Glacial Chronology over the Past 450 kyr Around the Margins of the Southern North Sea (UK and Netherlands) From Quartz Luminescence Dating

Abstract

Terrestrial glacigenic deposits containing evidence for the repeated growth of former ice sheets are distributed widely in North America and continental Europe. The chronology of the younger component of these deposits during the Last Glacial Maximum (LGM) is relatively well established, but considerably less is known about the extent and timing of earlier periods of Pleistocene glaciation. This study focuses on the well preserved glacigenic sediment and landform assemblages that are exposed across lowland areas of eastern Britain and the northern Netherlands, which document the repeated advance of Pleistocene British/Fennoscandinavian ice sheets. Previously, it is unknown whether the deposits belong to a single glaciation equated with Marine Isotope Stage (MIS) 12, or represent deposition over a number of separate cold climate stages. We have collected > 80 samples from glaciofluvial and glaciolacustrine deposits in this region for luminescence (OSL) dating with the approach of obtaining 5-10 replicate dates per stratigraphical unit. The luminescence characteristics of the samples including thermal stability, dose response, ability to measure a known dose, and presence of desirable components separated using LM-OSL (linear modulation) indicate that equivalent doses can be reliably measured across the timescale of interest. Furthermore, low concentrations of radioactive isotopes in sediments of this region enable the traditionally accepted age limit of luminescence dating to be considerably extended. The luminescence ages confirm that the largest glaciation in the UK occurred during MIS 12 (427 ± 26 kyr). An additional tight cluster of ages at 166 ± 8 kyr also indicates that major ice advances occurred synchronously in the UK and Netherlands during MIS 6, although the dimensions of the ice sheet in the UK appears to be of a similar or lesser extent than the LGM. This work also justifies that coherent sets of luminescence ages can be obtained with an overall uncertainty of < 10%, sufficient to delineate glaciation events at the isotope stage level but precluding discrimination of sub-isotope stage advances