Ogburn, Dennis, Samuel Connell, and Chad Gifford. “Provisioning of the Inka Army in Wartime: Obsidian Procurement in Pambamarca, Ecuador.” Journal of Archaeological Science 36, no. 3 (March 1, 2009): 740–51.
Dennis Ogburn, Samuel Connell, and Chad Gifford look at sources of obsidian found at the Pambamarca fortress complex to the north and east of Quito, which formed the northern frontier of the Incan empire during their two decades of warfare against the Cayambe and Carangui peoples of the northern Andes. The authors conclude that local communities were able to source obsidian directly or through exchange networks from sites as far south the Yanaurco-Quiscatola deposits in the cordillera between Pintag and Pifo.
Obsidian recovered from Incan sites was also sourced from multiple deposits, leading the authors to conclude that the invading army most likely used local tributary labor to supply them with obsidian as opposed to it being brought from further south or mined by the Inca at a single source. The authors suggest this may be evidence of a relatively quick colonization of the region by the Inca in the aftermath of their conquest in the late fifteenth and early sixteenth centuries.