Biolithites on the Jamaican Island Slope are undergoing considerable diagenetic alteration. Significant volumes of rock are in the process of being converted to biomicrite and pelmicrite by massive biological erosion and cementation by Mg-calcite micritic cement. Many rocks also display textures similar to some attributed to recrystallization or replacement in ancient limestones. Most neomorphic textures occur in rocks collected from the thermocline layer and especially affect the deeper rocks studied (278 m). Some of these puzzling textures are clearly due to contemporaneous mechanical sedimentation and growth of both Mg-calcite and coarse-grained aragonite crystalline cements, resulting in cement-supported fabrics. Crystalline cements also fill megascopic voids created by the dissolution of aragonite in undersaturated water of the thermocline layer. It is possible that some textures represent true neomorphism.