Reconstruction of Holocene foreland progradation using optically stimulated luminescence (OSL) dating: an example from Dungeness,UK

Abstract

Dungeness Foreland, southeast UK, is comprised of a series of distinctive gravel ridges overlying sub- and intertidal sands. The successful application of optically stimulated luminescence (OSL) to the Holocene sub- and intertidal sands at Dungeness provides a well-resolved chronology (precision ~5%) for exploring the sedimentary response of a gravel foreland to changes in sea level, storms, sediment supply and coastal dynamics. The nature of foreland progradation at Dungeness is revealed through a three-dimensional network of 35 new quartz OSL ages, and these data also constrain the timing of gravel emplacement. The OSL chronology places the early formation of the underlying shoreface in the west at ~5000 years ago, with ages decreasing progressively eastwards to ~2000 years ago beneath the main body of the present foreland, and 1000—600 years ago under the present-day ness in the east. The uppermost OSL ages for the subgravel sand unit provide maximum limiting ages for emplacement of the gravel, which together with ¹⁴C ages from organic deposits on the gravel surface provide bracketing ages for the deposition of the gravel. The short lag time between shoreface sand deposition and gravel ridge formation is indicative of a high degree of dependency of gravel foreland progradation on the pre-existence of an emergent sand substrate. Sigmoidal isochrons constructed using the subgravel sand OSL ages, and consideration of down-core OSL ages, demonstrates nonlinearity in coastal response; this is expressed in the form of changes in the direction of foreland progradation rather than temporal changes in sedimentation rate.