Pre-Upper Eocene Stratigraphy
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
Figures & Tables
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.
It is interesting to read early papers by reputable geologists such as E. DeGoyler (1918), J. W. Lewis (1932), or R. H. Palmer (1945), and to realize how little was known or understood about the geology of the southern portion of the North American continent in the early part of the 20th century.
Much early understanding of the geology of Cuba resulted from a series of studies conducted between 1936 and 1946 by the University of Utrecht, Holland, under the direction of L. M. R. Rutten. Some resultant publications are Rutten (1936), MacGillavry (1937), Thiadens (1937a, b), Vermut (1937), van Wessen (1943), Keijzer (1945), Hermes (1945), and De Vletter (1946). These authors outlined the components of a classic geosyncline. Between the late 1930s and late 1950s, Cuban geologists and paleontologists, such as P. R. Ortega y Ros, J. Broderman, P. Bermudez, and J. F. Albear, published several articles about the island’s geology.
The search for oil has contributed significantly to the present understanding of the island’s geology.