Prepared and Published with the Support of OPEN FILE REPORT MINNESOTA GEOLOGICAL SURVEY THE U.S. GEOLOGICAL SURVEY NATIONAL COOPERATIVE GEOLOGY MAPPING PROGRAM UNDER AWARD NUMBER G16AC00192, THE BEDROCK GEOLOGIC MAP OF THE SOUTHERN ARROWHEAD AREA, LAKE OFR-2016-04 Harvey Thorleifson, Director 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 AND ST. LOUIS COUNTIES, NORTHEASTERN MINNESOTA By Terrence J. Boerboom, Amy L. Radakovich, Mark A. Jirsa, and Val W. Chandler Minnesota Geological Survey University of Minnesota
2017 90°57’52”
Mrf Mnu Mrf Mnr Mnr 47°30’00” Mjm Mnb Mbc Mrc Mnr Mjm MmdMmg Mjx Mbc Mmg Mmg Mrf Mrc Mmm Mjm MroMnr Mro Mnu Mce Mjm Mrf Mnr Max Mcd Mca Mjx Mri Mri Mce Mmm Mmg Mjd Mrc 93°07’30” Mca Mmg Mbf Mrf MriMra
Mgf Mjt Mmi Mbq MbfMro MAP UNITS
Mwm Mgg Mca Mjt Mnr Mrc Mny Cook
S Ams Aqp Pab Pvt Mgg Mcb Mmg Mjl Mbi MroMro T58 R5 S Aqp Mri S Mbi Mri S S Mmg S ! Avc F Aqm M M S PabF Pab Ams Mjg Mbp F M Pab Aqp Paq Mpt Max Mjg Mbi Mbc Mbi Mro Mrf Mnl 47°30’00” F Avc Mvh Mgt Mjl Mbp Mra Paq PaqPaq Ams Ams Mvh Mce Mca Mbq Mro MbqMbcMbcMbi Aqm Aat F F Pab! ! Ams Pab Mmg Mjl Mju Mjh Mjx Mfl Mdh Mto M F Pab M Pab Ams Gilbert Mui Skibo Mgf Mjx Mbp MbqMroMbq
Chisholm M ! Avc Ams Mvh Mgg Mjx Mjx
Pvt Mpt Mju Mju Mro T58Mnr R6Mny ! Pvt Pab Amg !Paq Mvh ! Mcd Mja MjaMja MnbMbi Mro Mro F Avc T58 R7 Mbg Mbo Mny Pab T58 R19 Pvt Max T58 R8 Mjf MjfMjh Mjx Mbi Aqm Pab Pab Amm Paq Mju Mja Mjf Mri Mbi Mny Mnu Msf Mdj Mtg Aat Paq Pab Pab Ams Mgt T58 R9 Mbf Mbf Mnl Mnl LargoPab Ams Amm Pab Max Mvh T58 R10 Mjf MjxMjx Mbi Mrf Mbo M Amg T58 R11 Mjl Mfq Mjh Mro
! Ams AmgAmm Mvh Max T58 R12 Mfq Mjx Mri Mnm
Ams Max Mvh T58 R13 Mwg Mfq Mbc Mny
S T58 R14 Mca Mju Mbo
M Pab Amg S Pab Mvh Mfq Mja Mrf
F Paq M T58 R15 Mcb Mja Mbp
Paq F F T58 R16 Max Mvh Mny Msl Mdk Myg
M Mvh Mro Mbc
Aat Paq AmsM Paq Max Mnr Mjf Mbg Mbp Mbq Pab M Maple
T58 R22 T58 R21 Lavinia M Pvt Mwm Mbf Mro Mbf MnfMnk Aat M Ams Amm Mbg
Saint Clair Junction M Ams Mvh Mfq Mbf Mbi ! Pab T58 R17 Mfq Mbp ! Mbg F Paq Amg Mbg ! Max Mce Mcf Mfq MbpMbg Mnb Mbq Pab AmmAmg Pab! Mjl Mbf Mbg Mnb Paq Pab Pab Genoa Mgg Mfg Mbq Mbc Msk Mdt Myd
Paq Mju Mbq Mnc
! Max Mdd Mbp Mbi MbcMbi
Pvt M Paq Mui Mpt Mjl Mfg Mfg Mbi Mnm Pab F ! Whyte Pab F Pab T58 R20 T58 R18 ! Mgf Mnr Mbp Mnb Mbf Mbi Mbi Mbo Mnl ! Pab Mvh ! Mcd Mfg Mbf MbgMbf Mnk Paq M Mvh Mgt Mca Mju Mjh Msm Mdx Msy F Msh Mce Mfq Mro Mra Pab M Mca Mcb Mfq MbpMbg Mbg Mbg ! Pab Mce Mfg MbiMbf Mnk Paq Pab Mvh Mvh Mfq Mra Mra Mbp Mbo
Wolf Snowden Mxg Mbp Mbp
Paq ! ! Scott! Mwm Mra Mbp Pab Mahoning M Max
Pab Pab ! Mnb Mrf Mdb Msa
Paq ! ! ! Mfg Mfg Mfg Mra Mra Mnu Mnk
Paq S Mvh Mnb Mnb Mro Mnl Pab F Mxg
Mnr Mcg Mnb MroMro S Pab ! Pab Pab Mjl Mnb Mro M Pab Pab Pab ! Mnb Mfg Mnx Mra T57Mnb R6 Mnm Clappers Msh Mcf Mih Mju Mfg Mnb Mro Mra Mnk Mrc Mdn Msc Pab ! ! Mgg Mcf Mce Mxg MnbMra Pab ! Mnb MnbMra Mra Paq Sherwood Mda Mwg Mro Mxq Mra Mnb Pab! Mcg Mfg Mfg Mra Mnc Pab ! Mgf Mvh Mcf Mxq Mnl Mih McgMcg Mfq Finland Mnb Mnf Mri Mma Mom Max Mnb Mih MceMce Mce Mcb Mnb Hibbing Mgt Mjl Mfg Mro LittleMni MaraisMnb Mnl ! ! ! Mcg Mjl Mju ! Mnb Mnb Paq ! Mgg Mdd Mnb ! ! Reno Mgt T57 R11 Mvh Mju Mnb M Max Mxg Mnb Mro Mmt Moo Pab ! ! Mda Mca Mjl T57 R8 MnbMra Mro Palo Mcg Mju Mcb Mro Mna Mro Mvd ! Scott Junction Mfg Mro Paq Kirk T57 R7Mna Mro Mvd Mnc Pab ! Ramshaw ! ! Mcb Mfq MxgMro Mvd Mra Mro ! ! Mpt T57 R13 Mfg Map Symbols Mra Mgn Mog Paq T57 R14 Mvh Mxg Mnb AatPaq Pab T57 R16 T57 R12 Mfg Mro Mro Mjl Mnb Mnb Mnb Mnl T57 R19 Mcd Mju Mfq Mxg Mca Mna ! Mda Toimi Mxg Mxg MnbMnbMnb T57 R22Pab T57 R20 Mce Mxg Mxg MnrMnb Bell Harbor Mnb T57 R15 ! T57 R10 T57 R9 MxgMxg Mny Mnb Mrg Mgf Mof Pvt T57 R17 Mgf Mfg Mxg Mnx MnyMnb Cherry Mgg Mxg Mxg Mna Mnx Mna Mro Mnb! Mcg Mxg Mvd Mro Contacts and faults Keewatin ! Mxg Mnb Mnb Pab ! Mgt Mxg Mno MnbMfh Mui Mxg Mnb Mvd Mgg Mwm MxqKennedyMro LandingMca Mnb Mnb Mnb Mnb Mnl Mop Mda Mfg Mnb Mnb Pab Mui Mdd Mca Mfq Mxg Mxq Mnb Mnb ! Mxq Mnb Mvd MnxMnb Geologic contact T57 R18 Mxg Mro Mra Mra MnbMnbMnx Mpf Mgt T57 R21 Mxq Mxq Mna Mhq Keenan Max Jordan Mxq Mra Mro Mnb ! Mra Mnb Msm ! Mvd Mnb Mnb Mnb Mnb MroMroMro Mnb Outline of Cretaceous rocks Mxg Mnb Mro Mno Mro Mjh Mpc Mho Mxg Mxo Mro Fairbanks Mxg MraMra MsmMnb Mnr Mgn Mnu Mvd Mro Msl Mvh Mnb Mro Peary !Mda ! Mcb Mxo Mra Mro Msm MnbMroMnoMnb Mda Mmi Mjn Mra Mpf Msm Fault ! ! Mra Mno MnbMnoMro Mvh Mxq Mro Mxo MraMra MnoMsfMny Mns Mjf Mbb Mhg Mpt Darby Junction Mpf Mno Mih Mih Mxo Mxo Mnu Mvd Mro Mnb Mnb Mnb Mnb Mmt ! Mxo Mra Mno 5 5 5 Riley Mra Mro MnrMny Mro Mnb Mma Mxo IllgenMvd CityMnb Mnb Msm ! MvhMvh Lax Lake MnoMnb MnbMno Fault, reversed Mja Mbt Mht Forbes Makinen Mxg Mxo Mnu Mra Mno Mny! Mra Mro ! Mih Mxg Mny Msm Mcd ! Mra Mra Mra Msm Mnb Mnb Max MraMraMra Msl Mro MnbMny Mcf Mxg Mnu Mra Mny Mnu Mjx Mwm Mkf Mmt Mkf Mxg MraMra Mra Mny MnrMnbMno Hornby Mih Mxo Mnu MraMroMnb Mny Mro Mnr Dikes ! Mxo Mro T56 R10 T56Msl R7 Mnu Mnb Mnb Mnb Mjg Mkg MraMsm Mro Mpt Mkg Mro Mno Mro Mra Msm Mnu Mny Mnb Md Mwm Mny T56 R19 Mma Mnu MnbMno Mro T56 R12 T56 R8 Mnu Mju Mda Msr Mgn T56 R9 Mro Mro MnbMny Mnu Mro Mro Max Mfb T56 R11 Mra Mno Msm Mny Med McNair Mro Mnu Msm Mro T56 R13 Mvh Mcd Msf Mro T56 R14 ! Mxo Mnb Mjt Max Msb T56 R15 Mcb Mxo Mra Mra Msm T56 R18 T56 R17 T56 R16 Mmt Mro MsmMsf Mcd Mro T56 R22 T56 R21 T56 R20 Mvh Mra Msf Msl Onega Msm Mft Breda Mca Mvd Mvd Msm ! Mkg Mpf Mro Mjd Mde Mdd ! Mfb Mra MnbMnb Lake Mra Mnb Mnr Mcc Mra Mnb Mno Mno Zim Silver BayMno Mno Mn Mjm Mdp Mnl Mro Mnb ! Mno Mno Mnp Mra ! Mma Mvh Mrg Markham Mnp Mnp Mnb Mwm Mfb Mnb ! Mvh Mca MnoMnp Mno Mnb Mjl Mfb Mnm Mkf Mvh Msc Mno Mra Mr Max Mno MnoMnp Mro ! Mnb Mro Mno Mnb Mro Msk Mvh Mnr Msk Msl Mra Mjn Mwg Mnk Mxo Msy Mno Mro Mu Mnu Mxo Mxo T55Msm R7 Mwm Mnb Mro Mxo Mnb MnrMnb Msk Brimson Msc Msm Mfg Mfd Mnf Max Mfb Mud Mnb Mnb ! Mnb Mnb Mny Mxo Mxo !Mno Mnr Pdn Mvh Mnb MnyMnb Mkf Mxo Mro Mnr Mfq Mui Mnc Mkf Beaver BayMnb Msk MraMra Mnr Mvh Msc Mno ! Mrg T55 R8Mro Mra ! Silica Mof Folds Mcg Mdg Mna
! Rollins Mro
5
5 Mog Mro Msm 5 5 ! Msc Mxg Mno Casco Mbb Mkg Msl F Mwm Anticline
! Mbb Mbb Mro Mcf Mdo 5 5 Mnb
5 5 Mbt Msk Beaver Crossing Mra
Itasca Mrh Mom Mnu Mnp
5 5 5 5 ! Mnp Melrude Mbt Mom Mxg Mra S Mce Mih Mnd Mnp Mnp Monocline
! T55 R10 Mof Mno Mnu 5 5
5 5 Mbb Mog T55 R12 Wales Mnu
T55 R14 T55 R13Max Mag! T55 R9 Mno Mnp Mro
5
T55 R15 5 Mcd Mmi Mni 5 5 M T55 R17 Mbt MraMnu Mro T55 R18 Mbb Mna Mnu Syncline
T55 R22 T55 R21 T55 R20 T55 R19 T55 R16 Mbt MnoMnu 5
5 Max Moo 5
5 Mpc Mih T55 R11 Mcc Mzf Mno
5
5 Mbt Msc 5
5 5 MrgMra 5 5 MuiMui Mpc Mht Mom Mna Msb Linear Features Mrg Mrg
Mih Mvh Mrh Mna Mrg Mcb Mpg Mnp
5 5
5 5 Mvh Mra 5 Mna Mvh Mno Mvh Mnb MraMraMnb Mrg Flow contact
Mvh Mvh MnoMvd
5 5 5 Sax 5 5 Highland London Mno Mra Mro Mca Mgd Mnr
! ! ! Mna Mnb
5
5 Msr Mna 5
5 Max Mop MnaMna 5 Mui Mvh Mno
Mui Mna Mnb Msm Lidar foliation
Max 5 5 Mno MsfMnb Mxq Mag
Max Mra Mns
5 5 5 Mna Mvd
Aqm MuiMui Msa Msb 5 Hull 5 Mom Mna Mna
Max Mso Mno MsbMnbT54 R8Mra 5 ! 5 Mna 5 Lidar fracture Mxg Mbx Mnu
Max Mvh Mom Mna Mna 5 5 Lauren
Mbb Msr Mnb Mno
5 5 ! Whiteface 5
Mna Mno Mna 5
! 5 Mxo Mrh Mny
Mop Mna Msr Thin interflow sandstone
5 5 5 Max Mht
Mpg Mna
5 5 Mbb Mvh Mnu Mna 5 Mna Mbg Mfh 5 Mnx
Mwm Outcrop 5 5 Mnb 5 Cotton 5 Mzf Mof Mno
! T54 R10 Msa
5
5 Mbq Mud Mvh
5 Toivola 5 ! T54 R9
Msy
5 5 Mno 5
5 Max Mbt Mbc Meg Msh 5
5 Mvh T54 R11 Msc 5 Kelsey 5 T54 R12 Alger ! T54 R13 Msg !
T54 R15 T54 R14 Mna Mbf Mes 5
T54 R16 5 Meb 5 Dumblane 5 Mnu T54 R22 T54 R21 T54 R20 T54 R19 ! Mnp
5 Msy 5
T54 R17 5 Mbi Mls Meo 5
Mwm5
5 5 Mno Mno T54 R18 York Mhg
St. Louis Mbb Max ! Mbo Mlf Mep
5 5
Mhq Myg ! 5 5 Mho
Mno
5
5 Myd Mvh Mbp Mlg Mng
5 5 Silver Creek
! Mvh 5
5 Mni
Mhq Msc Mmm 5 Shaw 5 Mld Pvt Pvt Mnb
! Mno Mno MESOPROTEROZOIC 5
5 Stewart MvhMnb
MvhMvh Mbx 5
5 ! Mno Mna
Mvh Mna Mna MygMno Mmd Msd Pab 5
Elmer 5 Duluth Complex and 94 ° International 93 ° 5 ! 5 Mhg Mnb
Mbb Mvh Mhq Falls 5 5 Msc Mno Mna North Shore Volcanic Group Mmg Mli Paq
Payne Max Mna 5
5 Mtd Mvh ! Mui Myd
Mui Mbt 5
5 Mbt T53 R10 Mna 5
5 Mtd Mno Mdu Mtd Aqm 5 5 Mda 92 °
Mbb 5
5 Mui PALEOPROTEROZOIC 91 ° 5 5 Mnu Mno Mdl Msg Aat
Mni Mvh
5 5 Mnb
Mnu Mni 5 Meadowlands 5 Waldo Mnb Virginia, Thomson, and
Mnb Mdc Mso Avc 5 5 ! 90 ° ! Mui T53 R11 Mno Mnd Mnd Mno Mnb
T53 R22 T53 R21 T53 R12 Mnu Msc 5
5 T53 R14 T53 R13 Mnd Mna Rove Formations 5 T53 R15 5 48 °
T53 R19 T53 R17 T53 R16 Mui Mfh 48 ° Mdf Msp Aqp 5 T53 R20 5 Mno Ely
T53 R18 Mnd 5 5 Mno Mno Biwabik, Gunflint Mdm Wawina Mtu Mtf Ams ! 5 Mno Iron Formations Lake Mvh Mnd Mnd Mdl Mtt Mno r 5 Mtf County r i o Mds Mts Amg Mts u p e Canyon Mto e S ! MnoMnd k Mui Mdt Mnd Mna Mnb NEOARCHEAN L a Mdi Mtt Amm Birch Mtg Mno Mno Mvh Mto Mnb ! Mbb Mbb Mnb ° Mbt 90 Mbt ! Virginia Mno Granitoid rocks Mdr Mtu Mvh Mnb Mtg Mdc Schist and migmatite Grand St Louis Mtg MnoMnb Baden 47 ° Rapids County ! Metavolcanic and 47 ° Mno Mnb T52 R11 Prosit Mni Mno Mnd volcaniclastic rocks Duluth Hartley Spur ! Taft ! Mtg Mno ! Mnd Mnd 0 60 mi T52 R17 MnoLarsmont Island ! Mnu Mno Mna 92 ° ! Mvh ! T52 R18 T52 R13 Mnu T52 R12 T52 R22 T52 R19 T52 R16 T52 R15 Fredenberg Mda 0 80 km SOUTHERN ARROWHEAD AREA T52 R20 Mnu T52 R21 ! Mld ! MldMlg Mlg Mes ! Mdl Figure 1. Map of northeastern Minnesota showing the location and general geologic setting of the Southern Arrowhead map area. T52 R14 Mnd Knife River
Mlg MndMndMnb ! MnaMnd Mnd Mnb Mgd MndMnoMnb ! Coleraine Junction Mno Mld Msp Mnu Mnb Msp Mno Mda Mnd Mnb Mnb Msp Mny Mno Mno Mnd Mno Mno Mnb Msp Mnd Mnu Mno Mnd MnoMno Floodwood Mna ! Mnd ! MnaMnd Arlberg ! Mnb ! Mdt Mny Mno T51Mnd R12Mnd Mnd St. Louis County Lake County Bartlett Mda Mnd Mnb ! Mnd Mno 91° MnoMlf 93°07’30” 93° 92° French River Mnd (!!(! (! 47°30’ (!(!(!(!(!(!(!(!(! (!(! Mlg Mno (!(! (! (! (!(! Burnett Mdc Mlg Mna Mnd ! ! (! ! T51 R13 Mno (! (! (! (!( ! (! (! (! (! (! Mni Mno ! (! Mnd Mna (!(! (! ! Mnd ( ! T51 R15 Mdl MniMna (! ! (! (! T51 R18 Mnb (!(!(!(! (! (! ((! T51 R19 T51 R14 Mls Mnr Mnb Mno (!(! (!(! (!(! (! T51 R22 T51 R21 T51 R20 Meg Mld Mni (!(!(! (! (!(! (! Mdt (! (! ! Mdt (!(! (!!(! ! Mda ! !! (! (!(!(!(!(! ! ( (! Aitkin Mnd (((! (! ((!(! ( (! ! Mnb (! !(! (! (! (!(! Twig Station Mdc Mvh ( ! Mdc LakewoodMnb MndMnb T51 R17 T51 R16 Mdl Mes (! (! (! Paupores MdaMda Meg Mno Mdu Mny ! Mdc (! Brookston Mdb Mdc Mnu (! (! ! Mls ! Gowan ! Mdt (!(! ! Saginaw Mdc Mdl Mni (! (!
Mnu
Mdu !
5 ! Mdl 5 ( 5 Mdc 5 Four Corners Mda Mdo Meg Mny Mlf
Mdg Mes (!
! Mdl Mdu Mnd Mlf 5 5 Mda Mdg Mls 5
Mdu MdgWoodland Mlg (! (! 5 Mda 5 (! ! MdgMdo Mda Mnb 5
Mdb Mdc Mdo Mni (! 5
5 ! 5 5 ( 5
Mdt Mdl Mdp Mdg Mnb ! Mni (! 5 !(!(! Mda Mli (!(!(!( (! Mdu Mls Mny (!
Mda Mnb Mnb 5
T50 R15 Mnb Mno Mni 5
5 5 5 ! Meg 5 MdoMnp Mnb (! (! Mdc (! (!(! (!(!(!( MnbMno Mny Mnd (! !((!(! Mdl Mnb (!
Mdu Mdo Mdg Mes 5 5 5 Mda 5 !((!(! Mda MdoT50Mdg Mno R14 ( Mdt Mda Mny (!(! MnpMnp Mnb (! Mdc Mdo Mnb Mdl Mda Mdg ! Mdb Mdp Mdu Mnp (! (!(! Mda Mdg (!(! HermantownMdp Mdp (!(! Mdt Msd ! ! Mda Mdp Mda Mns (! (! T50 R19 T50 R18 Mdu Mnb T50 R21 T50 R17 Mdc Mdp Mdp T50 R22 T50 R20 Munger ! Duluth Mdl ! Mda MnpMnbMnp MepMdb Mdt Mda Mnb Mns (! Mnb Mdu Mda Mda Mdo Mtd (! Mda Mdl Mdu Mdg Mnp (! Lake Superior T50 R16 Mdt Mdc Mda Mda Mnb MepMdb Mdl Mda MdaMdu Mtd ! Mda (! Mda Mda ! Mvh MdgMni Mnp AdolphMdt Mnb (! (! ! Mdc Mdg Mdl Mdo (! (! MepMdb (! (! (! Mdt Mda (!(! (! Mda ! Mde Mda (!(! ( Mda MdaMduMdu (!!(!(!(! Mdc (!(!(!(!(!(! Mda Mde Mda !(!(!(!(!( 92° Mdp Mda ! (!(!((! Mda Mda (!! Mep Mdp 46°45’ ( Mdb Mdt (! T49 R22 T49 R21 T49 R20 T49 R19 T49 R18 T49 R17 Mda Mdc Proctor Mda Mdu (!(!(! Mdl 46°45’00” ! ! Mda ! 93° (! Mda (!(! Mdh Mdl Mda T49 R16 T49 R15 Mda 93°07’30” Mda! MepMdb Mdk Mdr Mda 1:100,000 Mdt Mdf Mda N Pvt Mdj Mdi 0 1.25 2.5 5 7.5 10 Mep Mfl Mdb Mds Mdm Figure 3. Map of the Southern Arrowhead area showing bedrock unit contacts (red), superimposed on imagery of tilt-filtered, micro-leveled
Mda Figure 2. Map of the Southern Arrowhead area showing bedrock outcrop (red), locations of drill holes for which bedrock core exists (black circles), Miles ! M Mdr Mdt MdrF Mfl
Mng Mdr Mds aeromagnetic data. Mdh MdhM Mep F
Mdb Mdk Mdr Mds and geologic contacts and faults (black lines). Outcrops are portrayed larger than true size for visibility. 0 2.5 5 10 15 20 M
Meo Mdt Mdr Mdh F Mdr Mdn Mdn Mdh Kilometers MdrMdj Mdi! ! Mdn Esko Meo Mdt MdkMdhMdt ! Mep Mdn Mdk Mdb Mdt Mdt Mdh! Mdn Mdh Mdn MeoMeb Mdt MdkMdk Mep MdtMdt Mdb Mdt Mdt MdtMdn Carlton Meb Mdb Mdn Mdt Meb Mdt ! Mdb Mdn Mdt Mep Meo Mdb Mdt Meb Mdt DESCRIPTION OF MAP UNITS Duluth Complex Mag Subophitic fine-grained ilmenitic gabbro from aeromagnetic maps Brownell Mdb Mdt Layered series Mbx Intrusive breccia dike Med Diabase dike in reversely polarized Ely’s Peak ! Meb MdtMdt Meb Mdn Gary MESOZOIC Layered Series at Duluth Mrh Remobilized rhyolite hybrid felsic melt basalts, but not in adjacent normally polarized Duluth ! ! Mdu Upper contact zone-ferrodiorite, ferromonzodiorite, Mfh Small felsic-intermediate hybrid intrusion Complex Mfl Coleraine Formation ferrogabbro Mud Ophitic olivine diabase New Duluth ! ! CRETACEOUS Kc Cretaceous conglomerate, sandstone, siltstone, Mdl Gabbroic zone-oxide olivine gabbro CORRELATION OF MAP UNITS mudstone, and lignite Mdc Cyclic zone-troctolite, augite troctolite, olivine Endion sill KEWEENAWAN SUPERGROUP Some intrusions are composed of several subunits that are shown in expanded form with call-out boxes. Kc Coleraine Formation gabbro, oxide-olivine gabbro Meg Granophyre, quartz ferromonzodiorite North Shore Volcanic Group MESOZOIC MESOPROTEROZOIC Mdf Cyclic zone 4-augite troctolite, olivine gabbro, Mes Diabase Schroeder-Lutsen sequence (normal magnetic polarity) unconformity troctolite, leucogabbro Mnl Schroeder basalts - ophitic to subophitic, olivine KEWEENAWAN SUPERGROUP Mdm Cyclic zone 3-olivine oxide microgabbro Northland intrusion tholeiite basalt flows T48 R16 MIDCONTINENT RIFT INTRUSIVE SUPERSUITE KEWEENAWAN SUPERGROUP Fond du Lac Formation Mds Cyclic zone 3-olivine gabbro, augite troctolite Mls Diabase, granophyric gabbro, ferromonzodiotite, Mnm Manitou River basalt - single flow of intergranular Mfl Arkosic sandstone, siltstone, shale, conglomerate Mdi Cyclic zone 2-olivine oxide microgabbro quartz monzodiorite basalt Mdr Cyclic zone 2-olivine gabbro, olivine oxide gabbro Mnf Feldspar-phyric rhyolite 46°37’30” NORTH SHORE VOLCANIC GROUP MIDCONTINENT RIFT INTRUSIVE SUPERSUITE Mdh Cyclic zone 2-troctolite, augite troctolite, olivine Lester River intrusion Mnk Pork Bay volcanic breccia - polymict, matrix- Beaver Bay Complex gabbro, oxide-olivine gabbro Mlf Granite, granodiorite, monzodiorite supported volcanic breccia in an unbedded sandy 92°23’00” Mfl Fond du Lac Formation Silver Bay intrusions Mdj Cyclic zone 1-microgabbro, olivine oxide gabbro, Mlg Ferrodiorite to granophyric gabbro matrix unconformity Msf Melanogranophyre olivine gabbro Mld Diabase Mnc Little Marais volcanic conglomerate - polymict Schroeder-Lutsen sequence Msl Foliated olivine ferrogabbro cumulate Mdk Cyclic zone 1-olivine gabbro, augite troctolite, oxide volcanic conglomerate in a red-poorly bedded sandy Msk Poikilitic olivine ferrogabbro cumulate troctolite St. Scholastica intrusion matrix Mnm Msm Vari-textured gabbro marginal phase Mdt Troctolitic zone-troctolite, augite troctolite, gabbroic Msd Diabase Mnl anorthosite Upper Southwest sequence (normal magnetic polarity) BEAVER BAY COMPLEX Mnf
Beaver River diabase Mdx Troctolitic zone-peridotite Lakeside intrusion Mna Andesite, basaltic andesite MISCELLANEOUS INTRUSIONS Mnk Mrf Ferrodiorite, non-to-poorly foliated Mdb Basal contact zone-olivine gabbro, augite troctolite Mli Diabase Mnb Undifferentiated basalt to basaltic andesite flows Beaver (temporal relationships uncertain) Mnc Silver Bay intrusions Mrc Ferrodiorite cumulate, foliated Mdn Troctolitic zone-melatroctolite, dunite Mnd Diabasic basalt River Kane Lake Split Rock unconformity SBI Sawmill Lake Diabase dikes Mri Intergranular olivine-oxide gabbro Tunnel intrusion Mni Icelandite diabase Endion sill Lester River intrusion intrusion Intrusion felsite Murphy Creek intrusion Mtd Diabase Mno olivine tholeiite basalts with ophitc texture Mft Mro Ophitic olivine diabase; main phase BRD Sonju Lake intrusion Milepost 7 ferrodiorite Msf Victor Head diabase Mra Anorthosite inclusion Mma Heterogeneous, poikilitic to ophitic augite troctolites Mnp Porphyritic basalt Msl Msk Msm Mvd Mpf SLI Mkf Msr Mrg Granitoid inclusion to augite-bearing troctolites Sawmill Lake intrusion Mnr Aphyric rhyolite Finland radar station granophyre Cloquet Lake layered series Mmt Troctolitic rocks; commonly poikilitic Msg Granophyre, granophryic granodiorite, monzodiorite, Mns Interflow sandstone, siltstone, and conglomerate FRSG Lax Lake gabbro Blesner Lake diorite Inclusions in Upper Manitou River gabbro Victor Head diabase monzogabbro, ferromonzodiorite Mnu Undifferentiated basalt, andesite, icelandite, rhyolite Beaver River CLLS LLG Mrf Mrc Mri Mro diabase BLD UMRG Mvd Ophitic olivine diabase, fine-grained, red-oxidized Greenwood Lake intrusion Mso Ophitic diabase, ferrodiorite with local interflow sediments Mrg Tunnel diabase Lakeside intrusion
Mgn Oxide olivine gabbro - noncumulate; based entirely Mny Porphyritic rhyolite Northland intrusion Stony Point diabase DULUTH COMPLEX Mra Mfg Mfq St. Scholastica diabase Milepost 7 sill on aeromagnetic signature and one drill core Stony Point diabase Mnx Unsorted, variably bedded, polymictic to tuffaceous Layered series Mgd Mes Meg Mls Mli Mld Mlg Mlf Msd Mso Msg Msp Mtd Mag Mbx Mpg Mud Mfh Mrh Mzf Mpf Ferrodiorite Mgf Ferrogabbroic cumulates, inferred from two drill Msp Ophitic diabase volcaniclastic rocks Upper sequence Mmm Lower sequence Mmg Mmd cores and very strong aeromatetic signature Hornfels inclusions (unknown magnetic polarity) Miscellaneous intrusions Mjh
Mju Mjf Mja Mjx Mjn Silver Creek diabase Sonju Lake intrusion Mgg Gabbroic cumulates, inferred from two drill cores, Two Harbors intrusions Mvh Hornfels of volcanic, typically basaltic, protolith; Layered Series and inclusions Mjg Mjl Mjt Mjd Mjm Mdd Lafayette Bluff diabase
at Duluth London intrusion Mjh Hybrid dike scattered outcrop, and variable aeromagnetic high Mtf Foliated gabbro inferred derivation primarily from Upper Southwest Mxq Mxg Mxo Harbors intrusions Two
Mjf Upper olivine ferromonzodiorite Mgt Troctolitic cumulates, inferred from one drill core and Mts Intergranular subpoikilitic olivine diabase sequence Mdc MESOPROTEROZOIC Mja Upper apatite-olivine ferrodiorite cumulate subdued aeromatnetic signature Mtt Troctolitic ophitic diabase Msh Hornfels of sedimentary protolith Highland intrusive complex Mdx Mdi Mdm Downer Mjx Upper oxide gabbro cumulate Mtu Unexposed magnetic anomaly inferred to be mafic Mdl Mdj intrusion Upper sequence Mkg Msb Mdf Mdu Mjg Upper olivine gabbro cumulate Boulder Lake intrusion intrusion Lower Southwest sequence Mdt Mdr Mcg Mcf Mce Mcd Lower sequence Boulder Lake Mds Murphy Creek Mfd Mju Upper cumulates undivided Mpc Picrite to troctolite Mto Gabbro, diabase, monzodiorite Ely’s Peak basalts (reversed magnetic polarity) intrusion Mdb Mdk intrusion Mui Mjt Lower troctolite cumulate Mbb Olivine gabbro, oxide-olivine gabbro Mtg Ferrodiorite, ferromonzodiorite, ferromonzonite Meb Subophitic basalt Mdn Mdh Mcc Mcb Mca Western Mpc Mmt Mma Mmi Mih Mjd Lower dunite cumulate Mbt Troctolite, augite troctolite, leucotroctolite Meo Ophitic basalt Mdg Mtg Myd Myg Md margin Mtu Mto Mtt Mts Mtf Mho Mhg Mhq Mjm Lower melatroctolite cumulate Lafayette Bluff diabase Mep Porphyritic basalt; basal flow locally pillowed Mgn Mgf Mgg Mgt Mdo Mht Partridge intrusion Mbb Mbt Mbp Mbo Mbi Mbf Mbc Mbq Mbg Mjl Lower cumulates, undivided Western margin intrusion Myg Granodiorite to monzodiorite Nopeming Sandstone (unknown magnetic polarity) River Mwm Greenwood Lake Hornfels Mjn Lower non-cumulate ophitic olivine gabbro to augite Mwm Generally troctolitic cumulates inferred from Myd Porphyritic ophitic diabase Mng Quartz arenite, siltstone, and quartz conglomerate troctolite Msc Msa Msy intrusion inclusions Upper Southwest sequence troctolite scattered drill core, rare outcrop, and subdued Mpt Mog Moo Mom Mop Mof Mn aeromag signature Silver Creek diabase PALEOPROTEROZOIC Anorthositic series Mna Mnb Mnd Mni Mno Mnp Mnr Mns Mnu Mny Mnx Finland granophyre Msy Vari-textured porphyritic diabase to monzonitic pods Max Mde Mdp Mda normal polarity (~1099 Ma) Mfg Leucogranite Partridge River intrusion Msa Altered diabase marginal phase ANIMIKIE GROUP Mu Mfq Quartz ferromonzodiorite Mpt Troctolitic cumulates; medium-grained, foliated, Msc Ophitic olivine diabase Pvt Virginia and Thomson Formations; argillite, slate, and Felsic series reversed polarity (~1106 Ma) Msh Mvh Lower Southwest sequence Mr Med ophitic, variably leucogratic graywacke Mwg Mfb Meb Cloquet Lake layered series London intrusion Pab Biwabik Iron Formation (capped locally by Sudbury Meo Ely’s Peak basalts Mcg Leucogranite Anorthositic series Mom Ferromonzodiorite Impact Layer) Mcf Upper monzodiorite and int-fels rocks Mda Anorthosite, troctolitic anorthosite, olivine gabbroic Moo Ophitic diabase Paq Pokegama Quartzite; quartz arenite, mudstone, and Mep Mce Upper gabbro to diorite anorthosite, leucogabbro, leucotroctolite; and Mog Ophitic gabbro conglomerate Mng Nopeming Sandstone Mcd Upper olivine gabbro to troctolite inclusions of same in younger intrusions Mof Foliated ferrogabbro unconformable and intrusive contacts Mcc Lower monzodiorite and intermediate rocks Max Mixed unit of anorthositic to gabbroic rocks; Mop Ferromonzonite to ferrodiorite marginal hybrid phase KENORA-KABETOGAMA DIKE SWARM Mcb Lower gabbro to diorite exposure insufficient to subdivide Highland intrusive complex Pdn Diabasic to gabbroic dike-normal magnetic polarity Pvt disconformity Sudbury Impact Layer Mde Troctolitic anorthosite, leucotroctolite Mhq Granophyric gabbro to quartz. monzonite (~1850 Ma) Mca Lower olivine gabbro to troctolite Pab Animikie Group Mdp Ophitic olivine leucogabbro, olivine gabbro, augite Mho Granophyric poikilitic olivine diabase to gabbro NEOARCHEAN Lax Lake gabbro troctolite Mhg Poikilitic gabbro to troctolite Paq Mxq Quartz monzodiorite Mht Troctolite WAWA SUBPROVINCE OF SUPERIOR PROVINCE unconformity Mxg Intergranular gabbro to diorite, non-foliated Felsic series Giants Range Batholith Pdn Kenora-Kabetogama Dike Swarm Mxo Ophitic olivine gabbro Mfb Granophyre inferred from aeromagnetic maps Kane Lake intrusion Aqm Porphyritic quartz monzonite, monzodiorite, and Mwg Mt.Weber intrusion-micrographic to intergranular Mkf Ferromonzodiorite to granophyric poikilitic gabbro granite; typically magnetic ALEOPROTEROZOIC
Blesner Lake diorite granophyre Mkg Gabbro, oxide gabbro, ophitic gabbro Aat Tonalitic, granodioritic, and amphibolitic orthogneiss unconformable and intrusive contacts P Mbg Micrographic leucogranite Mbq Quartz granophyric monzodiorite Miscellaneous intrusions and inclusions of the Duluth Split Rock felsite Midway Sequence WAWA SUBPROVINCE OF SUPERIOR PROVINCE Mbc Foliated ferrodiorite cumulate, varialy granophyric Complex Msr Fine-grained porphyritic felsite Avc Trachyandesitic to calc-alkalic volcanic, Downer intrusion Msb Mafic dioritic margin of intrusion volcaniclastic, and conglomeratic rocks Mbf Ferrodiorite, moderately granophyric, non-foliated Giants Range Batholith Mbi Intergranular gabbro, variably granophyric, non- Mfd Ferrodiorite ~ D3 foliated Unnamed Diabasic dikes Aqp Viking quartzofeldspathic porphyry intrusion Aqm
Mbo Ophitic olivine gabbro, moderately- to well-foliated Mui Oxide-rich ultramafic to mafic intrusions Mft Fine-grained ferromonzodiorite to ferrodiorite Mud Lake sequence (~2680 Ma) ~ D2 Mbp Poikilitic olivine diabase, non-foliated Mdg Ferromonzodiorite to granophyre composite dike intrudes unit Mkf Ams Graywacke-mudstone metamorphosed to zeolite to Aat Midway sequence Mdo Porphyritic ophitic olivine leucogabbro Mdd Diabase dike - intrudes normal polarity intrusive and greenschist facies Upper Manitou River gabbro Mih Metamorphosed gabbro, gabbronorite, ferrodiorite volcanic rocks Amg Gabbro and diabase sills and dikes metamorphosed to Avc 1 Mmm Melanogranophyre - micrographic quartz Mmi Magnetic inclusion of uncertain rock type Md Diabase dike - intrudes normal polarity intrusive and zeolite to greenschist facies unconformity NEOARCHEAN ferromonzonite volcanic rocks Amm Basaltic flows and autobreccia metamorphosed to Viking porphry Aqp
Mmd Diorite - intergranular olivine ferrodiorite to quartz Miscellaneous Intrusions Mn Diabase dike-normal magnetic polarity, inferred from zeolite to greenschist facies ~ D1 ferromonzodiorite Unnamed aeromagnetic maps Ams Mmg Gabbro - ophitic olivine gabbro to intergranular Mzf Prismatic ferromonzonite Mu Diabase dike-polarity unknown; short segments “The views and conclusions contained in this document are those of the authors Mud Lake sequence granophyric gabbro Mpg Granophyric gabbro mapped in outcrop and should not be interpreted as necessarily representing the official policies, Amm Amg Mgd Gabbro, diabase Mr Diabase dike-reversed magnetic polarity, inferred either expressed or implied, of the U. S. Government.”