Earth History, Ch. 181 Western U.S. orogenies. Earth History, Ch. 182 Late Cretaceous 75 Ma.

Earth History, Ch. 18 1

Western U.S.orogenies

Earth History, Ch. 18 2Late Cretaceous 75 Ma

Earth History, Ch. 18 3K/T boundary 65 Ma


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


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!


Whale evolution (Eocene-Holocene)

Terrestrial ancestor

Large, marineforms


Giant Eocene shark

Modern shark jaws


Paleogene life

• Other interesting newcomers to marine or marginal marine habitats:– Penguins – Pinnipeds (seals, sea lions, walruses)


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)


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!


Eocene fossil bat


Hyracotherium (“Eohippus”)earliest horse

Dog-sized

4 toes

3 toes


Diacodexis(early even-toed ungulate)


Eoceneelephants


Diatryma(a top predator--stay away from this turkey!)

8 ft


Paleogene life

• Oligocene was noteworthy for:– Paraceratherium, largest land mammal ever

(member of rhino family)– Origin of true monkeys– Expansion of big cats


Paraceratherium

18 ft at shoulder


Aegyptopithecus(Oligocene monkey)


Dinictis(Oligocene saber-tooth cat)


Oligocene mammalian fauna of Nebraska & South Dakota


Paleogene life

• Many groups of mammals became extinct during Eocene time or at the Eocene—Oligocene boundary

• Climate change probably is responsible for extinctions


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


Evidence for climate change


Antarcticcircumpolarcurrent

SA

ANTAU


Continued break-up of Pangaea

Earth History, Ch. 181 Western U.S. orogenies. Earth History, Ch. 182 Late Cretaceous 75 Ma.

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Transcript of Earth History, Ch. 181 Western U.S. orogenies. Earth History, Ch. 182 Late Cretaceous 75 Ma.