Comparison of rare earth element compositions of proximal and distal tephra (B-Tm) from the Changbaishan Eruption at AD 946.

Abstract

The B-Tm tephra, erupted from Mount Baekdu (Changbaishan) in A.D. 946, is widely distributed across East Asia. It represents a key stratigraphic marker for tephrochronology and the reconstruction of late Holocene volcanic activity. In this study, glass shards were collected from proximal deposits near the source and from distal deposits in Aomori Prefecture, Japan. Rare earth element (REE) compositions were analyzed using inductively coupled plasma mass spectrometry (ICP-MS). The REE patterns of both proximal and dSistal samples show overall similarity, especially in light REEs, indicating their effectiveness for tephra correlation. Slight differences in middle to heavy REEs may reflect grain-size sorting during atmospheric transport or post-depositional alteration. These results suggest that REE compositions, being less susceptible to chemical weathering, provide a reliable geochemical proxy for identifying tephras across varying depositional environments.