horizon: Any artifact, art style, or other cultural trait that has extensive geographical distribution but a limited time span. The term, in anthropology, refers to the spread of certain levels of cultural development and, in geology, the layers of natural features in a region; in soil science a horizon is a layer formed in a soil profile by soil-forming processes. The main meaning, however, refers to a phase, characterized by a particular artifact or artistic style that is introduced to a wide area and which may cross cultural boundaries. Provided that these 'horizon markers' were diffused rapidly and remained in use for only a short time, the local regional cultures in which they occur will be roughly contemporary. The term is less commonly used now that chronometric dating techniques allow accurate local chronologies to be built. Examples of art styles which fulfill these conditions is called a 'horizon style' -- such as Tiahuanaco or Chavín.