The foundation of both lithic provenance and prehistoric quarry studies lies in the construction of fine-scale geological bedrock maps. The U.S. Geological Survey, and the individual state surveys, have compiled geologic maps of the entire country, but these maps are typically at a resolution (1:24,000-scale or lower) that lacks sufficient detail for a given archaeological investigation. Moreover, bedrock descriptions that are useful to geologists frequently do not include the sort of lithic resource information an archaeologist needs. For example, detailed descriptions of cherts are notoriously neglected in bedrock descriptions.
To compensate for this lack of detail, LaPorta Geological Consultants combines fundamental geological methods with GPS survey techniques to produce our own detailed bedrock-geologic base maps. These maps include key bedrock formation boundaries and markers beds, but they also include various tectonic data (joint sets, cleavage, bedding planes and fault surfaces), which are necessary for prehistoric quarry predictive models. These same structural and stratigraphic data can also be used (via geometric construction) to complete maps in areas where dense vegetation or modern land usage make a complete walkover difficult. All geologic data are compiled into GIS-compatible map form.
***Updated Spring, 2014