Jeffrey A Homburg, Steven D. Shelley, William E. Hayden, Benjamin R. Vargas, Mitchell A. Keur, Manuel R. Palacios-Fest, and Michelle C. Long of Statistical ...
Geochemical Signatures of Protohistoric- and Historical-Period Activity Areas in Coastal Southern California Jeffrey A Homburg, Steven D. Shelley, William E. Hayden, Benjamin R. Vargas, Mitchell A. Keur, Manuel R. Palacios-Fest, and Michelle C. Long of Statistical Research, Inc. A horizon, marsh
• Nearly 300 surface-soil samples were collected from a 2-m grid in the excavation area.
• Evaluate patterns of geochemical distributions in
• Geochemical spatial distributions were mapped using ArcGIS.
• Geochemical data were compared in relation to artifact and feature distributions.
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• Geochemical spatial trends, especially of P and pH, are useful
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for reconstructing the intensity of human use and assessing the preservation of bone and shell in cultural deposits.
0
relation to the protohistoric- and historical-period occupation surface and associated activity areas
A, marsh
A, fan
Bk
ABkb
8.5
80% 60% 40% 20% 0%
20%
10%
0%
A, marsh
A, fan
Bk
ABkb
100%
A, marsh
80% 60% 40% 20% 0%
A, marsh
A, fan
Bk
ABkb
A, fan
Bk
ABkb
60%
40%
20%
0%
A, marsh
A, fan
Bk
These graphs show that the A horizon on the alluvial fan has a high concentration of lithic artifacts, charcoal, faunal bone, and shell compared to the A horizon of the contemporaneous marsh to the west. The concentration of lithic artifacts and charcoal is higher in the A horizon of the fan when compared to the underlying soil horizons exposed to the east, but the latter have comparable levels of shell and faunal remains.
ABkb
• Cultural features are concentrated where the soils have
7.5
neutral to slightly alkaline pH levels. On- and off-site pH levels are both excellent for bone and shell preservation.
7.0
6.5
pH
6.0
A, marsh
A, fan
Bk
ABkb
8
6
• Calcium carbonate and porosity levels appear to be natural
4
2
Organic Matter (%)
0
A, marsh
Santa Monica Bay
A, fan
Bk
ABkb
10
Calcium Carbonate (%)
Marina del Rey
Ballona Creek
Ballona Lagoon and Wetlands
CA-LAN-211
Calcium Carbonate (%)
Westchester Bluffs
• Organic matter content is highest in the A horizon of the
marsh, where oxidation losses are lowest. The A horizon associated with the alluvial fan has the next-highest levels of organic matter, which could possibly be related to foodprocessing and trash-disposal activities.
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Organic Matter (%)
Lithics Ubiquity (%)
30%
pH
8.0 100%
• Mehlich 2–extractable phosphorus is an excellent, long-term indicator of the intensity of cultural activities. Elevated P levels are strongly correlated with protohistoric- and historical-period hearth features at CA-LAN-211.
9.0
rather than the result of human activities. The highest calcium carbonate levels are in the marsh and Bk and buried A horizons of the alluvial fan, areas where the pH levels are highest.
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6
4
A Bk ABkb
2
0
A, marsh
A, fan
Bk
ABkb
60
50
El Segundo Sand Hills
Beach
Porosity (%)
-
Conclusions
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Extractable P (mg/kg)
• The following soil analyses were completed: Phosphorus (P) (Mehlich II extractant) Organic carbon (loss-on-ignition) Calcium carbonate (LOI) pH (1:1 soil:water, weight basis) Bulk density (clod method)
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ABkb, fan Phosphorus (mg/kg)
occupation surface at CA-LAN-211
Charcoal Ubiquity (%)
Methods
Bk, fan
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• Compile geochemical data for the upper
Shell Ubiquity (%)
Few studies undertaken after the pioneering work of Cook and Treganza in 1947, few studies have advanced the use of soil chemistry in archaeological studies in California. As part of the Playa Vista Archaeological and Historical Project in Los Angeles, a number of geochemical tests were used to search for patterning in protohistoricand historical-period activity areas associated with the approximate occupation surface at CALAN-211. Once we stripped the modern fill, we found that the eastern part of the site had been truncated mechanically prior to our fieldwork, thus exposing Bk and buried A horizons that predate the and protohistoric- and historicalperiod occupation surfaces.
Research Objectives
Faunal Bone Ubiquity (%)
Introduction
A, alluvial fan
Bluff
Salt Marsh Freshwater Marsh Archaeological sites
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Acknowledgments
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We appreciate the help of Playa Capital for funding this project. We thank a number of others for their assistance with this research, including Jeff Altschul, Donn Grenda, Richard Ciolek-Torrello, Chris Doolittle, John Douglass, Eli Adam, Lance Wollwage, Elizabeth Stoffers, Sam Dunlap, Martin Alcala, and Dana Alcala.
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10
Porosity (%)
0
A, marsh
A, fan
Bk
ABkb
