Varnish microlaminations: New insights from focused ion beam preparation

David Krinsley, Jeffrey Ditto, Kurt Langworthy, Ronald Dorn, Tyler Thompson

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

The cross-sectional texture of rock varnish varies considerably with the scale of analysis and technique used to image a sample. Each jump in resolution results in new insight, with the current state-of-the-art resting at the nanoscale. One key to nanoscale analysis involves focused ion beam (FIB) techniques used most frequently in material science and semiconductor failure analysis. FIB preparation remains challenging, however, for samples like rock coatings with heterogeneous density and abundant porosity. A new technique involving multiangle ion thinning and in situ plan-view lift-out facilitated a scanning transmission electron microscopy study of rock varnish from Death Valley. The results reveal variability in lateral continuity of nanometer microlaminae that can be interrupted by post-depositional diagenesis involving leaching of Mn and Fe, and this variability could explain why some of the visual varnish microlaminations (VML) used in paleoclimatic research can sometimes appear discontinuous. Because these breaks result from post-depositional processes, they do not undermine the paleoclimatic interpretations of VML.

Original languageEnglish (US)
Pages (from-to)159-173
Number of pages15
JournalPhysical Geography
Volume34
Issue number3
DOIs
StatePublished - Jun 1 2013

Keywords

  • desert
  • geomorphology
  • paleoclimate
  • rock coating
  • weathering

ASJC Scopus subject areas

  • Environmental Science(all)
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Earth and Planetary Sciences(all)

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