Ni/Co, and Cu/Zn ratios in the sediments were

The petrochemical industry and urban activities are widely recognized worldwide as a source of pollution to mangrove environments. They can supply pollutants such as trace elements that can modify the ecosystem structure and associated services, as well as human populations. Through geochemical data, multivariate statistical analysis and pollution indices such as the enrichment factor (EF), geo-accumulation index (Igeo), adverse effect index (AEI) and the pollution load index (PLI), we evaluated the factors that control trace element distribution, punctual sources and determined the pollution level of sediments and their potential biological impact in the mangrove ecosystem of Isla del Carmen, Mexico. The factor and cluster analysis highlighted that the distribution of trace elements is influenced by the mineralogy, texture as well as urban derived sources. The pollution indices showed values in the punctual sources from the urban area of EF > 10, Igeo > 3, AEI > 3, PLI > 1 by Cu, Zn and Pb. Finally, the results revealed that mangroves from Isla del Carmen has a major influence from urban activities and natural sources rather than oil industry and also indicate a degraded environment as a result of anthropogenic activities that could have knock-on effect for human health if polluted marine organisms derived from the urban mangroves are consumed. Capsule abstract Surface sediments show the influence of point sources on selected trace element concentrations correlated with human activities within the mangroves of Isla del Carmen, Mexico.

Combined petrographic and geochemical data of the siliciclastic sedimentary rocks from the Shemshak Group in the northeastern Alborz Mountains, north of Iran are described, together with their implications for palaeoweathering, their provenance, and tectonic setting. Based on field observations and modal composition, the sandstones are classified as litharenites. The chemical index of alteration (CIA) indicated that the source terrains underwent a moderate intensity of chemical weathering. The index of chemical variation (ICV) values indicated that the Shemshak Group rocks were immature and related to a source area with an active tectonic regime. Major, trace and rare earth element (REE) data suggested the domination of mixed sedimentary (recycled) and igneous rocks in the source area of the Shemshak Group. Petrographic and geochemical characteristics of Shemshak Group rocks suggest an active continental margin (ACM), which corresponds to the collision of the Iran plate with the Turan plate.

Stable carbon ( δ 13 C) and oxygen ( δ 18 O) isotopes of bivalve shells and calcareous sediments of the Mio-Pliocene Nhila Anticline, southeast Bengal Basin, Bangladesh have been investigated to obtain information on paleoclimate and paleoenvironment conditions during deposition. The δ 13 CPDB, δ 18 OPDB and δ 18 OSMOW values in bivalve shell range from -2.81‰ to -1.56‰, -3.57‰ to -2.39‰ and 27.18‰ to 28.40‰ in bivalve shells and -13.90‰ to -1.75‰, -4.71‰ to -2.13‰ and 26.01‰ to 28.66‰ in calcareous sediments, respectively. The δ 13 CPDB values in bivalve shells are comparable to that of calcareous sediments (~ -1.75‰) in the upper section, but δ 13 CPDB values in calcareous sediments are more negative excursion towards lower section (up to -13.90‰). These results signify that salinity gradients could modified the isotope values and/or strong influence of freshwater conditions. The variable δ 18 OPDB values in both bivalve shell and calcareous sediment suggesting diagenetic alteration of carbonates and water temperature effects. The more negative δ 18 OPDB values imply humid paleoclimatic conditions during the Mio-Pliocene sedimentation. Therefore, the δ 18 OPDB values of the Mio-Pliocene sediments of Nhila Anticline are probably controlled by paleotemperature leading to intensification of high rainfall. DOI: http://dx.doi.org/10.3329/jles.v8i0.20155 J. Life Earth Sci., Vol. 8: 113-117, 2013

This study focuses on the Jurassic (Huayacocotla and Pimienta Formations) and Upper Cretaceous (Mendez Formation) shales from the Molango Region, Hidalgo, Mexico. In this article, we discuss the mineralogy, major, and trace element geochemistry of the Mesozoic shales of Mexico. The goal of this study is to constrain the provenance of the shales, which belong to two different periods of the Mesozoic Era and to understand the weathering conditions and tectonic environments of the source region.

A sedimentological, petrographic, and geochemical study of beach, dune, and river sands was carried out along the northwestern Gulf of Mexico. The main goal of this work is to show how beach and dune sands are controlled texturally, compositionally, and chemically by the nearby rivers for each beach location using a particle size analyser, a polarized microscope, a X-ray fluorescence and ICP mass spectrometer to obtain the following: grain-size values from one river (Carrizal River) are similar in range to their counterpart beach sands but not similar to the dune sands (Barra del Tordo). Rivers (Panuco and Carrizal) are compositionally controlling the quartz and feldspar contents of their counterpart beach and dune sands (i.e., Playa Miramar and Barra del Tordo). Rivers (Soto La Marina River) are directly influencing the composition of the beach sands (La Pesca) based upon the total quartz content, beach and dune sands. The concentration of magnetite grain fractions (Barra del Tordo beach and dune sands) is not under the influence of the nearby river (Carrizal River). In this case the compositional influence of beach and dune sands is related to sediment discharges by other fluvial systems, redistribution of the beach and dune sands along the coast and deflation/winnowing of light minerals. The Eu positive anomaly in the beach and dune sands from the three sites (i.e. Playa Miramar, Barra del Tordo, La Pesca) is linked to an increase in the P(plagioclase)/K(potash feldspar) ratio. The (La/Lu)cn highest ratio for river sands (Carrizal River) suggests quartz enrichment compared to their beach and dune sands counterparts. The (Gd/Yb)cn ratio for one river (i.e., Carrizal River) indicates that it is low in heavy rare earth elements. HREE compared to their beach and dune sands counterparts indicates less concentration of heavy minerals as potential carriers of HREE seawards.

Major, trace and rare earth element (REE) geochemistry of carbonate rocks of the Neoproterozoic Shahabad Formation, southern India were studied in order to investigate the depositional environment and source for the REEs. The PAAS (Post Archaean Australian Shale) normalized REE + Y pattern of Shahabad limestones have consistent seawater-like pattern i.e., i) LREE depletion (average (Nd/Yb)SN = 0.64 ± 0.08), ii) negative Ce anomaly, iii) positive Gd anomaly (average GdSN/Gd* = 1.05 ± 0.16), iv) superchondritic Y/Ho ratio (average Y/Ho = 38.13 ± 21.35). The depletion of LREE and enrichment of HREE are clearly indicated by the (La/Yb)SN, (Dy/Yb)SN and (Nd/Yb)SN ratios, which suggest the retention of seawater characteristics in these limestones. The negative Ce anomaly reflects the incorporation of REE directly from seawater or from the pore water under oxic condition, and also reveals the mixing of two-component systems with terrigenous clay (detrital) in the marine sediments. The terrigenous input in these limestones is confirmed by positive correlation of ΣREE with Al2O3, negative correlation of ΣREE with CaO and differences in Y/Ho ratios. V, Cr, and Sc, are positively correlated with Ti, and strong positive correlation of ΣREE with Fe2O3, Ni, Cr, Sc, and Y also indicate the presence of terrigenous materials in the Shahabad limestones.

The weathering conditions, provenance, and tectonic setting of sands from the San Nicolás (SN) and San Carlos (SC) beaches along the Gulf of California, Mexico, have been studied using mineralogy, major element, and trace element data. The compositional similarity among 4 independent groups (each beach area consists of 2 grain-size groups, i.e. medium- and fine-grained sands) was tested statistically by the application of analysis of variance at the 99% confidence level to avoid misinterpretation. The X-ray diffraction and SEM-EDS data revealed that the fine-grained SN sands were abundant in rutile and zircon minerals. The higher SiO2/Al2O3 ratio of the SN sands than the medium- and fine-grained SC sands indicated that the compositional maturity was greatest for the SN sands (Fcalc = 366.756151 and (Fcrit)99% = 5.065158, where Fcalc > (Fcrit)99% indicates that the data populations are significantly different at 99% confidence level). The chemical index of alteration values for the SN (ca. 41-45) and SC (ca. 48-51) sands indicated low to moderate weathering intensity in the source region. The significant enrichment of the low rare earth element and the flat heavy rare earth element patterns of the SN sands indicated that the sources were largely felsic rocks. The low positive Eu anomaly in the SC sands was probably due to the contribution of sediments from intermediate rocks between felsic and mafic compositions. The comparison of rare earth element data of the sands with rocks located relatively close to the study areas revealed that the SN sands received a major contribution from felsic rocks and SC sands from intermediate rocks. The compositional difference between the SN and SC beach areas indicated that longshore currents played a less significant role. Discriminant function-based major element diagrams for the tectonic discrimination of siliciclastic sediments revealed a rift setting for the Gulf of California, which is consistent with the general geology of Mexico.

An acid leachable technique is employed in core samples (C1, C2 and C3) to develop a baseline data on the sediment quality for trace metals of River Uppanar, Cuddalore, southeast coast of India. Acid leachable metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn and Cd) indicate peak values at the sulphidic phase and enrichment of metals in the surface layers are due to the anthropogenic activities. Association of trace metals with Fe, Mn indicates their adsorption onto Fe-Mn oxyhydroxides and their correlation with S indicate that they are precipitated as metal sulphides. Factor analysis identified three possible types of geochemical associations and the supremacy of trace metals along with Fe, Mn, S and mud supports their geochemical associations. Factor analysis also signifies that anthropogenic activities have affected both the estuarine and fresh water regions of River Uppanar.

Two oceanographic cruises were taken during the winter (SAV I, November and December 2007) and summer (SAV II, July and August 2008) across the mouth of the Papaloapan River in the Gulf of Mexico. Surficial sediment samples were collected from shallow (16–30 m), intermediate (30 to 80 m), and deeper areas (≥300 m). Shallow water sediments are coarser, better-sorted, and primarily composed of sands during the winter, while those found in the summer are finer. At depths greater than 30 m, sediments are primarily fine-grained no matter the season. Major element analysis from shallow areas indicates higher SiO2 concentrations during the windy season with negative correlation against Al2O3 during both seasons, following the respective abundances of sand and muds. High organic carbon content was observed in shallow areas during the summer. Trace metals V, Ni, Cu, Zn, Pb, Li, Cr, Co, and Ba were evaluated. The first six metals showed higher average concentration in the deeper areas, although the highest values at some individual sampling sites for Cr, Co, Cu, and Ba were observed in the coastal area. Factor and cluster analysis were used to explain the sediment distribution pattern and the factors that determine the sediment characteristics within the study area. In shallow areas, four clusters were observed during the winter and five during the summer. The geochemical characteristics of the samples in each cluster suggest association with fluvial sediment input, textural characteristics, heavy minerals, and Cu and Ba concentration. To evaluate the variations in heavy metal concentration, metal enrichment factors (EFs) were calculated. Enrichment in V, Cr, Co, Zn, Ba, and Pb was detected at certain sites, whereas Cu behaved differently. The distribution of Cu enrichment suggests that it may be of natural origin, associated with the lithology of the volcanic continental area. The minor enrichment observed for other elements may be associated with river discharge. According to sediment quality guidelines, trace metal concentrations of Cu, Pb, and Zn present occasional risks to aquatic organisms.

Core sediments from Mullipallam Creek of Muthupet mangroves on the southeast coast of India were analyzed for texture, CaCO 3 , organic carbon, sulfur and acid leachable trace metals (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn and Cd). Textural analysis reveals a predominance of mud while CaCO 3 indicates dissolution in the upper half of the core, and reprecipitation of carbonates in reduction zones. Trace metals are diagenetically modified and anthropogenic processes control Pb and, to some extent, Ni, Zn and Fe. A distinct event is identified at 90 cm suggesting a change in deposition. Strong relationship of trace metals with Fe indicates that they are associated with Fe-oxyhydroxides. The role of carbonates in absorbing trace metals is evident from their positive relationship with trace metals. Comparison of acid leachable trace metals indicates increase in concentrations in the study area and the sediments act as a sink for trace metals contributed from multiple sources.

Major, trace and rare earth elements (REE) composition of sandstones from the Upper Cretaceous Sillakkudi Formation, Ariyalur Group, Cauvery Basin were studied to decipher their weathering and provenance history. Texturally, these sandstones are immature, poorly sorted and grain supported. Abundance of feldspars especially, plagioclase indicates rapid deposition of sediments from a nearby source rocks. Using the geochemical classification diagram the Sillakkudi sandstones are classified as fe-sand, quartz arenite, litharenite, sub-litharenite, sub-arkose, arkose, and wacke types, which is also supported by the petrography study. The transition trace elements like Co, Ni, and V are higher in the Sillakkudi sandstones than upper continental crust (UCC) values. However, the Sillakkudi sandstones are lower in Cr (mean ∼21) content than average UCC value (∼ 35). The poor correlation between Cr and Ni (r = 0.08, number of samples n = 20) imply that these sandstones were derived from felsic source rocks. Similarly, the Eu/Eu* (0.35–1.73), La/Sc (1.93–9.36), Th/Sc (0.41–6.57), Th/Co (0.14–5.01), Th/Cr (0.23–2.94), and Cr/Th (0.34–4.28) ratios support a felsic source for the Sillakkudi sandstones. The significant enrichment of Zr, Hf, and Th in fe-sand, sub-arkose and litharenite could be related to the presence of heavy minerals, especially zircon. However, the zircon geochemistry did not affect the REE distribution and its patterns in the Sillakkudi sandstones. The Chondrite normalized REE patterns of Sillakkudi sandstones are characterized by relatively flat HREE (Gd/YbCN = ∼ 0.73–2.41; subscript CN refers to chondrite normalized value), enriched LREE (La/SmCN = ∼ 3.39–5.82) and negative Eu anomaly (mean value Eu/Eu* = 0.80). The Gd/YbCN ratios (∼0.73–2.50) are less than 2.5, which suggest that these Sillakkudi sandstones were derived from the less HREE depleted source rocks. The comparison of REE patterns and its Eu anomalies to the source rocks reveals that the Sillakkudi sandstones received a major contribution of sediments from Dharwar craton.

International audience; The Rabanpalli Formation exhibits two types of shales, viz. grey and calcareous shales. These shales (grey and calcareous) have been analysed for major, trace, and rare earth elements to fi nd out their source rocks characteristics and paleo-oxygenation conditions. The grey shales have higher concentration of SiO2, Al2O3, Fe2O3, K2O, Zr, Th, U, V, Cr, La, Ce, and Y than calcareous shales, whereas calcareous shales are enriched in CaO, Mn, Sr, Ba, Cu, and Zn, which indicate that the carbonate phase minerals are higher in calcareous shales. The positive correlation of K2O with other elements, and abundance of Al2O3, Ba, Th, and Rb suggest that these elements are primarily controlled by the dominant clay minerals. La/Sc, Th/Sc, Th/Co, Th/Cr, and Cr/Th ratios of shales were compared with those of sediments derived from felsic and basic rocks (fi ne fraction), upper continental crust (UCC) and post-Archean Australian average shale (PAAS) ratios, which reveal that these ratios are within the range of felsic rocks. The La/Sc vs. Th/Co plot also suggests the felsic nature of the source rocks. The shales show slightly light rare earthelement (LREE) enriched and fl at heavy rare earth element (HREE) patterns with negative Eu anomaly, and are similar to the granitoids from Dharwar Craton, which suggest that the Archean Dharwar Craton contributed the sediments to the Bhima basin. The geochemical parameters such as U, authigenic U, U/Th, V/Cr, Ni/Co, and Cu/Zn ratios indicate that these shales were deposited under oxic environment.