Evolution of the Southern Caribbean Plate Boundary

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Print Version (594261 bytes) EOS, TRANSACTIONS AMERICAN GEOPHYSICAL UNION, VOL. 87, NO. 9, doi:10.1029/2006EO090001, 2006 Evolution of the Southern Caribbean Plate Boundary Alan Levander Department of Earth Science, Rice University, Houston, Texas, USA Michael Schmitz Venezuelan Foundation for Seismological Research, Caracas, Venezuela Hans G. Avé Lallemant Department of Earth Science, Rice University, Houston, Texas, USA Colin A. Zelt Department of Earth Science, Rice University, Houston, Texas, USA Dale S. Sawyer Department of Earth Science, Rice University, Houston, Texas, USA Maria B. Magnani Department of Earth Science, Rice University, Houston, Texas, USA Paul Mann Institute for Geophysics, University of Texas at Austin, Austin, Texas, USA Gail Christeson Institute for Geophysics, University of Texas at Austin, Austin, Texas, USA James E. Wright Department of Geology, University of Georgia, Athens, Georgia, USA Gary L. Pavlis Department of Geological Sciences, Indiana University, Bloomington, Indiana, USA James Pindell Department of Earth Science, Rice University, Houston, Texas, USA Abstract It is generally accepted that the cores of the continents, called cratons, formed by the accretion of island arcs into proto-continents and then by proto-continental agglomeration to form the large continental masses. Mantle-wedge processes, combined with higher melting temperatures during the Archean (2.5–3.8 billion years ago) and possibly thrust stacking of highly depleted Archean oceanic lithosphere, produced a strong, buoyant, upper mantle chemical boundary layer. This stabilizing mantle layer, known as the tectosphere, has shielded the Archean cratons from most subsequent tectonic disruption and is highly depleted in iron, providing the positive buoyancy that is required to ‘float’ the continents more than four kilometers above the surrounding ocean basins. What is not clear is whether today the continental mass is growing, shrinking, or is at steady state. A number of continental growth curves have been proposed; the most widely accepted models call for rapid continental growth in the late Archean and Paleoproterozoic (between 3.0 and ˜1.7 billion years ago), followed by slow growth to the present. Whether modern continental accretion and something akin to tectosphere formation are occurring today is an open question. It is not clear how island arcs accrete to the continents, or if modern arcs contribute to continental growth. Seismic observations of arcs worldwide show that the crustal velocity structure is too fast, and hence the chemical composition too silica-poor, to generate an average continental crust without substantial chemical and/or mechanical refining during or subsequent to accretion. Published 28 February 2006. Index Terms: 7205 Seismology: Continental crust (1219); 8111 Tectonophysics: Continental tectonics: strike-slip and transform; 8108 Tectonophysics: Continental tectonics: compressional. Print Version (594261 bytes) Citation: Levander, A., et al. (2006), Evolution of the Southern Caribbean Plate Boundary, Eos Trans. AGU, 87(9), doi:10.1029/2006EO090001. Copyright 2006 by the American Geophysical Union.

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