Episodic orogenic front migration in the northern Andes: Constraints from low‐temperature thermochronology in the Eastern Cordillera, Colombia

Abstract

New thermochronometric data from the Eastern Cordillera of the Colombian Andes reveal diachronous exhumation associated with Cenozoic contractional deformation in this sector of the northern Andes. We present a comprehensive account of exhumation patterns along a 150‐km‐long, across‐strike transect between ∼4° and 6°N by integrating 29 new apatite fission track (AFT) ages and 17 new zircon fission track (ZFT) ages with sparse published thermochronological data from this area. Our data reveal episodic eastward migration of the orogenic front at an average rate of 2.5–2.7 mm/a during the Late Cretaceous‐Cenozoic. We identify three major stages of orogen propagation: (1) slow propagation (0.5–3.1 mm/a) until early Eocene; (2) rapid orogenic advance (4.0–18.0 mm/a) during middle‐late Eocene, which accounts for ∼86% of the orogen's present width; and (3) slow orogen propagation (1.2–2.1 mm/a) from Oligocene to Holocene times. Our data demonstrate that in the course of changes in plate kinematics, the presence of inherited crustal anisotropies, such as the former rift‐bounding faults of the Eastern Cordillera, favor a nonsystematic progression of foreland basin deformation through time by preferentially concentrating accommodation of slip and thrust loading along these zones of weakness.

Tectonic History of the Andes and Sub‐Andean Zones: Implications for the Development of the Amazon Drainage Basin

“…4.9). In contrast, Parra et al (2009b) found that faster subsidence rates, at ~30 Ma in the foredeep, correspond with the onset of deformation in the hinterland, whereas faster exhumation rates at ~6 Ma have no expression in faster subsidence rates (see Fig. 4.9).…”

“…4.1) (Allmendinger et al 1997;Oncken et al 2006) and in the Northern Andes (see Fig. 4.1; Gómez et al 2001Gómez et al , 2005Toro et al 2004;Parra et al 2005Parra et al , 2009bBayona et al 2008). The coincidence in the onset of deformation for the Central and Northern Andes is signifi cant but is also expected.…”

“…This was documented by growth strata in both the western (Gómez et al 2001(Gómez et al , 2005 and eastern foothills of the Eastern Cordillera (see Fig. 4.6; Parra et al 2005Parra et al , 2009bMartínez 2006;Bayona et al 2008) and by thermochronology (Toro et al 2004;Parra et al 2009b). Therefore, the Eastern Cordillera has been uplifted as an enormous Laramide-type basement block Fig.…”

“…Particularly interesting is that the timing of or zircon uranium thorium-helium, ZHe) data suggesting that since ~6. (Parra et al 2009b;Fig. 4.9).…”

Thick-skin-dominated orogens; from initial inversion to full accretion: an introduction

“…4b) and the Balkans, indicate that thick-skin tectonics occurs at later stages of the orogenic build-up, when the taper angle is high, the thermal regime is elevated and an extra mechanism for out-of-sequence shortening is required to increase the orogenic taper further (see Nemčok et al 2006;Stuart et al 2011). The Eastern Cordillera, an example of the forceful retro-wedge detached at a depth of about 30 km (Mora et al 2008(Mora et al , 2010Parra et al 2009; Fig. 5), indicates that a new thick-skin tectonic event occurs at stages when the orogenic foreland refuses to flex under the advancing orogen and the orogen needs to build up extra strength in order to advance any further (Hermeston & Nemčok 2013).…”