CENOZOIC SEDIMENTATION HISTORY OF THE CENTRAL NORTH PACIFIC - INFERENCES FROM THE ELEMENTAL GEOCHEMISTRY OF CORE LL44-GPC3

The concentrations of thirty-nine elements in 324 samples show large variations in sediments down the 24.3 m length of LL44-GPC3, a piston core of pelagic clay from the central North Pacific (30-degrees 19'N, 157-degrees 49.9'W) that contains a relatively continuous record of sedimentation since the late Cretaceous. Strong interelement correlations identify five groups of elements whose variance is related and which we interpret to represent porewater salts, silicates, biogenic phosphates, and hydrothermal and hydrogenous oxyhydroxide precipitates. Interelement ratios, when combined with mineralogical, sedimentological, and site-backtrack data, indicate that at least five distinct sources contributed to the aluminosilicate fraction of the sediments in the core. Eight endmember sediment source components (two eolian, two volcanic, two biogenous, one hydrothermal, and one hydrogenous) are modeled and quantified by total inversion. Accumulation rates of these components and of thirty-nine elements vary dramatically for stratigraphically defined intervals within the Cenozoic. Continuous accumulation-rate profiles based on a model combining stratigraphic data and an assumed constant flux of hydrogenous Co yield a general sedimentation model that reflects variations in the sedimentary environment as the LL44-GPC3 site migrated from near the equator in the late Cretaceous to its present location north of Hawaii.