Oligocene climate dynamics towards the Oligocene-Miocene transition (IODP Expedition 342, North Atlantic)

渐新世-中新世过渡期的气候动态（IODP 342 号探险队，北大西洋）

• 批准号: 242360900
• 负责人: Privatdozent Dr. André Bornemann
• 金额: --
• 依托单位: Bundesanstalt für Geowissenschaften und Rohstoffe (BGR)
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2013
• 资助国家: 德国
• 起止时间: 2012-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/242360900?language=en
• 关键词: Oligocene; climate; dynamics; towards; Miocene

The Oligocene represents an early stage of the icehouse world that commenced after the formation of a permanent east Antarctic ice sheet ~34 Million years ago (Oi-1 glaciation). This interval is characterized by a high variability in the d18O of deep-sea benthic foraminifera and high-amplitude sea-level fluctuations probably related to southern hemisphere ice sheet instability. This variability culminates in a second major glaciation event during the earliest Miocene ~23 Million ago (Mi-1 event). Due to the scarcity of high-quality data sets across this time interval, however, the overall evolution and especially the mechanisms involved on long and short time scales (orbital to suborbital) are speculative and a matter of debate. During IODP Expedition 342 expanded sequences covering the Oligocene to early Miocene transition have been drilled at J-Anomaly Ridge off Newfoundland. These sediments contain exceptionally well-preserved calcareous microfossils and are characterized by high sedimentation rates allowing for the generation of a high-resolution proxy-record on precessional to suborbital time scales. This project aims at providing a 1.8-ky-resolution benthic foraminiferal stable isotope record covering the upper Oligocene to early Miocene (~26.5-21.7 Ma), corresponding to the second phase of Oligocene ice sheet growth on Antarctica. So far, high-resolution data sets from this time interval are rare and limited to the central Pacific and southern hemisphere. Thus, the sediments recovered off Newfoundland have a high-potential not only to provide a very high-resolution proxy data set, but also a North Atlantic view of this crucial interval of Earth s climate evolution. Since an enormous amount of geochemical analyses (approx. 3000 samples) are necessary to accomplish the goal of this project, the effort will be carried out in an international consortium including Expedition 342 participants from Germany (this proposal), the UK and South Korea. The time interval focused on in this proposal is the upper Oligocene part (~25.7 to 24 Ma) of the ~4.8 Ma long record. In addition, pristinely preserved, glassy planktic foraminiferal tests will be studied at a resolution of 20 kys to unravel the long-term climate evolution across the Mi-1 glaciation event. To achieve this goal, absolute sea-surface and thermocline temperatures will be estimated, using a dual-proxy approach (d18O, Mg/Ca). This will allow the reconstruction of North Atlantic surface ocean response to the Mi-1 event and how it was influenced by global climate dynamics.

渐新世代表了冰库世界的早期阶段，在大约3400万年前南极东部永久冰盖形成后开始（Oi-1冰川作用）。这段时间的特点是深海底栖有孔虫的d18 O变化很大，海平面波动幅度很大，可能与南半球冰盖的不稳定有关。这种变化在最早的中新世~ 2300万年前（Mi-1事件）期间的第二次主要冰川事件中达到高潮。然而，由于缺乏这一时间间隔内的高质量数据集，总体演变情况，特别是长短时间尺度（轨道到亚轨道）上所涉及的机制是推测性的，是一个有争议的问题。在IODP考察期间，在纽芬兰附近的J-异常岭钻探了342个扩展序列，覆盖了渐新世到早中新世的过渡。这些沉积物含有保存异常完好的钙质微体化石，其特点是沉积速率高，可以在岁差到亚轨道时间尺度上生成高分辨率的代理记录。该项目的目标是提供一个1.8千年分辨率的底栖有孔虫稳定同位素记录，覆盖渐新世晚期至中新世早期（~26.5-21.7 Ma），对应于南极洲渐新世冰盖生长的第二阶段。到目前为止，这一时间间隔的高分辨率数据集非常罕见，仅限于太平洋中部和南半球。因此，纽芬兰附近海域的沉积物不仅有很大的潜力提供一个非常高分辨率的代用数据集，而且还可以提供北大西洋对地球气候演变这一关键时期的看法。由于进行了大量的地球化学分析（大约。3000个样本）是完成本项目目标所必需的，这项工作将在一个国际财团中进行，该财团包括来自德国（本提案）、英国和韩国的远征342参与者。本建议所关注的时间段是~ 4.8Ma长记录的渐新世上部（~25.7 ~ 24 Ma）。此外，将以20千公里的分辨率研究原始保存的玻璃质南极有孔虫试验，以揭示Mi-1冰川事件的长期气候演变。为实现这一目标，将使用双重代用指标方法（d18 O、Mg/Ca）估计绝对海面和温跃层温度。这将有助于重建北大西洋表层海洋对Mi-1事件的反应，以及它如何受到全球气候动态的影响。

项目成果

Data report: revised composite depth scale and splice for IODP Site U1406

数据报告：修订后的 IODP 站点 U1406 的复合深度尺度和拼接

• DOI: 10.2204/iodp.proc.342.202.2017
• 作者: T.E. van Peer;D. Liebrand;C. Xuan;P.C. Lippert;C. Agnini;N. Blum;P. Blum;S.M. Bohaty;P.R. Bown;R. Greenop;W.E.C. Kordesch;D. Leonhardt;O. Friedrich;P.A. Wilson
• 通讯作者: P.A. Wilson