辽西热河生物群一新的巨龙型类恐龙     

周长付  吴文昊  关谷透  董枝明 《世界地质》2018,37(2):327-333

初步研究了辽西地区热河生物群的一具近完整的蜥脚类恐龙骨架,其代表了一新的巨龙型类恐龙——中国辽宁巨龙(Liaoningotitan sinensis gen.et sp.nov)。其主要特征为:上颌骨腹缘下凸,上颌齿列短且位于前部;颧骨前端近平齐于眶前窗的前缘;翼骨的方骨支基部收缩;上颌齿呈叠瓦状排列;上颌齿冠窄勺形,切面呈D字形,缺失唇侧沟和小锯齿;下颌齿9枚,明显小于上颌齿,排列稀松;下颌齿冠不对称,切面呈椭圆形,舌侧的沟和嵴发育,齿冠基部向舌侧膨大;肱骨近端扩展,约为长度的54.9%;肠骨前髋臼突前端较尖。初步的支序分析显示,辽宁巨龙属于巨龙型类恐龙,是比盘足龙和梁龙更为进步的类群。  相似文献   

Field observations of meteotsunami locally called “abiki” in Urauchi Bay, Kami-Koshiki Island, Japan     

Toshiyuki Asano  Toru Yamashiro  Norihiro Nishimura 《Natural Hazards》2012,64(2):1685-1706

A seasonal scale field observation extending over a period of 82?days was conducted in Urauchi Bay on Kami-Koshiki Island, to record meteotsunami events, disastrous secondary oscillations locally known as ??abiki.?? The bay has an elongated T-shape topography with a narrow mouth opening westward to the East China Sea. The area has suffered the effects of meteotsunami causing flooding in residential area and damage to fishing fleets and facilities. A comprehensive observation system for sea level, ocean currents and barometric pressure was deployed to cover the regions within and offshore from Urauchi Bay and the open sea near the island of Mejima in the East China Sea. Vigorous meteotsunami events, where the total height exceeded 150?cm, were observed over five-day periods during the observation period. One or two hours prior to the arrival of meteotsunami events at Kami-Koshiki Island, abrupt 1?C2?hPa pressure changes were observed at the Mejima observation site. Pressure disturbances were found to travel eastward or northeastward. The propagation speed was found to nearly coincide with that of ocean long waves over the East China Sea, and as a result, resonant coupling should be anticipated. The incoming long waves were also amplified by geometric resonance with eigen oscillations inherent in the T-shape topography of Urauchi Bay.  相似文献   

Fractures in Cretaceous granite as pathways of upwelling deep‐seated water at Kawachinagano City on Kii Peninsula,southwest Japan          下载免费PDF全文

Makoto Otsubo  Toru Shimizu  Ayumu Miyakawa  Tsutomu Sato  Michiko Ohwada  Kohei Kazahaya 《Island Arc》2016,25(4):298-300

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Surface velocity time series derived from satellite altimetry data in a section across the Kuroshio southwest of Kyushu     

Hirohiko Nakamura  Ayako Nishina  Kotaro Tabata  Masataka Higashi  Akimasa Habano  Toru Yamashiro 《Journal of Oceanography》2012,68(2):321-336

A time series of surface geostrophic velocity is developed using satellite altimetry data during 1992–2010 for a track across the Kuroshio southeast of Kyushu, Japan. The temporal mean geostrophic velocity is estimated by combining the along-track sea level anomaly and shipboard ADCP data. This approximately 6-km resolution dataset is successful in representing the Kuroshio cross-current structure and temporal variation of the Kuroshio current-axis position during 2000–2010. The authors use this dataset to examine the winter Kuroshio path destabilization phenomenon. Its seasonal features are characterized as follows: the velocity shear on the inshore side of the Kuroshio becomes stronger and the Kuroshio path state becomes unstable from the summer to winter. This evidence is consistent with the hypothetical mechanism governing the destabilization phenomenon discussed in a previous study. Furthermore, the interannual amplitude modulation of the seasonality is examined in relation to interannual variations in the winter northerly wind over the northern Okinawa Trough and the Pacific Decadal Oscillation (PDO) index. The destabilization phenomenon appears 15 times in the period 2000–2010. Ten cases are related to local wind effects, and 7 of these are also connected with the PDO index. This is probably because the winter northerly wind over the northern Okinawa Trough is regulated by the PDO signal in interannual time-scales. Only 4 cases are related to the PDO index, but their driving mechanism remains uncertain.  相似文献   

Sediment distribution and depositional processes along the fluvial to marine transition zone of the Mekong River delta,Vietnam     

Marcello Gugliotta  Yoshiki Saito  Van Lap Nguyen  Thi Kim Oanh Ta  Toru Tamura 《Sedimentology》2019,66(1):146-164

The area of coastal rivers with a combination of fluvial, tidal and wave processes is defined as the fluvial to marine transition zone and can extend up to several hundreds of kilometres upstream of the river mouth. The aim of this study is to improve the understanding of sediment distribution and depositional processes along the fluvial to marine transition zone using a comprehensive dataset of channel bed sediment samples collected from the Mekong River delta. Six sediment types were identified and were interpreted to reflect the combined action of fluvial and marine processes. Based on sediment‐type associations, the Mekong fluvial to marine transition zone could be subdivided into an upstream tract and a downstream tract; the boundary between these two tracts is identified 80 to 100 km upstream of the river mouth. The upstream tract is characterized by gravelly sand and sand and occasional heterolithic rhythmites, suggesting bed‐load supply and deposition mainly controlled by fluvial processes with subordinate tidal influence. The downstream tract is characterized by heterolithic rhythmites with subordinate sand and mud, suggesting suspended‐load supply and deposition mainly controlled by tidal processes with subordinate fluvial influence. Sediment distributions during wet and dry seasons suggest significant seasonal changes in sediment dynamic and depositional processes along the fluvial to marine transition zone. The upstream tract shows strong fluvial depositional processes with subordinate tidal influence during the wet season and no deposition with weak fluvial and tidal processes during the dry season. The downstream tract shows strong coexisting fluvial and tidal depositional processes during the wet season and strong tidal depositional processes with negligible fluvial influence during the dry season. Turbidity maxima are present along the downstream tract of the fluvial to marine transition zone during both wet and dry seasons and are driven by a combination of fluvial, tidal and wave processes.  相似文献   

Influence of interaction between small asperities on various types of slow earthquakes in a 3-D simulation for a subduction plate boundary   总被引：3，自引：1，他引：2  

Keisuke Ariyoshi  Takane Hori  Jean-Paul Ampuero  Yoshiyuki Kaneda  Toru Matsuzawa  Ryota Hino  Akira Hasegawa 《Gondwana Research》2009,16(3-4):534-544

Recently, the occurrence of slow earthquakes such as low-frequency earthquakes and very low-frequency earthquakes have been recognized at depths of about 30 km in southwest Japan and Cascadia. These slow earthquakes occur sometimes in isolation and sometimes break into chain-reaction, producing tremor that migrates at a speed of about 5–15 km/day and suggesting a strong interaction among nearby small asperities. In this study, we formulate a 3-D subduction plate boundary model with two types of small asperities chained along the trench at the depth of 30 km. Our simulation succeeds in representing various types of slow earthquakes including low-frequency earthquakes and rapid slip velocity in the same asperity, and indicates that interaction between asperities may cause the very low-frequency earthquakes. Our simulation also shows chain reaction along trench with propagation speed that can be made consistent with observations by adjusting model parameters, which suggests that the interactions also explain the observed migration of slow earthquakes.  相似文献   

Changes in trophic flow structure of Independence Bay (Peru) over an ENSO cycle     

Marc H. Taylor  Matthias Wolff  Jaime Mendo  Carmen Yamashiro 《Progress in Oceanography》2008,79(2-4):336

During the strong warm El Niño (EN) that occurred in 1997/98, Independence Bay (14°S, Peru) showed a ca. 10 °C increase in surface temperatures, higher oxygen concentrations, and clearer water due to decreased phytoplankton concentrations. Under these quasi-tropical conditions, many benthic species suffered (e.g. macroalgae, portunid crabs, and polychaetes) while others benefited (e.g. scallop, sea stars, and sea urchins). The most obvious change was the strong recruitment success and subsequent proliferation of the scallop Argopecten purpuratus, whose biomass increased fiftyfold. To understand these changes, steady-state models of the bay ecosystem trophic structure were constructed and compared for a normal upwelling year (1996) and during an EN (1998), and longer-term dynamics (1996–2003) were explored based on time series of catch and biomass using Ecopath with Ecosim (EwE) software. Model inputs were based on surveys and landings data collected by the Instituto del Mar del Perú (IMARPE). Results indicate that while ecosystem size (total throughput) is reduced by 18% during EN, mainly as a result of decreased total primary production, benthic biomass remains largely unchanged despite considerable shifts in the dominant benthic taxa (e.g. scallops replace polychaetes as secondary consumers). Under normal upwelling conditions, predation by snails and crabs utilize the production of their prey almost completely, resulting in more efficient energy flow to higher trophic levels than occurs during EN. However during EN, the proliferation of the scallop A. purpuratus combined with decreased phytoplankton increased the proportion of directly utilized primary production, while exports and flows to detritus are reduced. The simulations suggest that the main cause for the scallop outburst and for the reduction in crab and macroalgae biomass was a direct temperature effect, whereas other changes are partially explained by trophic interactions. The simulations suggest that bottom-up effects largely control the system.  相似文献   

Erratum to “Environmental control of short-term variation in the plankton community of inner Tokyo Bay, Japan” [Estuar., Coast. Shelf Sci. 78 (2008) 796–810]     

Toru Nakane  Kisaburo Nakata  Heather Bouman  Trevor Platt 《Estuarine, Coastal and Shelf Science》2008,80(4):598

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Electromagnetic Response of a Large Circular Loop Source on a Layered Earth: A New Computation Method   总被引：3，自引：0，他引：3  

Nagendra Pratap?SinghEmail author  Toru?Mogi 《Pure and Applied Geophysics》2005,162(1):181-200

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Kinetics of nitrate and ammonium uptake by the natural populations of marine phytoplankton in the surface water of the Oyashio region during spring and summer     

Akihiro Shiomoto  Katsuyuki Sasaki  Toru Shimoda  Satsuki Matsumura 《Journal of Oceanography》1994,50(5):515-529

The maximum uptake rate (_max) and affinity constant (K _s) for nitrate and ammonium were estimated in the surface water of offshore Oyashio in May (spring) and September (summer), 1990. The average _max/Chl.a for ammonium was 2.1 times larger than that of nitrate in both seasons. The average _max/Chl.a for both nitrogens were 3.5 times larger in summer than in spring. Water temperature and size composition of phytoplankton population were related to the seasonal difference in the _max/Chl.a. Phytoplankton population showed high affinity for both nitrogens in the spring and summer. In addition, the contribution of new production to total production was estimated by _max[_max–No₃/(_max–NO₃+_max–NH₄)]. The spring value was in the range of 0.26 to 0.45 (mean±SD=0.35±0.092), and the values in spring bloom were especially a little over 0.4. The summer value was in the range of 0.30 to 0.37 (0.34±0.04).  相似文献