Determination of Intensity of Earth's Magnetic Field During the Cretaceous and Tertiary Using Dated Chinese Basalts

过去对地球磁场强度的测量对于理解地核中产生地球磁场的过程，以及地球磁场如何和为什么极性反转至关重要。此外，地球磁场强度在地质时期内的变化可能表明下地幔对流状态对地核中发电机作用的调制，因此也可以携带有关海底扩张速度、热点火山活动和地球构造周期的信息。PIs提出了目前有争议的两个重要地球物理问题的研究：(1)获取中白垩世古强度（91 Ma），以检验白垩世超时期地磁场强度的问题，特别是在低反转率时期地磁场强度是持续低还是异常高；(2)测定7 Ma和32 Ma古玄武岩的古强度，以检验在30 ~ 80 Ma之间世界大部分海洋中观测到的相对较高幅度的海洋磁异常是否与磁场强度有关。＊＊＊

9706439 Zhao Measurements of the intensity of the Earth's magnetic field in the past are critical for understanding the processes in the core that give rise to the Earth's magnetic field, and how and why the Earth's magnetic field reverses polarity. In addition, variation of the intensity of the Earth's magnetic field over geologic time may signal modulation of dynamo action in the core by the convective state of the lower mantle, and thus could also carry information about the rates of sea-floor spreading, hot-spot volcanism and Earth's tectonic cycle. The PIs propose studies of two important geophysical problems which are currently debated: (1) to obtain mid-Cretaceous paleointensities (91 Ma) to examine the question of intensity of the geomagnetic field during the Cretaceous Superchron, in particular whether the field was persistently low or unusually high during times of low reversal rate; (2) to determine the paleointensity from 7 Ma and 32 Ma old basalts to test whether the field strength is responsible for the relatively higher amplitude of marine magnetic anomalies that is observed in most of the world's oceans between 30 and 80 Ma. ***