Thick-skin orogen–foreland interactions and their controlling factors, Northern Andes of Colombia

Abstract

The study draws from reflection seismic, in-situ stress and low-temperature geochronology data on the Eastern Cordillera–Llanos foreland basin system of Colombia, which is an example of the retro-wedge of the orogen with an advancing subduction zone. The system was obliquely converging during deposition of the Lower Oligocene–Lower Miocene Carbonera to recent Guayabo formations, recording it by the northeastward depocentre shift in the proximal Llanos Basin. While the southern portion of the foreland did not flex and undergo flexural normal faulting after Carbonera deposition, the northern portion did. The earthquake data indicate that the northern Eastern Cordillera undergoes strengthening by internal deformation, while the southern segment is already strong enough to undergo significant displacements dominantly along its bounding fault systems. Furthermore, the southern segment initiated detachment of the first thick-skin blocks from the proximal Llanos Basin. Such co-existence of different convergence maturity stages along the orogen strike allows unravelling of its development starting with internal deformation and foreland flexure, followed by mountain building and large-scale boundary fault displacements, to the large-scale foreland deformation. The onset of new foreland accretion seems to be controlled by the resistance of the foreland plate to flexing, given that the orogenic engine continues to drive convergence.Supplementary material:Discussion of evidences for dextral transpression in the Eastern Cordillera, data on exhumation history of the Eastern Cordillera and colour versions of Figures 4–6 are available at http://www.geolsoc.org.uk/SUP18629

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

“…This resembles lateral sand compaction in sandbox experiments before the appearance of the first, large-displacement faults (see Koyi 1995Koyi , 1997. By analogy, the internal deformation of the axial flat region of the Eastern Cordillera has served the same purpose since the Paleocene (see the timing in Mora et al 2013;Hermeston & Nemčok 2013), before the onset of intensive deformation along the Eastern Cordillera flanks, which was rapid during the Oligocene -Early Miocene and accelerated during the Late Miocene -Recent Silva et al 2013).…”

“…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). For the same reason, that is, the inability of the orogenic foreland to flex, the most extreme examples of vast areas affected by thick-skin tectonic events come from narrow foreland plates trapped between two orogens moving towards each other.…”

“…8 orogens characterized by high convergence rates, such as the Rocky Mountains in Alberta, can lack basement uplifts or any kind of compressional intraplate deformation in their foreland if the foreland does not contain any major intra-plate discontinuities, or if it lacks mechanical coupling with the orogen (Ziegler 1989). As indicated by examples from the West Carpathians (Nemčok et al 2001(Nemčok et al , 2006 and Eastern Cordillera (Hermeston & Nemčok 2013), the coupling can be enhanced either by a lack of any major potential detachment horizon or by the presence of significant regional buttresses.…”

“…This volume attempts to follow this strategy by examining the factors involved in the energy balance behind inversion and the potential subsequent full accretion from thick-skin regions worldwide (Baby et al 2013;Carola et al 2013;Carrera & Muñoz 2013;Iaffa et al 2013;Kober et al 2013;Moretti et al 2013;Nemčok et al 2013;Teixell & Babault 2013;Fig. 8a-d) and by considering the systematic data collection from the Northern Andes, an example of the forceful retro-wedge scenario (Bayona et al 2013;Caballero et al 2013a, b;Hermeston & Nemčok 2013;Jimenez et al 2013;Mora et al 2013;Moreno et al 2013;Silva et al 2013;Teixell & Babault 2013;Tesón et al 2013;Fig. 8a).…”

“…The advantage of the Eastern Cordillera natural laboratory is the relatively small amount of total shortening and the different stages of inversion development along its strike from south to north (see Hermeston & Nemčok 2013). This allows one to see the details of the transition from initial inversion to full inversion.…”