Geologic Unit: Baker Lake Usage: Baker Lake Porphyry (CO) Geologic age: Tertiary. Type section, locality, area and/or origin of name: Notable exposures in northwestern part of South Park, in secs. 17, 19, 20, 28, 29, and 30, T. 7 S., R. 75 W., and in secs. 24 and 25, T. 7 S., R. 76 W., Park Co., central CO.