1. Belt/Purcell Supergroup Oldest Rocks resting on NW Basement Rock
Glacier National Park

2. Extent of the Belt/Purcell Rocks
A-4
Extent of the Belt/Purcell Rocks
(from Burchfiel, Cowan, and Davis, 1992)

3. A-5
Belt-Age Rocks
(from Winston, 1971)

4. A-5
Belt Thickness
East
(Montana)
West
(Idaho)
15-20 km

5. Rock Types Shales Red Green Sandstones Limestones
Diabase Intrusions (Type of mafic igneous rock between a basalt & gabbro)
Belt Supergroup - Glacier National Park, Montana (Linda Kah).

6. Belt Structures - Shales/Sandstone
Laminations
Mudcracks
Ripples
Raindrop Impressions
Salt Crystal Impressions

7. Belt Structures - Limestones
Stomatolites

8. Shallow Marine - Intertidal Zone
Modern Stromatolites
Shallow Marine - Intertidal Zone

9. Sediment Source: East & West
(from Burchfiel, Cowan, and Davis, 1992)

10. Age of the Belt Basalt on top = 750 to 830 Myrs Age: Between about
Supergroup
Belt
Intrusiuons: ca. 1,200 Myrs
Mostly between
1,500 &
1,200 Myrs ?
Youngest Basement Rock - 1,576±13 Myrs

11. Interpretations Red Shale Green Shale Sandstone Limestone Stomatolites
Laminations
Mudcracks
Ripples
Salt Crystals
Western Source
Diabase Intrusions
Quiet: Land/shallow ocean
Quiet: Deeper ocean
Beach/river
Shallow tropical ocean
Quiet water / no animals
Arid land surface
Intertidal zone/beach
Salty Water
Land to the west
Hot spot / Divergent zone

12. Interpretations - Big Picture
Marine Embayment
Salty Lake
Inland Sea caused by Rifting

13. Continental Rift

14. Modern Inland Seas
Black Sea
Caspian Sea

15. Did the Belt Rifted Apart?
East
(Montana)
West
Belt
Supergroup
Where did it go?
Fault Bounded

16. Rodinia “Motherland” The World about 800 Myrs A-6 Montana (Belt)
New York
Rodinia “Motherland”

17. A-7

18. Rodinia Rifts (750 Myrs) Rifts to form the (pre-Pacific) Panthalassa
Ocean
Montana
Rifts to form the (pre-Atlantic) Iapetus Ocean
New York
Rodinia Rifts (750 Myrs)

19. Rifting of Rodinia

20. Windermere Supergroup
As Rift Spread Apart Seiments Accumulate on the Margin of North America
Windermere Supergroup
( Myrs)

21. Extent of the Windermere Rocks
A-4
Extent of the Windermere Rocks
(from Burchfiel, Cowan, and Davis, 1992)

22. Windermere-Aged (750-550 Myrs) Rocks
(from Winston, 1971)

23. Windermere: Toby Formation
Tillite
Late Proterozoic Ice Age

24. Major “Ice Ages” in Earth History5
Major “Ice Ages” in Earth History 4 3 2 1

25. Glacial Evidence for late Proterozoic Ice Age

26. Snowball Earth?

27. Post-Rifting West Coast Became a Passive Margin 750 to 200 Myrs Ago
Continental Shelf
Sediments
Ocean
North
America
Direction of Plate Motion

28. A-6
Belt Supergroup
Windermere
Supergroup
Continental Shelf
Deposits