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dc.contributor.authorNelson, Alan R.en_US
dc.contributor.authorHawkes, Andrea D.en_US
dc.contributor.authorSawai, Yukien_US
dc.contributor.authorHorton, Benjamin Peteren_US
dc.contributor.authorWitter, Rob C.en_US
dc.contributor.authorBradley, Lee-Annen_US
dc.contributor.authorCahill, Niamhen_US
dc.identifier.citationNelson, A. R., Hawkes, A. D., Sawai, Y., Horton, B. P., Witter, R. C., Bradley, L. & Cahill, N. (2021). Minimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zone. Geosphere, 17(1), 171-200.
dc.description.abstractLithology and microfossil biostratigraphy beneath the marshes of a central Oregon estuary limit geophysical models of Cascadia megathrust rupture during successive earthquakes by ruling out >0.5 m of coseismic coastal subsidence for the past 2000 yr. Although the stratigraphy in cores and outcrops includes as many as 12 peat-mud contacts, like those commonly inferred to record subsidence during megathrust earthquakes, mapping, qualitative diatom analysis, foraminiferal transfer function analysis, and 14C dating of the contacts failed to confirm that any contacts formed through subsidence during great earthquakes. Based on the youngest peat-mud contact’s distinctness, >400 m distribution, ∼0.6 m depth, and overlying probable tsunami deposit, we attribute it to the great 1700 CE Cascadia earthquake and(or) its accompanying tsunami. Minimal changes in diatom assemblages from below the contact to above its probable tsunami deposit suggest that the lower of several foraminiferal transfer function reconstructions of coseismic subsidence across the contact (0.1–0.5 m) is most accurate. The more limited stratigraphic extent and minimal changes in lithology, foraminifera, and(or) diatom assemblages across the other 11 peat-mud contacts are insufficient to distinguish them from contacts formed through small, gradual, or localized changes in tide levels during river floods, storm surges, and gradual sea-level rise. Although no data preclude any contacts from being synchronous with a megathrust earthquake, the evidence is equally consistent with all contacts recording relative sea-level changes below the ∼0.5 m detection threshold for distinguishing coseismic from nonseismic changes.en_US
dc.description.sponsorshipMinistry of Education (MOE)en_US
dc.description.sponsorshipNational Research Foundation (NRF)en_US
dc.rights© 2020 The Authors. This paper is published under the terms of the CC-BY-NC license.en_US
dc.titleMinimal stratigraphic evidence for coseismic coastal subsidence during 2000 yr of megathrust earthquakes at the central Cascadia subduction zoneen_US
dc.typeJournal Articleen
dc.contributor.schoolAsian School of the Environmenten_US
dc.contributor.researchEarth Observatory of Singaporeen_US
dc.description.versionPublished versionen_US
dc.subject.keywordsCoastal Subsidenceen_US
dc.subject.keywordsStratigraphic Evidenceen_US
dc.description.acknowledgementThis work was supported by the Earthquake Hazards Program of the U.S. Geological Survey (USGS) and by U.S. National Science Foundation awards: 1419824 to Horton and 1419846 to Hawkes. Collection and analysis of diatom samples by Sawai were supported by the Geological Survey of Japan and the Japan Society for the Promotion of Science of postdoctoral fellowships for research abroad. Horton was also funded by the Singapore Ministry of Education Academic Research Fund MOE2018-T2–1–030, the National Research Foundation Singapore, and the Sin- gapore Ministry of Education, under the Research Centres of Excellence initiative. The National Ocean Sciences Accelerator Mass Spectrometry facility (NOSAMS) at Woods Hole Oceanographic Institution (WHOI) supported the analysis of five 14C accelerator mass spectrometer (AMS) samples during Hawkes’ WHOI NOSAMS postdoctoral fellowship. We thank the Nature Conservancy for permission to study the stratigraphy beneath the marshes of Cox Island, and Eileen Hemphill- Haley for the format of Figures 9 and 10. Andrew Kemp (Tuffs University) provided key help in the field. Laura Brophy (2009) generously provided much unpublished data on plant communities and surveyed elevations on Cox Island. Jamie Delano (USGS, Golden) helped with graphics. This manuscript was much improved through reviews by Tina Dura (Virginia Polytechnic Institute and State University) and three anonymous reviewers. This work is Earth Observatory of Singapore contribution #332. This article is a contribution to PALSEA3 (Palaeo-Constraints on Sea-Level Rise) and International Geoscience Program (IGCP) Project 639, “Sea Level Change from Minutes to Millennia.”en_US
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