The Alder Group is a group of geologic formations exposed in the Mazatzal Mountains of central Arizona, US.[1] It dates to the Statherian Period of the Paleoproterozoic and records mountain-building events associated with the assembly of North America.

Alder Group
Stratigraphic range: 1720–1700 Ma
TypeGroup
Unit ofTonto Basin Supergroup
Sub-unitsBoard Canyon Formation
Houdon Formation
Flying W Formation
Breadpan Formation
UnderliesRed Rock Group
OverliesEast Verde River Formation
Thickness3,000 meters (9,800 ft)
Lithology
Primarymetasedimentary rock, metavolcanic rock
Location
Coordinates33°36′N 111°19′W / 33.60°N 111.32°W / 33.60; -111.32
RegionArizona
CountryUnited States
Type section
Named forAlder Creek, Arizona
Named byE.D. Wilson
Year defined1939
Alder Group is located in the United States
Alder Group
Alder Group (the United States)
Alder Group is located in Arizona
Alder Group
Alder Group (Arizona)

Description

edit

The formation consists of about 3,000 feet (910 m) of metavolcanic and metasedimentary rock[1] exposed in the Mazatzal Mountains.[2] The formation is underlain by the East Verde River Formation and overlain by the Red Rock Group. Together with the younger Mazatzal Group, these groups form the Tonto Basin Supergroup. The formation is mostly volcanic and volcaniclastic sedimentary rock, but with some sedimentary beds formed by weathering of continental rock (terrigenous beds). All have experienced metamorphism. The Alder Group is interpreted as basin fill of an intra-arc basin that formed along what was then the southern coast of Laurentia, the ancient core of North America.[1]

Formations

edit

The formation is divided (in ascending stratigraphic order) into the Breadpan, Flying W, Houdon, and Board Cabin Formations. The Breadpan and Houdon Formations are primarily metasedimentary rock, while the Flying W and Board Cabin Formations are primarily metavolcanic rock.[1]

History of investigation

edit

The unit was first designated as the Alder sedimentary series by D.H. Wilson in 1939, for exposures near Alder Creek in the Mazatzal Mountains. Wilson originally assigned the unit to the Yavapai Group and believed the beds had been metamorphosed in a single "Mazatzal Revolution".[3] In 1958, C.A. Anderson and S.C. Creasey mapped the unit into the Jerome, Arizona, area, raised it to group rank, and divided it into six formations.[4] That same year, Gordon Castil redesignated the unit as a formation and divided the unit in its original area in the Mazatzal Mountains into three unnamed members.[5]

In 1971, Anderson and coinvestigators refined the definition of the group, restricting it to the Mazatzal Mountains and reassigning the beds in the Jerome area to the Big Bug Group.[2]

In 1993, Karl Karlstrom and S.A. Bowring divided the Alder Group into the Breadpan, Flying W, Houdon, and Board Cabin Formations.[6]

References

edit
  1. ^ a b c d Cox, Rónadh; Martin, Mark W.; Comstock, Jana C.; Dickerson, Laura S.; Ekstrom, Ingrid L.; Sammons, James H. (1 December 2002). "Sedimentology, stratigraphy, and geochronology of the Proterozoic Mazatzal Group, central Arizona". GSA Bulletin. 114 (12): 1535–1549. doi:10.1130/0016-7606(2002)114<1535:SSAGOT>2.0.CO;2.
  2. ^ a b Anderson, C.A.; Blacet, P.M.; Silver, L.T.; Stern, T.W. (1971). "Revision of Precambrian stratigraphy in the Prescott-Jerome area, Yavapai County, Arizona". U.S. Geological Survey Bulletin. 1324-C. doi:10.3133/b1324C.
  3. ^ Wilson, E. D. (1 July 1939). "Pre-Cambrian Mazatzal Revolution in central Arizona". Geological Society of America Bulletin. 50 (7): 1113–1164. doi:10.1130/GSAB-50-1113. hdl:10150/629185.
  4. ^ Anderson, C.A.; Creasey, S.C. (1958). "Geology and ore deposits of the Jerome area, Yavapai County, Arizona". U.S. Geological Survey Professional Paper. 308. doi:10.3133/pp308.
  5. ^ Gastil, Gordon (1958). "Older Precambrian rocks of the Diamond Butte Quadrangle, Gila County, Arizona". Geological Society of America Bulletin. 69 (12): 1495. doi:10.1130/0016-7606(1958)69[1495:OPROTD]2.0.CO;2.
  6. ^ Karlstrom, K.E.; Bowring, S.A. (1993). "Proterozoic orogenic history of Arizona". In Reed, J.C.J.; Bickford, M.E.; Houston, R.S.; Link, P.K.; Rankin, D.W.; Sims, P.K.; Van Schmus, W.R. (eds.). Precambrian: Conterminous U.S. Geology of North America. Vol. C-2. Boulder, Colorado: Geological Society of America. pp. 188–211.