A RECORD OF ACCELERATED EROSION IN THE RECENT SEDIMENTS OF BLELHAM TARN IN THE ENGLISH LAKE DISTRICT

Two frozen cores from Blelham Tarn were subsampled and measured using mineral magnetic, loss-on-ignition (LOI), radiometric, granulometric a nd diatom analyses. A detailed chronology was established using varves , radioisotopes and diatoms. This has enabled an accurately dated reco nstruction of sedimentation over the past forty years. Despite a large increase in lake productivity, evidence suggests that the observed ex ponential increase in sedimentation rates can be attributed to erosion within the catchment. The predominant sediment source has been identi fied as surface soil. A comparison between the trend of accelerated se dimentation and the record of increased sheep stocking density for the area within which the most of the catchment lies, as well as observat ions of contemporary surface processes within the catchment, both sugg est that much of the recent erosion is a direct response to increased pressure from sheep grazing.