Evaluating the tephra input into Pacific Ocean sediments: distribution in space and time
Evaluating the tephra input into Pacific Ocean sediments: distribution in space and time
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DOI：
10.1007/s005310050222
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发表时间：
1998-12-01
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影响因子：
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通讯作者：
Schmincke, HU
中科院分区：
文献类型：
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作者：
Straub, SM;Schmincke, HU
我们研究了太平洋盆地火山对全球沉积物收支的贡献。它是世界上最古老的（1.74亿年）。它是最大的海洋盆地（约占地球表面积的49%），并且随着时间的推移，从板内火山和会聚边缘火山持续不断地涌入火山碎屑。对深海钻探计划（DSDP）和大洋钻探计划（ODP）65个航次的计算机化船上数据进行了筛选，以确定是否存在火山岩成分。将含火山灰和无火山灰的岩心部分（标准1.5-和0.30-m岩心捕集器部分）分离，无论火山灰的质量分数如何。计算了每个地点和时间跨度（“年龄单位”）的火山灰承载核心部分的百分比（“火山灰频率”）。年龄单位为第四纪、第三纪的亚纪和白垩纪的阶段。共有424个钻井点产出了1433个可用地层单位。50%的人不到1300万岁，仅相当于所研究的总时间间隔（1.245亿年）的约10%。含火山灰的年龄单位的百分比很高（83+/-6%），并与年龄单位的总数呈线性相关（R-2=0.998; n=17）。平均火山点频率（30-50%）波动，因为不同火山点频率级（0，1-33，34-67，68-100%火山点频率）的年龄单元的丰度随时间而变化。这表明新生代火山碎屑产量的增加是火山活动增加的结果，而不是火山源区空间扩展的结果。所恢复的新生代沉积物以火山爆发作用形成的远源火山碎屑为主。火山活动的脉冲发生在上新世-第四纪（约5百万年）。中新世中期（约12-15百万年）。然而，在古近纪和白垩纪沉积物中的爆发性火山活动记录要么没有被钻探，要么已经被俯冲破坏。白垩纪除外（约70-110百万年）火山脉冲，板内火山作用在火山碎屑岩记录中表现不佳，因为钻探地点在震源的近端范围（>500-1000 km）之外。因此，火山灰记录钻孔包含显着的差距，偏见火山灰体积的估计对体积较小的远端存款。大部分的火山灰体积都是由火山灰裙周围的海洋岛屿火山的质量消耗而积累的。大型板内火山的火山喷发速率为10，000 - 41，800 km（3）/m.y，大洋岛弧的火山喷发速率约为10-13 km（3）/km，即每百万年的长度。外推主要太平洋弧和热点链的寿命，结合对远端火山点组成部分的体积估计，表明火山点的最小值为9.3x10（6）km（3），相当于23 vol. %现存的太平洋海洋沉积物。火山灰体积的至少三分之二沉积在近端范围内，至少有一半来自板内来源。火山灰的大比例，它的成分，其本地化的积累造成显着的空间和时间变化，在太平洋海洋沉积物，应该有一个明显的影响，海洋，地壳和地幔之间的元素通量。
We studied the volcanic contribution to the global sediment budget in the Pacific Ocean basin. It is the world's oldest (174 m.y.) and largest (approximate to 49% of Earth's surface area) ocean basin and has had a high and continuous tephra influx from intraplate and convergent margin volcanoes through time. Computerized shipboard data from 65 legs of the Deep Sea Drilling Project (DSDP) and the Ocean Drilling Program (ODP) were screened for the presence of volcaniclastic components. Tephra-bearing and tephra-free core sections (standard 1.5- and 0.30-m core catcher sections) were separated, regardless of the mass fraction of tephra present. The percentage of tephra-bearing core sections ("tephra frequency") per site and time span ("age unit") was calculated. The age units were the Quater nary, the subepochs of the Tertiary, and the stages of the Cretaceous. A total of 424 drill sites yielded 1433 usable stratigraphic units. Fifty percent are younger than 13 m.y., corresponding to only approximately 10% of the total interval studied (124.5 m.y.). The percentage of tephra-bearing age units is high throughout (83+/-6%) and correlates linearly with the total number of age units (R-2=0.998; n=17). The average tephra frequency (30-50%) fluctuates, because the abundance of age units of different tephra frequency classes (0, 1-33, 34-67, 68-100% tephra frequency) varies with time. This indicates that the Cenozoic increase in tephra production results from increase in volcanicity and not spatial extension of volcanic source areas. The Cenozoic sediments that were recovered are dominated by distal tephra from explosive are volcanism. Pulses of are volcanism occurred in the Pliocene-Quaternary (since approximate to 5 m.y.) and mid-Miocene (approximate to 12-15 m.y.). However, the record of explosive are volcanism in Paleogene and Cretaceous sediments was either not drilled or has been destroyed by subduction. Except for the Cretaceous (approximate to 70-110 m.y.) volcanic pulse, intraplate volcanism is poorly represented in the tephra record because the drill sites are outside the proximal range (>500-1000 km) of the sources. Thus, the tephra record drilled contains significant gaps that bias the estimate of tephra volume towards the less voluminous distal deposits. Most of the volcaniclastic volume accumulated by mass wasting as volcaniclastic aprons surrounding ocean island volcanoes. Volcaniclastic production rates range from 10,000 to 41,800 km(3)/m.y, for large intraplate volcanoes and approximately 10-13 km(3)/km are length per million years for oceanic island arcs. Extrapolation over the lifetime of major Pacific arcs and hotspot chains, combined with a volume estimate of the distal tephra component, indicates a minimum of 9.3x10(6) km(3) of tephra, corresponding to 23 vol.% of the existing Pacific oceanic sediments. At least two thirds of the tephra volume was deposited in the proximal range and at least half of it is derived from intraplate sources. The large proportion of tephra, its composition, and its localized accumulation causes significant spatial and temporal variation in Pacific oceanic sediments that should have a perceptible impact on the elemental fluxes between ocean, crust, and mantle.