In the Alps, climatic conditions reflected in glacier and rock glacier activity in the earliest Holocene show a strong affinity to conditions in the latest Pleistocene (Younger Dryas). Glacier ...advances in the Alps related to Younger Dryas cooling led to the deposition of Egesen stadial moraines. Egesen stadial moraines can be divided into three or in some cases even more phases (sub-stadials). Moraines of the earliest and most extended advance, the Egesen maximum, stabilized at 12.2
±
1.0
ka based on
10Be exposure dating at the Schönferwall (Tyrol, Austria) and the Julier Pass-outer moraine (Switzerland). Final stabilization of moraines at the end of the Egesen stadial was at 11.3
±
0.9
ka as shown by
10Be data from four sites across the Alps. From west to east the sites are Piano del Praiet (northwestern Italy), Grosser Aletschgletscher (central Switzerland), Julier Pass-inner moraine (eastern Switzerland), and Val Viola (northeastern Italy). There is excellent agreement of the
10Be ages from the four sites. In the earliest Holocene, glaciers in the northernmost mountain ranges advanced at around 10.8
±
1.1
ka as shown by
10Be data from the Kartell site (northern Tyrol, Austria). In more sheltered, drier regions rock glacier activity dominated as shown, for example, at Julier Pass and Larstig valley (Tyrol, Austria). New
10Be dates presented here for two rock glaciers in Larstig valley indicate final stabilization no later than 10.5
±
0.8
ka. Based on this data, we conclude the earliest Holocene (between 11.6 and about 10.5
ka) was still strongly affected by the cold climatic conditions of the Younger Dryas and the Preboreal oscillation, with the intervening warming phase having had the effect of rapid downwasting of Egesen glaciers. At or slightly before 10.5
ka rapid shrinkage of glaciers to a size smaller than their late 20th century size reflects markedly warmer and possibly also drier climate. Between about 10.5
ka and 3.3
ka conditions in the Alps were not conducive to significant glacier expansion except possibly during rare brief intervals. Past tree-line data from Kaunertal (Tyrol, Austria) in concert with radiocarbon and dendrochronologically dated wood fragments found recently in the glacier forefields in both the Swiss and Austrian Alps points to long periods during the Holocene when glaciers were smaller than they were during the late 20th century. Equilibrium line altitudes (ELA) were about 200
m higher than they are today and about 300
m higher in comparison to Little Ice Age (LIA) ELAs. The Larstig rock glacier site we dated with
10Be is the type area for a postulated mid-Holocene cold period called the Larstig oscillation (presumed age about 7.0
ka). Our data point to final stabilization of those rock glaciers in the earliest Holocene and not in the middle Holocene. The combined data indicate there was no time window in the middle Holocene long enough for rock glaciers of the size and at the elevation of the Larstig site to have formed. During the short infrequent cold oscillations between 10.5 and 3.3
ka small glaciers (less than several km
2) may have advanced to close to their LIA dimensions. Overall, the cold periods were just too short for large glaciers to advance. After 3.3
ka, climate conditions became generally colder and warm periods were brief and less frequent. Large glaciers (for example Grosser Aletschgletscher) advanced markedly at 3.0–2.6
ka, around 600 AD and during the LIA. Glaciers in the Alps attained their LIA maximum extents in the 14th, 17th, and 19th centuries, with most reaching their greatest LIA extent in the final 1850/1860 AD advance.
The Sun sporadically produces eruptive events leading to intense fluxes of solar energetic particles (SEPs) that dramatically disrupt the near-Earth radiation environment. Such events have been ...directly studied for the last decades but little is known about the occurrence and magnitude of rare, extreme SEP events. Presently, a few events that produced measurable signals in cosmogenic radionuclides such as
C,
Be and
Cl have been found. Analyzing annual
C concentrations in tree-rings from Switzerland, Germany, Ireland, Russia, and the USA we discovered two spikes in atmospheric
C occurring in 7176 and 5259 BCE. The ~2% increases of atmospheric
C recorded for both events exceed all previously known
C peaks but after correction for the geomagnetic field, they are comparable to the largest event of this type discovered so far at 775 CE. These strong events serve as accurate time markers for the synchronization with floating tree-ring and ice core records and provide critical information on the previous occurrence of extreme solar events which may threaten modern infrastructure.
Deckenschotter (‘Cover Gravels’) are proximal glaciofluvial gravels located in the northern Alpine Foreland mainly beyond the extent of the Last Glacial Maximum. They cover Tertiary Molasse or ...Mesozoic bedrock with an erosional unconformity. In Switzerland, Deckenschotter are referred to as Höhere (Higher) and Tiefere (Lower) Deckenschotter based on their topographical positions with a significant phase of incision that separates these two units. For this study, we performed sedimentological analyses to identify the provenance, transport mechanisms and depositional environment of these gravels. In addition, we established the chronology of the Höhere Deckenschotter gravels at Stadlerberg using cosmogenic 10Be depth-profile dating technique. The inherited 10Be concentration then allowed estimation of a catchment-wide palaeo-denudation rate. The results from clast fabric investigations indicate that braided rivers within a glaciofluvial environment transported these sediments to the study site mainly as bedload. In addition, the petrographic composition of the deposits shows that a large portion of the gravels was derived through erosional recycling of Miocene Molasse conglomerates. Some material was additionally sourced in the northern Central Alps. We then conclude that gravel accumulation in the Swiss Alpine Foreland was completed at 1.9±0.2Ma. This age, however, represents a minimum age and the oldest 10Be depth-profile age ever obtained for a geological unit. Furthermore, a palaeo-denudation rate of c. 0.3–0.4mm/a was estimated for the catchment of Stadlerberg gravels. Finally, elevation differences between the bedrock underlying the Höhere Deckenschotter and the modern base level imply a long-term regional incision rate of c. 0.12mm/a.
•1.9±0.2Ma 10Be depth-profile age for gravels in the northern Alpine Foreland•Provenance from the northern Central Alps and reworked from Miocene Molasse•Transport mainly as bedload in braided rivers in a glaciofluvial system•0.12mm/a long-term bedrock incision rate•0.3–0.4mm/a palaeo-denudation rate estimation for the palaeocatchment
Based on cosmogenic
10Be data from four sites in the Alps we discuss geological uncertainties associated with the dating of former cirque and small valley glacier margins. At the Early Lateglacial ...Gschnitz site (Trins, Austria), a 3000
yr spread in
10Be exposure ages points to prolonged boulder instability. Three out of seven ages are not included in the mean age calculation, which yielded 15,400±1000
yr (indistinguishable from the oldest boulder age of 16,130±1040
yr). As a result of the distinctive morphology at Julier Pass (Switzerland) site we are able to exposure date the early (12,300±1300
yr) and the late (11,300±600
yr) Egesen stadial glacier advances (Younger Dryas equivalent), not just final retreat. At the Kromer site (Austria),
10Be exposure ages from five clast-supported boulders are indistinguishable within the analytical uncertainties (mean age: 8400±500
yr). In addition to moraine age, key factors that may lead to “too young” ages include degree of matrix- vs. clast-support of the boulders, post-depositional periglacial activity and tree coverage. At the Nägelisgrätli bedrock site near Grimsel Pass (Switzerland) exposure ages of 10,760–11,720
yr are consistent with Early Holocene cirque glacier retreat, and underline the marked lack of nuclide inheritance in bedrock exposures in the Alps.
Age-related trends are present in tree-ring widths (TRW), but their presence in tree rings isotope is debated. It is unclear how cambial age influences the relationships between TRW and isotopes. ...Tree-ring isotopes of alpine larch and cembran-pine trees showed only trends in the juvenile period (>100 years), which might mask the inter-relations between tree-ring proxies during cambial age. This work tries to unmask the age-trend influences by examining the correlations in TRW—stable isotopes with and without age-trend correction. The non-detrended and linear-detrended values of TRW, of δD and δ18O showed significant correlations for ages up to 100 years, but not afterward. However, the correlation values, after spline or first-difference time-series detrending, were not age-related. Thus, detrending methods affect the correlations in the juvenile phase and may affect climate-related interpretations. The correlations between TRW and δ13C were not age-related, while those among the isotopes were significant throughout the ages. The correlation between δ13C and δD was the exception, as it became significant only after age > 100 years, suggesting a different use of reserves in the juvenile phase. In conclusion, the relationships among the tree-ring parameters are stable in all the different detrend scenarios after the juvenile phase, and they can be used together in multi-proxy paleoclimatic studies. The data of the juvenile phase can be used after spline-detrending or first-difference time-series calculation, depending on the purpose of the analysis to remove age-related trends. The work also provides clues on the possible causes of juvenile age trends.
The analysis of the stable isotope of the tree-ring cellulose is an important tool for paleo climatic investigations. Long tree-ring chronologies consist predominantly of oaks and conifers in Europe, ...including larch trees (
Larix decidua
) and cembran pines (
Pinus cembra
) that form very long tree ring chronologies in the Alps and grow at the treeline, where tree growth is mainly determined by temperature variations. We analyzed δ
13
C, δ
18
O and δ
2
H isotopes in the cellulose extracted from tree-rings of wood samples collected at high altitude in the Swiss and Tyrol Alps, covering the whole Holocene period. We found that larch cellulose was remarkably more depleted in deuterium than that of cembran pine, with mean δ
2
H values of −113.4 ± 9.7‰ for larch and of −65.4 ± 11.3‰ for cembran pine. To verify if these depleted values were specific to larch or a property of the deciduous conifers, we extended the analysis to samples from various living conifer species collected at the Bern Botanical Garden. The results showed that not only the larch, but also all the samples of the deciduous larch family had a cellulose composition that was highly depleted in δ
2
H with regard to the other evergreen conifers including cembran pine, a difference that we attribute to a faster metabolism of the deciduous conifers. The δ
18
O values were not statistically different among the species, in agreement with the hypothesis that they are primary signals of the source water. While the δ
13
C values were slightly more depleted for larch than for cembran pine, likely due to metabolic differences of the two species. We conclude that the deciduous larch conifers have specific metabolic hydrogen fractionations and that the larch unique signature of δ
2
H is useful to recognize it from other conifers in subfossil wood samples collected for paleoclimatic studies. For climate information the absolute δ
2
H values of larch should be considered carefully and separate from other species.
Subfossil remains of wood and peat from six Swiss glaciers found in proglacial fluvial sediments indicate that glaciers were smaller than the 1985 reference level and climatic conditions allowed ...vegetation growth in now glaciated basins. An extended data set of Swiss glacier recessions consisting of 143 radiocarbon dates is presented to improve the chronology of glacier fluctuations. A comparison with other archives and dated glacier advances suggests 12 major recession periods occurring at 9850- 9600, 9300-8650, 8550-8050, 7700-7550, 7450-6550, 6150-5950, 5700-5500, 5200-4400, 4300-3400, 2800-2700, 2150-1850, 1400-1200 cal. yr BP. It is proposed that major glacier fluctuations occurred on a multicentennial scale with a changing pattern during the course of the Holocene. After the Younger Dryas, glaciers receded to a smaller extent and prolonged recessions occurred repeatedly, culminating around 7 cal. kyr BP. After a transition around 6 cal. kyr BP weak fluctuations around the present level dominated. After 3.6 cal. kyr BP less frequent recessions interrupted the trend to advanced glaciers peaking with the prominent ‘Little Ice Age’. This trend is in line with a continuous decrease of summer insolation during the Holocene.
This study reports on the cosmogenic 36Cl dating of two normal fault scarps in western Turkey, that of the Manastır and Mugırtepe faults, beyond existing historical records. These faults are elements ...of the western Manisa Fault Zone (MFZ) in the seismically active Gediz Graben. Our modeling revealed that the Manastır fault underwent at least two surface ruptures at 3.5 ± 0.9 ka and 2.0 ± 0.5 ka, with vertical displacements of 3.3 ± 0.5 m and 3.6 ± 0.5 m, respectively. An event at 6.5 ± 1.6 ka with a vertical displacement of 2.7 ± 0.4 m was reconstructed on the Mugırtepe fault. We attribute these earthquakes to the recurring MFZ ruptures, when also the investigated faults slipped. We calculated average slip rates of 1.9 and 0.3 mm yr−1 for the Manastır and Mugırtepe faults, respectively.
A brief review of the movements of Alpine glaciers throughout the Holocene in the Northern Hemisphere (European Alps) and in the Southern Hemisphere (New Zealand Southern Alps) is presented. It is ...mainly based on glacier studies where
14
C dating, dendrochronology and surface exposure dating with cosmogenic isotopes is used to establish the chronology of advances and retreats of glaciers. An attempt is made to draw some general conclusions on the temperature and climate differences between the Northern and Southern Hemisphere.
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