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Cyclostratigraphy and eccentricity tuning of the early Oligocene through early Miocene (30.1–17.1Ma): Cibicides mundulus stable oxygen and carbon isotope records from Walvis Ridge Site 1264

机译:早渐新世到早中新世的旋回地层和偏心调整(30.1-17.1ma):来自Walvis Ridge site 1264的Cibicides mundulus稳定的氧和碳同位素记录

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摘要

Few astronomically calibrated high-resolution (?5 kyr) climate records exist that span the Oligocene–Miocene time interval. Notably, available proxy records show responses varying in amplitude at frequencies related to astronomical forcing, and the main pacemakers of global change on astronomical time-scales remain debated. Here we present newly generated X-ray fluorescence core scanning and benthic foraminiferal stable oxygen and carbon isotope records from Ocean Drilling Program Site 1264 (Walvis Ridge, southeastern Atlantic Ocean). Complemented by data from nearby Site 1265, the Site 1264 benthic stable isotope records span a continuous ?13-Myr interval of the Oligo-Miocene (30.1–17.1 Ma) at high resolution (?3.0 kyr). Spectral analyses in the stratigraphic depth domain indicate that the largest amplitude variability of all proxy records is associated with periods of ?3.4 m?3.4 m and ?0.9 m?0.9 m, which correspond to 405- and ?110-kyr eccentricity, using a magnetobiostratigraphic age model. Maxima in CaCO3 content, ?18O and ?13C are interpreted to coincide with ?110 kyr eccentricity minima. The strong expression of these cycles in combination with the weakness of the precession- and obliquity-related signals allow construction of an astronomical age model that is solely based on tuning the CaCO3 content to the nominal (La2011_ecc3L) eccentricity solution. Very long-period eccentricity maxima (?2.4-Myr) are marked by recurrent episodes of high-amplitude ?110-kyr ?18O cycles at Walvis Ridge, indicating greater sensitivity of the climate/cryosphere system to short eccentricity modulation of climatic precession. In contrast, the responses of the global (high-latitude) climate system, cryosphere, and carbon cycle to the 405-kyr cycle, as expressed in benthic ?18O and especially ?13C signals, are more pronounced during ?2.4-Myr minima. The relationship between the recurrent episodes of high-amplitude ?110-kyr ?18O cycles and the ?1.2-Myr amplitude modulation of obliquity is not consistent through the Oligo-Miocene. Identification of these recurrent episodes at Walvis Ridge, and their pacing by the ?2.4-Myr eccentricity cycle, revises the current understanding of the main climate events of the Oligo-Miocene.
机译:很少有经过天文学校准的高分辨率(约5千吉尔)气候记录跨越渐新世-中新世时间间隔。值得注意的是,可用的代理记录显示,在与天文强迫有关的频率上,幅度的变化是不同的,而关于天文时标的全球变化的主要起搏器仍存在争议。在这里,我们从海洋钻探计划站点1264(东南大西洋的沃尔维斯里奇)提供了最新生成的X射线荧光岩心扫描和底栖有孔虫的稳定氧和碳同位素记录。补充来自附近1265站点的数据,Site 1264底栖稳定同位素记录以高分辨率(约3.0千瓦)跨越Oligo-中新世(30.1-17.1 Ma)的连续≤13毫米间隔。地层深度域中的频谱分析表明,所有代理记录的最大振幅变化都与?3.4 m?3.4 m和?0.9 m?0.9 m的周期相关联,分别对应于405和110 kyr偏心率。磁地层年龄模型。 CaCO3含量的最大值,?18O和?13C被解释为与?110 kyr偏心率最小值一致。这些周期的强表达与进动和与倾角相关的信号的弱点相结合,可以构建仅基于将CaCO3含量调整为标称(La2011_ecc3L)偏心率解决方案的天文年龄模型。沃尔维斯山脊的高振幅φ110-kyrφ18O周期反复发作,标志着很长周期的偏心最大值(φ2.4-Myr),表明气候/冰冻圈系统对气候旋进的短偏心率调制更敏感。相反,全球(高纬度)气候系统,冰冻圈和碳循环对405-kyr循环的响应(以底栖的18O信号,尤其是13C信号表示)在最小的2.4Myr期间更为明显。通过Oligo-中新世,高振幅φ110-kyrφ18O周期的反复发作与倾角的φ1.2-Myr振幅调制之间的关系不一致。对沃尔维斯山脊这些反复发作的识别,以及它们在?2.4-Myr偏心周期中的起搏,改变了目前对Oligo-中新世主要气候事件的认识。

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