Palaeoenvironmental reconstruction of Loch Duart (NW Scotland, UK) since the Last Glacial Maximum: implications from a multiproxy approach

A sediment core from the salt marsh fringing Loch Duart, NW Scotland, UK, containing Lateglacial to Holocene sediments, was analysed using a multi-element geochemical approach to elucidate the relative sea level (RSL) and palaeoenvironmental changes associated with the deglaciation of the British and Irish Ice Sheet. Elemental and isotopic measurements of rhenium, osmium, carbon and nitrogen, X-ray fluorescence scanning, radiocarbon dating, and foraminiferal analysis produced a suite of data that complements the existing biostratigraphic framework. This suite of bio-, litho- and chemostratigraphic analyses permits discussion of RSL changes that reflect the interplay between post-glacial eustatic rise and glacio-isostatic adjustment. The osmium-isotope (¹⁸⁷Os/¹⁸⁸Os) data, coupled with a new age–depth model, depict an RSL fall between 16.8 and 14.1 ka cal bp at an average rate of 2 mm a⁻¹. Falling RSL culminates in basin isolation and is followed by subsequent marine inundation from 11.6 ka cal bp. This RSL record preserves the local interaction between glacial isostatic adjustment and glacio-eustatic sea-level change, a relationship that is reflected in the sediment's ¹⁸⁷Os/¹⁸⁸Os signature. This is the first known application of the osmium isotope system in an isolation basin that is shown to be a viable proxy for RSL change, a technique that could be applied to glacially influenced isolation basins globally.