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A note on the characteristics and possible origins of desert varnishes from southeast Morocco
Author(s) -
Smith B. J.,
Whalley W. B.
Publication year - 1988
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/esp.3290130306
Subject(s) - manganese , varnish , geology , microanalysis , calcite , glaze , mineralogy , scanning electron microscope , geochemistry , substrate (aquarium) , chemistry , materials science , metallurgy , composite material , oceanography , coating , ceramic , organic chemistry
Two substrate‐controlled varnish types were identified from arid southeast Morocco: (1) patchy varnish interspersed with ‘silica glaze’ on silicified limestone and (2) a complete varnish cover on partially‐silicified limestone. Electron probe microanalysis was used in conjunction with scanning electron microscopy to investigate their chemical composition. In both instances, varnishes are predominantly silica and iron‐rich with localized concentrations of manganese. Inorganic fixation of iron and manganese is the preferred explanation, with manganese and iron derived predominantly from external sources—possibly wind‐blown dust. Some iron and silica may also be derived by outward migration from within the substrate, particularly on partially silicified limestone.