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Preliminary Results of a Study to Identify Archaeological Artifacts from San Salvador in Colton, CA, Using Ground Penetrating Radar

Chloe S. Sutkowski, Oscar Prado, Veronica Hernandez, & Jascha Polet

Published August 15, 2018, SCEC Contribution #8825, 2018 SCEC Annual Meeting Poster #320 (PDF)

Poster Image: 
We will present the preliminary results of an ongoing archaeo-geophysical survey at Pellissier Ranch in Colton, CA. Historical archives suggest that the 200-acre vacant lot was home to a significant portion of San Salvador, the largest non-native settlement in the mid-1800s along the Old Spanish Trail between New Mexico and Los Angeles. An overwhelmed Santa Ana River led to the Great Flood of 1862, which either washed away or buried beneath a thick layer of sandy river deposits, all adobe structures and settlers’ belongings. Artifacts are anticipated to be buried at a shallow depth of 1.5 – 3 meters, making them a good target for several different types of geophysical surveys.
Ground Penetrating Radar (GPR), Electro-Magnetic induction (EM), and ground-based magnetic gradiometry have proven successful in non-invasively identifying archaeological artifacts in a variety of different environments. In dry, southwestern sites, the most successful of these has historically been GPR. Much work has been accomplished by researchers at other sites in identifying buried adobe structural remains by their “adobe melt” signature in GPR profiles of adobe walls in the subsurface. We employ GPR using a 400 MHz antenna across this site and have imaged several anomalies that have a high probability of being related to San Salvador. The most noteworthy are a north-south trending canal signature buried at a depth of ~1.5 meters, an “adobe melt” signature at a depth of ~2.5 meters, and a feature that resembles a collapsed structure that is ~30 meters long in profile view. Significant hyperbolic signatures exist in the profiles that image the potential collapsed structure, located just below the strong reflector interface at a depth of 1 – 3 meters. We hypothesize that the strong reflections are caused by the significant difference in dielectric properties between the sandy river deposits and the adobe walls which would have dissolved quickly in the flood and been redeposited. As GPR continues to locate potential San Salvador artifacts, concentrated surveys using magnetic gradiometry and EM are being planned for confirmation. Our goal is to aid the Spanish Town Heritage Foundation in proving the cultural importance of this site before the city of Colton’s plans to develop the land are implemented.

Sutkowski, C. S., Prado, O., Hernandez, V., & Polet, J. (2018, 08). Preliminary Results of a Study to Identify Archaeological Artifacts from San Salvador in Colton, CA, Using Ground Penetrating Radar. Poster Presentation at 2018 SCEC Annual Meeting.

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