Basalt (OKTb;0)

State	Oklahoma
Name	Basalt
Geologic age	Phanerozoic \| Cenozoic \| Tertiary \| Pliocene
Original map label	Tb
Comments	Comments: Raton Basalt: Is oldest (of three) basaltic to latiandesitic effusive rock unit mapped in western part of Raton-Clayton volcanic field, Colfax Co, NM in Las Vegas-Raton basin. Caps highest and longest mesas in area. Includes many sheets of lava; vents are generally no longer marked by cinder cones. Analyzed specimens are olivine basalts, alkali basalts, a few trachy-basalts, and latibasalts. Rocks are medium to dark gray or black, very hard, and in part vesicular; some have silvery sheen on fresh break, aptly owing to fine diktytaxitic texture; are visibly porphyritic (typically olivine is the only phenocryst), but some flows have phenocrysts or xeno-crysts of other minerals; altered olivine phenocrysts appear as red or brown specks. Petrography and petrochemistry described. K-Ar ages range from 3.5 to 4.0 m.y. Age is Pliocene. (Scott, 1991)
Primary rock type	basalt
Secondary rock type
Other rock types
Lithologic constituents	Major Igneous > Volcanic > Mafic-volcanic > Basalt (Flow)
Map references	Heran, W. D., Green, G. and Stoeser, D. B., 2003, A Digital Geologic Map Database of Oklahoma: U. S. G. S. Open File Report 03-247
Unit references	Heran, W. D., Green, G. and Stoeser, D. B., 2003, A Digital Geologic Map Database of Oklahoma: U. S. G. S. Open File Report 03-247 Sapik, D.B. and Goemaat, R.L., 1973, Reconnaissance of the ground-water resources of Cimarron County, Oklahoma: U.S Geological Survey Hydrologic Investigations Atlas HA-373, scale 1:125,000, 3 sheets. (Geology on sheet 1 compiled by S.L. Schoff, 1943.) [http://pubs.er.usgs.gov/publication/ha373] Cederstrand, J.R., 1996c, Digital geologic map of Cimarron County, Oklahoma: U.S. Geological Survey Open-File Report 96-372, (1 diskette), URL address is: http://ok.water.usgs.gov/gis/geology [http://pubs.er.usgs.gov/publication/ofr96372] [http://ok.water.usgs.gov/gis/geology] Scott, G., Wilcox, R. E., and Mehnert, H. H., 1991, Geology of volcanic and subvolcanic rocks of the Raton-Springer area, Colfax and Union Counties, New Mexico: U.S.Geological Survey Professional Paper 1507. [http://pubs.er.usgs.gov/publication/pp1507]
Geographic coverage	Cimarron