De anticlinaal van Gronau bij Glanerbrug (Enschede) met gegevens over de ingang van de Alstätter Bocht

In this paper the results of some investigations near Enschede of the Geological Survey of the Netherlands, of two deep drillings near Gronau, West Germany, and some hand drillings performed by the author in the area of the Gronau anticline are described. From these results the author has reconstructed a picture of the geological history of the area east of Enschede. Special attention is paid to the opening of the so-called 'Alstätter Bucht', which formed to the east and southeast of Enschede in the Lower Cretaceous. In 'Wealden', Valanginien, and Hauterivian times the 'Alstätter Bucht' was mainly closed by a Triassic ridge; this ridge was running from Epe tot the site of drilling Enschede I. During transgressions in the Barremain, Aptian, and Albian the ridge was covered by the sea again. During the Hauterivian an island occurred just northeast of this ridge. It assumed that this island was the beginning of the 'Zoeke anticline'.