A Sequence Stratigraphic analysis of the Cedar Mountain Formation

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Brent Greenhalgh and Dr. Brooks Britt, Geology

The Cedar Mountain Formation (CMF) contains an abundance of Early Cretaceous dinosaur bone accumulations unrivaled in North America. The CMF also records the propagation of mountain building into western Utah tied to the Sevier fold and thrust belt. The fluvial nature of the CMF and its similarities to the underlying Morrison formation have made the details of its depositional history difficult to discern. Currently there is a great deal of controversy over the stratigraphic relationship between the members of the formation. The goal of my research was to better understand the complex sequence stratigraphy of the CMF.

This research project is currently in process, but preliminary results have confirmed that there is still much research to be done. Previous authors (Currie, 1997; Aubrey, 1996) have published sequence stratigraphic analyses for the CMF in the Uinta Mountains area.

Last summer, I spent time with my mentor working in the CMF in the Uinta Mountians. We quarried in the only CMF dinosaur quarry in Dinosaur National Monument. As part of the quarrying operation I measured a detailed stratigraphic section through the quarry. In addition I measured sections into Colorado and on the north slope of the Uinta Mountains. While measuring the section on the north slope of the Uinta mountains I discovered a new, partially articulated dinosaur. This discovery, tied with the measured section at the Dinosaur National Monument prompted the direction for my current research path.

In other fluvial successions vertebrate fossils have been found to correlate with significant stratigraphic surfaces, most of which represent periods of reduced sedimentation, or erosion (Straight & Eberth, 2002). These surfaces are critical to a sequence stratigraphic interpretation. Reading this literature prompted me to compare my measured sections with the sequence stratigraphic models proposed by the author’s previously mentioned. It became apparent that the previous authors models did not adequately explain the fossil occurrences (Figure 1).

The research I am now conducting is focused on whether bonebeds in the CMF correlate with significant surfaces. The goal of the research is to generate a sequence stratigraphic model for the CMF beyond the Uinta Mountains. I will be testing the utility of using fossil vertebrate remains to better understand the stratigraphy of the CMF in the Moab area. The Moab area is ideal for this type of study because of the abundance of vertebrate fossil localities and the outcrop exposures of the CMF. I anticipate that the fossil localities will correlate with significant stratigraphic surfaces in the area and that I will be able to generate a sequence stratigraphic models for the Moab area.

References

  • Aubrey, W.M., 1996, Stratigraphic architecture and deformational history of Early Cretaceous foreland basin, Eastern Utah and Southwestern Colorado, in Huffman, A.C. Jr., Lund, W.R., and Godwin, L.H., ed., Geological Resources of the Paradox Basin, Utah Geological Association Guidebook, v. 25, p. 211-220.
  • Currie, B.S., 1997, Sequence stratigraphy of nonmarine Jurassic-Cretaceous rocks, central Cordilleran foreland-basin system: Geological Society of America Bulletin, v. 109, p. 1206-1222.
  • Straight, W.H., and Eberth, D.A., 2002, Testing the utility of vertebrate remains in recognizing patterns in fluvial deposits: an example from the Lower Horseshoe Canyon Formation, Alberta: Palaios, v. 17, p. 472-490.

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