Summerville Formation
{{Short description|Geologic formation in Four Corners region, US}}
{{Infobox rockunit
| name = Summerville Formation
| image = Summerville Formation type.jpg
| caption = Summerville Formation at the type locality at Summerville Point, east side of the San Rafael Swell, Emery County, Utah
| type = Geological formation
| age = Oxfordian
{{fossil range|161|151}}
| period = Oxfordian
| prilithology = Mudstone, sandstone
| otherlithology = Gypsum
| namedfor = Summerville Point, Emery County, Utah
| namedby = James Gilluly & J.B. Reeside Jr.
| year_ts = 1928
| region = Four Corners,
(Southwestern United States)
| country = United States
| coordinates = {{coord|39.216|N|110.544|W|display=inline,title}}
| paleocoordinates = {{coord|31.9|N|54.7|W|display=inline}}
| unitof = San Rafael Group
| subunits = Bluff Sandstone
| underlies = Morrison Formation
| overlies = Todilto & Curtis Formations
| thickness = {{convert|100|m|ft|abbr=on}}
| extent = Henry Mountains, Paradox Basin
| area =
| map = Summerville Formation map.jpg
| map_caption = Summerville Formation outcrops in Utah, Colorado and New Mexico
}}
The Summerville Formation is a geological formation in New Mexico, Colorado, and Utah of the Southwestern United States. It dates back to the Oxfordian stage of the Late Jurassic.Wilcox 2007
Description
The formation consists of up to {{convert|100|meters|ft}} of red mudstone, with thin interbeds of green and red sandstone. The lower portion of the formation shows polygonal desiccation cracks and localized salt-hopper casts while the upper portion contains considerable gypsum, consistent with deposition in a sabkha on the margin of the Sundance Sea.It is exposed in the San Rafael Reef, the Waterpocket Fold, in the Henry Mountains, with additional exposures scattered across the region from the San Rafael Reef to the Paradox Basin, and in north-central New Mexico. The thin bedding is characteristic throughout the formation, but gypsum is not found in the San Juan Basin and some conglomerate is found on the south and southwestern margins of the formation.Lucas and Anderson 1992, p.81 The correlation of late Jurassic beds in northwestern New Mexico with the Summerville Formation in Utah has been questioned, and it has been suggested that they be assigned to the Beclabito Formation instead.{{cite journal |last1=Cather |first1=Steven M. |title=Jurassic stratigraphic nomenclature for northwestern New Mexico |journal=New Mexico Geological Society Special Publication |date=2020 |volume=14 |pages=145–151 |url=https://nmgs.nmt.edu/publications/special/14/NMGS_SP-14.pdf |access-date=31 October 2020}}
The Summerville Formation rests conformably on the underlying Curtis Formation (Utah and western Colorado) or Todilto Formation (southwest Colorado and New Mexico) but is separated from the overlying Morrison Formation by the regional J5 unconformity. It thins significantly in the Moab-La Sal area, the likely area of the divide between the marine Curtis basin to the northwest and the salina lake Todilto basin to the southeast. Here the formation is just {{convert|1.2|meters|feet|abbr=off}} thick and rests directly on Entrada Sandstone. In many locations the Summerville is separated from the Morrison by eolian sandstones, such as the Bluff Sandstone, variously assigned to the Morrison Formation or the San Rafael Group. The Morrison Formation represents a return to more humid conditions with increased clastic input.Lucas and Anderson 1992, p.80
The Bell Ranch Formation of northeastern New Mexico is correlative with the Summerville Formation.Lucas and Anderson 1992
The Summerville Formation is interpreted as recording a regression of the Sundance Sea to the north, with simultaneous infilling of both the Curtis and Todilto basins. This produced a depositional environment of very low relief, in which occasional encroachments of eolian sand during times of drought were subsequently worked into thin strata by wave action in ephemeral saline lakes.
File:Summerville Formation west of Hanksville.jpg|Evenly bedded Summerville Formation exposed along Utah Highway 24, 2.4 miles west of Hanksville, Utah
File:Closeup of Summerville Formation.jpg|Closeup of the Summerville Formation showing even bedding, 2.4 miles west of Hanksville, Utah.
File:Summerville Formation gypsum cracks.jpg|Summerville Formation with gypsum-filled cracks. U.S. quarter dollar (24 mm) for scale
Fossil content
The formation is almost completely lacking in body fossils.Lucas and Anderson 1992, p.84 However, theropod tracks were found in the formation in Utah, New Mexico, and Colorado.Weishampel 2004
= Avemetatarsalians =
| class="wikitable sortable" | ||||||
| colspan="7" align="center" | Avemetatarsalians of the Summerville Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| style="background:#FEF6E4;" rowspan="2" | PteraichnusLockley et al. 2008
| style="background:#FEF6E4;" | P. saltwashensis | style="background:#FEF6E4;" | Arizona | style="background:#FEF6E4;" | | style="background:#FEF6E4;" | | style="background:#FEF6E4;" | Pterosaur trackways. Includes the P. saltwashensis type locale. Specimens housed at the University of Utah. These tracks may actually be from the Morrison Formation. | rowspan=2 | | ||||||
| style="background:#FEF6E4;" | Indeterminate
| style="background:#FEF6E4;" | Arizona, near Summerville Also present in Colorado (Cactus Park, Furnish Canyon, Colorado National Monument) and Utah (Delmonte Mines, Starr Springs, Flaming Gorge, Ferron, Moab, Duchesne County). | style="background:#FEF6E4;" | | style="background:#FEF6E4;" | | style="background:#FEF6E4;" | Summerville, Furnish Canyon, Cactus Park, Delmonte Mines, Starr Springs, Ferron, and Moab specimens are housed in the University of Colorado's Dinosaur Tracks Museum in Denver. The Flaming Gorge and Colorado National Monument tracks remains in the field. Ferron specimens are also housed at the University of Utah. |
{{paleobiota-key-compact}}
History of investigation
The formation was first defined in 1928 for exposures in the San Rafael Reef.Gilluly and Reeside, 1927 Similar beds in northeastern Arizona and the San Juan Basin are assigned to the Wanakah Formation,Condon et al. 1988 but continue to be assigned to the Summerville Formation in north-central New Mexico.Koning and Read 2010
See also
{{commons category|Summerville Formation}}
Footnotes
{{Reflist}}
References
- {{cite journal |last1=Condon |first1=Steven M. |last2=Huffman |first2=A.C. |last3=Peterson |first3=Fred |last4=Aubrey |first4=W.M. |title=Revisions to stratigraphic nomenclature of Jurassic and Cretaceous rocks of the Colorado Plateau |journal=USGS Bulletins |date=1988 |issue=1633- A-C |doi=10.3133/b1633AC |url=https://pubs.usgs.gov/bul/1633a-c/report.pdf |access-date=30 April 2020}}
- {{cite journal |last1=Gilluly |first1=James |last2=Reeside |first2=J.B. Jr. |title=Sedimentary rocks of the San Rafael Swell and some adjacent areas in eastern Utah |journal=U.S. Geological Survey Professional Paper |date=1927 |issue=150–D |pages=D61–D110 |url=https://pubs.usgs.gov/pp/0150d/report.pdf |access-date=25 May 2020}}
- {{cite journal |last1=Koning |first1=D.J. |last2=Read |first2=A.S. |title=Geologic map of the southern Espanola Basin |journal=New Mexico Bureau of Geology and Mineral Resources Open-File Reports |date=2010 |issue=531 |url=https://ngmdb.usgs.gov/Prodesc/proddesc_97004.htm |access-date=30 April 2020}}
- Lockley, M.; Harris, J.D.; and Mitchell, L. 2008. "A global overview of pterosaur ichnology: tracksite distribution in space and time." Zitteliana. B28. p. 187-198. {{ISSN|1612-4138}}.
- {{cite journal |last1=Lucas |first1=Spencer G. |last2=Anderson |first2=O.J. |title=The Middle Jurassic Summerville Formation, northern New Mexico |journal=New Mexico Geology |volume=14 |number=4 |date=November 1992 |url=https://geoinfo.nmt.edu/publications/periodicals/nmg/14/n4/nmg_v14_n4_p79.pdf |access-date=4 June 2020}}
- {{cite book |last1=Wilcox |first1=William Thomas |title=Sequence stratigraphy of the Curtis, Summerville and Stump Formations, Utah and Northwest Colorado (master's thesis) |date=2007 |publisher=Miami University |location=Oxford, Ohio |url=https://etd.ohiolink.edu/!etd.send_file?accession=miami1177422597&disposition=inline |access-date=30 April 2020}}
- Weishampel, David B; et al. (2004). "Dinosaur distribution (Middle Jurassic, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 537–538. {{ISBN|0-520-24209-2}}.
Category:Geologic formations of Arizona
Category:Geologic formations of Oklahoma
Category:Geologic formations of Colorado
Category:Geologic formations of Utah
Category:Jurassic formations of New Mexico
Category:Jurassic geology of Oklahoma
Category:Jurassic geology of Utah
Category:Mudstone formations of the United States
Category:Sandstone formations of the United States
Category:Ichnofossiliferous formations
Category:Paleontology in Arizona