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, riftingpassive marginsubduction island arc (Japan-like) hits North AmericaIt 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 margincollision of continental fragment with North America – Avalonia: Acadian OrogenyAcadian mountains shed sediment into the interior of the continentcollision of North America with Africa and Europe assembles Pangaea
6 PangaeaThe 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 stripesMountain belts /terranes that run from one continent to anotherClimate belts that run from one continent to anotherFossils
11 How do we know Pangaea existed and finished forming in the Permian? Age patterns on ocean floor (reflected in magnetic stripesMountain belts /terranes that run from one continent to anotherClimate belts that run from one continent to anotherFossilsGlaciation
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 sandOrdovician: lots of limestone, whole continent is covered in water – no land eroding to make sedimentSilurian - 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 continentMore terrestrial deposits, including widespread coal swamps
20 CyclothemsRepeating sequences of sedimentary rocks that go from non-marine to marineRepeat tens to hundreds of times.What caused the many repetitions?Deltas growing off the rising Appalachian mountainsSmall changes in sea level across a low-lying area can cause big changes in shoreline
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, redbedsAtlantic Ocean formsAtlantic grows wider throughout the Mesozoic and CenozoicSo 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 happensTriassic: craton dry – very little rockJurassic: mostly dry, little deposition in Gulf CoastCretaceous: Great Cretaceous seaway cuts NA in half – marine rocks on west edge of craton.
26 Paleozoic to Triassic exotic terranes Paleozoic to Triassic exotic terranesSo 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 widerOrogenies: Antler, SevierAccreted terranes have ophiolites in between them
28 Jurassic CordilleraJurassic – well developed subduction complex like the Andes
29 Great Valley forearc turbidites Franciscan melangeGreat Valley forearc turbidites
30 Cretaceous timeWestern volcanoes shut down, and the subduction mountains erode away-Great Valley deep water rocks contain bits of granite from the magma chamber10 million years later – volcanoes start erupting in ColoradoLow 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 boundarySan Andreas Fault formsTensional tectonics across the Basin and Range – stretches to twice its width and creates fault block mountainsColorado Plateau rises intactSanta Barbara block spins around opening pull-apart basins that produce oilNorth America arches up, water drains off the Atlantic and Gulf Coast