Archaeological Investigations at Montaña de Oro State Park,

San Luis Obispo County, California

Field & Lab Methods

Field investigations were undertaken on Fridays during consecutive spring seasons from April 9 to June 11, 2004 and from April 8 to June 10, 2005. Field crews consisted of professional field technicians who assisted and supervised Cal Poly students enrolled in ANT-310, Archaeological Field Methods. The field strategy was designed to salvage portions of the site that were rapidly eroding from  the coastal cliff/bluff as a result of sea cliff retreat caused by exposure to surf, and exacerbated by modern and historic human activities (e.g., cattle grazing, trails, beach access). Sampling was restricted to the area of greatest impact along the coastal bluff. A variety of excavation strategies was employed in order to obtain adequate samples of both macro- and micro-constituents. The majority of the excavation volume targeted the recovery of macro-constituents from relatively large units (1 x 2 m) that were dry screened through 3 mm (1/8 inch) mesh. Soils were collected in labeled buckets and transferred to the Cal Poly Archaeological Laboratory for water (wet screen) processing through 3mm (1/8 inch) mesh. The soil from two 20 x 20 cm column samples (Units 1 and 3) was bagged in the field and transferred to the Cal Poly Archaeological Laboratory for wet screening through nested 3mm (1/8 inch) and 1.5mm (1/16 inch) mesh screens.

Macrosamples

Macrosampling strategies focused on 12 1 x 2 m excavation units (Units 1-9, 11-13). Soil was removed from the individual units in 10-cm levels with a variety of hand tools (shovel, pick-maddox, trowel, etc.) and placed either directly into screens or into buckets which were then transferred to screens. In 2004 and 2005, all formal artifacts, debitage and bone were collected from each level and placed in separate bags for each analytical category for later laboratory processing and analysis. Fire affected rock (FAR) was not quantified from the macrosample units.  Macrosampling strategies for invertebrates differed from 2004 and 2005. In 2004 all whole shells, all mussel shells at least 1/3 intact, and all large fragments of any species were collected. In 2005, only whole shells or nearly complete shells were collected. These strategies were employed because CA-SLO-9 is a relatively shell-rich midden, and recovery of 100% of the invertebrate remains would require inordinate amounts of time and labor that would, in turn, limit the recovery of other classes of materials. Shell was only collected in order to (1) develop a complete list of invertebrate taxa represented in the deposit (as column samples often do not yield examples of species that occur in low frequencies); (2) provide samples that could be measured to develop size profiles and (3) provide samples for oxygen isotope analysis and radiocarbon dating. Other aspects of the shell constituents were with micro-samples.

Microsamples

Archaeological Crew dry screening excavated materials in the field.

Microsamples (a single 1 x 1 m control unit [Unit 10] and two 20 x 20 cm column samples) were collected in order to obtain representative samples of fire-affected rock, fish bone, shell, and obsidian pressure flakes.  Soil from Unit 10 was excavated with hand tools in 10-cm levels. The soil was then reduced through 3 mm (1/8 inch) mesh screens and placed in labeled plastic bags within buckets. The buckets were then transferred to the archaeological laboratory at Cal Poly where the soil was processed with water through 3 mm (1/8 inch) mesh screens. Two 20 x 20 cm column samples were excavated with hand tools from Units 1 and 3 (CS1 and CS3) in 10 cm levels. Soil from each level was double bagged in labeled plastic and paper bags, placed in archive boxes and transferred to the Cal Poly Archaeological Laboratory for further processing.

Summary of Field Recovery

Excavation revealed a deposit between 70 cm and 120 cm deep. From a total recovery volume of 23.74 m3, 1.8 m3 were processed through 6 mm (1/4 inch) mesh, 21.3 m3 were processed through 3 mm (1/8 inch) mesh, and 0.24 m3 were processed through 1.5 mm (1/16 inch) mesh. The following table summarizes the field recovery from 2004 and 2005.

Summary of field recovery from CA-SLO-9

Field Methods

Laboratory Methods

At the end of the each field season, all materials were transferred to the Archaeological Laboratory at Cal Poly for storage until the following fall, when students in Archaeological Laboratory Methods classes processed them.

Materials recovered from the macro units were delivered to the laboratory in archive boxes containing individual unit bags. Materials within the bags were segregated into gross analytical categories (e.g., debitage, formal artifacts, obsidian, fish and non-fish bone, shell samples). At the laboratory, materials from the bags were washed and set aside to dry in labeled artifact drying screens. Once dry, materials were placed into 4 ml archival-quality curation bags. Formal and diagnostic artifacts were placed within their own bags, while debitage and shell (with the exception of whole Mytillus and shells from specific proveniences) were placed in lot bags. Fish bone was distinguished from non-fish bone (bird and mammal bone) and both were placed in separate lots.

Microsamples required further processing at the Cal Poly Laboratory. Soil from Unit 10 was reduced in the field, without water, through 3 mm (1/8 inch) mesh screens. Soil retained in the 3 mm screens was placed in labeled plastic buckets. At the laboratory, each level of soil was poured into labeled 3 mm (1/8 inch) mesh screens, and the material was carefully rinsed with water to remove any remaining soil. Materials were then set aside to dry. After the residues dried, Cal Poly archaeology students, under the supervision of the instructor, carefully sorted through all of the material, segregating formal artifacts, debitage, FAR, and bone. Column samples were delivered to lab, and the soil from each bag was individually poured into nested 3 mm (1/8 inch) and 1.5 mm (1/16 inch) mesh screens. Hoses were used to gently wash soil through the screens, leaving clean residue which was set aside to dry in screens labeled with provenience information and mesh size. After the material was dry, it was placed into labeled plastic bags. Later, Cal Poly archaeology students, also under the supervision of the instructor, sorted the 3 mm (1/8 inch) sample, separating all formal artifacts, shell, bone (both fish and non-fish), and debitage. The 1.5 mm (1/16 inch) samples were collected, and stored for possible future analysis.

All materials were then cataloged and entered into an Excel^® workbook.  Diagnostic and formal artifacts received individual numbers, while debitage was cataloged in lots. After identification, individual lots of fish bone retained single numbers, while all non-fish bone elements (except for unidentifiable fragments) were assigned a separate sub-letter within the catalog. Lots of shellfish received one number with the exception of whole Mytillus and shell fragments from specific proveniences that were retained for C14 dating. These were assigned their own numbers. Cataloged materials were segregated into analytical categories which were distributed to appropriate analysts.

Professor Terry Jones pauses from digging to inspects a possible cultural artifact from CA-SLO-9.

The field crew painstakingly sifts and screens excavated material.