New conodont δ18O records of Silurian climate change: Implications for environmental and biological events
New conodont δ18O records of Silurian climate change: Implications for environmental and biological events
复制标题
DOI：
10.1016/j.palaeo.2015.11.011
复制
发表时间：
2016-02
期刊：
影响因子：
--
通讯作者：
J. Trotter;I. Williams;C. Barnes;P. Männik;A. Simpson
中科院分区：
文献类型：
--
作者：
J. Trotter;I. Williams;C. Barnes;P. Männik;A. Simpson
根据牙形石δ 18 O组成（δ 18 Ophos），确定了志留纪气候的近连续、高度动态的记录，代表了四个古大陆的地层剖面。在晚奥陶世-早志留世冰期之后，许多小尺度气候循环表现出总体变暖趋势，直到Llandovery中期（Telychian早期-中期），然后逐渐冷却到Llandovery晚期。两个主要的，多步骤的冷却过渡相似的幅度和持续时间（+ 2‰的约1.5百万年内从发病到高峰期）发生在Llandover早期温洛克和温洛克晚期，前者在一个长期的冷却间隔（约1百万年）达到顶峰。这些温洛克δ 18 Ophosexcursions与Ireviken和Mulde生物和碳同位素（δ 13 C）事件密切相关。快速，大，但短暂的变化反映了气候不稳定的中期卢德洛，之前和期间的劳生物事件。主要的δ 18 O_3记录来自劳伦西亚和波罗的海，它们显示出大部分一致和同步的旋回，尽管在兰多维利和温洛克温暖的间隔中有轻微的偏移。这些偏移很可能反映了这些大陆相对古地理位置的差异，以及冰川-间冰期气候模式重大转变所驱动的海洋动力学变化。许多正δ 18 O_（18）最大值与整个志留纪的海平面低水位以及笔石动物群更替有关。δ 18 O_（18）的一阶正向大位移、全球δ 13 C_（13）C
A near-continuous, highly dynamic record of Silurian climate has been determined from conodont δ18O compositions (δ18Ophos), representing stratigraphic sections from four palaeocontinents. Following the late Ordovician–early Silurian glaciation, numerous small-scale climate cycles show an overall warming trend until the mid Llandovery (early-mid Telychian), then gradual cooling through the late Llandovery. Two major, multi-step cooling transitions of similar magnitude and duration (+ 2‰ within ~ 1.5 Myrs from onset to peak) occurred during the late Llandovery–early Wenlock and late Wenlock, the former culminating in a prolonged cool interval (~ 1 Myr). These Wenlock δ18Ophosexcursions coincided closely with the Ireviken and Mulde biotic and carbon isotope (δ13C) events. Rapid, large, but short-lived shifts reflect climate instability within the mid Ludlow, prior to and during the Lau bio-event. The prime δ18Ophosrecords are from Laurentia and Baltica, which show mostly consistent and synchronous cycles, albeit slightly offset for much of the Llandovery and warmer intervals of the Wenlock. These offsets most likely reflect differences in the relative palaeogeographic positions of these continents, and changes in ocean dynamics driven by major shifts in glacial–interglacial climate modes. Many of the positive δ18Ophosmaxima correlate with sea level lowstands, as well as graptolite faunal turnover throughout the Silurian. Strong correlations between the large, first-order, positive δ18Ophosshifts, increases in global δ13Ccarb, and the major Silurian bio-events (Ireviken, Mulde, Lau) imply that global climate change played an important role in producing these phenomena.