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• 11. [Article] Effective elastic thickness of the lithosphere along the Easter Seamount Chain

  Bathymetry and gravity data collected during Legs 5, 6, and 7 of the 1993 GLORIA Expedition and the recently released 2-min altimetry-derived global gravity grid are used to determine the effective elastic ...

  Citation × Citation Citation Abstract Copy Title: Effective elastic thickness of the lithosphere along the Easter Seamount Chain Author: Kruse, Sarah E., Duncan, Robert A., Liu, Zhengrong J., Naar, David F. Bathymetry and gravity data collected during Legs 5, 6, and 7 of the 1993 GLORIA Expedition and the recently released 2-min altimetry-derived global gravity grid are used to determine the effective elastic thickness of the lithosphere along the Easter Seamount Chain (ESC). Forward modeling, admittance, and coherence methods yield consistent results. With the exception of the eastern and western ends of the ESC the effective elastic thickness along the chain is similar to 1-4 km. The thin elastic thickness for the majority of the ESC seamounts is compatible with a young seafloor age at the time of loading derived from new radiometric ages of the seamounts along the chain and a magnetic isochron age interpretation of the Nazca plate seafloor age. The elastic thickness southeast of the Nazca fracture zone is similar to 6 km, apparently because of the seafloor age discontinuity across the fracture zone. The elastic thickness near the San Felix Island, at the eastern end of the ESC, is even greater (similar to 11 km), which is compatible with the estimated seafloor age at the time of loading. A slight increase in the effective elastic thickness of the far western part of the ESC suggests dynamic compensation or less thermal weakening of lithosphere above a plume channel versus directly above the plume center. These findings combined with published geochemistry support a hotspot origin for the ESC, complicated by large-scale plate boundary reorganizations and channeling of plume material to the East Pacific Rise. Title: Effective elastic thickness of the lithosphere along the Easter Seamount Chain Author: Kruse, Sarah E., Duncan, Robert A., Liu, Zhengrong J., Naar, David F. Bathymetry and gravity data collected during Legs 5, 6, and 7 of the 1993 GLORIA Expedition and the recently released 2-min altimetry-derived global gravity grid are used to determine the effective elastic thickness of the lithosphere along the Easter Seamount Chain (ESC). Forward modeling, admittance, and coherence methods yield consistent results. With the exception of the eastern and western ends of the ESC the effective elastic thickness along the chain is similar to 1-4 km. The thin elastic thickness for the majority of the ESC seamounts is compatible with a young seafloor age at the time of loading derived from new radiometric ages of the seamounts along the chain and a magnetic isochron age interpretation of the Nazca plate seafloor age. The elastic thickness southeast of the Nazca fracture zone is similar to 6 km, apparently because of the seafloor age discontinuity across the fracture zone. The elastic thickness near the San Felix Island, at the eastern end of the ESC, is even greater (similar to 11 km), which is compatible with the estimated seafloor age at the time of loading. A slight increase in the effective elastic thickness of the far western part of the ESC suggests dynamic compensation or less thermal weakening of lithosphere above a plume channel versus directly above the plume center. These findings combined with published geochemistry support a hotspot origin for the ESC, complicated by large-scale plate boundary reorganizations and channeling of plume material to the East Pacific Rise. Close

• 12. [Article] Temporal variations in plate convergence and eruption rates in the Western Cascades, Oregon

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Temporal variations in plate convergence and eruption rates in the Western Cascades, Oregon Author: Verplanck, Emily P., Duncan, Robert A. copyrighted by American Geophysical Union Title: Temporal variations in plate convergence and eruption rates in the Western Cascades, Oregon Author: Verplanck, Emily P., Duncan, Robert A. copyrighted by American Geophysical Union Close

• 13. [Article] Age of the Batoka basalts, norther Zimbabwe, and the duration of Karoo Large Igneous Province magmatism

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Age of the Batoka basalts, norther Zimbabwe, and the duration of Karoo Large Igneous Province magmatism Author: Briden, J. C., Jones, D. L., MacNiocaill, C., Duncan, Robert A., Randall, D. E. copyrighted by American Geophysical Union Title: Age of the Batoka basalts, norther Zimbabwe, and the duration of Karoo Large Igneous Province magmatism Author: Briden, J. C., Jones, D. L., MacNiocaill, C., Duncan, Robert A., Randall, D. E. copyrighted by American Geophysical Union Close

• 14. [Article] DuncanTimingCompositionContinental.pdf

  Citation × Citation Citation Abstract Copy Title: DuncanTimingCompositionContinental.pdf Author: Schlieder, Tyler D., Kent, Adam J.R., Duncan, Robert A., Thornber, Carl R., Al-Amri, Abdullah M. Title: DuncanTimingCompositionContinental.pdf Author: Schlieder, Tyler D., Kent, Adam J.R., Duncan, Robert A., Thornber, Carl R., Al-Amri, Abdullah M. Close

• 15. [Article] DuncanTimingCompositionContinentalAppendixAGeochemicalData.pdf

  Citation × Citation Citation Abstract Copy Title: DuncanTimingCompositionContinentalAppendixAGeochemicalData.pdf Author: Schlieder, Tyler D., Kent, Adam J.R., Duncan, Robert A., Thornber, Carl R., Al-Amri, Abdullah M. Title: DuncanTimingCompositionContinentalAppendixAGeochemicalData.pdf Author: Schlieder, Tyler D., Kent, Adam J.R., Duncan, Robert A., Thornber, Carl R., Al-Amri, Abdullah M. Close

• 16. [Article] DuncanTimingCompositionContinentalAppendixAGeochronolgyData.pdf

  Citation × Citation Citation Abstract Copy Title: DuncanTimingCompositionContinentalAppendixAGeochronolgyData.pdf Author: Schlieder, Tyler D., Kent, Adam J.R., Duncan, Robert A., Thornber, Carl R., Al-Amri, Abdullah M. Title: DuncanTimingCompositionContinentalAppendixAGeochronolgyData.pdf Author: Schlieder, Tyler D., Kent, Adam J.R., Duncan, Robert A., Thornber, Carl R., Al-Amri, Abdullah M. Close

• 17. [Article] Evolution of the Walvis Ridge-Rio Grande rise hot spot systen : implications for African and South American plate motions over plumes

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Evolution of the Walvis Ridge-Rio Grande rise hot spot systen : implications for African and South American plate motions over plumes Author: O'Connor, John M., Duncan, Robert A. copyrighted by American Geophysical Union Title: Evolution of the Walvis Ridge-Rio Grande rise hot spot systen : implications for African and South American plate motions over plumes Author: O'Connor, John M., Duncan, Robert A. copyrighted by American Geophysical Union Close

• 18. [Article] Geochronology of age-progressive volcanism of the Oregon High Lava Plains : implications for the plume interpretation of Yellowstone

  copyrighted by American Geophysical Union

  Citation × Citation Citation Abstract Copy Title: Geochronology of age-progressive volcanism of the Oregon High Lava Plains : implications for the plume interpretation of Yellowstone Author: Deino, Alan L., Grunder, Anita L., Duncan, Robert A., Jordan, Brennan T. copyrighted by American Geophysical Union Title: Geochronology of age-progressive volcanism of the Oregon High Lava Plains : implications for the plume interpretation of Yellowstone Author: Deino, Alan L., Grunder, Anita L., Duncan, Robert A., Jordan, Brennan T. copyrighted by American Geophysical Union Close

• 19. [Article] ⁴⁰Ar-³⁹Ar chronology for the volcanic history of the Southeast Greenland rifted margin

  Results of ⁴⁰Ar–³⁹Ar Ar dating constrain the age of the submerged volcanic succession, part of the seaward-dip ping reflector sequence of the Southeast Greenland volcanic rifted margin, recovered during ...

  Citation × Citation Citation Abstract Copy Title: ⁴⁰Ar-³⁹Ar chronology for the volcanic history of the Southeast Greenland rifted margin Author: Tegner, Christian, Duncan, Robert A. Results of ⁴⁰Ar–³⁹Ar Ar dating constrain the age of the submerged volcanic succession, part of the seaward-dip ping reflector sequence of the Southeast Greenland volcanic rifted margin, recovered during Leg 163. At the 3°Ne 6 drilling transect, the fully normally magnetized volcanic units at Holes 989B (Unit 1) and 990A (Units 1 and 2) are dated at 57.1 ± 1.3 Ma and 55.6 ± 0.6 Ma, respectively. This correlates with a common magnetochron, C25n. The underlying, reversely magnetized lavas at Hole 990A (Units 3–13) yield an average age of 55.8 ± 0.7 Ma and may correlate with C25r. The argon data, however, are also consistent with eruption of the lavas at Site 990 during the very earliest portion of C24. If so, the normally polarized unevittsohav be correlated to a cryptochron ( e.g., C24r -11 at ~55.57 Ma). The lavas at Holes 989B and 990A have typical oceanic compositions, implying that final plate separation between Greenland and northwest Europe took place at ~56 Ma. The age for Hole 989B lava is younger than expected from the seismic interpretations, posing questions about the structural evolution of the margin. An age of 49.6 ± 0.2 Ma for the basaltic lava at Site 9 88 (~6°N) points to the importance of postbreakup tholeiitic magmatism at the rifted margin. Together with results from Leg 152, a virtually complete time frame for ~12 m.y. of pre-, syn-, and postbreakup volcanism during rifted margin evolution in Southeast Greenland can now be assembled. This time frame includes continental type volcanism at ~6 1–60 Ma, synbreakup volcanism beginning at ~57 Ma, and postbreakup volcanism at ~49.6 Ma. These discrete time windows coincide with distinct periods of tholeiitic magmatism from the onshore East Greenland Tertiary Igneous Province and is consistent with discrete mantle-melting events triggered by plume arrival (~ 61–60 Ma) under central Greenland, continental breakup (~57–54 Ma), and passage of the plume axis beneath the East Greenland rifted margin after breakup (~50–49 Ma ), respectively. Title: ⁴⁰Ar-³⁹Ar chronology for the volcanic history of the Southeast Greenland rifted margin Author: Tegner, Christian, Duncan, Robert A. Results of ⁴⁰Ar–³⁹Ar Ar dating constrain the age of the submerged volcanic succession, part of the seaward-dip ping reflector sequence of the Southeast Greenland volcanic rifted margin, recovered during Leg 163. At the 3°Ne 6 drilling transect, the fully normally magnetized volcanic units at Holes 989B (Unit 1) and 990A (Units 1 and 2) are dated at 57.1 ± 1.3 Ma and 55.6 ± 0.6 Ma, respectively. This correlates with a common magnetochron, C25n. The underlying, reversely magnetized lavas at Hole 990A (Units 3–13) yield an average age of 55.8 ± 0.7 Ma and may correlate with C25r. The argon data, however, are also consistent with eruption of the lavas at Site 990 during the very earliest portion of C24. If so, the normally polarized unevittsohav be correlated to a cryptochron ( e.g., C24r -11 at ~55.57 Ma). The lavas at Holes 989B and 990A have typical oceanic compositions, implying that final plate separation between Greenland and northwest Europe took place at ~56 Ma. The age for Hole 989B lava is younger than expected from the seismic interpretations, posing questions about the structural evolution of the margin. An age of 49.6 ± 0.2 Ma for the basaltic lava at Site 9 88 (~6°N) points to the importance of postbreakup tholeiitic magmatism at the rifted margin. Together with results from Leg 152, a virtually complete time frame for ~12 m.y. of pre-, syn-, and postbreakup volcanism during rifted margin evolution in Southeast Greenland can now be assembled. This time frame includes continental type volcanism at ~6 1–60 Ma, synbreakup volcanism beginning at ~57 Ma, and postbreakup volcanism at ~49.6 Ma. These discrete time windows coincide with distinct periods of tholeiitic magmatism from the onshore East Greenland Tertiary Igneous Province and is consistent with discrete mantle-melting events triggered by plume arrival (~ 61–60 Ma) under central Greenland, continental breakup (~57–54 Ma), and passage of the plume axis beneath the East Greenland rifted margin after breakup (~50–49 Ma ), respectively. Close

• 20. [Article] High-resolution ⁴⁰Ar/³⁹Ar dating of the oldest oceanic basement basalts in the western Pacific basin

  Copyrighted by American Geophysical Union.

  Citation × Citation Citation Abstract Copy Title: High-resolution ⁴⁰Ar/³⁹Ar dating of the oldest oceanic basement basalts in the western Pacific basin Author: Staudigel, Hubert, Koppers, Anthony A. P., Duncan, Robert A. Copyrighted by American Geophysical Union. Title: High-resolution ⁴⁰Ar/³⁹Ar dating of the oldest oceanic basement basalts in the western Pacific basin Author: Staudigel, Hubert, Koppers, Anthony A. P., Duncan, Robert A. Copyrighted by American Geophysical Union. Close