Geology at submerged sites contain vital information about the archaeological site including its age, the type of environment, and whether the site is in secure stratigraphic context. One of the most effective ways to investigate the geology at a submerged site is to extract archaeological sediment cores. Archaeological core tube are 3” aluminum tubes that are driven into the sediment. The top end is then sealed creating a vacuum within the tube. Then, the sediment filled tube is pulled from the ground.
Processing the sediment core tubes involves cutting the tubes in half lengthwise, while avoiding inter-stratum contamination. Two lengthwise cuts are made parallel to each other on opposite sides of the core tube. Once the sediment has been then cut with a wire, the core is opened reveling the stratigraphic profile. The two side are then photographed. One side of the core is then reserved for future research, while the other side “working core” is used for radiocarbon dating, pollen sampling, particle size analysis, soil e-DNA, and foraminifera sampling.
Radiocarbon sampling tells us how old the sediment is within the core. We use those dates to guide us during archaeological excavations. It can also inform the researchers if the sediment has been disturbed by erosion.
Pollen sample reveal what type of plants were growing when the sediment was deposited. The type of plant that were growing during different time periods tell us what the environment was like. Particle size analysis will determine what type of energy the water had as the sediments were deposited. High energy will deposit sand where low energy will deposit silt or clay.
Soil e-DNA is a relatively new method used to inform us about what types of animals were living in the area at the time of deposition. Soil e-DNA has been used to develop the timeline of the opening and utilization of the ice-free corridor and the domestication of wheat in Europe.
Foraminifera are small plankton like creatures that live in very distinct water environments. By examining the foraminifera, we can tell if the water was fresh or salt, cold or warm, deep or shallow.
All of these sampling methods are then combined to reconstruct the paleoenvironment, paleo-biosphere, and rate of localized sea-level or water table rise for the project area. The radiocarbon dates will then constrain the environmental indicators within chronological order. From there, we can put together a story of what the climate was like, what types of animals where living with precontact peoples, and when Ice Age megafauna like mammoths went extinct throughout different time periods. This assistances in building a picture of how people may have lived on, and interacted with the paleo-landscape.