This week at El Polín Springs we continued excavating the units that we began on July 8. Early in the week, most of the units were still digging through a mixture of historic American period fill with some Spanish colonial materials. While these strata have yielded interesting artifacts, they do not really tell us much yet about the Spanish colonial period. What they do tell us is that the area we’re working in was graded by construction activity during the Presidio’s years as a U.S. Army post. That’s why material from different time periods is all jumbled together, such as Spanish colonial roof tiles mixed in with American brick.

As the week went by, some of the excavators began to come upon what we think are intact Spanish colonial deposits. In those areas, we are seeing high concentrations of roof and floor tiles, adobe brick fragments, some animal bone, and some pieces of majolica, a type of ceramic made in Puebla, Mexico. In some cases, these units go as deep as 80 centimeters below the surface! We will continue to excavate until we hit sterile soil, which is the natural soil that does not contain any cultural material. We’re not sure how much the historic landscape has been altered by more recent construction, and one of our main goals is to understand the stratigraphic sequence in various areas of the site.

In some excavation units, we have begun to find artifacts that support our theory that some Native Californians may have been living at El Polín Springs during the Spanish-colonial/Mexican period. Our artifacts of the week are two examples of this. Traditionally, Native Californians made many tools by flaking certain kinds of stone. The artifact on the right is a flaked piece of obsidian, a glass-like stone that is not local to San Francisco. The artifact on the left is the bottom of a very dark green glass bottle that has also been flaked along its broken edge so it that could be used as a scraping tool. Glass and obsidian have very similar physical properties, and it’s not unusual to find flaked glass tools at colonial sites. Artifacts like these demonstrate ways that indigenous peoples may have been preserving their culture while adapting to new conditions caused by colonization.