Table SD1, Piñeiro et al.

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Table SD1 Laser ablation inductively coupled plasma mass spectrometry zircon U-Pb analytical data

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We conducted U-Pb geochronology on 9 samples. To determine the depositional ages of volcanic rocks and maximum depositional ages, as well as the zircon provenance of sedimentary rocks, we analyzed more than 50 and over 100 zircon crystals per sample, respectively. The calculated 206U/238Pb Tuff Zirc ages and other age groups are detailed in Table SD1 and figures 7, and 8. The geographic sample locations are illustrated in figure 3. Zircon concentrates from all samples were separated at the Zirchron LLC laboratory in Tucson, Arizona. Each sample was unpacked, and pressure washed with water to remove any debris and/or foreign materials. The sample rock fragments were introduced into the sample chamber of an Electro Pulse Disaggregator (EPD, Marx generator), where electrical pulses were applied at a 1-2 Hz repetition rate and discharges of ~220 kV for 15 minutes. The material, ranging in size from 500 µ to 25 µ, was subsequently processed using traditional techniques involving the Wilfley water table, Frantz paramagnetic separator, and a one-step (3.32 gm/cc) heavy liquid MEI separation. Zircons from the non-magnetic fraction were mounted together with standards in a 1-inch diameter epoxy puck and polished following standard laboratory procedures. After performing cathodoluminescence imaging, we conducted U-Pb analyses using laser ablation ICP-MS at Washington State University. We utilized an Analyte G2 193nm excimer laser connected to the Element2 high-resolution inductively coupled plasma mass spectrometer. For the U-Pb measurements, our methodology closely followed that of Chang et al. (2006), with the exception of using the 193nm laser instead of the 213nm laser. The laser parameters for the U-Pb analyses included a spot size ranging from 25-35 µm, a repetition rate of 10 Hz with a power of approximately 5 J/cm2. He and Ar carrier gases delivered the sample aerosol to the plasma. Each analysis consisted of a short blank analysis followed by 250 sweeps through masses 202, 204, 206, 207, 208, 232, 235, and 238, taking approximately 30 seconds in total. Unknowns were run in sets of 10 analyses bracketed by standards. Data processing was conducted offline using the Iolite software (Paton et al., 2010). U and Th concentrations were monitored by comparison to the zircon standards 91500. Plesovice zircon (Sláma et al., 2008) was used as a primary standard and FC-1 (Paces and Miller, 1993), and Fish Canyon Tuff, (Schmitz and Bowring, 2001) as secondary standards. Common Pb correction was applied using the 207Pb method (Williams, 1998). U-Pb diagrams and ages were calculated using Isoplot (Ludwig, 2003).

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