The Carlile Shale is a Turonian age Upper Cretaceous series shale geologic formation in the central-western United States, including in the Great Plains region of Colorado, Kansas, Nebraska, New Mexico, North Dakota, South Dakota, and Wyoming.[ USGS.gov: Mineral resources of the Niobrara and Carlile Formations]
History of investigation
The Carlile Shale was first named by Grove Karl Gilbert for exposures at Carlile Spring, located about west of Pueblo, Colorado. He described it as a medium gray shale, capped with limestone or sandstone, and assigned it to the Benton Group.
By 1931, William Walden Rubey and his coinvestigators had mapped it into
Kansas and the
Black Hills. Rubey also first assigned it to the Colorado Group.
C.H. Dane assigned it to the
Mancos Shale in
New Mexico in 1948.
Description
The formation is composed of marine deposits of the generally retreating phase (hemi-cycle) of the
Greenhorn cycle of the Western Interior Seaway, which followed the advancing phase of the same cycle that formed the underlying
Graneros Shale and Greenhorn Formation.
As such, the lithology progresses from open ocean chalky shale (with thin limestones) to increasing carbonaceous shale to near-shore sandstone.
Near the center of the seaway, currents in the remnant shallows sorted skeletal remains into a mass of calcareous sand. The contact between the Carlile Shale and the overlying Niobrara Formation is marked by an unconformity in much of the outcrop area, but where an unconformity is not discernible, the boundary is typically placed at the first resistant, fine-grained limestone bed at the base of the Niobrara Formation.
Gallery
Fossil content
Upper Turonian series
plesiosaur remains are among the
that have been recovered from the strata of its Blue Hill Shale Member in Kansas.
[ Jstor.org: "Probable plesiosaur remains from the Blue Hill Shale (Carlile Formation)" in Kansas", Kansas Academy of Science, 2009.] The Carlile in eastern South Dakota contains shark teeth, fossil wood and leaves, and ammonites.
[[3] William A. Cobban and E.A. Merewether (1983), Stratigraphy and paleontology of mid-Cretaceous rocks in Minnesota and contiguous areas. USGS Professional Paper 1253.]
Reptiles
Crocodyliforms
Plesiosaurs
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| Megacephalosaurus | M. eulerti | Near Fairport, Kansas. | Fairport Chalk Member. | A skull & anterior cervical material (FHSM VP-321). | A Pliosauridae. | |
| Plesiosauria | | Mitchell County, Kansas. | Blue Hill Member. | Portions of a rib (FHSM VP-17299). | May represent a large Elasmosauridae or Pliosauroidea. | |
|
Squamates
Fish
Cartilaginous fish
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|
|
| Cretodus | C. houghtonorum | North-central Kansas. | Blue Hill Shale. | A partial skeleton consisting of 134 disarticulated teeth, 61 vertebrae, 23 placoid scales, and fragments of calcified cartilage. | A Mackerel Shark. | |
| Cretoxyrhina | C. mantelli | Dixon County, Nebraska. | Fairport Chalky Shale Member. | A tooth (UNSM 129549). | A large Mackerel Shark. | |
| Ptychodus | P. latissimus | Kansas. | Codell Sandstone Member. | 3 teeth. | A Ptychodontidae. | |
| P. mammillaris | North of Schoenchen, Ellis County, Kansas. | Fairport Chalk Member. | A medial tooth (FHSM VP-15284). | A Ptychodontidae. | |
| P. sp. | Ellis County, Kansas. | Blue Hill Shale Member. | A tooth contained in a coprolite (FHSM VP-13325). | A Ptychodontidae. | |
|
See also
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Volcanic mineralization of the Greenhorn cycle:
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Bentonite, sedimentary volcanic ash (named for the original Graneros/Greenhorn/Carlile classification), generally showing some weathered iron stain in the Colorado Group
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Pyrite, precipitation of volcanic sulfuric acid with oceanic iron as FeS2
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Limonite, pyrite in limestone weathered to HFeO2 (Rust or yellow ochre)
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Selenite, CaSO4 associated with Bentonite seams and ochre
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Plesiosaur stratigraphic distribution
