Testing the use of quartz 'micro-hole' photon-simulated luminescence for dating sediments from the central Lomonosov Ridge, Arctic Ocean

In the Arctic Ocean, direct dating methods are needed as an alternative to the radiocarbon (C-14) method and to various indirect approaches for a longer stratigraphy. In past attempts to develop a luminescence sediment dating, the use of fine-silt (4-11 mu m) mixture of quartz and feldspar grains from core tops has often produced large age overestimates by several ka. A recent application of micro-focused laser ('micro-hole') photon-stimulated luminescence (PSL) to medium-silt to fine-sand quartz grains (11-105 mu m) from the core tops at the Alaska margin has been usefully accurate. To extend this approach to the central Arctic Ocean and to a larger grain size range, we applied micro-hole PSL dating to >11 mu m quartz grains from core tops (0.5-2 cm horizon) from two sites on the central Lomonosov Ridge. We obtain a burial age estimate of ca. 2 ka for 11-62 mu m grains at a multicore site 18 MC within a perched intra-ridge basin, in accord with C-14 ages obtained on foraminifers. At nearby site 19 MC on the erosive ridge top, the micro-hole PSL dating of >90 mu m quartz grains produces a burial age estimate of ca. 25 ka, in accord with a foraminiferal C-14 age of ca. 26 ka. However, the 11-90 mu m grains from the same sample produce a much younger burial age estimate of ca. 9 ka. Thus, these two size fractions of quartz grains record different burial times and different deposition agents (icebergs vs. sea ice), providing insight into past sedimentary processes. Overall, our results confirm an earlier conclusion from microhole PSL dating study at the Alaska margin that medium to coarse silt fractions of quartz grains (11-90 mu m or at least 62 mu m) is the preferred material for direct dating of the last daylight exposure of detrital sediment in the Arctic Ocean. (C) 2012 Elsevier B.V. All rights reserved.