RUI: Paleomagnetic Phase of a Collaborative Study to Spatially and Temporally Delineate the Matuyama-Brunhes Polarity Reversal as Recorded in Tahitian Lava Flows

[805065]现有的放射性年龄测定和以前对大溪地熔岩的古地磁调查表明，大约78万年前，当地球磁场经历最后一次极性变化时，大溪地的大部分地区正在经历火山活动——松山反极性纪年的结束。P.I.建议继续对岛上适当地点记录的过渡场行为进行全面的古地磁研究。特别是，计划包括扩大塔希提岛北部的Chemin des 1000源末端的过渡磁化熔岩厚序列的采样，该部分已经提供了极性转变期间磁场变化的非常详细的记录。在瑞士日内瓦大学，将对这些玄武岩熔岩进行精确的40Ar-39Ar年龄测定，最终目标是在绝对时间内跟踪地球流体外核中发生的磁场逆转过程。

9805065HoffmanAvailable radiometric age determinations and previous paleomagnetic investigations on Tahitian lavas indicate that much of the island was experiencing volcanic activity some 780,000 years ago while Earth's magnetic field was undergoing its last change of polarity--the termination of the Matuyama reverse polarity chron. The P.I. proposes to continue a comprehensive paleomagnetic study of the recorded transitional field behavior at appropriate localities on the island. In particular, plans include extending sampling of the thick sequence of transitionally-magnetized lavas at the end of the Chemin des 1000 Sources in northern Tahiti, a section that has already provided a highly-detailed record of magnetic field changes well within the polarity transition. Precise 40Ar-39Ar age determinations will be conducted on these basaltic lavas at the Universityof Geneva, Switzerland, with the ultimate goal of following in absolute time the process of field reversal as it developed in Earth's fluid outer core.