(Basic Field Geology:  GEOL 4120/6120)
(Advanced Field Geology: Geol 4121-6121
)

GEOLOGIC MAP SYMBOLS
Lithologic and Stratigraphic Symbols


Qal Quaternary alluvium (mapped only as the flat floodplain along modern rivers & streams)
Qp Quaternary pediment surfaces and associated deposits
Qaf Quaternary alluvial fan deposits (recognized by fan-shaped landforms)
Qls Quaternary landslide deposits (recognized by scarp, hummocky land form and sharp toe; usually developed in Tertiary volcanics)
Qg Quaternary glacial deposits undifferentiated
Qgl glacial lacustrine (recognized by modern lakes and flat swampy modern meadows)
Qgt glacial till - use dotted line to indicate position of moraines (recognized by erratic boulders and hummocky topography)
Qgo glacial outwash (recognized by very flat surfaces or terraces above base level of modern streams)

Nv Neogene volcanic rock undifferentiated (mostly 17 - 2 Ma); some of these are mapped separately, others are included in the Anderson Ranch Member of the Sixmile Creek Formation
Nvb Neogene basalt, includes the 6.0 +/- 0.1 Ma Timber Hill basalt
Nvr Rhyolite - mostly pyroclastic flow, fall and surge deposits
Ts Tertiary (Neogene) Sixmile Creek Formation undifferentiated
Tsbh Big Hole River Member
Tsa Anderson Ranch Member
Tss Sweetwater Creek Member
Tr Tertiary (Paleogene) Renova Formation
Tdv Tertiary Dillon Volcanics undifferentiated (Mostly Paleogene - 52-30 Ma)
Tdvb basalt (Paleogene)
Tdva andesite (Paleogene)
Tdvr rhyolite, includes pyroclastic flow deposits and lava flows

KTb Cretaceous/Tertiary Beaverhead Formation/Group. Contains limestone angular conglomerate/breccia in a red sandstone matrix, red sandstone and siltstone, quartzite cobble comglomerate with red sandstone
KTi Late Cretaceous/Early Tertiary intrusive rock (70-140 Ma) associated with the Pioneer and Boulder Batholiths. Generally mapped by lithology, a - andesite, g - granite, r - rhyolite
Kcsc Cretaceous Cold Spring Creek Volcanics (white & pink tuffs, dark fragmental volcanicbreccia)
Kf Cretaceous Frontier Formation
Kb Cretaceous Blackleaf Formation undifferentiated
Kbv Upper volcaniclastic/shale member of the Blackleaf Fm (valley former)
Kblc Lower clastic member (includes Kblsh & Kbuc of Dyman) of the Blackleaf Fm
Kk Cretaceous Kootenai Formation undifferentiated
Kkg Gastropod Limestone Member
Kksh Upper Clastic (Shale) Member (valley former -- red shale with ribs of sandstone)
Kkm Middle Limestone Member
Kklc or Kkss Lower Clastic (Sandstone) Member (ribs of ss & congl. with red shale valleys)
Jm Jurassic Morrison Formation
TR d Triassic Dinwoody Formation - undifferentiated
TR du upper bedded carbonate member
TR dl lower shale member

Pp Permian Phosphoria Formation (includes Mead Peak Phosphatic Shale, Rex Chert, Park
City Limestone, Retort Phosphatic Oil Shale, Shedhorn Sandstone)
IPq Pennsylvanian/Permian Quadrant Sandstone (Quartzite)
MIPa Mississippian/Pennsylvanian Amsden Formation
Mbs Mississippian Big Snowy Formation/Group
Mm Mississippian Madison Group undifferentiated
Mmm Mission Canyon Limestone
Mml Lodgepole Limestone
Dt Devonian Three Forks Shale
Dj Devonian Jefferson Dolomite
Ch Cambrian Hasmark Dolomite
Cw Cambrian Wolsey Shale
Cf Cambrian Flathead Sandstone
 
pCu

Precambrian crystalline basement rocks undifferentiated. These are generally mapped using lowercase letters that designate lithologic units. g - granite, gn - gneiss, mg - mafic gneiss, m - marble, as - amphibolite schist, sh - schist, etc.; pick letters appropriate for rock type and area being mapped.

Structural Symbols
Normal contacts (black):
known location (+/- 10’)
approximate location (+/- 25’)
inferred location

Faults (red):
Thrust fault (teeth on upper plate)
Strike-slip fault (show apparent motion in plane of map)
Normal fault (show apparent motion) or ball on hanging wall

Folds (blue):
Axial trace of normal and overturned antiform or anticline
Axial trace of normal and overturned synform or syncline

Strike and Dip Symbols (black):
Strike and Dip of bedding (normal, vertical, overturned)
Strike and dip of foliation (normal and vertical)
strike and dip of joints (normal and vertical)


Colors:
All geologic maps and structure sections should be colored. The colors should be applied very lightly and evenly and should not obscure topographic lines or other detail on the base map. Most mistakes in coloring are made by applying colors that are too heavy or that are uneven. Following is a list of some “standard” colors found on geologic maps. For different formations of the same lithology, use different shades of the same color group. Yellow should be reserved for Quaternary units. If only one Quaternary unit is mapped it should be in yellow. If two are mapped, Qal should be yellow and the other unit light orange.

Colors by lithology:
surficial deposits yellow (preferred) or light orange
sandstone and conglomerate brown
shale, siltstone & mudstone green
carbonates blue
granitic rocks red
volcanics pink
basalt pink or black
metamorphic rocks use color appropriate for protolith

Colors by Age:
Quaternary yellow, pale yellow, white
Cenozoic brown, orange, rust
Mesozoic green, olive
Paleozoic blue, purple
Precambrian red, pink