Tectonics of the Caribbean Richard Robertson

Tectonics of the Caribbean

• Richard Robertson

• Seismic Research Unit, U.W.I.

• St. Augustine, Trinidad

• www.uwiseismic.com

Outline

• Definitions: Tectonics, Caribbean Plate

• Plate Tectonics

• Evolution of the Caribbean

• Physiographic/Tectonic Provinces

• Tectonics of the Caribbean

• Summary

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 => earthquakes, volcanoes & tsunamis

The Earth’s 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 Earth’s volume & 67% of its mass

• The Upper and lower mantle separated by the 670 km seismic discontinuity

Lithospheric Plates

Plate boundary settings

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)

The Caribbean

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 => A single geology and too many points of view

Evolution of the Caribbean Plate

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?

Physiographic regions

Geologic Provinces

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

Tectonics of the Caribbean - II

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

Caribbean Seismicity

• First motion studies indicate left-lateral strike slip at northern & right-lateral strike slip at southern boundary => 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

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

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.html

Seismic Research Unit

• Earthquake & Volcano Monitoring

• Research & Public Education

• www.uwiseismic.com

Thank you for listening!

• Earthquake & Volcano Monitoring

• Research & Public Education