Decoupling of stalagmite-derived Asian summer monsoon records from North Atlantic temperature change during marine oxygen isotope stage 5d   总被引：2，自引：0，他引：2  

Houyun Zhou  Jianxin Zhao  Chuan-Chou Shen  Yuexing Feng  Huazheng Guan  Chen-Feng You 《Quaternary Research》2008,70(2):315-321

The Asian monsoon is an important component of the global climate system. Seasonal variations in wind, rainfall, and temperature associated with the Asian monsoon systems affect a vast expanse of tropical and subtropical Asia. Speleothem-derived summer monsoon variation in East Asia was previously found to be closely associated with millennial-scale change in temperature in the North Atlantic region between 75 and 10 ka. New evidence recovered from East Asia, however, suggests that the teleconnection between summer monsoon in East Asia and temperature change in the North Atlantic region may have significantly reduced during 120 to ~ 110 ka, a period directly after the full last interglaciation and corresponding roughly to marine oxygen isotope stage 5d. This reduction may be due to the low ice volume in the North Hemisphere at that time, which makes the millennial-scale change in temperature in the North Atlantic region less effective in influencing the Asian summer monsoon. This is important for investigating the mechanisms controlling the Asian summer monsoon and the paleoclimatic teleconnection between East Asia and the North Atlantic region, and for predicting monsoon-associated precipitation in East Asia under a global-warming trend.  相似文献   

Microseismicity Induced by Heavy Rainfall Around Flooded Vertical Ore Veins     

H. Ogasawara  K. Fujimori  N. Koizumi  N. Hirano  S. Fujiwara  S. Otsuka  S. Nakao  K. Nishigami  K. Taniguchi  Y. Iio  R. Nishida  K. Oike  Y. Tanaka 《Pure and Applied Geophysics》2002,159(1-3):91-109

—?Microseismicity (M?M?M?M??6 were also monitored at a crustal movement monitoring station located several hundred meters from the veins. It was found that the opening of the vertical ore veins primary led to significant strain and tilt, but not to seismicity, because the delay and the longer duration of the seismicity were significant. Most seismic events involve thrusting mechanisms that are consistent with the present stress state of E-W-oriented tectonic compression, but are not consistent with the opening of the deepest ore vein. Interstingly, all the events within a few months of the heavy rainfall occurred near the faults that offset the deepest ore veins, wheareas all those events located away from the deepest ore veins occurred many months after the heavy rainfall. Consequently, the delayed diffusion of water appears to have played a dominant role in reducing rock strength, which led to seismicity in the Ikuno mine.  相似文献   

Evaluation of future storm surge risk in East Asia based on state-of-the-art climate change projection     

《Coastal Engineering》2014

The present study evaluates future storm surge risk due to tropical cyclones (typhoons) in East Asia. A state-of-the-art atmospheric general circulation model (GCM) outputs are employed as the driving force for simulating storm surges associated with the projected changes in climate. The reproducibility of tropical cyclone (TC) characteristics from the GCM in the Northwest Pacific (NWP) is confirmed by comparing with the observed best track data, and future typhoon changes were presented. Storm surge simulation is carried out for East Asia, with the finest nested domain on the Japanese coast. The probability of maximum storm surge heights with specified return periods is determined using extreme value statistics. We show a strong regional dependency on future changes of severe storm surges.  相似文献   

Highly fractionated Late Triassic I-type granites and related molybdenum mineralization in the Qinling orogenic belt: Geochemical and U–Pb–Hf and Re–Os isotope constraints     

《Ore Geology Reviews》2014

We present new data on the highly fractionated Late Triassic I-type Liyuantang granite, which is located in the middle segment of the South Qinling Subzone of central China and is associated with molybdenum mineralization. Zircon U–Pb dating indicates that the granite was emplaced at 210.1 ± 1.9 Ma, with a single zircon containing an inherited core that yielded an age of 449.8 ± 7.1 Ma. Magmatic zircons from the granite have ε_Hf(t) values of − 4.0 to + 1.5, whereas the inherited zircon core has a ε_Hf(t) value of − 5.3. Calculated Hf model ages of crust formation are indicative of substantial contributions from melting of Proterozoic crust that ranges in age from 1501 to 1155 Ma. The granite contains high concentrations of Si, Al, Na, and K, is enriched in Rb, Th, and U, has elevated Rb/Sr and Ga/Al ratios, and is depleted in Ti, Fe, Mn, Mg, Ca, and P, with significantly negative Eu anomalies (δEu = 0.33–0.50), similar to other highly fractionated I-type granites. These data indicate that the magmas that formed the Liyuantang pluton were produced during partial melting of Proterozoic garnet-absent quartz amphibolites. The magmas then fractionated apatite, feldspar, Ti-bearing phases, biotite, and hornblende prior to emplacement.Re–Os isotope analysis of molybdenite from the study area yields a mineralization age of 200.9 ± 6.2 Ma, suggesting that the Liyuantang molybdenum deposit formed during a previously unrecognized mineralization event. The present results, together with previous data, demonstrate that highly fractionated I-type granites associated with the second pulse of magmatism in the South Qinling subzone should be considered highly prospective for mineral exploration, focusing on Triassic–Early Jurassic granitoids.  相似文献   

A thermo-mechanical coupled constitutive model for clay based on extended granular solid hydrodynamics     

《Computers and Geotechnics》2016

  相似文献   

An experimental investigation into the influence of the damage openings on ship response     

《Applied Ocean Research》2016

Ship motions after damage are difficult to evaluate since they are affected by complex phenomena regarding fluid and structures interactions. The possibility to better understand how ship behavior in damage is influenced by these phenomena is important for improving ship safety, especially for passenger vessel.In this paper an experimental campaign is carried out on a passenger ferry hull, to show the effects of the water dynamics across damage openings on ship motions. Novel aspects of this research include the study of the effects of the damage position on the ship roll response. The study is carried out for still water and for beam regular waves at zero speed.Results from the experiments carried out underline that the roll behavior of a damaged ship is affected by the position of damage opening and not only by its size. Assuming the same final equilibrium conditions after flooding but characterized by different damage openings it is possible to observe how motions RAOs and roll decay characteristics modify according to the opening locations.  相似文献   

U–Pb ages and Hf isotopic record of zircons from the late Neoproterozoic and Silurian–Devonian sedimentary rocks of the western Yangtze Block: Implications for its tectonic evolution and continental affinity     

《Gondwana Research》2016

The relationship of the Yangtze Block with other continental blocks of the Rodinia and Gondwana supercontinents is hotly debated. Here we report U–Pb and Lu–Hf isotopic data for zircons from the latest Neoproterozoic Yanjing Group and the overlying Silurian–Devonian rocks on the western margin of Yangtze Block, which provide critical constraints on the provenance of these sediments and further shed light on the crustal evolution and tectonic affinity of the western Yangtze Block in the context of Rodinia and the subsequent Gondwanaland. Mica schist from the middle part of the Yanjing Group contains dominant Neoproterozoic detrital zircons (0.72–0.80 Ga) with a pronounced age peak at 0.75 Ga. Based on the euhedral to subhedral shapes, high Th/U ratios and exclusively positive εHf(t) values (+ 6 to + 14) for the zircon crystals, and the lack of ancient zircons, we consider the sediments as products of proximal deposition near a Neoproterozoic subduction system in western Yangtze. Combined with the age of rhyolite from the lower part of the Yanjing Group, these strata were estimated to have been deposited in a period between 0.72 and 0.63 Ga. In contrast, the Silurian–Devonian sediments exhibit dominant Grenvillian ages (0.9–1.0 Ga), with middle Neoproterozoic (0.73–0.85 Ga), Pan-African (0.49–0.67 Ga) and Neoarchean (~ 2.5 Ga) age populations, suggesting a significant change of sedimentary provenance and thus a different tectonic setting. Although the shift occurred in the Silurian, the age spectra turn to be consistent along the western margin of the Yangtze Block until the Devonian, indicating persistence of the same sedimentary environment. However, the related provenance of these Paleozoic sediments cannot be found in South China. The presence of abundant Grenvillian, Pan-African and Neoarchean ages, along with their moderately to highly rounded shapes, indicates the possibility of exotic continental terrane(s) as a possible sedimentary provenance. Considering the potential source areas around the Yangtze Block when it was part of the Rodinia or Gondwana, we suggest that the source of these Paleozoic sediments had typical Gondwana affinities such as the Himalaya region, north India, which is also supported by their stratigraphic similarity, newly published paleomagnetic data and the tectono-thermal events of northwestern fragments of Gondwana. This implies that after a prolonged subduction in the Neoproterozoic, the western margin of the Yangtze Block began to incorporate into the assembly of the Gondwana supercontinent and was able to accept sediments from northwestern margin of Gondwanaland as a result of early Paleozoic orogeny.  相似文献   

A new genus and species of aphids,Tanyaulus caudisetula gen. et sp. nov. (Hemiptera: Aphidoidea: Burmitaphidae) in mid-Cretaceous Myanmar amber     

《Cretaceous Research》2018

A new genus and species of aphids, Tanyaulus caudisetula gen. et sp. nov. (Hemiptera: Aphidoidea: Burmitaphidae), is described from mid- Cretaceous Myanmar amber. Autapomorphies for the new genus are stub-like hind wings, 7-segmented antenna, long rostrum equal to body length, 4 veins departing from the main vein, cubital veins distinctly separated, with a very short, curved basal proximal cubitus, one-branched M vein with distal fork arched at the base, distinct claval folds at wing bases and caudal protuberance with extended setae. The new fossil adds to our knowledge of the morphological diversity of Mesozoic Aphidoidea.  相似文献   

Response of ocean dynamics to multiple equilibria of the Kuroshio path South of Japan     

《Dynamics of Atmospheres and Oceans》2019

Variability of the Kuroshio path to the south of Japan plays a central role in the local climate change and exerts tremendous influences on the local atmosphere and ocean. In this study, the response of ocean dynamics, in terms of the eddy kinetic energy (EKE), potential vorticity (PV), relative vorticity, and eddy-mean flow interaction, to the Kuroshio path change is discussed. Kuroshio path south of Japan includes the near-shore non-large meander (nNLM), the off-shore non-large meander (oNLM), and the typical large meander (tLM). Analyses reveal that the distribution of EKE, PV, relative vorticity, and energy exchange between the eddy field and the mean flow respectively varies with the Kuroshio path: (1) The tLM has the maximum EKE along the path; (2) The positive and negative PV are located at the onshore and offshore side of Kuroshio axis, respevetively; (3) The distributions of anomalous relative voritcity of nNLM, oNLM, and tLM are consistent with sea surface height anomalies (SSHAs); (4) The tLM has the largest energy exchange between the eddy field and the mean flow in terms of the rate of barotropic energy conversion. On the other hand, the stability analysis of ocean currents suggests that the three Kuroshio paths south of Japan have their own intrinsic properties of the instability.  相似文献   

Paleoenvironmental changes and depositional history of the Korea (Tsushima) Strait since the LGM     

《Journal of Asian Earth Sciences》2007,29(1):84-104

Two deep cores (SSDP 102 and SSDP 105) from the southeastern inner shelves of Korea were examined in order to reconstruct the paleoenvironmental history of the Korea Strait during postglacial sea-level fluctuations. The results of the lithofaces, organic geochemical components, foraminiferal assemblages, and stable isotopes show that the Korea Strait was influenced in different ways by river discharges and open-ocean currents, according to their temporal and spatial variability.The results of core SSDP 105 indicate that the southeastern coast of Korea was probably a shallow coastal environment, such as a shoreface or beach, by about 17.5 cal ka. The area remained a coastal environment that was affected by high energy conditions and partly by freshwater input during the transgressive period of 17.5–8.1 cal ka. The area has changed to a modern-type shelf environment influenced by the inflow of the Tsushima Current and by the high supply of fine-grained sediments derived from the Nakdong River since 8.1 cal ka.Meanwhile, the results of core SSDP 102 taken from the Nakdong River mouth reveal that the river mouth area was most likely a terrestrial or fluvial environment at least before 13.9 cal ka. It then changed to the estuarine (deltaic) environment that was directly affected by the Nakdong River between 13.9 and 7.0 cal ka, and established a modern-type shelf (prodeltaic) environment, which is similar in many respects to the southeastern coast of Korea after temporarily undergoing erosion between 7.0 and 6.1 cal ka.  相似文献