Tectonics of the Caribbean

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Tectonics of the Caribbean

• Richard Robertson
• Seismic Research Unit, U.W.I.
• St. Augustine, Trinidad
• www.uwiseismic.com

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Outline

• Definitions Tectonics, Caribbean Plate
• Plate Tectonics
• Evolution of the Caribbean
• Physiographic/Tectonic Provinces
• Tectonics of the Caribbean
• Summary

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Tectonics

• The processes responsible for tectonic activity
• Field of study concerned with structures within
  the crust and with forces and movements that
  operate to create these
• Concerned with mountain building with the
  development of cratons and tectonic terranes gt
  earthquakes, volcanoes tsunamis

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The Earths layered structure

• Inner core 1216 km thick and consists of solid
  rock at very high temperature and pressure
• Outer core extends up to 2270 km from the centre
  of the earth and consists mainly of molten iron
  with about 10 nickel and traces of other
  materials
• Mantle extends to 2900 km and consists of
  silicate rocks due to high temperature and
  pressure the rocks are able to flow extremely
  slowly like a thick stick liquid
• The Mantle accounts for 83 of the Earths
  volume 67 of its mass
• The Upper and lower mantle separated by the 670
  km seismic discontinuity

Melting of the more fusible constituents of the
upper mantle produces magma
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Lithospheric Plates
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Plate boundary settings
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The Caribbean Plate

• A lithospheric plate consisting mainly of a
  unusually thick, oceanic plateau situated between
  two major continental regions
• A geologically complex region that displays a
  variety of plate boundary interactions including
  subduction (Lesser Antilles), transcurrent/strike-
  slip (north south) and sea-floor spreading
  (Cayman Trough)

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The Caribbean
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Evolution of Caribbean

• Allochthonous/Mobilist vs. In Situ/Fixist models
  for origin of Caribbean
• In-situ evolution
• Gulf of Mexico Caribbean region existed in the
  past i.e. during Triassic, Jurassic early
  Cretaceous
• Allocthonous evolution
• All accept significant amounts of eastward
  Caribbean migration relative to the Americas
• A Great Arc vs Multi-arc evolution of the region
• Interpretation of the facts gt A single geology
  and too many points of view

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Evolution of the Caribbean Plate
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The Caribbean IGCP Project 433

• Is the Caribbean Plate allochthonous or developed
  in situ?
• There is a single Great Arc or the compressive
  margins evolved as multiarcs?
• Why can not be reconcile local geology with the
  general models?

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Physiographic regions
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Geologic Provinces
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Tectonics of the Caribbean - I

• Result primarily from the interaction of one
  relatively small plate of lithosphere with
  surrounding plates
• The Caribbean geologically complex region
  variety of plate boundary interactions including
  
• Subduction (Lesser Antilles Central America)
• Transcurrent (strike-slip) on northern and
  southern boundaries
• Sea floor spreading in Cayman Trough

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Tectonics of the Caribbean - II

• Caribbean a lithospheric plate that consists
  mainly of anomalously thick, oceanic plateau
  located between 2 major continental regions gt
  tectonic interactions between thick oceanic crust
  and continental crust

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Caribbean Seismicity

• First motion studies indicate left-lateral strike
  slip at northern right-lateral strike slip at
  southern boundary gt left lateral and right
  lateral transform boundaries
• Thrust fault solutions, typical of upper parts of
  convergent plate boundaries occur at western and
  eastern margins of plate
• Depth of hypocentres and their positions relative
  to island arc volcanoes indicates Wadati-Benioff
  Zones dipping eastward beneath Central American
  westward beneath Lesser Antilles

Caribbean Earthquakes 1964 to 2002
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Summary

• The Caribbean is a geologically complex region
  which exhibits a variety of plate boundary
  interactions and by extension tectonic features
• It is a lithospheric plate that consists mainly
  of anomalously thick, oceanic plateau located
  between 2 major continental regions
• Despite recent advances in knowledge there is
  still disagreement over its evolution

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References

• Mattson, Peter, H. ed. (1977) West Indies island
  arcs. Benchmark Papers in Geology V. 33.
  Dowden, Hutchinson Ross, Inc., p. 361. (see
  Chapters 2, 32-35b)
• Jackson, Trevor, A. ed. (2002) Caribbean Geology
  into the Third Millennium transactions of the
  Fifteenth Caribbean Geological Conference.
  University of the West Indies Press, 279p.
• Donovan, Stephen K. and Jackson, Trevor, A.
  (1994) Caribbean Geology An Introduction. The
  University of the West Indies Publishers
  Association, Jamaica, 289p.
• http//www.ig.utexas.edu/CaribPlate/CaribPlate.htm
  l

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Seismic Research Unit

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