ARTHUR LAKES’ 1878 MAP OF THE FLORISSANT FOSSIL BEDS, COLORADO

The Florissant fossil beds of Colorado attracted significant scientific attention beginning with the Hayden Survey in 1873. This survey involved leading paleontologists of the time, including paleoentomologist Samuel Scudder and paleobotanist Leo Lesquereux. Scudder first visited the site in August 1877, riding by horseback along with Colorado’s pioneering geologist and illustrator Arthur Lakes. During the following winter, on February 20, 1878, Lakes completed an unpublished watercolor geologic map titled “Sedimentary Lacustrine basin at Florissant near South Park Supposed to be Upper Miocene” (sic). The original copy of the map is in the archive at Florissant Fossil Beds National Monument. It was donated to the National Park Service in 1988 by Harvard paleoentomologist Frank M. Carpenter, who purchased it along with Scudder’s personal library from the Boston Society of Natural History in 1944. The map is significant in its association with scientists of the Hayden Survey. The 1877 regional geologic map of central Colorado in the Hayden geologic atlas differs moderately from Lakes’ map in the outline of the lacustrine formation, indicated as “Tertiary Green River.” Lakes’ map shows localized rock units at a large scale, indicating the lake deposits as “Miocene sediment.” It was the first map to depict details of the area’s rock units and paleogeomorphic features, which are labeled as granite, volcanic lavas, Miocene sediment, sedimentary deposits around granitic islands, and sediment around a granitic spur. The map shows the outline of the lacustrine unit closely demarcating the outline of the actual lake, including tributary inlets, with few subsequent structural complexities. This feature was substantiated by several geologic maps in the decades that followed. The map also documents several important cultural features, in particular the location of the house of homesteader Charlotte Hill, who is recognized as the collector of many fossil plant and insect specimens that Scudder and Lesquereux designated as type specimens for new species. Lakes’ “Miocene sediment” is now recognized as the upper Eocene Florissant Formation, which includes lacustrine and fluvial deposits largely of volcaniclastic origin. A large portion of the mapped area was designated as Florissant Fossil Beds National Monument in 1969.