Geology Data

This is a seamless 1:500,000 scale GIS dataset of surficial geologic formations for the states of Arizona, Colorado, Nevada, New Mexico and Utah. The dataset was compiled and edge-matched from existing digital versions of the 1:500,000 scale state geologic maps (Green, 1992; Ramsey, 1996; Turner and Bawiec, 1996; Green and Jones, 1997; Hirschberg and Pitts, 2000). Similar geologic units were correlated only along state boundaries to facilitate edge matching. Correlation and merging of units along state boundaries was based on similar age and characteristics of units. Landsat TM images were visually interpreted to facilitate mapping and edge matching along state boundaries, when necessary. Whenever it was possible existing state specific geologic detail was maintained.

A soil substrate code was derived from geologic unit code using a modified soil classification scheme developed by NatureServe. Soil substrate codes and geologic unit codes were correlated based on bulk rock chemical compositions and characteristics. Soil substrate codes are as follows:

QYA	Quaternary age younger alluvium and surficial deposits
QOA	Quaternary age older alluvium and surficial deposits
EOS	Unconsolidated Aeolian sand deposits both active and stabilized
SND	Sandstone dominated formations of all ages
SLM	Siltstone and or mudstone dominated formations of all ages
SHL	Shale dominated formations of all ages
CLM	Carbonate dominated formations either limestone or dolomites of all ages
EVP	Evaporite units either halite, gypsum, or other saline mineral dominated formations of all ages
GSL	Metamorphic or igneous units with a dominantly silicic composition all ages
BMC	Metamorphic or igneous units with dominantly mafic composition all ages
H20	Water
UNK	Unable to assign a substrate type

Individual State 500K Geology—Digital Sources

Arizona

Hirschberg, D.M. and S.G. Pitts. 2000. Digital Geologic Map of Arizona: A Digital Database from the 1983 Printing of Wilson, Moore and Cooper, 1:500,000 scale map of Arizona. OF-00-409, US Geological Survey, Denver, Colorado.

Colorado

Green, G.N. 1992. The Digital Geologic Map of Colorado in ArcINFO Format. OF-92-0507, US Geological Survey, Denver, Colorado.

GIS data

New Mexico

Green, G.N. and G.E. Jones. 1997. The Digital Geologic Map of New Mexico 1:500,000 scale in ArcINFO Format. OF-97-0052, US Geological Survey, Denver, Colorado.

Nevada

Turner, R.M. and W.J. Bawic. 1996. Digital Map of Nevada at scale of 1:500,000. DDS 41, US Geological Survey, Denver, Colorado.

Utah

Ramsey, R.D. 1996. Digital Compilation of Geologic Map of Utah by L.F. Hintze, G.C. Willis, D.Y.M. Laes, D.A. Sprinkle and K.D. Brown. DDS 41, US Geological Survey, Denver, Colorado.