GEOLOGY 489 (Geotectonics) Spring, 2004 University of Illinois at Urbana-Champaign

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1 GEOLOGY 489 (Geotectonics) Spring, 2004 University of Illinois at Urbana-Champaign Instructors Steve Marshak NHB 302/253A Michael Stewart NHB Text (optional) Moores, E.M., and Twiss, R.J., 1995, Tectonics, W. H. Freeman and Co., New York. Books on Reserve (in the Geology Library) Brown, G.C. et al., eds., 1992, Understanding the Earth: A New Synthesis: Cambridge. Brown, G.C., and Mussett, A.E., 1993, The Inaccessible Earth, 2nd: Chapman and Hall. Condie, K.C., 1989, Plate Tectonics & Crustal Evolution (3rd ed.): Pergamon Press. Cox, A., and Hart, R.B., 1986, Plate Tectonics: How it works: Blackwell Scientific. Kearey, P., and Vine, F.J., 1996, Global Tectonics (2nd ed.): Blackwell Scientific Publ. Lillie, R.J., 1999, Whole Earth Geophysics: Prentice-Hall. Marshak, S., 2001, Earth: Portrait of a Planet: W.W. Norton & Co. Mussett, A.E., and Khan, M.A., 2000, Looking into the Earth: An Introduction to Geologic Geophysics: Cambridge Univ. Press. Piper, J.D.A., 1987, Palaeomagnetism and the Continental Crust: Open Univ. Press. Stüwe, K., 2002, Introduction to the Geodynamics of the Lithosphere: Quantitative Description of Geological Problems: Springer-Verlag van der Pluijm, B., and Marshak, S., 2004, Earth Structure: Introduction to Structural Geology and Tectonics (2nd ed.): W.W. Norton & Co. Windley, B.F., 1995, The Evolving Continents (3rd ed.): John Wiley & Sons. Class Format The class will be a mix of traditional lecture (with one of the instructors lecturing on a given topic), student presentations, and class discussion. The instructors will provide you with background information and attempt to bring everyone to the same level of understanding from which we can launch into the remainder of the class. Student Presentations Each student must choose at least three topics form the list below and prepare a presentation for the class. To the extent possible, base your presentation on recent scientific literature, focusing on advances in or challenges to accepted/favored hypotheses. See one of the instructors ahead of time with a list of references so we can insure you are following a fruitful path. One week prior to your scheduled presentation, you should provide the class with a reference to one journal article that will serve as the basis of discussion during/after your presentation. You should either put a Xerox of the article on reserve in the Geology Library, or put a PDF of the article on the Library's web page. On the day of your presentation, provide the class with an outline, figures from your presentation, and a list of references (in JGR format) from your research into the topic. Participation This class will only succeed if you participate by reading the papers provided and being prepared to discuss the topics during class. Thus, please plan to prepare for classes in advance, and come to class armed with questions. Final Exam The final exam will be written and will be comprehensive. Both faculty and student presentations will be fair game. The format of the exam will be clarified toward the end of the semester. Course Grade Your grade will be based on: Participation (30%); Oral presentations (35%); Final Exam (35%). 1

2 GEOLOGY 489 (Geotectonics) List of Topics Topic A: History of geotectonic concepts Early concepts of geotectonics. Contraction theory. Geosyncline theory. Expanding Earth idea. Topic B: Birth of plate tectonics theory Wegener and continental drift. Hess/Dietz and seafloor spreading. The proof of seafloor spreading. A scientific "revolution" Topic C: Paleomagnetism Magnetic fields, susceptibility; rock magnetism Polar-wander paths Seafloor magnetic anomalies. Magnetostratigraphy. Topic for Student Presentation: o Recent model of the geodynamo, and the cause of magnetic reversals. Topic D: Earth s internal structure and composition Seismically defined whole-earth layers. Earth s composition. Nature of lithosphere, asthenosphere, and "tectosphere". Mantle convection. Mantle plumes. Topic for Student Presentation: o Mantle convection models. o Geophysical evidence for mantle plumes. o Origin of the Columbia River basalts. o Evolution of the Yellowstone "hot spot." Topic E: Plate kinematics Relative plate velocity Absolute plate velocity Triple Junctions Topic for Student Presentation o Variation in spreading velocity on the Mid-Atlantic Ridge. o Eurasian-North American plate boundary north of Iceland. o Change in Pacific plate motion: evidence from Hawaiian-Emperor and Louisville Seamount chains, arguments against change(?). o Triple junction configuration at the Galapagos, Easter, or Juan Fernandez Microplate. o Subduction of spreading centers and the evolution of the triple junctions. (choose a specific example to work with). 2

3 Topic F: Plate Driving Mechanisms Mantle convection (basal drag?) Ridge-push force. Slab-pull force. Trench suction. Supercontinent cycle. o Rollback of Scotia Arc subduction zone o Mantle "return flow" at convergent boundaries. o Evaluation of evidence for and against one of the mechanisms. o Balance of forces models. o Latest ideas concerning the validity of the supercontinent cycle. Topic G: Oceanic Lithosphere & Mid-Ocean Ridge Processes Adiabatic Decompressive Melting. Morphology of a MOR: fast- vs. slow-spreading. Structure and composition of normal oceanic lithosphere: ophiolites, seismic data. Tectonic windows into slow-, intermediate- and fast-spread oceanic crust. Crustal construction at fast-, intermediate- and slow-spreading ridges. Evaluation MOR magmatic models. o Magmatism and spreading on ultra-slow spreading ridges. o Results of the MELTs experiment. o Hydrothermal vents, vent communities on MORs. o Melt migration through the oceanic lithosphere, construction of the lower crust, upper mantle and nature of the Moho. o Mantle flow beneath the oceanic lithosphere o Evidence for or against melt lenses beneath slow spreading ridges. o Geology of the Oman Ophiolite. o Steady-state magma chambers beneath MOR. Topic H: Convergent-margin tectonics The subduction system: trench, accretionary prism, volcanic arc. Styles of back-arc tectonics. Seismicity at convergent margins. Flux melting. Curvature of subduction zones. o Arguments for and against slab melting. o Along- and across-arc variations in magma composition. o Initiation of subduction. o Tomographic evidence for and against deep subduction below 600 km discontinuity. o Application of critical-taper theory to accretionary prisms. o The tectonic evolution of the Japan Sea. o The origin of ultra high-pressure metamorphism in Subduction Zones. o Explanations for the Laramide orogeny (USA), and the Pampean Ranges (Argentina). 3

4 Topic I: Continental crust and continental-interior tectonics Character and divisions of the continental crust. Origin of cratons. Intracratonic basins and structures. Continental interior fault-and-fold zones. o The lower crust: nature and composition. o Nature of the Moho beneath continental crust. o New Madrid seismic zone. o Erosion rates in continental interiors (past and present). o What causes "cratonization" in continents? Topic J: Strike-slip fault systems Tectonic setting of strike-slip systems. Transform vs. transcurrent faults. Transpression and transtension. o Lateral escape of Turkey: North & East Anatolian fault systems. o Predicting earthquakes on the San Andreas fault system. o The Alpine fault, New Zealand o Tectonic evolution of the Los Angeles basin, California. o Tectonic evolution of the Dead Sea. Topic K: Crustal Rifting Stages and geometries of rifting Causes and evidence of Rifting Rock assemblages in rifts o Metamorphic core complexes in Basin and Range. o Evolution of the East African rift. o Precambrian rifting in North America. o The GLIMPSE seismic-reflection lines of the Mid-Continent rift. o Tectonic history of the Basin and Range Province. o Structural architecture of the Basin and Range province. o Mesozoic rifts of eastern United States. Topic L: Continental Collision Basic stages during collisions. Fold-thrust belts Other consequences of collision (plateaus; slip lines; collapse) o Obduction of ophiolites. o Orogenic (extensional) collapse in Tibet. o Lithospheric delamination. o Accretion of exotic terranes. o Tectonic context of the south Tibetan detachment, and its relation to the Main Central Thrust in the Himalayas. o Mantled gneiss domes in collisional orogens. o Ultra high-pressure phases in collisional orogens. 4

5 Topic M: Precambrian Tectonics Archean high-grade gneiss belts (origin of the TTG assemblage). Archean granite-greenstone belts. Proterozoic orogenies. Assembly of Gondwana. o Evolution of Rodinia and Panotia (Neoproterozoic supercontinents and SWEAT) o Polar-wander paths for Precambrian continents. o The Dharmara orogen (ensialic orogens). o Stromatolite evolution. o The nature of Pan African orogenies, in Africa. o Architecture of the Superior Province. o The Penokean orogeny. Topic N: A Brief Synopsis of Phanerozoic tectonics in the conterminous USA Tectonics of the Appalachian orogen. Tectonics of the western Cordillera. Topics for Student Presentations o Tectonic evolution of the Colorado Plateau o The Antler orogeny. o Tectonic evolution of the Ouachitas. Topic O: Examples of Orogens Elsewhere in the World Topics for Student Presentations o Brief tectonic evolution of the Alps (Switzerland and Italy). o The tectonic evolution of the Altaids (central Asia) and the "Turkic" style of deformation. o Brief tectonic evolution of a portion of the Andes. 5