50,000 years of paleoenvironmental change recorded in meteoric waters and coeval paleoecological and cryostratigraphic indicators from the Klondike goldfields, Yukon, Canada

• Author / Creator

  Mahony, Matthew E

• A 50,000 year record of meteoric water isotopes (δ2H/δ18O) and paleoenvironmental conditions is presented from syngenetic ice-rich permafrost and macrofossils from eight sites in the Klondike area of central Yukon. Four sedimentary units are recognized based on cryostratigraphy, paleoecological indicators, and δ2H/δ18O of associated ground ice. Unit 1 (50,000-36,000 cal yrs BP) contains boreal indicators (large woody macrofossils indicating trees and shrubs) near the base of the unit and is bounded near the top by the appearance of arctic ground squirrel nests. The presence of arctic ground squirrel nests, a reliable indicator of steppe- tundra, coupled with the largely massive organic-rich silts and large syngenetic ice wedges, defines Unit 2 (36,000-27,000 cal yrs BP). Unit 3 (27,000-13,150 cal yrs BP) includes abundant arctic ground squirrel nests, while the silts are generally grey and less organic-rich, and ice wedges through the unit are rare. Unit 4 (13,150 cal yrs BP to present) lacks arctic ground squirrel nests and contains shrubs near the base of the unit and full-boreal indicators in the upper sections. δ2H/δ18O tracks large-scale climate trends with a shift from near-modern values near the base of Unit 1 to more depleted values, reaching a minima at the Last Glacial Maximum (LGM). Isotopic values increase abruptly at 15,000 cal yrs BP, marking a climate amelioration reaching maximum values during the early Holocene, followed by subsequent cooling after 9,000 cal yrs BP. Deuterium (d) excess shows no clear trends except a +9‰ anomaly from 29,000-22,000 cal yrs BP coinciding with the LGM. This period likely represents an enhanced seasonality of precipitation, either from increased winter or reduced summer precipitation. This multi-proxy permafrost record provides new insights on late Pleistocene-Holocene climate and environmental change in eastern Beringia, and highlights the potential to develop similar records in other unglaciated regions.

• Subjects / Keywords

  • Ground ice
  • Paleoenvironments
  • Beringia
  • Permafrost
  • Water isotopes
  • Yukon
  • D-excess

• Graduation date

  Fall 2015

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R34T6FF58

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.