Late Cretaceous to Miocene seamount accretion and mélange formation in the Osa and Burica Peninsulas (Southern Costa Rica): episodic growth of a convergent margin

• DOI: 10.1144/sp328.17
• Publication Date: 2009-12-23T18:32:55Z
• Authors: David Marc Buchs; Peter Oliver Baum...; Claudia Baumgartn...; Alexandre Nicolas...; Sarah-Jane Jackett; Marc-Olivier Dise...; Jérôme Stucki
• Keywords: Seamount; Margin (machine learning); Peninsula

Abstract Multidisciplinary study of the Osa and Burica peninsulas, Costa Rica, recognizes Igneous Complex Mélange – records a complex Late Cretaceous–Miocene tectonic–sedimentary history. The Complex, an accretionary prism ( sensu stricto ) comprises mainly basaltic lava flows, with minor sills, gabbroic intrusives, pelagic limestones radiolarites. Sediments or igneous rocks derived from upper plate are absent. Four units delimited on base stratigraphy geochemistry lie in contact along reactivated palaeo-décollement zones. They comprise fragments Coniacian–Santonian oceanic plateau (Inner Complex) to Middle Eocene seamounts (Outer Complex). unrelated other complexes Rica Panama exotic respect partly overthickened Caribbean Plate; they formed by multiple accretions between Cretaceous Eocene, prior genesis mélange. Events high-rate accretion alternated periods low-rate tectonic erosion. NW has block-in-matrix texture at various scales, produced sedimentary processes later tectonically enhanced. Lithologies debris flows hemipelagic deposits. Clastic components (grains large boulders) indicate mass wasting forearc deposits volcanic arc. Gravitational accumulation thick pile trench sediments culminated shallow-level accretion. Mass-wasting margin was probably triggered seamount subduction and/or reorganization larger scale. provides new geological constraints for associated processes, as well erosive/accretionary nature convergent margins devoid accreted sediments.