The Baiyun sag is a deep one developing on the slope of the Pearl River Mouth Basin. It occurs as a composite graben horizontally, and is composed of two sub-sags versus one low uplift. Vertically, the sedimentary arc...The Baiyun sag is a deep one developing on the slope of the Pearl River Mouth Basin. It occurs as a composite graben horizontally, and is composed of two sub-sags versus one low uplift. Vertically, the sedimentary architecture could be divided into three layers, i.e. the faulted layer on the bottom, the faulted-ductile stretching layer in the middle and the draping layer on the top. The main rifting stage of the sag is supposed to be characterized by ductile extension and thinning of the crust. The special deformation pattern is probably attributed to the fact that the Baiyun sag is located in the transfer zone of the pre-existing weak zone, which made the sag a strongly deformed area, characterized by the greatly thinned lithosphere and active magmatism. The highly rising mantle under the Baiyun sag should be an important mechanism responsible for the ductile deformation, which caused partial melting of the upper mantle. Upweiling to the upper crust and the sedimentary layers, the partial melting materials accommodated extensional strain and caused non-faulted vertical subsidence. Magma was collected under the transfer zone after the first stage of rifting, and transferred laterally in a direction perpendicular to the extension to the ENE and WSW parts of the sag and upwelled along the NW-trending basal faults, where WNW-trending shear faults developed in swarms. The faulting activity and sedimentation history of the Baiyun sag may have been affected by the ocean ridge jump around 24 Ma and the cessation of sea floor spreading around 16 Ma.展开更多
The study of new seismic data permits the identification of sediment gravity flows in terms of internal architecture and the distribution on shelf and abyssal setting in the Qiongdongnan Basin （QDNB）. Six gravity fl...The study of new seismic data permits the identification of sediment gravity flows in terms of internal architecture and the distribution on shelf and abyssal setting in the Qiongdongnan Basin （QDNB）. Six gravity flow types are recognized： （1） turbidite channels with a truncational basal and concordant overburden relationship along the shelf edge and slope, comprising laterally-shifting and vertically-aggrading channel complexes; （2） slides with a spoon-shaped morphology slip steps on the shelf-break and generated from the deformation of poorly-consolidated and high water content sediments; （3） slumps are limited on the shelf slope, triggered either by an anomalous slope gradient or by fault activity; （4） turbidite sheet complexes （TSC） were ascribed to the basin-floor fan and slope fan origin, occasionally feeding the deep marine deposits by turbidity currents; （5） sediment waves occurring in the lower slope-basin floor, and covering an area of approximately 400 km2, were generated beneath currents flowing across the sea bed; and （6） the central canyon in the deep water area represents an exceptive type of gravity flow composed of an association of debris flow, turbidite channels, and TSC. It presents planar multisegment and vertical multiphase characteristics. Turbidite associated with good petrophysical property in the canyon could be treated as a potential exploration target in the QDNB.展开更多
The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of co...The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of core F10B from the mud area southwest off Cheju Island(MSWCI)were generated to evaluate phytoplankton productivity and community structure changes in response to environmental evolution during the last 14 kyr.The contents of diatom,dinoflagellate and haptophyte biomarkers(brassicasterol,dinosterol and C37alkenones)display similar trends,with increasing phytoplankton productivity during the last 14kyr due to the increased influences of the Kuroshio,and especially due to the eddy-induced upwelling during the late Holocene.On the other hand,the contents of terrestrial biomarkers(C28+C30+C32n-alkanols)and terrestrial organic matter(TOM)proxies(TMBR′and BIT)all reveal decreasing TOM input into the area around the sampling site for the 14 kyr,mostly due to sea-level ris-ing.Phytoplankton biomarker ratios reveal a shift from a haptophyte-dominated community at 6.2 2.5 kyr BP to a diatom-dominated community at 2.5 1.45 kyr BP,likely caused by a stronger cold eddy circulation system at 2.5 1.45 kyr BP in the MSWCI.展开更多
Assemblages of benthic foraminifera in a sediment core(C02)near the western margin of the southern Yellow Sea Mud were studied to decipher the phase evolution of Holocene paleoenvironmental changes associated with the...Assemblages of benthic foraminifera in a sediment core(C02)near the western margin of the southern Yellow Sea Mud were studied to decipher the phase evolution of Holocene paleoenvironmental changes associated with the Holocene marine transgression.It appears that during the early Holocene(11.2 10.1 kyr BP),the faunal was dominated by low salinity and shallow water species Cribrononion subincertum,Buccella frigida and Ammonia beccarii,reflecting a near coast depositional environment.A rapid increase of the relative abundance of Ammonia compressiuscula between 10.1 9.3 kyr BP indicates that the sea level rose rapidly during that time period.From 9.3 7.7 kyr BP,the benthic foraminiferal assemblage was dominated by high percentage of A.compressiscula,suggesting that the sea level was relatively stable.An obvious transition of benthic foraminifera,from the A.compressiuscula-dominated assemblage to an Ammonia ketienziensis-dominated assemblage,occurred between 7.7 6.2 kyr BP,possibly corresponding to a second sea level rapid rise period in the Yellow Sea during the Holocene.This transition may correspond to the gradually strengthened Yellow Sea warm current(YSWC)and finally is established the modern-type circulation in the Yellow Sea.It may also mark the formation of the Yellow Sea cold bottom water(YSCBW)during that period.Since then,the benthic foraminiferal assemblage based on core C02 was dominated by typical YSCBW species,A.ketienziensis,Astrononion italicum and Hanzawaia nipponica,at 6.2 4 kyr BP.A non-deposition period occurred since 4 kyr BP,which possibly related to the hydrology changes caused by the East Asia monsoon.The two obvious benthic foraminiferal transitions recorded in core C02 during the early and middle Holocene provide evidence that the Yellow Sea has undergone a two-phase rapid sea level rise during the Holocene marine transgression.展开更多
Archaea have unique glycerol dialkyl glycerol tetraether（GDGT） lipids that can be used to develop paleotemperature proxies such as TEX86.This research is to validate proposed GDGT-proxies for paleotemperature determ...Archaea have unique glycerol dialkyl glycerol tetraether（GDGT） lipids that can be used to develop paleotemperature proxies such as TEX86.This research is to validate proposed GDGT-proxies for paleotemperature determination in the South China Sea（SCS）.Samples were collected from core-top sediments （0-5 cm） in the northern SCS.Total lipids were extracted to obtain core GDGTs,which were identified and quantified using liquid chromatography-mass spectrometry（LC-MS）.The abundance of isoprenoidal GDGTs（/GDGTs） ranged from 271.5 ng/g dry sediment to 1266.3 ng/g dry sediment,whereas the branched GDGTs（bGDGTs）,supposedly derived from terrestrial sources,ranged from 22.2 ng/g dry sediment to 56.7 ng/g dry sediment.The TEX_（86）-derived sea surface temperatures ranged from 20.9℃in the coast（water depth 〈 160 m） to 27.9℃offshore（water depth 〉 1000 m）.TEX86-derived temperatures near shore（〈 160 m water depth） averaged 23.1±2.5℃（n =4）,which were close to the satellite-derived winter mean sea surface temperature（average 22.6±1.0℃,n = 4）;whereas the TEX_（86）-derived temperatures offshore averaged 27.4±0.3℃（n = 7） and were consistent with the satellite mean annual sea surface temperature（average 26.8±0.4℃,n = 7）.These results suggest that TEX_（86） may record the sea surface mean annual temperature in the open ocean,while it likely records winter sea surface temperature in the shallower water.展开更多
The potential submarine geologic hazards were distinguished and categorized at the entrance of the Pearl River Estuary in the northern South China Sea, based upon the analysis of side scan sonar and sub-bottom profile...The potential submarine geologic hazards were distinguished and categorized at the entrance of the Pearl River Estuary in the northern South China Sea, based upon the analysis of side scan sonar and sub-bottom profiler surveying data of about 2500 km long, in an area about 2000 km^2 around the Wanshan Archipelago. The data obtained in the survey has the highest spatial resolution by far, which could reveal more detailed distributions and characteristics of the geologic hazards than before. In the study region, three paleo-channels that were buried about 10–30 m below the seabed were found; more than 10 shallow gas areas were discovered. The sand waves found in the region were generally small and located near the islands, and twenty pockmarks found on the seabed were mostly concentrated to north of Zhuzhou island. There are also many man-made obstacles in the region, such as wreckages, pipeline, etc. In this paper we provide a detailed distribution map of the submarine geologic hazards in this region for the first time, and discuss their formation and harmfulness, which will provide a scientific basis for marine engineering construction, marine geologic disaster prevention and mitigation.展开更多
The Yuxi （豫西） fold-thrust fracture belt is part of the gigantic fold-thrust fracture belt that extends NW in the southern North China plate. The contents of major elements of tectonites were analyzed by ICP-AES. T...The Yuxi （豫西） fold-thrust fracture belt is part of the gigantic fold-thrust fracture belt that extends NW in the southern North China plate. The contents of major elements of tectonites were analyzed by ICP-AES. The analysis of chemical compositions and new stress minerals indicates： extending from the surrounding country rocks to the center of the fracture belt, the Fe2O3 content gradually increases while the FeO content gradually decreases; regular increase, decrease or peak changes are shown for chemical compositions like SiO2, Al2O3, Fe2O3, MgO, CaO, FeO, loss on ignition, TIO：, K2O, Na2 O, etc.. New stress minerals are developed for the south branch and few for the north branch. The characteristics of chemical compositions and new stress minerals of the thrust fracture demonstrate that the fracture belt has undergone a process from a closed reducing environmental system to a relatively open. oxidizing environmental system, andcompressive fractures have resulted from compression in the late stages of evolution, and the dynamothermal metamorphism and thrusting intensities are different between the south and north branches of the belt, which is strong for the south branch but relatively weak for the north branch.展开更多
Natural hydrocarbon seeps in the marine environment are important contributors to greenhouse gases in the atmosphere. Such gases include methane, which plays a significant role in global carbon cycling and climate cha...Natural hydrocarbon seeps in the marine environment are important contributors to greenhouse gases in the atmosphere. Such gases include methane, which plays a significant role in global carbon cycling and climate change. To accurately quantify the methane flux from hydrocarbon seeps on the seafloor, a specialized in situ and online gas flux measuring(GFM) device was designed to obtain high-resolution time course gas fluxes using the process of equal volume exchange. The device consists of a 1.0-m diameter, 0.9-m tall, inverted conical tent and a GFM instrument that contains a solenoid valve, level transducer, and gas collection chamber. Rising gas bubbles from seeps were measured by laboratory-calibrated GFM instruments attached to the top of the tent. According to the experimental data, the optimal anti-shake time interval was 5 s. The measurement range of the device was 0–15 L min^(-1), and the relative error was ± 1.0%. The device was initially deployed at an active seep site in the Lingtou Promontory seep field in South China Sea. The amount of gas released from a single gas vent was 30.5 m^3 during the measurement period, and the gas flow rate ranged from 22 to 72 Lh^(-1), depending on tidal period, and was strongly negatively correlated with water depth. The measurement results strongly suggest that oceanic tides and swells had a significant forcing effect on gas flux. Low flow rates were associated with high tides and vice versa. The changes in gas volume escaping from the seafloor seeps could be attributed to the hydrostatic pressure induced by water depth. Our findings suggest that in the marine environment, especially in the shallow shelf area, sea level variation may play an important role in controlling methane release into the ocean. Such releases probably also affect atmospheric methane levels.展开更多
Overpressure is a hot topic in the study of sedimentary basins. It is important in generation, maturation migration, and accumulation of hydrocarbon, but the effects of overpressure on rock frame have not been investi...Overpressure is a hot topic in the study of sedimentary basins. It is important in generation, maturation migration, and accumulation of hydrocarbon, but the effects of overpressure on rock frame have not been investigated. In this study, experiments were carried out to study the effects of overpressure on rock frame structures using five core samples from the Junggar basin, Northwest China. The deformations and velocities for the samples were measured at different effective pressures related to non-equilibrium compaction and fluid expansion overpressure mechanisms. The results show that the effect of overpressure on rock frames gradually increases when the effective pressure drops down to a certain value （called critical pressure）. Moreover, non-equilibrium compaction mechanism has more effects on rock frames than fluid expansion mechanism under the same effective pressure. Furthermore to study rock frame structural changes, we use Kuster and Toksoz＇s expressions to simulate the effective aspect ratios of inclusions a （penny shapes） for different effective pressures. The results show that the a decreases dramatically when the effective pressure decreases from the critical pressure. Changes of a can be interpreted as responses to the rock frame changes when grains conform one another by rotating and self-adjusting. However, different mechanisms of overpressure have different effects on rock frames. The rock frame can be affected more easily by overpressure in shallow regions generated by non-equilibrium compaction mechanism. Once this kind of rock frames are preserved after overpressure releases to a normal hydrostatic pressure, they can be identified by their specific rock frame characters. This method provides a new way to study overpressure release and fluid migration and accumulation.展开更多
We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas.The areas of high concentrations are primarily outside the eastern mouth of the ...We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas.The areas of high concentrations are primarily outside the eastern mouth of the Qiongzhou Strait and on the west side of the Leizhou Peninsula,whereas the areas of low concentrations are located primarily in the eastern Qiongzhou Strait.The maximum Cd,Pb and Zn concentrations in the samples collected in our study do not exceed the official standards for marine sediments,whereas the concentrations of Cr and Cu slightly exceed the standards.Correlations exist between the concentrations of Cu,Pb,Zn,Cr and Cd,and the concentrations of these metals are positively correlated with the mean particle size(φ value),indicating that the finer sediments have adsorbed greater amounts of heavy metal elements than the coarser sediments.An evaluation of the potential environmental risks demonstrates that certain indices of heavy metal pollution and environmental risks are relatively low and may be assigned low risk levels,thereby indicating that,in terms of heavy metals,the marine sedimentary environment in this region is only mildly impacted.Our analysis of the contaminant origins shows that the heavy metals in this region primarily originate in the Pearl River Estuary and that a small amount of them is derived from local runoff.The elevated heavy metal concentrations from the upper sections of the cores started 130 years ago,which indicats that heavy metals in the surface sediments are primarily due to human activities associated with industrialization.展开更多
China has entered the area of new normal economy which requires the harmonious development of energy consumption,environmental protection and economic development.Natural gas hydrate is a potential clean energy with t...China has entered the area of new normal economy which requires the harmonious development of energy consumption,environmental protection and economic development.Natural gas hydrate is a potential clean energy with tremendous reserve in China.The successful field test of marine hydrate exploitation in South China Sea created a new record of the longest continuous gas production from natural gas hydrate.However,the corresponding fundamental research is still urgently needed in order to narrow the gap between field test and commercial production.This paper reviewed the latest advances of experimental study on gas production from hydrate reservoir in China.The experimental apparatus for investigating the performance of hydrate dissociation in China has developed from one dimensional to two dimensional and three dimensional.In addition,well configuration developed from one tube to complicated multi-well networks to satisfy the demand of different production models.Besides,diverse testing methods have been established.The reviewed papers preliminary discussed the mechanical properties and the sediment deformation situation during the process of hydrate dissociation.However,most reported articles only consider the physical factor,the coupled mechanism of physical and chemical factor for the mechanical properties of the sediment and the sand production problem should be studied further.展开更多
The coastal hard rock with a thickness of over 5 m and a distribution area of nearly 200 ha in the Haishan Island, south China, has long drawn researchers＇ attention. However, there were controversies over its format...The coastal hard rock with a thickness of over 5 m and a distribution area of nearly 200 ha in the Haishan Island, south China, has long drawn researchers＇ attention. However, there were controversies over its formation and classification, and these controversies in turn lead to the dispute of sea level changes and coastal uplift-subsidence of this area. To investigate its diagenesis and evolution, petrographic analysis, elemental geochemistry, isotopic analysis, and radiocarbon dating were used in the present study. Radiocarbon dating indicates that the deposition of the Haishan Coquinite commenced in the mid Holocene and lasted to -600 a B.P. Petrographic analysis shows that the Haishan Coquinite is cemented by low-Mg calcite, indicating that the cementation occurred in a meteoric environment. The elemental geochemistry and isotopic values demonstrate that the coquinite suffered strong leaching, which was thought to be responsible for the meteoric cementation of the coquinite. According to these results, the diagenesis of the coquinite is revealed： deposition of the Haishan Coquinite commenced in the mid Holocene in a shoal environment, initial cementation occurred and cement may be high-Mg calcite or aragonite; latterly the coquinite exposed to meteoric environment as a result of lowering of relative sea level, and the cement altered to low-Mg, which took the morphologies of bladed calcite rim and equant spar. A four-stage evolution model is proposed： （1） deposition stage, （2） initial cementation, （3） exposure to and cementation in meteoric environment, and （4） erosion stage. The published reports indicate that the hard rock should be designated as coquinite. Based on these studies, mid-Holocene sea level in this area was discussed, and the Haishan Island was proposed to uplift with a rate of ～5 mm/a in the last -600 a.展开更多
Onshore-offshore seismic experiments were carried out for the first time in northern South China Sea using large volume airgun sources at sea and seismic stations on land. The experimental results indicate that seismi...Onshore-offshore seismic experiments were carried out for the first time in northern South China Sea using large volume airgun sources at sea and seismic stations on land. The experimental results indicate that seismic signals from the new airgun array of R/V Shiyan 2 can be detected as far as 255 km. The signal effective area reaches nearly 50000 km2, which covers Hong Kong and Pearl River Delta. Compared with the old airgun array, the signal amplitude, propagation distance and effective area of the new airgun array have been increased notably, which demonstrates that the upgrade of the airgun source was successful. Comparisons with previous experimental results in other regions show that the shooting effect of the new airgun array is similar to those best airgun sources in the world. Especially, it is a new breakthrough in using the permanent seismic stations onshore to record long distance airgun signals offshore, which has great significance to the realization of the "seismic radar" concept and the 3D seismic surveys of crustal structure in coastal areas.展开更多
To investigate the thinning of the whole crust, and the contribution of the upper versus lower crust to the stretching since Cenozoic, we calculated the stretching factor of the northern margin of South China Sea with...To investigate the thinning of the whole crust, and the contribution of the upper versus lower crust to the stretching since Cenozoic, we calculated the stretching factor of the northern margin of South China Sea with data such as whole crustal thickness, depth of Cenozoic sedimentary basement and the horizontal displacement of faults. An isometric line drawing on whole crustal stretching factor is then obtained. Along the seismic Line 1530 in Baiyun sag, we also calculated the stretching factors of the upper and lower crust. The results suggest that the whole crustal thickness decreases seaward while the whole crustal stretching factor increases from shelf to slope. The Moho upwells highest beneath where the crust is thinned most. The value of the whole crustal stretching factor ranges from 1.5 to 6. Two areas were thinned intensely: the center of Yinggehai Basin, and the Baiyun sag in the Pearl River Mouth Basin. The calculation of the upper and lower crustal stretching factors from DSP1530 in Baiyun sag shows that the original crust of Baiyun sag should be thinned before deformation. Its pre-Cenozoic evolution as well as tectonic position during Cenozoic might be responsible for that.展开更多
Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred i...Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred in limited areas of the slope. Drillings in the BSR-distributed area (the District S) on the northern slope of the South China Sea suggested that gas hydrate only occurred at Sites SH2, SH3, and SH7 with high saturation (up to 20%-40%), and there is no hydrate at Sites SH1 and SH5 although the distance between SH1 to SH3 is only 500m. In this paper, we investigated seafloor gradient, fault development, temperature, and pressure in the District S on the northern slope of the South China Sea to understand the possible factors con- trolling BSR distribution and gas hydrate occurrence. The District S is a structurally fractured continental slope zone and its seafloor gradient varied greatly. The BSR-occurred areas have an average gradient of 19.89×10 2 whereas the BSR-free zone has the average gradient of 10.57×10 2 . The calculated relative structural intensities from fault densities and displacements show that the BSR-distributed areas tend to occur in the areas with a moderately high structural intensity, where faults frequently developed close to the seafloor that are possibly favored for lateral migration of gases. On the basis of temperatures and pressures at drilling sites, hydrate-occurred Sites SH2, SH3, and SH7 are located within the thermodynamically stable area for methane hydrate, and hydrate-absent Sites SH1 and SH5 are out of the thermodynamically stable area for methane hydrate formation, suggesting that both BSR and the thermodynamic stability are necessary for hydrate occurrence in the subsurface.展开更多
The relationship of species and abundance between the diatoms in the water and sediments from the southern South China Sea (SCS)were discussed, and the key environmental controlling factors were also investigated. Stu...The relationship of species and abundance between the diatoms in the water and sediments from the southern South China Sea (SCS)were discussed, and the key environmental controlling factors were also investigated. Studies show thathe diatom abundance is high in both water andsediments in the southeast part of the southern SCSand the varying trend is similar, while in the northwespart, the abundance is low, and the varying trend isdifferent. The dominant diatom species are Thalassionema nitzschioides and Nitzschia bicapitata inwater, and T. nitzschioides and Chaetoceros messanensis in sediments. The diatom species of smalsize and thin shell in water are more than in thesediments, while the diatom species of large size andthick shell in water are less. The percentage of species T. nitzschioides is higher in water of southeaspart than in that of northwest part, but it is similar insediments of both areas. It is shown that the southwest monsoon is the important factor influencingdiatom abundance and T. nitzschioides percentageand when the southwest monsoon is well developedthe distribution of diatom abundance and T. nitzschioides percentage are consistent in both water andsediments of the study area.展开更多
Quantitative studies on the evolution and dynamics of the deepwater area of Pearl River Mouth basin （PRMB） were carried out based on the latest geological and seismic data. The study area is generally in an extensio...Quantitative studies on the evolution and dynamics of the deepwater area of Pearl River Mouth basin （PRMB） were carried out based on the latest geological and seismic data. The study area is generally in an extensional state during the Cenozoic. The major extension happened in the earlier syn-rift stages before 23 Ma and the extension after 23 Ma is negligible. Two rapid subsidence periods, 32-23 Ma and 5.3-2.6 Ma, are identified, which are related to the abrupt heat decay during margin breakup and the collision between the Philippine Sea plate and the Eurasian plate, respectively. The strongest crustal thinning in the Baiyun （白云） sag may trigger the syn-rift volcanism along the weak faulted belt around the sag. The Cenozoic tectonic evolution of the study area could be divided into five stages： rifting （～50-40 Ma）, rift-drift transition （～40-32 Ma）, early post-breakup （～32-23 Ma）, thermal subsidence （～23-5.3 Ma） and neotectonic movement （～5.3-0 Ma）.展开更多
文摘The Baiyun sag is a deep one developing on the slope of the Pearl River Mouth Basin. It occurs as a composite graben horizontally, and is composed of two sub-sags versus one low uplift. Vertically, the sedimentary architecture could be divided into three layers, i.e. the faulted layer on the bottom, the faulted-ductile stretching layer in the middle and the draping layer on the top. The main rifting stage of the sag is supposed to be characterized by ductile extension and thinning of the crust. The special deformation pattern is probably attributed to the fact that the Baiyun sag is located in the transfer zone of the pre-existing weak zone, which made the sag a strongly deformed area, characterized by the greatly thinned lithosphere and active magmatism. The highly rising mantle under the Baiyun sag should be an important mechanism responsible for the ductile deformation, which caused partial melting of the upper mantle. Upweiling to the upper crust and the sedimentary layers, the partial melting materials accommodated extensional strain and caused non-faulted vertical subsidence. Magma was collected under the transfer zone after the first stage of rifting, and transferred laterally in a direction perpendicular to the extension to the ENE and WSW parts of the sag and upwelled along the NW-trending basal faults, where WNW-trending shear faults developed in swarms. The faulting activity and sedimentation history of the Baiyun sag may have been affected by the ocean ridge jump around 24 Ma and the cessation of sea floor spreading around 16 Ma.
基金supported by the 973 Project(no. 2007CB411705)the National Natural Science Foundations of China(no.40806019)+1 种基金the Key Laboratory of Marginal Sea Geology,Chinese Academy of Sciences (no.MSGL09-10)the Key Laboratory of Tectonics and Petroleum Resources(China University of Geosciences)project(no.TPR-2009-17)
文摘The study of new seismic data permits the identification of sediment gravity flows in terms of internal architecture and the distribution on shelf and abyssal setting in the Qiongdongnan Basin （QDNB）. Six gravity flow types are recognized： （1） turbidite channels with a truncational basal and concordant overburden relationship along the shelf edge and slope, comprising laterally-shifting and vertically-aggrading channel complexes; （2） slides with a spoon-shaped morphology slip steps on the shelf-break and generated from the deformation of poorly-consolidated and high water content sediments; （3） slumps are limited on the shelf slope, triggered either by an anomalous slope gradient or by fault activity; （4） turbidite sheet complexes （TSC） were ascribed to the basin-floor fan and slope fan origin, occasionally feeding the deep marine deposits by turbidity currents; （5） sediment waves occurring in the lower slope-basin floor, and covering an area of approximately 400 km2, were generated beneath currents flowing across the sea bed; and （6） the central canyon in the deep water area represents an exceptive type of gravity flow composed of an association of debris flow, turbidite channels, and TSC. It presents planar multisegment and vertical multiphase characteristics. Turbidite associated with good petrophysical property in the canyon could be treated as a potential exploration target in the QDNB.
基金supported by the National Basic Research Program of China (973 Program 2010CB428901)the National Natural Science Foundation of China (Grant Nos.41020164005,41221004)the ‘111’ Project
文摘The ecological environment in the East China Sea(ECS)and the Yellow Sea(YS)has changed significantly due to sea-level rising and the Kuroshio incursion since the last deglaciation.In this study,biomarker records of core F10B from the mud area southwest off Cheju Island(MSWCI)were generated to evaluate phytoplankton productivity and community structure changes in response to environmental evolution during the last 14 kyr.The contents of diatom,dinoflagellate and haptophyte biomarkers(brassicasterol,dinosterol and C37alkenones)display similar trends,with increasing phytoplankton productivity during the last 14kyr due to the increased influences of the Kuroshio,and especially due to the eddy-induced upwelling during the late Holocene.On the other hand,the contents of terrestrial biomarkers(C28+C30+C32n-alkanols)and terrestrial organic matter(TOM)proxies(TMBR′and BIT)all reveal decreasing TOM input into the area around the sampling site for the 14 kyr,mostly due to sea-level ris-ing.Phytoplankton biomarker ratios reveal a shift from a haptophyte-dominated community at 6.2 2.5 kyr BP to a diatom-dominated community at 2.5 1.45 kyr BP,likely caused by a stronger cold eddy circulation system at 2.5 1.45 kyr BP in the MSWCI.
基金supported by the National Basic Research Program of China (973 Program 2010CB428901)the National Natural Science Foundation of China (40976031,91228207)
文摘Assemblages of benthic foraminifera in a sediment core(C02)near the western margin of the southern Yellow Sea Mud were studied to decipher the phase evolution of Holocene paleoenvironmental changes associated with the Holocene marine transgression.It appears that during the early Holocene(11.2 10.1 kyr BP),the faunal was dominated by low salinity and shallow water species Cribrononion subincertum,Buccella frigida and Ammonia beccarii,reflecting a near coast depositional environment.A rapid increase of the relative abundance of Ammonia compressiuscula between 10.1 9.3 kyr BP indicates that the sea level rose rapidly during that time period.From 9.3 7.7 kyr BP,the benthic foraminiferal assemblage was dominated by high percentage of A.compressiscula,suggesting that the sea level was relatively stable.An obvious transition of benthic foraminifera,from the A.compressiuscula-dominated assemblage to an Ammonia ketienziensis-dominated assemblage,occurred between 7.7 6.2 kyr BP,possibly corresponding to a second sea level rapid rise period in the Yellow Sea during the Holocene.This transition may correspond to the gradually strengthened Yellow Sea warm current(YSWC)and finally is established the modern-type circulation in the Yellow Sea.It may also mark the formation of the Yellow Sea cold bottom water(YSCBW)during that period.Since then,the benthic foraminiferal assemblage based on core C02 was dominated by typical YSCBW species,A.ketienziensis,Astrononion italicum and Hanzawaia nipponica,at 6.2 4 kyr BP.A non-deposition period occurred since 4 kyr BP,which possibly related to the hydrology changes caused by the East Asia monsoon.The two obvious benthic foraminiferal transitions recorded in core C02 during the early and middle Holocene provide evidence that the Yellow Sea has undergone a two-phase rapid sea level rise during the Holocene marine transgression.
基金supported by the South China Sea-Deep program of the National Science Foundation of China #91028005(CLZ)the State Key Laboratory of Marine Geology of Tongji UniversityHD was supported by NSFC(Grant Nos.91028011 and 41076091)
文摘Archaea have unique glycerol dialkyl glycerol tetraether（GDGT） lipids that can be used to develop paleotemperature proxies such as TEX86.This research is to validate proposed GDGT-proxies for paleotemperature determination in the South China Sea（SCS）.Samples were collected from core-top sediments （0-5 cm） in the northern SCS.Total lipids were extracted to obtain core GDGTs,which were identified and quantified using liquid chromatography-mass spectrometry（LC-MS）.The abundance of isoprenoidal GDGTs（/GDGTs） ranged from 271.5 ng/g dry sediment to 1266.3 ng/g dry sediment,whereas the branched GDGTs（bGDGTs）,supposedly derived from terrestrial sources,ranged from 22.2 ng/g dry sediment to 56.7 ng/g dry sediment.The TEX_（86）-derived sea surface temperatures ranged from 20.9℃in the coast（water depth 〈 160 m） to 27.9℃offshore（water depth 〉 1000 m）.TEX86-derived temperatures near shore（〈 160 m water depth） averaged 23.1±2.5℃（n =4）,which were close to the satellite-derived winter mean sea surface temperature（average 22.6±1.0℃,n = 4）;whereas the TEX_（86）-derived temperatures offshore averaged 27.4±0.3℃（n = 7） and were consistent with the satellite mean annual sea surface temperature（average 26.8±0.4℃,n = 7）.These results suggest that TEX_（86） may record the sea surface mean annual temperature in the open ocean,while it likely records winter sea surface temperature in the shallower water.
基金supported by the Key Laboratory of Marginal Sea Geology, Chinese Academy of Sciences (No.MSGL13-03)
文摘The potential submarine geologic hazards were distinguished and categorized at the entrance of the Pearl River Estuary in the northern South China Sea, based upon the analysis of side scan sonar and sub-bottom profiler surveying data of about 2500 km long, in an area about 2000 km^2 around the Wanshan Archipelago. The data obtained in the survey has the highest spatial resolution by far, which could reveal more detailed distributions and characteristics of the geologic hazards than before. In the study region, three paleo-channels that were buried about 10–30 m below the seabed were found; more than 10 shallow gas areas were discovered. The sand waves found in the region were generally small and located near the islands, and twenty pockmarks found on the seabed were mostly concentrated to north of Zhuzhou island. There are also many man-made obstacles in the region, such as wreckages, pipeline, etc. In this paper we provide a detailed distribution map of the submarine geologic hazards in this region for the first time, and discuss their formation and harmfulness, which will provide a scientific basis for marine engineering construction, marine geologic disaster prevention and mitigation.
基金This paper is supported by the Key Basic Research Project funded by theChinese Academy of Sciences (No . KZCX2-SW-117) .
文摘The Yuxi （豫西） fold-thrust fracture belt is part of the gigantic fold-thrust fracture belt that extends NW in the southern North China plate. The contents of major elements of tectonites were analyzed by ICP-AES. The analysis of chemical compositions and new stress minerals indicates： extending from the surrounding country rocks to the center of the fracture belt, the Fe2O3 content gradually increases while the FeO content gradually decreases; regular increase, decrease or peak changes are shown for chemical compositions like SiO2, Al2O3, Fe2O3, MgO, CaO, FeO, loss on ignition, TIO：, K2O, Na2 O, etc.. New stress minerals are developed for the south branch and few for the north branch. The characteristics of chemical compositions and new stress minerals of the thrust fracture demonstrate that the fracture belt has undergone a process from a closed reducing environmental system to a relatively open. oxidizing environmental system, andcompressive fractures have resulted from compression in the late stages of evolution, and the dynamothermal metamorphism and thrusting intensities are different between the south and north branches of the belt, which is strong for the south branch but relatively weak for the north branch.
基金provided by the National Scientific Foundation of China (Nos. 41676046 and 41306045)the Knowledge Innovation Project of the Chinese Academy of Sciences (Nos. SIDSSE-201208 and SQ201110)+1 种基金the 'Hundred Talents Program' of the Chinese Academy of Sciencesfinancial support from China Scholarship Council
文摘Natural hydrocarbon seeps in the marine environment are important contributors to greenhouse gases in the atmosphere. Such gases include methane, which plays a significant role in global carbon cycling and climate change. To accurately quantify the methane flux from hydrocarbon seeps on the seafloor, a specialized in situ and online gas flux measuring(GFM) device was designed to obtain high-resolution time course gas fluxes using the process of equal volume exchange. The device consists of a 1.0-m diameter, 0.9-m tall, inverted conical tent and a GFM instrument that contains a solenoid valve, level transducer, and gas collection chamber. Rising gas bubbles from seeps were measured by laboratory-calibrated GFM instruments attached to the top of the tent. According to the experimental data, the optimal anti-shake time interval was 5 s. The measurement range of the device was 0–15 L min^(-1), and the relative error was ± 1.0%. The device was initially deployed at an active seep site in the Lingtou Promontory seep field in South China Sea. The amount of gas released from a single gas vent was 30.5 m^3 during the measurement period, and the gas flow rate ranged from 22 to 72 Lh^(-1), depending on tidal period, and was strongly negatively correlated with water depth. The measurement results strongly suggest that oceanic tides and swells had a significant forcing effect on gas flux. Low flow rates were associated with high tides and vice versa. The changes in gas volume escaping from the seafloor seeps could be attributed to the hydrostatic pressure induced by water depth. Our findings suggest that in the marine environment, especially in the shallow shelf area, sea level variation may play an important role in controlling methane release into the ocean. Such releases probably also affect atmospheric methane levels.
基金This paper is jointly supported by the National Natural Science Foundation of China (No.40602015)Research Foundation for Outstanding Young Teachers,China University of Geosciences (Wuhan) (CUGQNL0605)+1 种基金Open Foundation of the Key Laboratory of Theory and Technology of Petroleum Exploration and Development in Hubei Province (YQ2006KF17)Open Foundation of CAS Key Laboratory of Marginal Sea Geology,South China Sea Institute of Oceanology (MSGL0607).
文摘Overpressure is a hot topic in the study of sedimentary basins. It is important in generation, maturation migration, and accumulation of hydrocarbon, but the effects of overpressure on rock frame have not been investigated. In this study, experiments were carried out to study the effects of overpressure on rock frame structures using five core samples from the Junggar basin, Northwest China. The deformations and velocities for the samples were measured at different effective pressures related to non-equilibrium compaction and fluid expansion overpressure mechanisms. The results show that the effect of overpressure on rock frames gradually increases when the effective pressure drops down to a certain value （called critical pressure）. Moreover, non-equilibrium compaction mechanism has more effects on rock frames than fluid expansion mechanism under the same effective pressure. Furthermore to study rock frame structural changes, we use Kuster and Toksoz＇s expressions to simulate the effective aspect ratios of inclusions a （penny shapes） for different effective pressures. The results show that the a decreases dramatically when the effective pressure decreases from the critical pressure. Changes of a can be interpreted as responses to the rock frame changes when grains conform one another by rotating and self-adjusting. However, different mechanisms of overpressure have different effects on rock frames. The rock frame can be affected more easily by overpressure in shallow regions generated by non-equilibrium compaction mechanism. Once this kind of rock frames are preserved after overpressure releases to a normal hydrostatic pressure, they can be identified by their specific rock frame characters. This method provides a new way to study overpressure release and fluid migration and accumulation.
基金supported by China’s Offshore Marine Comprehensive Survey and Evaluation Project and the Science and Technology Fund of the South China Sea Branch(No.1315)
文摘We analyzed heavy metal concentrations in a number of surface sediments and cores from the Qiongzhou Strait and surrounding marine areas.The areas of high concentrations are primarily outside the eastern mouth of the Qiongzhou Strait and on the west side of the Leizhou Peninsula,whereas the areas of low concentrations are located primarily in the eastern Qiongzhou Strait.The maximum Cd,Pb and Zn concentrations in the samples collected in our study do not exceed the official standards for marine sediments,whereas the concentrations of Cr and Cu slightly exceed the standards.Correlations exist between the concentrations of Cu,Pb,Zn,Cr and Cd,and the concentrations of these metals are positively correlated with the mean particle size(φ value),indicating that the finer sediments have adsorbed greater amounts of heavy metal elements than the coarser sediments.An evaluation of the potential environmental risks demonstrates that certain indices of heavy metal pollution and environmental risks are relatively low and may be assigned low risk levels,thereby indicating that,in terms of heavy metals,the marine sedimentary environment in this region is only mildly impacted.Our analysis of the contaminant origins shows that the heavy metals in this region primarily originate in the Pearl River Estuary and that a small amount of them is derived from local runoff.The elevated heavy metal concentrations from the upper sections of the cores started 130 years ago,which indicats that heavy metals in the surface sediments are primarily due to human activities associated with industrialization.
基金Supported by Key Program of National Natural Science Foundation of China(51736009)National Natural Science Foundation of China(51806251 and 51676190)+5 种基金Youth Innovation Promotion Association,CAS(2019338)Pearl River S and T Nova Program of Guangzhou(201610010164)International S&T Cooperation Programme of China(2015DFA61790)Science and Technology Apparatus Development Program of the Chinese Academy of Sciences(YZ201619)Frontier Sciences Key Research Program of the Chinese Academy of Sciences(QYZDJ-SSW-JSC033)National Key Research and Development Program of China(2016YFC0304002,2017YFC0307306)
文摘China has entered the area of new normal economy which requires the harmonious development of energy consumption,environmental protection and economic development.Natural gas hydrate is a potential clean energy with tremendous reserve in China.The successful field test of marine hydrate exploitation in South China Sea created a new record of the longest continuous gas production from natural gas hydrate.However,the corresponding fundamental research is still urgently needed in order to narrow the gap between field test and commercial production.This paper reviewed the latest advances of experimental study on gas production from hydrate reservoir in China.The experimental apparatus for investigating the performance of hydrate dissociation in China has developed from one dimensional to two dimensional and three dimensional.In addition,well configuration developed from one tube to complicated multi-well networks to satisfy the demand of different production models.Besides,diverse testing methods have been established.The reviewed papers preliminary discussed the mechanical properties and the sediment deformation situation during the process of hydrate dissociation.However,most reported articles only consider the physical factor,the coupled mechanism of physical and chemical factor for the mechanical properties of the sediment and the sand production problem should be studied further.
基金supported by the Chinese Academy of Sciences (Grant no.KZCX3-SW-234)the National Natural Science Foundation of China (Grant no.40476025)the Science and Technology Program of Guangdong Province (Grant no.2004B33201002).
文摘The coastal hard rock with a thickness of over 5 m and a distribution area of nearly 200 ha in the Haishan Island, south China, has long drawn researchers＇ attention. However, there were controversies over its formation and classification, and these controversies in turn lead to the dispute of sea level changes and coastal uplift-subsidence of this area. To investigate its diagenesis and evolution, petrographic analysis, elemental geochemistry, isotopic analysis, and radiocarbon dating were used in the present study. Radiocarbon dating indicates that the deposition of the Haishan Coquinite commenced in the mid Holocene and lasted to -600 a B.P. Petrographic analysis shows that the Haishan Coquinite is cemented by low-Mg calcite, indicating that the cementation occurred in a meteoric environment. The elemental geochemistry and isotopic values demonstrate that the coquinite suffered strong leaching, which was thought to be responsible for the meteoric cementation of the coquinite. According to these results, the diagenesis of the coquinite is revealed： deposition of the Haishan Coquinite commenced in the mid Holocene in a shoal environment, initial cementation occurred and cement may be high-Mg calcite or aragonite; latterly the coquinite exposed to meteoric environment as a result of lowering of relative sea level, and the cement altered to low-Mg, which took the morphologies of bladed calcite rim and equant spar. A four-stage evolution model is proposed： （1） deposition stage, （2） initial cementation, （3） exposure to and cementation in meteoric environment, and （4） erosion stage. The published reports indicate that the hard rock should be designated as coquinite. Based on these studies, mid-Holocene sea level in this area was discussed, and the Haishan Island was proposed to uplift with a rate of ～5 mm/a in the last -600 a.
基金Supported by Knowledge Innovation Project of the Chinese Academy of Sciences(Grant No.KZCX2-YW-318)National Basic Research Program of China(Grant No.2007CB815905)+1 种基金National Natural Science Foundation of China(Grant No.40830852)the Australian Research Council(Grant No.DP0773081)
基金Supported by Chinese Academy of Sciences (Grant No. KZCX3-SW-234)National Natural Science Foundation of China (Grant Nos. 40674051, 40574019 and 40276015)+1 种基金Guangdong Natural Science Foundation (Grant No. 021557)South China Sea Institute of Oceanology (Grant No. LYQY200302)
文摘Onshore-offshore seismic experiments were carried out for the first time in northern South China Sea using large volume airgun sources at sea and seismic stations on land. The experimental results indicate that seismic signals from the new airgun array of R/V Shiyan 2 can be detected as far as 255 km. The signal effective area reaches nearly 50000 km2, which covers Hong Kong and Pearl River Delta. Compared with the old airgun array, the signal amplitude, propagation distance and effective area of the new airgun array have been increased notably, which demonstrates that the upgrade of the airgun source was successful. Comparisons with previous experimental results in other regions show that the shooting effect of the new airgun array is similar to those best airgun sources in the world. Especially, it is a new breakthrough in using the permanent seismic stations onshore to record long distance airgun signals offshore, which has great significance to the realization of the "seismic radar" concept and the 3D seismic surveys of crustal structure in coastal areas.
基金the Key Innovative Program of Chinese Academy of Sciences (Grant No. KZCX3-SW-234-3)the Basic Research Program of China (Grant No. 2007CB411704)the National Natural Science Foundation of China (Grant Nos. 40406012 and 40576027)
文摘To investigate the thinning of the whole crust, and the contribution of the upper versus lower crust to the stretching since Cenozoic, we calculated the stretching factor of the northern margin of South China Sea with data such as whole crustal thickness, depth of Cenozoic sedimentary basement and the horizontal displacement of faults. An isometric line drawing on whole crustal stretching factor is then obtained. Along the seismic Line 1530 in Baiyun sag, we also calculated the stretching factors of the upper and lower crust. The results suggest that the whole crustal thickness decreases seaward while the whole crustal stretching factor increases from shelf to slope. The Moho upwells highest beneath where the crust is thinned most. The value of the whole crustal stretching factor ranges from 1.5 to 6. Two areas were thinned intensely: the center of Yinggehai Basin, and the Baiyun sag in the Pearl River Mouth Basin. The calculation of the upper and lower crustal stretching factors from DSP1530 in Baiyun sag shows that the original crust of Baiyun sag should be thinned before deformation. Its pre-Cenozoic evolution as well as tectonic position during Cenozoic might be responsible for that.
基金supported by National Basic Research Program of China(Grant No. 2009CB219508)Chinese Academy of Sciences (Grant No.KZCX2-YW-GJ03)National Natural Science Foundation of China(Grant No. 91228206)
文摘Temperature and pressure on seafloor of the northern slope in the South China Sea are suitable for gas hydrate formation, but bottom simulation reflector (BSR), an indication of gas hydrate occurrence, only occurred in limited areas of the slope. Drillings in the BSR-distributed area (the District S) on the northern slope of the South China Sea suggested that gas hydrate only occurred at Sites SH2, SH3, and SH7 with high saturation (up to 20%-40%), and there is no hydrate at Sites SH1 and SH5 although the distance between SH1 to SH3 is only 500m. In this paper, we investigated seafloor gradient, fault development, temperature, and pressure in the District S on the northern slope of the South China Sea to understand the possible factors con- trolling BSR distribution and gas hydrate occurrence. The District S is a structurally fractured continental slope zone and its seafloor gradient varied greatly. The BSR-occurred areas have an average gradient of 19.89×10 2 whereas the BSR-free zone has the average gradient of 10.57×10 2 . The calculated relative structural intensities from fault densities and displacements show that the BSR-distributed areas tend to occur in the areas with a moderately high structural intensity, where faults frequently developed close to the seafloor that are possibly favored for lateral migration of gases. On the basis of temperatures and pressures at drilling sites, hydrate-occurred Sites SH2, SH3, and SH7 are located within the thermodynamically stable area for methane hydrate, and hydrate-absent Sites SH1 and SH5 are out of the thermodynamically stable area for methane hydrate formation, suggesting that both BSR and the thermodynamic stability are necessary for hydrate occurrence in the subsurface.
基金the Knowledge Innovation Project of the Chinese Academy of Sci-ences (Grant No. KZCX2-YW-318)the National Natural Science Foundation of China (Grant No. 40572102)+1 种基金the Ministry of Science and Technology of China (Grant No. 2006BAB19B03)the Sino-Australia Special Collaboration Funds (Grant Nos. 4061120030 and CH050099)
基金supported by the National Natural Science Foundation of China (40830852 and 41025007)the Chinese Ministry of Science and Technology Special Scheme (2007CB815905 and 2006BAB19B03)an Australian Research Council Project (DP0773081)
文摘由空至海的 CO2 的领域大小在华南海的三个珊瑚礁石区域交换(即 Nansha 岛的 Yongshu 礁石环礁，南部的华南海(SCS ) ；Xisha 岛的 Yongxing 岛，北方中央的 SCS；并且在海南岛的 Sanya 的 Luhuitou Fringing 礁石，北 SCS ) 在 2008 和 2009 的夏天期间揭示了那 CO2 (pCO2 ) 的部分压力显示出的空气和表面海水常规日报周期。最小的价值在早上发生在晚上和最大的价值。在每三个学习区域的空气 pCO2 出现了小日报变化，当时大日报变化在海水 pCO2 被观察。日报海水 pCO2 的变化振幅是 70 摩尔摩尔? 1 在 Yongshu 礁石泻湖， 420619 摩尔摩尔? 1 在 Yongxing 岛礁石公寓，和 264579 摩尔摩尔上? 1 在 Luhuitou Fringing 礁石的礁石公寓上，并且 324492 摩尔摩尔? 1 在就在这 fringing 礁石外面的一个邻近的区域。关于空间关系，在越过华南海的由空至海的 CO2 流动有大差别(例如 0.4 mmol CO2 m ? 2 d ? 1 在 Yongshu 礁石， 4.7 mmol CO2 m ? 2 d ? 1 在 Yongxing 岛，并且 9.8 mmol CO2 m ? 2 d ? 1 在 Luhuitou Fringing 礁石)。然而，这些积极的值建议 SCS 的珊瑚礁石生态系统可以是到空气的 CO2 的网络来源。另外的分析显示了那日报在浅水礁石公寓的表面海水 pCO2 的变化主要被生物新陈代谢的过程控制，当那些被两个生物新陈代谢和水动力学因素更深的水泻湖和外部礁石区域调整时。不同于开的海洋，无机的新陈代谢在在珊瑚礁石生态系统影响海水 pCO2 变化起一个重要作用。
基金Acknowledgements This work was supported by the Knowledge Innovation Project of the Chinese Academy of Sciences （Grant No. KZCX3-SW-220）, the National Natural Science Foundation （Grant No. 40476024） and the Foundation of Key Laboratory of Marginal Sea Geology, South China Sea Institute of 0ceanology, Chinese Academy of Sciences （Grant No. BYH03A04）.
文摘The relationship of species and abundance between the diatoms in the water and sediments from the southern South China Sea (SCS)were discussed, and the key environmental controlling factors were also investigated. Studies show thathe diatom abundance is high in both water andsediments in the southeast part of the southern SCSand the varying trend is similar, while in the northwespart, the abundance is low, and the varying trend isdifferent. The dominant diatom species are Thalassionema nitzschioides and Nitzschia bicapitata inwater, and T. nitzschioides and Chaetoceros messanensis in sediments. The diatom species of smalsize and thin shell in water are more than in thesediments, while the diatom species of large size andthick shell in water are less. The percentage of species T. nitzschioides is higher in water of southeaspart than in that of northwest part, but it is similar insediments of both areas. It is shown that the southwest monsoon is the important factor influencingdiatom abundance and T. nitzschioides percentageand when the southwest monsoon is well developedthe distribution of diatom abundance and T. nitzschioides percentage are consistent in both water andsediments of the study area.
基金supported jointly by the CAS Knowledge In-novation Program (No. KZCX2-YW-203)the National Basic Research Program of China (No. 2007CB411703)+2 种基金Key Labo-ratory of Marginal Sea Geology, Chinese Academy of Sciences (No. MSGL08-22)the MLR National Petroleum Resource Strategic Target Survey and Evaluation Programthe Tai-shan Scholarship Program of Shandong Province
文摘Quantitative studies on the evolution and dynamics of the deepwater area of Pearl River Mouth basin （PRMB） were carried out based on the latest geological and seismic data. The study area is generally in an extensional state during the Cenozoic. The major extension happened in the earlier syn-rift stages before 23 Ma and the extension after 23 Ma is negligible. Two rapid subsidence periods, 32-23 Ma and 5.3-2.6 Ma, are identified, which are related to the abrupt heat decay during margin breakup and the collision between the Philippine Sea plate and the Eurasian plate, respectively. The strongest crustal thinning in the Baiyun （白云） sag may trigger the syn-rift volcanism along the weak faulted belt around the sag. The Cenozoic tectonic evolution of the study area could be divided into five stages： rifting （～50-40 Ma）, rift-drift transition （～40-32 Ma）, early post-breakup （～32-23 Ma）, thermal subsidence （～23-5.3 Ma） and neotectonic movement （～5.3-0 Ma）.
