• Douglas Quarry - Morrison FM
• Upper Jurassic - 150 Ma
• Interbedded shale and sandstone
• Floodplains, rivers, lakes
• Highlands to the west
Jurassic Period - North America
• Subduction zone - chain of volcanic mountains along the west coast of
North America
• Nevadan Orogeny - 150 Ma
• Semi-arid climate - savanahs in the west
Jurassic Period - Morrison Fm
• How do we know what the environment was like?
• Reading the rocks
– Interbedded sandstone, shale, and bentonite
• Other fossils
• Plants, Small reptiles, mammals
• Clams and snails
Jurassic Period - Morrison Fm
• The dinosaurs
• Sauropods
• Apatosaurus, Barosaurus, Camarasaurus, and Diplodocus
• Theropods/Carnisaurs
• Allosaurus
• Ornithopods
• Stegosaurus
• Camptosaurus
Morrison Fm - Douglass Quarry
• How did the bones accumulate?
• A logjam of bones
Morrison Fm - Douglass Quarry
• The clues to the deposit:
• Lens - shaped sandstone deposit
• The bones
• Skulls, large leg bones, partial articulation, age range of individuals
• Condition of bones
• Animal behavior
Morrison Fm - Douglass Quarry
• Seasonal meandering stream
• Watering hole in the stream channel
• Migratory stopping place
• Seasonal flooding
• Mortality by flooding or drought stress?
• Accumulation in stream channel - point bar
Deposition in a Stream Channel
• Where does sediment accumulate within a channel
• velocity greatest on outside of bend = erosion: cutbank
• velocity is less on inside of bend= deposition: point bar