MI-94 Colorado Geologic Time Scale Bookmark Download Publication Details Illustrated bookmark with photos of Colorado’s colorful geology on the front and a geologic timescale on the back. Up to ten paper copies may be ordered for free, please contact us directly at cgs_pubs@mines.edu for those. Otherwise, this is a digital PDF download. MI-94D Citations Colorado Geological Survey. “MI-94 Colorado Geologic Time Scale Bookmark.” Colorado Geological Survey, 2015. https://coloradogeologicalsurvey.org/publications/geology-bookmark-colorado.