1 / 43

Alaska-wide records of LGM advances

Alaska-wide records of LGM advances. 3 Questions to consider:. How can you recognize what valleys had LGM glaciers? What are the strengths and limitations of using cosmogenic exposure dating on moraines in Alaska? What can one do with a state-wide compilation of dated moraine records?.

rhoda
Download Presentation

Alaska-wide records of LGM advances

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. Alaska-wide records of LGM advances

  2. 3 Questions to consider: How can you recognize what valleys had LGM glaciers? What are the strengths and limitations of using cosmogenic exposure dating on moraines in Alaska? What can one do with a state-wide compilation of dated moraine records?

  3. The Alaska Range AKR Kaufman and Manley, 2004

  4. 21.9±0.9 47.9±1.7 18.2±0.7 55.4±1.4 19.2±0.8 44.2±1.8 51.4±1.6 19.3±1.0

  5. 10 40 20 60 new data from Dortch, Owen

  6. Notable Alaska Range chronologies North-Central Alaska Range • 10Be ages on penultimate moraines in two areas point to MIS 4/3 age. 20 • 10Be ages on LLGM moraines in two areas are ~20 ka. • 10Be ages on late glacial moraine possibly YD in age. 30 Modified from Hamilton (1982)

  7. The Brooks Range BR Kaufman and Manley, 2004

  8. Age (ka) ? Hamilton, 1994 Hamilton, 2003

  9. Notable Brooks Range chronologies Central Brooks Range 20 30 Modified from Hamilton (1982) • Two moraines from penultimate advance younger than Old Crow Tephra (~140 ka) • 10Be ages in NE BR agree with 14C chron. • Hamilton (2003) reports 14C ages that constrain late-glacial advance to ~15 to 13.1 ka

  10. Spatial Patterns ELAs and moisture source Reconstructed ELAs from across the state consistently show moisture source in the west/southwest - North Pacific and Bering Sea

  11. Brooks Range ELAs Balascio et al., 2005

  12. Spatial Patterns ELAs and moisture source Reconstructed ELAs from across the state consistently show moisture source in the west/southwest - North Pacific and Bering Sea Spatial pattern of timing of the MIS 2 advance Enough information is at hand to conclusively show that the timing of MIS 2 max occurs at different ages in different regions across the state

  13. 26 22 21 24 20 18 21 retreat from MIS 2 terminal moraine (ka) Kaufman and Manley, 2004

  14. Summary

  15. Main Points MIS 4 1. The maximum Late Pleistocene advance in AK post-dates the LIG and pre-dates the global LGM, and seems to be 60-50 ka where dated. 2. MIS 2 pulse appears to be bimodal, ending either ~26 (in the north) or ~20 ka (elsewhere). 3. There is limited chronological control on late glacial moraines; could be YD in two places; late glacial moraines exist across AK.

  16. Main Points • The location of • the Aleutian Low 4. Several forcing factors for Alaskan climate: - Emergence of the Bering land bridge • N Pacific SST

More Related