First Advisor

Richard E. Thoms

Term of Graduation

Summer 1976

Date of Publication


Document Type


Degree Name

Master of Science (M.S.) in Geology


Earth Science




Paleontology -- Oregon -- Grant County, Ammonoidea -- Oregon -- Grant County, Paleontology, Stratigraphic



Physical Description

1 online resource (x, 213 pages)


Using the standard Jurassic zonal scheme, this work attempts to determine the ages of the four members of the Snowshoe Formation that crop out in the Izee area. As a corollary, regional correlations are possible. The stratigraphic relationship between the Snowshoe Formation, the subjacent Hyde Formation and the superjacent Trowbridge Formation is also investigated.

Over one thousand fossils were collected from five stratigraphic sections and eight localities. The sections were measured using tape and compass techniques and the relative stratigraphic ranges of the fossils calculated using a computer program written specifically for this project. The ammonite fauna, dominated by the families Hildoceratidae, Stephanoceratidae and Sonniniidae, is systematically described.

The Snowshoe Formation was deposited in marine waters of neritic depths during late Toarcian to early Callovian time, with the Bathonian apparently unrepresented. The lower member correlates in part with the Weberg and Warm Springs Members of the Snowshoe Formation in the Suplee area whereas the middle and Silvies members correlate in part with the Basey Member. Most of the Snowshoe Formation has, or probably has, correlatives within the North American continent. The lower contact of the Snowshoe Formation in the Izee area is gradational and the basal deposits non-diachronous whereas the upper contact is either diachronous or represents an unconformity.


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