Collaborative Research: Integrating Radioisotopic and Astronomical Time Scales for the Cretaceous

合作研究：整合白垩纪的放射性同位素和天文时间尺度

• 批准号: 0958905
• 负责人: Bradley Sageman
• 金额: $ 8.11万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-05-01 至 2014-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0958905&HistoricalAwards=false
• 关键词: Collaborative; Research; Integrating; Radioisotopic; Astronomical

The Cretaceous period, between about 146 and 66 million years ago, was a time of sustained global warming during which atmospheric CO2 levels likely surpassed 800 part per million, similar to the amount predicted for 2100 by ?business-as-usual? emission scenarios. Cretaceous strata record evidence of high sea level, remarkably cyclic sedimentation thought to reflect orbitally-forced climate oscillation, high biological productivity, large scale igneous activity, and major perturbations of the carbon cycle during ocean anoxic events (OAEs). Understanding these phenomena, and their influence on fluxes into and out of the marine carbon reservoir, can provide deep-time analogues and a rich context for possible greenhouse scenarios of the future. However, a major limitation on our understanding of these deep-time analogues is the lack of accurate chronologies for assessing timing and rates of climatic and oceanic change. This project comprises a complete re-calibration of the Cretaceous time scale via new radioisotopic dating of volcanic ash beds integrated with chemical profiling and time-series analysis of sediment sequences aimed at detecting the influence of earth?s orbit and solar energy budget on sediment deposited in a shallow ocean setting. This will provide a solid foundation for the Cretaceous in the next iteration of the geologic time scale and should help resolve a number of outstanding problems. Moreover, the intercalibration of the 40Ar/39Ar and U-Pb radioisotopic chronometers - based on a common set of sanidine and zircon-bearing volcanic ash samples - will provide geologic tests of these decay systems, thereby addressing a primary goal of the NSF-sponsored EARTHTIME initiative and the entire geochronology community. This project will support two graduate student theses at UW-Madison and forge collaborations with active research groups in Europe, Canada and the US. Because Cretaceous strata also supply most of the global petroleum and natural gas reserves, our efforts to improve the 4-D understanding of Cretaceous rocks has high societal relevance with respect to these energy resources. To raise public awareness we have developed an outreach plan with staff of Lake Pueblo State Park, CO, which had 1.8 million visitors in 2008 and is home to one of the world's most classic exposures of Cretaceous strata, including the Cenomanian-Turonian Global Boundary Stratotype Section and Point (GSSP). Working in collaboration with the Park and Pueblo County school kids, as well as scientists at the USGS in Denver, we will design and install signs that highlight the science of geologic age determination and significance of the GSSP.

白垩纪时期，大约距今 146 至 6600 万年前，是全球持续变暖的时期，在此期间，大气中的二氧化碳含量可能超过百万分之 800，与“一切照旧”预测的 2100 年含量相似。排放情景。白垩纪地层记录了高海平面、被认为反映了轨道强迫气候振荡的显着循环沉积、高生物生产力、大规模火成岩活动以及海洋缺氧事件（OAE）期间碳循环的主要扰动的证据。了解这些现象及其对进出海洋碳库通量的影响，可以为未来可能的温室情景提供深度类比和丰富的背景。然而，我们对这些深时类比的理解的一个主要限制是缺乏准确的年表来评估气候和海洋变化的时间和速率。该项目包括通过火山灰床的新放射性同位素测年，结合沉积物序列的化学剖面和时间序列分析，对白垩纪时间尺度进行彻底的重新校准，旨在检测地球轨道和太阳能收支对浅海环境中沉积物的影响。这将为下一次地质时间尺度迭代中的白垩纪提供坚实的基础，并有助于解决一些突出问题。此外，40Ar/39Ar 和 U-Pb 放射性同位素计时仪的相互校准（基于一组通用的含石英和锆石的火山灰样品）将为这些衰变系统提供地质测试，从而实现 NSF 赞助的 EARTHTIME 计划和整个地质年代学界的主要目标。该项目将支持威斯康星大学麦迪逊分校的两篇研究生论文，并与欧洲、加拿大和美国的活跃研究小组建立合作。由于白垩纪地层还供应全球大部分石油和天然气储量，因此我们提高对白垩纪岩石 4 维认识的努力与这些能源资源具有高度的社会相关性。为了提高公众意识，我们与科罗拉多州普韦布洛湖州立公园的工作人员制定了一项外展计划，该公园 2008 年接待了 180 万名游客，是世界上最经典的白垩纪地层暴露地之一，其中包括塞诺曼阶-土兰阶全球边界层型剖面和点 (GSSP)。我们将与帕克县和普韦布洛县的学生以及丹佛美国地质调查局的科学家合作，设计和安装标志，突出地质年龄测定的科学性和 GSSP 的重要性。