How desert varnish forms?

2005 ◽  
Author(s):  
Randall S. Perry ◽  
Vera M. Kolb ◽  
Bridget Y. Lynne ◽  
Mark A. Sephton ◽  
Nicola Mcloughlin ◽  
...  
Keyword(s):  
Desert Varnish

Impact of Climatic Change on an Arid Watershed: Nahal Yael, Southern Israel

1979 ◽  
Vol 11 (2) ◽  
pp. 153-171 ◽  
Author(s):  
William B. Bull ◽  
Asher P. Schick
Keyword(s):  
Climatic Change ◽  
Sediment Yield ◽  
Fracture Density ◽  
Dense Networks ◽  
Valley Fill ◽  
Water And Sediment ◽  
Desert Varnish ◽  
Gravel Size ◽  
Induced Changes ◽  
Geomorphic Surfaces

The Nahal Yael basin is underlain chiefly by schist, amphibolite, and granite. Thin (generally <1 m thick), grussy colluvium which covered the lower portions of granitic hillslopes in the late Pleistocene has now been stripped completely, causing marked contrasts in outcrop morphologies, even where there is no contrast of fracture density or petrologic characteristics. Formerly mantled slopes are now smooth and crumbly, and lack desert varnish. Previously unmantled slopes are rough and craggy, and varnished but little weathered. Such stripping suggests a change from a semiarid to a drier and/or warmer climate. Slopes underlain by amphibolite responded similarly to the climatic change, but the amphibolite was more deeply weathered, and the colluvium was only partially stripped. The least stripping of colluvium occurred on schist hillslopes, partly because schist outcrops require more rain to generate runoff, and partly because angular blocks of schist require larger flows for transport, compared to other slope lithologies. The stream subsystem responded to the climatically induced changes in the discharge of water and sediment from the hillslopes. Increase in sediment yield caused valley alluviation in the early Holocene, and a decrease in sediment yield later in the Holocene caused entrenchment of the valley fill. More granite and amphibolite gravel-size particles are transported now than when the hillslopes were extensively mantled. Dense networks of trails are not common on Holocene geomorphic surfaces, but are present on remnants of Pleistocene surfaces.

Making silica rock coatings in the lab: synthetic desert varnish

2005 ◽  
Author(s):  
Randall S. Perry ◽  
Vera M. Kolb ◽  
Ajish I. Philip ◽  
Bridget Y. Lynne ◽  
Nicola McLoughlin ◽  
...  
Keyword(s):  
Desert Varnish ◽  
Rock Coatings

Characteristics of desert varnish from nanometer to micrometer scale: A photo-oxidation model on its formation

2019 ◽  
Vol 522 ◽  
pp. 55-70 ◽  
Author(s):  
Xiaoming Xu ◽  
Yan Li ◽  
Yanzhang Li ◽  
Anhuai Lu ◽  
Ruixi Qiao ◽  
...  
Keyword(s):  
Photo Oxidation ◽  
Desert Varnish ◽  
Oxidation Model ◽  
Micrometer Scale
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