Scientific results of drilling the North Pacific Transect-猫眼课题宝

DOI：

10.2973/odp.proc.sr.145.146.1995

发表时间：

1995

期刊：

影响因子：

通讯作者：

中科院分区：

其他

文献类型：

作者：

D. Rea;I. Basov;L. Krissek

大洋钻探计划第145航次于1992年夏天从日本穿越北太平洋到达加拿大，这是自1971年深海钻探计划第18和19航次以来在亚北极太平洋的第一次深海钻探。这次巡航的所有新生代古海洋学目标都已实现。我们确定了北太平洋二氧化硅沉积的历史，并解决了晚中新世“二氧化硅开关”的时间时，二氧化硅沉积的轨迹从北大西洋到北太平洋。在底特律海山的侧翼钻在遥远的西北太平洋的深度样带允许重建的方解石补偿深度的北太平洋在过去的70 Ma。明治沉积舌被证明是一种漂流存款，其性质与北大西洋的沉积物相同。明治漂流物含有来自白令海地区的北源硅藻和矿物，自渐新世早期以来一直在积累。这意味着在过去的3500万年里，向南流动的底层水一直从白令海流向北太平洋盆地。目前，白令海的海水流出速度与北大西洋深水流出大西洋西北部的速度相同，为10至20 Sv（1 Sv = 10 m/s）。晚新生代冷却被确定为已进行到中新世结束时，冰筏碎片首次出现在腿145钻井现场。上新世中期的温暖间隔中断了高纬度的冷却约一百万年。大规模的北方半球冰川已开始，而突然在2.6马的快速增加，在交付的陆源半远洋和冰筏碎片沉积物的北太平洋。与此同时，深海环流开始改变西北太平洋深盆的沉积物沉积模式。从堪察加半岛（世界上最活跃的上新世-更新世火山场）和阿留申弧顺风恢复的灰层序列允许这些火山中心的地球化学演化被确定。一个数量级的增加，灰层的数量和厚度发生在2.6马。对过去4.0 Ma的高分辨率研究表明，间冰期期间生物沉积物通量一般较高。这一观察表明，在间冰期更迅速地循环的深海沃茨是营养物质的主要来源，以亚北极太平洋，而不是那些提供的区域径流或灰尘输入。北太平洋断面古海洋学背景介绍亚北极太平洋沉积物包含了晚中生代和新生代海洋学和气候变化的重要记录。现有的深海钻探项目（DSDP）的网站太少，回收的沉积物岩心通常太受旋转钻井的干扰，无法进行详细的重建。因此，在我们对地球海洋和气候系统演变的了解方面，该区域是一个重大空白。这一区域延伸超过35 × 10公里，包括两个主要的边界流（俄亥俄流和阿拉斯加流）和一个海洋和大气锋区（亚北极锋），据信它在短时间和长时间尺度上迁移了几个纬度。通过阿留申群岛和千岛群岛弧提供了沃茨的交换场所，对北太平洋中层水的性质产生了强烈的影响，可能是Rea，D.K.，路易斯安那州巴索夫，Scholl，D.W.，和Allan，J.F.（编），1995. Proc. ODP，Sci.结果，145：学院站，德克萨斯州（大洋钻探计划）。地质科学系，密歇根大学，安阿伯，MI 48109-1063，美国岩石圈研究所，俄罗斯科学院，Staromonetnyi Pereulok 22，莫斯科，109180，俄罗斯。4地质矿物学系，俄亥俄州州立大学，哥伦布，俄亥俄州43210-1398，美国。第145段科学小组的参与者名单见《初始报告》卷（Rea、Basov、Janecek、Palmer-Julson等人，1993年）。更深的沃茨。该地区是北美大陆的热量和水分的来源，也是世界海洋中最具生物生产力的地区之一。目前，北太平洋是起源于北大西洋北方和南大洋的深洋环流路线的终点，也是返回表层环流的起点。这些古老的深水沃茨营养丰富，氧气贫乏，对碳酸钙具有高度腐蚀性。最近的证据表明，在第四纪的不同时期，东北太平洋和西北太平洋深处的方解石保存较好（Keigwin，1987年; Keigwin等人，1992; Zahn等人，1991; Hovanet al.，目前尚不清楚这些变化和其他变化在多大程度上反映了深海环流的变化，而不是沉积条件的局部变化。在世界其他地区的工作已经确定了一系列事件或海洋环流和全球气候在新第三纪的快速变化。这些包括中新世中期和最晚的中新世，据信是南极冰川扩张的时期（Woodruff等人，1981; Savin等人，1981;肯内特，1985），上新世晚期北方半球冰的增长（沙克尔顿等人，一九八四年; Rea和Schrader，1985年），以及更新世中期冰量δ 1 8 θ信号幅度的最近增加（Ruddiman等人，1989年）。这些长期的变化似乎叠加在它们之上，大约在米兰科维奇时期持续更高的频率变化周期。这些变化对北太平洋的影响在很大程度上是未知的，因为在第145航次之前可利用的地点数量很少，而且一般没有钙质沉积物。第145航次钻井地点的战略位置位于海洋高地和北太平洋副极地环流内的深海盆地

Ocean Drilling Program Leg 145 crossed the North Pacific Ocean from Japan to Canada in the summer of 1992, the first deep ocean drilling in the Subarctic Pacific since the 1971 cruises of Deep Sea Drilling Project Legs 18 and 19. All of the Cenozoic paleoceanographic objectives of the cruise were accomplished. We determined the history of silica deposition in the North Pacific and resolved the timing of the late Miocene "silica switch" when the locus of silica deposition changed from the North Atlantic to the North Pacific. A depth transect drilled on the flanks of Detroit Seamount in the far northwestern Pacific allowed the reconstruction of the calcite compensation depth for the North Pacific over the past 70 Ma. The Meiji sediment tongue was shown to be a drift deposit, identical in nature to those better known from the North Atlantic. The Meiji Drift contains northern-source diatoms and minerals from the Bering Sea region and has been accumulating since the early Oligocene. This means that southward-flowing bottom water has been exiting the Bering Sea to the North Pacific basin for the past 35 million years. Presently, water exits the Bering Sea at the same rate, 10 to 20 Sv (1 Sv = I0 m/s), as North Atlantic Deep Water leaves the northwesternmost Atlantic. Late Cenozoic cooling was determined to have been underway by the end of Miocene time when ice-rafted debris first occurs at the Leg 145 drill sites. A middle Pliocene warm interval interrupted the high-latitude cooling for about a million years. Large-scale Northern Hemisphere glaciation is shown to have begun rather abruptly at 2.6 Ma by a rapid increase in the delivery of terrigenous hemipelagic and ice-rafted debris sediment to the North Pacific. At this same time abyssal circulation begins to modify sediment depositional patterns in the northwestern Pacific deep basin. The sequence of ash layers recovered downwind from both the Kamchatka Peninsula (the world's most active Pliocene-Pleistocene volcanic field) and the Aleutian arc allows the geochemical evolution of these volcanic centers to be determined. An order of magnitude increase in the number and thickness of ash layers occurred at 2.6 Ma. High-resolution studies of the past 4.0 Ma show that biogenic sediment fluxes are generally higher during interglacial periods. This observation indicates that more rapidly circulating deep ocean waters during interglacial episodes is the dominant source of nutrients to the Subarctic Pacific rather than those supplied by regional runoff or dust input. INTRODUCTION TO THE NORTH PACIFIC TRANSECT Paleoceanographic Setting Subarctic Pacific sediment contains a critical record of late Mesozoic and Cenozoic Oceanographic and climatic changes. Existing Deep Sea Drilling Project (DSDP) sites are too few and recovered sediment cores are generally too disturbed by rotary drilling to permit detailed reconstructions. The region therefore represents a significant gap in our knowledge of the evolution of the earth's ocean and climate system. This area extends over 35 × I0 km and includes two major boundary currents (the Oyashio and Alaskan currents) and an oceanic and atmospheric frontal zone (the Subarctic Front), which is believed to have migrated over several degrees of latitude on both short and long time scales. Passes through the Aleutian and Kuril arcs provide exchange sites for deep waters that exert a strong influence upon the properties of North Pacific Intermediate Water and possibly 'Rea, D.K., Basov, LA., Scholl, D.W., and Allan, J.F. (Eds.), 1995. Proc. ODP, Sci. Results, 145: College Station, TX (Ocean Drilling Program). department of Geological Sciences, The University of Michigan, Ann Arbor, Ml 48109-1063, U.S.A. 'Institute of the Lithosphere, Russia Academy of Sciences, Staromonetnyi Pereulok 22, Moscow, 109180, Russia. 4 Department of Geology and Mineralogy, The Ohio State University, Columbus, OH 43210-1398, U.S.A. Leg 145 Scientific Party is as given in list of participants in the Initial Reports volume (Rea, Basov, Janecek, Palmer-Julson, et al., 1993). deeper waters. The area is a source of heat and moisture for the North American continent and is one of the most biologically productive areas of the world ocean. At present, the North Pacific is the terminus of the deep ocean circulation route originating in the northern North Atlantic and the Southern Ocean, and the beginning of the return surface circulation. These old deep waters are nutrient-rich, oxygen-poor and highly corrosive to calcium carbonate. Recent evidence suggests that at various times in the Quaternary better calcite preservation occurred in both the deep northeast and northwest Pacific (Keigwin, 1987; Keigwin et al., 1992; Zahn et al., 1991; Hovanet al., 1991) It is not clear to what extent these and other changes reflect changes in deep-ocean circulation, as opposed to local changes in depositional conditions. Work in other regions of the world has defined a series of events or rapid changes in ocean circulation and global climate during the Neogene. These include the middle and latest Miocene, believed to be times of expansion of Antarctic glaciers (Woodruff et al., 1981; Savin et al., 1981; Kennett, 1985), the late Pliocene growth of ice in the Northern Hemisphere (Shackleton et al., 1984; Rea and Schrader, 1985), and the more recent increase in the amplitudes of the ice-volume δ 1 8 θ signal during the middle Pleistocene (Ruddiman et al, 1989). These longer term changes appear to have superimposed upon them ongoing higher frequency variability cycles at roughly Milankovitch periods. The effect of these changes upon the North Pacific has been largely unknown, given the small number of sites available prior to Leg 145 and the general absence of calcareous sediment. Strategic location of Leg 145 drilling sites situated upon oceanic highs and in the deep basins within the North Pacific subpolar gyre were intended

Scientific results of drilling the North Pacific Transect

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