Orocopia Schist

Mostly gray, fine-grained quartz-feldspar-mica schist, with sparse metabasalt and metachert. The unit is exposed in tectonic windows in the southwestern corner of Arizona. It is interpreted as metamorphosed marine sandstone that was tectonically emplaced beneath southwestern Arizona during early Tertiary subduction of Pacific Ocean sea floor. (65-165 Ma)
State Arizona
Name Orocopia Schist
Geologic age Late Cretaceous to Early Tertiary
Lithologic constituents
Major
Metamorphic > Schist > Quartz-feldspar-schist (Amphibolite epidote-amphibolite)
Minor
Metamorphic > Metaigneous > Metavolcanic > Metabasalt
Metamorphic > Metasedimentary > MetaclasticMetachert
Stratigraphic units Orocopia Schist
References

Richard, S.M., Reynolds, S.J., Spencer, J.E., and Pearthree, P.A., 2000, Geologic Map of Arizona: Arizona Geological Survey Map 35, 1 sheet, scale 1:1,000,000.

Haxel G.B., Jacobson, C.E., Richard, S.M., Tosdal, R.M., and Grubensky, M.J., 2002, The Orocopia Schist in southwest Arizona: Early Tertiary oceanic rocks trapped or transported far inland, in Barth, A., editor, Contributions to crustal evo

NGMDB product
Counties La Paz - Yuma