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The Lobe River (LR) watershed basement rock, Ntem Complex (NC), south Cameroon is covered by a thick lateritic soil. To better constrain the geology of the basement rock, textural, mineralogical and bulk geochemical (major, trace, and rare earth elements) analyses were undertaken on the recent stream sediments from the LR. The aims of this study were to investigate the provenance of sediments and to determine the weathering intensity of the source area. The ternary (Al 2O3–TiO2 –Zr) and binary (Th/Sc–Zr/Sc) diagrams suggested high sediment recycling and sorting, indicating that the bulk hydraulic energy of the LR controls the sediment texture. Despite the diagenetic processes of K-metasomatism observed on the A-CN-K plot, the (A-K)-C-N plot, Chemical Index of Alteration (CIA), and Plagioclase Index of Alteration (PIA) indicate that the studied sediments and their source areas underwent a high degree of chemical weathering. The heavy mineral suites imply heterogeneous provenance, including igneous, metamorphic and sedimentary source rocks. The ternary diagrams and Co/Th, La/Sc, Sc/Th, Cr/V, and Y/Ni elemental ratios indicate mostly felsic source rocks with lesser contribution from mafic components. The comparison of chondrite normalized REE patterns of LR sediments with potential source rocks reveals that the sediments were derived from the Precambrian basement rocks composed of tonalitic, trondhjemitic, and granodioritic suites, with remnants derived from Archean Greenstone Belt .

Mineralogic and geochemical studies were performed in the Tecolutla and Coatzacoalcos beach sediments, located at the SW Gulf of Mexico. The main concern of this article is to infer the weathering, provenance, and degree in which trace metal pollution affects the beach sediment composition. The chemical index of weathering (CIX) for the Tecolutla and Coatzacoalcos beach sediments indicate a moderate intensity of weathering in the source area. The SiO2/Al2O3 ratio values (>6) in the Tecolutla and Coatzacoalcos sediments suggested a high compositional maturity and recycling. A difference in the Al2O3/TiO2 ratios between the Tecolutla and Coatzacoalcos beach sediments points out that the sediments were derived from intermediate and felsic igneous rocks, respectively. A negative correlation for Al2O3 against TiO2 and P2O5, and trace elements Y, Nb, V, Sc, and Cr for the beach sediments suggests an association of these elements with detrital minerals rather than aluminosilicates. The provenance discrimination based on major element concentrations indicates an intermediate and a felsic provenance for the Tecolutla and Coatzacoalcos sediments. The major and trace element geochemistry of beach sediments are associated with a passive margin setting. The Enrichment factor (EF) and Geo accumulation index (Igeo) values show that the Tecolutla sediments are moderately enriched by Cu (EF ∼ 10–17) and Cr (1

Microtextures on quartz grains from the Huatabampo (HB) and Altata (AA) beaches, Gulf of California, were analyzed by a scanning electron microscopy (SEM) to infer the depositional history and provenance. In total, 41 microtextures were identified and grouped as mechanical, mechanical/chemical, and chemical mode of origins. Among them, twenty-three microtextures represent mechanical, eight represent mechanical/chemical, and ten represent chemical origin. The microtextures of chemical origin were further classified as dissolutional and precipitational origins. Oriented etch pits, solution pits, solution crevasses, and scaling are classified as of dissolutional origin. Silica globules, silica flower, silica pellicles, crystalline overgrowth, trapped diatoms, and halite crystals are grouped as chemical precipitational origin. The V-shaped marks, straight and curved scratches revealed the combination of fluvial and high energy subaqueous beach environments. The low frequencies of upturned plates, abrasion fatigue, meandering ridges, crescentic percussion marks, bulbous edges and elongated depressions suggest the low abundance of sediments derived by aeolian transport. The microtextures of chemical origin in few grains indicated the diagenetic processes in a silica saturated intertidal zone. The quartz grains from HB and AA beaches reveal varying sizes of conchoidal fractures indicate that they were derived mainly from crystalline source rocks. The association of straight and arcuate steps along with conchoidal fractures further support that the studied quartz grains were liberated from crystalline rocks. The dominance of angular to sub-angular grains indicates short transport and rapid deposition. In addition, straight and arcuate steps are delicate features which might have been destroyed during long transportation. Thus, the presence of straight and arcuate steps features together with angular to sub-angular grains support a nearby source.

The National Park Veracruz Reef System (PNSAV) located in the Veracruz coastal area, Gulf of Mexico is highly influenced by anthropogenic and natural impacts. In this study, we analyzed the total and bioavailable fractions of Cd and Pb contents in sediments recovered at 18 sites (~8–9 m water depth) in the Veracruz Reef System (VRS). An enrichment of Cd and Pb contents is identified in VRS, which indicates various anthropogenic activities that occurred in the region. The Cd total fraction observed in the Rizo reef surpassed the Mid-range effect (ERM), which is potentially toxic to marine organisms and human health. High Cd bioavailable fraction is observed in the Gallega and Galleguilla reefs in the northern part of the PNSAV, but they did not exceed the ERM and Low Range Effect (ERL) values. However, relatively high bioavailable Pb suggests a potential risk of exerting toxic effects to the environment and marine biota, since this metal can be very easily consumed by the benthic organisms living in this zone.

The petrography and geochemistry of clastic rocks collected from two sections from the Baluti Formation northern Iraq, have been investigated to infer the depositional environment of the Late Triassic Baluti Formation. Petrographic study of the carbonate unit shows that they consist mainly of heterogeneous poorly sorted grainstones and packstones, ooids, intraclasts, peloids, bioclasts and green algae (Halimeda). The abundant and heterogeneous size of these constituents suggests a subtidal lagoon/oolitic shoal depositional environment with an open marine water circulation . Trace element concentrations of the shales and marlstones reveal a wide difference in the depositional environment. The paleoclimate proxies (C-value, Sr/Cu, Rb/Sr, Ga/Rb, and Sr/Ba ratios) and presence of illite suggest a hot and arid to semiarid climates during the deposition of the Buluti sediments, which coincide with the Late Triassic global warming. The combined use of the Cd/Mo and Co*Mn proxies indicate the deposition mainly in open marine settings on the continental margin associated with upwelling and subordinate restricted marine settings. Trace element redox proxies (V/(V + Ni), Th/U, V/Cr, Ni/Co, and V/Ni ratios indicates anoxic to dysoxic to marginally oxic marine conditions. This difference in paleoredox conditions is likely to arise from the variation in the hydrographic conditions of the depositional basin including water depth, upwelling oxidation degree in the water column and salinity.

This study investigated the bulk sediment geochemistry, U–Pb ages and rare earth element (REE) geochemistry of one hundred detrital zircons recovered from the Brujas beach sands in southwestern Gulf of Mexico to understand the provenance and age spectra. The bulk sediments are high in Zr and Hf contents (∼1400–3773 ppm and ∼33–90 ppm, respectively) suggested the abundance of resistant mineral zircon. The chondrite normalized REE patterns of the bulk sediments are less fractionated with enriched low REE (LREE; La CN /Sm CN = ∼491–693), depleted heavy REE (HREE; Gd CN /Yb CN = ∼44–69) and a negative Eu anomaly (Eu/Eu ∗ = ∼0.44–0.67) suggested that the source rock is felsic type. The results of this study revealed highly varied contents of Th (∼4.2–321 ppm), U (∼20.7–1680 ppm), and Hf (∼6970–14,200 ppm) in detrital zircons compared to bulk sands. The total REE content (∼75 and 1600 ppm) and its chondrite-normalized pattern with positive Ce and negative Eu anomalies as well as low Th/U ratio of zircon grains indicated that they were dominantly of magmatic origin. U–Pb data of zircons indicated two age populations, with predominance of Permian-Triassic (∼216–286 Ma) and Neoproterozoic (∼551–996 Ma). The Permian-Triassic zircons were contributed by the granitoids and recycled metasedimentary rocks of the Chiapas Massif Complex. The major contribution of Neoproterozoic zircons was from the Chaucus, Oaxacan, and Chiapas Massif Complexes in Grenville Province, southern Mexico. U–Pb ages of zircons from the Brujas beach are consistent to the reported zircon ages from the drainage basins of Usumacinta, Coatzacoalcos, and Grijalva Rivers in southern Mexico, suggesting that the sediments delivered by the rivers to the beach area are vital in defining the provenance of placers.

A new multidimensional scheme consistent with the International Union of Geological Sciences (IUGS) is proposed for the classification of igneous rocks in terms of four magma types: ultrabasic, basic, intermediate, and acid. Our procedure is based on an extensive database of major element composition of a total of 33,868 relatively fresh rock samples having a multinormal distribution (initial database with 37,215 samples). Multinormally distributed database in terms of log-ratios of samples was ascertained by a new computer program DOMuDaF, in which the discordancy test was applied at the 99.9% confidence level. Isometric log-ratio (ilr) transformation was used to provide overall percent correct classification of 88.7%, 75.8%, 88.0%, and 80.9% for ultrabasic, basic, intermediate, and acid rocks, respectively. Given the known mathematical and uncertainty propagation properties, this transformation could be adopted for routine applications. The incorrect classification was mainly for the “neighbour” magma types, e.g., basic for ultrabasic and vice versa. Some of these misclassifications do not have any effect on multidimensional tectonic discrimination. For an efficient application of this multidimensional scheme, a new computer program MagClaMSys_ilr (MagClaMSys—Magma Classification Major-element based System) was written, which is available for on-line processing on http://tlaloc.ier.unam.mx/index.html . This classification scheme was tested from newly compiled data for relatively fresh Neogene igneous rocks and was found to be consistent with the conventional IUGS procedure. The new scheme was successfully applied to inter-laboratory data for three geochemical reference materials (basalts JB-1 and JB-1a, and andesite JA-3) from Japan and showed that the inferred magma types are consistent with the rock name (basic for basalts JB-1 and JB-1a and intermediate for andesite JA-3). The scheme was also successfully applied to five case studies of older Archaean to Mesozoic igneous rocks. Similar or more reliable results were obtained from existing tectonomagmatic discrimination diagrams when used in conjunction with the new computer program as compared to the IUGS scheme. The application to three case studies of igneous provenance of sedimentary rocks was demonstrated as a novel approach. Finally, we show that the new scheme is more robust for post-emplacement compositional changes than the conventional IUGS procedure.

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 mineralogy, geochemistry, and radiocarbon ages of two sediment cores (GMX1 and GMX2) collected from the deep sea area of the Southwestern Gulf of Mexico (∼876–1752 m water depth) were studied to infer the sedimentation rate, provenance, heavy metal contamination, and depositional environment. The sediments are dominated by silt and clay fractions. The mineralogy determined by X-Ray diffractometry for the sediment cores reveals that montmorillonite and muscovite are the dominant clay minerals. The sections between 100 and 210 cm of the sediment cores GMX1 and GMX2, respectively, are characterized by the G. menardii group and G. Inflata planktonic foraminiferal species, which represent the Holocene and Pleistocene, respectively. The radiocarbon-age measurements of mixed planktonic foraminifera varied from ∼268 to 45,738 cal. years B.P and ∼104 to 25,705 cal. years B.P, for the sediment cores GMX1 and GMX2, respectively. The variation in age between the two sediment cores is due to a change in sediment accumulation rate, which was lowest at the location GMX1 (0.006 cm/yr) and highest at the location GMX2 (0.017 cm/yr). The chemical index of alteration (CIA), chemical index of weathering (CIW), and index of chemical maturity (ICV) values indicated a moderate intensity of weathering in the source area. The total rare earth element concentrations (∑REE) in the cores GMX1 and GMX2 vary from ∼94 to 171 and ∼78 to 151, respectively. The North American Shale Composite (NASC) normalized REE patterns showed flat low REE (LREE), heavy REE (HREE) depletion with low negative to positive Eu anomalies, which suggested that the sediments were likely derived from intermediate source rocks. The enrichment factor of heavy metals indicated that the Cd and Zn concentrations in the sediment cores were impacted by an anthropogenic source. The redox-proxy trace element ratios such as V/Cr, Ni/Co, Cu/Zn, (Cu + Mo)/Zn, and Ce/Ce* indicated that the sediments were deposited under an oxic depositional environment. The similarity in major element concentrations, REE content, and the NASC normalised REE patterns between the cores GMX1 and GMX2 revealed that the provenance of sediments remained relatively uniform or constant during deposition for ∼4.5 Ma. The major and trace element based multidimensional discrimination diagrams showed a rift setting for the core sediments, which is consistent with the geology of the Gulf of Mexico.

Discrimination of active and passive margins is important from both academic and economic aspects. This can only be successfully achieved, however, if there are major compositional differences among sediments derived from different continental margins. A worldwide database of active and passive margin settings was established from published major and trace element geochemical data of Neogene to Quaternary siliciclastic sediments. These data were used to evaluate the performance of existing discrimination diagrams, which were shown to work unsatisfactorily with success values of mostly between 0% and 30%. Because these diagrams were not based on a statistically coherent methodology, we proposed two new discriminant functions from linear discriminant analysis of multinormally distributed isometric log-transformed ratios of major and combined major and trace elements. These new diagrams showed very high percent success values of about 87%–97% and 84%–86% for the active and passive margins, respectively, for the original database. Excellent performance of the multidimensional diagrams and related discriminant functions was confirmed from 11 test studies involving Quaternary to Holocene siliciclastic sediments from known tectonic margins. The expected result of an active or passive margin was obtained, with most samples plotting correctly in the respective field.

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.

Surface textures of quartz and ilmenite grains provide an insight in assessing current mechanical, chemical and mechanical-chemical processes in dune and beach sands of the Gulf of Mexico Coast (GMC) Mexico. The GMC area produces hybrid sands enriched in monocrystalline quartz and ilmenite-free grains. Quartz grains are observed in all dunes and beach localities of the central GMC close to the Trans-Mexican Volcanic Belt characterized by large conchoidal fractures (>100 μm), angular to subangular outlines, arcuate steps, high relief, and sharp edges associated with fluvial transport. Aeolian quartz features like meandering ridges, upturned plates, bulbous edges and adhering particles on quartz are only present in some GMC sites, whereas marine surface textures like straight and curved grooves are sparse. Chemical surface textures on quartz and ilmenite are a consequence of silica saturated low-energy subaqueous conditions and subaerial exposure, diagenesis and intermediate weathering processes in the dunes and beach sands. Ilmenite grains are common in all studied localities of the GMC, characterized by large conchoidal fractures (>100 μm), angular to subangular outlines, flat cleavage surfaces, arcuate steps and high relief. In some ilmenite grains, upturned plates, meandering ridges, bulbous edges and abrasion fatigue characterize aeolian surface features. Straight and curved grooves only characterize marine surface textures. To assess the prevailing transport mechanisms along the GMC, quartz and ilmenite grains from dunes and beach sands were selected based on surface texture observations. Our findings suggest that quartz and ilmenite grains are primarily transported and deposited along the coast by riverine input, a second-cycle of aeolian transport onshore, and recycling by marine longshore currents and waves.

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.

Sedimentological, geochemical, and X-ray diffraction (XRD) analyses in addition to the determination of biogenic fraction components (BFC) were performed in mollusk shells from carbonate beach samples collected on the northern coast of the Yucatan Peninsula, Mexico. The most abundant components of the BFC were bivalves and gastropods shells, ranging from 88.1 to 99.2 % and from 0.1 to 6.0 %, respectively, followed by minor percentages of foraminifera, coral fragments, bryozoa, oolites, spicules, and ostracods. A combination of major element, trace element, and XRD techniques were performed to show how the Mg/Ca and Mg/Sr ratios determine the possibility of a recrystallization process in bivalves and gastropods, which may be attributed to early diagenetic mechanisms caused by groundwater flows, subaerial exposure, high evaporation rates, and neomorphism. The rare earth element analyses gave the average anomalies for the following ratios (Pr/Yb)PAAS and MuQ ratio > 1, (Eu/Eu*)PAAS and MuQ and (Ce/Ce*)PAAS and MuQ < 1, suggesting little incorporation of sea water in the BFC of the shells from the Yucatan beach sands. This is also supported by the flat pattern trends of bivalves and gastropods based on the normalized patterns of light rare earth element compared to heavy rare earth element concentrations. This paper is also a contribution to the methodology of analysis of carbonate sands, i.e., whole bulk composition isolation into their main biogenic components and the accumulation of major, trace, and rare earth elements deposited into their shells, initially under subaquatic marine conditions and currently exposed to subaerial coastal influences based on the allochthonous character of the shells.

Compositional and geochemical analyses of sands collected from the Chachalacas (CHA) and Veracruz (VER) beach areas along the western Gulf of Mexico were studied to determine the provenance and tectonic setting of the source region. The modal composition showed that the proportion of quartz (Q) is lower in CHA than in VER sands. The average quartz-feldspar-lithic fragment (QFL) ratios for the CHA and VER sands are Q 75 F 8 L 17 and Q 86 F 4 L 10 , respectively. The X-ray diffractometer (XRD) and Scanning Electron Microscope equipped with EDAX spectrometer (SEM-EDS) data revealed that the CHA sands were abundant in heavy minerals like magnetite, ilmenite, and zircon. The rare earth element concentration (REE) is higher in CHA than in VER sands, which is due to the concentration of heavy minerals in CHA sands. The weathering indices such as chemical index of alteration (CIA), plagioclase index of alteration, and A–CN–K (A = Al 2 O 3 , CN = CaO ∗ + Na 2 O, K = K 2 O) plot suggested that the intensity of weathering in the source area was low to moderate. The index of chemical variability (ICV) for the CHA (∼1.9–3.0) and VER (∼0.82–1.33) sands indicated that the compositional maturity was higher for the VER sands. The concentrations of Co, Cr, Ni, and V are lower in VER sands than in CHA sands, indicating that the CHA sands were derived from the intermediate source rocks. Provenance modelling revealed that the CHA sands were associated with the mixture of basalt, andesite, dacite, and trachyandesite in the ratio of 5:20:25:50. The VER sands were best matched with a mixture having 75–90% dacite and 25–10% andesite compositions. The provenance difference between the two beach areas suggested that longshore current play a less significant role in mixing and homogenization of sands. The multidimensional tectonic discrimination diagrams revealed rift and collision settings for the VER and CHA beach areas, respectively, which is consistent with the general geology of the study areas.

Combined petrographic and geochemical methods are utilized to investigate the provenance, tectonic setting, palaeo-weathering and climatic conditions of the Cambrian Araba clastic sediments of NE Egypt. The ~ 60 m thick Araba Formation consists predominantly of sandstone and mudstone interbedded with conglomerate. Petrographically the Araba sandstones are mostly sub-mature and classified as subarkoses with an average framework composition of Q80F14L6. The framework components are dominated by monocrystalline quartz with subordinate K-feldspar, together with volcanic and granitic rock fragments. XRD analysis demonstrated that clay minerals comprise mixed-layer illite/smectite (I/S), illite and smectite, with minor kaolinite. Diagenetic features of the sandstone include mechanical infiltration of clay, mechanical and chemical compaction, cementation, dissolution and replacement of feldspars by carbonate cements and clays. The modal composition and geochemical parameters (e.g. Cr/V, Y/Ni, Th/Co and Cr/Th ratios) of the sandstones and mudstones indicate that they were derived from felsic source rocks, probably from the crystalline basement of the northern fringe of the Arabian–Nubian Shield. The study reveals a collisional tectonic setting for the sediments of the Araba Formation. Palaeo-weathering indices such as the chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) of the clastic sediments suggest that the source area was moderately chemically weathered. On the northern margin of Gondwana, early Palaeozoic weathering occurred under fluctuating climatic conditions.

TecSand is a new Java software that is used for deciphering the tectonic setting of clastic sediments and sedimentary rocks through two new multidimensional discrimination diagrams. For each sample, TecSand calculates four complex discriminant functions: DF1m1 and DF2m1 for the high-silica diagram and DF1m2 and DF2m2 for the low-silica diagram, each representing linear combinations of log-ratios of all major elements. These functions determine the position of each sample within island or continental arc, continental rift, and collision/convergent settings. The program also calculates the probability values for the three tectonic fields. TecSand provides a “ready for publication” report for each locality, including the adjusted major elements, log-transformed variables, DF1 and DF2 results, and probability values for individual samples. Validations from samples of known tectonic settings, evaluation of chemical changes, and applications to Precambrian clastic sediments have previously been demonstrated in the literature. Therefore, we illustrate the use of TecSand in 10 case studies covering ages from the Early Cambrian to the Holocene. The results obtained from these two diagrams were not only mutually consistent but also with other geological constraints. As an innovation, TecSand provides an overall synthesis of the two diagrams as total percent probability values. Comparison of the results of this study with the previously published tectonic discrimination diagrams reveals that two recent multidimensional discrimination diagrams are more efficient in discriminating tectonic settings. Although TecSand does provide graphics, which can be imported and modified in commercial software, plotting of the sample diagram is no longer required.

The aim of this work is to constrain the provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico (~1089–1785 m water depth). To achieve this, 10 piston sediment cores (~5–5.5 m long) were studied for mineralogy, major, trace and rare earth element geochemistry. Samples were analyzed at three core sections, i.e. upper (0–1 cm), middle (30–31 cm) and lower (~300–391 cm). The textural study reveals that the core sediments are characterized by silt and clay fractions. Radiocarbon dating of sediments for the cores at different levels indicated a maximum of ~28,000 year BP. Sediments were classified as shale. The chemical index of alteration (CIA) values for the upper, middle, and lower sections revealed moderate weathering in the source region. The index of chemical maturity (ICV) and SiO 2 /Al 2 O 3 ratio indicated low compositional maturity for the core sediments. A statistically significant correlation observed between total rare earth elements (∑REE) versus Al 2 O 3 and Zr indicated that REE are mainly housed in detrital minerals. The North American Shale Composite (NASC) normalized REE patterns, trace element concentrations such as Cr, Ni and V, and the comparison of REE concentrations in sediments and source rocks indicated that the study area received sediments from rocks intermediate between felsic and mafic composition. The enrichment factor (EF) results indicated that the Cd and Zn contents of the upper section sediments were influenced by an anthropogenic source. The trace element ratios and authigenic U content of the core sediments indicated the existence of an oxic depositional environment.

Provenance and tectonic setting of sandstone and mudstone units of the Miocene Sibuti Formation from northwest Borneo have been studied based on the mineralogy, major and trace element geochemistry data. The X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive spectrometry (SEM-EDS) data revealed that the sandstones and mudstones were abundant in quartz, pyrite, clay, and heavy minerals such as zircon, rutile, and some detrital cassiterite. Geochemically, the sandstones and mudstones are classified into quartz arenite, litharenite, sublitharenite, arkose, and wacke. Quartz arenites are enriched with SiO2, Zr, and Th and depleted in Al2O3, CaO, and other elements compared to other sandstone types, indicating high maturity and intensive weathering. Chemical index of alteration (CIA: 77–90), plagioclase index of alteration (PIA: 86–100), and A-CN-K diagram suggest intense weathering in the source area. Elemental ratios such as La/Sc, Th/Sc, Cr/Th, La/Co, and Th/Co are similar to sediments derived from the felsic rocks. Also, the provenance discrimination diagrams suggest recycled continental nature of these clastic sediments which are mostly derived from metasedimentary source (Rajang Formation). Discriminant-function diagram for the tectonic discrimination of siliciclastic sediments revealed that the sediments of Sibuti Formation were derived from a collision zone, which is consistent with the geology of the study area.

Coastal margins, especially the river-influenced coastal areas, are considered as active interfaces between the continental and oceanic environments, which have huge dispersal of detrital materials and heavy metal input. It is well determined that the fine-grained sediments are important reservoir for the accumulation of heavy metals. In this study, we analyzed the radiocarbon age, texture, organic matter, carbonate content, and geochemical compositions of two sediment cores (GM42 and GM44) retrieved in front of the Coatzacoalcos River mouth basin, southwestern Gulf of Mexico (∼864 and 845 m water depth, respectively). Our objective was to infer the sedimentation rate, intensity of weathering, provenance, and influence of anthropogenic activities on heavy metal contamination in sediments. The radiocarbon-age measurements of mixed planktonic foraminifera for core GM44 reveals an age of 21,289 ± 136 cal. years B.P., which fall within the Late Glacial Maximum (LGM; 21000 ± 2000 years B.P). The calculated sedimentation rate for core GM42 (~0.013 cm/year) is lower than in core GM44 (0.022 cm/year), which is probably due to the variations in detrital sediment input and/or seafloor topography. The weathering indices such as chemical index of alteration (CIA), chemical index of weathering (CIW), and plagioclase index of alteration (PIA) suggested that the source area experienced low to moderate intensity of chemical weathering under warm to humid climatic conditions. The SiO2/Al2O3, Al2O3/Na2O, and K2O/Al2O3 ratio values indicated moderate to high compositional maturity. The major and trace element concentrations suggested that the sediments were likely derived from intermediate source rocks. The heavy metal contents indicated that the sediments were not contaminated by the industrial waste disposals supplied by the Coatzacoalcos River. The redox proxy sensitive elements such as V, Cr, Cu, and Zn indicated an oxic depositional environment for the deep-sea sediment cores. The application of discrimination diagrams for the geochemistry data revealed a passive margin setting for the sediment cores. The compositional variations observed at the upper sections (

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

Two discriminant-function-based multidimensional major-element diagrams for the tectonic discrimination of siliciclastic sediments were recently published from a coherent statistical methodology of loge-ratio transformation and linear discriminant analysis. These diagrams were constructed based on worldwide examples of Neogene–Quaternary siliciclastic sediments from known tectonic settings. In this work, these two tectonic discrimination diagrams were first successfully tested from Holocene (

Detrital sand grains from three beaches (Tecolutla, Nautla, and Veracruz) along the western Gulf of Mexico were studied by a scanning electron microscope, to investigate the depositional environment and paleoclimate. Totally, 24 microtextures are identified; among them, 13 are grouped as mechanical origin, 5 as mechanical and/or chemical origin, and 6 as chemical origin. These microtextures are nonuniformly distributed among the three beach areas. Concoidal fractures, straight and arcuate steps at Tecolutla and Veracruz beaches indicate that the sand grains were derived from the crystalline rocks. The abundance of angular outline grains at the Nautla beach supports for short transportation probably close to the source area. The domination of rounded sand grains in the Veracruz beach reveals that the sediments were derived by the aeolian mechanism. Chattermark trials at the Veracruz beach sands are indicating a wet tropical climate. Chemical features like silica globules, silica pellicle, and trapped diatoms in the Tecolutla and Veracruz beach sands suggest a silica saturated environment. Similarly, chemical etching and solution pits are common in the Veracruz beach sands, which are probably linked to the contaminated sea water. Desiccation crack at Veracruz beach sands is an indicator of temperature changes in the beach environment. Broken benthonic foraminifera Elphidium discoidale sp. present in the Veracruz beach indicates a high-energy littoral environment.

Siliciclastic sediments owe their origin mainly to land sources. New discriminant-function-based major-element diagrams for the tectonic discrimination of siliciclastic sediments from three main tectonic settings: island or continental arc, continental rift, and collision, have been constructed for the tectonic discrimination of high-silica [(SiO2)adj = 63%–95%] and low-silica rocks [(SiO2)adj = 35%–63%], where (SiO2)adj refers to the SiO2 value obtained after volatile-free adjustment of the ten major-elements to 100 wt.%. These diagrams are based on worldwide examples of Neogene–Quaternary siliciclastic sediments from known tectonic settings, loge-ratio transformation of ten major-elements with SiO2 as the common denominator, and linear discriminant analysis of the loge-transformed ratio data. The success rates of these diagrams as judged from the original data varied from 84.5% to 93.6%. These diagrams were successfully tested on Neogene to Quaternary rocks not included in the original database. These discriminant diagrams were also successfully applied on older high-silica and low-silica sandstones and shales of Paleoarchean–Ediacaran age. Finally, these diagrams were shown to be useful against chemical changes related to analytical errors, weathering, recycling and post-depositional processes.

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.

This paper contributes to understanding the intractable problems in provenance study due to hydraulic sorting and geochemical heterogeneity in medium, fine, and very fine sands. For this purpose, detrital modes, major, trace, and rare earth element (REE) compositions of recent sands from the Playa Azul, Tecolutla, and Nautla beach areas of the western Gulf of Mexico have been investigated. Marked geochemical and petrographic differences occur among the three beach sands, even though they are separated just by 45 km. The average quartz-feldspar-lithic fragment (QtFL) ratios for the Playa Azul, Tecolutla, and Nautla sands are respectively Qt69–F10–L21, Qt57–F11–L32, and Qt37–F5–L58. The volcanic lithic fragment (Lv) − sedimentary lithic fragment (Ls) − [plutonic lithic (Lp) + metamorphic lithic fragments (Lm)] ternary diagram indicates that the Nautla sands are dominated by volcanic detritus, while the Tecolutla sands are dominated by sedimentary and volcanic detritus. The Playa Azul sands are dominated largely by sedimentary detritus. Geochemically, the three beach sands are quite distinctive from each other. The Playa Azul sands are higher in SiO2 content (∼64–84 wt.%) than in the Tecolutla sands (SiO2 = ∼47–69 wt.%). The Nautla sands are very low in SiO2 content ( In the three beach sands studied, the decrease in grain size is accompanied by a gradual decrease in SiO2 content and an increase in TiO2, Al2O3, Fe2O3, MgO, Zr, Hf, Cr, and V contents. Similarly, the ∑REE content increases with decreasing grain size. However, very fine sands in the Playa Azul and Nautla beaches are different in ∑REE content. This observation suggests that the provenance is more important in controlling the geochemical composition of beach sands than the grain size. The zirconium concentration in beach sands, however, is not related to the grain size. The comparison of REE patterns of beach sands with those of source rocks located relatively close to the study areas suggests that the Playa Azul sands were derived from felsic rocks, whereas a mixed provenance with contributions from felsic and intermediate rocks is more likely for the Tecolutla sands. In contrast, the REE distribution patterns of Nautla sands resemble those derived from basalt and basaltic andesite. However, selective concentration of magnetite grains in beach sands increases the LREE content and fractionates Eu resulting in a europium anomaly that is more negative than that displayed by Nautla sands. All of the above observations suggest that rivers delivering sands to the beaches are the important factors in controlling the composition of beach sands and that longshore currents play a less significant role.

Petrography and geochemistry (major, trace and rare earth elements) of clastic rocks from the Lower Cambrian Lalun Formation, in the Posht-e-badam block, Central Iran, have been investigated to understand their provenance. Petrographical analysis suggests that the Lalun conglomerates are dominantly with chert clasts derived from a proximal source, probably chert bearing Precambrian Formations. Similarly, purple sandstones are classified as litharenite (chertarenite) and white sandstones as quartzarenite types. The detrital modes of purple and white sandstones indicate that they were derived from recycled orogen (uplifted shoulders of rift) and stable cratonic source. Most major and trace element contents of purple sandstones are generally similar to upper continental crust (UCC) values. However, white sandstones are depleted in major and trace elements (except SiO2, Zr and Co) relative to UCC, which is mainly due to the presence of quartz and absence of other Al-bearing minerals. Shale samples have considerably lower content in most of the major and trace elements concentration than purple sandstones, which is possibly due to intense weathering and recycling. Modal composition (e.g., quartz, feldspar, lithic fragments) and geochemical indices (Th/Sc, La/Sc, Co/Th, Cr/Th, Cr/V and V/Ni ratios) of sandstones, and shales (La/Sc and La/Cr ratios) indicate that they were derived from felsic source rocks and deposited in a passive continental margin. The chondrite-normalized rare earth element (REE) patterns of the studied samples are characterized by LREE enrichment, negative Eu anomaly and flat HREE similar to an old upper continental crust composed chiefly of felsic components in the source area. The study of paleoweathering conditions based on modal composition, chemical index of alteration (CIA), plagioclase index of alteration (PIA) and A–CN–K (Al2O3 − CaO + Na2O − K2O) relationships indicate that probably chemical weathering in the source area and recycling processes have been more important in shale and white sandstones relative to purple sandstones. The results of this study suggest that the main source for the Lalun Formation was likely located in uplifted shoulders of a rifted basin (probably a pull-apart basin) in its post-rift stage (Pan-African basement of the Posht-e-badam block).

Petrography and stable isotopes (carbon and oxygen) geochemistry of limestones from the El Abra Formation, Actopan, were studied to identify their digenetic environments. The major petrographic types identified are mudstone, wackestone, grainstone, and boundstone. Most of the studied samples show positive δ 13 C values, except two samples (2 and 28), which are slightly negative values (-0.27‰ and -0.02‰). The organic remains identified in foraminiferal wackestone type can be responsible for the negative δ 13 C values. The δ 18 O values range from -12.41‰ to -4.02‰ and indicate meteoric diagenesis.

The marine stromatolitic dolomites of Palaeoproterozoic Vempalle Formation, of Cuddapah Basin, South India show significantly depleted δ18O (−8.19 to −18.25‰) and δ13C (−0.03 to −5.74) values and are consistent with the global Proterozoic data. A comparison of the stable isotope values from major localities of Proterozoic Basins of India has also been attempted in this study. Significantly depleted δ18O values of Vempalle carbonate samples could not be considered to be post-depositional modifications as there exists an inverse correlation relationship between C and O isotopic values. The Vempalle stromatolitic dolomite is likely to be precipitated in equilibrium with marine waters significantly depleted in oxygen isotopes (−10 to −15‰ SMOW) with respect to modern sea water. The negative δ13C values of the Vempalle carbonates are likely to be interpreted at the backdrop of global “icehouse” as there is an indication of dropstone-like features in the lower part of the Vempalle Formation just 2 km, southwest of the study area.

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.

Major, trace, REE, and stable isotopic composition of Maastrichtian limestones of Cauvery Basin were studied to decipher their depositional and post-depositional environment. The major oxides and trace elements concentration of these limestones were normalized using Post-Archean Australian Shale (PAAS) values. The concentration of CaO is having a significant enrichment, and MgO, K2O, Co, Ni, Cu, Zn, Pb, Ba, U, and Th are moderately depleted, whereas Sr and Na2O contents are relatively similar to the PAAS values. The PAAS-normalized REE + Y pattern of Maastrichtian limestones display relatively uniform pattern among the compositionally different limestones: (1) enriched LREE (average NdSN/YbSN = 5.03 ± 0.92); (2) positive Ce anomaly (average 1.79 ± 0.16); (3) negative GdSN/Gd* anomaly (average 0.52 ± 0.02); (4) low Y/Ho ratio (average Y/Ho = 0.14 ± 0.01). The average ΣREE contents in ferruginous, arenaceous, and biostromal limestones are 65, 64, and 52 ppm, respectively, which indicate that the mineralogical variation plays a major role in incorporation of ΣREE. The Kallankurichchi limestones have δ13C values range from −3.2 to −1.1‰PDB, and the δ18O values range between −7.8 and −5.5‰PDB. The negative δ13C and δ18O values and a moderate co-variation between δ13C and δ18O (r 2 = 0.35) indicate that the alteration of original isotopic composition is due to diagenesis. The positive Ce/Ce* confirms the clastic input into the system, and negative Mn* values and Th/U ratios (~0.29–1.4) in these limestones indicate their association with precipitation of carbonates in reducing (anoxic–dysoxic: Th/U ≤ 2) conditions.

The elemental content ( major, trace and rare earth elements) of 35 Aptian–Albian limestone samples from the Mural Formation has been determined to provide information on depositional conditions and provenance. The limestones of the Mural Formation show large variations in terrigenous and carbonate contents (1.2 to 42.3% and 57.7 to 98.8% respectively). Small variations are observed in CaO concentrations in the Tuape Shale, Cerro La Puerta and Mesa Quemada members whereas large variations are found in the Cerro La Ceja, Los Coyotes and Cerro La Espina members. The majority of the limestones show high values of Th, Sc and Zr. Large variations in ΣREE content are observed among different members of the Mural Formation. Most limestones from the Mural Formation record non-seawater-like REE+Y signatures. The limestones show large variations in Ce anomalies which may be due to mixing of sediment components (biogenic and authigenic phases) and detrital materials including Fe-colloids from fluvial input. Most of the limestones show positive Eu anomalies, but some samples show negative Eu anomalies (Eu/Eu ∗ : 0.42 to 2.62). The large variations in terrigenous percentage, high Al 2 O 3 and ΣREE contents, high La N /Yb N ratios, low Y/Ho ratios and non-seawater-like REE patterns suggest that the observed variations in ΣREE contents are mainly controlled by the amount of detrital sediments in the limestones of the Mural Formation. The limestones of the Mural Formation were deposited under both coastal and open shelf environments, and they exhibit non-seawater-like REE + Y patterns. The presence of terrigenous materials in these carbonates as contaminants effectively masks the seawater signature due to their high concentration of the REE. Thus, trying to decipher the palaeoceanographic conditions represented by ancient carbonate rocks should be done cautiously since limestones deposited under open marine environments may also be contaminated by some amount of terrigenous particles. The presence of small quantities of terrigenous materials in the limestones can also reveal source rock information. The La/Sc, La/Co, Th/Sc, Th/Cr, Th/Co and Cr/Th ratios suggest that the terrigenous materials present in the limestones were mainly derived from a nearby exposed basement of intermediate to felsic igneous rocks.

The carbon, oxygen, and strontium isotope compositions of carbonate rocks from the upper Miocene Kudankulam Formation, southern India, were measured to understand palaeoenvironment and carbonate diagenesis of this formation. Both carbon and oxygen isotope ratios of various carbonate phases including whole rocks, ooids, molluscan mold-fill and sparry pore-fill calcite cements are depleted in 18O and 13C compared to those of contemporaneous seawater, indicating that the Kudankulam carbonates underwent extensive meteoric diagenesis. Based on δ13C and δ18O values for sparry calcite cements (pore-fill and molluscan mold-fill) formed in the meteoric diagenetic realm (δ13C from −7.8‰ to −6.0‰ and −9.0‰ to −7.0‰; δ18O from −9.2‰ to −6.5‰ and −9.4‰ to −2.6‰, respectively), it is interpreted that the diagenetic system was open and was proximal to the vadose water recharge zone. The negative δ18O values of various carbonate components (about −9.4‰ to −4.1‰ for whole rocks; about −8.4‰ to −2.6‰ for ooids) suggest that during the late Miocene the paleoclimate of the study area was humid, unlike today, probably due to the intense Indian monsoon system. The carbon isotope compositions (−7.9‰ to −3.6‰ for whole rocks; −4.9‰ to −1.5‰ for ooids) are consistent with the interpretation that the paleo-ecosystem comprised a significant proportion of C4 type plants, supporting a scenario of expansion of C4 plants during the late Miocene in the Indian subcontinent as far south as the southern tip of India. The 87Sr/86Sr ratios of the Kudankulam carbonates (0.70920 to 0.72130) are much greater than those of the contemporaneous or modern seawater (between 0.7089 and 0.7091) and show a general decrease up-sequence. Such high Sr isotope ratios indicate significant radiogenic 87Sr influx to the system from the Archean rocks exposed in the drainage area, implying that the deep-seated Archean rocks were already exposed in southern India by the late Miocene.

The tsunami sediments deposited after the December 2004 tsunami were sampled immediately in the coastal environment of Tamil Nadu State on the southeast coast of India. Fifty-four sediment samples were collected and 14 representative samples were selected to identify the level of metal contamination in tsunami sediments. The results indicate that the sediments are mainly of fine to medium-grained sand and contain significantly high contents of dissolved salts in sediments (Na+, K+, Ca+2, Mg+2, Cl−) in water-soluble fraction due to seawater deposition and evaporation. Correlation of acid leachable trace metals (Cr, Cu, Ni, Co, Pb, Zn) indicate that Fe-Mn oxyhydroxides might play an important role in controlling their association between them. Enrichment of trace metals is observed in all the locations with reference to the background samples. High values of trace metals in the southern part of the study area are due to the large-scale industries along the coast, and they are probably anthropogenic in nature and of marine origin, which could cause serious environmental problems.

The study is based on physicochemical parameters (pH, DO, and salinity) and dissolved trace elements (Fe, Mn, Cr, Cu, Ni, Co, Pb, Zn, and Cd) of Uppanar River water (RW) and surface and bottom coastal waters (CW) off Cuddalore, southeast coast of India in 56 samples collected during 2001. High concentration of Fe and Mn in RW and CW indicates enrichment above the normal level. Physicochemical parameters do not exhibit significant relationship with trace metals. Enrichment of Pb is due to external input and excess level of Cu, Pb, Zn in RW and Cr, Cu, Ni, Pb in CW is identified. Fe-Mn oxides are the chief scavengers of trace elements in both the aquatic environments and it is supported by geochemical, statistical and comparative studies. The results signify that industrial growth has affected the aquatic environments and regular monitoring will help to adopt stringent pollution control measures for better management of the aquatic region.

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.

Quartz grains from the Kallamedu (late Maastrichtian) and lower Niniyur (Danian) Formations, Cauvery Basin, Southeast India were examined under a scanning electron microscope, and twenty three distinct microtextures were observed. These microtextures have been grouped into three modes of origin, viz. mechanical (thirteen features), mechanical and/or chemical (five features) and chemical (five features) origins. Quartz grains from the Kallamedu and lower Niniyur Formations show conchoidal fractures, straight steps and arcuate steps which are the characteristic microtextures of quartz grains derived from crystalline source rocks. Quartz grains from the upper Kallamedu and lower Niniyur Formations show angular to subangular outline, whereas those from the lower Kallamedu Formation show subangular to rounded outline. The dominance of angular to subangular grains and the presence of straight and arcuate steps suggest that these clastic sediments were undergone short transportation and rapid deposition. The presence of rounded grains in the lower part of the Kallamedu Formation suggests that significant amounts of quartz grains are of recycled origin. Vs, straight scratches and curved scratches, the characteristic features of marine environment, are common on the quartz grains from the lower Niniyur Formation, which is consistent with the previous interpretation. However, quartz grains from the lower Kallamedu Formation exhibit very low frequency of these features, whereas they are moderately present in the upper Kallamedu Formation, suggestive of a change in depositional conditions with time. The lower Kallamedu Formation exhibits planar and trough cross-beddings, which suggests the fluvial depositional environment. The unfossiliferous upper Kallamedu Formation contains appreciable amount of illite and mixed-layer (illite/smectite) clay minerals, which suggests that the saline conditions prevailed during its deposition. Microtextures on the quartz grains coupled with dominant clay mineral types suggest the deltaic depositional environments for the upper Kallamedu Formation.

An attempt is made to evaluate 6 tectonic setting discrimination diagrams (1 discriminant function and 5 bivariate diagrams) frequently used by many researchers. For this purpose, an extensive database was established for major element geochemistry derived from Miocene to Recent sand and sandstone (medium to fine-grained) samples collected from a variety of tectonic settings including (1) passive margin (PM) setting, (2) active continental margin (ACM) setting, and (3) oceanic island arc (OIA) setting. Our results suggest that the discrimination fields proposed to infer tectonic settings for six commonly used discrimination diagrams do not work properly for the analyzed Miocene to Recent sediments. The % success for these diagrams varies from 0% to about 62%. We therefore recommend that these diagrams be used with prudence.

Concentrations of major, trace, and rare-earth elements (REE) were measured in shallow marine limestone samples of the upper Miocene Kudankulam Formation, southern India, in order to investigate the geochemical variations among various litho-units. The CaCO3 content is higher in algal limestone (AL; 92 ± 1, n = 3) and clastic limestone (CL; 90 ± 2, n = 3) than sandy shell limestone (SSL; 81 ± 1, n = 3). All trace elements exhibit lower concentrations than post-Archean Australian Shale (PAAS) values, except one SSL sample. Large variations in ΣREE content are observed among CL, SSL, and AL (~14-142, ~68-124, and ~38-98, respectively). Almost all limestone samples analyzed from the Kudankulam Formation show a small negative cerium anomaly (Ce/Ce* ~0.8-0.9), except one AL sample, which lacks this cerium anomaly (Ce/Ce* ~1.04). Variations in Ce anomalies and ΣREE contents in Kudankulam limestone samples are mainly controlled by the amount of terrigenous sediments and diagenetic behavior. Shale-normalized REE ...

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.