Crustal structure of the Western Azuero Peninsula, Panama
Insights into the structure of accretionary complexes and forearc ophiolites
Carolina Ortiz-Guerrero (University of Florida)
Camilo Montes (Universidad del Norte)
David W. Farris (East Carolina University)
Catalina Agudelo (Universidad de los Andes)
Margarita Ariza Acero (University of Lausanne)
Juliana Ayala (Universidad de los Andes)
Jose David Avellaneda (Universidad de los Andes)
Alejandro Cortes-Calderon (ETH Zürich)
Billy Revelo-Obando (TU Delft - Applied Geophysics and Petrophysics)
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Abstract
Detailed geologic mapping (639 field stations in ~700 km2) and a ~50 km-long gravity survey (142 stations) in the western Azuero Peninsula revealed two faulted and folded slivers of oceanic crust attached to the trailing edge of the Caribbean Large Igneous Plateau (CLIP). Our new data, along with published geochronology, allowed us to reconstruct the Cretaceous forearc configuration of the trailing edge of the CLIP prior to seamount collision, ophiolite accretion, and whole-margin deformation. The ophiolite in western Azuero is composed of two tectonic slivers arranged in south-verging, imbricated thrust faults that stack a ~73 Ma pillow, flow, and picritic basalt and black chert, together with a ~ 89–93 Ma and older basalt flows and capping red chert sequences. Accretion of these slivers to form a supra-subduction zone ophiolite resulted from the middle Eocene collision and accretion of Galapagos seamounts against the trailing edge of the CLIP. Accreted seamounts are arranged in a north-verging antiformal stack duplex, and below the thrust sheets. Change in kinematics after fission of the Cocos-Nazca Plate during early Miocene times prompted the propagation of the Azuero-Sona fault zone flower structure, favouring the preservation of these slivers of oceanic crust.
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