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UNESCO/IUGS IGCP PROJECT 433
Caribbean Plate Tectonics
WORKSHOP ON THE NORTHERN CARIBBEAN PLATE BOUNDARY
Havana, March 19-27, 2001
E. Lidiak (egl+@ pitt.edu) and M. Iturralde-Vinent
(iturralde@mnhnc.inf.cu)
Leaders of IGCP Project 433
Purpose
A symposium and field workshop on the Northern Caribbean Boundary was held in Havana, Cuba, on March 19-27, 2001, as part of the 4th Cuban Geological and Mining Congress. The symposium, which included both oral and poster sessions and which was held on March 22, focused mainly on issues concerning the complex northern margin of the Caribbean plate in Cuba and its early geologic evolution. Among participants where scientist from Argentina, Canada, Chile, Colombia, Cuba, France, Great Britain, Italy, Mexico, New Zealand, Spain, USA.
A field trip to Central Cuba was held immediately after the Congress, March 24 to 27, in order to visit critical areas in the vicinity of Camagüey, central Cuba, where the northern Caribbean plate boundary is well exposed. This complex boundary near Camagüey encompasses elements of the passive continental margin, ocean crust and sediments, Cretaceous volcanic arc, as well as foreland and piggyback basins. The field excursion provided the participants with an excellent opportunity to examine in the field the structures and geologic relationships associated with this unique and critical tectonic boundary.
The Symposium
The purpose of the symposium was to focus on the characteristics of critical geologic terranes in central and eastern Cuba, Hispaniola, and Puerto Rico as they pertain to the northern Caribbean plate boundary in Cuba and to evaluate the present status of Caribbean plate tectonic models with respect to these field occurrences. Six special oral papers and 5 posters were presented. Each speaker was given 30 minutes, so extensive discussion followed each talk. These presentations were followed by a panel discussion period of several hours duration in which aspects of the northern plate boundary and the geology of Cuba were the subject of interesting debates and active exchange of data and interpretations.
The oral presentations and panel discussion was attended by a total of about 70-80 scientists. In the first presentation, M. Iturralde-Vinent (Cuba) gave an overview of the current state of plate tectonics in the Caribbean realm with special references to the geology of Cuba. He made the important point that detailed stratigraphic and tectonic data are critical to any viable plate tectonic model, but still there are many geologic units within the Caribbean, and specially in Cuba, whose origin and evolution is poorly understood, because the lack of modern studies. Therefore, understanding the Caribbean plate evolution will still require more field and laboratory research in key areas. Z. Gasparini (Argentina) then discussed the role of Jurassic marine reptiles in Cuba and their importance in evaluating early marine seaways in the early evolution of the Caribbean. This author suggested that the interchange of marine animals between western Tethys and the Pacific predate the break-up of Pangaea, as rocks of Lower and Middle Jurassic age yield fossils of marine reptiles in the eastern Pacific (Chile, Argentina, and in allochthonous terrains of Mexico, which show west-Tethyan affinities. The third and fourth presentations were made by G. Draper (USA). He discussed the high-pressure metamorphic rocks of central Cuba as metamorphic core complexes exposed as a result of low degree extensional faulting within the continental margin. He then discussed the early oceanic crustal terranes of central Hispaniola and the evidence they show for a mid-Cretaceous orogenic event and its possible relationship with the polarity subduction reversal of the Caribbean "Great Arc". G. Giunta (Italy) reported on the Motagua suture zone in Guatemala and its role as the northwestern boundary of the Caribbean plate. New geochemical data from the ophiolites suggest that there are both MORB and island arc complexes in the Motagua suture zone. The final oral presentation was made by J. Lewis (New Zealand) who described the tectonic and petrologic significance of peridotites and constituent chromitites as obducted fragments of contrasting mantle sections in the northern Caribbean region. These data, thou preliminary, indicate that the two large ophiolite outcrops of northeastern Cuba, yield distinct geochemical signature. M. Iturralde-Vinent then concluded with a discussion of the similarities and discrepancies that exist among the modern Caribbean plate tectonic models.
Posters presented as part of the northern Caribbean plate boundary Workshop included the following: New aspects of the geology of eastern Cuba (G. Millán-Cuba); Structural deformation phases at the northern plate boundary in Cuba (K. Nuñez-Cuba); Transitional marine environments in carbonate rocks of the Cretaceous volcanic arc of Cuba (R. Rojas-Cuba); Oceanic plagiogranites in Cuba (Sukar-Cuba); and Tectonic and geologic evolution of serpentinites in Puerto Rico (E. Lidiak-USA).
In the panel discussions that followed the oral presentations, the main issues centered on the origin of various critical geologic terranes in Cuba such as the Escambray, Purial, and Grenville metamorphic complexes, whether they are allochthonous or autochthonous, and how they can be integrated into the geologic evolution of the northern Caribbean plate boundary. For example, according to present knowledge, Purial massif is a vulcano-plutonic "island arc" complex of Cretaceous age, which present high P-low T metamorphism. Nevertheless, the present tectonic possition of this complex can hardly be associated with a subduction zone of any age. A lively discussion was also held on how the Rosario belt of western Cuba and the Placetas belt in central Cuba relate to the development of the ProtoCaribbean crust. Usually these belts have been interpreted as the southern basinward extention of the Bahamas platform, but another interpretation is that they represent the sediments and crust of the ProtoCaribbean.
Concerning the tectonic position of the Cuban Cretaceous vulcano-plutonic island arc suites, important unpublished information was presented to the audience, including high resolution seismic profiles of several areas of Cuba. The issue was if the island arc suite is allochthonous above the Escambray, with the roots located south of the Escambray; or if the island arc suite is allochthonous above the northern ophiolites and Placetas-Rosario belts, the Escambray been an allochthonous terrain located within the north diping subduction zone of the arc. Seismic data favour the second possibility, but the issue require more research.
After more than 5 hours of very often high-tuned discussions, many agree that there are some areas (call them terrains, belts or masifs) which are yet too poorly known as to be interpreted in a single easy manner, as it is currently assumed by some Caribbean plate tectonic models. More field and laboratory research focused on the petrology and internal structure of the Socorro (Grenvile), Escambray, Purial and Pinos metamorphic complexes, as well as on the stratigraphy and tectonic position of the Placetas and Rosario belts is urgently required before a fair interpretation of the origin of these geologic units can be reach. Available P-t path studies, absolute dating and geochemical data for the Escambray and Purial are still insufficient. Fortunately, several attendees to the meeting already agreed to work on some of these areas, and this is probably one of the most important results of the panel workshop.
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