Data Repository for 40 Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution

Transcription

1 Open File Report OF-AR-20 New Mexico Bureau of Geology and Mineral Resources A division of New Mexico Institute of Mining and Technology Data Repository for Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution Prepared By: Richard P. Esser, Philip R. Kyle and William C. McIntosh New Mexico Bureau of Geology, Socorro, NM Data Repository for: Bulletin of Volcanology Volume XX, Issue XX SOCORRO 2003

2 NEW MEXICO BUREAU OF GEOLOGY AND MINERAL RESOURCES Peter A. Scholle, Director and State Geologist a division of NEW MEXICO INSTITUTE OF MINING AND TECHNOLOGY Daniel H. López, President BOARD OF REGENTS Ex Officio Bill Richardson, Governor of New Mexico Michael J. Davis, Superintendent of Public Instruction Appointed Ann Murphy Daily, President, , Santa Fe Randall E. Horn, Secretary/Treasurer, , Albuquerque Sidney M. Gutierrez, , Albuquerque Anthony L. Montoya, Jr., , Socorro Robert E. Taylor, , Silver City NEW MEXICO GEOCHRONOLOGY RESEARCH LABORATORY STAFF WILLIAM MCINTOSH, Geochronologist MATT HEIZLER, Geochronologist LISA PETERS, Argon Laboratory Technician RICHARD ESSER, Argon Laboratory Technician BUREAU STAFF BRUCE D. ALLEN, Field Geologist RUBEN ARCHULETA, Metallurgical Lab. Technician II SANDRA H. AZEVEDO, Cartographer II ALBERT BACA, Lead Maintenance Carpenter JAMES M. BARKER, Associate Director for Operations, Senior Industrial Minerals Geologist PAUL W. BAUER, Associate Director for Government Liaison, Senior Geologist, Manager of Geologic Mapping Program LYNN A. BRANDVOLD, Senior Chemist BRIAN S. BRISTER, Petroleum Geologist RON BROADHEAD, Associate Director for Industry Liaison, Principal Senior Petroleum Geologist RITA CASE, Administrative Secretary II (Alb. Office) STEVEN M. CATHER, Senior Field Geologist RICHARD CHAMBERLIN, Senior Field Geologist SEAN D. CONNELL, Albuquerque Office Manager, Field Geologist RUBEN A. CRESPIN, Manager, Fleet/General Services JEANNE DEARDORFF, Assistant Editor NELIA W. DUNBAR, Analytical Geochemist RICHARD ESSER, Senior Lab. Associate ROBERT W. EVELETH, Senior Mining Engineer KARL FRISCH, GIS Technician PATRICIA L. FRISCH, Assistant Curator of Mineral Museum LEO O. GABALDON, Cartographer II NANCY S. GILSON, Editor KATHRYN E. GLESENER, Senior Cartographer/Manager, Cartography Section DEBBIE GOERING, Business Office Coordinator TERRY GONZALES, Information Specialist IBRAHIM GUNDILER, Senior Extractive Metallurgist LYNN HEIZLER, Senior Lab. Associate MATT HEIZLER, Assistant Director for Laboratories, Geochronologist LYNNE HEMENWAY, Geologic Information Center Coordinator GRETCHEN K. HOFFMAN, Senior Coal Geologist GLEN JONES, Assistant Director for Computer/Internet Services THOMAS J. KAUS, Cartographer I PHILIP KYLE, Professor, Geochemistry SUSIE KYLE, Administrative Secretary I LEWIS A. LAND, Hydrogeologist ANNABELLE LOPEZ, Petroleum Information Coordinator THERESA LOPEZ, Administrative Secretary I DAVID W. LOVE, Principal Senior Environmental Geologist JANE A. CALVERT LOVE, Managing Editor VIRGIL W. LUETH, Assistant Director for Public Outreach, Mineralogist/Economic Geologist, Curator of Mineral Museum MARK MANSELL, GIS Specialist DAVID MCCRAW, Senior Geologic Lab. Associate WILLIAM MCINTOSH, Senior Volcanologist CHRISTOPHER G. MCKEE, X-ray Facility Manager VIRGINIA T. MCLEMORE, Minerals Outreach Liaison, Senior Economic Geologist PATRICIA JACKSON PAUL, Geologic Lab. Associate LISA PETERS, Senior Lab. Associate L. GREER PRICE, Senior Geologist/Chief Editor ADAM S. READ, Senior Geological Lab. Associate BEN REBACH, Cartographer II WILLIAM D. RAATZ, Petroleum Geologist MARSHALL A. REITER, Principal Senior Geophysicist JOHN SIGDA, Geohydrologist GREGORY SANCHEZ, Mechanic-Carpenter Helper TERRY THOMAS, ICP MS Manager FRANK TITUS, Senior Outreach Hydrologist LORETTA TOBIN, Executive Secretary AMY TRIVITT-KRACKE, Petroleum Computer Specialist JUDY M. VAIZA, Assistant Director for Finance MANUEL J. VASQUEZ, Mechanic II SUSAN J. WELCH, Manager, Geologic Extension Service MAUREEN WILKS, Geologic Librarian, Manager of Publication Sales EMERITUS GEORGE S. AUSTIN, Emeritus Senior Industrial Minerals Geologist CHARLES E. CHAPIN, Emeritus Director/State Geologist JOHN W. HAWLEY, Emeritus Senior Environmental Geologist JACQUES R. RENAULT, Emeritus Senior Geologist SAMUEL THOMPSON III, Emeritus Senior Petroleum Geologist ROBERT H. WEBER, Emeritus Senior Geologist Plus research associates, graduate students, and undergraduate assistants.

3 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E830: Cape Evans, 25.0 mg anorthoclase (? % glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± 134 total gas age n=8 1.2e ± 60* plateau age MSWD=0.3 n=4 steps A-D ± 22* isochron age MSWD=1.2 n=8 Ar/ 36 Ar = ± ± 24* n=4 Weighted mean 95 ± 10* E830, Cape Evans: Anorthoclase, J= ± Disc.= ± e e e e ± e e e e ± A e e e e ± B e e e e ± A e e e e ± B e e e e ± 10 n=3 Weighted mean 263 ± 32* E83433: Cape Barne, mg anorthoclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± K e e e e e ± L e e e e e ± 1 total gas age n=11 4.4E ± 22* plateau age MSWD=2.8** n=8 steps A-H ± 4* isochron age MSWD=29.2** n=11 Ar/ 36 Ar = ± ± 2*

4 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E83433: Cape Barne, mg anorthoclase (~5% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± M e e e e e ± N e e-01 2.e e e ± O e e e e e ± 113 total gas age n=15 8.3e ± 24* plateau age MSWD=1.9 n=10 steps A-J ± 12* isochron age MSWD=4.6** n=15 Ar/ 36 Ar = ± ± 12* E83433: Cape Barne, mg anorthoclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± M e e e e e ± N e e e e e ± O e e e e e ± 65 total gas age n=15 6.5e ± 14* plateau age MSWD=1.8 n=9 steps A-I ± 4* isochron age MSWD=32.0** n=15 Ar/ 36 Ar = ± ± 4* E83433: Cape Barne, mg anorthoclase (~5% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± M e e e e e ± N e e e e e ± O e e e e e ± 50 total gas age n=15 8.5e ± 20* plateau age MSWD=1.1 n=9 steps A-I ± 8* isochron age MSWD=3.2** n=15 Ar/ 36 Ar = ± ± 14*

5 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E81001: Hooper's Shoulder, 97.4 mg anorthoclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± 19 total gas age n=11 3.8e ± 52* plateau age MSWD=0.5 n=7 steps A-G ± 8* isochron age MSWD=6.3** n=11 Ar/ 36 Ar = ± ± 6* E81001: Hooper's Shoulder, 93.3 mg anorthoclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± 17 total gas age n=9 3.1e ± 18* plateau age MSWD=2.5 n=4 steps C-F ± 10* isochron age MSWD=17.2** n=9 Ar/ 36 Ar = ± ± 6* E830: Cape Evans, mg anorthoclase (~1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± M e e e e e ± N e e e e e ± 931 total gas age n=12 2.9e ± 80* plateau age MSWD=5.7** n=5 steps D-H ± 8* isochron age MSWD=65.4** n=12 Ar/ 36 Ar = ± ± 2*

6 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E83448: Cape Royds, mg anorthoclase (~2% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± 25 total gas age n=11 1.8e ± 22* plateau age MSWD=0.6 n=5 steps B-F ± 10* isochron age MSWD=122** n=11 Ar/ 36 Ar = ± ± 4* AW82015: Turk's Head tephriphonolite, mg anorthoclase (~2% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 369 total gas age n=12 1.2e ± 34* plateau age MSWD=2.0 n=5 steps B-F ± 10* isochron age MSWD=31.9** n=12 Ar/ 36 Ar = ± ± 8* E81001: Hooper's Shoulder Cone, mg anorthoclase (~1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 412 total gas age n=12 8.1e ± 60* plateau age MSWD=1.8 n=5 steps C-G ± 10* isochron age MSWD=9.0** n=12 Ar/ 36 Ar = ± ± 2*

7 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E830: Cape Evans, 96.4 mg anorthoclase (~5% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e+00 4.e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 68 total gas age n=12 1.8e ± 220* plateau age MSWD=5.0** n=4 steps C-F ± 12* isochron age MSWD=12.1** n=12 Ar/ 36 Ar = ± ± 4* E83454: Aurora Cliffs trachyte, mg anorthoclase (~3% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 50 total gas age n=12 2.7e ± 32* plateau age MSWD=.6** n=4 steps D-G ± 10* isochron age MSWD=20.2** n=12 Ar/ 36 Ar = ± ± 8* E81002: Abbott Peak tephriphonolite, mg plagioclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 232 total gas age n=12 4.3e-15 5 ± 300* plateau age MSWD=10.2** n=5 steps B-F ± 38* isochron age MSWD=15.3** n=12 Ar/ 36 Ar = ± ± 14*

8 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E825: Bomb Peak trachyte, mg anorthoclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e-01 4.e e e ± 18 total gas age n=12 4.0e ± 12* plateau age MSWD=10.8** n=4 steps D-G ± 6* isochron age MSWD=6.6** n=12 Ar/ 36 Ar = ± ± 2* E80020: Three Sister's Cones, mg anorthoclase (~4% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 870 total gas age n=12 2.2e-14 ± * plateau age MSWD=1.1 n=4 steps C-F ± 4* isochron age MSWD=10.4** n=12 Ar/ 36 Ar = ± ± 2* AW82038: Turks Head tephrite, mg plagioclase (~5% glass) J= ± Disc.= ± A e+01 6.e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± 32 total gas age n=8 5.9e ± 60* plateau age MSWD=7.3** n=3 steps A-D ± 28* isochron age MSWD=5.4** n=8 Ar/ 36 Ar = ± ± 10*

9 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E83432: Cape Barne tephrite, 91.7 mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± 271 total gas age n=9 1.7e ± 38* plateau age MSWD=2.3 n=4 steps B-E ± 16* isochron age MSWD=4.0** n=9 Ar/ 36 Ar =290.6 ± ± 16* E77012: Tryggve Pt. dike phonotephrite, mg plagioclase (~1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± 3 total gas age n=8 1.1e ± 32* plateau age MSWD=134.5** n=7 steps B-I (no C) ± 18* isochron age MSWD=11.6** n=8 Ar/ 36 Ar = ± ± 14* E837: Inaccessible Island phonolite, 99.0 mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± 10 total gas age n=9 4.2e ± 12* plateau age MSWD=9.4** n=8 steps B-I ± 12* isochron age MSWD=10.9** n=9 Ar/ 36 Ar = ± ± 16*

10 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E83453: SW of Abbott Peak phonotephrite, mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 1411 total gas age n=11 3.6e ± 180* plateau age MSWD=15.0** n=7 steps C-I * isochron age MSWD=10.8** n=11 Ar/ 36 Ar = ± ± 18* E93011: NW of Hooper's Shoulder Cone, mg anorthoclase (~2% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 1 total gas age n=12 5.1e ± 38* plateau age MSWD=4.7** n=4 steps C-F ± 14* isochron age MSWD=66.9** n=12 Ar/ 36 Ar = ± ± 6* E93021: SE of Hooper's Shoulder Cone, mg anorthoclase (~2% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e-01 1.e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 202 total gas age n=12 4.5e-14 1 ± * plateau age MSWD=2.8** n=5 steps B-F ± 12* isochron age MSWD=20.6** n=12 Ar/ 36 Ar = ± ± 8*

11 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E93019: between William's Cliff and Turk's Head, mg anorthoclase (~2% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 542 total gas age n=12 2.9e ± 60* plateau age MSWD=3.0** n=5 steps B-F ± 18* isochron age MSWD=2.4** n=12 Ar/ 36 Ar = ± ± 20* E93020: William's Cliff, mg anorthoclase (~2% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± K e e e e e ± L e e e e e ± 111 total gas age n=12 3.5e ± * plateau age MSWD=0.5 n=9 steps B-J ± 10* isochron age MSWD=0.5 n=12 Ar/ 36 Ar = ± ± 18* E93005: Fang Ridge tephriphonolite, mg plagioclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e+00 1.e e e ± H e e e e e ± total gas age n=6 3.6e ± 0* plateau age MSWD=N.A. n=0 steps N.A. N.A. isochron age MSWD=25.0** n=6 Ar/ 36 Ar = ± ± 66*

12 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E93007: Fang Ridge tephriphonolite, mg plagioclase (<1% glass) J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± 103 total gas age n=8 5.9e ± 120* plateau age MSWD=0.9 n=0 steps F-J (no G) ± 28* isochron age MSWD=5.7** n=8 Ar/ 36 Ar = ± ± 20* E93023: NE of Abbott Peak, mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± 120 total gas age n=10 5.7e ± 20* plateau age MSWD=6.3** n=6 steps B-G ± 16* isochron age MSWD=4.2** n=10 Ar/ 36 Ar = ± ± 24* E93012: Fang Ridge tephrite, mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± 224 total gas age n=10 7.1e ± 800* plateau age MSWD=4.7** n=9 steps B-J ± 180* isochron age MSWD=8.5** n=10 Ar/ 36 Ar = ± ± 194*

13 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E93024: between Abbott Peak and E93011, mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± 222 total gas age n=10 5.4e ± 1* plateau age MSWD=1.8 n=3 steps E-G ± 20* isochron age MSWD=1.0 n=10 Ar/ 36 Ar = ± ± 18* E93010: west of Abbott Peak, mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± 60 total gas age n=10 6.2e ± 24* plateau age MSWD=3.8** n=6 steps B-G ± 18* isochron age MSWD=3.8** n=10 Ar/ 36 Ar = ± ± 20* E93008: Crash Nunatak, mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± 303 total gas age n=10 2.7e ± 0* plateau age MSWD=1.4 n=4 steps A-D ± 120* isochron age MSWD=1.1 n=10 Ar/ 36 Ar = ± ± 96*

14 Ar/ 39 Ar Analytical Data from: " Ar/ 39 Ar Dating of the Eruptive History of Mount Erebus, Antarctica: Volcano Evolution" E93032: Cape Barne tephrite, mg whole rock J= ± Disc.= ± A e e e e e ± B e e e e e ± C e e e e e ± D e e e e e ± E e e e e e ± F e e e e e ± G e e e e e ± H e e e e e ± I e e e e e ± J e e e e e ± 437 total gas age n=10 3.3e ± 100* plateau age MSWD=2.7** n=7 steps A-G ± 60* isochron age MSWD=2.3** n=10 Ar/ 36 Ar = ± ± 36* Isotopic ratios corrected for blank, radioactive decay, and mass discrimination, not corrected for interferring reactions. Individual analyses show analytical error only; plateau and total gas age errors include error in J and irradiation parameters. Analyses in italics are excluded from final age calculations. Flux Monitor (Fish Canyon sanidine) = Ma. Disc. = Mass Discrimination (1 a.m.u.) Correction Factors: ( Ar/ 39 Ar) = 0.022; ( 36 Ar/ 37 Ar) = ; and ( 39 Ar/ 37 Ar) = K/Ca = ( 39 Ar / 37 Ar ); Cl/K = ( 39 Ar / 38 Ar ) Plateau (weighted mean) age calculated by weighting each age analysis by the inverse of the variance. Plateau (weighted mean) error calculated using the method of Taylor (1982). Plateau ages are weighted by the inverse of the variance whereas total gas ages are weighted by 39 Ar. Errors are given at 1s and include the uncertainty in J-values (±0.25%). Ages are calculated using the decay constants recommended by Steiger and Jäger (1977). n= number of heating steps =analyses excluded from plateau weighted mean age. ø=analyses excluded from inverse isochron age. K/Ca = molar ratio calculated from reactor produced 39 Ar K and 37 Ar Ca. Cl/K = molar ratio calculated from reactor produced 38 Ar Cl and 39 Ar K * 2s error ** MSWD outside of 95% confidence interval, uncertainty increased by multiplying by the square root of the MSWD.

15 Names, identification numbers and respective locations for all Mt. Erebus Ar/ 39 Ar samples in this study. Sample Name Sample # Latitude Longitude Source Lower Hut Flow E ' S ' E Map Three Sister's Cones E ' S ' E Gazetteer Hooper's Shoulder Cones E ' S ' E Gazetteer Cape Evans E ' S ' E Map Nausea Knob E ' S ' E Map William's Cliff E ' S ' E GPS Cape Royds E ' S ' E Map Northeast Flow E ' S ' E Map Caldera Rim #1 E ' S ' E Map Cape Barne anorthoclase tephriphonolite E ' S ' E Map SE of Hooper's Shoulder E ' S ' E GPS NW of Hooper's Shoulder E ' S ' E GPS Bomb Peak E ' S ' E Gazetteer Aurora Cliffs E ' S ' E Map Between William's Cliff and Turks Head E ' S ' E GPS Turks Head tephriphonolite AW ' S ' E Gazetteer Between Abbott's Peak and E93011 E ' S ' E GPS NE of Abbott's Peak E ' S ' E GPS Tryggve Point dike E ' S ' E Gazetteer Turks Head tephrite AW ' S ' E Gazetteer SW of Abbott's Peak E ' S ' E Map West of Abbott's Peak E ' S ' E GPS Crash Nunatak E ' S ' E GPS Inaccessible Island E ' S 'E Gazetteer Abbott's Peak E ' S ' E Gazetteer Fang Ridge #1 E ' S ' E Gazetteer Fang Ridge #2 E ' S ' E Gazetteer Fang Ridge #3 E ' S ' E Gazetteer Cape Barne tephrite E83432/E ' S ' E Map Map: USGS 1:250,000 Map of Ross Island GPS: Navy VXE-6 helicopters Gazetter: Gazetter of the Antarctic (1989); NSF