Hoback Formation

{{Short description|Geological formation in Wyoming}}

{{Infobox rockunit

| name = Hoback Formation

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| type = Formation

| age = Paleogene

| period = Paleogene

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| namedfor =Hoback River

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| region = Wyoming

| country = United States

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| underlies =Pass Peak Conglomerate

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| thickness =4572 m

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The Hoback Formation is a geologic formation in west-central Wyoming, located within the Hoback Basin (directly north of the Green River Basin). It formed as a result of increased sedimentation rates from the Laramide Orogeny{{Cite journal|last=Dorr|first=John|date=January 1962|title=Early Cenozoic stratigraphy and vertebrate paleontology of the Hoback Basin, Wyoming|journal=GSA Bulletin|volume=63|page=59|doi=10.1130/0016-7606(1952)63[59:ecsavp]2.0.co;2}} and preserves fossils dating back to the late Paleogene period, through the early Eocene.

The Hoback Formation was likely formed in a forested floodplain environment during a period of humid climate, as indicated by plentiful coal, carbonaceous shale, and fossilized plant remains. Many of the beds observed are dull in color, indicating that they formed in a reducing environment - another sign of a floodplain depositional environment, as standing water and waterlogged soil would be present for a substantial portion of the year. A prominent sandstone facies (with crossbedding, overbank deposits, and large pebbly deposits), thought to represent a large stream, is also present through much of the formation.{{Cite journal|last=Spearing|first=Darwin|date=1969|title=Stratigraphy and sedimentation of the Paleocene-Eocene Hoback Formation, Western Wyoming|url=http://www.netl.doe.gov/kmd/CDs/Disk7/disk2/WGS/Stratigraphy%20and%20Sedimentation%20of%20the%20Paleocene-Eocene%20Hobac.pdf|journal=Wyoming Geological Association Guidebook|access-date=2016-08-08|archive-date=2017-02-18|archive-url=https://web.archive.org/web/20170218042515/http://www.netl.doe.gov/kmd/CDs/Disk7/disk2/WGS/Stratigraphy%20and%20Sedimentation%20of%20the%20Paleocene-Eocene%20Hobac.pdf|url-status=dead}}

Fossils found within the Hoback Formation include bone fragments, turtles, larger mammals, molluscs, scales, fish teeth, and a wide variety of fossilized plant material (including fossilized wood). Signs of early Cenozoic crocodiles have also been found.