GEOL 4361/5361 • Spring 2013
Advanced Structural Geology

Meeting Time: MWF 9-9:50 AM, SCI 201 "Structure Lab"
Syllabus (pdf) • Structural Geology Subject Review Sheet (pdf)

Course Schedule and Other Information Posted Whimsically!

UPDATED20 March.

20 March (W): Strain in shear zones: Concepts from Ramsay and Huber, 1983. For additional insights into strain and the strain ellipsoid, check out this pdf of Win Means Chapter 15, Strain Ellipsoids, from his wonderful book. This chapter covers some of the content we discussed on Monday.

Get psyched for thin sections this friday!

18 March (M): Introduced Strain via Means Chapter 14 and 15. For FRIDAY, please read the following.

• Williams, 1985, Muliply deformed terranes - problems of correlation. Journal of Structural Geology, v. 7, p. 269-280.

Also of interest:

• Park, 1969, Structural correlation in metamorphic belts, Tectonophysics, v. 7, p. 323-338.
• Tobisch and Paterson, 1988, Analysis and interpretation of composite foliations in areas of progressive deformation, Journal of Structural Geology, v. 10, p. 745-754.

8 March (F): Stress fields homework due. Handed out Chap. 13 and 14 from Means. End of chapter problems due Wednesday after Spring Break. Check Dropbox for additional reading, etc., that was posted this week.

6 March (W): Today we briefly introduce Means's Chapter 12 on stress fields. Compile and ink your maps. Rocks are being cut, billets are being turned into thin sections as you read this...! Yay!

By Friday please,

• do the problems in Means' Chapter 12 and turn in by 5 PM Friday, 8 March.
• download Rick Allemndinger's stereonet software for Mac and/or PC on to your computer (or iPad?). If you want, over spring break you can "play around" with the data sets that you obtained.

4 March (M): No class! Rest!

28 February through 3 March: Southern Manzano Mountains! What a great trip! Thanks for making it very likely the best field trip I have run in my 14 years at TTU [despite my getting the van stuck in the mud]! You all did an outstanding job and your enthusiasm and hard work, as well as your passion for rocks (!), were appreciated immensely! Be sure to get your data spreadsheets uploaded to the DB folder. Also upload any pics worth sharing.

18, 20, 22, 25, and 27 February: Scalars, vectors and the stress tensor!

15 February (F): Where we've been and where we're going... Pore fluid pressure, hydrostatic stress, lithostatic stress... Upcoming ideas... Heat flow, friction, strength of faults! YAY! [note added post-field trip: we may stray from the plan to focus on heat flow and friction so that we can work on the rocks we collected.]

Now, back into some mechanics and some nice readings for next week, if ya haven't already read the Sibson stuff. Most importantly, start with Handy et al. over the weekend. It's cool. Check out the Hubbert '45 paper and skim the section on "state of Texas"... You'll know what I mean. Then, the Hubbert (1951) paper is classic and the foundation of most modern structural geology text books. The Hubbert and Ruby (1959) paper is the classic paper on elevated fluid pressure and influences on low angle faults, and so one should be "in the know". Lastly, the Axen paper gives a geological example. The rest are for your reading pleasure.

Keep in mind: 1) Andersonian mechanics and the theoretically-predicted orientation of the compressive stresses with-respect-to nature; 2) mechanisms that might allow faults to slip at non-Andersonian orientations

• Axen and Sevlerstone, 1994, Stress state and fluid pressure level along the Whipple detachment fault, CA, Geology, v. 22, p. 835.
• Handy et al., 2008, Continental fault structure and rheology from fricationl-to-viscous transition downward.
• Hubbert, 1945, Strength of the Earth, AAPG.
• Hubbert, 1951, Mechanical basis for certain familiar geologic structures, GSA Bulletin, v. 62, p. 355-372.
• Hubbert and Willis, 1957, Mechanics of hydraulic fracturing, Transactions of Society of Petroleum Engineers of AIME, v. 210, p. 153-168, reprinted by AAPG.
• Hubbert and Rubey, 1959, Role of fluid pressure in the mechanics of overthrust faulting. GSA Bulletin, v. 70, p. 115-166.
• Sibson, R., 1977, Fault rocks and fault mechanisms, Jour. geol. Soc. Lond., v. 133, p. 191-213.
• Byerlee, 1978. Friction of Rocks. Pure and Applied Geophysics, v. 116, p. 615-626.
• Sibson, 1985, A note on fault reactivation, JSG, v. 7.
• Sibson, 1994, An assessment of field evidence for "Byerlee" friction, PAGEOPH, v. 142.

13 February (W): Refresher on strain terms and rock fabrics in relation to strain. Here's a ppt file with some of the ductiley deformed rocks with various kinematic indicators.

11 February (M): LANF head scratcher: Have a gander at this ppt file on the Whipple Mountains LANF and MCC (33 Mb file). Then, along with the reading of Davis (1988) and Davis and Lister (1988), do the following:

1. Demonstrate evidence for low-angle slip on the WDF.
2. Demonstrate evidence for age of faulting and slip event(s).
3. Interpret your arguments for the above 2 items in an essay on the structural eovlution of the WDF and MCC.A couple of typed pages should suffice, along with any sketches, restored sections, etc., that you see fit to make your contentions known.

6 February (W): LANF paradoxes, an introduction to the geological evidence for low-angle slip. Collected the Lapworth 'quiz'. Here are some additional papers to consider.

Metamorphic Core Complexes and The Geology of LANF's.

• Davis, G.H., and Hardy, 1981 The Eagle Pass detachment, SE Arizona, GSA Bulletin, v. 92, p. 749-762.
• Davis, G.H., 1983, Shear zone model for MCC's, Geology, v. 11, p. 342.
• Davis, G.A., et al., 1987, Structural evolution of the Whipple and South mountains shear zones, SW US. Geology, v. 14, p. 7-10.
• Davis, G.A., 1988, Rapid upward transport of mid-crustal mylonitic gneisses in the footwall of a Miocene detachment faul, Whipple Mountains, SE CA, Geologische Rundschau, v. 77, p. 191-209.
• Davis, G.A., and Lister, G., 1988, Detachment faulting in continental extension: Perspectives from the SW US Cordillera. GSA Special Paper 218.
• Lister and Davis, 1989, Origin of metamorphic core complexes and detachment faults... Journal of Structural Geology, v. 11, p. 65-84.

Seismicity and LANF's...

• Abers, 1991, Possible seismogenic shallow-dipping normal faults in Papua new Guinea, Geology, v. 19, p. 1205-1208.
• Abers, 2009, Geology, v. 37, p. 767-768 (related to Hreinsdottir paper below)
• Floyd et al.., 2001, Evidence for fault weakness and fluid flow within an active LANF, Nature, v. 411, p. 779-783.
• Hreinsdotter and Bennett, 2009, Active aseismic creep..., Geology, v. 37, p. 683-686.
• Wernicke, 1995, LANF's and seismicity: A Review. JGR, v. 100, p. 20159-20174.

Geologic evidence for low-angle slip

• Davis, G.A. et al., 1993, Kingston detachment fault, Geology.
• Forshee and Yin, 1995, Evolution of monolithological breccia deposits in supradetachment basins, Whipple Mountains, CA, Basin Research, v. 7, p. 181-197.
• Hayman et al., 2003, Quaternary low-angle slip on LANFs, Geology, v. 31, p. 343-346.
• Numelin et al., 2007, Late Pleistocene slip on a low-angle normal fault, Searles Valley, CA, Geosphere, v. 3, p. 163-176.
• Yin and Dunn, 1992, Structural and stratigraphic development of the Whipple-Chem... GSA Bulletin, v. 104, p. 659-674.

Detachment faults do not exist... or, at least didn't slip at low angles...

• Buck, 1988, Flexural rotation of normal faults, Tectonics, v. 7, p. 959-973.
• Christie-Blick et al., 2005, Obesrvations from the Basin and Range..., Geological Society of London, Special Pub. 282, p. 421-441.
• Garces and Gee, 2007, Paleomageetic evidence of large footwall rotations associated with LANFs at the MAR, Geology, v. 35, p. 279-282.

LANF Mechanics - I also added two Sibson papers to the list of papers on friction under 4 February. Ya might check those out, too.

• Anderson, E.M., 1905, The dynamics of faulting, Transactions of the Edinburgh Geological Society, v. 8, p. 387-402.
• Axen and Sevlerstone, 1994, Stress state and fluid pressure level along the Whipple detachment fault, CA, Geology, v. 22, p. 835.
• Axen, G., 1992, Pore pressure, stress incrase and fault weakening in LANF's, JGR, v. 97, p. 8979-8991.
• Axen, G.J., 2004, Mechanics of low-angle normal faults. In: Karner, G., Taylor, B., Driscoll, N. and Kohlstedt, D.L. (eds.), Rheology and Deformation in the Lithosphere at Continental Margins. Columbia University Press, New York, 46-91.
• Wills, S., and Buck, W.R., 1997, Sress-field rotation and rooted detachment faults: A Coulomb failure analysis: JGR, v. 102, p. 20500-20514.
• Wernicke and Axen, 1988, Flexure and LANFS, Geology, v. 16, 848-851.
• Yin, A., 1989, Origin of regional, rooted LANFs: A mechanical model and its tectonic implications. Tectonics, v. 8, p. 469-482.
• Yin, A., 1991, Mechanisms for the formation of domal and basinal detachment faults... JGR, v. 96, p. 14577-14594.
• Yin, A., 1994, Mechanics of wedge-shaped fault blocks 2. An elastic solution for extensional wedges. JGR, v. 99, p. 7045-7055.

Some recent studies

• Behr,W.M., Platt, J.P., 2011. A naturally constrained stress profile through the middle crust in an extensional terrane. Earth and Planetary Science Letters. doi:10.1016/j.epsl.2010.11.044
• Cooper et al., 2010, Footwall dip of a core complex detachment fault: Thermobarometric constrints from the northern Snake Range, Journal of Metmorphic Geology.
• Singleton and Mosher, 2012, Mylonitization in the lower plate of the Bucksin-Rawhide DF... Journal of Structural Geology, v. 39, p. 180-190.

4 February (M): A few paradoxes in faulting, mechanics and rocks. Here's a scan of my notes to make sure we are all on the same page as to the nature of the problem as depicted from a mechanical perspective. For this week, please read Axen 2004, pages 253-255 and 261-265 of Collettini, 2011, and Price, 1988. I have also provided some other interesting papers to consider.

General ideas to consider: Friction.

• Byerlee, 1978. Friction of Rocks. Pure and Applied Geophysics, v. 116, p. 615-626.
• Sibson, 1985, A note on fault reactivation, JSG, v. 7.
• Sibson, 1994, An assessment of field evidence for "Byerlee" friction, PAGEOPH, v. 142.

Extensional Faults

• Axen, 2004, Research focus: Significance of large-displacement, low-angle normal faults. Geology, v. 35, p. 287-288.
• Collettini, C., and Sibson, R.H., 2001, Normal faults normal friction?: Geology, v. 29, p. 927–930
• Collettini, 2011 LANF review, Tectonophysics, v. 510, p. 253-268.

Thrust faults

• Price, 1988, The mechanical paradox of large overthrusts. GSA Bulletin, v. 100, p. 1898-1908.
• Washington, 1990 and Price, 1990, Discussion and Reply. GSA Bulletin, v. 102, p. 529-532.

1 February (F): Fault rock analysis due. Scholz's coneptualization of fault rocks and process. Handed out the "Lapworth" orientation quiz.

Here's an overview of the B-P transition by Scholz. Please read this over the next few days.

• Scholz, C., 1988, The brittle-plastic transition and depth of seismic faulting: Geologische Rundschau, v. 77, p. 319-328.

30 January (W): Fault rocks and kinematics.

• Snoke and Tullis, 1998, An overview of fault rocks, in Fault-related rocks: A photographic atlas.

For background on the history of fault rock nomenclature check out these references.

• Engelder, 1974, Cataclasis and generation of fault gouge, GSA Bulletin, v. 85, p. 1515-1522.
• Sibson, 1977, Fault rocks and fault mechanisms, Journal of the Geological Society of London, v. 133, p. 191-213.
• Wise et al., 1984, Fault-related rocks: Suggestions for terminology, Geology, v. 12, p. 391-394 (as well as the Comments and Replies)

28 January (M): Fault rocks assignment. As you complete the assignment be sure to consider how the complexities of the rocks might hamstring one's ability to do kinematic and dynamic fault slip analysis.

25 January (F): Discussed Marrett and Peackock (1999) reviewed stress/strain terminology and concepts and introduced Riedel shears and fault rupture structures that may be used to evaluate displacement.

• Petit, 1987 Review of small-scale structures that may be used to evaluate displacement along faults.

23 January (W): Kinematics of fault slip and infering dynamics. Handout due next wednesday.

16 January (W): Syllabus, Review Sheet, Pre-test, readings for Friday. Please be ready to discuss the different methodologies and philosophies/idealogies as outlined in Pollard and Peackock/Marrett on Friday.

• Peackock and Marrett, 2000, Strain and Stress: Reply, Journal of Structural Geology, v. 22, p. 1369-1378.
• Pollard, 2000, Strain and Stress: Discussion, JSG, v. 22, p. 1359-1367.
• Marrett and Peackcock, 1999, JSG.
• Fletcher and Pollard, 1999, JSG.
• Tikoff and Wojtal, 1999, JSG.