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The '''Lytle Formation''' or '''Lytle Sandstone''' is an Early [[Cretaceous]] geologic unit with its northern exposure running north and south within the [[Front Range|Front Range foothills]] and the [[Dakota Hogback]] in northern [[Colorado]] and southern [[Wyoming]] where it is assigned [[Formation (geology)|formation rank]] within the [[Dakota Formation|Dakota Group]]. In south-central Colorado, the Lytle is a [[Stratigraphic unit#Member|member]] of the [[Purgatoire Formation]]. The formation is also mapped in the valley of the [[Cimarron River (Arkansas River tributary)|Dry Cimarron]] in northeastern [[New Mexico]], where it forms a prominent band in the lower parts of the cliffs.<ref name="zeigler-etal-2019">{{cite journal |last1=Ziegler |first1=Kate E. |last2=Ramos |first2=Frank C. |last3=Zimmerer |first3=Matthew J. |title=Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary |journal=New Mexico Geological Society Field Conference Series |date=2019 |volume=70 |issue=4 |pages=47-54 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/70/70_p0047_p0054.pdf |accessdate=1 September 2020}}</ref>
The '''Lytle Formation''' or '''Lytle Sandstone''' is a [[geologic formation]] found in [[Wyoming]], [[Colorado]],<ref name="finlay-1916">{{cite journal |last1=Finlay |first1=G.I. |year=1916 |title=-Description of the Colorado Springs quadrangle, Colorado |journal=U.S. Geological Survey Geologic Atlas of the United States Folio |volume=203 |url=https://pubs.usgs.gov/gf/203/text.pdf |accessdate=2 September 2020}}</ref> and [[New Mexico]].<ref name="waage-1953">{{cite journal |last1=Waage |first1=Karl M. |title=Refractory clay deposits of south-central Colorado |journal=U.S. Geological Survey Bulletin |date=1953 |volume=993 |doi=10.3133/b993}}</ref>
==Description==
The Lytle Formation is an [[early Cretaceous]] geologic unit with its northern exposure running north and south within the [[Front Range|Front Range foothills]] and the [[Dakota Hogback]] in northern [[Colorado]] and southern [[Wyoming]] where it is assigned [[Formation (geology)|formation rank]] within the [[Dakota Formation|Dakota Group]]. In south-central Colorado, the Lytle is a [[Stratigraphic unit#Member|member]] of the [[Purgatoire Formation]]. The formation is also mapped in the valley of the [[Cimarron River (Arkansas River tributary)|Dry Cimarron]] in northeastern [[New Mexico]], where it forms a prominent band in the lower parts of the cliffs.<ref name="zeigler-etal-2019">{{cite journal |last1=Ziegler |first1=Kate E. |last2=Ramos |first2=Frank C. |last3=Zimmerer |first3=Matthew J. |title=Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary |journal=New Mexico Geological Society Field Conference Series |date=2019 |volume=70 |issue=4 |pages=47-54 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/70/70_p0047_p0054.pdf |accessdate=1 September 2020}}</ref>


The Lytle was the last (youngest) non-marine unit to form in the [[Denver Basin]] before the region was fully inundated by the [[Western Interior Seaway]]. It was formed above sea level from sediments carried by heavily laden rivers flowing from the eroding uplifts of the [[Sevier orogeny]] several tens of millions of years before the [[Rocky Mountains]] rose. It is particularly noted for abundant brown chert pebbles washed in from the uplifted [[Permian]] rock far to the west.<ref name= PhotojOver >{{cite web |author= Jeremy McCreary |title= Colorado Geology Photojournals - A Tribute to Colorado's Physical Past and Present - Colorado Geology Overview |website= cliffshade |url= http://www.cliffshade.com/colorado/geo_overview.htm |access-date= 2019-08-30 }}</ref><ref name= GeolexUnit>{{cite web | title = Geologic Unit: Lytle | series = Geolex — Unit References | work = National Geologic Database | publisher = United States Geological Survey | url = https://ngmdb.usgs.gov/Geolex/UnitRefs/LytleRefs_9132.html |access-date = 2019-08-30 }}</ref>
The Lytle was the last (youngest) non-marine unit to form in the [[Denver Basin]] before the region was fully inundated by the [[Western Interior Seaway]]. It was formed above sea level from sediments carried by heavily laden rivers flowing from the eroding uplifts of the [[Sevier orogeny]] several tens of millions of years before the [[Rocky Mountains]] rose. It is particularly noted for abundant brown chert pebbles washed in from the uplifted [[Permian]] rock far to the west.<ref name= PhotojOver >{{cite web |author= Jeremy McCreary |title= Colorado Geology Photojournals - A Tribute to Colorado's Physical Past and Present - Colorado Geology Overview |website= cliffshade |url= http://www.cliffshade.com/colorado/geo_overview.htm |access-date= 2019-08-30 }}</ref><ref name= GeolexUnit>{{cite web | title = Geologic Unit: Lytle | series = Geolex — Unit References | work = National Geologic Database | publisher = United States Geological Survey | url = https://ngmdb.usgs.gov/Geolex/UnitRefs/LytleRefs_9132.html |access-date = 2019-08-30 }}</ref>
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[[Detrital zircon geochronology]] of the Lytle Formation in the [[Raton Basin]] suggests a [[late Jurassic]] age for this unit. However, it is possible that the lack of younger zircons reflects a hiatus in deposition of airfall material.<ref>{{cite journal |last1=Bartnik |first1=Samantha R. |last2=Hampton |first2=Brian A. |last3=Mack |first3=Greg H. |title=U-Pb Detrital Geochronology and Provenance Comparisons from the Nonmarine Strata of the Dakota Group, Lytle Sandstone, and Morrison Formation in Northeastern New Mexico |journal=New Mexico Geological Society Field Conference Series |date=2019 |volume=70 |pages=55-65 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/70/70_p0055_p0065.pdf |accessdate=19 May 2020}}</ref>
[[Detrital zircon geochronology]] of the Lytle Formation in the [[Raton Basin]] suggests a [[late Jurassic]] age for this unit. However, it is possible that the lack of younger zircons reflects a hiatus in deposition of airfall material.<ref>{{cite journal |last1=Bartnik |first1=Samantha R. |last2=Hampton |first2=Brian A. |last3=Mack |first3=Greg H. |title=U-Pb Detrital Geochronology and Provenance Comparisons from the Nonmarine Strata of the Dakota Group, Lytle Sandstone, and Morrison Formation in Northeastern New Mexico |journal=New Mexico Geological Society Field Conference Series |date=2019 |volume=70 |pages=55-65 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/70/70_p0055_p0065.pdf |accessdate=19 May 2020}}</ref>


==Fossils==
Known fossils are fragments of [[petrified wood]] eroded from the west as well as nondescript animal burrows.<ref name= GeolexUnit/>
Known fossils are fragments of [[petrified wood]] eroded from the west as well as nondescript animal burrows.<ref name= GeolexUnit/>

==History of investigation==
The formation was first named as the Lytle sandstone member of the Purgatoire Formation by G.I. Finlay in 1916, for exposures near [[Lytle, Colorado]]. Finlay found no fossils in the unit, but regarded it as likely [[early Cretaceous]] in age.<ref name="finlay-1916"/> Waage subsequently traced the unit into northern Colorado and northeastern New Mexico.<ref name="waage-1953"/>


==References==
==References==

Revision as of 17:47, 2 September 2020

For the Permian unit of the same name, see Lytle Limestone member of the Arroyo Formation.
Lytle Formation
Lytle Sandstone
Stratigraphic range: Early Cretaceous
South Platte Formation over Lytle Formation at Dinosaur Ridge, Colorado
TypeFormation/Formation Member
Unit ofNorth-central CO:Dakota Group
South-central CO:Purgatoire Formation[1]
UnderliesSouth Platte Formation (at Dinosaur Ridge)
Glencairn Formation (valley of the Dry Cimarron)
OverliesMorrison Formation (unconformably)
Thickness40–120 feet (12–37 m)
Lithology
PrimarySandstone
Otherconglomeratic sandstone (notably chert gravel), variegated claystone[1]
Location
Coordinates38°36′09″N 104°52′04″W / 38.6025°N 104.867778°W / 38.6025; -104.867778
RegionColorado
New Mexico
CountryUnited States
Type section
Named forLytle, Colorado
Named byG.I. Finlay
Year defined1916
Lytle Formation is located in the United States
Lytle Formation
Lytle Formation (the United States)
Lytle Formation is located in New Mexico
Lytle Formation
Lytle Formation (New Mexico)

The Lytle Formation or Lytle Sandstone is a geologic formation found in Wyoming, Colorado,[2] and New Mexico.[3]

Description

The Lytle Formation is an early Cretaceous geologic unit with its northern exposure running north and south within the Front Range foothills and the Dakota Hogback in northern Colorado and southern Wyoming where it is assigned formation rank within the Dakota Group. In south-central Colorado, the Lytle is a member of the Purgatoire Formation. The formation is also mapped in the valley of the Dry Cimarron in northeastern New Mexico, where it forms a prominent band in the lower parts of the cliffs.[4]

The Lytle was the last (youngest) non-marine unit to form in the Denver Basin before the region was fully inundated by the Western Interior Seaway. It was formed above sea level from sediments carried by heavily laden rivers flowing from the eroding uplifts of the Sevier orogeny several tens of millions of years before the Rocky Mountains rose. It is particularly noted for abundant brown chert pebbles washed in from the uplifted Permian rock far to the west.[5][1]

Detrital zircon geochronology of the Lytle Formation in the Raton Basin suggests a late Jurassic age for this unit. However, it is possible that the lack of younger zircons reflects a hiatus in deposition of airfall material.[6]

Fossils

Known fossils are fragments of petrified wood eroded from the west as well as nondescript animal burrows.[1]

History of investigation

The formation was first named as the Lytle sandstone member of the Purgatoire Formation by G.I. Finlay in 1916, for exposures near Lytle, Colorado. Finlay found no fossils in the unit, but regarded it as likely early Cretaceous in age.[2] Waage subsequently traced the unit into northern Colorado and northeastern New Mexico.[3]

References

  1. ^ a b c d "Geologic Unit: Lytle". National Geologic Database. Geolex — Unit References. United States Geological Survey. Retrieved 2019-08-30.
  2. ^ a b Finlay, G.I. (1916). "-Description of the Colorado Springs quadrangle, Colorado" (PDF). U.S. Geological Survey Geologic Atlas of the United States Folio. 203. Retrieved 2 September 2020.
  3. ^ a b Waage, Karl M. (1953). "Refractory clay deposits of south-central Colorado". U.S. Geological Survey Bulletin. 993. doi:10.3133/b993.
  4. ^ Ziegler, Kate E.; Ramos, Frank C.; Zimmerer, Matthew J. (2019). "Geology of Northeastern New Mexico, union and Colfax Counties, New Mexico: A Geologic Summary" (PDF). New Mexico Geological Society Field Conference Series. 70 (4): 47–54. Retrieved 1 September 2020.
  5. ^ Jeremy McCreary. "Colorado Geology Photojournals - A Tribute to Colorado's Physical Past and Present - Colorado Geology Overview". cliffshade. Retrieved 2019-08-30.
  6. ^ Bartnik, Samantha R.; Hampton, Brian A.; Mack, Greg H. (2019). "U-Pb Detrital Geochronology and Provenance Comparisons from the Nonmarine Strata of the Dakota Group, Lytle Sandstone, and Morrison Formation in Northeastern New Mexico" (PDF). New Mexico Geological Society Field Conference Series. 70: 55–65. Retrieved 19 May 2020.

[[Category::Cretaceous formations of New Mexico]]

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