Cation-ratio varnish dating and petroglyph chronology in southeastern Colorado

Loendorf, Lawrence L.

doi:10.1017/s0003598x00079692

Cited by 34 publications

(12 citation statements)

References 5 publications

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“…Rock coatings can be an excellent indicator of atmospheric and surficial conditions at the time of formation (Buzek and Šrámek 1985;Loendorf 1991;Liu and Broecker 2007;Dorn 2009;Sánchez et al 2009;Krinsley et al 2013). Rock coatings can form due to biological (Garcia-Vallès et al 1997;Tani et al 2003), physical (Dixon et al 2002, Durocher andSchindler 2011), and chemical processes Sanjurjo-Sánchez, Romaní, and Alves 2012).…”

Section: Formation Of Black Coatings Near Base Metal Smeltersmentioning

confidence: 99%

A Landsat-based study of black rock coatings proximal to base metal smelters, Sudbury, Ontario, Canada

Malcolm

Leverington

Schindler

2015

International Journal of Remote Sensing

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Past emission of metal-bearing particulate matter, sulphur dioxide (SO 2 ), and sulphuric acid by base metal smelters in the Sudbury region led to widespread loss of vegetation, contamination of soils, and formation of black coatings on rock surfaces. These black coatings formed through the incorporation of smelter-borne particulate matter into the partly dissolved uppermost layers of siliceous minerals on exposed rock, and are characterized by high heavy-metal content. This study involved assessment of the reflectance properties of black coatings in the Sudbury region, and determination of the geographic distribution of coatings through supervised classification of reflectance data derived from a Landsat Enhanced Thematic Mapper Plus (ETM+) image. Classifications involved the use of the Spectral Angle Mapper (SAM), Maximum Likelihood, and Feedforward Backpropagation Neural Network algorithms. The reflectance spectra of black coatings in the Sudbury region are relatively flat and featureless, and are characterized by reflectance values less than~13% across the visible, nearinfrared, and short-wave infrared. Spectral properties are similar to those of magnetite, a spinel-group mineral known to be present in Sudbury coatings. The presence of carbon-rich soot particles may be an important influence on the reflectance properties of coatings. SAM classification results are characterized by the widespread mislabelling of uncoated urban and open-pit sites as mantled by black coatings, and neural network results problematically mislabel some uncoated wetland sites as coated. Results generated by the Maximum Likelihood algorithm most usefully depict the distribution of exposed black coatings in the Sudbury region. The mapping of black coatings using remote-sensing methods can provide useful information on the spatial character of environmental degradation in the vicinity of smelters, and should be helpful in the monitoring of environmental recovery where emissions have been reduced or eliminated.

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Section: Formation Of Black Coatings Near Base Metal Smeltersmentioning

confidence: 99%

A Landsat-based study of black rock coatings proximal to base metal smelters, Sudbury, Ontario, Canada

Malcolm

Leverington

Schindler

2015

International Journal of Remote Sensing

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“…No other chronometric methods have been able to constrain the ages of rock rings, cairns, or rock alignments. Thus, we are unable to conduct blind tests against methods with independent assumptions similar to those carried out elsewhere (Loendorf, 1991;Herscher, 2000;Marston, 2003). .…”

Section: Stressing Uncertaintiesmentioning

confidence: 99%

A new strategy for analyzing the chronometry of constructed rock features in deserts

Cerveny

Kaldenberg²,

Reed

et al. 2006

Geoarchaeology

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The western Great Basin contains thousands of constructed rock features, including rock rings, cairns, and alignments. Unlike subtractive geoglyphs, such as the Nasca Lines of Peru, that remove desert pavement, these surface features alter the location and positioning of cobble-to bouldersized rocks. The chronology of surface rock features has remained unconstrained by numerical ages because no prior chronometric approach has been able to yield age control. We propose a new strategy for studying these features by analyzing anthropogenic modifications to rock coatings, an approach that permits the use of several dating methods, two of which are assessed here: radiocarbon dating of pedogenic carbonate and rock-varnish microlaminations. Initial results from Searles Valley, eastern California, suggest that constructed rock features may be as old as early Holocene and terminal Pleistocene. Archaeological surveys of desert areas would be greatly enhanced if they noted altered positions of rock coatings.

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“…Rock varnish has also been used to date when a rock was exposed or used for cultural activities (Dorn 2007; Loendorf 1991; Whitley 2008). The methods proposed include quantifying progressive accumulation of manganese and iron, a darkening appearance over time, changes in the ratio of mobile‐to‐immobile cations, finding historic materials such as steel in a petroglyph, the abundance of lead and other 20th century anthropogenic pollutants, the ratio of mobile and more stable carbon, the radiocarbon dating of carbonate, organic matter and oxalate within, under or on top of varnish, and microlaminations seen in varnish thin sections.…”

Section: Introductionmentioning

confidence: 99%

The Rock Varnish Revolution: New Insights from Microlaminations and the Contributions of Tanzhuo Liu

Dorn

2009

Geography Compass

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Rock varnish is a coating composed of clay minerals cemented to rock surfaces by oxides of manganese and iron. Although this dark brown-to-black accretion is most noticeable in arid regions, it occurs in all terrestrial weathering environments. Scholarly varnish research started with Alexander von Humboldt, when he asked how this external accretion forms and why manganese concentrations in varnish are 10 1 -10 2 greater than in potential source materials. In the ensuing two centuries, investigations into rock varnish have been characterized by researchers studying only a handful of samples who have often used limited data to draw general conclusions. In contrast, nearly two decades of work by Tanzhuo Liu of Columbia University has yielded more than 10,000 varnish microstratigraphies obtained from rock depressions, analyses of which have provided new insights into the origin of rock varnish and the nature of climatic change in deserts, in addition to opening new research avenues in geomorphology and geoarchaeology.

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Cation-ratio varnish dating and petroglyph chronology in southeastern Colorado

Cited by 34 publications

References 5 publications

A Landsat-based study of black rock coatings proximal to base metal smelters, Sudbury, Ontario, Canada

A Landsat-based study of black rock coatings proximal to base metal smelters, Sudbury, Ontario, Canada

A new strategy for analyzing the chronometry of constructed rock features in deserts

The Rock Varnish Revolution: New Insights from Microlaminations and the Contributions of Tanzhuo Liu

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