An extensive middle to late Pleistocene tephrochronologic record from east-central Alaska

Abstract

Chester Bluff (CB), in Yukon Charley Rivers National Preserve (YCNP), Alaska, contains an extensive middle to late Pleistocene tephra record within thick loess deposited on a terrace. The regionally prominent Old Crow (OC) tephra (140±10 ka), GI tephra (560±80 ka) of Fairbanks, the Preido Hill (PrH) tephra of the Klondike, and VT tephra (77.8±4.1 ka) of both the Klondike and Fairbanks were found at CB. The presence of these tephra beds will aid in correlating disparate paleoenvironmental records across eastern Beringia. There are 15 new tephra beds; 11 from the Wrangell volcanic field (WVF) and/or Hayes volcano, one from the Aleutian-Arc Alaska Peninsula (AAAP) and three unclassified beds. CB is normally magnetized, indicating the entire sequence is of Bruhnes age (<780 ka). Also present are at least two interglacials, one late–Middle Pleistocene, the other early–Middle Pleistocene. At least five more organic horizons representing interstadials or interglacials are present. Collectively, sediments at CB span most of the middle to late Pleistocene (i.e. ∼780 to <77.8±4.1 ka). The bluffs represent the most extensive middle-to-late Pleistocene sedimentary record yet established for Yukon or Alaska.