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