Petrology of igneous rocks from the seafloor of the Sulu and Celebes Sea

Results obtained during Leg 124 of Ocean Drilling Program substantiate new interpretations of the origin and evolution of these basins. In particular, it was discovered that both basins are floored by oceanic crust, but are quite different in age and initial evolution. The Sulu Sea was formed in late Early Miocene, about 19 Ma ago, at the same time as the cessation of the arc volcanism in the submerged Cagayan Ridge bounding the portion of Sulu Sea floored with oceanic crust, whereas the Celebes Sea was formed in Middle Eocene, about 43 Ma ago. The data obtained show that the Sulu seafloor and closely related Cagayan Ridge belong to a distinct tectono-magmatic system (arc-backarc developed in Early-Middle Miocene) with respect to the older Celebes Basin. The crust of the latter could have been generated both in mid-ocean ridge and back-arc settings. -from Authors