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GREGG MÜLLER ON MULLER ON LICHENOMETRY AND ENVIRONMENTAL HISTORY
| FEW PEOPLE WOULD connect the splashes of color of lichen crusts on rock with unraveling the history of landscapes, yet the meek but intriguing lichen can help researchers tell the stories of places. |
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Perhaps the most well-known application of lichens in environmental study has been their use as indicator species for air quality, particularly in northern Europe.1 Less well known is lichenometric dating, which essentially uses the size of lichens to date surfaces. If the relationship between the age of a lichen and its size is known, then the minimum age of the surface on which a lichen is growing can be inferred. |
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Lichens can live for a remarkably long time (perhaps as long as 3,ooo years) and can grow in environments that are too harsh for most other organisms.2 The primary application of lichenometry has been in the dating of relatively recent (less than 1,000 years) glacial and alpine landscape features where the time spans involved—and the lack of other suitable dating techniques such as dendrochronology (tree rings), radiometric carbon (carbon dating), or human artifacts—make dating problematic.3 |
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The most common application of the technique has been in dating naturally occurring surfaces—rockfalls, glacial moraines, mud flows, flood regimes, periglacial surfaces, and other geomorphic features. There has been curiously little application in the fields of archaeology, anthropology, and history even though anthropogenic surfaces and historical objects are often indispensable in establishing lichen growth rates.4 |
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My own work has focused on dating mining remains and earthworks associated with gold mining in the Box-Ironbark forests around Bendigo in central Victoria, Australia, considered to be a historical landscape of national and in-ternational significance.5 The mining sites are located in relatively dry, open forest, with low relief, irregular rainfall and hot summers, and are about as distant from arctic glaciers as one can imagine, but they share a number of char-acteristics with alpine environments in respect to dating. The relatively short time frames involved (about 150 years) and the lack of organic material make radiocarbon dating problematic. The variability of the climate means many of the native trees in central Victoria do not exhibit annual rings, so dendrochronology cannot be used. The sequence of mining exploitation further complicates the issue. |
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In the mid 1800s, hundreds of thousands of miners from all over the world descended on these gold fields, clearing the forests, turning over the soil, washing, panning, sluicing, digging deep mines, throwing up hills of "mullock" and in general disturbing the ground surface over huge areas. The introduction of industrial scale mining and the working and reworking of the fields up to the present day has resulted in a palimpsest of remains, where even small areas may have overlapping layers of early small-scale alluvial workings, deep mining, hydraulic sluicing, and recent fossicking (small-scale searching for gold, often reworking old mining sites, now usually undertaken with metal detectors or by panning). |
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