1. Chapter 14
Mesozoic Earth History Million years ago Triassic Jurassic Cretaceous

2. Geologic Time Scale

3. Main Happenings in Mesozoic
Breakup of Pangaea
Lots of mountain-building in western North America
Appearance + extinction of dinosaurs
More detail in the geologic record
More climate information!

4. Climate information in the geologic record
Evaporites: precipitation < evaporation = dry
Coal = lots of vegetation + lots of moisture
Sand dunes = dry

5. The hydrologic cycle and climate

6. Water moves heat from the equator to the poles
When water changes phase, it either releases or takes up energy
Evaporation: gaseous water carries energy
Humid regions don’t get as hot
Precipitation: releases energy as heat
Humid regions don’t get as cold
Ocean currents are the Earth’s heating and AC ducts, moderating our climate

7. Tectonic drivers of climate
Tectonics influences the hydrologic cycle
Mountains can block rainfall
Massive continents tend to have hotter, drier cores
Coastal regions are more moderate
Circumpolar currents prevent heat from reaching poles
N/S currents move heat effectively

8. End Permian land and oceans
Panthalassa
Pangaea was shaped like a ‘C’
Inside ocean: Tethys Sea
Outside ocean: Panthalassa
Tethys sea
Panthalassa

10. Breakup of Pangea 1: Triple Junctions
Seafloor spreading creates a triple junction: a point where 3 tectonic plates diverge
North America split off from S America and Africa

11. Triple Junctions

12. Seafloor spreading raises sea level
Seafloor spreading causes bulges in ocean basins
Big enough bulges and/or lots of them lowers the ocean volume
This can cause flooding of the continents.

13. Breakup of Pangaea 2: Opening of Gulf of Mexico
In Middle Jurassic, North America and South America separated
Gulf of Mexico began to open
Restricted basin at first – lots of evaporites deposited

14. Gulf of Mexico Salt

15. Breakup of Pangaea 3: Continued Widening of North Atlantic
In Late Cretaceous, Atlantic widened rapidly
Canada and Europe separated

16. Final Breakup In Late Cretaceous, Australia and Antarctica separated
In Cenozoic, Antarctica and South America separated

17. Global Plate Tectonics Jurassic to Present DayBy
L.A. Lawver, M.F. Coffin, I.W.D. Dalziel
L.M. Gahagan, D.A. Campbell, and R.M. Schmitz
2001, University of Texas Institute for Geophysics
February 9, 2001

40. Paleogeography of the World
During the Triassic Period

41. Paleogeography of the World
During the Jurassic Period

42. Paleogeography of the World
During the Late Cretaceous Period

43. Where did most North American mountain-building occur during Paleozoic?

44. Where did most North American mountain-building occur during Paleozoic?
East Coast - Appalachians

45. Cordillera Western margin of North America
Spanish for “mountain range”
Rocky Mountains, Sierra Nevadas

46. Cordillera Orogenies
General term refering to complex period of mountain-building Jurassic-Cenozoic
Farallon plate goes below N American plate
Nevadan orogeny – Late Jurassic/Early Cretaceous
Orogeny near the current W coast
Slope of subducting Farallon plate decreased ->
Sevier orogeny – Late Cretaceous
Further east (Utah)
Laramide orogeny – Late Cretaceous/Cenozoic
Even FURTHER east! Rockies

47. Global Sea-Level Rise A global rise in sea level during the Cretaceous
resulted in worldwide transgressions
marine deposition was continuous over much of the North American Cordillera

48. Cretaceous Flood Worldwide transgression
1/3 of land area of Earth submerged
100 Ma
Cretaceous Interior Seaway in North America

49. Cretaceous Interior Seaway
Paleogeography of North America during the Cretaceous Period

50. Western Interior Seaway

51. Western Interior Seaway

52. The Effects on Global Climates and Ocean Circulation Patterns
At the end of the Permian Period
Pangaea extended from pole to pole
Covered about one-fourth of Earth's surface
Surrounded by a global ocean that encompassed about 300 degrees of longitude
Such a configuration exerted tremendous influence on the world's climate
resulted in generally arid conditions over large parts of Pangaea's interior

53. Oceanic Circulation Evolved
From a simple pattern in a single ocean (Panthalassa) with a single continent (Pangaea)

54. Oceanic Circulation Evolved
to a more complex pattern in the newly formed oceans of the Cretaceous Period

55. Areas Dominated by Seas Are Warmer
Oceans absorb about 90% of the solar radiation they receive
continents absorb only about 50%
even less if they are snow covered
The rest of the solar radiation is reflected back into space
Therefore, areas dominated by seas are warmer than those dominated by continents