Key: Red and Orange

• Mainly Marine Stratified Sequences
  • To Oligocene
  • Te3 Eocene Jackson Group
  • Te2 Eocene Claihorne Group
  • Te1 Eocene Wilcox Group
  • Te Eocene
  • Ts Paleocene
  • PP1 Mulkan and Morrowan Series (Pennsylvanian)
  • C Cambrian
  • Cq basal Lower Cambrian clastic rocks
  • W Precambrian metasedimentary rocks (Precambrian)
  • Z Precambrian sedimentary rocks (Precambrian)
  • Y3 Missoula Group (Precambrian)
  • Y2 Wallace, Siyeh and Helena Formations (Precambrian)
  • Y1 Ravalli Group and Prichard Formation (Precambrian)
  • Y Precambrian metasemimentary rocks
  • X Precambrian metasedimentary rocks
• Continental Deposits
  • Toc Oligocene
  • Tec Eocene
  • Tel Eocene lacustrian deposits
  • Txc Paleocene
• Eugenosynclinal Deposits
  • Tee Eocene
• Volcanic Rocks
  • uTa Upper Tertiary andesite
  • Tmv Miocene volcanic rocks
  • Tmf Miocene felsic volcanic rocks
  • lTv Lower Tertiary volcanic rocks
  • lTf Lower Tertiary felsic volcanic
  • lTa Lower Tertiary andesite
  • Teb Eocene marine pillow basalts
  • Zv Precambrian volcanic rocks
  • Yv Precambrian volcanic rocks
  • Xv Precambrian volcanic rocks
  • Wv Precambrian volcanic rocks
• Intrusive Rocks
  • Mesozoic dikes
  • Zg granitic rocks
  • Yg2 Younger Y granitic rocks
  • Ys Syenite
  • Ya Anothosite
  • Ymi Mafic intrusives
  • Yg1 Older Y granitic rocks (Precambrian)
  • Xg granitic rocks (Precambrian)
  • Wg granitic rocks (Precambrian)
  • Wmi mafic intrusives (Precambrian)
• Metamorphic Rocks
  • Ym Paragneiss and schist
  • Ygn Orthosgneiss
  • Xm Precambrian orthogneiss and paragneiss
  • Wgn Precambrian orthogneiss and paragneiss