Geomorphic and exhumational response of the Central American Volcanic Arc to Cocos Ridge subduction

Abstract

[1] The timing of collision of the Cocos Ridge at the Middle America Trench remains one of the outstanding questions in the tectonic evolution of the Central American convergent margin. New analyses of the tectonic geomorphology of the Cordillera de Talamanca, the extinct volcanic arc inboard of the Cocos Ridge, coupled with low temperature thermochronometry data, provide insight into the cooling and erosional history of the arc from late Miocene to present. We identify a low-relief surface at high elevation along the northeastern flanks of the range, which represents a relict erosional landscape cut across shallow plutonic rocks of the arc edifice. Longitudinal profiles of rivers on this surface are isolated from steep downstream sections by prominent knickzones that are interpreted to reflect a migrating wave of transient incision generated during differential rock uplift of the range. Reconstruction of pre-incision profiles suggests that rock uplift during the growth of the Cordillera de Talamanca is no greater than $2 km. This inference is corroborated by results from our apatite (U-Th)/He and apatite fission track analyses along an elevation transect on Mt. Chirripó, the highest mountain in the Cordillera de Talamanca. Low-temperature cooling ages overlap significantly with published high-temperature 40 Ar/ 39 Ar ages; the combined results imply that rapid cooling in the late Miocene was related to secular cooling of a shallow pluton, rather than exhumation. Our results imply that rapid incision along downstream channel segments, differential rock uplift, and growth of the Talamanca as a bivergent orogenic wedge associated with the onset of Cocos Ridge subduction are relatively young characteristics of the range. A review of previously published radiometric ages and revised plate reconstructions for the late Miocene further suggest that the cessation of arc volcanism in both the Cordillera de Talamanca and the Cordillera Central of western Panama was coeval with the initiation of oblique subduction of the Nazca plate during the late Miocene. Thus, we conclude that the cessation of arc volcanism in the late Miocene (>5-8 Ma) and the onset of Cocos Ridge collision (<3 Ma) are separate events that reflect recent changes in the configuration of the plate boundary system.

Rapid pulses of uplift, subsidence, and subduction erosion offshore Central America: Implications for building the rock record of convergent margins

“…The linear western edge of the Malpelo Ridge, the CCR conjugate along the Panama Fracture Zone (PFZ) (Hoernle et al, 2002), implies that the arrival of the CCR at the trench is associated with the eastward-migrating triple junction formed by the trench and the Cocos-Nazca plate boundary (Morell et al, 2012). Prior to CCR subduction, the rugged bathymetry and lithospheric heterogeneity of the obliquely subducting Coiba, Balboa, and Panama Fracture Zones already infl uenced the forearc.…”

Density structure and geometry of the Costa Rican subduction zone from 3-D gravity modeling and local earthquake data

“…Estimates of a younger age for the arrival of the ridge place the event earlier than 3 Ma. (Morell et al, 2014;Vannucchi et al, 2013). A late Pliocene, or early Pleistocene arrival of the ridge would still account for the presence of a modified slab at depths exceeding 200 km.…”

“…Arrival time estimations range from 5-1 Ma, but the latest researches place the event at the early Pleistocene (Vannucchi et al, 2013) or late Pliocene (Morell et al, 2014). Hypothesis about the tectonic style include collision (LaFemina et al, 2009), flat subduction (Kolarsky et al, 1995), and steep angle subduction (Arroyo et al, 2003;Dzierma et al, 2011).…”

Las fallas Purires y Picagres, y su relación con la secuencia sísmica del Puriscal de 1990

“…El origen del CDCCR se relaciona con la colisión del levantamiento del Coco con el sur de Costa Rica (Montero, 1994;Marshall et al, 2000;Montero et al, 2013; Fig. 1), un evento tectónico que se inició hace alrededor de 2-3 Ma (MacMillan et al, 2004;Morell et al, 2012).…”

“…En el límite Mioceno-Plioceno, un importante evento tectónico ocurrió en la zona de estudio, el cual basculó al norte la secuencia sedimentaria y los depósitos volcánicos de la formación La Cruz (Denyer & Arias, 1991;Arias & Denyer, 1991a). Asimismo, el magmatismo del paleoarco de la cordillera de Talamanca terminó en el Mioceno Tardío (antes de 5-8 Ma; Morell et al, 2012). Ambos eventos geológicos se relacionan con la colisión del levantamiento del Coco con el sur de Costa Rica (Arias & Denyer, 1991a;Morell et al, 2012).…”