Problems with Radiocarbon Dating: The Minnesota Project

Summary

This is an abstract from the "SAA 2025: Individual Abstracts" session, at the 90th annual meeting of the Society for American Archaeology.

In 2009, a constitutional amendment in Minnesota took effect authorizing millions of dollars for arts and cultural heritage programs. The State Archaeologist developed a Statewide Survey (SWS) program to further knowledge of site locations, cultural contexts, and property types. One of the first projects was to examine dating issues associated with Brainerd ceramics whose absolute chronology was primarily based on dates from ceramic crusts. Forty (40) 14C dates were obtained from ceramic crusts and other organic materials associated with Brainerd ceramics. These dates demonstrated the previous chronological range of Brainerd began much too early. The suspected cause was old carbon contamination in ceramic crusts due to the inclusion of remains of aquatic plants and animals living in waters with dissolved ancient carbonates. This is known as the freshwater reservoir effect (FRE). Additional SWS projects were initiated to examine the FRE issue and other possible radiocarbon dating issues by examining modern organic samples from aquatic environments. This included dating the remains of four fish species obtained in 1939 (pre-bomb) from the Mississippi River by archaeologists excavating a nearby rockshelter.

This Resource is Part of the Following Collections

• Society for American Archaeology 90th Annual Meeting, Denver, CO (2025)   •
• SAA 2025: Individual Abstracts

Keywords

Record Identifiers

Abstract Id(s): 52933