Controls on timing of exhumation and deformation in the northern Peruvian eastern Andean wedge as inferred from low-temperature thermochronology and balanced cross section

Abstract

In northern Peru, a 500 km long regional balanced section has been constructed across the eastern Andean wedge, using fieldwork, industrial seismic sections, and wells. The structure is characterized by a thin-skinned thrust system involving the Eastern Cordillera (EC), the sub-Andean zone (SAZ), and the Marañón foredeep. In the SAZ and the easternmost foredeep the development of the thrust system has been driven by the combination of two structural events. Permian thrust faults had been reactivated to form a basement duplex underlying the SAZ and the foredeep. At the same time a Triassic-Jurassic extensional basin has been transported as a crustal ramp anticline on to the duplex roof fault, giving rise to the EC. The impingement of the EC was responsible for the deformation of the SAZ and the propagation of the thrust wedge. The minimum shortening calculated is 142 km, representing a shortening strain of~À28%. A sequential restoration calibrated by (U-Th)/He and Fission Track dating on apatites and vitrinite reflectance values shows that shortening rates vary from 7.1 mm yr À1 between 17 and 8 Ma to 3.6 mm yr À1 between 8 Ma and today and suggests that the thrust wedge commenced propagation between 30 and 24 Ma. When compared with other Andean thrust wedges, we suggest that the timing of the thrust wedge propagation is not a simple function of the distance to the hinge of the Bolivian orocline and the propagation is not controlled by the precipitation regime. We rather suggest that reactivated basement faults favored thrust wedge propagation.

A 60-million-year Cenozoic history of western Amazonian ecosystems in Contamana, eastern Peru

“…10AF, AJ-AK; Supplementary Data), further supporting a high sedimentation rate for the concerned interval. The seismite level that is cropping out between CTA-43 and CTA-76 attests to a tectonic activity, suggesting that thrust tectonic movements were active by early late Miocene times, which is in agreement with data available for the Central Andes Espurt et al, 2011;Armijo et al, 2015) and the northern Peruvian Subandean Zone (Eude et al, 2015).…”

“…The anilioid squamate from CTA-27 and sebecid mesoeucrocodylians have a similar range (Pol and Powell, 2011;Wallach et al, 2014). The mammalian fauna from the Contamana series also has a strong South American signature, with bonapartherioid and argyrolagid polydolopimorphians, paucituberculatans, and sparassodonts (e.g., Beck, 2012), but also South American native Kummel (1948), Roddaz et al (2010), Marivaux et al (2012), Antoine et al (2013), Louterbach et al (2014), Boonstra et al (2015), Eude et al (2015), references therein, and our own observations. ungulates, such as pyrotheres and astrapotheres -possibly closely related to notungulates though (Billet, 2010) and, as such, to perissodactyls (Buckley, 2015;Welker et al, 2015).…”

“…The concerned conglomerate further attests to a drastic change in the regional sedimentary dynamics, and its deposition probably coincided with the onset of a major exhumation phase in the eastern Cordillera of the Central Andes during the late Oligocene Eude et al, 2015). Unfortunately, we could not find any chrono-or biostratigraphic data higher up in that formation.…”

A 30 Ma history of the Amazon River inferred from terrigenous sediments and organic matter on the Ceará Rise

“…Campbell et al (2006) and Horbe et al (2013) argue that the Amazon River system expanded to its present architecture only during the Pliocene or even the Pleistocene. Our data supports a change in the river system, although this could result from both an expansion of the discharge area and an overall increase in sediment input from the Andes due to ongoing tectonic uplift and subsequent increase in erosion in this area (e.g., Eude et al, 2015;Mora et al, 2010;Oncken et al, 2006). In Figs.…”

“…Furthermore, the northern Peruvian Eastern Cordillera and Subandean Zone, as well as the Colombian Eastern Cordillera, started to form in the Late Oligocene-Early Miocene (e.g., Eude et al, 2015;Mora et al, 2013Mora et al, , 2010. These uplifts may have caused a temporary transcontinental connection to exist and are the most likely explanation for the observed εNd(0) values.…”