Master of Science in Geoscience
First Committee Member
S. M. Rowland, Chair
Second Committee Member
F. W. Bachhuber,
Third Committee Member
D. L. Weide
Graduate Faculty Representative
J. B. Case
Number of Pages
The Opd Unit of the Pogonip Group is a slope-forming carbonate sequence that crops out in the Arrow Canyon Range 75 miles north of Las Vegas, Nevada. It is composed mainly of grainstones, packstones, and intraformational conglomerates and also contains Calathium-bearing bioherms composed dominantly of wackestones. These rocks were deposited in a shallow-water, high-energy, subtidal, tropical marine environment. Nuia and Nuia-crinoid shoals developed on this shallow ramp and the area was frequently disturbed by storms.
Calathium-dominated carbonate mudmounds emerged on the Nuia and Nuia-crinoid shoals. Although Calathium dominated the mounds on a macroscopic scale, the mounds were build by unpreserved microorganisms. Calathium simply lived in the mounds and may have acted as sediment bafflers. Other mound dwellers included trilobites, crinoids, gastropods, nautiloids, brachiopods, and bryozoa.
The bioherms of the Opd Unit represent the transition from bioconstructions dominated by microorganisms during the Middle and Late Cambrian to those dominated by sessile benthonic macroorganisms during the Middle Ordovician.
Carbonate rocks; Nevada – Arrow Canyon; Ordovician Geologic Period; Paleoecology; Sedimentation and deposition
Geology | Paleontology | Sedimentology
Donovan, Jeffrey K., "Depositional Environments and Paleoecology of the Lower Ordovician Pogonip Group, Opd Unit, Arrow Canyon Range, Clark County, Nevada" (1992). UNLV Theses, Dissertations, Professional Papers, and Capstones. 1116.