The following are critical features of three serpentinite breccia beds within Unit IV, Hole 899B: (1) the fragments are angular and many display jigsaw/crackle textures; (2) sorting is generally absent, but larger boulders tend to occur in the in the middle and upper part of the thickest unit; (3) the breccia matrix appears to be generated by fragmentation of the clasts and there is a size continuum between the clasts and matrix; (4) minor internal deformation zones or slip zones occur, particularly along the margins of large blocks; and (5) the breccias are interpreted as being tabular, bedded units. All these features are common in subaerial giant landslide deposits, and the serpentinite breccias are interpreted as being equivalent submarine deposits, generated by slope failure along large nearby serpentinite fault scarps. Giant landslides are a typical feature of regions undergoing rapid extensional deformation, and such deposits may be relatively common in faulted submarine extensional environments. The basement topography at the time of formation of the serpentinite units clearly differed significantly from the present topography buried beneath the Iberia Abyssal Plain. As a result, the location of the source serpentinite escarpment is unknown. However, the large size of some of the fragments included within the serpentinite indicate that it was probably within a few kilometers of Site 899 and that the aggregate width of the belt of mantle serpentinite exposed in the Late Cretaceous at the Iberia Margin might have been 20 km.