K. F. Kuiper,1,2 A. Deino,3 F. J. Hilgen,1 W. Krijgsman,1 P. R. Renne,3,4 J. R. Wijbrans2 Calibration of the geological time scale is achieved by independent radioisotopic and astronomical dating, but these techniques yield discrepancies of 1.0% or more, limiting our ability to reconstruct Earth history. To overcome this fundamental setback, we compared astronomical and 40Ar/39Ar ages of tephras in marine deposits in Morocco to calibrate the age of Fish Canyon sanidine, the most widely used standard in 40Ar/39Ar geochronology. This calibration results in a more precise older age of 28.201 ± 0.046 million years ago (Ma) and reduces the 40Ar/39Ar method's absolute uncertainty from 2.5 to 0.25%. In addition, this calibration provides tight constraints for the astronomical tuning of pre-Neogene successions, resulting in a mutually consistent age of 65.95 Ma for the Cretaceous/Tertiary boundary. 1 Faculty of Geosciences, Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands. 2 Faculty of Earth and Life Sciences, Institute of Earth Sciences, Vrije Universiteit Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands. 3 Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA. 4 Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA.

The landscapes and archaeological sites of the southern North Sea, drowned in the period 12-6 ky BP, represent an almost unexplored field of research. Published palaeoenvironmental reconstructions are largely speculative, being based on few published sea-level index points and in the absence of detailed physical and chronological surveys. In this paper, we review the post-glacial geochronology for the southern North Sea, which includes 54 radiocarbon ages derived from peat, 17 from molluscs and one known dated artefact. The lack of detailed contextual information for many dated samples means that there remains uncertainty in some elevation data, and thus in the resulting interpreted sea level. The archaeological artefacts are mostly derived deposits and thus are of limited use in palaeoenvironmental reconstruction. Overall, the data are consistent with current models of relative sea-level change back to about 10 ky BP (∼45 m depth) but beyond this, there is very little published data. Much more detailed stratigraphic, microfossil and geochemical analysis is needed to help verify chronological data, help interpret the sedimentary settings in which fossils and artefacts are found, and contribute towards more reliable palaeoenvironmental and archaeological reconstructions of the history of the southern North Sea.