Middle to Late Holocene Glacial Variations, Periglacial Processes and Alluvial Sedimentation on the Higher Apennine Massifs (Italy)
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Quaternary Research 64 (2005) 176 – 184 www.elsevier.com/locate/yqres Middle to Late Holocene glacial variations, periglacial processes and alluvial sedimentation on the higher Apennine massifs (Italy) Carlo Giraudi* ENEA C.R. Casaccia, PO Box 2400-00100, ROMA A.D., Italy Received 2 July 2003 Available online 2 August 2005 Abstract The major climatic variations that have affected the summit slopes of the higher Apennine massifs in the last 6000 yr are shown in alternating layers of organic matter-rich soils and alluvial, glacial and periglacial sediments. The burial of the soils, triggered by environmental–climatic variations, took place in several phases. For the last 3000 yr chronological correlations can be drawn between phases of glacial advance, scree and alluvial sedimentation and development of periglacial features. During some periods, the slopes were covered by vegetation up to 2700 m and beyond, while in other phases the same slopes were subject to glacial advances and periglacial processes, and alluvial sediments were deposited on the high plateaus. Around 5740–5590, 1560–1370 and 1300–970 cal yr B.P., organic matter-rich soils formed on slopes currently subject to periglacial and glacial processes; the mean annual temperature must therefore have been higher than at present. Furthermore, on the basis of the variations in the elevation of the lower limit reached by gelifraction, it can be concluded that the oscillations in the minimum winter temperatures could have ranged between 3.0-C lower (ca. 790–150 cal yr B.P.) and 1.2-C higher (ca. 5740–5590 cal yr B.P.) than present minimum winter temperatures. During the last 3000 yr the cold phases recorded by the Calderone Glacier advance in the Apennines essentially match basically the phases of glacial advance in the Alps. D 2005 University of Washington. All rights reserved. Keywords: Apennine chain; Middle; Late Holocene; Glacial; Periglacial; Alluvial sediments; Buried soils; Palaeoclimate; Minimum winter temperatures Introduction The aims of the present work are to recognize the climatic and environmental changes that took place in the second half The Apennine chain forms the backbone of the Italian of the Holocene in the summit areas of the highest massifs in peninsula and extends down to the central area of the the Apennines (Gran Sasso, 2912 m; Maiella, 2797 m; Velino Mediterranean Sea (Fig. 1). The presence of limited glacial 2485 m, Monti Sibillini 2475 m; Fig. 1), and to assess the and periglacial environments on the mountain top, relative temperatures, compared with present temperatures, in included between areas of temperate climate, means that a number of past climatic phases. the climatic variations, even if small, can produce The oscillations of the Calderone Glacier, the sedimen- appreciable changes in the extent of these environments. tation of slope debris and alluvial deposits and the During the warmest periods of the Holocene, the peri- development of periglacial processes are considered in this glacial and glacial environments could have completely paper. The chronological frame was obtained with radio- disappeared and have later formed again as the conse- carbon dating of peat layers or wood fragments and the soils quence of cooling phases. interbedded between the sediments. Dating of the soils was performed on the total organic content in the Ah horizon, and the maximum dry weight of each dated sample was 200 g or less. AMS analyses have been performed on small * Fax: +39 0630486487. samples of the Ah horizon of soils, sampled by digging little E-mail address: [email protected]. holes in highly unstable scree slopes. All dates are in the 0033-5894/$ - see front matter D 2005 University of Washington. All rights reserved. doi:10.1016/j.yqres.2005.06.007 C. Giraudi / Quaternary Research 64 (2005) 176–184 177 Figure 1. Location of the Apennine chain and of the main mountain massifs. Shaded areas are above 1000 m. two-sigma calibrated range, obtained using INTCAL98 considers that thin soils often yield reliable dates that can be (Stuiver et al., 1998; Stuiver and van der Plicht, 1998; interpreted in a relatively simple way. Talma and Vogel, 1993). In the present paper, the buried soils are thin and Dating soils can be quite complex to interpret, in particular developed on very recent sediments, and the samples refer the B and C horizons (Geyh et al., 1971; Scharpenseel and to their uppermost organic matter-rich portion. The dating Schiffmann, 1977; Geyh et al., 1985; Matthews, 1993). In carried out on the five buried soils interbedded with the general, radiocarbon dating of soils do not yield dates relating alluvial sediments in the same exposure at Campo Imperatore to a precise moment, and their precision depends on the mean (Fig. 2) indicates that their age is between the 5th–6th residence time of organic matter. However, Matthews (1993) century A.D. and the present. The phases of pedogenesis that Figure 2. Stratigraphic sketch through the alluvial sediments in western Campo Imperatore (Gran Sasso Massif). Source of radiocarbon dates given in the text. 178 C. Giraudi / Quaternary Research 64 (2005) 176–184 produced most of the soils are thus necessarily brief, and the alluvial sediments present in the section. In the same zone, mean residence time even shorter. In various cases, moreover, just a few hundred meters distant, a soil overlain by alluvial the dates provided by the soils are confirmed by those of thin sediments has been dated 430–680 and 180–150 cal yr B.P. levels of peat or wood fragments. (250 T 40 14C yr B.P.; Beta-168678). It is therefore thought that the dates can to a fair degree of approximation indicate the age of the burial of the soils and Glacial phases can be used to bracket the environmental/climatic variations recognized in the present paper. On the Gran Sasso Massif is the only glacier in the Apennines, the Calderone Glacier, the most southerly one in Alluvial deposits all Europe (Gellatly et al., 1994). The chronological framework of the phases of glacial expansion (Giraudi, The alluvial deposits studied refer mainly to the Gran 2002, 2004) is based on dating by the radiocarbon method Sasso Massif as it is only on this massif that such sediments of soils interbedded with the till deposited at the threshold of outcrop over fairly extensive areas at high elevations the glacial cirque, and with the glacial drift a few hundred (1750–1550 m). meters away (Fig. 3). At Campo Imperatore, at an elevation of about 1700 m, The phases of glacial expansion may be summarized as alluvial sediments – overlying a soil dated 6170–5750 cal follows: yr B.P. (5200 T 60 14C yr B.P.; BO-285) and 6400–5950 cal yr B.P. (5410 T 80 14C yr B.P.; BO-253) – are found in an - the glacial expansion of the Calderone 1 stage is alluvial fan on the southwest slope of Mount Prena. bracketed by soils dated in the range 4520–4090 cal yr At Campo Imperatore, at around 1600 m asl, there are B.P. (3895 T 65 14C yr B.P.; UA-13828) and 2855–2725 soils dated 4830–4410 cal yr B.P. (4070 T 70 B.P.; Beta- cal yr B.P. (2650 T 60 14C yr B.P.; Beta-122057); 168676) and 2310–1990 cal yr B.P. (2130 T 50 14C yr B.P.; - the glacial expansion phase that gave rise to the formation Beta-168677) that underlie alluvial sediments. Also in the of the moraines of the Calderone 2 stage is bracketed by Northern Apennines, at Lake Ballano, at about 1550 m asl, soils dated 2855–2725 cal yr B.P. and 1410–1290 cal yr alluvial sediments overlie a thin layer of peat dated 4820– B.P. (1450 T 40 14C yr B.P.; Beta-145526); 4440 cal yr B.P. (4060 T 60 14C yr B.P.; Beta-154565). - the glacial expansion phase that produced the moraines On Mount Cavallo, in the Central Apennines, at about of the Calderone 3a stage is bracketed by soils dated 1750 m asl, sandy silty alluvial sediments overlie a layer 1410–1290 cal yr B.P. and 680–550 cal yr B.P. (670 T of peat dated 2970–2750 cal yr B.P. (2.750 T 110 14Cyr 40 14C yr B.P.; Beta-145532); B.P.; BO-176). - the expansion phase during which the moraines of the Again at Campo Imperatore, at about 1700 m asl, alluvial Calderone 3b stage were formed is younger than the soil sediments and interbedded buried soils (Giraudi, 2003, dated 680–550 cal yr B.P.; and 2005) are exposed (Fig. 2). - the expansion phase that gave rise to the moraines of the The first buried soil is dated in the range 1360–1270 cal Calderone 3c stage is very close to the glacier margin yr B.P. (1410 T 40 B.P.; Beta-164916), a date very similar to documented at the end of the 19th century and should that of a soil overlain by alluvial sediments in the eastern therefore date from the same period. part of Campo Imperatore dated 1420–1280 cal yr B.P. (1450 T 50 14C yr B.P.; Beta-162900). In the Northern Periglacial processes Apennines, at the head of the Parma Valley, on the shores of Lake Scuro, an alluvial sediment contains a wood fragment The periglacial processes taken into consideration in dated 1310–1080 cal yr B.P. (1310 T 60 14C yr B.P.; Beta- the present work are the sedimentation of slope debris, 154566): this date, close to but more recent than that the development of patterned ground and solifluctions.