Download Cenozoic

65Ma of climate change:
biogeography of the Cenozoic era
Mean annual temperatures in NW Europe and NW North
America (reconstructed from pollen data) shown in red
Cenozoic climate change: the record
from sub-Antarctic waters
thermal
maximum
Pal(a)eocene biogeography
Start:
http://www.scotese.com/paleocen.htm
Northern hemisphere
biogeography in the
early Cenozoic
(Paleocene/Early
Eocene thermal
maximum @ 55My BP)
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Arctic Ocean fresh (floating mats of Azolla algae);
CO2 ~2000 ppm (cf. 380 ppm @ PD)
Arctic MAT increased from ~18°C (Paleocene) to ~23°C (cf. -20°C @ PD)
Early mammals (ancestors of all major groups) likely originated in Asia in
late Paleocene and apparently migrated across the northern continents at
or about the time of the thermal maximum.
Sources:
Bowen, G.M. et al. 2002. Mammalian Dispersal at the Paleocene/Eocene Boundary. Science 295: 2062 - 2065.
Sluijs, A. et al., 2006. Subtropical Arctic Ocean temperatures during the Palaeocene/Eocene thermal maximum. Nature,
441: 610-613.
Early Tertiary coal deposits, Axel Heiberg Island
(stumps are dawn redwood: Metasequoia)
Plant macrofossils from early Tertiary
coalbeds, Axel Heiberg Island
Oligocene palaeogeography
http://www.scotese.com/oligocen.htm
Major EoceneOligocene fossil
flora sites in
the PNW
Eugene
John Day N.M.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Eo-Oligocene biogeography of
the Pacific NW
• John Day Fossil Beds National Monument,
Oregon
• Current vegetation: sagebrush “high
desert”; mean ann. ppt ~200 mm.
John Day chrono-stratigraphy
Deciduous
riparian
forest (alderelm-hickorywalnut), eastcentral
Oregon
(Whitecap
Knoll beds;
late Eocene)
Eocene-Oligocene
fossil beds near
Eugene, Oregon
Warm temperate forest
(alder-oak-sycamoresweet clover [Meliosma],
dawn redwood
[Metasequoia]
Source: Retallack, G.J. et al., 2004. Eocene-Oligocene extinction and paleoclimatic change near Eugene, Oregon.
Geological Society of America Bulletin, 116, 817-839.
Mid-Cenozoic paleoclimate;
west-central Oregon
Eugene @ PD: MAT ~11°C; P ~1300 mm
Source: Retallack, G.J. et al., 2004.
Cenozoic climatic decline and
the onset of glaciation
What prompted Cenozoic climate
decline and the onset of glaciation?
Main factors:
1. Continental drift
Isolation of Antarctica and initiation of subAntarctic oceanic circulation; ice-sheet formation
Isolation of Arctic Ocean; sea-ice formation
2. Orogenesis
Isolation of continental interiors, particularly of
Central Asia, as a result of uplift of the Himalayas
and Tibetan Plateau. High altitude areas = more
snow cover = high albedo = regional cooling.
Holocene
10 ka
The
Quaternary:
endpoint of
Tertiary
cooling
Pliocene
1.67 Ma
Colder - Warmer
When
did the
first
cold
phase
occur?
IRD = iceberg-rafted
detritus
IRD
Colder - Warmer
Local
extinctions
after the
first cold
phase
cold
Vegetation of Late Pliocene Holland
~ 2.4 Ma = beginning of Quaternary?
Ice and Change:
Quaternary Biogeography
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Nature of the evidence
Chronology
Fluctuating climates
Glacial phases
Interglacial phases
Iceworld: Wisconsinan glaciation
storm paths
Glacial interglacial
seesaw:
e.g. 9 glacial
phases in last
0.7 Ma?
l
lll
ll
l
Polar
Cold
continental
Oceanic
Polar
Palaeotemperatures
(50 - 20 ka BP) in
Britain derived from
beetle assemblages
Species ranges
Pollen analysis:
identification
based on shape
and
ornamentation of
grain
Pollen “rain”
Lakes
Bogs
Pollen
analysis
results:
% pollen and
pollen influx
The last
interglacial
- glacial
cycle
Glacial / periglacial
areas
~ 100 ka
European
vegetation
distribution:
13 ka BP
(= late glacial)
Full-glacial vegetation of
eastern North America
Laurentide Ice Sheet
Bio-indicators
of lowered sea
level in late
Quaternary
mammoth teeth
freshwater peat
oolites
(= lake deposits)
all continental
shelves exposed in
glacial phases
Exposed
continental
shelves
=
land
bridges
Trans-Beringia mammal migrations
during the Quaternary
Beaver
Lynx
Snow & mountain sheep
Moose
Elk
Bears
Wolverine
Wolf
Arctic fox
Arctic hare
Bison
Mountain goat
Coyote
Kit fox
(and humans)
Camels
Horse
Beringia: Arctic fish refuge?
refuge?
refuge?
Multiple trans-Beringian
migrations: the Bison case
Bison priscus
Bison antiquus
Bison bison
Quaternary fluctuations in
precipitation in the western US
“Provo”
relict
shoreline,
Lake
Bonneville
http://wwwpaztcn.wr.usgs.gov/rsch_highlight/articles/200409.htm
Lake levels
in US
Southwest;
full - late
glacial phase
= “pluvial”
Elevation vegetation
relations,
Grand
Canyon
area:
full-glacial
was cooler
and wetter
Douglas-fir: a
refuge relict
in the
Mexican
Sierras?
pine - fir forest
Glacial
Interglacial
Interglacial range
Glacial interglacial
migrations
(e.g. Holocene)
Glacial refuge
Refuges and migrations:
individualistic patterns
Refuges and migrations:
aquatic biota
Postglacial
migration
paths:
aquatic
biota
Glacial refuges
Ranges
and
refuges:
the
tropical
biotas
Inferred glacial
refuges in
tropical areas:
an extreme view
Climatic
deterioration
during
interglacial
phases
?
Climatic optima in early interglacial time:
the driving forces
Evidence for the Holocene
hypsithermal
The early part of the Holocene is
generally considered to have been a
“climatic optimum” with higher
temperatures (and lower rainfall?) than
at present. Can you find evidence of
this in the pollen records from the
Pacific Northwest?
Elsewhere, the ‘hypsithermal’
may have been wetter:
(e.g. the central Sahara)
Eroded lake beds,
Taouendi
Rock art,
Tassili Massif
Pollen evidence
(after Ritchie)