The Evolution of the Cocos-North America-Caribbean Triple Junction From Detrital Zircon Analysis

Abstract

The tectonic framework and Cenozoic evolution of the Cocos–North America–Caribbean (Co–NA–Ca) triple junction remain subjects of major geological importance due to their complexity and regional impact. New U–Pb zircon geochronology of detrital sediments and detailed structural and geomorphic mapping from southern Chiapas, Mexico, provide insights into the magmatic and tectonic evolution of this plate boundary section. We identify the Escuintla Shear Zone as a lithospheric boundary separating the Chortís Block from North America, connecting eastward to the Motagua Fault and westward to the Tonalá Shear Zone. This structure has functioned as a pathway for Miocene arc magmatism and currently separates pre-Jurassic crystalline rocks to the north from the Huixtla Intrusive Suite to the south—a set of plutons recording protracted magmatic activity from the Cretaceous. Structural and geochronological data show that the Escuintla and Tonalá shear zones accommodated left-lateral motion during the Miocene and were later reactivated as brittle faults, probably during the late Neogene. By integrating new zircon data with previously reported magmatic ages, we refine the timing and rate of the eastward Chortís Block migration (∼21.5 km/m.y.), estimating a total displacement of ∼1,050 km since the Cretaceous. Our results provide new constraints on the crustal architecture and tectonic history of the region and highlight the role of long-lived strike-slip faulting in controlling the spatial organization of arc magmatism and deformation. This region represents a structural node in the diffuse boundary between the Cocos, North American, and Caribbean plates— possibly acting as a true triple junction during recent geological times.