Ash layers in deep‐sea sediments as tracers of arc volcanic activity: Japan and Central America as case studies

Arc volcanic activity on opposite sides of the Pacific Ocean (Japan and Central America) has been investigated by examining the number of volcanic ash layers recorded in Neogene and Quaternary deep‐sea sediments. The data suggest that ash layers counted in deep‐sea sediments may provide a reliable record of arc volcanism. The study is based on a quantitative analysis of arc volcanic activity using cores collected on DSDP (Deep‐Sea Drilling Project) and ODP (Ocean Drilling Program) legs. Five distinct parameters which might affect ash distribution in marine sediments were reviewed: nature of the eruption, wind influence, settling conditions, diagenesis, and plate motion. Of these five, past atmospheric circulation was the most significant. The main constraint on the analysis is that temporal scattering of ash is not directly related to wind pattern variations. Results of this analysis are correlated with dating of terrestrial volcanic sequences. Although marine tephra records for individual regions reveal minor differences in the episodes of volcanic activity, a general correlation exists between activity of arc volcanism in Japan and in Central America. Two important pulses of arc volcanism occurred during Middle Miocene times (18–13 Ma) and Plio‐Quaternary times (5–0 Ma). These episodes of intense volcanism are separated by a well recorded quiescent period during Late Miocene times. These correlating episodes of the volcanic record indicate a direct link between arc volcanism and the global tectonic evolution of the Pacific ocean margins.