1 Introduction Sedimentary rocks archive important information for understanding how the earth system operates and how life and environments have evolved through earth history.Properly identifying characteristics of s...1 Introduction Sedimentary rocks archive important information for understanding how the earth system operates and how life and environments have evolved through earth history.Properly identifying characteristics of sedimentary rocks,along with the subsequent interpretation of depositional processes and sedimentary environments in a basin or locality.展开更多
Sediment core samples collected from Lake Chaohu were analyzed for 15 priority polycyclic aromatic hydrocarbons（PAHs）to assess the spatial and temporal distributions of the PAHs during lacustrine sedimentary process...Sediment core samples collected from Lake Chaohu were analyzed for 15 priority polycyclic aromatic hydrocarbons（PAHs）to assess the spatial and temporal distributions of the PAHs during lacustrine sedimentary processes and regional economic development.Assessing the PAH sedimentary records over an approximately 100-year time span,we identified two stages in the PAH inputs and sources（before the 1970 s and after the 1970s）in the eastern lake region near a village,whereas three stages（before the 1950 s,1950s–1990s and after the1990s）were identified in the western lake region near urban and industrial areas.Rapid increases in the PAH depositional fluxes occurred during the second stage due to increased human activities in the Lake Chaohu basin.The composition and isomeric ratios of the PAHs revealed that pyrolysis is the main source of PAHs in this lake.Strong positive relationships between PAH concentration and the total organic carbon concentration,sediment grain size（〈 4 μm）,as well as the local population and Gross Domestic Product indicated that the sedimentary conditions impact the depositional characteristics of the PAHs;simultaneously,socioeconomic activities,such as energy consumption and the levels of urban industrialization and civilization,affect both the composition and abundance of the PAHs.展开更多
Surface sediments were collected from Lake Manzala, the Mediterranean coastal wetland located to the east of the Nile Delta, Egypt, to assess the effect of drain effluent on the spatial variations of sedimentary chara...Surface sediments were collected from Lake Manzala, the Mediterranean coastal wetland located to the east of the Nile Delta, Egypt, to assess the effect of drain effluent on the spatial variations of sedimentary characteristics and heavy metal pollution. Grain-size compositions, textures, and heavy metal distribution patterns in sediments are presented using GIS technique. Results of the analysis of the sediment showed a clear effect of drain effluent, with an increase in fine fractions and homogeneous suspensions in transportation mode. Lake sediments were dominated by sandy mud textures, and mode of transportation was homogeneous sus- pension and rolling. Spatial distribution of heavy metals (Fe, Mn, Zn, Cu, Ni, Cr, and Pb) was studied in the lake’s surficial sediments, along with their relationship to drain effluent and their contamination status in the ecological system. Heavy metal pollution status was assessed by means of accepted sediment quality guidelines and contamination assessment methods (contamination factor, con- tamination degree, modified contamination degree, geo-accumulation, and enrichment factor). Among the determined heavy metals, Pb had the most ecological risk. Generally, the heavy metals in the surface sediments indicated pollution risk ranging from moderate to considerable, particularly, in those sites facing drains and inlets that had the highest toxic effluent. The results were interpreted by statistical means. A cluster analysis defined areas facing drain discharge and inlets as separated groups. ANOVA indicated that most of the sedimentation and studied metals directed this clustering.展开更多
On the platform of the Deep-time Digital Earth Program(DDE),sedimentary data are essential for achieving its scientific objectives.These data will take stratigraphic units as their core data carrier,for quantitative o...On the platform of the Deep-time Digital Earth Program(DDE),sedimentary data are essential for achieving its scientific objectives.These data will take stratigraphic units as their core data carrier,for quantitative or qualitative data analysis.The DDE Sedimentary Data Group is responsible for the management of the sedimentary data on the DDE platform and has now developed into a group of nearly 40 disciplinary experts.展开更多
In an area of about 305 km2, Seventeen stream sediment samples were taken from alluvium on the banks and floodplain of the Lokoundjé River and its tributaries. Sand samples after being dried in an oven, are subje...In an area of about 305 km2, Seventeen stream sediment samples were taken from alluvium on the banks and floodplain of the Lokoundjé River and its tributaries. Sand samples after being dried in an oven, are subjected to sedimentological analyses in laboratory. Amongst the analysis carried out;the particle size analysis helped to establish a precise textural description of the sediment and to understand the active mechanisms which occur during transport and particle deposition. The morphoscopy of quartz grains consists in determining the mode and duration of transport of the grains, thus allowing reconstructing the geological history of the latter. Heavy minerals are suitable to know the nature of the rock in which they come from and equal to specify their distributing province. The morphometry of pebble makes contributes for a better understanding to apprehension of the agents responsible for the transport of these materials. It appears that the alluvium of the Lokoundjé and its Bipindi tributaries are very fine to coarse. They are well segregated, classified, and homometric. It is the result of the actions of a hydrodynamic turbulent which is sometimes abrupt. From a morphoscopic point of view, using a binocular microscope, grains mainly belong to three categories based on their surface appearance: Grain unworn, the sub-dull and dull shiny. From the morphometric point of view, there is evidence of flattening and dissymmetry of pebbles which are slightly worn to form sub-spherical shapes. With regard to the study of heavy minerals, it has identified two mineralogical processions, which include a metamorphic process with the presence of Sillimanite and Andalusite. In addition, there is the presence of minerals such as green’s Hornblende, Tourmaline, and reflecting magmatic distribution. However, there are specific minerals such as zircon, which can be economically viable where the contents sometimes exceed 10 kg/m3. In the same vein, it has been noted the presence of gems like Topaze and Monazite which are real precursor auriferous accumulation.展开更多
Reworked detrital sediments were discovered in the syn-rift to post-rift Cretaceous to Quaternary(Pleistocene)detrital deposits of the Douala coastal sub-basin in the eastern margin of the South Atlantic Ocean at West...Reworked detrital sediments were discovered in the syn-rift to post-rift Cretaceous to Quaternary(Pleistocene)detrital deposits of the Douala coastal sub-basin in the eastern margin of the South Atlantic Ocean at West Cameroon.This contribution presents the geochemical,mineralogical,and sedimentological data to constrain the origin of these reworked sediments.The investigated samples are characterized by the high values of Plagioclase Index of Alteration(PIA,97.83–99.90),Chemical Index of Alteration(CIA,71.9–99.08),and Chemical Index of Weathering(CIW,98.67–99.90).Data gleaned from these indices suggest that the reworked sediments and their potential source rocks experienced severe weathering.The A-CN-K plot along with the mineralogical indicates a probably post-depositional K-enrichment.The high light rare earth elements(LREE)/heavy rare earth elements(HREE)ratios(15.82–79.13)suggest that the reworked were mainly derived from felsic igneous rocks.This interpretation is further confirmed by the Zr versus TiO2,TiO2/Al2O3,Th/Co versus La/Sc,and La/Th versus Th/Yb plots,which indicate felsic igneous and silicic source rocks.Meanwhile,the high variability of LREE/HREE ratios(15.82–79.13)and the positive Eu anomalies(1.10–1.32)of studied samples could indicate a little contribution of mafic source rocks.Analysis of the distribution of the heavy minerals(e.g.tourmaline,aluminum silicate,and rutile)revealed that these felsic and silicic source rocks are mainly granite and gneiss,probably belonging to the Nyong Group and the Western part of the Neoproterozoic Yaounde Group.The morphoscopic analyses of the host rocks(very angular to angular shapes)have revealed that the reworked sediments have proximal to subproximal onshore origins,probably from former sedimentary deposits,as is indicated by variation of their color.The tectonic discriminant diagram indicates the Oceanic Island Arc and Active Continental Margin which are inconsistent with the geological history of the Douala coastal sub-basin and could be explained by the recycling effect experienced by studied sediments which have been deposited in the coastal plain to the fluvial environment in the Low System Track context.展开更多
This work presents a study of the Paleogene sandstones of the Manika plateau in Kolwezi, DR Congo. These sandstones belong to the “Grès polymorphes” group, which together with the overlying “Sables ocre” make...This work presents a study of the Paleogene sandstones of the Manika plateau in Kolwezi, DR Congo. These sandstones belong to the “Grès polymorphes” group, which together with the overlying “Sables ocre” makes up the Kalahari Supergroup. Sedimentological and geochemical analyses have enabled us to characterize these sandstones and determine their origin, the conditions of their formation and the tectonic context in which they were developed. The results show that the sandstones are quartz arenites with a high level of mineralogical, textural and chemical maturity. They are recycled sandstones, formed in an intracratonic sedimentary basin, in the context of a passive continental margin, after a long fluvial transport of sediments. These sandstones initially come from intense alteration of magmatic rocks with felsic composition, mainly tonalite-trondhjemite-granodiorite (TTG) complexes, in hot, humid palaeoclimatic conditions and oxidizing environments.展开更多
A granulometric, mineralogical, morphoscopic and exoscopic study and Rock-Eval analysis carried out on samples taken in the Loango Bay and at Kivesso on the Congolese coast have made it possible to highlight the highl...A granulometric, mineralogical, morphoscopic and exoscopic study and Rock-Eval analysis carried out on samples taken in the Loango Bay and at Kivesso on the Congolese coast have made it possible to highlight the highly erosive character of the well-documented wet phases ca 9000 - 3000 years B.P. and ca 320 B.P. in the sub-region. Supported by carbon-14 dating, total organic carbon analyses highlight two major phases of peat deposit emplacement. The first, ca. 7000 years B.P., corresponds to the beginning of the deposition of the yellow formation in the entire Loango Bay;the second, ca. 320 years B.P., is contemporary with the deposition of peat in the Kivesso sector. The granulometric analysis of the sediments shows that they are essentially sandy-clay and very poor in silt, alternating with beds of silty clay sometimes rich in organic matter. These sands have a predominant mode of 0.200 mm and an average varying between 0.150 and 0.300 mm. They constitute the flood phase of the carrier current. They are associated with a population of mode 0.125 mm sometimes 0.050 mm with an average varying between 0.100 mm and 0.126 mm which corresponds to the settling phase. Morphoscopic examination showed several varieties of quartz that argue for a source of supply close to the depositional sites.展开更多
A multidisciplinary study of the sedimentology, geochemistry and mineralogy has been conducted to understand the linkage between marsh and alluvial sediments and also their potential sources in Eynak marsh, North of I...A multidisciplinary study of the sedimentology, geochemistry and mineralogy has been conducted to understand the linkage between marsh and alluvial sediments and also their potential sources in Eynak marsh, North of Iran. The influence of the upstream potential sources on recent sediment geochemistry has been discussed based on geochemical, sedimentological and mineralogical results. A spatial grain size distribution study was carried out to investigate the hydrodynamic and deposition system of the marsh. So, the surficial sediment sampling was carried out to describe the sedimentological parameters and elemental geochemistry of sediments in Eynak marsh. Mineralogical complexes are mainly made up of felsic minerals such as quartz, calcite, feldspar, pyrite, mica, and clay minerals (in very low values) indicated by high amounts of Al, Ca, and Ni. As expected, the mineralogy of sediments is controlled mainly by the rock formations. Also sediment textures are controlled by the hydrodynamic condition in the marsh. So its distribution has been influenced by distance from the entrance sediments to Eynak marsh. The results showed that there are no enrichments related to fine grain sediment distributions. An association of Al with the trace elements such as Sc, Y, La, Ce, and Zr indicates that their distributions are mainly controlled by the felsic rocks in the upstream. On the other side, due to the waste water entrance to the marsh, Ni and Pb concentration could be under the effects of anthropogenic activities around the marsh. Results represented high values for Mn concentration (min 462, max 1784 and average 1037 ppm) and it showed a significant correlation with Ca, Sr, and Mg. A redox habitat and constantly calm hydrodynamic circumstance in the study area, likely cause high concentration of Ca, Sr, and Mg, and Mn. And they are representing negative correlations with some elements such as Al, Be, Fe, K, and Na.展开更多
文摘1 Introduction Sedimentary rocks archive important information for understanding how the earth system operates and how life and environments have evolved through earth history.Properly identifying characteristics of sedimentary rocks,along with the subsequent interpretation of depositional processes and sedimentary environments in a basin or locality.
基金supported by the Mega-projects of Science Research for Water Environment Improvement(No.2012ZX07101-002)the National Natural Science Foundation of China(No.41303085)
文摘Sediment core samples collected from Lake Chaohu were analyzed for 15 priority polycyclic aromatic hydrocarbons（PAHs）to assess the spatial and temporal distributions of the PAHs during lacustrine sedimentary processes and regional economic development.Assessing the PAH sedimentary records over an approximately 100-year time span,we identified two stages in the PAH inputs and sources（before the 1970 s and after the 1970s）in the eastern lake region near a village,whereas three stages（before the 1950 s,1950s–1990s and after the1990s）were identified in the western lake region near urban and industrial areas.Rapid increases in the PAH depositional fluxes occurred during the second stage due to increased human activities in the Lake Chaohu basin.The composition and isomeric ratios of the PAHs revealed that pyrolysis is the main source of PAHs in this lake.Strong positive relationships between PAH concentration and the total organic carbon concentration,sediment grain size（〈 4 μm）,as well as the local population and Gross Domestic Product indicated that the sedimentary conditions impact the depositional characteristics of the PAHs;simultaneously,socioeconomic activities,such as energy consumption and the levels of urban industrialization and civilization,affect both the composition and abundance of the PAHs.
文摘Surface sediments were collected from Lake Manzala, the Mediterranean coastal wetland located to the east of the Nile Delta, Egypt, to assess the effect of drain effluent on the spatial variations of sedimentary characteristics and heavy metal pollution. Grain-size compositions, textures, and heavy metal distribution patterns in sediments are presented using GIS technique. Results of the analysis of the sediment showed a clear effect of drain effluent, with an increase in fine fractions and homogeneous suspensions in transportation mode. Lake sediments were dominated by sandy mud textures, and mode of transportation was homogeneous sus- pension and rolling. Spatial distribution of heavy metals (Fe, Mn, Zn, Cu, Ni, Cr, and Pb) was studied in the lake’s surficial sediments, along with their relationship to drain effluent and their contamination status in the ecological system. Heavy metal pollution status was assessed by means of accepted sediment quality guidelines and contamination assessment methods (contamination factor, con- tamination degree, modified contamination degree, geo-accumulation, and enrichment factor). Among the determined heavy metals, Pb had the most ecological risk. Generally, the heavy metals in the surface sediments indicated pollution risk ranging from moderate to considerable, particularly, in those sites facing drains and inlets that had the highest toxic effluent. The results were interpreted by statistical means. A cluster analysis defined areas facing drain discharge and inlets as separated groups. ANOVA indicated that most of the sedimentation and studied metals directed this clustering.
文摘On the platform of the Deep-time Digital Earth Program(DDE),sedimentary data are essential for achieving its scientific objectives.These data will take stratigraphic units as their core data carrier,for quantitative or qualitative data analysis.The DDE Sedimentary Data Group is responsible for the management of the sedimentary data on the DDE platform and has now developed into a group of nearly 40 disciplinary experts.
文摘In an area of about 305 km2, Seventeen stream sediment samples were taken from alluvium on the banks and floodplain of the Lokoundjé River and its tributaries. Sand samples after being dried in an oven, are subjected to sedimentological analyses in laboratory. Amongst the analysis carried out;the particle size analysis helped to establish a precise textural description of the sediment and to understand the active mechanisms which occur during transport and particle deposition. The morphoscopy of quartz grains consists in determining the mode and duration of transport of the grains, thus allowing reconstructing the geological history of the latter. Heavy minerals are suitable to know the nature of the rock in which they come from and equal to specify their distributing province. The morphometry of pebble makes contributes for a better understanding to apprehension of the agents responsible for the transport of these materials. It appears that the alluvium of the Lokoundjé and its Bipindi tributaries are very fine to coarse. They are well segregated, classified, and homometric. It is the result of the actions of a hydrodynamic turbulent which is sometimes abrupt. From a morphoscopic point of view, using a binocular microscope, grains mainly belong to three categories based on their surface appearance: Grain unworn, the sub-dull and dull shiny. From the morphometric point of view, there is evidence of flattening and dissymmetry of pebbles which are slightly worn to form sub-spherical shapes. With regard to the study of heavy minerals, it has identified two mineralogical processions, which include a metamorphic process with the presence of Sillimanite and Andalusite. In addition, there is the presence of minerals such as green’s Hornblende, Tourmaline, and reflecting magmatic distribution. However, there are specific minerals such as zircon, which can be economically viable where the contents sometimes exceed 10 kg/m3. In the same vein, it has been noted the presence of gems like Topaze and Monazite which are real precursor auriferous accumulation.
文摘Reworked detrital sediments were discovered in the syn-rift to post-rift Cretaceous to Quaternary(Pleistocene)detrital deposits of the Douala coastal sub-basin in the eastern margin of the South Atlantic Ocean at West Cameroon.This contribution presents the geochemical,mineralogical,and sedimentological data to constrain the origin of these reworked sediments.The investigated samples are characterized by the high values of Plagioclase Index of Alteration(PIA,97.83–99.90),Chemical Index of Alteration(CIA,71.9–99.08),and Chemical Index of Weathering(CIW,98.67–99.90).Data gleaned from these indices suggest that the reworked sediments and their potential source rocks experienced severe weathering.The A-CN-K plot along with the mineralogical indicates a probably post-depositional K-enrichment.The high light rare earth elements(LREE)/heavy rare earth elements(HREE)ratios(15.82–79.13)suggest that the reworked were mainly derived from felsic igneous rocks.This interpretation is further confirmed by the Zr versus TiO2,TiO2/Al2O3,Th/Co versus La/Sc,and La/Th versus Th/Yb plots,which indicate felsic igneous and silicic source rocks.Meanwhile,the high variability of LREE/HREE ratios(15.82–79.13)and the positive Eu anomalies(1.10–1.32)of studied samples could indicate a little contribution of mafic source rocks.Analysis of the distribution of the heavy minerals(e.g.tourmaline,aluminum silicate,and rutile)revealed that these felsic and silicic source rocks are mainly granite and gneiss,probably belonging to the Nyong Group and the Western part of the Neoproterozoic Yaounde Group.The morphoscopic analyses of the host rocks(very angular to angular shapes)have revealed that the reworked sediments have proximal to subproximal onshore origins,probably from former sedimentary deposits,as is indicated by variation of their color.The tectonic discriminant diagram indicates the Oceanic Island Arc and Active Continental Margin which are inconsistent with the geological history of the Douala coastal sub-basin and could be explained by the recycling effect experienced by studied sediments which have been deposited in the coastal plain to the fluvial environment in the Low System Track context.
文摘This work presents a study of the Paleogene sandstones of the Manika plateau in Kolwezi, DR Congo. These sandstones belong to the “Grès polymorphes” group, which together with the overlying “Sables ocre” makes up the Kalahari Supergroup. Sedimentological and geochemical analyses have enabled us to characterize these sandstones and determine their origin, the conditions of their formation and the tectonic context in which they were developed. The results show that the sandstones are quartz arenites with a high level of mineralogical, textural and chemical maturity. They are recycled sandstones, formed in an intracratonic sedimentary basin, in the context of a passive continental margin, after a long fluvial transport of sediments. These sandstones initially come from intense alteration of magmatic rocks with felsic composition, mainly tonalite-trondhjemite-granodiorite (TTG) complexes, in hot, humid palaeoclimatic conditions and oxidizing environments.
文摘A granulometric, mineralogical, morphoscopic and exoscopic study and Rock-Eval analysis carried out on samples taken in the Loango Bay and at Kivesso on the Congolese coast have made it possible to highlight the highly erosive character of the well-documented wet phases ca 9000 - 3000 years B.P. and ca 320 B.P. in the sub-region. Supported by carbon-14 dating, total organic carbon analyses highlight two major phases of peat deposit emplacement. The first, ca. 7000 years B.P., corresponds to the beginning of the deposition of the yellow formation in the entire Loango Bay;the second, ca. 320 years B.P., is contemporary with the deposition of peat in the Kivesso sector. The granulometric analysis of the sediments shows that they are essentially sandy-clay and very poor in silt, alternating with beds of silty clay sometimes rich in organic matter. These sands have a predominant mode of 0.200 mm and an average varying between 0.150 and 0.300 mm. They constitute the flood phase of the carrier current. They are associated with a population of mode 0.125 mm sometimes 0.050 mm with an average varying between 0.100 mm and 0.126 mm which corresponds to the settling phase. Morphoscopic examination showed several varieties of quartz that argue for a source of supply close to the depositional sites.
文摘A multidisciplinary study of the sedimentology, geochemistry and mineralogy has been conducted to understand the linkage between marsh and alluvial sediments and also their potential sources in Eynak marsh, North of Iran. The influence of the upstream potential sources on recent sediment geochemistry has been discussed based on geochemical, sedimentological and mineralogical results. A spatial grain size distribution study was carried out to investigate the hydrodynamic and deposition system of the marsh. So, the surficial sediment sampling was carried out to describe the sedimentological parameters and elemental geochemistry of sediments in Eynak marsh. Mineralogical complexes are mainly made up of felsic minerals such as quartz, calcite, feldspar, pyrite, mica, and clay minerals (in very low values) indicated by high amounts of Al, Ca, and Ni. As expected, the mineralogy of sediments is controlled mainly by the rock formations. Also sediment textures are controlled by the hydrodynamic condition in the marsh. So its distribution has been influenced by distance from the entrance sediments to Eynak marsh. The results showed that there are no enrichments related to fine grain sediment distributions. An association of Al with the trace elements such as Sc, Y, La, Ce, and Zr indicates that their distributions are mainly controlled by the felsic rocks in the upstream. On the other side, due to the waste water entrance to the marsh, Ni and Pb concentration could be under the effects of anthropogenic activities around the marsh. Results represented high values for Mn concentration (min 462, max 1784 and average 1037 ppm) and it showed a significant correlation with Ca, Sr, and Mg. A redox habitat and constantly calm hydrodynamic circumstance in the study area, likely cause high concentration of Ca, Sr, and Mg, and Mn. And they are representing negative correlations with some elements such as Al, Be, Fe, K, and Na.
