Sedimentological evidence for a possible channel incision event in the Carrizo Plain, California: The 1861-1862 ARkStorm event?

Matthew E. Kirby, Sinan O. Akciz, Joseph Carlin, Dahlia Serrato, & Samuel K. Hippard

Published September 11, 2022, SCEC Contribution #11997, 2022 SCEC Annual Meeting Poster #246

Offset channels are routinely used to determine slip rates and slip-per-earthquake measurements. Plots showing the distribution of slip along the strike of a fault are used to infer the slip distribution during previous earthquakes and even magnitudes and recurrence of large surface rupturing earthquakes. Along the faults that collectively form the San Andreas Fault (SAF) System, the underlying assumption for such interpretations is that channels form and incise on an average decadal frequency which is much more rapid than the earthquake recurrence along these faults. Grant et al. (2010) tried to validate this assumption by comparing limited radiocarbon age determinations from the fill of two channels in the Carrizo Plain to major flooding events interpreted from the sedimentary cores retrieved from the Santa Barbara Basin. We collected five, 1-2 m sediment cores for this project to conduct a detailed study of sedimentary cores from a sag pond along the SAF to extract the fine details of local spatiotemporal climatic variability within the last 1000 years in the Carrizo Plain. To date, all five cores – spreading the long axis of the Sag Pond – have been opened, described, photographed, and analyzed for various sedimentological components. All five cores contain evidence for multiple flood events as well as short-lived lakes and playa conditions. An initial age model using the 1963 AD 137Cs peak suggests that we have captured the 1861-1862 AD ARkStorm event. The event consists of 2(?) separate flooding episodes, resulting in a short-lived, perennial lake. These back-to-back events are ideal candidates for a channel incision event mid-19th century. 10 x AMS C-14 dates on detrital charcoal are pending to confirm, refute, or refine this initial age model.

Key Words
Sediments, Chronology, Channel Incision, Paleoclimatology, ARkStorm

Citation
Kirby, M. E., Akciz, S. O., Carlin, J., Serrato, D., & Hippard, S. K. (2022, 09). Sedimentological evidence for a possible channel incision event in the Carrizo Plain, California: The 1861-1862 ARkStorm event? . Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
San Andreas Fault System (SAFS)