Testing the applicability of a foraminifera-based transfer function for reconstructing late Holocene sea-level changes in southern California

Simona Avnaim-Katav, Ed Garrett, W. Roland Gehrels, Lauren N. Brown, Thomas K. Rockwell, Alexander R. Simms, John M. Bentz, & Glen M. MacDonald

In Preparation May 22, 2021, SCEC Contribution #11012

New data from Mission Bay, Los Peñasquitos and Carpinteria Slough combined with existing data from Seal Beach and Tijuana Slough are used to explore the potential of Southern California tidal marsh foraminifera for underpinning quantitative reconstructions of palaeoenvironmental change. Foraminiferal distributions are highly dependent on elevation and a newly developed transfer function provides decimeter-scale predictions of marsh elevation We predict elevation change over time from fossil foraminiferal assemblages from a Mission Bay salt marsh. Few fossil samples lack close analogues in the modern training set, indicating the applicability of the approach. A laterally continuous stratigraphic change with evidence of an abrupt ~0.5 m reduction in marsh surface elevation may be related to lateral spreading of water-saturated sediments due to strong ground shaking. Bayesian age-depth modelling indicates that this event is contemporaneous with a moderate to large-magnitude earthquake on the Rose Canyon fault during the mid-1700s. Foraminifera indicate a second change, however gradual, suggesting an anthropogenic rather than a seismic origin. A third stratigraphic change may have resulted from the 1938 Southern California floods. These findings support the applicability of our new foraminifera-based transfer function to reconstruct paleoenvironmental changes in a region susceptible to the significant impacts of large-magnitude earthquakes.

Citation
Avnaim-Katav, S., Garrett, E., Gehrels, W., Brown, L. N., Rockwell, T. K., Simms, A. R., Bentz, J. M., & MacDonald, G. M. (2021). Testing the applicability of a foraminifera-based transfer function for reconstructing late Holocene sea-level changes in southern California. Quaternary Research, (in preparation).