The Incapillo ignimbrite is an unwelded ignimbrite that covers a surface area of , extending to a distance of from the caldera. The ignimbrite appears in an eastward-heading ephemeral river valley and the southern Quebrada del Veladero, possibly also next to the Rio Salado headwaters. Thicknesses range from ; the ignimbrite is underlain by a lithic-and-ash rich surge deposit with a thickness of . The ignimbrite displays banding features away from the caldera and in Quebrada de Veladero football-sized clasts are mixed within fine ash. Rocks from the ignimbrites farther away from their source indicate the ignimbrite probably formed from the mixing of less viscous dacitic magma with rhyolite. The total volume of the ignimbrite is about . Ages have been found of 0.52 ± 0.03 and 0.51 ± 0.04mya ago. It is a rhyodacitic to rhyolitic ignimbrite with a high crystal and pumice and low lithic content. The dense rock equivalent volume is about . The volume of the Incapillo ignimbrite is comparable to that of the Katmai ignimbrite. The ignimbrite was probably formed from a low-height fountaining eruption without a high eruption column, forming a base surge first and pyroclastic flows later. The change from lava dome to ignimbrite-forming eruptions may have been triggered by the injection of hotter magmas into the magma chamber or less likely by changes in the tectonic context. During the eruption, a piston-like collapse formed the caldera.