Chapter 4 - Cenozoic tectonic evolution of the North Andes with constraints from volcanic ages, seismic reflection, and satellite geodesy

Abstract

We present a comprehensive dataset of 1100 radiometric volcanic ages extending back to 100Ma to revise the plate tectonic model for the northern Andes and predict normal versus flat-slab subduction. This chapter highlights the spatial magnitude (~1.3×106km2) of Caribbean flat slab subduction beneath South America in the last 50Myr and the importance of this flat subduction in basement involved mountain building as well as in shutting down arc volcanism in the North Andes. The Panama-Choco arc, the southwest boundary of the Caribbean plate, collided with the North Andes prompting a spike in volcanic activity from 15 to 5Ma. Five million years ago, volcanic activity abruptly ended again north of 5.5°N as the subducting Nazca lithosphere underthrust the shallow-dipping retreating Caribbean slab, which acted as a thermal blanket over the advancing asthenospheric wedge. Recent Global Positioning System (GPS) results show that the Panamá arc is continuing to collide eastward with the North Andean block (NAB) at approximately 16–17mm/yr, but the Choco arc has been accreted to the NAB. The NAB is “escaping” to the northeast (035°) at a rate of 8.6mm/yr driven by the subducting aseismic Carnegie Ridge and oblique subduction.