January 18, 2019

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Allison Haddon Coauthors Paper Analyzing the Pampean Flat‐Slab Region in the Journal Geochemistry, Geophysics, Geosystems

Allison Haddon (California) coauthored a paper entitled "S‐Wave Receiver Function Analysis of the Pampean Flat‐Slab Region: Evidence for a Torn Slab" published in the journal Geochemistry, Geophysics, Geosystems on pages 4021-4034 in Volume 19, Issue 10 on October 17, 2018. Her coauthor was Ryan Porter of Northern Arizona University.

Allison is a staff scientist based in California, with an M.S. in Geology and an emphasis in Geophysics from Northern Arizona University. She has experience as a scientific researcher and teaching assistant in the field of geology. Prior to joining Geosyntec, Allison worked as a lab instructor for geology during undergraduate and graduate school. Since joining Geosyntec, Allison has made meaningful contributions to multiple projects including superfund sites and litigation support efforts.

Published by the American Geophysical Union (AGU), the journal Geochemistry, Geophysics, Geosystems features original research papers on Earth and planetary processes, with a focus on understanding the Earth as a system.

AGU galvanizes a community of Earth and space scientists that collaboratively advances and communicates science and its power to ensure a sustainable future. AGU Publications journals span a wide range of subjects and the editors' welcome contributions from authors throughout the world.


Flat‐slab subduction is an atypical form of subduction where the downgoing plate assumes a low‐angle or subhorizontal geometry as it descends beneath the overriding plate. These systems have profound impacts on upper‐plate deformation and volcanism, yet there are outstanding questions regarding the causes, initiation, and termination of flat‐slab subduction. The Pampean flat‐slab region, located in the South American Cordillera, is an ideal locale to study the evolution of these systems due to its well‐constrained geologic history and the continuity of subduction along the western margin of the continent. In this work, we utilize S wave receiver functions (SRFs) to measure the thicknesses and geometry of the subducting Nazca plate lithosphere and the overriding South American plate within the region. Results from this study show overthickened Nazca Plate crust (~15–20 km thick) in the flat‐slab region. Prior to the slab steepening, SRFs indicate a velocity increase rather than a decrease at the top of slab crust, which is consistent with a transition from basalt to eclogite within the crust as it dehydrates. Margin parallel cross sections are consistent with differing transitions between flat‐subduction and more‐typical subduction occurring to the north and south. In the north, the transition appears to be gradual, consistent with slab bending. To the south, SRFs indicate an abrupt change, consistent with slab tearing. These differences are consistent with significant variations in slab rheology along the margin, which may reflect differing thermal regimes. This work has global implications for the three‐dimensional effects of flat‐slab subduction.

More Information

Learn more about the article: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018GC007868.
Learn more about the journal: https://agupubs.onlinelibrary.wiley.com/journal/15252027.
For consultation regarding S‐Wave receiver function, contact Allison Haddon at This email address is being protected from spambots. You need JavaScript enabled to view it..