IGCP Project short title: Caribbean Plate Tectonics Duration and ...
IGCP Project short title: Caribbean Plate Tectonics Duration and ... IGCP Project short title: Caribbean Plate Tectonics Duration and ...
20 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 Grenvile 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 is characterized by high Plow T metamorphism. Nevertheless, the present tectonic position 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 basin-ward deposits 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 Concerning the tectonic position of the Cuban Cretaceous vulcano-plutonic island arc suites, important unpublished information was presented to the audience, including highresolution seismic profiles of several areas of Cuba. The issue was to evaluate 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, then the Escambray is 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, isotopic 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. WORKSHOP ON THE GEOCHEMISTRY OF THE CARIBBEAN PLATEAU AND CRETACEOUS ISLAND ARC TERRANES, AND THEIR IMPLICATIONS FOR THE GEODYNAMICS OF THE CARIBBEAN Leicester, U.K., April 23-24, 2001 Convener: P.M.E. Thompson 20
21 The aim of the Workshop was for the main research groups in this field to discuss recent research on the Caribbean region, specifically on the Cretaceous Caribbean plateau, the island arc terranes associated with it, and the tectonic evolution of the Caribbean region. The workshop lasted 2 days: the first day was focussed on the Mesozoic tectonic and structural evolution of the region whereas the emphasis on the second day was on the magmatic evolution and geochemistry of the Caribbean plateau, and the island arc terranes. The Workshop hosted 35 participants from six countries (Colombia, United States, Italy, France, Germany and the UK). In addition, 30+ researchers from 5 other countries registered interest in the proceedings, but were not able to attend. Some of the main research groups were: 1. Leicester, UK; represented by Kerr (now Cardiff), Saunders, Tarney, Thompson and White 2. Grenoble, France; represented by Arndt, Jaillard and Lapierre and Mamberti 3. Palmero, Italy; represented by Coltorti and Giunta 4. Regional tectonic analysis group, represented by Draper, Maresch, Pindell and Stanek In total, 17 oral presentations were scheduled, though the emphasis was on informal discussion. To facilitate this, a long discussion session was scheduled at the end of each day, and the discussion chairs saught points to discuss from other participants prior to this. First day: Geophysical and tectonic models The chair of the first day's discussion was Roz White (Leicester), who led a discussion on how the geophysical and tectonic models discussed that day could fit in with the existence of the Caribbean plateau. It was agreed that Pindell's new comprehensive and detailed model for the tectonic evolution of the Caribbean did not rely on the presence of the Caribbean plateau: indeed the word plateau was never specifically mentioned in his talk. Plateau workers counteracted this by saying that a thick buoyant oceanic plateau would be very difficult to subduct, and would therefore significantly affect the tectonics of the Caribbean region, in particular the subduction polarity reversal. They cite the arrival of the buoyant and thick Caribbean plateau at the eastward dipping subduction zone as a mechanism for the flip, in a situation analagous to that seen in the Solomon Isles with the attempted subduction of the Ontong Java oceanic plateau. However, Pindell believes the subduction polarity reversal occurred at ca. 120 Ma (before the bulk of the plateau was formed), on the basis of the following pieces of evidence: 1. Abundant evidence for a large tectonic event around that time 2. Unconformities in many arc-related sequences at ca. 120Ma. 3. P-T paths from high-pressure metamorphic rocks 21
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21<br />
The aim of the Workshop was for the main research groups in this field to discuss<br />
recent research on the <strong>Caribbean</strong> region, specifically on the Cretaceous <strong>Caribbean</strong> plateau,<br />
the isl<strong>and</strong> arc terranes associated with it, <strong>and</strong> the tectonic evolution of the <strong>Caribbean</strong> region.<br />
The workshop lasted 2 days: the first day was focussed on the Mesozoic tectonic <strong>and</strong><br />
structural evolution of the region whereas the emphasis on the second day was on the<br />
magmatic evolution <strong>and</strong> geochemistry of the <strong>Caribbean</strong> plateau, <strong>and</strong> the isl<strong>and</strong> arc terranes.<br />
The Workshop hosted 35 participants from six countries (Colombia, United States,<br />
Italy, France, Germany <strong>and</strong> the UK). In addition, 30+ researchers from 5 other countries<br />
registered interest in the proceedings, but were not able to attend. Some of the main research<br />
groups were:<br />
1. Leicester, UK; represented by Kerr (now Cardiff), Saunders, Tarney, Thompson <strong>and</strong><br />
White<br />
2. Grenoble, France; represented by Arndt, Jaillard <strong>and</strong> Lapierre <strong>and</strong> Mamberti<br />
3. Palmero, Italy; represented by Coltorti <strong>and</strong> Giunta<br />
4. Regional tectonic analysis group, represented by Draper, Maresch, Pindell <strong>and</strong> Stanek<br />
In total, 17 oral presentations were scheduled, though the emphasis was on informal<br />
discussion. To facilitate this, a long discussion session was scheduled at the end of each day,<br />
<strong>and</strong> the discussion chairs saught points to discuss from other participants prior to this.<br />
First day: Geophysical <strong>and</strong> tectonic models<br />
The chair of the first day's discussion was Roz White (Leicester), who led a<br />
discussion on how the geophysical <strong>and</strong> tectonic models discussed that day could fit in with<br />
the existence of the <strong>Caribbean</strong> plateau. It was agreed that Pindell's new comprehensive <strong>and</strong><br />
detailed model for the tectonic evolution of the <strong>Caribbean</strong> did not rely on the presence of the<br />
<strong>Caribbean</strong> plateau: indeed the word plateau was never specifically mentioned in his talk.<br />
<strong>Plate</strong>au workers counteracted this by saying that a thick buoyant oceanic plateau would be<br />
very difficult to subduct, <strong>and</strong> would therefore significantly affect the tectonics of the<br />
<strong>Caribbean</strong> region, in particular the subduction polarity reversal. They cite the arrival of the<br />
buoyant <strong>and</strong> thick <strong>Caribbean</strong> plateau at the eastward dipping subduction zone as a<br />
mechanism for the flip, in a situation analagous to that seen in the Solomon Isles with the<br />
attempted subduction of the Ontong Java oceanic plateau. However, Pindell believes the<br />
subduction polarity reversal occurred at ca. 120 Ma (before the bulk of the plateau was<br />
formed), on the basis of the following pieces of evidence:<br />
1. Abundant evidence for a large tectonic event around that time<br />
2. Unconformities in many arc-related sequences at ca. 120Ma.<br />
3. P-T paths from high-pressure metamorphic rocks<br />
21
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