To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion condition...To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion conditions,the weakening characteristics,observable characteristics,softening characteristics of the dynamic parameters,dynamic failure characteristics,dynamic failure forms and dynamic microscopic characteristics were analyzed.Under each corrosion condition,the dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity tended to decrease with immersing time.The dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity exhibited an inverted U-shaped trend.Under dynamic impact,the failure process of acidly corroded samples can be divided into the following stages:the initial stage,elastic energy accumulation stage,local failure of coal and secondary rock crack expansion stage,coal fragment ejection stage,rock spalling stage and complete instability stage.Under dynamic impact,failure modes exist:coal crushing failure,rock fragmenting failure,rock splitting failure and full splitting failure.After impact failure,sample fragments are distributed in powder,granular,cone and block forms.Based on Zhu-Wang-Tang nonlinear viscoelastic properties,a model considering chemical corrosion and impact damage was proposed.The combined effects of chemical and impact-induced damage on the dynamic mechanical properties of coal-rock assemblages were systematically analyzed.展开更多
0 INTRODUCTION The Andean orogenic belt,a globally significant active continental margin(Lamb et al.,1997),extends in a north-south direction along the western coast of South America.The Colombian Andes,located in the...0 INTRODUCTION The Andean orogenic belt,a globally significant active continental margin(Lamb et al.,1997),extends in a north-south direction along the western coast of South America.The Colombian Andes,located in the northern segment of this orogen,constitute a vital component and host abundant Au-Cu resources.Three principal Au-Cu metallogenic belts(Chocó,Middle Cauca,and Antioquia)are developed from west to east across Colombia(Lesage et al.,2013;Sillitoe,2008;Figure 1a).展开更多
The marine-continental transitional shale of the Upper Permian Longtan Formation is widely distributed in Hunan and shows significant exploration potential.Frequent changes in lithofacies have however notably influenc...The marine-continental transitional shale of the Upper Permian Longtan Formation is widely distributed in Hunan and shows significant exploration potential.Frequent changes in lithofacies have however notably influenced the shale gas enrichment.The strata of the Longtan Formation in the Shaoyang Depression,central Hunan,were taken as the study object for this project.Three lithofacies assemblages were identified:shale interbedded with sandstone layer(SAL),sandstone interbedded with shale layer(ASL)and laminated shale layer(LSL).The SAL shale shows significant variability in hydrocarbon generation potential,which leads to shale gas characterized by'hydrocarbon generation in high total organic carbon(TOC)shale,retention in low TOC shale and accumulation in sandstone'.The ASL shale,influenced by the redox conditions of the depositional environment,shows a lower concentration of organic matter.This results in an enrichment model of'hydrocarbon generation and accumulation in shale,with sealing by sandstone'.The laminar structure of LSL shale causes both quartz and clay minerals to control the reservoir.Shale gas is characterized by'hydrocarbon generation in mud laminae,retention and accumulation in silty laminae,with multiple intra-source migration paths'.In the marine-continental transitional shale gas system,the enrichment intervals of different types of shale gas reservoirs exhibit significant variability.展开更多
The Middle Jurassic palynomorphs from the Yan'an Formation in Dongsheng region of Nei Monggol, consist of 63 species of fossil spores and pollen grains belonging to 34 genera, of which two species were described a...The Middle Jurassic palynomorphs from the Yan'an Formation in Dongsheng region of Nei Monggol, consist of 63 species of fossil spores and pollen grains belonging to 34 genera, of which two species were described as new. Based on statistical analysis of 3 863 specimens identified in 10 samples from Hantaichuan, Nianpanlianggou and Liugou sections, the sporo-pollen assemblage from the Yan'an Formation in Dongsheng region was established, which is generally characterized by the slight dominance of gymnospermous pollen grains (generally attaining proportion of 51%-54%), whereas the pteridophytic spores reach 46%-49% in abundance. In comparison with those of adjacent regions as well as Eurasia and North America, the present sporo-pollen assemblage is regarded to early Middle Jurassic (corresponding to Bajocian Stage) in geological age. According to the climatic conditions reflected by the palynoflora, the paleoclimate in Dongsheng region is suggested to be warm temperate or subtropical warm and humid during the early Middle Jurassic.展开更多
We collected fish abundance data in the Changjiang(Yangtze River) estuary and adjacent waters in November 1998,May 1999,November 2000,and May 2001.Using the data,we evaluated the characteristics of the fish assemblage...We collected fish abundance data in the Changjiang(Yangtze River) estuary and adjacent waters in November 1998,May 1999,November 2000,and May 2001.Using the data,we evaluated the characteristics of the fish assemblages at each site and investigated the effect of several environmental factors.We used a multivariate analysis,including community ordination methods such as detrended correspondence analysis(DCA) and canonical correspondence analysis(CCA),and two-way indicator species analysis(TWINSPAN).We analyzed the biological community structure and environmental factors to determine their spatial distributions,temporal dynamics,and seasonal variations.Among the fish species,five exceeded 5% of the total abundance:Harpodon nehereus(42.82%),Benthosema pterotum(13.85%),Setipinna taty(11.64%),Thryssa kammalensis(9.17%) and Apogonichthys lineatus(6.49%).These were separated into four ecological assemblages:hypsithermal-saline,hypsithermal-brackish,hypothermal-brackish,and hypothermal-saline.We evaluated the degree of influence of environmental factors on the fish community.Our analyses suggested that environmental factors including water depth,salinity,turbidity,transparency,nutrient,and suspended matter formed a synthetic spatial gradient between the coastal and pelagic areas.Ecological and environmental factors changed temporally from 1998 to 2001,and drove the fish community succession.The environmental factors driving the fish community structure included bottom temperature,water depth,bottom and surface pH,surface total phosphorous,and bottom dissolved oxygen.This investigation was completed before completion of the Three Gorges Dam;therefore the results of this study provide an important foundation for evaluating the influence of the human activities.展开更多
Based on the palynological data from Well Ta-19-36 and Well Ta-19-37 in the Ta＇nan Sag, and Well Ta-22-1 and Well Ta-21-1 in the Bayin Gobi Sag, a spore-pollen assemblage from the Damoguaihe Formation is named as Cic...Based on the palynological data from Well Ta-19-36 and Well Ta-19-37 in the Ta＇nan Sag, and Well Ta-22-1 and Well Ta-21-1 in the Bayin Gobi Sag, a spore-pollen assemblage from the Damoguaihe Formation is named as Cicatricosisporites minutaestriatus- Aequitriradites spinulosus-Protopinus sp. assemblage in the Tamutsag Basin, Mongolia. The assemblage is characterized by abundant gymnosperm pollen and diverse fern spores, counted 46.35%–65.57% and 34.43%–52.58% in percentage respectively. Among the gymnosperm pollen, Pinuspollenites sp.（2.66%–16.94%）, Protopinus sp.（0–11.38%） and Protopicea sp.（0–10.81%） are dominant; and Alisporites sp., Cerebropollenites sp., Podocarpidites sp., and Abietineaepollenites sp. are common. Some important elements, such as Chasmatosporites sp., Callialasporites prominulus, Parvisaccites sp., Parcisporites sp., Jiaohepollis cf. annulatus, J. bellus, J. verus, Polycingulatisporites sp., Schizaeoisporites certus, Classopollis annulatus are seen. Within the fern spores, Osmundacidites wellamanii（0.85%–4.93%）, Appendicisporites sp.（0–4.45%）, Baculatisporites comaumensis（0.80%–2.87%）, Cicatricosisporites sp.（0.51%–2.66%）, C. minor（0–2.14%）, Foraminisporis asymmetricus（0–2.40%）, Aequitriradites sp.（0– 2.19%） and Cyathidites minor（0–2.13%） are dominant; and some specie of Densoisporites, Cooksonites, Impardecispora, Pilosisporites, Schizaeosprites, Fixisporites, Leptolepidites, Trilobosporites, Kuylisporites, Klukisporites, Hsuisporites, Couperisporites, Maculatisporites are seen. The angiosperm pollen are rare in the assemblage, characterized by Clavatipollenites sp.（0–0.80%） and Songipollis sp.（0–0.27%）. The geological age of the Damoguaihe Formation is assigned to Hauterivian – Barremian of Early Cretaceous according to the palynological data, due to the fact that there existed a lot of diverse spores of the family Schizaeaceae and prosperous gymnosperm saccat pollen which the corpus and sacci are differentiated completely, and the presence of early angiosperm pollen of Clavatipollenites. However, the zircon U-Pb isotopic dating of the volcanic rocks in the Nantun Formation indicated that the overlying strata of the Nantun Formation, i.e. the Damoguaihe Formation must be younger than 127.0±2.0–137.9±1.5 Ma. This is consistent with the palynological data. Furthermore, the vegetation reconstructed on the palynological data of the Damoguaihe Formation is conifer forest with shrubs and grassland, belonging to the semi-humid or humid middle to south subtropical climate. Moreover, three new species, namely Biretisporites punctatus sp. nov., Chasmatosporites reticulates sp. nov. and Concentrisporites contractus sp. nov. are described here.展开更多
Three sporopollen assemblages are recognized for the first time from the Cretaceous Yimin Formation in the Hailar Basin of eastern Inner Mongolia. They are （in ascending order）： the lmpardecispora-Aequitriradites- ...Three sporopollen assemblages are recognized for the first time from the Cretaceous Yimin Formation in the Hailar Basin of eastern Inner Mongolia. They are （in ascending order）： the lmpardecispora-Aequitriradites- Clawttipollenites assemblage; the Triporoletes-Pilosisporites-Asteropollis assemblage; and the Appendicisporites- Asteropollis-Tricolpites assemblage, distributed in Members 1, 2 and 3 of the Yimin Formation respectively. Recognition of this biostratigraphic sequence is very important for the division and correlation of the Yimin Formation in the basin. Meanwhile, the age of the Yimin Formation is considered to be Barremian to Early Albian based on the palynological data.展开更多
Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the...Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradient from headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at the lower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysis of similarities （ANOSIM）, fish assemblages were significantly different in spatial variation but not in temporal variation. Although differences were observed both among sites and among stream orders, the lower R value in order-variation suggested stream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did not significantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis and non-metric Multi Dimensional Scaling analysis （NMS）, assemblages were separated into three groups at a Bray-Curtis similarity value of 42%： the upper, middle and lower groups. Following analysis of similarity percentages of species contributions （SIM- PER）, shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A. fasciatus contributed most to the differences amongst the three groups. Standard Deviation Redundancy Analysis （RDA） suggested that habitat structure （such as elevation, substrate, and flow velocity） contributed to the spatial and temporal pattem of fish assemblages in the Puxi Stream. In conclusion, the fish assemblages in Puxi Stream presented significant spatial but not temporal variation. Human disturbance has perhaps induced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblages in sites far from and immediately downstream from low-head dams [Current Zoology 56 （6）： 670-677, 2010].展开更多
Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exis...Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exists about the time when the transgressions occurred separately. In order to find out the process of the paleoenvironmental changes around the Bohai Sea in the late Quaternary, the foraminifera assemblages from a new borehole Lz908 in the southern coast of the Laizhou Bay were studied, and then the transgressive strata were indentified. Combined with accelerator mass spectrometry radiocarbon 14C（AMS14C） and optically stimulated luminescence（OSL） ages, the occurrence time of these transgressions were re-determined. The result showed that three major large-scale transgressions occurred separately at the beginning of marine isotopic stage 7（MIS7）, the last interglacial period（MIS5） and the Holocene. In addition, a small-scale transgression occurred in the mid-MIS6, and the corresponding transgressive stratum was deposited. The transgressive deposition of MIS3 was also discovered in this study. However, the characteristics of the foraminifera indicated the environment during this period was colder than that in the MIS5. By comparison with the global sea-level changes, the paleoenvironmental changes around the Bohai Sea in the late Quaternary can be consistent with the global climate changes.展开更多
Carbon isotope （δ13Corg） analyses of non-marine clastic rocks and neritic carbonates and black shales spanning the Silurian/Devonian transition are compared from two richly fossiliferous sequences in Qujing of East...Carbon isotope （δ13Corg） analyses of non-marine clastic rocks and neritic carbonates and black shales spanning the Silurian/Devonian transition are compared from two richly fossiliferous sequences in Qujing of East Yunnan and Zoige of Sichuan, South China. The two sections, Xishancun and Putonggou sections in South China, reveal positive δ13Corg shifts happening in the Upper Pridoli and Lower Devonian and reaching peak values as heavy as -25.2‰ （Xishancun） and -19.9‰（Putonggou） in the lowermost Lochkovian following the first occurrence of the thelodont Parathelodus and the conodont Icriodus woschmidti woschmidti （only in Putonggou Section and together with Protathyris-Lanceomyonia brachiopod fauna）. These results replicate a globally known positive shift in δ13Corg from the uppermost Silurian to the lowermost Devonian. The δ13Corg variations across the Silurian/Devonian Boundary （SDB） at the two sections in South China exhibit a shift in carbon isotopic composition similar to the detailed SDB curves from the borehole Klonk-1 drilled at top of the Klonk Global Standard Stratotype-Section and Point （GSSP） in the Prague Basin, Czech Republic. In addition, four microvertebrate assemblages, including the Liaojiaoshan, Xishancun, Yanglugou and Xiaputonggou assemblages, are recognized from the Silurian/Devonian transition exposed in the Xishancun and Putonggou sections, respectively. The results from both carbon isotope stratigraphy and microvertebrate assemblage sequences suggest that the SDB in South China is located at the base of the Xishancun Formation （between sample QX-20 and sample QX-21） in the Xishancun Section and the lower part of the Xiaputonggou Formation （between sample ZP-09 and sample ZP-10） in the Putonggou Section. The isotopic trend for organic carbon together with the changes of microvertebrate remains across the SDB can offer an approach to a potential correlation of the SDB from different sedimentary facies, which help to correlate the marine with non-marine deposits.展开更多
In 2012,an artificial reef system was deployed in Xiangshan Bay,China,to enhance its fishery resources. To determine the effect of the artificial reef system on the demersal nekton assemblages,a beforeafter-control-im...In 2012,an artificial reef system was deployed in Xiangshan Bay,China,to enhance its fishery resources. To determine the effect of the artificial reef system on the demersal nekton assemblages,a beforeafter-control-impact study design was applied. Comparisons of assemblages from impact and control habitats revealed that the assemblage in the impact area had a gradual response to reef deployment. The assemblages in the impact and control areas changed in different ways after reef deployment. During the study period,total biomass,species richness and average body weight in the control area remained relatively stable,whereas there were significant increases in these indicators in the impact area. Responses to the reefs differed among nekton species,inducing assemblage succession in the reefs post-deployment. Sparus macrocephalus and Cynoglossus abbreviat us benefited most from reef deployment. Conversely,smallsized shrimp Palaemon gravieri showed a progressive decrease in biomass following reef deployment. Overall,the artificial reef system diversified the demersal nekton assemblage,enhanced the total biomass,and increased the proportion of large-sized species.展开更多
Surveys were conducted in five voyages in Haizhou Bay and its adjacent coastal area from March to December 2011 during full moon spring tides. The ichthyoplankton assemblages and the environmental factors that affect ...Surveys were conducted in five voyages in Haizhou Bay and its adjacent coastal area from March to December 2011 during full moon spring tides. The ichthyoplankton assemblages and the environmental factors that affect their spatial and seasonal patterns were determined. Totally 35 and 12 fish egg and larvae taxa were identified, respectively. Over the past several decades, the egg and larval species composition has significantly changed in Haizhou Bay and its adjacent waters, most likely corresponding with the alteration of fishery resources, which are strongly affected by anthropogenic activities and climate change. The Bray-Curtis dissimilarity index identified four assemblages: near-shore bay assemblage, middle bay assemblage and two closely related assemblages(near-shore/middle bay assemblage and middle/edge of bay assemblage). The primary species of each assemblage principally reflected the spawning strategies of adult fish. The near-shore bay assemblage generally occurred in near-shore bay, with depths measuring <20 m, and the middle bay assemblage generally occurred in the middle of bay, with depths measuring 20 to 40 m. Spatial and seasonal variations in ichthyoplankton in each assemblage were determined by interactions between biological behavioral traits and oceanographic features, particularly the variation of local conditions within the constraint of a general reproductive strategy. The results of Spearman's rank correlation analysis indicated that both fish egg and larval abundance were positively correlated with depth, which is critical to the oceanographic features in Haizhou Bay.展开更多
The cell model developed since 1950s is a useful tool forexploring the behavior of particle assemblages, but it demandsfurther careful development of the outer boundary conditions so thatinteraction in a particle swar...The cell model developed since 1950s is a useful tool forexploring the behavior of particle assemblages, but it demandsfurther careful development of the outer boundary conditions so thatinteraction in a particle swarm is better represented. In this paper,the cell model and its development were reviewed, and themodifications of outer cell boundary conditions were suggested. Atthe cell outer boundary, the restriction of uniform liquid flow wasremoved in our simulation conducted in the reference frame fixed withthe particle.展开更多
According to multi- disciplinary research advances in recent years, three blocks which named Jiaoliao - Bohai block, central North China block and Ordos block are divided. The differences of the tectonic association, ...According to multi- disciplinary research advances in recent years, three blocks which named Jiaoliao - Bohai block, central North China block and Ordos block are divided. The differences of the tectonic association, types, styles and features in the space, and evolution from Archaean to Cenozoic in the time, between the former two blocks are discussed. Tectonic features and evolution in the four tectonic stages of Precambrian, Indo- China, Yanshanian and Cenozoic are emphasized especially here. All of them described above have inherit and neogenic property. The temporal-spatial change and interaction among basin assemblages in the above four stages are analyzed. Escape tectonic model is employed to interpret coeval compressive and extensional basins in the study area.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52034009 and 52174093)the Fundamental Research Funds for the Central Universities(Nos.2024ZKPYNY01,2023ZKPYNY03,and 2023YQTD02).
文摘To reveal the deterioration mechanism of coal-rock assemblages under chemical corrosion and dynamic loading,chemical corrosion and dynamic impact experiments were conducted.Under different chemical corrosion conditions,the weakening characteristics,observable characteristics,softening characteristics of the dynamic parameters,dynamic failure characteristics,dynamic failure forms and dynamic microscopic characteristics were analyzed.Under each corrosion condition,the dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity tended to decrease with immersing time.The dynamic elastic modulus,dynamic deformation modulus and dynamic peak intensity exhibited an inverted U-shaped trend.Under dynamic impact,the failure process of acidly corroded samples can be divided into the following stages:the initial stage,elastic energy accumulation stage,local failure of coal and secondary rock crack expansion stage,coal fragment ejection stage,rock spalling stage and complete instability stage.Under dynamic impact,failure modes exist:coal crushing failure,rock fragmenting failure,rock splitting failure and full splitting failure.After impact failure,sample fragments are distributed in powder,granular,cone and block forms.Based on Zhu-Wang-Tang nonlinear viscoelastic properties,a model considering chemical corrosion and impact damage was proposed.The combined effects of chemical and impact-induced damage on the dynamic mechanical properties of coal-rock assemblages were systematically analyzed.
基金supported by the National Natural Science Foundation of China(No.42572076)the Continental Gold Ltd.,Colombian Branch(No.CG-EXP-041-23).
文摘0 INTRODUCTION The Andean orogenic belt,a globally significant active continental margin(Lamb et al.,1997),extends in a north-south direction along the western coast of South America.The Colombian Andes,located in the northern segment of this orogen,constitute a vital component and host abundant Au-Cu resources.Three principal Au-Cu metallogenic belts(Chocó,Middle Cauca,and Antioquia)are developed from west to east across Colombia(Lesage et al.,2013;Sillitoe,2008;Figure 1a).
基金financial support from the National Natural Science Foundation of China(Grant Nos.U23B20155 and 42202140)the Science and Technology Innovation Program of Hunan Province(2023RC1021)+1 种基金the China Geological Survey(DD20221659)the Science and Technology Bureau,Changsha,China(kq2208261)。
文摘The marine-continental transitional shale of the Upper Permian Longtan Formation is widely distributed in Hunan and shows significant exploration potential.Frequent changes in lithofacies have however notably influenced the shale gas enrichment.The strata of the Longtan Formation in the Shaoyang Depression,central Hunan,were taken as the study object for this project.Three lithofacies assemblages were identified:shale interbedded with sandstone layer(SAL),sandstone interbedded with shale layer(ASL)and laminated shale layer(LSL).The SAL shale shows significant variability in hydrocarbon generation potential,which leads to shale gas characterized by'hydrocarbon generation in high total organic carbon(TOC)shale,retention in low TOC shale and accumulation in sandstone'.The ASL shale,influenced by the redox conditions of the depositional environment,shows a lower concentration of organic matter.This results in an enrichment model of'hydrocarbon generation and accumulation in shale,with sealing by sandstone'.The laminar structure of LSL shale causes both quartz and clay minerals to control the reservoir.Shale gas is characterized by'hydrocarbon generation in mud laminae,retention and accumulation in silty laminae,with multiple intra-source migration paths'.In the marine-continental transitional shale gas system,the enrichment intervals of different types of shale gas reservoirs exhibit significant variability.
文摘The Middle Jurassic palynomorphs from the Yan'an Formation in Dongsheng region of Nei Monggol, consist of 63 species of fossil spores and pollen grains belonging to 34 genera, of which two species were described as new. Based on statistical analysis of 3 863 specimens identified in 10 samples from Hantaichuan, Nianpanlianggou and Liugou sections, the sporo-pollen assemblage from the Yan'an Formation in Dongsheng region was established, which is generally characterized by the slight dominance of gymnospermous pollen grains (generally attaining proportion of 51%-54%), whereas the pteridophytic spores reach 46%-49% in abundance. In comparison with those of adjacent regions as well as Eurasia and North America, the present sporo-pollen assemblage is regarded to early Middle Jurassic (corresponding to Bajocian Stage) in geological age. According to the climatic conditions reflected by the palynoflora, the paleoclimate in Dongsheng region is suggested to be warm temperate or subtropical warm and humid during the early Middle Jurassic.
基金Supported by the High Technology Research and Development Program of China (863 Program)(Nos 2006AA09Z180,2004AA639790)the National Natural Science Foundation of China (No 40106013)the National Basic Research Program of China (973 program)(No 2001CB409703)
文摘We collected fish abundance data in the Changjiang(Yangtze River) estuary and adjacent waters in November 1998,May 1999,November 2000,and May 2001.Using the data,we evaluated the characteristics of the fish assemblages at each site and investigated the effect of several environmental factors.We used a multivariate analysis,including community ordination methods such as detrended correspondence analysis(DCA) and canonical correspondence analysis(CCA),and two-way indicator species analysis(TWINSPAN).We analyzed the biological community structure and environmental factors to determine their spatial distributions,temporal dynamics,and seasonal variations.Among the fish species,five exceeded 5% of the total abundance:Harpodon nehereus(42.82%),Benthosema pterotum(13.85%),Setipinna taty(11.64%),Thryssa kammalensis(9.17%) and Apogonichthys lineatus(6.49%).These were separated into four ecological assemblages:hypsithermal-saline,hypsithermal-brackish,hypothermal-brackish,and hypothermal-saline.We evaluated the degree of influence of environmental factors on the fish community.Our analyses suggested that environmental factors including water depth,salinity,turbidity,transparency,nutrient,and suspended matter formed a synthetic spatial gradient between the coastal and pelagic areas.Ecological and environmental factors changed temporally from 1998 to 2001,and drove the fish community succession.The environmental factors driving the fish community structure included bottom temperature,water depth,bottom and surface pH,surface total phosphorous,and bottom dissolved oxygen.This investigation was completed before completion of the Three Gorges Dam;therefore the results of this study provide an important foundation for evaluating the influence of the human activities.
基金support by the National Natural Science Foundation of China (grant no. 31270277)
文摘Based on the palynological data from Well Ta-19-36 and Well Ta-19-37 in the Ta＇nan Sag, and Well Ta-22-1 and Well Ta-21-1 in the Bayin Gobi Sag, a spore-pollen assemblage from the Damoguaihe Formation is named as Cicatricosisporites minutaestriatus- Aequitriradites spinulosus-Protopinus sp. assemblage in the Tamutsag Basin, Mongolia. The assemblage is characterized by abundant gymnosperm pollen and diverse fern spores, counted 46.35%–65.57% and 34.43%–52.58% in percentage respectively. Among the gymnosperm pollen, Pinuspollenites sp.（2.66%–16.94%）, Protopinus sp.（0–11.38%） and Protopicea sp.（0–10.81%） are dominant; and Alisporites sp., Cerebropollenites sp., Podocarpidites sp., and Abietineaepollenites sp. are common. Some important elements, such as Chasmatosporites sp., Callialasporites prominulus, Parvisaccites sp., Parcisporites sp., Jiaohepollis cf. annulatus, J. bellus, J. verus, Polycingulatisporites sp., Schizaeoisporites certus, Classopollis annulatus are seen. Within the fern spores, Osmundacidites wellamanii（0.85%–4.93%）, Appendicisporites sp.（0–4.45%）, Baculatisporites comaumensis（0.80%–2.87%）, Cicatricosisporites sp.（0.51%–2.66%）, C. minor（0–2.14%）, Foraminisporis asymmetricus（0–2.40%）, Aequitriradites sp.（0– 2.19%） and Cyathidites minor（0–2.13%） are dominant; and some specie of Densoisporites, Cooksonites, Impardecispora, Pilosisporites, Schizaeosprites, Fixisporites, Leptolepidites, Trilobosporites, Kuylisporites, Klukisporites, Hsuisporites, Couperisporites, Maculatisporites are seen. The angiosperm pollen are rare in the assemblage, characterized by Clavatipollenites sp.（0–0.80%） and Songipollis sp.（0–0.27%）. The geological age of the Damoguaihe Formation is assigned to Hauterivian – Barremian of Early Cretaceous according to the palynological data, due to the fact that there existed a lot of diverse spores of the family Schizaeaceae and prosperous gymnosperm saccat pollen which the corpus and sacci are differentiated completely, and the presence of early angiosperm pollen of Clavatipollenites. However, the zircon U-Pb isotopic dating of the volcanic rocks in the Nantun Formation indicated that the overlying strata of the Nantun Formation, i.e. the Damoguaihe Formation must be younger than 127.0±2.0–137.9±1.5 Ma. This is consistent with the palynological data. Furthermore, the vegetation reconstructed on the palynological data of the Damoguaihe Formation is conifer forest with shrubs and grassland, belonging to the semi-humid or humid middle to south subtropical climate. Moreover, three new species, namely Biretisporites punctatus sp. nov., Chasmatosporites reticulates sp. nov. and Concentrisporites contractus sp. nov. are described here.
基金This research is financialy supported by the National Natural Science Foundation of China(No.49894190)the Scientific Key Foundation of Daqing Oilfield Company Ltd.(No.QR/A04-2-01).
文摘Three sporopollen assemblages are recognized for the first time from the Cretaceous Yimin Formation in the Hailar Basin of eastern Inner Mongolia. They are （in ascending order）： the lmpardecispora-Aequitriradites- Clawttipollenites assemblage; the Triporoletes-Pilosisporites-Asteropollis assemblage; and the Appendicisporites- Asteropollis-Tricolpites assemblage, distributed in Members 1, 2 and 3 of the Yimin Formation respectively. Recognition of this biostratigraphic sequence is very important for the division and correlation of the Yimin Formation in the basin. Meanwhile, the age of the Yimin Formation is considered to be Barremian to Early Albian based on the palynological data.
基金supported by the National Basic Research Program of China (2009CB119200)Anhui Provincial Natural Science Foundation (090413080)Natural Science Foundation of Anhui Education Bureau (KJ2008B211,KJ2009A110)
文摘Spatial and temporal variation of fish assemblages were investigated seasonally from May 2007 to February 2008 across 11 study sites in a subtropical small stream, the Puxi Stream, of the Huangshan Mountain. Along the longitudinal gradient from headwater to downstream, fish species richness and abundance increased gradually, but then decreased significantly at the lower reaches. The highest species richness and abundance were observed in August and the lowest in February. Based on analysis of similarities （ANOSIM）, fish assemblages were significantly different in spatial variation but not in temporal variation. Although differences were observed both among sites and among stream orders, the lower R value in order-variation suggested stream order was not the optimal factor explaining the spatial variation of fish assemblages. In addition, dam construction did not significantly alter fish assemblages in the sites adjacent to and immediately downstream to dams. Using cluster analysis and non-metric Multi Dimensional Scaling analysis （NMS）, assemblages were separated into three groups at a Bray-Curtis similarity value of 42%： the upper, middle and lower groups. Following analysis of similarity percentages of species contributions （SIM- PER）, shifts in occurrence or abundance of S. curriculus, Z. platypus, R. bitterling and A. fasciatus contributed most to the differences amongst the three groups. Standard Deviation Redundancy Analysis （RDA） suggested that habitat structure （such as elevation, substrate, and flow velocity） contributed to the spatial and temporal pattem of fish assemblages in the Puxi Stream. In conclusion, the fish assemblages in Puxi Stream presented significant spatial but not temporal variation. Human disturbance has perhaps induced the decrease in species diversity in the lower reaches. However, no significant change was observed for fish assemblages in sites far from and immediately downstream from low-head dams [Current Zoology 56 （6）： 670-677, 2010].
基金The National Basic Research Program of China(973 Program)under contract No.2010CB951200the Marine Public Service Specific Research under contract No.201105020
文摘Controlled by climate changes, there were three large-scale transgressions and regressions around the Bohai Sea during the late Quaternary, which were accepted by most geologists. However, a big controversy still exists about the time when the transgressions occurred separately. In order to find out the process of the paleoenvironmental changes around the Bohai Sea in the late Quaternary, the foraminifera assemblages from a new borehole Lz908 in the southern coast of the Laizhou Bay were studied, and then the transgressive strata were indentified. Combined with accelerator mass spectrometry radiocarbon 14C（AMS14C） and optically stimulated luminescence（OSL） ages, the occurrence time of these transgressions were re-determined. The result showed that three major large-scale transgressions occurred separately at the beginning of marine isotopic stage 7（MIS7）, the last interglacial period（MIS5） and the Holocene. In addition, a small-scale transgression occurred in the mid-MIS6, and the corresponding transgressive stratum was deposited. The transgressive deposition of MIS3 was also discovered in this study. However, the characteristics of the foraminifera indicated the environment during this period was colder than that in the MIS5. By comparison with the global sea-level changes, the paleoenvironmental changes around the Bohai Sea in the late Quaternary can be consistent with the global climate changes.
基金supported by the Basic Research Projects of Science and Technology: Research on standard sections and some GSSPs in China (2006FY120300-6)the Major State Basic Research Projects (2006CB806400) of MST of China+2 种基金the Creative Research Project of CAS (KZCX2-YW-156)the National Natural Science Foundation of China (40930208)the Important National Science and Technology Specific Projects (2008ZX05008-001)
文摘Carbon isotope （δ13Corg） analyses of non-marine clastic rocks and neritic carbonates and black shales spanning the Silurian/Devonian transition are compared from two richly fossiliferous sequences in Qujing of East Yunnan and Zoige of Sichuan, South China. The two sections, Xishancun and Putonggou sections in South China, reveal positive δ13Corg shifts happening in the Upper Pridoli and Lower Devonian and reaching peak values as heavy as -25.2‰ （Xishancun） and -19.9‰（Putonggou） in the lowermost Lochkovian following the first occurrence of the thelodont Parathelodus and the conodont Icriodus woschmidti woschmidti （only in Putonggou Section and together with Protathyris-Lanceomyonia brachiopod fauna）. These results replicate a globally known positive shift in δ13Corg from the uppermost Silurian to the lowermost Devonian. The δ13Corg variations across the Silurian/Devonian Boundary （SDB） at the two sections in South China exhibit a shift in carbon isotopic composition similar to the detailed SDB curves from the borehole Klonk-1 drilled at top of the Klonk Global Standard Stratotype-Section and Point （GSSP） in the Prague Basin, Czech Republic. In addition, four microvertebrate assemblages, including the Liaojiaoshan, Xishancun, Yanglugou and Xiaputonggou assemblages, are recognized from the Silurian/Devonian transition exposed in the Xishancun and Putonggou sections, respectively. The results from both carbon isotope stratigraphy and microvertebrate assemblage sequences suggest that the SDB in South China is located at the base of the Xishancun Formation （between sample QX-20 and sample QX-21） in the Xishancun Section and the lower part of the Xiaputonggou Formation （between sample ZP-09 and sample ZP-10） in the Putonggou Section. The isotopic trend for organic carbon together with the changes of microvertebrate remains across the SDB can offer an approach to a potential correlation of the SDB from different sedimentary facies, which help to correlate the marine with non-marine deposits.
基金Supported by the Special Fund for Agro-Scientific Research in the Public Interest(No.201003068)the Key Programs for Science and Technology Development of Ningbo,China(No.2013C11014)
文摘In 2012,an artificial reef system was deployed in Xiangshan Bay,China,to enhance its fishery resources. To determine the effect of the artificial reef system on the demersal nekton assemblages,a beforeafter-control-impact study design was applied. Comparisons of assemblages from impact and control habitats revealed that the assemblage in the impact area had a gradual response to reef deployment. The assemblages in the impact and control areas changed in different ways after reef deployment. During the study period,total biomass,species richness and average body weight in the control area remained relatively stable,whereas there were significant increases in these indicators in the impact area. Responses to the reefs differed among nekton species,inducing assemblage succession in the reefs post-deployment. Sparus macrocephalus and Cynoglossus abbreviat us benefited most from reef deployment. Conversely,smallsized shrimp Palaemon gravieri showed a progressive decrease in biomass following reef deployment. Overall,the artificial reef system diversified the demersal nekton assemblage,enhanced the total biomass,and increased the proportion of large-sized species.
基金supported by the Fundamental Research Funds for the Central Universities(No.201022001201262004)+1 种基金the Public Science and Technology Research Funds Projects of Ocean(No.201305030)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20120132130001)
文摘Surveys were conducted in five voyages in Haizhou Bay and its adjacent coastal area from March to December 2011 during full moon spring tides. The ichthyoplankton assemblages and the environmental factors that affect their spatial and seasonal patterns were determined. Totally 35 and 12 fish egg and larvae taxa were identified, respectively. Over the past several decades, the egg and larval species composition has significantly changed in Haizhou Bay and its adjacent waters, most likely corresponding with the alteration of fishery resources, which are strongly affected by anthropogenic activities and climate change. The Bray-Curtis dissimilarity index identified four assemblages: near-shore bay assemblage, middle bay assemblage and two closely related assemblages(near-shore/middle bay assemblage and middle/edge of bay assemblage). The primary species of each assemblage principally reflected the spawning strategies of adult fish. The near-shore bay assemblage generally occurred in near-shore bay, with depths measuring <20 m, and the middle bay assemblage generally occurred in the middle of bay, with depths measuring 20 to 40 m. Spatial and seasonal variations in ichthyoplankton in each assemblage were determined by interactions between biological behavioral traits and oceanographic features, particularly the variation of local conditions within the constraint of a general reproductive strategy. The results of Spearman's rank correlation analysis indicated that both fish egg and larval abundance were positively correlated with depth, which is critical to the oceanographic features in Haizhou Bay.
基金Supported by the National Natural Science Foundation of China (No. 29836130).
文摘The cell model developed since 1950s is a useful tool forexploring the behavior of particle assemblages, but it demandsfurther careful development of the outer boundary conditions so thatinteraction in a particle swarm is better represented. In this paper,the cell model and its development were reviewed, and themodifications of outer cell boundary conditions were suggested. Atthe cell outer boundary, the restriction of uniform liquid flow wasremoved in our simulation conducted in the reference frame fixed withthe particle.
文摘According to multi- disciplinary research advances in recent years, three blocks which named Jiaoliao - Bohai block, central North China block and Ordos block are divided. The differences of the tectonic association, types, styles and features in the space, and evolution from Archaean to Cenozoic in the time, between the former two blocks are discussed. Tectonic features and evolution in the four tectonic stages of Precambrian, Indo- China, Yanshanian and Cenozoic are emphasized especially here. All of them described above have inherit and neogenic property. The temporal-spatial change and interaction among basin assemblages in the above four stages are analyzed. Escape tectonic model is employed to interpret coeval compressive and extensional basins in the study area.
