The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves
Abstract Juxtaposed terranes of highly varied tectonic history make up the contiguous U.S.: the tectonically active western U.S., the largely quiescent Archean and Proterozoic cratons of the central U.S., and the Phanerozoic orogen and rifted margin of the eastern U.S. The transitions between these...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
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Wiley
2018-08-01
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| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2018GC007476 |
| _version_ | 1797351801928810496 |
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| author | Emily Hopper Karen M. Fischer |
| author_facet | Emily Hopper Karen M. Fischer |
| author_sort | Emily Hopper |
| collection | DOAJ |
| description | Abstract Juxtaposed terranes of highly varied tectonic history make up the contiguous U.S.: the tectonically active western U.S., the largely quiescent Archean and Proterozoic cratons of the central U.S., and the Phanerozoic orogen and rifted margin of the eastern U.S. The transitions between these regions are clearly observed with Sp converted wave images of the uppermost mantle. We use common conversion point stacked Sp waves recorded by EarthScope's Transportable Array and other permanent and temporary broadband stations to image the transition from a strong velocity decrease at the lithosphere‐asthenosphere boundary (or LAB) beneath the western U.S. to deeper, less continuous features moving east that largely lie within the lithosphere. Only sparse, localized, weak phases are seen at LAB depths beneath the cratonic interior. Instead, we observe structures within the cratonic lithosphere that are most prominent within the Archean lithosphere of the Superior Craton. The transition from west to east is clearly revealed by cluster analysis, which also shows eastern U.S. mantle velocity gradients as more similar to the western U.S. than the ancient interior, particularly beneath New England and Virginia. In the western U.S., the observed strong LAB indicates a large enough velocity gradient (an average velocity drop of 10 ± 4.5% distributed over 30 ± 15 km) to imply that melt has ponded beneath the lithosphere. |
| first_indexed | 2024-03-08T13:05:47Z |
| format | Article |
| id | doaj.art-fa84c5169a2c425c82b9913afbb51ff8 |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-08T13:05:47Z |
| publishDate | 2018-08-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-fa84c5169a2c425c82b9913afbb51ff82024-01-18T19:36:25ZengWileyGeochemistry, Geophysics, Geosystems1525-20272018-08-011982593261410.1029/2018GC007476The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted WavesEmily Hopper0Karen M. Fischer1Department of Earth, Environmental, and Planetary Sciences Lamont‐Doherty Earth Observatory of Columbia University Palisades NY USADepartment of Earth, Environmental and Planetary Sciences Brown University Providence RI USAAbstract Juxtaposed terranes of highly varied tectonic history make up the contiguous U.S.: the tectonically active western U.S., the largely quiescent Archean and Proterozoic cratons of the central U.S., and the Phanerozoic orogen and rifted margin of the eastern U.S. The transitions between these regions are clearly observed with Sp converted wave images of the uppermost mantle. We use common conversion point stacked Sp waves recorded by EarthScope's Transportable Array and other permanent and temporary broadband stations to image the transition from a strong velocity decrease at the lithosphere‐asthenosphere boundary (or LAB) beneath the western U.S. to deeper, less continuous features moving east that largely lie within the lithosphere. Only sparse, localized, weak phases are seen at LAB depths beneath the cratonic interior. Instead, we observe structures within the cratonic lithosphere that are most prominent within the Archean lithosphere of the Superior Craton. The transition from west to east is clearly revealed by cluster analysis, which also shows eastern U.S. mantle velocity gradients as more similar to the western U.S. than the ancient interior, particularly beneath New England and Virginia. In the western U.S., the observed strong LAB indicates a large enough velocity gradient (an average velocity drop of 10 ± 4.5% distributed over 30 ± 15 km) to imply that melt has ponded beneath the lithosphere.https://doi.org/10.1029/2018GC007476lithospherelithosphere‐asthenosphere boundaryreceiver functionsUSA |
| spellingShingle | Emily Hopper Karen M. Fischer The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves Geochemistry, Geophysics, Geosystems lithosphere lithosphere‐asthenosphere boundary receiver functions USA |
| title | The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves |
| title_full | The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves |
| title_fullStr | The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves |
| title_full_unstemmed | The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves |
| title_short | The Changing Face of the Lithosphere‐Asthenosphere Boundary: Imaging Continental Scale Patterns in Upper Mantle Structure Across the Contiguous U.S. With Sp Converted Waves |
| title_sort | changing face of the lithosphere asthenosphere boundary imaging continental scale patterns in upper mantle structure across the contiguous u s with sp converted waves |
| topic | lithosphere lithosphere‐asthenosphere boundary receiver functions USA |
| url | https://doi.org/10.1029/2018GC007476 |
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