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The AAPG/Datapages Combined Publications Database

AAPG Special Volumes

Abstract

C. Bartolini, R. T. Buffler, and J. Blickwede, 2003, The Circum-Gulf of Mexico and the Caribbean: Hydrocarbon habitats, basin formation, and plate tectonics: AAPG Memoir 79, p. 638-655.

Copyright copy2003. The American Association of Petroleum Geologists. All rights reserved.

Previous HitGravityNext Hit Constraints on the Crustal Structure of Central America

Kevin Mickus

Department of Geosciences, Southwest Missouri State University, Springfield, Missouri, U.S.A.

ACKNOWLEDGMENTS

I would like to thank Carlos Aiken for the use of his Mexico Previous HitgravityNext Hit database. Useful discussions with Burke Burkart helped to clarify interpretations of the Previous HitgravityNext Hit data, especially palinspastic reconstructions in Guatemala. Reviews by Burke Burkart and G. R. Keller improved the manuscript.

ABSTRACT

Previous HitGravityNext Hit data from Central America and the adjacent offshore regions were analyzed in conjunction with seismic reflection/refraction Previous HitmodelsNext Hit, seismicity studies, geologic mapping, and well data to determine a Previous HitgravityNext Hit-based crustal structure for the region. Analysis of the Previous HitgravityNext Hit data included the construction of a Bouguer and three isostatic residual Previous HitgravityNext Hit-Previous HitanomalyNext Hit maps, and 2-D Previous HitgravityNext Hit Previous HitmodelsNext Hit across Guatemala/Belize, Nicaragua/Honduras, and Panama, respectively. The isostatic residual-Previous HitgravityNext Hit Previous HitanomalyNext Hit map that emphasizes anomalies caused by crustal and upper mantle sources was used to correlate Previous HitgravityNext Hit anomalies with known geologic/tectonic features and to emphasize possible previously unknown geologic features in the upper crust. These include granitic rocks in central Guatemala that are related to the Chiapas Massif in southeastern Mexico, basement uplifts under the carbonate platform sediments in northern Guatemala, and thin or dense sediments in the El Salvador depression. In Nicaragua and Honduras, the Nicaragua depression thickens toward the Costa Rican border, and the Mosquitia Basin is seen to consist of a series of depositional centers, possibly pull-apart basins. In Panama, Quaternary volcanic rocks are shown to occur close to the Choco Block boundary in the Gulf of Mexico. However, based on isostatic residual-Previous HitgravityNext Hit maxima over mafic igneous material in northern Panama, the boundary between the Chorotega and Choco Blocks may extend 150 km west of its present position.

The 2-D Previous HitgravityNext Hit Previous HitmodelsNext Hit indicate that the crustal thickness of the Maya and Chortis Blocks is approximately 36–38 km and approximately 22 km under Panama. However, the density of the upper mantle is higher under Panama than it is under Guatemala and Nicaragua. To model a large-amplitude Previous HitgravityNext Hit maximum along the Middle America subduction zone, a combination of an ophiolitic complex and a steeply dipping Cocos Plate was required. Isostatic residual-Previous HitgravityNext Hit anomalies indicate that the ophiolitic complex is not continuous along the Middle America trench but occurs in discontinuous steps. To explain a regional Previous HitgravityNext Hit maximum over the Nicaraguan volcanic belt, a deep (gt5 km) mafic (?) body was required; however, its exact position cannot be determined from Previous HitgravityNext Hit modeling alone. Previous HitGravityNext Hit modeling indicates that subduction does not occur between the Nazca and Caribbean Plates; however, this solution is not unique. If the boundary between the two plates is a transform boundary, this boundary must be dipping at a steep angle. To model a large amplitude Previous HitgravityTop maximum and minimum along the northern coast of Panama, a subducting plate (Caribbean) was required, with the Caribbean upper mantle being denser than that beneath Panama.

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