High-resolution optical dating for marine sediments from North Pacific Ocean

• Main Authors: 杉崎 彩子, スギサキ サイコ, Saiko SUGISAKI
• Format: Thesis
• Language: English
• Published: 2009
• Subjects: Okhotsk; Pacific; Sea ice
• Online Access: https://ir.soken.ac.jp/?action=repository_uri&item_id=1498; http://id.nii.ac.jp/1013/00001489/

Marine sediments contain important archives of past ocean and climate changes, but at high latitudes, such as the polar regions, the absence of carbonate has prevented the construction of accurate chronological models. To get an age model, a method which does not rely on carbonate is needed. In this thesis we have investigated the potential of optically stimulated luminescence (OSL) dating to establish a chronology for our deep sea sediment cores from the Northern Pacific area. OSL dating makes use of the omnipresent quartz and feldspar grains in the sediment so there is no limitation in the presence of the dosimeter. Optical dating is a widely accepted dating method for terrestrial sediments, but only few studies have tested its reliability in the marine environment. A luminescence age reflects the time that has elapsed since the sediment grains were last exposed to sunlight. The luminescence age equation contains two equally important factors: the equivalent dose and dose rate. The equivalent dose is the total radiation dose that crystals (quartz, feldspar) have absorbed during burial, and the dose rate is the rate at which the sample was exposed to ionising radiation in the environment. Dividing the equivalent dose by the dose rate gives the luminescence age of the sample. This study is focused on testing the reliability of the optical dating method when applied to marine sediments from the Northern Pacific ocean, more specifically in regions that are known for seasonal-sea ice. The aims of this thesis are (1) determine the accuracy of luminescence ages, e.g. by comparison with AMS 14 C dating and marine oxygen isotope stratigraphy where possible, (2) produce a high resolution sequence of absolute ages which can describe changes in sedimentation rate through time, and (3) test whether it is possible to date back to marine isotope stage 5e (MIS 5e). In this thesis we have made use of fine (4- 11 μm) grains of quartz extracted from the marine sediment cores taken in the south-western Sea of Okhotsk, the Bering ...