SESS 2_16022011_TPR3.pub


  

 

  

 

 

 

Il Quaternario 
Italian Journal of Quaternary Sciences 
24, (Abstract AIQUA, Roma 02/2011),  

Congresso AIQUA 
Il Quaternario Italiano: conoscenze e prospettive 

Roma 24 e 25 febbraio 2011 

HIGH-ALTITUDE ENVIRONMENTS AND GLACIERS FLUCTUATIONS 
IN THE WESTERN SECTOR OF THE AOSTA VALLEY DURING THE HOLOCENE 

 
Roberta Pini1*, Amelia Aceti1, Federica Badino1, Valter Maggi2, 

Giuseppe Orombelli2, Luca Raiteri3-4 & Cesare Ravazzi1 
1C.N.R., Istituto per la Dinamica dei Processi Ambientali, Milano 

2DISAT, Università di Milano – Bicocca 
3Regione Autonoma Valle d’Aosta, Soprintendenza Beni e Attività Culturali, Aosta 

4Dip. Biologia ed Evoluzione, Università di Ferrara 
*Corresponding author: R. Pini <roberta.pini@idpa.cnr.it> 

 
ABSTRACT: Pini R. et al., High-altitude environments and glaciers fluctuations in the western sector of the Aosta Valley 
during the Holocene (IT ISSN 0394-3356, 2011) 
Palaeobotanical and chronological data from high-altitude mire successions in the western Alps (Aosta Valley) are here 
compared with geomorphological evidences of glacier oscillations, to describe the history of glacial systems and the 
occurrence of phases of climatic optimum during the first half of the Holocene. These phases are marked by periods of 
glacier recession, rise of the forest limit up to altitudes above 2400 m and widespread tufa deposition at 2000 m 
altitude. These data are in good agreement with available information from the Central Italian, the Swiss and the 
Austrian Alps. 
 

RIASSUNTO: R. Pini et al., Ambienti d’alta quota e oscillazioni glaciali nel settore occidentale della Valle d’Aosta 
durante l’Olocene (IT ISSN 0394-3356, 2011) 
L’analisi integrata di dati paleobotanici e cronologici da successioni di torbiera d’alta quota nel settore occidentale della 
Valle d’Aosta e di evidenze geomorfologiche in aree interessate da avanzate glaciali oloceniche fornisce indicazioni 
sulla storia degli apparati glaciali e sull’esistenza di più fasi di optimum climatico durante la prima metà dell’Olocene. 
Queste fasi sono testimoniate da periodi di evidente recessione glaciale, innalzamento del limite delle foreste a quote 
superiori ai 2400 m e alla deposizione diffusa di travertini a 2000 m di quota. I dati ottenuti sono in accordo con quanto 
noto per le Alpi Centrali italiane, le Alpi svizzere e austriache. 
 

Key words: Holocene, Aosta Valley, mires, glaciers, tufa, prehistoric archaeology  
 

Parole chiave: Olocene, Valle d’Aosta, torbiere, ghiacciai, travertini, archeologia preistorica 

Among the stratigraphical archives yielding 
information on the structure of ancient natural and 
anthropic landscapes, mires are of particular 
interest. These habitats, widespread on the Alpine 
chain, develop well on crystalline bedrock along 
wide altitudinal transects, extending from the 
colline to the high-alpine belt. Detailed geological 
and geomorphological surveys in former 
glacialized areas nowadays occupied by mires 
provide interesting data on past glacier extent and 
fluctuations and help reconciling the chronology of 
local glacial history, trees immigration and forest 
development. 
This contribution focuses on recent investigations 
carried out by the authors on high-altitude mires 
and glacial systems in the western sector of the 
Aosta Valley. Relevant sites are: 
 
- the foreland of the Rutor Glacier (2510 m asl, 
La Thuile Valley: Fig. 1). Here a succession of 
compressed peat, 14C dated to 7600 – 9200 cal 
years BP and intercalated within minerogenic 
deposits, outcrops along the proglacial stream and 
provides information on former phases of glacial 
recession during the first half of the Holocene and 

on the history of vegetation development, both at 
local and regional scale (OROMBELLI, 1998; ACETI, 
2006); 
 
- the Crotte Basse mire (2365 m asl, southern 
slope of Mont Fallére, Aosta: Fig. 2). This 
stratigraphical sequence was cored in summer 
2009 and 2010, retrieving multiple cores along the 
succession of lacustrine – palustrine deposits. 
Pollen and geochemical analysis and 14C 
determinations are still in progress: available data 
testify to an early stage of vegetation development 
(before the Holocene onset) and the subsequent 
expansion of forests growing well above their 
present day altitudinal ranges. This forest 
displacement interacted with Mesolithic hunters 
and gatherers and Eneolithic farmers seasonally 
settling on nearby high-altitude areas for 
subsistence purposes (GUERRESCHI et al., 2010). 
 
- a 4m - thick tufa bank, outcropping at 1950 m 
asl on Mont Fallére. This deposit, rich in wood, 
charcoal, needles and cone imprints, testifies to 
the local development of Pinus sylvestris 
woodlands during the Holocene climatic optimum 

 
 
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Fig. 1, Panoramic view of the western and central lobes of the Rutor Glacier. The white line indicates the position of the 
moraine related to the 1980’s advance; an arrow shows the outcrop of compressed peat discussed in the text (photo: 
Amelia Aceti, summer 2005). 
Panorama dei lobi occidentale e centrale del Ghiacciaio del Rutor. La linea bianca indica la posizione della morena 
deposta dopo l’avanzata degli anni ’80; la freccia mostra la posizione dell’affioramento di torbe compresse discusse nel 
testo (foto: Amelia Aceti, estate 2005). 

Fig. 2, The Crotte Basse mire: this stratigraphic sequence provides information for the reconstruction of the 
vegetation and climate history of the area from the last part of the Late Glacial to the present (photo: Diego De Nisi, 
summer 2009). 
La torbiera delle Crotte Basse: questa sequenza stratigrafica illustra la storia della vegetazione e del clima dell’area in 
esame a partire dalla fine del Tardoglaciale fino ai giorni nostri (foto: Diego De Nisi, estate 2009).  

R. Pini et al. 



  

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Ms. received: 
Testo ricevuto il 

and allows for comparisons with the 
palaeobotanical information obtained from the 
Crotte Basse mire. Interestingly, this is not the only 
tufa deposit found on Mont Fallére: the slopes 
actually host several tufa layers, displaying 
massive to porous texture and varying in thickness 
from a few centimeters to several decimeters. 
 
DISCUSSION 
 
The stratigraphic section at the foreland of the 
Rutor Glacier testifies to prolonged phases of 
glacier recession framed between the early and 
the middle Holocene. Deposition of fine-grained 
material (lacustrine silt overlied by peat) above 
glacial sediments can be related to a phase of 
sudden glacier retreat dated to ca. 9500 years cal 
BP. The glacier maintained a reduced extent at 
least up to ca. 6500 years cal BP, possibly up to 
4900 years cal BP (considering the age of other 
peat layers found dislocated nearby the studied 
section). Forests never reached the proglacial 
Rutor area; palaeobotanical data indeed suggest 
that Abies alba was widespread along the valley 
slopes possibly up to an altitude of ca. 2000 – 
2200 m asl, while Pinus cembra developed at 
higher altitudes. 
The same chronological interval is testified at the 
Crotte Basse mire. Palaeobotanical and 
chronological data indicate the local occurrence of 
dense conifer forests dominated by Pinus cembra 
as early as ca. 8800 years cal BP, accompanied 
by Abies alba starting at ca. 8600 years cal BP. 
The full sun aspect enabled the growth of dense 
conifer forests up to an exceptional altitude (at 
least up to 2365 m asl). The widespread deposition 
of tufa at an unusual altitude (1900 - 2150 m asl) 
on Mont Fallére may represent an evidence for 
phases of climatic optimum. In particular, 
radiocarbon dating of the huge carbonatic bank 
found on the southern mountain slope established 
that tufa accumulated quickly between 5800 – 

9100 years cal BP. 
Generally speaking, glaciological and palaeobotanical 
data from the western Alps are in good agreement 
with those from the Central Italian, the Swiss 
(HORMES et al., 2001) and the Austrian Alps 
(NICOLUSSI & PATZELT, 2000) and speak for several 
phases of climatic optimum during the first half of 
the Holocene, characterized by recessional glacier 
phases and development of woody vegetation well 
above the modern treeline. Further studies are 
needed to understanding and characterize such 
phases and for a better definition of their timing 
and extent: are they short-lived, centennial phases 
or longer periods of climatic optimum? 
 
REFERENCES 
 
ACETI A. (2006) – La variabilità climatica 

nell’Olocene: studio di torbiere e ambienti d’alta 
quota nelle Alpi italiane. Unpublished PhD Thesis 
in Geological Sciences, Univ. Milano – Bicocca, 
115  

GUERRESCHI A., RAITERI L., DI MAIO P., RAVAZZI C., 
PINI R., GABRIELE P. & BASTER I. (2010) – A new 
high-altitude Mesolithic site on Mont Fallére 
(Aosta, northern Italy). First results on 
archaeology, environmental and landscape 
evolution. Convegno MESO 2010 – The 8th 
International Conference on Mesolithic in Europe 
(Santander, Spain). Abstract volume. 

HORMES A., MÜLLER B.U. & SCHLÜCHTER C. (2001) 
– The Alps with little ice: evidence for eight 
Holocene phases of reduced glacier extent in the 
Central Swiss Alps. The Holocene, 11, 255-265. 

NICOLUSSI K. & PATZELT G. (2000) – Discovery of 
early Holocene wood and peat on the forefield of 
the Pasterze Glacier, Eastern Alps, Austria. The 
Holocene, 10, 191-199. 

OROMBELLI G. (1998) – Le torbe del Rutor: una 
successione significativa per la storia olocenica 
dei ghiacciai e del clima nelle Alpi. Mem. Soc. 
Geogr. It., 55, 153-165. 

 

 
 
 January 14, 2011 
 14 gennaio 2011 

High-altitude environments and glaciers fluctuations ...