Reappraisal of the Neoproterozoic to middle Paleozoic fossils of North Korea and its tectonic implication

The tectonic affinity of the Korean Peninsula in reference to the Permo-Triassic collision of the Sino-Korean Craton (SKC) and the South China Craton (SCC) has been in the center of debates over the last three decades. Since the Imjingang Belt that runs through the middle part of the Korean Peninsula is thought to represent the major tectonic boundary, most part of North Korea, including the "Pyeongnam Basin" in the southern part, has been regarded as part of the SKC. However, differences in stratigraphy and the fossil occurrence have been recognized by local geologists between the southern part of "the Pyeongnam Basin" (SPB) and the northern part of the "Pyeongnam Basin" (NPB), and which have hardly been considered for the paleogeographical affinity of the regions so far. Here we provide a comprehensive review on 1,072 fossil taxa from the Neoproterozoic to middle Paleozoic sedimentary successions of North Korea, and utilize the data for determining tectonic affinity of the regions. Especailly, Cambrian trilobite genera from the SPB and NPB have been quantitatively compared with those of North China (the SKC) and the SCC, using similarity indices, the non-metric multidimensional scaling (NMDS), and PerMANOVA test. The results have revealed that the SPB is tied to the SCC, not to North China (the SKC), whereas the NPB is closely related to North China. The SCC affinity of the SPB is corroborated by stratigraphical features, such as the presence of the Precambrian-Cambrian boundary and the middle Paleozoic strata, which are largely absent in the SKC. Our results demonstrate that the SPB region likely originated from to the SCC, and thus further suggest that the collisional boundary of supracrustal rocks between the SKC and the SCC in the Korean Peninsula corresponds to the boundary of the NPB and the SPB. Accordingly, the extent of the newly-defined Pyeongnam Basin is restricted to the traditional NPB region. The SPB region is included in the extent of the newly-proposed Hwanghae District, which is bounded to the east with the Imjingang Belt by the Ryesonggang Fault. The South China Craton-originated rocks of the Hwanghae District and the Imjingang Belt are collectively termed the South China-affinity terrane (SAT).