Popouts and Related Fractures

Abstract

Observations from contemporary knapping are interpreted to offer insights on the formation of the unusual fractures, termed “popouts” here. Some of these have been known as “nacelle flakes.” A popout, sometimes resembling a flattened U, is detached by secondary fracturing from the ventral f ace of a flake during its production. The related “stepout fracture” also involves a secondary crack extending from the ventral face outward and then parallel to the dorsal surface, but without turning back to the ventral surface, as with the popout fracture. The manifestation of compression lips of bending breaks is shown to be akin to stepouts. The formation is considered for the above, as well as other related fractures, including compression wedges and lateral wedges encountered in transverse breakage by bending.