Paolo Roberto Federici

Morphometric Analysis on the Size, Shape and Areal Distribution of Glacial Cirques in the Maritime Alps (Western French‐Italian Alps)

Abstract The morphometry of 432 glacial cirques in the Maritime Alps (Western French‐Italian Alps), studied over several years of fieldwork, was analysed with the use of a geographical information system. Some of the parameters automatically evaluated from digital elevation models required an objective and relatively new definition. In particular, cirque length was measured along a line that, from the threshold midpoint, splits the cirque into two equivalent surfaces; cirque width was automatically drawn as the longest line inscribed in the cirque and perpendicular to the length line. Significant correlations were found among the different factors and parameters analysed. In particular, cirque shape analysis showed that cirques develop allometrically in the three dimensions, i.e. more in length and width than in altitudinal range. Nevertheless cirques of the Maritime Alps have a regular, almost circular shape (mean L/W value = 1.07). The correlations among length, width and area are all very high (r2= 0.8–0.9). In terms of size, cirques show a wide range in area from 0.06 to 5.2 km2 with a mean value of 0.4 km2. The largest cirques are found on SSW‐facing slopes and at high elevations. Small cirques can be found at all altitudes but all those at high elevation are part of compound cirques at the main head valleys. Most cirques (37%) are characterized by a northern aspect; NE and SW are also frequent directions.

Glacial history of the Maritime Alps from the Last Glacial Maximum to the Little Ice Age

Abstract A complete sequence of glacial deposits and moraines within the same valley system in the Maritime Alps, spanning from the Last Glacial Maximum (LGM) to the Little Ice Age is presented. The sequence is geomorphologically and morphostratigraphically coherent and most stadials have been chronologically constrained by their cosmogenic exposure ages, lichenometry and by correlation with radiocarbon-dated moraines in neighbouring valleys. The shape, extent and thickness of the palaeoglaciers at each stadial have also been reconstructed and their equilibrium line altitude calculated. The LGM moraine of the Gesso Basin bears a similar equilibrium line altitude and age to that of other LGM moraines across the Alps. The recognized Late-glacial stadials show strong similarities with the corresponding stadials of the central–eastern Alpine valleys, such as Gschnitz, Bühl, Daun and Egesen. The recalculation of the exposure ages of moraine boulders with a new production rate better defines the LGM (24.0 ka) and the Egesen Stadial (13.0 ka), while the Bühl Stadial (18.5 ka) is dated for the first time in the Alps. Three early Holocene glacial advances are defined and correlated to the Kartell, Kromer and Göschenen I stadials, widely recognized in other Alpine sectors. Lichenometric dates indicate a three-fold oscillation during the Little Ice Age (thirteenth, seventeenth and nineteenth centuries).

A New Approach for the Study of the Coast Indentation Index

Abstract The indentation index, which is the ratio between the real length of a coast and its Euclidean length, is a parameter applied to characterize rock coasts and to study their evolution. Rather than subjectively selecting two or more sectors of a rock coast, the method proposed in this paper considers analyzing the indentation index on the same coastline previously split into several adjacent tracts with equal Euclidean length. By digitizing the coastline in a GIS environment, it becomes possible to test several Euclidean length values on the same coastline, obtaining a different spatial variability of the indentation index with each trial. The best length values that maximize the spatial variability of the indentation index are those that determine an indentation index pattern characterized by high variance and low spatial autocorrelation. The spatial distribution of the indentation index can eventually be analyzed considering known littoral forces acting on the studied coast. When more than one Euclidean length value is found to maximize the variability of indentation index within the same coast, it is likely that there are one or more littoral forces acting or interacting differently at different scales.

GLACIER RETREAT IN THE MARITIME ALPS AREA

Abstract. In the southernmost tract of the Alps (Italian‐French Maritime Alps), extensively covered by glaciers during the Last Glacial Maximum, about 30 small glaciers were present by the end of the Little Ice Age. The aim of this paper is to document the progressive decrease towards exhaustion of these glaciers, located at the latitude of 44° N, highlighting the factors affecting their retreat. All available data sources were investigated for this work including: the annual glaciers fluctuations record, comparative analyses of historical maps and multi‐temporal oblique photographs and direct surveys in the field. The history of the Maritime Alps glaciers fluctuations was thoroughly reconstructed. Stationary conditions were observed from 1896 up to the beginning of the 1930s; since then they underwent phases of withdrawal with variable intensity. In the early 1990s, only six glaciers were still present, the extent of which were all was dramatically reduced. In the past two decades, the Maritime Alps glacier fronts experienced a global retreat of about 100 m, with a sharp acceleration after 2002. Currently ice patches along cirque walls and/or semi‐buried lenses of ice are still present; morphological evidence of permafrost creeping in the glacier forefield accounts for the incipient transition to periglacial landforms (i.e. rock glaciers). The main factors controlling glaciers retreat seem to have been their original extent at the beginning of the current regressive phase and their distance from the main chain divide. From a climatic point of view unfavourable factors for glaciers persistence have been in the last decades a remarkable and sharp temperature increase, a decrease in winter snowfall and a shift of the rainfall peak from autumn to spring.

First finding of a terrace with preserved marine deposit along the coast of Eastern Liguria (Italy)

Remnants of a loose coarse deposit were found on a rock terrace 28 m above the present day sea level, along the coast of Eastern Liguria. A general geomorphological analysis of the site was carried out. The deposit sedimentological characteristics were detailed and a morphometric analysis of the coarse fraction was carried out. This enabled us to infer the marine genesis of the deposit; it is the first time that a Quaternary marine deposit is found along the coast of Eastern Liguria. Details regarding the nature of the deep weathering processes (in particular oxidation and decarbonatation) that affected it were collected by means of thin section. The age of an old sea level can be inferred, due to the absence of absolute dating, only relating it to similar surfaces present throughout the coastline of the region and linking them to the sea level curves obtained from oxygen isotope records. On the basis of the collected data we propose the chronological attribution of the studied terrace to theδ18O stage 11, considering that the area might have been affected by tectonic uplift.RiassuntoSu un terrazzo in roccia, a 28 m sul livello del mare attuale lungo la costa della Liguria orientale sono stati rinvenuti i resti di un deposito sciolto e grossolano. È stata condotta un’analisi geomorfologica del sito, sono state descritte in dettaglio le sue caratteristiche sedimentologiche ed è stata compiuta un’analisi morfometrica dei clasti che ha permesso di provare l’origine marina del deposito; è la prima segnalazione di un deposito marino quaternario lungo la costa della Liguria orientale. Dall’osservazione del deposito in sezione sottile sono stati dedotti elementi sulla natura degli intensi processi di alterazione, in particolare ossidazione e decarbonatazione, che lo hanno interessato. Questo terrazzo marca un alto livello di stazionamento marino. L’attribuzione cronologica, in mancanza di datazioni radiometriche, è compiuta in maniera indiretta, rapportando questa superficie ad altre simili che sono presenti lungo la costa ligure e mettendole in relazione con le curve di fluttuazione del livello marino ottenute dalle serie isotopiche dell’ossigeno. Si propone, sulla base delle osservazioni effettuate, per il terrazzo in questione un’attribuzione allo stadioδ18O 11, non escludendo che esso possa avere subito un sollevamento per cause tettoniche.

Zoning and Mapping Landslide Hazard in the Castelnuovo di Garfagnana Region (Tuscany, Italy)

ISPRA and Tuscany Region Administration recently funded a project aimed at assessing and mapping landslide hazard of the area of the n. 250 “Castelnuovo di Garfagnana” map (1:50,000 scale). The area includes the upper Serchio River basin (Tuscany, Italy) and exhibits peculiar geological and geomorphological features and severe climatic conditions, which cause high landslide hazard. The project proceeded as follows: 1:10,000 geomorphological survey and landslide inventory map; Physical and mechanical properties of rocks (discontinuities, strength, rock mass classification) and soils (grain size, consistency); GIS oriented organization of the spatial distribution of the considered factors; GIS supported statistical analysis (spatial analysis, conditional and multivariate analyses, neural network technique); Landslide hazard map, where landslide hazard is subdivided into five classes based on instability probability; Final products: landslide hazard map at 1:50,000 scale, together with other related maps (landslide map, structural sketch, geotechnical sketch, isohyet map, etc.); explaining booklet; database.

MSUE Conditional Method Predictive Power, Milia Basin, Tuscany, Italy

An attempt to assess the predictive power of the MSUE Conditional Method was made in landslide susceptibility zonation of the Milia Basin, Tuscany, Italy. A detailed geomorphological mapping, combined with aerial photographs analysis, enabled us to build two landslide inventories using a time scale. The landslides related to a period before 1975 were used to create the models, while those related to a period after 1975 were used to validate the models predictive power. Five time invariant factors maps were also developed in a GIS environment. Finally, the inventory landslides maps and the five landslide-related factor maps were processed using a model in a GIS environment. The procedure was applied separately to the most frequent landslides typologies and for each different combination of the five factors. The comparison between the distribution of landslides after 1975 and the predicted distribution derived from susceptibility models established the predictive power of each model.

The study of large erratic boulders casts new light on some glacial palaeogeography problems in the Apuan Alps (Tuscany, Italy)

Erratic boulders of glacial origin, mainly made of jasper, marble and cherty limestone, are found in the main valleys of the Apuan Alps. Such boulders are especially widespread in the north-eastern sector of the Apuan Alps, sometimes in great number, and they bear witness to a 6 km long journey. Their size may vary greatly, but several erratic boulders are quite large, sometimes even larger than hundreds of cubic metres. The size of the boulders, in comparison to the limited dimensions of the small Apuan glaciers, as well as their number, leads to the hypothesis that they are the result of synglacial landslides, having fallen down on the ridges of moving glaciers. The types and distribution of the erratic boulders allow one to outline the dimensions of the main glacial bodies and assess the relationships between them. Moreover, the presence of erratic boulders opens new avenues of research in order to complete the description of the Apuan glaciation and its chronology by using the techniques of exposure age dating, which can be easily applied to erratic boulders.