BEDROCK GEOLOGIC MAP OF THE CENTRAL ARROWHEAD AREA,
Prepared and Published with the Support of
Research supported by the U. S. Geological Survey, National Cooperative Geologic Mapping Program, under USGS award
number G15AC00239. [The views and conclusions contained in this document are those of the authors and should not be interpreted
as necessarily representing the official policies, either expressed or implied, of the U. S. Government.], THE ST. LOUIS AND LAKE COUNTY BOARDS OF COMMISSIONERS,
AND the Minnesota Environment and Natural Resources Trust Fund
as recommended by the Legislative-Citizen Commission on Minnesota Resources
MINNESOTA GEOLOGICAL SURVEY
Harvey Thorleifson, Director
OPEN FILE REPORT
OFR-2016-04
LAKE AND ST. LOUIS COUNTIES, NORTHEASTERN MINNESOTA
By
Mark A. Jirsa, Terrence J. Boerboom, Amy L. Radakovich, Val W. Chandler, and Dean M. Peterson
91 30’ 00”
0
Ami
Alm
Agm
Alm
Aln
Aln
Alm
Aln
Aas
Adp
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M
Alm
Aln
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M
Aln
Abs
Ami
Abs
Aln
Abs
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Abs
Abi
Abi
Abi
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Aqp
F
F
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Alt
Als
Ali
F
Als
Ael
Alg
Alg
Asd
Als
Alg
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F
Alt
Alc
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Alt
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Ael
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F
Alt
Aeu
Amv Alh
Alh
AlcAlh
Alh
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M
M
Als
Amv
Alc
Ami
Amv
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Amv
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Alc
Agr
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Alb
Alc
Amv
Als
Als Amv Alc
Ami
Als
Alc
Als
Ami
Alc
Alb
Amv
P
Als
Aeg
AesAel
M
Amp
F
FM
Alc
Als
Ami
Al
Aqm
Alc
Alc
Als
Mkz
Aat
Agq
Agq
Ami
Agq
Agq
Agq
Pab
Agq
Agq
Aat
Aat
Aqm
Agq
Agq
Aat
Paq
Aqm
Pvt
Agq
Agq
Paq
Aqm
Aqm
Aqm
Asv
Asv
Asb
Aqm
Asb
Aqm
Aat
Paq
Aqm
Aqm
Asb
Aqm
Paq
Pab
Paq
Pab
Pvt
Pab
Pab
Asv
Amg
Amm
Amg
Amm
AmgAmg
Amg
Amg
Amm
Asb
Asb
Amg
Amm
Amg
Amm Amg
Amm
Amm
Amg
Amg
Amg
Amg
Paq
Aqp
Pab
Paq
Amm
Amm
Paq
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Biwabik
Mas
Pab
Pab
Pvt
Mpz
Mms
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M
M
Mai
Mnb
Mai
Mai
Mai
Mkl
Mgg
Mai
Mbt
Mai
Mai
Mmi
Mmi
Mai
Mai
Mai
Mpt
Mui
Mmi
Mmi
Mui
Mnb
Mpu
Mai
MncMnh
Mpx
Mnc
Mpu
Mnc
Mnh Mnh
Mnc
Mai
Mnc
Mnh
Mpx Mnm
Mpt
Mnh
Mpx
Mai
Mao
Mga
Mai
Mai
Mnm
Mpu
Mkc
MnhMnb
Mnh
Mpu
Mnm
MncMpx
Mnb
Mnb
Mnh
Mnc
Mnb
Mpu
Mgf
Mkl
Mkt
Mwg
Mkr
Mnm
Mwc
Mnh
Mnb
MnbMnm
Mnm
Mpu
Mai
Mnm
Mpu
Mnm
Mgg
Mgf
Mai
Maa
Mnh
Mnb
Mnb
Mgg
Mnh
Mcl
Mcl
Maa
Mcg
Maa
St. Louis County
Pvt
Lake County
1
Digital base modified from the Minnesota Department of
Transportation BaseMap data; digital base annotation by
the Minnesota Geological Survey.
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1
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2
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4
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5
4
6
5 MILES
7
8 KILOMETERS
contour interval 15 METERS
Universal Transverse Mercator Projection, grid zone 15
1983 North American Datum
Cu-Ni
Aas
F2 anticline
M
F2 syncline
Aks
Mcl
Olivine gabbro
Mcg
Gabbro to diorite
Coarse-grained to pegmatitic oxide-rich gabbro to olivine gabbro
Mns
Sulfide-bearing, heterogeneous troctolitic to gabbroic rocks
Mnt
Layered troctolite to melatroctolite
Partridge River intrusion: poorly to well-exposed troctolitic cumulate
hosting several Cu-Ni sulfide deposits along its basal contact
Mpv
DULUTH COMPLEX
Miscellaneous intrusions
Mui
Oxide-rich ultramafic to mafic intrusions within the Partridge River
intrusion
Mas
Aurora sill-syenite to monzonite
Mog
oxide-olivine gabbro sill
Aei
Iron-formation; typically chert-magnetite-hematite-bearing
Pd
Als
Mixed source metagraywacke, mudstone
Aeu
Upper Ely member mafic volcanic rocks
Ali
Iron-formation
Aes
Soudan Iron Formation member
NEOARCHEAN
Alc
Conglomerate, arkosic sandstone, mudstone
Ael
Lower Ely member mafic-intermediate volcanic rocks
Asz
Alt
Reworked dacitic tuff, arkosic graywacke, and mudstone
Mud Lake sequence
Alg
Gafvert Lake sequence-dacitic volcanic and volcaniclastic rocks
Amg
Alv
Gafvert Lake sequence-mafic-intermediate volcanic rocks
Alh
Hornblende-bearing arkosic-lithic sandstone
Alb
Conglomerate and volcaniclastic sedimentary rocks of mixed
provenance
Diabasic to gabbroic dike; typically less than 100 m wide
Shear zone-phyllitic to blastomylonitic, varied protoliths, typically
altered
Miscellaneous Intrusions
Asd
Syenite, monzonite, monzodiorite, diorite intrusions; includes Lost Lake
pluton
Al
Lamprophyric intrusion (several generations represented)
Porphyritic tonalite (dacite porphyry) intrusions
Mts
Sulfide bearing troctolite
Apt
Meh
Poorly exposed eastern zone of heterogeneous troctolitic rocks of
uncertain origin - likely part of either the Partridge River or South
Kawishiwi intrusions
Adp
Dacite porphry intrusion
Aqp
Quartzofeldspathic intrusions
Amp
Pyroxenite and hornblendite to monzonite; variably porphyritic
Atg
Tonalite-trondhjemite to leucogranite intrusion in unit Aat
Agr
Granite, granodiorite, monzonite intrusions
Asc
Mmd Miscellaneous fine to med-grained diabase dikes
Mms Miscellaneous fine to med-grained mafic sills & dikes
Poorly exposed zone inferred to be mixed Partridge River troctolitic
intrusives, anorthositic series rocks, and inclusions of volcanic rock
from the North Shore Volcanic Group
Lake Vermilion Formation
Mpx
Oxide-olivine anorthositic gabbro/oxide-augite anorthositic troctolite
associated with volcanic hornfels inclusions in the Partridge River
intrusion
Alr
Rhyolite to rhyodacite flows and fragmental volcanic rocks
Agl
Schist and migmatite
F
anticline
I
anticline, overturned
Amv
Graywacke-mudstone metamorphosed under zeolite to greenschist
facies conditions
Akv
Mnl
Akf
M
syncline
Akm
P
syncline, overturned
Figure 1. Generalized bedrock geology of northeastern Minnesota showing the
location of the Central Arrowhead map area. Red lettering denotes Mesabi Iron
Range (MIR) and the primary copper-nickel exploration district (Cu-Ni).
Als
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Age Dates
2016 Age Dates
Ali
Alc
Alt
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Alg
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Published Age Dates
Alv
Mpt
Alh
Mpa
Alb
Mpp
Alr
Mpm
Agl
Mps
Ams
Mpz
Asc
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Bass Lake sequence
Bald Eagle intrusion: funnel-shaped, concentrically zoned troctolitic to
gabbroic layered intrusion containing magnetic inclusions of uncertain
composition
Mpt
Troctolitic cumulates
Agq
Porphyritic quartz monzonite and monzodiorite
Aus
Mpa
Lower heterogeneous augite troctolite cumulates
Aqm
Porphyritic quartz monzonite and monzodiorite, magnetic
Abi
Iron-formation; typically chert-magnetite-hematite-bearing
Mbt
Troctolitic rocks
Mpp
Poikilitic anorthositic troctolite
Agh
Equigranular hornblende-quartz monzonite to granodiorite
Abf
Felsic volcanic and volcaniclastic rocks
Mbg
Gabbroic rocks
Mpm Melatroctolite to augite troctolite cumulates
Agd
Hornblende-augite diorite to tonalite
Abt
Mafic tuff and breccia
Mmi
Miscellaneous magnetic inclusions in the Bald Eagle intrusion, possibly
basaltic hornfels or gabbroic rocks of the anorthositic series
Mps
Sulfide-bearing, layered troctolitic cumulates
Aga
Massive to gneissic amphibolite and augite-amphibolite
Abd
Metagabbro, metadiabase
Heterogeneous troctolite and gabbro, locally sulfide bearing, forming
the contact zone of the Partridge River intrusion
Awt
Wakemup Bay tonalite to granodiorite
Abv
Metabasaltic rocks; typically pillowed flows and autobreccia
Agt
Purvis Lake tonalite
Newton Lake Formation
Abg
Britt granodiorite
Ans
Metagraywacke, locally tuffaceous
Ami
Mafic intrusions, undifferentiated; varied timing of emplacement
Ani
Iron-formation; chert-magnetite-hematite-bearing
Aat
Layered tonalitic and amphibolitic gneiss
Anf
Felsic volcanic and volcaniclastic rocks
Ad
Metadiorite
Ang
Metagabbro, metapyroxenite, metaperidotite; locally differentiated sills
Anv
Metabasalt; tholietic to komatiitic
Mpz
Anorthositic Series
Mta
Troctolitic anorthositic rocks
Troctolitic rocks
Mga
Gabbroic anorthositic rocks
Mgg
Gabbroic rocks
Maa
Anorthositic rocks, undivided
Mgf
Ferrogabbroic rocks
Mao
Olivine-bearing anorthositic gabbro to olivine gabbroic anorthosite
Tuscarora intrusion: incompletely mapped troctolitic to gabbroic
intrusion at the base of the Duluth Complex
Man
Noritic rocks
QUETICO SUBPROVINCE OF SUPERIOR PROVINCE
Ely Greenstone
Mai
Anorthositic xenoliths included in Layered Series intrusions
Mtt
Troctolitic rocks
Lac la Croix Granite-magnetic phase; rare migmatite
Aef
Felsic volcanic and volcaniclastic rocks
Felsic Series
Alm
Mtg
Gabbroic rocks
Lac la Croix Granite; leucogranite, non- to less magnetic phase
Micrographic to intergranular granophyre of the Mt. Weber intrusion
Aeg
Metagabbro, metadiabase sills and dikes
Mwg
Aln
South Kawishiwi intrusion: poorly to well-exposed troctolitic cumulate
hosting several Cu-Ni sulfide deposits along its basal contact
Tonalitic, trondhjemitic, and granodioritic gneiss and migmatite
Mwc
Locally porphyritic granophyric gabbro to ferromonzonite interpreted to
be a border phase of the Mt. Weber granophye
Atm
Agm
Granitoid-rich migmatite; 50-75% granitic neosome
Mkl
Anorthositic troctolite to troctolite cumulate
Asm
Schist-rich migmatite; 50-75% schistose and gneissic paleosome
Mkt
Augite-bearing troctolite cumulate, undivided
NORTH SHORE VOLCANIC GROUP
Abs
Biotite-plagioclase-quartz schist; graywacke protolith; minor neosome
Mka
Upper augite-bearing troctolite cumulate
Mnb
Aas
Amphibolitic schist and gneiss; basaltic to gabbroic protolith
Mkb
Lower augite-bearing troctolite cumulate
Mkc
Upper augite troctolite cumulate
Mnh
Basaltic hornfels
WAWA SUBPROVINCE OF SUPERIOR PROVINCE
Mkp
Poikilitic anorthositic troctolite inclusions in the South Kawishiwi
intrusion
Mnc
Hornfels derived from volcanogenic sandstone, commonly known as
the Colvin Creek sandstone
Aks
Graywacke, mudstone
Mkr
Troctolite cumulate
Aki
Iron-formation; typically thinly bedded, variably magnetic mudstone
Mko
Oxide-olivine gabbro to augite troctolite cumulate
Mnm Olivine oxide gabbro, possibly hornfels derived from NSVG basaltic
rocks
Akc
Conglomerate, arkosic sandstone, mudstone
Mkd
Lower augite troctolite cumulate
Akv
Intermediate volcanic and volcanoclastic rocks
Akf
Felsic volcanic and volcaniclastic rocks
Akm
Metabasalt (may represent fault or unconformity-bounded slivers of
older volcanic rocks)
Mgt
Mkz
Heterogeneous troctolitic rocks, locally sulfide bearing, forming the
contact zone of the South Kawishiwi intrusion
Basaltic hornfels of the North Shore Volcanic Group (NSVG), typically
non-magnetic
PALEOPROTEROZOIC
ANIMIKIE GROUP
Pvt
Virginia and Thomson Formations slate and graywacke
Pab
Biwabik Iron Formation
Paq
Pokegama Quartzite
Knife Lake Group
Mbt
Mbg
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Drill hole
Figure 2. Drill hole locations relative to the mapped bedrock geology.
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Abi
Abf
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LS1066.AD G
LS1082.AD G
Abt
Abd
Abv
Mai
Ans
Mwg
Ani
Mwc
Anf
Mnb
Ang
Mnh
Anv
Mnc
Aef
Mnm
Aeg
G
LS054.AD
G
LS1148.AD
G LS415C.AD
G LS331.AD
Aei
Aeu
Aes
Outcrops mapped during field work phase of this study
Outcrops inferred from lidar data
Outcrops digitized from prior published paper maps
Ael
Amg
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Figure 3. Outcrop history and locations relative to the mapped bedrock geology.
Amm
Al
Asv
Apt
Asb
Adp
Amv
Every reasonable effort has been made to ensure the accuracy of the factual data on which this map interpretation is
based; however, the Minnesota Geological Survey does not warrant or guarantee that there are no errors. Users may
wish to verify critical information; sources include both the references listed here and information on file at the offices of the
Minnesota Geological Survey in St. Paul. In addition, effort has been made to ensure that the interpretation conforms to
sound geologic and cartographic principles. No claim is made that the interpretation shown is rigorously correct, however,
and it should not be used to guide engineering-scale decisions without site-specific verification.
MISCELLANEOUS
INTRUSIONS
Mgg
South Kawishiwi Intrusion
BEAVER BAY
COMPLEX
Mms
Mcl
Mcg
Mgt
Mkl
Mkt
Mka
Mkb
Mkc
Mkr
Mkp
Mmd
Nickel Lake Macrodike
Mko
Mkd
Mnl
Mkz
Mnt
Partridge River Intrusion
Mns
Mui
Meh
Mpu
Mpx
Mpt
Mps
Mpa
Mpp
Mpm
MESOPROTEROZOIC
Mpz
Mpv
NORTH SHORE
VOLCANIC GROUP
Tuscarora Intrusion
Mtt
Mtg
Mas
Mog
Mms
Anorthositic series
Mai
Hornfels inclusions
Mta
Mga
Maa
Man
Mao
normal polarity (~1099 Ma)
Mnb
Mnh
Mnm
Mnc
reversed polarity (~1106 Ma)
Felsic series
Mwg
Mwc
intrusive contact
Pvt
Pab
disconformity
Animikie Group
PALEOPROTEROZOIC
Paq
unconformity
Pd
QUETICO SUBPROVINCE
Lac La Croix Granite
Alm
Aln
Adp
Kenora-Kabetogama Dike Swarm
WAWA SUBPROVINCE
Wakemup Bay
intrusion
Awt
Aga
Agd
Agb
Agh
Aqm
Asm
Abg
Agl
Atm
Lake Vermilion Formation
Ami
Knife Lake Group
Aki
Aus
Abs
Aks
Akc
Akv
Asz
Akf
Bass Lake
Akm
sequence
Newton Lake Formation
Abi
Abf
Abt
Abv
Abd
Ang
Ani
Ans
Anc
Anf
Gafvert Lake sequence
Als
Alc
Alb
Alr
Alh
Alt
Alv
Alg
Ams
Ali
Minntac
Mud Lake sequence
Ely Greenstone
Aes
Ael
Asc
Aef
Aeg
Aei
Amm
Amg
sequence
Asv
Amv
Agq
~ D3
Asd
Agt
Amp
Agr
~ D2
Al
Atg
Aat
Britt sequence
Aqp
fault and unconformity
Aeu
Anv
Asb
Midway sequence
Purvis
Apt
Britt Granodiorite
Agm
Miscellaneous Intrusions
Giants Range Batholith
Aas
The University of Minnesota is an equal opportunity educator and employer
Greenwood Lake Intrusion
Sedimentary rocks
Greenwood Lake intrusion: poorly exposed, well-differentiated
troctolitic to gabbroic layered intrusion with the stratigraphy understood
primarily from drill core
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!
!
!
!!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
F
Outcrop
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!!
!
!
!!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!!
!
!
!
!
Bald Eagle Intrusion
Mafic metavolcanic rocks, undifferentiated; typically pillowed flows
Mgf
Equigranular biotite granite/quartz Monzonite
!
!
!
!
Layered series
Trachyandesitic volcanic, volcaniclastic, and epiclastic rocks
Agb
!
!
!
!
! !!
!
!
!
!
!!
!
!
!
!
!!
!
!
!
!
! ! !
!
!
!!
! ! !
!
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!
! !
!
!
! !
!
!! !
!
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!!
!!
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!!
!
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!
!!
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!
!
!
!!
!!
!
!
!
!!
!
!
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!!
!
!
!
!
!
!
!
!!
!
!!
!
!
!
!
!
!
!
!
!
DULUTH COMPLEX
Mmi
Upper heterogeneous augite troctolite zone
Schistose biotitic metagraywacke and slate
Britt sequence
Mpu
Layered Series
Asb
Metavolcanic and
volcaniclastic rocks
Biwabik and Gunflint
Iron Formations
NOTE: Some labels in dark colored units are white for clarity
Minntac sequence
Schistose amphibolitic metabasaltic rocks
Schist and migmatite
CORRELATION OF MAP UNITS
Amm Basaltic flows and autobreccia metamorphosed under zeolite to
greenschist facies conditions
Midway Sequence
Ams
Gabbro and diabase sills and dikes metamorphosed under zeolite to
greenschist facies conditions
Asv
Granitoid rocks
Virginia, Thomson, and
Rove Formations (slate, graywacke)
Mkz
fault
Cloquet Lake Layered Series
Mnl
KENORA-KABETOGAMA DIKE SWARM
NEOARCHEAN
PALEOPROTEROZOIC
F3 synform
80 km
The views and conclusions contained in this document are those of the authors and should not be interpreted as
necessarily representing the official policies, either expressed or implied, of the U.S. Government. This map is submitted
for publication with the understanding that the U.S. Government is authorized to reproduce and distribute reprints for
governmental use. Supported by the U.S. Geological Survey, National Cooperative Geologic Mapping Program, under
assistance Award No. G14AC00210.
fault
BEAVER BAY COMPLEX
Nickel Lake macrodike: well-exposed, steeply dipping gabbroic to
troctolitic intrusion inferred to be a large feeder dike to the northern part
of the South Kawishiwi intrusion
0
Duluth Complex and
North Shore Volcanic Group
M
faults
MESOPROTEROZOIC
92°
MESOPROTEROZOIC
LOCATION DIAGRAM
DESCRIPTION OF MAP UNITS
60 mi
Duluth
F3 antiform
F
90 °
47°
F1 syncline
F
L
Grand
Rapids
47°
rior
upe
S
ake
MIR Virginia
F1 anticline
M
48°
Ely
Axial surface trace of folds
Abs
Akc
48°
magnetic anomaly
F
91°
90°
lidar fracture
Asm
Mkd
92°
Fractures, inferred
Agm
Aki
CENTRAL
ARROWHEAD
AREA
lidar foliation
Atm
Mko
94° International 93 °
Falls
bedding trace
Aln
Asd
91 30’ 00”
0
Foliations, inferred
Alm
Asz
470 30’ 00”
920 30’ 00”
SCALE 1:100 000
Ad
Paq
Pab
Paq Pab
Mtg
Pab
Pvt
Mai
Aat
Pvt
Mwg
Mpv
Mcl
MpzMpa
Mtt
Mnm
Mpt
McKinley
Ami
Man
Mmi
Mgt
Mga
Mgf
Mao
Mai
Mpu
Mnm
Abg
Maa
Mai
Mnm
Mpx
Mnc
Mpx
Mnc
Mgg
Mmi
Mnh
Mnh
Mnc
Mnc
Mpu
Mpx
Mpt
Agt
Mga
Mmi
MgaMga
Mpu
Mnh
Mnh
Mgt
Pd, mafic dike, Kenora-Kabetogama swarm
Mta
Mga
Mnb
Mao
Mpx Mpx
Mga
MnhMpx
Mpx
Awt
Mpu
Mai
Mai
Mpx
Mmi
Mms, mafic sill
Mpx
Mgt
Meh
F
Mga
Mga
Aga
Mpv
Mkp
Mai
Mao
Mnb
Mbg
Mmd, mafic dike
Mnt
Mmi
MpzMpa
Pab
Paq
Mai
Mai
Mai Mai
Mai
Mai
Mai
Mnm
Mnb
Mpt
Mai Mnb
Mkl
thrust fault
Agd
Meh
Mpt
Mnb
MaiMkl
Mta
Mnm
Mai
Mai
Meh
Mai
Mkp
Agh
Mns
Mkc
Mga
Mnb
Mnb
Paq
Asc
Ams
F
Pab
Pab
Paq
Meh
MpzMpa
Mas
Pab
Paq
Pab
Ams
Amm
Mas
Mpa
Mpt
Mpt Mpt
Mnb
Mnb
Mpt
Mai
Mai
Mnb
Pvt
Mpz
Amm
Pab
Paq
Hoyt Lakes MpzMpm
Paq
Paq
Paq
!
Amm
Mpt
MpaMpa
Mpa
Mta
Mui
Mpu
Mai
Mkr
Mkz
Mga
Mpa
Maa
Mai
Meh
Meh
Mpt
MuiMnbMnb
F
Mga
Mpa
Pvt
Pab
Mpm
Mpz Mpp
F
Mai
Mkt
Mkz
F
Mpa
Mpp
MpzMpm
Mpa
Asb
Paq
Pab
Mnb
Paq
Asb
Asb
Mpz
Mpz
MppMpp
Mpz
Mpm Mpa
Mui
MpzMpp
Mpm
Pab
Paq
Pab
Paq
Aqm
Asb
Paq
Paq
Aqm
Pab
Paq
Aqm
Aat
Mpz
Pvt
Mkl Mkl
Mkl
Mbt
Mbt
Mai
Mbt
Mbt
Mbt
Mkl
Mai
Mkt
Mai
MpzMpm Mpm
Mpp
Mai
Mkl
Mka
Mkc
Mkz
Mps
Mai
Maa
Maa
(
Line symbols
Dikes
Aqm
Mkr
Mbg
(
Agq
Mkc
Mai
Mps
Pvt
Mpp Mpa
Mpz
Mpz
MpzMpm MppPvt
Mpa
MpzMpp
Mpt
Mpz
Mpa
Mpm Mpt
Mpp
Pab
Pab
Asb
Pab Paq
Pab
Pab
Aqm
Aat
Babbitt
Pvt
Pvt
Pab
Paq
Pab
Paq
Pvt
Pvt
Mpz
Mms
Paq
Paq
Aqm
Aat
!
Pvt
Agq
Aqm
Mko Mkr
Pvt
PvtMms
Pvt
PvtMms
Pvt
Mms
Pab
Agq
Pab
Mkl
Agb
Mkb
Mta
Maa
Mmi
Mkl
Mko
Mko
Mpz
Pab
Mkl
fault
Maa
Mka
Pvt
Mms
Mkl
Agr
Mai
Pab
Mkz
Mka
Maa
Mkl
Mai
Mai
Pab
Agq
Mka
Mkp
contact
Mka
Maa
Mka Mkl
Mkz
Pab
Mka
Mka Mka
Mkz
Pab
Aqm
Aqm
Agq
Aat
Mka
Mka
Mko
MmsMkz
Aat
Agq
Mka
Mkc
Mkl
Atg
Mkp
MklMkl
Mkp
Mkp Mkl
Mkl MklMklMkl
Mkp
Mkl
Mkp Mkl
Mkc MkcMkl
Mkp
Mkp
Mkc
Mui
Mkt
Maa
Mkl
bndry
Mkl
Maa
Maa
Maa
Mkp
Mkp
Mkb
Mka Mkl
MkpMkl
Mai
Mkb
Mkb
Mka
Mkl
Mkp
Mkl
Mka
Mka
Mkl
Mkp
Mkl
Mkp
Mka
Mkl Mkl
Mkp
Mkp
Mkp
Mkp
Maa
Mta
Mkb
Mkl
Mkp
Mkr
Mkz
Pab
MkaMka
Mkl
Mkl
Mka Mkp
Mka
Mko
Pab
Mka
Mkb
Pab
Aga
Agd
Ami
MkcMkb
Mkp
Mka
Mkb
Mnt
Mnl
Mai
Mai
MklMkl Mkl
Mka
Mkb Mka
Mkl
Mai
Mkl
MkpMkl
Mko
Mai
Mai
Mkz
Pab
Mnb
Aqm
Aqm
Mai
Mai
Mkc
Mko
Mnh
Aat
G
Mko
Mai
Maa
Mkb
Agq
Ami
Aqm
Mkb
Mai
Pab
Agq
470 30’ 00”
Aat
Alc
Aqm
Asc
Ams Ams
Mai
Aat
Aat
Agl
Ams
Pab
Mkz
Aat
Aqm
MkcMkb
Mkc Mkc
Mkb
Mkb
Mkb
Mkb
Aqm
Aat
Agq
Mta
Mkb
Mkb
Mkz
Aat
Agq
Maa
Mta
Mta
Mta
Mkb
Mai
Mai
Mai
Mai
Mkp
Aat
Agr
MaiMai
Mai
Mkp Mai
Mkp Mai
Mkp
Mkb
Mkb
Mai
Mai
Mkc
Aqm
F
Aat
Agq
Mkc
Mkb
Mkb
Aat
Aat
Pab
Mko
Mai
Mai
Mai
Alc
Abg
Mai
Mai
Mai
Mai
Alc
Abg
Mta
Mai
Alc
Agr
Mkd
Agq
Atg
Mai
Agq
Aes
Alc
Mai
Mai
Mkd
Als
Ami
Mkz
Agq
Ami
Agl
Asv
M
Agq
Al
I
Alc
Maa
Mnt
Mnl
Mta
MaaMnlMns
Maa Mta Mnl
Maa
Mns
Mnl
Mnb
Mns
Mnt
Mta
Mta
Mnl
Mnl
Mns
Mai Mnt
Mkz
Agh
Aqm
Mta
Mta
Ael
Aqm
Mga
Man
Mnl
AlgAeg Aef
Agq
AefAgq
Aeg
Aqp
Aes
Mga
Maa
MaiMai
Aeg
Aeg
Mta
Agb
Mta
Amp
Mbt
Mta
Mtg
Mcg
Mog
Aqm
Agb
Aqp
Mas
Agd
Contacts and faults
Mcl
Mms
Mtt
Aga
Agq
Mai
Aes
Alc
Agl
Asv
F
Aqp
Aat
Ami
Ami
Aqm
Aeu
Aei
Alg
Aeg
Agd
Aef
Agt
Ael
Aeu
Agd
Ali
Ami
Als
Asv
Alc
MAP SYMBOLS
Mmd
Als
Aeu
Agh
Agq
F
Aeu
Als
Alb
Agl
Aei
Aeu
Aef
Aeg
Agh
Aeu
Mga
Mkz Mkb
Aeg
Aqp
Aqp
Aeu
AeiAeu
Aeu
Aeu
AeuAli
Ali
Ali
Aeu
Apt
Aei
Agh
Alg
Apt
Aeu
Agt
Ami
Alb
Aeg
Aeu
AefAgq
Aeu
Aeu
Aes
Agt
Aeg
Ael
Ael
Aeu
Aeu
Aeg
Aeu
Aeg
Agh
Aei
Ad Ad
Aef
Aei
Aef
Ael
Agr
Agr
Aeu
Aqp
Aei
Aes Aes
AesAlg
Aes
Ael
Ael
Ael
Aeg
Aeg
Ael
Aeg
Aef
Ael
Aei
Ael
Aeu
Aeu
Alg
Aes
Aei
Aei
MAP UNITS
Aeu
Aeg
Agr
Agr
Mkb
Als
Alc
Alb
Alg
Aes
Ael
Alc
Als
Alg
Aes
Aeu
G
Aei
Agh
Agq
Aeu
Aeu
Aei
Aei
Aqp
Aqp
Aqp
Aeg
Aef
Aes
M
Alb
Aqp
Aes
Aqp
Als
Alr
Amv
Amv
Alt
Aeu
Aeu
Alg
Aes
Aes
Alg
Aes
Aeu
AeiAeg
Aeu
Aei
AeuAgr
Aeu
Aeg
Agq
Aeu
Aei
Aei
Akc
Agr
Aeu
AeuAeg
Apt
AegAei
Aeu Aeg
AeiAeg
Aeu
Aeg
Aeg
Aei
Aei
Aei
Aei
Aqp
Aqp Aes
Als
Ami
AmiAlc
Amv
Alg
Aeu
Alg
Aei
Agr
Aeu
Aeg
Akc
Aks
Aeg Aeg
Aeu
Aeg
Apt
Aks
Agq
Aei
Aeg
Alc
Als
Alg
F
Ael
Aeg
Ael
Aes
AeuAqp
Aeg
I
I
M
Alc
Als
Ami
Alr
Abg
Als
I
M
M
F
M
M
I
Als
Als
Abg
M
Amp
Abg
Als
Abg
Amv
Amp
M
M
Als
Amp Amp
AmvAlc
Abg
Amv
Amv
Als
I
Alc
M
I
I
Ami
Ami
I
Ami
Ami
M
Aei
Aeu
Aei
Aeu
AeuAei
Ely
Ami
Aef
Aeg
M
Aei
Aei
Aeu
M
Aks
Aei
Aei
Aei
Aeg
Aef
Ael
I
M
P
Aeu
Aei
Aeg
Aei
Winton
M
Aks
Aeu
Aei
Ad
Aeu
M
Aeu
Ael
Ael
Alg
Aes AqpAeg
Amv
Als
Aeu
Aeu
Aeu
Aeu
!
Anv
Aeg
Asd
M
Aeg
Aei
F
M
Aef
Agr
Akc
Aeu
Aei
Aei
Aeu
Aeg
Aeu
Aef
Aeg
Aeu
Aeu
Aei
Anv
Aks
Ang
Akv
Akv
Ang
Ang
Aqm
P
I
M
F
Aes
Aeu
!
Anv
Asz
Aei
Aei
Aei
Aqp
Alg
Aeu
AqpAes
Ael
F
Aes
Ael
Aqp
Aqp
AqpAqp
Alt Alg
Alt
Alt
Asz
Ang
Anf
(
Aeu
Aeg
Ad
F
Aqp
Alg
Als
Aeg
Ad
Ael
Alg Aes
Alg
Ael
Aqp
Aeg
F
Alg
Asd
G
Ael
Alg
Tower
F
M
Aqp
Aes
Aes
Aes
Aeu
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(
Als
Aqp
Aei
Aeg
Aeg
Ad
AesAelAes
AefAeg
Aef
Ad
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Aes
Ael
Ael
F
Als
Aqp
M
Asd
Aqp
Alv
M
Alt
M
Alg
(
Als
Aei Aei
Aeu Aeu
Aqp
Aei
Alt Alt
Alg
Alg
Alg
Alg
Aqp Aqp
Aqp
Alg
Alg
Aqp
Aqp
Aeu
Aqp
Ael
Aes
Aqp
M
M
Alg
Alg
Ali
Alg
Al
Asz
Al
Als
F
(
(
(
(
(
(
(
Alt
M
(
(
(
(
(
(
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(
(
(
(
(
(
(
(
(
(
(
(
(
(
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Abv
(
(
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(
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(
( Abd
(
Aeu
(
( Ang
(
(
(
Anv
Ang
Anv
Asd
Ang
Aef
Aeg
Aeg
Aeu
Akc
Aei
Aei
Ang
Anf
Aks
Akc
Aks
Akm
Akf
Aeu
Akv
Anv
M
(
Ad
Amv
Abi
Aqp
Aqp
Aus
Abi
F
Abi
Aqp
Abv
Als
(
Abv(Abv
(
(
Abv
Aus
Abi
Abs
Abs
Al
Al
Ang
G
AeuAeg
Akf
Ang
Anv
Anv
Aks
Akm
Agr
Ang
Anv
Agr
Akf
Aei
Anf
Anv
(
Anv
M
Ami
Abt
Al
Anf
(
(
Aln
Awt
( Anf
Aas
Abs
Anv
Anv
Anv
Anv
Anv
Ang
F
Abs
(
Aks
Akf
Akf Akc
Apt
Anv
Anv
Ans
Ans
M
F
Aln
(
(
(
M
Abs
Abs
(
(
(
Ang
Ang
Anv
Akv
Ang
Ang
Ans
Ang
Ang
Ans
(
Abs
Aas
Atm
Aln
Anf
Ans
Anv
(
Abs
Aln
Aln
Abs
(
Ans
Anv
(
Atm
Awt
Ang
(
Ami
Aln
Abs
Ami
Amv
Amv
(
Abs
Aas Ang
Abs
Abs
Aln
Asm
(
AltF
(
Ang
Akf Aks
Ang
Ani
Anv
Ang
AngAnf
Anv
Ang
Akv
Anv
Ang
Ang
Akc
Akv
Ang
Akm
Anv
Aks
Minnesota Geological Survey
University of Minnesota
2016
480 00’ 00”
Akv
Ang Ang
Anv
Ang
Ang
Akv
Akv
Anv
F
Aas
Ang
Ang
F
Aln
Asz
(
Anv
Ang
Anv Ang
Ang
Anv
Ang
Ang AnvAng
Ang
Aks
Ang
Anv
(
(
Ang
Anv
Ang
(
Asz
(
(
Atm
Al
Aln
(
Abs
Aln
M
Ami
Aln
Atm
Abs
Abs
Aln
Aas
Ami
M
Aas
(
(
(
(Ang
Asz
Aln
M
Aln
Adp
MAas
Abs Abs
Aas
Abs
Agm
Agm
Aas
Abs
Aas
Abs
Adp
Aas
Aln
Agr Agr
Ang
F
Alm
Agm
Aas
AnvAng
F
Asm
Alm
Adp
(Anv
M
Alm
Aas
Aln Aln
F
Adp
480 00’ 00”
Aas
M
920 30’ 00”
Lake County
F
St. Louis County
Ad
~ D1
NEOARCHEAN