Origin of the Caribbean Plate Conference, Spain 2006

 

 

*Honorary Departmental Fellow, Institute of Geography and Earth Sciences, Aberystwyth, Wales

**Professor of Advanced Stratigraphy, Central University of Venezuela, Caracas.

 

An international research conference, entitled "Geology of the area between North and South America, with focus on the origin of the Caribbean Plate", took place in Sigüenza, Spain, from May 29 - June 2, 2006.  Fifty-five people from 11 countries attended the meeting, which was chaired by Drs. Albert W. Bally, Maria Antonieta Lorente and David G. Roberts.  Sigüenza authorities and volunteers lent a great deal of enthusiastic support, while BP, Repsol, Shell, Statoil and SEPM granted financial encouragement.

Sigüenza is a beautiful mediaeval town whose old centre includes fine stone architecture and a superb cathedral.  Steep cobbled streets ascend to a majestic, renovated 12th century castle, today a luxurious hotel, where our meeting took place.  The castle granted use of a splendid, arched stone meeting room and offered accommodation in atmospheric surroundings - a baronial dining hall and rooms furnished with antiques, ranged around a central courtyard.

We chose Sigüenza for the meeting because it is easily accessible by road or rail from Madrid or Barajas airport.  It offers conference facilities, cultural interest, restaurants and bars and is sited in countryside with castles and ancient villages among spectacular rock outcrops, visited in a mid-week field trip.  Importantly, its small size and location of conference attendees in the same hotel assured that people stayed more or less together and encouraged discussion.

Over 40 scientific papers and posters were presented and discussed (abstracts on this web page). Speakers had ample time (35 minutes) to present their work.  No one needed to rush and nobody went to sleep.  Fifteen minutes of question and answer followed each talk and round table discussion at the end of each day provided opportunity for further discussion.  Points raised were recorded and presented to the meeting each morning.  There was also a wrap up session at the end of the conference.  This format of relaxed interaction and discussion was very successful.  Positive feedback prompts us to plan Sigüenza II for 2009.

Perhaps the greatest obstacle to Caribbean understanding is the absence of ocean fracture patterns, magnetic anomalies and recognized spreading ridges (except for the centre of the Cayman Trough, Fig. 1).  Basaltic eruptions have thickened large areas of the Caribbean Plate and obscure its deeper architecture.  Where this has not occurred, the crust is thinned by extension and shows wedges of dipping flows characteristic of the change from rifting to spreading.  Nowhere has the original crust been sampled in place, but regional geological considerations (rifts in North and South America and obducted rocks on Cuba, Hispaniola, Puerto Rico, La Désirade, Costa Rica) suggest its Jurassic age.  Liassic-Lower Dogger volcaniclastic rocks in Costa Rica, upper Jurassic volcanic rocks on Cuba, Hispaniola, Puerto Rico and La Désirade and volcaniclastic rocks at least as old as Albian in the north-eastern Lesser Antilles suggest that plate margin volcanism began along with spreading.

The established idea is that the Caribbean Plate formed in the Pacific during the Jurassic (e.g. Pindell and Barrett, 1990) and thickened in the Cretaceous above a mantle plume or a hotspot.  While migrating eastwards the resulting plateau collided with a volcanic arc at the eastern, subducting margin of the plate, causing subduction to stop and reverse its polarity.  The plate then entered the space between North and South America, colliding with the Yucatán Peninsula and Colombia on entry and picking up pieces of continent.  The Yucatán Basin formed south of the Cuban section of arc.  Volcanic activity ceased when the arc collided obliquely and diachronously with the Florida-Bahamas platform and along northern South America in the Eocene to Oligocene.  The continental fragments of Yucatán and Colombia resurfaced after deep burial (ca. 75 km) and Hp/Lt metamorphism.  Cuba and the Yucatán Basin became detached from the Caribbean Plate and joined North America.  The remaining plate progressed eastwards, interacting diachronously with northern South America to create northern uplifts and complementary foreland basins and causing fragmentation and dispersal along the Greater Antilles.  Inter- or back-arc spreading in the Grenada Basin separated the Aves Ridge from the Lesser Antilles, which are the active remains of the arc that entered the Caribbean.  This model invokes major (up to 80°) rotation of the large continental blocks of Yucatán (from the Gulf of Mexico) and Chortis (from SW Mexico) and accretion of the latter to the northwestern part of the Caribbean Plate. It geometrically requires complex processes, such as slab rollback in different directions below the entering plate and the opening Yucatán Basin, for which there are no supporting data.

In the absence of in-place oceanic data, the in-place model turns to global analogues. The Caribbean, Scotia and Banda plates are strikingly similar in shape and dimension and share a common tectonic setting (Fig. 2).  Each lies between sinistrally offset major continental blocks to the north and south.  Divergent spreading patterns in oceanic areas both east and west of the plates show their extensional settings.  Each plate has a curved volcanic arc in the east. NW trending volcanic arcs bound Banda and the Caribbean in the west (Scotia is bounded by the NW trending Shackleton Ridge).  Scotia and Banda both carry spreading ridges and dated magnetic anomalies and both are known to have formed in place.  The similarities imply that the Caribbean Plate formed in place also, by NW-SE mid ocean spreading (Beata Ridge) followed by E-W back-arc spreading (Aves Ridge). It also suggests that the plate is rimmed by continental fragments and these are evidenced by continental rocks on Cuba, northern Hispaniola and Puerto Rico, crustal thicknesses, gravity data, ancient zircons in arc rocks and abundant high silica rocks such as tonalites and andesites.  The data indicate continental basement beneath the whole of Central America, which has always formed the western margin of the Caribbean Plate.

The Geological Society of London will present the conference proceedings in a Special Publication.  The volume will be unusual in that two of the editors, Keith James and Jim Pindell, champions of the different Caribbean models, will collaborate to present and discuss their different ideas.  Maria Antonieta Lorente will be an impartial third editor.  More than thirty articles will present new data.  Points arising from conference discussion will appear at the end of the book, along with comments from the conference chairs and with studies and ocean drill sites suggested to resolve the debate.

 

References:

James, K. H., 2005, A simple synthesis of Caribbean geology: Transactions, 16th Caribbean Geological Conference, Barbados, Caribbean J. of Earth Sciences, v. 39, p. 71-84.

 

James, K. H., 2006 Arguments for and against the Pacific origin of the Caribbean Plate: discussion, finding for an inter-American origin: Geologica Acta, v. 4, no. 1-2, p. 279-302.

 

James, K. H., 2006, Structural Geology: from local elements to regional synthesis: In: Bundschuh, J. and G. E. Alvarado (eds.) Central America: Geology, Resources and Hazards, Ed. Balkema, Chapter 11, p. 277-321.

 

Pindell, J. L., and S. F. Barrett, 1990, Geological evolution of the Caribbean region; A plate-tectonic perspective, in, Dengo, G. and J. E. Case, The Caribbean Region, The Geology of North America, vol. H, Geological Society of America, p. 405-432.

 

Pindell, J., L. Kennan, K-P. Stanek, W. V. Maresch 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.

 

Photographs:

 

Mid-week, half day conference trip to spectacular Triassic outcrops north of Sigüenza.

 

Conference committee and chairs in the courtyard of Sigüenza Castle (left to right: Cristina Rzepka de Lombas, Maria Antonieta Lorente, Keith James, Bert Bally, David Roberts, Lorenzo Villalobos)