Anomalous Topography in the Parece Vela Basin

Abstract

We present results of high-resolution bathymetric studies of the extinct Parece Vela Basin backarc spreading center in the northwestern Pacific, where we have identified an anomalous, extremely large mullion structure, here termed giant megamullion. We find that the giant megamullion is nearly ten times larger than the similar structures in the slow-spreading Mid-Atlantic Ridge (megamullions.) An off-axis rugged "chaotic terrain" was also identified in the Parece Vela Basin. We propose that amagmatic tectonics producing the giant megamullion and the chaotic te1～ rain occupied a significant part in crustal construction in the Parece Vela Basin evolution.