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

大约1.46亿至6600万年前的白垩纪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“一切照常”预测的2100年的水平相似。发射场景。白垩纪地层记录了高海平面、被认为反映轨道强迫气候振荡的显著旋回沉积、高生物生产力、大规模火成岩活动以及海洋缺氧事件（oae）期间碳循环的重大扰动的证据。了解这些现象及其对海洋碳库进出通量的影响，可以为未来可能的温室情景提供深时间的类似物和丰富的背景。然而，我们对这些深时间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率。该项目包括通过对火山灰床进行新的放射性同位素定年，结合化学剖面和沉积物序列时间序列分析，对白垩纪时间尺度进行全面重新校准，旨在检测地球的影响。S轨道和太阳能收支对浅海沉积物的影响。这将为下一次地质时间尺度的迭代白垩纪提供坚实的基础，并有助于解决一些悬而未决的问题。此外，40Ar/39Ar和U-Pb放射性同位素计时器的相互校准——基于一套常见的含硅和含锆石的火山灰样本——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界的一个主要目标。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关系。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，我们努力提高白垩纪岩石的4-D理解与这些能源资源具有高度的社会相关性。为了提高公众的认识，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180万游客，是世界上最经典的白垩纪地层暴露之一，包括塞诺曼尼亚-土鲁尼亚全球边界层型剖面和点（GSSP）。我们将与公园和普韦布洛县的学生以及丹佛美国地质勘探局的科学家合作，设计和安装标志，突出地质年龄测定的科学和GSSP的重要性。

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.