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Archeology for Interpreters > 5. How Do Archeologists Figure Out How Old Things Are?

Relative dating

Horizon markers and TPQ dating

A horizon involves ties and uniformity across space at a single point in time (Ashmore and Sharer 1996:41). In archeology, a horizon is a pattern characterized by widespread distribution of a complex of cultural traits that lasts a relatively short time. Events that might create the pattern of a horizon include a rapid military conquest or an effective religious mission. Examples from prehistory include the distribution of artifacts typical of the Inca in Peru, widely spread as a result of that people's known efficiency in conquest and empire building (Deetz 1996:64). In contrast, an archeological tradition is a persistent pattern of cultural traits in a restricted geographical area. Traditions not only suggest a strong degree of conservatism, but a stable pattern of permanent settlement that allows such developments to take place relatively undisturbed (Deetz 1996:64).

Terminus post quem dating, often referred to as TPQ dating, is defined as the date after which a stratum, feature, or artifact must have been deposited. When several artifacts are recovered from a single stratum, the TPQ date corresponds with the first possible date that the latest-occurring artifact could have made its way into the ground.

Try it yourself

What's the TPQ Date?

You have excavated a plantation kitchen site at Charles Pinckney National Historic Site. Artifacts you have recovered from one stratum include English tableware, cutlery, wine bottle glass, windowpane, nails, bone, and tobacco pipes. You can date several of the artifacts:

  • Creamware ceramic sherds date to after 1762 when creamware was first manufactured
  • One wine bottle seal is embossed with "C PINCKNEY 1766"
  • A 1722 English coin
  • A Spanish eight reales coin dating from 1746-1788

Based on the known dates of the artifacts listed above, what is the TPQ date of the stratum?

1722 1746 1762 1766 1788

TSM/MJB