1. North American Geological History

2. Proterozoic – Cambrian Cordillera
Cambrian – Ordovician:
Major rifting in Southern California (and presumably north and south along a now hard-to-find ancient continental edge.
Failed rifting in Grand Canyon region.
Passive margin in West; intracratonic seas over the Grand Canyon

3. Cambrian- Ordovician craton
Widespread shoreline facies (quartz-rich sandstones) with tidal features; closeness of Moon meant gigantic tides over huge regions on flat craton.
Widespread carbonates indicate almost all of continent underwater with little land to erode and produce sediment (except to the East).

4. So what did we figure out about the East Coast so far?
Proterozoic:
Cambrian:
Ordovician:
suture zone, rifting
passive margin
subduction island arc (Japan-like) hits North America
It hits an irregular coastline at an angle, causing a complex collision that happens at different times in different places.

5. OK, on to the rest of the Paleozoic
Silurian:
Devonian:
Miss/Penn:
Permian:
passive margin
collision of continental fragment with North America – Avalonia: Acadian Orogeny
Acadian mountains shed sediment into the interior of the continent
collision of North America with Africa and Europe assembles Pangaea

6. Pangaea
The Permian collision was only a piece of the formation of a supercontinent called Pangaea

7. How do we know Pangaea existed and finished forming in the Permian?
Age patterns on ocean floor (reflected in magnetic stripes

9. How do we know Pangaea existed and finished forming in the Permian?
Age patterns on ocean floor (reflected in magnetic stripes
Mountain belts /terranes that run from one continent to another
Climate belts that run from one continent to another
Fossils

11. How do we know Pangaea existed and finished forming in the Permian?
Age patterns on ocean floor (reflected in magnetic stripes
Mountain belts /terranes that run from one continent to another
Climate belts that run from one continent to another
Fossils
Glaciation

13. Let’s look at the formation and breakup of Pangaea over time…

14. Meanwhile, back on the craton…
Cambrian: lots of sandstones, limestone – some land to erode to make sand
Ordovician: lots of limestone, whole continent is covered in water – no land eroding to make sediment
Silurian - Devonian: evaporites in Michigan Basin because reefs around the edge restrict circulation

15. Middle Paleozoic Michigan Basin
Reefs around the edge, salty water in the middle

16. Late Paleozoic craton Remember what happened in the Appalachians?
As the big mountains started to go up, the sea drained off the continent
More terrestrial deposits, including widespread coal swamps

17. http://www. museum. state. il

18. Cyclothems
Repeating sequences of sedimentary rocks that go from non-marine to marine
Repeat tens to hundreds of times.

20. Cyclothems
Repeating sequences of sedimentary rocks that go from non-marine to marine
Repeat tens to hundreds of times.
What caused the many repetitions?
Deltas growing off the rising Appalachian mountains
Small changes in sea level across a low-lying area can cause big changes in shoreline

22. What do larger sea level changes do?

23. So looking at the whole Paleozoic…
Let’s watch the movie all the way from Cambrian on…

24. Then what happened to Pangaea?
Breaks up in Triassic: normal faults, basalt, redbeds
Atlantic Ocean forms
Atlantic grows wider throughout the Mesozoic and Cenozoic
So what tectonic facies has the East Coast been throughout this time?
Rift valley followed by passive margin

25. Mesozoic-Cenozoic Craton
Back to the movie to watch what happens
Triassic: craton dry – very little rock
Jurassic: mostly dry, little deposition in Gulf Coast
Cretaceous: Great Cretaceous seaway cuts NA in half – marine rocks on west edge of craton.

26. Paleozoic to Triassic exotic terranes
Paleozoic to Triassic exotic terranes
So what kind of plate boundary must the Cordillera be during this time?
Subduction Zone with lots of collisions (smaller and larger suture events)

27. Paleozoic-Triassic Cordillera
Paleozoic – subduction zone with many collisions of small things – island arcs, continental fragments – builds the NA continent wider
Orogenies: Antler, Sevier
Accreted terranes have ophiolites in between them

28. Jurassic Cordillera
Jurassic – well developed subduction complex like the Andes

29. Great Valley forearc turbidites
Franciscan melange
Great Valley forearc turbidites

30. Cretaceous time
Western volcanoes shut down, and the subduction mountains erode away-
Great Valley deep water rocks contain bits of granite from the magma chamber
10 million years later – volcanoes start erupting in Colorado
Low angle subduction moves the volcanoes of the subduction zone far inland from the trench

32. Cenozoic complications
We’ll do this by looking at the animations available at:

33. Cenozoic complications
Subduction of a diverging boundary
San Andreas Fault forms
Tensional tectonics across the Basin and Range – stretches to twice its width and creates fault block mountains
Colorado Plateau rises intact
Santa Barbara block spins around opening pull-apart basins that produce oil
North America arches up, water drains off the Atlantic and Gulf Coast