A side-scan sonar and high-resolution Chirp sub-bottom profile study of the natural and anthropogenic sedimentary record of Lower Lough Erne, northwestern Ireland

Abstract

A geophysical survey (side-scan sonar and high-resolution sub-bottom profiling) combined with established chrono- and bio-stratigraphic markers are used to reconstruct the evolutionary history of Lower Lough Erne, northwestern Ireland since the end of the last glacial. Discrete acoustic units define four prominent sedimentation cycles, one Late-glacial and three Holocene, within the seismic stratigraphy. Basin development is predominantly controlled by climate until the Mid Holocene when the effects of cultural activity are related to pronounced signatures in the seismic record. An enhanced reflector marking the termination of the Early Holocene sedimentation cycle is associated with the elm decline and forest clearance during the Neolithic (between approximately 5800 cal. BP and 5300 cal. BP). The associated increase in sediment input, by infilling minor topographic lows and basins, has a smoothing effect on the morphologic expression of the original basin. Onlapping and truncated reflectors in the penultimate acoustic unit define further modification of lake bed relief by removal of sediment from the system during engineered lowering of the lake levels that began in the 1880s. Acoustic anomalies identified on the side-scan sonar data are linked with cultural activity and are identified as having the potential to facilitate the recent establishment and migration of invasive zebra mussels through the Erne system.