摘要：Lithostratigraphical correlation and dinoflagellate cyst evidence point to the presence of a pronounced hiatus at the base of the London Clay and equivalent beds in NW Europe. Following a late Palaeocene regression, the sea became restricted to a small area in the central part of the North Sea Basin. In the subsequent 'London Clay' transgression the sea at first remained confined to the inner basin area, but during deposition of the ash-series it extended southwards over the southern North Sea area and into Germany, the Netherlands, and East Anglia. It was apparently not until after eruption of the ashes that the 'London Clay' sea became established over the S of England, Belgium, and northern France. Sedimentation was then more or less continuous in these southern areas during the lower Ypresian, but a phase of uplift and non-deposition in the central North Sea and Denmark resulted in a second hiatus above the ash-series.
