Electron spin resonance (ESR), optically stimulated luminescence (OSL) and terrestrial cosmogenic radionuclide (TCN) dating of quartz from a Plio-Pleistocene sandy formation in the Campine area, NE Belgium

Abstract

The chronostratigraphy of the typical quartz-rich white sands that are intensively quarried in the Campine area, northeastern Belgium, is poorly constrained. In the absence of biostratigraphical data, the age of the deposits, traditionally assigned to the Mol Formation, is thought to be late Pliocene based on sequence stratigraphical correlations (ca. 2.6–3.6 Ma). In an attempt to verify this age, we used a multi-dating method approach on two carefully selected samples in a palaeoseismological trench where the sediment was found to be vertically displaced by the Rauw fault. Three dating methods were used: electron spin resonance (ESR) dating, optically stimulated luminescence (OSL) dating and cosmogenic radionuclide (CRN) dating. In all three cases quartz was found to be a suitable dating material in terms of material properties. However, the ESR dating results based on Ti, Ti–Li and Al centres show strong internal inconsistencies, which can be explained by incomplete bleaching. As such, the youngest ESR ages obtained (ca. 5 Ma) are regarded as an absolute maximum age. In contrast, the OSL ages of ca. 1.5 Ma seem to underestimate the sequence stratigraphical age. The surface exposure CRN dating method using Bayesian inversion suggests that a palaeosurface developed around 1.55 ± 0.80 Ma, and eroded at a rate of ca. 15 m/Ma. Erosion probably accelerated after ca. 0.5–1 Ma and posterior to the last major movement along the Rauw fault.