APPENDIX 1. METHODS DETAIL

Zircon grains were separated by standard heavy liquid techniques, selected randomly, and analyzed by laser-ablation–inductively coupled plasma–mass spectrometry in different sessions at the Arizona LaserChron Center (ALC) of the University of Arizona ( 56 samples) and the Isotopic Radiogenic Lab at Washington State University (IRL, 22 samples). Separated single zircon crystals were mounted in epoxy (~500-1000 zircon crystals/sample), accompanied by standards (e.g. SL2 and R33 for ALC and Peixe and FC1 for IRL). Mount surfaces were grinded and polished in order to expose zircon crystals. Cathodoluminiscence (CL) images were made in order to map details in zircon crystals structures.
At ALC, zircon material is ablated from the sample surface using a DUV193 Excimer laser system operating at a wavelength of 193 nm, with typical 35 -25 micron spot size. Laser was operated at output energy (~40 mJ) with a repetition rate of 8 pulses per second. A pit created by the laser is ~15 microns in depth for a typical 20 second analysis. The ablated material is carried in He gas into the plasma source of an VG Isoprobe multicollector inductively coupled plasma mass spectrometer, allowing simultaneous analysis of U, Th, and Pb isotopes (Gehrels et al., 2008). 
Zircon U-Pb LA-ICP-MS conducted at the IRL at Washington State University used a New Wave Nd: YAG UV 213-nm laser coupled to a ThermoFinnigan Element 2 single collector, double-focusing, magnetic sector ICP-MS (Chang et al., 2006). Laser spot size was 30 mm and the repetition rate was 10Hz. The sample aerosol was delivered to the plasma by He and Ar carrier gases. Each analysis comprises a 30 seconds blank analysis followed by 250 or 300 sweeps through masses 204, 206, 207, 208, 232, 235, and 238. 
U-Pb data from both laboratories were reduced with in-house softwares. For young grains the 206U/238Pb age is more precise than the 207U/206Pb age due to low 207Pb intensity. The cross-over in precision occurs at ~ 1.4 Ga, but due to the tendency of zircons to have more Pb loss with age, a threshold that compromise precision and accuracy for old grains is commonly chosen at 1.0 Ga (Gehrels, 2011), and so interpreted ages are 206U/238Pb for grains <1.0Ga and 207Pb/206Pb for older grains. For our interpretations we used ages that yielded <10% one-sigma error and for grains >300 Ma those that yielded <25%, discordance and <10 reverse discordance. The results are presented in normalized, relative age probability plots so that the area beneath all curves is the same. Age peaks for interpretations are based on populations consisting of at least 3 grains. 

Low-temperature thermocronology
	Thermal inversion models are based on AFT grain ages, lengths of horizontal confined tracks, and measured angles with respect to the c axis. Etching diameter was used for the kinetic parameter (Dpar, Burtner et al., 1994), except for the samples west of the Machetá fault, in which we used chlorine composition. Input constraints for thermal modeling included: (1) a pre-depositional history with a wide range of ages and temperatures to fit the model to earlier histories, (2) the stratigraphic depositional age of the sample, which was controlled with biostratigraphic data, and (3) the depositional age of the youngest unit preserved in areas adjacent to the same structure as the modeled sample, which may correlate to the oldest possible age limit for the onset of exhumation. We stress that this is an estimate and an older age may be possible, since there can be deposition of growth strata while the limbs of the structures are being eroded. We limited thermal solutions by prescribing a maximum post-depositional heating of 10 °C/My, a gradual randomizer style, and a monotonic consistent path between the constraints consisting of two segments (Ketcham, 2005).

REFERENCES
Burtner, R. L., Nigrini, A., and Donelick, R. A., 1994, Thermochronology of Lower Cretaceous source rocks in the Idaho-Wyoming thrust belt: American Association of Petroleum Geologists Bulletin, v. 78, no. 10, p. 1613-1636.
Chang, Z. S., Vervoort, J. D., McClelland, W. C., and Knaack, C., 2006, U-Pb dating of zircon by LA-ICP-MS: Geochemistry Geophysics Geosystems, v. 7.
Gehrels, G., 2011, Detrital zircon U-Pb geochronology: Current methods and new opportunities, in Busby, C., and Azor, A., eds., Tectonics of Sedimentary Basins: Recent advances, Wiley-Blackwell Science, in press.
Gehrels, G., Valencia, V. A., and Ruiz, J., 2008, Enhanced precision, accuracy, efficiency, and spatial resolution of U-Pb ages by laser ablation-multicollector-inductively coupled plasma-mass spectrometry: Geochemistry Geophysics Geosystems, v. 9, no. 3, p. Q013017, doi:10.1029/2007GC001805.
Ketcham, R. A., 2005, Forward and Inverse Modeling of Low-Temperature Thermochronometry Data: Reviews in Mineralogy and Geochemistry, v. 58, p. 275-314.