Is it a karst terrain, a terrane, or both?

Posted to Speleogenesis.net on 10/28/2014

According to the U.S. Geological Survey, a terrane is defined as “A rock formation or assemblage of rock formations that share a common geologic history. A geologic terrane is distinguished from neighboring terranes by its different history, either in its formation or in its subsequent deformation and/or metamorphism.”  “Terrane” is also used to describe an area or region with a distinctive stratigraphy, structure, and geological history.  In a more specialized usage, a tectonostratigraphic terrane refers to an accreted or exotic terrane. In contrast, the term “terrain” typically refers to the elevation, slope, and orientation of land features.  It can be argued, therefore, that the karstic terrain (landscape) is a subset and consequence of the features and processes (stratigraphy, structure, and geologic history) that define the karst terrane in which it occurs.  To describe an area of karst as terrain ignores the subsurface suite of geologic factors that led to its creation.  Therefore, if one is simply describing the surface, calling it a karst terrain would seem to be correct.  However, caves are not part of the surface features of a karst area and, in fact, can exist without any surface indications whatsoever.  I would argue, therefore, that if one is discussing the surface and subsurface features of a karst area and particularly how they formed, the term “terrane” is more appropriate and inclusive.