This paper presents the results of a biostratigraphic analysis, based on planktonic foraminifers, of Ocean Drilling Program Leg 149 Sites 897-900 in the Iberia Abyssal Plain, off the coast of Portugal. Dissolution and changes in water-mass temperatures affect the quality of biozonation in some levels of the Pliocene, Miocene, and Paleocene/lower Eocene. Important hiatuses occur in the upper Cretaceous, Paleocene to middle/lower upper? Eocene and uppermost middle to lower upper Miocene in all the sites studied. A major hiatus in Hole 898A, spanning the Pliocene, late Miocene and the latest part of the middle Miocene, could be caused by erosion triggered by climatic cooling and/or erosion connected with middle-late Miocene local tectonic activity.

Date of initial receipt: 7 December 1994
Date of acceptance: 4 September 1995

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