GSC 111 Lecture Notes - Lecture 19: Chicxulub Crater, Laramide Orogeny, Younger Dryas
13 Jan 2017
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The Cenozoic World: Life After the KT Mass Extinction
1. Paleogeography of the Cenozoic
a. Late Cretaceous
i. Rifted apart North America from Africa and South America from Africa
ii. India and Madagascar still connect
iii. Australia and Antarctica still connected
b. After chicxulub impact event
i. India starts moving towards Asia
ii. South America and Australia connected to Antarctica
iii. Circumtropical ocean current connect most bodies of water water
c. Middle Eocene
i. Breakup of Antarctica and Australia, Atlantic and Arctic Oceans connect
d. Middle Miocene
i. Himalayans fully formed, Middle East and Central America still open
e. Modern
i. Middle East closed, Central America Seaway closed
ii. Australia has moved far enough north
2. Cenozoic climates and formation of the Antarctic and Arctic Ice Caps
a. Warming trends during Paleocene until early Eocene and then cooling trends
b. A few dramatic spikes but overall consist
i. Record buildup of glaciers
ii. Between Eocene and Oligocene
1. Creation of glaciers in Antarctica
c. Development of ice caps in Antarcitca
i. Tied to rifting of South America and Australia from Antarctica
1. Not enough of a gap between landmasses to develop a current to
Antarctica
ii. When they rift far enough, we can form a circumpolar current around
Antarctica
1. Cold water constantly circulates around Antarctica
iii. Widespread marine extinctions between Eocene and Oligocene
1. Extinction of foraminifera, calcareous nannoplankon, mollusks
iv. Changes in terrestrial fauna
v. Transition to grasslands from forests
1. Changes in terrestrial mammal faunas
a. Mammals adapted to forests go extinct
d. Climates become cooler and seasonally arid (less evaporation) during the
Miocene
i. Grasslands and herbaceous plants expand in North and South America
ii. Lack of summer moisture excludes shad-generating trees
e. Changes in oceanic circulation may have triggered the Ice Age
i. Isthmus of Panama forms from eastward moving island arc 3.0-3.5 mya
ii. High salinity water sinks before reaching the Arctic ocean
iii. Created in the northern hemisphere
f. Evidence for past glaciation
i. Erratic boulders
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