The Cancañiri Formation, also named as Cancañiri Tillite, is a Katian to Hirnantian geologic formation of central Bolivia. The pebbly, argillaceous sandstones, shales and siltstones of the up to 1,500 metres (4,900 ft) thick formation, were deposited in a glacial foreshore to deep water turbiditic environment. The formation is named after Cancañiri, a mining town close to Llallagua, where a local legend of a possessed woman is believed. The formation overlies the San Benito Formation in Cochabamba and the Amutara Formation in other parts. The Cancañiri Formation is overlain by the Uncía Formation.