Positioning the North China Block (NCB) in the Cambrian: Constraints From the Integrated Bio‐, Chemo‐ and Magnetostratigraphy

Abstract The Paleozoic paleogeographic and tectonic evolution of the North China Block (NCB) are poorly constrained due to the polarity ambiguity of its early Paleozoic paleopoles. Here we present magnetostratigraphic results of two upper Cambrian limestone‐dominated marine successions in the NCB that span the Steptoean positive carbon isotope excursion (SPICE), a global carbon‐cycle perturbation concomitant with trilobite extinctions. Stepwise thermal demagnetization reveals three‐component magnetizations with the high‐temperature component being a primary remanence as substantiated with paleomagnetic and rock magnetic analysis. A composite polarity sequence across the SPICE is established for the NCB and is correlated with coeval polarity sequence of Siberia, allowing to assign a reversed polarity for the NCB during the SPICE. This inter‐continental correlation, together with paleobiogeographic affinities, supports a southern hemispheric low‐latitude location adjacent to the west of East Gondwana for the NCB during the late Cambrian, thus constraining further paleogeographic‐tectonic reconstructions around East Gondwana during the Paleozoic.