Changes

===Early to Middle Eocene===

===Early to Middle Eocene===

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 [[Wikipedia:Basic_rock|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 [[Orogeny|orogenic]] activity (50 Ma; [[:file:St58OverviewFG32.JPG|Figure 12]]). Early in the Eocene, the large-scale low-angle [[Thrust fault|thrust sheets]], or gravity [[nappe]]s, 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 [[Wikipedia:Basic_rock|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 [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.

A large trough-shaped basin formed in front of the thrust sheets, deeper near the thrust front and shallower northward. Early 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 [[conglomerate]]s and [http://www.encyclopedia.com/doc/1O13-wildflysch.html 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 [[breccia]]s 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).

As the thrust sheets advanced, they overrode the lower to middle Eocene flysch, which had accumulated in front of them, and the flysch served as a lubricating medium for further thrusting. The subduction responsible for the uplift driving the thrusting ceased progressively from west to east, and volcanic activity continued in Oriente until the middle Eocene. Along what appears to be a north-dipping subduction zone and south of the Jardines de la Reina Cays (Camaguey trench) is a filled trench, which is a remnant of an accretionary prism. This trench could be related to the exposures in Haiti's southern peninsula and the Muertos Trench.

As the thrust sheets advanced, they overrode the lower to middle Eocene flysch, which had accumulated in front of them, and the flysch served as a lubricating medium for further thrusting. The [[subduction]] responsible for the uplift driving the thrusting ceased progressively from west to east, and volcanic activity continued in Oriente until the middle Eocene. Along what appears to be a north-[[dip]]ping subduction zone and south of the Jardines de la Reina Cays (Camaguey trench) is a filled trench, which is a remnant of an accretionary prism. This trench could be related to the exposures in Haiti's southern peninsula and the Muertos Trench.

In central and eastern Cuba, the thrust front advanced until the volcanic and basic intrusive rocks covered extensive areas of the massive shallow-water carbonates of the northern coast of the island (Yaguajay* belt, coastal and Gibara areas). After the front stopped advancing, compression from the south continued, tightly folding and then reverse faulting the succession of thrust plates. The result was the late Eocene structures shown in [[:file:St58OverviewFG33.JPG|Figure 13]]. As compression continued, the folds became sharper, and the faults began lateral motion, probably because the northward compression was not directed perpendicular to the front of the carbonate banks. It is possible that a deep-seated, crustal transcurrent fault was also involved.

In central and eastern Cuba, the thrust front advanced until the volcanic and basic intrusive rocks covered extensive areas of the massive shallow-water carbonates of the northern coast of the island (Yaguajay* belt, coastal and Gibara areas). After the front stopped advancing, compression from the south continued, tightly folding and then [[reverse fault]]ing the succession of thrust plates. The result was the late Eocene structures shown in [[:file:St58OverviewFG33.JPG|Figure 13]]. As compression continued, the folds became sharper, and the faults began lateral motion, probably because the northward compression was not directed perpendicular to the front of the carbonate banks. It is possible that a deep-seated, crustal [[Strike-slip fault|transcurrent]] fault was also involved.

In western Cuba, the northward-moving stack of thrust sheets did not reach the buttress of the Bahamas Platform, and the nappes came to rest on the sea floor toward the southern Gulf of Mexico. As a result, they are less deformed than they are to the east.

In western Cuba, the northward-moving stack of thrust sheets did not reach the buttress of the Bahamas Platform, and the nappes came to rest on the sea floor toward the southern Gulf of Mexico. As a result, they are less deformed than they are to the east.

It is possible that a large number of the present-day high-angle faults, some with reverse thrusting (Seibabo syncline), formed during the last phase of the orogeny.

It is possible that a large number of the present-day high-angle faults, some with reverse thrusting (Seibabo syncline), formed during the last phase of the orogeny.

The intense orogenic activity ceased toward the close of the middle Eocene or early late Eocene, and the uplifted, faulted, and folded orogenic complex was subsequently eroded and peneplained.

The intense orogenic activity ceased toward the close of the middle Eocene or early late Eocene, and the uplifted, faulted, and folded orogenic complex was subsequently eroded and [http://www.merriam-webster.com/dictionary/peneplain peneplained].

===Late Eocene to Present===

===Late Eocene to Present===