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Mesozoic Geology

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Title: Mesozoic Geology


1
Mesozoic Geology
  • Part 2
  • Chapter 14

2
Mesozoic
3
Last time
  • Pangea break up
  • East coast rx
  • Gulf coast rx
  • Today west coast

4
Gulf rocks
  • Cretaceous ocean, passive margin
  • Jurassic ocean opening, restricted basin
  • Triassic above sea level

Why no basalts, faults, evidence of rifting like
on east coast?
5
Paleozoic in Cordilleran mobile belt
  • Antler orogeny

6
Terranes of the western U.S.
  • Anything west of craton needs to be added
  • Accreted terranes

7
How to find edge of the craton
  • Mapping
  • Established with geochemistry

8
Geometry of Western U.S. sutures
9
Cordilleran mobile belt
  • Granites
  • Age Permian/Triassic boundary
  • Western Nevada
  • Granites
  • Age Triassic/Jurassic boundary
  • California
  • How formed?
  • How moved west through time?

10
Cordilleran mobile belt
  • Granites
  • Age Permian/Triassic boundary
  • Western Nevada
  • Sonoma orogeny
  • Granites
  • Age Triassic/Jurassic boundary
  • California
  • Nevadan orogeny

11
Sonoma orogeny
  • Addition of island arc onto southwest margin of
    N.A.

12
Nevadan orogeny
  • Typical subduction zone

13
Evidence of Nevadan orogeny
  • Igneous rocks
  • Lots of granite
  • Form batholiths

14
Evidence of Nevadan orogeny
  • Igneous rocks
  • Lots of granite
  • Form batholiths

15
Nevadan orogeny
  • Late Cretaceous, volcanoes and batholiths migrate
    east
  • How?

16
How to migrate volcanoes inland
17
Cretaceous
  • Paleozoic rocks thrust over Mesozoic rocks
  • Logical order of rock ages?

18
Cretaceous
  • Cambrian limestone on top of Jurassic sandstone
  • How? Why?

19
Cretaceous
  • Sevier Orogeny
  • Compression
  • Faults lift older rocks, thrust eastward

20
Mesozoic orogenies
  • Sonoma
  • Nevada
  • Sevier

21
Mesozoic sed rocks
Sandstone, shale, conglomerates
Sandstones with small-scale cross beds, Ripple
marks
Jurassic
Sandstones Large-scale cross beds Fossil
reptiles, scorpions etc.
Mud cracks, ripple marks Silty sandstone w/
gypsum Red beds, Fossils of amphibians, Dinos,
Trees, and ferns
Triassic
22
Triassic seds out west
23
Triassic seds out west
  • Petrified Forest National Park

24
Early Jurassic seds out west
  • Navajo Sandstone

25
Early Jurassic seds out west
  • Navajo Sandstone

26
Late Jurassic seds out west
  • Morrison formation
  • Sandstone, shale, conglomerate
  • Dino fossils!!!
  • Dinosaur National Monument, Utah

27
Cretaceous seds out west
  • Cretaceous Seaway
  • Just had Nevada and Sevier orogeny
  • Source of sediment?
  • In Seaway, what rock types expecting to find?
  • Any variations expected east-west?

28
Cretaceous Seawaywest-east cross section
  • Conglomerates and sandstone close to mountains
  • Shales to the east

29
  • Triassic sea level low, red beds
  • Jurassic desert to shallow marine rocks
  • Cretaceous Cretaceous sea way
  • Why is sea level rising?

30
Question
  • Compare/contrast
  • The tectonic setting and depositional environment
    of Mesozoic evaporites in Gulf of Mexico with
    evaporite sequences of Paleozoic

31
Paleozoic and Mesozoic evaporites
  • Tectonics
  • Paleozoic forming on craton
  • Mesozoic forming near plate margin
  • Depositional environment
  • Both restricted basins
  • Paleozoic restricted by reefs
  • Mesozoic restricted as oceans open

32
Mesozoic key points
  • Pangea breaks up
  • Triassic rifting on east coast, Sonoma orogeny
    on west coast, red beds in west
  • Jurassic evaporites in Gulf, Nevadan orogeny
    with granites, desert sed rocks then shallow
    marine rocks
  • Cretaceous sea level rise, Sevier orogeny with
    thrusting eastward, seds washed to east, Laramide
    orogeny at end
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