Tectonics of the Caribbean Richard Robertson


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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




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