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

本项目将研究晚白垩世北大西洋中深水团的环流与有机碳埋藏和温室海洋环流的关系。晚白垩纪是过去2.5亿年里最温暖的时期，也是全球碳循环受到最大扰动的时期。我们的试点数据（鱼残骸中的epsilon-Nd和d18O值）表明，在整个晚白垩世，除了区域到全球的碳埋藏事件，特别是海洋缺氧事件2和中cenomanian事件，在热带北大西洋西部存在一个单独的、独特的、本地来源的中间水团。在这些间隔期间，ε - nd发生了剧烈的变化，这表明底层水的混合增强了。1)低纬度水域下沉作为背景条件，2)全球有机碳埋藏时期更强烈的深层环流，这些证据的结合与温室海洋和海洋缺氧事件的主要模式预测相矛盾。该项目将使用Ocean Drilling Program/Deep Sea Drilling Program的岩心，对来自不同地点的年代久远的样本进行分析，以检验这些发现的普遍性。通过绘制中间水域和深水水域的分布图作为位置、深度和时间的函数，我们既可以限制深水在温室气候演变中的重要性，又可以提供海洋-大气气候模型可以比较的经验结果。该项目涉及州立大学之间的一种新的伙伴关系，并包括一些在地球科学领域代表性不足的团体的关键参与者。

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.