Point Lookout Sandstone
{{Short description|Geological formation in New Mexico and Colorado}}
{{Infobox rockunit
| name = Point Lookout Sandstone
| image = Mesa Verde National Park Point Lookout 2006 09 11.jpg
| caption = Point Lookout, Mesa Verde National Park
| type = Formation
| age = {{Geological range|Upper Cretaceous}}
| period = Santonian
| prilithology = Sandstone
| otherlithology = Shale
| namedfor = Point Lookout
| namedby = A. J. Collier
| year_ts = 1919
| region = Paradox Basin, San Juan Basin
| country = United States
| coordinates = {{coord|37.316|N|108.419|W|display=inline|type:mountain}}
| unitof = Mesaverde Group
| subunits = Hosta Tongue
| underlies = Menefee Formation
| overlies = Crevasse Canyon Formation
| thickness = {{convert|300|feet|m|abbr=on}}
| extent =
| area =
| map ={{Location map+ | United States#Colorado
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | United States#Colorado
| lat_deg = 37.316
| lon_deg = -108.419
| mark = Lightgreen pog.svg
| marksize = 12
}}
}}
| map_caption =
}}
File:Strat section Mesa Verde.png of formations exposed at the surface, Mesa Verde National Park, Colorado (USGS).]]
The Point Lookout Sandstone is a Cretaceous bedrock formation occurring in New Mexico and Colorado.
Description
The formation consists of two informal members. The lower is a sequence of thinly bedded sandstone and shale,{{sfn|Lucas|Heckert|2005}} while the upper is a massive medium- to fine-grained cross-bedded sandstone, light gray to buff in color, that is a conspicuous cliff-forming unit.{{sfn|Lucas|Heckert|2005}}{{sfn|Cather|2010}} Maximum thickness is {{convert|131
|meters|feet|abbr=off}}.{{sfn|Lucas|Heckert|2005}}
The lower contact is placed at the first thin sandstone bed above the shale of the Mancos Shale. The formation is overlain by the Menefee Formation.{{sfn|Lucas|Heckert|2005}}
The Point Lookout Sandstone was deposited in the Cretaceous Interior Seaway, as part of a regressive sequence as the seaway was receding. It is transitional between the marine environment of the underlying Mancos and the coastal plain environment of the overlying Menefee Formation.
Fossils
Dinosaur remains are among the fossils that have been recovered from the formation, although none have yet been referred to a specific genus.{{sfn|Weishampel|Dodson|Osmólska|2004}}
The ammonite Clioscaphites vermiformis was identified in the formation.{{sfn|Tschudy|1976}}
Resource geology
Exposures of the Point Lookout Sandstone at Apache Mesa in New Mexico contain heavy mineral deposits, rich in titanium, zirconium, rare earth elements, and other valuable metals. However, the deposits are much too small to be economical to mine as of 2021. The deposits represent a beach placer deposit similar to ones seen in the southeastern U.S. Atlantic coast, southeastern Australia, and India.{{sfn|McLemore|2017}}
History of investigation
The sandstone was first described by A. J. Collier for exposures in cliffs at Point Lookout, in Mesa Verde National Park, Montezuma County, Colorado, in the Paradox Basin,{{sfn|Collier|1919}} and later described by Allen and Balk in 1954 as part of the Mesaverde Group in the San Juan Basin in New Mexico.{{sfn|Allen|Balk|1954}}
See also
{{Portal|Earth sciences|Paleontology|Dinosaurs||}}
Footnotes
{{Reflist}}
References
- {{cite journal |last1=Allen |first1=J.E. |last2=Balk |first2=Robert |year=1954 |title=Mineral Resources of Fort Defiance and Tohatchi quadrangles, Arizona and New Mexico |journal=New Mexico Bureau of Mines and Mineral Resources Bulletin |volume=36 |url=https://geoinfo.nmt.edu/publications/monographs/bulletins/36/ |access-date=25 March 2021}}
- {{cite journal |last1=Cather |first1=Steven |year=2010 |title=Preliminary geologic map of the San Lucas Dam quadrangle, McKinley County, New Mexico |journal=New Mexico Bureau of Geology and Mineral Resources, Open-File Geologic Map |volume=OF-GM 212 |url=http://geoinfo.nmt.edu/publications/maps/geologic/ofgm/details.cfml?Volume=212 |access-date=4 June 2020}}
- {{cite journal |last=Collier |first=A.J. |year=1919 |title=Coal south of Mancos, Montezuma County, Colorado |journal=Contributions to Economic Geology, 1918; Part 2, Mineral Fuels: U.S. Geological Survey Bulletin |volume=691-K |pages=K293–K310 |doi=10.3133/b691K|doi-access=free }}
- {{cite journal |last1=Lucas |first1=Spencer G. |last2=Heckert |first2=Andrew B. |title=Mesozoic stratigraphy at Durango, Colorado |journal=New Mexico Geological Society Field Conference Series |date=2005 |volume=56 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/56/56_p0160_p0169.pdf |access-date=8 June 2020}}
- {{cite journal |last1=McLemore |first1=V.T. |title=Heavy mineral, beach-placer sandstone deposits at Apache Mesa, Jicarilla Apache Reservation, Rio Arriba County, New Mexico |journal=New Mexico Geological Society Field Conference Series |date=2017 |volume=68 |pages=123–132 |url=https://nmgs.nmt.edu/publications/guidebooks/downloads/68/68_p0123_p0132.pdf |access-date=25 March 2021}}
- {{cite encyclopedia |last=Tschudy |first=R.H. |year=1976 |title=Palynology of Crevasse Canyon and Menefee Formation of San Juan basin, New Mexico |editor1-last=Beaumont |editor1-first=E.C. |editor2-last=Shomaker |editor2-first=J.W. |editor3-last=Stone |editor3-first=W.J. |encyclopedia=Guidebook to coal geology of northwest New Mexico: New Mexico Bureau of Mines and Mineral Resources Circular |volume=154 |pages=48–55 |url=https://geoinfo.nmt.edu/publications/monographs/circulars/downloads/154/Circular-154.pdf |access-date=25 March 2021}}
- {{cite book |last1=Weishampel |first1=David B. |last2=Dodson |first2=Peter |last3=Osmólska |first3=Halszka |year=2004 |title=The Dinosauria |edition=2nd |location=Berkeley |publisher=University of California Press |isbn=0-520-24209-2}}
Category:Geologic formations of Colorado
Category:Cretaceous formations of New Mexico