MAP UNITS FOR THE GENERALIZED GEOLOGIC MAP OF THE UNITED STATES, PUERTO RICO, AND THE U.S. VIRGIN ISLANDS, 2005

PLUTONIC ROCKS SEDIMENTARY ROCKS (Suffix "g" indicates granitic rocks; "i," intermediate rocks; (Includes mixed sedimentary and volcanic rocks) "m," mafic rocks; "u," ultramafic rocks; "a," anorthosite)

Q Quaternary Tg Tertiary nT Neogene nTg Neogene pgT Paleogene pgTg

KT Cretaceous and Tertiary pgTi Paleogene

K Cretaceous pgTm c Mesozoic KTg Cretaceous and Tertiary

lc Lower Mesozoic (Triassic and Jurassic) Kg Cretaceous gc Paleozoic and Mesozoic cg Mesozoic

g Paleozoic lcg ug Upper Paleozoic (Pennsylvanian and Permian) lcm Lower Mesozoic mg Middle Paleozoic (Silurian, Devonian, and Mississippian) lcu lg Lower Paleozoic (Cambrian and Ordovician) gcm Paleozoic and Mesozoic

Zg Late Proterozoic and lower Paleozoic ugg Upper Paleozoic a Proterozoic mgg Middle Paleozoic Z Late Proterozoic mgm Y Middle Proterozoic gg Paleozoic

X Early Proterozo lgg Lower Paleozoic

A Archean Zgg Late Proterozoic and lower Paleozoic Zgm

ag Proterozoic

Zg Late Proterozoic VOLCANIC ROCKS Yg

Qv Quaternary Ym Middle Proterozoic

Tv Tertiary Ya nTv Neogene Xg Early Proterozoic TQv Tertiary and Quaternary Xm pgTv Paleogene Ag Archean

KTv Cretaceous and Tertiary u Age uncertain cv Mesozoic

Kv Cretaceous METAMORPHIC ROCKS l cv Lower Mesozoic (Triassic and Jurassic) (Suffix "n" indicates gneisses and associated rocks) gcv Paleozoic and Mesozoic Phanerozoic (amphibolite facies) gv Middle Paleozoic Phanerozoic (blueschist facies) gv Paleozoic gn Paleozoic lgv Lower Paleozoic Zgn Late Proterozoic and lower Paleozoic Zg v Late Proterozoic and lower Paleozoic Zn Late Proterozoic Zv Late Proterozoic Yn Middle Proterozoic Yv Middle Proterozoic Xn Early Proterozoic Xv Early Proterozoic An Archean

n Age uncertain

Glacier, river, or water body

Geologic contact Fault—Dashed where inferred Wisconsin glacial limit Normal fault Pre-Wisconsin glacial limit Thrust fault Low-angle detachment fault Strike-slip fault