{{Short description|Geologic formation in the United States}} {{Infobox rockunit | name = Pinkerton Trail Formation | image = | caption = | type = Formation | period = Carboniferous | age = {{Geological range|Moscovian}} | prilithology = Limestone | otherlithology = Shale | namedfor = Pinkerton Trail | namedby = Wengerd and Strickland | year_ts = 1954 | region = Four Corners | country = United States | coordinates = {{coord|37.456|-107.804}} | unitof = Hermosa Group | subunits = | underlies = Paradox Formation | overlies = Molas Formation | thickness = {{convert|600|feet||order=flip|abbr=on}} | extent = | area = | map = {{Location map+ | United States#Colorado | relief = 1 | width = 250 | float = center | places = {{Location map~ | United States#Colorado | lat_deg = 37.456 | lon_deg = -107.804 | mark = Green pog.svg | marksize = 12 }} }} | map_caption = }}
The '''Pinkerton Trail Formation''' is a geologic formation that is found in the Four Corners region of the United States. It contains fossils characteristic of the Atokan and Desmoinesian Ages of the Pennsylvanian.
==Description== The Pinkerton Trail Formation is the lowest member of the Hermosa Group, a group of geological formations deposited in the interior and margins of the Paradox basin during the Pennsylvanian. The Pinkerton Trail Formation consists of gray limestone with occasional beds of black shale. North of Durango, it contains significant clastic sediments. It rests on the Molas Formation and is overlain by the Paradox Formation.<ref name=Condon1992>{{cite journal |last1=Condon |first1=Steven M. |title=Geologic framework of pre-Cretaceous rocks in the Southern Ute Indian Reservation and adjacent areas, southwestern Colorado and northwestern New Mexico |journal=U.S. Geological Survey Professional Paper |series=Professional Paper |date=1992 |volume=1505-A |doi=10.3133/pp1505A |page=A22-A23|doi-access=free }}</ref> Its thickness is up to {{convert|600|ft||sp=us}} in the subsurface.<ref name=baars_etal>{{cite journal |last1=Baars |first1=D.L. |last2=Parker |first2=J. Wm. |last3=Chronic |first3=John |title=Revised Stratigraphic Nomenclature of Pennsylvanian System, Paradox Basin |journal=AAPG Bulletin |date=1967 |volume=51 |issue=3 |pages=393–403 |url=https://archives.datapages.com/data/bulletns/1965-67/data/pg/0051/0003/0350/0393.htm |access-date=27 July 2021}}</ref>
The formation is exposed in the Durango, Colorado area and is present in the subsurface in the San Juan basin<ref name=Condon1992/> and the Paradox basin.<ref>{{cite journal |last1=Thomaidis |first1=Nick |title=Stratigraphy and Oil and Gas Production of Southeast Utah |journal=Oil and Gas Fields of the Four Corners Area |date=1978 |volume=I-II |pages=62–64 |url=https://archives.datapages.com/data/fcgs/data/014a/014001/62_four-corners140062.htm |access-date=27 July 2021}}</ref> It was deposited by the advance of the sea (a ''transgression'') over the region, which deposited limestone atop the continental sediments of the Molas Formation.<ref name=Condon1992/>
==Fossils== The formation is fossiliferous, containing crinoids and fusulinids that place its age in the Atokan to Desmoinesian Ages of the Pennsylvanian.<ref name=Condon1992/>
==History of investigation== The formation was first designated by Sherman Wengerd and John Strickland in 1954 as part of their work raising the Hermosa Formation to group stratigraphic rank. It was named for exposures at the Pinkerton Trail, about {{convert|12|mi||sp=us}} north of Durango, Colorado.<ref>{{cite journal |last1=Wengerd |first1=Sherman A. |last2=Strickland |first2=John W. |title=Pennsylvanian Stratigraphy of Paradox Salt Basin, Four Corners Region, Colorado and Utah |journal=AAPG Bulletin |date=1954 |volume=38 |doi=10.1306/5CEAE07C-16BB-11D7-8645000102C1865D}}</ref> Baars, Parker, and Chronic proposed a subsurface reference section in 1967 in the Paradox basin.<ref name=baars_etal/>
==References== {{Reflist}}
Category:Carboniferous Colorado Category:Carboniferous southern paleotropical deposits Category:Limestone formations of the United States Category:Shale formations of the United States Category:Geologic formations of Colorado