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The Middle Eocene Climatic Optimum (MECO) is a global warming event mainly recognized in the marine domain and described less in the terrestrial environment. Here we present a comprehensive geochemical record of the MECO from the Escanilla Formation, a fluvial sedimentary succession in the southern Pyrenees, Spain, based on a suite of sampled paleosols, fluvial stromatolites, and pedogenic nodules. Our multiproxy approach involves using carbon and oxygen stable isotope compositions to identify the regional preservation of the MECO, calculate chemical weathering intensity and mean annual precipitation, perform clumped isotopes on carbonates, and identify clay mineralogy assemblages of paleosols. Results indicate that the Middle Eocene interval in the southern Pyrenees was characterized by low weathering rates under warm and arid climatic conditions. This is further supported by the presence of smectite, palygorskite, illite, and chlorite, which suggest seasonal rainfall but under generally dry conditions resulting in weak chemical weathering. Importantly, a negative organic carbon isotopic excursion indicates the regional, terrestrial impact of the MECO, highlighting that fluvial sedimentary successions even in active foreland basins can represent particularly interesting terrestrial archives of past changes in global climate. [ABSTRACT FROM AUTHOR]

The Middle Eocene Climatic Optimum (MECO) is a global warming event mainly described in the marine domain but less in the terrestrial domain. This study presents a comprehensive geochemical record of the MECO from the Escanilla Formation, a fluvial sedimentary succession in the southern Pyrenees, Spain, based on a suite of sampled paleosols, fluvial stromatolites and pedogenic nodules. Our multiproxy approach involves using carbon and oxygen stable isotope compositions to identify the regional preservation of the MECO, calculate chemical weathering intensity and identify the clay mineralogy of paleosols, as well as to estimate mean annual precipitation using temperature estimates based on clumped isotope compositions of carbonates. Results indicate that the Middle Eocene interval in the south central Pyrenees was characterized by low weathering rates under warm and arid climatic conditions. This is further supported by the presence of smectite, palygorskite, illite, and chlorite, which suggest seasonal rainfall but under generally dry conditions resulting in weak chemical weathering. Importantly, an isotopic excursion indicates a regional, terrestrial impact of the MECO, highlighting that fluvial sedimentary successions even in active foreland basins can represent particularly interesting terrestrial archives of past changes in global climate. [ABSTRACT FROM AUTHOR]

In this study, we present evidence of a Paleocene-Eocene Thermal Maximum (PETM) record within a 543-m-thick (1780 ft) deep-marine section in the Gulf of Mexico (GoM) using organic carbon stable isotopes and biostratigraphic constraints. We suggest that climate and tectonic perturbations in the upstream North American catchments can induce a substantial response in the downstream sectors of the Gulf Coastal Plain and ultimately in the GoM. This relationship is illustrated in the deep-water basin by (1) a high accommodation and deposition of a shale interval when coarse-grained terrigenous material was trapped upstream at the onset of the PETM, and (2) a considerable increase in sediment supply during the PETM, which is archived as a particularly thick sedimentary section in the deep-sea fans of the GoM basin. Despite other thick PETM sections being observed elsewhere in the world, the one described in this study links with a continentalscale paleo-drainage, which makes it of particular interest for paleoclimate and source-to-sink reconstructions. [ABSTRACT FROM AUTHOR]

Tracing methods of non-European EVOOs commercialized worldwide are becoming crucial for effective authenticity controls. Limited analytical studies of these oils are available on a global scale, similar to those of European EVOOs. We report for the first time the fatty acid concentrations, bulk-oil 2H/1H, 13C/12C, and 18O/16O ratios and fatty acid 13C/12C ratios of 43 authentic monovarietal EVOOs from different geographical regions in Argentina and Uruguay. The samples were obtained from a wide range of latitudes and altitudes along an E–W profile, from lowlands near the Atlantic Ocean to the pre-Andean highlands near the Pacific Ocean. Principal component scores were used to cluster EVOOs into three groups— central-western Argentina, central Argentina, and Uruguay—based on nine stable isotope ratios and the oleic-linoleic acid concentration ratio. The bulk 2H/1H and 18O/16O values and 13C/12C of palmitoleic and linoleic acids provide good tools for differentiating these oils via linear discriminant analysis. • Characterization of authentic EVOOs from regions in Argentina and Uruguay. • Argentinian and Uruguayan EVOOs differ in stable isotopes (SI, δ2H, δ13C, δ18O). • Minor differences were noted for fatty acid profiles, more for oleic/linoleic. • PCA and LDA allows discrimination of the oils according to geographical origin. • Suitability of SI for authenticity and traceability of EVOO is confirmed. [ABSTRACT FROM AUTHOR]

We investigated the within- and between-leaf variability in the carbon and nitrogen isotope composition (δ 13C and δ 15N) and total nitrogen (TN) content in two grapevine cultivars (Vitis vinifera cv. Chasselas and Pinot noir) field-grown under rain-fed conditions. The within-leaf variability was studied in discs sampled from base-to-tip and left and right regions from the margin to midrib. The intra- and interplant variability was studied by comparing leaves at different positions along the shoot (basal, median, apical). In leaves from both cultivars, a decrease in δ 13C from base to tip was observed, which is in line with an upward gradient of stomatal density and chlorophyll concentration. Less important, but still significant differences were observed between the right and left discs. The leaf TN and δ 15N values differed between cultivars, showed smaller variations than the δ 13C values, and no systematic spatial trends. The intraleaf variations in δ 13C, δ 15N, and TN suggest that stomatal behavior, CO 2 fixation, chlorophyll concentrations, and the chemical composition of leaf components were heterogeneous in the leaves. At the canopy scale, the apical leaves had less 13C and more 15N and TN than the basal leaves, indicating differences in their photosynthetic capacity and remobilizations from old, senescing leaves to younger leaves. Overall, this study demonstrates patchiness in the δ 13C and δ 15N values of grapevine leaves and species-specificity of the nitrogen assimilation and 15N fractionation. These findings suggest that care must be taken not to overinterpret foliar δ 13C and δ 15N values in studies based on fragmented material as markers of physiological and biochemical responses to environmental factors. [Display omitted] • Potential patchiness of δ 13C, δ 15N, and nitrogen content in leaves is explored. • Within-leaf δ 13C and δ 15N values varied up to 1.5 mUr. • Young apical leaves had lower δ 13C, higher N content, and δ 15N than old basal leaves. • Significant interspecific differences were found in leaf N content and δ 15N values. [ABSTRACT FROM AUTHOR]

Geochemical indicators are emerging as important predictors of soil organic carbon (SOC) dynamics, but evidence concerning the role of calcium (Ca) is scarce. This study investigates the role of Ca prevalence in SOC accumulation by comparing otherwise similar sites with (CaCO3-bearing) or without carbonates (CaCO3-free). We measured the SOC content and indicators of organic matter quality (C stable isotope composition, expressed as δ13C values, and thermal stability) in bulk soil samples. We then used sequential sonication and density fractionation (DF) to separate two occluded pools from free and mineral-associated SOC. The SOC content, mass, and δ13C values were determined in all the fractions. X-ray photoelectron spectroscopy was used to investigate the surface chemistry of selected fractions. Our hypothesis was that occlusion would be more prevalent at the CaCO3-bearing site due to the influence of Ca on aggregation, inhibiting oxidative transformation, and preserving lower δ13C values. Bulk SOC content was twice as high in the CaCO3-bearing profiles, which also had lower bulk δ13C values, and more occluded SOC. Yet, contrary to our hypothesis, occlusion only accounted for a small proportion of total SOC (< 10%). Instead, it was the heavy fraction (HF), containing mineral-associated organic C, which accounted for the majority of total SOC and for the lower bulk δ13C values. Overall, an increased Ca prevalence was associated with a near-doubling of mineral-associated SOC content. Future investigations should now aim to isolate Ca-mediated complexation processes that increase organo-mineral association and preserve organic matter with lower δ13C values. [ABSTRACT FROM AUTHOR]

The topographic history of an orogen, a key element to study the interactions of the climate and tectonic conditions that drove it, can be reconstructed by inverting the sedimentary record of its adjacent basins. Previous tectono-stratigraphic studies, including flexural models, and sparse stable oxygen and carbon isotope data from the South-Pyrenean foreland basin suggest a major topographic rise occurred in the late Paleocene-early Eocene. To further test this hypothesis, we present a stack of 658 stable isotope measurements on whole-rock marine carbonate mudstone from a 4800-m-thick composite sedimentary succession which provides a 12 Ma continuous record of environmental conditions during the early to middle Eocene (54 to 42 Ma). From the base of this record (at 54 Ma), oxygen isotopes (δ18O values) show a faster decrease rate than the coeval global negative excursion associated with the Early Eocene Climatic Optimum (EECO). This local alteration of the global δ18O signal indicates that topographic growth during this period, associated with significant tectonic activity, perturbed the oxygen isotopic composition of foreland waters. Thus, our data suggest that significant topographic uplift of the Pyrenean orogen started from at least 54 Ma and continued until ca. 49 Ma, reaching the maximum elevations of 2000 ± 500 m in this phase from previous isotope and flexural studies. In addition, our record shows that the long-term carbon stable isotope composition during this period remained relatively stable with no similarity to the global bell-shaped long-term trend of the EECO. This is consistent with the restricted physiography of the South-Pyrenean foreland basin, mainly influenced by local sedimentary and water inputs. Overall, the Pyrenean topographic growth from the late Cretaceous to the Miocene displays several growth stages that seem to be primarily determined by episodes of increased rate of tectonic plate convergence. The duration of these growth stages (several millions of years) is a possible documentation of the response time of mountain ranges to tectonic perturbations. The results of this work, therefore, demonstrate that stable isotope measurements on whole-rock sediments in foreland basins can provide key information for tectono-climatic and topographic reconstructions of mountain ranges. [ABSTRACT FROM AUTHOR]

Abstract: Subsurface granitic environments are scarce and poorly investigated. A multi‐disciplinary approach was used to characterize the abundant moonmilk deposits and associated microbial communities coating the granite walls of the 16th Century Paranhos spring water tunnel in Porto city (north‐west Portugal). It is possible that this study is the first record of moonmilk in an urban subsurface granitic environment. The morphology and texture, mineralogical composition, stable isotope composition and microbial diversity of moonmilk deposits have been studied to infer the processes of moonmilk formation. These whitish secondary mineral deposits are composed of very fine needle‐fibre calcite crystals with different morphologies and density. Calcified filaments of fungal hyphae or bacteria were distinguished by field emission scanning electron microscopy. Stable isotope analysis revealed a meteoric origin of the needle‐fibre calcite, with an important contribution of atmospheric CO2, soil respiration and HCO 3 − from weathering of Ca‐bearing minerals. The DNA‐based analyses revealed the presence of micro‐organisms related to urban contamination, including Actinobacteria, mainly represented by Pseudonocardia hispaniensis, Thaumarchaeota and Ascomycota, dominated by Cladosporium. This microbial composition is consistent with groundwater pollution and contamination sources of the overlying urban area, including garages, petrol stations and wastewater pipeline leakage, showing that the Paranhos tunnel is greatly perturbed by anthropogenic activities. Whether the identified micro‐organisms are involved in the formation of the needle‐fibre calcite or not is difficult to demonstrate, but this study evidenced both abiotic and biogenic genesis for the calcite moonmilk in this subsurface granitic environment. [ABSTRACT FROM AUTHOR]

Rationale The carbon, hydrogen and oxygen stable isotope composition ( δ13C, δ2H, and δ18O values) of plants and their products is linked to photosynthetic fractionation, environmental factors and agricultural practices. Therefore, they contribute to determining the purity of commercial vegetable oils and may provide information on their geographical origin. Methods Maize, olive, sunflower, groundnut, soybean and rice oils differing in sites of growth in the southern and northern hemispheres were characterized by bulk oil stable isotope ratios ( δ13Cbulk, δ2Hbulk, and δ18Obulk values), fatty acid (FA) concentrations and δ13CFA values using elemental analysis/isotope ratio mass spectrometry, gas chromatography/mass spectrometry, gas chromatography/flame ionization detection and gas chromatography/combustion/isotope ratio mass spectrometry. Principal component analysis was applied to examine the inherent structure of the data. Results The δ13Cbulk values of maize oils (−18.4 to −14.9 ‰) are typical for C4 plants, and those of olive (−30.2 to −28.2 ‰), sunflower (−30.2 to −29.2 ‰), groundnut (−29.3 ‰), soybean (−30.6 ‰), and rice (−34.5 ‰) oils are typical for C3 plants. The δ2Hbulk values vary from −161 to −132 ‰ for maize oils and −171 to −109 ‰ for C3 oils. The δ18Obulk values of all oils vary between 15.2 and 38.9 ‰. The major δ13CFA differences (>5 ‰) within plant species render the inter-C3-species comparison difficult. These differences are explained in terms of variations in the lipid biosynthetic pathways and blend of vegetable oils of different FA composition and δ13CFA values. The samples from the southern hemisphere are generally enriched in 13C compared with those from the northern hemisphere. Differences between the southern and northern hemispheres were observed in δ2H ( p < 0.001) and δ18Obulk ( p = 0.129) values for all C3 oils, and in δ13C18:1 ( p = 0.026) and δ18Obulk ( p = 0.160) values for maize oils. Conclusions The results of this study show that combining bulk and molecular stable isotope ratios, FA compositions and their statistical analysis helps the characterization of the geographic origin of oils. This methodology can be used to detect and source impurities in valuable vegetable oils commercialized worldwide. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A continuum of carbon, from atmospheric CO 2 to secondary calcium carbonate, has been studied in a soil associated with scree slope deposits in the Jura Mountains of Switzerland. This approach is based on former studies conducted in other environments. This C continuum includes atmospheric CO 2 , soil organic matter (SOM), soil CO 2 , dissolved inorganic carbon (DIC) in soil solutions, and secondary pedogenic carbonate. Soil parameters (pCO 2 , temperature, pH, C min and C org contents), soil solution chemistry, and isotopic compositions of soil CO 2 , DIC, carbonate and soil organic matter (δ 13 C CO 2 , δ 13 C DIC , δ 13 C car and δ 13 C SOM values) have been monitored at different depths (from 20 to 140 cm) over one year. Results demonstrated that the carbon source in secondary carbonate (mainly needle fiber calcite) is related to the dissolved inorganic carbon, which is strongly dependent on soil respiration. The heterotrophic respiration, rather than the limestone parent material, seems to control the pedogenic carbon cycle. The correlation of δ 13 C org values with Rock-Eval HI and OI indices demonstrates that, in a soil associated to scree slope deposits, the main process responsible for 13 C-enrichment in SOM is related to bacterial oxidative decarboxylation. Finally, precipitation of secondary calcium carbonate is enhanced by changes in soil pCO 2 associated to the convective movement of air masses induced by temperature gradients (heat pump effect) in the highly porous scree slope deposits. The exportation of soil C-leachates from systems such as the one studied in this paper could partially explain the “gap in the European carbon budget” reported by recent studies. [ABSTRACT FROM AUTHOR]

The Trepča Pb-Zn-Ag skarn deposit (29 Mt of ore at 3.45% Pb, 2.30% Zn, and 80 g/t Ag) is located in the Kopaonik block of the western Vardar zone, Kosovo. The mineralization, hosted by recrystallized limestone of Upper Triassic age, was structurally and lithologically controlled. Ore deposition is spatially and temporally related with the postcollisional magmatism of Oligocene age (23-26 Ma). The deposit was formed during two distinct mineralization stages: an early prograde closed-system and a later retrograde open-system stage. The prograde mineralization consisting mainly of pyroxenes (Hd54-100Jo0-45Di0-45) resulted from the interaction of magmatic fluids associated with Oligocene (23-26 Ma) postcollisional magmatism. Whereas there is no direct contact between magmatic rocks and the mineralization, the deposit is classified as a distal Pb-Zn-Ag skarn. Abundant pyroxene reflects low oxygen fugacity (<10-31 bar) and anhydrous environment. Fluid inclusion data and mineral assemblage limit the prograde stage within a temperature range between 390° and 475°C. Formation pressure is estimated below 900 bars. Isotopic composition of aqueous fluid inclusions hosted by hedenbergite (δD = -108 to -130‰; δ18O = 7.5-8.0‰), Mn-enriched mineralogy and high REE content of the host carbonates at the contact with the skarn mineralization suggest that a magmatic fluid was modified during its infiltration through the country rocks. The retrograde mineral assemblage comprises ilvaite, magnetite, arsenopyrite, pyrrhotite, marcasite, pyrite, quartz, and various carbonates. Increases in oxygen and sulfur fugacities, as well as a hydrous character of mineralization, require an open-system model. The opening of the system is related to phreatomagmatic explosion and formation of the breccia. Arsenopyrite geothermometer limits the retrograde stage within the temperature range between 350° and 380°C and sulfur fugacity between 10-8.8 and 10-7.2 bars. The principal ore minerals, galena, sphalerite, pyrite, and minor chalcopyrite, were deposited from a moderately saline Ca-Na chloride fluid at around 350°C. According to the isotopic composition of fluid inclusions hosted by sphalerite (δD = -55 to -74‰; δ18O = -9.6 to -13.6‰), the fluid responsible for ore deposition was dominantly meteoric in origin. The δ34S values of the sulfides spanning between -5.5 and +10‰ point to a magmatic origin of sulfur. Ore deposition appears to have been largely contemporaneous with the retrograde stage of the skarn development. Postore stage accompanied the precipitation of significant amount of carbonates including the travertine deposits at the deposit surface. Mineralogical composition of travertine varies from calcite to siderite and all carbonates contain significant amounts of Mn. Decreased formation temperature and depletion in the REE content point to an influence of pH-neutralized cold ground water and dying magmatic system. [ABSTRACT FROM AUTHOR]

The deposition of Late Pleistocene and Holocene sediments in the high-altitude lake Meidsee (located at an altitude of 2661 m a.s.l. in the Southwestern Alps) strikingly coincided with global ice-sheet and mountain-glacier decay in the Alpine forelands and the formation of perialpine lakes. Radiocarbon ages of bottom-core sediments point out (pre-) Holocene ice retreat below 2700 m a.s.l., at about 16, 13, 10, and 9 cal. kyr BP. The Meidsee sedimentary record therefore provides information about the high-altitude Alpine landscape evolution since the Late Pleistocene/Holocene deglaciation in the Swiss Southwestern Alps. Prior to 5 cal. kyr BP, the C/N ratio and the isotopic composition of sedimentary organic matter (δ15Norg, δ13Corg) indicate the deposition of algal-derived organic matter with limited input of terrestrial organic matter. The early Holocene and the Holocene climatic optimum (between 7.0 and 5.5 cal. kyr BP) were characterized by low erosion (decreasing magnetic susceptibility, χ) and high content of organic matter (Corg > 13 wt.%), enriched in 13Corg (> −18‰) with a low C/N (~10) ratio, typical of modern algal matter derived from in situ production. During the late Holocene, there was a long-term increasing contribution of terrestrial organic matter into the lake (C/N > 11), with maxima between 2.4 and 0.9 cal. kyr BP. A major environmental change took place 800 years ago, with an abrupt decrease in the relative contribution of terrestrial organic material into the lake compared with aquatic organic material which subsequently largely dominated (C/N drop from 16 to 10). Nonetheless, this event was marked by a rise in soil erosion (χ), in nutrients input (N and P contents) and in anthropogenic lead deposition, suggesting a human disturbance of Alpine ecosystems 800 years ago. Indeed, this time period coincided with the migration of the Walser Alemannic people in the region, who settled at relatively high altitude in the Southwestern Alps for farming and maintaining Alpine passes. [ABSTRACT FROM PUBLISHER]

Abstract: Stable isotopes of carbonates (δ13Ccarb, δ18Ocarb), organic matter (δ13Corg, δ15Norg) and major, trace and rare earth element (REE) compositions of marine carbonate rocks of Late Permian to Early Triassic age were used to establish the position of the Permian–Triassic boundary (PTB) at two continuous sections in the Velebit Mountain, Croatia. The chosen sections — Rizvanuša and Brezimenjača — are composed of two lithostratigraphic units, the Upper Permian Transitional Dolomite and the overlying Sandy Dolomite. The contact between these units, characterized by the erosional features and sudden occurrence of ooids and siliciclastic grains, was previously considered as the chronostratigraphic PTB. The Sandy Dolomite is characterized by high content of non-carbonate material (up to ~30wt.% insoluble residue), originated from erosion of the uplifted hinterland. A relatively rich assemblage of Permian fossils (including Geinitzina, Globivalvulina, Hemigordius, bioclasts of gastropods, ostracods and brachiopods) was found for the first time in Sandy Dolomite, 5m above the lithologic boundary in the Rizvanuša section. A rather abrupt negative δ13Ccarb excursion in both sections appears in rocks showing no recognizable facies change within the Sandy Dolomite, −2‰ at Rizvanuša and −1.2‰ at Brezimenjača, 11m and 0.2m above the lithologic contact, respectively. This level within the lower part of the Sandy Dolomite is proposed as the chemostratigraphic PTB. In the Rizvanuša section, the δ13Corg values decline gradually from ~−25‰ in the Upper Permian to ~−29‰ in the Lower Triassic. The first negative δ13Corg excursion occurs above the lithologic contact, within the uppermost Permian deposits, and appears to be related to the input of terrigenous material. The release of isotopically light microbial soil-biomass into the shallow-marine water may explain this sudden decrease of δ13Corg values below the PTB. This would support the hypothesis that in the western Tethyan realm the land extinction, triggering a sudden drop of woody vegetation and related land erosion, preceded the marine extinction. The relatively low δ15Norg values at the Permian–Triassic (P–Tr) transition level, close to ≈0‰, and a secondary negative δ13Corg excursion of −0.5‰ point to significant terrestrial input and primary contribution of cyanobacteria. The profiles of the concentrations of redox-sensitive elements (Ce, Mn, Fe, V), biogenic or biogenic-scavenged elements (P, Ba, Zn, V), Ce/Ce* values, and normalized trace elements, including Ba/Al, Ba/Fe, Ti/Al, Al/(Al+Fe+Mn) and Mn/Ti show clear excursions at the Transitional Dolomite–Sandy Dolomite lithologic boundary and the chemostratigraphic P–Tr boundary. The stratigraphic variations indicate a major regression phase marking the lithologic boundary, transgressive phases in the latest Permian and a gradual change into shallow/stagnant anoxic marine environment towards the P–Tr boundary level and during the earliest Triassic. [Copyright &y& Elsevier]

The stable isotope composition of waters (δ²H, δ18O) can be used as a natural tracer of hydrologic processes in systems affected by acid mine drainage. We investigated the δ²H and δ18O values of pore waters from four oxidizing sulfidic mine tailings impoundments in different climatic regions of Chile (Piuquenes at La Andina with Alpine climate, Cauquenes and Carén at El Teniente with Mediterranean climate, and Talabre at the Chuquicamata deposit with hyperarid climate). No clear relationship was found between altitude and isotopic composition. The observed displacement of the tailings pore waters from the local meteoric water line toward higher δ18O values (by ∼ +2‰ δ18O relative to δ²H) is partly due to water-rock interaction processes, including hydration and O-isotope exchange with sulfates and Fe(III) oxyhydroxides produced by pyrite oxidation. In most tailings, from the saturated zone toward the surface, isotopically different zones can be distinguished. Zone I is characterized by an upward depletion of ²H and 180 in the pore waters from the saturated zone and the lowermost vadose zone, due to ascending diffused isotopically light water triggered by the constant loss of water vapor by evaporation at the surface. In zone II, the capillary flow of a mix of vapor and liquid water causes an evaporative isotopic enrichment in ²H and 18O. At the top of the tailings in dry climate a zone III between the capillary zone and the surface contains isotopically light diffused and atmospheric water vapor. Intemperate climates, the upper part of the profile is affected by recent rainfall and zone III may not differ isotopically from zone II. [ABSTRACT FROM AUTHOR]

The 50 m-thick Berriasian organic-rich interval (BORI) of the Vaca Muerta Formation (Neuquén Basin, Argentina) represents one of the most attractive stratigraphic intervals for unconventional hydrocarbon exploration in the unit. Nevertheless, little is known about the environmental conditions prevailing during the accumulation of the sediments. To unravel the causes that favored the preservation of the organic matter (OM) in the BORI, a detailed multiproxy sedimentological approach was conducted. The study included the analyses of microfacies, palynological content, calpionellid-calcisphere dinocysts, mineralogy, spectral gamma-ray, inorganic geochemistry, Rock-Eval pyrolysis and stable carbon isotopes of whole rock carbonate (δ13C carb), and associated OM (δ13C org). The BORI presents a late Early to early Late Berriasian age and is subdivided into a lower and upper interval. The lower interval (25.6 m-thick) is primarily formed by radiolaritic wackestones and presents higher total organic carbon (TOC) content (4.2 wt% on average), mainly in the form of amorphous OM (AOM), with variable contribution of phytoclasts. The geochemical analyses (Si, Ni, Cu, Mo, U, V) indicate high productivity of the water column and overall sea bottom anoxia. Oppositely, the upper interval (24.4 m-thick) is mostly constituted by peloidal packstones/grainstones and presents a lower TOC content (1.5 wt% on average) mainly constituted by phytoclasts, with variable contribution of AOM. A decrease of the productivity and an increase of sea bottom oxygenation is recorded based on the geochemical analyses. The high OM content of the BORI responds to the combination of high productivity of the water column and sea bottom anoxia in response to the Berriasian transgression and a worldwide paleoclimatic change towards more humid conditions. The results of our study position the BORI as an attractive interval for unconventional hydrocarbon production due to its high TOC, low bulk clay mineral and high biogenic quartz content, granting an adequate geomechanical behavior. • The mineralogy and geochemistry of the Berriasian organic interval of the Vaca Muerta Fm was studied for the first time. • The interval presents a late Early to early Late Berriasian age (upper Calpionella -lower Calpionellopsis zones). • The high TOC content is in response to the high productivity of the water column and overall anoxia at the sea bottom. • The interval presents appropriate mineralogical and geochemical features for unconventional hydrocarbon production. [ABSTRACT FROM AUTHOR]

The Sasa Pb-Zn-Ag deposit belongs to the group of distal base metal skarn deposits. The deposit is located within the Serbo-Macedonian massif, a metamorphosed crystalline terrain of Precambrian to Paleozoic age. The mineralization, hosted by Paleozoic marbles, shows a strong lithological control. It is spatially and temporally associated with the calc-alkaline to shoshonitic post-collisional magmatism that affected the Balkan Peninsula during the Oligocene–Miocene time period and resulted in the formation of numerous magmatic–hydrothermal ore deposits. The mineralization at the Sasa Pb-Zn-Ag deposit shows many distinctive features typical for base metal skarn deposits including: (1) a carbonate lithology as the main immediate host of the mineralization; (2) a close spatial relation between the mineralization and magmatic bodies of an intermediate composition; (3) a presence of the prograde anhydrous Ca-Fe-Mg-Mn-silicate and the retrograde hydrous Ca-Fe-Mg-Mn ± Al-silicate mineral assemblages; (4) a deposition of base metal sulfides, predominately galena and sphalerite, during the hydrothermal stage; and (5) a post-ore stage characterized by the deposition of a large quantity of carbonates. The relatively simple, pyroxene-dominated, prograde mineralization at the Sasa Pb-Zn-Ag skarn deposit represents a product of the infiltration-driven metasomatism which resulted from an interaction of magmatic fluids with the host marble. The prograde stage occurred under conditions of a low water activity, low oxygen, sulfur and CO2 fugacities and a high K+/H+ molar ratio. The minimum pressure–temperature (P–T) conditions were estimated at 30 MPa and 405 °C. Mineralizing fluids were moderately saline and low density Ca-Na-chloride bearing aqueous solutions. The transition from the prograde to the retrograde stage was triggered by cooling of the system below 400 °C and the resulting ductile-to-brittle transition. The brittle conditions promoted reactivation of old (pre-Tertiary) faults and allowed progressive infiltration of ground waters and therefore increased the water activity and oxygen fugacity. At the same time, the lithostatic to hydrostatic transition decreased the pressure and enabled a more efficient degassing of magmatic volatiles. The progressive contribution of magmatic CO2 has been recognized from the retrograde mineral paragenesis as well as from the isotopic composition of associated carbonates. The retrograde mineral assemblages, represented by amphiboles, epidote, chlorites, magnetite, pyrrhotite, quartz and carbonates, reflect conditions of high water activity, high oxygen and CO2 fugacities, a gradual increase in the sulfur fugacity and a low K+/H+ molar ratio. Infiltration fluids carried MgCl2 and had a slightly higher salinity compared to the prograde fluids. The maximum formation conditions for the retrograde stage are set at 375 °C and 200 MPa. The deposition of ore minerals, predominantly galena and sphalerite, occurred during the hydrothermal phase under a diminishing influence of magmatic CO2. The mixing of ore-bearing, Mg-Na-chloride or Fe2+-chloride, aqueous solutions with cold and diluted ground waters is the most plausible reason for the destabilization of metal–chloride complexes. However, neutralization of relatively acidic ore-bearing fluids during the interaction with the host lithology could have significantly contributed to the deposition. The post-ore, carbonate-dominated mineralization was deposited from diluted Ca-Na-Cl-bearing fluids of a near-neutral pH composition. The corresponding depositional temperature is estimated at below 300 °C. [ABSTRACT FROM AUTHOR]

The Paleocene-Eocene Thermal Maximum (PETM) shows an extraordinary drop in the δ 13 C of carbonate and organic matter across the globe, suggesting massive release of 13 C-depleted carbon dioxide into the ocean and atmosphere over a very short time interval (probably < 20ky). We report a geochemical and mineralogical study of 106 samples spanning the most expanded PETM at the Dababiya Global Stratotype Standard section and Point (GSSP) near Luxor, Egypt. The field and laboratory observations reveal that the deposition occurred in a submarine channel extended laterally about 200 m with the deepest part (~ 0.88 m) at the designated GSSP, although all bio-zones are present. Stable isotope records of both carbonate and organic carbon show decreases starting 0.6 m below the Paleocene-Eocene boundary (PEB) and culminating at the erosion surface. A persistent shift in δ 15 N org values to near zero reflects a gradual increase in bacterial activity. High Ti, K and Zr and low Si contents at the PEB coincide with increased kaolinite contents, which suggests intense chemical weathering under more humid conditions at the PETM onset. Two negative Ce-anomalies indicate intervals of anoxic conditions during the lower and middle PETM (base and top of zone E1). The first anoxic event is represented by a negative Ce-anomaly, high V/C rand V/V + Ni ratios, negative Mn* and an abundance of idiomorphic pyrite crystals that indicate anoxic to euxinic conditions. The anoxic event (middle PETM) is marked by high U, Mo, V, Fe and abundant small sized (2–5 μm) pyrite framboids, increased Cu, Ni, and Cd at the same level suggesting anoxic conditions linked to high surface water productivity. Above this interval, oxic conditions returned as indicated by the precipitation of phosphorus and barium. These data reveal an expanded PETM interval marked by intense weathering as a crucial parameter during the recovery phase. [ABSTRACT FROM AUTHOR]

Profound environmental changes punctuated the Early Jurassic period, as recorded by marked carbon and oxygen isotope anomalies and major biotic crises. The response of low-latitude regions of Northern Gondwana to such intense changes is not documented as well as that of other Tethys areas. We present new calcareous nannofossil assemblages from three sections located in NW Algeria, in the Sahara and Tlemcen Basins, respectively. New stable carbon and nitrogen isotope data are provided from the Tlemcen Basin to reconstruct local environmental conditions in the wider context of a Toarcian greenhouse climate. We first established a solid chemo- and biostratigraphic framework by integrating stable carbon isotope data and calcareous nannofossil events. Calcareous nannofossil assemblages show common trends in the two basins, such as the occurrence in high proportions of the deep-dweller species Mitrolithus jansae , likely indicating stratification of the water column with a deep nutricline. This taxon dominated the assemblage during the negative carbon isotope excursion (CIE) interval, often used to delineate the base of the Toarcian anoxic event (T-OAE). Such a nannofossil record is unique in the Western Tethys domain, as M. jansae is known to drastically decrease in abundance during the T-OAE until its disappearance in the aftermath of the event. The NW Algeria nannofossil record indicates prolonged thermal stratification of water-masses, finally triggering hyper-oligotrophy and low productivity in shallow waters during the Toarcian CIE. Such peculiar conditions are likely related to the combined effects of a warm and arid climate dominating along the northern Gondwana margin and the presence of a strong clockwise gyre over the epicontinental shelf, which brought warm equatorial waters from the Tethys Ocean to the NW Algeria shelf. • The NW Algeria nannofossil record suggests prolonged thermal stratification of water-masses. • Hyper-oligotrophy and low productivity in shallow-waters occurred during the Toarcian Event. • Such conditions are likely related to the effects of a warm and arid climate of the Northern Gondwana. [ABSTRACT FROM AUTHOR]

The Apapa-Badagry Creek in southwestern Nigeria is a largely man-impact area being bordered to the north by sprawling residential estates and industries and to the south by recreational centers and villages. It also houses the Lagos Harbour and petroleum terminals. Sewage from these complexes is discharged into the creek, thus the pollutants impact the living faunas, such as benthic foraminifera. The implications of organic matter (OM) type and source on the diversity and abundance of living benthic foraminifera in the Apapa-Badagry Creek are investigated. Results show that the distribution of the living benthic foraminifera in this area is largely dependent on sediment type, OM source, and salinity and that only ten species of living benthic foraminifera thrive in muddy sediments with TOC < 2 wt%. Carbon and nitrogen isotopes (δ13C and δ15N) and C/N molar ratios reveal that the OM is of terrestrial origin (C 3 plants) and that it is not the ideal food for benthic foraminifera in this estuary, in particular, for Ammonia species. • The Apapa-Badagry Creek represents a typical marginal marine environment under great anthropogenic stress. • Benthic foraminifera are used as ecosystem indicators. • Stable isotopes of carbon and nitrogen (δ13C and δ15N) reveal the terrestrial origin of the sedimented organic matter. • Changes in assemblage structure and distribution are due to presence of organic matter nutrients, and salinity gradients. [ABSTRACT FROM AUTHOR]

Abstract: In an active tailings impoundment, we studied the evolution of freshly deposited tailings from alkaline, unoxidized to acidic, oxidized tailings tracing changes in pore water quality, mineralogy, and element pathways. The tailings originate from the giant porphyry copper deposit Chuquicamata (Chile), and were deposited in different basins with varying times of surface exposure (0 to five years) to the hyper-arid climate in the Atacama desert. Fresh alkaline tailings (pH9.1) had high concentrations of dissolved Na (1773mg/L), Ca (556mg/L), SO4 (2496mg/L) and Cl (1678mg/L) due to dissolution of primary gypsum, and high dissolved element concentrations in the flotation process water due to recycling of water from the tailings impoundment. High As and Mo concentrations resulted from desorption processes during the flotation, with minor contributions from As-rich river water and recycled tailings water. After draining of free water in freshly deposited tailings, evaporation-driven capillary rise was the dominant water transport in the vadose zone. In younger tailings (up to three years), the pH decreased due to sulfide oxidation to circumneutral values (6.4–8.6). The capillary fringe reached 1m depth, where ongoing evaporation enriched Na (up to 5483mg/L), K (742mg/L), and Cl (6892mg/L). In the vadose zone above 1m, the high daily temperature amplitude resulted in condensation of pore water in the uppermost 80cm of sedimented tailings. Subsequent capillary rise depleted uppermost tailings in soluble phases and increase superficial salt precipitation (halite, gypsum and Na–K–Ca–Mg sulfates). After four years, a 13cm thick oxidation zone with acidic pH (4.7) evolved. After five years, a well-defined oxidation zone (28cm thickness) with low pH (3.8) and high mobility of heavy metals was found (e.g., 247mg/L Fe, 177mg/L Cu, 61.8mg/L Zn). This mobility allowed transport and enrichment in the efflorescent salt crust (e.g., as Cu sulfates devilline, krohnkite and Cu-chlorides eriochalcite and atacamite), with SO4 dominantly from sulfide oxidation (−1.0 to 5.9‰ δ34S, −1.0 to 4.4‰ δ18Osulfates). Stable isotope data suggest that capillary rise from the water table reached the surface, most probably due to the reduction of pore size by precipitating secondary minerals, decreased water loss by clogging of pores and heat isolation by the efflorescent salt crust. The cycles of surface exposure and new tailings deposition in the last decades resulted in buried former oxidation zones, which showed lesser K and Cu concentrations in Fe oxides than recent oxidized tailings, most probably due to the transformation of jarosite and schwertmannite to Fe(3+) oxyhydroxides and dissolution of Cu sulfates. Pore water in the saturated deep tailings was highly dynamic and displayed influences of local groundwater, and mixing with acid rock drainage (ARD) and fresh tailings water, both infiltrating from the surface. At the tailings dam, seepage water varied in time between neutralized ARD and fresh tailings water with groundwater influence, due to the periodic shift of the deposition zone and the resulting shallow groundwater changes. Adjacent efflorescent salts include typical minerals found in the secondary porphyry copper deposits in northern Chile (e.g., atacamite), displaying the similarity between geochemical processes in weathered tailings impoundments and secondary enrichment zones of ore bodies, like Exotica from the Chuquicamata mine. [Copyright &y& Elsevier]

Abstract: Prevention of acid mine drainage (AMD) in sulfide-containing tailings requires the identification of the geochemical processes and element pathways in the early stages of tailing deposition. However, analyses of recently deposited tailings in active tailings impoundments are scarce because mineralogical changes occur near the detection limits of many assays. This study shows that a detailed geochemical study which includes stable isotopes of water (δ 2H, δ 18O), dissolved sulfates (δ 34S, δ 18O) and hydrochemical parameter (pH, Eh, DOC, major and trace elements) from tailings samples taken at different depths in rainy and dry seasons allows the understanding of weathering (oxidation, dissolution, sorption, and desorption), water and element pathways, and mixing processes in active tailings impoundments. Fresh alkaline tailings (pH 9.2–10.2) from the Cu–Mo porphyry deposit in El Teniente, Chile had low carbonate (0.8–1.1 wt.% CaCO3 equivalent) and sulfide concentrations (0.8–1.3 wt.%, mainly as pyrite). In the alkaline tailings water, Mo and Cu (up to 3.9 mg/L Mo and 0.016 mg/L Cu) were mobile as MoO4 2− and Cu(OH)2 0. During the flotation, tailings water reached equilibrium with gypsum (up to 738 mg/L Ca and 1765 mg/L SO4). The δ 34S vs. δ 18O covariations of dissolved sulfate (2.3 to 4.5‰ δ 34S and 4.1 to 6.0 ‰ δ 18O) revealed the sulfate sources: the dissolution of primary sulfates (12.0 to 13.2‰ δ 34S, 7.4 to 10.9‰ δ 18O) and oxidation of primary sulfides (− 6.7 to 1.7‰ δ 34S). Sedimented tailings in the tailings impoundment can be divided into three layers with different water sources, element pathways, and geochemical processes. The deeper sediments (>1 m depth) were infiltrated by catchment water, which partly replaced the original tailings water, especially during the winter season. This may have resulted in the change from alkaline to near-neutral pH and towards lower concentrations of most dissolved elements. The neutral pH and high DOC (up to 99.4 mg/L C) of the catchment water mobilized Cu (up to 0.25 mg/L) due to formation of organic Cu complexes; and Zn (up to 130 mg/L) due to dissolution of Zn oxides and desorption). At 1 m depth, tailings pore water obtained during the winter season was chemically and isotopically similar to fresh tailings water (pH 9.8–10.6, 26.7–35.5 mg/L Cl, 2.3–6.0 mg/L Mo). During the summer, a vadose zone evolved locally and temporarily up to 1.2 m depth, resulting in a higher concentration of dissolved solids in the pore water due to evaporation. During periodical new deposition of fresh tailings, the geochemistry of the surface layer was geochemically similar to fresh tailings. In periods without deposition, sulfide oxidation was suggested by decreasing pH (7.7–9.5), enrichment of MoO4 2− and SO4 2−, and changes in the isotopic composition of dissolved sulfates. Further enrichment for Na, K, Cl, SO4, Mg, Cu, and Mo (up to 23.8 mg/L Mo) resulted from capillary transport towards the surface followed by evaporation and the precipitation of highly soluble efflorescent salts (e.g., mirabilite, syngenite) at the tailing surface during summer. [Copyright &y& Elsevier]

The Oceanic Anoxic Event 2 (OAE2, ca. 94.6 Ma) is one of the major perturbations in the global carbon cycle during the Phanerozoic. Stable carbon isotopes (δ 13C) from marine and continental sedimentary environments document this carbon cycle perturbation with a pronounced (> 2‰) positive carbon isotope excursion (CIE). Although the OAE2 stratigraphic interval has been intensively studied in terms of paleoceanography and paleoclimatology, several climatic and carbon cycle aspects are not yet well-understood. In particular, cyclic short-term Milankovitch-scale δ 13C variations within the OAE2 and their potential implications for the global carbon cycle have been rarely addressed. Here, we present high-resolution (5 cm, ~2 kyr) δ 13C data spanning the OAE2 from the Paris Basin Chalk (Poigny Craie-701 drill-core) to show high amplitude short-term δ 13C oscillations, superimposed on the major CIE. Time-series analysis indicates that short-term oscillations are astronomically paced, with eccentricity cycles being the most prominent. Orbital forcing of δ 13C variations is further supported by time-series analysis of the English Chalk (Eastbourne section). We suggest that orbitally paced carbon cycle oscillations were amplified by considerable emission of greenhouse gases from volcanism that caused the overall CIE. Astronomical calibration of the whole OAE2 (the perturbation and recovery phases) from the Poigny record provides a duration equivalent to eight to eight and a half short eccentricity cycles. Cyclostratigraphic correlations among several OAE2 key records indicate the same duration of the whole CIE. However, duration of the interval from the onset of CIE till the Cenomanian-Turonian boundary (CTB) is significantly different from one basin to another. In particular, a difference of almost two short eccentricity cycles is highlighted between the Anglo-Paris and Western Interior basins. According to cyclostratigraphic approach and correlations, the entry of W. devonense was at least 200 kyr later in the Western Interior Basin (WIB, USA) than in Europe. Key calcareous nannofossil biohorizons (e.g., Quadrum gartneri) are also stratigraphically upshifted in the WIB with respect to the European sections, hence concurring with the hypothesis of a younger CTB in the WIB. We ascribe such significant temporal offset to diachroneity of the CTB, which is likely the result of different, regional biotic responses to the global OAE2 paleoenvironmental perturbation. • OAE2 d13C data from the Paris Basin shows orbitally forced carbon-cycle variations. • OAE2 time interval spans eight to eight and a half short eccentricity cycles. • The CTB in Western Interior and Anglo-Paris basins is about 200-kyr diachronous. • Prominent d13C cycles within the OAE2 is related to extreme greenhouse conditions. [ABSTRACT FROM AUTHOR]

The end-Cretaceous mass extinction (66 Ma) has long been associated with the Chicxulub impact on the Yucatan Peninsula. However, consensus on the age of this impact has remained controversial because of differing interpretations on the stratigraphic position of Chicxulub impact spherules relative to the mass extinction horizon. One side argues that the impact occurred precisely at the Cretaceous-Paleogene boundary, thus coinciding with the mass extinction; the other side argues that the impact predated the Cretaceous-Paleogene boundary, based on the discovery of primary impact spherules deposits in NE Mexico and Texas near the base of planktic foraminiferal zone CF1, dated at 170 k.y. before the Cretaceous-Paleogene boundary. A recent study of the most pristine Chicxulub impact spherules discovered on Gorgonilla Island, Colombia, suggested that they represent a primary impact deposit with an absolute age indistinguishable from the Cretaceous-Paleogene boundary. Here, we report on the Gorgonilla section with the main objective of evaluating the nature of deposition and age of the spherule-rich layer relative to the Cretaceous-Paleogene boundary. The Gorgonilla section consists of light gray-yellow calcareous siliceous mudstones (pelagic deposits) alternating with dark olive- brown litharenites (turbidites). A 3-cmthick dark olive-green spherule-rich layer overlies an erosional surface separating Maastrichtian and Danian sediments. This layer consists of a clast-supported, normally graded litharenite, with abundant Chicxulub impact glass spherules, lithics (mostly volcanic), and Maastrichtian as well as Danian microfossils, which transitions to a calcareous mudstone as particle size decreases. Mineralogical analysis shows that this layer is dominated by phyllosilicates, similar to the litharenites (turbidites) that characterize the section. Based on these results, the spherulerich layer is interpreted as a reworked early Danian deposit associated with turbiditic currents. A major hiatus (>250 k.y.) spanning the Cretaceous-Paleogene boundary and the earliest Danian is recorded at the base of the spherule-rich layer, based on planktic foraminiferal and radiolarian biostratigraphy and carbon stable isotopes. Erosion across the Cretaceous-Paleogene boundary has been recorded worldwide and is generally attributed to rapid climate changes, enhanced bottom-water circulation during global cooling, sea-level fluctuations, and/or intensified tectonic activity. Chicxulub impact spherules are commonly reworked and redeposited into younger sediments overlying a Cretaceous-Paleogene boundary hiatus of variable extent in the Caribbean, Central America, and North Atlantic, while primary deposits are rare and only known from NE Mexico and Texas. Because of their reworked nature, Gorgonilla spherules provide no stratigraphic evidence from which the timing of the impact can be inferred. [ABSTRACT FROM AUTHOR]

The End-Cretaceous is characterized by one of the five major extinction in Earth history by a major crash in the biodiversity associated with a carbon isotope negative excursion. These events are thought to have been triggered by both meteorite impact and Deccan traps activity. The studied sections are located in the Goynuk-Mudurnu basin (Central Turkey), which includes sediments from Jurassic to Paleogene. This basin corresponds to a fore-arc basin located in the northern part of the Tethys ocean. The aim of the study was to reconstruct the paleoenvironmental changes associated with the KPg events, using a multiproxy approach including sedimentological, biostratigraphical, mineralogical and geochemical analysis (bulk rock and clay mineralogy, stable isotopes, mercury and TOC contents, major and trace elements, magnetic susceptibility and thin sections analyses). Three bentonite layers containing zircons were detected in both sections close to the KPg boundary and were sampled for dating by U-Pb geochronology. Sharp negative excursions in ∂18O and ∂13C values point to changes in temperature and productivity through the KPg transition. A strong decrease in carbonate content across the KPg section highlights a decrease in productivity and ocean acidification. The Hg concentration profile is characterized by a gradual increase in the uppermost Maastrichtian (CF1 biozone) culminating at the KPg. All this can be interpreted as the results of increased volcanic activity linked to Deccan Volcanism volcanism which played a key role in increasing atmospheric CO2 and SO2 levels that resulted in global warming and acidified oceans, increasing biotic stress that predisposed faunas to extinction at the KPg. [ABSTRACT FROM AUTHOR]

The Toarcian Ocean Anoxic Event (TOAE) took place in the Early Jurassic (∼183 My) and is characterized by the widespread deposition of organic matter-rich black shales in deep basins, and by a negative carbon isotope excursion (NCIE) reflecting profound environmental changes. This event is well documented in the sedimentary record of deeper marine settings, in which the TOAE is marked by the presence of organic-rich shales. However evidence of the TOAE in shallower environments is less documented, mainly due to incomplete sedimentary records, sea-level fluctuations and lack of reliable biostratigraphic markers. Here we present data from a new extremely shallow section in Morocco (Dadès Gorges, Central Atlas), located along the northern Gondwana margin. This section consists of alternating dolomitic limestones and paleosols, which contain clear relicts of dinosaur tracks and sedimentary features, including stromatolites, ripple marks, mud cracks and fossil roots. The chemostratigraphic profiles show a significant increase in mercury (Hg), just below a negative excursion in carbonate D13C values (–3‰), that we attribute to the TOAE, which coincided with several cyclical emersion episodes. These results confirm the presence of the NCIE from the TOAE in the most shallow environments of the Tethys. The observed Hg anomalies are probably linked with the volcanic activity (Karoo Ferrar province). This marker combined with stable isotopes is therefore a very promising correlative tool. [ABSTRACT FROM AUTHOR]

Mass extinctions generally involve a complex array of interrelated causes and are best evaluated by a multi-proxy approach as applied here for the end-Cretaceous mass extinction. This study documents and compares the planktic foraminiferal records, carbonate dissolution effects, stable isotopes, and magnetic susceptibility in France (Bidart), Austria (Gamsbach) and Tunisia (Elles) in order to explore the environmental conditions during the uppermost Maastrichtian Plummerita hantkeninoides zone CF1 leading up to the mass extinction. Planktic foraminiferal assemblages at Bidart and Gamsbach appear to be more diverse than those at Elles, with unusually high abundance (20–30%) and diversity (~ 15 species) of globotruncanids in the two deep-water sections but lower abundance (< 10%) and diversity (< 10 species) at the middle shelf Elles section. Oxygen isotopes in zone CF1 of Elles record rapid climate warming followed by cooling and a possible return to rapid warming prior to the mass extinction. The onset of high stress conditions for planktic foraminifera is observed ~ 50–60 cm below the KTB at Bidart and Gamsbach, and ~ 4.5 m below the KTB at Elles due to much higher sediment accumulation rates. These intervals at Bidart and Gamsbach record low magnetic susceptibility and high planktic foraminiferal fragmentation index (FI) at Elles, Bidart and Gamsbach. An increased abundance of species with dissolution-resistant morphologies is also observed at Gamsbach. The correlative interval in India records significantly stronger carbonate dissolution effects in intertrappean sediments between the longest lava flows, ending with the mass extinction. Based on current evidence, this widespread dissolution event stratigraphically coincides with the climate cooling that follows the Late Maatrichtian global warming and may be linked to ocean acidification due to Deccan volcanism. The estimated 12,000–28,000 Gigatons (Gt) of CO 2 and 5200–13,600 Gt of SO 2 introduced into the atmosphere likely triggered the carbonate crisis in the oceans resulting in severe stress for marine calcifiers leading to mass extinction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Bučim deposit represents a post-collisional porphyry Cu-Au system. • Oxidation of Fe2 + to Fe3 + in the potassic alteration zone promoted sulphate reduction. • The barren phyllic alteration zone records infiltration of hot and saline magmatic fluids. • The chlorite alteration zone reflects a lithostatic/hydrostatic transition. • The barren argillic alteration zone records incursion of a cold and diluted meteoric fluid. The Bučim porphyry Cu-Au deposit is situated in the westernmost part of the Serbo-Macedonian Massif, Republic of North Macedonia. The deposit is hosted by Precambrian gneisses with tectonically imbedded rare lenses of Palaeozoic amphibolites. The mineralization is spatially associated with intrusions of andesitic to trachyandesitic magmatic bodies. The geochemical signature of the intrusions and their radiogenic age suggest that the Bučim porphyry Cu-Au deposit represents a product of the Oligocene/Early Miocene post-collisional magmatic activity. The Vršnik intrusion, the youngest among four intrusions at the Bučim deposit, has not been subjected to later magmatic overprints and was therefore selected for studying the evolution of ore-forming fluids in post-collisional porphyry Cu-Au systems. The Cu-Au mineralization is spatially associated with hydrothermal alteration assemblages within and around the Vršnik intrusion. The infiltration of hot, near-neutral, oxidized, and highly saline and metal-rich aqueous solutions developed a mineralized potassic alteration zone. The fluid inclusion study suggests the formation temperature and pressure of 600-645⁰C and 0.675 kbar, respectively. This alteration zone is characterized by the replacement of amphibole with biotite and crystallization of hydrothermal biotite, magnetite, and hematite within the fine-grained groundmass of the intrusion. The oxidation of ferrous to ferric iron in this alteration zone has been recognized as a possible trigger for sulfate reduction and the consequent deposition of sulfide mineralization. The fluid inclusion study reflects that the barren phyllic alteration zone represents a product of infiltration of hot and saline fluids with a high metal-transport capability. Anyhow, sericitization and silicification suggest a low pH that might have played a significant role in preventing Cu deposition. The stable isotope composition of carbonates associated with the phyllic alteration zone point to a contribution of magmatic CO 2. The mineralized chlorite alteration zone is mainly well developed along the contact between the intrusion and surrounding gneisses and reflects conditions of a high water/rock ratio. The fluid inclusion assemblages composed exclusively of vapor-rich inclusions indicate fluid flashing, probably associated with the transition from the lithostatic to hydrostatic regime at the point when the system cooled down to approximately 400⁰C. The liquid + vapor fluid inclusion assemblages point to dilution and cooling episodes, apparently related to mixing of ore-bearing fluids and meteoric water. The decrease in temperature as well as the decrease in the fluid salinity are associated with the mobility of metals transported in forms of their chloride complexes, including Cu, Au and Ag. The barren argillic alteration zone was developed under the influence of relatively cold and diluted fluids, with very limited capability for transport of metals. The water/rock ratio was relatively high but lower comparing the chlorite alteration zone. The presented study revealed that development of hydrothermal alteration zones and evolution of ore-forming fluids in post-collisional porphyry Cu-Au systems are comparable with those known from subduction-related magmatic arcs. [ABSTRACT FROM AUTHOR]

Abstract: This study investigates the sedimentological and geochemical changes that occurred during the last 2200years in the meromictic Lake Lucerne (Switzerland), one of the largest freshwater lakes of Central Europe. The stable isotope composition (δ13C and δ18O values) of bulk carbonates is compared to changes in grain-size distribution (clay and silt fraction), natural trace element input (titanium and thorium concentrations), and organic material abundance (Corg, nitrogen and phosphorus) and composition (C/N ratios and hydrogen and oxygen indexes). A drop in carbonate accumulation and in the δ18O values of sediments between ca. AD 500 and 700 followed a large and consistent rise in chemical weathering, marked by increases in the silicate-clay fraction and in crustal element concentrations. During the following millennium, there was a long-term decreasing trend in the lithogenic trace element input and in the phosphorus loading, suggesting decreasing terrigeneous input from runoff water. The major sedimentological change over the studied period occurred after ca. AD 1800 with a significant increase in the erosion-driven silt-fraction and in the sedimentation rate. During the last century, human-induced increase in nutrient input to the lake highly enhanced the accumulation of organic matter in sediment. Changes in nutrients and oxygen conditions in the hypolimnion of Lake Lucerne during the eutrophication period (i.e., the last 40years) highly modified the geochemical fluxes compared to the relatively stable oligotrophic conditions that prevailed during the previous 2000years. Before the 19th century, climate driven meromixis had a limited impact on the organic matter flux to the sediments, but the accumulation of carbonate considerably decreased during periods of lower mechanical erosion rates and high chemical weathering rates. [Copyright &y& Elsevier]

Abstract: Carbon and oxygen isotope compositions of the needle fibre calcite (NFC) from two soils observed in quarries (Villiers and Savagnier) in the Swiss Jura Mountains are used to investigate the processes involved in the formation of these calcite crystals in pedogenic environments. NFC occurs in soils with different macroscopic and microscopic morphologies. Three groups of microscopic morphologies are distinguished: simple needles (SN), simple needles with overgrowths (SNO), and simple needles with nanofibres (SNN), nanofibres being either organic or mineral in nature. These groups correspond to different stages in the formation and evolution of NFC. Evaluation of the δ13C and δ18O values of NFC and late calcite cements (LCC) in relationship to the composition of the carbonate host rock (CHR), and δ13CDIC from the soil waters, indicate that both NFC and LCC are precipitated in isotopic equilibrium with the soil waters. Similar δ13C and δ18O values of the elongated NFC and the rhombohedral calcite crystals of the LCC suggest that the precipitation of these different calcite habits is not due to changes in physicochemical conditions. The growth of NFC crystals inside an organic mould formed by the fungal hyphae could explain the formation of calcite crystals in the shape of a needle in isotopic equilibrium with the local environment. The comparison of the δ13C and δ18O signatures of the various NFC morphological groups suggests that they likely evolve in the soil solution from calcite crystals liberated during the degradation of fungal hyphae walls. The NFC may be a proxy of the soil conditions (temperature and vegetation) during its precipitation, and also an indicator of biogenic (fungal) activity. [Copyright &y& Elsevier]

Stratigraphic cycles preserved in sedimentary successions are controlled by the interaction of tectonics, climate, sediment supply and sea-level variations. Understanding the influence of these drivers on sedimentary systems dynamics is crucial to understand and extract information from sedimentary archives. In the deep marine deposits of the Ainsa foreland basin (lower to middle Eocene, southern central Pyrenees, Spain), the origin of well-preserved cyclicity between channelized sandy submarine fans and hemipelagic deposits remains subject to debate because of the absence of chronostratigraphic constraints on high resolution geochemical proxies. Here, we contrast a combination of newly acquired and legacy geochemical datasets (carbon and oxygen stable isotopes, organic matter content, major and trace elements and the mineralogical composition of bulk hemipelagic sediments) tuned by a new age model to global "target" curves to discuss the possible drivers of the stratigraphic cycles found in the deep marine sediment gravity flow deposits of the Hecho Group. Our new age model is based on magnetostratigraphic and biostratigraphic datasets acquired on a composite section going from the Banaston system to the distal deposits of the Sobrarbe deltaic complex. Four major polarity zones are identified in the studied succession covering the time span from C21n (lower members of the Banaston system) to C19r (Sobrarbe deltaic complex). Our age model is corroborated by the identification of the nannoplankton zone NP16 in the Guaso system (C20n). Comparison between global carbon isotope curve and local isotope dataset shows some differences, suggesting the preservation of a local isotope signal modulated by eustatism, changes in the environment of deposition and/or restriction in water circulation in the Ainsa basin. Yet, comparison of the stratigraphic record with global sea-level curves highlights that sands are mainly delivered to the basin during lowstands, pointing to the important role of eustasy even in an active foreland tectonic context. The exception to the rule is the Banaston member II, whose deposition during a sea-level highstand seems to be controlled by the growth of tectonic structures. • New age model for the deep marine sediment gravity flow deposits of the upper Hecho Group in the Ainsa basin. • Complete stable carbon and oxygen isotope records for the Hecho group. • Dominant but not exclusive delivery of sands during sea-level lowstands. [ABSTRACT FROM AUTHOR]

An exhaustive biostratigraphic study based on the calcareous nannofossil content from Lower and Middle Jurassic Lusitanian Basin sections in Portugal is here presented. Located at the strategic intersection of important Jurassic water masses during a period of drastic environmental changes, the Lusitanian Basin conveyed mixed phytoplanktonic communities in its surface waters. Approximately 800 m of exceptionally continuous Lower and Middle Jurassic series bearing detailed ammonite biostratigraphy and two Global Stratotype Section and Point are studied. Vertical and lateral ubiquity of calcareous nannofossils in marine sediments and rapid evolutionary rate and radiation make this fossil group a remarkable biostratigraphic tool. Nearly 100 bioevents are acknowledged in ~24 Myr time span this work refers to, bridging 11 nannofossil zones and 29 subzones. A thorough revision of the existing literature referring to Early and Middle Jurassic calcareous nannofossil biostratigraphy is presented, and causes and implications for zonal marker discrepancies discussed under a palaeoceanographic and Jurassic nannofossil evolution angle. In order to create a solid biostratigraphic frame and to compare it with C and O stable isotopic trends, brachiopod calcite shells were analysed for geochemistry. This work yields for the first time a very detailed and inclusive biostratigraphic scheme for the Early and Middle Jurassic epochs. [ABSTRACT FROM AUTHOR]