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Erosion rates & patterns
inferred from
cosmogenic 10Be in the
Susquehanna River Basin
Joanna M. ReuterThesis Defense
March 11, 2005
Paul Bierman, advisor
Motivation:• Applied questions
–Chesapeake Bay sedimentation
• Basic science questions
–Topographic change over time
–Relationships between erosion rate and landscape characteristics
Cosmogenic 10Be in fluvial sediment
Sediment yield
Erosion rates Landscape characteristics
• Tectonics
• Climate
• Vegetation
• Topography
• Bedrock geology
Geographic information
systems (GIS)
Cosmic ray bombardment
produces 10Be in quartz.
O 10Be
Quartz
Cosmic Rays
0
1
2
3
0 50 100% % %
Depth
(meters)
Production Rate
10Be is a proxy for erosion rate.
Time scale:
104-105 years
Virtual Tour
of the
Susquehanna
River Basin
EXPLANATION
Forested
Agricultural
Developed
Barren
EXPLANATION
Cities & towns
Coal fields
EXPLANATION
Major dams
EXPLANATION
Basin Selection
and
Sampling Approach
Advantage:
Sediment yield
Disadvantage:
Complex basins
EXPLANATION
Glaciated
Part glaciated
Non-glaciated
USGS Basins
GIS-selected
basins
EXPLANATION
GIS-selected
Basins
GIS-selected Basins
mean
slope:
3.4º mean
slope:
8.0º
GIS-selected Basins:
Nested Basins
Bedrock Samples
Summary of Groups of
Samples
• USGS Basins
–mostly large, complex
• GIS-selected Basins
–small, simple
• Bedrock Samples
10Be Concentrations
and
Inferred Erosion Rates
0.001
0.01
0.1
1
10
1000 1 2 3 4 5 6 7
REG_ID_NUMBER
10
BeN
orm
__
__
___
___
___
___
AK
all
RP
YU
SR
CA
ID
LL
SQ
SM
OC
PR
PN
VZ
BO
WU
LO
RG
NC
ME
NM
BH
HM
SL
NY
WP
TR
Expon. (all)Region
No
rmali
zed
10B
e (
10
5ato
ms g
-1q
uart
z)
Great
Smoky
Mountains
Namibia Australia
Europe
Bolivia
Himalayas
Data sources:
Matmon et al., 2003; Bierman and Caffee, 2001; Schaller et al., 2001; Morel et
al., 2003; Safran et al., in press; Vance et al., 2003; Duncan, unpublished data
Susquehanna
Results for USGS Basins
if assumptions have been met
xx
0
10
20
30
40
50
60
70
0.1 10 1000 100000
Basin area (km2)
10 B
e e
rosio
n r
ate
allAP SSVR SSVR SHPD SCAppalachian PlateausValley and RidgePiedmontSeries1Series9
10Be
erosion
rate
(meters/
million
years)
16 ± 1014 ± 4
0
10
20
30
40
50
60
70
0 5 10 15 20 25
Mean slope of basin (degrees)
Erosion
rate
(meters/
million
years)
0
10
20
30
40
50
60
70
0 5 10 15 20 25
Mean slope of basin (degrees)
0
10
20
30
40
50
60
70
0 5 10 15 20 25
Mean slope of basin (degrees)
0
10
20
30
40
50
60
70
0 5 10 15 20 25
Mean slope of basin (degrees)
Slope
0
10
20
30
40
50
60
70
0 5 10 15 20 25
Mean slope of basin (degrees)
0
10
20
30
40
50
60
70
0 5 10 15 20 25
Mean slope of basin (degrees)
R2 = 0.72
no correlation0
10
20
30
40
50
60
70
0 5 10 15 20 25
Mean slope of basin (degrees)
R2 = 0.37
R2 = 0.51
10Be Erosion of the Appalachians
0
10
20
30
40
50
60
0 5 10 15 20 25 30
Mean slope of basin (degrees)
Susquehanna
Great Smoky Mountains
Erosion
rate
(meters/
million
years)
R2 = 0.54
Smokies data from Matmon et al., 2003
60
50
40
30
20
10
0
Bedrock Samples
4.0
2.5 m/My
4.0
4.9 m/My
Bedrock samples
from Namibia:
Source:
Bierman and Caffee, 2001
Summary of Results
• Erosion rate correlates positively with
basin slope
• No discernible relationship exists between
lithology and erosion rate
• Results for non-glaciated USGS basins are
robust
• For basins impacted by glaciation, 10Be
results cannot be directly interpreted as
erosion rates
• Bedrock outcrops are eroding slowly
10Be Erosion Rates
Compared to
Sediment Yield
10Be vs.
• Sediment
generation
• Time scale: 104-105
years
• Representative of
full rock erosion
• Export of sediment
from the basin
• Period of record, 2
to 29 years
• Suspended load
only; does not
include dissolved
load or bedload
Source of sediment yield data:
Gellis et al. (2005), Williams and Reed (1972), and unpublished data from A. Gellis
Sediment
Yield
For comparison, present both as erosion rates (m/My)
R2 = 0.32
1
10
100
1000
0 20 40 60 80 100
Cleared land (% of basin area)
1
10
100
1000
0 20 40 60 80 100
Cleared land
(% of basin area)
Erosion
rate
(m/My)
Erosion
rate
(m/My)
10Be
Sediment yield
Appalachian Plateaus
Valley and Ridge
Piedmont
• Davis’s Geographical Cycle
• Hack’s Dynamic Equilibrium
• Statistical Steady State
• Perturbations
Testing
Geomorphic Models
of Topographic
Change
Geographical Cycle (Davis)
Image sources:
http://www.staff.amu.edu.pl/~sgp/gw/wmd/wmd.html
http://epswww.unm.edu/facstaff/gmeyer/eps481/481tectclimateveg_files/frame.htm#slide0032.htm
“Youth”
“Maturity”
“Old Age”
xImage source:
http://epswww.unm.edu/facstaff/gmeyer/eps481/481tectclimateveg_files/frame.htm#slide0032.htm
Dynamic Equilibrium (Hack)
“It is assumed that within a single erosional system all
elements of the topography are mutually adjusted so
that they are downwasting at the same rate.”
slope
ero
sio
n r
ate
lithologic resistance
slo
pe
lithologic resistance
Dynamic Equilibrium (Hack)
ero
sio
n r
ate
Image source:
Hack (1960)
Dynamic Equilibrium (Hack)
Statistical Steady State
x
Statistical Steady State
Geographical Cycle
Peneplain
Dynamic Equilibrium
Uniformly eroding
topography
Statistical Steady State
Changing topography,
constant relief
Mountains
Perturbation
More stableLess stable
x
Hack’s Equilibrium?
0
5
10
15
20
25
30
35
0 10 20Mean slope of basin (degrees)
10B
e e
rosio
n r
ate
(m
/My)
Series1
VR sandstone
VR shale
Linear (Series1)
slope
ero
sio
n r
ate
lithologic resistance
slo
pe
lithologic resistance
ero
sio
n r
ate
0
5
10
15
20
25
30
35
1.502.503.50
10B
e e
rosio
n r
ate
(m
/My)
VR
shale
VR
sandstone
0
5
10
15
20
25
1
Mean s
lope o
f basin
(degre
es)
shale sandstone
Basin lithologyBasin lithology
Geographical Cycle
Peneplain
Dynamic Equilibrium
Uniformly eroding
topography
Statistical Steady State
Changing topography,
constant relief
Mountains
Perturbation
More stableLess stable
x
x
Is Relief Changing?
• Slow erosion of
ridges:
– Bedrock samples
– High elevation, low
slope sandstone
basins
• Capacity for rapid
stream incision:
– Holtwood Gorge
7 m/My
9 m/My
13 m/My
Mechanism for
reduction
of relief:
Slope retreat
Geographical Cycle
Peneplain
Dynamic Equilibrium
Uniformly eroding
topography
Statistical Steady State
Changing topography,
constant relief
Mountains
Perturbation
More stableLess stable
x
x?
Perturbation?
Background:10Be data from the Sierra Nevada
Riebe et al. (2001)
No base level fall,
no correlation with slope:
Base level fall,
correlation with slope:
0
10
20
30
40
50
60
0 5 10 15 20 25
R2 = 0
R2 = 0.37
0
10
20
30
40
50
60
0 5 10 15 20 25
R2 = 0.72
0
10
20
30
40
50
60
0 5 10 15 20 25
10Be
erosion
rate
(m/My)
Slope (degrees)
10Be
erosion
rate
(m/My)
10Be
erosion
rate
(m/My)
average: 22
average: 13
average: 9Gradient in erosion rates across basin would have to be maintained by differential rock uplift
for statistical steady
state to apply
Geographical Cycle
Peneplain
Dynamic Equilibrium
Uniformly eroding
topography
Statistical Steady State
Changing topography,
constant relief
Mountains
Perturbation
More stableLess stable
x
x
x
Evidence for a Miocene Perturbation• Offshore sedimentary record: increased sediment
delivery (Poag and Sevon, 1989; Pazzaglia and
Brandon, 1996)
• Fission track: period of rapid exhumation
beginning in the Miocene (Blackmer et al., 2001)
• Detrital chert and detrital fission track data
suggest stream capture and drainage
reorganization in the central Appalachians (Naeser
et al., 2004)
Rates and patterns of erosion in the
Susquehanna River Basin may reflect ongoing
adjustment to Miocene stream capture and base-
level fall.
0
10
20
30
40
50
60
0 5 10 15 20 25
R2 = 0
R2 = 0.37
0
10
20
30
40
50
60
0 5 10 15 20 25
R2 = 0.72
0
10
20
30
40
50
60
0 5 10 15 20 25
10Be
erosion
rate
(m/My)
Slope (degrees)
10Be
erosion
rate
(m/My)
10Be
erosion
rate
(m/My)
average: 22
average: 13
average: 9
Global Compilation of10Be Data from
Fluvial Sediment:
A Brief Overview
Regions with 10Be erosion rate data from sedimentPublished data from:Bierman and Caffee, 2001; Brown et al., 1995; Brown et al., 1998; Clapp et al., 2000;
Clapp et al., 2002; Granger et al., 1996; Heimsath et al., 1997; Heimsath et al., 2001;
Hewawasam et al., 2003; Kirchner et al., 2001; Matmon et al., 2003; Morel et al., 2003;
Riebe et al., 2000; Riebe et al., 2003; Schaller et al., 2001; Vance et al., 2003
In press, in preparation, and unpublished data from:Bierman, Duncan, Johnsson, Nichols, Reuter, Safran
Topography
Tectonics
Climate
Vegetation
Topography
Tectonics
Climate
Vegetation
Lithology
1
10
100
1000
10000
0 20 40 60 80 100TRCVMEAN
ero
s_re
p________________
SQ
Mean tree cover in basin (percent)10B
e e
ros
ion
ra
te (
me
ters
per
mil
lio
n y
ears
) Vegetation
Susquehanna
Mean tree cover in basin (percent)10B
e e
ros
ion
ra
te (
me
ters
per
mil
lio
n y
ears
) Vegetation
n = 454
Mean annual precipitation in basin (millimeters)10B
e e
ros
ion
ra
te (
me
ters
per
mil
lio
n y
ears
) Climate
n = 454
Precipitation of 3 driest months/total precipitation10B
e e
ros
ion
ra
te (
me
ters
per
mil
lio
n y
ears
) Climate
uniformseasonal
n = 454
R2 = 0.37
p < 0.001
Mean slope of basin (degrees)10B
e e
ros
ion
ra
te (
me
ters
per
mil
lio
n y
ears
) Topography
n = 454
R2 = 0.39
p < 0.001
10B
e e
ros
ion
ra
te (
me
ters
per
mil
lio
n y
ears
)
Mean basin elevation (meters)
Topography
n = 454
R2 = 0.44
p < 0.001
Peak ground acceleration (m/s2) with 10% probability of exceedance in 50 years1
0B
e e
ros
ion
ra
te (
me
ters
per
mil
lio
n y
ears
) Tectonics
n = 454
R2 = 0.50
p < 0.001
• Tectonics– Susquehanna River Basin erosion rates are relatively
low and similar to other passive margin and tectonically quiescent settings
• Topography– Slope matters
– Elevation and erosion rate are not correlated within the region
• Climate– Relatively uniform intra-annual distribution of
precipitation, and correspondingly low erosion rates
– Glaciation disrupts isotopic steady state and precludes simple interpretation of erosion rates from 10Be
Conclusions
• Vegetation and land use– 10Be results are robust to land use impacts
– Contemporary sediment yields for the Piedmont are high relative to background 10Be sediment generation rates
• Lithology– No clear impact of lithology on erosion rate in the
Susquehanna River Basin
• History– Rates and patterns of erosion may reflect ongoing
adjustment to Miocene stream capture and base-level fall
Conclusions
• Funding: NSF, USGS, UVM
• Paul Bierman
• Jen Larsen, Megan McGee, Bob Finkel
• Milan Pavich, Allen Gellis
• Donna Rizzo, Beverley Wemple, Cully Hession
• Luke Reusser, Matt Jungers, and all the other Geo grads, faculty, & staff
• Eric Butler
Acknowledgments
Erosion rates
– Sediment yield
Landscape characteristics
• Topography
– Relief
from Ahnert, 1970Mean relief h (m)
Mean
den
ud
ati
on
rate
d (
m/1
,000 y
ears
)
For example:
Erosion rates
– 10Be in fluvial sediment
Landscape characteristics
• Topography
– Relief
from Vance et al., 2003
For example:
Results for
non-glaciated
USGS basins
are robust
within a factor
of 2
0
10
20
30
40
50
60
70
0.1 10 1000 100000Basin area (km
2)
0
10
20
30
40
50
60
70
0 10 1000 100000
Basin area (km2)
180 260
Erosion
rate
(m/My)
from
sediment
yield
Erosion
rate
(m/My)
from10Be
0
10
20
30
40
50
60
70
0.1 10 1000 100000
Basin area (km2)
10 B
e e
rosio
n r
ate
all
AP SS
VR SS
VR SH
PD SC
Appalachian Plateaus
Valley and Ridge
Piedmont
10Be
erosion
rate
(meters/
million
years)
Factors of possible importance for
understanding sediment dynamics
and/or interpreting 10Be data
• Multiple lithologies, varying quartz content
• Glaciation
• Human impact
– Agriculture
– Logging
– Development
– Coal mining
– Dams
Results for USGS Basins
if assumptions have been met
0
10
20
30
40
50
60
70
0.1 10 1000 100000
Basin area (km2)
10 B
e e
rosio
n r
ate
all
AP SS
VR SS
VR SH
PD SC
Appalachian Plateaus
Valley and Ridge
Piedmont
10Be
erosion
rate
(meters/
million
years)
Summary
LithologyRock Type (Susquehanna)
Erodibility metric (Rio Puerco)
No
Yes
Vegetation Tree cover No
Climate Mean annual precipitation
Seasonality of precipitation
No
Yes
Topography
Slope
Relief
Elevation
Yes
Yes
Yes
Tectonics Seismic hazard assessment Yes
Relates to 10Be erosion rate?
Landscape
characteristic Metric
0.001
0.01
0.1
1
10
1000 1 2 3 4 5 6 7
REG_ID_NUMBER
10
BeN
orm
__
__
___
___
___
___
AK
all
RP
YU
SR
CA
ID
LL
SQ
SM
OC
PR
PN
VZ
BO
WU
LO
RG
NC
ME
NM
BH
HM
SL
NY
WP
TR
Expon. (all)Region
No
rmali
zed
10B
e (
10
5ato
ms g
-1q
uart
z)
Great
Smoky
Mountains
Namibia Australia
Europe
Bolivia
Himalayas
Susquehanna
Data sources:
Matmon et al., 2003; Bierman and Caffee, 2001; Schaller et al., 2001; Morel et
al., 2003; Safran et al., in press; Vance et al., 2003; Duncan, unpublished data
Summary: 10Be and Sediment Yield
• Sediment yield is out of equilibrium with 10Be in the Piedmont
Recommended