Archaeological Field Methods

The Nate Harrison Historical Archaeology Project

Palomar Mountain - San Diego, California
The Official Site of the SDSU Historical Archaeology Field School

Archaeological Field Methods

Archaeological fieldwork began with the selection of a site datum. The point had to be off-site in order to avoid its excavation in the future, but near enough to facilitate easy transit, survey, and mapping use. Flat, shaded areas are also beneficial for laser theodolite set-up and care. The datum selected at the Harrison site fulfilled all of these criteria and was located approximately 100’ southeast of the cabin cobbles. It was on relatively flat ground under a large tree (Figure 73). In the event that excavations occurred in the vicinity of the datum, this point was deemed 10,000N/10,000E, placing the true 0/0 datum, which could not be compromised. Two secondary data points were established in relation to the primary 10,000N/10,000E datum: one 50’ to the west at 10,000N/9,950E and the other 50’ to the north at 10,050N/10,000E. The elevation or Z for the primary datum was also established arbitrarily at 10,000’. Elevations for the secondary data points were calculated with a string level, plumb bob, and measuring tapes. The Z for the west back sight (N10,000/9,950E) was 9,997.05; the Z for the north back sight (N10,050, E10,000) was 10,007.55 (Figure 74). All measurements were in feet, the same unit of measurement employed by Nate Harrison and his contemporaries on the mountain. The scale can be easily converted to the metric system at any time.

Grounds Keeping

The site area was completely overgrown at the start of the field school and required significant plant removal (Figure 75). Preparations for excavation also included the cutting of many large tree limbs and small trees (Figure 76). The field school spent its first few days on the mountain removing the vegetative growth from the site (Figure 77). The plant material they removed was placed on top of a plastic tarp that formed the platform of the back dirt pile (Figure 78). Students flagged the artifacts that were encountered during this process, to be mapped later with their provenience.

The Grid

The crew used the laser transit to lay out a 5’ grid over much of the site area for horizontal spatial control (Figures 79 and 80). Wooden stakes marked the corners of the units. The grid was oriented to true north, 13º east of magnetic north. Pink flagging tape with unit coordinates were affixed to the northeast corner of each unit. The stone foundation was treated as a large feature, the interior of which measured approximately 9’ by 12’. Features are excavated with respect to themselves, not the grid. In order to maximize spatial analysis within the structure and profile mapping potential while maintaining reasonably sized units for excavation, the feature was subdivided into twelve 3’ by 3’ units, four along the north and south faces and three along the east and west faces (Figure 81).

The Excavation Register

Each unit was assigned a number as it was excavated that corresponded with the Excavation Register (ER) and associated ER forms. The Excavation Register listed the number of units or features sequentially, their northeast corner coordinate according to the grid, a general description, the date it was assigned, and the initials of the person who assigned it. Once the ER# was assigned, the crew followed the exact steps outlined in the abridged field manual (Appendix A). These opening pre-excavation steps included opening photographs (Figure 82), sketch maps of surface finds, and triangulation mapping of any features within the unit. Once a layer was completely excavated, students completed profile maps (Figure 83) and triangulation-based plan maps of any features at the nexus between the base of the layer excavated and the top of the next natural layer. They also inventoried all of the materials that were recovered from that specific context (Figure 84). ER forms were ultimately completed for each individual archaeological context (Figures 85 and 86).

Digging Strategy

The crew excavated almost exclusively with trowels, as the degree of disturbance at the site was unknown. The recovery of multiple complete vessels reaffirmed this decision. All fill was carried from the site in buckets to the screening area and pushed through 1/8” wire mesh (Figures 87 and 88). In addition, units were dug in an effort to maximize understanding of the site’s stratigraphy, resulting in a checkerboard pattern of units both inside and outside of the structure. Excavating every other unit within the structure enabled a future composite drawing of five different profile maps that spanned the cabin area, 2 along its long axis and 3 parallel to its shorter sides. Each was at regular 3’ intervals. Likewise, a checkerboard approach to the patio area offered additional opportunities to understand the differential use of space by the site’s inhabitants. During the first season of excavation, two main areas of the site were investigated. The interior of the cabin was excavated first, in hopes of learning as much as possible about the architecture, construction, and destruction of the cabin, as well as gaining insight into the different living areas within the structure (Figure 89). The second area of interest was the patio, the space just to the west of the cabin (Figure 90). Historical photographs showcased this area as a main locus of activity for Harrison.

Layers and Levels

Whereas historical archaeologists traditionally excavate in natural stratigraphic layers, prehistoric fieldwork is frequently undertaken in levels. Excavations at the Harrison site attempted to unite these two approaches, as this frontier site likely transcends simplistic categorizations of native or non-native materials. The site’s natural stratigraphy was always followed, but layers larger than 3” (10 cm) were divided into 3” levels within the layer. As a general rule, the natural contour of the land was followed. Thus, the top fill layer of excavation for all of the units was the top 3 inches, even though the apparent stratigraphic fill episode was often deeper. In addition, the extreme dryness of the soil warranted extra precaution in excavation as few natural layers were immediately visible in the profiles and sidewalls.

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