1 / 57

7 field seasons and 250 cosmogenic exposure ages: Laurentide Ice Sheet history and dynamics

The Clyde River project, on northeastern Baffin Island. 7 field seasons and 250 cosmogenic exposure ages: Laurentide Ice Sheet history and dynamics. 4 Questions to consider:. Why can’t blockfields be used as evidence for LGM refugia?

yvon
Download Presentation

7 field seasons and 250 cosmogenic exposure ages: Laurentide Ice Sheet history and dynamics

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The Clyde River project, on northeastern Baffin Island 7 field seasons and 250 cosmogenic exposure ages: Laurentide Ice Sheet history and dynamics

  2. 4 Questions to consider: Why can’t blockfields be used as evidence for LGM refugia? Recall that we’re presently in the “Goldilocks Paradigm.” How is the Goldilocks model incorrect? 3. What are weathering zones really telling us? What is potentially wrong with a story that is based on only a few cosmogenic exposure ages?

  3. N 10 km Clyde Foreland

  4. Differentially-weathered fiord landscapes

  5. Extent of “fresh” zone indicates extent of LGM ice Future work . . .

  6. Weathered uplands are covered, but not eroded, during the LGM

  7. Boulder: 17.5±1.9 ka Tor: ≥67.5±7.2 ka

  8. Tor: ≥64.1±2.2 (Be) ≥61.4 ± 2.7 (Al) Cobble: 11.6±0.9 (Be) 14.8±1.7 (Al) Boulder: 10.2±1.1

  9. Future work . . .

  10. Future work . . . Updated from Briner et al., 2003, QSR

  11. Locations of “LGM” erratics ? ? ? ? 520-580 m 620-690 m 410-610 m 380-430 m

  12. Shear zone Shear zone warm-based Cold- based Cold- based Ice Stream

  13. Shear zone Shear zone warm-based Cold- based Cold- based Ice Stream

  14. N 10 km North South

  15. North South

  16. S N glacially scoured

  17. S N no evidence of glacial erosion glacially scoured

  18. S N no evidence of glacial erosion some evidence of glacial modification glacially scoured

  19. Cosmogenic Exposure ages: Bedrock and Erratics 11.4+0.5 ka 11.6+0.3 ka 80.0+3.4 ka 9.5+0.3 ka 23.7+1.0 ka 28.3+0.7 ka 32.5+1.1 ka 22.0+0.7 ka 9.5+0.7 ka 23.3+0.7 ka 9.4+0.4 ka

  20. highest areas: no observable glacial modification erosive ice (<2 m of erosion) some glacial modification of upland bedrock erosive ice (>2 m of erosion) 11.4+0.5 ka 11.6+0.3 ka 80.0+3.4 ka 9.5+0.3 ka 23.7+1.0 ka 28.3+0.7 ka 32.5+1.1 ka 22.0+0.7 ka 9.5+0.7 ka 23.3+0.7 ka 9.4+0.4 ka Clarke et al., in prep.

  21. Future work . . .

  22. Future work . . .

  23. Future work . . .

  24. Future work . . .

  25. 1. LGM ice at shelf break Uplands covered by cold-based ice WZs mark of basal thermal regimes 4. Ice streams occupied fiords ? ? ? What we’ve learned: weathered fresh

  26. N 10 km

  27. 55.8±1.3 30.1±0.7 50.0±1.2 5.5±0.3 4.0±0.3 5.1±0.3 3.9±0.3

  28. 55.8±1.3 30.1±0.7 50.0±1.2 5.5±0.3 Al/Be burial age: ~430 ka 4.0±0.3 5.1±0.3 3.9±0.3

  29. Byrd Glacier, Antarctica LANDSAT-1 image

  30. Lambert Glacier: an Antarctic ICE STREAM JPL - RADARSAT AMP

  31. ice-sheet scale patterns in basal thermal regime…

  32. JPL - RADARSAT AMP

  33. 4 Questions to consider: Why can’t blockfields be used as evidence for LGM refugia? Recall that we’re presently in the “Goldilocks Paradigm.” How is the Goldilocks model incorrect? 3. What are weathering zones really telling us? What is potentially wrong with a story that is based on only a few cosmogenic exposure ages?

  34. 2D numerical glacier model run in MatLab Bob Anderson and Mark Kessler (University of Colorado) Published: Kessler et al. 2006

More Related