The intercept is a poor estimate of a calibrated radiocarbon age

Telford, Richard J.; Heegaard, Einar; Birks, H. J. B.

doi:10.1191/0959683604hl707fa

Cited by 337 publications

(217 citation statements)

References 12 publications

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“…La probabilité médiane, une valeur statistique robuste, est utilisée pour présenter les datations calibrées (Telford et al 2004 5). Les sols de ces plages enfouies montrent un déve-loppement avancé avec la présence d'un horizon Aej, suggé-rant l'existence d'un délai important entre l'émersion et l'enfouissement des surfaces.…”

Section: Temps Et Pédogenèseunclassified

Émersion des terres et développement des sols bien drainés au lac Guillaume-Delisle, Québec subarctique

Lafortune

Filion

Hétu

2007

gpq

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Dans la région du lac Guillaume-Delisle, au Québec subarctique, des cônes de déjection d’âge et d’altitude variables se sont déposés tout au cours de l’Holocène sur des plages soulevées, offrant ainsi la possibilité d’étudier une chronoséquence holocène de sols. Le cadre temporel a été établi par la datation radiocarbone de 38 horizons organiques enfouis et la mise à jour de la courbe d’émersion des terres pour la région. L’émersion se serait effectuée selon un taux moyen de 5,6 m/siècle entre 8500 et 4500 années cal. BP et de 1,2 m/siècle après 4500 années cal. BP. Les analyses morphologiques et chimiques ont montré que les sols et paléosols subarctiques sableux, bien drainés et soustraits à l’influence des combes à neige, sont formés principalement par l’accumulation dans l’horizon B de matière organique humifiée combinée à de l’aluminium et du fer (podzolisation). L’enrichissement de l’horizon B en fer et en aluminium se fait lentement en suivant une fonction linéaire. La durée de pédogenèse requise pour obtenir le seuil minimal (Fep+Alp) de 0,4 % pour l’horizon Bf fixé par le Système canadien de classification des sols serait d’environ 12 400 années. Bien que théorique, cette durée indique à quel point les conditions nécessaires à la formation des podzols sont difficiles à réunir dans les sols subarctiques où la végétation demeure basse et le couvert nival peu épais.In the Lake Guillaume-Delisle area, alluvial fans of various ages and elevations were deposited throughout the Holocene over raised beach deposits, which allowed the studying of a subarctic soil chronosequence. The temporal framework is based on 38 14C dates obtained from buried organic soil horizons, and on an update of the Lake Guillaume-Delisle emersion curve. Postglacial uplift due to glacio-isostatic rebound occurred at a mean rate of 5.6 m/century from 8500 to 4500 cal. yr BP, and of 1.2 m/century after 4500 cal. yr BP. Soil morphology and chemistry showed that well-drained sandy soil and paleosoil development, when not influenced by late-lying snowpatches and snowmelt, is characterized by B horizons having a dominant accumulation product of amorphous material composed mainly of humified organic matter combined with Al and Fe (podzolisation). However, pedogenic development is weak and would take about 12 400 years to reach the minimum values of (Fep+Alp) ≥0,4% required for meeting the criteria of a Bf horizon in the Canadian system of soil classification, according to a linear function. Although theoretical, this value indicates that conditions required for Podzol formation are hard to reach in subarctic soils with low vegetation and thin snow cover

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Section: Temps Et Pédogenèseunclassified

Émersion des terres et développement des sols bien drainés au lac Guillaume-Delisle, Québec subarctique

Lafortune

Filion

Hétu

2007

gpq

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“…Of note, some levels (190cm, (Fig. 3), which was the one that best tit (highest correlation coefficient), taking into account maximum probability intervals at a 2 (J range, which is considered a robust statistical value (Telford et al, 2004). For the chronological model, the sample taken at 186.4 cm was excluded because of the high mineral content (35%) observed in nearby levels ( Fig.…”

Section: Ash Content (% Dry Wt)mentioning

confidence: 99%

Biomarkers and inorganic proxies in the paleoenvironmental reconstruction of mires: The importance of landscape in Las Conchas (Asturias, Northern Spain)

Ortíz

Borrego

Gallego

et al. 2016

Organic Geochemistry

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A B S T R A C TWe determined the lipid distributions (n-alkanes, n-alkan-2-ones, n-alkanoic acids), total organic carbon (TOC), total nitrogen (TN), CajMg and ash content in Las Conchas mire, a 3.2 m deep bryophytedominated mire in Northern Spain covering 8000 cal yr BP. Bog conditions developed in the bottom 20 cm of the profile, and good preservation of organic matter (OM) was inferred from n-alkanoic acid distribution, with the exception of the uppermost 20 cm (last ca. 200 yr). Microbial synthesis of long chain saturated fatty acids from primary OM likely produced a dominance of short chain n-alkanoic acids with a bimodal distribution, as well as the lack of correspondence between the n-alkane and n-alkanoic acid profiles in the upper 20 cm. This was accompanied by an increase in ash content, a decrease in TOC and variation in n-alkane ratio s, thereby suggesting significant changes in the mire, namely drainage and transformation to a meadow, in the last ca. 200 yr. The distribution of n-alkan-2-ones indicated an increase in bacterial source from the bottom of the record to 94 cm, whereas their distribution in the upper part could be attributed mainly to plant input andjor the microbial oxidation of n-alkanes. The different n-alkane proxies showed variations, which we interpreted in terms of changes in vegetation (Sphagnum vs. non-Sphagnum dominated phases) during the last 8000 cal yr BP. C 23 was the most abundant homolog throughout most ofthe record, thereby suggesting dominant humid conditions alternating with short drier phases. However, such humid conditions were not linked to paleoclimatic variation but rather to geomorphological characteristics: Las Conchas mire, at the base of the Cuera Range, receives continuous runoff-even during drier periods-which is not necessarily accompanied by additional mineral input to peat, producing the development of Sphagnum moss typical of waterlogged ecotopes and damp habitats. Thus, although geochemical proxies indicated an ombrotrophic regime in the mire, geomorphological characteristics may make a considerable contribution to environmental conditions.

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“…For the topmost section of the record, a linear interpolation through the median has been used (Telford et al, 2004) to avoid negative sedimentation rates. We also used a more conservative approach to account for the possible existence of hiatuses associated to certain abrupt lithological changes present along the core.…”

Section: Radiocarbon Dating and Age-depth Modelmentioning

confidence: 99%

Vegetation and fire history since the last glacial maximum in an inland area of the western Mediterranean Basin (Northern Iberian Plateau, NW Spain)

Morales‐Molino

García-Antón

2014

Quat. res.

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We reconstructed vegetation responses to climate oscillations, fire and human activities since the last glacial maximum in inland NW Iberia, where previous paleoecological research is scarce. Extremely sparse and open vegetation composed of steppic grasslands and heathlands with scattered pioneer trees suggests very cold and dry conditions during the Oldest Dryas, unsuitable for tree survival in the surroundings of the study site. Slight woodland expansion during the Bolling/Allerod was interrupted by the Younger Dryas cooling. Pinewoods dominated for most of the early Holocene, when a marked increase in fire activity occurred. Deciduous trees expanded later reaching their maximum representation during the mid-Holocene. Enhanced fire activity and the presence of coprophilous fungi around 6400-6000 cal yr BP suggest an early human occupation around the site. However, extensive deforestation only started at 4500 calyr BP, when fire was used to clear the tree canopy. Final replacement of woodlands with heathlands, grasslands and cereal crops occurred from 2700 cal yr BP onwards due to land-use intensification. Our paleoecological record can help efforts aimed at restoring the natural vegetation by indicating which communities were dominant at the onset of heavy human impact, thus promoting the recovery of currently rare oak and alder stands.

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The intercept is a poor estimate of a calibrated radiocarbon age

Cited by 337 publications

References 12 publications

Émersion des terres et développement des sols bien drainés au lac Guillaume-Delisle, Québec subarctique

Émersion des terres et développement des sols bien drainés au lac Guillaume-Delisle, Québec subarctique

Biomarkers and inorganic proxies in the paleoenvironmental reconstruction of mires: The importance of landscape in Las Conchas (Asturias, Northern Spain)

Vegetation and fire history since the last glacial maximum in an inland area of the western Mediterranean Basin (Northern Iberian Plateau, NW Spain)

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