Late Quaternary sea-level change and evolution of Belfast Lough, Northern Ireland: new offshore evidence and implications for sea-level reconstruction

The interplay of eustatic and isostatic factors causes complex relative sea-level (RSL) histories, particularly in paraglacial settings. In this context the past record of RSL is important in understanding ice-sheet history, earth rheology and resulting glacio-isostatic adjustment. Field data to develop sea-level reconstructions are often limited to shallow depths and uncertainty exists as to the veracity of modelled sea-level curves. We use seismic stratigraphy, 39 vibrocores and 26 radiocarbon dates to investigate the deglacial history of Belfast Lough, Northern Ireland, and reconstruct past RSL. A typical sequence of till, glacimarine and Holocene sediments is preserved. Two sea-level lowstands (both max. −40 m) are recorded at c. 13.5 and 11.5k cal a bp. Each is followed by a rapid transgression and subsequent periods of RSL stability. The first transgression coincides temporally with a late stage of Meltwater Pulse 1a and the RSL stability occurred between c. 13.0 and c. 12.2k cal a bp (Younger Dryas). The second still/slowstand occurred between c. 10.3 and c. 11.5k cal a bp. Our data provide constraints on the direction and timing of RSL change during deglaciation. Application of the Depth of Closure concept adds an error term to sea-level reconstructions based on seismic stratigraphic reconstructions.