This document summarizes research on evidence of Quaternary tectonics in the Insubria region located between Lakes Como and Maggiore in Northern Italy. The researchers mapped two major structures, the Gonfolite backthrust east of Como and the Albese con Cassano anticline west of Como, that both show signs of recent deformation. For the Gonfolite backthrust, new field mapping suggests it offsets Pliocene and possibly younger deposits, in contrast to previous interpretations of late Miocene age. For the Albese con Cassano anticline, studies confirm it has accumulated around 200 meters of vertical displacement since the Middle Pleistocene and growth has been accompanied by strong local earthquakes. Overall

1. ABSTRACT
In the foothills of the Southern Alps between Lake Garda and
Lake Maggiore, the relations between the recent tectonic evolution
and the accompanying seismic potential have been overlooked.
Published interpretations of structures consider shortening to cease
at the end of the Messinian; this is in contrast with geomorphic and
stratigraphic evidence for Plio-Pleistocene reverse faulting and
folding presented in this paper.
Evidence for Quaternary shortening near Lake Garda includes
Quaternary folds with 200 m of structural relief recorded by Lower-
Middle Pleistocene deposits. These crop out on top of the Caste-
nedolo and Ciliverghe Hills, within the epicentral area of the histori-
cal December 25, 1222 Brescia earthquake (epicentral intensity IX
MCS, Me 6.2; GUIDOBONI, 2002).
Shortening further west may also be occurring, but there is no
record of local damaging historical earthquakes along the foothills
of the Alps. This motivated us to review available data and undertake
new reconnaissance field work, in order to better understand the
Quaternary tectonic evolution of the Southern Alps near Lake Como
in the Insubria region.
We focused our studies on two major structures located east and
west of Como, respectively, the Gonfolite backthrust and the Albese
con Cassano anticline. The Gonfolite backthrust, first recognized by
BERNOULLI et alii (1989) and reported as late Miocene in age, is
accompanied by geomorphic features consistent with Quaternary
compressional structures. Our new field mapping suggests that this
thrust offsets deposits of Pliocene and possibly younger age. Neotec-
tonic evidence for the recent evolution of Albese con Cassano anticline
was first presented by OROMBELLI (1976). Our investigations confirm
Orombelli’s observations, and suggest that the Albese con Cassano is
an actively growing anticline that accumulated ca. 200 m of post-Mid-
dle Pleistocene vertical displacement. In addition, paleoliquefaction
features in Mid-Pleistocene proglacial deposits at this site suggest that
growth of this fold has been accompanied by strong local earthquakes.
Evidence of Quaternary tectonics in the Insubria region is con-
sistent with that observed in the well-known seismic area near Lake
Garda. Therefore, the seismic potential of this area should be care-
fully re-evaluated based on the examination of available geological
data and the results of new ad hoc paleoseismological analyses. Cur-
rent assessment of seismic hazard, based only on the historical seis-
mic catalog, supposedly heavily underestimates the earthquake
potential in one of the most vulnerable areas of the whole Europe.
KEY WORDS: Quaternary tectonics, Central-Southern Alps,
seismic hazard, compressional tectonics.
RIASSUNTO
Considerazioni sulla tettonica Quaternaria della Regione
dell’Insubria (Lombardia, Italia Nord-Occidentale e Ticino, Sviz-
zera sud-orientale).
In questo studio vengono illustrate alcune potenziali evidenze di
riattivazione tettonica tardo-quaternaria nel settore del fronte sudal-
pino compreso tra i laghi Maggiore e Garda. Le evidenze di tettonica
quaternaria nella zona di pianura a sudovest del Lago di Garda in-
cludono pieghe con circa 200 metri di rilievo strutturale in sedimenti
del Pleistocene inferiore-medio, affioranti nell’area epicentrale del
terremoto di Brescia del 25 gennaio 1222 (Intensità epicentrale IX
MCS, Me 6.2).
Nonostante l’assenza di notizie di terremoti storici abbia fatto
sinora ritenere l’area ad ovest di Brescia, verso i laghi di Como e
Maggiore, sostanzialmente stabile ed asismica, il raccorciamento tet-
tonico potrebbe essere tuttora attivo anche qui, sulla base della si-
smicità di bassa magnitudo che si allinea al piede dei rilievi prealpi-
ni fra Brescia e Lecco, dei dati geodetici, e della presenza di
deformazioni quaternarie segnalate da vari autori.
Questo ha spinto gli autori del presente lavoro a rivedere i dati
esistenti e a raccoglierne ulteriori, al fine di comprendere meglio
l’evoluzione quaternaria del fronte alpino meridionale nella regione
dell’Insubria (fra il Lago di Como e il Ticino). Qui vengono analizza-
te le due maggiori strutture nell’area: l’anticlinale di Albese con Cas-
sano e la dorsale del retroscorrimento della Gonfolite Lombarda.
Quest’ultima struttura, sinora datata al Miocene superiore, presenta
tuttavia evidenze morfologiche consistenti con strutture quaternarie
compressive. Nuovi dati di rilevamento indicano che questa struttu-
ra coinvolge depositi Pliocenici e probabilmente anche più recenti.
A sua volta, l’anticlinale di Albese con Cassano è una struttura
che è risultata aver accumulato circa 200 metri di spostamento verti-
cale post Pleistocene medio. Inoltre, il ritrovamento di paleoliquefa-
zioni in depositi proglaciali medio-pleistocenici suggerisce che la
crescita della struttura sia stata accompagnata da significativi terre-
moti locali. Nel complesso quindi, le evidenze di tettonica quaterna-
ria nella regione dell’Insubria, una delle aree più vulnerabili dell’in-
tera Europa, sono consistenti con quanto osservato nell’area
bresciana. La modestissima pericolosità sismica attribuita all’area
Insubrica, essenzialmente sulla base del catalogo sismico, potrebbe
quindi essere sottostimata. Ciò suggerisce la necessità di un riesame
attento, attualmente in corso, degli indizi geologici e geomorfologici,
di tettonica recente, anche attraverso l’analisi di possibili evidenze
paleosismiche.
TERMINI CHIAVE: Tettonica Quaternaria, Alpi Centro-Meri-
dionali, pericolosità sismica, tettonica compressiva.
INTRODUCTION
Active shortening and related seismicity in Northern
Italy is the result of the growth of two thrust belts of
opposite polarity, the Alps and the Apennines (e.g. SERVA,
1990; DOGLIONI, 1993; CASTELLARIN & CANTELLI, 2000;
BOCCALETTI & MARTELLI, 2004; fig. 1a).
Pleistocene shortening in the Southern Alps and
northern Po Plain has been documented on geological
basis to decrease from east to west (e.g. SERVA, 1990;
BIGI et alii, 1990; FANTONI et alii, 2004; GALADINI et alii,
2005; CASTELLARIN et alii, 2006). Historical seismicity fol-
lows the same trend, and the frequency of strong seismic
events decreases from Friuli toward Lake Garda, and then
Lake Maggiore, where no historical seismicity with epi-
central intensity greater than VI MCS is documented (e.g.
WORKING GROUP CPTI, 2004; fig. 1b). Furthermore,
Boll.Soc.Geol.It. (Ital.J.Geosci.), Vol. 126, No. 2 (2007), pp. 411-425, 11 figs.
Remarks on the Quaternary tectonics of the Insubria Region
(Lombardia, NW Italy, and Ticino, SE Switzerland)
GIANCANIO SILEO (*), FRANCESCA GIARDINA (*), FRANZ LIVIO (*), ALESSANDRO M. MICHETTI (*),
KARL MUELLER (**) & EUTIZIO VITTORI (***)
(*) University of Insubria, Dip. di Scienze Chimiche e Ambien-
tali, via Valleggio, 11 - 22100 Como, giancanio.sileo@uninsubria.it.
(**) University of Colorado, Boulder, CO, USA.
(***) Italian Agency for Environment Protection and Technical
Services (APAT), Rome, Italy.
SGI Bollettino Dgs10 143
Queste bozze, corrette e accompagnate dall’al-
legato preventivo firmato e dal buono d’ordine,
debbono essere restituite immediatamente alla
Segreteria della Società Geologica Italiana
c/o Dipartimento di Scienze della Terra
Piazzale Aldo Moro, 5 – 00185 ROMA
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 411

2. based on GPS data, the western Southern Alpine moun-
tain front is currently characterized by noteworthy short-
ening rates of ca. 1.1 mmyr-1
, even though half of the
value (2.2 mmyr-1
) inferred for the seismically-active east-
ern Southern Alps in Friuli (e.g. SERPELLONI et alii, 2005;
D’AGOSTINO et alii, 2006).
West of the Veneto-Friuli regions, the best evidence of
active shortening is shown in the Lake Garda area. Desio
(1965) described the morphological and stratigraphic
expression of several Pleistocene anticlines outcropping
southwest of Lake Garda, near Castenedolo and Ciliv-
erghe (fig. 1a). These structures were subsequently stud-
ied by other workers, including BARONI & CREMASCHI
(1986), CASTALDINI & PANIZZA (1991), CURZI et alii
(1992), LOCATELLI & VERCESI (1998), CARCANO & PICCIN
(2002). At least 200 m of structural relief has been docu-
mented in the Lower Pleistocene marine deposits affected
by the Castenedolo anticline (CURZI et alii, 2002). A simi-
lar Middle Pleistocene uplift has been recently derived
from magnetostratigraphic analysis along a borehole
drilled southwest of Castenedolo (SCARDIA et alii, 2006).
Faulting and tilting in Middle Pleistocene glacial deposits
has been observed in the Ciliverghe Hill, belonging to the
same structure of Castenedolo (BARONI & CREMASCHI,
1986). The presence of Quaternary structures inferred
from geological data is in agreement with the historical
and instrumental seismicity data. Castenedolo and Ciliv-
erghe are located within the epicentral area of the Decem-
ber 25, 1222, Brescia earthquake (MAGRI & MOLIN, 1986;
GUIDOBONI, 1986; SERVA, 1990; GUIDOBONI, 2002),
arguably the largest historical seismic event that has
occurred in the Po Plain (WORKING GROUP CPTI, 2004):
the intensity IX MCS attributed to this earthquake is
equivalent to a macroseismically – derived magnitude of
6.2 (see GUIDOBONI, 2002). Besides, the seismicity of this
area and the mechanism of faulting has been more
recently documented by the November 24, 2004, Salò
earthquake (e.g. MICHETTI et alii, 2004; fig. 1b), a moder-
ate event characterized by a reverse faulting focal mecha-
nism (an overview of the historical seismicity near Salò is
available in INGV, 2004). Likewise, a south-verging, blind
reverse fault has been hypothesized as the causative tec-
tonic structure for the May 12, 1802, Soncino earthquake
by BURRATO et alii (2003; fig. 1). Based on a detailed
analysis of drainage network anomalies, these Authors
suggest that the Southern Alps beneath the Po Plain in
Lombardia are characterized by active shortening accom-
modated by thrust faulting and growing anticlines. This is
in agreement with interpretations by ROEDER (1992),
who, based on structural analysis of subsurface data
along the Po Plain piedmont belt in Lombardia, indicated
«draping and/or warping of Pliocene sediments over
deeper thrust architecture related to recent foothills
thrusting at low strain rate».
Even if the studies described above consistently pro-
pose a Quaternary tectonic setting due to late Alpine
shortening, the interpretation of the nature and features
of Quaternary deformation along the Lombardia foothills
and piedmont belt is still controversial. Several Authors
suggest that shortening in the western Southern Alps vir-
tually ceased in the late Messinian after the so-called
«Lombardic Tectonic Phase» (14 to 6 Myr B.P.; e.g. SCHU-
MACHER et alii, 1996), due to the northward propagation
of the Northern Apennines lithospheric flexure, which
tilted and deactivated the pre-existing south verging
Alpine structures (e.g. BERNOULLI et alii, 1989; DOGLIONI,
1993; FANTONI et alii, 2004; CASTELLARIN et alii, 2006;
SCARDIA et alii, 2006). Others point out that during the
Late Alpine deformation the inner Western Alps are char-
acterized by Neogene to ongoing extension (MANCK-
TELOW, 1992; SUE & TRICART, 2003; GROSJEAN et alii,
2004). PICOTTI et alii (1995) and BERTOTTI et alii (1997)
have argued that even the Central-Southern Alps and the
Northern Apennines are currently experiencing crustal
extension, because of a post-Messinian state-of-stress
change related to the bulging of the Apennine Foreland.
In the area between Lake Maggiore and Lake Como,
this poor understanding of the Quaternary tectonic set-
ting has resulted in contrasting interpretations of the
observed evidence of neotectonics and paleoseismicity
(e.g. CASTALDINI & PANIZZA, 1991; ZANCHI et alii, 1997).
For instance, opposing interpretations have been pre-
sented to explain the Quaternary uplift of Mt. Morone,
east of Varese (e.g. FELBER, 1993; ZANCHI et alii, 1997;
BINI et alii, 2001; figs. 2 and 3). BINI et alii (2001) suggest
that the uplift could be interpreted as due either to
reverse faulting along the Gonfolite backthrust or to late-
Alpine extensional tectonics.
This motivated us to review available data and under-
take new reconnaissance field work, in order to better
understand the Quaternary tectonic evolution of the South-
ern Alps near Lake Como in the Insubria region. In the first
step of this project, we focused our studies on two major
structures located east and west of Como, respectively, the
Gonfolite backthrust and the Albese con Cassano anticline,
both displaying evidence of recent deformation according
to literature data (e.g. OROMBELLI, 1976; FELBER, 1993;
ZANCHI et alii, 1997; BINI et alii, 2001). We seek to demon-
strate whether 1) these features are produced by active
shortening or extension, and 2) they can be compared to
the Quaternary deformation observed in the seismically-
active portion of the western Southern Alps near Lake
Garda. This paper illustrates initial results of new field
mapping and geomorphic analyses along these two struc-
tures. In the next step of this research, we have conducted
a more regional study in collaboration with ENI Explo-
ration and Production, including the reinterpretation of
subsurface data in the whole Lombardia sector of the Po
Plain and adjoining foothills; results from this further
research will be presented elsewhere in a companion
paper. The revision of the available literature based on new
field data collected so far and presented here allows to
draw some significant conclusions, even if preliminary, on
the Quaternary tectonics of the Insubria region, and to
delineate a rather new scenario for its seismicity potential.
GEOLOGICAL AND GEOMORPHOLOGICAL SETTING
OF THE INSUBRIA REGION
Insubria extends between Lake Maggiore and Lake
Como along the foothills of the western Southern Alps
(fig. 1a). The oldest strata exposed here include Late Tri-
assic to Early Jurassic mainly carbonatic sediments
deposited in the Jura-Cretaceous Lombardian Basin fol-
lowing the opening of the Tethys Ocean (WINTERER &
BOSELLINI, 1981; GIANOTTI & PEROTTI, 1987; BERTOTTI et
alii, 1993). The outset of the Alpine orogenesis then shed
sequences of flysch (Cretaceous to Eocene) and molasse
southward into the Po Plain Foredeep. The latter is repre-
412 G. SILEO ET ALII
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 412

3. sented by the Oligo-Miocene sequence of the Lombardian
Gonfolite Group, which outcrops in Western Lombardy
and is largely represented in the subsurface of the north-
ern Po Plain (SCIUNNACH & TREMOLADA, 2004; FANTONI
et alii, 2004). The Gonfolite Group is made by up to 3000 m
of resedimented conglomerates and sandstones, and can
be linked to a foredeep tectonic basin superimposed on
an active continental margin (e.g. GELATI et alii, 1988,
1991). After deep erosion during the Messinian as a result
of a drop of the regional base level, Pliocene marine clays
were deposited in small troughs within the piedmont belt
(e.g. «Argille di Castel di Sotto»; BINI et alii, 2001; fig. 4).
Locally, coarse alluvial deposits are found beneath the
Pliocene clays, such as in the area west of Como («Ponte-
gana Conglomerates», tentatively dated at the late
Messinian; see BINI et alii, 2001, and reference therein;
fig. 4). This succession is covered by the Quaternary
glacial and fluvio-glacial sediments related to climatic-
driven fluctuations of the ice tongues of the Abduan glac-
ier system (BINI et alii, 2001).
REMARKS ON THE QUATERNARY TECTONICS OF THE INSUBRIA REGION 413
Fig. 1 - a) Structural setting
of Northern Italy (from CA-
STELLARIN et alii, 2006, modi-
fied); inset shows the study
area, small triangles indicate
the location of the Castene-
dolo and Ciliverghe hills,
Soncino and Salò; b) seismi-
city map of Northern Italy
showing events with MCS in-
tensity higher than 5, modi-
fied from the CPTI seismic
catalogue (WORKING GROUP
CPTI, 2004).
– a) Assetto strutturale del
Nord Italia (da CASTELLARIN et
alii, 2006, modificato); l’inser-
to indica l’area di studio, i pic-
coli triangoli indicano l’ubica-
zione dei rilievi di Castenedolo
e Ciliverghe e delle località di
Socino e Salò citate nel testo;
b) carta della sismicità dell’Ita-
lia Settentrionale che include
tutti gli eventi con le intensità
MCS maggiori di 5 (da CPTI,
GRUPPO DI LAVORO, 2004, mo-
dificato).
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 413

4. Insubria underwent thin-skinned shortening during
the phase of the Alpine orogenesis that generated the
Southern Alps (e.g. DOGLIONI, 1993; FANTONI et alii,
2004), producing a system of mostly south-verging thrusts
and folds (e.g. SCHÖNBORN, 1992). Sediments deposited
in the foredeep of the Southern Alps during this period
and the external part of the belt are deeply buried
beneath the Po Plain as shown in seismic reflection data
(PIERI & GROPPI, 1981). These are represented by the
Upper Oligocene to Lower Miocene deepwater clastic
strata of the Gonfolite Lombarda Group (GELATI et alii,
1988), that unconformably overlie the mainly carbonatic
Meso-Cenozoic succession.
From the geomorphic point of view, Insubria
stretches east-west across the Lombardia and Ticino
foothills at the junction between the Alps and the Po
Plain, with elevations ranging from 198 m (the level of
Lake Como) and 1704 m a.s.l. (the elevation of Mt. Gen-
eroso, the highest peak in the area). The digital elevation
model shown in fig. 2 clearly illustrates the strong glacial
imprint on the landscape, described in detail by several
authors, such as NANGERONI (1970), OROMBELLI (1976),
BERNOULLI et alii (1989), MONTRASIO (1990), MOSCA-
RIELLO et alii (2000) and BINI et alii (2001).
Since the Middle Pleistocene, several major glacial
expansions covered this area with large, up to 2 km
thick, ice tongues (NANGERONI, 1970; BINI et alii, 1998;
MOSCARIELLO et alii, 2000; MUTTONI et alii, 2003). Suc-
cessive advances and retreats of glacial flows coming
from the Central Alps occupied the valleys and reached
the piedmont belt and the northern Po Plain. In particu-
lar, during the Late Pleistocene the Insubria region was
affected by several important glacial pulsations of the
major ice tongue coming from Valtellina, i.e. the Abduan
glacier (e.g. BINI et alii, 2001). During the Last Glacial
Maximum (LGM, 22 to 20 kyr B.P.; e.g. IVY HOCHS et alii,
2004, and references therein) in the area between Como
and Varese the landscape was mostly covered by ice, and
the whole drainage network was filled by glacial tongues
up to an elevation of 1100 m near Mt. Generoso and 800
m in the surrounding of Como town (fig. 2; e.g. BINI et
alii, 1998, and references therein). During the LGM and
previous glacial maxima, in this sector the glacial
processes were dominantly erosional, and most of the
glacial to fluvio-glacial sediments have a post-LGM age.
The major accumulation of glacial deposits took place
further south, between Como and Milan, where the huge
piedmont lobes and terminal moraines of the Abduan
glacier were located during the LGM. The area south of
the Varese and Como foothills is also characterized by a
gently south-sloping fluvio-glacial and fluvial outwash
plain (sandur-like environment), essentially built during
the LGM. This wide low-gradient depositional surface is a
typical feature of all the piedmont belts around the Po
Plain, and corresponds to the so-called «Livello fonda-
mentale della pianura» of PETRUCCI & TAGLIAVINI (1969),
who first defined the basic features of this regional geo-
morphic unit (see CASTIGLIONI & PELLEGRINI, 2001;
MARCHETTI, 2002; and references therein).
Two major tectonic structures in the Insubria region
show geomorphic features clearly unrelated to glacial ero-
sion and indicative of a recent tectonic activity, the Gon-
folite backthrust and the Albese con Cassano anticline.
The evidence for Quaternary deformation and faulting
along these structures has been already described in the
literature by several Authors (e.g. OROMBELLI, 1976; FEL-
BER, 1993; ZANCHI et alii, 1997; BINI et alii, 2001). In the
next sections we revise the published data and describe
414 G. SILEO ET ALII
Fig. 2 - Digital elevation model and location map of the study area: CO - Como; VA - Varese; LC - Lecco; MdN - Madonna della Neve; AcC - Albese
con Cassano; Nov - Novazzano.
– Modello digitale del rilievo e carta delle località dell’area di studio citate: CO - Como; VA - Varese; LC - Lecco; MdN - Madonna della Neve; AcC - Albese
con Cassano; Nov - Novazzano.
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 414

5. the results of new field mapping and geomorphic analy-
ses. We show that the evidence of Quaternary shortening
along these tectonic structures can be compared with
those previously described for the Southern Alps struc-
tures southwest of Lake Garda.
THE GONFOLITE BACKTHRUST
West of the city of Como, the Gonfolite backthrust is
located at the base of a 20 km long, steeply inclined,
north-facing mountain front (figs. 2 and 3). During the
construction of a railway tunnel in the Como area, a tec-
tonic contact between the Gonfolite Lombarda Group
and the carbonatic Mesozoic Succession was documented
and mapped for the first time (e.g. BERNOULLI et alii,
1989). This structure is the surface expression of a major
north-verging backthrust, reportedly dated to the Torton-
ian (see FANTONI et alii, 2004; SCIUNNACH & TREMOLADA,
2004, for recent revisions of the relevant literature).
Despite many Authors regard the Gonfolite back-
thrust as a Miocene structure, evidence for more recent
activity has been pointed out (e.g. BINI et alii, 1992; FEL-
BER, 1993; ZANCHI et alii, 1995, 1997; BINI et alii, 2001).
ZANCHI et alii (1997) and BINI et alii (2001) were able to
show that the whole mountain front in the hangingwall of
the Gonfolite backthrust (figs. 3 and 4) displays evidence
for a post-Miocene to Pleistocene uplift, and that Pliocene
to Pleistocene deposits in the surroundings are affected
by systematic fracturing and faulting at the meso-scale
with centimetric to decimetric offsets. Near Novazzano
(fig. 2), FELBER (1993) described a tectonic contact
between the Gonfolite Lombarda Group and the Pliocene
Formation of the Castel di Sotto Clays, outcropping along
the thalweg of a small valley. He interpreted this contact
as a possible normal fault, due to the normal drag of the
Pliocene bedding along the fault plane. ZANCHI et alii
(1995, 1997) revised this outcrop giving the same inter-
pretation of normal faulting.
The drainage along the Faloppia Valley, one of the
originally south-sloping valleys carved in the Lombardia
foothills during the Messinian drop of the Mediterranean
Sea level (see FINCKH, 1978; FELBER et alii, 1991, 1994),
was later inverted due to the raising of the Gonfolite
relief.
Around Monte Morone (figs. 2 and 3), ancient termi-
nal moraines have a single arc morphology in map view,
while younger terminal moraines are arranged in two
separate lobes. The uplift of Monte Morone influenced
the morphology of the local terminal moraines associated
to the Lake Lugano ice tongue. Mt. Morone elevation is
496 m a.s.l., more than 100 m higher than the surround-
ing glacial outwash plain; this value can be taken as a
rough estimate of the minimum local vertical uplift. The
lack of direct dating does not allow to more precisely con-
strain the timing of this uplift. Since the onset of major
Quaternary glaciations in the Southern Alps is regarded
as having occurred at ca. 0.9 Myr B.P. (e.g. BINI et alii,
1998; MUTTONI et alii, 2003; SCARDIA et alii, 2006), it is
reasonable to hypothesize that the uplift of Monte
Morone occurred during the Middle Pleistocene.
The systematic offset of karstic conduits and collapse
of speleothems beneath the Mt. Campo dei Fiori at the
western margin of the Gonfolite backthrust near Varese
REMARKS ON THE QUATERNARY TECTONICS OF THE INSUBRIA REGION 415
Fig. 3 - Shaded relief 3D map (from 20 m resolution DEM courtesy of Regione Lombardia), of the Gonfolite Backthrust area, view from
northwest; vertical exageration 3X.
– Modello tridimensionale dell’area del retroscorrimento della Gonfolite, visto da nord-ovest (dal modello digitale del terreno, con risoluzione di
20 m, messo a disposizione dalla Regione Lombardia; esagerazione verticale 3X).
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 415

6. (fig. 2) are interpreted by BINI et alii (1992) as due to
Quaternary shortening. Speleothems of the Mt. Campo
dei Fiori cave system have been dated to ca. 350 kyr B.P.
based on U-Th dating, and the observed collapses and
deformations of the cave system is regarded as younger
than 350 kyr B.P. This is interpreted as evidence of paleo-
seismicity due to the growth of a south-verging fold fac-
ing the north-verging Gonfolite backthrust during the
Middle Pleistocene.
It is important to remark that ZANCHI et alii (1997) pre-
ferred interpretation is that the overall pattern of Plio-Plei-
stocene tectonic activity in the area is characterized by
surface north-south extension due to «superficial accom-
modation of deformations related to south-verging blind
thrusting active at depth, locally producing differential
uplifting and possibly reactivation of some of the major
Late Miocene thrust surfaces». However, these Authors
indicate that alternative active tectonic models are possible.
In order to review these literature data and provide
better constraints for the age, nature and amount of post-
Messinian to recent displacement along the Gonfolite
backthrust we conducted new field mapping and geomor-
phological analysis (figs. 3 and 4). We first mapped at
1:10,000 scale the area along the thrust from Como to Mt.
Morello (fig. 2). During the field work, we re-visited the
outcrop described by FELBER (1993) and ZANCHI et alii
(1995; 1997) in a ca. 15 m deep stream incision near
Novazzano, where a fault plane juxtaposes the Oligo-
Miocene conglomerates of the Lombardian Gonfolite
Group against the Pliocene Formation of the «Castel di
Sotto Clays». The outcrop was better exposed than in
1993 and 1997 (as made clear by the comparison of the
present-day aspect of the outcrop shown in fig. 5 with fig.
9 in ZANCHI et alii, 1995), probably because of the valley
floor downcutting occurred during the November 2000
and November 2002 flooding events in the Lombardia and
Ticino Region. Our re-examination of this outcrop con-
firms previous observations about the bedding of the Gon-
folite Lombarda Group (strike N190, dip 70°-80°). Also,
the geometry of the upper part of the fault plane corre-
sponds to that described by other Authors; the fault plane
is almost vertical and dips to the north, and the Castel di
Sotto Clays are dragged against the fault plane, while few
tens of meters away from the fault plane this formation
takes again the original horizontal bedding. However, in
the lower part of the fault plane, certainly newly exposed,
the dip progressively shift to the south moving down
along the exposed section, bringing the Gonfolite Group
directly above the Castel di Sotto Clays. The Castel di
Sotto Clays in this lower part of the fault plane are over-
416 G. SILEO ET ALII
Fig. 4 - Geological sketch map of the Gonfolite backthrust area.
– Carta geologica schematica dell’area del retroscorrimento della Gonfolite.
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 416

7. turned, with a planar bedding dipping south by 70°-80°
(fig. 5). We interpreted this fault plane as an outcrop of
the Gonfolite backthrust documented by BERNOULLI et
alii (1989). Field mapping around the Novazzano site
allowed us to confirm that the Gonfolite backthrust
largely affects the Castel di Sotto Clays, as shown in the
geological section of fig. 6. Minimum amount of vertical
component of Pliocene offset is 200 m. Therefore, in con-
trast to previous interpretations, the Gonfolite backthrust
did not cease its activity in the Late Miocene.
REMARKS ON THE QUATERNARY TECTONICS OF THE INSUBRIA REGION 417
Fig. 5 - Outcrop of the Gonfolite backthrust at the Novazzano site (see location in fig. 2): a) the tectonic contact between Castel di Sotto Clays
and Gonfolite Lombarda Group; b) our interpretation; c) particular of the overturned Castel di Sotto Clays in the footwall of the Gonfolite
backthrust (photos taken by Giancanio Sileo on July 2004).
– Il retroscorrimento della Gonfolite in località Novazzano (si veda l’ubicazione in fig. 2): a) il contatto tettonico tra le Argille di Castel di Sotto e il
Gruppo della Gonfolite Lombarda; b) l’interpretazione degli autori; c) particolare delle Argille di Castel di Sotto uncinate nel footwall del retroscor-
rimento (foto scattate da Giancanio Sileo nel mese di luglio 2004).
Fig. 6 - Geological cross section across the Gonfolite backthrust.
– Sezione geologica attraverso il retroscorrimento della Gonfolite.
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 417

8. Unfortunately, until now we were not able to observe
reverse displacement of Pleistocene deposits along the
fault zone. Direct observations of the fault plane can be
done in fact only in a few spots, due to the dense vegeta-
tion cover and diffuse man occupation of land, and in
these spots there are no exposures of well bedded Pleis-
tocene sediments across the fault zone. For instance, in
the Novazzano site only coarse glacial deposits outcrop in
the upper part of the section of fig. 5, but they are badly
exposed and it is impossible to understand if they are
faulted or not (see also ZANCHI et alii, 2005). Further
work is in progress to stratigraphically define the
youngest movements along the fault using geophysical
prospecting and exploratory trenching. However, we were
able to confirm the presence of normal fault systems at
the mesoscale affecting the Pliocene and Pleistocene
deposits in the nearby Mendrisiotto area, interpreted by
ZANCHI et alii (1997) as the accommodation at surface of
continuing fault slip on deep-seated South-Alpine com-
pressional structures. Our new data therefore support the
interpretation mentioned above about the recent reactiva-
tion of some Late Miocene thrust.
Also the geomorphic relations along the fault strongly
suggest a Quaternary activity for the Gonfolite back-
thrust. The new field data allow to precisely constraint
the trace of the backthrust, and therefore to better under-
stand the relationships between the fresh geomorphologic
expression of the Gonfolite reliefs and the presence of the
fault. In the Chiasso Plain and near Novazzano the front
of the Gonfolite relief is in contact with the Mesozoic car-
bonatic sequence of the Lombardian Basin. Near Mt.
Olimpino we mapped outcrops of the Liassic formations
of the «Moltrasio Limestone» and «Rosso Ammonitico» at
a distance of a few tens of meters from the outcrop of the
Oligo-Miocene marls and conglomerates at the base of
the Gonfolite range front. All the Lias to Oligocene
418 G. SILEO ET ALII
Fig. 7 - Shaded relief map of the study area with the mountain front sinuosity analysis and corresponding indexes. We calculated the moun-
tain front sinuosity index using a common GIS software and a 20 m Digital Elevation Model courtesy of the Regione Lombardia. The sinuo-
sity index is a basic reconnaissance tool to identify areas with active tectonic deformations. Through this index, it is possible to evaluate the
level of tectonic activity of a fault-generated mountain front, calculating the ratio between the length of the front and the length of the strai-
ght line between beginning and end of the front. Values of the sinuosity index increase as the erosional processes dominate, producing more
irregular mountain fronts (e.g. BULL & MCFADDEN, 1977; WELLS et alii, 1988; KELLER & PINTER, 1996; SILVA et alii, 2005). The sinuosity
index of the Gonfolite Range front is ca. 1.2, indicating an active tectonic mountain front. The higher value along the Albese con Cassano hill
is consistent with the presence of a blind thrust.
– Mappa in scala di grigio dell’area di studio e indice di sinuosità del fronte montuoso. I valori dell’indice, consistenti nel rapporto tra la lunghezza
del fronte e quella della linea retta congiungente i due estremi, sono stati calcolati mediante un comune software GIS ed il DEM a 20 metri messo
a disposizione dalla Regione Lombardia. Questo indice è uno strumento di riconoscimento per identificare le aree con deformazioni tettoniche
attive. I valori di sinuosità aumentano allorchè i processi erosivi sono dominanti producendo fronti molto irregolari (e.g., BULL & MCFADDEN,
1977; WELLS et alii, 1988; KELLER & PINTER, 1996; SILVA et alii, 2005). L’indice di sinuosità ottenuto dall’analisi del fronte montuoso del retro-
scorrimento della Gonfolite ha un valore di circa 1.2 che indica un fronte tettonico attivo. Il valore di sinuosità più alto lungo il fronte della collina
di Albese con Cassano è coerente con la presenza di un blind thrust.
20 143-Dgs10(411-426) 25-06-2007 14:57 Pagina 418

9. sequence is missing. This contact is therefore clearly the
surface expression of the Gonfolite backthrust (SILEO et
alii, 2005), and is constantly located along the break in
slope at the base of the Gonfolite range front. As already
pointed out, in this area Quaternary glacial erosion was
very strong and the pulsations of the Abduan ice tongue
obliterated all preexistent structures and relief. In partic-
ular, in the Chiasso plain several episodes of glacial
advances and retreats are well documented (BINI et alii,
2001). Since the glacial flow was from the north, and the
Gonfolite range front is facing north (figs. 2 and 3), the
base of the range front should not be coincident with the
fault trace. In other words, due to the glacial erosion the
range front should have been retreated somewhere south
of the trace of the backthrust. Glacial erosional processes
wiped out the bedrock Mesozoic carbonatic formations in
the Chiasso Plain but apparently they did not affect seri-
ously the Gonfolite reliefs, which are made by much
softer rocks. This is a serious geomorphic anomaly for a
landscape carved by glacial erosion. Lack of retreat of the
Gonfolite mountain front is a strong evidence that fault
slip has been capable, during the Quaternary, to with-
stand the glacial erosive activity. This is also suggested by
the very regular curved trace of the range front in map
view (fig. 2), for a length of about 20 km, with the concav-
ity facing south. It seems very unlike that this regular
morphology is only controlled by selective erosional
processes. In fact, as shown in fig. 7 the sinuosity index of
this front is ca. 1.2, indicating an active tectonic moun-
tain front (KELLER & PINTER, 1996). Again, if the mor-
phology of the Gonfolite relief was due to erosion, it is
not clear why the harder carbonate bedrock in the foot-
wall has been almost completely removed while the rela-
tively softer conglomerates and marls in the hangingwall
today form an outstanding range front.
Summarizing, the Gonfolite backthrust did not cease
to slip in the late Miocene, as commonly accepted in the
literature. Shortening was certainly reactivated during the
Pliocene, as observed near Novazzano, and produced sig-
nificant uplift along the Gonfolite range front. Geomor-
phic evidence and mesostructural analysis (ZANCHI et alii,
1995, 1997; BINI et alii, 2001) along the whole range front
strongly suggest that shortening and fault slip along the
Gonfolite backthrust took place also during the Quater-
nary. Vertical uplift during Middle Pleistocene is poorly
constrained, likely in the order of 100 m at Mt. Morone,
located near the western termination of the Gonfolite
relief.
THE ALBESE CON CASSANO ANTICLINE
Observations related to Quaternary deformation and
displacement at this site have been already described by
OROMBELLI (1976) and ZANCHI et alii (1997). The Albese
con Cassano Hill (fig. 8) is an east-west trending ridge,
located at the foothills of Lake Como (fig 2), linked to the
presence of an east-west trending smooth anticline
(Albese con Cassano anticline; fig. 2), which locally
affects the southward dipping Mesozoic mainly carbon-
atic succession. Based on new detailed field mapping, we
interpret this structure as the western termination of the
Mt. Barro thrust (BERSEZIO et alii, 1990; fig. 2) which,
due to a reduced cumulated displacement, is here blind
and marked only by its associated fault related folding.
Commonly, drainage pattern is strongly influenced by
tectonic structures and can record their medium to long
term activity (BURBANK & ANDERSON, 2001). A stream
which crosses an uplifting area can in fact maintain its
antecedence or be diverted, depending on the ratio
between uplift and erosional rates. In the closeness of
Albese con Cassano Hill, the Cosia Stream and two tribu-
taries change their trend from north-south to east-west,
recording an abrupt deviation in the local drainage pat-
tern (figs. 7 and 8); the drainage divide is marked by the
presence of three wind gaps, aligned with the deviated
streams. This diversion has been ascribed to the growing
of the Albese con Cassano anticline, which has locally
prevailed over the erosive strength of the Cosia Stream
(see CHUNGA et alii, 2006, and references therein). As
already illustrated in the past (NANGERONI, 1970;
OROMBELLI, 1976), a sequence of glacial and fluvioglacial
deposits (informally here called Albese con Cassano Con-
glomerates) outcrops on top of this relief. Facies analysis
of the Albese con Cassano Conglomerates clearly relates
them to a sandur-like depositional environment (well-
bedded, well-rounded gravel and sand of open pro-glacial
REMARKS ON THE QUATERNARY TECTONICS OF THE INSUBRIA REGION 419
Fig. 8 - 3D image of the Mt. Bolettone area derived from the 20 m
DEM of Regione Lombardia; view from south. White triangles indi-
cate wind gaps on the Albese con Cassano Hill; note the path of the
Cosia Stream and its tributaries (highlighted in white) clearly diver-
ted just north of the hill.
– Immagine tridimensionale, con vista da sud, dell’area del Monte Bo-
lettone (ricavata dal DEM dalla Regione Lombardia con risoluzione di
20 metri) I triangoli bianchi indicano i wing gaps sul rilievo di Albese
con Cassano. Si noti il tracciato del torrente Cosia ed i suoi affluenti
(evidenziati in bianco) chiaramente deviati a nord del rilievo.
20 143-Dgs10(411-426) 25-06-2007 14:58 Pagina 419

10. alluvial plain). Field mapping at 1:10,000 scale performed
for the new Geological Map of Italy, Sheet n. 75, «Como»
(CARG Project, Geological Survey of Italy), allowed us to
study in detail the spatial and vertical distribution of the
Albese con Cassano Conglomerates. They crop out in two
sites, between Como ad Lecco (Albese con Cassano and
Madonna della Neve sites; fig. 2) at an elevation ranging
between 550 m and 650 m a.s.l., directly overlying the
Moltrasio Limestone Fm. At the Albese con Cassano site
they are mainly horizontal on top of the hill and appar-
ently south-dipping moving south (see the geological map
of fig. 14 in ZANCHI et alii, 1996; and our fig. 9); these
conglomerates can be therefore seen as growth strata,
recording the progressive deformation of the Albese con
Cassano anticline. Their limited distribution in space is
due to the extensive erosional activity exerted by the Abd-
uan Glacier during the Quaternary. These conglomerates
could therefore be preserved only in particular positions,
acting like a sort of geomorphic refugee, while they com-
pletely lack, at the same elevations, in other nearby locali-
420 G. SILEO ET ALII
Fig. 9 - Geologic sketch map of Albese con Cassano area (from CHUNGA et alii, 2006, modified). The reverse fault just north of Albese con Cassano
is illustrated in fig. 11a; the soft-sediment deformations in fig. 11b-d are located at the junction between the Cosia and the Valloni streams.
– Carta geologica schematica dell’area di Albese con Cassano (modificato da CHUNGA et alii 2006). La faglia inversa a nord di Albese con Cassano
è illustrata in fig. 11a; le deformazioni nei sedimenti lacustri illustrate in fig. 11b fino in fig. 11d, sono posizionati alla giunzione fra i torrenti
Cosia e Valloni.
20 143-Dgs10(411-426) 25-06-2007 14:58 Pagina 420

11. ties along the mountain front and in the surrounding
hills. Unfortunately, there is no absolute dating for these
conglomerates but, based on regional stratigraphy, degree
of weathering and soil development, they have been
attributed to the Middle Pleistocene (OROMBELLI, 1976;
NANGERONI, 1970; BINI, 1993). As already pointed out,
this age is in agreement with the glacial chronology com-
monly accepted for the Southern Alps (e.g. BINI, 1993;
MUTTONI et alii, 2003; SCARDIA et alii, 2006), which refers
the beginning of the formation of the most important
Lario Amphitheatre’s frontal moraines to the Middle
Pleistocene.
As already illustrated by OROMBELLI (1976), facies
analysis of the Albese con Cassano Conglomerates has
demonstrated that they have been deposed as part of a
wide glacial outwash plain, which is definitely incompat-
ible with their present geomorphic setting and elevation.
In fact, they outcrop over 200 m higher than the facing
plain (ca. 350 m a.s.l .), that represents the upper part of
the regional gentle sloping surface of the LGM outwash
plain described above («Livello Fondamentale della Pia-
nura»). In agreement with OROMBELLI (1976), we also
consider the Albese con Cassano Conglomerates correla-
tive to similar cemented conglomerates preserved
beneath the adjacent fluvio-glacial plain, and encoun-
tered during the excavation of water wells (fig. 10).
Additional field observations confirm the Quaternary
activity of the Albese con Cassano anticline (figs. 9 and
11). As already described by OROMBELLI (1976) and
ZANCHI et alii (1997), the oldest depositional units are dis-
placed by a secondary steep reverse fault (figs. 9 and 11a).
The vertical offset of about 5 m affecting the conglomer-
ates and underlying glacial till indicates recent tectonic
shortening. This outcrop was newly exposed after a land-
slide in late 2003 and has been subsequently covered by
reparation works. Also, the glaciolacustrine deposits
entrenched in the basal Middle Pleistocene units (fig. 9)
and outcropping along the Cosia Stream valley floor show
evidence for coseismic liquefaction probably related to
a local seismogenic source, as recently discussed by
CHUNGA et alii (2006; fig. 11b-c).
Summarizing into a consistent structural framework
all the observed evidence for Quaternary uplift and defor-
mation, we propose that the Albese con Cassano Hill is a
growing anticline that has absorbed ca. 200 m of vertical
displacement from Middle Pleistocene to present. This is
clearly indicated by the evident anomaly in the drainage
pattern, the presence of a syntectonic sequence of
deformed conglomerates (growth strata), and reverse dis-
placement along a secondary fault. The age of the Albese
con Cassano Conglomerates is at the moment the main
source of error. We regard this structure as an active
fault-propagation fold formed above a blind thrust fault
(fig 10), representing the western termination of Mt.
Barro fault, a ca. 20 Km long south-verging thrust in the
Mesozoic carbonatic succession of the Lombardy sedi-
mentary sequence. East of Mt. Barro this thrust is seg-
mented by a north-south major structural lineament
(Lecco Line; JADOUL & GAETANI, 1986; GIANOTTI & PE-
ROTTI, 1986; BERSEZIO et alii, 1990).
REMARKS ON THE QUATERNARY TECTONICS OF THE INSUBRIA REGION 421
Fig. 10 - Geological cross section of the Albese con Cassano anticline. The folded Mesozoic sequence has been interpreted as due to a Quater-
nary fault propagation fold formed above the blind Mt. Barro thrust.
– Sezione geologica attraverso l’anticlinale di Albese con Cassano. Il piegamento della sequenza Mesozoica è stata interpretato come l’effetto della
propagazione di una faglia quaternaria al disopra del blind thrust del Monte Barro.
20 143-Dgs10(411-426) 25-06-2007 14:58 Pagina 421

12. 422 G. SILEO ET ALII
Fig. 11 - Field observations of Quaternary shortening and paleoseismicity in the Mid-Pleistocene glacial deposits outcropping
on top of the Albese con Cassano hill (see locations in fig. 2): a) reverse fault (ca. 5 m of displacement) in the basal Mid
Pleistocene glacial deposits, i.e. from top to the bottom, fluvioglacial polygenic conglomerates and glacial till; b) and c) soft-
sediment deformation in younger Mid-Pleistocene proglacial lake deposits; d) paleoliquefaction in the same deposits.
– Osservazioni di terreno nei depositi glaciali Medio-Pleistocenici affioranti alla sommità del rilievo di Albese con Cassano (vedi
fig. 2): a) faglia inversa (circa 5 m di dislocazione) nei depositi glaciali basali Medio-Pleistocenici, i.e., dall’alto verso il basso,
conglomerati poligenici e till glaciale; b) e c) deformazioni in sedimenti lacustri proglaciali Medio-Pleistocenici; d) paleoliquefa-
zioni negli stessi depositi.
20 143-Dgs10(411-426) 04-07-2007 8:50 Pagina 422

13. DISCUSSION AND CONCLUSIONS
The revision of the literature data, new field mapping
at 1:10,000 scale and detailed geomorphic observation
allow us to confirm previous interpretations by ROEDER
(1992) and ZANCHI et alii (1997) about the post-Messi-
nian to Quaternary reactivation of Late Miocene thrusts
in the Insubria region at low strain rates, and under a
continued north-south shortening. A similar conclusion
has been drawn by BURRATO et alii (2003), based on the
study of the causative fault of the May 12, 1802, Soncino
earthquake (fig. 1), for the whole frontal sector of west-
ern Southern Alps underneath the Po Plain. The resulting
scenario is therefore different from the reported deacti-
vation of the western Southern Alps after the main phase
of emplacement of the foredeep fold and thrust belt
(«Lombardic Phase» of SCHUMACHER et alii, 1996; 14 to
6 Myr B.P.).
Based on previous geological studies, GPS data, and
new data presented in this paper, we can argue that the
Insubria region is currently contracting at a very slow
velocity (averaging 1 mm/yr). We reach this conclusion
based on evidence from long term strain in the Quater-
nary deposits and in spite of a lack of large historical
earthquakes. We also suggest that strain rates in the lake
Maggiore and Lake Como are lower than in the Lake
Garda region. This is consistent with both long and short
term patterns of contraction in the Northern Apennines
and Southern Alps, which can be related to rotational
opening of the Tyrrhenian Sea (BURRATO et alii, 2003;
GIARDINA et alii, 2004; SERPELLONI et alii, 2005; D’AGO-
STINO et alii, 2005). However, evidence of Quaternary
shortening in the Insubria region is not very different in
terms of both a) style of faulting and folding, and b) local
fault parameters (as derived from observed uplift rates)
from that known southwest of Lake Garda.
We suggest that the strong effect of glaciations in this
region, including excavation of deep valleys and deposi-
tion of large terminal moraines at the active mountain
front, has obscured additional evidence of active shorten-
ing. In a similar stratigraphic and geomorphic setting,
and within a moderately active tectonic region, the identi-
fication of reliable strain and chronological markers is
not an easy task. Very detailed geomorphic and strati-
graphic investigation is needed to detect the relatively
small tectonic signal in the local landscape. Only specific
careful geomorphological and geological analysis might
allow to evaluate more precisely the displacement history,
amount and nature of each Quaternary structure identi-
fied in the study area. It should be clear that the research
in this field is still at an early stage. One goal of this note
is to promote further study on the poorly documented
Quaternary tectonic of this region.In fact, none of the
known Quaternary tectonic structures in the Lombardian
Southern Alps has been quantitatively characterized until
now. At present, what we know about the growing anti-
clines near Lake Garda, located within the epicentral area
of the Me 6.2, December 25, 1222, Brescia earthquake
(GUIDOBONI, 2002) is only the amount of Middle Pleis-
tocene structural relief (ca. 200 m; CURZI et alii, 1992).
For the causative structure of the Me 5.7, May 12, 1802,
Soncino earthquake, we only have a preliminary estimate
of the fault size (10 km of fault length by 6 km of fault
width) and coseismic slip (less than 0.5 m at depth; maxi-
mum surface vertical displacement ca. 0.15 m; BURRATO
et alii, 2003). In agreement with this conclusion our
knowledges about the two major Quaternary tectonic
structures in the Insubria region, bring us to suppose that
they have controlled the recent growth of the Gonfolite
Range Front west of Como, and of the Albese con Cas-
sano Hill east of Como. We assessed a fault length of ca.
20 km for both structures, and a Middle Pleistocene
structural relief of ca. 200 m for the Albese con Cassano
anticline. A vertical uplift of a few hundreds of meters
during the Middle Pleistocene along the Gonfolite back-
thrust hangingwall is also a reasonable estimate, but this
value is poorly supported by the available data.
If our hypothesis will be confirmed, eventual data on
earthquakes magnitude and recurrence times associated
to the investigated structures should be taken into account
in future seismic hazard estimates.
At this preliminary point of our work, the review of
the literature data and our new mapping and investiga-
tions suggest that Quaternary shortening should occur in
a continuous belt in the foothills of Southern Alps
between Lake Garda and Lake Maggiore. North-south
directed Quaternary shortening and its relations with the
current seismicity level has been well documented in the
eastern part of the Southern Alps (e.g. SERVA, 1990;
CASTALDINI & PANIZZA, 1991; BENEDETTI et alii, 2001;
GALADINI et alii, 2005). New detailed geoological and
paleoseismological investigations are needed in order to
prove, but also to disprove, that similar relations are valid
also in the western Southern Alps and in particular in the
Insubria region.
ACKNOWLEDGEMENTS
The authors wish to thank Cipriano Carcano, Sergio Rogledi,
Leonello Serva, Carlo Doglioni and Giorgio Pasquaré for the helpful
discussions and suggestions. Revisions from Kurt Decker and an
anonymous referee allowed us to considerably improve the paper.
Andrea Berlusconi greatly helped during the field mapping of the
Gonfolite backthrust. PRIN 2005 funding to A.M. Michetti, and
APAT (Agency for Environment Protection and Technical Services-
Geological Survey of Italy, G. Sileo Ph.D. project grant) supported
this research.
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REMARKS ON THE QUATERNARY TECTONICS OF THE INSUBRIA REGION 425
Received 22 July 2005; revised version accepted 20 Juanary 2006.
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