Lichenometric Dates Research Articles

THE SYMBIOSIS OF LICHENOMETRY AND RADIOCARBON DATING: A BAYESIAN CHRONOLOGY OF ALPINE HUNTING IN COLORADO’S SOUTHERN ROCKY MOUNTAINS, USA

ABSTRACTArchaeologists keep a limited arsenal of methods for dating stone features at alpine sites. Radiocarbon (14C) dating is rarely possible, and it is common that dates do not accurately represent the activity of interest (stone feature construction). In this paper I review a legacy set of 89 14C dates for stone driveline sites built by hunter-gatherers in Colorado’s Southern Rocky Mountains. I amend the sample of dates using chronometric hygiene and focus on dates with direct association to hunting features. I then present a newly calibrated set of 29 lichenometric dates for rock features at these sites and use hygiene protocols to remove inaccurate dates. Size-frequency lichenometry, though poorly known in archaeology, provides a way to date stone features indirectly by measuring the growth of long-lived lichens that colonize rock surfaces after construction events. Bayesian modeling of the combined set of dates suggests that the tradition of alpine game driving spans over 6000 years BP, with abundant use over the last 2000 years. Archaeologists must use multiple methods for dating stone features in alpine environments. This Bayesian analysis is a formal effort to combine lichenometry and 14C dating for archaeological interpretation.

Correlating floodplain geochemical profiles with archival historical mining records to establish depositional chronologies of river sediment

Chronological markers in fluvial sediments can provide useful information on geomorphic response to historic catchment disturbance, and help explain historic channel morphodynamics. We concentrate on the River Nent catchment in Northern England, which was heavily impacted by lead and zinc mining in the 18th and 19th centuries. We date a 2 m deep profile of fine (<2mm) floodplain sediments using ore extraction records, covering the period 1845 to 1913, based on a significant correlation between zinc concentrations and zinc-ore extraction (r = 0.78, n = 27; p < 0.01). These dates were constrained with a basal OSL date of 2.7 ± 0.3 ka (Agemin to Agemean 1.4–3.0 ka) and existing lichenometric dates for surface gravels. Earliest lead contaminated sediments at the base of the profile most likely resulted from Roman mining operations within the catchment. Local mine-worker population statistics were used to simulate pre-1845 lead ore extraction; where above-average peaks in lead concentration, recorded at the 125–130 cm, 105–110 cm and 95–100 cm horizons, were linked to respective peaks in lead ore extraction in 1825, 1850 and 1866. Estimates of historic sediment delivery volumes at a 0.062 km2 sink site at Blagill, approximately 6.5 km downstream of the headwaters to the Nent, were estimated through coupling the chronological markers with accumulated sediment thickness and reach area. Sediment delivery was seen to be strongly enhanced by phases of metal mining, with peaks between 1800 and 1825 reflecting the final stages of lead mining, and later between 1892 and 1895, reflecting the peak extraction of zinc. Although lag times between ore extraction peaks and sediment delivery to the Blagill site introduce uncertainty to the proposed chronology, we conclude that where good local mining statistics are available, our approach provides a useful alternative or may be used in conjunction with other commonly used methodologies.

A Multi-Method Approach to Dating: Persistent Occupation of the Alpine Tundra at Rollins Pass, Colorado

ABSTRACT This paper examines chronological methods for reoccupied archaeological sites with surface arrangements of stone features in the alpine tundra. It is challenging to interpret feature dates in the tundra due to sample scarcity and poor context. I use a case study from a communal hunting site in the Rocky Mountains of North America to argue that archaeologists should use multiple dating methods to disentangle complex site formation histories. The High Grade (5BL148) game drive is located in Colorado’s Southern Rocky Mountains and includes 30 stone walls, 52 hunting blind pits, and a short line of cairns. Dating results suggest occupations from 4650 b.c.–a.d. 1850, based on artifact typologies, radiocarbon dates on charcoal and bone collagen, and lichenometric dates on stone walls.

The geomorphological role of snow since the Little Ice Age in the Sierra de Ancares (NW Spain)

On the Pico Cuiña cirque, Sierra de Ancares (León, Spain), the seasonal snow cover undergoes both slow and rapid mass displacements. Push associated with moving snow is responsible for an intense geomorphological activity, which is characterised by the plucking and transport of fragments of the bedrock, the abrasion of rock surfaces and the deposition of the mobilized material. Pronival ramparts are the most characteristic accumulation geoform created by pushing snow. Its study enabled us to verify the functionality of the nival processes and to prove the relative antiquity of some of them. The use of lichenometric techniques, based on the prior construction of a growth curve for lichens of the Rhizocarpon subgenus, has made possible to date sectors of the pronival ramparts. Lichenometric dates show a series of events of geomorphic activity of the snow cover fitting chronologically within the so-called Little Ice Age. It can be deduced from the observation of the current geomorphic dynamics of the snow cover that, although Little Ice Age temperature decrease might be important, particularly in the summer, the role of the variations in snow precipitation must be also taken into consideration.

Lichenometry in Iceland, results and application

This paper proposes a review of the use of lichenometry in Iceland since 1970, using different techniques to solve the chronology of geomorphic processes. Most users have sought to date proglacial landforms in two main areas: around the southern ice-caps of Vatnajokull and Mýrdalsjokull and in the Trollaskagi peninsula in the north. 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. Finally, the accuracy of lichenometry quickly weakens after few decades of surface exposure and the method loses rapidly any absolute aptitude. At the end, absolute dates proposed in the literature are not very trustworthy, and lichenometry should be used for relative dating only.

Glacial history of the Maritime Alps from the Last Glacial Maximum to the Little Ice Age

Abstract A complete sequence of glacial deposits and moraines within the same valley system in the Maritime Alps, spanning from the Last Glacial Maximum (LGM) to the Little Ice Age is presented. The sequence is geomorphologically and morphostratigraphically coherent and most stadials have been chronologically constrained by their cosmogenic exposure ages, lichenometry and by correlation with radiocarbon-dated moraines in neighbouring valleys. The shape, extent and thickness of the palaeoglaciers at each stadial have also been reconstructed and their equilibrium line altitude calculated. The LGM moraine of the Gesso Basin bears a similar equilibrium line altitude and age to that of other LGM moraines across the Alps. The recognized Late-glacial stadials show strong similarities with the corresponding stadials of the central–eastern Alpine valleys, such as Gschnitz, Bühl, Daun and Egesen. The recalculation of the exposure ages of moraine boulders with a new production rate better defines the LGM (24.0 ka) and the Egesen Stadial (13.0 ka), while the Bühl Stadial (18.5 ka) is dated for the first time in the Alps. Three early Holocene glacial advances are defined and correlated to the Kartell, Kromer and Göschenen I stadials, widely recognized in other Alpine sectors. Lichenometric dates indicate a three-fold oscillation during the Little Ice Age (thirteenth, seventeenth and nineteenth centuries).

Evaluating the schmidt hammer as a method for distinguishing the relative age of late holocene moraines: svellnosbreen, jotunheimen, norway

In this study we used the chmidt hammer to assess the relative exposure ages of previously dated ittle ce ge moraines deposited by vellnosbreen glacier in otunheimen southern orway. chmidt hammer measurements were taken on moraine surfaces which have been deglaciated for 79–259 years since the ittle ce ge, to reconstruct and date previous snout positions. Dating used a typical linear ittle ce ge age‐calibration curve and the ages of unknown surfaces were predicted based on chmidt hammer measurements with the support of lichenometric dates. Calibrated ages exhibited potential dating errors of ±63–103 years, which were estimated using 95% confidence intervals associated with two control points based on moraines of known ages. chmidt hammer R‐value variability was identified and sources of significant errors were attributed to variations in boulder surface texture and the incorporation of weathered boulders into moraines through push mechanisms and paraglacial reworking.

Communal hunting along the Continental Divide of Northern Colorado: Results from the Olson game drive (5BL147), USA

The Olson site (5BL147) is a multi-component rock walled game drive located in the James Peak wilderness area of Northern Colorado, USA. It is one part of a much larger game drive complex located at Rollins Pass, situated above modern tree limit and along the Continental Divide, at approximately 3600 m above sea level. Byron Olson and James Benedict conducted work at the site in the late 1960s. We combined their efforts with our recent field and lab work to produce a synthetic overview of the site. At least 45 blinds and 1307 m of rock walls are present, to funnel game upslope to waiting hunters. Radiocarbon and lichenometric dates suggest occupations spanning the last 3200 years, with diagnostic tools suggesting even older use. Lithic analysis of the debitage and tools, from both excavated (blinds) and surface contexts (intercept and processing areas), provides possible scenarios for the use of the site. Large game drives of the Colorado alpine zone represent accumulated landscapes of artifacts and features, the byproduct of many years of construction, use, and re-use, and built for a variety of reasons.

Holocene glacier fluctuations of Grovabreen and Holocene snow-avalanche activity reconstructed from lake sediments in Grningstlsvatnet, western Norway

On the southern side of Grovabreen, a plateau glacier in inner Sunnfjord, western Norway, sedimentological analyses of two lake-sediment cores from Groningstolsvatnet have been made in order to reconstruct the Holocene history of Grovabreen and of local snow-avalanche activity. The lake catchment was deglaciated about 9470 cal. BP and glaciers were absent from the catchment between 9470 and 4700 cal. BP, except for a glacier episode, correlated with the 8200 cal. BP Finse event, between 8420 and 7880 cal. BP. The glacier has existed continuously from 4700 cal. BP to the present, reaching its maximum extension around AD 1840 according to lichenometric dates. Single minerogenic particles &gt;1 mm in the sediments retrieved from Groningstolsvatnet are interpreted as dropstones from dirty snow-avalanches eroding the valley sides and deposited on the frozen lake. A local snow-avalanche chronology has been constructed for the last 10000 calendar years, based on the distribution of dropstones in the cores, with pronounced snow-avalanche activity peaking around 10 100 and 8600 cal. BP. This was at a minimum during the period when there were no glaciers in the lake catchment between-7800 and 4700 cal. BP, but increased somewhat around 7100 and 7400 cal. BP. Other marked snow-avalanche episodes occurred around 4000, 3000, 1900 and 1300 cal. BP, and during the recent decades. The snow-avalanche record is largely in accordance with similar records from western Norway and also with a winter-precipitation curve reconstructed from the Jostedalsbreen region.

A soil chronosequence from neoglacial moraines in western norway

A soil chronosequence is presented based upon podzols developed on Holocene moraine crests in the Jardalen cirque complex, western Norway. Simple and inexpensive field and laboratory tests provide information on soil depth development, pH changes, silt/clay translocation and B‐horizon reddening and thickness with age. Chronological control on historical moraine ages is provided by lichenometric dates, which support a 5 cm/100 year soil development rate for the first 700 years of pedogenesis. This initial rapid depth development tails off to a maximum rate of 0.06 cm/100 years between c. 1.5 ka and 10 ka BP based upon a Preboreal/Younger Dryas age for the oldest moraines and associated soils in the Jardalen cirque.

Little Ice Age glacial activity in Peter Lougheed and Elk Lakes provincial parks, Canadian Rocky Mountains

Dendrochronological, lichenometric, and 14C studies at 14 glacier sites in Peter Lougheed and Elk Lakes provincial parks were used to develop a chronology of Little Ice Age glacial events. The earliest indications of glacial activity are represented by moraines deposited prior to the 16th century. A major glacial expansion in the 17th century is recorded at three sites, where I4C dates show glaciers reached their maximum down-valley positions. Lichenometric dates and tree growth suppression records show a phase of glacial activity early in the 18th century, for which there is only sparse morainic evidence. Most moraines in the area date from a glacial advance culminating in the mid-19th century, and moraine formation was complete everywhere by the late 1800's. Recessional moraines are rare in the study area and indicate that ice-front retreat has been relatively continuous since the 19th century. The glacial chronology developed in this work is comparable to that reconstructed for both the Main Ranges of the Canadian Rockies and the Coast Ranges of the southern Cordillera.

A 2000-year lichen-snowkill chronology for the Colorado Front Range, USA

Measurements of Rhizocarpon subgenus Rhizocarpon thalli in fixed-area (100-m 2) sample plots at 295 randomly selected localities above timberline in the Colorado Front Range suggest six episodes of widespread, shallow, lichen snowkill during and immediately following the Audubon glacial interval. Recolonization of lichen-free areas began in cal. AD 210, 375, 570, 700, 1025, and 1255. In contrast to the 'Little Ice Age', when snowkill was restricted to narrow bands peripheral to modern late- lying snowpatches, Audubon snowkill destroyed all crustose lichens in more than 90% of the study area. Heavy April or May snowstorms, occurring after redistribution of snow by wind had diminished, are thought to have been responsible; cool, cloudy summers and warm subnivean winter temperatures may also have been involved. Audubon snowkill episodes lasted for relatively brief periods, and were superimposed on the broader pattern of late-Holocene climatic change. They did not necessarily trigger glaciation or cause geomorphic instability, but are thought to have temporarily discouraged human use of the Front Range alpine region through their adverse effects on large-game-animal populations. Lichenometric dates for landforms in areas of potential snowkill should be evaluated using rock- weathering criteria or other independent age evidence.

On the accuracy of lichenometric dates: an assessment based on the 'Little Ice Age' moraine sequence of Nigardsbreen, southern Norway

Families of lichenometric dating curves are constructed using four historically-dated moraine ridges on the glacier foreland of Nigardsbreen (Jostedalsbreen ice cap), southern Norway. A further 20 'Little Ice Age' moraine ridges are dated in terms of median-predicted dates derived from the families of curves. Four approaches are used to assess the accuracy of the median-predicted dates: (1) the extent to which the dates form a temporal sequence; (2) the extent to which they agree with local independent evidence of glacier variations; (3) the extent to which dates agree when the moraine sequences on the two sides of the glacier foreland are dated separately; and (4) the extent to which they agree when section Rhizocarpon is differentiated from lichens of the Rhizocarpon subgenus as a whole. It is concluded that under conditions favourable for lichenometric dating, median-predicted dates have attained an accuracy of ~10% on the 'Little Ice Age' timescale. Realistic error limits are considered to be of the order of ±20 years for the oldest moraines and ±5 years for the youngest. Previous dates for the Nigardsbreen moraine sequence derived from single lichenometric dating curves may be ~5% less accurate. It is suggested that the range of predicted dates obtained from families of lichenometric dating curves can be used as a conservative surrogate for accuracy.

Aranuian vegetation history of the Arrowsmith Range, Canterbury II. Revised chronology for moraines of the Cameron Glacier

Abstract The chronology for the younger Marquee and Arrowsmith moraine sets of the Cameron Glacier is revised. This is done by using new lichen growth curves for Rhizocarpon geographicum and R. candidum, developed for moraines of the Mueller Glacier at Mount Cook and calibrated with ages determined from rock weathering rind thicknesses. A new rock weathering rind curve was established for this purpose. The new lichenometric dates (greatest age estimated by either lichen, years B.P.) for the Cameron Glacier moraines are: Arrowsmith set: A1 c.170|A2 c.410|A2b c.480|A3 c.1010;A4 c. 1480|A5 c. 1960|Younger Marquee set: B1 c. 2320|B2 c. 3080|B3 c. 4480|B4 c. 5390. The kinds of vegetation and soils on the morainic time series are briefly indicated.

Rates and causes of proglacial river terrace formation in southeast Iceland: an application of lichenometric dating techniques

The immediate proglacial areas of most of the Oraefajökull outlet glaciers in southeast Iceland are characterized by well‐developed river terraces, formed by the recent downcutting of the major meltwater streams. This paper examines the rates and causes of dissection in two contrasting cases, using lichenometric dating to establish the ages of individual terraces. An age–size curve for the aggregated Rhizocarpon sub‐genus is developed from lichen measurements on dated recessional moraines, and is compared with similar curves obtained by previous workers. Levelling profiles of the terraces are then used in conjunction with the lichenometric dates to determine mean rates of net erosion between each dated surface, and to study the associated variations in channel slope. The results obtained for the Svinafellsá show that the timing and rates of downcutting have been closely related to frontal movements of the Svinafellsjökull glacier. The Kotá terraces, however, may have been formed independently of glacier fluctuations, and are thought to represent stages in the gradual recovery of the stream from the aggradational effects of the 1727 jökulhlaup.

Use of an aggregated Rhizocarpon‘species' in lichenometry: an evaluation

A regular relationship exists between the growth of lichen species within the Section Rhizocarpon and Rhizocarpon alpicola. This can be quantified and used to adjust lichenometric dates to take into account differences in the growth rates of the two groups. R. alpicola colonises deposits later than Section Rhizocarpon species, although subsequent growth by R. alpicola is rapid. If the two groups arc not separated, important dating errors may arise.

Lichenometry as a relative-age dating method in Mount Cook National Park, New Zealand

Abstract A study of the Holocene glacial sequence at Mount Cook National Park, New Zealand lead to revision of proposed chronology and re-examination of lichenometric dates for the area. Glacial deposits were up to one order of magnitude older than was previously thought and the original lichen record has been re-calibrated using the new dates. Additional measurements of lichens were collected from the eastern end of the Park and compared with ages of the moraines. A revised lichen growth curve was produced for glacial deposits formed during the last 1000 years. The rate of lichen growth declined on some older surfaces with increased competition from vascular plants. Calibration of the lichen growth curve was only possible where independent dates were available. Rates of rock weathering rind development, soil development, and plant succession were all useful for the re-calibration. Many radio-carbon dates greatly aided the construction of the chronology.

Experiments on the reproducibility and reliability of lichenometric dates, Storbreen gletschervorfeld, Jotunheimen, Norway

Matthews, J. A. Experiments on the reproducibility and reliability of lichenometric dates, Storbreen gletschervorfeld, Jotunheimen, Norway. Norsk geogr. Tidsskr. 29, 97–109. Experiments are made on the reproducibility of lichenometric dates and a method outlined for obtaining reliable lichenometric dates and a measure of their accuracy. The paper is based on field measurements of Rhizocarpon geographicum growing on 10 former ice margins, Storbreen gletschervorfeld, Jotunheimen, southern Norway. The whole population of largest lichens was measured on each margin and 144 lichenometry curves constructed from randomly sampled sub-sets of the data. The effect on predicted dates of varying the number of fixed points and varying the number of largest lichens per margin is analysed. Reproducibility of dates is measured by the dispersion of individual predictions about the mean prediction. Each mean prediction is the best estimate available of the true age of each margin. It is argued that ‘preferred predictions’ are, in this case, the mean prediction based on five largest lichens per margin and an overall mean of predictions based on one, five and ten largest lichens per margin. Use of families of lichenometry curves is reassessed by comparing mean predicted dates from 40 non-independent lichenometry curves with the ‘preferred predictions’. The ‘preferred predictions’ for the four margins of unknown age are: 1867–71 (M5), 1852–53 (M4), 1824–27 (M3), 1810 (M2). Previously published predicted dates, based on families of lichenometry curves and necessary for the establishment of an areal chronology for the Storbreen gletschervorfeld, are substantiated. Previously published results of lichenometric dating, based on single lichenometry curves, are criticised and widespread use of the principle of reproducibility is advocated.

Families of lichenometric dating curves from the Storbreen gletschervorfeld, Jotunheimen, Norway

Matthews, J. A. Families of lichenometric dating curves from the Storbreen gletschervorfeld, Jotunheimen, Norway. Norsk geogr. Tidsskr. 28, 215–235. Lichenometric dating, based on Rhizocarpon geographicum, is applied to the establishment of an areal chronology for deglaciation of the Storbreen gletschervorfeld, central southern Norway. A simple approach permitting many lichenometry curves to be constructed in the same area is adopted, each curve differing in the number of sites per surface or the number of lichens per site employed in its construction. Nine lichenometry curves of exponential form are constructed from largest lichens on four past glacier margins of known age, and the age of four margins of unknown age predicted. Median predicted ages are 1811, 1833, 1854 and 1871 and all predictions fall within an overall range of 17 years, 10 years, 10 years and 7 years respectively. The reproducibility of the predicted ages, together with independent supporting evidence, suggests that families of lichenometry curves allow considerable confidence to be placed in the lichenometric dates and are a promising addition to lichenometric dating technique in general.

Holocene Glacier and Climatic Variations, Kebnekaise Mountains, Swedish Lapland

Detailed mapping of well-preserved moraine systems fronting 23 small glaciers in the Kebnekaise Mountains in Swedish Lapland reveals that the Holocene was punctuated by four prolonged intervals of glacier expansion. The youngest interval corresponds to the well-known Little Ice Age and lasted from at least A. D. 1500 until the 20th century. Minor fluctuations superimposed on this broad interval of expansion are dated by lichenometry and historical records; they culminated about A.D. 1916, 1890, 1850, 1780, 1710, and 1500 to 1640. The next youngest interval, which also involved a number of minor fluctuations spread over several centuries, is associated with C14 dates of 2320±160 years B. P. (St-3811) and 2460±90 years B. P. (I-6854) (Corrected for variation in atmospheric C14: 2370 and 2475–2720 years B. P., respectively). The two oldest glacial intervals center around tentative lichenometric dates of 5000 and 8000 years B. P., respectively.Advances of the two older intervals were the least extensive. Advances of the two youngest intervals were approximately equal in magnitude although the relative extents of drift sheets suggest that in many cases the older of these two intervals may have been slightly more intense. Within the Little Ice Age the advances between A. D. 1500 and 1640 were commonly the most extensive.Two features commonly encountered in the Kebnekaise Mountains point to the complexity of moraine construction. The first involves large moraine ridges that were built up over a time span of up to 8000 years by proximal enlargement of an original moraine obstruction by drift related to successively younger advances. The second feature involves numerous moraines that have survived documented glacier overriding essentially intact.