1. Map showing areas of limonitic hydrothermal alteration in the Lake City caldera area, western San Juan Mountains, Colorado Yale Public content 1986. 2002-06-01T04:00:00Z. 2002-06-01T04:00:00Z. Geological Survey (U.S.). The Survey ; For sale by Branch of Distribution, U.S. Geological Survey. English. Public. Colorado and Lake City.