Site 806

Abstract

Principal results: Ocean Drilling Program (ODP) Site 806 (proposed Site OJP-1) is located on the northeastern margin of the Ontong Java Plateau, close to the equator (latitude 0°19.1'N, longitude 159°21.7'E) in 2520 m of water, roughly 125 km northeast of Deep Sea Drilling Project (DSDP) Sites 289/586. The site represents the shallow end member on a transect that was designed to detect depthrelated paleoceanographic signals in Neogene sediments. We occupied this site with the objective to obtain a high-resolution carbonate record in an undisturbed setting, which could serve as a standard section for studies of ocean history, including biostratigraphy, chemostratigraphy, and acoustic stratigraphy. Site 806 was positioned at the proposed location (OJP-1), on a 2-km-wide terrace interrupting a gentle incline sloping to the northeast. We used a single-channel-seismic (SCS) line acquired by the Thomas Washington during ROUNDABOUT Cruise 11 (0600 UTC, 21 December 1989). The seismic profile shows a full set of reflectors, comparable with those at Sites 289/586, with little or no disturbance.Three holes were drilled, using the advanced hydraulic piston corer (APC) and the extended core barrel (XCB), with full recovery with the APC. Hole 806A, a dedicated hole, was cored with the APC to 83.7 mbsf into upper Pliocene sediments. Hole 806B was cored with the APC to 320 mbsf, at which point refusal occurred within the lower upper Miocene. The hole was continued with XCB coring to 743.1 mbsf, with 423.1 m of sediment cored and 331.2 m recovered (78%). Coring ended in the lowermost Miocene because of poor recovery. The hole was then logged. Hole 806C was cored with the APC to 309.6 mbsf and coring with the XCB was then begun. The aim was to core with the XCB to the lower middle Miocene a second time, and then drill ahead to search for the Oligocene/Miocene boundary. The attempt was successful. Drilling terminated in uppermost Oligocene sediments at 776.4 mbsf, with 278 m cored for a recovery rate of 73% and 188.8 m drilled without coring. SITE 806The entire sedimentary sequence encountered is considered as one lithologic unit (Unit 1), consisting of upper Oligocene to Pleistocene foraminifer nannofossil ooze and chalk to nannofossil ooze and chalk with foraminifers. Foraminifer abundances mostly range between 15% and 30%, with occasional excursions to 10% and 50%. Radiolarians are a minor constituent throughout the section. The ooze-chalk transition was placed between 338 and 340 mbsf; it is gradational and shows alternation of layers of varying induration, beginning at about 200 mbsf. The age of the sediments at the transition is ca. 10 Ma. Sedimentation throughout the time interval represented seems to have been continuous at this site.Unit I is divided into two subunits at the ooze-chalk transition, as follows:Subunit IA (0-339 mbsf) consists of Pleistocene to upper middle Miocene foraminifer nannofossil ooze to nannofossil ooze with foraminifers. Carbonate content generally ranges from 90% to 95%, except in the Pleistocene...

Atmospheric CO2 estimates for the last 17 million years based on foraminiferal δ11B at Ocean Drilling Program Sites 806 and 807 in the Western Equatorial Pacific

“…Sites 806 and 807 have high quality age models (Shackleton et al, 1991). The age model for Site 806 from 0-1.35 Ma is based on Lea et al (2000), while from 1. it is based on Lisiecki and Raymo, (2005), and Wara et al (2005) is the source of information 160 for sediments older than 5.875 Ma.…”

Atmospheric CO<sub>2</sub> estimates for the Miocene to Pleistocene based on foraminiferal δ<sup>11</sup>B at Ocean Drilling Program Sites 806 and 807 in the Western Equatorial Pacific

“…Sites 806 and 807 have high quality age models (Shackleton et al, 1991). The age model for Site 806 from 0-1.35 Ma is based on Lea et al (2000), while from 1.352-5.875 Ma it is based on Lisiecki and Raymo, (2005), and Wara et al (2005) is the source of information for sediments older than 5.875 Ma.…”