The Palisades is a key reference site for the middle Pleistocene of eastern Beringia: New evidence from paleomagnetics and regional tephrostratigraphy

• Published in: Quaternary Science Reviews
• Main Authors: Jensen, Britta J.L., Reyes, Alberto V., Froese, Duane G., Stone, David B.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2013
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; SDG 14 - Life Below Water; Palisades; The Bluff; The Palisades; Yukon; Old Crow; Yukon river; Alaska; Beringia
• Online Access: https://pure.qub.ac.uk/en/publications/the-palisades-is-a-key-reference-site-for-the-middle-pleistocene-of-eastern-beringia-new-evidence-from-paleomagnetics-and-regional-tephrostratigraphy(d4ad9e72-9b19-4688-a97e-cd6ceb6c6ddf).html; https://doi.org/10.1016/j.quascirev.2012.11.035; http://www.scopus.com/inward/record.url?partnerID=yv4JPVwI&eid=2-s2.0-84873271546&md5=af554d514d114c9941a313a1c7d45ce8

The Palisades, in central Alaska, is one of the most prominent exposures of Quaternary sediments on the Yukon River. Perennially-frozen silt and sand at the Palisades are presently thought to preserve paleoenvironmental records from the Holocene to ~Marine Isotope Stage (MIS) 8 and, beneath a major unconformity, the earliest Pleistocene (~2 Ma). We present new paleomagnetic and tephrochronologic constraints that substantially revise the age of the sediments at the Palisades. We describe 15 new tephra beds, including five beds below the prominent PAL tephra that correlate to known tephra with independent age control from other sites in eastern Beringia. These five known tephra include Chester Bluff tephra, which is present in east-central Alaska and the Yukon, and the newly named Alyeska Pipeline and Taylor Highway tephra from central Alaska; all are constrained to the middle Pleistocene. Paleomagnetic transects from the base of the bluff to the MIS 5e forest bed yield normal polarity, with the exception of a brief reversal event between Old Crow tephra (124 ± 10 ka) and the MIS 5e forest bed that is likely the first documentation of the Blake paleomagnetic event in Alaskan loess. The detailed tephrostratigraphy and paleomagnetic data collectively suggest that most of the sedimentary record at the Palisades is middle Pleistocene in age. The Palisades thus preserves a rare record of late to middle Pleistocene paleoenvironments with multiple regionally distributed tephra beds.