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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 kitchen site. Artifacts 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