Abstract

Nanometer-scale element mapping and spectroscopy of desert varnish from the northern Sonoran Desert in southwestern Arizona reveal a dynamic disequilibrium system characterized by postdepositional mineralogical, chemical, and structural changes activated by liquid water. Lack of equilibrium is suggested by the large variety of coexisting Mn phases. Sparse secondary Ba and Sr sulfates also occur, as do carbonaceous particles. Individual Mn-oxide particles contain variable concentrations of Ba and Ce, reflecting their role as repositories of trace elements, presumably derived from atmospheric aerosols. Desert varnish is analogous to more familiar sediments in displaying authigenic and diagenetic structures, but with total sediment thicknesses <1 mm and structures at the nanometer scale. As such, it is neither a weathering rind nor patina, but a unique subaerial sediment that is in dynamic disequilibrium. Our results suggest continuing adjustment of varnish to changing environmental conditions.

Original languageEnglish (US)
Pages (from-to)215-218
Number of pages4
JournalGeology
Volume36
Issue number3
DOIs
StatePublished - Mar 2008

Fingerprint

diagenesis
desert
disequilibrium
sediment thickness
repository
structural change
sediment
weathering
spectroscopy
environmental conditions
trace element
oxide
aerosol
sulfate
liquid
varnish
water
particle
chemical

Keywords

  • Desert varnish
  • Diagenesis
  • Mn
  • Rock varnish
  • Sonoran desert
  • Subaerial sediment

ASJC Scopus subject areas

  • Geology

Cite this

Nanometer-scale complexity, growth, and diagenesis in desert varnish. / Garvie, Laurence; Burt, Donald; Buseck, P R.

In: Geology, Vol. 36, No. 3, 03.2008, p. 215-218.

Research output: Contribution to journalArticle

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N2 - Nanometer-scale element mapping and spectroscopy of desert varnish from the northern Sonoran Desert in southwestern Arizona reveal a dynamic disequilibrium system characterized by postdepositional mineralogical, chemical, and structural changes activated by liquid water. Lack of equilibrium is suggested by the large variety of coexisting Mn phases. Sparse secondary Ba and Sr sulfates also occur, as do carbonaceous particles. Individual Mn-oxide particles contain variable concentrations of Ba and Ce, reflecting their role as repositories of trace elements, presumably derived from atmospheric aerosols. Desert varnish is analogous to more familiar sediments in displaying authigenic and diagenetic structures, but with total sediment thicknesses <1 mm and structures at the nanometer scale. As such, it is neither a weathering rind nor patina, but a unique subaerial sediment that is in dynamic disequilibrium. Our results suggest continuing adjustment of varnish to changing environmental conditions.

AB - Nanometer-scale element mapping and spectroscopy of desert varnish from the northern Sonoran Desert in southwestern Arizona reveal a dynamic disequilibrium system characterized by postdepositional mineralogical, chemical, and structural changes activated by liquid water. Lack of equilibrium is suggested by the large variety of coexisting Mn phases. Sparse secondary Ba and Sr sulfates also occur, as do carbonaceous particles. Individual Mn-oxide particles contain variable concentrations of Ba and Ce, reflecting their role as repositories of trace elements, presumably derived from atmospheric aerosols. Desert varnish is analogous to more familiar sediments in displaying authigenic and diagenetic structures, but with total sediment thicknesses <1 mm and structures at the nanometer scale. As such, it is neither a weathering rind nor patina, but a unique subaerial sediment that is in dynamic disequilibrium. Our results suggest continuing adjustment of varnish to changing environmental conditions.

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