At the close of the middle Eocene, most of the strong orogenic deformation in Cuba had occurred, and the general distribution of the pre–upper Eocene structures and stratigraphic units was essentially as it is now. The younger Tertiary sediments began to accumulate over the now-essentially inactive, largely peneplained, submarine mountain chain, reflecting some large-scale deformation that included folding and faulting. The overall movements during the remainder of the Tertiary have been of a slow, continuous uplift, with much of Cuba emerging by the Miocene. The younger Tertiary sedimentation consisted mostly of the filling of topographic depressions, although erosion of uplifts and filling of subsiding areas also occurred. It should be noted that Gulf Oil, with the exception of a few areas in central Cuba, did little work on the younger Tertiary; therefore, much of the following is derived from published information, namely, Iturralde-Vinent (1977 , 1988 ), Jakus (1983) , and Fernandez et al. (1987) . As shown in Figure 148 , the post–middle Eocene will be described according to the following areas: Northern coast = Havana to Oriente Provinces Southwestern basin = Los Palacios Basin, Habana-Matanzas, and western Las Villas South-central basin = Central Depression (Gulf of Ana Maria) Southeastern basins = Guanacayabo-Nipe Basin, central syncline, Guantanamo depression, and southern coast (only the stratigraphic unit of the Oriente southern coast will be listed). A characteristic of most upper Eocene and later sediments is their richness in fossils, mostly large and small

In this section, only the stratigraphy of the rocks deposited before and during the violent events of the Cuban orogeny will be described. The deformation probably reached its peak during the early–middle Eocene. The reason for this rather indefinite time assignment is that no index faunas have been found to separate the middle from the lower Eocene in the syn-orogenic flysch sediments, much less in the wildflysch that characterizes the culmination of the orogeny. The only evidence that the orogeny is pre–upper Eocene is a widespread, well-defined unconformity below an upper Eocene orbitoid-rich limestone that, although occasionally deformed, was not involved in the strong orogenic tectonism. As will be seen later, the tectonic events that marked the end of the orogeny were not exactly synchronous all over Cuba. In the south, the orogenic deformation started in the late Maastrichtian to Paleocene, whereas in the north, the deformation started in the early Eocene. The molasse (or erosion of already inactive topography) cycle startedinthe southinthe early Eocene while thrusting proceeded in the north in the middle Eocene with the production of associated flysch deposits (or erosion of an active orogenic front). The mo-lasse was carried piggyback by the northward advancing thrusts while contemporaneous flysch was being generated in the north. Stratigraphy and structure are intimately intertwined in Cuba; the significance of structural features can be understood only through the knowledge of stratigraphy. Therefore, in this chapter, the stratigraphy will be described first to establish a plausible preorogenic paleogeography.As previously mentioned, many

Impact stratigraphy is an extremely useful correlation tool that makes use of unique events in Earth's history and places them within spatial and temporal contexts. The K-T boundary is a particularly apt example to test the limits of this method to resolve ongoing controversies over the age of the Chicxulub impact and whether this impact is indeed responsible for the K-T boundary mass extinction. Two impact markers, the Ir anomaly and the Chicxulub impact spherule deposits, are ideal because of their widespread presence. Evaluation of their stratigraphic occurrences reveals the potential and the complexities inherent in using these impact signals. For example, in the most expanded sedimentary sequences: (1) The K-T Ir anomaly never contains Chicxulub impact spherules, whereas the Chicxulub impact spherule layer never contains an Ir anomaly. (2) The separation of up to 9 m between the Ir anomaly and spherule layer cannot be explained by differential settling, tsunamis, or slumps. (3) The presence of multiple spherule layers with the same glass geochemistry as melt rock in the impact breccia of the Chicxulub crater indicates erosion and redeposition of the original spherule ejecta layer. (4) The stratigraphically oldest spherule layer is in undisturbed upper Maastrichtian sediments (zone CF1) in NE Mexico and Texas. (5) From central Mexico to Guatemala, Belize, Haiti, and Cuba, a major K-T hiatus is present and spherule deposits are reworked and redeposited in early Danian (zone P1a) sediments. (6) A second Ir anomaly of cosmic origin is present in the early Danian. This shows that although impact markers represent an instant in time, they are subject to the same geological forces as any other marker horizons—erosion, reworking, and redeposition—and must be used with caution and applied on a regional scale to avoid artifacts of redeposition. For the K-T transition, impact stratigraphy unequivocally indicates that the Chicxulub impact predates the K-T boundary, that the Ir anomaly at the K-T boundary is not related to the Chicxulub impact, and that environmental upheaval continued during the early Danian with possibly another smaller impact and volcanism.