Formation of passive-roof duplexes in the Colombian Subandes and Perú

Abstract

Passive-roof duplexes are important features for accommodating shortening in active orogens, but their occurrences have been previously demonstrated only with significant subsurface data or after their exhumation. In this study, we describe a series of thin-skinned passive-roof duplexes along the Subandean front in Colombia and compare them with potential analogues in southern Peru. We suggest type localities for this structural style, which display conditions favorable for formation of these structures. It appears that passive-roof duplexes in the Subandean zones are mostly late Miocene features. Our main data for placing temporal and thermokinematic constraints on their development are 25 apatite fission-track (AFT) analyses, including track-length distributions. We show that these areas require high shortening, surface erosion, and downstream sedimentation rates at the time of their formation, as well as two distinct low-friction detachments. These features, which have been previously described by analog models, appear to have been conditioned by a phase of late Miocene topographic growth and denudation in the hinterland and subsequent increase in accommodation as well as sedimentation rates in the foreland.

GPS velocities and the construction of the Eastern Cordillera of the Colombian Andes

“…Abundant evidence shows that crustal shortening on the flanks of the Eastern Cordillera has occurred [e.g., Bayona et al, 2008;Cediel et al, 2003;Colletta et al, 1990;Cortés et al, 2006;Dengo and Covey, 1993;Egbue and Kellogg, 2012;Mora et al, 2008Mora et al, , 2010aMora et al, , 2010bMora et al, , 2010cMora et al, , 2014 and that therefore the high terrain is, at least in part, the result of crustal thickening and isostatic balance. This crustal shortening has been built, at least in part, on structures that initially developed during a Mesozoic stage of crustal extension when grabens and normal faults formed [e.g., Cediel et al, 2003;Jimenez et al, 2013;Moreno et al, 2013;Roeder and Chamberlain, 1995;Roure et al, 1997;Sarmiento-Rojas et al, 2006;Tesón et al, 2013].…”

“…Most, however, suggest that crustal shortening responsible for the Eastern Cordillera began earlier. Some have concluded that initiation of important shortening began in Middle Miocene time [e.g., Bayona et al, 2008;Colletta et al, 1990;Cooper et al, 1995;Dengo and Covey, 1993;Gómez et al, 2005b;Hoorn, 1993;Hoorn et al, 1995;Mora et al, 2014], but a consensus suggests that a nonnegligible amount of shortening occurred earlier in Cenozoic time [e.g., Babault et al, 2013;Bande et al, 2012;Bayona et al, 2013;Caballero et al, 2013;Campos and Mann, 2015;Cediel et al, 2003;Egbue and Kellogg, 2012;Gómez et al, 2003;Hoorn et al, 2010;Horton et al, 2010;Martinez, 2006;Mora et al, 2010bMora et al, , 2010cOchoa et al, 2012;Parra et al, 2009aParra et al, , 2009bParra et al, , 2012Sánchez et al, 2012;Saylor et al, 2011Saylor et al, , 2012Villamil, 1999]. GPS velocities can be used to test whether crustal thickening in 3-6 Myr could build the Eastern Cordillera, or a longer duration is needed.…”

“…This similarity, plus the difference between plants living in lowlands and highlands today, led to the deduction that the Sabana de Bogotá, and by extension the entire Eastern Cordillera (Figure ) rose from low elevations, <1000 m, to their present‐day heights since ~3 Ma. Subsequent studies of cooling ages of exhumed rock along the eastern flank of the Eastern Cordillera show an abrupt acceleration in cooling, suggesting rapid exhumation since ~3 Ma and again with the inference that the Eastern Cordillera rose substantially since ~3 Ma [ Mora et al ., , , , ]. These inferences of large, Pliocene or Quaternary surface uplift differ from most such inferences elsewhere, because either global cooling since ~3 Ma or accelerated erosion that might be due to global cooling, such by increased glaciation in elevated terrain, offer explanations for the apparent increases in surface elevations [e.g., Molnar and England , ; Zhang et al ., ].…”

Deciphering exhumation and burial history with multi‐sample down‐well thermochronometric inverse modelling

“…) are considered here, in the Eastern Cordillera and the Middle Magdalena Valley (MMV). The Eastern Cordillera features complex structure, including imbricate and out‐of‐sequence thrusting, passive‐roof duplexes and anastomosing faults (Mora et al ., , ), rendering interpretation of burial and exhumation histories challenging, while the Middle Magdalena Valley is the site of rapid burial beginning in the Eocene and accelerating in the Mio‐Pliocene (Parra et al ., ).…”

Gangdese culmination model: Oligocene–Miocene duplexing along the India-Asia suture zone, Lazi region, southern Tibet

“…Physical experiments predict that passive roof duplexes are more common in zones of efficient surface erosion (Mora et al, 2014, and references therein), consistent with critical taper wedge mechanics of thin-skinned thrust belts (e.g., Davis et al, 1983). Since their first recognition, it has been postulated that efficient sediment storage in the adjacent monocline along the deformation front is critical to the formation of passive roof duplexes (Mora et al, 2014). In the Lazi region, evidence that might support the existence of a passive roof duplex includes: (1) the presence of imbricate, foreland-dipping (south-dipping) thrust sheets, (2) the absence of an emergent, hinterland-dipping fault, (3) early Miocene syntectonic sedimentation in a contractional setting in the upper Kailas Formation and the Liuqu Formation and (4) growth structures in the Liuqu Formation ( Fig.…”