Th230-U234 dating of pedogenic carbonates in gravelly desert soils of Vidal Valley, southeastern California

Dryland Alluvial Fans

“…Many geomorphic surfaces in arid and semi-arid regions, including but not exclusively alluvial fan surfaces, are crusted by various forms of calcrete (Butzer, 1964;Lattman, 1973;Goudie, 1983;Wright and Alonso-Zarza, 1990;AlonsoZarza et al, 1998;Nash and Smith, 1998;Stokes, Nash and Harvey, 2007). As well as providing the basis for correlation and relative dating of geomorphic surfaces (Dumas, 1969;Harvey, 1978), absolute dating is also possible using the uranium/thorium methodology (Ku et al, 1979;Candy et al, 2003;Candy, Black and Sellwood, 2004) (see below, Section 14.5.2.3). Calcrete is not only important for its correlation or dating potential but it also modifies geomorphic processes on fan surfaces by modifying infiltration behaviour (McDonald et al, 1997) and erosional resistance (Harvey, 1978(Harvey, , 1987Van Arsdale, 1982).…”

“…Several modern methods are now available for numerically dating alluvial fans These range from dating the sediments themselves, e.g. luminescence dating (Wintle, 1991), recently applied by Pope and Wilkinson (2005) and Robinson et al (2005), to dating pedogenic calcretes, using the U/Th method (Ku et al, 1979;Candy et al, 2003;Candy, Black and Sellwood, 2004), to dating surface exposure using cosmogenic nucliides (e.g. Harbor, 1999;Anderson, Repka and Dick, 1996).…”

Luminescence dating without sand lenses: An application of OSL to coarse-grained alluvial fan deposits of the Lost River Range, Idaho, USA

“…Such clast-coatings, if dense and relatively free of contamination by detritus, can be suitable for U-series dating (e.g., Ku et al, 1979;Pierce 1985;Ludwig and Paces, 2002). Datable thicknesses of clastcoatings may accumulate in 1 ka or less (e.g., Blisniuk et al, 2012).…”

Datation de deux niveaux marins sur la côte du Haut Atlas atlantique à 275 000 ans et à 120 000 ans.

“…Les apports éventuels de 230 Th non radiogéniques qui vieilliraient l'échantillon sont donc négligeables et, par conséquent, les activités des carbonates dans ces échantillons n'ont pas besoin d'être corrigées, comme cela a été proposé par Ku (1979) et par Hillaire-Marcel (1989 Le niveau 120 000 ans est bien établi à l'échelle mondiale (Harmon et al, 1978;Hoang et Taviani, 1991;Chen et al, 1991;Reyss et al, 1993).…”