Data Repository for 40 Ar/ 39 Ar Age Constraints on the Duration of Resurgence at the Valles Caldera, New Mexico

Transcription

1 Open File Report OF-AR-6 New Mexico Bureau of Geology and Mineral Resources A division of New Mexico Institute of Mining and Technology Data Repository for Ar/ 39 Ar Age Constraints on the Duration of Resurgence at the Valles Caldera, New Mexico Prepared By: Erin H. Phillips,, Fraser Goff 3, Philip R. Kyle,, William C. McIntosh,, Nelia W. Dunbar Department of Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM 878 USA New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, Socorro, NM 878 USA 3 Department of Earth and Planetary Sciences, University of New Mexico, Albuquerque, NM 873 USA Data Repository for: Journal of Geophysical Research Volume XX, Issue XX SOCORRO 6

2 Summary of Ar/ 39 Ar ages for the first Valles caldera ring fracture rhyolite, post-collapse intracaldera units, Bandelier Tuff, and selected megabreccia blocks. a Sample Unit Rock type n b MSWD c Age (± σ) Final age determination (± σ) Ring-fracture Rhyolite EP- Cerro del Medio (Valle Grande Member) rhyolite lava 8.3. ±.3 Ma EP-39 Cerro del Medio (Valle Grande Member) rhyolite lava ±.8 Ma Pooled age:.9 ±.7 Ma f Resurgent Dome Rhyolites EP-7 Redondo Creek Member pumiceous rhyolite lava.9.8 ±.7 Ma F3- Redondo Creek Member rhyolite lava..7 ±. Ma F3-3 Redondo Creek Member rhyolite lava..3 ±.8 Ma EP-HF Redondo Creek Member rhyolite lava ±.7 Ma EP- Deer Canyon Member lithic tuff..9 ±.3 Ma EP- Deer Canyon Member lithic tuff 9.6. ±.7 Ma F3-b Deer Canyon Member rhyolite lava 3.. ±. Ma EP-3 Deer Canyon Member lithic tuff.7.7 ±. Ma EP-3 Deer Canyon Member rhyolite lava.87.6 ±.3 Ma EP- Deer Canyon Member lithic tuff.7.7 ±. Ma EP-9 Deer Canyon Member lithic tuff.3.7 ±. Ma EP-3 Deer Canyon Member rhyolite lava ±.7 Ma Upper Bandelier Tuff EP-3 upper Bandelier Tuff plinian fall deposit ±.7 Ma EP- outflow facies upper Bandelier Tuff ignimbrite ±. Ma EP- intracaldera upper Bandelier Tuff welded ignimbrite ±.6 Ma EP-8 intracaldera upper Bandelier Tuff welded ignimbrite ±.3 Ma Lower Bandelier Tuff EP-3 lower Bandelier Tuff megabreccia block clast of welded ignimbrite ±.9 Ma EP- lower Bandelier Tuff megabreccia block clast of welded ignimbrite ±.38 Ma Age range:.8 ±.7 to.39 ±.7 Ma g Age range:.9 ±.3 to.83 ±.7 Ma g Preferred age:.6 ±. Ma (EP-) h Pooled age:.68 ±.3 Ma f Tertiary Volcanic Rocks F3-- d dacitic lava megabreccia block (Polvadera Group) dacitic lava na.. ±.8 Ma EP-8 e dacitic tuff megabreccia block (Keres Group) dacitic tuff ±.83 Ma a All analyses are by single crystal laser fusion of sanidine exept EP-8 (laser step heating of biotite) and F3-- (laser step heating of groundmass concentrate). b Number of analyses used to calculate weighted mean age c Mean square of weighted deviates; a goodness of fit parameter d Analyzed by laser step heating of groundmass concentrate (heated in 8 heating steps). Six heating steps used to calculate plateau age. e Analyzed by laser step heating of biotite separate in two heating steps. Age is weighted mean age of B steps only. f Pooled ages: a weighted mean age is calculated for all crystals from multiple samples from the same geologic unit, by the same methods used to calculate individual weighted mean ages. Used if ages from multiple samples are statistically indistinguishable at the σ confidence interval and are of the same lithology and eruptive history. g Age ranges: a range of ages for a geologic unit from the youngest to the oldest. Used if a geologic unit is physically variable and occurs in multiple isolated localities, or if field evidence shows the unit was erupted over a span of time. h Preferred age: the age of a single sample from a geologic unit that is found to be the most precise. Used if the Ar/ 39 Ar age of one sample is clearly more precise than ages for other samples within the unit.

3 AR/ 39 AR SINGLE CRYSTAL SANIDINE DATA ID Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (x -3 ) (x - mol) (%) (Ma) (Ma) UPPER BANDELIER TUFF EP-san,K:6, single crystal sanidine; J=.736±.%; D=.73±.; NM-6; Lab#=378 *EP-san,D:6, single crystal san; J=.67±.%; D=.8±.9; NM-6; Lab#= * * * * * * * * * * * * * * * * * * * *# Mean age ± σ n=33 MSWD= ±.8.6. EP-3san,K6:6, single crystal sanidine; J=.73±.%; D=.73±.; NM-6; Lab#= # # # # # # Mean age ± σ n=8 MSWD=.8 9. ± EP-san,H8:6, single crystal sanidine; ID#<: J=.73±.%, D=.±.7; ID# : J=.793±.%, D=.737±.9; NM-6; Lab#= # #

4 AR/ 39 AR SINGLE CRYSTAL SANIDINE DATA ID Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (x -3 ) (x - mol) (%) (Ma) (Ma) # # # # # # # # # # # Mean age ± σ n=8 MSWD=3.37. ± EP-8san,H:6, single crystal sanidine; ID#<: J=.733±.%, D=.±.7; ID# : J=.787±.%, D=.737±.9; NM-6; Lab#= # # # Mean age ± σ n= MSWD= ±..3.3 DEER CANYON MEMBER EP-3san,H:6, single crystal sanidine; J=.736±.%; D=.±.7; NM-6; Lab#= # # # Mean age ± σ n= MSWD= ± EP-3san,H9:6, single crystal sanidine; ID#<: J=.733±.%, D=.±.7; ID# : J=.789±.%, D=.737±.9; NM-6; Lab#=

5 AR/ 39 AR SINGLE CRYSTAL SANIDINE DATA ID Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (x -3 ) (x - mol) (%) (Ma) (Ma) # # # Mean age ± σ n=3 MSWD= ± EP-3san,H:6, single crystal sanidine; J=.73±.%; D=.73±.; NM-6; Lab#=376 # Mean age ± σ n= MSWD=.7 3. ±3..7. EP-san,H7:6, single crystal sanidine; ID#<: J=.73±.%, D=.±.7; ID# : J=.79±.%, D=.737±.9; NM-6; Lab#=37 # # # # # # # # # # # # Mean age ± σ n= MSWD=.7.6 ±9.3.7.

6 AR/ 39 AR SINGLE CRYSTAL SANIDINE DATA ID Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (x -3 ) (x - mol) (%) (Ma) (Ma) EP-9san,J:6, single crystal sanidine; J=.739±.%; D=.73±.; NM-6; Lab#= # Mean age ± σ n= MSWD= ± EP-san,H:6, single crystal sanidine; J=.736±.%; D=.±.7; NM-6; Lab#= # # Mean age ± σ n= MSWD=.. ± EP-san,H3:6, single crystal sanidine; J=.736±.%; D=.±.7; NM-6; Lab#=37 # # # # # Mean age ± σ n=9 MSWD=.6 6. ±3...7 F3-b san,n:7, single crystal sanidine, J=.77±.%, D=.±., NM-7, Lab#= # # Mean age ± σ n=3 MSWD=. 7.8 ±8.3.. REDONDO CREEK MEMBER EP-HFsan,H:6, single crystal sanidine; ID#<: J=.733±.%, D=.±.7; ID# : J=.78±.%, D=.737±.9; NM-6; Lab#=378 #

7 AR/ 39 AR SINGLE CRYSTAL SANIDINE DATA ID Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (x -3 ) (x - mol) (%) (Ma) (Ma) # # # # # Mean age ± σ n=3 MSWD=.9 9. ± EP-7san,H:6, single crystal sanidine; ID#<: J=.738±.%, D=.73±.; ID# : J=.78±.%, D=.737±.9; NM-6; Lab#= # # # # # Mean age ± σ n= MSWD= ± F3- san,n:7, single crystal sanidine, J=.739±.%, D=.±., NM-7, Lab#= # Mean age ± σ n= MSWD=. 7. ±6..7. F3-3 san,n:7, single crystal sanidine, J=.73±.%, D=.±., NM-7, Lab#=78 #

8 AR/ 39 AR SINGLE CRYSTAL SANIDINE DATA ID Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (x -3 ) (x - mol) (%) (Ma) (Ma) # # Mean age ± σ n= MSWD=.. ±..3.8 CERRO DEL MEDIO EP-san,J8:6, single crystal sanidine; ID#<: J=.733±.%, D=.73±.; ID# : J=.739±.%, D=.737±.9; NM-6; Lab#=377 # # # # Mean age ± σ n=8 MSWD=.3 6. ±.6..3 EP-39san,J9:6, single crystal sanidine; ID#<: J=.736±.%, D=.73±.; ID# : J=.7377±.%, D=.737±.9; NM-6; Lab#=

9 AR/ 39 AR SINGLE CRYSTAL SANIDINE DATA ID Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (x -3 ) (x - mol) (%) (Ma) (Ma) Mean age ± σ n=3 MSWD=.9.7 ± MEGABRECCIA BLOCKS EP-san,H3:6, single crystal sanidine; J=.733±.%; D=.73±.; NM-6; Lab#=376 # # Mean age ± σ n=3 MSWD= ± EP-3san,J3:6, single crystal sanidine; J=.73±.%; D=.73±.; NM-6; Lab#=3766 # Mean age ± σ n= MSWD= ±..6.9 Notes: Isotopic ratios corrected for blank, radioactive decay, and mass discrimination, not corrected for interferring reactions. Errors quoted for individual analyses include analytical error only, without interferring reaction or J uncertainties. Mean age is weighted mean age of Taylor (98). Mean age error is weighted error of the mean (Taylor, 98), multiplied by the root of the MSWD where MSWD>, and also incorporates uncertainty in J factors and irradiation correction uncertainties. Decay constants and isotopic abundances after Steiger and Jaeger (977). # symbol preceding sample ID denotes analyses excluded from mean age calculations. Ages calculated relative to FC- Fish Canyon Tuff sanidine interlaboratory standard at 8. Ma Decay Constant (LambdaK (total)) =.3e- Samples and monitors from irradiation NM-6 were analyzed during two different time intervals, resulting in two different J-factors for some samples. The two J-factors were not averaged because of possible variations in the actual discrimination values between the two analysis periods and/or variations in the geometry of crystals in irradiation disks. Correction factors: ( 39 Ar/ 37 Ar) Ca =.7 ± e- (NM-6).7 ± e- (NM-6).7 ± e- (NM-7) ( 36 Ar/ 37 Ar) Ca =.8 ± e-6 (NM-6).8 ± e- (NM-6).8 ± e-6 (NM-7) ( Ar/ 39 Ar) K =. ± 3e- (NM-6).3 ± 9e- (NM-6). ± 3e- (NM-7)

10 AR/ 39 AR STEP HEATED BIOTITE DATA ID Power Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* 39 Ar Age ±σ (Watts) (x -3 ) (x - mol) (%) (%) (Ma) (Ma) EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#=3767- A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#=3767- A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#=3767- A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#= A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#= A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#= A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#= A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#= A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#= A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD=

11 AR/ 39 AR STEP HEATED BIOTITE DATA ID Power Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* 39 Ar Age ±σ (Watts) (x -3 ) (x - mol) (%) (%) (Ma) (Ma) EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#= A B Integrated age ± σ n= Plateau ± σ steps A-B n= MSWD= B STEP DATA ID Power Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* Age ±σ (watts) (x -3 ) (x - mol) (%) (Ma) (Ma) EP-8 bi, J:6, 3- xtals bi, J=.73±.%, D=.73±., NM-6, Lab#=3767 6B B B B B B # B B B B Mean age ± σ n=9 MSWD= ± Notes: Isotopic ratios corrected for blank, radioactive decay, and mass discrimination, not corrected for interfering reactions. Errors quoted for individual analyses include analytical error only, without interfering reaction or J uncertainties. Integrated age calculated by summing isotopic measurements of all steps. Integrated age error calculated by quadratically combining errors of isotopic measurements of all steps. Plateau age is inverse-variance-weighted mean of selected steps. Plateau age error is inverse-variance-weighted mean error (Taylor, 98) times root MSWD where MSWD>. Plateau error is weighted error of Taylor (98). Decay constants and isotopic abundances after Steiger and Jäger (977). Weight percent K O calculated from 39 Ar signal, sample weight, and instrument sensitivity. Ages calculated relative to FC- Fish Canyon Tuff sanidine interlaboratory standard at 8. Ma Decay Constant (LambdaK (total)) =.3e-/a Correction factors: ( 39 Ar/ 37 Ar) C a =.7 ± e- ( 36 Ar/ 37 Ar) C a =.8 ± e-6 ( Ar/ 39 Ar) K =. ± 3e- For B step data, mean age is weighted mean age of Taylor (98). Mean age error is weighted error of the mean (Taylor, 98), multiplied by the root of the MSWD where MSWD>, and also incorporates uncertainty in J factors and irradiation correction uncertainties. # symbol preceding sample ID denotes analyses excluded from mean age calculations.

12 Ar/ 39 Ar GROUNDMASS CONCENTRATE DATA ID Power Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* 39 Ar Age ±s (Watts) (x -3 ) (x - mol) (%) (%) (Ma) (Ma) F3--wr,M:7, 9. mg wr, J=.77±.%, D=.±., NM-7, Lab#=7- # A B C D E F G # H Integrated age ± σ n= ±. KO=.%.97.9 Plateau ± σ steps B-G n=6 MSWD= ± Notes: Isotopic ratios corrected for blank, radioactive decay, and mass discrimination, not corrected for interfering reactions. Errors quoted for individual analyses include analytical error only, without interfering reaction or J uncertainties. Integrated age calculated by summing isotopic measurements of all steps. Integrated age error calculated by quadratically combining errors of isotopic measurements of all steps. Plateau age is inverse-variance-weighted mean of selected steps. Plateau age error is inverse-variance-weighted mean error (Taylor, 98) times root MSWD where MSWD>. Plateau error is weighted error of Taylor (98). Decay constants and isotopic abundances after Steiger and Jäger (977). # symbol preceding sample ID denotes analyses excluded from plateau age calculations. Weight percent K O calculated from 39 Ar signal, sample weight, and instrument sensitivity. Ages calculated relative to FC- Fish Canyon Tuff sanidine interlaboratory standard at 8. Ma Decay Constant (LambdaK (total)) =.3e-/a Correction factors: ( 39 Ar/ 37 Ar) C a =.7 ± e- ( 36 Ar/ 37 Ar) C a =.8 ± e-6 ( Ar/ 39 Ar) K =. ± 3e-

13 AR/ 39 AR STEP HEATED SANIDINE DATA ID Power Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Ar* 39 Ar Age ±σ (Watts) (x -3 ) (x - mol) (%) (%) (Ma) (Ma) EP-san crushed and etched,m:6, 7.8mgsan, J=.69±.%, D=.8±.9, NM-6, Lab#=- # A B C D E F G # H # I # J # K Integrated age ± σ n= 86.6 KO=7. %.7.9 Plateau ± σ steps B-G n=6 MSWD= EP-san surface etched,a:6, 3.93mgsan, J=.68±.%, D=.8±.9, NM-6, Lab#=- # A B C D E F G H I # J # K # L Integrated age ± σ n= 36.3 KO=6.8 %.9.8 Plateau ± σ steps B-I n=8 MSWD= EP-3san crushed and etched,c3:6, 6.mgsan, J=.637±.%, D=.8±.9, NM-6, Lab#=- # A # B C D E F G # H # I # J # K # L Integrated age ± σ n= 7.3 KO=6.3 %.39.9 Plateau ± σ steps C-G n= MSWD= EP-3san surface etched,c:6, 33.3mgsan, J=.67±.%, D=.8±.9, NM-6, Lab#=- # A B C D E F # G # H # I # J # K # L Integrated age ± σ n= 9. KO=6.9 %.9.7 Plateau ± σ steps B-F n= MSWD= Notes: Isotopic ratios corrected for blank, radioactive decay, and mass discrimination, not corrected for interfering reactions. Errors quoted for individual analyses include analytical error only, without interfering reaction or J uncertainties. Integrated age calculated by summing isotopic measurements of all steps. Integrated age error calculated by quadratically combining errors of isotopic measurements of all steps. Plateau age is inverse-variance-weighted mean of selected steps. Plateau age error is inverse-variance-weighted mean error (Taylor, 98) times root MSWD where MSWD>. Plateau error is weighted error of Taylor (98). Decay constants and isotopic abundances after Steiger and Jäger (977). # symbol preceding sample ID denotes analyses excluded from plateau age calculations. Weight percent K O calculated from 39 Ar signal, sample weight, and instrument sensitivity. Ages calculated relative to FC- Fish Canyon Tuff sanidine interlaboratory standard at 8. Ma Decay Constant (LambdaK (total)) =.3e-/a Correction factors: ( 39 Ar/ 37 Ar) Ca =.7 ± e- ( 36 Ar/ 37 Ar) Ca =.8 ± e- ( Ar/ 39 Ar) K =.3 ± 9e-

14 AR/ 39 AR STEP HEATED QUARTZ DATA ID Power Ar/ 39 Ar 37 Ar/ 39 Ar 36 Ar/ 39 Ar 39 Ar K K/Ca Cl/K Ar* 39 Ar Age ±σ (Watts) (x -3 ) (x - mol) (%) (%) (Ma) (Ma) EP-qtz,A&A3:6,.7mg qtz, J=.638±.%, D=.6±.8, NM-6, Lab#=38- A B C D E F G H I Integrated age ± σ n=9 9. KO=.6 %.66.3 Plateau ± σ steps A-I n=9 MSWD= EP-3qtz,D&D3:6, 3.3mg qtz, J=.639±.%, D=.6±.8, NM-6, Lab#=3- A B C D E F G H I Integrated age ± σ n=9 3.3 KO=. % 3.. Plateau ± σ steps A-I n=8 MSWD= Notes: Isotopic ratios corrected for blank, radioactive decay, and mass discrimination, not corrected for interfering reactions. Errors quoted for individual analyses include analytical error only, without interfering reaction or J uncertainties. Integrated age calculated by summing isotopic measurements of all steps. Integrated age error calculated by quadratically combining errors of isotopic measurements of all steps. Plateau age is inverse-variance-weighted mean of selected steps. Plateau age error is inverse-variance-weighted mean error (Taylor, 98) times root MSWD where MSWD>. Plateau error is weighted error of Taylor (98). Decay constants and isotopic abundances after Steiger and Jäger (977). Weight percent K O calculated from 39 Ar signal, sample weight, and instrument sensitivity. Ages calculated relative to FC- Fish Canyon Tuff sanidine interlaboratory standard at 8. Ma Decay Constant (LambdaK (total)) =.3e-/a Correction factors: ( 39 Ar/ 37 Ar) C a =.7 ± e- ( 36 Ar/ 37 Ar) C a =.8 ± e- ( Ar/ 39 Ar) K =.3 ± 9e-

15 AR/ 39 AR PLOTS: The following figures display Ar/ 39 Ar data on age probability distribution diagrams, inverse isochrons, and age sprectra. Uncertainties are reported at the ± sigma confidence level, unless otherwise noted. On age probability distribution diagrams, open circles denote analyses excluded from weighted mean age and gray probability curve represents the curve that results if these analyses are included. On inverse isochron plots, pink points and numbers denote analyses excluded from isochron age and correspond to analyses eliminated from weighted mean age displayed on age probability distribution diagrams. Red error envelope is the error on the isochron and is displayed at the sigma uncertainty level. Large tick on inside of y-axis marks the atmospheric Ar/ 36 Ar ratio of 9.. Mol 39 Ar x - K/Ca 8 a) EP- age probability distribution diagram 3 % Radiogenic Analyses.6 ±. Ma MSWD = Age (Ma) b) EP- inverse isochron Ar/ Ar Isochron age =. ±. Ma.6 Ar/ 36 Ar Intercept = 97. ± MSWD =., n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for outflow facies upper Bandelier Tuff (EP-).

16 Mol 39 Ar x - K/Ca 8 a) EP-3 age probability distribution diagram % Radiogenic Analyses.3 ±.7 Ma MSWD = Age (Ma) b) EP-3 inverse isochron Ar/ Ar Isochron age =. ±.3 Ma Ar/ 36 Ar Intercept = 99 ± 8 MSWD =.8, n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for basal Plinian fall deposit of upper Bandelier Tuff (EP-3).

17 Mol 39 Ar x - K/Ca 8 a) EP- age probability distribution diagram 3 % Radiogenic Analyses.6 ±.6 Ma MSWD = Age (Ma) b) EP- inverse isochron Ar/ Ar Isochron age =.6 ±. Ma 8.6 Ar/ 36 Ar Intercept = 38 ± MSWD =.9, n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for intracaldera upper Bandelier Tuff (EP-).

18 Mol 39 Ar x - K/Ca 8 a) EP-8 age probability distribution diagram % Radiogenic Analyses.3 ±.3 Ma MSWD = Age (Ma) b) EP-8 inverse isochron Ar/ Ar Isochron age =.67 ±.37 Ma Ar/ 36 Ar Intercept = 337 ± 8 MSWD =., n = Ar/ Ar 6 3 Age probability distribution diagram (a) and inverse isochron (b) for intracaldera upper Bandelier Tuff (EP-8).

19 Mol 39 Ar x - K/Ca a) EP-3 age probability distribution diagram % Radiogenic Analyses.6 ±.3 Ma MSWD = Age (Ma) b) EP-3 inverse isochron Ar/ Ar Isochron age =.3 ±. Ma Ar/ 36 Ar Intercept = 37 ± MSWD =.68, n = Ar/ Ar 8 Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon lava (EP-3).

20 Mol 39 Ar x - K/Ca a) EP-3 age probability distribution diagram 3 % Radiogenic Analyses.83 ±.7 Ma MSWD = Age (Ma) b) EP-3 inverse isochron Ar/ Ar Isochron age =.6 ±.38 Ma Ar/ 36 Ar Intercept = 3 ± 8 MSWD =., n = Ar/ Ar 7 3 Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon lava (EP-3).

21 Mol 39 Ar x - K/Ca a) EP-3 age probability distribution diagram % Radiogenic Analyses.7 ±. Ma MSWD = Age (Ma) b) EP-3 inverse isochron Ar/ Ar Isochron age =.39 ±.3 Ma Ar/ 36 Ar Intercept = 3 ± 6 MSWD =.7, n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon tuff (EP-3).

22 Mol 39 Ar x - K/Ca a) EP- age probability distribution diagram 3 % Radiogenic Analyses.7 ±. Ma MSWD = Age (Ma) b) EP- inverse isochron Ar/ Ar Isochron age =.36 ±.38 Ma Ar/ 36 Ar Intercept = ± MSWD =.88, n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon tuff (EP-).

23 Mol 39 Ar x - K/Ca a) EP-9 age probability distribution diagram % Radiogenic Analyses.7 ±. Ma MSWD = Age (Ma) b) EP-9 inverse isochron Ar/ Ar Isochron age =.7 ±.8 Ma Ar/ 36 Ar Intercept = 3 ± 3 MSWD =., n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon tuff (EP-9).

24 Mol 39 Ar x - K/Ca a) EP- age probability distribution diagram % Radiogenic Analyses.9 ±.3 Ma MSWD = Age (Ma) b) EP- inverse isochron Ar/ Ar Isochron age =. ±. Ma Ar/ 36 Ar Intercept = 36 ± 3 MSWD =., n = Ar/ Ar 6 3 Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon tuff (EP-).

25 Mol 39 Ar x - K/Ca a) EP- age probability distribution diagram % Radiogenic Analyses. ±.7 Ma MSWD = Age (Ma) b) EP- inverse isochron Ar/ Ar Isochron age =.9 ±. Ma Ar/ 36 Ar Intercept = 9 ± 6 MSWD =., n = Ar/ Ar 3 Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon tuff (EP-).

26 K/Ca Mol 39 Ar x -.. a) F3-b age probability distribution diagram % Radiogenic Analyses. ±. Ma MSWD = Age (Ma) b) F3-b inverse isochron Ar/ Ar Isochron age =. ±. Ma Ar/ 36 Ar Intercept = 97 ± 3 MSWD =., n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for Deer Canyon lava (F3-b).

27 Mol 39 Ar x - K/Ca. a) EP-HF age probability distribution diagram 3 % Radiogenic Analyses.39 ±.7 Ma MSWD = Age (Ma) b) EP-HF inverse isochron Ar/ Ar Isochron age =.7 ±.38 Ma Ar/ 36 Ar Intercept = 36 ± 8 MSWD =.7, n = Ar/ Ar 9 Age probability distribution diagram (a) and inverse isochron (b) for Redondo Creek lava (EP-HF). For clarity, only those analyses included in the weighted mean ages are shown on inverse isochron.

28 Mol 39 Ar x - K/Ca. a) EP-7 age probability distribution diagram % Radiogenic Analyses.8 ±.7 Ma MSWD = Age (Ma) b) EP-7 inverse isochron 36 Ar/ Ar Isochron age =.7 ±. Ma Ar/ 36 Ar Intercept = 97 ± MSWD =, n = Ar/ Ar 7 Age probability distribution diagram (a) and inverse isochron (b) for Redondo Creek lava (EP-7). For clarity, only those analyses included in the weighted mean ages are shown on inverse isochron.

29 K/Ca Mol 39 Ar x - 3 a) F3- age probability distribution diagram % Radiogenic Analyses.7 ±. Ma MSWD = Age (Ma) b) F3- inverse isochron Ar/ Ar Isochron age =.3 ±. Ma Ar/ 36 Ar Intercept = 3 ± 9 MSWD =., n = Ar/ Ar 8 Age probability distribution diagram (a) and inverse isochron (b) for Redondo Creek Lava (F3-).

30 K/Ca Mol 39 Ar x -.. a) F3-3 age probability distribution diagram % Radiogenic Analyses.3 ±.8 Ma MSWD = Age (Ma).3 b) F3-3 inverse isochron Ar/ Ar Isochron age =.3 ±.7 Ma Ar/ 36 Ar Intercept = 98 ± 8 MSWD =.3, n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for Redondo Creek Lava (F3-3).

31 Mol 39 Ar x - K/Ca a) EP- age probability distribution diagram 3 % Radiogenic Analyses. ±.3 Ma MSWD = Age (Ma) b) EP- inverse isochron Ar/ Ar Isochron age =.7 ±.3 Ma.6 Ar/ 36 9 Ar Intercept = 98 ± MSWD =.3, n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for southern flow lobe of Cerro del Medio (EP-).

32 Mol 39 Ar x - K/Ca a) EP-39 age probability distribution diagram 3 % Radiogenic Analyses.39 ±.8 Ma MSWD = Age (Ma) b) EP-39 inverse isochron Ar/ Ar Isochron age =.3 ±.3 Ma.6 3 Ar/ 36 Ar Intercept = 3 ± MSWD =, n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for southern flow lobe of Cerro del Medio (EP-39).

33 Mol 39 Ar x - K/Ca a) EP- age probability distribution diagram % Radiogenic Analyses.699 ±.38 Ma MSWD = Age (Ma) b) EP- inverse isochron Ar/ Ar Isochron age =.673 ±.6 Ma. Ar/ 36 Ar Intercept = 37 ± 9 MSWD =., n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for clast from lower Bandelier Tuff megabreccia block (EP-).

34 Mol 39 Ar x - K/Ca a) EP-3 age probability distribution diagram % Radiogenic Analyses.6 ±.9 Ma MSWD = Age (Ma) b) EP-3 inverse isochron Ar/ Ar Isochron age =.68 ±.8 Ma Ar/ 36 Ar Intercept = 9 ± MSWD =., n = Ar/ Ar Age probability distribution diagram (a) and inverse isochron (b) for clast from lower Bandelier Tuff megabreccia block (EP-3).

35 Mol 39 Ar x - K/Ca.8.. EP-8 age probability distribution diagram % Radiogenic Analyses 8. ±.83 Ma MSWD = Age (Ma) Age probability distribution diagram for biotite from dacitic tuff megabreccia block (EP-8). Black points and curve represent A-steps in laser step heating analysis and red points and curve represent B-steps. Open circles and squares denote analyses excluded from the weighted mean ages.

36 F3-- Age Sprectra % Radiogenic K/Ca Apparent Age (Ma).. A. ±.8 Ma (MSWD =.) B C D E FG H Cumulative 39 Ar Released Age spectra for dacitic lava megabreccia block (F3--).

37 a) EP- K/Ca 6.. % Radiogenic Cl/K.6 ±. Ma (MSWD = 3.66) Apparent Age (Ma).. A A.3 ±. Ma (MSWD = 3.3) B B C C D E F D E G H F G I Cumulative 39 Ar Released K/Ca 3 3 a) EP-3.8. % Radiogenic Cl/K Apparent Age (Ma)... A.6 ±.3 Ma (MSWD = 9.).66 ±.8 Ma (MSWD =.8) H I B B C C D E F E G F G H D L A Cumulative 39 Ar Released Age spectra for crushed and etched sanidine used in the excess argon study for (a) upper Bandelier Tuff sample EP- and (b) Deer Canyon sample EP-3. Black spectra are for crushed and etched portion and red spectra are for surface etched portion. Labels for high temperature steps were removed for clarity. Each sample was heated in or incremental heating steps.

38 K/Ca a) EP- % Radiogenic Cl/K - Apparent Age (Ma) Integrated Age =.66 ±.3 Ma G H I 7 A 9 F Cumulative 39 Ar Released K/Ca 8 b) EP-3 - % Radiogenic Cl/K Apparent Age (Ma) 6 Integrated Age = 3. ±. Ma A 3 G H I Cumulative 39 Ar Released Age spectra for step heated quartz used in the excess argon study for (a) upper Bandelier Tuff sample EP- and (b) Deer Canyon sample EP-3. Heating steps that did not release significant 39 Ar are not shown. The integrated ages include these steps, but their effect is negligible.

39 ELECTRON MICROPROBE ANALYTICAL METHODS: Analyses were performed using the New Mexico Bureau of Geology and Mineral Resources Cameca SX- electron microprobe with three wavelength dispersive spectrometers and high-speed backscattered electron detectors. Backscattered electron images were obtained for mineral separates and polished thin sections and quantitative analyses were completed for phases of interest. ELECTRON MICROPROBE DETECTION LIMITS Oxide or Element Detection Limit SiO TiO Al O 3 MgO CaO MnO FeO Na O K O Cl F SrO BaO Cr O 3 P O SO ZrO.7 wt.%. wt.%. wt.%. wt.%.9 wt.%. wt.%. wt.%. wt.%.7 wt.%. wt.%. wt.%. wt.%. wt.%. wt.%. wt.%. wt.%.7 wt.% ELECTRON MICROPROBE STANDARD ANALYSES AND ACCEPTED VALUES Orthoclase VG-68 Number of Analyses: 6 8 Average Standard Deviation Accepted Value Average Standard Deviation Accepted Value SiO TiO.7.3. Al O FeO MnO.3..3 MgO.. CaO Na O K O P O.. F..9 SO..3 Cl.. SrO.. BaO.7.3. Donovan, personal communication Jarosewich E., Nelen, J.A., and Norberg, J.A., 98, Reference samples for electron microprobe analyses, Geostandards Newsletter, v., p. 3-7

40 ELECTRON MICROPROBE ANALYSES OF FELDSPAR Sample Unit SiO Al O 3 FeO CaO Na O K O SrO BaO Total Or Ab An UPPER BANDELIER TUFF EP-- Qbt nd nd EP-- Qbt nd nd.3 7 EP--3 Qbt nd EP-- Qbt nd EP--6 Qbt nd.. 8 EP--7 Qbt nd nd EP--8 Qbt nd nd EP--9 Qbt nd nd.3 EP-- Qbt nd nd.7 7 EP-- Qbt nd nd EP-- Qbt nd nd.7 8 EP--3 Qbt nd..9 7 EP-8- Qbt nd EP-8- Qbt nd nd. 3 6 EP-8-3 Qbt nd EP-8- Qbt nd EP-8-6 Qbt nd EP-8-7 Qbt nd nd. 8 EP-8- Qbt EP-8- Qbt nd EP-8- Qbt nd EP-8-3 Qbt nd EP-8- Qbt nd EP-8- Qbt nd nd 99.3 EP-8-6 Qbt nd nd.37 EP-3- Qbt nd nd EP-3- Qbt nd EP-3- Qbt nd nd EP-3- Qbt nd nd. 3 7 EP-3-6 Qbt nd nd.6 6 EP-3-7 Qbt nd nd EP-3- Qbt nd nd.7 6 EP-3- Qbt nd nd. 3 6 EP-3- Qbt nd EP-3-6 Qbt nd nd. 3 7 EP-3-7 Qbt nd nd.99 7 EP-- Qbt nd nd. 7 EP-- Qbt nd nd EP--3 Qbt nd EP-- Qbt nd nd EP-- Qbt nd nd EP--6 Qbt nd nd EP--7 Qbt nd nd EP--8 Qbt nd EP--9 Qbt nd nd EP-- Qbt nd nd DEER CANYON MEMBER EP-- Qvdc nd nd EP-- Qvdc nd EP--3 Qvdc nd.7. 9 EP-- Qvdc nd EP-- Qvdc nd nd.99 8 EP--6 Qvdc nd nd.96 6 EP--8 Qvdc nd nd. 6 EP--9 Qvdc nd nd.6 7 EP-- Qvdc nd EP-- Qvdc nd EP--3 Qvdc nd nd EP-- Qvdc nd nd.99 8 EP-- Qvdc nd EP-ts- Qvdc nd EP-- Qvdc nd nd EP-- Qvdc nd nd EP--3 Qvdc nd nd EP-- Qvdc nd nd EP-- Qvdc nd nd EP--6 Qvdc nd nd.97 9 EP--7 Qvdc nd nd EP--8 Qvdc nd nd EP--9 Qvdc nd nd. 7 EP-- Qvdc nd nd EP-- Qvdc nd nd EP-- Qvdc nd nd EP--3 Qvdc nd nd.9 6 EP-- Qvdc nd nd.3 7 EP-- Qvdc nd..9 8 EP--7 Qvdc nd nd EP--8 Qvdc nd nd.9 7 EP--9 Qvdc nd..8 7 EP-- Qvdc nd nd.6 8 EP-- Qvdc nd EP--3 Qvdc nd nd EP-- Qvdc nd nd.7 7 EP-- Qvdc nd nd. 3 7 EP--6 Qvdc nd nd.88 6 EP-9- Qvdc nd nd.6 8

41 ELECTRON MICROPROBE ANALYSES OF FELDSPAR Sample Unit SiO Al O 3 FeO CaO Na O K O SrO BaO Total Or Ab An EP-9-3 Qvdc nd EP-9- Qvdc nd.3 7 EP-9- Qvdc nd. 8 EP-9-6 Qvdc nd nd EP-9-7 Qvdc nd nd EP-9-9 Qvdc nd.6 EP-9- Qvdc nd EP-9- Qvdc nd EP-9-3 Qvdc nd.7 7 EP-9- Qvdc nd nd. 8 EP-3- Qvdc nd nd.67 7 EP-3-3 Qvdc nd nd. 3 6 EP-3- Qvdc nd nd.7 7 EP-3-6 Qvdc nd nd EP-3-7 Qvdc nd nd. 3 6 EP-3-9 Qvdc nd nd EP-3- Qvdc nd nd. 7 EP-3- Qvdc nd EP-3- Qvdc nd EP-3-3 Qvdc nd EP-3- Qvdc nd nd EP-3- Qvdc nd.9. 8 EP-3-6 Qvdc nd.. 8 EP-3- Qvdc nd EP-3- Qvdc nd nd EP-3-3 Qvdc nd nd. 7 EP-3- Qvdc nd EP-3- Qvdc nd nd.8 7 EP-3-6 Qvdc nd.. EP-3-9 Qvdc nd nd EP-3- Qvdc nd EP-3- Qvdc nd nd.67 7 EP-3- Qvdc nd nd. 7 EP-3- Qvdc EP-3- Qvdc nd nd.38 7 EP-3-3 Qvdc nd nd. 7 EP-3-6 Qvdc nd nd.3 EP-3-7 Qvdc nd EP-3-8 Qvdc EP-3-9 Qvdc nd nd EP-3- Qvdc nd nd EP-3- Qvdc nd nd. 7 EP-3- Qvdc nd EP-3-3 Qvdc nd nd EP-3- Qvdc nd nd EP-3- Qvdc nd EP-3-6 Qvdc nd EP-3-7 Qvdc nd nd EP-3-8 Qvdc nd EP-3ts-8 Qvdc nd REDONDO CREEK MEMBER EP-7- Qvrc EP-7- Qvrc EP-7-3 Qvrc EP-7- Qvrc EP-7-6 Qvrc EP-7-8 Qvrc EP-7-9 Qvrc EP-7- Qvrc EP-7- Qvrc nd EP-7-3 Qvrc EP-7- Qvrc nd.6. 3 EP-7- Qvrc EP-7-6 Qvrc EP-7-7 Qvrc EP-7-8 Qvrc EP-7-9 Qvrc EP-7- Qvrc EP-7- Qvrc EP-7- Qvrc EP-7-3 Qvrc EP-7- Qvrc EP-7- Qvrc EP-7-6 Qvrc nd.. 7 EP-9- Qvrc EP-9- Qvrc EP-9-3 Qvrc EP-9- Qvrc EP-9- Qvrc EP-9-6 Qvrc EP-9-7 Qvrc EP-9-8 Qvrc EP-9-9 Qvrc nd EP-9- Qvrc EP-9- Qvrc nd EP-9- Qvrc EP-9-3 Qvrc EP-9ts-7 Qvrc

42 ELECTRON MICROPROBE ANALYSES OF FELDSPAR Sample Unit SiO Al O 3 FeO CaO Na O K O SrO BaO Total Or Ab An EP-9ts-8 Qvrc EP-9ts- Qvrc EP-9ts-3 Qvrc EP-9ts-6 Qvrc EP-9ts-9 Qvrc EP--noHF- Qvrc EP--noHF-3 Qvrc nd EP--noHF- Qvrc EP--noHF-6 Qvrc EP--noHF-7 Qvrc EP--noHF-8 Qvrc EP--noHF- Qvrc EP--noHF- Qvrc EP--noHF- Qvrc EP--noHF- Qvrc EP--noHF- Qvrc nd.33.8 EP--noHF-6 Qvrc EP--noHF-8 Qvrc nd EP--noHF- Qvrc nd EP--HF- Qvrc EP--HF- Qvrc EP--HF-3 Qvrc nd EP--HF- Qvrc nd EP--HF- Qvrc EP--HF-6 Qvrc nd EP--HF-7 Qvrc EP--HF-8 Qvrc EP--HF-9 Qvrc EP--HF- Qvrc EP--HF- Qvrc EP--HF- Qvrc EP--HF-3 Qvrc EP--HF- Qvrc EP--HF- Qvrc nd EP--HF-6 Qvrc EP--HF-7 Qvrc nd EP-3- Qvrc EP-3- Qvrc nd EP-3-3 Qvrc EP-3- Qvrc nd EP-3- Qvrc EP-3-6 Qvrc EP-3-7 Qvrc EP-3-8 Qvrc EP-3-9 Qvrc EP-3- Qvrc nd EP-3- Qvrc EP-3- Qvrc nd EP-3-3 Qvrc nd EP-3- Qvrc nd.9 76 EP-3-6 Qvrc EP-3-7 Qvrc EP-3-8 Qvrc EP-3-9 Qvrc EP-3- Qvrc EP-3- Qvrc EP-3-6 Qvrc EP-3-8 Qvrc nd EP-3-9 Qvrc EP-3-3 Qvrc nd EP-3-3 Qvrc CERRO DEL MEDIO EP-39- Qvvf nd EP-39- Qvvf EP-39-3 Qvvf nd nd.96 7 EP-39- Qvvf nd..3 8 EP-39- Qvvf nd.8. 3 EP-39-6 Qvvf nd nd EP-39-7 Qvvf nd nd EP-39-8 Qvvf EP-39-9 Qvvf nd EP-39- Qvvf nd EP-39- Qvvf nd nd EP-39- Qvvf nd EP-39-3 Qvvf nd.6. 7 EP-39- Qvvf nd EP-39-6 Qvvf nd EP-39-7 Qvvf nd EP-39-8 Qvvf nd nd. 6 3 EP-39-9 Qvvf nd EP-39- Qvvf nd nd EP-- Qvvf nd nd EP-- Qvvf nd nd EP--3 Qvvf nd..9 3 EP-- Qvvf nd EP-- Qvvf nd nd. 7 6 EP--6 Qvvf nd EP--7 Qvvf nd