A LATE PALEOCENE EARLY EOCENE BENTHIC FORAMINIFERAL RECORD FROM BOVLSTRUP, DENMARK, SHOWING A REMARKABLE AGGLUTINATED FAUNA

The Bovlstrup well, Denmark, provides a detailed record of benthic for aminifera from the Upper Palaeocene and Lower Eocene deposits. The inv estigated interval spans four lithe-units: an informal Grey Clay unit, the Holmehus Formation, the Olst Formation and the Rosnes Clay Format ion (Danian?-Ypresian). Five interval zones based on benthic foraminif era have been established. Three of these zones (Zones 2, 3, and 4) co ntain exclusively agglutinated faunas. No foraminifera have previously been found in the Olst Formation (Late Thanetian-Early Ypresian), but at Bovlstrup the formation contains a remarkable low-diversity agglut inated fauna (Zone 4). A programme of relatively dense sampling yielde d information that may be lost in commercial oil well analysis. The fi ve foraminiferal zones at Bovlstrup are correlated to established Nort h Sea zonations, and the recognition of the faunas of Zones 3 and 4 le ads to the conclusion that the zonation of King (In: Jenkins, D. G. & Murray, J. W. (Eds), Stratigraphical Atlas of Fossil Foraminifera, Ell is Horwood, 1989) can be refined. The benthic faunas indicate changes in the bottom environment both at the sea Boor and within the overlyin g water mass. A transition from a calcareous fauna to an agglutinated fauna is interpreted as the result of a change from a neutral to a sli ghtly acidic environment at the sea floor. There is a fluctuation in w ater depth through the studied section with a minimum water depth duri ng the Thanetian and Early Ypresian. Volcanic ash layers in the Olst F ormation presumably resulted in low pH values, thereby causing the ext reme low diversity of the benthic foraminiferal faunas.