Role of in situ cosmogenic nuclides ¹⁰be and ²⁶al in the study of diverse geomorphic processes

Abstract

The central premises of applications of the in situ cosmogenic dating method for studying specific problems in geomorphology are outlined for simple and complex exposure settings. in the light of these general models, we discuss the information that can be derived about geomorphic processes, utilizing concentrations of in situ produced cosmogenic radionuclides "Be (half-life = 1-5 ma) and 26Al (half-life = 0.7 ma) in a variety of geomorphic contexts: glacial polish and tills; meteorite impact craters; alluvial fans; paleo-beach ridges; marine terraces; sand dunes; and bedrock slopes. We also compare 'oBe-26A1 data with results obtained by other dating methods. We conclude that the technique of measuring in situ cosmic ray produced nuclides holds promise for quantitative studies of processes and time-scales in a wide range of geomorphological problems.

Late Quaternary erosion in southeastern Australia: a field example using cosmogenic nuclides

“…Our geomorphologic rate determinations here are based on concentrations of the cosmogenic nuclides, 10 Be and 26 Al, produced in situ in bedrock, saprolite, and river or catchment sediments (see reviews in Lal, 1991;Nishiizumi et al, 1993;Bierman, 1994;Cerling and Craig, 1994;Bierman and Steig, 1996). Nuclide concentrations measured from quartz have been shown to reflect the exposure history of the sample and are dependent on the production and decay rates of the nuclide, as well as the erosion rate of the sample (Lal and Arnold, 1985;Nishiizumi et al, 1986;Lal, 1988;Nishiizumi et al, 1991).…”

The Age and Origin of the Little Diomede Island Upland Surface

“…Knowing the half-life of 10 Be (1.5 Ma), one can determine the length of time that the rock has been exposed at the surface (i.e., exposure age). For details regarding the use of cosmogenic isotopes as a surface exposure dating technique, see papers by Davis and Schaeffer (1955), Phillips et al (1986), Lal (1991), Zreda et al (1991), Nishiizumi et al (1993), Kurz and Brook (1994), Zreda and Phillips (1994), Bierman et al (1995), Clark et al (1995), Gosse et al (1996), and Bard (1997).…”

In-Situ Cosmogenic 14C: Production and Examples of its Unique Applications in Studies of Terrestrial and Extraterrestrial Processes

“…Nishiizumi et al 1993;Lal 1998). This was not possible before the development of the in-situ cosmogenic method.…”

“…From these examples it becomes clear that the diverse type of nuclear studies, which can be carried out using 10 Be and 26 Al as in-situ tracers (cf. Nishiizumi et al 1993), can be further qualified by including 14 C in the analyses, thus providing additional information on the (recent) exposure history of the sample in the last 10,000 years or so.…”