Kelly Limestone

Kelly Limestone
Stratigraphic range: Tournaisian–Visean PreꞒ Ꞓ O S D C P T J K Pg N
Type	Formation
Sub-units	Ladron Member Calosa Member
Underlies	Sandia Formation
Overlies	Basement rock
Thickness	30 m (98 ft)
Lithology
Primary	Limestone
Location
Coordinates	34.090°N 107.196°W / 34.090; -107.196
Region	New Mexico
Country	United States
Type section
Named for	Kelly, New Mexico
Named by	C.L. Herrick
Year defined	1904
Kelly Limestone (the United States) Show map of the United States Kelly Limestone (New Mexico) Show map of New Mexico

The Kelly Limestone is a geologic formation in New Mexico, United States. Its fossil assemblage is characteristic of the Early to Middle Mississippian.^[1]

Description

The Kelly Limestone consists of approximately 30 meters (98 ft) of marine limestone.^[1] It is found in the Lemitar, Ladron, and Magdalena Mountains of west-central New Mexico, US.^[2] The formation rests on Precambrian basement rock and is overlain by the Sandia Formation. The Kelly Limestone is divided into a lower Calosa Member and an upper Ladron Member, which are separated by an unconformity.^[1]

The Kelly Limestone likely correlates with the Arroyo Penasco Group in northern New Mexico and the Leadville Limestone of Colorado.^[1] These were deposited in a major marine transgression (advance of the ocean across the continent) in the Mississippian.^[2]

Fossil content

The formation contains fossil conodonts indicating that it ranges from Tournaisian to Visean (Early to Middle Mississippian) in age.^[1]

The lower Caloso Member contains fossils of the brachiopods Beecheria chouteauensis and Spirifer centronatus and the fusulinids Latiendothyra, Medioendothyra, and Tuberendothyra. The upper Ladron Member contains a diverse fossil assemblage, including brachiopods such as Rhipidomella and Linoproductus, blastoid echinoderms such as Pentremites conoideus, cnidarians such as Zaphriphyllum casteri, and numerous species of microscopic algae and foraminiferans.^[2]

Economic resources

The Kelly Limestone was the principal ore-bearing formation of the historic Magdalena, New Mexico mining district. The ore takes the form of replacement deposits in the limestone produced by nearby igneous intrusions.^[3] The best ore was found in the so-called "silver pipes" beds, which were dense dolomitic limestone contrasting with the high-calcium limestone making up most of the rest of the formation.^[4]

History of investigation

The formation was first named as the Graphic-Kelly Formation by C.L. Herrick in 1904 for exposures near the mining town of Kelly, New Mexico.^[5] The hyphenated name was found objectionable, and the formation was renamed as the Kelly Limestone by C.H. Gordon in 1907.^[6] In 1976, A.K. Armstrong and B.L. Mamet divided the formation into the Caloso and Ladron Members.^[2]

See also

• List of fossiliferous stratigraphic units in New Mexico
• Paleontology in New Mexico

References

1. Armstrong, A.K.; Mamet, B.L.; Repetski, J.E. (1992). "Stratigraphy of the Mississippian System, south-central Colorado and north-central New Mexico". U.S. Geological Survey Bulletin. 1787-EE. doi:10.3133/b1787EE.
2. Armstrong, A.K.; Mamet, B.L. (1976). "Biostratigraphy and regional relations of the Mississippian Leadville limestone in the San Juan Mountains, southwestern Colorado". U.S. Geological Survey Professional Paper. Professional Paper. 985. doi:10.3133/pp985.
3. Loughlin, G.F.; Koschmann, A.H. (1942). "Geology and ore deposits of the Magdalena mining district, New Mexico". U.S. Geological Survey Professional Paper. 200. doi:10.3133/pp200. hdl:2027/mdp.39015080069993.
4. Loughlin & Koschmann 1942, p. 16.
5. Herrick, C.L. (1904). "Laws of formation of New Mexico mountain ranges". American Geologist. 33 (5): 301–312. Retrieved January 11, 2022.
6. Gordon, C.H. (1907). "Mississippian (Lower Carboniferous) formations in the Rio Grande Valley, New Mexico". American Journal of Science. 4. 24 (139): 58–64. Bibcode:1907AmJS...24...58G. doi:10.2475/ajs.s4-24.139.58. Retrieved January 11, 2022.