Application of Developed Grid-GA Distributed Hydrologic Model in Semi-Humid and Semi-Arid Basin

A grid and Green-Ampt based(Grid-GA)distributed hydrologic physical model was developed for flood simulation and forecasting in semi-humid and semi-arid basin. Based on topographical information of each grid cell extracted from the digital elevation model (DEM) and Green-Ampt infiltration method, the Grid-GA model takes into consideration the redistribution of water content, and consists of vegetation and root interception, evapotranspiration, runoff generation via the excess infiltration mechanism, runoff concentration, and flow routing. The downslope redistribution of soil moisture is explicitly calculated on a grid basis, and water exchange among grids within runoff routing along the river drainage networks is taken into consideration. The proposed model and Xin’anjiang model were applied to the upper Lushi basin in the Luohe River, a tributary of the Yellow River, with an area of 4 716 km2 for flood simulation. Results show that both models perform well in flood simulation and can be used for flood forecasting in semi-humid and semi-arid region.

Fossil Equidae in the Linxia Basin with Biostratigraphic and Paleozoogeographic Significance

The Linxia Basin is characterized by an abundance of Cenozoic sediments,that contain exceptionally rich fossil resources.Equids are abundant in the Linxia Basin,the fossil record of equids in this region including 16 species that represent 10 genera.In comparison to other classic late Cenozoic areas in China,the Linxia Basin stands out,because the fauna and chronological data accompanying Linxia equids render them remarkably useful for biostratigraphy.The anchitheriines in the region,such as Anchitherium and Sinohippus,represent early equids that appeared in the late stages of the middle and late Miocene,respectively.Among the equines,most species of Chinese hipparions have been identified in the Linxia Basin and some species of the genera Hipparion and Hippotherium have FAD records for China.Furthermore,Equus eisenmannae is one of the earliest known species of Equus in the Old World and is well-represented at the Longdan locality.Some species with precise geohistorical distributions can serve as standards for high-resolution chronological units within this framework.Located at the eastern margin of the Tibetan Plateau and subject to considerable uplift,the Linxia Basin has served as a biogeographic transition area for equids throughout the late Cenozoic.

Geochemistry and origins of hydrogen-containing natural gases in deep Songliao Basin,China:Insights from continental scientific drilling

The different reservoirs in deep Songliao Basin have non-homogeneous lithologies and include multiple layers with a high content of hydrogen gas.The gas composition and stable isotope characteristics vary significantly,but the origin analysis of different gas types has previously been weak.Based on the geochemical parameters of gas samples from different depths and the analysis of geological settings,this research covers the diverse origins of natural gas in different strata.The gas components are mainly methane with a small amount of C_(2+),and non-hydrocarbon gases,including nitrogen(N_(2)),hydrogen(H_(2)),carbon dioxide(CO_(2)),and helium(He).At greater depth,the carbon isotope of methane becomes heavier,and the hydrogen isotope points to a lacustrine sedimentary environment.With increasing depth,the origins of N_(2)and CO_(2)change gradually from a mixture of organic and inorganic to inorganic.The origins of hydrogen gas are complex and include organic sources,water radiolysis,water-rock(Fe^(2+)-containing minerals)reactions,and mantle-derived.The shales of Denglouku and Shahezi Formations,as source rocks,provide the premise for generation and occurrence of organic gas.Furthermore,the deep faults and fluid activities in Basement Formation control the generation and migration of mantle-derived gas.The discovery of a high content of H_(2)in study area not only reveals the organic and inorganic association of natural-gas generation,but also provides a scientific basis for the exploration of deep hydrogen-rich gas.

Geochemical fingerprints and hydrocarbon potential of Paleocene mudrocks in the Tano Basin, Ghana: insights from biomarkers and stable carbon isotopes

The Paleocene mudrocks in Ghana’s Tano Basin have received limited attention despite ongoing efforts to explore hydrocarbon resources.A thorough geochemical analysis is imperative to assess these mudrocks’petroleum generation potential and formulate effective exploration strategies.In this study,a comprehensive geochemical analysis was carried out on ten Paleocene rock cuttings extracted from TP-1,a discovery well within the Tano Basin.Various analytical techniques,including total organic carbon(TOC)analysis,Rock–Eval pyrolysis,gas chromatography-mass spectrometry,and isotope ratio-mass spectrometry,were employed to elucidate their hydrocar-bon potential and organic facies.Thefindings in this study were subsequently compared to existing geochemical data on Paleocene source rocks in the South Atlantic marginal basins.The results indicated that the Paleocene samples have TOC content ranging from 0.68 to 2.93 wt%.The prevalent kerogen types identified in these samples were Type Ⅱ and Type Ⅲ.Molecular and isotope data suggest that the organic matter found in the Paleocene mudrocks can be traced back to land plants and lower aquatic organisms.These mudrocks were deposited in a transi-tional environment withfluctuating water salinity,charac-terized by sub-oxic redox conditions.Maturity indices,both bulk and molecular,indicated a spectrum of maturity levels within the Paleocene mudrocks,spanning from immature to marginally mature,with increasing maturity observed with greater depth.In comparison,the organic composition and depositional environments of Paleocene source rocks in the Tano Basin closely resemble those found in the Niger Delta Basin,Douala,and Kribi-Campo Basins,the Kwanza Formation in Angola,and certain Brazilian marginal basins.However,it is worth noting that Paleocene source rocks in some of the basins,such as the Niger Delta and Brazilian marginal basins,exhibit rela-tively higher thermal maturity levels compared to those observed in the current Paleocene samples from the Tano Basin.In conclusion,the comprehensive geochemical analysis of Paleocene mudrocks within Ghana’s Tano Basin has unveiled their marginal hydrocarbon generation potential.The shared geochemical characteristics between the Paleocene mudrocks in the Tano Basin and those in the nearby South Atlantic marginal basins offer valuable insights into source rock quality,which is crucial for shaping future strategies in petroleum exploration in this region.

Reservoir characteristics and controlling factor of tight sandstone in Shuixigou Group in Taibei depression,Turpan-Hami basin

The positive structure belts surrounding the Taibei Sag,Turpan-Hami Basin,have been the main targets for oil and gas exploration for years and are now left with remaining resources scattering in reservoirs adjacent to source rocks in the sag,where the Shuixigou Group with substantial oil and gas potential constitutes the primary focus for near-source exploration.Consequently,characterization of development and key controlling factors of reservoir space becomes a must for future exploration in the area.This study investigates the development traits,genesis,and controlling factors of the Xishanyao and Sangonghe formations in the Shengbei and Qiudong Sub-sags of the Taibei Sag with techniques such as cast thin-section observation,porosity and permeability tests,high-pressure mercury injection,and saturation fluid NMR analysis of reservoir rocks.The findings reveal that the Shuixigou Group in the Taibei Sag consists of lithic sandstone.Reservoirs in the group are mostly poor in terms of physical properties,with undeveloped primary pores dominated by intergranular dissolved pores as a result of a strong compaction.Comparative analysis of key controlling factors of the Sangonghe Formation reveals significant distinctions in sandstone particle size,sand body thickness,genesis and distribution,provenance location,and source rock type between the Qiudong area and Shengbei area.Vertically,the coal seams of the Xishanyao Formation exhibit heightened development with shallower burial depth and lower maturity compared to those of the Sangonghe Formation.Consequently,this environment fosters the formation of organic acids,which have a stronger dissolution effect on minerals to develop secondary dissolution pores,and ultimately resulting in better reservoir physical properties.Overall,the reservoirs within the Qiudong area of the Taibei Sag demonstrate superior characteristics compared to those in the Shengbei area.Furthermore,the reservoir physical properties of the Xishanyao Formation are better than those of the Sangonghe Formation.The research findings will provide valuable guidance for the exploration and development of lithological oil and gas reservoirs within the Taibei Sag.

Multi-Model Approach for Assessing the Influence of Calibration Criteria on the Water Balance in Ouémé Basin

Hydrological models are very useful tools for evaluating water resources, and the hydroclimatic hazards associated with the water cycle. However, their calibration and validation require the use of performance criteria which choice is not straightforward. This paper aims to evaluate the influence of the performance criteria on water balance components and water extremes using two global rainfall-runoff models (HBV and GR4J) over the Ouémé watershed at the Bonou and Savè outlets. Three (3) Efficacy criteria (Nash, coefficient of determination, and KGE) were considered for calibration and validation. The results show that the Nash criterion provides a good assessment of the simulation of the different parts of the hydrograph. KGE is better for simulating peak flows and water balance elements than other efficiency criteria. This study could serve as a basis for the choice of performance criteria in hydrological modelling.

Genetic relationship between formation,accumulation and migration and dispersion of peat materials in Paleogene——Take the Qiongdongnan Basin as an example

Coal-type source rocks include both coal and terrigenous marine source rocks.By studying the distribution of secondary depressions,uplifts,as well as the characteristics of peat formation and accumulation in the northern marginal sea basin of the South China Sea,and combining them with coal formation characteristics observed in other basins,five genetic theories on the relationship between peat accumulation and dispersed organic matter accumulation are proposed.The northern marginal sea basin of the South China Sea is characterized by“disadvantageous coals formation and favorable terrigenous marine source rocks formation.”This paper provides a distribution map of coal seams and terrigenous marine source rocks in the Qiongdongnan Basin and determines their distribution patterns.Research shows that the migration of sedimentary facies in the basins and inner depressions led to the formation and migration of the peat accumulation centers.In addition,the vertical migration of the peat accumulation centers led to planar migration,which is actually a type of coupling relationship.Previous research results have revealed that the formation of coal-type source rock is multi-phased.The marginal sea basin is composed of several fault-depression basins,with each basin developing a second order of depression and uplift.There is no unified basin center or depositional center to be found.As a result,the concentration centers of coal-forming materials also vary greatly.Based on the distribution characteristics of coal-type source rocks in different basins within the marginal sea basins of the South China Sea,the research results have practical significance and provide guidance for exploring coal-type oil and gas reservoirs in this area.

Preliminary Palynostratigraphic Data on the Middle Albian-Lower Cenomanian of the Tarfaya Basin, Southwest Morocco

The Tarfaya-Laayoune-Boujdour basin is of great interest to oil exploration;on this aspect, there has been exploration by the Moroccan National Office of Hydrocarbons and Mining, which has shown indices of oil and/or gas recorded in most wells drilled in the Moroccan Atlantic margin. FD-1 well, object of this study, is one of these wells located in the offshore Tarfaya-Laayoune-Boujdour basin. A palynological examination of the processed samples revealed the existence of organic palynomorphs, well conserved and rich in dinoflagellate cysts. The latter are composed of worldwide marker taxa of high stratigraphic resolutions. Thus, the middle upper Albian (3408 - 3408.5 m) is determined by the presence of Cribroperidinium tensiftense, Tehamadinium coummia, Spiniferella cornuta, Chichaouadinium vestitum, Dinopterygium alatum and Litosphaeridium arundum. The upper Albian (3406.5 - 3408 m) is characterized by the FOs of marker taxa: Cyclonephelium chabaca, Cribroperidinium auctificum and Chichaouadinium vestitum. Lastly, the upper Albian-lower Cenomanian transition is defined between 3404 m and 3406.50 m, as suggested by the FOs of Chichaouadinium boydii, Dinopterygium tuberculatum, Sepispinula ancorifera, Litosphaeridium conispinum, Prolixosphaeridium conulum and Xenascus ceratioides.

Industrial Carbon Emission Distribution and Regional Joint Emission Reduction:A Case Study of Cities in the Pearl River Basin,China

China’s low-carbon development path will make significant contributions to achieving global sustainable development goals.Due to the diverse natural and economic conditions across different regions in China,there exists an imbalance in the distribution of car-bon emissions.Therefore,regional cooperation serves as an effective means to attain low-carbon development.This study examined the pattern of carbon emissions and proposed a potential joint emission reduction strategy by utilizing the industrial carbon emission intens-ity(ICEI)as a crucial factor.We utilized social network analysis and Local Indicators of Spatial Association(LISA)space-time trans-ition matrix to investigate the spatiotemporal connections and discrepancies of ICEI in the cities of the Pearl River Basin(PRB),China from 2010 to 2020.The primary drivers of the ICEI were determined through geographical detectors and multi-scale geographically weighted regression.The results were as follows:1)the overall ICEI in the Pearl River Basin is showing a downward trend,and there is a significant spatial imbalance.2)There are numerous network connections between cities regarding the ICEI,but the network structure is relatively fragile and unstable.3)Economically developed cities such as Guangzhou,Foshan,and Dongguan are in the center of the network while playing an intermediary role.4)Energy consumption,industrialization,per capita GDP,urbanization,science and techno-logy,and productivity are found to be the most influential variables in the spatial differentiation of ICEI,and their combination in-creased the explanatory power of the geographic variation of ICEI.Finally,through the analysis of differences and connections in urban carbon emissions under different economic levels and ICEI,the study suggests joint carbon reduction strategies,which are centered on carbon transfer,financial support,and technological assistance among cities.

Quantitative geochemical reconstruction of Eocene paleoenvironment in Fushun Basin,northeast China

The quantitative estimation of key parameters of paleotemperature and paleoprecipitation is crucial for paleoclimate reconstruction.Geochemical data from mod-ern sediments are highly consistent with climate data,and their relationship can provide an important reference for the quantitative reconstruction of the paleoclimate.In this study,detailed inorganic geochemical analysis was carried out using high-precision sampling of the Paleogene(LFD-1 well)Guchengzi,Jijuntun and Xiloutian Formations in the Fushun Basin located in the mid-latitudes of the Northern Hemisphere.The Eocene Guchengzi Formation(54.51–47.8 Ma)and Jijuntun Formation(47.8–41.2 Ma)in the Fushun Basin were found to have been deposited under a humid climate.The lower(41.2–40.1 Ma)and upper(40.1–37.8 Ma)parts of the Xiloutian Formation were character-ized by semiarid and semihumid–semiarid climates,respec-tively,which is very similar to the paleoclimatic information reflected by organic carbon isotopes.The Eocene Thermal Maximum 2(ETM2,~53.7 Ma),Early Eocene Climatic Optimum(EECO,~53.1–46.5 Ma),Eocene Thermal Maxi-mum 3(ETM 3,~52.8 Ma),and Middle Eocene Climatic Optimum(MECO,~40.7–40.1 Ma)events significantly enhanced chemical weathering during these periods.The rapid increase in pCO_(2)concentration leads to an increase in temperature,precipitation,and surface runoff,exhibiting strong chemical weathering.The mean annual temperature(MATa)and mean annual precipitation(MAPa,MAPb,and MAPc)were estimated using parameters,such as the corrosion index without potassium(CIA-K),CaO/Al_(2)O_(3),and(Na_(2)O+K_(2)O)/Al_(2)O_(3).Comparing MAPa,MAPb,and MAPc with the MAP estimated using pollen data,MAPa and MAPb were found to be more sensitive to the climate during high precipitation periods(precipitation>1000 mm,Guchengzi Formation),and the recovered average precipi-tation was similar to MAP.In contrast,MAPc was more sensitive to the climate during low precipitation periods(precipitation<1000 mm,Jijuntun,and Xiloutian Forma-tions),with higher accuracy.To fully consider the influence of soluble inorganic salts Ca^(2+)and Na^(+),multivariate linear equations of CIA-K and CaO/Al_(2)O_(3)with CIA,and CIA-K and CaO/Al_(2)O_(3)with MAP were constructed,namely MAPd and MAPe.The results show that MAPe has the highest per-formance and can be effectively used to estimate the change of paleoprecipitation in Northeast Asia.

The organic geochemistry of crude oil in the Saltpond Basin(Ghana):Organic source input,depositional environment,and thermal maturity

The Saltpond Basin,situated within the South Atlantic margin of Ghana,is a significant area for petro-leum exploration but has received relatively limited research attention.Previous studies have examined source rock com-position,but data on crude oil organic chemistry are lack-ing,hindering understanding of the basin’s petroleum system and evolution.To address this gap,we analyzed biomarkers and stable carbon-isotope ratios in Saltpond Basin crude oil using gas chromatography–mass spectrometry and gas chromatography–isotope ratio mass spectrometry to eluci-date organic matter source,depositional environment,and thermal maturity.Findings were compared with oils from the West African segment of the South Atlantic margin,namely the Tano Basin and the Niger Delta Basin,to iden-tify potential correlations and gain insights into regional variations.Molecular and isotopic results unveiled a sig-nificant prevalence of organic matter derived from lower marine organisms.Patterns of organic matter deposition and preservation in Saltpond oil samples suggested a suboxic marine transitional environment,contradicting conventional understanding of terrestrial dominance in such settings.Moreover,the potential for degradation processes to obscure differentiation between terrestrial and marine organic mat-ter origins underscores the complex nature of organic mat-ter dynamics in transitional marine environments.Analysis of molecular thermal maturity indices suggested Saltpond oils were expelled from source rocks exhibiting thermal maturity at the early maturity stage.Correlation analysis unveiled genetic disparities among crude oils sourced from the Saltpond Basin and those from the Tano and Niger Delta Basin,primarily due to variations in source input and depo-sitional environment conditions.Saltpond oil exhibits lower terrestrial organic input than Tano Basin’s crude oils,which also have less terrestrial input than Niger Delta Basin crude oils.Additionally,its paleodepositional environment nota-bly differs from oils in the Tano Basin(anoxic transitional marine-lacustrine settings)and the Niger Delta Basin(sub-oxic–oxic terrigenous deltaic or marine or lacustrine envi-ronments).Thermal maturity range of Saltpond oil is com-parable to oils in the Tano Basin but lower than oils in the Niger Delta Basin.Thesefindings provide valuable insights into petroleum generation history and unique organic geo-chemical characteristics within the Saltpond Basin,essen-tial for exploration,production,and environmental manage-ment efforts in the region.Furthermore,correlation studies provide evidence that distinct biological,geological,and paleoenvironmental conditions shaped various oil types in the West African segment of the South Atlantic margin.

Scale dependence of forest fragmentation and its climate sensitivity in a semi-arid mountain:Comparing Landsat,Sentinel and Google Earth data

Landscape fragmentation is generally viewed as an indicator of environmental stresses or risks,but the fragmentation intensity assessment also depends on the scale of data and the definition of spatial unit.This study aimed to explore the scale-dependence of forest fragmentation intensity along a moisture gradient in Yinshan Mountain of North China,and to estimate environmental sensitivity of forest fragmentation in this semi-arid landscape.We developed an automatic classification algorithm using simple linear iterative clustering(SLIC)and Gaussian mixture model(GMM),and extracted tree canopy patches from Google Earth images(GEI),with an accuracy of 89.2%in the study area.Then we convert the tree canopy patches to forest category according to definition of forest that tree density greater than 10%,and compared it with forest categories from global land use datasets,FROM-GLC10 and GlobeLand30,with spatial resolutions of 10 m and 30 m,respectively.We found that the FROM-GLC10 and GlobeLand30 datasets underestimated the forest area in Yinshan Mountain by 16.88%and 21.06%,respectively;and the ratio of open forest(OF,10%<tree coverage<40%)to closed forest(CF,tree coverage>40%)areas in the underestimated part was 2:1.The underestimations concentrated in warmer and drier areas occupied mostly by large coverage of OFs with severely fragmented canopies.Fragmentation intensity of canopies positively correlated with spring temperature while negatively correlated with summer precipitation and terrain slope.When summer precipitation was less than 300 mm or spring temperature higher than 4°C,canopy fragmentation intensity rose drastically,while the forest area percentage kept stable.Our study suggested that the spatial configuration,e.g.,sparseness,is more sensitive to drought stress than area percentage.This highlights the importance of data resolution and proper fragmentation measurements for forest patterns and environmental interpretation,which is the base of reliable ecosystem predictions with regard to the future climate scenarios.

Megafossils of Betulaceae from the Oligocene of Qaidam Basin and their paleoenvironmental and phytogeographic implications

Understanding the paleoenvironment and phytogeographical history of the Tibetan Plateau,China relies on discovering new plant fossils.The Qaidam Basin has long been regarded as an ideal‘field laboratory’to investigate the paleoclimate and paleobiological evolution of the northern Tibetan Plateau.However,fossil angiosperms from the Qaidam Basin are rare,and our knowledge of its paleovegetation is poor.Here,we report fossil leaves and fruits of Betulaceae found from the Oligocene Shangganchaigou Formation of northwestern Qaidam Basin(Huatugou area).Comparative morphological analysis led us to assign the fruits to the Betula subgenus Betula and the leaves to Carpinus grandis.These findings,together with other reported fossil plants from the same locality,reveal a close floristic linkage between the Qaidam Basin and Europe during the Oligocene.The northern pathway of this floristic exchange may have crossed through the Qaidam Basin during the late Paleogene.This floristic linkage may have been facilitated by the continuous narrowing of the Turgai Strait and stronger westerlies,which transported moisture and provided favorable climatic conditions.Indeed,fossil plants collected from the Qaidam Basin suggest that during the Oligocene this region had warm and humid deciduous broad-leaf forest,which differs from the region’s modern vegetation and indicates that the Qaidam Basin may have been a suitable region for these plants to flourish and spread during the Oligocene.

Establishing the relationship between land use land cover,normalized difference vegetation index and land surface temperature:A case of Lower Son River Basin,India

The study explores the intricate interplay between land use land cover(LULC),normalized difference vegetation index(NDVI),and land surface temperature(LST)within the Lower Son River Basin in India from 1991 to 2020.The region’s ecological balance has been increasingly strained due to rapid urbanization and changing land use patterns.Through a combination of Landsat TM&OLI/TIRS satellite imageries and geospatial analysis techniques,this study unveils the intricate connection between land use and land cover changes,vegetation,and land surface temperature variations.The study area is classified into three altitudinal zones(Zone I:39–300 m,Zone II:301–600 m and Zone III:601–1,247 m)to examine the changes in depth.The area has seen significant changes in LULC,vegetation and LST in all the three altitudinal zones.The findings hold significant implications for sustainable land management and environmental conservation strategies in the Lower Son River Basin.As per the result,103,438 ha of vegetation was converted into agriculture land and 82,572 ha of agricultural land was transformed into settlements from 1991 to 2020.This trend shows human pressure on the land resource in the study area.Minor increase in water body is seen which is attributed to commissioning of Bansagar dam.Zone I has seen highest settlement growth while Zone III experienced severe deforestation of around 15%.Zone II and III needs attention for holistic sustenance.Analysis of LST shows that it has increased by 0.82℃ from 1991 to 2020 which is a red flag.The study underscores the critical importance of balanced land use practices to preserve ecological integrity and mitigate the adverse effects of urbanization and climate change.

Formation mechanism of hydrochemical and quality evaluation of shallow groundwater in the Upper Kebir sub-basin,Northeast Algeria

This study investigates the hydrochemical formation mechanism of shallow groundwater in the Upper Kebir upstream sub-basin(Northeastern Algeria).The objective is to evaluate water quality suitability for domestic purposes through the application of water quality index(WQI).A total of 24 water points(wells and borewells)evenly distributed in the basin were collected and analyzed in the laboratory for determining the major ions and other geochemical parameters in the groundwater.The groundwater hydrochemical types were identified as Cl–Na and Cl–HCO_(3)^(–)Na,with the dominant major ions were found in the order of Na^(+)>Ca^(2+)>Mg^(2+)for cations,and Cl^(−)>SO_(4)^(2−)>HCO_(3)^(–)>NO_(3)^(−)for anions.Results suggest that weathering,dissolution of carbonate,sulfate,salt rocks,and anthropogenic activities were the major contributors to ion content in the groundwater.The Water Quality Index(WQI)was calculated to assess the water quality of potable water.Approximately 50%of the sampled sites exhibited good water quality.However,the study highlights significant NO_(3)contamination in the study area,with 50%of samples exceeding permissible limits.Therefore,effective treatment measures are crucial for the safe consumption of groundwater.

Characteristics and genetic mechanism of the Mesoproterozoic rift system,Ordos Basin,China

The Mesoproterozoic rifts are developed in the Ordos Basin located in the western margin of the North China Plate.Based on the latest 3D seismic data and previous research results,this study intends to discuss the zonal differential deformation characteristics and genetic mechanism of the Mesoproterozoic rifts in the Ordos Basin.NE-trending rifts are developed in the Mesoproterozoic in the south-central Ordos Basin,the main part of which are located near the western margin of the North China Plate.NNW-trending rifts are developed in the north of the basin,while NW-NNW rifts in the Mesoproterozoic in Hangjinqi area.The genetic mechanism of the Mesoproterozoic rifts is related to regional extensional stress field,plate boundary conditions and internal preexisting structures.The main extensional stress direction strikes NWW-SSE(120°)in the western margin of the North China Plate,based on the forward rift trend of the northern Mesoproterozoic.In Hangjinqi area,the reactivation of the existing NWtrending Wulansu fault and NW-NW-trending Daolao fault,results in dextral shear stress field.The boundary between the western margin of the North China Plate and its adjacent plates forms a nearly NS-trending preexisting basement tectonic belt,which intersects with the NWW-SSE(120°)extensional stress at an acute angle of 60°.Therefore,the western margin of the North China Plate is formed by oblique normal faults under oblique extension.Due to the long time span of Columbia Supercontinent breakup(1.8e1.6 Ga),the oblique rift in the south-central Ordos Basin is formed under the continuous oblique extension at the western margin of the North China Plate.

Effects of biodegradation on diamondoid distribution in crude oils from the Bongor Basin,Chad

The sensitivity of biodegradation on diamondoids was investigated using a series of biodegraded oil samples from the Ronier tectonic unit of Bongor Basin,Chad.The results suggest that diamondoids,including adamantanes(As)and diamantanes(Ds),are relatively resistant to biodegradation and obvious biodegradation was observed in oils with a Peters-Moldowan(PM)biodegradation rank of 6 or more.Overall,the sensibility of biodegradation on diamondoids is generally similar to hopanes and regular steranes.As biodegradation evolves,the changes in concentration and components of diamondoids show that the biodegradation process is selective and stepwise.The significant increase of MD/MA and DMD/DMA for oils with a PM ranking 6t indicates that diamantanes are generally more resistant to biodegradation than adamantanes.The similar trends of DMA/MA,EA/MA,MD/D,DMD/MD and other relevant indexes,show that higher alkylation homologs are more resistant to biodegradation.The commonly used diamondoid ratios,such as MAI,EAI,MDI and DMID-1,are obviously affected by biodegradation at the stage of high-level biodegradation,which may indicate that these ratios should be used with caution in case of severely degraded oils.

Elemental Compositions of Clinopyroxenes from Southern Okinawa Trough Basalt:Implications for Magmatism and Structural Environment in an Initial Back-Arc Basin

The major and trace elemental compositions of clinopyroxene from basalt were used to characterize the nature of the primitive magma and structural environment beneath the southern Okinawa Trough(SOT),which is an initial back-arc basin at a continental margin.The clinopyroxenes in the basalt were augite with variable Mg^(#)contents(73.37-78.22).The regular variations in major oxide contents(i.e.,CaO,FeO,TiO_(2),and Cr)with decreasing Mg#implied that the clinopyroxenes evolved from being enriched in Mg,Ca,and Cr to being enriched in Fe and Ti.The clinopyroxenes had relatively low rare earth element concentrations(7.51×10^(-6) to 12.68×10^(-6))and negative Eu anomalies(δEu=0.67-0.95).The Kd_(cpx) values of clinopyroxenes(0.2-0.26),which were used to examine whether the clinopyroxene was equilibrated with its host basalt,demonstrate that these clinopyroxene phenocrysts were not captured crystals but were instead produced by crystallization differentiation of the magma.The calculated clinopyroxene crystallization temperatures showed a narrow range of 990-1061℃,and their crystallization pressures ranged from 2.0 to 3.2 kbar.The geochemistry features of these clinopyroxenes indicated that the parent magma belonged to the subalkaline tholeiitic magma series and suggested that the magma experienced crystallization differentiation of olivine,plagioclase,and clinopyroxene,where the crystallization of plagioclase occurred earlier than that of clinopyroxene.Combined with geophysical data,this research on primitive magma and its crystallization differentiation from clinopyroxene indicates that the SOT is in the stage of‘seafloor spreading’and that basaltic rocks produced from tholeiitic magma represent the generation of oceanic crust.

Hydrogeophysical and Structural Investigations Using VES: A Case Study of Dosso Region in the Southwestern Part of the Meso-Cenozoic Iullemmeden Basin (Southwestern Niger)

A regional study connecting geolelectrical surveys with geology and hydrogeology was carried out in the western part of the Iullemmeden basin, precisely in the Dosso region in Niger. One hundred and four (104) vertical electrical sounds have been realized, among them nineteen representative were thus be used as parametric surveys. The local resistivity values of the geological formations of Quaternary range from 100 Ω⋅m to 1000 Ω⋅m (sands and lateritic sandstones). The Oligo-Miocene formation of the Continental terminal (Ct) shows resistivity values ranging from 1 to 5 Ω⋅m (brackish groundwaters) to 1500 Ω⋅m (clay sandstones) while the Upper Cretaceous formation of the Continental “hamadien” (Ch) indicates values ranging from 20 Ω⋅m (sandy clay) to 5000 Ω⋅m (clayey sandstones). The geological formations of Paleocene have values from 2 Ω⋅m (marls) to 60 Ω⋅m (calcareous marl), while the Precambrian basement exhibits values of granite around 300 Ω⋅m to 60,000 Ω⋅m. The update of the structural settings reveals many faults in the study area which explain both the shape of the basin and the geometry of the aquifers. Tectonics is also consistent with the hydraulic characteristics of aquifers. In addition, brackish groundwaters were identified as perched aquifer groundwaters in different depths in Dosso region. They probably come from the marine brines during the regression of the Paleocene Sea.

Long-term hydrochemical monitoring and geothermometry:understanding groundwater salinization and thermal fluid contamination in Mila’s basin,Northeastern Algeria

The regular hydrochemical monitoring of groundwater in the Mila basin over an extended period has provided valuable insights into the origin of dissolved salts and the hydrogeochemical processes controlling water salinization.The data reveals that the shallow Karst aquifer shows an increase in TDS of 162 mg L^(-1) while the ther-mal carbonate aquifer that is also used for drinking water supply exhibits an increase of 178 mg L^(-1).Additionally,significant temperature variations are recorded at the sur-face in the shallow aquifers and the waters are carbo-gaseous.Analysis of dissolved major and minor elements has identified several processes influencing the chemical composition namely:dissolution of evaporitic minerals,reduction of sulphates,congruent and incongruent car-bonates’dissolution,dedolomitization and silicates’weathering.The hydrogeochemical and geothermometric results show a mixing of saline thermal water with recharge water of meteoric origin.Two main geothermalfields have been identified,a partially evolved water reservoir and a water reservoir whosefluid interacts with sulphuric acid(H_(2)S)of magmatic origin.These hot waters that are char-acterized by a strong hydrothermal alteration do ascend through faults and fractures and contribute to the contamination of shallower aquifers.Understanding the geothermometry and the hydrogeochemistry of waters is crucial for managing and protecting the quality of groundwater resources in the Mila basin,in order to ensure sustainable water supply for the region.A conceptual model for groundwater circulation and mineralization acquisition has been established to further enhance under-standing in this regard.