Site U1337

Abstract

Integrated Ocean Drilling Program (IODP) Site U1337 (3°50.009?N, 123°12.352?W; 4463 meters below sea level [mbsl]; PEAT-7C site survey) (Fig. F1; Table T1) was sited in order to collect an early middle Miocene segment of the Pacific Equatorial Age Transect (PEAT) equatorial megasplice and is on ~24 Ma crust between the Galapagos and Clipperton Fracture Zones, ~390 km southeast of Site U1335.

Site U1337 is on a plateau between high topography to the south of the site, a gentle but pockmarked ridge to the north, and a deep to the east (Fig. F1). Sediment cover is thick on the plateau (300–600 ms two-way traveltime [TWT]; ~200–500 m) (Fig. F2) but highly variable along the edges. Nevertheless, the seafloor is relatively flat because the sediment has filled in the basement topography, with a relief of ~200 ms TWT. To the north, along seismic Line 6, the seafloor is dissected by a series of karstlike holes that cut through the seismic layering (Fig. F1). Based on correlation to the central equatorial Pacific seismic stratigraphy of Mayer et al. (1985), middle Miocene sediment has been exposed. Site U1337 is now north of the equatorial high-productivity zone but should have been within ±2° of the Equator between 8 and 24 Ma. The north–south grain of abyssal hill topography in the vicinity of Site U1337 is typically covered by 300–500 ms TWT of sediment (~250–400 m) but is often interrupted by areas of significant erosion, as in the east of the PEAT-7 survey area (Fig. F1).

Based on stage-pole reconstructions of Pacific plate motion and observations of basement age from previous drilling sites, an aeromagnetic line south of the proposed site (Horner-Johnson and Gordon, 2003), and magnetic anomaly maps (Cande et al., 1989), we estimate that Site U1337 is on 24 Ma crust. The best control on age is information from Deep Sea Drilling Project (DSDP) Site 79, ~180 km (1.6°) east and 1.3° south of Site U1337, apparently on the same ridge segment. The base of Site 79 reaches the Miocene/Oligocene boundary, or 23 Ma on the PEAT timescale.

More information

Identifiers

Catalogue record

Export record

Altmetrics