During the summer of 1900, Elmer S. Riggs, assistant curator of paleontology at the Field Columbian Museum, Chicago (now the Field Museum of Natural History), and field assistants Harold W. Menke and Victor H. Barnett, excavated dinosaur fossils at four quarries between Grand Junction and Fruita, Colorado. These quarries included:

• Quarry No. 12 > No Thoroughfare Canyon
• Quarry No. 13 > Riggs Hill, 5 miles west of downtown Grand Junction
• Quarry No. 14 > North of the mouth of Wedding Canyon, 2 miles south of Fruita
• Quarry No. 15 > Dinosaur Hill located 1 mile south of Fruita

At Quarry No. 12 the coraco-scapula and other specimens of a herbivore dinosaur, Camarasaurus grandis, were recovered from the Brushy Basin Member of the Morrison Formation.

Site Geology

The Brushy Basin Member is the youngest and most widespread subunit of the Late Jurassic-age (approx. 145–155 Ma) Morrison Formation, characterized by brightly colored, thick bentonitic mudstones and sandstones. It represents a large, arid to semi-arid floodplain dotted with lakes, containing volcanic ash from distant western volcanoes.

Site Photos

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References

Chenowith, W.L., 1991, Guidebook for Dinosaur Quarries and Tracksites Tour, Western Colorado and Eastern Utah: Grand Junction Geological Society, pp 17-18. https://gjgs.org/ 

Lohman, S.W., 1981, The Geologic Story of Colorado National Monument: U.S. Geological Survey Bulletin 1508, xii, 142 p., https://doi.org/10.3133/b1508 

Lull, R. S, 1930, Skeleton of Camarasaurus lentus recently mounted at Yale: American Journal of Science, 5 (109), pp. 1-5. https://doi.org/10.2475/ajs.s5-19.109.1

Menke, H. W., 1900, Field Columbia Museum (Field Museum of Natural History, Chicago), Department of Geology: Photo Archives. https://dams.fieldmuseum.tech/portals/museum-media/ 

Riggs, Elmer S., 1901, The Forelimb and Pectoral Girdle of Camarasaurus (Morosaurus): Field Columbian Museum Publication 63, Vol. 1 No. 10, pp. 274-287.

Scotese, C.R., Vérard, C., Burgener, L., Elling, R. P., and Kocsis, A.T., 2025, Phanerozoic-scope supplementary material to “The Cretaceous World Plate Tectonics, Paleogeography, and Paleoclimate” from the PALEOMAP project: London Geological Society Special Publications Vol. 544, pp. 31-202. https://doi.org/10.1144/SP544-2024-28  

Torcida Fernández-Baldor, F., Díaz-Martínez, I., Huerta, P. et al., 2021, Enigmatic tracks of solitary sauropods roaming an extensive lacustrine megatracksite in Iberia: Scientific Reports No. 11 Article 16939. https://doi.org/10.1038/s41598-021-95675-3  

Walters, B. and Kissinger, T., National Park Service (NPS), 2025, Camarasaurus lentushttps://www.nps.gov/dino/learn/nature/camarasaurus-lentus.htm