Precambrian Geology of the Lake Superior Region
THE MAKING OF LAURENTIA
Jim Miller
University of Minnesota Duluth
The
Geologic
Record in
Minnesota
LAURENTIA
KENORALAND
Precambrian
Geology of
Minnesota
Direct Evidence:
OUTCROP
More Direct Evidence: DRILL CORE
Image from Dale Setterholm, MGS
Location of core hole
Drill core
1st vertical derivative of aeromagnetic data
Drill hole locations provided by Minnesota Department
of Natural Resources, Division of Lands and
Minerals, Hibbing 2002
Indirect Evidence: GEOPHYSICAL DATA
Supporting Evidence:
GEOCHRONOLOGY AND GEOCHEMISTRY
Geologic Paradigms
and Principles
Terrane 1:
The
Minnesota
River Valley
Gneiss
Terrane
>3.0 Ga
THE
MINNESOTA
RIVER
VALLEY
GRANITIC GNEISS
Early Continent Formation
Terrane 2:
The Superior
Province
(GraniteGreenstone
Terrane)
2.7-2.5 Ga
GREENSTONE
Metamorphosed Basalt
Pillowed Structures indicative
of submarine eruption
SEDIMENTARY ROCKS
BANDED IRON FORMATION
GRAYWACKE
GRANITE BATHOLITHS
Partially-melted Crust
(~ 2.6 Ga)
The Superior
Province
Multiple
Accreted
Terranes
TECTONIC MODEL FOR THE SUPERIOR PROVINCE
Accretion of Island Arcs, Oceanic Plateaus, and Protocontinents
SUPERIOR PROVINCE
A major episode of continental
growth creating KENORALAND,
the core of North America
Kenoraland
Terrane 3:
The Penokean
(and Yavapi
and Mazatzal)
Orogen
1.9-1.6 Ga
Making
Laurentia
MESABI-TYPE IRON FORMATION
Geologic Marker of a Major
Evolutionary Event
STROMATOLITES
(Fossilized Algal Mats)
A Key to the Origin of
Mesabi-type Iron Formation
Mary Ellen Mine
Shark Bay, Australia
LTV Mine
The 1.85 Ga Sudbury Impact
The First Major Extinction Event ??
Penokean
Orogeny
1.85 Ga
Thomson Dam
Eveleth
St. Cloud
Penokean Mountains (1.85 -1.75 Ga)
DENUDATION OF A MOUNTAIN BELT
SIOUX QUARTZITE
and Related 1.7 Ga Mature Sandstones
Flambeau
Rib Mtn
Sioux
Baraboo
The Amazing Shrinking Penokean
(From Holm et al., 2008)
NICE (Northern Interior Continental Evolution) Working Group: R. Anderson, T. Boerboom,W. Cannon,
V. Chandler, D. Holm, M. Jirsa, J. Miller, D. Schneider, K. Schulz, W.R. Van Schmus, and L. Woodruff.
GRENVILLE OROGENY
1150-950 Ma
Adding Laurentia
to the Supercontinent:
Rodinia
Terrane 4:
The
Midcontinent
Rift
1.1 Ga
An Attempt
at Unmaking
Laurentia
Initiation of
the MCR
by the
impact of a
starting
mantle
plume
A. Rift Magmatism
Basalt
Flows
Gabbro
Crust
Mantle
The Evolution of
The Midcontinent Rift
1,109-1,086 Ma
Mantle
Plume
B. Sediment Infilling
Sandstone
1,090-900 Ma
C. Compression
1,000-900 Ma
Origin of MCR
Igneous Rocks
BASALT – The Rock of Oceanic Crust
NORTH SHORE
Continental Flood Basalts
ICELAND
HAWAII
Massive
Basalt
Amygdaloidal
Basalt
AGATES
Gemstone of
Minnesota
Formation of
Lake Superior
Agates
High Falls on the Baptism River
Shovel
Point
RHYOLITE
The other volcanic rock type
Palisade Head
INTRUSIVE IGNEOUS ROCKS
Gabbro
Magmas trapped
in the Crust
Duluth
Complex
Layered Gabbro
Beaver
Bay
Complex
Granite
SEDIMENTARY ROCKS
of the Midcontinent Rift
Freda Sandstone
Interflow Conglomerate
LATE-STAGE FAULTING
The Douglas Fault at Amnicon Falls State Park
Basalt
Sandstone
Why isn’t Duluth a Sea-side Resort?
FINALLY, THE
STABLE
CONTINENTAL
INTERIOR
OF NORTH AMERICA
The
Precambrian
Research
Center
at UMD