SUBDUCTION-INDUCED FRAGMENTATION OF THE NAZCA PLATE OFF PERU - MENDANA FRACTURE-ZONE AND TRUJILLO TROUGH REVISITED

The Mendana Fracture Zone and the Trujillo Trough are two major intra-oceanic features on the Nazca Plate off Peru. During the SEAPERC cruise of the R/V Jean Charcot in 1986, Sea Beam bathymetric data, single-channel seismic records, geomagnetic and gravity measurements, and heat flow data have been obtained over these two areas. In this paper, we confirm that the Mendana Fracture Zone is actively opening perpendicular to its trend, resulting in the formation of new oceanic crust since about 3.5Ma. We calculate that this new rift is propagating westward along the fracture zone at a velocity of about 10cm yr-1 (or 2cm yr-1 with respect to the trench). This extensional feature appears to be genetically linked with the Trujillo Trough, located 200km to the north. This trough is bounded to the east by a left-lateral transpressive fault which became active probably at the time when the Mendana Rift started. We then discuss a possible mechanism to explain the origin of these two areas of intraoceanic deformation. -Authors