The Yangtze River,with a length of approximately 6300 km,holds the distinction of being the largest river in East Asia that empties into the Pacific Ocean.Its formation is intricately linked to regional tectonic activ...The Yangtze River,with a length of approximately 6300 km,holds the distinction of being the largest river in East Asia that empties into the Pacific Ocean.Its formation is intricately linked to regional tectonic activity and climate fluctuations.However,the exact timeline for the formation of the Yangtze River remains elusive.This study investigates the provenance of the Late Cenozoic strata in the Wangjiang Basin,situated in the Lower Yangtze River,through the application of detrital zircon U-Pb dating.Seven sand samples were analyzed,leading to the identification of new U-Pb detrital zircon ages(n=577).Our study reveals that the sand materials found in the Pliocene gravel beds of the Anqing Formation originate predominantly from the Yangtze River.The findings of our study,along with the provenance tracing of boreholes in the Yangtze River Basin and the shelf sea in East China,provide compelling evidence for the continuous presence of the Yangtze River throughout the Pliocene period.The development of the Yangtze River during the Pliocene is intricately connected to both the tectonic adjustments occurring at the southeastern margin of the Tibetan Plateau and the intensification of the Asian Monsoon.展开更多
A new Quercus （Fagaceae） morphospecies is described based on well-preserved fossil leaves.The fossils were collected from Yangyi Formation of the Upper Pliocene at the Yangyi coalmine,Baoshan,western Yunnan,China.De...A new Quercus （Fagaceae） morphospecies is described based on well-preserved fossil leaves.The fossils were collected from Yangyi Formation of the Upper Pliocene at the Yangyi coalmine,Baoshan,western Yunnan,China.Details of the microstructure of mesophyll tissue are preserved because lithification of the fossils was not complete.The fossil laminas possess typical characteristics of Quercus sect.Heterobalanus：quite thick and coriaceous cuticle; secondary veins bifurcating near the margin in the middle and top of the leaf; and upper epidermis with adaxial hypodermis.Based on a detailed morphological and anatomical comparison with all living and fossil species of Quercus sect.Heterobalanus,the fossil leaves prove to be different in their sparse and garland-shaped multicellular trichomes on the lower epidermis,and so it is described as a new species Quercus yangyiensis He,Li et Sun sp.nov.The much sparser trichomes of our fossils compare well with those of living Quercus sect.Heterobalanus and indicate a more humid climate during the deposition of the Yangyi Formation in the Late Pliocene.展开更多
The Lower Pliocene of the Linxia Basin in Gansu Province is one of only a few representative sections for the Early Pliocene sedimentary records in northern China, and even in East Asia. Recently,abundant mammalian fo...The Lower Pliocene of the Linxia Basin in Gansu Province is one of only a few representative sections for the Early Pliocene sedimentary records in northern China, and even in East Asia. Recently,abundant mammalian fossils were found from the base of red clays of the Lower Pliocene Hewangjia Formation at Duikang in Guanghe County within this basin. Previously, the Pliocene mammals were sparsely found in China, and most were collected from fluvial and lacustrine deposits in the eastern Loess Plateau. Mammals from the widely distributed Pliocene Hipparion Red Clay are less in number.The known fossils from Duikang include 20 species and belong to the Shilidun Fauna. Their faunal components are similar to the Early Pliocene Gaozhuang Fauna from Ynshe, Shanxi. On the other hand, some taxa from Duikang have not been found in the Gaozhuang Fauna, are slightly more primitive in evolutionary level, and appeared mainly in the Late Miocene. As a result, the age of the Duikang fossils may be slightly earlier than that of the Gaozhuang Fauna and closer to the lower boundary of the Piiocene. The Duikang fossiliferons bed is 0.8 m above the top of the Late Miocene Linshu Formation, and the first occurrence of the three-toed horse Hipparion pater can be regarded as a biostratigraphical marker of the Miocene/Pliocene boundary. In conclusion, Duikang is an ideal candidate locality to establish as the stratotype of the lower boundary of the Chinese terrestrial Pliocene.展开更多
The uplift of the Ailao Shan-Diancang Shan （ASDS） along the Ailao Shan-Red River （ASRR） shear zone is an important geological event in the southeastern margin of Qinghai-Tibet Plateau tectonic domain in the Late C...The uplift of the Ailao Shan-Diancang Shan （ASDS） along the Ailao Shan-Red River （ASRR） shear zone is an important geological event in the southeastern margin of Qinghai-Tibet Plateau tectonic domain in the Late Cenozoic, and it preserves important information on the structures, exhumationai history and tectonic evolution of the ASRR shear zone. The uplift structural mode and uplift timing of the ASDS is currently an important scientific topic for understanding the ASDS formation and late stage movements and evolution of the ASRR shear zone. The formation of the ASDS has been widely considered to be the consequence of the strike-slip movements of the ASRR shear zone. However, the shaping of geomorphic units is generally direct results of the latest tectonic activities. In this study, we investigated the timing and uplift structural mechanism of the ASDS and provided the following lines of supportive evidence. Firstly, the primary tectonic foliation of the ASDS shows significant characteristic variations, with steeply dipping tectonic foliation developed on the east side of the ASDS and the relatively horizontal foliation on the west side. Secondly, from northeast to southwest direction, the deformation and metamorphism gradually weakened and this zone can be further divided into three different metamorphic degree belts. Thirdly, the contact relationship between the ASDS and the Chuxiong basin-Erhai lake is a normal fault contact which can be found on the east side of the ASDS. 40^Ar/^39 Argeochronology suggests that the Diancang Shan had experienced a fast cooling event during 3-4 Ma. The apatite fission track testing method gives the age of 6.6-10.7 Ma in the Diancang Shan and 4.6-8.4 Ma in the Ailao Shan, respectively. Therefore the uplift of the ASDS can be explained by tilted block mode in which the east side was uplifted much higher than the west side, and it is not main reason of the shearing movements of the ASRR shear zone. The most recent uplift stages of the ASDS happened in the Pliocene （3-4 Ma） and Late Miocene （6-10 Ma）.展开更多
Specimens of fossil wood preserved lignified in Pliocene brown coal and identified as Pinus armandii Francher come from an opencast coalmine at Longling in western Yunnan Province, China. Phytochemical investigation o...Specimens of fossil wood preserved lignified in Pliocene brown coal and identified as Pinus armandii Francher come from an opencast coalmine at Longling in western Yunnan Province, China. Phytochemical investigation of the fossil wood isolated using liquid column chromatography seven compounds （1-7） including a new fluorene derivative named 11,11-dimethyl-11H-benzo[b]fluorene. A further 28 volatiles were detected by gas chromatography-mass spectrometry （GC-MS）. Spectroscopic investigation methods, including MS and 1D and 2D-NMR techniques elucidated the structure of the seven compounds. Two types of natural products, isopimara and stilbene commonly occuring in extant and Pliocene fossil P. armandii indicate phytochemical fidelity during burial under certain circumstances in sediments. Discovery of stilbenes that can inhibit the activities of wood-destroying fungi in the Pliocene P. armandii prompts the assumption that the chemical preservation of this Pliocene fossil wood of P. armandii in brown coal might contribute to the presence of inner natural inhibitors against wood-destroying fungi.展开更多
Based on core,logging,lab test and seismic data,sedimentary characteristics and pattern of marine hyperpycnal flow,the distribution rules of hyperpycnal flow reservoir,prediction method of favorable hyperpycnal flow r...Based on core,logging,lab test and seismic data,sedimentary characteristics and pattern of marine hyperpycnal flow,the distribution rules of hyperpycnal flow reservoir,prediction method of favorable hyperpycnal flow reservoir zones,hydrocarbon accumulation model in hyperpycnal flow reservoir in D block of Bay of Bengal were investigated,and the favorable exploration zone and well sites were predicted.Pliocene in D block has typical hyperpycnal flow sediment,which is a set of fine-medium sandstone held between thick layers of marine mudstone and features a series of reverse grading unit and normal grading unit pairs.The hyperpycnal flow sediment appears as heavily jagged box shape,bell shape and tongue shape facies on log curves with linear gradient,and corresponds to multiple phases of deep channels on the seismic section and high sinuous channel on stratal slices.The sedimentary bodies formed by a single phase hyperpycnal flow which include five types of microfacies,namely,supply channel(valley),channel complex,branch channel,levee and sheet sand.The hyperpycnal flow sediments appear in multiple branches,multiple generations and stages in space,forming high-quality reservoirs in strips on the plane and superposition vertically,with fairly good physical properties.The channel complex sandstone,with large thickness,coarse particle size and good physical properties,is the most favorable exploration facies.Based on the guidance of the sedimentary model,distribution of the channel complex microfacies was delineated in detail by seismic reflection structure analysis,spectrum waveform characteristic analysis,slice and attribute fusion,and combined with the structural feature analysis,the favorable drilling zone was sorted out,effectively guiding the exploration deployment of the block.展开更多
In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of th...In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of the rocks.Petrographic and geochemical analyses of major and minor elements of the samples were used for this purpose.This Formation is composed of three major facies including conglomerate,fine sandstone,and mudstone.The source formations which were recognized to be supplying sediments to the Cheleken Formation depositional basin include Lalun,Ziarat,Tizkuh,Dalichai,and Cretaceous formations.According to the discrimination diagrams and other ratios for minor elements of the studied samples,a complex of felsic to intermediate igneous rocks in the source region was deciphered.The depositional environment of the rocks experienced humid and semi-arid climatic conditions during deposition.According to the CIW index,the samples underwent a high level of weathering(97%)in the source area or during transportation.From a tectonic point of view,the Cheleken Formation was deposited in an Active Continental Margin setting.展开更多
The Qinghai Lake in North China is the largest interior plateau lake in Central Asia, and is sensitive to climate change and the environmental effects of Tibetan Plateau uplift. An almost continuous 626 m long sedimen...The Qinghai Lake in North China is the largest interior plateau lake in Central Asia, and is sensitive to climate change and the environmental effects of Tibetan Plateau uplift. An almost continuous 626 m long sediment core was drilled in an in-filled part of the southern lake basin in the Scientific Drilling at Qinghai Lake.展开更多
Calcareous nannofossils were observed to reconstruct the surface water conditions during late Pliocene climate transition (2.55 to 2.88 Ma) from the southern Gardar Drift, in the subpolar North Atlantic IODP Site U131...Calcareous nannofossils were observed to reconstruct the surface water conditions during late Pliocene climate transition (2.55 to 2.88 Ma) from the southern Gardar Drift, in the subpolar North Atlantic IODP Site U1314 (56°21.9’1N, 27°53.3’W). A total of 24 species from 14 genera were identified by polarizing microscope observation. The coccolith assemblages are dominated by species belonging to genus Reticulofenestra with different (size-defined) morphotype. Hence, changes in paleoceanographic condition are shown by the size variation of Reticulofenstraspecimens. Before ~2.76 Ma, the studied interval is characterized by the presence of an abundant larger Reticulofenstra group. It indicates warm oligotrophic and stable surface waters. At ~2.76 Ma the abundance of large Reticulofenstra decreased abruptly and alternated with small Reticulofenstra, suggesting collapse of sea surface stability with strong mixing condition. This event coeval with the final closure of the Central American Seaway (CAS) and the onset of intensified North Hemisphere Glaciation (NHG). Subsequently, the size variation of Reticulofenestra specimens exhibits a sequential pattern that is somewhere consistent with the interglacial-glacial cycle. The pattern begins with a gradual increase in size upward during interglacial suggesting warm oligotrophic and stable condition, and ends with an abrupt decrease in coccolith size during glacial suggesting eutrophic or strong mixing condition and destabilized sea surface waters.展开更多
The palaeodiversity of flowering plants in Yunnan has been extensively interpreted from both a molecular and fossil perspective. However, for cryptogamic plants such as ferns, the palaeodiversity remains poorly known....The palaeodiversity of flowering plants in Yunnan has been extensively interpreted from both a molecular and fossil perspective. However, for cryptogamic plants such as ferns, the palaeodiversity remains poorly known. In this study, we describe a new ferny fossil taxon, Drynaria lanpingensis sp. nov. Huang,Su et Zhou(Polypodiaceae), from the late Pliocene of northwestern Yunnan based on fragmentary frond and pinna with in situ spores. The frond is pinnatifid and the pinnae are entirely margined. The sori are arranged in one row on each side of the primary vein. The spores have a semicircular to bean-shaped equatorial view and a tuberculate surface. Taken together with previously described fossils, there are now representatives of three known fossil taxa of Drynaria from the late Pliocene of western Yunnan.These finds suggest that Drynaria diversity was considerable in the region at that time. As Drynaria is a shade-tolerant plant, growing preferably in wet conditions in the understory of forests, its extensive existence may indicate forest vegetation and humid climates in western Yunnan during the late Pliocene.This is in line with results from floristic investigations and palaeoclimatic reconstructions based on fossil floras.展开更多
A set of pull\|apart basins were formed along the Weixi—Qiaohou right\|lateral slip shear zone of the western part of Honghe fault zone during the period from Miocene to Quaternary.A rock suite of alkaline basalt\|tr...A set of pull\|apart basins were formed along the Weixi—Qiaohou right\|lateral slip shear zone of the western part of Honghe fault zone during the period from Miocene to Quaternary.A rock suite of alkaline basalt\|trachyte\|leucite phonolite is distributed in the Pliocene basin developed in the middle and northern parts of the fault. The location of these rocks and the features of the basin indicate the close relationship between the rock suite and the strike\|slipping.. The sedimentological and chronological evidences prove that Dianxi plateau uplifted quickly in the Pliocene. We can get the information about the plutonic process of the uplift of the plateau from this alkaline rock association. There are mainly olivine\|pyroxene\|trachyandesite and biotite\|trachyte in the rock association. The rocks are often of porphyritic texture and block or semi\|directional flowage structure while the matrix is of trachytic or microcrystalline texture. The phanerocrysts are diopsidic augite, rimpylite, biotite and perthite (olivine sometimes can be seen). The matrix are made up of alkaline feldspar microcrystalline (30%～50%), short\|grained diopside (10%～15%), light\|colored volcanic glass (0～15%) and some magnetite, while feldspar microcrystalline in some rocks are arranged directionally. And there are sharp\|edged or round pyroxenite enclaves and hemicrystalline of short grained sinaite, biotite sinaite and felsic breccia in the trachyte, with good demarcation line. The pyroxenite enclaves in the trachyte are of different size, and the size of the biggest ones are 10cm or so with the characteristic of plastic yield flowing. Sinaite hemicrystalline may come from the older intrusions of Pliocene and Eocene epoch.展开更多
In Europe,fossil fruits and seeds of Rhodoleia(Hamamelidaceae)have been described from the Upper Cretaceous to the Miocene,whereas no fossil record of Rhodoleia has been reported in Asia,where the modern species occur...In Europe,fossil fruits and seeds of Rhodoleia(Hamamelidaceae)have been described from the Upper Cretaceous to the Miocene,whereas no fossil record of Rhodoleia has been reported in Asia,where the modern species occur.Herein,21 fossil leaves identified as Rhodoleia tengchongensis sp.nov.are described from the Upper Pliocene of Tengchong County,Yunnan Province,Southwest China.The fossils exhibit elliptic lamina with entire margins,simple brochidodromous major secondary veins,mixed percurrent intercostal tertiary veins,and looped exterior tertiaries.The leaf cuticle is characterized by pentagonal or hexagonal cells,stellate multicellular trichomes,and paracytic stomata.The combination of leaf architecture and cuticular characteristics suggests that the fossil leaves should be classified into the genus Rhodoleia.The fossil distributions indicate that the genus Rhodoleia might originate from Central Europe,and that migrated to Asia prior to the Late Pliocene.Additionally,insect damage is investigated,and different types of damage,such as hole feeding,margin feeding,surface feeding,and galling,are observed on the thirteen fossil leaves.Based on the damage frequencies for the fossil and extant leaves,the specific feeding behavior of insects on Rhodoleia trees appears to have been established as early as the Late Pliocene.The high occurrence of Rhodoleia insect herbivory may attract the insect-foraging birds,thereby increasing the probability of pollination.展开更多
The Qaidam Basin is a key area for understanding the paleoenvironmental and faunal history of the Tibetan Plateau.The fossil schizothoracine fish,Hsianwenia wui,evolved extraordinarily thickened bones to adapt to the ...The Qaidam Basin is a key area for understanding the paleoenvironmental and faunal history of the Tibetan Plateau.The fossil schizothoracine fish,Hsianwenia wui,evolved extraordinarily thickened bones to adapt to the aridification of the Qaidam Basin during the Pliocene.However,the nature of the bone thickening itself remains elusive.To promote the further investigation of the physiological mechanism of the pachyostosis and the phylogenetic interrelationships of Hsianwenia and all relevant cyprinids,here we present a comprehensive morphological study of Hsianwenia.We have new information on the anterior part of the cranial cavity,a large supraneural 3 in the Weberian apparatus,numerous procurrent caudal fin rays supported by the preural centrum(Pu)5,and a neural arch on Pu2.We also find the differentiated pattern of the bone-thickening:the pachyostosis exists in the endoskeleton but not in the dermal skeleton;it is more obvious in ventral bones than in dorsal ones,when the thickening is present in the dorsally and ventrally grouped endoskeletal bones(e.g.,the epineural and epipleural intermuscular bones).Considering the integrity of musculoskeletal system manipulating the chewing activities,we suspect that the thickened pharyngeal jaws and the hard food processing might be associated with the unique hind protrusion(cleithral“humeral”process)of the dermal pectoral girdle of Hsianwenia.展开更多
Basaltic rocks and their content of ultramaf</span><span style="font-family:Verdana;">i</span><span style="font-family:Verdana;">c xenoliths are common in the Ghab Pliocene ...Basaltic rocks and their content of ultramaf</span><span style="font-family:Verdana;">i</span><span style="font-family:Verdana;">c xenoliths are common in the Ghab Pliocene Volcanic Field in northwestern Syria in the form of lava flows, cinder cones and pyroclastic deposits. The rocks occur within the Ghab pull-</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">apart graben that formed by sinister strike slip faults within the zone that defines the boundary between the African and the Arabian plates. Three petrographic types occur: basanite, olivine basalt and more commonly alkali olivine basalt. The peridotite xenoliths are spinel lherzolite and harzburgit</span><span style="font-family:Verdana;">e.</span><span style="font-family:Verdana;"> Geochemical analysis indicates that the basalts are mostly alkaline to subalkaline. </span><span style="font-family:Verdana;">A distinctive feature of these rocks is the narrow compositional var</span><span style="font-family:Verdana;">iations in the content of most major oxides and minor elements, SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> (44.33 - 46.43 wt%) and MgO (4.01 - 8.28 wt%). Some of the refractory and high field strength elements and incompatible minor elements in the basalts are relatively high (Cr average = 303 ppm and Ni average = 185 ppm) compared with </span><span style="font-family:Verdana;">their content in average basalts. These geochemical characteristics reflect cr</span><span style="font-family:Verdana;">ystallization of the Ghab basalts from pristine and primary magmas that have experienced minimal fractional crystallization and crustal contamination. Similarly, chemical compositions of the ultramafic xenoliths vary within a restricted geochemical range. They are compatible with the generation of these rocks from partial melting of a primitive mantle pyrolite to yield the xeno</span><span style="font-family:Verdana;">liths</span><span style="font-family:Verdana;">.</span><span style="font-family:Verdana;"> These magmatic processes operated during the Pliocene in a regional </span><span style="font-family:Verdana;">transtensional stress environment attending the development of the Dead Sea Rift.展开更多
Apatite fission track （AFT） thermochronology of seven samples from the Xiaonanchuan （小南川） pluton in the Kunlun （昆仑） pass area was carried out, for the purpose of determining the timing of cooling and the re...Apatite fission track （AFT） thermochronology of seven samples from the Xiaonanchuan （小南川） pluton in the Kunlun （昆仑） pass area was carried out, for the purpose of determining the timing of cooling and the relation between the exhumation and the morphotectonic processes. The AFT ages yield low denudation rates of 0. 020--0. 035 mm/a during the late Miocene, which correspond to a stable geomorphic and weak tectonic uplifting environment. The low denudation rates can be considered as the approximate tectonic uplifting rates. The AFT geochronology shows puroxysmully rapid cooling since the Pliocene and an apparent material unroofing of more than 3 km in the Xiaonanchuan area. This was not the result of simple denudation. The rapid cooling was coupled with the intensive orogeny since the Pliocene, which was driven by tectonic uplifting. The accelerated relief building was accompanied by a series of faulting, which caused the basin and the valley formation and sinking. The space pattern of the AFT ages also shows differential uplifting, which decreases northwardly. This trend is supported by the regional AFT data, which indicate that the exhumation decreases northwardly in eastern Kunlun. This trend also exists in cast-west orientation from the western Kunlun range to the eastern. The uplif- ting trend is also supported by gcomorphic characteristics including the elevation and the relief differences well as the distribution of the Late Cenozoic volcanism.展开更多
Glaciogene sedimentary rocks have been found in modem tills of the Grove Mountains, east Antarctica during the 1998 - 1999 Chinese National Antarctic Research Expedition （CHNARE）. Based on the lithilogic and sedimen...Glaciogene sedimentary rocks have been found in modem tills of the Grove Mountains, east Antarctica during the 1998 - 1999 Chinese National Antarctic Research Expedition （CHNARE）. Based on the lithilogic and sedimentary features, these sedimentary rocks are correlated with Cenozoic sedimentary strata of the Pagodroma Group in the neighboring Prince Charles Mountains and the Sorsdal Formation in VestFold Hills. Sedimentary clasts contain sparsely Late Tertiary spores and pollens, including ： Toroisporis （ Lygodiaceae）, Osmunda, Granulatisporites （ Pteridaceae？） , Polypodiaceae, Podocarpus , Araucariaceae, Artemisia , Rhus , Nothofagidites , Proteacidites （Proteaceae） , Quercus , Fraxinoipollenites （ Oleaceae ） , Oleoidearumpollenites（ Oleaceae ）, Operculumpollis, and Tricolpopollenites. Most of the pollen and spores contained in these samples originate from local sources according to the conditions of their preservations as well as correlations with the microfossil assemblages found in the neighboring areas. The majority of the pollen assemblages, as represented by Podocarpus and Nothofagus, belong to the Weddellian biogeocenose, however some exotic components from the old sedimentary basement rocks may have been included during erosion of the proximal ice sheet. If the source areas of glaciogenic sedimentary rocks that bear the pollen and spores are assumed to be local, or in the up glacier areas, the pollen assemblages in these samples might represent an inland flora during a warmer period of the ice-sheet evolutionary history. The finding of the Artemisia and Chenopodiaceae in the pollen assemblages implies that they may belong to late Tertiary （most probably Pliocene）. The absence of diatoms in the samples analyzed may indicate that there are no Cenozoic marine strata in the interior of the east Antarctica beyond the Grove Mountains. The significances of the finding of the Nothofagus in these pollen assemblages are discussed on the basis of current knowledge about the age, distribution and ecological conditions of this kind of fossils found in Sirius Group or other strata outcropped in Antarctica. As a preliminary conclusion, we think that the existence of the Cenozoic glaciogenenic rocks and their pollen assemblages present new evidence for a large scale glacial retreat history in Grove Mountains of east Antarctica, and thus support a dynamic East Antarctic Ice Sheet （EAIS）. This is consistent with the interpretations of Webb et al. （1984）.展开更多
Tectonically, the northwestern South China Sea （SCS） is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Ying...Tectonically, the northwestern South China Sea （SCS） is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Yinggehai Basin, the Qiongdongnan Basin and Xisha Trough in the east, and the Zhongjiannan Basin in the south. Since the Pliocene （5.3 Ma）, the Yinggehai Basin has experienced repeated accelerating subsidence, high thermal fluid, and widely developing mud-rich overpressure chambers, abundant mud diapers and crust-mantle mixed CO2. While a large central canyon was developed in the Qiongdongnan Basin, new rift occurred in the Xisha ~rough. These characteristics demonstrate a single tectonic unit for the northwestern SCS, for which we have undertaken stress field modeling to understand its plate deformations and sedimen- tary responses. Our results demonstrate that an extension tectonic event occurred after 5.3 Ma in theYingge- hal-Qiongdongnan-Xisha trough area, which is characterized by thinner crust C〈16000 m）, half-graben or graben structural style and thicker sedimentary sequences （〉3 500 m）. A new rift system subsequently was developed in this area; this event was mainly driven by the combined effects of different movement veloc- ity and direction of the three micro-plates, and the far-field effect of the continental collision between the Indian Plate and the Tibetan Plateau, and subduction of the Pacific Plate underneath the Eurasian Plate.展开更多
Combined data of physical property, benthic foraminifera, and stable isotopes from ODP Sites 1148, 1146, and 1143 are used to discuss deep water evolution in the South China Sea （SCS） since the Early Miocene. The re...Combined data of physical property, benthic foraminifera, and stable isotopes from ODP Sites 1148, 1146, and 1143 are used to discuss deep water evolution in the South China Sea （SCS） since the Early Miocene. The results indicate that 3 lithostratigraphic units, respectively corresponding to 21-17 Ma, 15-10 Ma, and 10-5 Ma with positive red parameter （a^＊） marking the red brown sediment color represent 3 periods of deep water ventilation. The first 2 periods show a closer link to contemporary production of the Antarctic Bottom Water （AABW） and Northern Component Water（NCW）, indicating a free connection of deep waters between the SCS and the open ocean before 10 Ma.After 10 Ma, red parameter dropped but stayed higher than the modern value （a^＊=0）, the CaCO3 percentage difference between Site 1148 from a lower deepwater setting and Site 1146 from an upper deepwater setting enlarged significantly, and benthic species which prefer oxygen-rich bottom conditions dramatically decreased. Coupled with a major negative excursion of benthic δ^13Cat ～10 Ma,these parameters may denote a weakening in the control of the SCS deep water by the open ocean.Probably they mark the birth of a local deep water due to shallow waterways or rise of sill depths during the course of sea basin closing from south to east by the west-moving Philippine Arc after the end of SCS seafloor spreading at 16-15 Ma. However, it took another 5 Ma before the dissolved oxygen approached close to the modern level. Although the oxygen level continued to stabilize, several Pacific Bottom Water （PBW） and Pacific Deep Water （PDW） marker species rapidly increased since ～6 Ma,followed by a dramatic escalation in planktonic fragmentation which indicates high dissolution especially after ～5 Ma. The period of 5-3 Ma saw the strongest stratified deepwater in the then SCS, as indicated by up to 40﹪ CaCO3 difference between Sites 1148 and 1146. Apart from a strengthening PDW as a result of global cooling and ice cap buildup on northern high latitudes, a deepening sea basin due to stronger subduction eastward may also have triggered the influx of more corrosive waters from the deep western Pacific. Since 3 Ma, the evolution of the SCS deep water entered a modern phase, as characterized by relative stable 10﹪ CaCO3 difference between the two sites and increase in infaunal benthic species which prefer a low oxygenated environment. The subsequent reduction of PBW and PDW marker species at about 1.2 Ma and 0.9 Ma and another significant negative excursion of benthic δ^13Cto a Neogene minimum at ～0.9 Ma together convey a clear message that the PBW largely disappeared and the PDW considerably weakened in the Mid-Pleistocene SCS. Therefore, the true modern mode SCS deep water started to form only during the ＂Mid-Pleistocene climatic transition＂ probably due to the rise of sill depths under the Bashi Strait.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42030305W2411033)Research Foundation of Chutian Scholars Program of Hubei Province(No.8210403)。
文摘The Yangtze River,with a length of approximately 6300 km,holds the distinction of being the largest river in East Asia that empties into the Pacific Ocean.Its formation is intricately linked to regional tectonic activity and climate fluctuations.However,the exact timeline for the formation of the Yangtze River remains elusive.This study investigates the provenance of the Late Cenozoic strata in the Wangjiang Basin,situated in the Lower Yangtze River,through the application of detrital zircon U-Pb dating.Seven sand samples were analyzed,leading to the identification of new U-Pb detrital zircon ages(n=577).Our study reveals that the sand materials found in the Pliocene gravel beds of the Anqing Formation originate predominantly from the Yangtze River.The findings of our study,along with the provenance tracing of boreholes in the Yangtze River Basin and the shelf sea in East China,provide compelling evidence for the continuous presence of the Yangtze River throughout the Pliocene period.The development of the Yangtze River during the Pliocene is intricately connected to both the tectonic adjustments occurring at the southeastern margin of the Tibetan Plateau and the intensification of the Asian Monsoon.
基金financially supported by the National Basic Research Program of China(973 Program)(No.2012CB822003)the National Natural Science Foundation of China(No.41172022)Specialized Research Fund for the Doctoral Program of Higher Education(No.20120211110022)
文摘A new Quercus （Fagaceae） morphospecies is described based on well-preserved fossil leaves.The fossils were collected from Yangyi Formation of the Upper Pliocene at the Yangyi coalmine,Baoshan,western Yunnan,China.Details of the microstructure of mesophyll tissue are preserved because lithification of the fossils was not complete.The fossil laminas possess typical characteristics of Quercus sect.Heterobalanus：quite thick and coriaceous cuticle; secondary veins bifurcating near the margin in the middle and top of the leaf; and upper epidermis with adaxial hypodermis.Based on a detailed morphological and anatomical comparison with all living and fossil species of Quercus sect.Heterobalanus,the fossil leaves prove to be different in their sparse and garland-shaped multicellular trichomes on the lower epidermis,and so it is described as a new species Quercus yangyiensis He,Li et Sun sp.nov.The much sparser trichomes of our fossils compare well with those of living Quercus sect.Heterobalanus and indicate a more humid climate during the deposition of the Yangyi Formation in the Late Pliocene.
基金supported by the Ministry of Science and Technology of China (2006FY120300 and 2006CB806400)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-120, Q09)the National Natural Science Foundation of China (40730210), and the All-China Stratigraphic Commission
文摘The Lower Pliocene of the Linxia Basin in Gansu Province is one of only a few representative sections for the Early Pliocene sedimentary records in northern China, and even in East Asia. Recently,abundant mammalian fossils were found from the base of red clays of the Lower Pliocene Hewangjia Formation at Duikang in Guanghe County within this basin. Previously, the Pliocene mammals were sparsely found in China, and most were collected from fluvial and lacustrine deposits in the eastern Loess Plateau. Mammals from the widely distributed Pliocene Hipparion Red Clay are less in number.The known fossils from Duikang include 20 species and belong to the Shilidun Fauna. Their faunal components are similar to the Early Pliocene Gaozhuang Fauna from Ynshe, Shanxi. On the other hand, some taxa from Duikang have not been found in the Gaozhuang Fauna, are slightly more primitive in evolutionary level, and appeared mainly in the Late Miocene. As a result, the age of the Duikang fossils may be slightly earlier than that of the Gaozhuang Fauna and closer to the lower boundary of the Piiocene. The Duikang fossiliferons bed is 0.8 m above the top of the Late Miocene Linshu Formation, and the first occurrence of the three-toed horse Hipparion pater can be regarded as a biostratigraphical marker of the Miocene/Pliocene boundary. In conclusion, Duikang is an ideal candidate locality to establish as the stratotype of the lower boundary of the Chinese terrestrial Pliocene.
基金supported by the National Natural Foundation of China(No.40872149,40472100 and 40930419)
文摘The uplift of the Ailao Shan-Diancang Shan （ASDS） along the Ailao Shan-Red River （ASRR） shear zone is an important geological event in the southeastern margin of Qinghai-Tibet Plateau tectonic domain in the Late Cenozoic, and it preserves important information on the structures, exhumationai history and tectonic evolution of the ASRR shear zone. The uplift structural mode and uplift timing of the ASDS is currently an important scientific topic for understanding the ASDS formation and late stage movements and evolution of the ASRR shear zone. The formation of the ASDS has been widely considered to be the consequence of the strike-slip movements of the ASRR shear zone. However, the shaping of geomorphic units is generally direct results of the latest tectonic activities. In this study, we investigated the timing and uplift structural mechanism of the ASDS and provided the following lines of supportive evidence. Firstly, the primary tectonic foliation of the ASDS shows significant characteristic variations, with steeply dipping tectonic foliation developed on the east side of the ASDS and the relatively horizontal foliation on the west side. Secondly, from northeast to southwest direction, the deformation and metamorphism gradually weakened and this zone can be further divided into three different metamorphic degree belts. Thirdly, the contact relationship between the ASDS and the Chuxiong basin-Erhai lake is a normal fault contact which can be found on the east side of the ASDS. 40^Ar/^39 Argeochronology suggests that the Diancang Shan had experienced a fast cooling event during 3-4 Ma. The apatite fission track testing method gives the age of 6.6-10.7 Ma in the Diancang Shan and 4.6-8.4 Ma in the Ailao Shan, respectively. Therefore the uplift of the ASDS can be explained by tilted block mode in which the east side was uplifted much higher than the west side, and it is not main reason of the shearing movements of the ASRR shear zone. The most recent uplift stages of the ASDS happened in the Pliocene （3-4 Ma） and Late Miocene （6-10 Ma）.
基金supported by the National Natural Science Foundation of China(No.40403014)the Knowledge Innovation Program of the Chinese Academy of Sciences(KZCX1-10-01,KZCX2-SW-118)
文摘Specimens of fossil wood preserved lignified in Pliocene brown coal and identified as Pinus armandii Francher come from an opencast coalmine at Longling in western Yunnan Province, China. Phytochemical investigation of the fossil wood isolated using liquid column chromatography seven compounds （1-7） including a new fluorene derivative named 11,11-dimethyl-11H-benzo[b]fluorene. A further 28 volatiles were detected by gas chromatography-mass spectrometry （GC-MS）. Spectroscopic investigation methods, including MS and 1D and 2D-NMR techniques elucidated the structure of the seven compounds. Two types of natural products, isopimara and stilbene commonly occuring in extant and Pliocene fossil P. armandii indicate phytochemical fidelity during burial under certain circumstances in sediments. Discovery of stilbenes that can inhibit the activities of wood-destroying fungi in the Pliocene P. armandii prompts the assumption that the chemical preservation of this Pliocene fossil wood of P. armandii in brown coal might contribute to the presence of inner natural inhibitors against wood-destroying fungi.
基金Supported by the CNPC Overseas Science and Technology Project(CNODC/CAL/KJZX/2015-016)
文摘Based on core,logging,lab test and seismic data,sedimentary characteristics and pattern of marine hyperpycnal flow,the distribution rules of hyperpycnal flow reservoir,prediction method of favorable hyperpycnal flow reservoir zones,hydrocarbon accumulation model in hyperpycnal flow reservoir in D block of Bay of Bengal were investigated,and the favorable exploration zone and well sites were predicted.Pliocene in D block has typical hyperpycnal flow sediment,which is a set of fine-medium sandstone held between thick layers of marine mudstone and features a series of reverse grading unit and normal grading unit pairs.The hyperpycnal flow sediment appears as heavily jagged box shape,bell shape and tongue shape facies on log curves with linear gradient,and corresponds to multiple phases of deep channels on the seismic section and high sinuous channel on stratal slices.The sedimentary bodies formed by a single phase hyperpycnal flow which include five types of microfacies,namely,supply channel(valley),channel complex,branch channel,levee and sheet sand.The hyperpycnal flow sediments appear in multiple branches,multiple generations and stages in space,forming high-quality reservoirs in strips on the plane and superposition vertically,with fairly good physical properties.The channel complex sandstone,with large thickness,coarse particle size and good physical properties,is the most favorable exploration facies.Based on the guidance of the sedimentary model,distribution of the channel complex microfacies was delineated in detail by seismic reflection structure analysis,spectrum waveform characteristic analysis,slice and attribute fusion,and combined with the structural feature analysis,the favorable drilling zone was sorted out,effectively guiding the exploration deployment of the block.
文摘In the present study,the Lower-Middle Pliocene Cheleken Formation in the south of Ghaemshahr city was studied to determine the provenance of the comprising sediments,paleoclimatic conditions,and tectonic setting of the rocks.Petrographic and geochemical analyses of major and minor elements of the samples were used for this purpose.This Formation is composed of three major facies including conglomerate,fine sandstone,and mudstone.The source formations which were recognized to be supplying sediments to the Cheleken Formation depositional basin include Lalun,Ziarat,Tizkuh,Dalichai,and Cretaceous formations.According to the discrimination diagrams and other ratios for minor elements of the studied samples,a complex of felsic to intermediate igneous rocks in the source region was deciphered.The depositional environment of the rocks experienced humid and semi-arid climatic conditions during deposition.According to the CIW index,the samples underwent a high level of weathering(97%)in the source area or during transportation.From a tectonic point of view,the Cheleken Formation was deposited in an Active Continental Margin setting.
基金supported by the National Natural Science Foundation of China(grants No.40599420,40872114 and 41140028)the National Basic Research Program of China(grant No.2010CB833400)+1 种基金the Central University Research Foundation(grant No.310827152014)the State Key Laboratory of Loess and Quaternary Geology
文摘The Qinghai Lake in North China is the largest interior plateau lake in Central Asia, and is sensitive to climate change and the environmental effects of Tibetan Plateau uplift. An almost continuous 626 m long sediment core was drilled in an in-filled part of the southern lake basin in the Scientific Drilling at Qinghai Lake.
文摘Calcareous nannofossils were observed to reconstruct the surface water conditions during late Pliocene climate transition (2.55 to 2.88 Ma) from the southern Gardar Drift, in the subpolar North Atlantic IODP Site U1314 (56°21.9’1N, 27°53.3’W). A total of 24 species from 14 genera were identified by polarizing microscope observation. The coccolith assemblages are dominated by species belonging to genus Reticulofenestra with different (size-defined) morphotype. Hence, changes in paleoceanographic condition are shown by the size variation of Reticulofenstraspecimens. Before ~2.76 Ma, the studied interval is characterized by the presence of an abundant larger Reticulofenstra group. It indicates warm oligotrophic and stable surface waters. At ~2.76 Ma the abundance of large Reticulofenstra decreased abruptly and alternated with small Reticulofenstra, suggesting collapse of sea surface stability with strong mixing condition. This event coeval with the final closure of the Central American Seaway (CAS) and the onset of intensified North Hemisphere Glaciation (NHG). Subsequently, the size variation of Reticulofenestra specimens exhibits a sequential pattern that is somewhere consistent with the interglacial-glacial cycle. The pattern begins with a gradual increase in size upward during interglacial suggesting warm oligotrophic and stable condition, and ends with an abrupt decrease in coccolith size during glacial suggesting eutrophic or strong mixing condition and destabilized sea surface waters.
基金supported by the National Natural Science Foundation of China (31300187,U1502231)the Major Program of National Science Foundation of China (31590823)
文摘The palaeodiversity of flowering plants in Yunnan has been extensively interpreted from both a molecular and fossil perspective. However, for cryptogamic plants such as ferns, the palaeodiversity remains poorly known. In this study, we describe a new ferny fossil taxon, Drynaria lanpingensis sp. nov. Huang,Su et Zhou(Polypodiaceae), from the late Pliocene of northwestern Yunnan based on fragmentary frond and pinna with in situ spores. The frond is pinnatifid and the pinnae are entirely margined. The sori are arranged in one row on each side of the primary vein. The spores have a semicircular to bean-shaped equatorial view and a tuberculate surface. Taken together with previously described fossils, there are now representatives of three known fossil taxa of Drynaria from the late Pliocene of western Yunnan.These finds suggest that Drynaria diversity was considerable in the region at that time. As Drynaria is a shade-tolerant plant, growing preferably in wet conditions in the understory of forests, its extensive existence may indicate forest vegetation and humid climates in western Yunnan during the late Pliocene.This is in line with results from floristic investigations and palaeoclimatic reconstructions based on fossil floras.
文摘A set of pull\|apart basins were formed along the Weixi—Qiaohou right\|lateral slip shear zone of the western part of Honghe fault zone during the period from Miocene to Quaternary.A rock suite of alkaline basalt\|trachyte\|leucite phonolite is distributed in the Pliocene basin developed in the middle and northern parts of the fault. The location of these rocks and the features of the basin indicate the close relationship between the rock suite and the strike\|slipping.. The sedimentological and chronological evidences prove that Dianxi plateau uplifted quickly in the Pliocene. We can get the information about the plutonic process of the uplift of the plateau from this alkaline rock association. There are mainly olivine\|pyroxene\|trachyandesite and biotite\|trachyte in the rock association. The rocks are often of porphyritic texture and block or semi\|directional flowage structure while the matrix is of trachytic or microcrystalline texture. The phanerocrysts are diopsidic augite, rimpylite, biotite and perthite (olivine sometimes can be seen). The matrix are made up of alkaline feldspar microcrystalline (30%～50%), short\|grained diopside (10%～15%), light\|colored volcanic glass (0～15%) and some magnetite, while feldspar microcrystalline in some rocks are arranged directionally. And there are sharp\|edged or round pyroxenite enclaves and hemicrystalline of short grained sinaite, biotite sinaite and felsic breccia in the trachyte, with good demarcation line. The pyroxenite enclaves in the trachyte are of different size, and the size of the biggest ones are 10cm or so with the characteristic of plastic yield flowing. Sinaite hemicrystalline may come from the older intrusions of Pliocene and Eocene epoch.
基金granted by the National Natural Science Foundation of China(Nos.41302009,41402008,41172022 and 41172021)the Foundation of the State Key Laboratory of Paleobiology and Stratigraphy,Nanjing Institute of Geology and Paleontology,CAS(No.133102)the NSF EAR-0746105 to YSL
文摘In Europe,fossil fruits and seeds of Rhodoleia(Hamamelidaceae)have been described from the Upper Cretaceous to the Miocene,whereas no fossil record of Rhodoleia has been reported in Asia,where the modern species occur.Herein,21 fossil leaves identified as Rhodoleia tengchongensis sp.nov.are described from the Upper Pliocene of Tengchong County,Yunnan Province,Southwest China.The fossils exhibit elliptic lamina with entire margins,simple brochidodromous major secondary veins,mixed percurrent intercostal tertiary veins,and looped exterior tertiaries.The leaf cuticle is characterized by pentagonal or hexagonal cells,stellate multicellular trichomes,and paracytic stomata.The combination of leaf architecture and cuticular characteristics suggests that the fossil leaves should be classified into the genus Rhodoleia.The fossil distributions indicate that the genus Rhodoleia might originate from Central Europe,and that migrated to Asia prior to the Late Pliocene.Additionally,insect damage is investigated,and different types of damage,such as hole feeding,margin feeding,surface feeding,and galling,are observed on the thirteen fossil leaves.Based on the damage frequencies for the fossil and extant leaves,the specific feeding behavior of insects on Rhodoleia trees appears to have been established as early as the Late Pliocene.The high occurrence of Rhodoleia insect herbivory may attract the insect-foraging birds,thereby increasing the probability of pollination.
文摘The Qaidam Basin is a key area for understanding the paleoenvironmental and faunal history of the Tibetan Plateau.The fossil schizothoracine fish,Hsianwenia wui,evolved extraordinarily thickened bones to adapt to the aridification of the Qaidam Basin during the Pliocene.However,the nature of the bone thickening itself remains elusive.To promote the further investigation of the physiological mechanism of the pachyostosis and the phylogenetic interrelationships of Hsianwenia and all relevant cyprinids,here we present a comprehensive morphological study of Hsianwenia.We have new information on the anterior part of the cranial cavity,a large supraneural 3 in the Weberian apparatus,numerous procurrent caudal fin rays supported by the preural centrum(Pu)5,and a neural arch on Pu2.We also find the differentiated pattern of the bone-thickening:the pachyostosis exists in the endoskeleton but not in the dermal skeleton;it is more obvious in ventral bones than in dorsal ones,when the thickening is present in the dorsally and ventrally grouped endoskeletal bones(e.g.,the epineural and epipleural intermuscular bones).Considering the integrity of musculoskeletal system manipulating the chewing activities,we suspect that the thickened pharyngeal jaws and the hard food processing might be associated with the unique hind protrusion(cleithral“humeral”process)of the dermal pectoral girdle of Hsianwenia.
文摘Basaltic rocks and their content of ultramaf</span><span style="font-family:Verdana;">i</span><span style="font-family:Verdana;">c xenoliths are common in the Ghab Pliocene Volcanic Field in northwestern Syria in the form of lava flows, cinder cones and pyroclastic deposits. The rocks occur within the Ghab pull-</span><span style="font-family:Verdana;"> </span><span style="font-family:Verdana;">apart graben that formed by sinister strike slip faults within the zone that defines the boundary between the African and the Arabian plates. Three petrographic types occur: basanite, olivine basalt and more commonly alkali olivine basalt. The peridotite xenoliths are spinel lherzolite and harzburgit</span><span style="font-family:Verdana;">e.</span><span style="font-family:Verdana;"> Geochemical analysis indicates that the basalts are mostly alkaline to subalkaline. </span><span style="font-family:Verdana;">A distinctive feature of these rocks is the narrow compositional var</span><span style="font-family:Verdana;">iations in the content of most major oxides and minor elements, SiO</span><sub><span style="font-family:Verdana;">2</span></sub><span style="font-family:Verdana;"> (44.33 - 46.43 wt%) and MgO (4.01 - 8.28 wt%). Some of the refractory and high field strength elements and incompatible minor elements in the basalts are relatively high (Cr average = 303 ppm and Ni average = 185 ppm) compared with </span><span style="font-family:Verdana;">their content in average basalts. These geochemical characteristics reflect cr</span><span style="font-family:Verdana;">ystallization of the Ghab basalts from pristine and primary magmas that have experienced minimal fractional crystallization and crustal contamination. Similarly, chemical compositions of the ultramafic xenoliths vary within a restricted geochemical range. They are compatible with the generation of these rocks from partial melting of a primitive mantle pyrolite to yield the xeno</span><span style="font-family:Verdana;">liths</span><span style="font-family:Verdana;">.</span><span style="font-family:Verdana;"> These magmatic processes operated during the Pliocene in a regional </span><span style="font-family:Verdana;">transtensional stress environment attending the development of the Dead Sea Rift.
基金This paper is financially supported by the China Geological Survey(Nos.1212010610103,200313000005)and the National Natural Sci-ence Foundation of China(Nos.40672137,40372104).
文摘Apatite fission track （AFT） thermochronology of seven samples from the Xiaonanchuan （小南川） pluton in the Kunlun （昆仑） pass area was carried out, for the purpose of determining the timing of cooling and the relation between the exhumation and the morphotectonic processes. The AFT ages yield low denudation rates of 0. 020--0. 035 mm/a during the late Miocene, which correspond to a stable geomorphic and weak tectonic uplifting environment. The low denudation rates can be considered as the approximate tectonic uplifting rates. The AFT geochronology shows puroxysmully rapid cooling since the Pliocene and an apparent material unroofing of more than 3 km in the Xiaonanchuan area. This was not the result of simple denudation. The rapid cooling was coupled with the intensive orogeny since the Pliocene, which was driven by tectonic uplifting. The accelerated relief building was accompanied by a series of faulting, which caused the basin and the valley formation and sinking. The space pattern of the AFT ages also shows differential uplifting, which decreases northwardly. This trend is supported by the regional AFT data, which indicate that the exhumation decreases northwardly in eastern Kunlun. This trend also exists in cast-west orientation from the western Kunlun range to the eastern. The uplif- ting trend is also supported by gcomorphic characteristics including the elevation and the relief differences well as the distribution of the Late Cenozoic volcanism.
基金support from the Chinese National Science Foundation(Grant No.40202034).
文摘Glaciogene sedimentary rocks have been found in modem tills of the Grove Mountains, east Antarctica during the 1998 - 1999 Chinese National Antarctic Research Expedition （CHNARE）. Based on the lithilogic and sedimentary features, these sedimentary rocks are correlated with Cenozoic sedimentary strata of the Pagodroma Group in the neighboring Prince Charles Mountains and the Sorsdal Formation in VestFold Hills. Sedimentary clasts contain sparsely Late Tertiary spores and pollens, including ： Toroisporis （ Lygodiaceae）, Osmunda, Granulatisporites （ Pteridaceae？） , Polypodiaceae, Podocarpus , Araucariaceae, Artemisia , Rhus , Nothofagidites , Proteacidites （Proteaceae） , Quercus , Fraxinoipollenites （ Oleaceae ） , Oleoidearumpollenites（ Oleaceae ）, Operculumpollis, and Tricolpopollenites. Most of the pollen and spores contained in these samples originate from local sources according to the conditions of their preservations as well as correlations with the microfossil assemblages found in the neighboring areas. The majority of the pollen assemblages, as represented by Podocarpus and Nothofagus, belong to the Weddellian biogeocenose, however some exotic components from the old sedimentary basement rocks may have been included during erosion of the proximal ice sheet. If the source areas of glaciogenic sedimentary rocks that bear the pollen and spores are assumed to be local, or in the up glacier areas, the pollen assemblages in these samples might represent an inland flora during a warmer period of the ice-sheet evolutionary history. The finding of the Artemisia and Chenopodiaceae in the pollen assemblages implies that they may belong to late Tertiary （most probably Pliocene）. The absence of diatoms in the samples analyzed may indicate that there are no Cenozoic marine strata in the interior of the east Antarctica beyond the Grove Mountains. The significances of the finding of the Nothofagus in these pollen assemblages are discussed on the basis of current knowledge about the age, distribution and ecological conditions of this kind of fossils found in Sirius Group or other strata outcropped in Antarctica. As a preliminary conclusion, we think that the existence of the Cenozoic glaciogenenic rocks and their pollen assemblages present new evidence for a large scale glacial retreat history in Grove Mountains of east Antarctica, and thus support a dynamic East Antarctic Ice Sheet （EAIS）. This is consistent with the interpretations of Webb et al. （1984）.
基金The major project of the China National Science and Technology "Large Oil and Gas Fields and Coal bed Gas Development" under contract No.2011ZX05023-003-003the Fundamental Research Funds for the Central Universities under contract No.1350219123
文摘Tectonically, the northwestern South China Sea （SCS） is located at the junction between three micro-plates, i.e., the Indochina, South China and Zhongsha-Xisha micro-plates, and involves three basins, i.e., the Yinggehai Basin, the Qiongdongnan Basin and Xisha Trough in the east, and the Zhongjiannan Basin in the south. Since the Pliocene （5.3 Ma）, the Yinggehai Basin has experienced repeated accelerating subsidence, high thermal fluid, and widely developing mud-rich overpressure chambers, abundant mud diapers and crust-mantle mixed CO2. While a large central canyon was developed in the Qiongdongnan Basin, new rift occurred in the Xisha ~rough. These characteristics demonstrate a single tectonic unit for the northwestern SCS, for which we have undertaken stress field modeling to understand its plate deformations and sedimen- tary responses. Our results demonstrate that an extension tectonic event occurred after 5.3 Ma in theYingge- hal-Qiongdongnan-Xisha trough area, which is characterized by thinner crust C〈16000 m）, half-graben or graben structural style and thicker sedimentary sequences （〉3 500 m）. A new rift system subsequently was developed in this area; this event was mainly driven by the combined effects of different movement veloc- ity and direction of the three micro-plates, and the far-field effect of the continental collision between the Indian Plate and the Tibetan Plateau, and subduction of the Pacific Plate underneath the Eurasian Plate.
基金This paper is supported by the National Natural Science Foundation of china (Nos. 40576031, 40476030, 40631007).
文摘Combined data of physical property, benthic foraminifera, and stable isotopes from ODP Sites 1148, 1146, and 1143 are used to discuss deep water evolution in the South China Sea （SCS） since the Early Miocene. The results indicate that 3 lithostratigraphic units, respectively corresponding to 21-17 Ma, 15-10 Ma, and 10-5 Ma with positive red parameter （a^＊） marking the red brown sediment color represent 3 periods of deep water ventilation. The first 2 periods show a closer link to contemporary production of the Antarctic Bottom Water （AABW） and Northern Component Water（NCW）, indicating a free connection of deep waters between the SCS and the open ocean before 10 Ma.After 10 Ma, red parameter dropped but stayed higher than the modern value （a^＊=0）, the CaCO3 percentage difference between Site 1148 from a lower deepwater setting and Site 1146 from an upper deepwater setting enlarged significantly, and benthic species which prefer oxygen-rich bottom conditions dramatically decreased. Coupled with a major negative excursion of benthic δ^13Cat ～10 Ma,these parameters may denote a weakening in the control of the SCS deep water by the open ocean.Probably they mark the birth of a local deep water due to shallow waterways or rise of sill depths during the course of sea basin closing from south to east by the west-moving Philippine Arc after the end of SCS seafloor spreading at 16-15 Ma. However, it took another 5 Ma before the dissolved oxygen approached close to the modern level. Although the oxygen level continued to stabilize, several Pacific Bottom Water （PBW） and Pacific Deep Water （PDW） marker species rapidly increased since ～6 Ma,followed by a dramatic escalation in planktonic fragmentation which indicates high dissolution especially after ～5 Ma. The period of 5-3 Ma saw the strongest stratified deepwater in the then SCS, as indicated by up to 40﹪ CaCO3 difference between Sites 1148 and 1146. Apart from a strengthening PDW as a result of global cooling and ice cap buildup on northern high latitudes, a deepening sea basin due to stronger subduction eastward may also have triggered the influx of more corrosive waters from the deep western Pacific. Since 3 Ma, the evolution of the SCS deep water entered a modern phase, as characterized by relative stable 10﹪ CaCO3 difference between the two sites and increase in infaunal benthic species which prefer a low oxygenated environment. The subsequent reduction of PBW and PDW marker species at about 1.2 Ma and 0.9 Ma and another significant negative excursion of benthic δ^13Cto a Neogene minimum at ～0.9 Ma together convey a clear message that the PBW largely disappeared and the PDW considerably weakened in the Mid-Pleistocene SCS. Therefore, the true modern mode SCS deep water started to form only during the ＂Mid-Pleistocene climatic transition＂ probably due to the rise of sill depths under the Bashi Strait.
