Modern foraminifera, δ13C, and bulk geochemistry of central Oregon tidal marshes and their application in paleoseismology

Simon E. Engelhart, Benjamin Horton, Christopher H. Vane, Alan R. Nelson, Robert C. Witter, Sarah R. Brody, Andrea D. Hawkes

Research output: Contribution to journalArticle

35 Scopus citations

Abstract

We assessed the utility of δ13C and bulk geochemistry (total organic content and C:N) to reconstruct relative sea-level changes on the Cascadia subduction zone through comparison with an established sea-level indicator (benthic foraminifera). Four modern transects collected from three tidal environments at Siletz Bay, Oregon, USA, produced three elevation-dependent groups in both the foraminiferal and δ13C/bulk geochemistry datasets. Foraminiferal samples from the tidal flat and low marsh are identified by Miliammina fusca abundances of >45%, middle and high marsh by M. fusca abundances of <45% and the highest marsh by Trochamminita irregularis abundances >25%. The δ13C values from the groups defined with δ13C/bulk geochemistry analyses decrease with an increasing elevation; -24.1±1.7‰ in the tidal flat and low marsh; -27.3±1.4‰ in the middle and high marsh; and -29.6±0.8‰ in the highest marsh samples. We applied the modern foraminiferal and δ13C distributions to a core that contained a stratigraphic contact marking the great Cascadia earthquake of AD 1700. Both techniques gave similar values for coseismic subsidence across the contact (0.88±0.39m and 0.71±0.56m) suggesting that δ13C has potential for identifying amounts of relative sea-level change due to tectonics.

Original languageEnglish (US)
Pages (from-to)13-27
Number of pages15
JournalPalaeogeography, Palaeoclimatology, Palaeoecology
Volume377
DOIs
StatePublished - May 1 2013

All Science Journal Classification (ASJC) codes

  • Earth-Surface Processes
  • Ecology, Evolution, Behavior and Systematics
  • Oceanography
  • Palaeontology

Keywords

  • Bulk geochemistry
  • Cascadia
  • Earthquake
  • Foraminifera
  • Oregon
  • Paleoseismology
  • Relative sea level
  • δC

Fingerprint Dive into the research topics of 'Modern foraminifera, δ<sup>13</sup>C, and bulk geochemistry of central Oregon tidal marshes and their application in paleoseismology'. Together they form a unique fingerprint.

  • Cite this