The late Holocene history of Lake Cahuilla: Two thousand years of repeated fillings within the Salton Trough, Imperial Valley, California

Thomas K. Rockwell, Aron J. Meltzner, Erik C. Haaker, & Danielle V. Madugo

Submitted July 30, 2020, SCEC Contribution #10218

We compiled 122 radiocarbon dates gleaned from nearly 400 dates from paleoseismic sites with stratigraphic control and from shoreline geologic and archeological sites to constrain the timing of the past seven lakes that filled the Salton Trough. We developed three models in OxCal that make different assumptions about the types of constraints afforded by different types of samples. Model 1 assumes all charcoal, wood, seeds, twigs, and “peats” that were collected from below the +13 m shoreline are derived from material that grew within the basin, and therefore date a dry period between lakes. Model 2 does not assume that samples collected from lake deposits at sites higher than 8 m above sea level (close to the shoreline) are necessarily associated with a dry period as some of the samples may have been derived from above the shoreline; for each lake, these dates provide a maximum age on the end of the lake highstand rather than dating the dry period prior to the highstand. For Model 2, we calculate the probability distribution for the beginning and end of each lake. Model 3 is derived from Model 2, except that here we treat bulk dates on peat-like deposits as providing a maximum age on the beginning of the lake highstand, as these samples likely contain a mix of detrital material from sources of different ages. Because this model further relaxes the assumption that certain samples date the dry period between lakes, it is the most conservative of our three OxCal models. The three models yield similar results, with the likely age range for each lake highstand in Model 1 plotting between the likely ages for the beginning and end of each highstand in Models 2 and 3, which we take to confirm the robustness of these lake age models. The best estimated ages of the highstands of the past seven lakes, based on Model 1, are 1718-1733 CE (Lake A), 1594-1643 CE (Lake B), 1455-1510 CE (Lake C), 1147-1230 CE (Lake D), 1055-1099 CE (Lake E), 918-990 CE (Lake F), and 164-9 BCE (Lake G).

Key Words
Lake Cahuilla, High precision 14C dating, regional lake chronology for paleoseismology and archaeology

Rockwell, T. K., Meltzner, A. J., Haaker, E. C., & Madugo, D. V. (2020). The late Holocene history of Lake Cahuilla: Two thousand years of repeated fillings within the Salton Trough, Imperial Valley, California. Quaternary Science Reviews, (submitted).

Related Projects & Working Groups
Paleoseismology of the southern San Andreas fault (SoSAFE), Earthquake Geology