Integrated Solid Earth Sciences

Summer School on Tectonic Exhumation

Dates: 7/27 - 8/04/06

Summer School Schedule, updated 6.27.07

Some further adjustments to schedule may be necessary…

Friday, July 27:       Participants arrive at Colorado College.   Airport pickups and check in for participants.

Faculty have a meeting at 3:30 p.m.  to acquaint with facilities and make final preparations.

Outdoor meal and social hour on patio by El Diente Apartments, in view of Pikes Peak:  Mexican fajitas buffet served by La Casita.

Saturday, July 28:  Day 1 of Summer School

Art Snoke (lead)

Morning session -- What is exhumation? -- historical roots, world-wide examples (tectonic, erosional, etc.), and a field-based approach including activities related to the interpretation of geologic maps and cross sections (e.g., identifying low-angle normal faults).

Peter Koons

Discussion of driving forces and boundary conditions; conception of mathematical modeling approaches

Afternoon session –

Part I: Student introductions.

Part II: Case study of the exhumation of an high-grade igneous and metamorphic terrane: Ruby-East Humboldt metamorphic core complex, NE Nevada, with associated activities based on geologic maps, cross sections, and especially petrographic thin sections and related hand samples.

Evening: Social get-together and meal at Morreale coach house/patio.

Sunday, July 29:  All day field trip

Eric Leonard (CC), Chris Siddoway (CC), and Shari Kelley (NMGS)

Field trip to the Wet Mountains, Arkansas River Canyon, and adjacent Wet Mtns valley, focusing on the multi phase exhumation of this Precambrian-cored mountain range.

--The trip offers a look at a new, unfamiliar geological terrain, in which students will seek observational cues and consider information from previous research that helps get at the tectonic exhumation story (±polyphase).  Together the group will assess prospects for interesting research problems.  In addition, there will be a field introduction to AFT thermochronology and use of the AFT partial annealing zone as a structural marker in basement rocks.

Dinner at Old Mission café in Canon City, en route back to Colorado Springs.

Monday, July 30:

Morning: Shari Kelley (lead)  AFT Thermochronology

1. The basics of going from a rock to a fission-track age.

2. The basics of (U-Th)/He thermochronology.

3. The basics of heat flow and how isotherms are affected by topography and variations in lithology.

Group discussion of:   a) Concept of Horizontal isotherms / when valid? exceptions to be aware of?                      Case studies:  new results from St Elias ranges, AK; examples from Himalayas and  Southern Alps [NZ].

     b)  how advection perturbs the geochron ; insights for  anomalous thermochron dates; c) heat flow equation.

Afternoon:  Lab activity: counting and measuring fission tracks. Selection of apatite grains for (U-Th)/He  analysis; measurement procedures; introduction to Durango apatite standard.

Introduction to software: computer programs, AFTsolve and HeFTy. Students use real data to learn about extracting cooling histories from AFT age and length data, and (U-Th)/He  data.

Beer and Posters 

Evening:  Open time for further  student work using Thermochron applications or AFT thin sections

Tuesday, July 31: Barbara Carrapa (lead)

Morning: -- Sedimentation / detrital studies  lecture. 

Recommended reading:  Garzanti et al., 2007; Najman et al., 1997; Garver et al., 1999; Bernet et al., 2001; Carrapa et al., 2003

Afternoon: Sedimentation / detrital studies  activities (e.g. pebble counting, sst. petrography and eventually detrital thermochronology using both Ar/Ar and AFT).

       Afternoon II: Student posters and beer

Evening: Summer School “banquet”  (intentionally situated at the midway point)

Wednesday, August 1:

Field trip to Denver Basin, led by  Shari Kelley and Bob Raynolds

Thursday, August 2: Donna Whitney (lead) / contributions from POK on UHP settings

Morning:  Presentation and discussion of how metamorphic geology (P-T-t paths, metamorphic textures, structural petrology) can provide information about exhumation processes; case studies from continental orogens (northern North American Cordillera; eastern Mediterranean).

Reading:  Teyssier et al., 2005,  Flow of partially molten crust and origin of detachments during collapse of the Cordilleran orogen. In: Bruhn, D., and Burlini, L. (eds.), High-Strain Zones: Structure and Physical Properties. Geol Soc London Sp Publ 245, 39-64.

Afternoon I: Presentation and discussion of the metamorphic geology of exhumed high-pressure and ultrahigh-pressure rocks; case study (with maps, thin sections, other images) from high-pressure metamorphic complex in Turkey.

Reading: Gerya  et al. 2002, Exhumation of high-pressure metamorphic rocks in a subduction channel: A numerical simulation. Tectonics, 21 (6), Art. No. 1056.

Afternoon II:  Analog modeling (POK) / preliminary to finite element modeling next day.  Intro, Lab and results: ~ 2 hours.

Critical Wedgery: 1-sided and 2-sided orogens; 1 Sandbox per  ~3-5 students, for examination of particle paths within an equilibrium framework of wedge dynamics; making predictions and testing hypotheses.

Basic theory from 2-D introduction in Enlow and Koons, 1998; sp. simplified form of  eq. 15.

Critical taper equation and equilibrium of forces: Davis et al., 1983, and Dahlen, 1990

Discuss:  Predicted distribution of high-grade terrains and the geo-thermochron record (to continue in to next day).

Readings:

Enlow, R. L. and P.O. Koons. 1998 Critical wedges in three dimensions; analytical expressions from Mohr-Coulomb constrained perturbation analysis, Journal  Geophysical Research,  103, 4897-4914.

Kundu P. K. & Cohen, I. M. , 2002, Fluid Mechanics, Academic. 730 pp. ISBN 0-12-178251-4

Koons, P.O., and E. Kirby, 2007; Topography, denudation, and deformation: The role of surface processes on fault evolution; in: Tectonic Faults; Agents of change on a dynamic Earth.  Ed. Handy, M. R., Hirth, G., N., Hovius, MIT Press p 205-230.

For Dahlen1990, and Davis et al 1983, see http://acad.coloradocollege.edu/dept/gy/ises/ReferencesCourseNotes2007.php

Evening:  final meal, probably will arrange outdoors on west patio

Friday, August 3:

Morning:  Peter Koons (lead): Isostasy, viscosity, and exhumation: Analog- Numerical models of subduction

                             Analog viscous models to formulate physical model for Subduction zones: UHT and UHP.

Materials:  fish  tank, silly putty, and corn syrup. Can set up tripod-and-camera for timed photos to be made into QuickTime video

Afternoon:  Geophysics-geodynamics-modelling  activities  (numerical and analog)

Introduction to dynamics of viscous fluids via examination of Navier Stokes and characterization of the earth in terms of geologically meaningful dimensionless numbers; Grashof , Peclet etc.,

Finite element (FEM) solution of Navier Stokes as an approximation of analog and natural exhumation; software description at http://www.comsol.com/products/es/

Mechanical-Erosional coupling: Move toward rheological influence on exhumation and exhumation on integrated lithospheric strength looking at the examples of Tectonic Aneurysm and Channel flow

                  Examples, including Himalayan, St Elias?, and reference to local, Colorado examples brought in other participants.

Where to now?    !!wide ranging discussion and culmination of the Summer School !!

Current and future directions of research in exhumation –

-- Paleo-climate information

-- Silicate Earth GCM

Saturday, August 4: Departures