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，约1.46亿至6600万年前，是一个持续的全球变暖的时间，在此期间，大气中的二氧化碳含量可能超过百万分之800，类似于2100年预测的数量。一切照旧吗排放情景。白垩纪地层记录了高海平面的证据、显着的周期性沉积作用，被认为反映了轨道强迫的气候振荡、高生物生产力、大规模的火成活动以及海洋缺氧事件（OAE）期间碳循环的重大扰动。了解这些现象及其对进出海洋碳库的通量的影响，可以为未来可能的温室效应情景提供深时模拟和丰富的背景。然而，我们对这些深时类似物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度。该项目包括一个完整的重新校准白垩纪的时间尺度，通过新的放射性同位素测年的火山灰床结合化学剖面和时间序列分析的沉积序列，旨在检测地球的影响？s轨道和太阳能收支对沉积在浅海环境的沉积物。这将为白垩纪在下一个地质年代的迭代提供一个坚实的基础，并应有助于解决一些悬而未决的问题。此外，40 Ar/39 Ar和U-Pb放射性同位素计时器的相互校准-基于一组常见的透长石和锆石火山灰样品-将提供这些衰变系统的地质测试，从而解决NSF赞助的EARTHTIME倡议和整个地质年代学社区的主要目标。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进行合作。由于白垩纪地层也提供了全球大部分的石油和天然气储量，我们努力提高对白垩纪岩石的4-D理解，这对这些能源资源具有很高的社会意义。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一起制定了一项推广计划，该公园在2008年有180万游客，是世界上最经典的白垩纪地层暴露之一，包括Cenomanian-Turonian全球边界层型剖面和点（GSSP）。与公园和普韦布洛县的学校的孩子们，以及科学家在美国地质调查局在丹佛合作，我们将设计和安装标志，突出地质年龄确定的科学和GSSP的意义。