Lichenometric dating: Science or pseudo-science?

Geographia Polonica vol. The paper presents problems faced when using a new method for defining the growth curves of the thalli of the rockylichen Rhizocarpon spp in the Polish section of the Tatra and Karkonosze Mountains. These were mainly representativeof substrates located in the central parts of these zones. In the new lichenometric curve which was constructed forthe Tatra and Karkonosze Mts. Therefore the curve can be easily used for dating items located in any part of the altitude zone for which thecurve was defined. The paper also tackles the problem regarding the number of thalli that should be assessed when dating. The shape of the thallus growth curve is strongly influenced by the landforms either convex or concave and the vertical extent of the zone in which the measurement is performed. The presence of multiannual snow patches in close proximity and air pollution also influence thallus growth onthe mountains investigated. The geomorphic processes taking place turned out to be a significant problem for proper dating of the items — depending on their interpretation they can either help dating or obscure the reconstruction of the event. Keywords : Rhizocarpon , lichenometry , Tatra Mts.

The biology behind lichenometric dating curves

The use of the lichen genus Rhizocarpon in lichenometric dating with special reference to Holocene glacial events. T1 – The use of the lichen genus Rhizocarpon in lichenometric dating with special reference to Holocene glacial events. N2 – Lichenometry is one of the most widely used methods of dating the surface age of substrata including rock surfaces, boulders, walls, and archaeological remains and has been particularly important in dating late Holocene glacial events.

The study critically favours the importance of lichens in estimating palaeoclimatic events and its use in depicting the future discretion regarding.

Alestalo, J.. Dendrochronological interpretation of geomorphic processes. Fennia Alexander, C. Radiocarbon dating of the rate of movement of two solifluction lobes in the Ruby Range, Yukon Territory. Quaternary Research Anderson, E. Instruments for measuring soil creep. Andrews, J. Techniques of till fabric analysis. A lichenometrical study of the north-western margin of the Barnes Ice Cap: A geomorphological technique.

Geography Bulletin Ottawa Bannister, Bryant. Bergsma, E..

Use of bomb-14C to investigate the growth and carbon turnover rates of a crustose lichen

This paper proposes a review of the use of lichenometry in Iceland since , using different techniques to solve the chronology of geomorphic processes. Based on the results of over 35 published studies, lichenometry has been widely applied in Iceland, proposing numerical ages absolute dating and relative ages relative dating of different surfaces. Increasing awareness of methodological limitations of the technique, together with more sophisticated data processing, has led some authors to claim that lichenometric ‘ages’ are robust and reliable.

However, the different measurement techniques used make it difficult to compare regions or studies in the same area. These problems are exacerbated in Iceland by rapid environmental changes across short distances and more generally by lichen species mis-identification in the field. Moreover, the reliability of lichenometric dates is discredited by their lack of correspondence with tephrochronologic data, whatever the lichenometric method used.

This technique is properly called lichenometric dating, as lichenometry is a broader term that may encompass measurements of lichens for other purposes.

Skip to search form Skip to main content You are currently offline. Some features of the site may not work correctly. DOI: Loso and D. Doak and R. Loso , D. Doak , R. Abstract Contemporary variants of the lichenometric dating technique depend upon statistical correlations between surface age and maximum lichen sizes, rather than an understanding of lichen biology.

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Lichenometry

Lichenometry is used to date late-Holocene terminal moraines that record glacier fluctuations. Traditionally, it relies upon dating curves that relate diameters of the largest lichens in a population to surface ages. Although widely used, the technique remains controversial, in part because lichen biology is poorly understood.

Lichenometric dating of coseismic rockfall related to the Great Lisbon Earthquake in affecting the archaeological site of “Tolmo de.

Toggle navigation ScienceBase-Catalog. Your browser does not have support for cookies enabled. Some features of this application will not work. Mark H Garnett, and Tom Bradwell, Use of bombC to investigate the growth and carbon turnover rates of a crustose lichen:. Summary The reliability of lichenometric dating is dependent on a good understanding of lichen growth rates. The growth rate of lichens can be determined from direct measurement of growing lichens or indirect methods by measuring lichens growing on surfaces of known age, although there are limitations to both approaches.

Radiocarbon 14C analysis has previously been used in only a handful of studies to determine lichen growth rates of two species from a small area of North America. These studies have produced mixed results; a small amount of carbon turnover appears to occur in one of the species Caloplaca spp. We investigated the use of bombC analysis to determine the growth rate of a different crustose species Pertusaria pseudocorallina common to Northern Europe. This observation strongly suggests that a degree of carbon turnover probably occurs in Pertusaria pseudocorallina, and that bombC analysis alone cannot be used to determine lichen age or absolute growth rates in this lichen species.

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3A common aim of many applied lichenometric studies is dating various 5​Because of the aim of most lichenometric studies in Iceland is to date proglacial.

We use cookies to ensure that we give you the best experience on our website. By continuing to browse this repository, you give consent for essential cookies to be used. You can read more about our Privacy and Cookie Policy. Evans, D. We therefore reject previous conclusions that any one technique is demonstrably inferior to the other, at least for dating glacial landforms created over the last years in SE Iceland.

Comparisons of climate trends and recession rates indicate that air temperature anomalies, particularly those of the summer, are the strongest driver of glacier retreat. Summer and annual temperature trends, not the NAO, clearly show that recent accelerated global warming is driving the marked recession of the period Last Modified: Easter Disclaimer Trading name.

A-Z Index Accessibility. You are in: Home Research Durham Research Online Testing lichenometric techniques in the production of a new growth-rate curve for the Breidamerkurjokull foreland, Iceland, and the analysis of potential climatic drivers of glacier recession.

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Have you why noticed an old stone wall and wondered how why it has been there? If there is lichen growing on the wall, the lichen has why likely been living there since the time the wall was made, so if you could figure out how old the lichen is then you could deduce the age of the wall. Geologies use this method, called lichenometry , and ecological methods to establish dates and temporal pollution as they seek to construct a pollution from the available evidence.

In this geology xanthoria project, you will use history as a method for dating why recent events in your area, such as the moss of a manmade or geological feature or a disturbance in your area for example, the building of a stone xanthoria, the indicator of a rock slide, or when a road was cut. A trained xanthoria can “read” absolute history in layers of rocks. The ability to establish dates and temporal sequences of rock formations is, in fact, essential for piecing together the pollution’s history.

More than 50 boulder labyrinths along the Swedish Bothnian coast have been dated using a lichenometric method. The lichen used for this study is Rhizocarpon.

In archaeology , palaeontology , and geomorphology , lichenometry is a geomorphic method of geochronologic dating that uses lichen growth to determine the age of exposed rock , based on a presumed specific rate of increase in radial size over time. The measured growth rates of R. Lichenometry can provide dates for glacial deposits in tundra environments, lake level changes, glacial moraines , trim lines , palaeofloods, [10] rockfalls, seismic events associated with the rockfalls, [2] talus scree stabilization and former extent of permafrost or very persistent snow cover.

Among the potential problems of the technique are the difficulty of correctly identifying the species, delay between exposure and colonization, varying growth rates from region to region as well as the fact that growth rates are not always constant over time, dependence of the rate of growth upon substrate texture and composition, climate, and determining which lichen is the largest. Several methods exist for dating surfaces with help of lichenometry; the most simple relies on a single largest lichen while other methods use more.

There are also differences in the way the lichen is measured; while some suggest that the largest diameter should be measured, other scientists prefer the diameter of the largest inscribed circle.

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Lichenometry is a method of numerical dating that uses the size of lichen colonies on a rock surface to determine the surface’s age. Lichenometry is used for rock surfaces less than about 10, years old. The basic premise of lichenometry is that the diameter of the largest lichen thallus growing on a moraine, or other surface, is proportional to the length of time that the surface has been exposed to colonisation and growth. Data on lichen growth rates can enable estimates of both the age of the thallus and the period of exposure of a rock surface to be made.

The biology behind lichenometric dating curves. Different metrical and statistical devices have been used to collect lichenometric lichen, including the.

Lichens are a symbiosis of two organisms, algae and fungi, which colonise exposed surfaces and can be measured to date the approximate age of the surface. The study of lichens is therefore important to help establish a timescale of events. It is generally believed that the larger the lichen, the longer it has colonised the surface, and therefore that larger lichen means an older surface. However, researchers have found a ‘Green Zone’ and the hypothesis suggests that lichens are larger at the proximal side of the moraine closest to the glacier base of terminal moraines ridge of sediment that is deposited when a glacier retreats than at other locations Haines-Young, This hypothesis is tested by data which was collected from six dated moraines on the glacial foreland of Nigardsbreen in the Jostedal, Norway.

Five transects were taken across each moraine, each consisting of 3 metre x 3 metre quadrats where the five largest lichens were measured Innes, In addition to measuring the lichen thalli diameters, 3 other factors were also measured: aspect, gradient and vegetation cover. These factors are important to determine why the largest lichens are found in a particular location, whether it supports the hypothesis or not.

If the data collected from Nigardsbreen supports the ‘Green Zone’ hypothesis, there are implications for using lichens to date surfaces of unknown age. Keywords: Lichenometry, Nigardsbreen, Rhizocarpon geographicum , ‘Green Zone’, slope aspect, slope gradient. The purpose of this investigation is to measure diameters of the lichen Rhizocarpon geographicum on proximal, crest and distal side of the moraine furthest from the glacier slopes on terminal moraines on a glacial foreland.

This is to determine if the size of the lichen varies across the moraine and to identify any influencing factors which may be contributing to a size variation.

Cisca Wijmenga, NWO-Spinozalaureaat 2015


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