Fox Hills Formation
| Fox Hills Formation | |
|---|---|
| Stratigraphic range: Late Cretaceous, | |
A ridge capped by a sandstone bed of the Fox Hills Formation west of Limon, Colorado | |
| Type | Geological formation |
| Unit of | Montana Group (MT, ND) |
| Sub-units | Fairpoint member (SD), Trail City member (ND, SD), Timber Lake (ND, SD), Lincoln member (CO), etc. |
| Underlies | Lance (WY)/Hell Creek (MT)[1] Laramie Formation (CO) |
| Overlies | Pierre (USA)/Bearpaw (CAN)[1] Lewis Shale (WY, MT)[1] |
| Thickness | 75-225 feet |
| Lithology | |
| Primary | Sandstone |
| Other | Shale |
| Location | |
| Region | Alberta, Colorado, Montana, North Dakota, South Dakota and Wyoming |
| Country | United States/Canada |
| Type section | |
| Named for | Fox Hills between Cheyenne and Moreau Rivers, South Dakota |
| Named by | Meek and Hayden[1] |
| Year defined | 1862[1] |
The Fox Hills Formation is a Cretaceous geologic formation in the northwestern Great Plains of North America. It is present from Alberta on the north to Colorado in the south.
Fossil remains of dinosaurs, including tyrannosaurs, as well as large marine reptiles, such as mosasaurs, have been recovered from the formation.[2]
Lithology
The Fox Hills Formation consists of marginal marine yellow to grey sandstone with shale interbeds.[1][3] It was deposited as a regressive sequence of barrier islands during the retreat of the Western Interior Seaway in Late Cretaceous time. [4] In its eastern extent, the formation is underlain by the marine Pierre Shale in the United States and by the equivalent Bearpaw Formation in Canada, while in western ranges in Montana and Wyoming it overlies the Lewis Shale. The Fox Hills is overlain by continental sediments of the Laramie Formation in Colorado and the Lance Formation in Wyoming, the latter being the equivalent of the overlying Hell Creek Formation in Montana.[1]
Fossil content
Plants
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Taxa | Species | Locality | Material | Notes | Images |
|---|---|---|---|---|---|
| Marmarthia | M. johnsonii | Belongs to Lauraceae, similar to Lindera.[5] | |||
| Mesocyparis | M. borealis | Belongs to Cupressaceae, similar to Thuja.[5] | |||
| Nilssoniocladus | N. comtula | A Cycaceoid.[5] | |||
| N. yukonensis | [5] | ||||
| Paloreodoxites | P. plicatus | Incertae sedis, a palm-like monocot. | |||
| Rhamnus | R. salicifolius | Similar to R. caroliniana.[5] | |||
| Zingiberopsis | Z. magnifolia | Belongs to Zingiberaceae, related to Alpinia.[5] | |||
| Cornus | C.sp | A Dogwood.[5] | |||
| Cercidiphyllum | C.ellipticum | A katsura.[5] | |||
| Asimina | A.knowltonia | A pawpaw.[5] | |||
| Paranymphaea | P.hastata | A water lily.[5] | |||
| Platanites | P.marginata | A sycamore (plane tree). | |||
| Metasequoia | M.sp | A Dawn redwood.[5] | |||
| Glyptostrobus | G.sp | A Swamp Cypress.[5] | |||
| Taxodium | T.olrikii | A bald cypress, also found in Hell Creek.[5][6] | |||
| Osmunda | O.hollicki | A royal fern.[5] |
Mollusks
Color key
|
Notes Uncertain or tentative taxa are in small text; |
| Taxa | Species | Locality | Material | Notes | Images |
|---|---|---|---|---|---|
| Palaeocypraea[7] | P.squyeri |
See also
References
- ^ a b c d e f g "Geologic Unit: Fox Hills". National Geologic Database. Geolex — Significant Publications. United States Geological Survey. Retrieved 2017-02-13.
- ^ Getman, Myron RC (1994). "Occurrences of Mosasaur and other reptilian fossil remains from the Fox Hills Formation (Maastrichtian: late Cretaceous) of North Dakota" (Document). St. Lawrence University Dept. of Geology theses.
- ^ Lexicon of Canadian Geologic Units. "Fox Hills Formation". Retrieved 2010-02-01.
{{cite web}}: CS1 maint: deprecated archival service (link) - ^ Henry W. Roehler (1993). "Stratigraphy of the Upper Cretaceous Fox Hills Sandstone and Adjacent Parts of the Lewis Shale and Lance Formation, East Flank of the Rock Springs Uplift, Southwest Wyoming" (PDF). U.S. Geological Survey Professional Paper (1532). Washington: United States Government Printing Office: 6. Bibcode:1993usgs.rept....6R. doi:10.3133/pp1532. Retrieved 2026-01-12.
The shorelines of the Fox Hills Sandstone were deposited as chains of barrier islands. The [west shore] barrier islands are as much as 7 miles long and consist of mostly lower, middle, and upper shore-face sandstone lithofacies.
- ^ a b c d e f g h i j k l m n Peppe, Daniel J.; Erickson, J. Mark; Hickey, Leo J. (May 2007). "Fossil leaf species from the Fox Hills Formation (Upper Cretaceous: North Dakota, USA) and their paleogeographic significance". Journal of Paleontology. 81 (3): 550–567. Bibcode:2007JPal...81..550P. doi:10.1666/05067.1. ISSN 0022-3360.
- ^ Johnson, Kirk R. (2002), "Megaflora of the Hell Creek and lower Fort Union Formations in the western Dakotas: Vegetational response to climate change, the Cretaceous-Tertiary boundary event, and rapid marine transgression", The Hell Creek Formation and the Cretaceous-Tertiary boundary in the northern Great Plains: An Integrated continental record of the end of the Cretaceous, Geological Society of America, doi:10.1130/0-8137-2361-2.329, ISBN 978-0-8137-2361-7, retrieved 2026-03-16
{{citation}}: CS1 maint: work parameter with ISBN (link) - ^ "Near Mingusville (now Wibaux) (Cretaceous of the United States)". PBDB.org.