Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not ...Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not fully understood.In this study,evolutions of sedimentary facies and palaeoenvironment and their influences on the development of source rocks in diverse tectonic regions of the Qiongdongnan Basin were investigated.The results show that during the Oligocene and to Miocene periods,the sedimentary environment of this basin progressively varied from a semi-closed gulf to an open marine environment,which resulted in significant differences in palaeoenvironmental conditions of the water column for various tectonic regions of the basin.In shallow-water areas,the palaeoproductivity and reducibility successively decrease,and the hydrodynamic intensity gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In deep-water areas,the water column of the Yacheng and Lingshui strata has a higher palaeoproductivity and a weaker hydrodynamic intensity than that of the Sanya-Meishan strata,while the reducibility gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In general,the palaeoenvironmental conditions of the water column are the most favorable to the development of the Yacheng organic-rich source rocks.Meanwhile,the Miocene marine source rocks in the deep-water areas of the Qiongdongnan Basin may also have a certain hydrocarbon potential.The differences in the development models of source rocks in various tectonic regions of continental margin basins should be fully evaluated in the exploration and development of hydrocarbons.展开更多
The Fengzhou loess section is very typical in the Qinling Mountains. The section, which is about 82 m thick and underlain by Neogene red clays, consists of 33 layers of loess and 33 layers of palaeosol. It covers the ...The Fengzhou loess section is very typical in the Qinling Mountains. The section, which is about 82 m thick and underlain by Neogene red clays, consists of 33 layers of loess and 33 layers of palaeosol. It covers the Brunhes normal polarity zone and Matuyama reversed polarity zone, and the B/ M boundary is located in the middle part of loess layer 8 (L8). The loess of the Matuyama reversed polarity zone records the Jaramillo, Olduvai and Reunion normal polarity subchrons. The boundary between the Matuyama reversed polarity zone and Gauss normal polarity zone (M / Ga) appears on the lithological boundary between loess and Neogene red clays. Loess accumulation in the Fengzhou section started before 2.48 Ma B.P. Based on the stratigraphical structure, the material composition and magnetic susceptibility curve of the Fengzhou loess section, the palaeoclimatic changes during the last 2.48 Ma in the Qinling Mountains are subdivided into 66 cold-dry and warm-humid stages, equivalent to 33 climatic cycles.展开更多
Jehol Biota in western Liaoning and northern Hebei has been a hot topic of global concern,a large number of exquisite fossils were found in Yixian group Sihetun,such as Sinosauropteryx,Protarchaeopteryx, Caudipteryx a...Jehol Biota in western Liaoning and northern Hebei has been a hot topic of global concern,a large number of exquisite fossils were found in Yixian group Sihetun,such as Sinosauropteryx,Protarchaeopteryx, Caudipteryx and Confuciusornis.Scientists consider the discovering of Sinosauropteryx discovered so far as the earliest ancestor of birds.According to the dates of root layer,we can see warm and humid,lakes展开更多
A detailed analysis of the diatoms from the sedimentary sequence exposed in Abu Qada basin, west central Sinai, was used to determine the palaeoenvironmental changes during the Lower to Middle Miocene. A total of 85 d...A detailed analysis of the diatoms from the sedimentary sequence exposed in Abu Qada basin, west central Sinai, was used to determine the palaeoenvironmental changes during the Lower to Middle Miocene. A total of 85 diatom species and varieties belonging to 37 genera were identified from 154 samples collected throughout the stratigraphic succession. The lithological characters of the studied samples varied between sandstone, silty interbeds, sandy shales, shales, and terminated with anhydrite and limestones. These rock units are included in two lithostratigraphic formations(Rudies and Kareem), which are separated by a marked unconformity. The distribution and preservation of fossil diatoms in the sedimentary record are examined with the aim of outlining the temporal and spatial variation in the composition of the diatom assemblages, in order to estimate the changes in depositional environments during the Lower to Middle Miocene. The distributional pattern of the recorded diatom taxa distinguished four diatom eco-zones. The environment of each eco-zone is deduced and a proposed paleobathymetric change and depositional history of the Miocene sediments in the studied area are given.展开更多
A compiled selected literature on some groups of microfossils of the Mesozoic and Cenozoic of the James Ross Basin,eastern Antarctic Peninsula,is presented here,in order to show how the microbiota has been modified ov...A compiled selected literature on some groups of microfossils of the Mesozoic and Cenozoic of the James Ross Basin,eastern Antarctic Peninsula,is presented here,in order to show how the microbiota has been modified over time,triggered by environmental changes.The analyzed microfossils consist of palynomorphs(mostly pollen grains,spores,and dinoflagellate cysts),foraminifers and bryozoans.Dinoflagellate cysts and pollen-spores have been recorded in Jurassic to Pleistocene sedimentary outcrops.Dinoflagellate cysts proved to be good indicators for productivity and/or nutrient availability,surface water temperature and chemistry,the position of ancient shorelines and paleoceanographic trends.Pollen and spores allowed reconstruction of floral community and thus characterization of the climate that prevailed on the continent.Foraminifera,recovered from the Lower Cretaceous to the Pleistocene sedimentary rocks,provided information about the bathymetry,showing different marine settings(e.g.,coastal,inner neritic,outer neritic,upper bathyal)in different localities.The bryozoan record is restricted to the Cenozoic.Their colonial growth-forms reflect several environmental conditions such as shallow waters with a low rate of sedimentation,hard substrate and moderate or strong current action for the analyzed localities.The study of the Antarctic ecosystems based on the fossil microbiota and their response to the climate and the continental configuration changes,allowed understanding of the composition and dynamics of the polar environments,which have an important role in the Earth climate.展开更多
The sediments in core YS01 recovered from the South Yellow Sea mud deposit zone contain abundant benthic foraminifera,particularly shallow continental shelf species,but rare of planktonic foraminifera.The benthic fora...The sediments in core YS01 recovered from the South Yellow Sea mud deposit zone contain abundant benthic foraminifera,particularly shallow continental shelf species,but rare of planktonic foraminifera.The benthic foraminifera are dominated by stenohaline cold shallow-water species and euryhaline brackish-water species.In this paper,the palaeoenvironmental changes were discussed based on the grain-size compositions and benthic foraminiferal assemblages.Six different benthic foraminiferal assemblages were discriminated by species analysis from the foraminiferal fauna.According to AMS14C dating data in core YS01,we identified four main stages of marine environmental changes since the last deglaciation:a near-shore depositional stage(13.1–9.5 kyr B.P.),a transitional stage from near-shore deposition to shallow-sea deposition(9.5–5.6 kyr B.P.),a high sea level stage with shallow-sea deposition(5.6–2.9 kyr B.P.),and a stable shallow-sea depositional stage(2.9 kyr B.P.to the present).展开更多
The Xihu Lake is Located on the southern Fildes Peninsula. A drill hole is 2.6 m deep and total 102 samples were collected by Dr. Xie Youyu during 1985-1986. The samples from drill hole in the Xihu Lake contain abunda...The Xihu Lake is Located on the southern Fildes Peninsula. A drill hole is 2.6 m deep and total 102 samples were collected by Dr. Xie Youyu during 1985-1986. The samples from drill hole in the Xihu Lake contain abundant and well-preserved diatoms and Cysts (Chrysophata), 131 species and variaties of diatoms belonging to 21 genera were reoognized. As a result of the detailed research on the diatom assemblages from the Xihu Lake sediments, 9 diatom assemblages were distinguished. From diatom and Cysts (Chrysophyta) data, the changes of the Palaeoenvironments and Palaeoclimate and their age are discussed.展开更多
The Volgian-Valanginian succession of shallow-water deposits from the Olenek section(Anabar-Lena region,Arctic Siberia)has been studied by sedimentological and palaeontological methods.High-resolution biostratigraphy ...The Volgian-Valanginian succession of shallow-water deposits from the Olenek section(Anabar-Lena region,Arctic Siberia)has been studied by sedimentological and palaeontological methods.High-resolution biostratigraphy of studied interval is based on the ammonites,foraminifers,marine and terrestrial palynomorphs.Foraminiferal and palynological zones have important regional implications providing well-constrained biostratigraphy of the Anabar-Lena region.Sedimentological studies together with ecological analysis of the associations of microbenthos,microphytoplankton and terrestrial palynomorphs allow the palaeoenvironmental reconstructions for the marginal area of the Anabar-Lena palaeosea and coastal land areas.展开更多
Based on palynological and geochemical data (Organic Carbon-Corg and Sulphur-S) of sedimentary samples from a vibrocore, considerations about the palaeoenvironmental evolution of Itapeva Lake region during the Holocen...Based on palynological and geochemical data (Organic Carbon-Corg and Sulphur-S) of sedimentary samples from a vibrocore, considerations about the palaeoenvironmental evolution of Itapeva Lake region during the Holocene are made. The analysed core (BOXVI) consists in its lowermost part of a fine to medium sand packet, rich in glauconitic minerals, whose upper limit is considered to be the Holocene-Pleistocene contact. Using Cluster analysis on palynomorphs combined with Corg and S data, it was possible to distinguish four zones related to the Holocene transgression-regression cycle. Variations in Corg and S data permitted the recognition of changes in palaeosalinity. Zone 1 represents the beginning of the Holocene sedimentation; palynomorphs composition reveals a marsh environment under predominating freshwater conditions. In Zone 2, the occurrence of dinoflagellate cysts and high S values, indicating brackish water, reflects Holocene sea level highstand around 5100yrs. B.P. High concentration of Cyperaceae associated with a significant increase in Corg in Zone 3 indicates a typical marsh environment influenced at least sometimes by higher saline water, reflecting a regression phase. Salvinia natans (L)All. and Cyperaceae grains are considered to be the most significant palynomorpha in Zone 4, characterising a freshwater marsh. Based on the occurrence of dinoflagellates sample 2, Operculodinium sp., related to marine to estuarine environments, a question arises regarding about the time at which Barrier Ⅳ became completely closed.展开更多
Comprehensive field investigations and laboratory analyses show that palaeolakes, including fresh-mesohaline water Megalake Tengger and other semi-connected, isolated water bodies, during late Pleistocene covered an a...Comprehensive field investigations and laboratory analyses show that palaeolakes, including fresh-mesohaline water Megalake Tengger and other semi-connected, isolated water bodies, during late Pleistocene covered an area of more than 20000 km2, which is more than half of the Tengger Desert in NW China. Stratigraphic correlation and chronological evidence indicate that before ca. 42000 aBP the area was more arid. The palaeolakes started to develop around 40000 uncal. 14C aBP but until 37000 14C aBP their scope was limited. High water levels established from 35000 14C aBP lasted until 22000 14C aBP. Lake levels regressed between 22000 and 20000 14C aBP but transgressed from 20000 to 18600 14C aBP. Subsequently, water level declined further and the Megalake Tengger finally desiccated at around 18000 14C aBP. Megalake Tengger possessed a fresh-mesohaline water property, implying that the regional precipitation increased significantly. During the period of Megalake Tengger, the climate was warmer-humid展开更多
The Eocene palaeovegetation landscape and palaeoclimate reconstructed from the pollen records in the Jiuquan Basin, northwest China provide some important information on the early uplift of the Tibetan Plateau and the...The Eocene palaeovegetation landscape and palaeoclimate reconstructed from the pollen records in the Jiuquan Basin, northwest China provide some important information on the early uplift of the Tibetan Plateau and the origin and evolution of the aridification in northwest China. The records show the arid-semiarid scrubs with open forest palynofloras controlled by the subtropical high existed in northwest China during the 40.2-33.4 Ma. Four pollen assemblages are found: Nitrariadites-Cheno-podipollis-Pinaceae assemblage (40.2-37.9 Ma) is followed by Chenopodipollis-Nitrariadites assemblage (37.9-34.6 Ma), Pinuspollenites & Abietineaepollenites-Chenopodipollis assemblage (34.6-33.9 Ma), and Chenopodipollis-Nitrariadites assemblage (33.9-33.4 Ma). The percentage of thermophilic types is in anti-correlation with that of the dry types, which means the palaeoclimate is relatively warmwet or cold-dry during most of that time. Such aridity may be related to the water vapor reduction and the planetary wind system movement northward in response to the cooling caused by small-ephemeral icesheets.展开更多
Palynological records were selected from the profiles of three research sites in the mountainous interior of southern China(Dajiuhu at Shennongjia in the western part of Hubei Province, Dahu in the Nanling Mountains, ...Palynological records were selected from the profiles of three research sites in the mountainous interior of southern China(Dajiuhu at Shennongjia in the western part of Hubei Province, Dahu in the Nanling Mountains, and Gantang in the northern part of Fujian Province). It can be inferred that the forest vegetation growing in the south of the Qinling Mountains-Huaihe River was luxuriant during the late glaciation. The species succession with ecological significance in palaeoflora(Abies sp., Fagus sp. and Alnus sp.) revealed that there was a certain amount of precipitation and effective humidity in the mountain lands between Qinling Mountains-Huaihe River and Nanling Mountains. This ecological environment favored the zonal distribution of mountainous forest vegetation. The late glacial maximum featured a cold, wet climate that completely differed from the cold-dry climate on the Loess Plateau, and on the steppe and desert steppe of the Qinghai-Tibet Plateau. Besides being influenced by the predominant factors driving the Northern Hemisphere climate, the cold-wet climate feature of the mountainous interior of southern China was closely associated with some geographical factors such as the latitudinal position, proximity to the ocean, and the topography and landforms.展开更多
The palynological assemblages from two Albian-Cenomanian boundary sections in North Bulgaria are described.The samples analyzed yielded a diverse palynological content including dinoflagellate cysts and miospores.Base...The palynological assemblages from two Albian-Cenomanian boundary sections in North Bulgaria are described.The samples analyzed yielded a diverse palynological content including dinoflagellate cysts and miospores.Based on dinocyst nutrient and productivity indices a phase of enhanced nutrient availability and high primary productivity is inferred for the latest Albian interval.The pronounced predominance of peridinioid dinocysts in this interval,namely O.verrucosum,O.scabrosum and especially P.infusorioides is considered to reflect eutrophic conditions.It coincides with the increased phosphorus mass accumulation occurring at the top part of the Upper Albian Dekov Formation.OAE 1d is indicated in the Tolovitsa karst spring section,based on palynofacies dominated by high amounts of granular amorphous organic matter(AOM)related to anoxic environmental conditions.These sections serve as evidence suggesting a relationship between Cretaceous peridinioid cysts(including Palaeohystichphora infusorioides,Ovoidinium verrucosum,O.scabrosum)and anoxic/suboxic conditions and/or high primary productivity.The pollen spectrum inferred relatively stable vegetation patterns of surrounding continental areas during and after the Albian/Cenomanian boundary interval and the times of OAE 1d formation.The hinterland vegetation integrated mainly pteridophyte spores and gymnosperms.The area was part of the Southern Laurasian floral province which was characterized by warm temperate to subtropical humid climate.Angiosperms were still minor part of this vegetation.展开更多
The plant opal is a kind of noncrystalline opal （SiO<sub>2</sub>·nH<sub>2</sub>O） filled in the cell systems of higher plants. Plants of different genera and species have the opal assemb...The plant opal is a kind of noncrystalline opal （SiO<sub>2</sub>·nH<sub>2</sub>O） filled in the cell systems of higher plants. Plants of different genera and species have the opal assemblages of dif-展开更多
The O-C isotope compositions of reef-facies carbonates of NY-1 (Nanyong-1) core in Nansha area can be divided into 4 stages. The average values of δ18O (‰) and δ13C (‰) for the 4 stages are (I) -5.0, -0.5; (11) -7...The O-C isotope compositions of reef-facies carbonates of NY-1 (Nanyong-1) core in Nansha area can be divided into 4 stages. The average values of δ18O (‰) and δ13C (‰) for the 4 stages are (I) -5.0, -0.5; (11) -7.7, -5.3; (III) -6.4, -2.8; (IV) 1.3, 2.1, respectively. The characters of δ18O fluctuating curves of stage II are low frequencies, small amplitudes and corresponding correlation with glacial and mterglacial stages. It has positive correlations between δ18O and δ13C values in stages III and IV, which are genetically related to dolomitization. The characteristics of 4 stages also exist in Δ87Sr and in Pb isotope compositions The maximun. minimum and all the positive values of Δ87Sr in the core of the whole hole occur in stage 11 The characters of frequently changing fluctuation appear in stage IV for both Pb and Sr isotope compositions The lead with high μ values was taken in during dolomitization. The history of palaeoclimatic and palaeoenvironmental changes in Nansha region during展开更多
The Eastern Himalayas are renowned for their high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate past plant biodiversity preserved as fossils throughout the easte...The Eastern Himalayas are renowned for their high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate past plant biodiversity preserved as fossils throughout the eastern Himalayan Siwalik succession(middle Miocene-early Pleistocene).Here,we present a summary of plant diversity records that document Neogene floristic and climate changes.We do this by compiling published records of megafossil plant remains,because these offer better spatial and temporal resolution than do palynological records.Analyses of the Siwalik floral assemblages based on the distribution of the nearest living relative taxa suggest that a tropical wet evergreen forest was growing in a warm humid monsoonal climate at the deposition time.This qualitative interpretation is also corroborated by published CLAMP(Climate Leaf Analysis Multivariate Program) analyses.Here,we also reconstruct the climate by applying a new common proxy WorldClim2 calibration.This allows the detection of subtle climate differences between floral assemblages free of artefacts introduced by using different methodologies and climate calibrations.An analysis of the Siwalik floras indicates that there was a gradual change in floral composition.The lower Siwalik assemblages provide evidence of a predominance of evergreen elements.An increase in deciduous elements in the floral composition is noticed towards the close of the middle Siwalik and the beginning of the upper Siwalik formation.This change reflects a climatic difference between Miocene and Plio-Pleistocene times.This review helps us to understand under what paleoenvironmental conditions plant diversity occurred and evolved in the eastern Himalayas throughout the Cenozoic.展开更多
Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle...Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme.As one of the typical Sturtian-Marinoan interglacial deposits,the Datangpo Formation was widely distributed in South China with shales continuously deposited.The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval.Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province.Based on measured episodicδ^(13)C_(org) perturbations,three positive shifts and three negative excursions are identified.Aδ^(13)C_(org)-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally.Meanwhile,theδ^(13)C_(org) vertical gradients changed dynamically throughout the formation.This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation,coinciding with the potential oxygenation.展开更多
The history of amber and its trade in Lebanon dates back to ancient times,during the Phoenician civilization.Amber in Lebanon can be found in over 450 outcrops,comprising approximately 10%of the country’s land.Some o...The history of amber and its trade in Lebanon dates back to ancient times,during the Phoenician civilization.Amber in Lebanon can be found in over 450 outcrops,comprising approximately 10%of the country’s land.Some of these outcrops are Late Jurassic(Kimmeridgian)in age,while the majority are Early Cretaceous(early Barremian).The Early Cretaceous amber found in Lebanon is the oldest amber with extensive biological inclusions,making it a crucial source of knowledge regarding continental palaeobiodiversity during the Early Cretaceous period.This period is widely recognized as witnessing the first occurrence and early evolution of angiosperms,representing a critical time for the co-evolution between flowering plants and insects.In Lebanese amber,biological inclusions often serve as records of the earliest representatives of modern living insect families or the youngest ones for extinct families.展开更多
基金supported by the National Natural Science Foundation of China(42272162)the Natural Science Foundation of Guangdong Province(2021A1515011381 and 2021A1515011635)the Science Project of the CNOOC(KJZH-2021-0003-00).
文摘Hydrocarbon resources in the Qiongdongnan Basin have become an important exploration target in China.However,the development of high-quality source rocks in this basin,especially in its deep-water areas,are still not fully understood.In this study,evolutions of sedimentary facies and palaeoenvironment and their influences on the development of source rocks in diverse tectonic regions of the Qiongdongnan Basin were investigated.The results show that during the Oligocene and to Miocene periods,the sedimentary environment of this basin progressively varied from a semi-closed gulf to an open marine environment,which resulted in significant differences in palaeoenvironmental conditions of the water column for various tectonic regions of the basin.In shallow-water areas,the palaeoproductivity and reducibility successively decrease,and the hydrodynamic intensity gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In deep-water areas,the water column of the Yacheng and Lingshui strata has a higher palaeoproductivity and a weaker hydrodynamic intensity than that of the Sanya-Meishan strata,while the reducibility gradually increases for the water columns of the Yacheng,Lingshui,and Sanya-Meishan strata.In general,the palaeoenvironmental conditions of the water column are the most favorable to the development of the Yacheng organic-rich source rocks.Meanwhile,the Miocene marine source rocks in the deep-water areas of the Qiongdongnan Basin may also have a certain hydrocarbon potential.The differences in the development models of source rocks in various tectonic regions of continental margin basins should be fully evaluated in the exploration and development of hydrocarbons.
文摘The Fengzhou loess section is very typical in the Qinling Mountains. The section, which is about 82 m thick and underlain by Neogene red clays, consists of 33 layers of loess and 33 layers of palaeosol. It covers the Brunhes normal polarity zone and Matuyama reversed polarity zone, and the B/ M boundary is located in the middle part of loess layer 8 (L8). The loess of the Matuyama reversed polarity zone records the Jaramillo, Olduvai and Reunion normal polarity subchrons. The boundary between the Matuyama reversed polarity zone and Gauss normal polarity zone (M / Ga) appears on the lithological boundary between loess and Neogene red clays. Loess accumulation in the Fengzhou section started before 2.48 Ma B.P. Based on the stratigraphical structure, the material composition and magnetic susceptibility curve of the Fengzhou loess section, the palaeoclimatic changes during the last 2.48 Ma in the Qinling Mountains are subdivided into 66 cold-dry and warm-humid stages, equivalent to 33 climatic cycles.
文摘Jehol Biota in western Liaoning and northern Hebei has been a hot topic of global concern,a large number of exquisite fossils were found in Yixian group Sihetun,such as Sinosauropteryx,Protarchaeopteryx, Caudipteryx and Confuciusornis.Scientists consider the discovering of Sinosauropteryx discovered so far as the earliest ancestor of birds.According to the dates of root layer,we can see warm and humid,lakes
文摘A detailed analysis of the diatoms from the sedimentary sequence exposed in Abu Qada basin, west central Sinai, was used to determine the palaeoenvironmental changes during the Lower to Middle Miocene. A total of 85 diatom species and varieties belonging to 37 genera were identified from 154 samples collected throughout the stratigraphic succession. The lithological characters of the studied samples varied between sandstone, silty interbeds, sandy shales, shales, and terminated with anhydrite and limestones. These rock units are included in two lithostratigraphic formations(Rudies and Kareem), which are separated by a marked unconformity. The distribution and preservation of fossil diatoms in the sedimentary record are examined with the aim of outlining the temporal and spatial variation in the composition of the diatom assemblages, in order to estimate the changes in depositional environments during the Lower to Middle Miocene. The distributional pattern of the recorded diatom taxa distinguished four diatom eco-zones. The environment of each eco-zone is deduced and a proposed paleobathymetric change and depositional history of the Miocene sediments in the studied area are given.
文摘A compiled selected literature on some groups of microfossils of the Mesozoic and Cenozoic of the James Ross Basin,eastern Antarctic Peninsula,is presented here,in order to show how the microbiota has been modified over time,triggered by environmental changes.The analyzed microfossils consist of palynomorphs(mostly pollen grains,spores,and dinoflagellate cysts),foraminifers and bryozoans.Dinoflagellate cysts and pollen-spores have been recorded in Jurassic to Pleistocene sedimentary outcrops.Dinoflagellate cysts proved to be good indicators for productivity and/or nutrient availability,surface water temperature and chemistry,the position of ancient shorelines and paleoceanographic trends.Pollen and spores allowed reconstruction of floral community and thus characterization of the climate that prevailed on the continent.Foraminifera,recovered from the Lower Cretaceous to the Pleistocene sedimentary rocks,provided information about the bathymetry,showing different marine settings(e.g.,coastal,inner neritic,outer neritic,upper bathyal)in different localities.The bryozoan record is restricted to the Cenozoic.Their colonial growth-forms reflect several environmental conditions such as shallow waters with a low rate of sedimentation,hard substrate and moderate or strong current action for the analyzed localities.The study of the Antarctic ecosystems based on the fossil microbiota and their response to the climate and the continental configuration changes,allowed understanding of the composition and dynamics of the polar environments,which have an important role in the Earth climate.
基金the China Geological Survey Project(Nos.121201005000150004 and GZH201100202)by the Taishan Scholar Project.
文摘The sediments in core YS01 recovered from the South Yellow Sea mud deposit zone contain abundant benthic foraminifera,particularly shallow continental shelf species,but rare of planktonic foraminifera.The benthic foraminifera are dominated by stenohaline cold shallow-water species and euryhaline brackish-water species.In this paper,the palaeoenvironmental changes were discussed based on the grain-size compositions and benthic foraminiferal assemblages.Six different benthic foraminiferal assemblages were discriminated by species analysis from the foraminiferal fauna.According to AMS14C dating data in core YS01,we identified four main stages of marine environmental changes since the last deglaciation:a near-shore depositional stage(13.1–9.5 kyr B.P.),a transitional stage from near-shore deposition to shallow-sea deposition(9.5–5.6 kyr B.P.),a high sea level stage with shallow-sea deposition(5.6–2.9 kyr B.P.),and a stable shallow-sea depositional stage(2.9 kyr B.P.to the present).
文摘The Xihu Lake is Located on the southern Fildes Peninsula. A drill hole is 2.6 m deep and total 102 samples were collected by Dr. Xie Youyu during 1985-1986. The samples from drill hole in the Xihu Lake contain abundant and well-preserved diatoms and Cysts (Chrysophata), 131 species and variaties of diatoms belonging to 21 genera were reoognized. As a result of the detailed research on the diatom assemblages from the Xihu Lake sediments, 9 diatom assemblages were distinguished. From diatom and Cysts (Chrysophyta) data, the changes of the Palaeoenvironments and Palaeoclimate and their age are discussed.
基金Financial support:Russian Science Foundation 18-17-00038Scientific support:Russian FSI 0331-2019-0004IGCP 679,632
文摘The Volgian-Valanginian succession of shallow-water deposits from the Olenek section(Anabar-Lena region,Arctic Siberia)has been studied by sedimentological and palaeontological methods.High-resolution biostratigraphy of studied interval is based on the ammonites,foraminifers,marine and terrestrial palynomorphs.Foraminiferal and palynological zones have important regional implications providing well-constrained biostratigraphy of the Anabar-Lena region.Sedimentological studies together with ecological analysis of the associations of microbenthos,microphytoplankton and terrestrial palynomorphs allow the palaeoenvironmental reconstructions for the marginal area of the Anabar-Lena palaeosea and coastal land areas.
文摘Based on palynological and geochemical data (Organic Carbon-Corg and Sulphur-S) of sedimentary samples from a vibrocore, considerations about the palaeoenvironmental evolution of Itapeva Lake region during the Holocene are made. The analysed core (BOXVI) consists in its lowermost part of a fine to medium sand packet, rich in glauconitic minerals, whose upper limit is considered to be the Holocene-Pleistocene contact. Using Cluster analysis on palynomorphs combined with Corg and S data, it was possible to distinguish four zones related to the Holocene transgression-regression cycle. Variations in Corg and S data permitted the recognition of changes in palaeosalinity. Zone 1 represents the beginning of the Holocene sedimentation; palynomorphs composition reveals a marsh environment under predominating freshwater conditions. In Zone 2, the occurrence of dinoflagellate cysts and high S values, indicating brackish water, reflects Holocene sea level highstand around 5100yrs. B.P. High concentration of Cyperaceae associated with a significant increase in Corg in Zone 3 indicates a typical marsh environment influenced at least sometimes by higher saline water, reflecting a regression phase. Salvinia natans (L)All. and Cyperaceae grains are considered to be the most significant palynomorpha in Zone 4, characterising a freshwater marsh. Based on the occurrence of dinoflagellates sample 2, Operculodinium sp., related to marine to estuarine environments, a question arises regarding about the time at which Barrier Ⅳ became completely closed.
基金This work was supported by the National Natural Science Foundation of China (Grant No. 49971015) the National Key Project for Basic Research on Desertification in Northern China (Grant No. G2000048700).
文摘Comprehensive field investigations and laboratory analyses show that palaeolakes, including fresh-mesohaline water Megalake Tengger and other semi-connected, isolated water bodies, during late Pleistocene covered an area of more than 20000 km2, which is more than half of the Tengger Desert in NW China. Stratigraphic correlation and chronological evidence indicate that before ca. 42000 aBP the area was more arid. The palaeolakes started to develop around 40000 uncal. 14C aBP but until 37000 14C aBP their scope was limited. High water levels established from 35000 14C aBP lasted until 22000 14C aBP. Lake levels regressed between 22000 and 20000 14C aBP but transgressed from 20000 to 18600 14C aBP. Subsequently, water level declined further and the Megalake Tengger finally desiccated at around 18000 14C aBP. Megalake Tengger possessed a fresh-mesohaline water property, implying that the regional precipitation increased significantly. During the period of Megalake Tengger, the climate was warmer-humid
基金the National Key Program for Developing Basic Sciences (Grant No. 2005CB422001)the National Science Foundation of China (Grant Nos. 40334038, 40421101)the President Fund of Chinese Academy of Sciences
文摘The Eocene palaeovegetation landscape and palaeoclimate reconstructed from the pollen records in the Jiuquan Basin, northwest China provide some important information on the early uplift of the Tibetan Plateau and the origin and evolution of the aridification in northwest China. The records show the arid-semiarid scrubs with open forest palynofloras controlled by the subtropical high existed in northwest China during the 40.2-33.4 Ma. Four pollen assemblages are found: Nitrariadites-Cheno-podipollis-Pinaceae assemblage (40.2-37.9 Ma) is followed by Chenopodipollis-Nitrariadites assemblage (37.9-34.6 Ma), Pinuspollenites & Abietineaepollenites-Chenopodipollis assemblage (34.6-33.9 Ma), and Chenopodipollis-Nitrariadites assemblage (33.9-33.4 Ma). The percentage of thermophilic types is in anti-correlation with that of the dry types, which means the palaeoclimate is relatively warmwet or cold-dry during most of that time. Such aridity may be related to the water vapor reduction and the planetary wind system movement northward in response to the cooling caused by small-ephemeral icesheets.
基金supported by the National Key Basic Research Program of China (Grant No. 2015CB953804)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe National Natural Science Foundation of China (Grant Nos. 41472141 & 41072127)
文摘Palynological records were selected from the profiles of three research sites in the mountainous interior of southern China(Dajiuhu at Shennongjia in the western part of Hubei Province, Dahu in the Nanling Mountains, and Gantang in the northern part of Fujian Province). It can be inferred that the forest vegetation growing in the south of the Qinling Mountains-Huaihe River was luxuriant during the late glaciation. The species succession with ecological significance in palaeoflora(Abies sp., Fagus sp. and Alnus sp.) revealed that there was a certain amount of precipitation and effective humidity in the mountain lands between Qinling Mountains-Huaihe River and Nanling Mountains. This ecological environment favored the zonal distribution of mountainous forest vegetation. The late glacial maximum featured a cold, wet climate that completely differed from the cold-dry climate on the Loess Plateau, and on the steppe and desert steppe of the Qinghai-Tibet Plateau. Besides being influenced by the predominant factors driving the Northern Hemisphere climate, the cold-wet climate feature of the mountainous interior of southern China was closely associated with some geographical factors such as the latitudinal position, proximity to the ocean, and the topography and landforms.
基金carried out in the frame of the IGCP Project 609 "Climate-environmental deteriorations during greenhouse phases:Causes and consequences of short-term Cretaceous sea-level changes "
文摘The palynological assemblages from two Albian-Cenomanian boundary sections in North Bulgaria are described.The samples analyzed yielded a diverse palynological content including dinoflagellate cysts and miospores.Based on dinocyst nutrient and productivity indices a phase of enhanced nutrient availability and high primary productivity is inferred for the latest Albian interval.The pronounced predominance of peridinioid dinocysts in this interval,namely O.verrucosum,O.scabrosum and especially P.infusorioides is considered to reflect eutrophic conditions.It coincides with the increased phosphorus mass accumulation occurring at the top part of the Upper Albian Dekov Formation.OAE 1d is indicated in the Tolovitsa karst spring section,based on palynofacies dominated by high amounts of granular amorphous organic matter(AOM)related to anoxic environmental conditions.These sections serve as evidence suggesting a relationship between Cretaceous peridinioid cysts(including Palaeohystichphora infusorioides,Ovoidinium verrucosum,O.scabrosum)and anoxic/suboxic conditions and/or high primary productivity.The pollen spectrum inferred relatively stable vegetation patterns of surrounding continental areas during and after the Albian/Cenomanian boundary interval and the times of OAE 1d formation.The hinterland vegetation integrated mainly pteridophyte spores and gymnosperms.The area was part of the Southern Laurasian floral province which was characterized by warm temperate to subtropical humid climate.Angiosperms were still minor part of this vegetation.
基金Project supported by the National Natural Science Foundation of China
文摘The plant opal is a kind of noncrystalline opal （SiO<sub>2</sub>·nH<sub>2</sub>O） filled in the cell systems of higher plants. Plants of different genera and species have the opal assemblages of dif-
基金Report D-00044 of The Multidisciplinary Oceanographic Expedition Team of Chinese Academy of Sciences to tbe Nansha Archipelago. Part of funds was supported by the National Natural Science Foundation of China.
文摘The O-C isotope compositions of reef-facies carbonates of NY-1 (Nanyong-1) core in Nansha area can be divided into 4 stages. The average values of δ18O (‰) and δ13C (‰) for the 4 stages are (I) -5.0, -0.5; (11) -7.7, -5.3; (III) -6.4, -2.8; (IV) 1.3, 2.1, respectively. The characters of δ18O fluctuating curves of stage II are low frequencies, small amplitudes and corresponding correlation with glacial and mterglacial stages. It has positive correlations between δ18O and δ13C values in stages III and IV, which are genetically related to dolomitization. The characteristics of 4 stages also exist in Δ87Sr and in Pb isotope compositions The maximun. minimum and all the positive values of Δ87Sr in the core of the whole hole occur in stage 11 The characters of frequently changing fluctuation appear in stage IV for both Pb and Sr isotope compositions The lead with high μ values was taken in during dolomitization. The history of palaeoclimatic and palaeoenvironmental changes in Nansha region during
基金RAS and TEVS were supported by NERC/NSFC BETR Project NE/P013805/1.
文摘The Eastern Himalayas are renowned for their high plant diversity.To understand how this modern botanical richness formed,it is critical to investigate past plant biodiversity preserved as fossils throughout the eastern Himalayan Siwalik succession(middle Miocene-early Pleistocene).Here,we present a summary of plant diversity records that document Neogene floristic and climate changes.We do this by compiling published records of megafossil plant remains,because these offer better spatial and temporal resolution than do palynological records.Analyses of the Siwalik floral assemblages based on the distribution of the nearest living relative taxa suggest that a tropical wet evergreen forest was growing in a warm humid monsoonal climate at the deposition time.This qualitative interpretation is also corroborated by published CLAMP(Climate Leaf Analysis Multivariate Program) analyses.Here,we also reconstruct the climate by applying a new common proxy WorldClim2 calibration.This allows the detection of subtle climate differences between floral assemblages free of artefacts introduced by using different methodologies and climate calibrations.An analysis of the Siwalik floras indicates that there was a gradual change in floral composition.The lower Siwalik assemblages provide evidence of a predominance of evergreen elements.An increase in deciduous elements in the floral composition is noticed towards the close of the middle Siwalik and the beginning of the upper Siwalik formation.This change reflects a climatic difference between Miocene and Plio-Pleistocene times.This review helps us to understand under what paleoenvironmental conditions plant diversity occurred and evolved in the eastern Himalayas throughout the Cenozoic.
基金Special thanks to Erik Tihelka for improving the English.This study was supported by the National Natural Science Foundation of China(41602126)the China Geological Survey(DD20160018,DD20221661)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0706)Liu Bao-jun Academician Research Funds subsidized by Chengdu Center of China Geological Survey.
文摘Palaeoclimatic and palaeoenvironmental reconstructions of the Cryogenian Period have attracted attention in relation to the debated“Snowball Earth”hypothesis and the early evolution of metazoan life.The carbon cycle and redox conditions of the Sturtian-Marinoan non-glacial interval have been subjected to much controversy in the past decades because of the lack of a high-resolution stratigraphic correlation scheme.As one of the typical Sturtian-Marinoan interglacial deposits,the Datangpo Formation was widely distributed in South China with shales continuously deposited.The previous zircon dating data of the Datangpo Formation provide important ages for global constrain of the Sturtian-Marinoan non-glacial interval.Here we present a high-resolution straitigraphic study of the organic carbon isotopes of the Datangpo Formation from a drill core section in northern Guizhou Province.Based on measured episodicδ^(13)C_(org) perturbations,three positive shifts and three negative excursions are identified.Aδ^(13)C_(org)-based chemostratigraphic correlation scheme is proposed herein that works well for the Datangpo Formation regionally.Meanwhile,theδ^(13)C_(org) vertical gradients changed dynamically throughout the formation.This discovery implies that a significant ocean circulation overturn might have occurred in the upper Datangpo Formation,coinciding with the potential oxygenation.
文摘The history of amber and its trade in Lebanon dates back to ancient times,during the Phoenician civilization.Amber in Lebanon can be found in over 450 outcrops,comprising approximately 10%of the country’s land.Some of these outcrops are Late Jurassic(Kimmeridgian)in age,while the majority are Early Cretaceous(early Barremian).The Early Cretaceous amber found in Lebanon is the oldest amber with extensive biological inclusions,making it a crucial source of knowledge regarding continental palaeobiodiversity during the Early Cretaceous period.This period is widely recognized as witnessing the first occurrence and early evolution of angiosperms,representing a critical time for the co-evolution between flowering plants and insects.In Lebanese amber,biological inclusions often serve as records of the earliest representatives of modern living insect families or the youngest ones for extinct families.
