Regional Geography and Geology of the Upper Colca Project Area

The Chivay obsidian source is located on the margins of the Peruvian altiplano above the Colca Valley in southern Peru. The geographical position of the obsidian source area (71.5° S, 15.6° W) at on the western edge of the altiplano above the richly productive Colca valley had bearing on circulation of Chivay obsidian in regional prehistory. This chapter begins with an overview of the geographical relationships in the Upper Colca study area including climate, biotic zones, and resource availability. The chapter will then describe the ecological and geological context in the Colca Valley, and the influences that spatial relationships may have had in prehistory.

Figure 4-1. View of the volcanic Chivay source area above the town ofChivay in the Colca valley. The high point in the center-right of the frame, Cerro Ancachita, is above the Maymeja area. This view is from the Arequipa highway to the south-west of the Chivay source at 4720 masl.

Subsequently, further details on the geological structures in the area of the Chivay obsidian source will be presented, together with the geomorphological process that have influenced obsidian procurement in the area. Finally, this chapter concludes with a discussion the formation of silicic lavas and tool-quality obsidian, and the research that has been conducted to date documenting Tertiary obsidian flows in the Colca Valley.