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Cretaceous Intensity of Earth's Magnetic Field from Thellier Analyses of Single Plagioclase Crystals

通过泰利尔对单个斜长石晶体的分析得出的白垩纪地球磁场强度

基本信息

批准号：
0003393
负责人：
John Tarduno
金额：
$ 21.98万
依托单位：
University of Rochester
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2001
资助国家：
美国
起止时间：
2001-01-01 至 2003-06-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=0003393&HistoricalAwards=false
关键词：
Cretaceous Intensity Earth Magnetic Field

项目摘要

Tarduno EAR-0003393 Theoretical considerations and modeling results suggest a relationship between geomagnetic field intensity and polarity reversal rate. No clear relationship, however, is apparent in available paleointensity data. The investigators address this issue using a new paleointensity measurement approach that uses analyses of single plagioclase crystals. These crystals, which contain magnetic inclusions that retain paleofield values, are less susceptible to alteration during paleointensity experiments than some whole rock samples. Results from Thellier-Thellier experiments on plagioclase crystals separated from basalts that formed during the Cretaceous Normal Polarity Superchron (Rajmahal Traps) suggest a time-averaged paleomagnetic dipole moment three times that thought to have typified times of frequent geomagnetic reversals in the Cenozoic and early Cretaceous/late Jurassic. This result leads to their hypothesis that there is a correlation between times of low reversal frequency and high geomagnetic field strength. They propose to test this hypothesis through a study of high- and low-latitude mid-Cretaceous flood basalt sites. These rocks will allow the investigators to examine the spatial (latitudinal) and temporal variation of geomagnetic field intensity during the Cretaceous Normal Polarity Superchron.

理论考虑和建模结果表明地磁场强度和极性反转率之间存在关系。然而，在现有的古强度数据中，没有明显的关系。研究人员使用一种新的古强度测量方法来解决这个问题，该方法使用单个斜长石晶体的分析。这些晶体，其中包含磁性包裹体，保留古磁场值，是不太容易改变在古强度实验比一些完整的岩石样品。Thellier-Thellier对从白垩纪正极性超时（Rajmahal Traps）形成的玄武岩中分离出的斜长石晶体进行的实验结果表明，时间平均古地磁偶极矩为三倍，被认为是新生代和早白垩世/晚侏罗世频繁地磁反转的典型时间。这一结果导致了他们的假设，即低反转频率和高地磁场强度之间存在相关性。他们建议通过研究高纬度和低纬度的白垩纪中期泛滥玄武岩遗址来验证这一假设。这些岩石将使研究人员能够研究白垩纪正极性超时期间地磁场强度的空间（纬度）和时间变化。