A mineral magnetic study of Holocene sedimentation in Lough Catherine, Northern Ireland

A suite of 6 m long Mackereth cores collected from Lough Catherine, Northern Ireland, form the basis of a study of sediment accumulation rates throughout the Holocene. A data set produced by measuring the magnetic susceptibility, artificially induced remanent magnetisations and density of the sediment was used to correlate the cores by means of a sequence slotting algorithm. The resulting sediment accumulation pattern was dated by reference to previous¹⁴C and palynological studies. The interpretation of the magnetic logs was complicated by the authigenic formation of the magnetic mineral greigite (Fe₃S₄) and by magnetite dissolution discovered during a period of low sediment accumulation between the end of the Lateglacial period (10,100¹⁴C years B.P.) and the elm decline (5,200 B.P.). More traditional methods of core analysis based on sediment density and also new palynological studies were used to correlate sections of the cores where the magnetic results were least amenable to core matching on account of low downcore variability and low accumulation rate. The accumulation rate, a direct indication of catchment denudation, has accelerated fivefold during the Holocene. The sediment accumulation rate has increased most dramatically since the elm decline at 5,200 B.P., reflecting the increasing degree of human disturbance.