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

2. 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.

3. PALEOPROTEROZOIC ACCRETED TERRANES Creation and Growth of LAURENTIA

4. THE MIDCONTINENT RIFT _______________
An attempt at continental rifting 1.1 billion years ago

5. The Evolution of the Midcontinent Rift 1,109-1,086 Ma 1,090-900 Ma

7. Fissure
Eruption

8. Massive
Basalt
Amygdaloidal
Basalt

9. Amygdules – Gas bubble fillings
Chlorite & Zeolite
Zeolite
Epidote & Feldspar
Thompsonite

10. LAKE SUPERIOR
AGATES
Gemstone of
Minnesota

11. Formation of
Lake Superior
Agates

12. BASALT FLOW SURFACES Aa AA
Pahoehoe
HAWAII
Pahoehoe
NORTH SHORE

13. RHYOLITE The other volcanic rock type Palisade Head
High Falls on the Baptism River
Palisade Head Rhyolite
RHYOLITE
The other volcanic rock type
Palisade Head

14. INTRUSIVE IGNEOUS ROCKS
Gabbro
Subvolcanic emplacement of magmas
Duluth
Complex
Layered Gabbro
Beaver
Bay
Complex
Granite

15. Origin of MCR Igneous Rocks

16. of the Midcontinent Rift
SEDIMENTARY ROCKS
of the Midcontinent Rift
Cutface Creek
Sandstone
Freda
Sandstone

17. LATE-STAGE FAULTING The Douglas Fault at Amnicon Falls State Park
Basalt
Fault
Sandstone

18. Why isn’t Duluth a Sea-side Resort?
Blame it on Grenville & Rodinia

19. Assembly
of Rodinia
1200 – 750 Ma
Li et al., 2008

20. Li et al., 2008

21. of Rodinia by a Superplume
Deconstruction
of Rodinia by a Superplume
750 Ma
Li et al., 2008

22. Early Evolution of Life Chapter 9 Midterm I returned – PROMISE!
Next Lecture
Early Evolution of Life Chapter 9 Midterm I returned – PROMISE!