Tracking Atmospheric and Vegetation Change Across Cenomanian-Turonian Oceanic Anoxic Event II

追踪塞诺曼阶-土伦阶海洋缺氧事件 II 期间的大气和植被变化

• 批准号: 0643290
• 负责人: Bradley Sageman
• 金额: $ 18.14万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0643290&HistoricalAwards=false
• 关键词: Tracking; Atmospheric; Vegetation; Change; Across

This award supports a multidisciplinary paleobotanical and biogeochemical study that will link marine and terrestrial records of a Mesozoic ocean anoxic event (OAE). These geologically brief (600-800 kyr) episodes of enhanced organic carbon burial took place mainly during a time of peak greenhouse warming in the Cretaceous. It has been suggested that some of them caused perturbations in the carbon cycle large enough to impact atmospheric CO2 at levels comparable to, or greater than glacial scale oscillations. Yet the history of atmospheric CO2 before, during, and after an OAE has never been directly evaluated using a terrestrial pCO2 proxy. This project will investigate the links between changes in the biogeochemical cycling of carbon, regional climatic change, and regional scale changes in plant biodiversity and ecology associated with the Cenomanian-Turonian (C-T, +-94 Ma) OAE II in the Western Interior basin of North America. Three main interrelated hypotheses will be tested: (1) was enhanced marine organic carbon production, burial, and preservation during OAE II initiated as a feedback of the marine system to increased concentrations of atmospheric carbon dioxide for a period of time before onset of the event? (2) Did enhanced marine carbon burial and preservation, as indicated by a significant positive isotopic excursion in marine carbonate and organic carbon, result in a draw down of atmospheric carbon dioxide? and (3) Did fluctuations in atmospheric CO2 before and during OAE II cause global climatic shifts which, in turn, resulted in landscape scale shifts in the dominance/diversity structure of terrestrial plant communities? Did these changes play any role in the rise of the angiosperms? These hypotheses will be tested by examining the rate and magnitude of change in atmospheric paleo-pCO2 (using the stomatal index-pCO2 proxy) and regional mean annual temperature (using leaf margin analysis) on dispersed plant cuticle and macrofloras respectively, collected mainly from marginal marine sections of the Dakota and Straight Cliffs Formations of southwestern Utah. Timing the changes in pCO2 and temperature relative to marine carbon burial will be possible due to detailed correlation of the terrestrial sections to the C-T stratotype in offshore marine facies of Colorado, where a high resolution temporal framework has been established. An online archive of modern cuticle morphotypes developed as part of this project will be used to distinguish dispersed fossil cuticles throughout the C-T interval. Paleoecological analyses of the dispersed cuticle record will be used to track regional vegetation dynamics in response to CO2 and climatic fluctuations throughout the C-T interval. The broader impacts of the project include scientific contributions to basic research on a subject of great societal relevance (understanding relationships between carbon cycle events and climate change), training of future geoscientists, and dissemination of results through innovative teaching initiatives. Two key innovations that distinguish the project are a contribution to geoinformatics via development of an online digital database for cuticle and macrofloral material, and a substantive effort to engage under-represented groups in geoscience through weekend enrichment classes (called Project Excite).

该奖项支持多学科的古植物学和地球化学研究，将海洋和陆地记录的中生代海洋缺氧事件（OAE）。 这些地质上短暂（600-800 kyr）的有机碳埋藏增强事件主要发生在白垩纪温室效应达到峰值期间。 有人认为，其中一些对碳循环造成的扰动大到足以影响大气中的二氧化碳，其水平相当于或大于冰川尺度振荡。 然而，大气CO2的历史之前，期间和之后的OAE从来没有直接评估使用陆地pCO 2代理。 该项目将调查与北美西部内陆盆地Cenomanian-Turonian（C-T，+-94 Ma）OAE II相关的碳的地球化学循环变化、区域气候变化和植物生物多样性和生态学的区域尺度变化之间的联系。 三个主要的相互关联的假设将进行测试：（1）是加强海洋有机碳的生产，埋葬，并在OAE II开始作为一个反馈的海洋系统，以增加大气中的二氧化碳浓度的一段时间之前的事件？(2)海洋碳酸盐和有机碳同位素显著的正偏移表明，海洋碳埋藏和保存的加强是否导致大气二氧化碳的减少？（3）OAE II前后大气CO2浓度的变化是否导致全球气候变化，进而导致陆地植物群落优势度/多样性结构的景观尺度变化？ 这些变化对被子植物的兴起有什么作用吗？ 这些假设将通过检查的速度和幅度的变化，在大气中的古二氧化碳分压（使用气孔指数pCO 2代理）和区域平均年温度（使用叶缘分析）分散的植物角质层和macroflora分别，主要是从边缘的海洋部分的达科他州和直崖形成的西南部犹他州。 由于陆地剖面与科罗拉多近海海相C-T层型的详细相关性，相对于海洋碳埋藏的pCO 2和温度变化的时间将是可能的，其中已经建立了高分辨率的时间框架。 作为该项目的一部分，开发的现代角质层形态类型的在线档案将用于区分整个C-T间隔的分散化石角质层。 分散角质层记录的古生态分析将用于跟踪区域植被动态响应CO2和整个C-T间隔的气候波动。 该项目的更广泛影响包括对具有重大社会意义的主题（了解碳循环事件与气候变化之间的关系）的基础研究作出科学贡献，培训未来的地球科学家，并通过创新的教学举措传播成果。 区分该项目的两个关键创新是通过开发角质层和macrofloral材料的在线数字数据库对地理信息学的贡献，以及通过周末丰富课程（称为Project Excite）参与地球科学中代表性不足的群体的实质性努力。