Download Structure of the Lithosphere and the Sedimentary Record: Where do

Structure of the Lithosphere
and the Sedimentary Record:
Where do they Meet?
Michelle Kominz
Western Michigan University
Overview
•  Original Earthscope Goals and how they relate
to the sedimentary record.
•  Overview of basins: What aspects of the
stratigraphic record relate to Earthscope scope.
•  Tectonic Subsidence analysis
•  Basin subsidence - overview of observations
•  Several examples
•  Several targets
Earthscope 1
•  What is a continent?
•  How are continental structure and deformation
related?
•  How does crust and mantle rheology vary with
with depth?
•  Lithospheric Strength and Crust-Mantle
Coupling.
•  How and where are forces generated in the
upper mantle, and how and where are they
transferred to the crust?
• How and where are forces generated in
the upper mantle, and how and where
are they transferred to the crust?
• The stratigraphic record tells us when
and how the crust experienced
deformation.
Strata Inform Earthscope:
• Foreland basins
• Forearc/Backarc basins
• Passive margins
• Cratonic basins
• Pull-apart (trans-tensional) basins
• How does crust and mantle
• Stratigraphic models require an understanding of
rheology vary with with depth? the lithospheric structure and rheology.
Earthscope Informs Strata:
• Foreland basins
• Forearc/Backarc basins
• Passive margins
• Cratonic basins
• Pull-apart (trans-tensional) basins
Basins:
Fig. modified from Reynolds et al. 1991
Distance (km)
0
50
100
Sediment Supply
150
200
Eustatic
Sea Level
0
Depth
(m)
500
Tectonic Subsidence
The 3 main controls on sedimentation are generally taken to
be: Eustasy, Sediment Supply and Tectonic Subsidence.
Basins:
Fig. modified from Reynolds et al. 1991
Distance (km)
0
50
100
150
Sediment Supply
Eustatic
Sea Level
0
Depth
(m)
Compaction
500
Tectonic Subsidence
Isostasy
200
Sediment
Dynamics
Crustal thickness and strength is crucial
for both forward and inverse
stratigraphic modeling:
• Flexural strength - 2D models are dependent on
strength of lithosphere
Isostasy
• Thermal models
• hydrocarbon maturation
Tectonic Subsidence
• subsidence history
• Model testing - e.g., magmatic vs. amagmatic
extensional basins
Basins:
• Foreland basins
• Forearc/Backarc basins
• Passive margins
• Cratonic basins
• Pull-apart (trans-tensional) basins
Basins
Porosity (%)
0
20
40
60
80
0
Tectonic Subsidence Analysis
Backstripping:
1
2
3
Measured
Section
T5
T4
T3
T2
T1
T0
Observed
Sediment
Thickness
T1
Decompacted
Sediment
Thickness, S*
T1
4
T1
5
T0
T0
T2
First
Reduction
R1
T0
T2
6
T2
T
0
Depth
paleowaterdepth
equivalent basin for
sediment thickness S*
T
1
R1
Theoretical
Thermal
Subsidence
T
2
T
3
T
4
T
5
Passive Margins:
1
6
7 5
8
2
3
1
4
6
8
1
Paleozoic Miogeocline
Southern Canadian
Rocky Mountains
8
6
U.S. Atlanntic margin.
U.S. cordilleran Miogeocline
Passive Margins:
R1
Subsidence
(m)
0
120
100
200
100
300
200
400
300
500
400
600
500
700
600
800
700
100
80
Time (Ma)
60
low φ high φ
40
20
0
Ancora
Bass River
low φ high φ
Van Sickel et al., 2004 Basin Research
2
Basins
7
3 6
Foreland basins:
5
4
1
8
1
2
3
2
3
4 5
Southern Alberta Basin
San Rafael Swell, Utah
6
8
7
6 Hoback Basin, Wyoming
7 Green River Basin, Wyoming
Basins
Forearc Basins:
7
1,2
3
5
9
8
6
4
3
1
1 Great Valley
2
2
3
Sacramento Basin
Peninsular Ranges
7
7Oregon Coast Range
8
Cratonic Basins:
3,4
7
2
5
6
1
8
1
2
3
4
1 Illinois Basin 3 Willison Basin, North Dakota
2 Michigan Basin 4 Willison Basin, Saskatchewan
8
Passive Margins - Kirschner et al.
•  Passive margins form where
continents rift and form new
ocean basins
Block Diagram, Extension:
All Continents
All Oceans
Stretched
Continental Crust
z
z/β
wβ
w
When newly stretched margin
displaces ocean, the area of the
oceans decreases and sea level rises.
Funck et al., 2003
Blue = Kominz
& Scotese,
2005
Red = Data
from Steckler &
Watts, 1978
Sediment thickness data from Divins, 2006
•  Assume sediment grain density =
2.7 g/cm3
•  Use porosity vs depth curves to
obtain the bulk density
•  Blue is Oceanic Sed. (z<1000m &
WD > 2000m)
•  Red is Marginal Sed.
•  Use Airy isostatic model to remove
the sediment
Bathymetry data from U.S. Department of
Commerce, 2006, after Smith & Sandwell, 1997
Calculating Extension
Total tectonic
subsidence = TTS
Modified from Ziegler & Cloetingh, 2004
•  Fit a subsidence curve and determine β
ßmodel is the stretching factor
using the breakup age and TTS
required to thin crust at sea level, to
•  We assume rifting proceeds via a
its current thickness
modified uniform extension model (β =
δ)
•  We calculate ß twice using different
physical parameters
–  Parsons and Sclater (1977)
–  Stein and Stein (1992)
•  Preferred model
–  Different Teq and ß
Crustal Thickness
• 
• 
One output from the model is an
estimate of the crustal thickness of
the stretched continental margin.
There is very little data available
for comparison
•  Testing the Model
• 
• 
Good general correlation with
seismic crustal thickness data
from the margins of North America
& Australia
On average our model overestimates crustal thickness, and
thus underestimates extension
Sources: Diebold et al., 1988; Perry et
al., 2002; Funck et al., 2003; Brown et
al., 2003
Crustal Thickness
Kirschner et al. submitted, Tectonics
According to Kirschner et al.’s model
results, thinned continental crust
extends beneath the non-marine
continent from Long Island
through the Delmarva Peninsula.
This region has been extensively
studied and provides some
interesting questions.
Backstripping
Sea Level:
T1
T5
T4
Decompacted
Sediment
Thickness, S*
First
Reduction
R1
T1
60
80
1
2
T1
3
T0
T0
T0
T2
T2
5
6
T2
T1
paleowaterdepth
equivalent basin for
sediment thickness S*
T0
Depth
40
4
T3
T2
T
0
20
0
Observed
Sediment
Thickness
Measured
Section
Porosity (%)
0
T
1
R1
Theoretical
Thermal
Subsidence
T
2
T
3
T
4
T
5
Sea Level Change &
Non-Thermal Tectonics
Height
T0
T1
T2
T3
T4
T5
Sea Level
Kominz et al. 2008
Sea level estimates from backstripping 11 coastal plain
boreholes from New Jersey and Delaware.
Eustatic estimates are significantly lower than those of
Haq et al. (1987) but also diverge during the Late
Cretaceous and Paleocene from estimates based
on ridge and ocean volumes of Müller et al., (2008).
Due to passage of N.J. over the subducted Farallon
slab beginning ≈ 50 Ma?
Epeirogeny
Kominz et al. 2008
Sea level estimates from backstripping 11 coastal plain
boreholes from New Jersey and Delaware.
Eustatic estimates are significantly lower than those of
Haq et al. (1987) but also diverge during the Late
Cretaceous and Paleocene from estimates based
on ridge and ocean volumes of Müller et al., (2008).
Due (in part) to passage of N.J. over the subducted
Farallon slab beginning ≈ 50 Ma? Spasojevic et al.,
(2009), Müller et al., (2008).
Details - Recent
Hayden et al., 2008, Kulpecz et al., in prep.
The regional R2 pattern of the MD, VA, Delaware portions of the Salisbury
Embayment is quite different from N.J. and requires several tectonic events,
including a long-term subsidence event in the mid to Late Miocene. The
center of the Eocene impact crater is showing the opposite sense of motion,
suggesting an in-plane stress event.
Besides the subducted Farallon slab are there fundamental crustal differences
between N.J. and MD/VA?
Impact Event
Hayden et al., 2008, Kulpecz et al., in prep.
All crater-interior cores show slow uplift immediately after the impact event
followed by an unconformity and rapid uplift after several million years.
This is consistent with a model in which rapid sedimentation generates a negative
thermal anomaly which temporarily offsets the positive, crustal, thermal
anomaly generated by the impact event.
Imaging the structure of crust beneath the crater would go a long way to resolving
issues of the effect of an impactor on the crust and on subsequent tectonics.
Cratonic Basins:
3,4
7
2
5
6
1
8
1
2
3
4
1 Illinois Basin 3 Willison Basin, North Dakota
2 Michigan Basin 4 Willison Basin, Saskatchewan
8
Cratonic Basins
Backstripping
of many wells
within the
basin reveals
variations in
the pattern of
subsidence
through time.
Central gravity high
Precambrian rift
Cratonic Basins
Model for Michigan Basin formation: emplacement of excess mass followed by
stress-induced crustal weakening.
Can you image the anomalous
mass?
Might the strain-weakening
generate observable anisotropy?
Central gravity high
Precambrian rift
Targets:
• Foreland basins
• Forearc/Backarc basins
Passive
margins
• P
assive margins
Cratonic
basins
• C
ratonic basins
• Pull-apart (trans-tensional) basins
Structure of the Lithosphere
and the Sedimentary Record:
Where do they Meet?
Michelle Kominz
Western Michigan University
Thank you