Dextral Shear, Terrane Accretion and Basin Formation in the Northern Andes: Explained only by Interaction with a Pacific-Derived Caribbean Plate
Lorcan Kennan, James Pindell, 2007. "Dextral Shear, Terrane Accretion and Basin Formation in the Northern Andes: Explained only by Interaction with a Pacific-Derived Caribbean Plate", The Paleogene of the Gulf of Mexico and Caribbean Basins: Processes, Events and Petroleum Systems, Lorcan Kennan, James Pindell, Norman C. Rosen
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Pacific-origin models for the Caribbean Plate imply strong Cretaceous interaction with the northern Andes, and this is reflected in regional structure, stratigraphy and magmatic history. Intra-American models for the origin of the Caribbean Plate do not imply this interaction and cannot explain the dramatic contrasts in Cretaceous orogenesis and magmatism between the northern Andes (Ecuador, Colombia) and the central Andes (central Peru to Bolivia). In this paper we summarize the contrasts between the Northern and Central Andes, focusing on fault offsets, magmatic history, and dated history of uplift, unroofing and erosion. The Central Andes show persistent large magnitude subduction and more or less continuous arc magmatism. Associated deformation is dominantly compressional or extensional, without significant strike-slip offsets, all related to more or less head-on relatively rapid subduction of the Farallon Plate. The Farallon Plate was also subducted beneath the Panama Arc at the rear of the Caribbean Plate. In contrast, the Northern Andes shows a protracted history of accretion of oceanic plateau basalt and island arc terranes, combined with large magnitude dextral shear, without large magnitude subduction and associated arc magmatism. All the accreted terranes have a distinctive Caribbean Plate geochemical character. Regional plate reconstructions clearly show that the Caribbean Plate originated in the eastern Pacific. A tight fit against northwestern South America and southern Mexico clearly implies that the Northern Andes deformation was caused by northward migration of the Caribbean Plate. The age of associated intense dextral shear is well constrained to the interval 100-40 Ma, and these deformation events are never seen in the Central Andes. As late as Eocene time, the triple junction between South America, the Caribbean, and the Farallon Plate, where the Panama arc joined western South America, was located west of Ecuador, and strike-slip pull-apart basins such as the Talara, Tumbes and Manabi Basins directly relate to the northward migration of the triple junction. Features associated with the subduction of the Nazca Plate only establish themselves in Ecuador, and then Colombia, as the triple junction migrates.