Located in the south-central portion of the state, new geologic mapping of the frequently-visited Baraboo Hills has resulted in a revision of the stratigraphy of the Precambrian-aged bedrock. The Baraboo Quartzite is now divided into four informal members, and the maximum depositional age for the Baraboo Quartzite is 1714±17 million years old. These revisions have provided markers to constrain the structural history of the area during this ancient time, which contains evidence for a complicated and prolonged history of sedimentation and deformation.