Enhanced Terrestrial Weathering in the North American Interior across the Paleocene/Eocene Boundary

古新世/始新世边界北美内陆陆地风化增强

• 批准号: 0518437
• 负责人: D Kelly
• 金额: --
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2009-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0518437&HistoricalAwards=false
• 关键词: Enhanced; Terrestrial; Weathering; North; American

It is important to understand the past responses of earth's terrestrial geochemical reservoirs to atmospheric perturbations in order to predict future impacts on the existing environment. The "initial Eocene thermal maximum" (IETM, ca. 55 Ma) was a short-lived (~100 - 200 kyr) global warming event driven by a sudden increase in greenhouse gases similar in temporal scale to present-day anthropogenic influxes. This influx was postulated to have been due to a massive release of methane from marine gas hydrates. The subsequent increased levels of atmospheric greenhouse gases [carbon dioxide (CO2) and methane (CH4)] had a worldwide impact on the earth's surficial processes and functional partitioning of biogeochemical cycles. Marine records of the IETM clearly document the isotopic and mineralogic shifts triggered by this perturbation, while the response on subaerially exposed landmasses is not as well understood. Of particular interest is the transient character of this climatic overshoot, which reflects the presence of negative feedbacks (accelerated weathering reactions) that stabilized climate by reducing atmospheric levels of greenhouse gases. We propose to study the influence of this climatic warming on sedimentation patterns and weathering rates within the remarkably fine-textured sedimentary members of the Williston Basin (WB) in western North Dakota. These units contain well preserved, multi-proxy information (i.e., palynomorph/ macrofloral fossils, authigenic minerals and paleopedogenic features, well-preserved organic materials) that lends itself well to temporal and spatial cross-correlation. This study poses the hypothesis that the fine resolution stratigraphic package in the WB records a sympathetic terrestrial signal/response to the release of isotopically-light marine methane hydrate and subsequent global warming. To investigate this hypothesis, we will use 1) whole sediment composition, 2) semi-quantitative clay mineralogy, and 3) stable isotope geochemistry to ascertain alterations and rates in sedimentary process and sub-aerial weathering intensity in response to the warmer global climate hypothesized to have prevailed during the IETM. Our preliminary investigations provide evidence indicating that a record of the IETM is preserved within the WB and that there is a definitive shift in sediment geochemistry across this boundary. This integrated record can be tied to well-documented IETM records in neighboring contemporaneous interior basins (e.g., Bighorn Basin of Wyoming) and will augment our understanding of mid-latitude sub-continental response to rapid climate change.Broader Impacts: It is important to compare the reality of a well-preserved multi-proxystratigraphic record to thermodynamic models of biogeochemical fluxes and estimated physical reconstructions from an interdisciplinary aspect. The linkage of our records to those preserved in the Big Horn Basin will build a stronger understanding of sub-continental land mass responses to rapid global warming. The principle investigators will utilize the information to strengthen fledgling research programs in paleoenvironmental reconstruction and paleopedology. This study will be a mechanism for graduate/ undergraduate students to develop research projects. Once investigative work has yielded a comprehensive data set, a colloquium field trip class will be conducted, with participants conducting weekly discussions in preparation for a two-week field excursion through the Western Interior Basin (WIB) province (Williston, Powder River, Bighorn, Wasatch, and Green River Basins). This will provide students an opportunity to view and synthesize sub-continental scale information. Manuscripts from this project will be published in recognized interdisciplinary earth science journals and a linked website devoted to the WIB with specific focus on the work encompassed by this study will be constructed for access by the academic community. Finally, results of this proposed research will be incorporated into a public outreach program at the University of Wisconsin Geology Museum.

重要的是要了解地球陆地地球化学储层对大气扰动的过去反应，以预测未来对现有环境的影响。 “初始始新世热最大”（IETM，加利福尼亚州55 Ma）是一个短暂的（〜100-200 kyr）的全球变暖事件，这是由于颞尺度与当今人为流入相似的温室气体突然增加而驱动的。据推测，这种涌入是由于海洋气体水合物大量释放了甲烷。随后的大气温室气体[二氧化碳（CO2）和甲烷（CH4）]的水平增加对地球的表面过程和生物地球化学周期的功能分配产生了影响。 IETM的海洋记录清楚地记录了这种扰动引起的同位素和矿物质学转变，而对亚大赛暴露的地体的反应尚未充分了解。特别令人感兴趣的是这种气候过大的瞬态特征，这反映了负面反馈（加速风化反应）的存在，这些反馈通过降低大气的温室气体水平来稳定气候。我们建议研究这种气候变暖对北达科他州威利斯顿盆地（WB）质地非常细的沉积成员内的沉积模式和风化速率的影响。这些单元包含保存完好的多种信息信息（即palynomorph/ palynomorph/大型化石，身份元素矿物质和古生物学特征，保存完好的有机材料），它们非常适合时间和空间交叉相关。这项研究提出了以下假设：WB中的细分辨率地层套件记录了同位光闪光海洋甲烷水合物的释放以及随后的全球变暖。为了研究这一假设，我们将使用1）整个沉积物组成，2）半定量粘土矿物学和3）3）稳定的同位素地球化学来确定沉积过程的改变和速率，以及响应于在IETM期间盛行的温暖的全球气候，以响应较温暖的全球气候。我们的初步调查提供了证据，表明IETM的记录保留在WB内，并且在该边界之间的沉积物地球化学发生了明显的转变。这种综合记录可以与据据例的IETM记录相关联（例如，怀俄明州的大角盆），将增强我们对中纬度次陆次陆战响应的理解，对快速气候变化的反应。BROADER的影响：比较良好的多型型和多型模型的现实是，鲍尔德式和传播的模型非常重要跨学科方面的估计物理重建。我们的记录与保存在大喇叭盆地中的记录的联系将使人们对次大陆土地质量对快速全球变暖的反应有更深入的了解。原则研究人员将利用这些信息来加强古环境重建和古生物学中的刚起步研究计划。这项研究将是研究生/本科生开发研究项目的机制。一旦调查工作产生了全面的数据集，将进行座谈会的野外旅行类别，参与者每周进行讨论，以准备通过西部内部盆地（WIB）省（Williston，Powderon，Powder River，Bighorn，Bighorn，Wasatch和Green River盆地）进行为期两周的野外游览。这将为学生提供查看和综合次生尺度信息的机会。该项目的手稿将发表在公认的跨学科地球科学期刊上，并链接到专门针对WIB的网站，具体关注这项研究所包含的工作，将由学术界的访问构建。最后，这项拟议的研究的结果将纳入威斯康星大学地质博物馆的公共外展计划中。