The dataset comprises two elements: 1) logs of nine sedimentary profiles recorded in three locations in southern Iceland and 2) geochemical analyses of tephra samples taken from these profiles. The three locations were Heimaey (V), an island in the Vestmannaeyjar archipelago (four profiles); Seljaland (S) in southern Iceland (two profiles), and Húshólmi (H) on the Reykjanes peninsula (three profiles). All three locations are associated with the earliest phases of the settlement of Iceland by the Norse in the ninth century CE. The datasets were collected to establish a tephrochronological framework for the three sites. The logs are based on field observations made by Prof. Andrew Dugmore (University of Edinburgh) and Dr Richard Streeter (University of St Andrews) in June 2023. The geochemical analyses were carried out by Dr Streeter and conducted using an Electron Probe Micro Analyser (EPMA). Full details about this dataset can be found at https://doi.org/10.5285/dd570900-245c-4586-82b7-e548cbdc4ac5