Collaborative Research: Testing Hypotheses of Global Warming during Three Major Mass Extinctions

合作研究：检验三次大规模灭绝期间全球变暖的假设

• 批准号: 0643394
• 负责人: John Eiler
• 金额: $ 24.21万
• 依托单位: California Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-03-15 至 2010-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0643394&HistoricalAwards=false
• 关键词: Collaborative; Research; Testing; Hypotheses; Global; Collaborative; Research; Testing; Hypotheses; Global

Mass extinctions are geologically brief episodes during which a large fraction of extant species became extinct, and have profound consequences for the biosphere, environment and global geochemical cycles. Impact of a large body with the earth is recognized as the singular or dominant cause of the best understood mass extinction at the end of the Cretaceous, and impacts generally are widely suspected of driving mass extinctions deeper in the geological record. Alternatively, mass extinctions might be consequences of endogenous changes in earth's environment, including build-up of atmospheric greenhouse gases and/or volcanic aerosols, variations in atmospheric oxygen content, or biospheric production of toxic sulfide compounds. These hypothesized 'kill mechanisms' differ from one another in the predicted timing, magnitude and distribution of surface and ocean temperature change. Therefore, high-resolution temperature records could discriminate among these competing hypotheses, and potentially expand the depth of our understanding of changes in the earth's surface that accompanied these seminal events.We propose to examine the temperature history of the atmosphere and surface ocean through three major mass-extinction events using a new geothermometric technique based on 'clumping' of 13C and 18O into bonds with each other in the carbonate mineral lattice. Our goal is to obtain the first quantitative (about 2 degrees C) and time-resolved records of growth temperatures of continental soil carbonates and shallow marine carbonate fossils across the Permian/Triassic and Triassic/Jurassic boundaries, and, for comparison, a record across the better-understood Cretaceous/Paleogene boundary. Given the prominence of climate change in hypothesized causes of mass extinctions and the dearth of quantitative paleothermometry at these key times, we believe these data could lead to a breakthrough in our understanding of the causes of mass extinctions.The key to our approach is that the new carbonate clumped-isotope thermometer we will use is based on a homogeneous equilibrium (a reaction involving components of a single phase) and so can rigorously constrain temperature without any information about the isotopic composition of water from which carbonate grew. Because we can use this thermometer to independently constrain temperature, we will also be able to interpret the deltaO18 values of paleosol carbonates and marine fossils as proxies for the deltaO18 of meteoric and ocean waters from which they grew (i.e., because we will be able to 'tease apart' the carbonate-water fractionation at an independently known temperature). In the case of soil carbonates, we will further supplement our thermometric data by estimating pCO2 of the atmosphere based on deltaC13 measurements.This research is a collaborative effort between Caltech and the University of Washington. Broader impacts of this project are that it will support one Ph.D student and three summer research fellowships for undergraduate students at Caltech. Eiler will also use this grant to help support high school student summer internships. We anticipate that this study will provide a model for a new and widely applicable approach to reconstructing past climates through combined 'clumped isotope' thermometry and conventional stable isotope studies, and thus will contribute to the development of instruments and methods for geochemistry. Finally, our results will speak to the relationship between climate change and extinction, and thus has relevance for predicting the possible consequences of modern global warming.

大规模灭绝是地质上的简短发作，在此过程中，很大一部分现存的物种已灭绝，并对生物圈，环境和全球地球化学周期产生了深远的影响。大物体在地球上的影响被认为是白垩纪结束时最能理解的质量灭绝的奇异或主要原因，并且通常被广泛怀疑在地质记录中更深入地驱动质量灭绝。另外，质量灭绝可能是地球环境中内源性变化的后果，包括大气温室气体和/或火山气溶胶的积聚，大气氧含量的变化或有毒硫化物化合物的生物圈产生。这些假设的“杀戮机制”在表面和海洋温度变化的预测时间，大小和分布中彼此不同。 Therefore, high-resolution temperature records could discriminate among these competing hypotheses, and potentially expand the depth of our understanding of changes in the earth's surface that accompanied these seminal events.We propose to examine the temperature history of the atmosphere and surface ocean through three major mass-extinction events using a new geothermometric technique based on 'clumping' of 13C and 18O into bonds with each other in the carbonate mineral lattice.我们的目标是获得第一个定量（约2度C）和大陆土壤碳酸盐和浅海碳酸盐化石的生长温度的时间分辨记录，跨二叠纪/三叠纪和三叠纪/侏罗纪边界，以及相比，在整个杂货不出的清真寺/古凝剂边界中的记录。鉴于在这些关键时期，气候变化在大规模灭绝的原因和量化淡淡温度学的匮乏中的突出性，我们认为这些数据可能会导致我们对大规模灭绝原因的理解的突破。我们方法的关键是，我们将基于新的碳酸盐 - 基于一个新的碳酸盐，我们将基于一个单一的综合习惯（一种反应的综合），因此是一种反应式的综合量限制温度，没有任何有关碳酸盐生长的水的同位素组成的信息。因为我们可以使用该温度计来独立限制温度，所以我们还将能够解释古氧碳酸盐和海洋化石的三o18值作为陨石和海水的三角洲的代理，它们从中得以生长（即，因为我们将能够以独立的碳酸盐水平为独立的碳酸盐水条，因此我们将能够将其淡化。就土壤碳酸盐而言，我们将通过基于Deltac13测量的大气估算大气的PCO2来进一步补充我们的温度数据。这项研究是Caltech与华盛顿大学之间的协作努力。该项目的更广泛的影响是，它将为加州理工学院的本科生提供一位博士学位和三项夏季研究奖学金。艾勒还将使用这笔赠款来帮助支持高中生的暑期实习。我们预计，这项研究将为一种新的且广泛的方法提供模型，以通过组合的“集结同位素”热法和常规稳定同位素研究来重建过去的气候，因此将有助于地球化学工具和方法的发展。最后，我们的结果将讲述气候变化与灭绝之间的关系，因此与预测现代全球变暖的可能后果具有相关性。