High Resolution Secular Variation in Oxygen, Carbon, Strontium Isotopic Composition

这项研究将记录许多同位素(18O、13C、87Sr/86Sr)和元素(Li/A1)示踪剂在泥盆纪-石炭纪的变化幅度、速率和相对时间。在地球历史上的这段时期，以海洋碳酸盐的18O和13C的急剧变化为标志，记录了要么全球表面温度急剧下降30-40度，要么海水的18O成分丰富。将对来自爱尔兰Dinant Synclum(比利时)-Waulsortian序列的Devono-石炭纪珊瑚礁序列和阿尔伯塔盆地的时间等效序列中的非生物海相碳酸盐进行化学示踪配对分析，以验证海洋18O组分的变化是由于海底扩张脊热液蚀变增强而导致18O通量增加的假设。分析~(87)Sr/~(86)Sr的变化有助于了解地幔与壳源的相对贡献；Li/Al比值将记录地幔玄武岩的高温、热液蚀变与低温海底风化的优势增强或减弱。这项研究的具体目标包括：(1)评估化学示踪剂之间在时间和大小上的相关性，以确定它们是否对常见的地质过程作出反应；(2)确定化学变化的经验时间常数，以限制元素通量流入大洋的大小；以及(3)基于经验关系的定量模拟，以评估大洋中脊玄武岩中海水循环在确定古海洋18O组分中的作用。

This research will document the magnitude, rates and relative timing of change among numerous isotopic (18O, 13C, 87Sr/86Sr) and elemental (Li/A1) tracers through the Devono-Carboniferous interval. This period in Earth's history, which is marked by a dramatic shift in 18O and 13C of marine carbonates records either a dramatic decrease in global surface temperature of 30-40 degree, or an enrichment in 18O composition of seawater. Paired analysis of chemical tracers will be performed on non-biological marine carbonates from Devono-Carboniferous reefal sequences of the Dinant Synclinorium (Belgium) - Waulsortian Sequence of Ireland and the time equivalent succession of the Alberta Basin to test the hypothesis that a shift in ocean 18O composition was caused by an increase in 18O flux associated with enhanced hydrothermal alteration at submarine spreading ridges. Analysis of 87Sr/86Sr variation will provide insight on relative contributions from mantle versus crustal sources; Li/Al ratios will record the increasing versus decreasing dominance of high temperature, hydrothermal alteration versus low temperature submarine weathering of mantle-derived basalts. Specific goals of the research include: (1) evaluation of correlations, in time and magnitude, of variation among chemical tracers to determine whether they are responding to a common geologic process; (2) determination of empirical time constants of change in chemistry to constrain the magnitude of elemental fluxes into an out of the ocean; and (3) quantitative modelling, based on empirical relationships, to assess the role of seawater cycling through mid- ocean ridge basalt in defining the 18O composition of the paleocean.