Todilto Formation

Luciano Mesa Member near Abiquiu, New Mexico

The formation consists of evaporites. It is divided into a lower calcareous shale (the Luciano Mesa Member) up to 6 meters (20 feet) thick, and an upper gypsum bed (the Tonque Arroyo Member).[1][2]

Based on varve counts in the Luciano Mesa Member, the formation was laid down in a geologically brief period of time,[3] likely in a salina (a coastal body of saline water) that was replenished both by rivers and by seepage or periodic flooding from the Sundance Sea.[2] The varves show a 10 to 13 year periodicity that is interpreted as the solar sunspot cycle, showing that this cycle has existed for at least 160 million years.[3] The contact with the underlying Entrada Formation is very sharp and may indicate the Todilto Sea formed catastrophically from a breach in a barrier between the basin and the Sundance Sea.[4] The presence of dasyclad algae in the Luciano Mesa Member indicates at least some marine flooding.[5]

Dasyclad algae have been found in the Luciano Mesa Member. Evidence has been found for stromatolites in the formation near Mesa Montañosa 35.3806°N 107.8763°W / 35.3806; -107.8763.[6]

The formation is mined for gypsum in the northern Albuquerque Basin, including along the La Bajada escarpment south of I-25, near San Felipe Pueblo, and at White Mesa near San Ysidro.[7] It has also yielded uranium ore.[8]

The formation was first described by H.E. Gregory in 1917 for exposures at Todilto Park in the San Juan Basin. He assigned it to his (now defunct) La Plata Group.[9] It has sometimes been included in the Morrison Formation.[10]

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

• Anderson, Roger Y.; Kirkland, Douglas W. (1960). "Origin, Varves, and Cycles of Jurassic Todilto Formation, New Mexico". AAPG Bulletin. 44. doi:10.1306/0BDA5F75-16BD-11D7-8645000102C1865D.
• Ahmed Benan, Cheikh A.; Kocurek, Gary (December 2000). "Catastrophic flooding of an aeolian dune field: Jurassic Entrada and Todilto Formations, Ghost Ranch, New Mexico, USA". Sedimentology. 47 (6): 1069–1080. doi:10.1046/j.1365-3091.2000.00341.x.
• Gregory, H.E. (1917). "Geology of the Navajo country; a reconnaissance of parts of Arizona, New Mexico, and Utah". U.S. Geological Survey Professional Paper. Professional Paper. 93. doi:10.3133/pp93. Retrieved 16 September 2020.
• Gabelman, John W.; Boyer, W.H. (April 1988). "Uranium deposits in Todilto limestone, New Mexico: The Barbara "J" No. 1 mine". Ore Geology Reviews. 3 (1–3): 241–276. doi:10.1016/0169-1368(88)90021-2.
• Kirkland, D.W.; Denison, R.E.; Evans, R. (1995). "Middle Jurassic Todilto Formation of northern New Mexico and southwestern Colorado: Marine or nonmarine?" (PDF). New Mexico Bureau of Mines & Mineral Resources Bulletins (147). Retrieved 29 April 2020.
• Lucas, Spencer G.; Anderson, O.J. (November 1992). "The Middle Jurassic Summerville Formation, northern New Mexico" (PDF). New Mexico Geology. 14 (4). Retrieved 4 June 2020.
• Lucas, Spencer G.; Anderson, Orin J. (2000). Gierlowski-Kordesch, Elizabeth H.; Kelts, Kerry R. (eds.). "The Todilto Salina Basin, Middle Jurassic of the U.S. Southwest". AAPG Studies in Geology. 46: 153–158. Retrieved 29 April 2020.
• Ulmer-Scholle, Dana S. (2005). "STROMATOLITES IN THE TODILTO FORMATION?" (PDF). New Mexico Geological Society Field Conference Series. 56: 380–388. Retrieved 18 April 2020.
• Weber, Robert H; Kottlowski, Frank E. (1958). "Gypsum resources of New Mexico" (PDF). New Mexico Bureau of Mines and Mineral Resources Bulletin. 68. Retrieved 5 December 2020.
• Wood, G.H.; Northrop, S.A. (1946). "Geology of Nacimiento Mountains, San Pedro Mountain, and adjacent plateaus in parts of Sandoval and Rio Arriba Counties, New Mexico". U.S. Geological Survey Oil and Gas Investigations Preliminary Map. OM-57. doi:10.3133/om57.