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[0] VML [2] Model proponents have not yet explored the implications of the VML record. [3] This model explains VML observations. Specific HRTEM observations in different VML reveal more nm-scale bacterial fragments in wet periods. [4] Wording to accommodates alternating climatic changes producing VML. However, the silica binding process does not explain VML. [1] 
This model could explain VML observations, whereby conditions of greater alkalinity and fewer wetting events would generate drier VML events and more wetting events would generate wetter VML events.
Rock Varnish Chapter 8 in Geochemical Sediments and Landscapes
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