Transcript Earth History GEOL 2110 The Cryptozoic (Precambrian) SuperEon Part 3: The Meso- and Neoproterozoic Eras.

Earth History
GEOL 2110
The Cryptozoic (Precambrian)
SuperEon
Part 3: The Meso- and Neoproterozoic Eras
Major Concepts
• After the formation of the Paleoproterzoic continent of
Laurentia, new marginal terranes continued to be
added to the “south” in the Mesoproterzoic.
• The most significant of these terranes was the Grenville
which was a mobile belt formed by the collision of
Amazonia and Laurentia between 1.2 and 0.9 Ga
• A major starting plume event at 1.1 Ga impacted the
lithosphere under what would become Lake Superior.
This brought on the development of the Midcontinent
Rift – an aborted attempt at continental rifting.
• Toward the end of the Proterozoic Eon (~1.0 Ga), one
of the largest supercontinents in earth history formed,
Rodinia, which had Laurentia at its core.
PALEOPROTEROZOIC ACCRETED TERRANES
Creation and Growth of LAURENTIA
_______________
THE
MIDCONTINENT
RIFT
_______________
An attempt at
continental rifting
1.1 billion years
ago
A. Rift Magmatism
Basalt
Flows
Gabbro
1,109-1,086 Ma
Crust
Mantle
The Evolution of
the Midcontinent
Rift
Mantle
Plume
B. Sediment Infilling
Sandstone
1,090-900 Ma
C. Compression
1,000-900 Ma
Fissure
Eruption
Massive
Basalt
Amygdaloidal
Basalt
Amygdules – Gas bubble fillings
Chlorite & Zeolite
Epidote & Feldspar
Zeolite
Thompsonite
LAKE SUPERIOR
AGATES
Gemstone of
Minnesota
Formation of
Lake Superior
Agates
BASALT FLOW SURFACES
Aa
AA
Pahoehoe
HAWAII
Pahoehoe
NORTH SHORE
High Falls on the Baptism River
Palisade Head Rhyolite
RHYOLITE
The other volcanic rock type
Palisade Head
INTRUSIVE IGNEOUS ROCKS
Gabbro
Subvolcanic
emplacement of
magmas
Duluth
Complex
Layered Gabbro
Beaver
Bay
Complex
Granite
Origin of MCR
Igneous Rocks
SEDIMENTARY ROCKS
of the Midcontinent
Rift
Cutface Creek
Sandstone
Freda
Sandstone
LATE-STAGE FAULTING
The Douglas Fault at Amnicon Falls State Park
Basalt
Sandstone
Why isn’t Duluth a Sea-side
Resort?
Blame it on Grenville & Rodinia
Assembly
of Rodinia
1200 – 750 Ma
Li et al., 2008
Li et al., 2008
Deconstruction
of Rodinia by a
Superplume
750 Ma
Li et al., 2008
Next Lecture
Early Evolution of Life
Chapter 9
Midterm I returned – PROMISE!