by Erica D’Elia – Assistant Lab Director
If you have been following our biweekly updates you already know that the CART team is hard at work surveying a new site. But you might not be familiar with what this entails. This work is being conducted consistent with Fairfax County Park Policies 103 and 203 and in accordance with Virginia Department of Historic Resources (VDHR) guidelines which designates different phases of archaeological work and objectives for each. We are currently performing a Phase I Survey with the goals of identifying any historic or prehistoric sites located on the park, defining the boundaries of any sites discovered, and assessing the need for Phase II work. Phase II involves determining the significance of the resource. Archaeological sites can be considered significant under either National Register of Historic Places criteria developed by the National Park Service or under local criteria developed by Fairfax County. It is always preferable to avoid disturbing a locally or nationally significant site. However, if avoidance is not prudent or feasible, a Phase III entails the development of a treatment plan in consultation with VDHR.
In order to identify sites within the park’s boundaries we use a systematic survey of the property. Typically, this takes the form of shovel test pits (STPs) dug at regular intervals along a grid. So let’s pretend that this square outline is our park.
In the field, our first task was to establish a baseline in the form of Cartesian grid from which to conduct our work. In order to keep track of where we are on our grid we use a system of coordinates called Northing and Easting. In this example the point furthest southwest is our datum (the red dot on the image below) or the point from which we measure all other points on the site (and now you know how the Archaeological Society of Virginia – Northern Virginia Chapter’s monthly publication, the Datum Point, got its name!) Its coordinates are North 0/East 0 (N0/E0). Using a surveyor’s total station from the datum we shot in a line of points (black dots) 15 meters apart running West-East. This is our baseline (blue line).
To get a sense of our grid imagine lines running North-South and East-West every 15 meters. These are called transects, represented by dashed lines in the image below.
Now, the real fun begins. We work in teams of two and move North along each point digging a small hole every fifteen meters. Eventually we’ll dig holes across the entire site. As you move North the Northing increases, likewise, as you move East the Easting increases. In the image below each dot represents an STP. The STP represented by the green dot is located at N60/E45 and the purple dot is N30/E90. Can you figure out the coordinates for the yellow dot?
Of course these maps are pretty ideal. In the real world parks aren’t perfect squares and their boundaries do not align along cardinal directions, Plus, we’re in the woods, so we have all sorts of fun tree, vine, and thorn obstacles. Not to mention the ticks, mosquitoes, and poison ivy. We use a compass and measuring tape or pace out how many steps we take in 15 meters to make sure we are moving in the correct direction the correct distance.
Digging an STP is relatively simple. We’ll mark a piece of flagging tape with the coordinates and tie it to a nearby tree. Then, we’ll clear the ground surface. We’ll take note of any interesting natural or cultural features nearby such as trash scatters or creeks. Using a shovel we’ll create a circular outline where we’ll dig our hole, typically about 40 cm in diameter. As we dig the hole we’ll pay careful attention to any changes in soil color, texture, and composition as that indicates different natural or cultural processes that occurred over time. Once we’ve excavated no less than 10 cm into subsoil (unless we hit an obstruction or it fills with water) we’ll know we are finished. All of the soil is screened through ¼” mesh so that we can recover any artifacts. We might find historic period artifacts such as glassware, nails, and ceramics or we might find prehistoric flakes and stone tools. Although finding artifacts is always exciting, the truth is most of our STPs are negative, meaning no artifacts were found.
Recordation is extremely important to all stages of archaeology. We take notes about every STP we dig. We record things like the depth of each layer, any artifacts found, and use Munsell books to describe the soil. When we’re finished we fill the hole back in and move to the next location to repeat the process.
As we continue the survey we will start to note certain patterns; areas where we found artifacts and areas where we did not. This helps us to determine the locations of archaeological sites and make plans for additional work in those areas. In the map below pink dots represent prehistoric artifacts and the yellow dots represent historic artifacts. The circles correspond with artifact clusters defining potential sites. If any of these sites exhibit potential research value, it is on to Phase II…
(Answer: The yellow dot is located at N120/E120)