APPENDIX 1.   ANALYTICAL METHODS 

Palynology
A total of 381 palynological samples were analyzed for the western (77 samples), western axial (164 samples) and eastern axial (140 samples) domains.  Palynological samples were prepared by digesting 30 g of sample in HCl and HF, then oxidizing if necessary (Traverse 2007). The fuming HNO3 technique was used to prepare the coals.  Light microscopy was used for routine palynological analyses, and at least 200 palynomorphs per sample were counted where possible.  Identification of the fossils was done by comparing with morphological electronic database that contains every pollen/spore taxon described for the tropics of South America (Jaramillo et al. 2010).  The dating of the samples follows the biostratigraphic zonation of Jaramillo et al. (2011).  This zonation has been calibrated with magnetic stratigraphy, carbon isotopes, radiometric ages, and microfossil biostratigraphy (Jaramillo et al. 2011).

Sandstone Petrography
A total of 121 thin sections were analyzed for the western (10 samples), western axial (58 samples), eastern axial (36 samples) and eastern (17) domains. Three hundred framework points of fine-medium grained sandstones were counted per thin section using the Gazzi-Dickinson technique (Ingersoll et al. 1984) to eliminate compositional variation due to grain size.  Thin sections were stained for identification of potassium feldspars.  Detrital modes exclusive of carbonate, glauconite, intraclast, heavy mineral grains were calculated from the point-count results following the technique of Dickinson (1985) and were plotted in QmFLt, StVtLmLpt ternary diagrams. Raw data and recalculated detrital modes are in Appendix 2.

Fragments identified in each thin section:

Qm= monocrystalline quartz
Qpd=  polycrystalline quartz, diffuse borders
Qps= polycrystalline quartz, sedimentary
Qpf= polycrystalline quartz, foliated
Qc= chert

Pgl= Plagioclase
Fk= potassium feldspars, microcline
Fu= unidentified feldspar

Ls= sedimentary lithic fragment
Lm=metamorphic lithic fragment
Lv= volcanic lithic fragment
Lu: unidentified lithic fragment

Recalculated and normalized parameters for ternary diagrams:
Qt= total quartz (Qm, Qpd, Qpf, Qps, Qc)
F= total feldspar Pgl, Fk, Fu
L= unstable lithic fragments (Ls, Lm, Lv, Lu)
Lt= total lithic and polycrystalline fragments (Qpd, Qpf, Qps, Qc, Ls, Lm, Lv, Lu)
St= total sedimentary fragments (Qps, Qc, Ls)
Vt= total volcanic fragments (Lv)
Mt+Pt= total metamorphic and plutonic rocks fragments (Qpd, Qpf, Lm)

Heavy Minerals
A total of 41 heavy mineral separations were analyzed for the western (7 samples), western axial (21 samples), and eastern axial (13 samples) domains.  For heavy mineral sample preparation and analysis we have used a wide size range 63-500 µm in order to established the entire heavy mineral spectrum of the sample (Mange & Maurer, 1992). Samples were manually fragmented and disgregated.  The material was then sieve in disposable sieves, and subsequently pan for hydraulic separation. The heavy fraction was then finally concentrated with lithyum polytungstate (LSTR) with a density of 2.95 g/cm3.  The heavy fraction was then mounted within Melmount resine (refractive index=1,539) on glass slides. The translucent fraction was identified from their optical properties within an optical polarized microscope (Mange & Maurer, 1992). Three hundred translucent grains were counted using the line method after Galehouse (1969). Despite being overestimated by fragmentation, the Muscovite was included in the count given the observed abundance and genetic implications. Biotite fragments were not counted because its mechanical weakness, but we report its presence.  

Geochronology 
A total of 25 sandstone samples were analyzed for the western (6 samples), western axial (13 samples), eastern axial (4 samples) and eastern (4) domains. Except the 6 samples of the western domain, all the analyses were carried at the Arizona Laserchron in the University of Arizona. The other three samples were analyzed with a single collector ICP-MS at the University of Washington.

One sample from the western axial domain was included from Horton et al. (2010b).  We also considered six samples published by Saylor et al. (2011, 2012) for the Paz de Río Area.

U/Pb by Laser Ablation Multi-Collecor -ICP-MS (LA-MC-ICP-MS)
Sample preparation was done using standard procedures, which include mechanical crushing, fragmentation, pulverization and manual sieving with disposal 400 µm sieves. This fraction was concentrated in the water table followed by magnetic separation with the Frantz isodynamic and finally the non-magnetic fraction was separated using heavy liquids (Methylene Iodide, 3.30-3.33 g/cm3) in order to get highly pure zircon concentrates.
U/Pb analyses were done at the Arizona LASERCHRON laboratoy following the procedures described by Gehrels et al. (2006; 2008). Unknowns and standard zircons were mounted in the central half of the mount area, to reduce possible fractionation effects.
Detrital zircons grains to be analyzed were selected randomly from all of the zircons mounted from each sample. For magmatic zircons tips and cores were selected for analysis, in order to check for the younger magmatic crystallization age and inherited domains. In detrital samples cores of grains were preferred to avoid possible thin metamorphic overgrowth.
Zircon crystals were analyzed in polished epoxy grain mounts with a Micromass Isoprobe multicollector ICP-MS equipped with nine Faraday collectors, an axial Daly collector, and four ion-counting channels. The Isoprobe is equipped with an ArF Excimer laser ablation system, which has an emission wavelength of 193 nm. The collector configuration allows measurement of 204Pb in the ion-counting channel while 206Pb, 207Pb, 208Pb, 232Th and 238U were simultaneously measured with Faraday detectors. All analyses were conducted in static mode with a laser beam diameter of 35-50 diameter, operated with an output energy of ~32 mJ (at 23 kV) and a pulse rate of 9 Hz. Each analysis consisted of one 20-second integration on peaks with no laser firing and twenty 1-second integrations on peaks with the laser firing. Hg contribution to the 204Pb mass position was removed by subtracting onpeak background values. Inter-element fractionation was monitored by analyzing an inhouse zircon standard, which has a concordant TIMS age of 564 ± 4 Ma (2σ) (Gehrels, unpublished data). This standard was analyzed once for every five unknowns in detrital grains. Uranium and Th concentrations were monitored by analyzing a standard (NIST 610 Glass) with ~500 ppm Th and U. The lead isotopic ratios were corrected for common Pb, using the measured 204Pb, assuming an initial Pb composition according to Stacey and Kramers (1975) and respective uncertainties of 1.0, 0.3 and 2.0 for 206Pb/204Pb, 207Pb/204Pb, and 208Pb/204Pb. The age of standard, calibration correction from standard, composition of the common Pb, and the decay constant uncertainty are grouped and are known as the systematic error. For these samples the systematic errors range between ~1.0-1.4% for 206Pb/238U and ~0.8-1.1% for 206Pb/207Pb
Weight average and concordia age calculations as well as detrital zircon histograms were plotted using Isoplot 3.0 (Ludwig, 2007) and Arizona LASECRHON Excel macro age pick program. The latter is available at http://sites.google.com/a/laserchron.org/laserchron/home. Results are included in Table 2 for the magmatic rocks and Table 3 for the detrital zircons.

U-Pb LA-ICP-MS at Washington State University
All LA-ICP-MS U-Pb analyses were conducted at Washington State University using a New Wave Nd: YAG UV 213-nm laser coupled to a ThermoFinnigan Element 2 single collector, double-focusing, magnetic sector ICP-MS. Laser spot size and repetition rate were 30 microns and 10 Hz, respectively. He and Ar carrier gases delivered the sample aerosol to the plasma. Each analysis consisted of a short blank analysis followed by 300 sweeps through masses 204, 206, 207, 208, 232, 235, and 238, taking approximately 35 seconds.
LA-ICP-MS isotopic analyses are affected by two forms of inter-element fractionation that must be corrected (Kosler and Sylvester, 2003). Time-dependent fractionation results from the more efficient volatilization of Pb over U as the laser excavates successively deeper levels in the ablation pit during an analysis, which in turn leads to an increase in 206Pb/ 238U and 207Pb/235U ratios with time (Eggins et al., 1998). By definition, time-dependent fractionation is zero at the beginning of the analysis. Regression of time series data to the intercept at t = 0, therefore, yields the point at which time- dependent fractionation equals zero.
Time-independent (or static) fractionation is the largest source of uncertainty in LA-ICP-MS U–Pb geochronology and results from mass and elemental static fractionation in the plasma and also poorly understood laser-matrix effects (Kosler and Sylvester, 2003). It is corrected by normalizing U/Pb and Pb/Pb ratios of the unknowns to the zircon standards (Chang et al., 2006). For this study we used two zircon standards: Peixe, with an age of 564 Ma (Dickinson and Gehrels, 2003), and FC-1, with an age of 1099 Ma (Paces and Miller, 1993). Peixe was used to correct the 238U/206 Pb and 235U/ 207Pb ratios and FC-1 was used to correct the 207Pb/ 206Pb ratios.
Common Pb can represent a proportionally large contribution to the total Pb in Mesozoic and younger U-poor zircons. However, common Pb is typically not significant in LA-ICP-MS analyses, most likely because it is concentrated in cracks and inclusions, which can be avoided. When this is not possible, the influence of common Pb is easy to recognize on Tera-Wasserburg diagrams because analyses tend to line up on a steep linear trajectory that can be anchored at a reasonable 207Pb/206Pb common lead composition (y-intercept) (DeGraaff–Surpless et al., 2002). Common Pb corrections were made on these analyses using the 207Pb method (Williams, 1998). Uranium-lead data were reduced using Isoplot (Ludwig, 2007). The final crystallization ages that we report are Concordia or intercept ages, which were determined by using the following procedure. In most of our samples, the majority of analyses form a single dominant cluster around a single spot on or just above concordia in Tera-Wasserburg space, which we interpret to be the approximate age of the sample. Analyses that gave 207Pb/206 Pb ages overlapping in uncertainty with their 206Pb/238U ages were judged to be concordant. The reported error ages followed two uncertainties: the first is derived from the concordant or intercept age calculation alone (time dependent), and the second represents our systematic uncertainty during that session (time independent), with the error from the standards quadratically added to the analytical error.

APPENDIX 2 Sandstones Petrography Results 

APPENDIX 3 Heavy Minerals Results

APPENDIX 4 Geochronology Results

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