Spacio-temporal distribution patterns of North Sea Basin Early Oligocene (Rupelian) pteropoda (holoplanktonic gastropods: Mollusca, Gastropoda, Euthecosomata) are studied. These patterns indicate three short term invasions of a single pteropod species during the Rupelian. These invasions are indicated here as Clio blinkae Event, Praehyalocylis laxeannulata Event and Clio jacobae Event. The conspicuously short occurrences of the species, their abundances and some lithological features of the pteropod bearing strata lead to the conclusion that these plankton events are linked to sea level high-stands allowing currents from the worlds oceans to enter into the North Sea Basin.

This paper presents the results of a detailed rock magnetic and magnetostratigraphic study of the Lower Oligocene Rupelian unit-stratotype. Notwithstanding the relatively low intensity of the natural remanent magnetisation and the diverse and often unstable behaviour during demagnetisation, close-spaced sampling and accurate polarity determinations allowed us to determine the magnetic polarity zonation. The recognition of the characteristic magnetic polarity and the correlation with the standard magnetobiochronologic time scale yields an accurate chronostratigraphic dating of the Boom Clay Formation. The boundary between the geomagnetic chrons C12n and C12r nearly coincides with the lithostratigraphic boundary between theTerhagen and Putte Members. Rock magnetic techniques point to magnetite and probably also iron sulphides as the main magnetic remanence carriers. These magnetic minerals could, however, not be identified with classical mineralogical techniques performed on magnetic extractions. The failure to detect them may be due to the low concentration of these minerals, the small grain size, and the close physical relation with pyrite.