Changes

The early to middle Eocene was characterized by intense orogenic activity (50 Ma; [[:file:St58OverviewFG32.JPG|Figure 12]]). Early in the Eocene, the large-scale low-angle thrust sheets, or gravity nappes, that first moved in the Maastrichtian began to move at a greater rate. The volcanic section, along with the [[Oceanic crust|oceanic basement]], rode over the platform to deep water province, probably along the line separating the basic igneous-volcanic province from the platform to deep basin province. As thrusting proceeded, additional thrusts formed within the carbonate section in front of and north of the basic igneous-volcanic front. As a result, the thrust sheets were generally arranged from older and more southerly sourced at the top of the stack to younger and more northerly sourced at the base.

The early to middle Eocene was characterized by intense orogenic activity (50 Ma; [[:file:St58OverviewFG32.JPG|Figure 12]]). Early in the Eocene, the large-scale low-angle thrust sheets, or gravity nappes, that first moved in the Maastrichtian began to move at a greater rate. The volcanic section, along with the [[Oceanic crust|oceanic basement]], rode over the platform to deep water province, probably along the line separating the basic igneous-volcanic province from the platform to deep basin province. As thrusting proceeded, additional thrusts formed within the carbonate section in front of and north of the basic igneous-volcanic front. As a result, the thrust sheets were generally arranged from older and more southerly sourced at the top of the stack to younger and more northerly sourced at the base.

A large trough-shaped basin formed in front of the thrust sheets, deeper near the thrust front and shallower northward. Lower to middle Eocene flysch deposition in the trough began with sediments derived from limestones, such as the Sagua* and San Martin* formations, followed by an increase in volcanic and intrusive-derived detritus, such as the lower Vega* and lower Manacas (Pica Pica) formations, and finally, capped by the intrusive and volcanic-derived coarse conglomerates and wildflysch of the upper Vega* (Rosas*) and upper Manacas (Vieja) formations. In central Cuba, the rocks of the deep-water Vega* Formation became coarser grained through time. In western Cuba, the fine-grained clastics and other pelagic sediments of the Manacas Formation changed abruptly to the coarse breccias of the Vieja Member. The breccia clasts reflect the lithology of the associated fault blocks. This suggests some subaerial erosion in central Cuba, whereas western Cuba was largely submarine.

A large trough-shaped basin formed in front of the thrust sheets, deeper near the thrust front and shallower northward. Lower to middle Eocene flysch deposition in the trough began with sediments derived from limestones, such as the Sagua* and San Martin* formations, followed by an increase in volcanic and intrusive-derived detritus, such as the lower Vega* and lower Manacas (Pica Pica) formations, and finally, capped by the intrusive and volcanic-derived coarse conglomerates and wildflysch of the upper Vega* (Rosas*) and upper Manacas (Vieja) formations. In central Cuba, the rocks of the deep-water Vega* Formation became coarser grained through time. In western Cuba, the fine-grained clastics and other [http://www.merriam-webster.com/dictionary/pelagic pelagic] sediments of the Manacas Formation changed abruptly to the coarse breccias of the Vieja Member. The breccia clasts reflect the lithology of the associated fault blocks. This suggests some subaerial erosion in central Cuba, whereas western Cuba was largely submarine.

South of the front of the advancing volcanic and basic intrusive-rock thrust plate, a second series of basins developed parallel to the northern trough. Within these basins, which were carried piggyback by the thrust plate, lower Eocene igneous-derived sediments accumulated, but under quieter tectonic conditions (the Taguasco*, Bijabo*, Santa Clara*, Alkazar, Bacunayagua, Capdevila, and Universidad formations, for example).

South of the front of the advancing volcanic and basic intrusive-rock thrust plate, a second series of basins developed parallel to the northern trough. Within these basins, which were carried piggyback by the thrust plate, lower Eocene igneous-derived sediments accumulated, but under quieter tectonic conditions (the Taguasco*, Bijabo*, Santa Clara*, Alkazar, Bacunayagua, Capdevila, and Universidad formations, for example).