Cosmogenic Chlorine-36 Chronology for Glacial Deposits at Bloody Canyon, Eastern Sierra Nevada

Abstract

Deposits from mountain glaciers provide an important record of Quaternary climatic fluctuations but have proved difficult to date directly. A chronology has been obtained for glacial deposits at Bloody Canyon, California, by measurement ofthe accumulation of chlorine-36 produced by cosmic rays in boulders exposed on moraine crests. The accumulation ofchlorine-36 indicates that episodes of glaciation occurred at about 21, 24, 65, 115, 145, and 200 ka (thousand years ago). Although the timing of the glaciations correlates well with peaks of global ice volume inferred from the marine oxygen isotope record, the relative magnitudes differ markedly. The lengths of the moraines dating from 115 ka and 65 ka show that the early glacial episodes were more extensive than those during the later Wisconsin and indicate that the transition from interglacial to full glacial conditions was rapid.

Paleoclimate reconstruction along the Pole–Equator–Pole transect of the Americas (PEP 1)

“…Thus these ages provide maximum and minimum limiting ages, respectively, for the glacial deposits that they are associated with. The accumulation of cosmogenic isotopes in rock surfaces has also been used to date glacial events in North America (e.g., Phillips et al, 1990Phillips et al, , 1997Gosse et al, 1995).…”

Antarctic glacial chronology : new constraints from surface exposure dating

“…Glacial moraines, deposited at glacier margins, are also amenable to surface exposure dating (Gosse et al, 1995a;Gosse et al, 1995b;Phillips et al, 1997;Phillips et al, 1996a;Phillips et al, 1990) . Glaciers are efficient agents of erosion and typically remove many meters of bedrock during a glaciation.…”

“…The technique has been used to develop glacial chronologies where chronologie controls were previously unobtainable (e.g., Gosse et al, 1995;Phillips et al, 1990). The technique is well suited to Antarctiea where low erosion rates have resulted in the preservation of abundant ancient glacial deposits.…”

Geomorphological applications of cosmogenic isotope analysis

“…Ice-marginal moraines: glacial history; climatic change. Brown et al (1991), Brook et al ( , 1995a, , Gosse et al (1995a, b), Phillips et al (1990Phillips et al ( , 1996Phillips et al ( , 1997, Zreda and Phillips (1995), Ivy-Ochs et al (1996), Fabel et al (1997, Jackson et al (1997Jackson et al ( , 1999, Chadwick et al (1997), Steig et al (1998), Davis et al (1999), Fabel andHarbor (1999), Gualtieri et al (2000), Shanahan and Zreda (2000), Tschudi et al (2000), Marsella et al (2000), Phillips et al (2000) Barrows et al (2001Barrows et al ( , 2002, Briner et al (2001;, Licciardi et al (2001), Owen et al (2001Owen et al ( , 2002a, Kaplan et al …”

“…Locations for such studies are worldwide, ranging from the British Isles (Bowen et al, 2002) to eastern Russia (Gualtieri et al, 2000), the western USA (Zreda and Phillips, 1995;Gosse et al, 1995a, b;Phillips et al, 1996Phillips et al, , 1997Phillips et al, , 1990Chadwick et al, 1997;Licciardi et al, 2001;James et al, 2002), western Canada (Jackson et al,1997(Jackson et al, , 1999, eastern Canada (Steig et al, 1998;Davis et al, 1999;Marsella et al, 2000;Kaplan et al, 2001;Miller et al, 2002), East Africa (Shanahan and Zreda, 2000), southeast Australia and Tasmania (Barrows et al, 2001(Barrows et al, , 2002, the Himalayas and Tibetan Plateau (Phillips et al, 2000;Owen et al, 2001Owen et al, , 2002aTaylor and Mitchell, 2002;Schäfer et al, 2002a), and Antarctica (Brown et al, 1991;Brook et al, , 1995aFabel et al,1997). A focal issue for a number of these and other studies of glacial deposits has been the chronology of glacial fluctuations marking the Late Glacial Maximum and the global synchrony, or otherwise, of the Younger Dryas (Ivy-Ochs et al, 1996Tschudi et al, 2000;Briner et al, 2001Briner et al, , 2002Phillips and Bowen, 2002;Bourlès et al, 2002;Schäfer et al, 2002b).…”