Lect 5

Question 1

Megafauna

Answer 1

Fauna over 44kg
-well know in LGM
Include: woolly mammoth, sabre tooth tiger etc.

Question 2

LGM Megafauna extinction

Answer 2

35 species in N/S America went extinct @ LGM end

= Termination 1

Question 3

LGM Extinction Causes

4 of them

Answer 3

Over chill
Over kill
Over ill
Over grill

Question 4

Over-Chill theory

Answer 4

-climate change (YD event) = particular cold snap 
Problems:
-no evidence of frozen fauna
-lived through other cold spells (LGM)
-low latitudes = v.little Temp decr.

Question 5

Over-Kill theory

Answer 5

[Martin 1960]
Land bridge between Asia-Alaska became un-ice covered post deglaciation = migration humans
HUMANS OVERHUNTED FAUNA

evidence: •Clovis points killing 14 Mammoths
•Last megafauna Refugia corresponds to last places inhabited by humans (Caribbean)

Problems:

• small population wiping out megafauna over 3 continents in <1000yrs
• some species survived
• Africa unaffected

Question 6

Over-ill theory

Answer 6

Hyper disease introduced by humans wiped out un-immune fauna
Problems:
-no evidence of disease in faunal remains
-DNA found no evidence of disease

Question 7

Over-Grill theory

Answer 7

Impact event like the YDIH wiped them out
Evidence:
-Crater beneath Greenland ice sheet
(Multiple dates for it though 2Ma-11k Bp)

Question 8

Ice Cores

Answer 8

Detailed source of palaeo-climate info; specifically the Quaternary

Question 9

Ice Cores as proxies

Answer 9

Local:
Temperature (delta D & 18O, borehole Temp)

Regional:
Dust fluxes (Ca conc. wildfire particles)

Global:
Trapped air (atmosphere composition)

Problems:
Resolution (counting layers) decreases w/ time as ice Cores become plastic at depth

Question 10

DO Events

Answer 10

SEEN IN ICE CORES
Saw tooth profile of RAPID WARMING & SLOW COOLING

GISP 2: 20-27 DO events identified by rapid isotopic ratio changes — 12 degree warming in < 10 yrs

Limitations:

• Dating & correlating between records isn’t easy
• hard to detect back in time
• was warming global or just regional?

Question 11

Correlating DO Events

Answer 11

• Methane synchronisation: correlate Antarctica & Greenland
• stalagmite U-Th dating: cave in Austria records DO events

Question 12

Hemispheric asymmetry

Answer 12

• Greenland warming linked to Antarctic Cooling

* Asian monsoon = strong and S.Am monsoon = weak

Question 13

Bipolar Seesaw

Answer 13

Antarctic Isotopic Max. (AIM) corresponds to gaps between DO events (cooling periods)

Causes:

• Gulf Stream related?
• sea ice extent?

Question 14

Heinrich Events

Answer 14

SEEN IN MARINE SED.
-Deviation from normal sedimentation due to Ice Rafted Debris (IRD) Events
6 Heinrich events: H1-H6
—> occur right before DO Events (implies they initiate warming)
—slow cooling then IRD event then DO event

Question 15

Heinrich Event teleconnections

Answer 15

Magnitude varies:
Brazilian margin records: peak Fe/Ca & cont. weathering + incr. rainfall
Arabian Sea = decr. Rainfall