An Integrated Study of Paleointensity during Mesozoic and Tertiary using Dated Basalt, Submarine Basaltic Glass, and Single Plagioclase Crystals

利用定年玄武岩、海底玄武岩玻璃和单斜长石晶体对中生代和第三纪古强度进行综合研究

• 批准号: 0207389
• 负责人: Xixi Zhao
• 金额: $ 27.71万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-07-01 至 2005-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0207389&HistoricalAwards=false
• 关键词: Integrated; Study; Paleointensity; during; Mesozoic

ZhaoEAR-0207389The record of the intensity of Earth's magnetic field during the past (paleointensity) carries important information about the geodynamo and probably about the state of Earth's interior that is not contained in the record of paleodirection. Firm conclusions regarding long-term paleointensity variation and its role in mantle dynamics require averages of many more data than are currently available. For this reason, the investigators propose to carry out new determinations of Earth's field during Mesozoic and Tertiary time using dated rock materials from Siberia, Kazakhstan, China, the Faroe Islands, and Ontong Java and Kerguelen plateaus. The principal objectives of this study are focused on three important geophysical problems which are currently debated: (1) to obtain reliable paleointensities to test the hypothesis that there was an extended period of low field intensity in the Mesozoic and, if so, to better define its onset and termination; (2) to determine mid-Cretaceous paleointensities to test the recent suggestion that the field strength was unusually high during the Cretaceous Normal Superchron (CNS); and (3) to obtain mean paleointensity values during the Tertiary period of high reversal frequency for comparison with those for the mid-Cretaceous period of low reversal frequency to see whether there is a correlation between reversal rate and geomagnetic field strength. The rock units the investigators have targeted for sampling and those they currently have available have high potential of providing valuable paleointensity data to address these questions of fundamental importance in geophysics. The opportunity to compare paleointensity results from these different geologic materials is a strong secondary motivation for this research.

过去地球磁场强度的记录（古强度）包含了关于地球发电机的重要信息，可能还包含了古方向记录所不包含的关于地球内部状态的信息。关于长期古地震强度变化及其在地幔动力学中的作用的可靠结论需要比目前可用的更多数据的平均值。因此，研究人员建议利用西伯利亚、哈萨克斯坦、中国、法罗群岛、翁通爪哇和凯尔盖伦高原的年代岩石材料，对中生代和第三纪的地球磁场进行新的测定。本研究的主要目的是解决目前存在争议的三个重要地球物理问题：（1）获得可靠的古地震强度，以检验中生代存在一个长时间低场强的假设，并更好地确定其开始和结束的时间;（2）确定白垩纪中期的古地震强度，以验证最近提出的白垩纪正常超时（CNS）场强异常高的说法;（3）获得高反转频率的第三纪和低反转频率的白垩纪中期的平均古地磁强度值，并与之进行对比，探讨反转频率与地磁场强度之间是否存在相关性。研究人员取样的岩石单位和他们目前拥有的岩石单位具有很高的潜力，可以提供有价值的古强度数据，以解决这些在地球物理学中具有根本重要性的问题。比较这些不同地质材料的古强度结果的机会是这项研究的一个强大的次要动机。