This dataset contains the sediment descriptions and diatom data from a series of isolation basins in northwest Scotland. The data are from different areas in northwest Scotland: Raasay, Fearnmore, Loch Ewe, Reiff, and Inverkirkaig. For each area, sediment gouge and Russian cores were taken at possible isolation basin sites; the collection dates, location information (latitude/longitude) and sediment descriptions are provided for the coring sites in each area. The accompanying diatom counts are provided for cores that underwent diatom analysis. Data derived from NERC Grant NE/X009343/1 part of grant NSFGEO-NERC: Collaborative Research: How important are sea-level feedbacks in stabilizing marine-based ice streams? The project focusses on constraining the relative sea-level history of northwest Scotland, around the former Minch Ice Stream, to provide records for testing models of the interplay between ice-sheets, glacio-isostatic adjustment, and relative sea-level changes. Samples were collected 2022- 2025 and diatom analysis undertaken 2022- 2026.