greg retallack - the once and future global cooling: lessons from prehistory
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The once and future global The once and future global cooling: lessons from cooling: lessons from
prehistoryprehistory
Gregory J. RetallackGregory J. Retallack
University of OregonUniversity of Oregon
Eocene-Oligocene paleosols Badlands National Park, South Dakota
Grassland expansion changed the world Grassland expansion changed the world Since 35 Ma, 0-25% of land, but not AntarcticaSince 35 Ma, 0-25% of land, but not Antarctica
Crumb structure (mollic epipedon) in tall grasslandpaleosol (Mollisol) Dayville, OR: late Miocene (7 Ma)
Grassland soil (Mollisol) Lake Nakuru National Park, Kenya
Smell the grass
cis-3-hexenalcarbon gray, hydrogen white,
oxygen red
QUATERNARY RECORD 1: PALEOSOLS
Quaternary Palouse Loess,eastern Washington
Paleosols near Kahlotus, WA, data from Busacca (1998)
Paleosols near Dayton, WA
QUATERNARY 2: SOIL TYPESPalouse Loess near Clyde, Washington, alternation of
interglacial deep-calcic grassland and glacial
shallow-calcic sagebrush23.7 ka
36.1 ka
40.1 ka
46.2 ka
Mt St Helens ash S
Mt St Helens ash C
thermoluminescence dates from Busacca (1998)
Earthworm fabric in 46 ka Nix grassland paleosolTaenidium (cicada) burrow
in 40 ka Tlal sagebrush paleosol
Also in paleosols,are fossil mam-mals (Rensberger
& Barnosky, 1993), & phytoliths
(Blinnikov et al 2002)
Modern dry grasslandnear Benge, Washington
Modern sagebrushnear Denio, Nevada
QUATERNARY 3: ECOSYSTEM SHIFTS
Longview Ranch, Oregon, with green Oligocene paleosols in hill
CENOZOIC 1: PALEOSOLS IN DEEP TIME
CENOZOIC 2:JOHN DAY FM OLIGOCENEWell dated (Ar/Ar, paleomagnetic) fossiliferous sequence
CENOZOIC 3: SHRUB/GRASS TRACES
Taenidiumcicada burrowof sagebrush
Edaphichniumearthworm chimney
of grassland
Pallichnusdung beetle nests
of grassland
Blocky structurered forested
paleosol (Alfisol),Painted Hills, OR:Oligocene (31 Ma)
Crumb structure(mollic epipedon)in tall grassland
paleosol (Mollisol)Dayville, OR:
late Miocene (7 Ma)
Crumb structure (mollic epipedon)in short grassland paleosol (Mollisol)Kimberly, OR: mid-Miocene (19 Ma)
Merychippus seversus Dayville, OR: mid-Miocene (16 Ma)
CENOZOIC 4: VEGETATION FROM SOIL
PHYTOLITHS-36-0 Ma abundant grassland phytoliths (Strömberg, 2002, 2004)
PEDOGENIC δ13Ccarb
-40 Ma of 20-40% C4(Fox and Koch, 2003)
PALEOSOLS-bunch then sod grasslands at warm- wet times-dry times expanded sagebrush (not grassland)
CENOZOIC 5: VEGETATION
Red forested non-calcareous paleosols (Alfisols) pass upwards into brown
calcareous grassland paleosols (Andisols) by mid-Oligocene (30Ma)
Painted Hills, Oregon
Paleoprecipitation estimated from paleosol Bt (blue)
or Bk (red) follows decline in atmospheric CO2
CENOZOIC 6: CLIMATE FROM SOIL
Chesapeake impact structure35 Ma (from Voytek, 2005)
Columbia River Basalts, Oregon, Washington (17-15 Ma) (Camp and Ross 2004)
Steinheim Crater, Germany 15 ma (3.8 km) by E. Stabenow
CLIMATE 1: TRANSIENT SPIKES35 Ma (Priabonian) and 16 Ma (Langhian)
transient spikes of warm-wet CO2
due to impacts and flood basalts
Ethiopian flood basalts 35 Ma (from Wood and Guth 2010)
PRO. Mountain uplift promotes weathering and albedo (Ruddiman and Raymo 1988)
CON. Physical not chemical weathering, metamorphic CO2
CLIMATE 2: HIMALAYAN COOLING?
PRO. Thermal isolationices Antarctica, consumes H2O, raises albedo (Kennett 1978)
CON. Warms mid-latitudes,minor reductions ofatmospheric H2O,CO2 and albedo
CLIMATE 3: ANTARCTIC CURRENT?
CLIMATE 4: GRASSLAND EXPANSION? Grasslands not due to drying, expanding into wetter regions-from 35-0 Ma expanded from 0-25% of land
Mollic and near-mollic paleosol records from 3 continents (Retallack 2001)
COEVOLUTION 1: GRASSES-GRAZERS
from Retallack 2007
BIOLOGICALMECHANISM-adaptation toothers not toenvironment
-grasses bestwithstand
grazers
-grazers bestcope with phytoliths
and growthof grasses
Paratomarctus euthos middle Miocene, Valentine
Formation, Gordon Quarry, Nebraska
Hesperocyon gregarius 32 Ma
Canis meso-melas (living)
Mesocyon sp. 27 Ma
Tomarctus euthos 16 Ma
5 cm
from Radinsky 1969
Prorean gyrus
COEVOLUTION 2: PACK HUNT & HERDS
-prorean gyrus found in pack hunting wolves and dogs, not foxes
-prorean gyrus appears in boro-phagine dogs of Nebraska 19 Ma
Agate Springs, NE: Miocene (19Ma)by Jay Matternes
bear dog den (Daphaenodon)
cursorial, hypsodont, tridactyl(Parahippus tyleri) Dung cake of ruminant
Mollisol paleosol
Silica husk of grass
(Panicum elegans)
- pack hunting- running escape- prey herding- hypsodont grazing- siliceous grasses- dung cakes- weedless sod- mollic soil
COEVOLUTION 4: DUNG AND SOD
y = 1.7492Ln(x) - 8.4142R2 = 0.7439
0
2
4
6
8
10
12
0 500 1000 1500 2000 2500 3000 3500 4000
Mean annual precipitation (mm)
So
il o
rgan
ic c
arb
on
(kg
/m2 )
Australia from Wynn et al. 2005, Africa from Zinke et al 1984
COOLING 1: CARBON STORAGE - organic C like net primary productivity increases with precipitation-grasslands rule strategic zone (300-1200 mm mean annual precip.)
African grasslands
Australian woodlands
COOLING 2: TRANSPIRATION
- grasslands have moist soil, dry air
-woodlandshave drier
soil (20-30%),moist air
-water vapor is a green-house gas,
although easily rained out
Nairobi National Park, Kenya Kakamega Forest, Kenya
COOLING 3: ALBEDO - grasslands light (albedo 15-19 %), covered by snow (albedo 40-85%)
-woodlands dark (albedo 8-13%) hard to cover with snow
CARBON FARMING 1: MOTIVATION - global warming due to CO2 could be offset by C storage in farm soils
-tests already underway in Australia, baseline soil C assay, then carbon
credit payment for gains
CARBON FARMING 2: TECHNIQUES 1. CELL GRAZING Pen cattle with electric for each days grazing: grazing takes out weeds leaving sod grasses.
2. PASTURE CROPPING Drill seed and raise crop through sod: prevents soil oxidation by plowing.
3. CONTOUR COPPICING Plant trees at inflexion point in slopes: prevents gully erosion.Electric fence and cell grazing, Horsham, Victoria
There’s some good news beneath the horizon,
Next to swamps, grassland soils have more carbon,
Since these are the soils that we already use
We can manage soil carbon and curb soil abuse,
It was just coevolution, a process by which we got sod.By grazing so hard on grassy sward,The Ice Age no longer seems odd.Still we have coevolution, a way that we can go forthAnd use the soil against big oilTo try to cool the Earth.
CONCLUSIONS
Grassland soil (Mollisol), Dionysiou, central Greece.