Jones, James V. III (ORCID: 0000-0002-6602-5935) Haeussler, Peter J. (ORCID: 0000-0002-1503-6247) Bradley, Dwight C. (ORCID: 0000-0001-9116-5289) Friedman, Richard M. Layer, Paul W. (ORCID: 0000-0003-1378-2585) 20220218 tabular digital data Anchorage, Alaska U.S. Geological Survey, Alaska Science Center Suggested Citation: Jones, J.V. III, Haeussler, P.J., Bradley, D.C., Friedman, R.M., Layer, P.W., 2020, U-Pb and 40Ar/39Ar geochronologic data for selected rocks from the western Alaska Range, Alaska: U.S. Geological Survey data release, https://doi.org/10.5066/P92ZOY4D https://doi.org/10.5066/P92ZOY4D This dataset includes four tables with isotopic data and ages for selected igneous bedrock samples collected in 2001 through 2003 from the Western Alaska Range, southcentral Alaska: (1) the concentration of uranium (U) and thorium (Th), ratios of multiple isotopes of lead (Pb) and U, and the age of multiple analytical aliquots, or fractions, of zircon for each sample; (2) the 40Ar/39Ar analytical data and interpreted ages for each rock sample; (3) the sample location, rock characteristics, and interpreted ages for each sample; (4) a data dictionary table, provided as a reference guide for the user. U-Pb zircon dates from igneous rocks aid in the interpretation of the age of original formation (i.e., crystallization age) of the bedrock unit. 40Ar/39Ar dates aid in the interpretation of the age of original formation (i.e., crystallization), rock cooling through distinct temperature ranges, and (or) reheating of the bedrock unit. These data are used to understand the geologic history of the western Alaska Range and surrounding regions of south-central Alaska. Bulk samples for U-Pb geochronology were processed into concentrated mineral separates of zircon and analyzed by isotope-dilution thermal ionization mass spectrometry (ID-TIMS) techniques at the University of British Columbia. Bulk samples for 40Ar/39Ar were processed into crushed whole-rock or into concentrated mineral separates of biotite or hornblende and analyzed by 40Ar/39Ar methods at the University of Alaska Fairbanks. Detailed interpretations of the data and a discussion of the results of the study can be found in the journal Geosphere (Jones et al., 2020). 2020 publication date Complete None planned -152.42 -150.55 62.01 61.28 USGS Metadata Identifier USGS:ASC437 ISO 19115 Topic Category GeoscientificInformation NASA GCMD Earth Science Keyword Thesaurus Earth science Isotope ratios Isotopic age Igneous rocks USGS Thesaurus Geology Geochronology Geochemistry Isotopic analysis Radiometric dating Uranium-lead analysis Uranium-thorium analysis Potassium-argon analysis USGS Geographic Names Information System (GNIS) Alaska Alaska Range Revelation Mountains Tordrillo Mountains None It is requested that the authors and the USGS Alaska Science Center be cited for any subsequent publications that reference this dataset. U.S. Geological Survey, Alaska Science Center Mailing and Physical

4210 University Drive

Anchorage Alaska 99508 USA 907-786-7000 ascweb@usgs.gov Jones, J.V. III Todd, E. Box, S.E. Haeussler, P.J. Holm-Denoma, C.S. Karl, S.M. Graham, G.E. Bradley, D.C. Kylander-Clark, A.R.C. Friedman, R.M. Layer, P.W. 2020 journal article Geosphere 17(1):118-153 online GeoScienceWorld Jones, J.V. III, Todd, E., Box, S.E., Haeussler, P.J., Holm-Denoma, C.S., Karl, S.M., Graham, G.E., Bradley, D.C., Kylander-Clark, A.R.C., Friedman, R.M., Layer, P.W. 2020. Cretaceous to Oligocene magmatic and tectonic evolution of the western Alaska Range: Insights from U-Pb and 40Ar/39Ar geochronology. Geosphere 17(1):118-153. https://doi.org/10.1130/GES02303.1 https://doi.org/10.1130/GES02303.1 Zircon crystals were selected from sample, annealed and chemically abraded, spiked with a 233-235U205Pb tracer solution, and dissolved. Resulting solutions were dried, loaded onto Re filaments, and analyzed using a thermal ionization mass spectrometer. Analytical blanks were 0.2 pg for U and up to 1.0 pg for Pb. U fractionation was determined directly on individual runs using the 233-235U205Pb isotopic tracer. Pb isotopic ratios were corrected for fractionation of 0.30%/amu, based on replicate analyses of NBS-982 reference material. EARTHTIME U-Pb synthetic solutions were analyzed on an ongoing basis to monitor accuracy. All measured isotopic ratios are reported with associated analytical uncertainty at the 2-sigma level. Mineral and whole-rock samples for argon dating were irradiated with monitor mineral MMhb-1 with preferred age of 523.5 Ma (Renne et al., 1998). Samples and the monitors were step-heated or fused using a 6-watt argon-ion laser. Argon purification was achieved using a liquid nitrogen cold trap and SAES Zr-Al getter at 400 degrees C. The argon isotopes were measured and corrected for system blank and mass discrimination, as well as neutron induced reactions on calcium, potassium and chlorine. Typical full-system 8 min laser blank values (in moles) were generally 2e-16 mol 40Ar, 3e-18 mol 39Ar, 9e-18 mol 38Ar, and 2e-18 mol 37Ar, and 2e-18 mol 36Ar, which are 10-50 times smaller than the sample/standard volume fractions. Correction factors for nucleogenic interferences during irradiation were determined from irradiated CaF2 and K2SO4 and were: (39Ar/37Ar)Ca = 7.06e-4, (36Ar/37Ar)Ca = 2.79e-4, and (40Ar/39Ar)K = 0.0297. Mass discrimination was monitored by analyzing air shots with an assumed 40Ar/36Ar value of 295.5 (Nier, 1950). The mass discrimination during these experiments was 1.3% per mass unit. No significant variation in discrimination over the course of the analyses was measured and so a single value was used in data reduction. Ages with +/- 1 sigma error were calculated using the decay constants of Renne et al., 2010. The integrated age is the age given by the total gas measured and is equivalent to a potassium-argon (K-Ar) age. A plateau age is reported if three or more consecutive gas fractions representing at least 50 percent of the total gas released that are within two standard deviations of each other and with an overall Mean Square Weighted Deviation (MSWD) less than or equal to 2.5. Attribute values fall within expected ranges. Users should note that the data tables are released in Comma Separated Values format (.csv) which present the data with the correct number of significant figures; however, some software programs may alter the values and truncate trailing zeroes. This data set is complete; no data were omitted. All collected samples have horizontal positions measured using hand-held GPS units with positional accuracy of 3 meters or less. Zircon grains were separated from crushed and ground samples using standard magnetic and heavy liquid techniques and hand-picked under binocular microscope. Selected grains were annealed at high temperatures, chemically abraded, spiked with a 233-235U205Pb tracer solution, and then dissolved. Resulting solutions were dried and loaded onto Re filaments. Isotopic ratios were measured by a modified single collector VG-54R or 354S thermal ionization mass spectrometer equipped with analogue Daly photomultipliers. Analytical blanks were 0.2 pg for U and up to 1.0 pg for Pb. U fractionation was determined directly on individual runs using the ET535 mixed 233-235U205Pb isotopic tracer. Pb isotopic ratios were corrected for fractionation of 0.30%/amu, based on replicate analyses of NBS-982 reference material and the values recommended by Thirlwall (2000). Data reduction used the Excel-based program of Schmitz and Schoene (2007). Standard concordia diagrams were constructed and regression intercepts and weighted averages calculated with Isoplot (Ludwig, 2003). All errors are quoted at the 2σ or 95% confidence level, unless otherwise noted. Isotopic ages were calculated with the decay constants λ238=1.55125E-10 and λ235=9.8485E-10 (Jaffey et al., 1971). Detailed analytical procedures are described in the document: "UBC_UPb_IDTIMS_methods.pdf" included in this data package. Unknown Mineral separation was done at the Geochronology Laboratory at the University of Alaska Fairbanks (UAF). For 40Ar/39Ar analysis, bulk rock samples were crushed, sieved, washed and hand-picked to obtain pure hornblende and biotite mineral separates. In some cases, phenocryst-free groundmass (whole rock) was crushed, sieved, and washed. Samples and standards were wrapped in aluminum foil and loaded into aluminum cans of 2.5 cm diameter and 6 cm height. The samples were irradiated in position 5c of the uranium enriched research reactor of McMaster University in Hamilton, Ontario, Canada for 20 megawatt-hours. After irradiation, the samples and standards were returned to UAF and loaded into an ultra-high vacuum extraction line. The standards were fused, and the samples heated, using a 6-watt argon-ion laser. Argon purification was achieved using a liquid nitrogen cold trap and a SAES Zr-Al getter at 400 degrees C. The argon isotopes were analyzed in a VG-3600 mass spectrometer, fitted with a single Daly detector, and operated in peak mode. Detailed analytical procedures are described in the document: "UAF_40Ar39Ar_methods.pdf" included in this data package. Unknown LITERATURE CITED: Jaffey, A.H., Flynn, K.F., Glendenin, L.E., Bentley, W.C., Essling, A.M., 1971. Precision measurements of half-lives and specific activities of 235U and 238U. Physical Reviews C 4(5):889-906. https://doi.org/10.1103/PhysRevC.4.1889 Jones, J.V. III, Todd, E., Box, S.E., Haeussler, P.J., Holm-Denoma, C.S., Karl, S.M., Graham, G.E., Bradley, D.C., Kylander-Clark, A.R.C., Friedman, R.M., Layer, P.W. 2020. Cretaceous to Oligocene magmatic and tectonic evolution of the western Alaska Range: Insights from U-Pb and 40Ar/39Ar geochronology. Geosphere 17(1):118-153. https://doi.org/10.1130/GES02303.1 Ludwig, K.R., 2003. User's Manual for Isoplot 3.00 : A Geochronological Toolkit for Microsoft Excel, Berkeley Geochronology Center, Special Publication no. 4. https://www.bgc.org/isoplot Nier, A.O., 1950. A Redetermination of the Relative Abundances of the Isotopes of Carbon, Nitrogen, Oxygen, Argon, and Potassium. Physical Review 77(6):789-793. https://doi.org/10.1103/PhysRev.77.789 Renne, P.R., Deino, A.L., Walter, R.C., Turrin, B.D., Swisher, C.C. III, Becker, T.A., Curtis, G.H., Sharp, W.D., Jaouni, A.R., 1994. Intercalibration of astronomical and radioisotope time. Geology 22(9):783-786. https://doi.org/10.1130/0091-7613(1994)022%3C0783:IOAART%3E2.3.CO;2 Renne, P.R., Swisher, C.C., Deino, A.L., Karner, D.B., Owens, T.L., DePaolo, D.J., 1998. Intercalibration of standards, absolute ages and uncertainties in 40Ar/ 39Ar dating. Chemical Geology 145(1-2):117-1522. https://doi.org/10.1016/S0009-2541(97)00159-9 Renne, P.R., Mundil, R., Balco, G., Min, K., Ludwig, K.R., 2010. Joint determination of 40K decay constants and 40Ar*/40K for the Fish Canyon sanidine standard, and improved accuracy for 40Ar/39Ar geochronology. Geochimica et Cosmochimica Acta 74(18):5349-5367. https://doi.org/10.1016/j.gca.2010.06.017 Samson, S.D., Alexander, E.C., 1987. Calibration of the interlaboratory 40Ar/39Ar dating standard, MMhb-1. Chemical Geology: Isotope Geoscience section 66(1-2):27-34. https://doi.org/10.1016/0168-9622(87)90025-X Schmitz, M.D., Schoene, B., 2007. Derivation of isotope ratios, errors, and error correlations for U-Pb geochronology using 205Pb-235U-(233U)-spiked isotope dilution thermal ionization mass spectrometric data. Geochemistry, Geophysics, Geosystems 8(8):Q08006. https://doi.org/10.1029/2006GC001492 Thirlwall, M.E., 2000. Inter-laboratory and other errors in Pb isotope analyses investigated using a 207Pb–204Pb double spike. Chemical Geology 163(1-4):299-322. https://doi.org/10.1016/S0009-2541(99)00135-7 Unknown Point 0.0001 0.0001 Decimal degrees North American Datum of 1983 (NAD83) Geodetic Reference System of 1980 (GRS80) 6378137 298.257222101 geochronology_dataDictionary_westAKRange_jones.csv Table describing all fields in each of the three data tables included in this data package. Includes field names, a brief description of each field, and units of measure, as applicable. The table contains 77 records and is presented in comma separated value (CSV) format. Author defined Table Name of the data table in which the field is found. Author defined geochronology_40Ar39Ar_westAKRange_jones.csv Filename of data table included in this data package. Author defined geochronology_U-Pb_IDTIMS_westAKRange_jones.csv Filename of data table included in this data package. Author defined geochronology_sampleSummary_westAKRange_jones.csv Filename of data table included in this data package. Author defined Field Field name found in data tables included in this data package (single words or concatenated abbreviations that describe the contents of the field). Author defined Name of each field in the CSV data tables Description Brief description of the contents of 'Field'. Author defined Brief description of the contents of 'Field'. Units The unit of measurement for applicable data fields. Author defined n/a not applicable Producer defined % percent Author defined 10e-13 mol 10e-13 moles Author defined Ma Mega-annum, or millions of years Author defined mg milligram Author defined Mol % mole percent Author defined mV millivolt Author defined mW milliwatt Author defined pg picogram Author defined ppm parts per million Author defined geochronology_sampleSummary_westAKRange_jones.csv Table with sample information, including location, rock description, and summary of geochronology analyses. The table contains 33 records and is presented in comma separated value (CSV) format. Author defined Sample Sample number as collected in the field; internal USGS identifier. Author defined Sample identifier; most labels consisting of the last two digits of the year collected, an abbreviation identifying the collector, and a number and possible suffix. Corresponds to the 'Sample' field in all tables included with this data package. AK_Region Part of Alaska where samples were collected Author defined South-central Alaska Samples collected in South-central Alaska Author defined AK_Subregion Geographic areas where samples were collected Author defined South-central Alaska Samples collected in Western Alaska Range Author defined Latitude Latitude of sample field location in NAD83 Author defined 61.2894 62.0007 Decimal degree (NAD83) 0.0001 Longitude Longitude of sample field location in NAD83 Author defined -152.4027 -150.5509 Decimal degree (NAD83) 0.0001 Rock_Class Sample rock classification Author defined igneous rock class = igneous Author defined Rock_Type Sample rock type Author defined This attribute contains general rock descriptions. Rock_Comment Sample rock comment Author defined This attribute contains additional descriptive information on rock type and/or location. Analysis_Type Type of geochronologic analysis Author defined 40Ar/39Ar This attribute denotes argon-argon radiometric dating procedures were performed on igneous rock. Author defined U-Pb ID-TIMS This attribute denotes specific zircon age dating analysis procedures were performed on igneous rock. Author defined Analysis_Lab Laboratory or contractor where data were collected Author defined UAF Laboratory located at the University of Alaska in Fairbanks, Alaska, United States of America. Author defined UBC Laboratory located at the University of British Columbia in Vancouver, British Columbia, Canada. Author defined LabID Sample name assigned by laboratory corresponding directly to the internal USGS identifier Sample. Author defined Alphanumeric code consisting of an internal laboratory identifier or USGS identifier code and a hyphenated alphanumeric character sequence, with a possible suffix. Sample_Material Mineral or rock material that was used for analysis Author defined biotite Mineral or rock material that was used: biotite Author defined hornblende Mineral or rock material that was used: hornblende Author defined zircon Mineral or rock material that was used: zircon Author defined whole rock Mineral or rock material that was used: whole rock Author defined Preferred_Age Preferred age of the sample material Author defined 1.8 122.4 Ma (Mega-annum or millions of years) Preferred_Age_Unc_2sig Uncertainty (2-sigma) of the preferred age Author defined 0.0 6.0 Ma (Mega-annum or millions of years) Preferred_Age_Type Type of age preferred for this sample Author defined 40Ar/39Ar plateau age Type of preferred age: 40Ar/39Ar plateau age Author defined 40Ar/39Ar weighted average age Type of preferred age: 40Ar/39Ar weighted average age Author defined 206Pb/235U age of oldest fraction Type of preferred age: 206Pb/235U age of oldest fraction Author defined 206Pb/235U age of youngest fraction Type of preferred age: 206Pb/235U age of youngest fraction Author defined weighted average 206Pb/238U age Type of preferred age: weighted average 206Pb/238U age Author defined Preferred_Age_Comment Preferred age comment Author defined General supplemental comments amplifying how Preferred_Age was calculated. geochronology_U-Pb_IDTIMS_westAKRange_jones.csv Table of U-Pb zircon ID-TIMS data, reporting the isotopic concentration of uranium (U) and thorium (Th) measured in individual grains, isotopic ratios of lead and uranium, and the age of each grain calculated from the isotope ratios. The table contains 34 records and is presented in comma separated value (CSV) format. Author defined Sample Sample identifier, as assigned by the sample collector in the field; internal USGS identifier. Corresponds to 'Sample' field in all tables included in this data package. Author defined The value is a unique alphanumeric sequence for each sample but is repeated with an iteration suffix in this table because multiple measurement steps for each sample are analyzed, as noted in attribute Mineral_fraction_name. Mineral Mineral analyzed Author defined zircon Mineral analyzed = zircon Author defined Mineral_fraction_name Internal laboratory identifier of mineral fraction analyzed Author defined The attributes in this data set are a concatenation of field Sample and a dash with a sequential alphanumeric suffix. Mineral_fraction_weight Total weight of mineral grains in fraction aliquot, in milligrams Author defined 0.004 0.128 mg (milligrams) U_conc_ppm Uranium concentration, in parts per million Author defined 30 7428 ppm (parts per million) Th_conc_ppm Thorium concentration, in parts per million Author defined 0.4 91.2 ppm (parts per million) Th_U_ratio Total ratio of thorium to uranium Author defined 0.048 0.998 206Pb_rad Radiogenic 206Pb concentration, in 10e-13 mol Author defined 0.417 34.654 10e-13 mol 206Pb_rad_mol_perc Mol percent 206Pb with respect to radiogenic, blank, and initial common Pb Author defined 72.38 99.70 % (percent) Pb_rad_common_ratio Measured ratio of radiogenic lead to common lead corrected for spike and fractionation Author defined 1.0 97.4 Pb_common_pg Common lead concentration, in picograms Author defined 2.12 27.98 pg (picograms) 206Pb_204Pb_ratio Total ratio of 206Pb to 204Pb Author defined 67.0 6268.0 208Pb_206Pb_ratio Total ratio of 208Pb to 206Pb Author defined 0.02 0.32 207Pb_206Pb_ratio Total ratio of 207Pb to 206Pb Author defined 0.05 0.05 207Pb_206Pb_ratio_unc_2sig_perc Uncertainty (2-sigma) on total ratio of 207Pb to 206Pb, in percent Author defined 0.21 21.86 % (percent) 207Pb_235U_ratio Total ratio of 207Pb to 235U Author defined 0.03373 0.08374 207Pb_235U_ratio_unc_2sig_perc Uncertainty (2-sigma) on total ratio of 207Pb to 206Pb, in percent Author defined 0.406 23.339 % (percent) 206Pb_238U_ratio Total ratio of 206Pb to 238U Author defined 0.00497 0.01266 206Pb_238U_ratio_unc_perc Uncertainty (2-sigma) on total ratio of 207Pb to 206Pb, in percent Author defined 0.170 2.001 % (percent) Error_correlation Error correlation of the 207Pb/235U and 206Pb/238U ratios. Author defined 0.448 0.963 207Pb_206Pb_age 207Pb/206Pb age, in millions of year before present Author defined 11.0 310.0 Ma (mega-annum or millions of years) 207Pb_206Pb_age_unc_2sig_abs Uncertainty (2-sigma) on 207Pb/206Pb age, in millions of years before present Author defined 5.0 497.0 Ma (mega-annum or millions of years) 207Pb_235U_age 207Pb/235U age, in millions of years before present Author defined 33.70 81.65 Ma (mega-annum or millions of years) 207Pb_235U_age_unc_2sig_abs Uncertainty (2-sigma) on 207Pb/235U age, in millions of years before present Author defined 0.24 16.00 Ma (mega-annum or millions of years) 206Pb_238U_age 206Pb/238U age, in millions of years before present Author defined 31.95 81.09 Ma (mega-annum or millions of years) 206Pb_238U_age_unc_2sig_abs Uncertainty (2-sigma) on 206Pb/238U age, in millions of years before present Author defined 0.10 1.20 Ma (mega-annum or millions of years) Preferred_fraction_age Preferred fraction age for calculation of sample age, selected from one of the two following fields containing calculated ages: "207Pb_206Pb_age" or "206Pb_238U_age" Author defined 31.95 81.09 Ma (mega-annum or millions of years) Preferred_fraction_unc_2sig_abs Two-sigma uncertainty on preferred grain age Author defined 0.10 1.24 Ma (mega-annum or millions of years) Preferred_fraction_age_type Method used to calculate the values in "Preferred_fraction_age" field for each individual mineral fraction Author defined 206Pb_238U_age Method used = 206Pb_238U_age Author defined Interpreted_age_included Indication of whether or not analysis was used in calculation of field "Preferred_age" Author defined Y Yes, analysis was used. Author defined N No, analysis was not used. Author defined geochronology_40Ar39Ar_westAKRange_jones.csv Table of whole rock argon detection data, reporting the isotopic concentration of argon and associated elemental components measured in sample, isotopic ratios, and the age of each sample calculated from the isotope ratios. The table contains 327 records and is presented in comma separated value (CSV) format. Author defined Sample Sample identifier, as assigned by the sample collector in the field; internal USGS identifier. Corresponds to 'Sample' field in all tables included in this data package. Author defined Sample identifier; most labels consisting of the last two digits of the year collected, an abbreviation identifying the collector, followed by a number and suffix. LabID Sample name assigned by laboratory corresponding directly to the internal USGS identifier Sample and mineral analyzed. Author defined Alphanumeric code consisting of UAF and a hyphenated number. Lab Laboratory in which experiment was conducted Author defined UAF Geochronology Laboratory, University of Alaska Fairbanks Author defined Sample_material Mineral or rock material that was used for analysis. Author defined biotite Mineral or rock material that was used: biotite Author defined hornblende Mineral or rock material that was used: hornblende Author defined whole rock Mineral or rock material that was used: whole rock Author defined Monitor_mineral Reference mineral used to monitor neutron flux Author defined MMhb-l hornblende standard for 40Ar/39Ar Samson and Alexander 1987; Renne et al 1994 Monitor_mineral_age Published age of monitor mineral Author defined The monitor mineral used for all analyses in this data set is MMhb-1 with age 523.5 Ma. J_value Measure of neutron fluence Author defined 0.002456 0.002551 J_unc Uncertainty (1-sigma) in measure of neutron fluence Author defined 6.72e-06 3.64e-05 Laser_power_mW Laser power for each heating step, in milliwatts. Blank cells indicate an integrated analysis. Author defined 200 9000 mW (milliwatts) Integrated Indication that values in row were calculated by weighting individual heating steps by the fraction of 39Ar released. Blank cells indicate a heating step fraction. Author defined Integrated The term 'Integrated' indicates the values were calculated by weighting the individual heating steps by the fraction of 39Ar released. Author defined 39Ar_cum Cumulative 39Ar released at this step. Blank cells indicate an integrated analysis. Author defined 0.0003 1.0 percentage in decimal format 40Ar_mV Abundance of 40Ar in measurement Author defined 22.42 153999.82 mV (millivolts) 40Ar_mV_unc Uncertainty (1-sigma) in 40Ar measurement Author defined 0.14 1101.33 mV (millivolts) 39Ar_mV Abundance of 39Ar in measurement Author defined 0.29 7721.56 mV (millivolts) 39Ar_mV_unc Uncertainty (1-sigma) in 39Ar measurement Author defined 0.02 36.04 mV (millivolts) 38Ar_mV Abundance of 38Ar in measurement Author defined -0.03 1166.16 mV (millivolts) 38Ar_mV_unc Uncertainty (1-sigma) in 38Ar measurement Author defined 0.01 6.02 mV (millivolts) 37Ar_mV Abundance of 37Ar in measurement Author defined -0.002 15.144 mV (millivolts) 37Ar_mV_unc Uncertainty (1-sigma) in 37Ar measurement Author defined 0.022 134.694 mV (millivolts) 36Ar_mV Abundance of 36Ar in measurement Author defined -1.009 181.674 mV (millivolts) 36Ar_mV_unc Uncertainty (1-sigma) in 36Ar measurement Author defined 0.018 1.486 mV (millivolts) Perc_atm_40Ar Percent atmospheric 40Ar in measurement Author defined -154.9 120.2 % (percent) Perc_atm_40Ar_unc Uncertainty (1-sigma) in percent atmospheric 40Ar in measurement Author defined 0.1 158.0 % (percent) Ca_K_ratio Calcium to potassium ratio as determined from 37 argon derived from calcium and 39 argon derived from potassium; 37Ar(Ca)/39Ar(K). Author defined -0.027 73.276 Ca_K_ratio_unc Uncertainty (1-sigma) in calcium to potassium ratio Author defined 0.000 29.908 Cl_K_ratio Chlorine to potassium ratio as determined from 38 argon derived from chlorine and 39 argon derived from potassium; 38Ar(Cl)/39Ar(K). Author defined -0.0068 1.7918 Cl_K_ratio_unc Uncertainty (1-sigma) in chlorine to potassium ratio Author defined 0.00002 2.07310 40Ar_39Ar_K Ratio of radiogenic 40Ar to 39Ar derived from potassium Author defined -17.675 4848.175 40Ar_39Ar_K_unc Uncertainty (1-sigma) in ratio of radiogenic 40Ar to 39Ar from potassium Author defined 0.030 1595.774 Age_Ma Age calculated from ratio of radiogenic 40Ar to 39Ar from potassium, in millions of years. Author defined -83.1 4609.3 Ma (Mega-annum or millions of years) Age_Ma_unc Uncertainty (1-sigma) in calculated age, in millions of years. Author defined 0.1 1304.7 Ma (Mega-annum or millions of years) UBC_UPb_IDTIMS_methods.pdf "University of British Columbia (UBC) Pacific Centre for Isotopic and Geochemical Research (PCIGR) U-Pb zircon ID-TIMS methods": Document that describes the laboratory methods and data modeling for zircon U-Pb geochronology chemical abrasion thermal ionization. Provided in PDF format. Author defined UAF_40Ar39Ar_methods.pdf "University of Alaska Fairbanks Geochronology Laboratory 40Ar/39Ar analytical methods": Document that describes the laboratory methods and data modeling for whole rock argon dating geochronology. Provided in PDF format. Author defined U.S. Geological Survey USGS ScienceBase Team Mailing and Physical

Denver Federal Center, Building 810, Mail Stop 302

Denver Colorado 80225 USA 1-888-275-8747 sciencebase@usgs.gov The U.S. Geological Survey, Alaska Science Center is the authoritative source of these data, distributed by ScienceBase (a USGS Trusted Digital Repository). Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data for other purposes or on all computer systems, nor shall the act of distribution constitute any such warranty. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. CSV, PDF Tabular data in CSV format; supplemental documentation in PDF format; FGDC metadata in XML and HTML formats. https://doi.org/10.5066/P92ZOY4D None 20250528 U.S. Geological Survey, Alaska Science Center Mailing and Physical

4210 University Drive

Anchorage Alaska 99508 USA 907-786-7000 gs-ak_asc_datamanagers@usgs.gov FGDC Content Standard for Digital Geospatial Metadata (CSDGM) FGDC-STD-001-1998