Latest pulse of Earth: Evidence for a mid-Cretaceous superplume
Latest pulse of Earth: Evidence for a mid-Cretaceous superplume
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DOI：
10.1130/0091-7613(1991)019
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发表时间：
1991-06
期刊：
影响因子：
5.8
通讯作者：
R. Larson
中科院分区：
文献类型：
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作者：
R. Larson
对过去1.5亿年地球海洋地壳预算的计算揭示了120至80 Ma之间洋壳形成率增加了50%至75%。洋壳生成的这种“脉动”既表现在洋脊的扩展速度增加上，也表现在大洋高原的年龄分布上。它主要是一种突然发生的太平洋现象，峰值生产率发生在120至100 Ma之间。从100到80 Ma，脉冲强度下降，在80 Ma时，速率显著下降。有一个持续减少，从80至30 Ma的白垩纪/第三纪边界附近的第二个高峰在65 Ma。在过去的3千万年里，洋壳几乎以稳定的速度形成。由于脉冲主要出现在太平洋洋坪和洋脊生产，并符合正常磁极的白垩纪长间隔，我解释它作为一个“超级羽”，起源于约125马附近的核心/地幔边界，上升对流通过整个地幔，爆发下白垩纪中期太平洋盆地。现在塔希提岛下的南太平洋“超级井”可能是最初上升流的残余。超级羽流如何阻止磁场逆转4100万年是一个推测的问题，但它可能涉及显着改变的温度结构在核/幔边界和对流行为的外核。
A calculation of Earth's ocean crustal budget for the past 150 m.y. reveals a 50% to 75% increase in ocean crust formation rate between 120 and 80 Ma. This "pulse" in ocean crust production is seen both in spreading-rate increases from ocean ridges and in the age distribution of oceanic plateaus. It is primarily a Pacific Ocean phenomenon with an abrupt onset, and peak production rates occurred between 120 and 100 Ma. The pulse decreased in intensity from 100 to 80 Ma, and at 80 Ma rates dropped significantly. There was a continued decrease from 80 to 30 Ma with a secondary peak near the Cretaceous/Tertiary boundary at 65 Ma. For the past 30 m.y., ocean crust has formed at a nearly steady rate. Because the pulse is seen primarily in Pacific oceanic plateau and ridge production, and coincides with the long Cretaceous interval of normal magnetic polarity, I interpret it as a "superplume" that originated at about 125 Ma near the core/mantle boundary, rose by convection through the entire mantle, and erupted beneath the mid-Cretaceous Pacific basin. The present-day South Pacific "superswell" under Tahiti is probably the nearly exhausted remnant of the original upwelling. How this superplume stopped magnetic field reversals for 41 m.y. is a matter of speculation, but it probably involved significant alteration of the temperature structure at the core/mantle boundary and the convective behavior of the outer core.