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 mid- Cretaceous 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

Cretaceous Seaway Rock Types Conglomerate Alluvial Fan Conglomerate Deltaic SS and Coal Deltaic SS and Marine Shale Black Shale Chalk Carbonate

Cretaceous Chalk Deposits Accumulation of Carbonate Micro-organism Calcareous ooze White Cliffs of DoverCarbonate Ooze Carbonate Microfossils Niobrara Chalk of Nebraska

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* * 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 Pierre Shale

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 Calcereous ForaminferaSiliceous Diatoms 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 Ontang–Java Oceanic Plateau Deccan Flood Basalts

Summary of the Mesozoic

The Modern World Emerges Tectonics Next Lecture The Cenozoic Era The Modern World Emerges Tectonics