Sediment cores are an extremely useful tool used in conjunction with archaeological studies. Basically, a geologist uses a long narrow metal (generally aluminum) tube to sample the soil deposits in the bottom of a lake or wetland. The soils are removed, dried, and analyzed in a laboratory.
The reason sediment core analysis is interesting is because the bottoms of a lake or wetland are records of the silt and pollen and other objects and materials which have fallen into the lake over time. The lake water acts as both a sorting device and as a preservative since the deposits fall in chronological order and (if not subject to dredging) are not normally otherwise disturbed by humans. So, a tube extended down into these sediments collects a sample of 2-5 inch diameter of undisturbed deposits which reflect changes over time.
Sediment columns can be dated using AMS radiocarbon dates from tiny pieces of charcoal in the sediments. Pollen and phytoliths recovered from soils can provide data about the predominant climate; stable isotope analysis can suggest plant colony type dominance. Tiny artifacts such as micro-debitage can appear in soil columns. Identifying periods when the amount of soil deposited within a given time increases steeply can be an indication of increased erosion after adjacent land was cleared.
Sources and Studies
Feller, Eric J., R. S. Anderson, and Peter A. Koehler 1997 Late Quaternary Paleoenvironments of the White River Plateau, Colorado, USA. Arctic and Alpine Research 29(1):53-62.
Head, Lesley 1989 Using palaeoecology to date Aboriginal fish-traps at Lake Condah, Victoria. Archaeology in Oceania 24:110-115.
Horrocks, M., et al. 2004 Microbotanical remains reveal Polynesian agriculture and mixed cropping in early New Zealand. Review of Palaeobotany and Palynology 131:147-157.
Kelso, Gerald K. 1994 Palynology in historical rural-landscape studies: Great Meadows, Pennsylvania. American Antiquity 59(2):359-372.
Londoño, Ana C. 2008 Pattern and rate of erosion inferred from Inca agricultural terraces in arid southern Peru. Geomorphology 99(1-4):13-25.
Lupo, Liliana C., et al. 2006 Climate and human impact during the past 2000 years as recorded in the Lagunas de Yala, Jujuy, northwestern Argentina. Quaternary International 158:30-43.
Tsartsidou, Georgia, Simcha Lev-Yadun, Nikos Efstratiou, and Steve Weiner 2008 Ethnoarchaeological study of phytolith assemblages from an agro-pastoral village in Northern Greece (Sarakini): development and application of a Phytolith Difference Index. Journal of Archaeological Science 35(3):600-613.