[1] 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.

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The gi ant pis ton core MD01-2387 taken from the east ern Celebes Sea ba sin pro vides a ma rine tephrostratigraphy with high res o lu tion for in fer ring ex plo sive vol ca nism in the area sur round ing the ba sin for the past 350 kyr. The se quence con tains 65 tephra lay ers com posed of vol ca nic min er als and glassy par ti cles. The compositional char ac ter is tics of crys tal en riched tephra lay ers and the 87 Sr/ 86 Sr of the glass par ti cles (0.7039 to 0.7042) sug gest that these ashes were re leased by the vol ca noes in the Mindanao-Molucca Sea col li sion zone, in clud ing the south Phil ip pine Arc sys tem, the Sangehi Arc and the Halmahera Arc. The up ward de crease of tephra lay ers in this core in di cates a de clin ing trend of ex plo sive vol ca nic ac tiv ity of this col li sion zone, par tic u larly, af ter ca. 180 ka in the late Mid dle Pleis to cene. This re cord also sug gests that the shoshonitic vol ca nism in Cen tral Mindanao be came ex tinct at ca. 151 ka, which is much younger than what reported previously by onland investigations.