Rock Varnish (desert varnish): An Internet Primer for Rock Art Research


Ronald I. Dorn
Professor of Geography
Arizona State University

        The dark rock coating called rock varnish (or desert varnish) has reached a new level of understanding and maturity in the first decade of the 21st century.  The critical breakthrough came from a decade-long project of basic research by Dr. Tanzhuo Liu of Lamont-Doherty Earth Observatory.  Dr. Liu prepared and analyzed over ten thousand microsedimentary basins of rock varnish microlaminations.  Whereas prior researchers had written papers based on one sample, or at most a few dozen, Dr. Liu compiled a massive data base that has now launched varnish microlaminations (VML) as the ideal method to understand petroglyph chronology in the Holocene and terminal Pleistocene (
        At the same time, rock varnish was viewed holistically within a new framework.  Rock coatings like varnish are an important part of the picture of rock art conservation and research, but rock coatings must be considered from the larger site context.  Specifically, it has become apparent that monitoring of rock art panel stability has reached a crisis need internationally.  Thus, RASI was developed to "triage" rock art panels.

        This page is meant to provide quick access to state-of-the-art knowledge about rock varnish and its use in understanding the priceless heritage of rock art.

Table of Contents    

Topic Basics Detailed writings
What is rock varnish (desert varnish)? web page

Entry in Encyclopedia of Geomorphology

Chapter 8 in Geochemical Sediments and Landscapes and Chapter 10 in Rock coatings (Elsevier, 1998, 429 pp)
How do other rock coatings differ from rock varnish? web page 2013 paper on rock coatings in general

Desert Rock Coatings
How does rock varnish form? Entry in Encyclopedia of Geomorphology Chapter 8 in Geochemical Sediments and Landscapes and Microbial Origin of Rock Varnish

New nanoscale insights, 2013 paper.
How does rock varnish relate to rock art conservation? The use of rock varnish in rock art conservation connects to using the Rock Art Stability Index (RASI). Detailed study on fire and rock art at Whoopup Canyon, Wyoming .
What can rock varnish tell about past rock art environments? Entry in Encyclopedia of Geomorphology Use varnish to understand the Quaternary (and results of independent blind test)
Dating rock art using rock varnish 2013 Article by Dr. David Whitley on using varnish microlaminations to date the earliest rock art in the Americas

in The Human Journey & Ancient Life in California's Deserts
Here are examples of dating petroglyphs from: Arizona, Wyoming, Nevada, California.

Here are examples of dating geoglyphs from California.

Varnish can be used to authenticate rock art.
Where can I go for help, if I want a petroglyph sample dated? The best place is to contact the 
VML (Varnish Microlaminations) Dating Lab:
This paper presents the revolution in the use of varnish microlaminations to date Holocene features.