Changes

The geology of Cuba has been a challenge to geologists because of features such as the presence of well-preserved Jurassic ammonites, the rich Tertiary foraminiferal faunas (including remarkable Paleogene orbitoids), the gigantic Upper Cretaceous rudistids, the spectacular limestone Mogotes of Pinar del Rio, the extensive outcrops of ultrabasic igneous rocks, the chromite and manganese deposits, and the extraordinary structural complexity. In addition to these features, the numerous petroleum seeps, many of them coming out of basic igneous rock, have attracted much attention.

The geology of Cuba has been a challenge to geologists because of features such as the presence of well-preserved Jurassic ammonites, the rich Tertiary foraminiferal faunas (including remarkable Paleogene orbitoids), the gigantic Upper Cretaceous rudistids, the spectacular limestone Mogotes of Pinar del Rio, the extensive outcrops of ultrabasic igneous rocks, the chromite and manganese deposits, and the extraordinary structural complexity. In addition to these features, the numerous petroleum seeps, many of them coming out of basic igneous rock, have attracted much attention.

==Regional setting==

==Regional setting==

Cuba is the largest of the Caribbean islands and has an arclike shape, concave to the south ([[:file:St58OverviewFG3.JPG|Figure 1]]). This shape has tempted some authors to call Cuba an island arc. The truth is much more complex. The broad and deep Strats of Florida separate Cuba from Florida, and the narrow, and relatively shallow, Nicholas and Old Bahamas channels separate Cuba from the Bahamas. To the northwest, Cuba adjoins the Gulf of Mexico and is separated from the Yucatan Platform by the narrow but deep Yucatan Channel. To the south, the Yucatan Basin appears to be enclosed between Cuba to the north and the Cayman Ridge, which is the westward continuation of the Sierra Madre in the southern Oriente province. Cuba, the Cayman Basin, and the Cayman Ridge appear to constitute a physiographic province between the stable margin of the North American craton and the highly mobile Caribbean Basin. This province is separated from the Chortis-Nicaraguan rise block, including Jamaica and Hispaniola, by the east to west pull-apart basin of the Cayman trough, whose spreading center has been recording the eastward migration of the Caribbean plate since the late Eocene.

Cuba is the largest of the Caribbean islands and has an arclike shape, concave to the south ([[:file:St58OverviewFG3.JPG|Figure 1]]). This shape has tempted some authors to call Cuba an island arc. The truth is much more complex. The broad and deep Strats of Florida separate Cuba from Florida, and the narrow, and relatively shallow, Nicholas and Old Bahamas channels separate Cuba from the Bahamas. To the northwest, Cuba adjoins the Gulf of Mexico and is separated from the Yucatan Platform by the narrow but deep Yucatan Channel. To the south, the Yucatan Basin appears to be enclosed between Cuba to the north and the Cayman Ridge, which is the westward continuation of the Sierra Madre in the southern Oriente province. Cuba, the Cayman Basin, and the Cayman Ridge appear to constitute a physiographic province between the stable margin of the North American craton and the highly mobile Caribbean Basin. This province is separated from the Chortis-Nicaraguan rise block, including Jamaica and Hispaniola, by the east to west pull-apart basin of the Cayman trough, whose spreading center has been recording the eastward migration of the Caribbean plate since the late Eocene.

[[file:St58OverviewFG4.JPG|thumb|300px|{{figure number|2}}Cuba generalized geologic map.<ref name=Pardo_2009 />]]

file:St58OverviewFG3.JPG|{{figure number|1}}Regional setting of Cuba.<ref name=Pardo_2009>Pardo, Georges, 2009, The geology of Cuba: AAPG Studies in Geology 58, 73 p.</ref>

file:St58OverviewFG4.JPG|{{figure number|2}}Cuba generalized geologic map.<ref name=Pardo_2009 />

Over most of its length, the northern coast of Cuba is the dividing line between stable conditions (at least since the Middle Jurassic) to the north and west and very complex ones to the south. Although it is geologically deformed ([[:file:St58OverviewFG4.JPG|Figure 2]]), the part of the northern coast of Cuba extending from eastern Natanzas to western Oriente belongs to the Florida-Bahamas carbonate bank province. To the south, in part under an upper Eocene or younger cover, is a relatively narrow belt, 45-160 km (28-99 mi) wide, of intensely folded and faulted Middle Jurassic to middle Eocene rocks consisting, from north to south, of:

Over most of its length, the northern coast of Cuba is the dividing line between stable conditions (at least since the Middle Jurassic) to the north and west and very complex ones to the south. Although it is geologically deformed ([[:file:St58OverviewFG4.JPG|Figure 2]]), the part of the northern coast of Cuba extending from eastern Natanzas to western Oriente belongs to the Florida-Bahamas carbonate bank province. To the south, in part under an upper Eocene or younger cover, is a relatively narrow belt, 45-160 km (28-99 mi) wide, of intensely folded and faulted Middle Jurassic to middle Eocene rocks consisting, from north to south, of:

* the ophiolitic basic igneous-volcanic (called igneous-volcanic because of being a mixture of intrusive and volcanic rocks with a general predominance of volcanic rocks) terranes, with ultrabasic intrusive rocks, many types and great thicknesses of basic, basaltic to andesitic volcanic rocks, volcanic-derived sediments, and granodioritic intrusives

* the ophiolitic basic igneous-volcanic (called igneous-volcanic because of being a mixture of intrusive and volcanic rocks with a general predominance of volcanic rocks) terranes, with ultrabasic intrusive rocks, many types and great thicknesses of basic, basaltic to andesitic volcanic rocks, volcanic-derived sediments, and granodioritic intrusives

* the southwestern sedimentary terranes, with primarily thin stratigraphic sections of platform to pelagic carbonates and cherts but locally with great thicknesses of older, continental-derived sandstones and shales showing various degrees of metamorphism

* the southwestern sedimentary terranes, with primarily thin stratigraphic sections of platform to pelagic carbonates and cherts but locally with great thicknesses of older, continental-derived sandstones and shales showing various degrees of metamorphism

The most striking feature about the geology of the island is the great disparity between the ophiolite-volcanic sequence of the basic igneous-volcanic terranes and the sedimentary sequences of the north-central and southwestern sedimentary terranes. Except for a few notable cases, essentially no relationship exists between these sedimentary and igneous terranes. There has been much argument about how the terranes came into contact and became structurally mixed, but it is generally accepted today that the ophiolite-volcanic sequence is totally allochthonous. [[:file:St58OverviewFG5.JPG|Figure 3]] shows a map of Cuba's major structural features and terrane distribution, and [[:file:St58OverviewFG6.JPG|Figure 4]] shows, in cross section, the structural relations between the various terranes.

The most striking feature about the geology of the island is the great disparity between the ophiolite-volcanic sequence of the basic igneous-volcanic terranes and the sedimentary sequences of the north-central and southwestern sedimentary terranes. Except for a few notable cases, essentially no relationship exists between these sedimentary and igneous terranes. There has been much argument about how the terranes came into contact and became structurally mixed, but it is generally accepted today that the ophiolite-volcanic sequence is totally allochthonous. [[:file:St58OverviewFG5.JPG|Figure 3]] shows a map of Cuba's major structural features and terrane distribution, and [[:file:St58OverviewFG6.JPG|Figure 4]] shows, in cross section, the structural relations between the various terranes.

Other than the Yucatan Basin, Cuba is probably the only place in the Caribbean with complete sections representative of the early Caribbean region after the separation of North and South America and before the formation of the present Caribbean plate in the Tertiary.

Other than the Yucatan Basin, Cuba is probably the only place in the Caribbean with complete sections representative of the early Caribbean region after the separation of North and South America and before the formation of the present Caribbean plate in the Tertiary.

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file:St58OverviewFG25.JPG|{{figure number|5}}Cuba. 163 Ma: Callovian. PC = Precambrian; PZ = Paleozoic.<ref name=Pardo_2009 />

file:St58OverviewFG25.JPG|{{figure number|5}}Cuba. 163 Ma: Callovian. PC = Precambrian; PZ = Paleozoic.<ref name=Pardo_2009 />

file:St58OverviewFG26.JPG|{{figure number|6}}Cuba. 144 Ma: early Tithonian.<ref name=Pardo_2009 />

file:St58OverviewFG26.JPG|{{figure number|6}}Cuba. 144 Ma: early Tithonian.<ref name=Pardo_2009 />

Paleogeographic maps (Figures 5-14) illustrate the possible past distribution of the most characteristic stratigraphic units. These maps are on a continental drift base modified from the Ocean Drilling Stratigraphic Network (ODSN) created in 2005 by the University of Bremen, with Florida occupying a fixed position. In all maps, Cuba is shown in its present position relative to Florida, although different parts of the island came from various places.  

Paleogeographic maps (Figures 5-14) illustrate the possible past distribution of the most characteristic stratigraphic units. These maps are on a continental drift base modified from the Ocean Drilling Stratigraphic Network (ODSN) created in 2005 by the University of Bremen, with Florida occupying a fixed position. In all maps, Cuba is shown in its present position relative to Florida, although different parts of the island came from various places.  

In these maps, autochthonous nappes, allochthonous nappes, and subduction will be used to describe, respectively, the thrusting toward the continent of the sediments, the basic igneous-volcanic rocks, and the subduction. Supported by observations in Cuba and elsewhere, these maps (as well as cross sections discussed later) show subduction as the main cause of the uplift of a convergent continental margin or ocean floor, whereas the nappes are the result of sedimentary or volcanic cover sliding away, under the force of gravity, from the area uplifted by subduction.

In these maps, autochthonous nappes, allochthonous nappes, and subduction will be used to describe, respectively, the thrusting toward the continent of the sediments, the basic igneous-volcanic rocks, and the subduction. Supported by observations in Cuba and elsewhere, these maps show subduction as the main cause of the uplift of a convergent continental margin or ocean floor, whereas the nappes are the result of sedimentary or volcanic cover sliding away, under the force of gravity, from the area uplifted by subduction.

Burke,<ref name=Burke_1988>Burke, K., 1988, Tectonic evolution of the Caribbean: Annual Review of Earth and Planetary Sciences, v. 16, p. 201-230.</ref> Pindell and Barrett,<ref name=Pindellandbarrett_1990>Pindell, J. L., and S. F. Barrett, 1990, Geologicla evolution of the Caribbean region, a plate-tectonic perspective, ''in'' The geology of North America, v. H: The Caribbean region: Geological Society of America, p. 405-432.</ref> Iturralde-Vinent,<ref name=Iturraldevinent_1996>Iturralde-Vinent, M. A., ed., 1996, Ofiolitas y arcos volcanicos de Cuba (Cuban ophiolites and volcanic arcs), ''in'' International Union of Geological Sciences-United Nations Educational, Scientific, and Cultural Organization International Geological Correlation Programe, Contribution 1, Project 364 (Geological correlation of ophiolites and volcanic arc terrane in the Circum-Caribbean realm), 254 p.</ref> Cobiella-Reguera,<ref name=Cobiellareguera_2005>Cobiella-Reguera, J. L., 2005, Emplacement of Cuban ophiolites: Geologica Acta, v. 3, no. 3, p. 273-294.</ref> Garcia-Casco et al.,<ref name=Garciacascoetal_2006>Garcia-Casco, A., R. L. Torres-Roldan, M. A. Iturralde-Vinent, G. Millan, K. Nunez Cambra, C. Lazaro, and A. Rodriguez Vega, 2006, High pressure metamorphism of ophiolites in Cuba: Geologica Acta, v. 4, no. 1-2, p. 63-88.</ref> Giunta et al.,<ref name=Giuntaetal_2006>Giunta, G., L. Beccaluav, and F. Siena, 2006, Caribbean plate margin evolution: constraints and current problems: Geologica Acta, v. 4, no. 102, p. 265-277.</ref> and Pindell et al.<ref name=Pindelletal_2006>Pindell, J. L., L. Kennan, K. P. Stanek, W. V. Maresh, and G. Draper, 2006, Foundations of Gulf of Mexico and Caribbean evolution: Eight controversies resolved: Geologica Acta, v. 4, no. 1-2, p. 303-341.</ref> have interpreted the Cretaceous Cuban subduction as northeast dipping and reversing polarity to the southwest during the Upper Cretaceous. Cuba's geology suggests that the subduction was continuously north dipping, and this concept is discussed in more detail below.

Burke,<ref name=Burke_1988>Burke, K., 1988, Tectonic evolution of the Caribbean: Annual Review of Earth and Planetary Sciences, v. 16, p. 201-230.</ref> Pindell and Barrett,<ref name=Pindellandbarrett_1990>Pindell, J. L., and S. F. Barrett, 1990, Geologicla evolution of the Caribbean region, a plate-tectonic perspective, ''in'' The geology of North America, v. H: The Caribbean region: Geological Society of America, p. 405-432.</ref> Iturralde-Vinent,<ref name=Iturraldevinent_1996>Iturralde-Vinent, M. A., ed., 1996, Ofiolitas y arcos volcanicos de Cuba (Cuban ophiolites and volcanic arcs), ''in'' International Union of Geological Sciences-United Nations Educational, Scientific, and Cultural Organization International Geological Correlation Programe, Contribution 1, Project 364 (Geological correlation of ophiolites and volcanic arc terrane in the Circum-Caribbean realm), 254 p.</ref> Cobiella-Reguera,<ref name=Cobiellareguera_2005>Cobiella-Reguera, J. L., 2005, Emplacement of Cuban ophiolites: Geologica Acta, v. 3, no. 3, p. 273-294.</ref> Garcia-Casco et al.,<ref name=Garciacascoetal_2006>Garcia-Casco, A., R. L. Torres-Roldan, M. A. Iturralde-Vinent, G. Millan, K. Nunez Cambra, C. Lazaro, and A. Rodriguez Vega, 2006, High pressure metamorphism of ophiolites in Cuba: Geologica Acta, v. 4, no. 1-2, p. 63-88.</ref> Giunta et al.,<ref name=Giuntaetal_2006>Giunta, G., L. Beccaluav, and F. Siena, 2006, Caribbean plate margin evolution: constraints and current problems: Geologica Acta, v. 4, no. 102, p. 265-277.</ref> and Pindell et al.<ref name=Pindelletal_2006>Pindell, J. L., L. Kennan, K. P. Stanek, W. V. Maresh, and G. Draper, 2006, Foundations of Gulf of Mexico and Caribbean evolution: Eight controversies resolved: Geologica Acta, v. 4, no. 1-2, p. 303-341.</ref> have interpreted the Cretaceous Cuban subduction as northeast dipping and reversing polarity to the southwest during the Upper Cretaceous. Cuba's geology suggests that the subduction was continuously north dipping, and this concept is discussed in more detail below.

The paleogeographic history presented here is in general agreement with that of Pszczolkowski.<ref name=Pszczoklowski_1999>Pszczolkowski, A., 1999, The exposed passive margin of North America in western uba, Caribbean basins, ''in'' P. Mann, ed., Sedimentary basins of the world: Amsterdam, Elsevier Sciene B.V., v. 4, p. 93-121.</ref> Differences are, for example, the position of the Guajaibon–Sierra Azul belt, the origin of the middle Cretaceous quartzose clastics, and the dip of the subduction zone.

The paleogeographic history presented here is in general agreement with that of Pszczolkowski.<ref name=Pszczoklowski_1999>Pszczolkowski, A., 1999, The exposed passive margin of North America in western Cuba, Caribbean basins, ''in'' P. Mann, ed., Sedimentary basins of the world: Amsterdam, Elsevier Sciene B.V., v. 4, p. 93-121.</ref> Differences are, for example, the position of the Guajaibon–Sierra Azul belt, the origin of the middle Cretaceous quartzose clastics, and the dip of the subduction zone. '''Stratigraphic unit names followed by an asterisk (i.e., Capitolio*) were originally named by Gulf Oil Company geologists and might, or might not, be used today in the same context.'''

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file:St58OverviewFG30.JPG|{{figure number|10}}Cuba. 80 Ma: Santonian.<ref name=Pardo_2009 />

file:St58OverviewFG30.JPG|{{figure number|10}}Cuba. 80 Ma: Santonian.<ref name=Pardo_2009 />

file:St58OverviewFG31.JPG|{{figure number|11}}Cuba. 67 Ma: Maastrichtian.<ref name=Pardo_2009 />

file:St58OverviewFG31.JPG|{{figure number|11}}Cuba. 67 Ma: Maastrichtian.<ref name=Pardo_2009 />

===Early(?)-Middle Jurassic===

===Early(?)-Middle Jurassic===

Very little is known about the pre-Late Jurassic history of the island except that the lower part of the San Cayetano clastics might be Lower Jurassic (163 Ma; [[:file:St58OverviewF25.JPG|Figure 5]]). The San Cayetano must have been deposited over an initially rifting basement that probably included fragments of continental crust as well as basaltic flows. This is supported by the pre-Neocomian granodioritic klippen of La Rana, Tres Guanos, and Rancho Veloz and the occurrences of the El Sabalo and Nueva Maria tholeitic basalts underlying the sedimentary section of the northern Rosario belt and Cifuentes* belt of the Sierra de Camajan.

Very little is known about the pre-Late Jurassic history of the island except that the lower part of the San Cayetano clastics might be Lower Jurassic (163 Ma; [[:file:St58OverviewFG25.JPG|Figure 5]]). The San Cayetano must have been deposited over an initially rifting basement that probably included fragments of continental crust as well as basaltic flows. This is supported by the pre-Neocomian granodioritic klippen of La Rana, Tres Guanos, and Rancho Veloz and the occurrences of the El Sabalo and Nueva Maria tholeitic basalts underlying the sedimentary section of the northern Rosario belt and Cifuentes* belt of the Sierra de Camajan.

It can also be assumed that, prior to the deposition of the Upper Jurassic rocks, a large area of basement was exposed to the northwest, extending from Florida's Sarasota arch to the Maya Mountains. The nature of this basement is generally unknown, but it must have been of granitic to granodioritic composition as indicated by the arkosic nature of the San Cayetano Formation. In south Florida, several wells have penetrated an undifferentiated Jurassic–Triassic volcanic section and Paleozoic granite. The basement must also have included Paleozoic sediments known to outcrop in the Maya Mountains, present as fragments in San Cayetano conglomerates, and, perhaps, as exotics in the Cayo Coco Formation. The bulk of the San Cayetano Formation accumulated south of this basement high.

It can also be assumed that, prior to the deposition of the Upper Jurassic rocks, a large area of basement was exposed to the northwest, extending from Florida's Sarasota arch to the Maya Mountains. The nature of this basement is generally unknown, but it must have been of granitic to granodioritic composition as indicated by the arkosic nature of the San Cayetano Formation. In south Florida, several wells have penetrated an undifferentiated Jurassic–Triassic volcanic section and Paleozoic granite. The basement must also have included Paleozoic sediments known to outcrop in the Maya Mountains, present as fragments in San Cayetano conglomerates, and, perhaps, as exotics in the Cayo Coco Formation. The bulk of the San Cayetano Formation accumulated south of this basement high.

As rifting continued, new oceanic crust formed with outpouring of basalts (El Sabalo) and serpentinization of the upper mantle.

As rifting continued, new oceanic crust formed with outpouring of basalts (El Sabalo) and serpentinization of the upper mantle.

==References==

==References==

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