Kinematics and Convergent Tectonics of the Northwestern South American
Plate during the Cenozoic.
The interaction of the northern Nazca and southwestern Caribbean oceanic
plates with South America, and the collision of the Panama-Choco arc
have significant implications on the evolution of the northern Andes. We
integrate an alternative interpretation of the Nazca and Caribbean
kinematics with the magmatic and deformation history in the region. The
northeastward migration of the Caribbean plate caused a progressive
change in the geometry of the subducting Farallon plate, causing
flat-slab subduction throughout the late Eocene-late Oligocene,
inhibition of magmatism and eastward migration of the Andean
deformation. Meanwhile, the Paleocene-Eocene highly oblique convergence
of the Caribbean plate against South America changed by the mid-Eocene,
when the Caribbean plate began to migrate in an easterly direction.
These events and the late Oligocene breakup of the Farallon plate,
prompted a Miocene plate reorganization, with further plate
fragmentation, changes in convergence obliquity, steepening of the
subducting slabs and renewal of magmatism. This tectonics was
complicated by the accretion of the Panama-Choco arc to South America,
which was characterized by early Miocene subduction erosion of the
forearc and trench advance, followed by breakoff of the subducting slab
east of Panama and collisional tectonics from the middle Miocene. By 9
Ma the Coiba and Malpelo microplates were attached to the Nazca plate,
resulting in an abrupt change in convergence directions, that correlates
with the main pulse of Andean orogeny. During the late Pliocene, the
Nazca slab broke, triggering the modern volcanism south of 5.5º N.
Seismicity data and tomography support the proposed reconstruction.