Decadal-Scale In Situ Scanning of a Stalagmite From Southwest China Reveals Blake Geomagnetic Excursion Structure

We present a decadal-scale paleomagnetic analysis of a stalagmite collected from Shuixi Cave, southwest China, spanning 89−123 ka. Our findings include: (a) Magnetite is the dominant magnetic mineral, and paleomagnetic directions can be obtained via demagnetization; (b) Magnetic scanning at 0.1-mm resolution captures key magnetic features, identifying eight reversed intervals; (c) The consistency between two measurements confirms the reliability of in situ magnetic scanning and shows that reversed intervals can be discerned from shifts in inclination and declination. Comparison with global geomagnetic records suggests that this interval consists of three major phases, namely the Blake, post-Blake, and Skalamaelifell, characterized by four, two, and two reversed intervals occurring at 108,810−119,090 years BP, 99,780−103,140 years BP, and 90,950−94,470 years BP, respectively. These decadal-resolution results illuminate the fine structure of the previously-proposed Blake interval and highlight the potential of high-resolution in situ magnetic scanning of precisely dated speleothems for resolving geomagnetic behavior.