Presentation on theme: "Cosmogenic exposure dating -principles and applications Quaternary glacial history of Beringia -overview with case studies Late Quaternary glacial history."— Presentation transcript:
Cosmogenic exposure dating -principles and applications Quaternary glacial history of Beringia -overview with case studies Late Quaternary glacial history of the Eastern Canadian Arctic -the Clyde River Project
My biased reading suggestions: (be familiar with lots more, but be sure to read these) Quaternary glacial history of Beringia Late Quaternary glacial history of the Eastern Canadian Arctic 1. Brigham-Grette, 2001, QSR v. 20, p. 15-24. 2. Briner and Kaufman, submitted, Journal of Quaternary Science. Read this for discussion: 3. letter to the editor debate on Beringian Ice Sheet - Brigham-Grette and Gualtieri et al., 2004; Grosswald and Hughs, 2004, QR, v. 62. 1. England, 1998, JQS, v. 13, p. 275-280. 2. Miller et al., 2002, QSR, v. 21, p. 33-48. vs. 3. Briner et al., 2006, GSAB, v. 118, p. 406-420.
3 Questions to consider: 1.How would you explain cosmogenic exposure dating to your Dad (elementary school teacher) and Mom (engineer)? 2. What are three ways that cosmogenic radionuclides are used? 3. How would you critique a dataset of cosmogenic exposure ages?
Erratics from intermediate and high elevation bedrock (n=27) Low-elevation bedrock (n=10) Intermediate-elevation bedrock (n=11) High-elevation bedrock (n=12) Relative Probability Briner et al., 2006, GSAB
Cold- based Cold- based warm-based Shear zone Shear zone Ice Stream
Application #3: burial studies 11.4±0.5 ka 102.3±3.4 ka
Tor exposed at surface becomes saturated with 10 Be and 26 Al 10 Be and 26 Al accumulate in upper ~2 m of rock
Tor shielded by cold-based ice Once shielded: 10 Be and 26 Al radioactively decay differentially
With constant exposure ratio of isotope production eventually decreases
Upon burial or shielding ratio decreases below the constant exposure line
84.4±2.0 ka High elevation Al/Be burial age: ~420 ka
High elevation 102.3±3.4 ka Al/Be burial age: ~475 ka
High elevation 11.4±0.5 ka 102.3±3.4 ka Al/Be burial age: ~475 ka
Overview: 1. Exposure dating 2. Glacial erosion 3. Burial history