Big news – our excavations have uncovered a building foundation at El Polín Springs. We first began to suspect that we had encountered an important feature last Wednesday, when large serpentinite stones were uncovered in Unit N1033-E983. The stones were closely packed together and because they do not normally appear in the soil we are excavating, we knew that their presence was attributed to cultural, not natural, factors.

We expanded the excavation area to better understand the stone feature, and discovered that we had hit a corner of the foundation of a former adobe building! The construction methods and size of the foundation are very similar to the stone foundations that were used to build the presidio’s main quadrangle. Additionally we are finding artifacts in close association with the foundation that date to the Spanish-colonial/Mexican period. Now that we have defined this building corner, we are putting new excavation units in to determine the size and orientation of the building.

We didn’t dig up this artifact, at least not from the ground. This is a “memory map” drawn by Mariano Guadalupe Vallejo, who was commandant of El Presidio de San Francisco from 1831-1834. Years later, in 1878, he commissioned an artist, Edward Vischer, to draw the presidio as Vallejo remembered it from his first visit here in 1824. The original drawing is stored at the Bancroft Library at UC Berkeley. This map provides a critical documentary link between the foundation that we discovered and the people who lived at El Polín. In the upper right corner, there is a small dark circle representing El Polín Springs. Immediately below, two small rectangles are labeled “Casas de Marcos Briones y Miramontes” (next to the blue arrow). The building we discovered is most likely the one represented by one of those rectangles! Marcos Briones was a soldier stationed at El Presidio de San Francisco, and his extended family lived at El Polín Springs from about 1815-1848.

This week’s update is from our field laboratory. One of the great things about the lab is that we get to process the materials in the field as we dig them up. Usually during the excavation process you don’t get to analyze and see material until after the “field season”. The lab set-up is a unique opportunity for us to get a glimpse at the artifacts as they emerge from the ground. Work in the laboratory helps to paint a more vivid picture of what was happening at the site. Already the material we are discovering is helping to guide the decisions we are making in the field.

For example, in Units N987/E988 and N987/E989, we are excavating a dark soil with not many cultural materials, or so we thought. When the buckets of dirt were transported to the field laboratory for wetscreening and processing, a different picture began to form. The units have yielded some interesting artifacts including possibly flaked bottle glass, a Spanish-era button, a metal roller skate and multiple chert flakes. Information gleaned from this laboratory work let us know we should continue to dig here. Currently excavators are at 120 centimeters below surface. We are continuing to find a mixed deposit at the lower levels, and a geologist who visited the site this week suggested that this area may have been a marshy flat at some point, where things may have sunk to lower depths as they were deposited.

Our artifact of the week was found in Stratum 5 of Unit N1080 E978. The artifact is two pieces of a Bos taurus (Cattle) ulna that mend back together. Animal bones are being analyzed to tell us not only what people were eating, but how they were preparing it. Beef was a staple food item in the diet of people during the Spanish-era. Cattle were brought to Alta-California from Mexico, and thrived in the arid and lush enviroment.