Microfossil measures of rapid sea-level rise: Timing of response of two microfossil groups to a sudden tidal-flooding experiment in Cascadia

B. P. Horton, Y. Milker, T. Dura, K. Wang, W. T. Bridgeland, L. Brophy, M. Ewald, N. S. Khan, S. E. Engelhart, A. R. Nelson, R. C. Witter

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Comparisons of pre-earthquake and post-earthquake microfossils in tidal sequences are accurate means to measure coastal subsidence during past subduction earthquakes, but the amount of subsidence is uncertain, because the response times of fossil taxa to coseismic relative sea-level (RSL) rise are unknown. We measured the response of diatoms and foraminifera to restoration of a salt marsh in southern Oregon, USA. Tidal flooding following dike removal caused an RSL rise of ~1 m, as might occur by coseismic subsidence during momentum magnitude (Mw) 8.1-8.8 earthquakes on this section of the Cascadia subduction zone. Less than two weeks after dike removal, diatoms colonized low marsh and tidal flats in large numbers, showing that they can record seismically induced subsidence soon after earthquakes. In contrast, low-marsh foraminifera took at least 11 months to appear in sizeable numbers. Where subsidence measured with diatoms and foraminifera differs, their different response times may provide an estimate of postseismic vertical deformation in the months following past megathrust earthquakes.

Original languageEnglish (US)
Pages (from-to)535-538
Number of pages4
JournalGeology
Volume45
Issue number6
DOIs
StatePublished - Jun 1 2017

All Science Journal Classification (ASJC) codes

  • Geology

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