Dating recent alluvial sediments in the Wicklow Mountains

Abstract

Modern floodplain sediments in the Wicklow Mountains display a stratigraphy and sedimentology that contrasts them with earlier Holocene alluvium. During previous research ¹⁴C dates of lightly constrained stratigraphies in one valley indicated a commencement date between 190+/-60 yr BP and 580+/-50 yr BP and mining generated enhanced lead metal values in another valley implied a commencement date there of AD 1780–1800. The paper presents the results of a ¹⁴C dating programme the objects of which were to date (a) more definitively their commencement throughout the Wicklow Mountains and (b) their internal stratigraphies with a view to establishing a Hood chronology. AMS and radiometric ¹⁴C dating techniques were applied to organic fractions and paniculate organic matter extracted from thin organic-rich layers within sampled sedimentary sequences. The dates spanned 780+/-60 BP to 3396+/-46 BP and provided neither a Coherent commencement period nor an accurate chronostratigraphy and the modern sediments appear to be dominated by old carbon derived from the catchment blanket peats. Although these results show that the immediate research aims cannot be achieved using ¹⁴C dating they have led to a clearer understanding of the sourcing and dynamics of the modern style of sedimentation.