Earth History
GEOL 2110
The Mesozoic Era
Cretaceous Trangression
And Mesozoic Life
Major Concepts
• A major transgression in the Cretaceous created a Great
Interior Seaway where great accumulation of marine and
non-marine sediment were deposited in the Great Plains
• Climate in the Cretaceous was uniformly warm due to a
lack of polar ice caps, an abundance of water surface,
large volcanic eruptions
• After the Permo-Triassic extinction, radiation of marine life
was driven by reactions of species to predatation.
• Synapsid reptiles of the Triassic gave way to dinosaurs
during the Jurassic and Cretaceous
• Flowering plants (angiosperms) bloomed in the midCretaceous and supplied a rapidly reproducing supply of
food to the dinosaurs
• The mass extinction at the end of the Cretaceous was not
as abrupt as first described, suggesting a non-impact cause
Events of the Mesozoic Era
Great Inland Seaway
The Last Epicontinental Sea
Alluvial Fan Conglomerate
Cretaceous Seaway
Rock Types
Deltaic SS and Coal
Chalk Carbonate
Deltaic SS and Marine Shale
Black Shale
Calcareous ooze
Cretaceous Chalk Deposits
Accumulation of Carbonate Micro-organism
Niobrara
Chalk of
Nebraska
Carbonate Ooze
Carbonate Microfossils
White Cliffs of Dover
Deposits along the Eastern Shore of
the Cretaceous Seaway
Lignite and
Fine Sandstone
Weathered Archean
Gneiss
Cretaceous Paleoclimate
Unlike the Permian, globe
seemed uniformly warm
Humid (rare evaporites)
No glacial deposits
Extensive water coverage
promoted solar heating
Cretaceous Black Shales
Evidence of Uniformly Warm Ocean Waters
Organic –rich muds due
to :
- Rapid deposition of C
- Rapid mud deposition
- O-poor deep waters*
Pierre Shale
* Oxygen is more soluble in
cold water leading to
vigorous circulation of cold,
dense oxygenated water in
the deep ocean when
temperature is strongly
zoned. Not the case when
oceans are uniformly warm
Mesozoic Marine Life
After the Permo-Triassic Extinction
Bryozoans, Brachiopods, Rugose and
Tabulate Coral, and Crinoids give way to:
Bivalves, Gastropods, Mollusks, Modern
Coral Crustaceans, Cephlapods,
Echoniderms, Diverse Fish and Swimming
Reptiles
PREDATOR-PREY
RELATIONS RULE THE SEAS
Mesozoic Marine Life
Bivalves Dominate
Rudistid clams
Inoceramids
Mesozoic Marine Life
Ammonites – the index fossil of the Mesozoic
Mesozoic Marine Life
Micro-organisms
Siliceous Diatoms
Calcereous Foraminfera
Coccoliths
Mesozoic Marine Life
Mososaurs, plesiosaurs, teleost fish, ammonites, turtles ----
Mesozoic Land Life
The Land Before Time
Flowering Plants Evolve
Rapid regeneration
provided ample
food supply for
dinosaurs
Pollinating insects
(moths and bees)
become important
partners
The Cretaceous-Tertiary Extinction
~ half of life is exterminated
Evidence for a Meteor Impact
Volcanic
Glass
Spherules
Shocked
Quartz
Cretaceous Volcanism
Deccan Flood
Basalts
Ontang–Java
Oceanic Plateau
Summary of the Mesozoic
Next Lecture
The Cenozoic Era
The Modern World Emerges
Tectonics