Browsing by Author "Song, Sheng-Rong"

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A 2 Ma record of explosive volcanism in southwestern Luzon: Implications for the timing of subducted slab steepening
(2009-06-25)
Ku, Yueh-Ping
;
Chen, Chang-Hwa
;
Song, Sheng-Rong
;
Iizuka, Yoshiyuki
;
Shen, Jason Jiun-San
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.
Late Quaternary Explosive Volcanic Activities of the Mindanao-Molucca Sea Collision Zone in the Western Pacific as Inferred from Marine Tephrostratigraphy in the Celebes Sea
(2009-08-01)
Ku, Yueh-Ping
;
Chen, Chang-Hwa
;
Song, Sheng-Rong
;
Iizuka, Yoshiyuki
;
Shen, Jason Jiun-San
The giant piston core MD01-2387 taken from the eastern Celebes Sea basin provides a marine tephrostratigraphy with high resolution for inferring explosive volcanism in the area surrounding the basin for the past 350 kyr. The sequence contains 65 tephra layers composed of volcanic minerals and glassy particles. The compositional characteristics of crystal enriched tephra layers and the (87)Sr/(86)Sr of the glass particles (0.7039 to 0.7042) suggest that these ashes were released by the volcanoes in the Mindanao-Molucca Sea collision zone, including the south Philippine Arc system, the Sangehi Arc and the Halmahera Arc. The upward decrease of tephra. layers in this core indicates a declining trend of explosive volcanic activity of this collision zone, particularly, after ca. 180 ka in the late Middle Pleistocene. This record also suggests that the shoshonitic volcanism in Central Mindanao became extinct at ca. 151 ka, which is much younger than what reported previously by onland investigations.