From seamount accretion to tectonic erosion

Formation of Osa Mélange and the effects of Cocos Ridge subduction in southern Costa Rica

Paola Vannucchi, Donald Myron Fisher, Sara Bier, Thomas W. Gardner

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

The Costa Rica portion of the Middle America Trench (MAT) is characterized by active tectonic erosion, a process that causes the removal of material from the base of the upper plate as the plate boundary migrates upward. Offshore studies demonstrate accelerated subduction erosion starting at the Miocene-Pliocene boundary, as the result of subduction of thickened Galapagos related crust, as presently represented by the Cocos Ridge. The subduction of the Cocos Ridge also caused uplift and exposure of the outer forearc on the Osa Peninsula, which offers a window to explore the tectonic evolution of the area. The rocks outcropping on Osa Peninsula are a middle Eocene-middle Miocene mélange dominated by basalt, chert, and limestone resulting from accretion of seamounts. The accretion-dominated period of the MAT evolution ended at the Miocene-Pliocene boundary, when thickened crust, a paleo-Cocos Ridge, produced at the Galapagos hot spot arrived at the trench. The thick crust caused uplift and severe tectonic erosion of the accretionary edifice allowing exhumation of the Osa Mélange. The change from accretion to erosion caused the outer forearc to be offset along subvertical faults that define small (kilometer to tens of kilometers size) blocks that are going through differential vertical movements in response to the morphology of the subducting ridge. Subduction accretion and erosion are two processes that can alternate in time and space or coexist along the same margin, so that mass removal can develop on a previously growing margin and completely remove an accretionary prism.

Original languageEnglish (US)
Article numberTC2004
JournalTectonics
Volume25
Issue number2
DOIs
StatePublished - Apr 1 2006

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Costa Rica
seamounts
Tectonics
seamount
erosion
ridges
Erosion
tectonics
subduction
accretion
trench
crusts
Miocene
peninsulas
crust
margins
Pliocene
uplift
Calcium Carbonate
vertical movement

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology

Cite this

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title = "From seamount accretion to tectonic erosion: Formation of Osa M{\'e}lange and the effects of Cocos Ridge subduction in southern Costa Rica",
abstract = "The Costa Rica portion of the Middle America Trench (MAT) is characterized by active tectonic erosion, a process that causes the removal of material from the base of the upper plate as the plate boundary migrates upward. Offshore studies demonstrate accelerated subduction erosion starting at the Miocene-Pliocene boundary, as the result of subduction of thickened Galapagos related crust, as presently represented by the Cocos Ridge. The subduction of the Cocos Ridge also caused uplift and exposure of the outer forearc on the Osa Peninsula, which offers a window to explore the tectonic evolution of the area. The rocks outcropping on Osa Peninsula are a middle Eocene-middle Miocene m{\'e}lange dominated by basalt, chert, and limestone resulting from accretion of seamounts. The accretion-dominated period of the MAT evolution ended at the Miocene-Pliocene boundary, when thickened crust, a paleo-Cocos Ridge, produced at the Galapagos hot spot arrived at the trench. The thick crust caused uplift and severe tectonic erosion of the accretionary edifice allowing exhumation of the Osa M{\'e}lange. The change from accretion to erosion caused the outer forearc to be offset along subvertical faults that define small (kilometer to tens of kilometers size) blocks that are going through differential vertical movements in response to the morphology of the subducting ridge. Subduction accretion and erosion are two processes that can alternate in time and space or coexist along the same margin, so that mass removal can develop on a previously growing margin and completely remove an accretionary prism.",
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From seamount accretion to tectonic erosion : Formation of Osa Mélange and the effects of Cocos Ridge subduction in southern Costa Rica. / Vannucchi, Paola; Fisher, Donald Myron; Bier, Sara; Gardner, Thomas W.

In: Tectonics, Vol. 25, No. 2, TC2004, 01.04.2006.

Research output: Contribution to journalArticle

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AU - Gardner, Thomas W.

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