Tara Beresh
November 2, 2016
There are many approaches to observing and interpreting the
archaeological past. Techniques such as excavation, ground penetrating radar,
and survey are all common methods for contributing new data to the record. Another method for obtaining information about
prehistoric cultural activity and the environmental factors that predicated
them, is the study of geoarchaeology.
Geoarchaeology uses geomorphology, or the study of landform origins and
changes over time to interpret the sediments and soils at archaeological sites.
In a nutshell, geoarchaeology incorporates geology and the earth sciences to
tell us more about what the natural setting was like for past cultures. Knowing
this information can help us to determine what the climate might have been
like, what the water resources might have been and how environments have
changed over time, affecting the subsistence strategies and inhabitants of that
area.
Today I was assigned the task of accompanying two fellow crew members
and a teaching assistant into the Chaco Wash to analyze the sediment layers in
a segment of an alluvial fan. The arroyo wall was approximately 5 meters high
and 2.25 meters wide. The feature we were most particularly interested in was a layer
of flattened stones from the Bonito Phase (AD 1000-1100) that had a sherd in them located two meters below the surface. Our objective was to
determine the context of this layer by facing (using a trowel to scrape and flatten) the vertical surface of the wash, exposing different layers from past
water flow patterns and sediment deposits such as clay, silt, and sand. Some
archaeologists have studied this horizontal layer of flattened stones and
believe it to be the remnants of a path across the channel. Archaeologists can tell from
the amounts of iron and other mineral buildup where water has previously flowed
or collected for long periods of time. If there are stone structures present in
an arroyo wall it might suggest that there was a water management system put in
place by prehistoric communities. Curtaining is a term that refers to the
dappled appearance on the surface of a sandy arroyo wall that has been visibly
altered by rain and wind, much like a piece of paper that has been wet and
dried.
Creating a sediment profile involves mapping the layers of varied
sediments on graph paper and identifying the sediment types. We take
measurements of the width and length of each sediment layer using various
measuring devices and ladders to reach the highest layers in the wall. In
addition, we use a Munsell Soil Color Chart to record the color shade of each
sediment layer and then determine the textures of these sediments by mixing
about a tablespoon of each sediment type with water and attempt to create a
ribbon of soil between a thumb and forefinger. Depending on the grittiness and
cohesiveness, a category is assigned to the soil type and recorded for future
reference.
Working outside in a wash filled with cottonwood trees in bright hues
of yellow and orange is one of the greatest advantages of working in the field
of archaeology; however, doing archaeology also demands a heavy dose of
teamwork and focus to accrue accurate data in hot climates, often covered in
crumbling dirt and sweat. Living and working day in and day out with a crew of
10-15 people in a small space, both in the field and at camp can be a
challenge, but the dynamic of support and compassion that can develop among
colleagues in a long term, shared environment is immensely rewarding. You
quickly find yourself learning from people you might have never imagined having
anything in common with. I strongly believe that field school is an excellent
way to expand one’s perspectives about people and human relationships, test
endurance levels, and become prepared for demanding schedules and sometimes
strenuous physical endeavors.
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