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A Robust Test of the Milankovitch Cycle Hypothesis Predictions for Influencing Abyssal Hill Morphology: A Pilot Study

影响深海山形态的米兰科维奇循环假说预测的稳健检验：一项试点研究

基本信息

批准号：
1656136
负责人：
John Goff
金额：
$ 12.03万
依托单位：
University of Texas at Austin
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-03-01 至 2019-02-28
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1656136&HistoricalAwards=false
关键词：
Robust Test Milankovitch Cycle Hypothesis

项目摘要

Vast regions of the ocean floor are covered by features called abyssal hills, highly linear ridges that are formed at the volcanic mid-ocean ridges, and then rafted away as the tectonic plates spread apart. A new hypothesis contends that the topography of abyssal hills is closely linked to changes in sea level, and therefore to changes in Milankovitch cycles of the orbit of the Earth. If true, then the implications are potentially enormous: mapping the topography of the seafloor could be used to investigate Earth history, and thereby greatly enrich our understanding of Earth's varying climate associated with the changes in the orbit of the Earth. The hypothesis to be investigated suggests that the rising and falling global sea level, controlled primarily by Milankovitch-scale variability in Earth's orbit, modulates the intensity of volcanic eruptions at mid-ocean ridges and, in turn, the formation of abyssal hills on the seafloor. However, a connection between abyssal hills and Milankovitch cycles has been disputed by other researchers. There are two fundamental objections: (1) decades of observational evidence have shown that abyssal hills are dominantly fault-generated structures, rather than volcanic constructs, and (2) the Milankovitch Cycle hypothesis predicts that the width of abyssal hills will increase with spreading rate, contrary to observations indicating the opposite is true. Nevertheless, modulation of mid-ocean ridge volcanism by changes in sea level is a plausible and, indeed, exciting prospect, and recent work on abyssal sediments provides independent evidence in support of the hypothesis. The central problem is that, if there is a topographic signal of sea level-modulated volcanism in the morphology of abyssal hills, measuring this effect will require decoupling it from the dominant fault-generated component. This project will develop a methodology for measuring, if it exists, an age-dependent component of abyssal hill topography. The central hypothesis is that fault-generated topography is random with respect to crustal age, and can thus be treated as a correlated random noise process superimposed on any age-dependent (possibly volcanic) signal; this hypothesis is consistent with prior studies that model fault scaling parameters with random distributions governed by scaling laws. The proposed methodology will stack, or average, large quantities of data as a function of crustal age so that the random component (noise) destructively reduces while non-random component (signal) constructively sums. Characterization of the abyssal hill covariance structure is necessary to determine the expected variance of the stacked signal, and thus to rigorously test the null hypothesis that no age-dependent topographic signal exists; the null hypothesis can be rejected if the stacked profile exceeds the bounds for a given confidence level. The methodology will be applied to three large regions along the flanks of the East Pacific Rise that provide the most comprehensive bathymetric coverage available along the ridge flanks.

洋底的大片区域被称为深海丘陵的特征所覆盖，这些特征是在火山洋中脊形成的高度线性的脊，然后随着构造板块的扩张而漂流。一种新的假说认为，深海丘陵的地形与海平面的变化密切相关，因此与地球轨道米兰科维奇周期的变化密切相关。如果这是真的，那么其影响可能是巨大的：绘制海底地形图可以用来研究地球历史，从而大大丰富我们对与地球轨道变化相关的地球气候变化的理解。有待研究的假设表明，主要受地球轨道米兰科维奇尺度变化控制的全球海平面上升和下降，调节了大洋中脊火山爆发的强度，进而调节了海底深海丘陵的形成。然而，深海丘陵和米兰科维奇旋回之间的联系受到其他研究人员的质疑。有两个基本的反对意见：（1）几十年的观测证据表明，深海丘陵主要是断层生成的结构，而不是火山构造，（2）米兰科维奇循环假说预测，深海丘陵的宽度将随着扩张速度的增加而增加，与观察相反，相反的是。尽管如此，海平面变化对大洋中脊火山活动的调节是一个似乎合理的、确实令人兴奋的前景，最近关于深海沉积物的工作为支持这一假设提供了独立的证据。核心问题是，如果在深海丘陵的形态中存在海平面调制火山活动的地形信号，则测量这种影响将需要将其与主要的断层生成成分分离。该项目将制定一种方法，用于测量深海丘陵地形中与年龄有关的组成部分（如果存在的话）。中心的假设是，断层生成的地形是随机的地壳年龄，因此可以被视为一个相关的随机噪声过程叠加在任何年龄相关（可能是火山）的信号，这一假设是一致的模型故障缩放参数与随机分布的比例律与以前的研究。所提议的方法将把大量数据作为地壳年龄的函数加以叠加或平均，以便随机分量（噪声）破坏性地减少，而非随机分量（信号）建设性地相加。深海丘陵协方差结构的表征是必要的，以确定叠加信号的预期方差，从而严格测试零假设，没有年龄依赖的地形信号存在;零假设可以被拒绝，如果叠加的配置文件超过了给定的置信水平的界限。这一方法将应用于东太平洋海隆两侧沿着的三个大区域，这些区域提供了沿着海隆两侧现有的最全面的测深覆盖面。