Inner shelf seismic stratigraphy off the north coast of Northern Ireland: new data on the depth of the Holocene lowstand

Abstract

New seismic stratigraphic data are presented from the inner shelf off the north coast of Northern Ireland. The sequence preserved comprises an acoustic basement of till or solid bedrock, overlain by a fine-grained, acoustically transparent unit interpreted as glacio-marine sediment. This is overlain by an upper, reflective sandy unit which contains a discontinuous but widespread internal reflector, interpreted as peat that developed during a late glacial/Holocene relative sea-level fall and continued to accumulate until subsequent inundation. The depth of the Holocene lowstand is estimated at −30 m MSL on the basis of the seaward extent of the sandy unit and its intercalated peaty horizons, the presence of erosional notches and a widespread break in slope at this depth. The lowstand is not definitively dated but on the basis of dated deposits in adjacent locations is inferred to have occurred between 10 000 and 11 000 14C yr BP.