Week 5 7/6-7/9

Greetings! This week the I&E gang were down at Timucuan Ecological and Historical Preserve/ Kingsley Plantation (TIMU) performing a multi-instrument geophysical survey of a suspected enslaved persons graveyard. It seems that a field school inadvertently discovered human remains during their testing and asked SEAC if we could come out and discover the extent of the graveyard.

Starting on the 6th, we arrived and began mapping. It is important in geophysical surveys to know your surroundings. We wanted to place our grids in and around the field school’s units, but we had to take into account a few things. First, we had to know what instruments we were using and what their limitations were. Since it is always better to use more than one type of instrument when doing geophysical surveys, we used 3: a dual fluxgate gradiometer–a type of magnetometer, an electrical resistivity meter, and a ground-penetrating radar or GPR.

Each of these instruments have their limitations and they must be taken into account before the first grid is even laid down. The magnetometers are extremely sensitive to metals and devices that give off electric frequencies (in Hertz). We saw that there was a power-line above us, so we offset all the grids 20 meters so that they wouldnt interfere with that aspect of the survey. Resistivity meters are dependent on the condition of the soil since they detect the resistance of electric current through the ground. In order for this to happen the soil must have some moisture content. At TIMU the soil was sand and because the weather had been scorching for the last week and a half, it left the first 30-40cm almost completely devoid of moisture. The resistivity meter functions by putting two or more metal tines into the soil and they are only 25cm long. This meant that the instrument would not yield useful data, but it is the primary reason that multiple instruments are used on surveys because it is almost impossible to predict such conditions.

After the instrument limitations were taken into account, we set up grids and mapped. We initially set up 4 grid, but when we discovered how fast we could take GPR and gradiometer readings we extended our search area to almost 14 grids.

The 7th-9th saw us out performing various tasks like setting up new grids; running the GPR/resistivity/gradiometer; shooting in the locations of obstacles such as gopher tortoise burrows, trees, and previous excavation units; setting up and moving tape and cones for those running the equipment; taking photos and other documentation tasks; and finally troubleshooting and fixing the equipment.

Geophysical analysis in archaeology is a very important tool that all archaeologists should utilize. It allows us to do something we usually only dream about–look into the ground and see what’s in it without disturbing it or digging it up more so than it needs. As an aspiring archaeologist who loves technology this survey was very exciting and I look forward to performing more as well as analyzing the data in the future.


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