Abstract

The western flank of the West Mariana Ridge and the distal Parece Vela Basin have been mapped for the first time using a modern multibeam echosounder. The new data reveal the Ridge to be composed of 82 volcanic peaks, of which 25 have summits with water depths of <1000 m and 11 have summits with depths of <500 m deep. Five of the volcanoes have summit craters, and two are guyots; the remaining 75 seamounts are peaked volcanoes. One volcanic peak has a summit water depth of 16 m, and two in the central region have summits as shoal as ∼7 m. The erosional character of the volcanoes suggests a younging toward the south. The western flank of the West Mariana Ridge is buried by a sediment apron that merges with the distal Parece Vela Basin. The sediment apron is incised by a series of canyon-channel systems that head on the upper flank or summit of the West Mariana Ridge and trend downslope to the west. Several of the channels are sediment filled with an incised thalweg, suggesting a multiphase evolution to the channel systems. None of the channels have a pelagic drape, whereas the seafloor adjacent to the channels does, suggesting recent activity. The lack of guyots, the apparent younging of the volcanoes to the south, and the youth of channel activity suggest the West Mariana Ridge may be either recently or is presently tectonically active with the evidence suggesting uplift.

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