earth history, ch. 181 western u.s. orogenies. earth history, ch. 182 late cretaceous 75 ma
TRANSCRIPT
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Earth History, Ch. 18 1
Western U.S.orogenies
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Earth History, Ch. 18 2Late Cretaceous 75 Ma
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Earth History, Ch. 18 3K/T boundary 65 Ma
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Earth History, Ch. 18 4
The Paleogene World
• Two-fold subdivision of Cenozoic: Paleogene, Neogene
• Previously, Cenozoic was divided into Tertiary (Paleocene-Pliocene) and Quaternary (Pleistocene-Holocene)
• Know periods and epochs!
Cen
ozoi
cPaleogene
Neogene
Paleocene
Eocene
Oligocene
Miocene
Pliocene
HolocenePleistocene
65
24
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Earth History, Ch. 18 5
Paleogene life
• In marine realm, most groups that survived end-Cretaceous mass extinction recovered and diversified during Paleogene– Planktonic forams, calcareous
nannos, mollusks, arthropods
• Demise of giant marine reptiles opened the door to whales (Eocene) and giant sharks!
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Earth History, Ch. 18 6
Whale evolution (Eocene-Holocene)
Terrestrial ancestor
Large, marineforms
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Earth History, Ch. 18 7
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Earth History, Ch. 18 8
Giant Eocene shark
Modern shark jaws
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Earth History, Ch. 18 9
Paleogene life
• Other interesting newcomers to marine or marginal marine habitats:– Penguins – Pinnipeds (seals, sea lions, walruses)
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Earth History, Ch. 18 10
Paleogene life
• On land…………..– Diversification and “modernization” of angiosperms
– By early Oligocene time, half of all angiosperm genera were ones that still exist today
• Origin of grasses– Earliest forms were sedge-like (discontinuous growth)
– Late Oligocene-Neogene forms capable of continuous growth (able to withstand grazing pressure)
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Earth History, Ch. 18 11
Paleogene life
• Explosive adaptive radiation of mammals!– By Eocene time, most
modern orders of mammals had appeared, including primates, carnivores and horses
Cantius, climbing around inour family tree!
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Earth History, Ch. 18 12
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Earth History, Ch. 18 13
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Earth History, Ch. 18 14
Eocene fossil bat
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Earth History, Ch. 18 15
Hyracotherium (“Eohippus”)earliest horse
Dog-sized
4 toes
3 toes
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Earth History, Ch. 18 16
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Earth History, Ch. 18 17
Diacodexis(early even-toed ungulate)
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Earth History, Ch. 18 18
Eoceneelephants
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Earth History, Ch. 18 19
Diatryma(a top predator--stay away from this turkey!)
8 ft
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Earth History, Ch. 18 20
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Earth History, Ch. 18 21
Paleogene life
• Oligocene was noteworthy for:– Paraceratherium, largest land mammal ever
(member of rhino family)– Origin of true monkeys– Expansion of big cats
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Earth History, Ch. 18 22
Paraceratherium
18 ft at shoulder
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Earth History, Ch. 18 23
Aegyptopithecus(Oligocene monkey)
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Earth History, Ch. 18 24
Dinictis(Oligocene saber-tooth cat)
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Earth History, Ch. 18 25
Oligocene mammalian fauna of Nebraska & South Dakota
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Earth History, Ch. 18 26
Paleogene life
• Many groups of mammals became extinct during Eocene time or at the Eocene—Oligocene boundary
• Climate change probably is responsible for extinctions
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Earth History, Ch. 18 27
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Earth History, Ch. 18 28
Paleogene paleogeography and climate
• Beginning in late Eocene, climate rapidly became cooler and drier– Relatively heavy oxygen isotope ratios
(consistent with growth of continental glaciers)– Establishment of circum-polar currents around
Antarctica
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Earth History, Ch. 18 29
Evidence for climate change
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Earth History, Ch. 18 30
Antarcticcircumpolarcurrent
SA
ANTAU
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Earth History, Ch. 18 31
Continued break-up of Pangaea