High‐Resolution Tracking of Baltica's Northward Drift in the Ordovician

Abstract We investigated the paleogeography of Baltica via a paleomagnetic study of 471‐454 Ma limestones from the Siljan (Sweden) impact structure. Stepwise thermal demagnetization isolated a well‐defined magnetization component that unblocks up to the Curie temperature of magnetite and passes fold and reversal tests, indicative of a primary magnetization. Paleolatitude data show that Baltica experienced an initial stationary phase at approximately 55°S from 471 to 467 Ma, followed by a rapid northward drift (∼35 cm/yr) after 467 Ma. This motion slowed to ∼15 cm/yr at ∼463 Ma until 454 Ma when Baltica reached 33°S. A notable correlation was found between Baltica's latitude and the relative proportion of magnetite and hematite in the carbonates; they are relatively hematite rich at 55°S and magnetite rich by 33°S. Our results provide a high‐precision model how Baltica moved in the Ordovician with potential environmental implications regarding the oxidation state of the ocean at that time.