Chronostratigraphy of glaciations and permafrost episodes in the Cordillera of western North America

Abstract

Glaciations in the Cordillera of western North America began during the Late Miocene in the St Elias Range and coastal ranges near Anchorage, Alaska. Radiometric dating of the tephra and lava flows intercalated in the succession of older tills, loesses and outwash deposits permits the reconstruction of the probable early glacial sequence along the Cordillera. No one site shows the complete sequence, but the available data suggest synchroneity of the major glacial events throughout the region.The first evidence for cold conditions at low elevations at midlatitudes is from 3.5 Ma BP. By 2.8 Ma, alpine glaciations may have occurred in the Sierra Nevada and ice wedges had formed in bedrock near Fairbanks, Alaska. Three more major glaciations complete with contemporary periglacial and permafrost landforms had occurred by 1.65 Ma, while at least six more major cold events can be recognized during the Quaternary period. Once again, expansion of permafrost conditions occurred during each event and forms an integral part of the evidence for climatic change.

Quartz weathering in freeze–thaw cycles: experiment and application to the el'gygytgyn crater lake record for tracing siberian permafrost history

“…Permafrost is usually associated with and documented in proximity to glaciated (or formerly glaciated) areas in the periglacial realm (e.g. Harris 1994; Murton 2005). Yet, little is known about the age and continuity of permafrost conditions, since permafrost is a thermal and not a stratigraphical phenomenon.…”

Evidence for early glaciation of southeastern Beringia

“…For more than a century of glaciological research, the investigated region has been assumed to be never glaciated (Table 1), in periglacial proximity to but nevertheless beyond the limits of late Miocene (Spurr 1897;Péwé 1975;Eyles and Eyles 1989;Lagoe et al 1993;Harris 1994;Rea and Snoeckx 1995;White et al 1997;Trop and Ridgway 2007;Bill et al 2018) and subsequent Cordilleran ice sheet (CIS) glaciations of late Pliocene and thereafter (Froese et al 2000;Duk-Rodkin et al 2004, 2010Hidy et al 2013Hidy et al , 2018.…”

“…Based on isotopic investigations of lavas, some diamictons north of the Wrangell Mountains were deposited more than 10 Ma (Denton and Armstrong 1969), and glacially striated and faceted clasts in those diamictons have been interpreted as locally derived (Eyles and Eyles 1989). Terrestrial glaciation in the St. Elias, Chugach, and Wrangell mountains was well underway by 5.5 Ma (Péwé 1975;Lagoe et al 1993;Harris 1994;White et al 1997;Gulick et al 2003;Trop and Ridgway 2007).…”

“…Based on permafrost dating, climate conducive to an ice age developed sometime between 2.9 and 2.6 Ma (Froese et al 2000(Froese et al , 2008Duk-Rodkin et al 1996;Berger et al 2008; Barendregt and Duk-Rodkin 2011; Duk-Rodkin and Headley et al 2012;Hidy et al 2013Hidy et al , 2018. At ϳ2.2 Ma, an ice sheet evidently extended as far south as Iowa (Harris 1994), and data of Jackson et al (2012) indicate that Yukon probably also experienced that stadial. Yukon became even colder between 1.77 and 1.50 Ma, and additional stadials and interstadials occurred after 1.33 Ma (Bond and Lipovsky 2010; Duk-Rodkin and Barendregt 2011).…”

Global heat budget, plate tectonics and climatic change

“…Figure 1 shows a comparison of the mean daily ground temperature at 10 cm in the surface of the soil on lithalsa #2, Fox Lake, Yukon Territory, with the mean daily temperature at 50 cm in the shallow waters of the lake, about 3 m away. Lithalsas are palsa-like mounds formed in mineral substrates (Harris 1993). The temperatures during the part of the year when the lake is unfrozen are rather similar, although the lake water takes longer to heat up and to cool down.…”