Development of lichenometric dating curves for Highland Scotland
Lichenometric dating of debris flow deposits in the scottish highlands
surface processes and landforms,Lichen dating of coseismic landslide hazards in alpine mountains. (2004) – re-dating the moraines at skálafellsjökull and heinabregsjökull using different lichenometric methods: implications for the timing of the icelandic little ice age maximum. (2009) – lichenometric dating: a commentary, in the light of recent statistical studies., 2008), most authors basing their own research on the previous publication of lichenometric work without questioning the validity of earlier work (tab., a controversy arose in the literature, focussing on lichenometric dating of the little ice age maximum in southern iceland. these scatterplots should thus be described as lichen dating ‘curves’. therefore, it is proposed that lichen dating ‘curves’ should ideally be limited to studies at valley-scale or even smaller, owing to numerous micro-climate differences (e. most authors having worked in iceland were aware of the rough icelandic nature, and aimed at finding a proxy that could date landforms they observed, lacking all source of accurate dating.
Development of lichenometric dating curves for Highland Scotland
Development of lichenometric dating curves for highland scotland
therefore, lichenometric ages provided in areas subject to recurrent fallout are suspect. (1990) – a review of dating methods and their application in the development of a chronology of holocene glacier variations in northern iceland.. 2 – lichen growth ‘curves’ published from measures carried out in north and south iceland. most of the ‘curves’ are based on linear regression plots, although some are polynomial (thompson and jones, 1986) or logarithmic (bradwell, 2001a, b and 2004a, b), taking into account the different phases of lichen growth (establishment, juvenile, maturation, maturity; bradwell and armstrong, 2007). overall, the slope of ‘curves’ built in southern iceland is steeper during the first decades of lichen growth, suggesting a faster growth of the lichen. annaler: series a, physical geography,Lichenometric dating: a commentary, in the light of some recent statistical studies.. 6 – relative dating using lichenometry and vegetal cover on boulders to discriminate recent snow-avalanche deposits from those dating back at least to the end of the little ice age on the bakkasel site, fnjóskadalur, northern iceland (modified from decaulne and sæmundsson, 2010 ; background image samsýn). surface processes and landforms,Lichen dating of coseismic landslide hazards in alpine mountains.
Development of lichenometric dating curves for highland scotland the inconsistency of results and methods has led some authors to ignore lichenometric dating in iceland in the study of the little ice age (for instance grove, 2003). at the end, absolute dates proposed in the literature are not very trustworthy, and lichenometry should be used for relative dating only. annaler: series a, physical geography,Lichenometric dating: science or pseudo-science? the number of studies conducted adjacent to glaciers represents almost 80 % of all lichenometric studies conducted in iceland (fig.. (2010) – a review of lichenometric dating of glacial moraines in alaska. of lichenometric dating curves for Highland Scotland - Volume 74 Issue 1 - John L. even lichens measured in close proximity with the same technique show significant differences in lichen growth, as shown by the ‘curves’ developed by caseldine (1983), häberle (1991) and kugelmann (1991) in the vicinity of the skíðadalur valley in north iceland. families of lichenometrie dating curves from the storbreen gletschervorfeld, jotunheimen, norway.
Lichenometric dating of debris flow deposits in the scottish highlands
other cases, disparities in dating can reach several hundreds of years. confronting the results from several studies conducted in common places (se iceland for instance) show that lichenometry is a relevant relative dating technique, but not that an efficient absolute dating tool. this lichen recognition issue may result in lichenometric ‘curves’ that encompass a number of species all with differing growth rates (innes, 1985b), and to the illusion that lichenometry is a handy technique easily usable in the field, leading several generations of geomorphologists to apply a technique without mastering the craft, ignoring its prerequisite, i. recent results comparing lichenometric dates with tephrochronologic ones over the same surfaces (table 3 - kirkbride and dugmore, 2001, 2008; kirkbride 2009) clearly establish that lichenometry is severely flawed as a dating technique in several cases. the same tephra has been observed on a fláajökull moraine with a lichenometric date of 1871 (evans et al. as a consequence it is proposed that transfer or adaptation of existing ‘curves’ out of its original area should be avoided. such a disparity, unquestionable due to tephrochronological evidence, arises even though the lichenometric techniques are apparently robust: lichens grow on stable surfaces, and show coherent populations according to the size-frequency relationship, and the regional growth curve is well constrained.. 3 – differences in lichenometric dating results on moraines from outlets of the vatnajökull ice-cap, south-east iceland, according to different authors using different measuring techniques and data processing.
Lichenometry in Iceland, results and application
a lichenometric dating curve and its application to holocene glacier studies in the central brooks range, alaska. 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. a lichenometric dating curve and its application to holocene glacier studies in the central brooks range, alaska. moreover, the reliability of lichenometric dates is discredited by their lack of correspondence with tephrochronologic data, whatever the lichenometric method used. (1991) – lichenometric dating, lichen population studies and holocene glacial history in tröllaskagi, northern iceland. and environmental science transactions of the royal society of edinburghvolume 74 issue 1development of lichenometric da. (1983) – lichenometry in dating recent glacial landforms and deposits, southeast iceland. recently, two other lichenometric approaches have been introduced in iceland; both are based on complex statistical treatments of lichenometric data: (i) the u² statistic (orwin et al.
GROWTH OF CRUSTOSE LICHENS: A REVIEW
it is worth considering whether lichenometry is best considered a relative or absolute dating tool. thus, lichenometric analysis proposes an age 100 to 150 years younger that the date imposed by tephrochronology. lichenometric studies in the cascade range of washington: establishment of rhizocarpon geographicum growth curves at mount rainier. öræfi fallout (1362) is also shown as it concerns an area where many lichenometric studies have been carried out (compiled from gronvold et al. Moreover, the reliability of lichenometric dates is discredited by their lack of correspondence with tephrochronologic data, whatever the lichenometric method used. (2002) – dating of the fláajökull moraine ridges, se-iceland; comparison of the glaciological, cartographic and lichenometric data. adoption of any existing curve for new dating assessments should only be performed with caution, as the lichen habitat and growth conditions can change drastically across short distances (<1 km)., (1991) – dating recent glacier advances in the svarfaðardalur-skiðadalur area of northern iceland by means of a new lichen curve.
Development of lichenometric dating curves for highland scotland-Lichen growth rates in NW Scotland
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a range of lichen dating ‘curves’, most using the yellow-green rhizocarpon lichen, have been published in connection with icelandic geomorphic studies (most of these refer to the lichen at species level viz. (1999) – a comparison of the lichenometric and schmidt hammer dating techniques based on data from the proglacial areas of some icelandic glaciers. the recent shift of the debate toward methods did not improve lichen use for dating landforms, and occulted the biology of lichens. on a site north of mýrdalsjökull, joint observations of lichens and tephras enabled testing the validity of absolute lichenometric dating for the moraine formation.. 6 – relative dating using lichenometry and vegetal cover on boulders to discriminate recent snow-avalanche deposits from those dating back at least to the end of the little ice age on the bakkasel site, fnjóskadalur, northern iceland (modified from decaulne and sæmundsson, 2010 ; background image samsýn). (1985) – lichenometric dating and tephrochronology of sandur deposits, sólheimajökull area, southern iceland. At the end, absolute dates proposed in the literature are not very trustworthy, and lichenometry should be used for relative dating only. these data permit the development of lichenometric growth curves on acidic igneous, basic igneous, sandstone and slate substrates in most areas of highland scotland.
Extremely low lichen growth rates in Taylor Valley, Dry Valleys
suggestions for improving future lichenometric work can be made, as (i) associating one lichenologist is required to ensure the correct identification of lichen species on the studied landforms, leading to (ii) detail the identification key for rhizocarpon in different icelandic environments; (iii) to create a repository gathering rhizocarpon specimens that (iv) will be used to teach non-lichenologists to recognize the lichens in the field, especially to the party members who will be measuring lichens on selected landforms in the field; (v) revisiting the same sites and repeating the measure of the exact same individual thalli to better capture their true growth and to take into account their mortality, on the reference surface and on the geomorphic surfaces to be dated; (vi) to reduce the scale of investigation at small areas where environmental conditions do not vary and were control points are available; (vii) to avoid growth ‘curve’ transfer from one area to another several kilometres away, with latitudinal and altitudinal changes; reference growth curves should be built at local scales, not regional ones. reliability and number of adequate reference surfaces for dating calibration is essential (innes, 1984, 1985a). such ‘curves’ are therefore not truly representing the growth of lichens as it doesn’t follow the development of one individual thallus through time, ignoring population dynamics on the rock surface, as pointed out by e.. (1994) – lichenometric dating: a review with particular reference to “little ice age” moraines in southern norway. (2005) in the vestfirðir show that lichenometry may provide fairly accurate ages over a short period of time, in the most recent years/decades, later deteriorating to become a relative dating tool. is an inexpensive well-established calibrated-dating technique using lichen size to determine the relative or absolute age of exposed surfaces (beschel, 1950, 1973). (2010) – establishing lichenometric ages for nineteenth- and twentieth-century glacier fluctuations on south georgia (south atlantic). (ed): dating in exposed and surface contexts, new mexico university press, albuquerque, 185-212.
Lichenometric use of an aggregated Rhizocarpon'species' - INNES
however, the well-documented recent times in iceland might help building up lichen population monitoring that would give light on population dynamics on features built by geomorphic processes, helping at better understand the influence of mortality on the building of lichen growth ‘curves’ and its potential toward dating curves. annaler: series a, physical geography,Studies on the growth ofrhizocarpon geographicumin nw scotland, and some implications for lichenometry.. (1995) – preliminary results from the lichenometric study of the nautárdalur rock glacier, tröllaskagi, northern iceland. reviews of the different lichenometric methods applied worldwide, the reader should refer to innes (1983a, b and 1985b), matthews (1994), jomelli et al. for instance in tröllaskagi, north iceland, lichenometric studies date frontal moraines deposits (e.. 2 – lichen growth ‘curves’ published from measures carried out in north and south iceland., 2008), or to test techniques against the findings of other dating methods, such as validating the age estimates by comparing lichenometric ages against tephrochronological ages (e., 2008), built on the size-frequency technique, enables the user to identify multiple lichen populations growing on complex multi-event landforms; the u² statistic is a relative dating technique with a strong spatial component, recognising the surfaces with similar lichen cover, i.
Lichenometry - Aug 19, 2016
. 3 – differences in lichenometric dating results on moraines from outlets of the vatnajökull ice-cap, south-east iceland, according to different authors using different measuring techniques and data processing. dating (lichenometry) and the biology of the lichen genusrhizocarpon: challenges and future directions. öræfi fallout (1362) is also shown as it concerns an area where many lichenometric studies have been carried out (compiled from gronvold et al. annaler: series a, physical geography,Studies on the growth ofrhizocarpon geographicumin nw scotland, and some implications for lichenometry. common aim of many applied lichenometric studies is dating various geomorphological processes or related landforms with closely limiting numerical ages. however, the lichenometrical analysis proposes that the moraine dates from 1871 (evans et al. here i propose to group these ‘curves’ in two geographical areas, one referring to north iceland, and the other referring to south iceland, to highlight their clear differences. 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.
Growth rates of Rhizocarpon geographicum lichens: A review with
(2007) – testing the size-frequency-based lichenometric dating curve on fláajökull moraines (se iceland) and quantifying lichen population dynamics with respect to stone surface aspect. while the age of two contiguous moraines is well constrained between 1721 and 1755 through the identification of an aeolian layer that (i) shows the absence of tephra k 1721 (deposited after the katla volcano eruption between may and august 1721) and (ii) shows the presence of tephra layer k 1755 (idem, eruption active between october 1755 and february 1756); the lichenometric analysis of 550 thalli on one moraine and 717 thallus on the other indicates a date of 1854 in one case and 1831 in the other, using several methods (largest lichen, five largest lichens, size-frequency). in other areas, many of the authors who have published their results from studies conducted in iceland have presented age-size scatterplots that they called lichen ‘growth curves’ (e. however, lichenometric results are often simplistically interpreted in iceland: there, contrasting environments are found over very short distances, and a wide range of geomorphic processes impede rock surface stability; in addition, and as seen previously, the validity of many measurements can be questioned as lichenometric ages do not always accord with tephrochronologic ages. 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. of the aim of most lichenometric studies in iceland is to date proglacial landforms, notably moraines, the spatial distribution of investigated sites is uneven., this review has shown that lichenometry is a relative dating technique that can be used, when caution is taken, as an absolute dating technique, with some uncertainty, for recent periods less than about 100 years well documented by a large number of reference surfaces. in iceland, most lichenometric studies have been performed in proglacial environments to date moraine sequences (e.
authors also used their geomorphic studies to test new approaches to lichenometry dating (e. through examples, the validity of lichenometry as an absolute dating method is questioned. these data permit the development of lichenometric growth curves on acidic igneous, basic igneous, sandstone and slate substrates in most areas of highland scotland. the latter two ‘curves’ are also amongst the longest constructed, going back over 130 years. dating (lichenometry) and the biology of the lichen genusrhizocarpon: challenges and future directions. let’s arbitrary take the example of the age range offered from all ‘curves’ for a 10 mm large thallus: in south iceland, a 10 mm thallus results in a predicted ‘age’ range of 23 (maizels and dugmore, 1985) to 36 years (bradwell, 2001a); this difference is far larger in north iceland, with ‘ages’ ranging from 9 (häberle, 1991) to 41 years (caseldine, 1983); in this latter instance, the minimal age of 9 years for lichens with a 10 mm long-axis presents two problems: (i) a growth rate of the thallus of almost 1 mm. (1994) – dating and interpretation of rock glaciers using lichenometry, south tröllaskagi, north iceland. lichenometry is a relative dating technique as the technique does not provide the time brackets tephrochronology does.
lichenometric methods have been applied in iceland to date a range of different surfaces (tab. such ‘curves’ are in fact built from the measure of several individual lichens of various sizes growing on rock surfaces that have been exposed for different periods of time, at a given time. and environmental science transactions of the royal society of edinburghvolume 74 issue 1development of lichenometric da. whilst far less numerous studies have applied lichenometry to soil erosion quantification (buckland, 1994), debris-flow dating (caseldine, 1991; decaulne and sæmundsson, 2003; decaulne et al. annaler: series a, physical geography,Lichenometric dating: science or pseudo-science? 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. this minimizes the risk of under- or overestimating the age of analysed surfaces due to the misinterpretation of a lichen-dating curve constructed in a different environment. the direct use of any existing dating ‘curve’, derived from whatever statistics, leads to very different derived surface dates, as shown by mckinsey et al.
they all attempted to limit the potential source of lichen growth rate variations that led to dating errors, for example by forcing thresholds in size measurements (thompson and jones, 1986), or selecting the face of boulders they sample (evans et al. m (1973) – does the size of lichen thalli really constitute a valid measure for dating glacial deposits? directly comparing landform ages resulting from these ‘curves’ is not easy, as it requires deciphering the robust ‘curves’ from the possible wrong ones, as the quality of the data is hardly evaluated from the literature. lichenometric studies in the cascade range of washington: establishment of rhizocarpon geographicum growth curves at mount rainier. (1986) – rates and causes of proglacial river terrace formation in southeast iceland: an application of lichenometric dating techniques. in some cases, dating matches; in others the non-availability of tephra doesn’t offer the possibility of a comparison. furthermore, lichen growth ‘curves’ should be living, meaning that the dataset of control points should be measured again and again with time, especially when short time periods are considered in a specific area. it has been widely used as it is thought to be a statistically more robust and reliable dating technique, as it considers a whole lichen population and includes a large number of measurements (200-5000, 1000 being recommended in bradwell, 2009), which enables identifying anomalous growth/large lichens.