Lec 6 Extinction 2: Part 4

Front 1

What was the setting like in the late eocene?

Back 1

- Antarctica and Australia were still in contact through the Mid Eocene [lastpart of Pangaea/Gondwanaland still intact]

-there was evidently a Bering land bridge, the climate wasstill warm, and there were many epicontinental seas

Front 2

One of the victims exhibits five events or pulses of extinction, which group is this?

Back 2

Planktonic foraminifera

Front 3

Of the Planktonic foraminifera, which group was completely lost?

Back 3

the spinose tropical forms

Front 4

the cool water species of the planktonic foraminifera did what?

Back 4

migrated closer to the equator, and also dominated at higher latitudes, coincident with a major sea level fall (global cooling), and the loss of 50%of the species of calcareous nannoplankton

Front 5

what other planktonic foraminifera did we see major losses in?

Back 5

Benthic (bottom-dwelling)

Front 6

ultimately with the planktonic foraminifera, we see extinction of many

Back 6

cool water species, but note thatthe survivors were also cool water forms, this correlates with another majorsea level fall

Front 7

what is the most important thing to remember when it comes to mammal loses?

Back 7

mammal losses are generally delayed compared to losses in foraminifera, so that major mammal losses coincide with relatively minor foraminiferal losses

Front 8

There is a transition of mammals in the late eocene/oligocene what is it

Back 8

from browsers and arboreal farms to inhabitants of less heavily forested open terrain

Front 9

What was the major loses of mammals?

Back 9

the huge Paleogene [Paleocene to Oligocene] mammals were lost, andodd-toed ungulates suffered greater losses than the geologically youngereven-toed ungulates

Front 10

What does the record show of both mammals and plants in the late eocene/oligocene

Back 10

the record is incomplete

Front 11

the Mid Eocene was characterized by

Back 11

tropical to subtropical floras inEurope, much of North America, and Australia

Front 12

by the Mid Oligocene, the floras were

Back 12

low diversity temperate to cool floras;postulated temperature drops were as high as 10°C

Front 13

corroborating evidence is seen in the leaf styles of angiosperms; thatevidence described and illustrated:

Back 13

As mean temperature increases, so does the proportion of species having leaves with smooth or entive orgins. late eocence-oligocene fossil floras show decline in proportions of leaves with entire margins, suggesting a significant drop in global temp.

Front 14

What was the cause of the late eocene/oligocene extinction?

Back 14

global cooling

Front 15

thesis verified by what

Back 15

oxygen isotopes

Front 16

Explain the how the 18O:16O works

Back 16

polar ice is isotopically lighter, incorporating a higher proportion of water molecules with O16 han the ocean water from which the water was evaporated. thus, as temperature drops and the ice caps expand, more and more 16O istied up in the polar caps, the oceans become depleted in 16O, and the δ18O

Front 17

this rapid global cooling was probably initiated by

Back 17

rifting of Australia fromAntarctica in the Late Eocene

Front 18

explain how

Back 18

Antarctica became isolated in an oceanographic sense by establishment of a circum-antertic current, which deflected warm waters travelling from the equator, thus truggering cooling and growth of an ice cap

Front 19

there are several Ir anomalies and microtektite horizons near this Eocene-Oligocene transition,however we think it is unlikely to explain the mass extinction of catastrophic events. why?

Back 19

Because there was pulses of extinctions, the interval are to long