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Paleoclimate signal from the late Eocene New Jersey continential slope: A multi-proxy approach.

机译：来自始新世晚期新泽西大陆斜坡的古气候信号：一种多代理方法。

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摘要

Previous studies have documented that global climate cooled in the late Eocene at the million-year time scale. However, the precise details and timing of this cooling remain unresolved. This study proposes that the late Eocene million-year time scale cooling trend was punctuated by precessional Milankovitch cyclicity and that the cooling trend was interrupted by a warm pulse during the latest Eocene. The late Eocene paleoclimate was studied on the New Jersey Continental Margin from slope sediments recovered during Leg 150 of the Ocean Drilling Program. A multiproxy approach that included the following analyses was used: (1) grain size, (2) bulk mineralogy, (3) petrographic thin sections, (4) stable oxygen isotopes from planktonic foraminifera Globigerina spp., (5) geophysical FMS logs (Formation Microscanner; measuring conductivity), (6) spectral analysis, and (7) comparison to global records from previously published work.;A general cooling trend from the middle to the late Eocene is indicated by an increase in siliciclastic sediment, decrease in calcium carbonate, and grain size coarsening. These lithologic changes document the transition from carbonate to siliclastic sedimentation that accompanied the paleoclimatic cooling and was previously documented for this margin. An increase in global ice volume through the late Eocene is also documented by stable oxygen isotopes obtained from the tests of Globigerina spp. Low resolution sampling at a 40 ka resolution showed delta18O values increasing from -3.67 per mil up to -2.83 per mil over a span of 1,050,000 years between 35.3 Ma and 34.25 Ma. High resolution sampling, one sample every 5 ka, over the interval from 34.75 Ma to 34.25 Ma show delta18O values ranging at -3.0 per mil and is interpreted as warming. These delta 18O values and interpretation are consistent with global composite stable isotope records and interpretations that document a warm period at the close of the late Eocene just before a dramatic short term global cooling in the early Oligocene. This cooling period lasted only a few hundred thousand years.;Orbital forcing of paleoclimate in the late Eocene is shown at high resolution by spectral analysis. Strong spectral peaks were found at intervals of 23.8 years and 19.2 years, which are very close to the Milankovitch precessional frequencies of 23ka and 19ka. Strong spectral peaks were also found at intervals of 23.4ka, and 18.7ka for the middle Eocene. The silica diagenesis found in the middle Eocene carbonates is thought to be the cause of the slight deviations in cyclicity. Precession within the late Eocene is also manifested by increases and decreases in planktonic foraminiferal productivity, measured directly by grain size analysis, and correlated to the oxygen isotope data.
机译：先前的研究已经证明，始新世晚期的全球气候以百万年的时间尺度冷却。但是，该冷却的确切细节和时间安排仍未解决。这项研究表明，始新世末年的百万年尺度的冷却趋势是由进动的米兰科维奇周期所打断的，而冷却趋势被最新始新世期间的暖脉动所打断。在新泽西州大陆边缘研究了晚始新世古气候，该海洋边缘是在海洋钻探计划第150条腿部期间从斜坡沉积物中回收的。使用了包括以下分析在内的多代理方法：（1）粒度，（2）整体矿物学，（3）岩石薄片，（4）浮游有孔虫Globigerina spp。，（5）地球物理FMS测井（地层显微扫描仪;测量电导率），（6）频谱分析，以及（7）与以前发表的工作的全球记录进行比较;;始新世中期到晚期的总体降温趋势表明硅质碎屑沉积增加，钙减少碳酸盐，晶粒尺寸粗化。这些岩性变化记录了伴随古气候冷却而从碳酸盐岩到硅质沉积的过渡，并且先前已记录了该边缘。从gloglogerina spp的测试获得的稳定的氧同位素也记录了始新世晚期以来全球冰量的增加。在40 ka分辨率下进行的低分辨率采样显示，在35.3 Ma至34.25 Ma之间的1,050,000年中，delta18O值从-3.67 / mil增加到-2.83 / mil。在34.75 Ma至34.25 Ma的时间间隔内，每5 ka进行一次高分辨率采样，其delta18O值范围为-3.0 / mil，被解释为变暖。这些δ18O值和解释与全球复合稳定同位素记录和解释一致，这些记录和解释记录了始新世末期正好在渐新世早期发生全球短期剧烈冷却之前的暖期。该冷却期仅持续了几十万年。通过光谱分析以高分辨率显示了始新世晚期古气候的轨道强迫。在23.8年和19.2年之间发现了很强的光谱峰，这与米兰科维奇进动频率23ka和19ka非常接近。在中始新世也以23.4ka和18.7ka的间隔发现了强光谱峰。在中新世碳酸盐中发现的二氧化硅成岩作用被认为是循环性略有偏差的原因。始新世晚期的进动还表现为浮游有孔虫生产力的增加和减少，直接通过粒度分析测量，并与氧同位素数据相关。

著录项

  • 作者

    Applebaum, Robert H.;

  • 作者单位

    City University of New York.;

  • 授予单位 City University of New York.;
  • 学科 Geology.;Physical Oceanography.;Paleontology.
  • 学位 Ph.D.
  • 年度 2008
  • 页码 155 p.
  • 总页数 155
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;海洋物理学;古生物学;
  • 关键词

  • 入库时间 2022-08-17 11:39:11

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