Major Highlights of the Mesozoic

Age of the Dinosaurs

Mammals develop

Pangaea breaks up

Glacier’s retreat

A couple of transgressions/regression

Major mountain building in the west

Lots of sediments deposited

Mass extinctions at the end of the Mesozoic

Plate tectonics of the Mesozoic

End of the Permian, Pangaea

Glaciers to the south (retreating)

Arid Climate for the rest

Reptiles evolving and becoming dominate

4 stages of break up for Pangaea

1) Late Triassic: Rifting begins between Laurasia and Gondwana. N. America begins separation from Africa

2) E. Jurassic: Gondwana begins to break up. Rift zones form

3) Late Jurassic: Antarctic splits from Africa and S. America. Africa and South America begin splitting. Atlantic Grows

4) Actually into the Cenozoic.

End of Cretaceous most continents separated

Greenland doesn’t fully separate till stage 4

How does the change in plate location affect climate?

Climate is largely controlled by ocean circulation

End of Permian large continuous ocean

Partially responsible for arid climate

Temperature gradients between locations affect atmospheric circulation

In general, more ocean circulation and higher temperature gradients lead to warmer climate but also less arid in places

By the end of the Mesozoic, fairly warm climate world-wide

Evidence for warmer climate and plate tectonics

Evaporate deposits

Red beds: Oxidation of sedimentary deposits. Generally found in arid environments

Mesozoic Dune deposits

Sea level changes of the Mesozoic

Higher rates of plate tectonics caused sea levels to rise

North America:

End of Permian: Absaroka Sequence

Continued into the early Jurassic

Zuni Cratonic sequence from Early Jurassic to Late Cretaceous

Cretaceous is highest sea level since Ordovician

Sundance Sea in Jurassic

Cretaceous interior Seaway

Deposits from these seaways are noted today in the Southwest

Chinle Formation: Triassic

Navajo Sandstone: Jurassic

Petrified forest AZ

Morrison formation

Important due to dinosaur fossils

Worlds richest source of Jurassic dino fossils

Deposited during Sundance sea

Western Mountain Building

Cordilleran Mobile belt builds

Antler Orogeny (Devonian)

Sonoma Orogeny (Permian to Triassic)

Island arc collides with west coast

Nevadan Orogeny (Jurassic to Cretaceous)

Granite emplaced at depth due to subduction zone

Sierra Nevada mtns, Idaho Batholith, Coast range (BC)

Sevier orogeny (Cretaceous)

Thrust faulting of sediments east of Sierra Nevada mountains

Laramide Orogeny (Cretaceous to Permian)

Development of modern day Rocky Mountains.

Also deformed areas North and South

Continued into Permian

Created by shallow angle subduction

Resources

Several Coal beds developed during this time

Persian Gulf oil deposits are from this time

Oil reserves in Texas and gulf coast of North America from Cretaceous sea way

Mesozoic red beds in Europe important iron resource

Kimberlite pipes emplaced in Africa

Gold deposited in Sierra Nevada Mountains at this time

Life in the Mesozoic

At the end of Paleozoic massive extinction

90% marine invertebrates

Lowered populations of many others (brachiopods)

Small rebound in MZ

Ocean invertebrates in MZ dominated by cephalopods, belemnites, bivalves and gastropods

Other Marine organism:

Sharks

Fish

Marine Crocodiles

Steneosaurs

Marine Reptiles

Ichthyosaurs

Up to 18 meters long

Came to surface to breath

Bore live young

Aggressive predator

Plesiosaurs

Predator

Laid eggs

Dinosaurs

Two orders of dinosaurs

Saurischia

Lizard Pelvic structure

Ornithischia

Bird like pelvic structure

Page 661 in text for better breakdown

Some saurischian dinosaurs were carnivores and some were herbivores

Ornithischian dinosaurs were herbivores

All dinos evolved from common reptile ancestor

Archosaur

Early Triassic

Development of Birds?

Jur. fossils of Archaeopteryx

Features of theropod dinos (teeth, hind limbs)

Has feathers

Fused pelvic structure

Experts still question if it is the ancestor of birds

Development of Mammals

Ancestor of mammals was the cynodont

Developed from Therapsids (mammal like reptiles)

How do we know?

Differences between reptiles and mammals

Two primary skeletal differences

Inner ear

Reptiles: one bone

Mammals: three bones

Jaw

Reptiles: several bones, hinges different

Mammals: one bone

Other differences as well : teeth, skull etc

(Pgs. 668-671)

End of Cretaceous:

Mammals were small generally not bigger than a cat

Three groups present by this time

Monotremes

Egg laying mammals

Marsupials

Pouched mammals (newborns not fully formed)

Placentals

Live young (fully formed at birth)

How did plate tectonics affect development of organisms?

Plants

Late Paleozoic:

Lycopsids

Ferns

Mesozoic

Seed plants expand

Gymnosperms

Cycads developed

Conifers diversify

Angiosperms develop in early Cretaceous

Extinction at the end of the MZ

85% of all species went extinct

Common belief is Meteorite hit the earth

Evidence to support this

Impact structure in Chicxulub (Yucatan)

Iridium anomoly

Other contributors

Deccan Traps flood basalts were erupting

Possible change of atmosphere and climate

Warmer climate was changing in many places

Shallow seas of Cretaceous were regressing