Activity at Incapillo commenced after Maricunga Belt volcanism, with further eruptions occurring between 6.5 and 3.5 million years ago. The Incapillo ignimbrite formed through non-explosive extrusion and covers an area of 80.47 square kilometers. It is a rhyodacitic to rhyolitic ignimbrite with high crystal and pumice content, and has a volume of approximately 20.4 cubic kilometers.