Rates of Sedimentation in the Central Arctic Ocean
The Arctic Ocean is presently undergoing geoscientific investigations of the type that occurred during the late 1940's through 1960's in the Atlantic, Indian and Pacific oceans. Seismic reflection and refraction data are scarce in the Arctic Ocean and large areas are virtually unsampled with respect to piston or gravity coring. The vast majority of available cores are less than10 m in length and largely lack biostratigraphically useful calcareous and siliceous microfossils. No drill cores exist from the ridges or deep basins in the central Arctic Ocean. Considering the limited geophysical and geological data available, it is not surprising that current concepts about Arctic Ocean sedimentation rates are diverging. The main point of difference is whether or not strongly subdued rates of sedimentation persisted in the central Arctic Ocean during Plio-Pleistocene times. The low sedimentation rate scenario is based on age models suggesting Plio-Pleistocene rates that vary between about 0.04 and 0.4 cm/ka. This scenario is chiefly derived from cores raised from ridges in the Amerasian Basin and implies that the majority of cores presently available extend well into, or encompass the entire, Pliocene. The contrasting high sedimentation rate scenario is based on age models suggesting rates that vary from about one to a few cm/ka, derived from cores from ridges and basins in both the Amerasian and Eurasian parts of the central Arctic Ocean. The latter scenario implies that most short cores rarely extend beyond the Pleistocene. Early paleomagnetic chronologies of sediment cores retrieved from the Amerasian Basin were based on the assumption that zones with negative inclination represented genuine polarity reversals. The first encountered down-core zone with negative inclination was interpreted to be the Brunhes/Matuyama boundary. This approach yielded mm-scale Plio-Pleistocene sedimentation rates. Biostratigraphy, cyclostratigraphy, and OSL dating, subsequently have indicated that many of these negative inclination changes represent Brunhes geomagnetic excursions, thus providing cm-scale Pleistocene sedimentation rates. All longer-term, Cretaceouos through Cenozoic, sedimentation rates derived from seismic reflection and tectonic models of bedrock age are on the order of cm/ka.