부산대학교 도서관

The Tonian supercontinent Rodinia is hypothesized to have included almost all Proterozoic continental blocks. Competing models variably place South China at the core or periphery of Rodinia or separated from it entirely. Tonian paleogeographic models also vary in whether they incorporate hypothesized large and rapid oscillatory true polar wander associated with the ca. 810–795 Ma Bitter Springs Stage. Here, we present paleomagnetic data paired with U-Pb chemical abrasion isotope dilution thermal ionization mass spectrometry zircon geochronology from the Tonian Xiajiang Group in South China to establish the craton's position and test the Bitter Springs Stage true polar wander hypothesis. Fine-grained siliciclastic sediments and ashes of the Xiajiang Group post-date the Jiangnan Orogeny, which united the Yangtze and Cathaysia blocks. A U-Pb zircon date of 815.73 ± 0.18 Ma from a tuff near the base of the Xiajiang Group constrains the Jiangnan Orogeny to have ended between ca. 830 and 816 Ma. The paleomagnetic and geochronologic data constrain South China to high latitudes ca. 813 Ma and indicate a relatively stable high-latitude position from ca. 821 to 805 Ma. These high-latitude constraints either connect the craton to Rodinia along its periphery or disconnect it from the supercontinent entirely. The difference in pole position between the pre-Bitter Springs Stage Xiajiang Group pole and the syn-Bitter Springs Stage Madiyi Formation pole is significantly less than that predicted for the Bitter Springs Stage true polar wander hypothesis. If this pole difference is interpreted as true polar wander superimposed upon differential plate motion, it requires South China to have been separate from Rodinia.