Collaborative Research: A New Generation, User-Friendly Time Scale for the Cretaceous Period

合作研究：新一代、用户友好的白垩纪时间尺度

• 批准号: 0318584
• 负责人: Timothy Bralower
• 金额: --
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-01-01 至 2007-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0318584&HistoricalAwards=false
• 关键词: Collaborative; Research; New; Generation; User

To attempt to constrain the future effects of global warming, geologists are increasingly focussing studies on periods of warm climate in the rock record. One of most representative intervals of such warm, "greenhouse" climate occurred in the Cretaceous Period from 140 to 65 million years before present. Recent investigations of Cretaceous climate have shown rapid swings that seem to have occurred over millennia or less. These changes had dramatic effects on evolution. One of the major problems facing geologists in constraining the exact environmental effects of these warming events is that they took place over periods an order of magnitude shorter than that resolvable using traditional techniques to date rocks. Thus we cannot determine the rates of important processes such as evolution nor can we constrain the fluxes of materials such as CO2 between reservoirs. This collaborative, multidisciplinary project involving the University of North Carolina at Chapel Hill, Brown University and consulting scientists at other universities seeks to improve the precision and accuracy of the Cretaceous time scale by: (1) compiling time scales based on the fossil record (biostratigraphy) of microscopic marine organisms (foraminifera and nannoplankton) with higher resolution than previously attainable; (2) refining the calibration between time scales based on biostratigraphy, reversals in the Earth's geomagnetic polarity, and fluctuations in the Earth's orbit that are all recorded in rocks, (3) improving the correlation between biostratigraphy and recently acquired radiometric age dates; (4) calibrating large portions of the Cretaceous time scale to elapsed time using the orbital time scale, and (5) correlating and scaling the different stratigraphic elements in a logical fashion. We also propose to publish this time scale and associated data in a user-friendly format so that all geologists can estimate ages of samples with the minimum of error. To do this we will make the time scale available to the geologic community on the world wide web as downloadable Excel files. Combined with the biostratigraphic work that will be conducted in well-known rock exposures from the deep sea and land areas, these Excel files will include macros that calculate the ages of samples from their depths. Thus all a geochemist, for example, needs to do to plot data is to download the file and input the depth of samples. All of our data will also be archived on the web providing a ready means of future revision. The new generation time scale proposed will provide improved precision and resolution that will enable geologists to study abrupt changes in the Cretaceous Earth. Moreover, the mode of communication of the time scale will improve accuracy in diverse geologic applications.

为了控制全球变暖对未来的影响，地质学家越来越多地把研究重点放在岩石记录中气候温暖的时期。这种温暖的“温室”气候最具代表性的时期之一发生在距今1.4亿至6500万年前的白垩纪。最近对白垩纪气候的研究表明，这种快速波动似乎发生在几千年或更短的时间内。这些变化对进化产生了巨大的影响。地质学家在确定这些变暖事件对环境的确切影响时面临的一个主要问题是，它们发生的时间比用传统技术测定岩石年代的时间短了一个数量级。因此，我们无法确定演化等重要过程的速率，也无法限制储存库之间二氧化碳等物质的通量。这个多学科合作项目涉及北卡罗来纳大学教堂山分校、布朗大学和其他大学的咨询科学家，旨在通过以下方式提高白垩纪时间尺度的精度和准确性：(1)根据微观海洋生物（有孔虫和纳米浮游生物）的化石记录（生物地层学）编制时间尺度，分辨率比以前更高；(2)改进了基于岩石记录的生物地层学、地磁极性反转和地球轨道波动的时间尺度之间的校准；(3)改进了生物地层学与最近获得的放射性年龄数据之间的相关性；(4)利用轨道时间尺度将白垩纪的大部分时间尺度校准为经过的时间；(5)以逻辑方式将不同的地层元素进行关联和标度。我们还建议以用户友好的格式发布此时间尺度和相关数据，以便所有地质学家都可以以最小的误差估计样品的年龄。为了做到这一点，我们将把时间尺度作为可下载的Excel文件在万维网上提供给地质社区。结合生物地层学工作，将在深海和陆地区域的著名岩石暴露中进行，这些Excel文件将包括计算深度样品年龄的宏。因此，举例来说，地球化学家绘制数据所需要做的就是下载文件并输入样本的深度。我们所有的数据也将在网上存档，为将来的修订提供一个现成的手段。提出的新一代时间尺度将提供更高的精度和分辨率，使地质学家能够研究白垩纪地球的突变。此外，时间尺度的通信方式将提高在不同地质应用中的精度。