The first stratigraphic analysis of what was to become the Morrison Formation was executed in 1873 by Arch. Marvine who measured section along Bear Creek Canyon, from the Precambrian metamorphics in the west to the Cretaceous strata in the east, (Hayden 1874). Published in F. V. Hayden’s monograph on the geology of western states and territories in 1874, Marvine’s section was the first survey of the local Jurassic rock.
The name paleontologist O.C. Marsh and others used to describe the Front Range rock unit, the “Atlantosaurus Beds,” did not satisfy the requirements for a rock unit so G. H. Eldridge named the Jurassic strata of the Dakota Hogback the “Morrison Formation” in 1896 (Eldridge 1896). The location of the original type section near Bear Creek seemed obscure, and Waldschmidt and LeRoy designated a new type section of the Morrison Formation in 1944, at the Alameda road cut over the Dakota Hogback, (Waldschmidt and LeRoy, 1944).
In 2001 Houck, suggested moving the type locality of the Morrison Formation once more to the I-70 road cut through the hogback, approximately 1.5 miles to the north, (Houck 2001).
All together, these workers have provided a framework for understanding the type area of the Morrison Formation, along a stretch of the Dakota Hogback now known as Dinosaur Ridge.
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The section of the Dakota Hogback known as "Dinosaur Ridge." Photo copyright MNHM / M. T. Mossbrucker |
Questions that still need resolution include the stratigraphic relationship between the major historic dinosaur quarries: are they synchronous or even isochronous as Lakes suggested, or diachronous as Turner and Peterson found the northern quarries, 1, 8, and 5, in relation to the only southern major site, Quarry 10, (Turner and Peterson, 1999). |
Morrison Natural History Museum Research Associate Bryan Turner has planned a project that will hopefully shed light upon this mystery.
In early 1877 H. C. Beckwith, accompanied by Arthur Lakes, discovered the first dinosaur remains from what would be called the Morrison Formation, north of Morrison, Colorado (Kohl and McIntosh, 1997). Beckwith left excavations almost as soon as they began, leaving Lakes to excavate the fossils, which were sent to O.C. Marsh at Yale College’s Peabody Museum of Natural History, (Kohl and McIntosh, 1997). Over the next two years, Lakes and his crew of former students and townsmen uncovered two species which have become icons of the Jurassic - the peculiarly armored herbivore Stegosaurus, distinguished by its tall triangular plates, and the long-necked, robust sauropod Apatosaurus.
Nota Bene:
This is a modified excerpt from M.T. Mossbrucker and R.T. Bakker "A Guide to the Paleontology of the Upper Jurassic Morrison Formation of Morrison, Colorado: New Interpretations and Discoveries." Bulletin of the Morrison Natural History Museum, Volume 1, page 2.
Acknowledgement: Thanks to Bryan Turner for his editorial skill.
References:
Eldridge, G.H., 1896, Mesozoic geology, IN Geology of the Denver basin in Colorado: U.S. Geological Survey Monograph, 27, p. 51-151.
Hayden, F. V. 1874. Annual Report of the United States Geological and Geographical Survey of the Territories, Embracing Colorado. Annual Report of the United States Geological and Geographical Survey, plate I.
Kohl, M. and McIntosh J. S. (Eds.), 1997, Discovering Dinosaurs in the Old West: The Field Journals of Arthur Lakes. Washington D.C., Smithsonian Institution Press.
Turner, C.E., and Peterson, Fred 1999. Biostratigraphy of Dinosaurs in the Upper Jurassic Morrison Formation of the Western Interior, U.S.A. in Gillette, David, editor, Vertebrate Paleontology in Utah: Miscellaneous Publication 99-1, Utah Geologic Survey, p. 77-102.
Waldschmidt, W.A. and LeRoy, L.W., 1944, Reconsideration of the Morrison formation in the type area, Jefferson County, Colorado: Geological Society of America Bulletin, v. 55, no. 9, p. 1097-1114.
