Geochemical Parameters Research Articles

Living benthic foraminifera from Almirante Câmara and Grussaí canyons and adjacent slope areas (Campos Basin, Southwest Atlantic): Response to trophic and hydrodynamic conditions

Living (rose Bengal stained) benthic foraminiferal faunas, grain size, geochemical parameters (total organic matter, chlorophyll-a, pheophytin-a, molecular markers, and vertical flux of particulate organic matter) were investigated in 14 stations in two submarine canyons Almirante Câmara and Grussaí considered mature and immature, respectively, and on the adjacent continental slope, from 400 to 1300 m water depth, in the southwestern Atlantic Ocean. Samples were retrieved during two campaigns, in the austral winter 2008 and the austral summer 2009. The density, richness, and species composition of the benthic foraminiferal fauna decrease with depth in the canyons and along the adjacent slope transects, reflecting the availability and quality of sedimentary organic matter. Both canyons act as traps of labile organic matter, mainly towards the head of the Almirante Câmara canyon, promoting high specimen density, species richness, and the occurrence of species indicative of pulses of phytodetritus (e.g., Bolivina pacifica, Nonionella opima, and Nonionella stella). Towards the deeper regions of Almirante Câmara canyon and in the adjacent slope area, the lower abundance, diversity, and richness reflect more oligotrophic conditions and an adverse environment in terms of easily metabolizable organic matter. This multiproxy study demonstrates that the canyons in the southeastern Brazilian continental margin play an important role in accumulating organic matter.

Pore systems and their correlation with oil enrichment in various lithofacies of saline lacustrine shale strata

The potential of China's saline lacustrine shale oil resources is enormous. Currently, the storage space of saline lacustrine shale oil remains unclear, posing significant challenges for commercial development. In this study, we selected the samples from the typical saline lacustrine shale strata of the Lucaogou Formation, Jimusar Sag, Junggar Basin and investigated the pore systems and their relationship with oil content S1 of different lithofacies. The pore structures were quantified by using the combination of low-pressure N2 adsorption and mercury intrusion. TOC assessment, rock pyrolysis, and XRD were utilized for characterizing the organic geochemical and mineralogical parameters. The results showed that the organic matter comprising type III mainly appears in the clay-enriched lithofacies (types I2, II1 and III2), while the organic matter types I, II1 and II2 can be found in other lithofacies. Regarding the nine lithofacies, siltstone has the highest oil content S1, followed by the felsic-enriched lithofacies (types III3 and III1). The enrichment of oil in siltstone, carbonate rocks, and felsic-enriched lithofacies (types III3 and III1) is primarily attributed to macropores. Conversely, in clay-enriched lithofacies (types I2, II1 and III2), the oil content S1 is attributed to both the mesopore fractal dimensions (D1 and D2) and the TOC content. Moreover, the higher the complexity of the mesoporous structure (D2) and the larger the macropore surface area in clayey carbonate felsic shale (II3), the greater the oil content S1. It is further observed that, macropores with size range between approximately 60 nm and 3000 nm are abundant in siltstone and felsic mineral-enriched lithofacies (i.e., carbonate felsic shale III3 and felsic shale III1). Furthermore, the siltstone shows the widest oil-rich macropore size range (range of 70–1000 nm), followed by felsic shale (III1) (range of 150–1000) and carbonate felsic shale (III3) (range of 100–110 nm). Siltstones and felsic-enriched shales are optimal for exploiting saline lacustrine shale deposits.

Microbially mediated sulfur oxidation coupled with arsenate reduction within oligotrophic mining-impacted habitats.

Arsenate [As(V)] reduction is a major cause of arsenic (As) release from soils, which threatens more than 200 million people worldwide. While heterotrophic As(V) reduction has been investigated extensively, the mechanism of chemolithotrophic As(V) reduction is less studied. Since As is frequently found as a sulfidic mineral in the environment, microbial mediated sulfur oxidation coupled to As(V) reduction (SOAsR), a chemolithotrophic process, may be more favorable in sites impacted by oligotrophic mining (e.g. As-contaminated mine tailings). While SOAsR is thermodynamically favorable, knowledge regarding this biogeochemical process is still limited. The current study suggested that SOAsR was a more prevalent process than heterotrophic As(V) reduction in oligotrophic sites, such as mine tailings. The water-soluble reduced sulfur concentration was predicted to be one of the major geochemical parameters that had a substantial impact on SOAsR potentials. A combination of DNA stable isotope probing and metagenome binning revealed members of the genera Sulfuricella, Ramlibacter, and Sulfuritalea as sulfur oxidizing As(V)-reducing bacteria (SOAsRB) in mine tailings. Genome mining further expanded the list of potential SOAsRB to diverse phylogenetic lineages such as members associated with Burkholderiaceae and Rhodocyclaceae. Metagenome analysis using multiple tailing samples across southern China confirmed that the putative SOAsRB were the dominant As(V) reducers in these sites. Together, the current findings expand our knowledge regarding the chemolithotrophic As(V) reduction process, which may be harnessed to facilitate future remediation practices in mine tailings.

Constraining the oxygen requirements for modern microbial eukaryote diversity.

Eukaryotes originated prior to the establishment of modern marine oxygen (O2) levels. According to the body fossil and lipid biomarker records, modern (crown) microbial eukaryote lineages began diversifying in the ocean no later than ~800 Ma. While it has long been predicted that increasing atmospheric O2 levels facilitated the early diversification of microbial eukaryotes, the O2 levels needed to permit this diversification remain unconstrained. Using time-resolved geochemical parameter and gene sequence information from a model marine oxygen minimum zone spanning a range of dissolved O2 levels and redox states, we show that microbial eukaryote taxonomic richness and phylogenetic diversity remain the same until O2 declines to around 2 to 3% of present atmospheric levels, below which these diversity metrics become significantly reduced. Our observations suggest that increasing O2 would have only directly promoted early crown-eukaryote diversity if atmospheric O2 was below 2 to 3% of modern levels when crown-eukaryotes originated and then later met or surpassed this range as crown-eukaryotes diversified. If atmospheric O2 was already consistently at or above 2 to 3% of modern levels by the time that crown-eukaryotes originated, then the subsequent diversification of modern microbial eukaryotes was not directly driven by atmospheric oxygenation.

Rare Earth Element Characteristics of Shales from Wufeng-Longmaxi Formations in Deep-Buried Areas of the Northern Sichuan Basin, Southern China: Implications for Provenance, Depositional Conditions, and Paleoclimate.

To explore the sedimentary environment and the background of the source area of organic-rich shales in the Wufeng-Longmaxi Formations in the northern Sichuan Basin, samples from Well XX1 in the area were subjected to geochemical testing and analysis of organic carbon content, trace elements, and rare earth elements (REEs). The results show that the total content of REE (ΣREE) of the shale in the Wufeng-Longmaxi Formations varied from 183.08 to 234.66 μg/g with an average of 212.59 μg/g, which is significantly higher than the content of the North American shale composite. The fluctuations in the total amount of REEs in the shale of the Wufeng-Longmaxi Formations reflect certain differences in the geochemical conditions of the Upper Ordovician-Lower Silurian shale. The ratios of LREE/HREE, LaN/YbN, LaN/SmN, and GdN/YbN and the distribution of normalized REE patterns indicate that the source supply or sedimentary structural background may have changed during the shale deposition period of the Wufeng Formation, while the shale deposition period of the Longmaxi Formation may be in a relatively stable source supply and sedimentary structural background. There is no significant correlation between δCe and ΣREE, and the obviously negative Eu abnormity and the weak Ce abnormity indicated that the diagenesis had a limited impact on REEs. Geochemical parameters such as values of ∑REE, δEu, δCe, Ceanom, and LaN/YbN indicate that the climate during the Wufeng-Longmaxi Formation shale deposition period was warm and humid, and the shale was deposited mainly in the suboxic-anoxic water environment. The deposition rate was stable and slow, providing good conditions for the production and preservation of organic matter. At the same time, this shows that the water environment of Wufeng Formation is more anoxic and reductive than that of Longmaxi Formation, which is more conducive to the preservation of organic matter. The correlation between ΣREE and the content of Sc, Ti, Cr, Co, Zr, Nb, Th, Hf, Ta, and other elements indicates that the sources of REEs in the shale of Wufeng and Longmaxi Formations in the study area are similar, mainly terrestrial clasts, and some may come from the sea. The REE distribution pattern shows that the shale provenance of the Wufeng-Longmaxi Formations mainly comes from the upper crust. The La/Yb-∑REE diagram shows that the sediment-parent rocks are mainly early sedimentary rocks and these sediment-parent rocks have granite provenance characteristics. Compared to La/Yb, LREE/HREE, LaN/YbN, and other REE characteristic parameters, it is inferred that the tectonic background of the study area is dominated by passive continental margin.

Geochemistry of Crude Oils from the Bazhenov Horizon (West Siberia)

Abstract —The Bazhenov horizon is the main source rock stratum of the West Siberian petroleum province, which possesses significant resources of hard-to-recover hydrocarbons, making it a unique exploration target. The study summarizes geochemical data on crude oils (39 samples) collected from pools within the Bazhenov and Tutleima formations. A comparative analysis of the carbon isotope composition and geochemical parameters calculated from the composition of the identified saturated and aromatic compounds (pristane/phytane, C29/C27 steranes, C35/C34 homohopanes, tricyclane index, relative concentrations of dibenzothiophenes) confirm a common aquatic genotype of the studied oils and their genetic affinity to the organic matter of the same age. At the same time, significant variations in the main physical and chemical characteristics of the studied Bazhenov oils may be caused their fractionation during migration processes.

Organic Geochemical Evaluation of the Black Shale interbeds Within the Lithological Succession of the Al Aziziyah Formation, NW Libya

The samples under investigation represent the black shale in interbeds within the Al Aziziyah Formation, located in the NW part of Libya and were analysed using geochemical techniques method and a variety of organic geochemical parameters. The aim of this study is to assess the type of organic matter, thermal maturity, and environment of deposition, based on biomarker distributions and Rock-Eval pyrolysis. The Gas chromatograms of the saturated hydrocarbon fractions of the study samples display a smooth high-end member distribution of the n- n-alkanes extending beyond nC34. The sample displayed evidence of biodegradation as suggested by the presence of the loss of some of the lower molecular weight n-alkanes. The predominance of high molecular weight n-alkane in the study sample suggests a significant input of higher land plant organic matter into these sediments. Geochemical (Rock-Eval, Tmax. values ranging from 416-4390C typical of immature range). Another related feature of these rocks extracted is the presence of a high relative abundance of gammacerane, indicating an anoxic marine hypersaline source depositional environment. The relatively high abundance of common land-plant-derived biomarkers, such as oleananes, is a clear indication of major terrigenous input to the source of these extractable organic matters. The high abundance of C24 tetracyclic terpanes could be associated with higher land-plant, algae, or microbial sources, thereby suggesting a mixed source input. TOC valued < 0.5 wt.%, in the analyzed samples can be considered as a poor source rock generative potential. Based on this study, it can be said that the interbedded shales of the Al Aziziyah Formation seem to have received substantial amounts of land-derived organic matter that has been transported into an open marine subtidal depositional setting had prevailed and was deposited in a photosynthetic-organisms dominated environment (thereby suggesting a mixed source input).

Reactive transport modelling of tailings hydrogeochemistry under a composite cover

Quantitative forecasts of acid mine drainage (AMD) production are important for remediation planning. Reactive transport simulations corresponding to a detailed sampling location at a covered legacy tailings impoundment in northern Ontario, Canada, were conducted to quantitatively assess the predominant hydrogeochemical reactions. The simulations span the period from the end of tailings deposition (circa 1970) to early 2020, 12 years after remediation by a five-layer composite cover. The conceptual model of uncovered tailings weathering and subsequent geochemistry of the covered tailings system was implemented in 1D using the multi-component reactive transport code MIN3P. Transient monthly infiltration, post-cover boundary condition changes, and a dynamic temperature regime were incorporated. The shrinking core model, including parallel O2(aq) and Fe3+ oxidation reactions for the waste rock in the cover and the underlying tailings, was implemented to simulate the oxidation of As-bearing pyrite, chalcopyrite, and sphalerite. Primary carbonate and aluminosilicate host minerals promoted acid-neutralization reactions. Precipitation of secondary phases and sorption/desorption of Cu, Zn, and arsenite were incorporated into the model. The overall agreement between key simulated and field-measured post-cover aqueous geochemical parameters suggests that the conceptual model captured the primary hydrogeochemical processes in the covered tailings. A lack of reliable data on initial tailings mineralogy and pre-cover hydrogeochemistry increased simulation uncertainty. Simulated reaction rates indicate that where intact, the cover decreased sulfide oxidation rates by both O2(aq) and Fe3+ and improved pore-water quality over time. Simulation results indicate that elevated concentrations of Zn and As are likely to persist in the tailings regardless of cover performance, whereas concentrations of Cu and Al are the parameters most sensitive to cover effectiveness.

Late Devonian gabbro-dolerite-monzonite-granodiorite complex in the basin of the Severnaya Sosva River (Northern Urals): New data on composition, age, and geochemistry

Subject research. Hypabyssal intrusive gabbro-dolerite-monzonite-granodiorite complex from the northern part of the Tagil megazone. Material and methods. Intrusive rocks situated among the Devonian strata of the East Tagil structural-formation zone at the North Urals were studied. Petrographic studies, silicate (XRF) analyses and determination of rare elements by ICP-MS method, study of U-Pb isotopic systematics in zircons from monzonites and quartz diorites, processing and interpretation of the data obtained using discrimination and spider diagrams, as well as indicator geochemical parameters were carried out. Results. It was found that the age and structural position of the studied rocks can correlate with the well-known Late Devonian Ivdel complex, differing from the typical composition of the latter by a significant content of rocks of medium and moderately acidic composition. The geochemical parameters demonstrate values characteristic of both suprasubduction (island-arc) and oceanic volcanites, which may indicate the formation of rocks of the studied complex in an environment of termination of the subduction process and separation of the subducted slab. The presence of significant volumes of diorites and monsodiorites is probably stimulated by contamination of crustal matter by the mantle melts. Conclusions. The obtained geological, petrographic, isotope-geochronological, and geochemical data do not contradict the model of separation of the subducted slab and the arrival of mantle highly depleted matter (close to oceanic basalts N-MORB) after the termination of the subduction process.

Accurate prediction of salinity in Chott Djerid shallow aquifers, southern Tunisia: Machine learning model development

ABSTRACT A backpropagation neural network (BPNN) was used to predict salinity levels in the Chott Djerid shallow aquifers. A set of 51 water samples was collected from the Chott Djerid plio-quaternary aquifers for geochemical analysis. Major elements and nitrates were ascertained by using high performance liquid-ion chromatography. The BPNN was trained on a dataset of 51 water samples with variable geochemical parameters. Our results indicated a high accuracy when applying a model with 13 inputs, 1 hidden layer (6 neurons) and 1 output (TDS in mg/L). The collected data were split into 80% for training the model and 20% for testing and cross validation. The result was evaluated using various statistical performance criteria (i.e., MSE, RMSE, R2, SSE, SD, Accuracy, Sensitivity, specificity, and Kappa test); it showed that BPNN model properly predicted the salinity of the Chott Djerid plio-quaterny water samples (RMSE = 0.0402; R2 = 0.9721 and SSE = 0.0146). The BPNN was able to capture the complex relationship between salinity levels and other aquifer parameters. The potential application of BPNNs for predicting salinity levels in shallow aquifers was crucial in supporting decision-makers for water management; it provided valuable insights into the salinity fluctuation of the studied shallow aquifers.

Geochemical modelling of heavy metal deposition in a geothermal heat exchanger

Heavy metal deposition and corrosion of carbon and low alloy steels exposed to geothermal two-phase fluids and brine solutions under acidic fluid conditions have been widely reported. Similarly, near neutral conditions can result in the precipitation of arsenic and antimony scales that can limit heat exchange. Geochemistry modelling has been undertaken to explain observed deposition and scaling in a two-phase geothermal fluid heat exchanger with a view to predicting the risk of heavy metal deposition and corrosion and heavy metal scaling in geothermal process fluids for new and existing energy facilities. Understanding of the geochemical parameters that control deposition, scaling and corrosion will allow the prediction of the risk of heavy metal deposition and scaling at the design stage for geothermal energy plants and assist in the selection of materials and processes that will give reliable long-term performance. The developed models have application in other industries for prediction of risk of scaling and corrosion and for process development support for example for the gettering of heavy metals from contaminated liquids and soils.

Applied geochemistry for the discrimination between mafic and ultramafic rocks in Cu-Ni-PGE-bearing layered complexes: A case study at the la Jovita-Las Águilas belt, Sierra Grande de San Luis, Argentina

The Virorco intrusive body is comprised in La Jovita-Las Águilas mafic-ultramafic belt, Sierra Grande de San Luis, Argentina. The ultramafic rocks of this belt carry a base metal sulphide mineralization and platinum group minerals. Macroscopic description of mafic and ultramafic rocks, done by the mining exploration companies, can not differentiate the mineral percentages. Therefore, considering the geochemical composition of the already classified mafic-ultramafic rocks of surface samples from the mentioned belt, we established compositional ranges of geochemical parameters (MgO, Al2O3, Na2O, Sr and Cr) for both mafic and ultramafic rocks. Linking the geochemical data of drill cores made by Castillian Resources Corp. company over the Virorco body, with the mentioned ranges, it was possible to discriminate between mafic and ultramafic rocks present in such drill cores. This provides a useful prospecting tool to identify the mafic and ultramafic units that carry the mineralization and to correlate mineralized units from the different drill cores. This method can be applied, not only on the bodies of the mentioned belt, but in other similar deposits elsewhere. The methodology proposed in the present contribution was validated by the Machine Learning algorithm Random Forrest with a 91% success rate.

Assessment of Groundwater Quality in Owerri and Its Environments, Southeast Nigeria

Physico-Chemical and bacteriological characteristics of eleven boreholes located within Owerri city were examined. The bacteriological analyses were carried out using the method of inoculation and incubation of specimens and counted on colonies. Titration method was used to determine chlorides and nitrates while Cu2+, Zn2+ and Mn2+ used atomic absorption spectroscopy (AAS). Iron concentration was read off using benzylideneacetone (BDA) Lovibondcolour comparator while the total dissolved solids were determined gravimetrically. The water is usually clear at average temperature of 27˚C. The bacteriological parameters are within the acceptable World Health Organization (WHO) standard and safe for human consumption. The pH is 6.0 -7.5, total dissolved solids vary from 12.4mg/l to 49.4mg/l. The anions of chloride and nitrate are 67mg/L to 125mg/L and 0.003 mg/L to 23.1 mg/L respectively. Concentrations of cations include iron; 1.86mg/l, copper; 1.2mg/l, zinc; 2.1mg/l and manganese; 0.05mg/l. The results show that the groundwater within the city is suitable for drinking and other uses compared to the WHO standard. The environmental conditions of the borehole locations as well as the total drill depth should be emphasized. Government monitoring agency should ensure adequate drill depth to at least 200ft in the south- western area and north- eastern areas from 250ft to 300ft as this may reduce the injurious variations in the geochemical parameters in some boreholes.

Methane diffusion affects characteristics of benthic communities in and around microbial mat-covered sediments in the northeastern Japan sea

We investigated relationships between features of benthic macrofaunal communities and geochemical parameters in and around microbial mat-covered sediments associated with a methane seepage on Sakata Knoll in the eastern Japan Sea. A depression on top of the knoll corresponds to a gas-hydrate-bearing area with seepage of methane-rich fluid, and microbial mats cover the seafloor sediments. Sediment cores were collected at three sites for this study: one within a microbial mat, a second a few meters outside of the microbial mat, and a third from a reference site outside the gas-hydrate-bearing areas. Morphological analysis showed that the site inside the microbial mat had higher macrofaunal density and biomass compared with the other sites. 18S rRNA gene analysis showed that annelids were dominant in the surface sediment inside the microbial mat with the possible occurrence of microbial anaerobic oxidation of methane (AOM), whereas in the surface sediments outside the microbial mat and at the reference site the predominant species belonged to phylum Cercozoa. Morphological analysis also showed that the surface sediment inside the microbial mat noticeably favored annelids, with dorvilleid Ophryotrocha sp. and ampharetid Neosabellides sp. identified as major constituents. Statistical analysis showed that sulfidic sediment conditions with concentrations of H2S up to 121 μM resulting from AOM likely resulted in the predominance of annelids with tolerance to sulfide. Both the 18S rRNA genes and macrofaunal characteristics showed that benthic biodiversity among the three sites was greatest outside the microbial mat. The site outside the microbial mat may represent geochemical transition conditions, including a lower rate of upward methane gas-flow compared with the site inside the microbial mat. The high biodiversity there might result from the presence of species specifically suited to the transition zone as well as species also found in photosynthesis-based communities of the background environment.

Mercury sequestration pathways under varying depositional conditions during Early Jurassic (Pliensbachian and Toarcian) Karoo-Ferrar volcanism

Major extinction events appear coincident with the emplacement of large igneous provinces (LIPs) throughout Earth's past, but the cause-and-effect relationship is often poorly understood due to challenges in the stratigraphical correlation between LIP occurrence and sedimentary archives. Large igneous provinces are thought to have released large amounts of greenhouse gasses and toxic compounds (including mercury) into the global ocean-atmosphere system, leading to major climatic and environmental perturbations and ecosystem deterioration. In recent years, the analyses of bulk sedimentary mercury (Hg) concentrations have increasingly been used to assess the temporal occurrence and geographic reach of LIPs, as observed through elevated Hg concentrations in sedimentary archives which otherwise show no direct evidence of volcanism at those times.Mercury can be sequestered into sediments in different ways, but dominant Hg sequestration pathways can vary through space and time depending on the depositional environment and changes therein, which may disguise changes in global Hg fluxes into Earth's surficial environments, significantly complicating the interpretation of sedimentary Hg-records. Here, we statistically analyse sedimentary geochemical records from three distinctly different depositional environments that occurred during the Toarcian Oceanic Anoxic Event (T-OAE, at ∼183 Ma, and coincident with Karoo-Ferrar LIP volcanism), and assess the temporal and spatial variability in dominant Hg sequestration pathways during LIP volcanism.The geochemical data show significantly different affinities of mercury with assessed sedimentary geochemical parameters in each of the studied successions. Principal component analyses (PCA) of sedimentary geochemical data (including Hg), from the restricted, anoxic-euxinic Cleveland Basin (Yorkshire, UK) show that Hg covaries mostly with organic-sulphide-associated elements and to a lesser extent with the redox-sensitive elements, as opposed to the semi-restricted, sub-oxic Cardigan Bay Basin (Wales, UK) and the well-connected, oxygenated Subbetic Basin (South Iberian Palaeomargin, SE Spain), where Hg covaries dominantly with the redox-sensitive elements and secondarily with detrital elements. These findings show that mineral phases and materials other than organic matter need to be considered as dominant Hg carriers in non-anoxic depositional settings. Furthermore, observed differences between the studied sites regarding the dominant Hg-sequestration processes, suggest temporal and spatial variance in Hg drawdown fluxes, and possibly local marine residence times.

Increased sediment connectivity between deltas and deep-water fans in closed lake basins: A case study from Bozhong Sag, Bohai Bay Basin, China

The connection between deltaic clinothem growth and the formation of down-dip deep-water systems on continental margins has been extensively discussed as a crucial component of sequence stratigraphic theory. However, in lacustrine settings, the growth of deltaic clinothems and outlying deep-water fans remains comparatively poorly understood. In the southwestern Bozhong Sag, Bohai Bay Basin, China, both lacustrine deltas and outlying sub-lacustrine fans were developed during the Oligocene, providing an opportunity to investigate the connection between lacustrine deltaic clinothem growth and the formation of outlying sub-lacustrine fans in deep-lacustrine systems. We employ 3D seismic data, well data, core data, and sandstone grainsize data to analyze the stacking patterns and internal architectures of these two sedimentary systems in the lower and upper successions of our study interval, SQEd2L. In addition, elemental geochemical parameters were utilized to reveal the paleoclimatic signature of the different stratigraphic successions. Our results suggest that there are two main types of deltaic clinothem stacking patterns in the lower and upper successions of SQEd2L, respectively: (1) in the lower succession, progradational to aggradational stacking patterns have a flat to steeply rising rollover trajectory, and (2) in the upper succession, aggradational to progradational and degradational stacking patterns have a slightly rising to flat and slightly falling trajectory. Meanwhile, the sub-lacustrine fans with straight channels and thick lobe complexes are coupled with progradational and aggradational (PA) deltaic clinothems in the lower succession. In the upper succession, small-scale sub-lacustrine fans with sinuous channels and thin lobe complexes are coupled with aggradational to progradational and degradational (APD) deltaic clinothems. The sediment connectivity between lacustrine deltas and sub-lacustrine fans stands in stark contrast to their counterparts in marine basins (such as marine APD clinothems coupled with large-scale deep-water fans, while marine PA clinothems rarely produce deep-water fans). In addition, two contrasting paleoclimatic stages have been identified in SQEd2L, namely the earlier humid stage in the lower succession and the later semiarid climatic stage in the upper succession. A comprehensive analysis of the differences between lacustrine and marine basins indicates that climatic variations play a pivotal role in deep-lacustrine deposition. Consequently, a climate-cycle-driven, sediment-supply-dominated sedimentary model of delta-to-fan sediment connectivity is proposed that incorporates the efficiency of terrigenous sediment dispersal into deep-lacustrine floors and the architecture of sub-lacustrine fans. The findings of this study further refine the implementation of the sequence stratigraphy paradigm and enhance the understanding of delta-to-fan sediment connectivity in deep-lacustrine depositional systems.

Geochemical prerequisites for the formation of oil and gas accumulation zones in the South Turgay basin, Kazakhstan

This study predicts favorable oil and gas source-rock formation conditions in the Aryskum Depression of the South Turgay Basin, Kazakhstan. This study assesses the thermal maturity and characteristics of organic matter by determining its environmental conditions using data from geochemical analysis of core (pyrolysis) and oil (biomarkers and carbon isotopic compositions) samples. According to the geochemical parameters obtained by pyrolysis, the oil generation potential of the original rocks of most studied samples varies from poor to rich. The facies–genetic organic matter is predominantly humic and less frequently humus–sapropel, indicating organic matter accumulation in the studied samples were under moderately reducing conditions (kerogen III and II types) and coastal–marine environments (kerogen type I). The carbon isotopic compositions of oils derived from the Jurassic deposits of the Aryskum Depression also indicate the sapropelic and mixed humic–sapropelic type of organic matter (kerogen II and I). Biomarker analysis of oils indicates original organic matter formation in an anoxic environment.

GROUND WATER QUALITY AND ITS IMPACT ON HUMAN HEALTH IN DUNGARPUR DISTRICT OF RAJASTHAN, INDIA

Abstract. Dungarpur, one of the most backward districts of India, is a predominantly tribal region of Rajasthan state. Ground water is the major source of drinking water in the region. High concentrations of Fluoride (F) and Iron (Fe) have been reported in the region which poses high risk of rampant water-borne diseases. This study evaluates the ground water quality for drinking purpose in terms of 10 hydro-geochemical and two biological parameters in context of causative factors like land use and geology of the region. The occurrence of water borne diseases in resident population has been examined in association with quality of drinking water and priority areas for policy intervention have been identified. Water samples have been collected from 173 drinking water sources and 346 households consuming water from the selected sources have been surveyed for prevalence of water borne diseases. Water quality surfaces have been mapped in terms of F, Total Dissolved Solids (TDS), Hardness, Fe, alkalinity, Faecal Coliform (FC), E. Coli, and Water Quality Index (WQI) computed on the basis of 10 geochemical parameters, using Inverse Distance Weighted (IDW) method. Results reveal that the north-eastern part comprising Aspur, Sabla and part of Sagwara tehsils predominantly has ‘very poor’ to ‘unsuitable’ water quality. The western part has excessive faecal contamination. Entire district has high levels of TDS and hardness, while excessive Fe and F occur in specific regions. Disease incidence closely corresponds to the geochemical and microbial composition of water. Higher values of WQI correspond with occurrence of Phyllites and Mica Schists.

Identification and estimation of hydrological contributions in a mixed land‐use catchment based on a simple biogeochemical and hydro‐meteorological dataset

AbstractWater pathways and water contamination in mixed land‐use catchments are complex to understand. Runoff‐generating sources can be numerous and water pathways modified by anthropogenic elements. Monitoring surveys considering geochemical and microbial parameters, are often carried out on such catchment, but are often simple in terms of studied parameters. Nonetheless, they can be helpful to identify the specific signatures of the main runoff‐generating sources and estimate their contribution to total runoff at the outlet of mixed land‐use catchments. Based on a monthly biogeochemical monitoring program conducted between 2017 and 2019 in the Ratier catchment (19.8 km2) near Lyon (France), a step‐by‐step approach was developed to: (1) identify the main runoff‐generating sources using a perceptual model of the Ratier catchment, (2) identify the respective biogeochemical signatures of each source using this biogeochemical dataset and hydro‐meteorological indicators and (3) estimate their contribution to the stream total runoff using an End‐Member Mixing Analysis method. We identified three main runoff‐generating sources outside of rainy periods: a colluvium aquifer, a fractured gneiss aquifer and a saprolite layer. The monitored geochemical datasets were found divided into three groups matching these sources. Contributions of these sources were estimated based on representative tracer concentrations. Microbial parameters showed a homogeneous agricultural and anthropogenic contamination among the catchment surface water, but also deeper into the fractured gneiss groundwater. This approach showed the potential of using simple monitoring datasets to identify runoff‐generating sources and estimate their contribution to total runoff.

KAOLIN FORMATION IN YATAĞAN (MUĞLA) LIGNITE DEPOSIT

The 30-km-long and 10-km-wide, coal-bearing Yatağan Basin is located in SW Anatolia, close to the eastern coast of the Aegean Sea, Türkiye. The basement consists of Menderes Massif metamorphics in the NW part of this intermontane basin, c. 80-km2-large area (Turgut lignite deposit). The Neogene and Quaternary sedimentary filling comprises fluvioterrestrial, limnic and telmatic sediments which contain a mineable coal seam up to 15 m thick, unconformably overlain the basement. Two fresh and six weathered samples were picked up from the Menderes Massif gneiss outcrops of the catchment area. Eight sedimentary rocks, inorganics over and underlying the coal seam, were obtained from four borehole cores. All samples were examined under the optical microscope; XRD, SEM-EDX and ICP-MS analyses were later performed. This study aims to examine the mineralogical content and geochemical processes of the sedimentary rocks from different formations, namely Sekköy and Turgut Formations, which are over- and underlying the lignite horizon, to assess the clay mineral formations and transformations. Gneiss samples contain mainly quartz, plagioclase, K-feldspar, muscovite and biotite with a lesser amount of tourmaline, chlorite, garnet, apatite, zoisite, zircon and Fe-oxides. The -2 µm fraction consists mainly of illite, with fewer smectite and kaolinite. Sericitizitation of feldspar is the main product in gneisses. Coal over-and underlying sedimentary rock samples contain mainly quartz, plagioclase, K-feldspar, muscovite, and biotite with less pyrite and iron oxides. The -2 µm fraction of the sedimentary rock samples consists of variable clay mineral contents. Kaolin content is higher in acidic conditions with an opposite correlation to smectite occurrences. The geochemistry of Menderes Massif gneisses shows that it gave felsic material to the catchment area, whereas the geochemistry of sedimentary rocks is not coherent in all cases. Geochemical parameters like CIA and PIA proved that weathering processes of the source materials prevailed during the generation of these sedimentary units.