The Holocene 10,2 (2000) pp. 191–199

Discovery of early-Holocene wood and peat on the forefield of the Pasterze , Eastern , Kurt Nicolussi and Gernot Patzelt (Institute of High Mountain Research, University of Innsbruck, Innrain 52, A-6020 Innsbruck, Austria)

Received 18 February 1999; revised manuscript accepted 22 June 1999

Abstract: During recent years a number of fragments of Pinus cembra and Larix decidua as well as peat were found in front of the tongue of the Pasterze Glacier in the Eastern Alps. These were washed out by the stream from under the present ice. The wood originates from trees which reached ages of up to 400 years or more. Radiocarbon dating shows them to come from the early Holocene. They indicate that between cal. bc 8100 and cal. bc 6900 the Pasterze Glacier was smaller than at present. The Pasterze Glacier advanced around cal. bc 6900. A lump of peat shows that around cal. bc 6300 at the latest the Pasterze Glacier was again smaller than today. The radiocarbon age of the fulvic acid fraction of the peat suggests that growth could have continued until cal. bc 5430–5080. Further wood samples, dated to around cal. bc 4800 and cal. bc 3800, show that at these times the Pasterze Glacier was smaller than at present. The Pasterze Glacier had a relatively limited extent over long periods in the early Holocene. Thus mostly favourable climatic conditions can be inferred for these time periods.

Key words: Glacier fluctuations, Holocene, Eastern Alps, Austria, Pasterze Glacier, tree-line, dendrochronol- ogy, tree-rings, Larix decidua, Pinus cembra.

Introduction (Patzelt, 1985), hardly interrupted the retreat of the Pasterze Gla- cier (Wakonigg, 1991). Currently the length of the tongue is Direct evidence of early-Holocene glacier variations is relatively decreasing by about 15 m per year (Lieb, 1998a; 1998b). sparse, partly because later more advanced glacier positions The present altitude of the glacier front coincides with the destroyed many . This lack of knowledge is also valid potential tree-line, which lies at approximately 2100 m a.s.l. in for the identification of minimum glacier extents during the early the area around the Pasterze Glacier, but the present forest cover is Holocene. Lack of direct information has often been bridged reduced by anthropogeneous impact. During periods of maximum indirectly by using climatic reconstructions based on, for example, glacier extension, however, the Pasterze Glacier reached well into pollen analyses. Wood and peat found on the forefield of the Pas- the wooded area. Accordingly, logs and stumps have often been terze Glacier in the Eastern Alps provides new insight into early- found on the lower part of the forefield (Schlagintweit and Schlag- Holocene glacier history. intweit, 1850; Seeland, 1881; Paschinger, 1948; Patzelt, 1969). The Pasterze Glacier (N 47°06Ј10Љ,E12°41Ј70Љ) is situated in Wood relicts from glacier forefields can be used for reconstruc- the Hohe mountain group. In the vicinity of this glacier tions of glacier history in several ways (e.g., Furrer and annual mean air temperature at 2000 m above sea level is c.1°C Holzhauser, 1984). In principle, dendrochronological analysis per- and total annual precipitation c. 1200 mm (Tollner, 1969). With mits precise dating of tree death and thus a former glacier advance an area of 19.8 km2 and a length of about 9 km (Lang and Lieb, or even – especially for LIA advances – maximum extent. At the 1993) the Pasterze Glacier is the largest glacier in Austria. It same time, the tree-ring series gives the time period during which extents over about 1700 m of altitude, its tongue presently termin- the glacier did not reach the position of the tree, indicating a ating at c. 2070 m a.s.l. (Figure 1). smaller extent. As yet, absolute datings of wood remains from During the last ‘’ (LIA) culmination in the mid- glacier forefields have been limited to the last millennium mostly. nineteenth century the tongue of the Pasterze Glacier reached For former periods with a sufficient number of samples, however, down to 1890 m a.s.l. (Patzelt, 1969). Since then it has retreated tree-ring series can be at least relatively synchronized. Their almost continuously, only interrupted by stagnation or slight absolute ages have to be determined by radiocarbon dating advance in the years around 1920 (Wakonigg, 1991). The advance because of the lack of dated chronologies of sufficient length (e.g., period around 1980, which was widely observed in the Alps Holzhauser, 1997; Nicolussi and Patzelt, 1996). Wood is a  Arnold 2000 0959-6836(00)HL378RP 192 The Holocene 10 (2000)

Figure 1 The lower part of the Pasterze Glacier and surrounding area. particularly suitable material for radiocarbon dating; the number of The first discoveries, of two logs and a number of peat remains, tree-rings accurately indicates the time period represented by the were made in 1990 by H. Slupetzky (1993). Radiocarbon dating sample, and difficulties involved in the dating of soils are avoided. gave surprisingly early ages of 8000 ± 80 BP and 8345 ± 80 BP (cal. bc 7030–6760 and cal. bc 7485–7290; calibration after Stuiver and Reimer, 1993) for sample TREE I and 9180 ± 80 BP Findings and methods (cal. bc 8335–8080) for TREE II. One of the two logs from which only small wood samples were collected at first was recovered The retreat of the Pasterze Glacier during recent decades has led after radiocarbon dating was carried out (Slupetzky, 1993). A to the formation of a forefield where glacifluvial processes prevail, cross-section of this log (TREE I/PAZ-5) was made available for which includes an outwash lake (Figure 2). The proglacial area dendrochronological analysis. The two radiocarbon datings of this is characterized by a more or less braided glacial stream, log have been made at two laboratories (Table 2) and differ mark- depending on the amount of meltwater, with changing runoff edly. As the two samples for these radiocarbon datings have not channels. Repeatedly, logs and pieces of wood have been found been taken dendrochronologically defined from the log TREE on it during recent years. These include obviously modern wood I/PAZ-5, tree-ring sequences of differing age were probably material such as pieces of boards and beams, assumed to originate recorded and analysed. The condition of the log supports this from construction work in the area around the Pasterze Glacier, explanation of the differing results. Initially without knowledge but also untreated logs and log fragments, some of which were of the findings made by H. Slupetzky, the authors found and heavily weathered. Allochthonous peat remains have also been sampled a number of pieces of wood of various sizes, including released from the ice. parts of logs and also branches, during annual inspections of the proglacial area made since 1991 (Table 1). Additionally lumps of peat with diameters up to 25 cm were found. Some of the peat fragments, many of them very compressed, lay near to pieces of wood. Neither the wood nor the peat was found in situ, but having been transported by the glacial stream from beneath the ice and deposited when the transport capacity of the stream decreased. The wood and peat remains were found from about 30 m to about 300 m away from the glacier front. Between 1991 and 1997, new wood and peat material was found on the forefield every year. Towards the end of this period, however, only smaller pieces were collected. In 1998, for the first time, no new material could be found although the proglacial area was inspected twice. The size of the pieces of wood varies markedly. Besides smaller fragments, with lengths of some decimetres, pieces of logs of up to 295 cm length (PAZ-25) were found. Not all of them included contained the pith (Table 1). Some of the wood fragments con- sisted of the peripheral parts of logs. For these samples, the miss- ing number of tree-rings to the pith was estimated on the basis of Figure 2 The proglacial area in front of the partially debris-covered gla- the radius of curvature radius of the piece and the widths of the cier tongue of the Pasterze (photograph by K. Nicolussi, 23 August 1997). measured tree-rings (Table 1; Figure 3). Kurt Nicolussi and Gernot Patzelt: Discovery of early-Holocene peat and wood at the Pasterze Glacier, Austrian Alps 193

Table 1 The early-Holocene wood material from the forefield of the Pasterze Glacier. For samples with missing inner part, the minimum age of the tree includes the estimated number of rings for this inner part. For samples with compressed tree-rings at the outside of the log, which cannot be measured, the estimated number of these tree-rings was included (see Figure 3)

Sample Tree species Pith preserved Mean tree-ring width Measured tree-ring series Estimated minimum tree-age (mm) (n) (n)

PAZ-1 Pinus cembra yes 0.60 210 230 PAZ-2 Pinus cembra – 0.58 91 165 PAZ-4 Pinus cembra yes 0.30 301 390 PAZ-5a Pinus cembra yes 1.14 143 225 PAZ-16 Larix decidua – 0.29 311 440 PAZ-21 Larix decidua – 0.40 143 230 PAZ-22 Larix decidua – 0.62 116 145 PAZ-23 Larix decidua – 0.40 175 275 PAZ-24 Pinus cembra yes 0.51 128 155 PAZ-25 Larix decidua yes 1.87 88 95 PAZ-26 Larix decidua – 0.25 248 400 PAZ-27 Larix decidua yes – – c. 100 PAZ-28 Larix decidua – 0.52 114 205 PAZ-29 Larix decidua yes 0.33 76 76 PAZ-31 Pinus cembra – 0.37 121 170 PAZ-32 Pinus cembra yes 1.52 76 76 PAZ-33 Larix decidua – 0.77 144 150 a TREE I (Slupetzky, 1993).

Table 2 Results of the radiocarbon dating of subfossil wood and peat remains from the forefield of the Pasterze Glacier

Sample Material Radiocarbon dated Lab. no. Radiocarbon age Calibrated agea Calibrated age, 1␴ rangea tree-rings (no. of series) (yr BP) (yr cal. bc) (yr cal. bc)

PAZ-1 wood 1–16 Hd 14819- 8210 ± 25 7252, 7214, 7207, 7265–7090 14353 7174, 7147, 7114, 7103 PAZ-2 wood 17–42 Hd 16847- 8615 ± 32 7576 7585–7540 16360 PAZ-4 wood 260–290 Hd 14252- 8240 ± 25 7265 7300–7100 14873 PAZ-5b wood –c VRI 1231 8000 ± 80 7001, 6835, 6818 7030–6760 PAZ-5b wood –c Hv 17781 8345 ± 80 7425 7485–7290 PAZ-16 wood 1–31 Hd 16846- 8238 ± 34 7264 7300–7200 16365 PAZ-22 wood 1–17 GrN 23757 8780 ± 35 7897, 7760, 7740 7925–7705 PAZ-23 wood 1–16 Hd 17613- 8844 ± 27 7932 7960–7910 17699 PAZ-24 wood 75–99 Hd 17614- 5066 ± 20 3932, 3872, 3811 3945–3800 17687 PAZ-25 wood 65–77 Hd 17615- 8816 ± 36 7917 7945–7730 17692 PAZ-27 wood (c. 1–40) GrN 23775 9040 ± 35 8040 8085–8025 PAZ-29 wood 1–76 GrN 23794 9010 ± 40 8032 8060–8015 PAZ-31 wood 98–121 GrN 23758 8820 ± 35 7919 7950–7735 PAZ-32 wood 1–14 GrN 23776 5995 ± 25 4859 4890–4840 PAZ-34T peat – GrN-23777 7510 ± 50 6368 6390 ± 6225 PAZ-34T alkali extract – GrN 23903 7470 ± 60 6351, 6325, 6297, 6380–6185 6284, 6245 PAZ-34T fulvic acid – GrN 23904 6330 ± 140 5266 5430–5080 a Radiocarbon age calibration of Stuiver and Reimer (1993), using CALIB rev. 3.0.3. b TREE I (Slupetzky, 1993). c Sample not dendrochronologically defined, dated material from the outside the log (Slupetzky, 1993).

Nearly all sampled wood was at least partially compressed. The For wood samples with missing pith, the estimated number of outer parts, especially, of several pieces were so compressed that missing inner rings is added to the minimum lifespan (Table 1). a dendrochronological analysis of these sections was not possible. Missing peripheral parts, like missing sapwood sections in sample The number of tree-rings was estimated for each of these com- PAZ-28 for instance, on the other hand, were not included in the pressed sections. For samples with preserved pith, this figure, minimum lifespan given. together with the dendrochronologically recorded tree-rings, pro- In one case (PAZ-27; Table 1), the tree-rings could hardly be vides the basis for determining the minimum lifespan of the trees. differentiated, and the wood was compressed to three times its 194 The Holocene 10 (2000)

Figure 3 Age of the early-Holocene wood material from the forefield of the Pasterze Glacier, according to radiocarbon and dendrochronological dating. The chronology of the wood samples is based on the calibrated ages of the dendrochronologically defined radiocarbon ages. The dendrochronological position of the radiocarbon sample of the log PAZ-5 (= TREE I; Slupetzky, 1993) was estimated. normal density (Grosser, 1977). For this sample, a dendrochrono- only Larix was recorded before cal. bc 7600, after this date, with logical analysis was not possible, and the minimum lifespan could the exception of samples PAZ-16 and PAZ-26, only Pinus cembra only be estimated. For the remaining wood material from the gla- material was found. Some of the Boreal wood from the glacier cier forefield, tree-ring widths could be measured, though the forefield reached considerable ages. Tree-ring series of more than samples were partially compressed. These measurements were 300 rings could be constructed for some samples. In addition to made to provive a basis at least for relative dating of the material. this, some logs show compressed sections in the most peripheral Some pieces of wood, although they had rings which could be parts, in which the tree-ring widths cannot be measured. This pro- analysed, nevertheless could not be securely synchronized with vides individual ages of more than 400 years for some logs (Table other samples according to ring characteristics. Such pieces were 1). This minimum lifespan sometimes includes estimated numbers radiocarbon dated. Some pieces with few or very compressed tree- of tree-rings of missing central parts of logs. The analysed tree- ring sequences, which do not allow dendrochronological analysis, ring widths are mostly low (Table 1), which can be explained by have not as yet been dated. A defined number of tree-rings was the altitude in which the trees grew. taken from the wood samples for radiocarbon dating (Table 2). Only the sample PAZ-29, a small branch, was found to have a In addition to being radiocarbon dated, the peat was investigated terminal ring. This piece even showed parts of the bark. It was pollen-analytically by W. Kofler (Institute of Botany, University not possible to define the terminal ring on any of the other frag- of Innsbruck, 1998). ments. On the other hand, parts of the strongly compressed outer sections of the trees that died around cal. bc 7000 probably consist of sapwood. This holds true especially for sample PAZ-5, which Results has a bark-like appearance on the outside. The wood fragments could only be partially synchronized Radiocarbon dating and dendrochronological synchronization among themselves (PAZ-21, PAZ-23, PAZ-28 and PAZ-33, and show that the wood from 15 samples was growing earlier than PAZ-16 and PAZ-26, respectively). The very similar records of about cal. bc 6900, and that two others, as well as a lump of peat, samples PAZ-21, PAZ-23 and PAZ-28 suggest that these three grew within the three following millennia (Table 2; Figure 3). pieces come from the same tree (Figure 4). These wood samples Dated samples practically cover the period between cal. bc 8100 were, however, found over a period of three summers. Most prob- and cal. bc 6900, corresponding to the Boreal, except there is little ably the samples PAZ-16 and PAZ-26 also originate from a com- evidence of tree growth around cal. bc 7700/7600. According to mon tree. They, too, were washed out in different years. the uncalibrated radiocarbon datings of PAZ-2, PAZ-4 and PAZ- As yet there is little comparable material which has been found 22, which fall into this period, the tree-ring series of this samples from the Eastern Alps and which could be synchronized with the overlap slightly (Table 2). For sample PAZ-5 (= TREE I; Slup- early-Holocene wood from the Pasterze Glacier using the charac- etzky, 1993), of which a dendrochronologically undefined sample teristics of tree-rings. Some of the latter were successfully synch- was taken for radiocarbon dating, the younger result (Table 2) ronized with the tree-ring series of a larch log from a high-altitude was considered realistic and hence used. The wood samples PAZ- bog near Serfaus, approximately 170 km west of the Pasterze Gla- 32 and PAZ-24, which were radiocarbon dated to c. cal. bc 4800 cier. Both the mean record of samples PAZ-21/23/28/33 and the and c. cal. bc 3800 (5995 ± 25 BP and 5066 ± 20 BP; Tables 1 series PAZ-22 can be synchronized with this larch record (Figure and 2), are chronologically isolated. 5). The synchronizations show an overlap, however limited, The wood remains found belong to the species of Larix decidua between the mean record of PAZ-21/23/28/33 and the series PAZ- and Pinus cembra. With one exception (PAZ-31; Tables 1 and 2), 22 (Figure 3). This relative dating means that sample PAZ-22 Kurt Nicolussi and Gernot Patzelt: Discovery of early-Holocene peat and wood at the Pasterze Glacier, Austrian Alps 195

Figure 4 Synchronization of four early-Holocene wood findings from the Pasterze Glacier: PAZ-21, PAZ-23, PAZ-28 and PAZ-33.

Figure 5 Synchronization of the mean series of PAZ-21/23/28/33 and the series PAZ-22 with the tree-ring record KPD-3/8 from Western . cannot be shifted to the beginning of the Boreal, which would be a situation close to the tree-line or open-forest conditions. A wood possible according to the 1␴ range of the calibrated radiocarbon fragment of Salix in the peat material shows that this species was age of PAZ-22 (Figure 3). Thus there is practically no gap in the present at the site. The forest-forming species like Picea abies, wood remains from the forefield of the Pasterze Glacier around Pinus cembra and Larix decidua probably grew very close to the cal. bc 7600. peat, without forming a dense stand (Kofler, 1998). The peat found appears to be somewhat younger than the The log fragment PAZ-32 was dated to c. cal. bc 4800 Boreal wood remains (Table 2). All three available radiocarbon (5995 ± 25 BP; Tables 1 and 2), which is slightly younger than datings fall into the Atlantic period. Peat and alkali extract gave the fulvic acid of the peat material PAZ-34T (Table 2). Large virtually similar results of cal. bc 6390–6225 (7510 ± 50 BP) and parts of the section of this log are missing, which prevents more cal. bc 6380–6185 (7470 ± 60 BP). Compared to this, the fulvic precise dating of the death of the tree. Virtually the entire section acid fraction of the peat material provided a markedly younger as well as still-projecting parts of branches of the log PAZ-24 age of cal. bc 5430–5080 (6330 ± 140 BP). As the peat sample have been preserved. As with PAZ-5 (Table 1) the outermost parts consists of redeposited material, it is not possible to determine of the log consist of compressed sections of wood with a bark- the beginning of the formation of the peat complex from which like appearance. The compressed wood prevented continuous sample PAZ-34T comes. The radiocarbon age of the fulvic acids, measurements to the outside of the log; the lifespan of this tree which are mobile and usually younger than the other fractions, of about 155 years could therefore only be estimated. Neverthe- however, provides some indication of the minimum duration of less, this estimate provides evidence of the time of death of the the peat formation (Matthews, 1985). Based on these results, peat tree. With an age of c. cal. bc 3800 (5066 ± 20 BP) sample PAZ- formation can be assumed to have occurred from at least c. cal. 24 is the youngest piece of subfossil wood from the Pasterze Gla- bc 6300 to around or shortly after cal. bc 5430–5080 for a part cier so far found. of the forefield of the Pasterze Glacier which is still ice-covered at present. Discussion The pollen-analytical investigation of the peat material (Kofler, 1998) shows 75% of arboreal pollen, which is typical for sites Origin of the wood and peat material near the tree-line. The presence of light-demanding species and Determining the growth sites of the trees is essential for assessing the high contribution of Salix (30%) provide further indicators for the findings of wood from the Pasterze Glacier. These sites must 196 The Holocene 10 (2000) lie up the valley of the present termination of the glacier. In prin- the outermost rings, is included, the period of a glacier being ciple, either the valley bottom or the presently treeless slopes smaller than today goes back to at least cal. bc 8400–8300. Taking would be possible sites. The latter, however, are very steep, so into account the 1␴ range of the calibration this tree could be frequently avalanches would probably have prevented the growth much older, however. This would lead to a marked gap between of several hundred-year-old trees. More over only the lower parts TREE II and the Boreal wood samples. Hence an interruption of of these slopes would be possible sites for the growth of the trees, tree growth in the forefield of the Pasterze Glacier caused by a as the tree-line around the Pasterze Glacier can be assumed to be glacier advance shortly before cal. bc 8100 has to be considered at c. 2100 m a.s.l. (Schiechtl et al., 1984; Slupetzky, 1993). Thus possible. this line lies only a little above the proglacial area (approximately The Boreal wood findings clearly end at c. cal. bc 6900. It is 2070 m a.s.l.) and the altitude at which the wood remains were assumed that this is due to an advance of the Pasterze Glacier. found. Even under the assumption of a slightly higher tree-line This assumption is supported by the very compressed outermost due to more favourable climatic conditions, and disregarding the sections of samples PAZ-1, PAZ-5 and PAZ-16/26. avalanche situation in the glacier forefield, the trees must have The extent and duration of this glacier advance remain unclear. grown within the ice-covered area of the mid-twentieth century. Around cal. bc 6300, at the latest, the peat finding (PAZ-34T) In view of the avalanche situation near the present glacier tongue, indicates peat formation in a part of the forefield of the Pasterze it seems possible that the trees grew as much as 1–1.5 km upval- Glacier which is still ice-covered today. If the glacier buried the ley of the present glacier front. Because of the topographic situ- site of the peat formation before cal. bc 6300, this radiocarbon ation, the sites of growth of the subfossil wood remains must lie date brackets the early Atlantic advance. The date of cal. bc 6300, on the presently ice-covered valley bottom. This is supported by however, gives only a maximum duration of the advance period, the finding of a log with stump (PAZ-25) and also lumps of peat as the investigated peat material does not necessarily date the (see also Slupetzky, 1993). beginning of the peat formation. As the peat material found is The peat findings further indicate that not all logs or parts of allochthonous it cannot be ruled out that the Pasterze Glacier did logs were necessarily killed by a glacier advance. The flatness of not reach the site of the peat formation with the advance of c. cal. the tongue of the Pasterze Glacier up to its boundary formed by bc 6900 and thus, during the early Atlantic, was not bigger than the steep step of the so-called Hufeisenbruch suggests a relatively at present. flat valley bottom, probably with roches moutone´es. Measure- The advance of the Pasterze Glacier around cal. bc 6900 (8000 ments of the ice thickness show marked overdeepening in some BP) is contemporary with the Venediger oscillation. The latter parts (N. Span, Institute of Meteorology and Geophysics, Univer- was initially dated to the period between 8700 and 8000 BP sity of Innsbruck, personal communication). It can be assumed (approximately cal. bc 7700 to cal. bc 6900) on the basis of radi- that under longer ice-free conditions more or less extensive bogs ocarbon dated minimum ages of moraines and pollen records from formed on the valley bottom. Trees growing on the neighbouring bogs in the vicinity of the glacier forefields in the Venediger roches moutone´es could have fallen into the bogs after their natu- mountain group (Patzelt and Bortenschlager, 1973). Two clearly ral death, where they were preserved. During subsequent glacier separated ridges outside the LIA maximum extents of the advances they became surrounded by till. Thus not all wood Simony-, Dorfer- and Schlatenkees were found to have remains necessarily need to indicate glacier advances, which minimum ages before 7500 BP (cal. bc 6300). No age difference makes it easier to explain the range of dates for the death of the could be found between these so-called Venediger moraines. A wood found. The surface condition of some of the wood further pollen record at the Rostocker Hu¨tte near Simonykees shows three supports a former storage in peat material. marked depressions of the tree-line during the first part of the Holocene, slightly after 8720 ± 150 BP (cal. bc 7910–7580), Glacier variations in the Boreal and early Atlantic around 8340 ± 130 BP (cal. bc 7500–7100) and around With few exceptions, the wood found dates approximately to the 8040 ± 120 BP (cal. bc 7250–6700). A further pollen record from Boreal. The tree-ring series of these samples cover nearly the a site near Schlatenkees also shows a marked reduction of the entire period from about cal. bc 8100 to cal. bc 6900. Only around forest vegetation for the same period. Based on the climatic min- cal. bc 7600 is there less evidence or a gap, according to the ima indicated by these pollen records a date between 8700 and results available at present (Figure 3). It is currently unclear 8000 BP (c. cal. bc 7700 to cal. bc 6900) was inferred for the whether the smaller number of samples indicates a glacier deposition of the Venediger moraines. advance, or is due to a purely random distribution of the wood This model must be modified in view of the findings of wood found. Another possible cause would be a decrease of the forest in the forefield of the Pasterze Glacier. According to these, the cover around cal. bc 7600, as pollen records from the nearby Venediger period was climatically mostly favourable. It seems Venediger mountain group show a depression of the tree-line at possible that a minor glacier advance occurred the time around this time (Patzelt and Bortenschlager, 1973). The limited time to cal. bc 7700, for which few wood remains were found on the the next evidence found for the growth of trees (Figure 3), on the forefield of the Pasterze Glacier (Figure 3). This coincides with other hand, means that a possible glacier advance could not have a depression of the tree-line indicated by the pollen records been extensive. (Patzelt and Bortenschlager, 1973). However, new investigations Possibly the very compressed sample PAZ-27 and the branch of glaciers in the Venediger mountain group (G. Patzelt, unpub- PAZ-29 record an advance of the Pasterze Glacier around cal. lished data) have produced a minimum age of c. 8200 BP (c. bc 8000. This advance, however, could not have reached the cal. bc 7200) for the deposition of the Venediger moraines of Sim- samples PAZ-21/23/28/33, PAZ-25 and PAZ-31, which date vir- onykees. In view of the findings at the Pasterze Glacier, the Vene- tually to the same time or only little later, and it could therefore diger moraines, which mark glacier extents outside the LIA have been only a minor advance of relatively little importance. maximum, were probably deposited in the Preboreal. The findings of wood from the forefield of the Pasterze Glacier At the end of the period of tree growth documented by wood provide evidence of a period of predominantly limited extent of from the forefield of the Pasterze Glacier around cal. bc 6900, on the ice lasting c. 1200 years from about cal. bc 8100 to cal. the other hand, there is evidence for a glacier advance period, bc 6900. Probably the glacier was smaller than at present through- during which the Pasterze Glacier is assumed to have been larger out the period. If TREE II (Slupetzky, 1993), for which there is than at present. The new investigations of glaciers in the Vene- only an estimated number of 200 to 300 tree-rings and a radiocar- diger mountain group confirm generally larger glacier extents for bon dating of 9180 ± 80 BP (VRI-1291; cal. bc 8335–8080) for this advance (G. Patzelt, unpublished data). A bog at Zettalunitz- Kurt Nicolussi and Gernot Patzelt: Discovery of early-Holocene peat and wood at the Pasterze Glacier, Austrian Alps 197 kees in the Venediger group was covered by glacial sediments 1993), as well as to other problems that may occur with radiocar- shortly after c. 8000 BP (c. cal. bc 6900); this situation indicates bon dating (Geyh, 1990; Holzhauser, 1997). a glacier extent comparable with the LIA maximum. An inwash Data from Scandinavia indicates a period of glacier advance of glacial material into a bog outside the LIA moraines of Simony- after cal. bc 6900 (8000 BP). Dahl and Nesje (1994) found evi- Kees was dated slightly younger to c. 7600 BP (c. cal. bc 6450). dence for a glacier advance culminating around 7590 ± 120 BP Few findings of Boreal wood remains comparable with those (cal. bc 6480–6230) in the Finse area of southern Norway. Before from the Pasterze Glacier have been reported from other glaciers. this, the glaciers here were smaller than today at least since the A Pinus cembra fragment from the forefield of in early Boreal. Based on the deposition of silty material in the lake the Western Alps was radiocarbon dated to 8160 ± 220 BP (cal. sediments of Vuolep Allakasjaure in northern Sweden between bc 7450–6750), the site of the finding suggests that the extent was 7765 ± 100 BP (cal. bc 6700–6420) and 7210 ± 100 BP (cal. bc then comparable with that in the 1920s (Ro¨thlisberger et al., 6170–5950), Karle´n (1988) assumed that the first major period of 1980). Wood remains found on the forefield of the Unteraargla- glacier advances in the Holocene occurred around 7500 BP. cier, Western Alps, with radiocarbon dates of c. 8000 BP (c. cal. bc 6900) and c. 7700 BP (c. cal. bc 6500), respectively, are Data from the later Atlantic indicating a smaller extent of this glacier than today (Hormes et For this period there are as yet merely single findings from the al., 1998). Osborn and Luckman (1988) also reported findings Pasterze Glacier, allowing only limited interpretation of the data. comparable to those at the Pasterze Glacier from the Athabasca Based on the radiocarbon age of the fulvic acid fraction of the Glacier, Canada. Two peat remains which were found near the peat sample indicating a smaller extent of the Pasterze Glacier present termination of the glacier tongue provided radiocarbon than at present, peat formation, starting not later than c. cal. ages of 8230 ± 80 BP (cal. bc 7410–7050) and 8000 ± 90 BP (cal. bc 6300 could have lasted at least until cal. bc 5430–5080 ± bc 7040–6710). From these findings a smaller glacier extent than (6330 140; Table 2). Possibly this small glacier extent may have at present was inferred for the period from 8200 to 8000 BP (c. lasted until after cal. bc 4800. Then the tree PAZ-32 grew at a cal. bc 7200 to cal. bc 6900; Osborn and Luckman, 1988). site which is still ice-covered today. Also for the Unteraarglacier The advance of the Pasterze Glacier around cal. bc 6900 (8000 a smaller extent than today is proved for the same time by findings BP) discussed in this paper is partly inconsistent with results from of wood with radiocarbon ages of c. cal. bc 4900 and cal. bc 4700 ± ± ± the Western Alps. A number of investigations of sections of gyttja (6032 36, 6032 28, 5804 28; Hormes et al., 1998), respect- and peat close to the present termination of the glacier tongue ively. Again there is evidence from Rutor Glacier in the Western were carried out at Rutor Glacier in the Aosta Valley, Alps for a relatively small glacier extent around cal. bc 4900, (Armando et al., 1975; Armando and Charrier, 1985; Porter and which is comparable to the situation at the Pasterze Glacier. At Orombelli, 1985; Burga, 1991; 1993; Orombelli and Mason, Rutor Glacier peat close to the present termination of the glacier ± 1997). In addition to this, peat material redeposited in the forefield tongue was covered by glacial material after 6055 95 BP (cal. area was investigated (Charrier and Peretti, 1975). The radiocar- bc 5070–4830; Burga, 1991; 1993). Virtually at the same time, bon ages of the dated peat and gyttja samples range from 9000 Frosnitzkees in the Eastern Alps showed a maximum glacier ± BP to 3500 BP (cal. bc 8000 to cal. bc 1800; Armando et al., extent comparable to the LIA around 6130 130 BP (cal. 1975; Charrier and Peretti, 1975; Orombelli and Mason, 1997). bc 5220–4910; Patzelt and Bortenschlager, 1973). Datings for gla- The basal gyttja samples of these sections were dated to ciers in Scandinavia also show an advance period around cal. 9015 ± 495 BP (cal. bc 9000–7400, Orombelli and Mason, 1997) bc 4900, which, however, did not reach the LIA extents (Karle´n, and 8270 ± 95 BP (cal. bc 7430–7090; Burga, 1991; 1993). The 1988; Dahl and Nesje, 1994). If the tree PAZ-32 was covered by base of the overlying peat sections also gave a wide range of an advance of the Pasterze Glacier which falls within the Frosnitz dates between 9070 ± 120 BP (cal. bc 8330–7970; Orombelli and oscillation, this glacier reacted much later than others, and it can Mason, 1997) and 6735 ± 100 BP (cal. bc 5690–5500; Burga, be assumed that the Pasterze Glacier did not reach a larger exent 1991; 1993). While Burga (1991; 1993) assumes an undisturbed during the Frosnitz oscillation. sequence of gyttja and peat, Orombelli and Mason (1997) do not The youngest subfossil wood so far found at the Pasterze Gla- rule out that the peat growth was interrupted by glacier advances. cier (PAZ-24) died at c. cal. bc 3800 (Table 2). This provides Armando et al. (1975) also report alternating sequences of peat evidence that before this date the glacier was smaller than at and sediment layers. These investigations suggest the Rutor Gla- present for at least almost two centuries. The condition of the log cier was small during most of the Boreal, which is in agreement shows that this tree was overrun by an ice advance. This advance with the findings of wood at the Pasterze Glacier. According to of the Pasterze Glacier around cal. bc 3800 corresponds to the Burga (1991; 1993) Rutor Glacier would not have been larger Rotmoos-I oscillation (Bortenschlager, 1970), which ended at than at present in the period between 8270 ± 95 BP and 6055 ± 95 approximately the same time. A comparable finding to that of BP (cal. bc 7430–7090 and cal. bc 5070–4830). sample PAZ-24 was made at the Tschierva Glacier in eastern A peat deposit was found in situ at 2160 m a.s.l. in the forefield (Schollenberger, 1976, in Ro¨thlisberger et al., 1980). area of Gauli Glacier in Switzerland (Wa¨spi, 1993). The site was There a part of a log, found in front of the glacier snout in 1968, ± ice-covered until the beginning of the 1960s. Several basal indicating a smaller ice extent, was dated to 5160 70 BP (cal. samples as well as material from the top of peat with a maximum bc 4040–3800). The end of the peat formation in a profile which depth of 50 cm were radiocarbon dated. The basal age was lies relatively close to the present termination of Rutor Glacier ± 7830 ± 75 BP (cal. bc 6700–6500); samples from overlying parts (Orombelli and Mason, 1997) was dated to 5045 95 BP (cal. of the section were dated to 8015 ± 110 BP and 8165 ± 100 BP bc 3950–3780). This date provides a minimum age for the glacial (cal. bc 7045–6660 and cal. bc 7300–7030), which is remarkable sediments covering the section. Evidence for glacier advances as it shows inverted ages. These radiocarbon dates indicate that around 5100 BP (c. cal. bc 3900), following a period of favour- Gauli Glacier was smaller than in the 1960s at the end of the able climatic conditions, was also found in Scandinavia (Karle´n, Venediger oscillation. Whether these dates are accurate cannot be 1988). decided at this stage, as Wa¨spi (1993) assumes on the basis of the pollen assemblage that the radiocarbon ages of the basal peat Conclusions are several hundred years too old. Some of the inconsistencies are due to the marked variations of the radiocarbon content in the The dating of wood found on the forefield of the Pasterze Glacier atmosphere around 8200 BP (c. cal. bc 7200; Pearson et al., in recent years shows that at least between cal. bc 8100 and cal. 198 The Holocene 10 (2000) bc 6900 this glacier was not larger than at present. A minor gla- Industrialists, and the Austrian Science Fund, project P13065- cier advance around cal. bc 8000 seems possible, however. During GEO. this advance the glacier could not have been very large as trees were still growing in the glacier forefield. At the transition between Boreal and Atlantic, the dated wood samples docu- References menting tree growth on the forefield, end with an advance of the Pasterze Glacier around cal. bc 6900. The maximum extent of the Armando, E. and Charrier, G. 1985: La torbiera del Rutor (Valle glacier during this advance is not known. At least during parts of d’Aosta). Relazioni sui risultati conseguiti dallo studio palinostratigrafico the Atlantic peat formation and tree growth was possible on parts di nuovi affioramenti torbosi segnalati alla fronte attuale del ghiacciaio. of the forefield of the Pasterze Glacier which are ice-covered at Geografia Fisica e Dinamica Quaternaria 8, 144–49. present. According to the dating of an allochthonous peat sample Armando, E., Charrier, G., Peretti, L. and Piovano. G. 1975: Ricerche sull’ evoluzione del clima e dell’ ambiente durante il Quaternario nel set- the glacier was smaller than at present by around cal. bc 6300 at tore delle Alpi Occidentali Italiane. Bollettino del Comitato Glaciologico the latest. Dating of the fulvic acid fraction of the peat material Italiano 23, 7–25. suggests that this period of smaller glacier extent than today may Bortenschlager, S. 1970: Waldgrenz- und Klimaschwankungen im pol- possibly have lasted until about cal. bc 5200. Another date on lenanalytischen Bild des Gurgler Rotmooses. Mittl. Ostalp.-dinar. Ges. wood provides evidence that the Pasterze Glacier was smaller than Vegetationskunde 11, 19–26. at present around c. cal. bc 4800. An advance of the Pasterze Burga, CA.A. 1991: Vegetation history and palaeoclimatology of the Glacier was dated to c. cal. bc 3800; before this the glacier was Middle Holocene: pollen analysis of alpine peat bog sediments, covered smaller than today for a period of at least 155 years. formerly by the Rutor Glacier, 2510 m (Aosta Valley, Italy). Global Ecol- It has been shown that the Pasterze Glacier was smaller than it ogy and Biogeography Letters 1, 143–50. is now during many periods in the early Holocene, some of which —— 1993: Das mittelholoza¨ne Klimaoptimum Europas: Palynologische Untersuchungen an einem ehemaligen hochgelegenen Moor am Rutor- were lengthy. The finding of Boreal wood on the forefield of the Gletscher, 2510 m (Aosta-Tal, Italien). Dissertationes Botanicae 196, Pasterze Glacier indicates climatic conditions mainly unfavour- 335–46. able for glaciers for most of the Venediger oscillation, which has Charrier, G. and Peretti, L. 1975: Analisi palinologica e datazione radio- so far been dated at 8700–8000 BP (cal. bc 7700–6900). These metrica 14C di depositi torbosi intermorenici della regione alpina piemon- findings from the Pasterze Glacier agree with those from other tese, applicate allo studio del clima e dell’ ambiente durante il Quaternario glaciers in the Alps, such as the Rutor Glacier. The advance per- superiore. Bollettino del Comitato Glaciologico Italiano 23, 51–66. iod at the transition between the Boreal and Atlantic, identified at Dahl, S.O. and Nesje, A. 1994: Holocene glacier fluctuations at Hardang- the Pasterze Glacier, on the other hand, does not entirely agree erjøkulen, central-southern Norway: a high resolution composite chron- with the results from the Rutor Glacier. There is evidence for ology from lacustrine and terrestrial deposits. The Holocene 4, 269–77. glacier advances at the beginning of the Atlantic both from other Furrer, G. and Holzhauser, H. 1984: Gletscher- und klimageschichtliche Auswertung fossiler Ho¨lzer. Zeitschrift fu¨r Geomorphologie, Suppl. Bd. glaciers in the Eastern Alps and from Scandinavia. 50, 117–36. The maximum extents of the Pasterze Glacier during the glacier Gamper, M. and Oberha¨nsli, H. 1982: Interpretation von Radiocarbon- advances discussed in this paper are not known. This question daten fossiler Bo¨den. Physische Geographie 1, 83–90. cannot be determined on the basis of the allochthonous wood and Geyh, M.A. 1990: Radiocarbon dating problems using acetylene as coun- peat findings. Possibly the glacier terminated at a position inside ting gas. Radiocarbon 32, 321–24. or only little beyond its present extent around c. cal. bc 6900 Grosser, D. 1977: Die Ho¨lzer Mitteleuropas. Berlin: Springer-Verlag. for instance. The topographic situation of the Pasterze Glacier in Holzhauser, H. 1997: Fluctuations of the Grosser Aletsch Glacier and the connection with long periods of favourable climate in the early Gorner Glacier during the last 3200 years: new results. In Frenzel B., Holocene may explain why the glacier remained comparatively Boulton G.S, Gla¨ser B. and Huckriede, U., editors, Glacier fluctuations small during these advances. The Pasterze Glacier is characterized during the Holocene, Pala¨oklimaforschung 16, 35–58. Hormes, A., Schluchter, CA. and Stocker, T.F. 1998: Minimal extension by relatively high-lying accumulation areas and a large flat glacier ¨ phases of Unteraarglacier () during the Holocene based on 14C tongue which is connected to the former over steep drops and ice analysis of wood. Radiocarbon 40, 809–17. falls (Figure 1). It can be assumed that once the Pasterze Glacier Karle´n, W. 1988: Scandinavian glacial and climatic fluctuations during had retreated to a position far behind its present termination a the Holocene. Quaternary Science Reviews 7, 199–209. long climatic deterioration or period of conditions favouring gla- Kofler, W. 1998: Pollenanlyse Probe Paz-34T. Unpublished report, 4 pp. cier expansion was necessary to bring the glacier to approximately Lang, H. and Lieb, G.K. 1993: Die Gletscher Ka¨rntens. Klagenfurt. its present extent. Investigations at the Pasterze Glacier indicate Lieb, G.K. 1998a: Gletschermessungen 1995 an und in der Umgebung that such conditions were rare in the early Holocene. der Pasterze (Glocknergruppe). Zeitschrift fu¨r Gletscherkunde und Glazi- Possibly periods in the early Holocene favourable for glacier algeologie 34(1), 85–88. growth were intensive enough to cause other, smaller and more —— 1998b: Gletschermessungen 1996 und 1997 an der Pasterze (Glocknergruppe). Zeitschrift fu¨r Gletscherkunde und Glazialgeologie sensitive glaciers to reach positions comparable with those in the 34(1), 89–94. ‘Little Ice Age’, though these periods were too short to cause the Matthews, J.A. 1985: Radiocarbon dating of arctic-alpine palaeosols and Pasterze Glacier to expand to extents comparable with those in the reconstruction of Holocene palaeoenvironmental change. In Chambers, recent centuries. F.M., editor, Climate change and human impact on the landscape, London: Chapman & Hall, 83–96. Nicolussi, K. and Patzelt, G. 1996: Reconstruction galcier history in Tyrol Acknowledgements by means of tree-ring investigations. Zeitschrift fu¨r Gletscherkunde und Glazialgeologie 32, 207–15. We wish to thank H. Slupetzky for providing a stem disk of TREE Orombelli, G. and Mason, P. 1997: Holocene glacier fluctuations in the I/PAZ-5 for dendrochronological analysis, as well as B. Kromer, Italian alpine region. In Frenzel, B., Boulton, G.S., Gla¨ser, B. and Huck- riede, S., editors, Glacier fluctuations during the Holocene, Pala¨oklimafor- Heidelberg, and J. van der Plicht, Groningen, for the radiocarbon schung 24, 59–65. datings and the two referees Jean Grove and Giuseppe Orombelli Osborn, G. and Luckman, H.B. 1988: Holocene glacier fluctuations in for valuable comments on the manuscript and improvements of the Canadian Cordillera (Alberta and British Columbia). Quaternary the English text. The investigations were partially supported by Science Reviews 7, 115–28. the Quaternary Commission of the Austrian Academy of Sciences, Paschinger, V. 1948: Pasterzenstudien. Carinthia II. Sonderheft IX/II, the Provincial Group of Tyrol of the Confederation of Austrian 1–119. Kurt Nicolussi and Gernot Patzelt: Discovery of early-Holocene peat and wood at the Pasterze Glacier, Austrian Alps 199

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