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Andrea in Ecuador |
Finding the evidence to enrich our understanding of the past involves predictions, patience, and a whole lot of paperwork. If you've ever wondered why archaeologists dig square or rectangular holes it's because it makes mapping and organizing our findings a bit easier. We can map the location of our excavated holes using a metric grid system. We excavate in metric units as well; the holes are usually 1 x 1, 1 x 2 or 2 x 2 meter "units" which makes it easy for us to determine the volume of soil we have excavated (in cubic meters) and the density of artifacts per volume of soil excavated. In this way, we can measure key differences that may reflect different human activities. For example, a household trash deposit, or midden, may have high numbers of mixed artifacts, bone, charcoal, and other plant remains, while and area that was used for agriculture will only have a few specific artifact types scattered lightly across a broad area but may contain a higher percentage of seeds. Since we are only looking at a small sample in the total area of Colonial Sicalpa, we rely on artifact assemblages and densities to help us interpret activities ass well as orientation and context of various architectural elements like walls, floors, and floors below floors. Natural deposits like pumice and ash, and evidence of earthquakes also help us determine a string of events and understand the context and state of the artifacts and cultural features that we find.
How do you figure out where to dig in the first place? For this project, Ross tapped into the local knowledge of the people, got permission to dig in places that sounded fruitful and then used small test holes to look for concentrations of artifacts or possible built features. Once he determined some "hot spots" he expanded these test holes to bigger excavation units and the fun and paperwork began.
For excavation, Ross used a system called the Harris matrix to organize excavation data. In this system, each "deposit" or "cut" (whether natural or human-caused) was given a context number. During excavation, when a new stratigraphic layer was reached (e.g. when a sandy soil with no artifacts switches to a blackened soil with lots of artifacts) he assigned a new context number. As we excavated, we determined the relationship of the stratigraphic layers, and therefore events, to one another. From this you can create a context diagram based on your observations and interpretations. This diagram is useful during analysis when you can determine the age of various deposits based on something diagnostic (like a coin with a date on it (thanks Mike) or a style of pottery that was only made or imported after a certain date). Many of these temporal or time-oriented determinations hinge upon the historic records of the period which were generally created and preserved by religious orders. These historic documents can be very useful in determining the relationships of artifacts to people, such as import and export materials, goods, and ideas. However historical archaeology also provides the hard evidence that can sometimes disprove what historic documents falsely claim, or enrich our understanding beyond what the historic documents recorded.
During excavation we use various tools--shovels, trowels, pickaxes and brushes. Most of the time we sift the soil through a screen (in this case with 1/4 inch mesh openings) in order to separate the soil from the artifacts. Anything larger than a 1/4 inch in size is collected, washed, weighed, counted and analysed. Sometimes we take samples in bulk for finer analysis later. In this project we have collected a 5 liter soil sample for each context and brought them back to "the palace" to be processed using the flotation technique...flowing water helps to separate "light fraction" materials (e.g. charcoal, seeds and very light bones) from the rest of the soil matrix. This is what I´ve been using the flotation machine for, but it can also be done in a bucket of water (the flotation machine is much faster).
