Cosmogenic 3He surface-exposure dating of stone pavements: Implications for landscape evolution in deserts

Abstract

The formation of stone pavements, a ubiquitous gravel armor mantling landforms in arid regions of the world, has been previously attributed to erosion by wind and water or alternating shrinking and swelling of soil horizons, implying that gravel is concentrated at the land surface in a time-transgressive manner. A newly proposed model for pavement evolution differs from these models in that pavement clasts are continuously maintained at the land surface in response to deposition and pedogenic modification of windblown dust. In-situ cosmogenic 3 He surface-exposure ages on volcanic and alluvial landforms in the Mojave Desert of California are used to understand pavement evolution over geologic time scales and to test this new model. These exposure ages are stratigraphically consistent, show internal consistency at each site, and, for stone pavements adjacent to pristine, continuously exposed volcanic bedrock, are indistinguishable at the 1 level. We conclude that stone pavements are born at the surface and that pavements may provide one of the longest-term records of geologic, hydrologic, and climatic processes operating on desert surfaces.

Dating desert pavements – First results from a challenging environmental archive

“…Anderson et al (2002), Wells et al (1995) and McFadden et al (1998) applied thermoluminescence dating (TL) on desert pavements in the Mojave desert, USA, while Matmon et al (2009) used optically stimulated luminescence dating (OSL) for their investigations in the Negev desert of southern Israel. However, in all of these studies, the dating results are presented, but no details about the luminescence characteristics are given and discussed.…”

“…However, Dietze et al (2011) demonstrate that these relative age indicators are problematic, because there is no direct relationship between the surface properties, soil development and the age of desert pavements. Numerical dating of the clasts of desert pavements using cosmogenic 3 He and 10 Be surface exposure dating was e. g. applied by Wells et al (1995) and Matmon et al (2009), with a focus on dating the beginning of desert pavement formation and investigating their surface stability over time. However, the process of dust trapping and therefore the dating of the eolian fines below the desert pavement can best be dated by luminescence dating techniques (Aitken, 1985).…”

Revisão dos conhecimentos sobre o significado das linhas de seixos

“…A partir da análise do isótopo cosmogênico 3 He, WELLS et al (1995) propuseram um modelo de formação dos pavimentos de pedra em desertos. A mesma técnica, utilizando porém o isótopo 10 Be, foi aplicada para determinar os processos envolvidos na geração das linhas de seixos em perfis lateríticos na África (BRAUCHER et al 1998a) e no Brasil (BRAUCHER et al 1998b(BRAUCHER et al , 2004.…”

Desert pavement dynamics: numerical modeling and field‐based calibration

“…Desert pavements have long been used as relative-age indicators on arid-region alluvial surfaces (Wells et al, 1985;McFadden et al, 1987;Bull, 1991;Wells et al, 1995;Anderson et al, 2002;Valentine and Harrington, 2006). Pavements form as eolian sediments are progressively accumulated on desert surfaces.…”