In this study, we present an age-depth profile for a large diameter piston core (EW9709 PC-07) collected at 8.8 degrees N, 135.4 degrees W in the central North Pacific Ocean. The core was collected by the R/V Ewing in 1997 as part of the site reconnaissance for Leg 199 of the Ocean Drilling Program. Most of this 16 meter core is not datable by conventional biostratigraphic methods. Red clays dominate the uppermost portion (top approximately 3.5 m) while silicious clays and carbonate-rich intervals occur in the lower portion. This lower section includes datable Miocene radiolarians. Fish teeth ichthyoliths are abundant throughout the core. To generate an age-depth profile, strontium isotopic compositions were determined on ichthyoliths previously cleaned of contaminants using a newly improved reductive cleaning procedure. Ages were determined by reference to the recently refined strontium isotope curve for Neogene seawater. For the lower portion of the core, a very good correlation exists between the radiolarian biostratigraphy and the strontium isotope technique employed here. The base of the core is placed at approximately 20 Ma. Correlation with radiolarian ages indicates an upcore linear sedimentation rate of 1.9 mm/kyr to a depth of 6.0 m, which is placed at 15 Ma. The sedimentation rate decreases to approximately 0.9 mm/kyr between 15 Ma and 11 Ma (2.5 m), reflecting northward movement of the site away from the equatorial high productivity zone. From 11 Ma to present, a linear sedimentation rate of approximately 0.25 mm/kyr is calculated, reflecting dominantly eolian deposition. Correlation of fish teeth ages with recently obtained magneto-stratigraphic ages from a nearby drillcore (Site 1218, Leg 199) also show a good match for a majority of the core. These comparisons lend confidence to the fish teeth Sr dating technique, which will be an important tool for obtaining precise time calibration on red clay cores from the Pacific pelagic clay province. This information is critical to the evaluation of terrigenous flux rates of eolian dust in global paleoclimate reconstructions.

West: -135.2400 East: -135.2200 North: 8.5300 South: 8.4800

Expedition: 199

Site: 199-1218

Provider: SEDIS Publication Catalogue

Data set link: http://sedis.iodp.org/pub-catalogue/index.php?id=2004-037339 (c.f. for more detailed metadata)

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