Geophysical Reconnaissance Survey for ODP Leg 117 in the Northwest Indian Ocean

Abstract

Cruise 2704 of the Robert D. Conrad (RC2704) in the spring of 1986 acquired reconnaissance data necessary for the location and interpretation of ODP Leg 117 drill sites. In addition, three regions were examined in detail using underway geophysical techniques, and geologic and hydrologic samples were collected while on station. These regions include (1) a channel/levee complex of the Indus Fan, (2) the western flank of Owen Ridge, and (3) the southeastern margin of Oman. This report represents preliminary analysis of the underway geophysical data. The first of the three surveys adds to the growing knowledge of meandering channels recently discovered in other deep-sea fans. Tied to DSDP Site 224, the Owen Ridge survey documents the age and nature of uplift of the ridge. Speculations concerning the age of Owen Basin, integrated with survey data offshore Oman and published reports of onshore geology, provide a new hypothesis concerning the multiphase tectonic history of the northwest Indian Ocean.