晚第四纪热带西太平洋Noelaerhabdaceae科颗石长度和质量变化及其影响因素

选取热带西太平洋暖池北部边缘西菲律宾海本哈姆高原(Benham Rise)MD06-3050站位的柱状样沉积物样品,利用双向圆偏光法拍摄并合成图像,通过SYRACO人工智能软件自动识别并测量和计算Noelaerhabdaceae科颗石的平均长度和平均质量。研究结果显示,自35万年以来,Noelaerhabdaceae科平均颗石长度和质量的变化趋势具有较强的相似性,两者的冰期/间冰期变化特征均不明显。根据颗石长度和质量计算得到的颗石钙化作用指标曲线与前两者的变化趋势也存在一定的相似性,说明研究海区颗石的平均质量和长度均可作为指示颗石藻钙化作用程度的指标。通过与冰芯记录的大气pCO_(2)变化曲线进行对比,发现在大气pCO_(2)浓度较高的冰期终止期以及间冰期早期,该科颗石的钙化作用相对较低,表明pCO_(2)在一定程度上影响了颗石藻的钙化作用。此外,对颗石的平均长度和质量进行23 ka周期滤波,两滤波曲线的变化与北纬15°夏季平均日照辐射曲线的变化较为一致,指示了地球天文轨道参数对颗石藻演化的调控作用。

汶川地震同震滑坡物质在震区的滞留和运移及其对龙门山地形演化的影响

2008年M_W7.9汶川地震导致龙门山断裂发生强烈地壳变形,同时引发的巨量同震滑坡加速了该地区的地表剥蚀和河流侵蚀.然而,目前尚缺少系统的数据定量研究滑坡物质的运移以及河流侵蚀速率随时间的演化规律,这些对理解龙门山前缘物质的再分配以及强震对活动造山带地形塑造的作用至关重要.为此,本研究在汶川地震后的6年间,对震区沱江上游3条支流湔江、石亭江、绵远河流域进行了多期次的定点现代河沙采样.通过系统测量河沙中的石英10Be浓度,并与震前已发表的数据进行对比,发现如下基本特点:(1)震后河沙10 Be浓度均有明显降低,表明同震滑坡物质对河沙的稀释作用;(2)震后河流对河沙的运移量增加为震前的1.3~18.5倍,因此震后龙门山地区侵蚀速率短期显著增加;(3)初步估计得到汶川地震产生的滑坡物质被完全运移出造山带所需要的时间至少为100~4000年,接近龙门山地区强震复发周期;(4)震间和同震产生的构造变形和地表剥蚀在空间上具有互补性.考虑到地表剥蚀引起的地壳均衡反弹效应,认为类似汶川地震的强震有利于龙门山的隆升.认识震前、震时和震后的地壳变形及侵蚀过程有助于更好地理解单次强震事件对高原边界龙门山地形演化的作用.

南海西北部沉积物捕获器中颗石藻通量和属种组成变化记录

本文利用沉积物捕获器回收的连续时间序列沉降颗粒物样品,研究了南海西北部海南岸外陆坡外缘海域颗石藻的通量和属种组成变化及其环境意义。研究发现,东亚夏季风引起的海南岸外上升流以及冬季风导致的混合层深度增加都会刺激该区域颗石藻的生长,其中夏季上升流的影响尤为显著。从颗石粒属种组成来看,Florisphaera profunda是南海西北部中深层(1 000m)水体中主要的颗石粒优势种,此外Emiliania huxleyi,Gephyrocapsa oceanica和Gephyrocaps ericsonii等属种含量也颇高。然而在将颗石粒折算成颗石球数量后,Emiliania huxleyi则成为主要优势种。沉积物捕获器中F.profunda的相对百分含量与颗石粒总通量呈显著的负相关,表明F.profunda的相对含量与总的颗石藻生产力有着密切联系。本结果对于利用沉积物中的颗石藻记录,尤其是F.profunda相对含量变化,恢复和重建古海洋环境尤其是古海洋生产力的研究提供了直接的理论证据。

Structural Organization and Tectono-Metamorphic Evolution of the Pan-African Suture Zone: Case of the Kabye and Kpaza Massifs in the Dahomeyide Orogen in Northern Togo (West Africa)

The Kabye and Kpaza Massifs correspond to two main granulitic suites in the suture zone of the Pan-African Dahomeyide orogenic belt, in northern Togo. The Kabye Massif is composed of an important west verging nappe pile subdivided into two petrographic units. The nappes in its western petrographic unit are made up of leucocratic garnetbearing granulites defined as the “Lassa-Soumdina Granulites” (GLS). The eastern petrographic unit consists of mela-nocratic granulites, with metagabbroic structures, called the “Ketao-Sirka Granulites” (GKS). These two petrographic units are separated by the Panalo Mylonitic Zone (ZMP). This major west verging zone includes a syn-Dn + 2 dextral shear contact. The Kpaza Massif comprises nappes of melanocratic granulites (GKM), comparable to the GKS of the Kabye Massif. All these granulitic nappes include boudins of pyroxenites or meta-anorthosites, and ultramafic rocks represented by serpentinites, talcschists, actinolite- and chlorite-schists which generally mark thrust soles. The GLS nappes are thrust over the Kara-Niamtougou orthogneissic unit (UKN) which is considered as the easternmost structural unit of the Dahomeyide external zone. On the other hand, the GKS nappes underlie those of the Binah meta-volcano sedimentary Complex (CB) which belongs to the Dahomeyide internal zone. As regards the Kpaza Massif, it occurs as a geologic window tectonically enclosed in the Mono Complex nappes (CM) corresponding to the southern part of the CB. The organization of the Kabye and Kpaza Massifs, as west verging nappe piles, and their relationships with the surrounding structural units express the tangential and folding tectonics that structured the Pan-African belt in northern Togo. The microstructures and mineral parageneses of the granulites and associated rocks in these two massifs indicate a polyphase tectono-metamorphic evolution: a syn-Dn granulitization (collision phase);a syn-Dn + 1 amphibolitization (obduction or tangential phase);and a syn- to post-Dn + 2 greenschist facies retrogressive metamorphism (post-nappe folding phase).

Hydro-geochemistry of groundwater and surface water in Dschang town(West Cameroon):Alkali and alkaline-earth elements ascertain lithological and anthropogenic constraints

The study aims to identify a suitable site for open and bore well in a farmhouseusing ground magnetic survey in south India.It also aims to define depth to granitoid and structural elements which traverse the selected area.Magnetic data(n=84)measured,processed and interpreted as qualitative and quantitatively.The results of total magnetic intensities indicate that the area is composed of linear magnetic lows trending NE-SW direction and circular to semi-circular causative bodies.The magnetic values ranged from-137 nT to 2345 nT with a mean of 465 nT.Reduction to equator shows significant shifting of causative bodies in the southern and northern directions.Analytical signal map shows exact boundary of granitic bodies.Cosine directional filter has brought out structural element trending NE-SW direction.Results of individual profile brought to light structurally weak zone between 90 m and 100 m in all the profile lines.Sudden decrease of magnetic values from 2042 nT to 126 nT noticed in profile line 6 between 20 m and 30 m indicates fault occurrence.Magnetic breaks obtained from these maps were visualized,interpreted and identified two suitable sites for open and bore well.Radially averaged power spectrum estimates depth of shallow and deep sources in 5 m and 50 m,respectively.Euler method has also been applied to estimate depth of granitoid and structural elements using structural indexes 0,1,2,and 3 and found depth ranges from<10 m to>90 m.Study indicates magnetic method is one of the geophysical methods suitable for groundwater exploration and site selection for open and borewells.

Characterization of Clay of the Benin Used in Ruminale Feeding. Complete Determination of the Smectites Contained in These Clays

In this work, by the use of several physico-chemical complementary methods for the characterization of soil (diffraction of x-rays, chemical analysis, density, cationic exchange capacity, specific sur faces, m?ssbauer, granulometry, etc.), the smectite of the three clayey localities of Benin (Gbédji-Kotovi, Massi-Sèhouè and Zogbodomey) was notably studied. Thus, these three sites principally contain principally smectite, kaolinite and quartz in variable proportion. This smectite is a beidellite. Its chemical formula is proposed. The specific surfaces and the cationic exchange capacity of the samples are determined. For these samples, the fraction lower than 2 μm is practically beidellitic for Gbédji-Kotovi and Massi-Sèhouè (more than 82% of beidellite) and practically kaolinitic (70% of kaolinite) for Zogbodomey. So, used as additive food to ruminant, the clay of Gbédji-Kotovi and Massi-Sèhouè will induce an enteric reduction of methane more than clay of Zogbodomey.

Distribution and U-Pb Ages of Newly Recognized Regional-Scale Dyke Swarms of the Leo Man Craton

Over 20 sets of dolerite dykes crosscutting Paleoproterozoic basement in West Africa were distinguished via the interpretation of regional and high resolution magnetic airborne data of West African Craton

New Computerized Method for the Geochemical Classification of Precambrian Carbonate Rocks: Case of a Set of African Cap Carbonates

Post-sedimentary transformations have masked or completely obliterated the structures and textures of Precambrian carbonate rocks. Therefore, methods of classification of the carbonate rocks founded on the observation of primary structures or textural characteristics are ill-adapted. Consequently, only certain geochemical classification methods allow us to distinguish the various rock-types in the case of Neoproterozoic carbonates. After presenting the most suitable geochemical classifications, we propose a new classification into 14 groups based on a regular ternary diagram with computerized data input. For each sample of carbonate rock, analysis of calcium and magnesium contents allows us to calculate the input data for our diagram i.e. the percentages of Calcite, Dolomite and Insoluble Residue. To automate the application of this diagram, input parameters are created in a descriptive file “Roches.ternaires.txt” using an option called “Ternaires” in the “Diagrammes” software developed by Roland Simler. Thirty cap carbonates of Africa are used to validate this new method.

Ore Texture,Mineralogy and Whole Rock Geochemistry of the Iron Mineralization from Edea North Area,Nyong Complex,Southern Cameroon:Implication for Origin and Enrichment Process

This study presents the ore texture, mineralogy and whole rock geochemistry of iron occurrence from the Edea North area located at the upper limit of the Nyong Unit, part of the Congo craton. This iron mineralization is of magnetite quartzite type enclosed by metamorphic rocks of the granulite facies. Two main facies have been identified over the study area including the banded and the massive facies. The mineralogical set of these facies is in majority represented by magnetite, quartz and pyroxene martite in addition to minor biotite, apatite, and amphibole. Magnetite presents as irregular and elongated minerals which can contain quartz inclusions of various shapes and sizes, as blasts clustering, around pyroxenes and isolated xenomorphic magnetite minerals in the silicate phases. Quartz varies from fine to coarse-grained and ribbon quartz. This indicates re-crystallization and deformation during metamorphism. Electron microprobe analysis on magnetite and martite show Fe2O3 contents that vary between 96.11 and 99.76. Whole rock chemical data showed that Fe-contents are as high as 62.9 wt%. The SiO2 content varies between 33.8 wt% and 51.2 wt%. Iron oxides and SiO2 are negatively correlated. Moreover, the low positive correlations between Al2O3 and HFSE, and LILE suggest a contribution of clastic materials in the protolith of studied materials. The samples show low contents of V, Cr, Ba, Zr with respect to igneous rocks. This may infer a sedimentary origin for the studied rocks;furthermore, these materials may have undergone hydrothermal alteration. The REE patterns reveal enrichment in LREE compared to HREE. Some samples show positive Eu (1.82) and other negative anomalies Eu (0.54 to 0.97). The lack of Ce anomalies suggests that the depositional environment of the Edea North iron occurrence was anoxic or suboxic. Overall, the Edea North iron occurrence may have undergone significant input from hydrothermal sources with imprints of the clastic during its deposition.

The Marine Benthic Algae Diversity of Gabon: Case of the Rocky Foreshore of Cap Estérias

This study has allowed to classify the marine macroalgae from the intertidal zone on the Atlantic side of Cap Estérias (Gabon). This area has a rich biodiversity but very few studies in the knowledge of benthic macroalgae have been done. The first study on the knowledge of the algae of the Gabonese coast was made in February 1974 by John and Lawson. This article has been revised to transcribe books and our study would aim to update the existing collection. The algae census is spread over a year from August 2020 to August 2021 and is the first detailed study carried out over a year, with regard to this part of the Gabonese coast. This study has allowed to know the specific diversity, to determine the structure of the flora and its spread out over time. The results show a significant algal diversity of thirty five (35) identified species. Three classes of macroalgae were determined and the percentage of species in the class (%EC): Floridaophyceae at 50% EC, Phaeophyceae at 30% EC and Ulvophyceae at 20% EC. The red algae are the most common in the area with sixteen (16) species determined against twelve (12) species of brown algae and seven (7) species of green algae. The Phaeophyceae class presents the Dictyotaceae family which is the most diverse with 7 species found. Some species seen appear in the collection of John et al., but others are new species encountered in Gabon such as Caulerpa sertularioides, Bryopsis plumosa (two Ulvophytes), Padina arborescens which is a Pheophyte and Galaxaura filamentosa, Digenea simplex,Hildenbrandia rubra, Asparagopsis armata and Caulacanthus ustulatus which are Rhodophytes. Some species are permanently present, they are found in all seasons but with significant abundance from July to September.

Urban Wastewater Treatment by Adsorption of Organic Matters on Modified Bentonite by(Iron-Aluminum)

In this research, the natural bentonite clay (from Maghnia, western Algeria) was purified (Na+- montmorillonite, CEC = 91 meq/100 g), noted (puri.bent) and modified with mixed hydroxy-Fe-Al (FeAl-PILC). The purified bentonite clay and FeAl-PILC were heated at 383 K for 2 hr and characte-rized by the chemical analyses data, XRD, and N2 adsorption to 77 K techniques. Puri.bent and FeAl-PILC were applied to fix the organic matter (OM) present in urban wastewater from the city of Sidi Bel-Abbes (western Algeria). The adsorption of organic matter was followed by spectro-photometry at 470 nm, and the adsorption data were a good fit with Freundlich isotherm for pu-ri.bent but for FeA-lPILC, were well fit by Elovitch isotherm model. The maximum adsorption ca-pacity (qm) was 571.6 mg/g for puri.bent and 1120.69 mg/g for FeAl-PLC. The degree of OM removal was 67% for puri.bent and 97% for FeAl-PILC. FeAl-PILC can be considered as a promising adsorbent for the removal of OM from wastewater.

Linker gadolinium as charge channel and singlet oxygen activation site in graphitic carbon nitride for enhancing photocatalytic decomposition of tetracycline

Reactive oxygen species are essential in photocatalytic water treatment.In this paper,Gd doped carbon nitride(CN)photocatalysts were prepared by simple thermal polymerization for the photocatalytic degradation of tetracycline under visible light irradiation.The photodegradation rate of 1.OGdCN is as high as 95%in 18 min,and the photocatalytic performance is much higher than that of CN.The improvement of photocatalytic performance is mainly attributed to the fact that Gd ion implantation directly provides active sites for oxygen activation and induces the formation of N vacancies.The results of characterizations show that the introduction of Gd in CN can improve the conversion ability of activated oxygen,carrier separation and energy band structure adjustment.Therefore,1.0GdCN photocatalyst can be employed for efficient photocatalytic synthesis of tetracycline.Furthermore,three ways of photocatalytic degradation of tetracycline were revealed by high performance liquid chromatographymass spectrometry.This work provides insights into the doping strategy of CN to improve the production of reactive oxygen species for environmental remediation.

Littoral landforms of Lake Hulun and Lake Buir(China and Mongolia):Wind-driven hydro-sedimentary dynamics and resulting clastics distribution

Two rectangular-shaped lakes,Lake Hulun and Lake Buir,located at the boundary between China and Mongolia,only c.75 km apart and therefore experiencing similar wind fields,have been studied based on satellite images and field surveys in order to compare their geomorphological and sedimentological characteristics.The wind-driven hydrodynamics,which have a significant effect on the development of littoral landforms and on sediment distribution,have been discussed for the two similar lakes that experienced a prevailing wind perpendicular to their long axis.A conceptual model related to wind-driven water bodies and sediment distribution is proposed.Wave-influenced to wave-dominated deltas,beaches,spits,and eolian dune deposits develop around these two lakes,with a strikingly similar distribution pattern.These features locally inform the longshore drift and help reconstruct the water circulation induced by wind forcing.Under the NW prevailing wind regime,the spits developed on the SW coast with a NW—SE extension,which was influenced by the NW—SE longshore currents.The same influence was observed in the delta extension in the NE area.The differences lie in the presence of fan deltas in the NW region of Lake Hulun,but not in Lake Buir.Additionally,the width of the beach and eolian deposits on the downwind coast of Lake Hulun is three times greater than that of Lake Buir which were caused by the differences in sediment supply and wind fetch between the two lakes.Lake Hulun and Lake Buir provide two reliable examples to understand the relationship among the wind field,provenance,hydrodynamics,landforms,and asymmetrical distribution of clastics in elongated lakes.They also represent relevant modern analogs,which may also be of guiding significance to wind-driven sand body prediction in lacustrine basins.

A proto-monsoonal climate in the late Eocene of Southeast Asia:Evidence from a sedimentary record in central Myanmar

The Burma Terrane has yielded some of the earliest pieces of evidence for monsoonal rainfall in the Bay of Bengal.However,Burmese ecosystems and their potential monsoonal imprint remain poorly studied.This study focuses on the late Eocene Yaw Formation(23°N)in central Myanmar,which was located near the equator(c.5°N)during the Eocene.We quantitatively assessed the past vegetation,climate,and depositional environments with sporomorph diagrams,bioclimatic analysis,and sequence biostratigraphy.We calculated the palynological diversity and drew inferences with rarefaction analysis by comparing with four other middle to late Eocene tropical palynofloras.Palynological results highlight a high floristic diversity for the palynoflora throughout the section formed by six pollen zones characterized by different vegetation.They indicate that lowland evergreen forests and swamps dominated in the Eocene Burmese deltaic plains while terra firma areas were occupied by seasonal evergreen,seasonally dry,and deciduous forests.This vegetation pattern is typical to what is found around the Bay of Bengal today and supports a monsoon-like climate at the time of the Yaw Formation.Bioclimatic analysis further suggests that in the late Eocene,the Yaw Formation was more seasonal,drier,and cooler compared to modern-day climate at similar near-equatorial latitude.More seasonal and drier conditions can be explained by a well-marked seasonal migration of the Intertropical Convergence Zone(ITCZ),driver of proto-monsoonal rainfall.Cooler temperatures in the late Eocene of central Myanmar may be due to the lack of adequate modern analogues for the Eocene monsoonal climate,while those found at other three Eocene Asian paleobotanical sites(India and South China)may be caused by the effect of canopy evapotranspirational cooling.Our data suggest that paleoenvironmental change including two transgressive-regressive depositional sequences is controlled by global sea level change,which may be driven by climate change and tectonics.The high diversity of the Yaw Formation palynoflora,despite well-marked seasonality,is explained by its crossroads location for plant dispersals between India and Asia.

Clumped Isotope Analysis of Calcite and Dolomite Mixtures Using Selective Acid Extraction

Acid extraction methods have been used in the last half century to selectively extract the CO_(2)produced from different carbonate minerals in mixed samples.However,these methods are often time-consuming and labor intensive.Their application to clumped isotope(Δ47)analysis has not been demonstrated.We propose here an acid extraction method with phosphoric acid for bulk stable and clumped isotope analysis that treats mixtures of calcite and dolomite the same regardless of the proportional composition.CO_(2)evolved from calcite is extracted by allowing a reaction with phosphoric acid to proceed for 10 min at 50℃.We then extract CO_(2)evolved from dolomite by rapid ramping the acid temperature from 50 to 90℃and allowing the reaction to complete.The experimental results show that our method yields accurate calcite and dolomiteΔ_(47)values from mixed samples under different proportional compositions.Our method also displays equal or higher accuracy for calciteδ^(13)C and dolomiteδ^(13)C andδ^(18)O values from mixtures when compared to previous studies.Our approach exhibits higher sample throughput than previous methods,is adequate for clumped isotopic analysis and simplifies the reaction progression from over 24 h to less than 2 h,while maintaining relatively high isotopic obtaining accuracy.It yet poorly resolves calciteδ18O values,as found with previous methods.

Green process of biomass waste derived fluorescent carbon quantum dots for biological imaging in vitro and in vivo

In the context of the circular economy,the huge amounts of biomass waste should be converted into value-added materials and energy to diminish pollution,atmospheric CO_(2)levels and costly waste disposal.Biological imaging usually uses expensive and toxic chemicals e.g.,organic dyes,semiconductor quantum dots,calling for safer,greener,cheaper fluorescent probes for biological imaging in vitro and in vivo.In these regards,carbon quantum dots(CQDs)-based fluorescent probes using biomass waste as a precursor may have much higher potential.Here we transformed the biomass waste of peach leaves into value-added fluorescent CQDs through a low-cost and green one-step hydrothermal process.The obtained CQDs show excitation-dependent photoluminescence properties with a fluorescence lifetime of 5.96 ns and a quantum yield of 7.71%without any passivation.In addition,the CQDs have a fine size of 1.9 nm with good hydrophilicity and high fluorescent stability over pH 4.0-11.0 range.Fluorescence imaging of in vitro cell cultures and in vivo with zebrafish show that CQDs possess ultra-low toxicity and remarkable performance for biological imaging.Even when CQDs present at a concentration as high as500μg/m L,the organism can still maintain more than 90%activity both in vitro and in vivo,and present bright fluorescence.The cheaper,greener,ultra-low toxicity CQDs developed in this work is a potential candidate for biological imaging in vitro and in vivo.