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