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Provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico unraveled by geochemical analysis
Abstract
The aim of this work is to constrain the provenance and depositional history of continental slope sediments in the Southwestern Gulf of Mexico (~1089–1785 m water depth). To achieve this, 10 piston sediment cores (~5–5.5 m long) were studied for mineralogy, major, trace and rare earth element geochemistry. Samples were analyzed at three core sections, i.e. upper (0–1 cm), middle (30–31 cm) and lower (~300–391 cm). The textural study reveals that the core sediments are characterized by silt and clay fractions. Radiocarbon dating of sediments for the cores at different levels indicated a maximum of ~28,000 year BP.
... The ICV (Compositional Variability Index) and SiO2/Al2O3 indices are commonly used to recognize sediment chemical and textural maturity, as well as sediment recycling (Cullers, 2000;Armstrong-Altrin et al., 2015). These indices show high dispersion in their values (Fig. 15B, Table 3), which suggests a great variation in the deposit's chemical and textural maturity. ...
... But these values may also be partly due to disturbance generated by the post-depositional clay injection, as observed in petrography (Fig. 3). The predominance of values greater than 10 in the SiO2/Al2O3 ratio (Table 3) reveals the sediments high textural maturity (Armstrong-Altrin et al., 2015), which suggests a possible contribution from recycled sources (Wang and Zhou, 2013;Armstrong-Altrin et al., 2015), as observed in the grouping of SiO2, Na2O, Pb and Zr by the PCA vectors (Fig. 14). ...
... Utilizing geochemical data from sediments to understand the sedimentary processes is important due to the sensitiveness of some trace elements in identifying minor components that are not easily recognised through petrographic studies (Garrels and Mackenzie 1971;Garver et al. 1996;Gallala et al. 2009). The geochemistry of the soil sediments is a vital tool to know the maturity of the sediments (Suttner and Dutta 1986), pedogenesis (Újvári et al. 2008), compositional variation and sediment recycling (McLennan et al. 1993), origins and tectonic settings of the sediments (Armstrong-Altrin et al. 2015a;Armstrong-Altrin et al. 2015b;Verma and Armstrong-Altrin 2013;Verma and Armstrong-Altrin 2016;Maynard et al. 1982;Bhatia 1983;Bhatia and Crook 1986;Roser and Korsch 1986) and paleooxygenation condition (Hallberg 1976). ...
... Several classification schemes have been devised to discriminate the tectonic settings of sedimentary rocks Armstrong-Atrin 2013, 2016;Armstrong-Altrin et al. 2015a;Armstrong-Altrin et al. 2015b;Maynard et al. 1982;Bhatia and Crook 1986;Roser and Korsch 1986). Verma and Armstrong-Altrin (2013) proposed high and low-silica discrimination diagrams to differentiate rift, arc and collision scenarios using major elemental concentrations. ...
The objective of the work is to understand the provenance and tectonic setting of the Karewa deposits of South Kashmir, NW Himalayas using major, trace and rare earth elements. Major elemental analysis shows that sediments are rich in SiO2 followed by Al2O3, Fe2O3, CaO, MgO, K2O, Na2O, P2O5, TiO2 and MnO. The geochemical classification diagram of Heron and Pettijohn suggested that the sediments were classified as lith-arenites, trending toward wackes, which suggested the immaturity of the sediments. The SiO2/Al2O3 ratio of 3.99 to 4.9 and Al2O3/TiO2 ratio of 12.2 to 18.7 reflected that the Karewa sediments were derived largely from intermediate and felsic sources. On V-Ni-(Th*10) ternary plot, the samples fall near the felsic source with an extension towards the mafic source rock field. Moreover, the fractionated chondrite normalized rare earth element patterns with enriched light rare earth elements (LREE) and nearly flat heavy rare earth elements (HREE) and negative europium anomalies (0.59 to 0.74) suggested that these rocks were derived from felsic to intermediate rocks of the upper continental crust with some contamination by a mafic component. The Th/Sc and Zr/Sc plot of the sediments suggest both compositional variation and new addition of Zr in the sedimentary system. Using high and low silica multidimensional discrimination diagrams and single axis discrimination plot, the source rocks of Karewa deposits show affinity towards passive margin and collision—arc tectonic settings. The ratios of Cu/Zn, U/Th and Ni/Co indicate that the Karewa sediments were deposited in oxidizing environmental conditions.
... The low Ni/Co versus V/(V+Ni) [78] and Ni/Co versus V/Cr ratios [54] of the studied stromatolites indicate that they were deposited in the oxic-dysoxic zone of the lake (Figures 8 and 9). Trace element concentrations of carbonate deposits are used frequently to investigate the redox conditions [79,80]. U/Th ratio is lower than 1.25, it explains the oxic depositional environment [81]. ...
... wt.%) with less amount of SiO 2 (0.22-7.88 wt.%) and CaO (0.96-1.85 wt.%). The correlation between MgO and other oxides (SiO 2 , Al 2 O 3 , K 2 O, TiO 2 , Fe 2 O 3 ) has strong negative correlation (r = − 0. [78][79][80][81][82][83][84][85][86][87][88], which clearly shows that Salda Lake fed lesser from different modes of origin and clastic input, except for serpentinite rocks. When trace element contents were examined according to PAAS, it was observed that it was enriched only in Ni, Co and As. ...
Stromatolites are the oldest recognized fossil recordings of life on Earth. Therefore, their study of them represents one of the most interesting topic that investigates the physio-chemical environmental conditions (formations and precipitations) at which the stromatolites formed. This work deals with the rare earth elements (REEs) geochemical characteristics and the redox-sensitive trace elements behavior of the stromatolites newly formed in Salda Lake, a closed system alkaline lake surrounded by serpentinite rocks in SW Turkey. The representative stromatolite samples collected from Salda Lake show higher contents of MgO (up to 41.5 wt.%), CO2+OH (up to 56.6 wt.%), and MgO/CaO ratio (up to 42.2 wt.%) referring to the stromatolites had been controlled by microorganisms and deposited in subtidal areas having hydro-magnesite and aragonite mineralogy. The average trace element contents of the stromatolites are 8.4 ppm V, 0.09 ppm Cr, 3.50 ppm Co, 95.6 ppm Ni, 0.73 ppm Cu, 1.55 ppm Rb, 37.6 ppm Sr, 0.59 ppm Y, 17.7 ppm Zr, 3.60 ppm Nb, 21 ppm Ba, 0.05 ppm Hf, 3.5 ppm As, 0.02 ppm Cd, 0.05 ppm U, 0.05 ppm Th, 2.85 ppm Pb, and 6.60 ppm Zn. The Post-Archean Australian Shale (PAAS)-normalized REE patterns of the stromatolites reveal that the heavy REEs (HREEs) are enriched relative to the light REEs (LREEs) with highly negative Y and Ce-anomalies and positive Eu-anomalies. This refers to the stromatolites formed in predominantly oxidizing environmental conditions at partially warm lake waters. In addition, the hydromagnesite composition of the Salda Lake stromatolites indicates that they were precipitated from the waters influenced by Mg-rich meteoric waters fed from the serpentinite rocks around the Lake.
... Major-and trace-element compositions of surficial sediments and their natural levels in relation to the source rocks have also been investigated in several other semi-enclosed basins or large bays worldwide, including the Black Sea (Kiratli and Ergin, 1996), the Baltic Sea (Shahabi-Ghahfarokhi et al., 2021), the Baffin Bay (Loring, 1984), the Gulf of Mexico (Armstrong-Altrin et al., 2015), the Kara Sea (Loring et al., 1998), the Bengal Bay (Tripathy et al., 2014;Li et al., 2017;Sun et al., 2019), and the Japan Sea (Ohta et al., 2004;Cha et al., 2007). ...
... Trace metals hosted preferentially in mafic and ultramafic rocks, such as Ni and Cr (Hiscott, 1984;Garver et al., 1996;Armstrong-Altrin et al., 2015) are known to carry clear provenance signals even in distal segments of the sediment routing system (von Eynatten et al., 2003;Garzanti, 2016). The spatial distribution of Ni and Cr across the Po-Adriatic region is overwhelmingly controlled by the source-rock lithology of river catchments combined with sediment loads at fluvial mouths ( Fig. 14a, b). ...
The Po-Adriatic region offers an excellent case for reconstructing sediment provenance and transport pathways of a multi-sourced sediment-routing system. Through a comprehensive set of ∼1400 geochemical data, a model for provenance and sediment flux was built based on distinct compositional fingerprints of 53 fluvial systems and their comparison to coastal, shelf and deep-marine sediments. Geochemically unique catchment lithologies (mafic/ultramafic rocks, limestones and dolostones) were used as end-members to assess exclusive source-rock signatures. Following calibration with sedimentary facies, selected key elements and element ratios poorly sensitive to particle size (Ni/Cr, MgO, Ni/Al2O3, Cr/V, Ca/Al2O3 and Ce/V) were adopted as provenance indicators. The high-Ni and high-Cr source-rock signature of mafic/ultramafic rocks widely exposed in the Po River watershed and along the Albanian Dinarides contrasts markedly with the high-Ca (and locally high-Mg) geochemical composition of Eastern Alpine, Apennine, and Eastern Adriatic (Montenegro, Croatia, Slovenia) river catchments, which are, instead, carbonate-rich and virtually ophiolite-free. Relatively high Ce values from Apulian river samples serve as a key marker for a minor, but very distinct sediment provenance from southern Apennine alkaline volcanic rocks.
Despite along-shore mixing and dilution with sediment sourced from other river catchments, the geochemical signature of Adriatic shelf muds primarily reflects composition of sediment eroded from the contiguous continental areas. Chromium-rich and nickel-rich detritus generated in mafic and ultramafic complexes of the Western Alps and conveyed through the Po River into the Adriatic Sea records a geochemical signal that can be traced downstream as long as 1000 km, from the Alpine zone of sediment production to the area of final deposition, offshore Apulia.
While longitudinal dispersion linked to the general cyclonic, counter-clockwise Adriatic circulation is prevailing along the Western Adriatic Sea, conspicuous detrital input from transversal pathways to the deep sea is revealed across the Eastern Adriatic shelf using heavy metals as provenance tracers. Estimates of fluvial sediment loads and compositional fingerprinting of fluvial, coastal and shelf sediments indicate that previously neglected ophiolite-rich successions of Albania represent a major sediment-conveyor to the offshore sinks (Southern Adriatic Deep and Mid-Adriatic Deep) through significant cross-shore and NNW-directed sediment transport in the Eastern Adriatic Sea. A cut-off value of the Ni/Cr ratio targeted around 0.8 represents an effective tool for the differentiation in marine sediments of Ni-rich (serpentine-rich) ophiolite detritus of Albanian origin from mafic/ultramafic sources of Alpine affinity. High trace-metal contents found within the Adriatic deep basin are mostly of natural origin and only minimally reflect metal contamination.
... UCC patterns indicate the higher mobility of these depleted elements and their general abundance in river and marine sediments (Chester and Jickells, 2012;Armstrong-Altrin et al., 2015). ...
... The increasing sequences of CaO (2.17 < 2.78 < 3.16 > 2.48 wt. %) and Sr (65 < 158 < 207 > 194 mg kg −1 ) indicate that secondary marine effects and their highest relation to cluster 3 samples (Armstrong-Altrin et al., 2015;Yalcin et al., 2021). Fluorine, Br, and I also show increasing sequences similar to CaO and Sr in the SECS clusters. ...
Southeastern landmass of Sri Lanka is laid on the Vijayan Complex (VC) rocks, a Precambrian basement characterized with specific geological features since the mineralized contact zone of the Highland–Vijayan boundary is nearby. However, the coastal sedimentation of such a basement is rarely interpreted. Hence, the mineralogy and geochemistry of surface sediments exposed along 45 km long southeast (SE) coast were studied to find the compositions and to interpret the terrestrial compart. Studied beach faces expose as sandy siliciclastic sediments with scatter depositions of black and red colored heavy sediments, as 10–15 cm beds, within 1–3 km from deltaic environments. X-ray diffraction analysis of such heavy placers indicate the presence of predominant ilmenite, almandine garnet, zircon, monazite and ferrihydride. The sediments from other areas are rich in lighter minerals of quartz, albite and magnesium-calcite representing the average beach sediment mineralogy of SE coast. Upper continental crust normalized X-ray fluorescence data show an enriched tendency of Zr (9.8) > V > Nb > Th > TiO2 (6.2) > Cr (2.5) > MnO > Fe2O3 > As > Y > Zn and depleted tendency of Pb (0.8) > CaO > P2O5 > Sr > Sc > Cu (0.1) indicating the leachability of depleted elements and strong recycling processes of High Field Strength Elements (HFSE). Hierarchical cluster analysis and Pearson correlation matrices indicate the presence of four geochemically related sample clusters. These analyses further showed that the cluster 1 relates to heavy sediments deposits with higher terrigenous influences while cluster 4 relates to siliciclastic sediments with higher marine influences. Hence, geochemical anomalies of cluster 1 to 4 show decreasing abundances for HFSE and opposite tendencies for CaO, Sr, I, Br, and F confirming the mineralogical results. Higher terrigenous influenced sediment samples evident for the presence of solid phases of titanium carriers (As-V-TiO 2), phosphorus-HFSE carriers (Pb-Th-P2O5-Y-Cl-Nb-Zr), authigenic carbonates (Sr-Br-CaO) and Fe-Mn coatings (Zn-Cr-MnO-Fe2O3-Cu). Compatibility variable ratios of Th/Sc, Zr/Sc, TiO2/Zr, Cr/Th and V/Th respectively show 15.16, 364.38, 20.85, 2.95 and 9.73 values for the coast. Based on the international and VC published average lithological data, present study concluded the primary sources for the sedimentation have felsic signatures showing relations to granitic gneisses and granitic intrusive rocks of VC. Apart from the terrestrial provenances, the coastal area is affected by lower secondary influences of anthropogenic, marine inorganic and organic matters.
... This diagram allows to evaluate the mineral stability (e.g. Descourvieres et al., 2011;Nagarajan et al., 2014;Armstrong-Altrin et al., 2015;Hu et al., 2015;Sahoo et al., 2016). Using the geochemical classification diagram of Herron (1988), most Miocene sediment samples lie in the shale category (Fig. 11). ...
Geochemical studies of major and trace elements were conducted on Miocene sediments from three sections of the Lower Chelif Basin, Northern Algeria. Geochemical proxy records demonstrate that the Lower Chelif Basin has experienced weak to moderate weathering and the Index of Compositional Variability (ICV) values suggest that these sediments were, in general, enriched in rocks forming minerals. Al2O3 versus (vs.) K2O diagrams indicate that, in Miocene sediments, the minerals containing Al2O3 and K2O are primarily illite; likely derived from K-feldspar decomposition. The application of the Al2O3 vs TiO2 binary plot, as a provenance indicator, indicates that all the samples fall along the basalt + rhyolite/granite line indicating that the sediments derived from mixed source sediments the composition of which ranges from mafic and felsic rocks. Compared to Upper Continental Crust (UCC) composition, Miocene sediments depict strong depletion in SiO2, Al2O3, MnO, Na2O, K2O, Zr and Sr during the weathering process as well as an enrichment in Cr and Cu. Calculated percentage variation plotted against the Chemical Index of Alteration (CIA) diagrams provides a basis for assessing the chemical mobility during weathering in the Chelif Basin. For the study stratigraphical range, Si, Al, Mn, Na and K show depletion in relation to Ti. Sodium decreases more rapidly than K, suggesting a Na-plagioclase alteration higher than that of K-feldspar. During the Tortonian, the chemical motilities of Rb and K are tightly correlated (r = 0.72), but the former decreases lesser. Calculated values of C-proxy suggest a roughly semi-arid to semi-moist climate during the Burdigalian-Langhian, arid to semi-arid during the Tortonian and more humid conditions during the Messinian. Sr/Ba ratio ranging from 0.44 to 6.48 indicates a palaeoenvironment with variable salinity during the Miocene.
... The Sr-Ba ratio is a geochemical indicator of paleosalinity in sediments and has been used to indicate the changes and evolution environments of transgression in the Beibu Gulf [22,32,33]. Previous studies in deltaic environments have found that Sr/Ba is <1 in freshwater (rivers), <1-3 in brackish water (delta front), <3-8 in saline water (prodelta), and >8 in normal seawater (shallow sea environment and residual sand) [34,35]. ...
The geochemical characteristics of a 2.1 m BBW25 core, collected from the Beibu Gulf, have been investigated in terms of the major and trace elements, organic matter, and CaCO3 and AMS 14C dating by XRF, ICP-OES, ICP-MS, and more. We have found through previous research that there are issues with unclear delineation of sedimentary evolution environments and inexact responses between chemical weathering intensity and major paleoclimate events in the Beibu Gulf. The AMS 14C dating results indicate that the sedimentary age at the bottom was 19.24 ky b.p. CaCO3, δ13C, C/N, and Sr/Ba indexes show a sedimentary environment change from terrestrial to marine environments and a “jump” of ~4000 years in continent–ocean changes. The evolution of the sedimentary environment of Beibu Gulf was divided into three environments and five sub-environments. The changes in chemical weathering intensity indicators recorded by the CIX and the Fe/Al ratio respond well to the East Asian monsoon cycle, the meltwater events, and the alternation of cold and warm events. This study explains the chemical weathering intensity and sedimentary environment in the BBW25 core by geochemical characteristics and further reveals the paleoenvironmental characteristics and possible driving mechanisms over the past ~20,000 years.
... Trace element ratios, such as V/Cr, U/Th, and the authigenic U index (AU = XU-(YTh)/3; Table 4), serve as valuable tools for discussing the paleoenvironment prevailing during deposition. Specifically, U/Th ratios greater than 1.25 and V/Cr ratios exceeding 4.5 are indicative of an anoxic environment, while U/Th ratios below 0.75 and V/Cr ratios less than 2 suggest oxic conditions [34,35]. The deposition of the Sanaga valley alluvial clay deposits is established to have occurred under oxic conditions, with an average U/Th ratio of 0.24 and V/Cr ratio of 1.17 (Table 3). ...
This research investigates the physico-chemical, mineralogical and geochemical attributes of alluvial clayey sediments in the Nkoteng-Mbandjock regions of the Sanaga valley, Cameroon. The primary objective is to elucidate the source area-weathering and provenance of these sediments. Grain size distribution analyses were conducted using the Robinson-Kӧln's pipetting method. The physico-chemical parameters were evaluated by an HACH-HQ11d brand electric pH meter, while the mineralogical compositions were determined by X-ray Diffraction. Major and trace element concentrations were measured employing X-ray Fluorescence and Inductively Coupled Plasmas-Mass Spectrometry. Textural classification identified the Sanaga valley alluvial clay deposits as predominantly silty clayey and clayey muddy. Geochemical classification diagram positioned them in the shale and Fe-shale fields. Weathering indices of alteration exhibited a consistent trend indicating a high degree of weathering in the source rock. A low Na2O/K2O ratio (average 0.18) and a high Index of Compositional Variability (ICV; average 2.29) suggested immature sediments. Additionally, low SiO2/Al2O3 ratio (average 3.93) implied an origin from stable settings with recycled inputs. These characteristics were further supported by elemental ratios such as Zr/Sc (average 47.12), U/Th (average 0.24) and Th/Sc (average 1.48). Furthermore, indicators like V/Cr (average 1.17), U/Th (average 0.24) and authigenic U (average −1.67) values suggested the deposition of the Sanaga valley alluvial clay under oxic conditions. The collective analysis of major and trace element distribution revealed felsic sources with minimal contributions from mafic rocks. These findings contribute to a comprehensive understanding of the geological processes and conditions influencing the composition and characteristics of the studied alluvial clay deposits in the Sanaga valley.
... conditions. These elements are often enriched in sediments deposited in an anoxic environment, while they are deficient in sediments deposited in oxic conditions because of their high solubility [51][52][53][54]. Vanadium (V), which is frequently enriched in reducing sediments, is employed in the current study as a redox-sensitive element [41,52,55]. ...
Reconstruction of the depositional environment of the Paleocene-Eocene Sinjar Formation from two outcrop sections in northwestern and northeastern Iraq has been evaluated using the traditional petrographic and facies analysis supported by X-ray diffraction and scanning electron microscopy with a focus on the Paleocene-Eocene (P-E) transition boundary. To this end, major and trace elemental geochemistry was conducted and various paleoenvironmental proxies for the paleoredox, paleoclimate, paleosalinity and paleoproductivity were determined in order to evaluate the changes in widely acknowledged environmental and climatic indicators and the elemental enrichment/depletion across the P-E boundary. The redox-sensitive trace element enrichment and the ir ratios (V/V + Ni, V/Cr, and U/Th) indicate that normal oxygenated circumstances prevailed during the late Paleocene deposition, and that anoxic conditions and a gradual commencement of oxygen depletion occurred during the early Eocene deposition. The coeval increase in the P 2 O 5 content, P/Ti, and P/Al ratios in the Eocene sediments suggests an increase in nutrients and primary productivity due to the effect of upwelling currents during early Eocene. The conditions can be verified by observing a small change in salinity levels from low to high across the P-E boundary, which can be indicated by the Sr/Ba ratios. In addition, certain minerals such as Mg-calcite, dolomite, and palygorskite are commonly present, and paleoclimatic changes can be observed across the P-E transition from arid to semiarid and then to humid conditions, which can be recorded from C-values, Sr-Cu, Rb/Sr ratios, and clay mineralogy. These conditions were noted in the Sinjar Formation, which is made up of many microfacies such as lime mudstone, wackstone, packstone, grainstone and boundstone. These microfacies were deposited in a shallow marine environment that extended from tidal flats to reef slopes, with a developed reef environment that included back reef, reef core, and fore reef environments.
... Subba Rao (1960) observed that the silty clay materials of the Pennar, Krishna and Godavari rivers, are poor in organic matter. In the Suddagedda river estuary, sandy sediments have been found to be poor in organic matter content, while fine-grained materials are rich in organic matter (Venkata Rao and Subba Rao, 1974;Armstrong-Altrin et al., 2015). These authors further documented that the sandy types are poor in organic matter, while materials containing higher amount of clay are rich in organic matter. ...
To know the distribution of brackish water Ostracoda and to investigate the sediment characteristics, a core (105 cm) has been collected from the Gadilam river estuary and it was sub-sampled into 21 samples at 5 cm width regular interval. All the sediment samples were analyzed as per standard micropaleontological techniques in order to investigate the distribution and occurrence of ostracod fauna. A total of 27 ostracod taxa belonging to 16 genera, 12 families, 3 superfamilies and 2 sub-order of the order Podocopida, have been identified based on published articles Throughout the core (from top to bottom) the calcareous forms were noticed. The ostracod species Kalingella mckenziei and Jankeijcythere mckenziei are widely distributed in the core and they outnumbered the rest of the species. The faunal assemblages recorded are tropical, brackish to neritic (shallow marine) and benthic in nature (Hemicytheridea paiki, Hemicytheridea bhatiai, Jankeijcythere mckenziei, Kalingella mckenziei, Neosinocythere dekrooni, Paijenborchellina sp., Stigmatocythere indica and Tanella gracilis). In the analyzed core, there is no faunal assemblage at the depth between 80-85 and 95-105 cm. The sediment characteristics such as calcium carbonate, organic matter and sand-silt-clay ratio also determined and correlated with the observed ostracod populations. Based on the detailed study, it is noticed that high calcium carbonate and low organic matter of the sediment are congenial for population abundance. From the overall distribution of Ostracoda in all the subsamples, siltysand is found to an accommodative substrate for the prosperity of Ostracoda. The statistical aspect of ostracod carapace-valve ratio has been studied to identify the rate of sedimentation which infers a faster rate of deposition of sediments in the Gadilam River estuary.
... Therefore, geochemical sediment analysis and the application of multivariate statistical techniques to the collected data have been developed and refined to assess the potential risks associated with toxic metals in aquatic environments (Tepe and Aydin, 2017). Researchers commonly employ pollution indexes such as the contamination factor (CF), enrichment factor (EF), pollution load index (PLI), and potential ecological risk index (ERI) to assess the extent of pollution in sediment samples (Li et al., 2015;Armstrong-Altrin and Machain-Castillo, 2016;Tokatli, 2019;Ustaoğlu and Islam, 2020;Armstrong-Altrin et al., 2015Chougong et al., 2021). ...
... Numerous additional research endeavors have been undertaken to advance our understanding of various aspects, such as weathering processes and paleogeography, carried out by scholars like Absar et al. [12], Zimmermann and Spalletti [13], Akkoca and Karatas [14], Tobia and Mustafa [15]. Further contributions have been made in exploring the paleoenvironmental conditions and provenance history of these rocks by Armstrong-Altrin et al. [16], Jafarzadeh and Hosseini-Barzi [17], Dostal and Keppie [18], as well as Armstrong-Altrin [19] and Armstrong-Altrin et al. [20]. The primary focus of many of these studies has been directed towards the middle Paleozoic sequence, encompassing sequence stratigraphy as demonstrated by Al-Juboury et al. [21], depositional environments and facies analysis as highlighted by Al-Juboury and Al-Hadidy [22], and palynostratigraphy investigations carried out by Sherwani et al. [23] and Al-Hasson [9]. ...
In this study, 12 outcropped rock samples from the Khabour, Kaista, Ora, and Harur formations (Paleozoic) in the Khabour Valley were studied. The location is innorthern Iraq, in the Imbricated Thrust Zone, northeast of Duhok City. Rock-Eval Pyrolysis was utilized to assess the thermal maturity, organic matter composition, hydrocarbon potential, and organic richness of the Khabour, Kaista, Ora, and Harur formations situated within the Khabour Valley. The content of Total Organic Carbonranges from 0.19 to 0.37 wt.%, with an average of 0.29 wt.% for the Khabour formation, 2.07 to 3.09 wt.% for the Kaista formation, 0.58 wt.% for the Ora formation, and 0.31 to 1.55 wt.% for the Harur formation. The source rock was ratedpoor based on the TOC wt.% content. According to the results, the Khabour Valley formations have low amounts of S2 (average 0.12 mg HC/g Rock, range 0.01-0.29mg HC/g Rock) and Hydrogen Index (HI) (average 15.2 mg HC/g TOC, range 2-41mg HC/g TOC). Drawing insights from the analysis of Rock-Eval data, theformations exhibit kerogen types classified as type IV kerogen. According to thecross plot of S2 versus TOC%, all the samples show a poor potentiality to createhydrocarbons. The graph of HI vs Tmax demonstrates that Tmax ranges from immature to postmature.
... Major, trace and REEs ratios have wide been used to infer the source-rock compositions from which the sediments were derived [8,9,47,48]. Al 2 O 3 and TiO 2 show less fractionation during sedimentary process(es), transportation, weathering profile, and diagenesis [10,49]. Khan et al. [8] and Girty et al. [48] used Al 2 O 3 /TiO 2 ratio to differentiate felsic and mafic source rock compositions of the derived sediments. ...
Geochemical characterization of Shahbazpur structure (Bengal Foredeep) in terms of elemental abundances obtained from INAA are presented by investigating core samples from Shabazpur gas-field, Bangladesh. Major oxides' abundances were 12.4-20.8, 0.63-1.03, 4.45-8.02, 0.05-0.09, 2.60-4.10 and 1.31-1.87% for respectively. Elemental ratios and enrichment pattern (× 1.10-2.11 UCC) indicate that sedimentary processes originated from Himalayan felsic source-rock. Weathering index and Th/U(= 5.90-6.59), V/Cr(= 1.07-1.38) ratios revel that sediments/rocks were experienced moderate to high degree of chemical weathering with oxidizing environment. LaTh -Sc immobile trace elements diagram invoke depositional tectonic settings which was transitional between active and passive continental margin.
... SiO 2 predominantly occurs in detrital quartz particles, and the contents of SiO 2 are thus consistent with the trends of quartz contents. In general, alkali and alkaline-earth metals such as Ca, K, and Na are removed and depleted in the soil profiles, whereas residual Al 2 O 3 is preferentially enriched, which are the result of the weathering of igneous rocks (Armstrong-Altrin et al., 2015). Nevertheless, the trends of Na 2 O, K 2 O, CaO, and Al 2 O 3 showed a slight discrepancy with above rule, which suggests that the variation of major elements can be controlled by many factors, and not simply the susceptibility of minerals to weathering. ...
Mineralogical investigations on fluvial sedimentary sequences could provide historical environmental information on the effects of human activities and natural events. This study aims to identify the provenance, mineralogical distribution mechanism, and environmental significance of sediments of the Yellow River based on topographic analysis, statistics, weathering and recycling indices. In total, 107 samples were collected from sedimentary sequences in the source area, and the upper, middle, and lower reaches and analyzed for grain size, major elements, and mineral composition. The results showed that the climate conditions were cold and arid, where weak hydrolysis under continental weathering and strong erosion accelerated physical weathering. Clay minerals primarily originated from the Tibetan Plateau, whereas the middle and lower reaches received input of aeolian deposits from Northern China. Quartz and feldspar in the middle and lower reaches may derive from the source area and upper reaches. Meanwhile, calcite and dolomite formed through diagenesis, with loess input from the Chinese Loess Plateau. Regarding heavy minerals, the dominant determinative factors of pyrite were post-depositional diagenesis and leaching. Hematite and amphibole primarily formed through magnetite conversion and contribution from regional sources, respectively. Moreover, the mineral distribution mechanism significantly affected the mobility and distribution of geochemical elements through diagenesis and alteration. The findings are instrumental in reconstructing the environmental evolution of large-scale watersheds across multiple climatic zones.
... Oxidizing environments are characterized by low values of Uranium (U), whereas oxygen-depleted environments are rich in U content [75][76][77][78]. In addition, trace elemental ratios (Cu/Zn, Ni/Co, V/Ni, and V/Cr) have been used to interpret the paleo-redox conditions [79][80][81][82][83][84][85]. ...
The Eocene deposits of Egypt provide a wide variety of shallow marine facies and fossil assemblages, allowing paleoenvironmental reconstructions in this warmhouse climate interval. Forty-three rock samples have been collected from two middle Eocene sections, exposed at southeast Beni-Suef area in northern Egypt. The studied outcrops are lithologicsally subdivided into two rock units named from base to top as follows: (1) the Qarara Formation (Lutetian) and (2) the El Fashn Formation (Bartonian). Most investigated rock samples showed richness in benthic foraminiferal assemblages and only rare occurrences of index planktonic foraminifera. They yielded 160 foraminifera species which belong to 4 suborders, 19 superfamilies, 34 families, and 59 genera. The stratigraphic distribution of the identified species allowed us to define four local benthic bio-ecozones: (1) Bolivina carinata Lowest Occurrence Zone (Lutetian), (2) Cibicides mabahethi/Cancris auriculus primitivus Concurrent-Range Zone, (3) Nonion scaphum Lowest Occurrence Zone, and (4) Brizalina cooki/Nonionella insecta Concurrent-Range Zone (Bartonian). These biozones are described and discussed in detail and correlated to stratigraphic equivalents in Egypt. The rareness of index planktonic foraminifera through the studied sections does not allow a precise biostratigraphic and chronostratigraphic correlation. The shale samples show low TOC values, which may be related to low productivity, high sediment influx, and/or prevailing oxic conditions. Bulk rock geochemistry, consistent with the benthic foraminifera ecological preferences, indicated that the studied sections were deposited in moderate to high oxygen levels and warm climatic conditions in a typical shelf marine setting. The identified species showed strong similarities with nearby southern Tethys areas, reflecting migration via the trans-Sahara seaway, and minor similarities with those identified from the northwestern Tethys and the North Atlantic province attributed to the change in the environmental and climatic conditions, such as cooler, latitudinal zoned climatic conditions along the northwestern Tethys, which was unsuitable for their biological demands. The warming trend identified from Lutetian to Bartonian intervals corresponds to the onset of the Middle Eocene Climatic Optimum (MECO).
... Combined data of petrography and major oxides of the clastic sediments can infer the tectonic settings in which the sediments were deposited and the distinct sources of the studied sandstone (Bhatia, 1983;Bhatia & Crook, 1986;Roser & Korsch, 1986;Armstrong-Altrin et al., 2004;Armstrong-Altrin et al., 2015a, 2015bEl-Anwar & Gomaa, 2016;Zaid, 2017aZaid, , 2017bAhmad et al., 2022). The modal composition when plotted in the QFL and QmFLt plots of Dickinson and Fig. 14 A QFL plot after Dickinson and Suczeck (1979) shows a recycled orogenic provenance for the Therria Sandstone; B QmFLt plot after Dickinson et al. (1983) shows a quartzose recycled and craton interior domain as provenance for Therria Sandstone Suczek (1979) and Dickinson (1983) resides in the domain of recycled orogen; these data indicates that quartzose recycled and craton interior were the sandstone sources ( Fig. 14A and B). ...
Petrography and geochemistry (major element oxide) have been carried out to reveal the compositional variation, palaeoclimatic conditions and depositional environment of Therria Sandstone Member of Shella Formation from Assam-Arakan Basin, India. Therria Sandstone is made up of fine to coarse-grained sandstone with occasional gritty texture formed by granule-sized grains and fine shale layers. The grain size changes have revealed an eight number of cyclicity. It is deposited in fluvial to brackish lagoon environments as indicated by presence of compound trough cross stratification and coal layers. The source rock of the Therria sandstone was mostly metamorphic as indicated by the metamorphic lithic fragments, semi-quantitative weathering index (wi = 2), Quartz-Feldspar and Rock fragments (QFR) plotting, assemblage of heavy minerals like garnet, kyanite, sillimanite. Semi-quantitative weathering index (wi = 2) indicates that it has formed in a humid tropical climate and in a low-relief catchment area. Humid climate is also supported by the QFR plot and presence of high amount smectite. Different geochemical weathering indices like Chemical Index of Alteration (CIA), Plagioclase Index of Alteration (PIA), Index of Chemical Variability (ICV) indicate a high degree of weathering which, in turn, supports a high precipitation in that area and a humid climate.
... Zircon is an accessory mineral in both igneous and metamorphic rocks. Zircon is extremely resistant to weathering and abrasion, and hence is common in sedimentary rocks and in alluvial and beach placer deposits (Dryden and Dryden 1946;Armstrong-Altrin et al. 2015). Zircon occurs in a range of colours, such as colourless, red, brown, yellow, grey, pink, and green (Abdel-Karim et al. 2017). ...
Heavy minerals (HMs) are used in many high-tech applications (e.g. nuclear reactors, photovoltaic cells, electronics, green, and nano- and space technology), and thus global demand is increasing day by day. This review article is focused on the global distribution, genesis, economic geology, exploration and exploitation, demand (i.e. past, present, and future status of annual
global production, consumption, and price), applications (geological and industrial uses), and major environmental issues mostly related to the HM sand industry. Heavy mineral deposits are distributed in more than 45 countries. Major HM deposits are located in Australia, Asia, and Africa, as secondary coastal placers bordering the Indian Ocean. Onshore and offshore deposits in the Americas, Europe, and other countries also contribute to the global HM market. Heavy mineral deposits are categorised as primary (magmatic, hydrothermal, metamorphic) or secondary (weathered, eroded, and transported sediments) deposits. Titanium, zirconium, and rare earth element (REEs) bearing minerals are key industrial commodities in the current global market. The heavy mineral industry has experienced healthy growth in unit price and global production due to increased demand generated by rapidly expanding economies such as those of China and India. Global production of zircon, ilmenite, and rutile has gradually increased over the last few decades. Global apparent consumption of ilmenite declined slightly from 1970 to 1995, in part due to introduction of stringent regulatory measures and government environmental policies in Europe and North America, as the main consumers of HMs at present. Mining and utilisation planning following the United Nations Sustainable Development Goals are highly appropriate for the sustainability of the HM industry, and to overcome ecological challenges, health issues, and social resistance towards HM exploitation. Finally, we forecast changes in production and price of three HMs (ilmenite, rutile, and zircon) for the decade from 2020 to 2030, assuming there are no disturbances in production due to external factors such as the Covid-19 global pandemic or unfavourable geopolitical interventions.
... Geochemical records and parameters associated with siliciclastic sediments are common potential tools to establish the tectonic setting of known sedimentary basins [65,66,39,17] . McLennan et al. [65] and Ojo et al. [17] , documented that chemical compositions, sandstones can be categorized into different tectonic settings; magmatic island arcs (average SiO 2 : <58%, K 2 O/Na 2 O < 1), Andean-type continental margins (SiO 2 : 68% to 74%, K 2 O/ Na 2 O < 1), Atlantic-type continental margins (average SiO 2 : <89%, K 2 O/Na 2 O > 1). ...
Sandstones sampled from Patti Formation, Southern Bida Basin, were studied geochemically using Inductively Coupled Plasma Atomic Emission Spectrophotometer (ICP-AES) and an Inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique to evaluate their weathering and tectonic setting as well as to deduce the paleo-climatic conditions that existed during their deposition. Geochemically, SiO2 range from 73.9% to 86.2%, Al2O3 (6.7%~17.1%), Fe2O3 (1.1%~1.9%), K2O (0.1%~0.7%) while MgO, CaO, Na2O, P2O5, MnO and TiO2 were <1%. Enriched in Ba (Av. 622.94), Sr (Av. 153.63), Rb (Av. 55.08) and Zr (Av. 51.86) relatively similar in composition to UCC. High SiO2 but low other major oxides signify high mobility during processes of weathering. This was confirmed by high value (>80%) for indices like chemical index of alteration, chemical index of weathering, plagioclase index of alteration, mineralogical index of alteration and relatively lower values for weathering index of parker, recently used alpha indices (αAl E) of sodium (326.17αΑl Na<344.40), magnesium (100.54αΑl mg<398.55), calcium (12.07αΑl Ca<198.99), potassium (4.43αΑl K<64.33), strontium (0.84αΑl E<21.40), barium (0.45 αΑl Ba<10.52) and rubidium (0.0008αΑl Rb<0.06), supported by AI2O3-(CaO*+Na2O)-K2O and CIA vs. SiO2 plots that imply intense weathering in the source area. The obtained high CIA values (>80) indicates a steady-state of weathering under a warm/humid climate as confirmed by the SiO2 vs. Al2O3+ K2O + Na2O plot. High average SiO2 (75.41wt%) with K2O/Na2O ratio >1 (15.63), low Fe2O3 (1.27wt %), Al2O3 (15.82wt%) and TiO2 (0.46) suggest passive margin tectonic setting. This is supported by enriched ΣREE (209.64 ppm), ΣLREE (195.78), LREE/HREE (27.78) and negative Eu/Eu* (0.68), plots of log (K2O/Na2O) vs. SiO2 and SiO2/Al2O3 vs. K2O/Na2O. Major elements discriminant-function multi-dimensional diagram, DF1 (arcrift-col) vs. DF2 (arc-rift-col), for high-silica sediments revealed a continental rift tectonic setting. Thus, the Patti Formation sandstone underwent a high degree of weathering under a humid climatic condition within a continental rift tectonic setting.
... Among the major oxides, Al 2 O 3 and TiO 2 generally show a low degree of fractionation during weathering processes (Armstrong-Altrin et al. 2015). Hence, the Al 2 O 3 /TiO 2 ratio can be used as a valuable proxy for determining the provenance of sedimentary sediments. ...
The Zola-Chay River is one of 14 permanent rivers feeding Lake Urmia in northwestern Iran and a significant amount of material eroded from surrounding rocks has entered this lake. In this study, mineralogy and concentrations of major and trace elements of the Zola-Chay river sediments were measured on a 26 km-long NE–SW trending section with the aim of evaluating the provenance and source-area weathering. Quartz, orthoclase, plagioclase, and muscovite are the principal constituents accompanied by some minor accessory minerals, such as illite, kaolinite, calcite, dolomite, pyrite, hematite, apatite, rutile, epidote, ilmenite, zircon, and monazite. Values of the index of compositional variability (ICV) in the studied samples range from 0.99 to 1.21, indicating that these sediments are immature. The chemical index of weathering (CIW) (54.04 to 61.10), plagioclase index of alteration (PIA) (55.66 to 66.20), and chemical index of alteration (CIA) (62.50 to 72.51) values of the sediments, together with geochemical proxies, such as the K2O/Rb and Rb/Sr ratios, reveal a weak to intermediate chemical weathering in the study area. Multivariate plots of major oxides and trace elements, along with geochemical indicators, such as Al2O3/TiO2, Ti/Zr, Cr/Th, Th/Co, La/Co, La/Sc, Cr/Ni, Th/Sc, Ce/Sc, Zr/Sc, Eu/Eu*, (La/Sm)N, (Gd/Yb)N, (La/Lu)N, and LREE/HREE ratios, imply that the Zola-Chay River sediments probably originated from a felsic–intermediate precursor. Combining the results obtained from field observations and geochemical investigations show that Neoproterozoic rhyolites–rhyodacites along with Precambrian–Paleozoic rhyolites–granites–diorites are the probable provenance of the Zola-Chay River sediments.
... As the most direct manifestation of the interaction between human activities and the natural environment, land use land cover (LULC) has become one of the most important way to understand the regional environmental change [1]. At the same time, it has become the main content of the international geosphere biosphere program and the international human program of global environmental change and is the research hotspot in the current academic circles [2]. With the help of dynamic change model, transfer model, and overlay buffer analysis, this paper analyzes the spatial model and regional differences of LUCC in the study area and selects the indicators of ecological security construction based on P.S.R (pressure-state-response) model and obtains the environmental security assessment results through system assessment and GIS remote sensing analysis [3]. ...
Land resources are an important foundation for human survival and development. In recent years, land resources have experienced rapid industrialization and urbanization. With the expansion of urban construction land and the sharp decline of natural and agricultural landscapes, ecological and social problems have gradually surfaced. Based on the intuitive interpretation of LandsatTM/ETM +/OLI image data from 2016 to 2020, this work created an annual land use reference database. The use of resources and the recovery of nutrients from vegetable waste are necessary measures to achieve sustainable and environmentally friendly agriculture. Collecting and analyzing data from the literature are to determine the risk of vegetable waste pollution and the possibility of resource utilization. The amount of vegetable waste produced and the total amount of nitrogen, total phosphorus, and total potassium pollution in the study area are estimated, and ArcGIS is used to characterize TN (total nitrogen) and TP (total phosphorus). The spatial distribution of TK (total potassium) pollution intensity and pollution risk comprehensive index determines the key areas of vegetable waste nonpoint source pollution control in the region and compares the resource utilization potential of vegetable waste based on the demand for fertilizer. This paper combines the research of the subject; takes cultivated land as the research object; clarifies the main pollutants, contaminated area, content, and distribution of cultivated land; uses factor analysis method to conduct a preliminary study on the causes of heavy metal contaminated soil in the study area; and adopts a source-sink balance model, analyze the cumulative characteristics of soil pollution. Based on geographical information system (GIS) and remote sensing technology, this paper investigates the risk assessment of vegetable waste pollution and discusses the analysis of resource potential.
... Th/K ratios of sedimentary rocks can provide important information on source rock composition when climate, hydraulic sorting, and postdepositional chemical changes are taken into consideration. Provenance shift may be accompanied by changes in mineral composition that can be reflected in Th-K data (Parkinson 1996;Bessa and Hesselbo 1997;Leeder et al. 1998;Ehrenberg and Sva 2001;Deconinck et al. 2003;Schnyder et al. 2006;Inwood et al. 2013;Simíček and Bábek 2015;Armstrong-Altrin et al. 2015;Chavez et al. 2016;Akinlotan 2018;Bábek et al. 2018;Nkongho et al. 2022;Ramezani et al. 2022;Akono et al. 2022). Data for the proximal Mandawa Basin sediments as depicted in lithological columns (Figs. 7 and 9) and binary diagrams (Figs. 10 and 11) do not show sufficient variation to constrain shifts in provenance, possibly due a homogeneous sediment source area or sediments were well mixed prior to deposition (Fralick and Kronberg 1997;Garzanti et al. 2008;Amorosi and Sammartino 2018;Ekoa Bessa et al. 2021;Mounteney et al. 2021;Lučić et al. 2021). ...
Spectral gamma ray log (SGRL) data has been widely employed to derive subsurface lithological information and to perform well correlation when the core is not available. Previous studies mainly targeted homogenous facies whereas few attempts addressed heterolithic successions. The SGRL investigation here aimed at deriving lithofacies and further constrain conditions of deposition prevailing during the early Jurassic (Mbuo, Nondwa, and Mihambia Fms.) in the Mandawa Basin, onshore Tanzania, where core and outcrop data is rare. By use of binary discrimination diagrams of U, Th, and K, composition fields were defined for various lithofacies types (black shale, red shale, siltstone, sandstone, chert, anhydrite, halite, and carbonate) compiled from literature data. Sediment composition for two wells in the Mandawa Basin was then deduced from cuttings and SGRL data and compared with literature-derived geochemical provenance data from adjacent regions and strata. Binary discrimination diagrams revealed the presence of multi-mineral components in the heterolithic facies type, which in concert with diagenetic and detrital mineral dilution effects, led to low compositional contrasts between provenance fields and to overlap of different lithofacies types, complicating interpretation and limiting the effectiveness of the SGRL-based facies differentiation. For the early Jurassic strata, an upward increase in the Th/K ratio suggests an enhanced terrigenous influx into the basin due to intensified weathering. High Th/U and Th/K in the study region indicate a relatively shallow, well mixed, and oxic depositional setting in proximity to the source area opposing the more distal, deeper, and reduced depositional settings that prevailed in the southern central part of the basin. Th/U and Th/K excursions in the Nondwa and Mihambia formations suggest a shift towards less oxic depositional conditions upon two major marine incursions, corroborated by a decline in the clastic fraction and concomitant increase in carbonate.
... Geochemical data of detrital sediments have stable geochemical properties during weathering, transportation, and diagenesis; therefore, they can provide reliable information on provenance 65,66 . To infer the provenance of sedimentary rocks, several authors have proposed major-based (e.g., Al 2 O 3 , TiO 2 , and K 2 O) discrimination diagrams in various studies of unknown basins 67,68 . ...
The Ordovician–Silurian transition was a critical period in geological history, during which profound changes in climatic, biotic, and oceanic conditions occurred. To explore the provenance, palaeoclimate, and palaeoredox conditions in the Sichuan Basin during the Late Ordovician–early Silurian interval, we conducted mineralogical, geochemical, and isotopic analyses of three formations (Wufeng, Guanyinqiao and Longmaxi formations) in the Xindi No. 2 well. The ternary and bivariate diagrams indicate that the provenance is mainly felsic igneous rocks and originated mainly from a collisional setting, presumably due to an active continental margin. The chemical index of alteration (CIA) values in the lower Wufeng and Longmaxi formations are relatively high (67.48–73.57), indicating a warm and humid climate. In contrast, the CIA values declined rapidly (58.30–64.66) during the late Katian to early Hirnantian, which had a fluctuating cold and dry climate and was interrupted by a transient warm and humid climate. The palaeoredox indices (Mo concentrations and Moauth/Uauth, U/Th, V/Cr, Ni/Co, and V/V + Ni values) during the Late Ordovician–early Silurian indicate two cycles of water column euxinia. The first cycle occurred during Wufeng Formation deposition, with bottom waters evolving from oxic-suboxic to suboxic-anoxic. Most samples show relatively low redox-sensitive trace element concentrations during the Guanyinqiao Formation, pointing to oxic-suboxic conditions. The second cycle, during the late Hirnantian, transitioned from oxic to euxinic water conditions. Our δ13Corg data are comparable to previously reported records and exhibit a strong correlation between the Hirnantian isotopic carbon excursion (HICE), climate change, and redox conditions. We suggest that the variations in the δ13C values are related to two elements: (1) increased photosynthetic activity under oxic water conditions, and (2) increased carbonate weathering exposed by the glacio-eustatic sea- level. In addition, the high δ13Corg values might indicate a more shelf-proximal setting during Xindi No. 2 well deposition. The δ13Corg isotopic data effectively constrain the timing of the Late Ordovician mass extinction (LOME) and the evolution of the temporal changes in the climatic and ocean redox conditions, suggesting an apparent stratigraphic coincidence between climate and redox fluctuations and two-phase extinctions, which implies a strong causal relationship. The LOME was systematically driven by the combination of cooler glacial temperatures, glacio-eustatic sea-level fluctuations, and anoxic water conditions that caused the two pulses of extinction in the Yangtze shelf sea.
The Chittagong Tripura Fold Belt (CTFB), the folded eastern part of the Bengal Basin is critical for understanding sediments origin and tectonic evolution linked to interactions among the Indian, Eurasian, and Burma plates. The upper Bhuban and Bokabil sediments (Surma Group) from Atharamura anticline, Tripura, India were analyzed using whole-rock geochemistry and petrography to assess their provenance, tectonics, weathering, and depositional milieu in this least explored area. Petrographic study indicates sub-lithic arenite to sub-arkosic composition, with moderate-high quartz, feldspar poor containing metamorphic and sedimentary lithic fragments (Bh Q88.3F3.0L8.6; Bk Q83.5F7.6L8.8), indicating significant recycled orogen source. Geochemical characteristics such as Eu/Eu* (0.6, 0.7), La/Sc (3.2, 2.4), Th/Sc (1.7, 1.4), Th/Co (1.9, 1.8), CIA/WIP (∼1–2), high Hf, Zr/Sc, low K2O/Al2O3 and enriched LREEs, depleted HREEs, and negative Eu anomalies, indicate a recycled provenance of felsic origin that underwent moderate to intense chemical weathering in active continental margin settings. Radiolarian chert, volcanic lithic fragments with Barail-like recycled sediments strongly suggests an additional detritus from uplifted Indo-Burman Ranges from the east. Elevated Th/U and Th/Rb ratios, sediment immaturity and poor sorting suggest first-cycled detritus. This study indicate that Tripura Neogene sediments are chiefly Himalayan-derived, with minor inputs from IBR and Meghalaya Plateau. The sediments were deposited under brackish near shore to shallow marine oxic basins to the west of the uplifted IBR during the Miocene. The study offers insights into regional geological processes, facilitating correlation of foreland Neogene basins and enhances understanding of the geological evolution of the CTFB.
The sedimentary sequence of the Ninama Basin is associated with the latest phase of the continental Deccan volcanism of the Indian peninsula. It occurs as inter-, intratrappeans with a 39-m thick sequence comprising Sukhbhadar Formation and Ninama Limestone. The investigation aims to reconstruct its depositional setting based on the lithofacies and inorganic geochemistry to understand the influence of paleosalinity, paleoredox, paleodepth, provenance and paleoclimate on the sedimentation pattern. It is characterized by clastic and chemically formed rocks, including shale, mudstone, siltstone, sandstone and limestone. Facies analysis has revealed seven lithofacies, amongst which four are clastic facies, shale (SH), calcareous shale (CSH), silty mudstone (SM) and lithic greywacke (LGW), and three are carbonate facies, namely, grey-black limestone (GBL), cherty limestone (CL) and marlite (ML). Using geochemical analysis of major oxides and trace elements, ratios of Ca/(Ca+Fe), Sr/Ba, V/(V+Ni), V/Cr, Fe/(Ca+Mg), Ti/Al, Na/K, K/(Fe+Mg), CIA-K and MAP were determined and used to interpret and note the changes in the depositional system. The combined results of the lithofacies and geochemistry indicate that the deposition occurred in three phases. Phase 1 is characterized by high energy conditions in the shallow to moderate depth brackish-saline lake with oxic to dysoxic conditions; Phase 2 is characterized by anoxic deep fresh to the brackish water basin; and Phase 3 is characterized by semiarid conditions, saline, anoxic waters, high evaporation leading to shallowing of the lake, and low to moderate terrestrial input. This lacustrine basin in the paleotopographic low of the Deccan Volcanic Province is characterized by distinct lithology governed by various depositional parameters. A composite depositional model is constructed for the Ninama Basin, reflecting three phases of evolution that are dominantly controlled by the paleoenvironment.
Paleocene Therria sandstone of the Shella formation has been studied for the tectono-provenance and depositional environment significance from petrography, clay minerals and geochemistry. The Sandstone is dominated by quartz grains followed by rock fragments, mica, feldspars, clay matrix and cements. Abundance of monocrystalline undulatory quartz variety indicates contribution from medium grade metamorphic sources, primarily of gneisses. Petrographically, the sandstone is classified as litharenite (lithicwacke) with an average recalculated modal composition Q91.4 F0.6 R7.9. Moderate to high concentration of SiO2 has a typical negative correlation coefficient (r) with Al2O3 implying differentiation of clay and quartz during the sedimentation processes. Fe2O3 has negative r, K2O, MgO and P2O5,TiO2 and Na2O has positive r with Al2O3. Again, Al2O3 has a high positive correlation (r= 0.94) with TiO2 suggesting the presence of Iron bearing heavy mineral and cements, associated with clay minerals. A high SiO2/Al2O3 (avg. 6.381) ratio indicate an influence of weathering, transportation and recycling processes simultaneously increasing gritty quartz and total quartz abundance. XRD analysis peaked the clay minerals of kaolinite, illite-montmorillonite, vermiculite, traces of illite and goethite substantiated by high CIA values. The high values of various weathering indices; avg. wt% of CIA: 96.40, CIW: 99.44, PIA: 99.82, ICV: 0.62, ternary plot (A-CN-K) and binary plot of ICV against CIA shows that the rocks have been subjected to intensive weathering. The high PIA obtained suggest an extreme alkalis weathering of source rock weathering and presence of alteration products such as kaolinite. ICV bears close resemblance with PAAS (0.88). Accessory minerals like zircon, rutile, anatase, garnet, sillimanite, kyanite, opaques and Iron oxide are suggestive of their cosmopolitan source. The sandstone is derived primarily from a recycled orogen with inconsequential contribution from mixed transitional continental sources and deposited in a passive continental margin dominantly. The environment of deposition is the realm of semi-humid to humid climatic conditions Qp/(F+RF): Qt/(F + RF) =0.05 (avg.) with low relief or moderate hills inferred from semiquantitative weathering index (wi=2). Introduction:
The undocumented Nkolkosse area belongs to the southern domain of the Pan African Fold Belt in Cameroon. Petrography and whole rock geochemistry reveal that the area is made up mainly of medium-grade gneiss of amphibolite facies. The mineral association in rock is quartz + potassic feldspar + plagioclase + biotite + muscovite ± rutile ± zircon ± opaque minerals. Their SiO2 contents are very high, varying from 76.37 to 80%, while the concentrations of Al2O3 are low (9.61–11.08%) and very low for CaO (< 1%). The average value of K2O/Na2O ratios is greater than 1 (1.40). All these characteristics point to metasedimentary rocks as revealed by the binary diagram TiO2 vs. SiO2, in which all the samples plot in the field of paragneiss. The inferred protoliths of Nkolkosse metasedimentary rocks yield the composition of arkoses and lithic arenites. These protoliths are from mature to immature sediments, resulting from chemical weathering of a felsic source and have experienced a high degree of sedimentary recycling, which supports the recycled nature of those meta-sediments with little contribution from igneous rocks. The protoliths of the Nkolkosse gneiss are from the upper continental crust and were deposited in a passive to active continental margin, within a subduction tectonic setting. These results are concomitant with other results described in the Central African Fold Belt in Cameroon, Brazil, and the northwestern edge of the Congo craton, inferring that they were forming a single block.
A multiproxy approach involving grain size, geophysical (resistivity, magnetic susceptibility, and P-wave velocity), mineralogical (XRD), and geochemical (elemental, stable isotopes) data has been applied to core SP9 (128 cm long) to reconstruct natural and anthropogenic changes since ≈1850 AD (anno domine) (dating by ²¹⁰Pb and ¹²⁷Cs methods) in a distal region of Sepetiba Bay (SB), Rio de Janeiro State (SE Brazil). The analyzed core is a fine-grained sedimentary sequence (except its upper 20 cm). It comprises detrital particles derived from felsic and intermediate source rocks, as suggested by the fields defined by the biplot Zr vs TiO2 and the Al2O3/TiO2 ratios. Despite the increase in particle size at the top of the core, there was a progressive increase in the organic matter and potentially toxic elements (PTEs) contents and nutrients such as N and P. The geophysical data allowed us to identify the presence of subsurface (biogenic) gas, which suggests the occurrence of eutrophication processes in the study area despite its location in the outer region of the bay. Core SP9 records cyclical changes over the last ≈170 years in the mineralogical and elemental composition of the sediments and type of organic matter supplied to the bottom. These changes are associated with phases of more significant oceanic influence, salinity variations in the study area, and greater or lesser oxygen depletion in the sediment. These changes may have resulted from climatic oscillations or variations in the configuration and extension of the Ponta da Pombeba spit. The extent of this structure and the anthropic activities have contributed to the contamination of this area since 1975 AD. However, statistical analyses (Pearson correlations and principal components analysis) suggest that the transport and accumulation of PTEs (mainly Cd and Zn) did not strictly follow the general pattern of sedimentary dynamics prevailing in the studied area. Results indicate that this area became strongly polluted by Cd and Zn and with high ecological risk due to dredging and spoil disposal activities at sites close to the study area. It is noted that the environmental degradation reached higher levels here than in areas close to the primary source of the metals, the disabled Ingá Mercantil Company, in Madeira Island. This work demonstrates the temporal effect of dredge disposal activities in a distal region of Sepetiba Bay for the first time. It is a strong indicator that dredged spoil areas must be selected carefully, since healthy areas can become degraded due to the dumping of polluted waste.
Air pollution and soil contamination have caused major environmental damage in the industrial complex of Gabes. This study aimed to evaluate the abilities of biochar to modify soil properties and assess the adaptation of alfalfa (Medicago sativa L.) plants in contaminated soils from the Gabes Region. The experiment was executed with soil samples from three sites (S1, S2 and S3) located at different distances from the industrial zone of Gabes. Additionally, a control soil was included for comparison. Pot experiments were performed under controlled conditions, with or without biochar. After 60 days, the accumulation of heavy metals in plants (roots, shoots and nodules) was determined. Moreover, oxidative stress biomarkers, such as malondialdehyde (MDA) content, glutathione-S-transferase (GST) and catalase (CAT), were evaluated. Soil microbiological properties, including bacterial functional diversity and fluorescein diacetate hydrolytic (FDA) activity, were analyzed, along with soil chemical properties. Our results revealed that biochar supplementation can improve microbial functions and cation-exchange capacity (CEC), thereby increasing the availability of nutrients to plants. Interestingly, the application of biochar resulted in decreased concentrations of copper (Cu) and zinc (Zn) in plants, which may be attributed to a reduction in their bioavailability in the soil. The accumulation of heavy metals in alfalfa organs was positively correlated with the levels of MDA and antioxidant enzymes in both leaves and roots. In this study, the addition of biochar reduced the antioxidant mechanisms of alfalfa and mitigated the negative effects of metals, resulting in a positive impact on growth and chlorophyll content. Our data highlights the beneficial effects of biochar on enhancing crop productivity and remediating contaminated soil.
This paper discusses the source area-weathering and tectonic settings of alluvial sediments from Lake Chad Basin (LCB). The grain size distribution has been performed by the Robinson-Kӧln's pipetting method. An HACH-HQ11d brand electric pH meter measures the pH and Eh values. Some sand grains and aggregates were examined by scanning electron microscopy with an Energy Dispersive Spectroscopy. The bulk mineralogy was performed with X-TRA Thermo-ARL Diffractometer. The geochemistry of whole samples was assessed by X-ray Fluorescence Spectrometry. Four profiles constituted of different levels characterized by variation in colors and textures have been examined. The textural variation is linked to the alternation of wet and dry periods in the LCB. Microtextural observations reveal sub-rounded to angular particles with secondary silica precipitation on their surfaces. This suggests fluvial transport and short periods of aeolian movements. The clayey and clayey sandy facies are dominated by kaolinite, quartz and illite while the sandy samples are dominated by quartz, kaolinite, illite, goethite and rutile. Amount major elements, SiO 2 , Al 2 O 3 and Fe 2 O 3 have the highest contents and this is consistent with the mineralogical composition. The sediments are mature and classified as Fe-shale, Fe-sand and (sub)litharenite. The sediments are formed under oxic paleoenvironmental conditions. The rock sources underwent variable degree of weathering which reveals the impact of climate change prevailing in LCB. The trace element distribution shows no chemical differentiation as a result of low sediment recycling. Most of the discriminant plots indicate a felsic nature of the original sources rocks. The samples plot in the fields of passive margin and collision in a lesser extent. The collision setting may be related to the complex history of felsic source rocks which derived from the Pan African orogeny and the Cameroon Volcanic Line activities.
This paper discussed the source area-weathering and tectonic settings of alluvial sediments from the Lake Chad Basin (LCB). Four profiles of different levels characterised by variation in colours and textures have been examined. The textural variation was linked to the alternation of wet and dry periods in the LCB. Micro-textural observations by Scanning Electron Microscopy (SEM) revealed sub-rounded to angular particles with collision impact and sometimes adhered particles on their surfaces. This suggested fluvial transport and short periods of aeolian movements. The bulk mineralogy performed with X-TRA Thermo-ARL Diffractometer showed that the clayey and clayey sandy facies are dominated by kaolinite, quartz and illite whilst the sandy samples are made up of quartz, kaolinite, illite, goethite and rutile. The geochemistry of whole samples was assessed by X-Ray Fluorescence Spectrometry. Amount the major elements, SiO2, Al2O3 and Fe2O3 have the highest contents, and this is consistent with the mineralogical composition. The sediments are mature and classified as Fe-shale, Fe-sand and (sub)litharenite. Trace elements behaviour suggested a detrital origin, low sediment recycling and oxic depositional environment. The rock sources underwent variable degrees of weathering which revealed once more the impact of climate change prevailing in LCB. The discriminant plots indicated a felsic nature of the original source rocks in a context of passive margin.
The Yangtze River discharges a large amount of sediment into the East China Sea and has a significant impact on the sedimentary evolution of the Hangzhou Bay. The differences of the impacts of Yangtze type fragment on the sediments of Hangzhou Bay in spatiotemporal distribution are not well studied. Based on the previous studies, this
study collects borehole HZW1907, which is near Zhoushan sea area. This study systematically analyzed core
observation and description, particle size, foraminifera, 14C dating and the geochemical characteristics of organic and
inorganic elements with the core sediments. Through these data, this study focuses on sedimentary process, the
paleosalinity, the weathering process, the geochemical composition of sediments and the depositional system of the
Yangtze River-Hangzhou Bay-East China Sea shelf. Especially, based on the two unit mixing model of rare earth
element composition, the spatiotemporal distribution of Yangtze River sediment to the Hangzhou Bay is quantitatively
discussed. The results show that the estuary area of the Hangzhou Bay has experienced three stages of evolution:
incised valley cutting, valley filling and valley burial in the glacial period since the late Pleistocene, and the
corresponding development of riverbed facies (between about 33.9 ka BP and 23.9 ka BP), flood plain facies (about
23.9 to 12.3 ka BP), ancient estuary facies (about 12.5 to 9.5 ka BP), shallow sea facies (about 9.5 to 6.0 ka BP),
modern estuary facies (about 6.0 ka BP to present); The relationship between Ga/Rb and K2O/Al2O3 in sediments
reveals that Eastern China has experienced cold-dry to warm-wet climate change since 33.6 ka BP; The content of TS
and TOC reflect sedimentary environment from fresh water to unstable brackish-water, finally changing into seawater
environment, which is contemporaneously consistent with the continental shelf of the East China Sea; During the late
Pleistocene, bedding facies and flood plain facies developed in the Hangzhou Bay area, and the clasts mainly came
from the Qiantang River Basin, which the geochemistry showed the characteristics of felsic igneous rocks. Since the
Holocene, the sediments of paleo-estuaries, nearshore shallow marine and modern estuaries show the mixing trend of
Qiantang River type clasts and Yangtze River type clasts. The geochemical composition shows the characteristics of
intermediate-mafic igneous rocks, which implied the strong influence of the Yangtze River materials; Based on
(Gd/Yb)UCC of the Yangtze River and Qiantang river basins, the simulation results show that there is a great difference
between the estuary area and the top area of Hangzhou Bay, which is affected by the Yangtze River material. During
the paleo-estuarine facies in the early Holocene, The Yangtze River provides 78% of the debris for the estuary of
Hangzhou Bay, while the top area was about 39%; During the shallow sea facies, the Yangtze River provided more than
80% of the debris for the Hangzhou Bay area, and there was no significant difference between the estuary and the top of
the bay; In modern estuarine facies, the Yangtze River provided 76% for estuarine sediments, while the top of the bay is
only about 22%; This simulation method plays an important role in the analysis of source-to-sink transport along the
coast, and is expected to be generally applicable to other coastal-shelf-river systems
In western Greece is the Pindos Foreland Basin, a geological depression that contains approximately 2500 m of mainly Upper Eocene to Lower Oligocene submarine fans deposits. Despite the extensive stratigraphic and structural research that has defined the basin as a foreland basin that developed adjacent to Pindos Orogen, the impact of orogenic history and erosion on sedimentation has not been evaluated. This study investigates the origin and tectonic setting of the central Pindos Foreland Basin using new provenance data. Petrographic and geochemical analyses suggest that the succession was primarily sourced by sedimentary, felsic, and intermediate igneous, and low-grade metamorphic source rocks. The geochemical analysis reveals that the sediments are immature and have undergone little to moderate weathering, and low degrees of sediment recycling and sorting. A secondary mafic source with high Cr and Ni contents and high Cr/V ratios. The provenance data indicate that Pin-dos Orogen represents the source region and agree with the existing sedimentological and palaeocurrent research. The Pindos sedimentary and Pelagonian volcano-sedimentary units, mixed with a mafic source (Pindos ophiolitic units) and low grade metamorphics produce the observed chemical and petrographic variance. Multidimensional discrimination diagrams suggest sediment sources from a collisional setting and confirm the active continental edge setting. The provenance data display an up-section increase in lithic fragments, recording the growing history of the Pindos orogen and the gradual exhumation of the source regions. This study offers an example of the sedimentary provenance trend in an evolving pro foreland basin.
O presente trabalho teve como foco principal, estudar as fácies lacustres da Formação Pariquera-Açu como fonte de matéria-prima para a indústria cerâmica de revestimento, em especial na produção de porcelanato. Para alcançar os objetivos propostos, foi realizado o estudo geológico através do mapeamento e reconhecimento das litologias presentes, onde amostras foram coletadas e posteriormente encaminhadas para laboratórios para a realização das análises de Difração de raios X, Fluorescencia de raios X, capacidade de troca catiônica e caracterização tecnológica para uso como revestimento cerâmico. De acordo com os resultados obtidos, o conjunto litológico destas fácies é representado essencialmente por rochas argilosas e plásticas, apresentando composição essencialmente sílico aluminosa com alto conteúdo dos óxidos de SiO2 e Al2O3, onde predominam os minerais quartzo, microclínio e calcita e os argilominerais caulinita e illita. De acordo com os resultados tecnológicos, a maioria das amostras foram classificadas nos Grupos BIII (poroso) e BIIb (semi-poroso). Os baixos resultados de MRF á seco e de elementos fundentes das amostras estudadas, limitam seu uso como matéria-prima única na produção de revestimento cerâmico por via seca e úmida, porém algumas amostras apresentaram densidade aparente (DA) à seco elevada e cor de queima clara, o que permite utiliza-lá na composição de massas para a fabricação de porcelanatos esmaltados pelo processo de via úmida. Palavras-chave: porcelanato, Formação Pariquera-Açu, Vale do Ribeira, matéria-prima cerâmica, litogeoquímica.
An evaluation was done to better understand the utilization of empirical formulas and discrimination diagrams in the determination of sediment origin, frequently in Central Africa. For this purpose, a database was established for geochemical data (major and trace elements) collected from present-day environments or Mesozoic deposits with variable environments and source geologies from two countries of Central Africa (Cameroon and Nigeria). The plotting of modern sediments and ancient rocks in the same diagrams has revealed the low impact of diagenetic processes on the chemical compositions. The results suggest that the proximal provenance proposed by several authors that used empirical formulas and discriminant diagrams to infer the origin of sediments are not always appropriate for all types of sediments. This study shows that chemical index of weathering (CIW) and plagioclase index of alteration (PIA) derive from chemical index of alteration (CIA). It is therefore recommended that they should be used with caution while taking into account the regional geological settings, the location of source area, the paleoweathering of source rocks, and hydraulic-sorting effects. In addition, it is also recommended to use other diagrams such mobile alkaline earth metals versus chemical index of alteration (CIA).
Introdução. A análise de proveniência sedimentar abrange a restauração dos elos existentes entre a rocha sedimentar e suas respectivas áreas fonte de sedimento. Objetivo e Metodologia. A unidade fundamental é a composição sedimentar detrítica. Entretanto, a composição detrítica não é reflexo unicamente da composição das rochas das áreas fontes, mas também da sobreposição de diversos agentes e processos, interdependentes, modificadores da assinatura de proveniências, atuantes desde a formação e o intemperismo da rocha fonte até processos diagenéticos durante o soterramento. Resultados. Por critérios didáticos, estes fatores e agentes podem ser sumariados em: tectônica e reciclagem sedimentar, natureza e composição das áreas-fonte, clima, relevo, transporte sedimentar e diagênese. Conclusão. Não se deve pressupor que a composição detrítica reflita, unicamente, composição da rocha fonte, mas ela é o produto desse conjunto complexo de fatores interdependentes. A análise de proveniência constitui uma ferramenta muito útil na exploração de hidrocarbonetos, principalmente em termos de caracterização preditiva das qualidades petrofísicas de reservatórios.
Three sediment cores recovered from the Alvarado Lagoon System (ALS) in the Gulf of Mexico were used to reconstruct the history of metals and metalloids and their environmental importance. The sedimentary profiles were dated with 210Pb and verified with 137Cs. Maximum ages of 77 and 86 years were estimated. Sediment provenance was described by sedimentological and geochemical proxies. The chemical alteration index (CIA) and weathering index (CIW) revealed moderate to high intensity of weathering in the source area that is controlled tropical climatic conditions, runoff, and precipitation in the basin that feeds sediments to this coastal lagoon. The Al2O3/TiO2 ratios indicated that the sediments were derived from intermediate igneous rocks. The enrichment factor values revealed the lithogenic and anthropic contribution of metals and metalloids. Cd is classified under the category extremely severe enrichment; agricultural activities, fertilizers, herbicides, and pesticides containing Cd are expected to supply this metal to the ecosystem. Factor Analysis and Principal Components provided two main factors, terrigenous and biological origins; ANOVA indicated that there are significant differences between the cores for the parameters analyzed and revealed that there are differences in depositional environments between the recovery zones of the cores. The ALS presented natural variations associated with the climatic conditions, terrigenous input, and its relationship with the hydrological variations of the main rivers. The contribution of this work was to identify the magnitude of the natural component versus the human contribution, mainly of risk metals such as Cd, to support better management of the hydrological basin that affects the ALS.
The Lower Cretaceous syn‐rift deposits of the Douala Basin (Mundeck Formation), located in the equatorial West African margin were investigated in order to determine the palaeoenvironment and organic matter source, redox conditions, palaeoclimate, and tectonic settings, based on facies, organic and inorganic geochemical analyses. The sediments consist of pebble, coarse, medium‐ to fine‐grained sandstone, siltstone, and grey to black fossiliferous shales. The shales are characterized by an average total organic carbon (TOC) of 1.02%, fair to poor source generative potential with present‐day hydrogen index values, which range from 31 to 350 mg HC/g TOC suggesting that the shale contains Type III kerogens with mainly gas generative potential. The organic particles are dominated by phytoclasts (40% on average) and non‐fluorescent amorphous organic matter (34% on average). The palynomorphs represent about 26% on average with a large amount of pollen grain and a minor amount of dinoflagellate cysts and microforaminifera test linings. The inferred depositional environment of the studied sediments is an alluvial fan to fluvio‐lacustrine with shallow marine incursion. This depositional environment received the contribution of aquatic algae and microorganisms with a large amount of terrestrial organic matter, evidenced by the presence of some dinoflagellate cysts and microforaminifera test linings, and relatively higher amounts of SiO2, Al2O3, and phytoclasts. The presence of trace elements such as Ba, Sr, V, Ni, Co and Cr in the analysed samples and their ratio, suggest suboxic to anoxic conditions of deposition with low salinity. The warm to cold and dry climatic conditions prevailed during the deposition of the Mundeck deposits and sediments from active continental margin setting during the lower Cretaceous periods in the Douala Basin as confirmed by inorganic geochemical data. This study sheds light on the early stage of the evolution of the Douala Basin which could be integrated into the context of a mid‐Jurassic to lower Cretaceous regional evolution of the opening of a passive margin. This evolution is characterized by an alluvial fan, fluviatile, lacustrine, lagoon and marine depositional system. This depositional system is recognized as part of the petroleum system recognized within the syn‐rift deposits in the others basins along the West African margin, where giant hydrocarbons have been discovered. Based on facies analysis, geochemical and palynofacies data, the palaeoenvironment of the lower Cretaceous syn‐rift Mundeck Formation of the Douala Basin has been proposed. The shales contain Type III kerogens with mainly gas‐generative potential. The result highlights petroleum prospectivity and the early‐stage evolution of the Douala Basin.
The Early Cretaceous paleoclimate has significant influence on global ecosystem and abundant clues were recorded in both marine and terrestrial sediments. However, much less studies were conducted on the terrestrial strata than the marine strata, leading to the significance of the Early Cretaceous paleoclimate in terrestrial systems is currently unclear. In this study, we present the terrestrial sedimentary characteristics and geochemical data of the upper member of the Lower Cretaceous Liupanshan Group (Liwaxia, Madongshan and Naijiahe formations) in the Liupanshan Basin (North China) and revealed the evolution of paleoenvironment and paleoclimate recorded in the terrestrial lake. The results show that the total REE concentrations of samples from these formations range from 79.94 to 195.54 ppm, 76.94 to 162.37 ppm, and 30.06 to 205.78 ppm, respectively. All samples display obvious negative Eu anomaly and negligible Ce anomaly with the enrichment of LREE and depletion of HREE. These mudstones were rich in Na 2 O, TFe 2 O 3 and several trace elements (e.g., Ba, Sr, and Rb) and depleted in other elements (e.g., Al 2 O 3 , CaO, Th, Zr, and Hf,). The major element composition and other geochemical indicators (e.g., CIA) indicate that the collected mudstones have experienced weak weathering during transportation. Based on the geochemical characteristics, the source of the Liwaxia-Naijiahe Formation has a felsic provenance, derived from the predominantly acidic magmatic rocks in the Qinling-Qilian Orogenic Belt. Multiple geochemical indicators show that the Liwaxia Formation was deposited in a semiarid-arid, anoxic, and low-moderate salinity environment, while the Madongshan-Naijiahe Formation were deposited an arid, anoxic, and high salinity environment. As a typical terrestrial salified lake in North China, the salinization of the sedimentary water bodies and the formation of black shales in the Madongshan-Naijiahe Formation might be related to an oceanic anoxic event in the hothouse climate in the Early Cretaceous.
The Late Ordovician-Early Silurian period witnessed the second largest Phanerozoic mass extinction, Hirnantian glaciation and volcanic events. Wufeng, Guanyinqiao and Longmaxi formations were developed in South China across the Ordovician-Silurian transition.To infer the weathering conditions, provenance, tectonic setting of the source area in western South China during this period, we measured the mineralogical and geochemical characteristics of 42 samples of Wufeng-Longmaxi formations taken from Xindi No. 1 well, south west of Sichuan Basin. These shales and argillaceous limestones mainly consist of quartz, clay mineral, carbonate, feldspar, and minor amounts of pyrite. Geochemically, the rocks from three formations are enriched in CaO and MgO and slightly depleted in SiO 2 , Al 2 O 3 and K 2 O. Chondrite-normalized rare earth elements (REE) patterns display a negative Eu anomaly, a slight enrichment in LREE and a flat HREE. Paleoweathering indices (CIA and PIA) and Th/U ratios indicate that the sediments experienced moderate-intense to weak chemical weathering in the source area. CIA values of the lower Wufeng Formation range from 64.88 to 70.88, indicating a warm and humid climate. Upward the CIA values on the top of Wufeng Formation decrease from 62.56 to 62.93, the CIA values of the Guanyinqiao and lowest Longmaxi formation are consistently low values (58.48-67.12) , suggesting a cold and dry climate which is consistent with Gondwana glaciation in Hirnantian period. Geochemical discrimination diagrams revealed that the rocks of the three formations were derived from felsic igneous source rocks and deposited in an active continental margin setting.
Geochemical analyses were used to determine the origin and identify the main factors that lead to the metal trace distribution on the surface sediments from the continental slope of Sergipe in Brazil. Sediment samples were collected during the dry and rainy periods, from 36 sampling points distributed at water depths from 400 to 3000 m. In general, no effect of seasonality was observed on the metal concentrations and no significant differences were observed between the depth ranges. The correlation analysis indicated the continental origin as the most predominant, followed by authigenic deposition. Anthropogenic enrichment was not noted, nor was the possibility of adverse aquatic biota effects. The results made it possible to understand the contribution of rivers in the transport and transfer of particulate matter to the coastal region, in addition to providing new information on the content of trace metals in tropical Atlantic sediments.
The hinterland of Campo is marked by Archean, Paleoproterozoic, and Cretaceous geological formations. Petrographic, mineralogical and geochemical analyzes of beach sediment samples were performed to determine the origin, alteration, and paleoclimate of the various coastal sediment layers and to reconstruct the structural context of the source region. The beach sediments are fine to medium-grained in size. Morphoscopic examination showed a predominance of very angular and shiny quartz grains. These data reflect a relatively close source with transport in a fluvial environment. The Chemical Index of Alteration (CIA: average = 79.94%), Plagioclase Index of Alteration (PIA: average = 85.31%), as well as the A–CN–K and (A-K)-C-N triangular diagram, show that the weathering affected the source area rocks. The ratios of SiO2/Al2O3, K2O/Na2O, and the chemical composition variation index (ICV ∼ 1.32) show that the sediment samples are immature to mature in terms of texture and chemical composition. Al2O3/TiO2 ratio values ranged from 3.04 to 33.44, indicating an intermediate to felsic rock signature, confirmed by Zr vs TiO2, La/Sc, and Th/Co binary diagrams. Geochemical results reveal a passive marginal continental environment. The passive margin emerged during the opening of the South Atlantic Ocean, which is compatible with the overall geology and structural setting of the studied area.
In this study, five sediment cores (N57, N59, N60, N61, and N63) were recovered from the deep-sea area of the northeastern Gulf of Mexico (~1851 m, ~3057 m, ~3542 m, ~3726 m, and ~3738 m water depth, respectively). The grain size, mineralogy, geochemistry, and radiocarbon ages of the sediment cores were analyzed. N57 and N59 cores were characterized by detrital components enriched in SiO2, Al2O3, and Fe2O3 contents. On the other hand, the N60, N61, and N63 cores were abundant with planktonic foraminifer and depleted in detrital components. The weathering indices like Chemical Index of Alteration (CIA), Chemical Index of Weathering (CIW), and Plagioclase Index of Alteration (PIA) revealed a low intensity of weathering in the source area. The enrichment Factor (EF), Pollution Load Index (PLI), and Geo-accumulation Index (Igeo) indicated that the sediments were moderately contaminated. 14C ages of foraminifer species indicated a maximum age of 1683 ± 52 calibrated years B.P.KeywordsDeep seaWeatheringForaminiferPollution indexRadiocarbonMicrofossil
For a provenance study and characterization of different types of sedimentological processes that affect weathering, information on chemical weathering of sediments is critical. We can estimate major elements of sedimentary geochemistry by using the various Weathering Indices (WIs) models. The present study is a fair attempt in the development of a web dashboard – SedWeather to analyze chemical weathering of sediments using major elemental geochemistry. It offers a flexibility to constrain sediments and rock composites and to demonstrate weathering profiles & source rock chemical makeup in various compositional space diagrams including Al2O3 – CaO-Na2O – K2O, Al2O3 – CaO-Na2O-K2O – Fe2O3-MgO, M – F – W; illustrates different various Weathering Indices (WIs) including CIW, CPA, CIA, PIA, CIX, ICV, WIP and W in boxplots, scatter matrix, correlation matrix against major oxides and ratios. It is possible to alter the Python code in accordance with the data and user requirement by altering the arguments and adding more relevant charts and plots to fit the data. SedWeather's performance in evaluating chemical weathering is demonstrated in evaluating sediments of Surma and Barail sandstones, Mizoram Foreland Basin, NE India, sediments of Manasbal Lake, Kashmir, India, and channel sediments, overbank sediments, suspended sediments of the Ganga basin, having their own provenance history.
A closed-system batch reaction experiment was conducted for 270 days to evaluate the effects of interaction between Gulf of Mexico (GOM) seawater and Mississippi River sediments on the system’s dissolved rare earth elements (REE) concentrations and neodymium isotopic compositions (εNd). This study specifically focuses on geochemical reactions involving silicic sediments derived from weathering of the North American continent as they affect the REEs and εNd of seawater along continental margins, in contrast to previous studies that investigated the influence of basaltic rocks and sediments on REEs and εNd in the ocean. Our results show that the dissolution of labile phases of lithogenic Mississippi River sediments leads to an approximately 100-fold increase in dissolved REE concentrations within the first 33 days of the experiment. Secondary mineral precipitation appears to lower the REE concentrations between days 33 and 270 of the experiment, although seawater REE concentrations remain elevated compared to initial values. The two-way elemental transfer involving dissolution and precipitation results in a net increase by a factor of 24 ± 12 (mean ± 1σ) in the dissolved REE concentrations by the end of the experiment (i.e., day 270). The dissolved REE concentration maxima observed after 33 days of the experiment represent the mobilization of approximately 0.37% of the REE content of the operationally defined “exchangeable” fraction of the riverine sediments. The εNd values of the reactive lithogenic components were -9.77 and -9.95, which are similar to the GOM value of -9.81 ± 0.36. Because of the similarity between εNd values, changes in the seawater Nd isotope value throughout the experiment were subtle (mean ± std, reacted seawater εNd of -9.87 ± 0.17). The highest REE concentrations coincided with the most radiogenic εNd (-9.65 ± 0.23; day 33), which suggests that REE concentrations and εNd compositions of the GOM may be buffered by fluxes from sediments in the system. Our results are comparable to previous studies involving basaltic rocks and/or sediments of basaltic composition in that they demonstrate that silicic, river sediments are highly reactive in marine environments with regard to REE mobilization. The experimental results further suggest that “boundary exchange” plays an important role in influencing the εNd of seawater along continental margins dominated by large river systems, although the impacts of boundary exchange will be most profound where ambient seawater and river sediments have distinct Nd isotopic compositions (e.g., basaltic, or Precambrian shield material). Finally, our results indicate that the εNd value of GOM seawater is largely controlled by the lithogenic sediment delivered to the basin by the Mississippi River.
From April 8th to 19th 2010 we studied the hydrodynamic patterns and zooplankton bio-mass in the Coatzacoalcos River discharge influence area to determine the zooplankton biomass, abundance, and distribution, and its dependence on physical variables. The physical variables were temperature, salinity, relative density (σT) and the speed and direction of currents. Zooplankton biomass was obtained from organism samples taken using zoo-plankton close-open systems and absolute intensity acoustic data from an Acoustic Dop-pler Current Profiler (ADCP). The Coatzacoalcos River forms an anticyclonic eddy to the east of the plume and a smaller cyclonic eddy is formed to the west. Currently, velocities (103 mm s −1) measured using the ADCP indicate a highly dynamic area. The vertical positions of the thermocline, pycnocline and halocline indicate that they are modulated by a cold, wind-mixed layer. Zooplankton biomass, abundance and distribution were modulated by physical parameters including salinity, which affected the temporal and spatial distribution of zooplankton biomass. The largest zooplankton biomass concentrations were sampled near the coast and to the west of the Coatzacoalcos river plume, in the mixed base layer.
La simulación de la circulación dentro de la Bahía de Campeche es efectuada mediante un modelo hidrodinámico nolineal de gravedad reducida. Las ecuaciones son resueltas numéricamente sobre una malla espacial uniforme, descentrada y de 30 km de resolución. Las fuentes perturbadoras son los flujos a través del Canal de Yucatán y del Estrecho de Florida. Los resultados del modelo indican la presencia de giros ciclónicos en la Bahía de Campeche los cuales se desplazan hacia el oeste.
doi: https://doi.org/10.22201/igeof.00167169p.1990.29.2.791
Petrographic, major and trace element compositions of sandstones from the Pliocene Gabir Formation, Central Eastern Desert, Egypt have been investigated to determine their provenance, intensity of paleo-weathering of the source rocks and their depositional tectonic setting. Gabir Formation is composed mainly of sandstones alternating with limestone and shale beds. The Gabir sandstone is yellowish gray to yellowish brown color, calcareous and fossiliferous. The composition of this formation refers to shallow warm agitated marine conditions. Texturally, Gabir sandstones are immature, poorly sorted and grain supported. Abundance of feldspars indicates rapid deposition of sediments from a nearby source rocks. Their average modal composition (Q71.35F16.6L12.05), classifies them as sublitharenite and arkose with subordinate litharenite and subarkose, which is also supported by geochemical study. Chemical analyses revealed that sandstones have high SiO2, K2O > Na2O, and low Fe2O3 values, which are consistent with the modal data. Also, sandstone samples are enriched in most trace elements such as Ba, Sr, Ni, Cr and Zr and depleted in U and Th. The petrography and geochemistry suggest that Gabir sandstones were deposited in an active continental margin basin. They were mainly derived from granitic and low grade metamorphic sources. The CIA values (41.69–74.84) of the Gabir sandstones indicate low to moderate degree of chemical weathering, which may reflect cold and/or arid climate conditions in the source area. The source rocks are probably identified to be Proterozoic granites, metagabbros and metavolcanics, which must have been exposed during rifting, initiated during Oligocene and continued till post Miocene.
To test the suitability of using shale geochemistry as a provenance indicator of a source with an ultramafic component, we used I.C.P. Mass Spectrometry to analyze 130 samples from seven localities from Newfoundland to New York. These samples represent mud from the foreland basin produced during the collision of the Taconic arc with North America in the Ordovician. The sandstones in the flysch contain detrital chromite and other detritus that indicate that the source contained ultramafic rocks, presumably from ophiolites emplaced during collision. This setting is an ideal test case for examining the spatial and temporal variation in Cr and Ni geochemistry of shale derived from ophiolite-bearing highlands. Shale samples with high concentrations of Cr and Ni have a Cr/Ni ratio of ∼ 1.4, which is approximately the Cr/ Ni ratio for ultramaflc rocks (∼ 1.6), suggesting only minor geochemical partitioning, but sandstones have a Cr/Ni ratio of > 3.0, suggesting significant sedimentary fractionation. Analyses of samples taken upsection in a single stratigraphic section suggest that proximity to the source influences Cr and Ni concentrations. A decrease in Cr and Ni concentrations through time suggests that uplift and erosion of the thrust complex (non-ophiolitic) diluted the ultramafic signal. We attribute significant along-strike variation in Cr and Ni concentrations to the relative proportion of ultramafic rocks in the source region. This case study shows that Cr and Ni geochemistry of shale from basin strata can be used to determine the lateral and temporal variability of ultramafic rocks in an active orogenic setting.
Sediment samples collected at DSDP Leg 96 Mississippi Fan Sites 615, 616, 620, 621, and 623, Orca Basin Site 618, and Pigmy Basin Site 619 were analyzed for 22 major, minor, and trace elements. This study was undertaken to docu- ment the downhole variability in inorganic geochemistry between sites. The mineralogy of the clays, including those from Sites 614, 617, and 622 on the fan, was determined by X-ray diffraction to define the principal clay minerals pres- ent at the sites, examine any downhole trends in clay mineralogy, and aid in the interpretation of the geochemical signa- ture of the sediments. Clay mineral composition at all the sites is smectite:illi te:chlorite:kaolinite in the approximate percentage ratio 50:20:20:10. Geochemical results indicate only slight variation between and within the sites, with the exception of a discrete unit of carbonates that occurs near the bottom of Site 615. Variation in the major, minor, and trace element composition can be explained by a change in the relative abundance of quartz, clay minerals, and carbon- ates.
This work applies a statistical methodology involving the calculation of success rates to evaluate a total of 28 tectonomagmatic discrimination diagrams: four bivariate (Ti/Y-Zr/Y; Zr-Zr/Y; Ti/1000-V; and Nb/Y-Ti/Y); six ternary (Zr-3Y-Ti/1000; MgO-Al2O3-FeOt, Th-Ta-Hf/3; 10MnO-15P2O5-TiO2; Zr/4-Y-2Nb; and La/10-Nb/8-Y/15); and three old (Score1-Score2; F1-F2; and F2-F3) and three sets of new discriminant function diagrams (each set consisting of five DF1-DF2 type diagrams proposed during 2004-2008). I established and used extensive geochemical databases of Miocene to Recent fresh rocks from island arcs, back arcs, continental rifts, ocean-islands, and mid-ocean ridges. Rock and magma types were inferred from a SINCLAS computer program. Although some of the existing bivariate and ternary diagrams did provide some useful information, none was found to be totally satisfactory, because success rates for pure individual tectonic settings typically varied from very low (1.1-41.6%) to only moderately high values (63.6-78.1%) and seldom exceeded them. Additionally, only 'combined' tectonic settings were discriminated, or numerous samples plotted in overlap regions designated for two or more tectonic settings or even in areas outside any field. Furthermore, these old diagrams are generally characterized by erroneous statistical basis of closure problems or constant sum constraints in compositional data and by subjective boundaries drawn by eye. All such diagrams, therefore, should be abandoned and replaced by the new sets of discriminant function diagrams proposed during 2004-2010. These diagrams, especially those of 2006-2010 based on the correct statistical methodology and the boundaries drawn from probabilities, showed very high success rates (mostly between 83.4% and 99.2%) for basic and ultrabasic rocks from four tectonic settings and should consequently be adopted as the best sets of tectonomagmatic discrimination diagrams at present available for this purpose. Three case studies from Turkey (Kula, Eastern Pontides, and Lycian-Tauride) were also provided to illustrate the use of two new sets of discriminant function diagrams (2006-2008). For the Kula area, both sets of major- and trace-element based diagrams provided results consistent with a rift setting. For the Pontides area, trace-element based diagrams suggested an arc setting to be more likely, according to both basic and intermediate rocks. For the Lycian ophiolites, however, only the major-element based set of diagrams could be applied, and because of alteration effects, the tectonic inference between an arc or a MORB setting could not be decisive. A newer set of immobile element based, highly successful diagrams currently under preparation (2010) should provide a complementary set to the existing diagrams (2006-2008) for a better application of this important geochemical tool. Further work on these lines is still necessary to propose discrimination diagrams for other types of magmas such as those of intermediate silica compositions.
We applied an alternative Monte Carlo simulation approach to obtain precise and accurate critical values (with 3 to 8 decimal places) for the Student's t test for normal samples of degrees of freedom up to 6000 and for two-sided confidence levels of 50% to 99.9% and correspondingly for one-sided confidence levels of 75% to 99.95%. As an innovation, unlike the existing literature precision estimates of critical values are also individually reported. Prior to our work, critical values (with 2 or 3 decimal places) were available in tables in the published literature. Twenty-eight regression models were evaluated to obtain the best regression fitting of the tabulated data. All conventional polynomial (from quadratic up to 8th order) regressions failed for this purpose. New equations based on double or triple natural logarithm-transformations are proposed for all not-tabulated degrees of freedom, including fractional values if required as well as for probability computations. More importantly, we suggest that these kinds of log-transformations are likely to be useful for all cases where conventional polynomial regressions fail to perform satisfactorily. To demonstrate the utility of these new critical values and best-fit equations, we provide specific examples of applications in geochemistry, chemistry and medicine. The probability estimates, obtained from the present explicit approach, are consistent with commercial and freely available software. Additionally, a more extensive application of our t values is given for processing inter-laboratory data for geochemical reference materials granites G-1 and G-2 from U.S.A. as well as for evaluating geochemical data for basic rocks from the Canary and Azores Islands.
Siliciclastic sediments owe their origin mainly to land sources. New discriminant-function-based major-element diagrams for the tectonic discrimination of siliciclastic sediments from three main tectonic settings: island or continental arc, continental rift, and collision, have been constructed for the tectonic discrimination of high-silica [(SiO2)adj = 63%–95%] and low-silica rocks [(SiO2)adj = 35%–63%], where (SiO2)adj refers to the SiO2 value obtained after volatile-free adjustment of the ten major-elements to 100 wt.%. These diagrams are based on worldwide examples of Neogene–Quaternary siliciclastic sediments from known tectonic settings, loge-ratio transformation of ten major-elements with SiO2 as the common denominator, and linear discriminant analysis of the loge-transformed ratio data. The success rates of these diagrams as judged from the original data varied from 84.5% to 93.6%. These diagrams were successfully tested on Neogene to Quaternary rocks not included in the original database. These discriminant diagrams were also successfully applied on older high-silica and low-silica sandstones and shales of Paleoarchean–Ediacaran age. Finally, these diagrams were shown to be useful against chemical changes related to analytical errors, weathering, recycling and post-depositional processes.
A sedimentological, petrographic, and geochemical study of beach, dune, and river sands was carried out along the northwestern Gulf of Mexico. The main goal of this work is to show how beach and dune sands are controlled texturally, compositionally, and chemically by the nearby rivers for each beach location using a particle size analyser, a polarized microscope, a X-ray fluorescence and ICP mass spectrometer to obtain the following: grain-size values from one river (Carrizal River) are similar in range to their counterpart beach sands but not similar to the dune sands (Barra del Tordo). Rivers (Panuco and Carrizal) are compositionally controlling the quartz and feldspar contents of their counterpart beach and dune sands (i.e., Playa Miramar and Barra del Tordo). Rivers (Soto La Marina River) are directly influencing the composition of the beach sands (La Pesca) based upon the total quartz content, beach and dune sands. The concentration of magnetite grain fractions (Barra del Tordo beach and dune sands) is not under the influence of the nearby river (Carrizal River). In this case the compositional influence of beach and dune sands is related to sediment discharges by other fluvial systems, redistribution of the beach and dune sands along the coast and deflation/winnowing of light minerals. The Eu positive anomaly in the beach and dune sands from the three sites (i.e. Playa Miramar, Barra del Tordo, La Pesca) is linked to an increase in the P(plagioclase)/K(potash feldspar) ratio. The (La/Lu)cn highest ratio for river sands (Carrizal River) suggests quartz enrichment compared to their beach and dune sands counterparts. The (Gd/Yb)cn ratio for one river (i.e., Carrizal River) indicates that it is low in heavy rare earth elements. HREE compared to their beach and dune sands counterparts indicates less concentration of heavy minerals as potential carriers of HREE seawards.
The Hawkesbury Sandstone is an important groundwater reservoir in the southern part of the Sydney Basin, Australia. However, its diagenesis and provenance and its impact in reservoir quality are virtually unknown. The present study aims to reconstruct the parent rock assemblages of the Hawkesbury Sandstone, their tectonic provenance, and the physiographic conditions under which these sediments were deposited. Samples from the EAW 18a and EDEN 115 field representing the Middle Triassic Hawkesbury Sandstone were studied using a combination of petrographic, mineralogical, and geochemical techniques. The Hawkesbury Sandstone is yellowish brown in color, siliceous, and partly calcareous; it originated as sands were deposited in fluvial channels. Texturally, Hawkesbury Sandstone is medium- to coarse-grained, mature, and moderately well sorted. Scarcity of feldspars indicates that the rock is extensively recycled from a distant source. Hawkesbury Sandstone has an average framework composition of Q(92.07)F(0.31)R(7.62), and 95.9% of the quartz grains are monocrystalline. The Hawkesbury Sandstone is mostly quartz arenites with subordinate sublithic arenites, and bulk-rock geochemistry supports the petrographic results. Petrographic and geochemical data of the sandstones indicate that they were derived from craton interior to quartzose recycled sedimentary rocks and deposited in a passive continental margin of a syn-rift basin. The cratonic Lachlan Orogen is the main source of Hawkesbury Sandstone. The chemical index of alteration, plagioclase index of alteration, and chemical index of weathering values (3.41-87.03) of the Hawkesbury Sandstone indicate low-moderate to high weathering, either of the original source or during transport before deposition, and may reflect low-relief and humid climatic conditions in the source area. Diagenetic features include compaction: kaolinite, silica, mixed-layer clays, siderite, illite, and ankerite cementation with minor iron-oxide, dolomite, chlorite, and calcite cements. Silica dissolution, grain replacement, and carbonate dissolution greatly enhance the petrophysical properties of many sandstone samples.
This paper focuses on intensifying maize-based cropping systems in the Sierra de Santa Marta Region of Veracruz, Mexico. Following a description of the study area, the paper examines the historical forces that have shaped regional maize-based cropping systems, current maize production practices, and major productivity and sustainability constraints. Potential solutions to these constraints, some of which have been successfully tested in the area, are described and possible productivity and sustainability impacts are appraised in qualitative terms. The appraisal provides the basis for a quantitative analysis of the farm-level costs and benefits associated with the adoption of the alternative practices. A farmer-based approach to extension is described and implementation costs are estimated.
The weathering condition, provenance, and tectonic setting of sands from the San Nicolás (SN) and San Carlos (SC) beaches along the Gulf of California, Mexico have been studied using mineralogy, major, and trace element data. The compositional similarity among four independent groups (each beach area consists two grain-size groups, i.e., medium and fine-grained sands) was tested statistically by the application of ANOVA (Analysis Of Variance) at 99% confidence level to avoid misinterpretation. The X-ray diffraction (XRD) and SEM-EDS data revealed that the fine-grained SN sands were abundant in rutile and zircon minerals. The higher SiO2/Al2O3 ratio of the SN sands than the medium and fine-grained SC sands indicated that the compositional maturity was greatest for the SN sands (Fcalc = 366.756151 and (Fcrit)99% = 5.065158, where Fcalc > (Fcrit)99% indicates that the data populations are significantly different at 99% confidence level). The chemical index of alteration (CIA) values for the SN (~ 41 -45) and SC (~ 48 - 51) sands indicated low to moderate weathering intensity in the source region.
Our aim is to determine the mean compositions of modern island and continental arcs, along with dispersion estimates, and use them to evaluate their similarities and differences in such subduction settings. First, following the conventional approach, the statistical parameters of mean, median, and standard deviation were simply calculated from the available combined data from all island or continental arcs. However, it is mandatory to ascertain from significance tests that all island or continental arcs used for these estimates are statistically similar in their compositions before combining the data from different arcs and calculating the mean values and their uncertainties for the chemical parameters of interest. A new computer program, Univariate Data Analysis System (UDASYS), was developed for this purpose because the available programs are not efficient for applying the significance test of analysis of variance (ANOVA) to large numbers of sample groups, as in the present work. Compositional data for 16 island and 12 continental arcs around the world were compiled and processed in UDASYS. The best compositional estimates for all three types of magmas (basic, intermediate, and acid) from island and continental arcs were statistically evaluated to document, for the first time, significant differences for 64–94% of the geochemical parameters under study. These differences in large-ion lithophile elements, light rare earth elements, high-field strength elements, and numerous log-ratios are likely caused by different types of underlying crust beneath island and continental arcs. More specifically, the examination of two nearby arcs, Izu-Bonin (island) arc and Japan (continental) arc, confirmed that about 65–77% of the parameters showed significant differences, which may be related to the different types of crusts beneath these spatially close areas. The differences between the log-ratios of island and continental arc basic magmas further indicate that new multi-dimensional discrimination diagrams can certainly be proposed in future to discriminate such basic magmas from these two very similar tectonic settings, which at present is possible only from diagrams for intermediate and acid magmas.
The accumulation of heavy metals in soil and water is a serious concern due to their persistence and toxicity. This study investigated the vertical distribution of heavy metals, possible sources and their relation with soil texture in a soil profile from seasonally waterlogged agriculture fields of Eastern Ganges basin. Fifteen samples were collected at ∼0.90-m interval during drilling of 13.11 mbgl and analysed for physical parameters (moisture content and grain size parameters: sand, silt, clay ratio) and heavy metals (Fe, Mn, Cr, Cu, Pb, Zn, Co, Ni and Cd). The average metal content was in the decreasing order of Fe > Mn > Cr > Zn > Ni > Cu > Co > Pb > Cd. Vertical distribution of Fe, Mn, Zn and Ni shows more or less similar trends, and clay zone records high concentration of heavy metals. The enrichment of heavy metals in clay zone with alkaline pH strongly implies that the heavy metal distributions in the study site are effectively regulated by soil texture and reductive dissolution of Fe and Mn oxy-hydroxides. Correlation coefficient analysis indicates that most of the metals correlate with Fe, Mn and soil texture (clay and silt). Soil quality assessment was carried out using geoaccumulation index (I
geo), enrichment factor (EF) and contamination factor (CF). The enrichment factor values were ranged between 0.66 (Mn) and 2.34 (Co) for the studied metals, and the contamination factor values varied between 0.79 (Mn) and 2.55 (Co). Results suggest that the elements such as Cu and Co are categorized as moderate to moderately severe contamination, which are further confirmed by I
geo values (0.69 for Cu and 0.78 for Co). The concentration of Ni exceeded the effects-range median values, and the biological adverse effect of this metal is 87 %. The average concentration of heavy metals was compared with published data such as concentration of heavy metals in Ganga River sediments, Ganga Delta sediments and upper continental crust (UCC), which apparently revealed that heavy metals such as Fe, Mn, Cr, Pb, Zn and Cd are influenced by the dynamic nature of flood plain deposits. Agricultural practice and domestic sewage are also influenced on the heavy metal content in the study area.
In the Kachchh Mainland, the Jumara Dome mixed carbonate-siliciclastic succession is represented by the Jhurio and Patcham formations and siliciclastic-dominating Chari Formation (Bathonian to Oxfordian). The Jumara Dome sediments were deposited during sea-level fluctuating, and were interrupted by storms in the shallow marine environment. The sandstones are generally medium-grained, moderately sorted, subangular to subrounded and of low sphericity. The sandstones are mineralogically mature and mainly composed of quartzarenite and subarkose. The plots of petrofacies in the Qt-F-L, Qm-F-Lt, Qp-Lv-Ls and Qm-P-K ternary diagrams suggest mainly the basement uplift source (craton interior) in rifted continental margin basin setting. The sandstones were cemented by carbonate, iron oxide and silica overgrowth. The Chemical Index of Alteration values (73% sandstone and 81% shale) indicate high weathering conditions in the source area. Overall study suggests that such strong chemical weathering conditions are of unconformity with worldwide humid and warm climates during the Jurassic period. Positive correlations between Al2O3 and Fe2O3, TiO2, Na2O, MgO, K2O are evident. A high correlation coefficient between Al2O3 and K2O in shale samples suggests that clay minerals control the major oxides. The analogous contents of Si, Al, Ti, LREE and TTE in the shale to PAAS with slightly depleted values of other elements ascribe a PAAS like source (granitic gneiss and minor mafics) to the present study. The petrographic and geochemical data strongly suggest that the studied sandstones/shales were deposited on a passive margin of the stable intracratonic basin.
210Pb activities were analyzed in surface sediments from the Coatzacoalcos River (Gulf of Mexico) to evaluate its distribution according to sediment grain size and in different geochemical compartments by using sequential extraction techniques. The geochemical fractionation experiments provided compatible results: by using the Tessier’s method [1] more than 90% of the 210Pb activity in the samples was found the residual fraction (primary and secondary minerals) and the remaining (<10%) in the iron and manganese oxides fraction of the sediments; whereas using the Huerta-Diaz and Morse method [2] the 210Pb content was found in comparative amounts in the reactive, the silicate, and the pyrite fractions (accounting together for >80%), and the rest was found in the residual fraction. The grain size fractionation analyses showed that the 210Pb activities were mostly retained in the clay fraction, accounting up to 60–70% of the 210Pb total activity in the sediment sample and therefore, it is concluded that the separation of the clay fraction can be useful to improve the analysis of low 210Pb content sediments for dating purposes.
The Middle Miocene Kareem sandstones are important oil reservoirs in the southwestern part of the Gulf of Suez basin, Egypt. However, their diagenesis and provenance and their impact on reservoir quality, are virtually unknown. Samples from the Zeit Bay Oil Field, and the East Zeit Oil Field represent the Lower Kareem (Rahmi Member) and the Upper Kareem (Shagar Member), were studied using a combination of petrographic, mineralogical and geochemical techniques. The Lower Rahmi sandstones have an average framework composition of Q95F3.4R1.6, and 90% of the quartz grains are monocrystalline. By contrast, the Upper Shagar sandstones are only slightly less quartzose with an average framework composition of Q76F21R3 and 82% of the quartz grains are monocrystalline. The Kareem sandstones are mostly quartzarenite with subordinate subarkose and arkose. Petrographical and geochemical data of sandstones indicate that they were derived from granitic and metamorphic terrains as the main source rock with a subordinate quartzose recycled sedimentary rocks and deposited in a passive continental margin of a syn rift basin. The sandstones of the Kareem Formation show upward decrease in maturity. Petrographic study revealed that dolomite is the dominant cement and generally occurs as fine to medium rhombs pore occluding phase and locally as a grain replacive phase. Authigenic quartz occurs as small euhedral crystals, locally as large pyramidal crystals in the primary pores. Authigenic anhydrites typically occur as poikilotopic rhombs or elongate laths infilling pores but also as vein filling cement. The kaolinite is a by-product of feldspar leaching in the presence of acidic fluid produced during the maturation of organic matter in the adjacent Miocene rocks.
Quantified paleoecology and gamma-ray spectrometry have been applied in the analysis of the Kimmeridge Clay, a highly organic-rich British Jurassic mudrock. Decreasing benthic oxygen trends are reflected in decreasing species richness and dominance-diversity values. Similarly, the degree of fragmentation of the benthos reflects the benthic energy levels and covaries with benthic oxygen. The calculation of authigenic uranium values from data gathered by gamma-ray spectrometry shows enrichment in more oxygen-deficient environments. The good correlation between the independently derived paleoecological and authigenic U data indicates the importance of these techniques in environmental analysis of marine petroleum source rocks.
Petrographic, major, trace, and rare earth element compositions of sandstones from the upper Miocene Kudankulam Formation, Southern India, have been investigated to determine their provenance, tectonic setting, and weathering conditions. All sandstone samples are highly enriched in quartz (Q) but poor in feldspar (F) and lithic fragments (L). The major-element concentrations of these sandstones reveal the relative homogeneity of their source. Geochemically, the Kudankulam sandstones are classified as arkose, subarkose, litharenite, and sublitharenite. The CIA values (chemical index of alteration; mean value similar to 44.5) for these sandstones and the A-CN-K diagram suggest their low-weathering nature. Similarly, their Fe2O3* + MgO (mean similar to 2.7), Al2O3/SiO2 (similar to 0.09), K2O/Na2O (similar to 2.2) ratios and TiO2 contents (similar to 0.3) are consistent with a passive-margin setting. The Eu/Eu* (similar to 0.5), (La/Lu)(cn) (similar to 21), La/Sc (similar to 5.9), Th/Sc (similar to 1.9), La/Co (similar to 5.7), Th/Co (similar to 1.8), and Cr/Th (similar to 5.3) ratios support a felsic source for these sandstones. Chondrite-normalized REE patterns with LREE enrichment, flat HREE, and negative Eu anomaly also are attributed to felsic source-rock characteristics for Kudankulam sandstones. Total REE concentrations of these sandstones reflect the variations in their grain-size fractions. The source rocks are probably identified to be Proterozoic gneisses, charnockites, and granites of the Kerala Khondalite Belt, which must have been exposed at least since the late Miocene. Finally, the unusual Ni enrichment in the Kudankulam sandstones, unaccompanied by a similar enrichment in Cr, Co, and V, may be related to either the presence of pyrite in the sandstones or, more likely, the fractionation of garnet from the source rocks during transportation.
A means of relating geochemical concentrations to existing sandstone classification schemes is based on three chemical parameters: the CiO2/Al2O3 ratio, the Fe2O3/K2O ratio, and the Ca content. The Ca content is used to differentiate noncalcareous from calcareous sandstones and shales and to separate siliciclastic from carbonate rocks. Sandstones are classified the same by this scheme as by petrographic analysis about 84% of the time, and shales are effectively discriminated from sandstones. -from Author
The lower reaches of the Coatzacoalcos River in southeast Mexico is an area of intense industrial development. The physico-chemical characteristics of the area have exhibited differences over the years. Apparently from the associated outcroppings of limestone in the Uxpanapa River Basin, the major elements that are dissolved show higher concentrations of Ca, Mg and HCO 3 - in the waters supplied by this river. The water in the Calzadas River contains high concentrations of Ca, SO 4 and HCO 3 - that are associated with the saline domes crossed by this river. Due to industrial discharges, the sulfate concentration is very high in the water and air during April. Nitrate concentration diminishes with salinity. Higher nitrate as well as nitrite and ammonia levels are present during flood season. Phosphate concentration, associated with high oxygen levels, is higher in January. Zn, Cu and Cr are higher during the dry season (April) when dilution is minimal and low levels of TOC are present. The smaller concentrations of Zn and Cu observed in January are associated with high TOC values in water. The lower levels of Cr present in August are associated with high amounts of suspended matter. Pajaritos Lagoon and Teapa-L, with large industrial discharges, have the highest nutrient and dissolved metal concentrations in the area. Air particles smaller than 2.5 µm contain Fe, V, Ti, Cu, Zn, and high amounts of S. These anomalous concentrations of sulfates and metals are attributed to anthropogenic sources.
This study uses grain-size distributions to contrast sediment transport processes in the Tecolutla and Nautla deltas on the high-energy Veracruz coastal margin, southwestern Gulf of Mexico. Both tropical deltas formed at mouths of short, seasonal high-flood discharge rivers that carry large volcaniclastic loads down steep mountain slopes directly to the coast. Baseline studies of deltaic sediments are needed to help develop protection measures for the increasing delta populations endangered by devastating floods. Eleven environments in each delta are distinguished on the basis of mean size, standard deviation and skewness in surficial sediment samples. These textural parameters are used to interpret transport processes that prevail in the environments of the two deltas. The Tecolutla system discharges more water and carries a greater sediment load than the Nautla. The Tecolutla loses a greater proportion of coarser fractions by overbank transport on its natural levees and flood-plain, and it also traps more finer-grained fractions in its larger marshes, mangroves and upper estuary. Consequently, grains reaching the Tecolutla's lower estuary are of finer mean size and better sorted than those reaching the Nautla's lower estuary. Moreover, a larger proportion of the Tecoluta's sediment load bypasses the lower estuary and is released seaward beyond the river mouth. This conclusion is independently confirmed by the delta's prograding, gentle cuspate form and higher proportions of fluvioclastic light and volcanic mineral components traced from its lower estuary to nearshore settings. In contrast with the Tecolutla, textural evidence suggests erosion and reworking from marine environments and accretion onto the Nautla coast and lower estuary by wave-driven currents. Corroborating evidence is the Nautla's truncated coastal configuration and, in its lower estuary, a masking of the river's volcanic and light minerals by locally concentrated heavy minerals and carbonates.
Sandstone petrography and shale geochemistry from the lower Jurassic Ab-e-Haji Formation, in the southern part of Tabas block, were used to constrain provenance, tectonic setting and weathering conditions. The sandstones consist mainly of quartz and sedimentary and low grade metamorphic lithic fragments and therefore, show quartzolithic nature (Qm38-F2-Lt60, Qt58-F2-L40). However, modal analysis as well as highly labile lithics in Ab-e-Haji sandstones point to short transport of sandstone components from a recycled source of a fold thrust belt to its nearby foreland basin. Discrimination diagrams based on major and trace elemen content point to a role of recycled sources for the deposition of Ab-e-Haji Formation, which at the upper part of the section were probably mixed with a minor felsic source. Negative Eu anomalies, similar to those displayed by Post-Archean Australian Shale (PAAS), along with depleted Ca, Na, Cs, Ba and Rb, and low K2O/Al2O3 ratios in studied shales, suggest low abundance of feldspar in the source terrane. Depletion of transition metals (Cu, Sc, Ni, Cr, and V) can be explained by derivation from a more silicic and fractionated source than the PAAS. Moreover, the geochemical results from La-Th-Sc diagram as well as La/Sc, Th/Cr, and Th/Sc ratios of Ab-e-Haji sediments are within the range of fine-grained sediments derived from silicic sources. The chondrite-normalized rare earth elements (REE) patterns of samples are similar to those of PAAS, with light REE enrichment, a negative Eu anomaly, and almost flat heavy REE pattern, similar to those of a source rock with felsic and (meta) sedimentary components. Most probably, displacement of intrabasinal faults, such as the active Kuh-Banan basement fault, and exposure of supracrustal successions (fold thrust belt) provided a mixed source area that supplied the sediments for the Ab-e-Haji foreland basin. This tectonic activity could have been related to the Eo-Cimmerain orogeny in central Iran during the Late Triassic to Jurassic. Furthermore, the point counting data from Ab-e-Haji sandstones imply a semi humid climatic condition, which is supported by the CIA (chemical index of alteration) values for the shales of this formation, which indicate moderate to intense weathering of the parent rocks in the source area.
Petrographic, major, trace, and rare-earth element geochemistry of sands from three beaches of México (Cazones, Acapulco, and Bahía Kino) were studied to determine their provenance. The textural study reveals that the proportion of quartz is higher in Bahía Kino (~48-83 %) than in Cazones (~22-48 %) and Acapuclo (~20-48 %) sands. Most of the sand samples are classified as felsic sands using SiO2 content. The variations in SiO2, Fe2O3, MgO, TiO2 contents and Al2O3/TiO2, K2O/Na2O, SiO2/Al2O3 ratios among the three study areas reflect differences in source rock characteristics. The low Chemical Index of Alteration values (CIA: ~38-58) suggest the prevalence of week weathering conditions in the source regions. A steady weathering trend identified in the A-CN-K diagram for Acapulco and Cazones sands is indicative of uplift along the source region and indicates that sands were derived from diverse sources. A major variation in ΣREE content is observed in Acapulco sands (~22-390 ppm) than in Cazones (~49-83 ppm) and Bahía Kino sands (~50-89 ppm), and is likely due to differences in fractionation of minerals. However, all the sand samples show similar REE patterns with enriched LREE, depleted HREE and a negative Eu anomaly. The comparison of REE data of sands with those of source rocks located relatively close to the study areas suggest that Cazones and Acapulco sands were derived from felsic and intermediate rocks, whereas Bahía Kino sands were derived from felsic rocks.
Published data from several Holocene organic carbon-rich continental margin sediments have been used to geochemically characterize their environment of deposition. It can be shown that a relationship exists between the accumulation rate of organic carbon and excess heavy metals (Cu, Ni, Zn). Sediments from stagnant anoxic basins such as the Black Sea, however, are geochemically different. Several Cretaceous black shales from the Atlantic Ocean show characteristics close to those of the Black Sea data. Therefore, their paleoenvironment should be much more comparable to the present Black Sea than to areas of upwelling. The trace element geochemistry of Cretaceous black shales from the Atlantic cannot be explained by a simple mixing model, using average shale and plankton data as end members. A significant contribution of metals from normal seawater to these sediments, such as from sulfide precipitation or scavenging of reduced species, is indicated.
Geochemical and isotopic approaches to constraining provenance of sedimentary rocks complement the information inferred from petrography. Geochemical approaches have several advantages, including applicability to both matrix-rich sandstones and shales and ability to constrain provenance age and geochemical history. Five provenance components, or terrane types, have been defined on the basis of whole-rock chemical and Nd-isotopic composition, including Old Upper Continental Crust, Recycled Sedimentary Rocks, Young Undifferentiated Arc, Young Differentiated Arc, and various Exotic Components, such as ophiolites. Among the most important geochemical characteristics that define these provenance types are Nd isotopic composition (reflecting average provenance age), europium anomalies (reflecting intracrustal igneous differentiation processes), large-ion lithophile element enrichments (provenance composition), alkali and alkaline earth depletions (weathering and alteration), Zr and Hf enrichments (heavy mineral enrichments), and high Cr abundances (ultramafic sources). Pb isotopic compositions of whole rocks and framework (quartz, feldspar) and accessory (e.g., zircon, monazite) grains constrain the age and crustal history of sediment sources. The U-Pb system may be used to date the time of crystallization of small populations and, for favorable circumstances, individual sand-sized grains of detrital quartz. The Early Proterozoic Pokegama Quartzite contains detrital quartz populations that give a Pb-Pb age of 2647 ± 1 6 Ma, consistent with detrital zircon ages and with the age of the Archean Superior Province, from which this formation is mainly derived. The initial Pb isotopic composition may be approximated by the Pb isotopic composition of leached feldspars, due to their low U/Pb and Th/Pb ratios. Pb isotopic compositions of detrital feldspars may also provide information about sedimentary provenance. Itfeldspars from the Pokegama Quartzite and Early Proterozoic Chelmsford Formation fall within the field of Archean Superior Province igneous K-feldspars. They are distinct from K-feldspars found in other potential provenance terranes, including the Penokean Orogen or, in the case of the Pokegama, the Minnesota River Valley gneisses.
Monte Carlo method was used to simulate precise and accurate critical values (with 2 to 7 decimal places) of Fisher's F test for degrees of freedom (nu(1) and nu(2)) of up to 2000 and confidence levels of 20% to 99.9% for two-sided or two-tailed test (or equivalently to 60% to 99.95% for one-sided or one-tailed test). Unlike the existing literature, we present 15 new critical value tables along with 15 additional tables of the error estimates of individual values. For the two degrees of freedom horizontal (nu(1)) as well as vertical (nu(2)) the critical values orrespond to 1(1)30(5)100(10)160(20)200(50)400(100)1000 and 6(1)30(5)100(10)160(20)200(50)400 (100)1000(200)2000, respectively, where the numbers before and after the parenthesis are the initial and final values for which critical values were simulated and the numbers in parenthesis indicate the step size how the initial value of degrees of freedom approached to the final one. Thus these critical values consist of 62x62 values for each of the eleven confidence levels. Even though a large number (3844 for each confidence level, amounting to a total of 42284 values for all confidence levels) of new values of F were simulated, values do not exist for many different degrees of freedom in the range of 1-2000. This problem of unavailable critical values was resolved by evaluating regression models based on simple polynomial functions as well as those involving log-transformation of the independent variable. New best-fit equations were thus proposed to estimate the not-tabulated critical values as well as for the estimation of probability of calculated F value. This methodology of log transformations should be useful also for other kinds of applications involving polynomial fitting. We compared these simulated results with commercial as well as freely available software. The new precise and accurate critical values were used to illustrate the application of analysis of variance (ANOVA) and Fisher's F tests to geochemical data for international geochemical reference material granite G-2 from U.S.A. We also present the methodology to statistically compare geochemical data for ultrabasic, basic and intermediate magmas from eight regions of the Eastern Alkaline Province of Mexico and U.S.A. Finally, we use these as well as the discordant outlier-free data for ultrabasic and basic rocks in multi-dimensional discrimination diagrams to explore the tectonic setting for this volcanic province, which was inferred to be mainly an extensional zone or a continental rift.
Two discriminant-function-based multidimensional major-element diagrams for the tectonic discrimination of siliciclastic sediments were recently published from a coherent statistical methodology of loge-ratio transformation and linear discriminant analysis. These diagrams were constructed based on worldwide examples of Neogene–Quaternary siliciclastic sediments from known tectonic settings. In this work, these two tectonic discrimination diagrams were first successfully tested from Holocene (<0.0117–0 Ma) beach and deep-sea sediments from the Gulf of Mexico. These diagrams were used to decipher tectonic settings of 11 case studies of the Precambrian clastic sedimentary rocks (~512–2800 Ma) from Argentina, USA, Ghana, Spain, Norway, India, China, and Australia. The test and application results obtained from these discrimination diagrams were generally consistent with the geology of the Precambrian source areas. Therefore, the two multidimensional diagrams can be considered as a useful tool for successfully discriminating the tectonic setting of older sedimentary basins, which may consist of one or more tectonic assemblages. Comparison of results of this study with the previously published tectonic discrimination diagrams is illustrated and the probable reasons for some inconsistent inferences were also discussed.
Wuliangsu Lake is located in the upper reaches of the Yellow River and its catchment is found in the Hetao Basin, one of the three largest irrigation districts in China. A 56 cm-length sediment core was collected from the south side of the lake. Geochronology radiometric methods using Cs-132 and Pb-210 were subsequently used to date the short sediment core. The concentrations of elements (Al, Fe, Ca, Mg, Na, K, Ti, Co, V, Cr, Be, Ba, Sr, Cu, Pb, Zn, Mn, Ni, and P) were studied in the solid phase at each 1-cm section. Based on correlation analysis and principal component analysis, four groups of elements were identified. The first group included total P, Cu, and Mn, which indicate anthropogenic activities such as agriculture, industry, and sewage effluents. The second group included Co, Pb and Zn that were influenced by both anthropogenic and natural factors. The third group consisted of Ca and Sr. The concentration profiles of Ca and Sr displayed a negative correlation with the remaining elements (Al, K, Fe, Mg, Be, etc.), which comprised the fourth group that were mainly terrigenous. In addition, the enrichment factors (EFs) for all elements, used as a means of identifying and quantifying human interference, was evaluated. The EFs for Cu, Mn, Pb, Zn, Co and P showed significant variation. Finally, with constrained clustering analysis of EFs for Cu, Mn, Pb, Zn, Co and P, the stages of regional environment were orderly and objectively divided. Before the 1960s, EFs for heavy metals displayed relatively constant values, suggesting a little human influence. The increasing severity of heavy metal accumulation, evidenced by enhancement of EFs for heavy metals, began to appear in the 1960s, which corresponded to local environmental development and therefore reflects strengthened human impacts. The EFs of total phosphorus and heavy metals then increased rapidly especially at the beginning of the 21st century. (C) 2013 Elsevier Ltd and INQUA. All rights reserved.
Detrital sand grains from three beaches (Tecolutla, Nautla, and Veracruz) along the western Gulf of Mexico were studied by a scanning electron microscope, to investigate the depositional environment and paleoclimate. Totally, 24 microtextures are identified; among them, 13 are grouped as mechanical origin, 5 as mechanical and/or chemical origin, and 6 as chemical origin. These microtextures are nonuniformly distributed among the three beach areas. Concoidal fractures, straight and arcuate steps at Tecolutla and Veracruz beaches indicate that the sand grains were derived from the crystalline rocks. The abundance of angular outline grains at the Nautla beach supports for short transportation probably close to the source area. The domination of rounded sand grains in the Veracruz beach reveals that the sediments were derived by the aeolian mechanism. Chattermark trials at the Veracruz beach sands are indicating a wet tropical climate. Chemical features like silica globules, silica pellicle, and trapped diatoms in the Tecolutla and Veracruz beach sands suggest a silica saturated environment. Similarly, chemical etching and solution pits are common in the Veracruz beach sands, which are probably linked to the contaminated sea water. Desiccation crack at Veracruz beach sands is an indicator of temperature changes in the beach environment. Broken benthonic foraminifera Elphidium discoidale sp. present in the Veracruz beach indicates a high-energy littoral environment.
Previous studies clearly demonstrate that the detrital fraction of central North Pacific sediment is derived almost exclusively from wind-born particles from the arid and semi-arid regions in Asia. These conclusions are based, in part, on trajectories observed for westerly wind systems and on a grainsize distribution for central North Pacific sediment which can only be explained by eolian transport. These observations have been verified by comparing the mineralogy, neodymium isotopic composition, and trace element geochemistry of the sediment with its Asian source region. However, recent geochemical investigations consistently highlight compositional differences exemplified by a MREE (middle rare earth element) depletion and a lower Th/Sc ratio in eolian material extracted from North Pacific sediment when compared to bulk China loess, the continental analog of the eolian material. These geochemical differences persist even when the bulk loess is subjected to the same extraction procedure. Here we present experiments demonstrating that these compositional differences are caused by a combination of grainsize fractionation during transport and partial dissolution of REE- and Th-bearing phosphatic phases during the extraction procedure. Two bulk loess samples from China were separated into several different grain size fractions and a split of each fraction was subjected to the extraction procedure commonly used to isolate terrigenous material from marine sediment. All extracted and unextracted sample pairs were analyzed for P, Th, Sc, Fe, La, Ce, Sm, Eu, Yb, and Lu. The amount of P removed by the extraction procedure correlates well with both the observed MREE depletion and the decrease in Th/Sc and is most pronounced in the finest grained samples. These correlations strongly suggest that the extraction procedure dissolves inorganic phosphate phases which are rich in MREEs and Th. A comparison of the compositions of the 2–3 mm loess size fractions with central North Pacific sediment shows that both of these materials are identical.
In order to study natural concentration of heavy metal in sand sediments of the Oman Sea and its relationship with composition and provenance of the deposits, the concentrations of Cd, Co, Cu, Sr, Pb, Cr, Zn, Ni, Mn and Fe were determined. Relationships between the heavy metal concentration with composition of the sediments and rocks existing in the rivers drainage basins of the area were studied. The results indicate that the Zn and Cu concentrations are closely related to biotite and muscovite contents of the sediments. The amounts of Sr, Cd and Pb change similarly to the variation of calcium carbonate content in the sand sediments. The Fe and Mn concentrations show correlations with the total amount of heavy minerals. The distribution pattern of Cr resembles the pyroxene content. The Co and Ni concentrations fluctuate similarly to the variation of the amphiboles and the intrusive igneous fragments, respectively.
The Neoproterozoic (830-815 Ma) Shuangqiaoshan (SQS) and (833-817 Ma) Xikou (XK) groups are two of a series of sedimentary sequences in the Jiangnan Orogen, which are located in the southeastern Yangtze Block, South China and witnessed the assemblage and breakup of the supercontinent Rodinia. Through a multidisciplinary approach, including petrology and geochemistry of the clastic sedimentary rocks, we reconstruct the sedimentary provenance and paleoweathering of the sedimentary basin and characterize the formation and evolution of the Jiangnan Orogen and its role in Rodinia. The SQS Group consists of texturally immature sandstones composed of unsorted and angular to subangular clastic grains dominated by lithic fragments (54-80%) (mostly chert, metasedimentary, and sedimentary grains) accompanied by variable amounts of quartz (14-40%) and feldspar (0-18%). Sandstones from the XK Group are characterized by lower quartz (5-16%) but higher feldspar (16-47%) and lithic fragments (47-78%) (mostly volcanic detritus). All samples lie along a provenance-dependent compositional trend, suggesting that hydraulic sorting and recycling of heavy minerals were insignificant. Moderate Eu/Eu* (0.6-1.0) and (LaNb)n (4.8-8.4) values and predominant Neoproterozoic euhedral detrital zircons indicate that sedimentary detritus was largely sourced from locally distributed Neoproterozoic intermediate to felsic igneous rocks. Potential sources include the ca. 930-900 Ma Pingshui plagiogranite, the ca. 930-890 Ma Shuangxiwu andesite, and the ca. 850 Ma Zhenzhushan dacite and basalt. The modeled average composition of the SQS detritus consists of 80% dacite, 10% andesite, and 10% basalt, whereas the XK detritus consists of 70% dacite, 20% andesite, and 10% basalt. The SQS and XK rocks record mild to moderate chemical weathering in their source areas. Some samples plot away from the predicated weathering trend in the A-CN-K diagram, reflecting replacement of the detrital calcic plagioclase by authigenic albite during postdepositional metasomatism. Textural and chemical immaturity, non-steady-state weathering, and signatures of immobile elements are indicative of a tectonically active setting, likely a continental arc environment, for deposition of the SQS and XK groups. The Yangtze Block is thus considered to be located in the periphery of Rodinia during ca. 833-815 Ma.
Mineralogical, textural, geochemical, and weathering characteristics of loess deposits in Golestan province of Iran suggest that they are mostly derived from felsic igneous rocks and are related to Quaternary palaeoclimate. Whole-rock analyses indicate heavy minerals such as zircon, tourmaline and phyllosillicate minerals (e.g. muscovite, chlorite, illite) exert a significant control on the chemical composition. The loess samples display uniform chemical composition, indicative of similar alteration history. Chemical index of alteration suggests a weak to moderate degree of weathering in a felsic source area. Scanning electron micrographs of quartz grains reveal abundant silt-sized quartz particles, a result of glacial grinding during the Late Pleistocene in Central Asia. Subsequently, these silt particles were transported from Central Asia to their depositional site by wind and paraglacial processes. Local topography of northeast Iran (Alborz Mountains) acted as a major barrier, entrapping the airborne particles on the plains of Golestan province. Copyright © 2012 John Wiley & Sons, Ltd.
Concentrations of Al, Fe, Mn and rare earth elements (REE) were measured in 122 samples of suspended particulate matter (SPM) and 70 surficial sediments from the Zuari estuary and the adjacent shelf to understand their distribution, provenance and estuarine processes. Concentrations of SPM were low in the upper estuary, increased seaward with high values in the lower estuary and then decreased at stations in the bay in all seasons. The distributions of mean ΣREE, Al and Fe along transect imitate each other and resemble inverted bowl-shaped pattern, with high and identical values at the lower estuary. The mean ΣREE, Al and Fe of sediment along transect showed two peak high values, one in the upper estuary and another in the bay amid low values corresponding to the lower estuary. The variations in the mean ratio of ΣREESPM/ΣREESED along transect resembled that of mean SPM at each station. The ΣREE of sediments in shallow shelf were close to that of the bay and, decreased seaward with increasing depth. PAAS-normalized REE patterns of every SPM/sediment sample revealed MREE- and HREE-enrichment with positive Ce and Eu anomalies. Ce/*Ce was inversely correlated with Eu/*Eu and salinity and, directly correlated with Mn concentrations. The results indicate that the REE of SPM/sediment is dominated by Fe, Mn ore dust and, its distribution along transect is controlled by the estuarine turbidity maximum (ETM). The ETM and seasonal circulation in the estuary controlled mixing and advective transport of particulates to the shelf during monsoon and, into the estuary during dry season. This study indicates sediment contribution to the shelf from tropical, minor rivers that are controlled by hydrodynamic conditions in the estuaries and should not be underestimated.
The Oligocene–Miocene Zivah Formation is characterised by alternation of sandstone, conglomerate, and
shale that were deposited in a fluvial dominated delta on the shelf of Eastern Paratethys. Petrographically,
the sandstones mostly include volcanic rock fragment, plagioclase and minor amounts of K feldspar,
quartz, pyroxene, opaque minerals and biotite. Heavy mineral analysis and geochemical analysis of detrital
clinopyroxene and apatite have been used to determine the provenance and tectonic setting of the
Zivah Formation sandstones, in three outcrop sections from the Moghan region in NW Iran. The heavy
mineral assemblage of the Zivah Formation sandstones is dominated by clinopyroxene and apatite with
minor amounts of amphibole, zircon, garnet and epidote. The abundance of a mafic heavy-mineral suite
such as clinopyroxene relative to metamorphic and felsic heavy mineral suites such as epidote, garnet
and zircon indicates that deposition of Zivah Formation is more likely to have occurred at a convergent
plate boundary, and sourced by a volcanic arc.
The geochemical composition of detrital clinopyroxene grains from the Zivah Formation indicates that
these detrital grains probably crystallized from calk-alkaline magmas. They also show an orogenic tectonic
setting at the time of deposition of the Zivah Formation. Compositions of detrital apatites of the
Zivah Formation are also consistent with the widespread distribution of mafic/intermediate volcanic
rocks of both alkaline and calc-alkaline composition. All of these data as well as the composition of volcanic
rocks of the southern parts of the Moghan Basin is consistent with the derivation of these sediments
from areas with calc-alkaline volcanic rocks like Talysh and Arasbaran (Qharadagh)–Lesser Caucasus.
The Age Calibration Program, CALIB, published in 1986 and amended in 1987 is here amended anew. The program is available on a floppy disk in this publication. The new calibration data set covers nearly 22 000 Cal yr (approx 18 400 14C yr) and represents a 6 yr timescale calibration effort by several laboratories. The data are described and the program outlined. -K.Clayton
The Late Carboniferous palaeo-tectonic setting of the West Junggar region is comprised of arcs alternating with basins. Geochemical analysis of the sedimentary rocks associated with these arc-related basins was conducted to better constrain the provenance and tectonic setting.Major and trace element geochemistry data of Late Carboniferous mudstones and sandstones in the Hala-alat Mountains suggest that these sedimentary rocks and their source areas are characterized by the following four features: (1) sediments experienced a simple recycling process; (2) a low degree weathering conditions in the source areas; (3) compositional immature of the sedimentary rocks; (4) dominated by intermediate to felsic provenance, with a few intermediate to mafic sediments. Integrated with the palaeo-flow data and previous authors’ works, a fore-arc basin model is proposed for the tectonic setting of the sedimentary rocks. The Sawur arc is the primary provenance and supplies the major intermediate to felsic detrital fragments. The Bozchekul-Chingiz arc and Kexia oceanic island arc are the other two secondary sources.
We collected riverbed and suspended sediments in the upper Yangtze River (the headwaters, Jinsha, Yalong, Minjiang and Daduhe Rivers) flowing on the eastern Tibetan Plateau and analyzed their trace element concentrations. The results show that: (1) selected fractionations of different elements in the riverbed and suspended sediments indicate the influence of sedimentary sorting. Higher concentrations of transition elements V, Ti, Ni, Co, Cr, and Sc in the riverbed sediments of Jinsha River catchment from Shigu to Panzhihua imply enrichment of mafic minerals owing to high density. Enrichments of high field strength elements Zr, Hf, Nb and Ta in the riverbed sediments relative to the suspended sediments reflect the characteristics of heavy minerals accumulation into coarse-grained fraction. The lower Eu/Eu* ratios in the riverbed sediments can also be attributed to the enrichment of heavy minerals such as monazite and allanite in the processes of transportation and sorting; (2) the upper Yangtze riverbed and suspended sediments show a mixing trend of felsic and mafic endmembers. Granitoids are important source rocks for the sediments in the source area and the Permian Emeishan continental basalts dominate the geochemistry of the sediments in the Jinsha River catchment from Shigu to Panzhihua. Moreover, industrial activities in the Panzhihua City may have an important contribution to the upper Yangtze River sediments.
The determination of rare earth elements (REE) in geological samples has become increasingly important in recent years as their physical and chemical characteristics have been widely studied. Inductively coupled plasma mass spectrometry (ICP-MS) is an ideal analytical technique for the determination of this elemental group, with good sensitivity and determination limits while offering a range of modes for sample introduction. If REE are separated from their matrix and pre-concentrated, using for example cation-exchange procedures, determination limits of better than 1 ng g–1 can be achieved.
Anaerobic oxidation of methane in anoxic sediments at cold seeps often leads to formation of authigenic carbonates close to the seafloor along continental margins. Recent work, however, indicated that the redox conditions in sediments may vary to some degree during seepage activity. In order to shed new light on the extent of this variability, authigenic carbonates from Alaminos Canyon lease block 645 of the northern Gulf of Mexico have been characterized by means of inorganic and organic geochemistry. The carbonates were collected from seep deposits representing various seafloor morphologies, including extensive pavements, mounds, fractured carbonate slabs surrounded by dense bivalve shells, and vestimentiferan tubeworm colonies. The deposits almost entirely consist of aragonite. The δ18O values of aragonite vary from + 2.6 to + 5.8‰ V-PDB, suggesting precipitation in slight disequilibrium with the surrounding pore fluids. The δ13C values of aragonite between − 33.9 and − 20.4‰ V-PDB agree with variable amounts of carbonate derived from oxidation of thermogenic methane and crude oil. Methane was primarily oxidized in an anaerobic process as revealed by the presence of 13C-depleted molecular fossils of methane-oxidizing archaea (δ13C values as negative as − 118‰) and sulfate-reducing bacteria (δ13C values as negative as − 97‰), the syntrophic partners in the anaerobic oxidation of methane. The observed inventories of molecular fossils in the authigenic carbonates mirror those of known consortia of anaerobic methane oxidizing archaea (ANME) and sulfate-reducing bacteria, namely the ANME-2/Desulfosarcina/Desulfococcus (DSS) and ANME-3/Desulfobulbus (DBB) consortia. In contrast, the same carbonates exhibit shale-normalized rare earth elements patterns that all display real negative Ce anomalies (Ce/Ce* < 0.78), suggesting that at least temporarily oxic conditions prevailed. The episodic occurrence of oxic conditions is confirmed by the presence of molecular fossils of aerobic methanotrophic bacteria, including 4α-methylcholesta-8(14),24-dien-3β-ol, and two bacteriohopanepolyols, aminotetrol and aminotriol. The δ13C values of the biomarkers of aerobic methanotrophs are as negative as − 58‰ and are consequently less 13C-depleted than the molecular fossils of the prokaryotes performing anaerobic oxidation of methane, a pattern in accord with culture experiments. Overall, our results suggest that redox conditions at cold seeps are variable. This variability probably reflects changes in seepage flux. The combination of an inorganic and an organic geochemical approach used here is promising to better assess the variability and diversity of past fluid and gas expulsion at seeps.
The Portscatho Formation, within the allochthonous unit of the Middle and Upper Devonian Gramscatho Group, is a thick sequence of deep-water sandstones and interbedded slates deposited by southerly-derived turbidity currents into the Gramscatho basin of S Cornwall. Throughout an approximately 3.5 km thick sequence, the Portscatho Formation is petrographically and chemically coherent, except that the upper section shows a higher proportion of metamorphic clasts, high, but variable Cr, and low, uniform Zr abundances. Complementary framework mode and bulk geochemistry indicate that the sandstones were derived from a dissected continental magmatic arc of predominantly acidic composition, similar to average upper continental crust, but with an admixture of minor intermediate/basic material. Flysch deposition took place in a fore-arc setting.-from Authors
Grenville-age granulite facies rocks in southern, central, and northeastern Mexico have distinctive geologic features that suggest a common tectonic evolution. The similarities include northwest-trending structural grain from Oaxaca to Tamaulipas, massif-type anorthosite-charnockite complexes, protoliths rich in sedimentary rocks of shallow-marine platform or continental rift-related facies devoid of calc-alkaline volcanic rocks, common metamorphism under granulite facies conditions, U-Pb zircon ages of about 1.0 Ga., and an apparently common history of uplift and cooling. Altogether, this evidence strongly suggests a coherent geologic history for this block. Paleontologic data from the overlying sedimentary sequences indicate that Oaxaquia was not part of Laurentia during most of the Paleozoic. This precludes emplacement of Oaxaquia in its present position by simple lateral displacement from the southern United States as well as a Taconic time of emplacement. Oaxaquia was probably emplaced to its present position during late Paleozoic time. The concept of a Mesoproterozoic ``Oaxaquia'' microcontinent extending for about 1000 km in Mexico needs to be considered in the reconstruction of the Grenville orogen as a whole and for the Paleozoic tectonic interactions between eastern Laurentia and western Gondwana.