TABLE DR1. SUMMARY OF SHRIMP U-Pb ZIRCON RESULTS FOR SAMPLES D2-83 AND D2-24.

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1 Data Repository Item, Siddoway p. 1 DR20008 TABLE DR1. SUMMARY OF SHRIMP U-Pb ZIRCON RESULTS FOR SAMPLES D2-83 AND D2-24. Grain Spot U (ppm) Th (ppm) Th/U Pb * (ppm) 204 Pb 206 Pb f 208 % 238 U 206 Pb ± Total Radiogenic Age (Ma) 207 U 206 Pb ± 207 Pb 206 Pb ± 206 Pb 238 U ± D D Note: Uncertainties given at the one σ level. Error in the AS3 reference zircon calibration was 0.48% for the analytical session (not included in above errors but required when comparing data from different mounts).

2 Data Repository Item, Siddoway p. 2 * Correction for common Pb made using measured 238 U/ 206 Pb and 207 Pb/ 206 Pb ratios following Tera and Wasserburg (1972) as outlined in Williams (1998). f 206 % denotes the percentage of 206 Pb that is common Pb. REFERENCES CITED Tera, F., and Wasserburg, G., U-Th-Pb systematics in three Apollo 14 basalts and the problem of initial Pb in lunar rocks, Earth & Planetary Science Letters, 14, Williams, I.S., U-Th-Pb Geochronology by Ion Microprobe. In: McKibben, M.A., Shanks III, W.C. and Ridley, W.I. (eds), Applications of microanalytical techniques to understanding mineralizing processes, Reviews in Economic Geology, 7, 1-35.

3 Data Repository Item, Siddoway p. 3 Figure DR1. Cathodoluminescence images of zircons in samples D2-24 and D2-83, with SHRIMPII ion beam spots indicated. The textural setting and mineral textures are evident for the zircons, which are in situ grains in polished thin sections. Reflected light photomicrographs taken after U-Pb analysis were used to locate the analysis spots accurately.

4 Data Repository Item, Siddoway p. 4 TABLE DR2: Ar/ 39 Ar ANALYTICAL DATA Temp Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar / 39 Ar 39 Ar, K cps# Cum.% 39 Ar Ar* Ar*/ 39 Ar ( C) (x 10-3 ) (counts) 3 K released (%) Sample D2-3 Biotite (J = ; wt = g) Age±1 s.d. (Ma) ± ± ± ± ± ± ± ± Step yielded insufficient quantities of gas for age determination. Sample D2-3 K-feldspar (J = ; wt = g) 450 (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (10) ± (10) ± (10) ± (10) ± (10) ± (10) ±.5 Note: λ = x /yr. Corrected for line blank. Corrected for line blank and 37 Ar decay. # Counts per second. Sensitivity based on air aliquot 3.965x10-14 mol/count.

5 Data Repository Item, Siddoway p. 5 Temp ( C) TABLE DR2: Ar/ 39 Ar ANALYTICAL DATA (CONTINUED) Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar / 39 Ar 39 Ar, K cps# Cum.% 39 Ar Ar* Ar*/ 39 Ar (x 10-3 ) (counts) 3 K released (%) Age ± 1 s.d. (Ma) Sample D2-80 Biotite (J = ; wt = g) ± ± ± ± ± ± ± * ± Step yielded insufficient quantities of gas for age determination. Sample D2-80 K-feldspar (J = ; wt = g) 450 (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± 25.6 Note: λ = x /yr. Corrected for line blank. Corrected for line blank and 37 Ar decay. # Counts per second. Sensitivity based on air aliquot 3.965x10-14 mol/count.

6 Data Repository Item, Siddoway p. 6 Temp ( C) TABLE DR2: Ar/ 39 Ar ANALYTICAL DATA (CONTINUED) Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar / 39 Ar 39 Ar, K cps# Cum.% 39 Ar Ar* Ar*/ 39 Ar (x 10-3 ) (counts) 3 K released (%) Age ± 1 s.d. (Ma) Sample D2-83 Biotite (J = ; wt = g) ± ± ± ± ± ± ± ± Step yielded insufficient quantities of gas for age determination. Sample D2-83 K-feldspar (J = ; wt = g) 450 (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (10) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (30) ± (10) ± (10) ± (10) ± (10) ± Element failed on this step. Note: λ = x /yr. Corrected for line blank. Corrected for line blank and 37 Ar decay. # Counts per second. Sensitivity based on air aliquot 3.965x10-14 mol/count.

7 Data Repository Item, Siddoway p. 7 Ar/ 39 Ar ANALYTICAL PROCEDURES High purity mineral separates (>99% pure) were prepared from crushed and sized rock chips using conventional heavy liquid and magnetic separation techniques. Single crystals of K-feldspar and multigrain aggregates of biotite were analyzed. Mineral separates were wrapped individually in Sn foil, along with biotite standard GA1550 (97.9 Ma, McDougall and Harrison, 1988) used to monitor the neutron dose. Samples were vacuum sealed in super silica quartz tubes and irradiated for 15 hours in position L-67 of the Ford Reactor at the University of Michigan. Argon analyses were performed in the Noble Gas Laboratory at the University of Arizona. Extraction of gas from the samples was accomplished using a double-vacuum, resistance-heated tantalum furnace with furnace temperature control via a thermocouple in contact with the bottom of the crucible and mounted on the outer (low) vacuum side of the furnace. Three SAES getters were used for purification of the extracted gas. Pumping is through either a turbomolecular pump or a Varian ion pump. Isotopic analyses were performed using a VG50 mass spectrometer with an ioncounting electron multiplier. Machine mass discrimination and sensitivity were determined from repeated analysis of atmospheric argon. Data reduction was completed on a PC using in-house programs. Samples were corrected for blanks, neutron-induced interfering isotopes, decay of 37 Ar and 39 Ar, mass discrimination, atmospheric argon, as well as H 35 Cl, H 36 Cl and H 37 Cl. Correction factors used to account for interfering nuclear reactions were determined by analyzing argon extracted from irradiated CaF 2 and K 2 SO 4 and are ( 36 Ar/ 37 Ar) Ca = ; ( 38 Ar/ 37 Ar) Ca = ;( 39 Ar/ 37 Ar) Ca = ; ( Ar/ 39 Ar) K = 0.020; ( 38 Ar/ 39 Ar) K = Results of Ar/ 39 Ar step heating experiments are shown in Table 2 in data repository, and age spectra are shown in Figure 4. All ages are calculated using the decay constants recommended by Steiger and Jager (1977). Stated precisions for Ar/ 39 Ar K ages include all uncertainties in the measurement of isotope ratios and are quoted at the 1σ level. The errors do not include an error associated with the J parameter which is < 0.5%. Heating schedules for K-feldspar analyses were chosen in order to maximize the amount of gas extracted prior to breakdown of the feldspar in vacuo. Isothermal duplicates were performed on the C steps to test for chlorine-correlated excess argon (Harrison et al., 1993, 1994), however no correlation exists between Ar*/ 39 Ar K )and ( 38 Ar/ 39 Ar K ) for the samples analyzed. The textures of brittle deformation and dynamic recrystallization in the K-feldspar samples analyzed indicate that they are not ideal candidates for multi-diffusion domain modeling (Lovera et al, 1989). An unrealistically low activation energy (10.4 kcal/mole) obtained by modelling the Arrhenius data for D280 K-feldspar and an element failure on the last step (1550 C) of the D2-83 Kfeldspar experiment prevented us from pursuing modelling experimental results further for these samples. However it was possible to model experimental results for D2-3 K-feldspar using the method and programs developed by Lovera et al. (1989; see also Three domains with an activation energy of 30.4 kcal/mol and log Do/r 2 = were used to model the Arrhenius and log r/r o plots. Domain distribution parameters obtained were then used to forward model age spectra after a T-t history consistent with AFTT and petrologic constraints was specified. Figure 4 shows the fit to the experimental data using the T-t history shown in Figure 4. An inconsistency exists between the model and low temperature portion of the K-feldspar age spectrum, however the model shown incorporates the AFTT constraints.

8 Data Repository Item, Siddoway p. 8 REFERENCES CITED Harrison, T.M., Heizler, M.T., Lovera, O.M., Chen, W. and Grove, M., 1994, A chlorine disinfectant for excess argon released from K-feldspar during step-heating, Earth and Planetary Science Letters, v. 123, p Harrison, T.M., Heizler, M.T., and Lovera, O.M., 1993, In vacuo crushing experiments and K- feldspar thermochronometry: Earth and Planetary Science Letters, v. 117, p Lovera, O. M., Richter, F. M. and Harrison, T. M., 1989, The Ar/39Ar geothermometry for slowly cooled samples having a distribution of diffusion domain sizes, Journal of Geophysical Research, v. 94, p. 17,917-17,935. McDougall, I., and Harrison, T.M., 1999, Geochronology and thermochronology by the Ar/ 39 Ar method: New York, Oxford University Press, 2 nd edition, 269 p. Steiger, R.H., and Jager, E., 1977, Subcommision on geochronology: Convention on the use of decay constants in geo- and cosmochronology: Earth and Planetary Science Letters, v. 36, p

9 Data Repository Item, Siddoway p. 9 TABLE DR3. FISSION TRACK ANALYTICAL RESULTS Sample number Number of grains Standard track density Fossil track density Induced track density χ 2 probability, % Relative error (%) Central age, ± 1σ (Ma) Length* (µm) Deviation (µm) D (4900) (343) (1319) ± ± 0.1 (103) 1.4 D (4900) (569) (1825) 93 < ± ± 0.2 (47) 1.3 ANALYTICAL PROCEDURES Parentheses enclose number of tracks counted (density) or measured (track lengths). Standard and induced track densities were measured on mica external detectors (geometry factor = 0.5), and fossil track densities were measured on internal mineral surfaces. Rock samples were crushed and the mineral separates obtained using conventional heavy liquid and magnetic techniques. Apatite grains were mounted in epoxy resin on glass slides, ground and polished to reveal an internal surface, and then etched for 20 s at room temperature in 5N HNO 3 to reveal spontaneous fission tracks. Apatite mount-mica external detector, and standard glass-mica external detector mounts were irradiated at the Oregon State University Nuclear reactor in the slow soaker position B-3 (Thermal column number 5) that has a Cd for Au ratio of 14 at the column face. Apatite ages were determined using the external detector method, utilizing an automated stage. Mounts were counted at a magnification of 1250x under a dry 100x objective. Ages were calculated using the zeta calibration method (zeta = 361 ± 10 for dosimeter glass CN5) following the procedures of Hurford and Green (1983) and Green (1985). Ages are reported as central ages (Galbraith and Laslett, 1993). Analytical errors were calculated using the conventional method (Green, 1981). The chi-square test performed on single-grain data (Galbraith, 1981) determines the probability that the counted grains belong to a single age population (within Poissonian variation). If the χ 2 value is less than 5%, it is likely that the grains counted represent a mixed-age population with real age differences between single grains. The relative error or age dispersion (spread of the individual grain data) is given by the relative standard deviation of the central age. Where the dispersion is low (<15) the data are consistent with a single population, and the mean/pooled ages and the central age converge. Track lengths were measured using confined fossil fission tracks using only those that were horizontal [Laslett et al., 1984]. Track lengths were measured using a projection tube and a digitizing tablet attached to a microcomputer. Explanation of the modeling undertaken to produce the time-temperature paths in Figure 5b: Using the Ar/ 39 Ar data as an upper temperature constraint, the apatite fission track (AFT) data for these two samples were modeled using the genetic algorithm approach (Gallagher, 1995). While modeling of only two samples, especially those collected by dredging, so that the relative crustal depth of each is unconstrained, will not yield a definitive thermal history, it will constrain an envelope of thermal histories that are consistent with the raw AFT data and available geologic constraints. Assuming that samples D2-3 and D2-80 originated from the same region of exhumed crust the thermal histories for each sample are compatible if sample D2-3 resided structurally lower in the crust than D2-80. Thus, following rapid cooling due to exhumation accompanying mylonitization that had ceased by ~90 Ma, as shown by Ar/ 39 Ar data, sample D2-80 cooled to

10 Data Repository Item, Siddoway p. 10 within the apatite PAZ whereas D2-3 remained at temperatures above the base of the PAZ. The rate of cooling then appears to have slowed quite dramatically which is necessary for sample D2-80 to retain some shortened tracks before a later period of more rapid cooling pushed sample D2-80 to temperatures cooler than the top of the PAZ (<60 C). Sample D2-3 also has a few short tracks, consistent with some time resident in the lower part of the PAZ near temperatures of 100 C before the later rapid cooling that must have been underway by ~71 Ma. With only two samples it is difficult to pin down the onset of this later rapid cooling, but the best fit models of D2-80 suggests it was initiated at ~80 Ma. REFERENCES CITED Galbraith, R.F., 1981, On statistical models for fission track counts: Journal of the International Association of Mathematical Geologists, v. 13, p Galbraith, R.F., and Laslett, G.M., 1993, Statistical models for mixed fission track ages: Nuclear Tracks and Radiation Measurements, v. 21, p Gallagher, K., 1995, Evolving temperature histories from apatite fission-track data: Earth and Planetary Science Letters, v. 136, p Green, P.F., 1981, A new look at statistics in fission track dating: Nuclear Tracks and Radiation Measurements, v. 5, p Green, P.F., 1985, Comparison of zeta calibration baselines for fission-track dating of apatite, zircon and sphene: Chemical Geology (Isotope Geoscience Section), v. 58, p Hurford, A.J., and Green, P.F., 1983, The zeta age calibration of fission track dating: Isotope Geoscience, v. 1, p Laslett, G.M., Gleadow, A.J.W., and Duddy, I.R., 1984, The relationship between fission track length and density in apatite: Nuclear Tracks and Radiation Measurements, v. 9, p