3D MODELING OF THE CERRO TORO DEEP-WATER AXIAL CHANNEL-BELT, SIERRA DEL TORO, MAGALLANES BASIN,...
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Transcript of 3D MODELING OF THE CERRO TORO DEEP-WATER AXIAL CHANNEL-BELT, SIERRA DEL TORO, MAGALLANES BASIN,...
3D MODELING OF THE CERRO TORO DEEP-WATER AXIAL CHANNEL-BELT, SIERRA DEL TORO, MAGALLANES
BASIN, CHILE: FROM OUTCROP OBSERVATIONS TO SUBSURFACE
UNCERTAINTY
Lisa Stright, Zane Jobe, Anne Bernhardt and Steve GrahamGeological and Environmental Sciences, Stanford University
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Axial deep-water channel belt in the Andean foredeep
• Retro-arc foreland basin
• Deep-water sedimentation of arc derived detritus in elongate foreland trough
• Gentle folding and faulting during post-depositional (Miocene) uplift and deformation
• Late Cenozoic glaciation has led to spectacular 3D exposuresHubbard et al,
2008
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Condor Conglomerate (Barton et al., 2007; O'Byrne et al, 2007)
Silla Syncline(Bernhardt et al., in review;
Crane and Lowe, 2008;Beaubouef, 2004)
Sierra del Toro: Looking to the south
>1000 m
EW
Wildcat Conglomerate(Jobe et al., in review;
Hubbard et al., 2007, 2008)
At least 3 channel complex sets– Condor (Barton et al. 2008), Guanaco, Wildcat (Jobe et al. 2009)Condor: (Barton et al., 2008; O’Byrne et al. 2007b)
• 3 distinct channel complexes aggrade and stack to the west• conglomeratic channel fill comprised of dune and bar forms• complexes 50-80m thick, 1.0 - 1.5km wide
Guanaco: (Jobe et al., in review) • at least 5 individual channels, 5 - 70m thick and 0.1 – 1.0 km wide• aggrade and stack vertically and to the east• observed on northern sections only
Wildcat: (Jobe et al., in review) • downcuts to the south (?) and amalgamates the Guanaco • max thickness 300m, width 3.5 km along 6 km• outer bend margin angle 9° and inner bend margin angle 7°• paleoflow divergence in uppermost sections, loss of confinement (?)
~12 km
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Study Area – northern exposure of Sierra del ToroN
orth
~15 km
WE
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Study Area – southern exposure of Sierra del ToroN
orth
Looking to the north
~15 km1. Wildcat downcuts?
2. Guanaco south?
3. Undifferentiatedstratigraphic level?
4. Condor and undifferentiated relationship?
W E
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Structure and Stratigraphy: North (up-system)
500m
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Transformation Volume – Displacements in x, y and z
Northern
Central
Southern
N
E W
Southern
NorthernCentralN
-S Transect
Northern restoration
dz
dxdx, dy and dz
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Palinspastic restoration of mapped outcropping conglomerate units
N
WE
paleoflow
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Modeling the Channel Complexes
WE
~ 1.5 km
12001000 800 600 400 200 0
1400 mE W
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Condor Channel complex
Total thickness of 3 channel complex: 500m• Lowest: vertically aggrades and stacks to the west• Middle: shift to the west, aggradation• Upper: shift back to the east
Strong structural control along these sections
1400 m
paleoflow
N
12001000 800 600 400 200 0
E W
EW
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Guanaco Channel complex
• Smaller and thinner exposures
• Upper 4 Guanaco channels eroded/incorporated into the Wildcat
At or below the resolution of the modeling
800 600 400 200 0
paleoflow
N
northern
southern
12001000 800 600 400 200 0
1400 m
1400 m12001000southern section
WE
E W
northern section
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Wildcat Channel Complex
W E
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Wildcat Channel Complex
Because the Guanaco is not observed on the southern section, downcutting is at least
Modeling reveals a 600m erosion over a distance of 8km
The magnitude of erosion predicted by the model is tightly coupled with structural interpretation
N S12001000
0 500 1000m
800600400200
paleoflow
paleoflow
N
400m
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Undifferentiated Conglomerate
Position “tied” to the uppermost CondorSteps down similar to the Wildcat channel complexPoor outcrop exposure control
1400 m12001000 800 600 400 200 0
12001000 800 600 400 200 0
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Biased sampling generate uncertainty in interpretation– Limited exposures– Eroded section– Limited ability to measure and describe all data
Visually data digitally in 3D– Helps to reduce the uncertainty in stratigraphic relationships– Analyze potential stacking patterns– Platform for discussion
Stratigraphic uncertainty tightly controlled by uncertainty in structural interpretation and restoration– Magnitude of downcutting of the uppermost channel complex– Width and thicknesses of channel complexes
No outcrop exposure is truly 3D -> interpretation uncertainty
Modeling the deep-water channel belt deposits of Sierra del Toro
SUMMARYINTRODUCTION Observations Modeling Analysis AAPG 2010
Future Work
• Channel-fill architecture modeling (after Jobe et al., in press)
• 3D forward seismic reflectivity modeling to use as analog for subsurface seismic surveys
• Dimensional characterization of the channel complexes: – width– height– asymmetry– sinuosity– stackinguncertainty and ranges of
all of these parameters
15Hz
25Hz
INDUSTRY SPONSORSINDUSTRY SPONSORS
SPODDS Students:Julie Fosdick, Anne Bernhardt,Zane Jobe, Katie Maier, Jon Rotzien, Larisa Masalimova,Glenn Sharman, Blair Burgreen
Advising Committee:Stephen Graham, Andre Journel, Gary Mavko, Don Lowe