1. An introduction to various styles of extension found
throughout the lithosphere See instructor notes below for each
slide!
2. Outline Normal faulting Transtensional faulting Variations
across the entire lithosphere The variety of rifted margins
3. Outline Normal faulting Transtensional faulting Variations
across the entire lithosphere The variety of rifted margins
4. Based on experiments and an activity developed by Robert
Burger, Smith College The evolution of normal faults: how the crust
responds to extension
5. Here are a few figures of a normal fault typically found in
an intro textbook
http://geomaps.wr.usgs.gov/archive/socal/geology/inland_empire/images/guataemala.jpg
http://geomaps.wr.usgs.gov/parks /deform/ Great images to introduce
fault components and their terms!!
6. But what is missing?? How does a fault behave through time?
Does it always have the same geometry? Is there always just one
fault? If not, how does a set of faults form and interact? How does
the earths surface respond during faulting? How does it change?
What new rocks form in the process? How do they form? How are they
affected by the faulting??
7. How do we get from this to this?
8. Lets take a look!! Watch the following movie of a sandbox
experiment Layers represent strata in the earth The experiment uses
the apparatus below: layers of sand are filled in and the walls are
pulled apart (in the photo below you see an example of compression,
not extension) Photo courtesy of Jack Loveless, Smith College
9. Extension in a Sandbox This video is from the SERC teaching
colletction:
http://serc.carleton.edu/NAGTWorkshops/structure/activities/6662.html
Evolution of Normal Fault Systems During Progressive Deformation,
by Robert Burger, Smith College
10. Watch the movie a second time What did you notice?? What
can you say about these questions?? How does a fault behave through
time? Does it always have the same geometry? Is there always just
one fault? If not, how does a set of faults form and interact? How
does the earths surface respond during faulting? How does it
change? What new rocks form in the process? How do they form? How
are they affected by the faulting??
11. 20 and 40 seconds into the movie This image is from the
SERC teaching colletction:
http://serc.carleton.edu/NAGTWorkshops/structure/activities/6662.html
Evolution of Normal Fault Systems During Progressive Deformation,
by Robert Burger, Smith College
12. 60 and 80 seconds into the movie This image is from the
SERC teaching colletction:
http://serc.carleton.edu/NAGTWorkshops/structure/activities/6662.html
Evolution of Normal Fault Systems During Progressive Deformation,
by Robert Burger, Smith College
13. 100 and 112 seconds into the movie This image is from the
SERC teaching colletction:
http://serc.carleton.edu/NAGTWorkshops/structure/activities/6662.html
Evolution of Normal Fault Systems During Progressive Deformation,
by Robert Burger, Smith College
14. NOT ALL FAULTS ARE STRAIGHT Listric Faults
15. Watch a second movie: same experiment, same questions,
different fault geometry How does a fault behave through time? Does
it always have the same geometry? Is there always just one fault?
If not, how does a set of faults form and interact? How does the
earths surface respond during faulting? How does it change? What
new rocks form in the process? How do they form? How are they
affected by the faulting??
16. Listric faults This video is from the SERC teaching
colletction:
http://serc.carleton.edu/NAGTWorkshops/structure/activities/6662.html
Evolution of Normal Fault Systems During Progressive Deformation,
by Robert Burger, Smith College
17. What did you see? How does a fault behave through time?
Does it always have the same geometry? Is there always just one
fault? If not, how does a set of faults form and interact? How does
the earths surface respond during faulting? How does it change?
What new rocks form in the process? How do they form? How are they
affected by the faulting??
18. What else did you see? This image is from the SERC teaching
colletction:
http://serc.carleton.edu/NAGTWorkshops/structure/activities/6662.html
Evolution of Normal Fault Systems During Progressive Deformation,
by Robert Burger, Smith College
19. What new rocks form in the process? How do they form? How
are they affected by the faulting?? This image is from the SERC
teaching colletction:
http://serc.carleton.edu/NAGTWorkshops/structure/activities/6662.html
Evolution of Normal Fault Systems During Progressive Deformation,
by Robert Burger, Smith College
20. Observations: Summary Faults may form at one angle and the
angle changes through time (dip becomes shallower) More than one
fault forms Different sizes and amount of offset May dip in two
directions Faults are active for a time, become inactive, new
faults form New sediment is deposited in the lows created The new
layers become tilted by the ongoing faulting New layers may vary in
thickness This is evidence of growth faulting
21. Examples from the Loreto Basin, Gulf of California Evidence
of growth faulting: - new sedimentary layers are thicker where more
accommodation space is created next to the fault - fanning of dips:
youngest layers are less tilted than older layers Figure from:
Rebecca J. Dorsey and Paul J. Umhoefer, 2000, Tectonic and eustatic
controls on sequence stratigraphy of the Pliocene Loreto basin,
Baja California Sur, Mexico, Geological Society of America
Bulletin;112, no. 2; 177-199.
22. Multiple faults seen in cross-section from earlier map More
than one fault forms!! Figure from: Rebecca J. Dorsey and Paul J.
Umhoefer, 2000, Tectonic and eustatic controls on sequence
stratigraphy of the Pliocene Loreto basin, Baja California Sur,
Mexico, Geological Society of America Bulletin;112, no. 2;
177-199.
23. A geologic map of faults doesnt reveal the evolution (the
growth and activity) of an entire set faults Figure from: Rebecca
J. Dorsey and Paul J. Umhoefer, 2000, Tectonic and eustatic
controls on sequence stratigraphy of the Pliocene Loreto basin,
Baja California Sur, Mexico, Geological Society of America
Bulletin;112, no. 2; 177-199.
24. How do we determine that evolution in the real world? And
get beyond the sandbox? Detailed mapping combined with Structural
analysis Basin analysis Detailed stratigraphic analysis Dating
Basin reconstruction Work done by MARGINS and GeoPRISMS teams of
researchers from a variety of disciplines aims to unravel the
extension step by step and understand how continental lithosphere
ruptures!
25. Outline Normal faulting Transtensional faulting Variations
across the entire lithosphere The variety of rifted margins
26. How does the crust respond to transtension: oblique, normal
and strike-slip faults Lets start by reviewing typical strike-slip
features
27. Here are a few figures of a strike-slip fault typically
found in an intro textbook Great images to introduce fault terms!!
http://geomaps.wr.usgs.gov/parks/deform/strikeslip.gif
Right-lateral strike-slip fault Left-lateral strike-slip fault
Oblique-slip fault http://geomaps.wr.usgs.go
v/parks/deform/7faults.ht ml
28. Strike-slip faults can produce a range of structures! But
its only a start!
29. Wilcox et. al. (1973) predictive model
30. Bends and step-overs of strike-slips faults create a
variety of features
31. Pull-apart basin
32. Transpression and Transtension: Variations on the pure
strike-slip features
33. Outline Normal faulting Transtensional faulting Variations
across the entire lithosphere The variety of rifted margins
34. Continental Rifts: display a variety of geometries and
features Narrow versus wide Symmetric versus asymmetric Core
complexes Some rifts have them, some dont Varying styles and
processes For more details, see Whitney, D.L., Teyssier, C., Rey,
P.F., Buck, W.R., 2013, Continental and oceanic core complexe:
Geological Society of America Bulletin, 26 p.,
doi:10.1130/B30754.1. and the references therein.
35. Huismans, R.S. and Beaumont, C., 2007, Roles of
lithospheric strain softening and heterogeneity in determining the
geometry of rifts and continental margins, in KARNER, G. D.,
MANATSCHAL, G. & PINHEIRO, L. M. (eds), Imaging, Mapping and
Modelling Continental Lithosphere Extension and Breakup. Geological
Society, London, Special Publications, 282, pp. 111138.
36. Core Complexes Different styles of deformation Image from:
Whitney, D.L., Teyssier, C., Rey, P.F., Buck, W.R., 2013,
Continental and oceanic core complexe: Geological Society of
America Bulletin, 26 p., doi:10.1130/B3075 4.1.
37. Outline Normal faulting Transtensional faulting Variations
across the entire lithosphere The variety of rifted margins
38. Rifted Margins: not all the same!! Old end members:
Volcanic (magma- rich) versus amagmatic (magma-poor) New kid on the
block: heavily- sedimented
39. Newer studies show different types of rifted margins, each
with a unique Oceanic-Continental Transition (OCT) O.C.T. Typical
intro text book figure of a rifted margin But wait! Theres more!!
TASA Graphic Arts http://geology.isu.edu/Alamo/r
ocks/deposition_ocean.php
40. Previously recognized end members: Magma-rich and Magma
poor
41. 1. Non-Volcanic Margins (Hyper- Extended): Thin,
magma-starved crust Mantle exhumed to near surfaceBoillot &
Froitzheim (2001) O.C.T. 2. Volcanic Rifted Margins: Thick mafic
crust constructed by robust syn-rift magmatism. Geoffroy (2005)
C.R. Geoscience O.C.T. Schematic diagrams of these end Members
42. MARGINS work plus work in other places has led to the
recognition of heavily-sedimented margins that produce a new type
of continental crust
43. 3. Non-Oceanic New Crust: Geometry similar to that of
volcanic margins, but crust is not volcanic (at some margins).
Intermediate seismic velocities, crust is syn- rift sediments, with
mafic magmatic intrusions. Where does all the sediment come from?
Need large non-local input (= big river). Nova Scotia margin (Funck
et al., 2004) O.C.T. New end memberhybrid crust
44. Iberia- Newfoundland: Magma-Poor, hyper-extended NW
Europe-East Greenland, NW Australia: Magma- Dominated N. Gulf of
California: Non-Oceanic New Crust Sawyer et al., 2007, Scientific
Drilling, No.5 Examples of the three end members
45. References (websites used are noted on individual slides)
Boillot, G. and Froitzheim, N., 2001, Non-volcanic rifted margins,
continental break-up and the onset of sea-floor spreading: some
outstanding questions, Geological Society, London, Special
Publications 2001, v. 187, p. 9-30. Brune, Sascha , Anton A. Popov,
and Stephan V. Sobolev, 2012, Modeling suggests that oblique
extension facilitates riftingand continental break-up, JOURNAL OF
GEOPHYSICAL RESEARCH, v. 117, B08402, doi:10.1029/2011JB008860,
2012 Dorsey, Rebecca J., and Umhoefer, Paul J., 2000, Tectonic and
eustatic controls on sequence stratigraphy of the Pliocene Loreto
basin, Baja California Sur, Mexico: Geological Society of America
Bulletin, v. 112, no. 2, p. 177-199 Funck, T., Jackson, H.R.,
Louden, K.E., Dehler, S.A., and Wu, Y., 2004, Crustal structure of
the northern Nova Scotia rifted continental margin (eastern Canada:
Journal of Geophysical Research, v. 109, B09102,
doi:10.1029/2004JB003008 Geoffroy, Laurent, 2005, Volcanic passive
margins: C. R. Geoscience 337 (16): 13951408 Huismans, R.S. and
Beaumont, C., 2007, Roles of lithospheric strain softening and
heterogeneity in determining the geometry of rifts and continental
margins, in KARNER, G. D., MANATSCHAL, G. & PINHEIRO, L. M.
(eds), Imaging, Mapping and Modelling Continental Lithosphere
Extension and Breakup. Geological Society, London, Special
Publications, 282, pp. 111138. Sanderson, D.J., and Marchini,
W.R.D., 1894, Transpression: Journal of Structural Geology, v. 6,
n. 5, p. 449-458. Sawyer, D.S., Coffin, M.F., Reston, T.J., Stock,
J.M., and Hopper, J.R., 2007, COBBOOM: The Continental Breakup and
Birth of Oceans Mission. Scientific Drilling, No. 5, September, p.
13-25. Whitney, D.L., Teyssier, C., Rey, P.F., Buck, W.R., 2013,
Continental and oceanic core complexes: Geological Society of
America Bulletin, 26 p., doi:10.1130/B30754.1. Wilcox, R.E.,
Harding, T.P., Seely, D.R., 1973. Basic wrench tectonics:
Association of Petroleum Geologists Bulletin, v. 57, no. 1, p.
74-96.