An Astronomically-tuned High Resolution Benthic Isotope Stratigraphy for the Late Paleocene and Early Eocene

天文调谐的古新世晚期和始新世早期高分辨率底栖同位素地层学

• 批准号: 0959117
• 负责人: James Zachos
• 金额: $ 18万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-15 至 2013-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0959117&HistoricalAwards=false
• 关键词: Astronomically; tuned; Resolution; Benthic; Isotope

TOWARD AN ASTRONOMICALLY-TUNED HIGH-RESOLUTION BENTHIC ISOTOPE STRATIGRAPHY FOR THE PALEOCENE AND EARLY EOCENEJAMES ZACHOS, UNIVERSITY OF CALIFORNIA, SANTA CRUZEAR-0959117ABSTRACTThe late Paleocene to early Eocene (~58 to 52 Mya) represents one of the most climatically dynamic periods of Earth?s past. It is characterized by a gradual long warming trend that culminates in the warmest conditions of the last 90 m.y., the Early Eocene Climatic Optimum. Recent investigations, however, have found that the long-term warming trend was punctuated by several short-lived (transient) warming events (tens of thousands of years in duration), referred to as hyperthermals or Eocene thermal maxima. These events, which include the extreme Paleocene-Eocene Thermal Maximum (PETM, ~56 Mya), are thought to have a common origin, possibly involving orbital forcing amplified by carbon cycle feedbacks. Other proposed driving mechanisms, particularly for the PETM, include volcanic outgassing and/or the decomposition of marine methane hydrates. To assess whether the PETM and other thermal maxima were triggered by orbital or other forcing, we intend to establish the temporal relationship of these events to the long-term background variability (i.e., periodicity) in climate and the cabon cycle. To this end, utilizing a deep sea core recovered from the south Atlantic, we will construct the first high-resolution, astronomically-tuned benthic foraminiferal stable carbon and oxygen isotope time series for a ~5-6 m.y. segment of the upper Paleocene-lower Eocene. These and other records will allow us to establish the relative timing and phasing of the thermal maxima to excursions in the carbon cycle, thus providing constraints for quantitatively evaluating the nature of climate ? carbon cycle coupling during periods of warming. In addition to this application, the astronomically-tuned isotope time-series will serve as a standard isotope reference section by which all other Paleocene and early Eocene deep-sea sequences can be compared. In this capacity, it will be possible to use the carbon isotopes to correlate and calibrate segments of marine sedimentary sections to our tuned record, thereby significantly improving the accuracy of age models. This will facilitate transfer of the astronomical calibrations to sections with exceptional magnetostratigraphy, and thus the geomagnetic polarity time-scale.

古新世晚期至始新世早期（~58 ~ 52亿a）是地球气候变化最活跃的时期之一。年代的过去。它的特点是一个逐渐变暖的长期趋势，在最后90万年的最温暖条件下达到顶峰，即始新世早期气候最佳。然而，最近的研究发现，长期的变暖趋势被几个短暂的（短暂的）变暖事件（持续数万年）所打断，这些事件被称为超热事件或始新世热最大值。这些事件，包括古新世-始新世极热期（PETM， ~56亿a），被认为有一个共同的起源，可能与碳循环反馈放大的轨道强迫有关。其他提出的驱动机制，特别是对于PETM，包括火山脱气和/或海洋甲烷水合物的分解。为了评估PETM和其他热极大期是否由轨道或其他强迫触发，我们打算建立这些事件与气候和碳循环的长期背景变率（即周期性）的时间关系。为此，我们将利用从南大西洋回收的深海岩心，构建首个高分辨率、天文调谐的上古新世-下始新世~5-6 m.段的底栖有孔虫稳定碳氧同位素时间序列。这些和其他记录将使我们能够确定热最大值与碳循环偏移的相对时间和阶段，从而为定量评估气候的性质提供约束条件。变暖期间的碳循环耦合。除此之外，天文校正的同位素时间序列将作为标准同位素参考剖面，用于比较所有其他古新世和早始新世深海序列。在这种情况下，将有可能使用碳同位素将海洋沉积剖面与我们的调谐记录相关联和校准，从而显著提高年龄模型的准确性。这将有助于将天文校准转移到具有特殊磁地层学的部分，从而转移到地磁极性时间尺度。