Collaborative Research: Tracking North Atlantic Water Column Structure and Circulation Through the Late Cretaceous Using Oxygen and Neodymium Isotopes in Fish Debris

该项目将研究晚白垩世北大西洋中深层水团的环流与有机碳埋藏和温室海洋环流的关系。晚白垩世包含了过去2.5亿年来全球碳循环最温暖的条件和最大的扰动。我们的试点数据(鱼类残渣中的epsilon-ND和d18O值)表明，在整个晚白垩世，除了区域到全球碳埋藏事件，特别是海洋缺氧事件2和新生代中期事件之外，热带西北大西洋存在一个单独的、局部来源的中间水团。在这些时间间隔内，epsilon-ND发生了戏剧性的变化，这表明底水混合作用增强。1)低纬度水域下沉为背景条件，2)在全球埋藏有机碳期间更活跃的深层循环的证据相结合，与关于温室海洋和海洋缺氧事件的主要范式的预测相矛盾。该项目将利用大洋钻探方案/深海钻探方案岩心对来自不同地点的定年样品进行分析，以检验这些发现的一般性。通过绘制作为位置、深度和时间函数的中水和深水的分布，我们将约束深水在温室气候演变中的重要性，并提供可与海洋-大气气候模型进行比较的经验结果。该项目涉及州立大学之间的新伙伴关系，并包括关键参与者，他们是地球科学中代表性不足的团体的成员。

This project will investigate circulation of intermediate and deep water masses in the Late Cretaceous North Atlantic relative to organic carbon burial and greenhouse ocean circulation. The Late Cretaceous includes the warmest conditions and the largest perturbations to global carbon cycle of the past 250 million years. Our pilot data (epsilon-Nd and d18O values in fish debris) suggest a separate and distinct, locally-sourced intermediate water mass was present in the tropical western North Atlantic throughout the Late Cretaceous except during regional to global carbon burial events, specifically, ocean anoxic event 2 and the mid-Cenomanian event. During these intervals there are dramatic shifts in epsilon-Nd that suggest enhanced bottom water mixing. The combination of evidence for 1) sinking of waters at low latitudes as a background condition and 2) more vigorous deep circulation during times of global burial of organic carbon contradict predictions of leading paradigms regarding both greenhouse oceans and ocean anoxic events. This project will test the generality of these findings through analyses of well-dated samples from a variety of sites using Ocean Drilling Program/Deep Sea Drilling Program cores. By mapping the distribution of intermediate and deep water waters as a function of position, depth, and time we will both constrain the importance of deep water in the evolution of greenhouse climates and provide empirical results against which ocean-atmosphere climate models can be compared. The project involves a new partnership between state universities and includes key participants who are members of groups underrepresented in the Earth Sciences.