Seafloor spreading in the Mariana trough: results of Leg 60 drill site selection surveys ( DSDP).

Abstract

A detailed geophysical and geological survey of the Mariana Trough, an actively extensional back-arc basin, was conducted in 1976 and 1977 to provide data for selection of drilling sites for DSDP Leg 60. These surveys revealed large-scale bathymetric trends, sediment distribution, crustal seismic veolocity structure, and earthquake activity that suggest the basin is opening around an axial spreading center tectonically similar to the slowly spreading Mid-Atlantic Ridge. There are, however, significant differences in the character of the trough, such as poorly defined magnetic anomalies, extreme bathymetric relief, and the frequent occurrence of low-magnitude earthquake but absence of larger seismic events. Seafloor spreading in the Mariana Trough may be characteristic of the initial opening stages of any oceanic rift system, whether or not it is in a back-arc setting.-Authors