scholarly journals Paleoenvironmental reconstruction of the Pleistocene site of Oued Sarrat (Northwestern Tunisia) using mineralogical and geochemical data

2018 ◽  
Vol 27 (2) ◽  
pp. 316-322
Author(s):  
Narjess Karoui-Yaakoub ◽  
Moncef Said Mtimet ◽  
Semeh Bejaoui ◽  
Bienvenido Martínez-Navarro
Keyword(s):  
High Energy ◽  
Geochemical Data ◽  
Paleoenvironmental Reconstruction ◽  
Total Contribution ◽  
Chemical Test ◽  
Calcium Carbonates ◽  
Mineralogical Study ◽  
Marine Influence ◽  
Middle And Late Pleistocene ◽  
Geochemical Analyses

The mineralogical and geochemical analyses of Pleistocene sediments and mollusks shells (gastropods and bivalves) from the archaeopaleontological site of Oued Sarrat (Tejerouine, NW Tunisia) permitted us to determine the paleoenvironmental conditions and to reconstruct the local depositional environment during the Middle and Late Pleistocene. The mineralogical cortege of the sediments, for all the analyzed samples, records the characteristics of a mixture ofsilica and calcite dominance with a small fraction of gypsum and aragonite. The mineralogical analyses of all mollusk species reflect a cortege dominated by aragonite, associated with low amounts of calcite, silica, hematite and goethite. We consider that the domin- ance of aragonite indicates that the tests have not yet or little undergone mineralogical transformations linked to the phenomena of fossilization, as evidenced by the absence or low calcite content. On the other hand, the low percentages of silica, goethite and hematite are probably related to the existence of impurities and sediments trapped in lodges, or  adhered to the shell surface. The mineralogical data confirm a composition dominated by calcium carbonates, expressed by high contents of CaO and CO2, reflecting a chemical test of organisms’ development in continental environment.This kind of environment is characterized by the absence of MgO, which is usually present in the organisms’ tests developed in marine environment. However, the contents of SiO2, Fe2O3, Al2O3 are related, as it was reported during the mineralogical study, to the lithological impurities trapped mainly in the lodges of helicides. Mineralogical and geochemical data tracing, carried out on sediments and tests, converge to deduce the establishment of paleoenvironment attributable to fluvial deposition of sufficiently high energy where the ultrafine fractions of clay minerals are remarkably lacking. The absence of indicators of marine chemistry such as magnesium in sediments and in the tests of organisms confirms almost total contribution of the continental meteoric water without marine influence. Such environment, however, is affected by intermittent episodes of aridity as attested by the presence of evaporate minerals such as gypsumand aragonite.

Mapping Magmatic and Hydrothermal Processes from Routine Exploration Geochemical Analyses

2020 ◽  
Vol 115 (3) ◽  
pp. 489-503 ◽  
Author(s):  
Scott Halley
Keyword(s):  
Inductively Coupled Plasma ◽  
Mining Industry ◽  
Analysis Data ◽  
Ore Deposits ◽  
Mineral Deposits ◽  
Geochemical Data ◽  
High Quality ◽  
Inductively Coupled ◽  
Hydrothermal Processes ◽  
Geochemical Analyses

Abstract Analytical methods used by commercial assay laboratories have improved enormously in recent years. Inductively coupled plasma-atomic emission spectroscopy and inductively coupled plasma-mass spectrometry methods now report analyses for half of the periodic table with exceptional detection limits and precision. It is becoming commonplace for mining companies to use such methods routinely for the analysis of drill samples throughout mineral deposits. Improvements in software and computing power now allow rapid interrogation of upward of 100,000 assay samples. Geochemical analyses are quantitative, are independent of observer bias, and can form the basis for robust geologic and mineralogical models of mineral deposits, as well as shed light on scientific questions. In particular, consistently collected, high-quality geochemical analyses can significantly improve and systematize logging of lithological and hydrothermal alteration mineralogic changes within drill core. In addition, abundant, high-quality geochemical data provide insights into magmatic and hydrothermal processes that were previously difficult to recognize and that have obvious applications to mineral exploration and improved genetic models of ore deposits. This paper describes a workflow that mining industry geologists can apply to their multielement analysis data to extract more information about magma compositions and gangue mineralogy.

Depositional environments, sediment characteristics, palaeoecological analysis and environmental assessment of an internationally protected shallow Mediterranean lagoon, Gialova Lagoon – Navarino Bay, Greece

2014 ◽  
Vol 105 (3) ◽  
pp. 189-206 ◽  
Author(s):  
P. Avramidis ◽  
G. Iliopoulos ◽  
N. Kontopoulos ◽  
D. Panagiotaras ◽  
P. Barouchas ◽  
...  
Keyword(s):  
Natura 2000 ◽  
Enrichment Factors ◽  
Depositional Environments ◽  
Geochemical Characteristics ◽  
Geochemical Data ◽  
Sediment Characteristics ◽  
Protection Area ◽  
Moment Measures ◽  
Geochemical Analyses ◽  
International Conventions

ABSTRACTThis study presents sedimentological, palaeoecological and geochemical data from a shallow Mediterranean coastal lagoon which has been severely influenced by human intervention over the last 70 years. The Gialova Lagoon is protected by international conventions and is listed in the Natura 2000 European Community Network as Special Protection Area (SPA) and Site of Community Importance (SCI). The spatial variability of sediment characteristics such as grain size, total organic carbon (TOC) and moment measures, mean, sorting, kurtosis and skewness were calculated. Moreover, micro- and macrofossil and sediment geochemical analyses were carried out on six gravity core samples. Study of the above parameters indicates that the anthropogenic impact and intervention are reflected in the micro- (ostracods, foraminifera, charophytes) and macrofossil (molluscs) taxa corresponding to different depositional environmental facies, representing a brackish lagoon with the influence of (a) fresh water inflow, (b) shallow marine environment and (c) hypoxic and dystrophic conditions. The geochemical characteristics and the calculation of the degree of sediment contamination using enrichment factors (EF), contamination factors (Cif) and the index of geo-accumulation (Igeo) indicate a recent relative improvement of the lagoon towards the upper layers of the gravity cores, rendering the lagoon as unpolluted to moderately polluted. This combinatorial study of sediment geochemical characteristics, as well as the downcore micro- and macrofossil assemblages, can be considered as a baseline for future monitoring in accordance with European Union directives, and for any future engineering interventions for the lagoon environmental maintenance and conservation; as this is the first time that geochemical and downcore palaeoecological data have been presented from this lagoon.

Characterising sediments of a tropical sediment-starved shelf using cluster analysis of physical and geochemical variables

2015 ◽  
Vol 12 (2) ◽  
pp. 204 ◽  
Author(s):  
Lynda C. Radke ◽  
Jin Li ◽  
Grant Douglas ◽  
Rachel Przeslawski ◽  
Scott Nichol ◽  
...  
Keyword(s):  
Large Data ◽  
High Energy ◽  
Rate Coefficients ◽  
Geochemical Data ◽  
Clustering Methods ◽  
Data Set ◽  
Β Diversity ◽  
Published Evidence ◽  
Baseline Information ◽  
Geochemical Variables

Environmental context Australia's tropical marine estate is a biodiversity hotspot that is threatened by human activities. Analysis and interpretation of large physical and geochemistry data sets provides important information on processes occurring at the seafloor in this poorly known area. These processes help us to understand how the seafloor functions to support biodiversity in the region. Abstract Baseline information on habitats is required to manage Australia's northern tropical marine estate. This study aims to develop an improved understanding of seafloor environments of the Timor Sea. Clustering methods were applied to a large data set comprising physical and geochemical variables that describe organic matter (OM) reactivity, quantity and source, and geochemical processes. Arthropoda (infauna) were used to assess different groupings. Clusters based on physical and geochemical data discriminated arthropods better than geomorphic features. Major variations among clusters included grain size and a cross-shelf transition from authigenic-Mn–As enrichments (inner shelf) to authigenic-P enrichment (outer shelf). Groups comprising raised features had the highest reactive OM concentrations (e.g. low chlorin indices and C:N ratios, and high reaction rate coefficients) and benthic algal δ13C signatures. Surface area-normalised OM concentrations higher than continental shelf norms were observed in association with: (i) low δ15N, inferring Trichodesmium input; and (ii) pockmarks, which impart bottom–up controls on seabed chemistry and cause inconsistencies between bulk and pigment OM pools. Low Shannon–Wiener diversity occurred in association with low redox and porewater pH and published evidence for high energy. Highest β-diversity was observed at euphotic depths. Geochemical data and clustering methods used here provide insight into ecosystem processes that likely influence biodiversity patterns in the region.

scholarly journals Big Choanae, Larger Face: Scaling Patterns Between Cranial Airways in Modern Humans and African Apes and Their Significance in Middle and Late Pleistocene Hominin Facial Evolution

2019 ◽  
Vol 31 (1-2) ◽  
pp. 5-13 ◽  
Author(s):  
M. Bastir
Keyword(s):  
Energy Demand ◽  
Regression Models ◽  
High Energy ◽  
Middle Pleistocene ◽  
Facial Skeleton ◽  
Large Airways ◽  
Middle And Late Pleistocene ◽  
Shed Light ◽  
3D Landmarks ◽  
Large Face

This study aimed to understand the ontogenetic and allometric relationships in scaling between the anterior and posterior openings of the cranial airways and facial size, in order to shed light on the mechanisms that might underlie the evolution of a large face and large airways in Middle Pleistocene hominins and Neandertals. Sizes were calculated from 3D landmarks measured on the facial skeleton and airway structures of 403 skulls from two ontogenetic series of H. sapiens and P. troglodytes, an adult sample of gorillas and 11 Middle Pleistocene hominins and Neandertals. RMA regression models were used to compare the patterns in scaling between the anterior and posterior airways in relation to overall facial size. Our results show that the size of the anterior airways correlates more positively with facial size than the size of the posterior airways. This ontogenetic mechanism could explain the large faces and noses in the Neandertal lineage despite the adverse effects of such a phenotype for respiratory air-conditioning in cold climates. A large facial size could be a developmentally constrained consequence of generating airways large enough to provide the necessary oxygen for high energy demand in this large-brained and heavy-bodied hominin lineage.

scholarly journals ENVIRONMENTAL GEOCHEMICAL AND MINERALOGICAL STUDY OF THE PELLANA LIGNITE (PREFECTURE OF LAKONIA)

2004 ◽  
Vol 36 (1) ◽  
pp. 300
Author(s):  
Α. Χατζηαποστόλου ◽  
Σ. Καλαϊτζίδης ◽  
Σ. Παπαζησίμου ◽  
Κ. Χρηστάνης ◽  
Δ. Βάγιας
Keyword(s):  
Power Generation ◽  
Trace Elements ◽  
Major Elements ◽  
Geochemical Data ◽  
Element Mobility ◽  
Minor Elements ◽  
Mineral Phases ◽  
Wide Range ◽  
Mineralogical Study ◽  
Type Factor

The aim of this study is to estimate the environmental impacts in case of exploitation the Pellanalignites for power generation. The object of the study is to predict the element mobility during lignite combustion using mineralogical and geochemical data from bulk-lignite samples and their ashes of two cores from this area. The mineralogical determinations on the ashes revealed that quartz, K-feldspars and illitemicas are the major mineral phases contained in the lignite. The identification of anhydrite in ashes implies the presence of gypsum, althought neoformation of anhydrite from organic associated with Ca+2 and SO42 can not be excluded. These minerals correspond to primary phases. Oxides and hydroxides occur subordinately and probably represent minerals that do not correspond to primary phases. The results of the elemental analysis show that the major elements (>1000 ppm) are AI, Fe, Ca, Mg and Κ in the bulk samples of both cores. Minor elements (100-1000 ppm) are Na, Mn and Ba, while the concentrations of Be, Bi, Cd, Ce, Co, Cs, Cu, Eu, Ga, Hf, La, Li, Lu, Mo, Nb, Nd, Pb, Rb, Sb, Se, Sm, Sn, Sr, Tb, Te, Th, TI, U, Y, Yb and Zr do not exceed 100 ppm. The concentrations of many elements like As, Ba, Cr, Ni, V and Zn have a wide range among the bulk samples. In order to assess the geochemical affiliation of the studied elements, R-type factor analysis was applied on the element contents of bulk lignite and ash. The elements Ca, S, V, As, Μη, Mo, Na, Sb, Hf, Zr and U provide both organic and inorganic affiliations, while Se and Nb provide organic affiliations. To approach the mobility of each trace element, the relative enrichment factor (RE) was calculated. The most depleted trace elements according to RE mean (<0.5) are Hf and Sb, while the elements Se and Ba are moderately depleted (0.7>RE mean>0.5).

scholarly journals Paleoenvironmental Interpretation of Last Millennium Sediments in the Marriaga Swamp, Atrato Delta, Colombia

2021 ◽  
Vol 31 (1) ◽  
pp. 9-24
Author(s):  
Liliana Betancurth Montes ◽  
Julio Eduardo Cañón Barriga
Keyword(s):  
Heavy Metal ◽  
Organic Carbon Content ◽  
Last Millennium ◽  
Paleoenvironmental Reconstruction ◽  
Biological Productivity ◽  
Dry Period ◽  
Statistical Correlations ◽  
Paleoenvironmental Interpretation ◽  
Geochemical Analyses ◽  
Flooding Events

This paper presents the first paleoenvironmental reconstruction of the last 1,130 a of the Marriaga Swamp in the Atrato River delta in northwestern Colombia. The geochemical analyses of a 220 cm sediment core retrieved from the swamp reveal interesting climatic episodes and sedimentary changes in the last millennium. We split the core into three segments, according to sediment features, organic carbon content (OC), and geological ages. Records show different alternations of humid and dry periods, biological productivity, carbonate precipitation, weathering grade, and high heavy metal concentrations. The segments also concur with the geochemical differences determined by (Zr+Rb)/Sr, Ca/Ti Mn/Fe, OC/Ti, Mg/Ca Ba/Al, Sr/Al, and Ca/Al ratios. The older sequence (between 1,130 ± 90 a and 870 ± 70 a) shows a dry period with intermittent flooding events and high OC production in subareal conditions, followed by a more humid environment between 870 ± 70 a and 530 ± 40 a, with depletion of trace element ratios and OC. The more recent period (530 ± 40 a to present) evinces an environment dominated by the fluvial regime, based on a lower Ca/Al ratio and a rise of OC. The statistical correlations display three main clusters that distinguish among organic-biological productivity, bedrock source components, and heavy metal inputs.

scholarly journals Extreme and high synchrotron peak blazars beyond 4FGL: The 2BIGB γ-ray catalogue

2020 ◽  
Vol 493 (2) ◽  
pp. 2438-2451
Author(s):  
B Arsioli ◽  
Y-L Chang ◽  
B Musiimenta
Keyword(s):  
Gamma Ray ◽  
Spectral Energy Distribution ◽  
Broad Band ◽  
High Energy ◽  
Spectral Energy ◽  
Large Area ◽  
Data Repositories ◽  
Total Contribution ◽  
Public Data ◽  
Γ Ray

ABSTRACT This paper presents the results of a γ-ray likelihood analysis over all the extreme and high synchrotron peak blazars (EHSP and HSP) from the 3HSP catalogue. We investigate 2013 multifrequency positions under the eyes of Fermi Large Area Telescope, considering 11 yr of observations in the energy range between 500 MeV and 500 GeV, which results in 1160 γ-ray signatures detected down to the TS=9 threshold. The detections include 235 additional sources concerning the Fermi Large Area Telescope Fourth Source Catalog (4FGL), all confirmed via high-energy TS (Test Statistic) maps, and represent an improvement of ∼25 per cent for the number of EHSP and HSP currently described in γ-rays. We build the γ-ray spectral energy distribution (SED) for all the 1160 2BIGB sources, plot the corresponding γ-ray logN−logS, and measure their total contribution to the extragalactic gamma-ray background, which reaches up to ∼33 per cent at 100 GeV. Also, we show that the γ-ray detectability improves according to the synchrotron peak flux as represented by the figure of merit parameter, and note that the search for TeV peaked blazars may benefit from considering HSP and EHSP as a whole, instead of EHSPs only. The 2BIGB acronym stands for ‘Second Brazil-ICRANet Gamma-ray Blazars’ catalogue, and all the broad-band models and SED data points will be available on public data repositories (OpenUniverse, GitHub, and Brazilian Science Data Center-BSDC).

Oxygen and carbon stable isotopes of Mytilus galloprovincialis Lamarck, 1819 shells as environmental and provenance proxies

The Holocene ◽  
2019 ◽  
Vol 30 (1) ◽  
pp. 65-76 ◽  
Author(s):  
Stefania Milano ◽  
Bernd R Schöne ◽  
Igor Gutiérrez-Zugasti
Keyword(s):  
Stable Isotopes ◽  
Mytilus Galloprovincialis ◽  
Shell Growth ◽  
Geochemical Data ◽  
Carbon Stable Isotopes ◽  
Northern Spain ◽  
Mollusc Shell ◽  
Geochemical Composition ◽  
Mussel Shells ◽  
Geochemical Analyses

Mollusc shell stable isotopes are commonly used to reconstruct past environmental conditions. However, despite being abundant components of natural and anthropogenic fossil accumulations, the geochemical composition of mussel shells ( Mytilus spp.) has rarely received attention in palaeoenvironmental studies. This study tests the suitability of oxygen isotopes (δ18Os) of Mytilus galloprovincialis as palaeothermometer. For 1 year, mussels and water samples were collected twice a month from Berria Beach, in Northern Spain. The geochemical data of the shells indicate that water temperatures can be reconstructed with an average offset of 1.2 ± 0.7°C with respect to the measured values. Furthermore, no prolonged shell growth cessations are observed. These results validate M. galloprovincialis as reliable recorders of seasonal water temperature fluctuations, supporting their use in palaeoenvironmental studies. In addition, further shell and water collections were carried out in the upper and lower areas of a nearby estuary. The geochemical analyses of these shells were aimed to test whether oxygen and carbon stable isotopes (δ13Cs) may be used as novel proxies to identify the shell provenance at local scale. The results show that the δ18Os versus δ13Cs correlation direction varies along the coast–upper estuary geographical gradient, suggesting it to be a potential new proxy to distinguish between marine and estuarine mussel specimens.

scholarly journals A Geochemical Overview of Mid-Archaean Metavolcanic Rocks from Southwest Greenland

Geosciences ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 266 ◽  
Author(s):  
Kristoffer Szilas
Keyword(s):  
Magma Mixing ◽  
Geochemical Data ◽  
Calc Alkaline ◽  
Present Contribution ◽  
Data Set ◽  
Basaltic Rocks ◽  
The North ◽  
Metavolcanic Rocks ◽  
Geochemical Analyses ◽  
Southwest Greenland

The present contribution reviews bulk-rock geochemical data for mid-Archaean (ca. 3075–2840 Ma) metavolcanic rocks from the North Atlantic Craton of southwest Greenland. The data set includes the most recent high quality major and trace element geochemical analyses for ten different supracrustal/greenstone belts in the region. When distilling the data set to only include the least altered metavolcanic rocks, by filtering out obviously altered samples, mafic/ultramafic cumulate rocks, late-stage intrusive sheets (dolerites) and migmatites, the remaining data (N = 427) reveal two fundamentally distinct geochemical suites. The contrasting trends that emerge from the filtered geochemical data set, which best represents the melt compositions for these mid-Archaean metavolcanic rocks are: (1) tholeiitic (mainly basaltic) versus (2) calc-alkaline (mainly andesitic). These two rock suites are effectively separated by their La/Sm ratios (below or above three, respectively). It is demonstrated by geochemical modelling that the two contrasting suites cannot be related by either fractional crystallization or crustal assimilation processes, despite occurring within the same metavolcanic sequences. The tholeiitic basaltic rocks were directly mantle-derived, whereas the petrogenesis of the calc-alkaline andesitic rocks involve a significant (>50%) felsic component. The felsic contribution in the calc-alkaline suite could either represent slab-melt metasomatism of their mantle source, mafic-felsic magma mixing, or very large degrees of partial melting of mafic lower crust. At face value, the occurrence of andesites, and the negative Nb-Ta-Ti-anomalies of both suites, is consistent with a subduction zone setting for the origin of these metavolcanic rocks. However, the latter geochemical feature is inherent to processes involving crustal partial melts, and therefore independent lines of evidence are needed to substantiate the hypothesis that plate tectonic processes were already operating by the mid-Archaean.

Late Quaternary climate variability as recorded by micropalaeontological diatom data and geochemical data in the western Ross Sea, Antarctica

2013 ◽  
Vol 25 (6) ◽  
pp. 804-820 ◽  
Author(s):  
R. Tolotti ◽  
C. Salvi ◽  
G. Salvi ◽  
M.C. Bonci
Keyword(s):  
Continental Slope ◽  
Ross Sea ◽  
Late Quaternary ◽  
Ice Sheet ◽  
Geochemical Data ◽  
Flow Paths ◽  
Ice Flow ◽  
Quaternary Climate ◽  
History Of ◽  
Geochemical Analyses

AbstractCores acquired from the Ross Sea continental shelf and continental slope during the XXX Italian Programma Nazionale di Ricerche in Antartide (PNRA) were analysed and yielded interesting micropalaeontological, biostratigraphic diatom results and palaeoceanographic implications. These multi-proxy analyses enabled us to reconstruct the glacial/deglacial history of this sector of the Ross embayment over the last 40 000 years, advancing our understanding of the Last Glacial Maximum (LGM) environmental and sedimentological processes linked to the Ross Sea ice sheet/ice shelf fluctuations in a basin and continental-slope environment, and allowed us to measure some of the palaeoceanographic dynamics. The central sector of the Ross Sea and part of its coast (south of the Drygalski Ice Tongue) enjoyed open marine conditions in the pre-LGM era (27 500–24 000 years bp). The retreat of the ice sheet could have been influenced by a southward shift of a branch of the Ross gyre, which triggered early deglaciation at c. 18 600 cal bp with a significant Modified Circumpolar Deep Water inflow over the continental slope at c. 14 380 cal BP. We assume that a lack of depositional material in each core, although at different times, represents a hiatus. Other than problems in core collection, this could be due to the onset of modern oceanographic conditions, with strong gravity currents and strong High Salinity Shelf Water exportation. Moreover, we presume that improvements in biostratigraphy, study of reworked diatom taxa, and lithological and geochemical analyses will provide important constraints for the reconstruction of the LGM grounding line, ice-flow lines and ice-flow paths and an interesting tool for reconstructing palaeo-sub-bottom currents in this sector of the Ross embayment.

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