A 2 Ma record of explosive volcanism in southwestern Luzon: Implications for the timing of subducted slab steepening

Abstract

New chemical and isotopic analyses of the tephra layers plus deep-sea tephrostratigraphic record from two cores from either side of Luzon Island (Philippines) have allowed the identification of two periods of explosive volcanic activity originating from the Macolod Corridor in the southwestern part of the Luzon. The first period extended from prior to 1355 ka to 1977 ka, and the second period extended from 478 ka to the present, separated by a period of relative quiescence. The time intervals between large explosive eruption events in each period were 31 +/- 15 ka and 156 +/- 52 ka, respectively. Combined with published chronological and geochemical data from onshore volcanic deposits, the tephrostratigraphic record shows that the locus of large explosive eruptions has migrated southwestward from the northeastern section to the middle and southwestern sections of the Macolod Corridor. The period of relative quiescence is characterized by monogenetic volcanism in the central section of the corridor. The migration of active volcanism across the southwestern part of Luzon during the Quaternary is used to infer the evolution of the subducting South China Sea crust. The period of relative quiescence represents a period of adjustment of the subducted slab by steepening, which began around 1355 ka or shortly thereafter and finished at around 478 ka.