LITHIC RAW MATERIAL IDENTIFICATION TECHNIQUES FOR THE NC PIEDMONT: A GUIDE TO VISUAL IDENTIFICATION FOR ARCHAEOLOGISTS

The North Carolina Geological Survey (NCGS) conducts detailed geologic mapping within the Orange and Chatham county portions of the Carolina terrane as part of STATEMAP, and frequently encounters fine-grained volcanogenic rock suitable for use in lithic artifacts. Fine-grained volcanogenic material can be challenging to identify during routine field mapping and an impromptu “best attempt” at identification must be made. The resulting field observations, ground truthed with geochemical analysis when possible, have led to informal logic-trees for initial field identifications.

NCGS geologists, in conjunction with feedback from the NC archaeology community, have created a Lithic Material Identification Guide that summarizes the field geologist’s thought processes to identify fresh rock material. The guide consists of two flow charts (“Tuff, Lava, or Sedimentary Rock?” and “Composition of Lavas and Tuffs”); a “Frequently Asked Questions” section to answer questions that may arise while using the flow charts; a “Less Common Textures” section to cover textures not mentioned in the flow charts; and a “Glossary of Terms” to provide brief, non-technical definitions of geologic terms used in the guide. This identification guide is not intended as a geologic rock identification guide. It was written specifically for identification of lithic material and therefore does not encompass the entire range of textures and rock types observed in the Carolina terrane.

The NC Department of Transportation has begun requiring the use of the guide by contractors in archaeological surveys. The guide expands and standardizes the rock types and textures previously identified and recorded in archaeological surveys. Coupled with GIS, the use of a standardized nomenclature for lithic raw material may allow a better understanding of the migration and trading routes via the use of lithic raw materials from diverse quarry sites.