Core recovery (%): 100.6Oldest sediment cored: Depth (mbsf): 278.60 Nature: nannofossil ooze with foraminifers Youngest age: Quaternary Oldest age: late Miocene Measured velocity (km/s): 1.61 Kroenke, L. W., Berger, W. H., Janecek, T. R., et al., 1991. Proc. ODP, Init. Repts., 130: College Station, TX (Ocean Drilling Program).Shipboard Scientific Party is as given in the list of participants preceding the contents. Principal results: Site 807 (proposed Site OJP-5A) is located on the northern rim of the Ontong Java Plateau (latitude 3 C 36.4'N, longitude 156 37.5'E) in 2805 m of water, roughly 475 km northwest of Deep Sea Drilling Project (DSDP) Sites 289/586. Site 807 was occupied with three major objectives: (1) to provide Paleogene and Cretaceous sediments for studies of pre-Neogene paleoceanography; (2) to obtain basement rock for studies of the origin of the Ontong Java Plateau; and (3) to provide a second shallow-water site, off the equator, for comparison with Sites 803 and 806 on the Neogene equatorial depth transect.
HOLE 807CDateThe site is located on a single-channel seismic (SCS) line acquired by the Thomas 'Washington during the EURYDICE Cruise 9 survey at 0255 UTC, 11 April 1975. The site was resurveyed on 26 January 1990 from 1117 to 1737 UTC and crossed again on 26 February during the approach to the site and before dropping the beacon. The beacon was dropped at 1608 UTC, 26 February 1990, in a location believed to be protected from bottom-current activity (i.e., within a shallow basement graben about 0.5 km from the footwall of the northern side of the graben).Three holes were drilled at Site 807 between 1608 UTC, 26 February 1990, and 1800 UTC, 23 March 1990. Hole 807A was cored with the advanced hydraulic piston corer (APC) and the extended core barrel (XCB) to 822.9 mbsf with 87.1% recovery (103.4% in the section cored with the APC [0-254.4 mbsf], and 79.8% in the section cored with the XCB [254.4-822.9 mbsf]). The hole was successfully logged and a good suite of geophysical measurements was obtained. Hole 807B was cored with the APC to 278.6 mbsf, at which point 120,000-lb. of overpull was encountered on Core 130-807B-30H, forcing abandonment of the hole. Average recovery was 100.6%.
SITE 807A reentry cone with about 58 m of 16.5-in. casing was set at Hole 807C and, after running in and cementing about 350 m of 11.75-in. casing, the hole was washed to 780.0 mbsf. Coring with the rotary core barrel (RCB) then began. Hole 807C was cored with the RCB to 1528.4 mbsf with 33.8% recovery. Hole 807C was also successfully logged to the total depth drilled, and a complete set of geophysical measurements, including formation microscanner (FMS) data, was obtained. Preliminary analyses of the shipboard data indicate that a complete, undisturbed record of the last 10 m.y. was recovered in the uppermost 280 m of sediment obtained from the two holes cored with the APC.The Neogene section is around 591 m thick, and recovery in the Neogene and upper Oligocene sediments cored with the APC and the XCB (APC, 10...