GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 97-3
Presentation Time: 8:50 AM


MORRIS, Hunter W., SCHUBERT, Thomas Orion and HARTMAN, Joseph H., Harold Hamm School of Geology & Geological Engineering, University of North Dakota, 81 Cornell Street Stop 8358, Grand Forks, ND 58202

A Sed/Strat classroom exercise (UND Geol 411) was devised to practice standard clastic observations and to carry lab results into a field activity. The samples used were collected by C.M. Hines on Friday, September 16, 1859, on “Clear Fork of the Powder river.” Hines reported “At various points along this stream we found large masses of fossil shells, specimens of which were procured.” The National Museum of Natural History (NMNH) Paleobiology ledger (USNM-PAL 1970–1972) records by F.B. Meek’s hand on May 14, 1862: “Clear Fork” [now Clear Creek]. F.V. Hayden (collector) under W.F. Raynolds. At this time, however, the Raynolds–Hayden train crossed the headwaters of Clear Creek, while Hines went down Clear Creek valley with the H.E. Maynadier command. Hines' procurement (USNM 1972) is represented by fossils (“Viviparus leai”) in matrix. Antebellum fossil specimens (in NMNH collections) are rarely associated with matrix or described in a sedimentary context. Relocating antebellum type locality from a generalized locality description (e.g., “Clear fork” = L2172–L2175) can prove difficult. The ascribed “Fort Union–Lignite Tertiary” “age” can be revised to the early Eocene “Wasatch” Formation based on fossil content and location.

The classroom exercise is divided into field and lab observations. The two available USNM 1972 (L2175) samples weighing 163 and 49 g, respectively (Block 1, 2). The blocks vary in value and chroma with a hue of 10YR (shells – pale yellowish brown, grayish orange, very pale orange, dark yellowish orange; fresh matrix – grayish orange; weathered matrix – pale yellowish brown, moderate yellowish brown, dark yellowish brown). Fresh sediment is slightly HCl-reactive on fresh grains and less so reactive on iron-impregnated weathered surfaces. Hand sample observation: Relatively well-lithified, iron-stained, fossiliferous, subangular, moderately sorted, slightly calcareous, fine-grained quartz sandstone. Gains observed and measured under microscope confirm “field” observations. A silty fine-grained sandstone was derived by Ro-Tap. An SEM elemental analysis indicates the abundance of quartz, with goethite, calcite, and minor percentage clays (e.g., illite). The next step is for students to examine (this summer) outcrops along Clear Creek near Buffalo, Wyoming, in search of a fossiliferous, fairly resistant channelform sandstone as described.