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By M. Iturralde-Vinent and Ed Lidiak

The Latinamerican Geological Colloquium are held every three years in Germany, with extensive participation of South and Central American geologists. Members and the co-leader of IGCP Project 433 have attended the 17th meeting (see report forSttutgart) and now the 18th meeting. Attendance at the 18th meeting was less than the previous one, but the quality of the oral presentations and posters was equally high, as was the excellent organization. Four members of the IGCP Project 433 attended the meeting, two from Cuba (K. Nuñez and M. Iturralde-Vinent) and two from Germany (W. Maresch, P.- K. Stanek).

K. Nuñez presented a poster about the "Plate boundary between the North American and Caribbean plates, structural deformational phases" where four phases were described. Krebs, Maresch and coworkers reported on the "Geochronology and petrology of high pressure metamorphic rocks of the Rio San Juan complex, Northern Dominican Republic". Iturralde’s Keynote presentation was about "IGCP Project 433 Caribbean Plate Tectonics, the origin and evolution of the Caribbean. Status of the debate: The multiple arc vs single arc hypothesis". This presentation focused on three issues: (1) The reconstruction of terranes in the Caribbean and the problems of restoring the original position and original dimensions of the terranes, as well as the problems of explanining the complex composition of some terranes. (2) The growing complexity of the origin and composition of circum Caribbean ophiolite belts. It is now well stablished that these belts encompass rocks of different ages, and distinct composition and origins, from oceanic plateau to suprasubduction environments. (3) The multiple arc vs single arc hypothesis. Utilizing the model of J. Pindell as a base, the possibility was discussed that the leading convergent edges of the Caribbean Plate may have developed as a series of distinct arcs and no as a single one.

Several presentations by non-members of the Project were extremely interesting, especially a series of reports about the study of the interactions between the Pacific plates and the SOAM-CARIB plates. New evidences were presented concerning infra-plate erosion taking place in several portions of the subduction zone in Central and South American trenches. These data additionally support the contention, by several authors, that the Nicoya complex of Costa Rica contains fragments of the Caribbean Plate.

The abstracts of the presentations are available from Terra Nostra 2: 2003: 1-93. They may be found at: http://www.geo.tu-freiberg.de/dynamo/LAK_18/Tagungsband-gesamt-24-3-03-final.pdf.

Abstracts

The multiarc hypothesis of the Caribbean evolution
Manuel A. Iturralde-Vinent, e-mail: iturralde@mnhnc.inf.cu

There are several plate tectonic interpretations of the Caribbean origin and evolution, but in independence of this, is important to understand how, how many, and for how long were active the convergent margins of the Caribbean associated with volcanic arcs. In the present time there are two convergent margins: the Lesser Antilles and Central America, but in the past there may have been more.

The multiarc hypothesis substain that during the evolution of the Caribbean realm several independent volcanic arcs have been active. The multiarcs being identified taking into account several criteria, as: 1. Change in the trend of the axial part (vulcano-plutonic core) of one arc with respect to the other; 2. Major unconformities and tectonic events separating one arc from the other; 3. A particular geochemistry of each arc's igneous suite; and 4. Simultaneous evolution of two or more independent arcs.

In some convergent edges of the Caribbean plate two or more arcs are superimpossed for a particular time, giving the impression that there was only one arc evolving since the Early Cretaceous; but in other segments of the convergent edges each arc occupy a distinct belt during particular time lapses. The interpretation that some segments of the arc became inactive as they collided with the continental margins of NOAM and SOAM, do not correlate with the actual timing of the collisional events.

The Plate Boundary Between The North American And Caribbean Plates, Structural Deformational Phases
Kenya Nuñez Cambra
Instituto de Geología y Paleontología. Vía Blanca s/n e/ Carretera Central y Línea del ferrocarril. San Miguel del Pedrón. Ciudad de la Habana. CP 11 000. Cuba. E-mail: kenya@igp.minbas.cu

The work was aimed at determining structural characteristic and updating the geological map of San Antonio del Sur area, located in Oriente province, Cuba. As result, this study contains new structural data collected from the field observation. The tectono-stratigraphical column for the area was worked out and the geological map was updated. It has also allowed for a better synthesis on the tectonic evolution of the area.
The following evolutional stage and deformational phases were stablished:
First: Cretaceous period marked by the volcanic island arc. At that time the volcano-sedimentary rocks were formed and later deformed in the Campanian to early Maastrichtian with first deformation phase (D1). Consist of very close (F1) macro folds, which are almost isoclinal.
Second: Late Maastrichtian. The cretaceous volcanic rocks were thrusted by ophiolite complex. According to the observation, the sense of thrusting from SE to NW. The second deformation phase (D2) consist of folds from micro to meso fold (F2) with vergence towards NNW.
Third: Oligocene - Miocene . The deformation by transpressional movement and generation of the thrust movement from SW toward the NE gave rise to the third deformation phase (D3). This deformation almost perpendicular form superimposed folds above the D1 and D2. Open folds characterize the F3 folds, with fold axis oriented to the NNW (350º).
Fourth: Oligocene - Miocene to Recent. Transpressional-transtensional tectonic movement became active along the Oriente fault; the sinistral sense of the movement generated the fourth, predominately brittle, deformational phase (D4). It is characterized by gently dipping fold (F4) with fold axis oriented to the NW.

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Last revised: April 16, 2003