This paper presents geomorphological and geochronological evidence for ice sheet oscillations during the deglaciation of the last Irish Ice Sheet. Cosmogenic exposure age results (36Cl ages; n = 18) demonstrate that the ice margin had retreated into central Ireland by c. 19 ka, with ice restricted to the uplands west of the River Shannon by c. 16.7 ka. These dates are consistent with dated ice margins on the east coast of Ireland. The geomorphological evidence points to streaming ice draining eastward within the Irish interior and a transition from streaming to surging ice dynamics during recession, as the ice sheet split into separate lobes. Up to four substantial, non-synchronous readvances of individual lobes over several kilometres are observed. These were in part caused by surging behaviour in the ice sheet, indicating the role of internal disequilibria in local to regional-scale advances. Despite the existence of an extensive proglacial ice-contact lake, Palaeolake Riada, which formed at the ice margin during retreat into the Shannon drainage basin, cosmogenic exposure age results demonstrate that water submersion did not affect surface exposure ages obtained from glacial boulders, indicating that the ice contact lake existed for too short a time span to have had an effect on boulder exposure ages. A key finding is that the ice retreat into central Ireland was earlier than in some parts of Britain, such as eastern Scotland, and highlights the complexity of the glacial record across Great Britain and Ireland.

The Monte San Nicola (MSN) section on Sicily (Italy) hosts the Gelasian and Quaternary Global Stratotype Section and Points (GSSP). Despite its importance, the spatial and temporal continuity of the succession at MSN remains hotly debated and has not yet been convincingly proven, as tectonic deformation may disrupt and reduce continuity. Such deformation and lack of continuity would potentially make the section unsuitable for defining global chronostratigraphic boundaries and units. To solve the continuity problem, we conducted a visual inspection of the cycle pattern in the field. This method uses astronomical target curves and a simplified modelled log in the time domain that considers the anticipated expression of both glacial cycles and sapropels. Identification of the cycle pattern is specifically used 1) as an impartial check on the completeness and continuity of the succession, 2) to determine the optimal cyclic composite section and trajectory for logging and sampling, and 3) to establish a reliable astronomical tuning that is largely independent of previous attempts. Our field observations are in excellent agreement with the modelled ideal log, resulting in a robust tuning and age model. The tuning, which shows that a complete and continuous succession is preserved in the NW gully complex at MSN, is largely consistent with the tuning proposed by the SAGE team for the Mandorlo section located in the same complex. The SE complex, which currently hosts the GSSP, is more deformed, resulting in a tectonic reduction of the stratigraphy. Finally, we argue that the NW complex may serve as future Astro-Unit-Stratotype (AUS) for the Gelasian Stage with the astronomically controlled cycles being formally defined as Astrochronozones. Such a designation may provide an additional argument for relocating the GSSP at the same stratigraphic level from the more strongly deformed SE complex to the NW complex at Monte San Nicola. • Visual cyclostratigraphy of Monte San Nicola with sapropels and ice ages is presented (85). • Succession is continuous and despite deformation suitable to establish robust tuning (84). • SE complex currently hosting the GSSP type section is tectonically more deformed (80). • NW complex may serve as Astro-Unit-Stratotype for Gelasian Stage in the future (78). • NW complex likely superior for locating Gelasian, Pleistocene and Quaternary GSSP (81).