Transcript Paleogene
Western U.S. orogenies Earth History, Ch. 18 1 Late Cretaceous 75 Ma Earth History, Ch. 18 2 K/T boundary 65 Ma Earth History, Ch. 18 3 The Paleogene World Pliocene Neogene Miocene Cenozoic • Two-fold subdivision of Cenozoic: Paleogene, Neogene • Previously, Cenozoic was divided into Tertiary (Paleocene-Pliocene) and Quaternary (PleistoceneHolocene) • Know periods and epochs! Holocene Pleistocene 24 Oligocene Paleogene 65 Earth History, Ch. 18 Eocene Paleocene 4 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! Earth History, Ch. 18 5 Whale evolution (Eocene-Holocene) Large, marine forms Terrestrial ancestor Earth History, Ch. 18 6 Earth History, Ch. 18 7 Giant Eocene shark Modern shark jaws Earth History, Ch. 18 8 Paleogene life • Other interesting newcomers to marine or marginal marine habitats: – Penguins – Pinnipeds (seals, sea lions, walruses) Earth History, Ch. 18 9 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) Earth History, Ch. 18 10 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 in our family tree! Earth History, Ch. 18 11 Earth History, Ch. 18 12 Earth History, Ch. 18 13 Eocene fossil bat Earth History, Ch. 18 14 Hyracotherium (“Eohippus”) earliest horse Dog-sized 4 toes 3 toes Earth History, Ch. 18 15 Earth History, Ch. 18 16 Diacodexis (early even-toed ungulate) Earth History, Ch. 18 17 Eocene elephants Earth History, Ch. 18 18 Diatryma (a top predator--stay away from this turkey!) 8 ft Earth History, Ch. 18 19 Earth History, Ch. 18 20 Paleogene life • Oligocene was noteworthy for: – Paraceratherium, largest land mammal ever (member of rhino family) – Origin of true monkeys – Expansion of big cats Earth History, Ch. 18 21 Paraceratherium 18 ft at shoulder Earth History, Ch. 18 22 Aegyptopithecus (Oligocene monkey) Earth History, Ch. 18 23 Dinictis (Oligocene saber-tooth cat) Earth History, Ch. 18 24 Oligocene mammalian fauna of Nebraska & South Dakota Earth History, Ch. 18 25 Paleogene life • Many groups of mammals became extinct during Eocene time or at the Eocene— Oligocene boundary • Climate change probably is responsible for extinctions Earth History, Ch. 18 26 Earth History, Ch. 18 27 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 Earth History, Ch. 18 28 Evidence for climate change Earth History, Ch. 18 29 Antarctic circumpolar current ANT AU SA Earth History, Ch. 18 30 Continued break-up of Pangaea Earth History, Ch. 18 31