Hormes, A., Schlüchter, C., Stocker, T.F., 1998. Minimal extension phases of Unteraarglacier (Swiss Alps) during the Holocene based on 14C analysis of wood. Radiocarbon 40, 809-817 (original) (raw)
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Radiocarbon, 1997
Tree trunks and wood fragments in minerotrophic fen peat that accumulated as the result of a jökulhlaup in the outwash plain of Unteraarglacier were radiocarbon-dated using conventional ß-counting. Different pretreatment methods were tested on two wood samples to determine the reliability of our dates. We dated the wood compounds after extended acid-alkali-acid treatment, as well as extraction of cellulose and lignin. The results of the samplesPicea(B-6687) andPinus cent-bra(B-6699) show insignificant differences of…
New tree-ring evidence for the Late Glacial period from the northern pre-Alps in eastern Switzerland
Quaternary Science Reviews, 2018
The rate and magnitude of temperature variability at the transition from the Last Glacial Maximum into the early Holocene represents a natural analog to current and predicted climate change. A limited number of high-resolution proxy archives, however, challenges our understanding of environmental conditions during this period. Here, we present combined dendrochronological and radiocarbon evidence from 253 newly discovered subfossil pine stumps from Zurich, Switzerland. The individual trees reveal ages of 41e506 years and were growing between the Allerød and Preboreal (~13 0 900e11 0 300 cal BP). Together with previously collected pines from this region, this world's best preserved Late Glacial forest substantially improves the earliest part of the absolutely dated European tree-ring width chronology between 11 0 300 and 11 0 900 cal BP. Radiocarbon measurements from 65 Zurich pines betweeñ 12 0 320 and 13 0 950 cal BP provide a perspective to prolong the continuous European tree-ring record by another~2000 years into the Late Glacial era. These data will also be relevant for pinpointing the Laacher See volcanic eruption (~12 0 900 cal BP) and two major Alpine earthquakes (~13 0 770 and~11 0 600 cal BP). In summary, this study emphasizes the importance of dating precision and multi-proxy comparison to disentangle environmental signals from methodological noise, particularly during periods of high climate variability but low data availability, such as the Younger Dryas cold spell (~11 0 700 and 12 0 900 cal BP).
Permafrost and Periglacial Processes, 2010
Fossil wood stem remains of larch (Larix decidua) found 1 m below the surface at the base of the front of the Piancabella rock glacier (46827 0 02 00 N, 9800 0 07 00 E, 2480 m a.s.l.) had a conventional age range of 845 AE 50 14 C y BP (UZ-5545/ETH-34417), corresponding to a calibrated calendar age range of 1040-1280 AD (790 AE 120 cal BP) with a statistical probability of 95.4 per cent. Based on geomorphological, climatological and geophysical observations, we infer that (1) the treeline in the Medieval Warm Period was about 200 m higher than in the middle of the 20 th century, which corresponds to a mean summer temperature as much as 1.28C warmer than in AD 1950, and (2) that ice within this rock glacier is probably several centuries old and so predates recent climatic events such as the Little Ice Age.
Holocene, 2001
Glacially deformed pieces of wood, organic lake sediments and clasts of reworked peat have been collected in front of Alpine glaciers since ad 1990. The palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today's shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers. Glacial transport of the material is indicated by wood anatomy, incorporated silt, sand and gravel particles, missing bark and deformed treerings. A total of 65 samples have been radiocarbon dated so far, and clusters of dates provide evidence of eight phases of glacier recession: 9910-9550, 9010-7980, 7250-6500, 6170-5950, 5290-3870, 3640-3360, 27409910-9550, 9010-7980, 7250-6500, 6170-5950, 5290-3870, 3640-3360, -26209910-9550, 9010-7980, 7250-6500, 6170-5950, 5290-3870, 3640-3360, and 15309910-9550, 9010-7980, 7250-6500, 6170-5950, 5290-3870, 3640-3360, -1170 Allowing for the timelag between climatic fluctuations, glacier response and vegetation colonization, these recession phases may lag behind climatic changes by 100-200 years.
The Holocene, 2015
A deeper understanding of past vegetation dynamics is required to better assess future vegetation responses to global warming in the Alps. Lake sediments from Lac de Bretaye, a small subalpine lake in the Northern Swiss Alps (1780 m a.s.l.), were analysed to reconstruct past vegetation dynamics for the entire Holocene, using pollen, macrofossil and charcoal analyses as main proxies. The results show that timberline reached the lake’s catchment area at around 10,300 cal. BP, supporting the hypothesis of a delayed postglacial afforestation in the Northern Alps. At the same time, thermophilous trees such as Ulmus, Tilia and Acer established in the lowlands and expanded to the altitude of the lake, forming distinctive boreo-nemoral forests with Betula, Pinus cembra and Larix decidua. From about 5000 to 3500 cal. BP, thermophilous trees declined because of increasing human land use, mainly driven by the mass expansion of Picea abies and severe anthropogenic fire activity. From the Bronze...
The Holocene, 2005
To reconstruct the vegetation history of the Upper Engadine, continuous sediment cores covering the past 11 800 years from Lej da Champfèr and Lej da San Murezzan (Upper Engadine Valley, c. 1800 m a.s.l., southeastern Switzerland) have been analysed for pollen and plant macrofossils. The chronologies of the cores are based on 16 and 22 radiocarbon dates, respectively. The palaeobotanical records of both lakes are in agreement for the Holocene, but remarkable differences exist between the sites during the period 11 100 to 10 500 cal. BP, when Lej da Champfèr was affected by re-sedimentation processes. Macrofossil data suggest that Holocene afforestation began at around 11 400 cal. BP. A climatic deterioration, the Preboreal Oscillation, stopped and subsequently delayed the establishment of trees until c. 11 000 cal. BP, when first Betula, then Pinus sylvestris/mugo, then Larix 300 years later, and finally Pinus cembra expanded within the lake catchment. Treeline was at c. 1500 m during the Younger Dryas (12 542 Á/11 550 cal. BP) in the Central Alps. Our results, along with other macrofossil studies from the Alps, suggest a nearly simultaneous afforestation (e.g., by Pinus sylvestris in the lower subalpine belt) between 1500 and 2340 m a.s.l. at around 11 400 to 11 300 cal. BP. We suggest that forest-limit species (e.g., Pinus cembra, Larix decidua) could expand faster at today's treeline (c. 2350 m a.s.l.), than 550 m lower. Earlier expansions at higher altitudes probably resulted from reduced competition with low-altitude trees (e.g. Pinus sylvestris) and herbaceous species. Comparison with other proxies such as oxygen isotopes, residual D 14 C, glacier fluctuations, and alpine climatic cooling phases suggests climatic sensitivity of vegetation during the early Holocene. The Holocene 15,5 (2005) pp. 672 Á/686 # 2005 Edward Arnold (Publishers) Ltd
Lateglacial environmental variability from Swiss tree rings
Quaternary Science Reviews, 2008
Evidence of annually resolved environmental variations during the Allerød interstadial is presented using 81 fossil Scots pine tree-ring series from Gaenziloo and Landikon, near Zurich, Switzerland. The absolute age of the trees ranges between 11,920 and 10,610 14 C BP, which was determined by wiggle-matching radiocarbon ages to the Cariaco 14 C data set. From the two sites we created a composite floating Allerød chronology on the basis of their 632 years of overlap (r ¼ 0.57), after individual spline detrending. Merging both data sets resulted in a Lateglacial tree-ring chronology covering 1050 years. Regional curve standardization (RCS) was applied to preserve low-frequency information. Growth behavior of the fossil trees was compared with a recent composite pine data set from the central Swiss Alps and reveals distinct differences. The new Allerød RCS chronology reveals major Lateglacial variations, such as the Gerzensee oscillation, the abrupt climate shift towards the Younger Dryas and some short-term events. Radiocarbon ages agree well with those from other sites on the Swiss Plateau. For hemispheric comparisons we used the annual layer thickness record from the NGRIP ice core and the gray-scale varve record from the Cariaco basin. Even though the amplitudes are not yet fully understood, similarities on decadalto-centennial scales are apparent. r
Vegetation history and …, 2005
The altitude of the Alpine tree-line has often been used as proxy for the climatic conditions in the Holocene epoch. The usual approach for establishing a record for this proxy is the analysis of pollen and macro remains. We analysed living trees and subfossil logs from the timberline ecotone in the innermost Kauner valley in the Central Eastern Alps in order to assemble a Holocene dendrochronological tree-line record. Data sets comprising age and height of living Stone Pines (Pinus cembra L.) were collected at one site. Sections of 170 subfossil Stone Pine logs from five other sites were dendrochronologically analysed and dated. Besides using dendrochronological analyses, radiocarbon dating served as a means of obtaining the age of some logs. For most of the samples we could provide dendrochronological dates (1-year dating precision, back to 5125 b.c.) or wiggle matched dates (between approx. 7100 and 5040 b.c., dating precision with 95% probability: ±7 years). In the first half of the 19th century the tree-line was located at about 2180 m a.s.l. in the innermost Kauner valley. After approximately a.d. 1860 the altitude of the upper limit of the occurrence of Pinus cembra individuals (tree-species-line) and, being closely linked, also that of the tree-line both rose. The current tree-line (trees >2 m) is located at 2245 m a.s.l. due to climatic conditions around 1980. Additionally we observed saplings up to a present (a.d. 2000) tree-species-line at approx. 2370 m a.s.l. The dendrochronologically analysed subfossil logs found at up to 2410 m a.s.l. date from within the last 9000 years (be
The Holocene, 2009
An ultra-long tree-ring width chronology (9111 years long, 7109 BC to AD 2002) has been established based on the analysis and dating of 1432 subfossil/dry dead wood samples and cores from 335 living trees. The material was collected from treeline or near-treeline sites ( c. 2000 to 2400 m a.s.l.) mainly in the Eastern Alps. The availability of preserved samples through time at high altitudinal sites is influenced by Alpine forest history and is partly climatically controlled, as shown by comparisons of the sample depth record of the Eastern Alpine Conifer Chronology (EACC) with the Holocene glacier record. The similarity of variations over time between the sample depth of the chronology and the mid-Holocene GISP2 10Be record suggest a relationship between sample depth and solar activity. The Eastern Alpine Conifer Chronology has already been used as a dating base in environmental studies, eg, on glacier fluctuations, as well as in archaeological studies.