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首页> 外文期刊>Paleoceanography >Late Quaternary changes in intermediate water oxygenation and oxygen minimum zone, northern Japan: A benthic foraminiferal perspective
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Late Quaternary changes in intermediate water oxygenation and oxygen minimum zone, northern Japan: A benthic foraminiferal perspective

机译：日本北部中层水的氧合和最低氧区的第四纪晚期变化：底栖有孔虫的观点

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摘要

A strong oxygen minimum zone (OMZ) currently exists at upper intermediate water depths on the northern Japanese margin, NW Pacific. The OMZ results largely from a combination of high surface water productivity and poor ventilation of upper intermediate waters. We investigated late Quaternary history ( last 34 kyr) of ocean floor oxygenation and the OMZ using quantitative changes in benthic foraminiferal assemblages in three sediment cores taken from the continental slope off Shimokita Peninsula and Tokachi, northern Japan, at water depths between 975 and 1363 m. These cores are well located within the present-day OMZ, a region of high surface water productivity, and in close proximity to the source region of North Pacific Intermediate Water. Late Quaternary benthic foraminiferal assemblages experienced major changes in response to changes in dissolved oxygen concentration in ocean floor sediments. Foraminiferal assemblages are interpreted to represent three main groups representing oxic, suboxic, and dysoxic conditions. Assemblage changes in all three cores and hence in bottom water oxygenation coincided with late Quaternary climatic episodes, similar to that known for the southern California margin. These episodes, in turn, are correlated with orbital and millennial climate episodes in the Greenland ice core including the last glacial episode, Bolling-Allerod (B/ A), Younger Dryas, Preboreal ( earliest Holocene), early Holocene, and late Holocene. The lowest oxygen conditions, marked by dysoxic taxa and laminated sediments in one core, occurred during the B/ A and the Preboreal intervals. Suboxic taxa dominated mainly during the last glacial, the Younger Dryas, and most of the Holocene. Dysoxic conditions during the B/ A and Preboreal intervals in this region were possibly caused by high surface water productivity at times of reduced intermediate ventilation in the northwestern Pacific. Remarkable similarities are evident in the late Quaternary sequence of benthic foraminiferal assemblage change between the two very distant continental margins of northern Japan and southern California. The oscillations in OMZ strength, reflected by these faunal changes, were widespread and apparently synchronous over wide areas of the North Pacific, reflecting broad changes in intermediate water ventilation and surface ocean productivity closely linked with late Quaternary climate change on millennial and orbital timescales.
机译：目前，在日本北部边缘西北太平洋的中层较高水深处存在一个强氧最低限度带（OMZ）。 OMZ主要是由于地表水生产率高和上层中层水通风不良造成的。我们使用了三个沉积岩心的底栖有孔虫组合的定量变化，研究了第四纪晚期海底充氧和OMZ的变化，这些沉积物取自日本北部下北田和十胜的大陆坡，水深在975至1363 m之间。这些核心位于当今的OMZ（地表水生产率高的区域）内，并且紧邻北太平洋中级水源区域。晚第四纪底栖有孔虫组合经历了重大变化，以响应海底沉积物中溶解氧浓度的变化。有孔虫组合被解释为代表三个主要组，分别代表有氧，亚缺氧和低氧条件。在所有三个核心的组合变化，因此在底部水域的氧合作用，与第四纪晚期的气候事件相吻合，类似于南加州边缘。这些事件又与格陵兰岛冰芯的轨道和千年气候事件有关，包括最后一次冰川事件，Bolling-Allerod（B / A），Younger Dryas，Preboreal（最早的全新世），早期全新世和晚期全新世。在B / A和Preboreal间隔期间，最低的氧气条件发生在低氧分类单元和一个岩心的层状沉积物中。在最后的冰川，年轻的树蛙和大部分全新世中，羧基类群占主导地位。在该区域的B / A和Preboreal间隔期间的缺氧条件可能是由于西北太平洋中间通风减少时地表水生产率高所致。在日本北部和加利福尼亚南部两个非常遥远的大陆边缘之间的底栖有孔虫组合变化的第四纪晚期序列中，明显相似。这些动物区系变化所反映的OMZ强度波动在北太平洋广大地区普遍存在，并且显然是同步的，反映了中间水通风和地表海洋生产力的广泛变化与千禧年和轨道时间尺度后期第四纪气候变化密切相关。

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