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rivers did form new terraces during warm periods or
cold-to-warm transitions. In contrast, they seemed
to cut down and deepen their valleys following
interglacial periods, which reflect responses driven
by climate change, mainly at orbital (Milankovitch)
frequencies (Bridgland et al. 2004a, b; Bridgland &
Westaway 2008; Ortiz et al. 2009).
Consequently, terraced carbonate deposits hold
the potential to provide significant palaeoclimatic
data in karstic regions and, when preserved they
retain more accessible genetic information com-
pared with the poorly lithified detrital terraced
deposits that, being easily eroded and reworked by
weathering, pedogenic processes and landslides,
do not retain unequivocal evidence of their geo-
morphologic evolution. An interesting case study
on this subject is offered by the results of the geo-
morphological, sedimentological investigation and
dating of calcareous tufa terraced deposits exposed
in Elsa Valley (Southern Tuscany Italy).
Aim of this study was to demonstrate that among
subaerial continental deposits, not only detrital
lacustrine deposits, but also terraced fluvial carbon-
ates/calcareous tufa can be considered reliable reg-
isters of climate variations, since their development
seems to be mainly controlled by water availability
more than ambient temperature. In this paper the
four depositional and downcutting events recog-
nized and dated in the calcareous bodies of Valdelsa
terraced succession are reported and correlated with
the major climate changes occurred during the Late
Quaternary glacial period in the European/Mediter-
ranean area and in particular in Central Italy
(Giraudi 2000, 2001, 2004; Narcisi 2001; Sadori
et al. 2004; Magny et al. 2006; Drescher-Schneider
et al. 2007).
Elsa River (Canuti & Tacconi 1975; Barazzuoli
et al. 2002) which is the main tributary of the
Arno River.
The southern portion of the Valdelsa Basin is
characterized by a complex Quaternary succession
of subaerial deposits (Capezzuoli & Sandrelli
2004; Capezzuoli et al. 2007, 2008) made of
mainly carbonate, unconformity-bounded, units
that can be referred to Synthems that is, the basic
unconformity-bounded unit of
'Unconformable
Boundary Stratigraphic Units'
[(UBSU);
ISSC
1987; Salvador 1994].
The oldest units, the Early-Middle Pleistocene
Strove (STR) and Campiglia dei Foci (CDF)
Synthems (Capezzuoli et al. 2007), forming sub-
horizontal plateaux that characterize the local land-
scape (Fig. 2a), represent two consecutive episodes
of a wide lacustrine-paludal environment.
The general uplifting of the region marked the
end of the Early-Middle Pleistocene lacustrine
sedimentation that was followed by the progressive
incision and selective erosion of the carbonate
plateaux down to the underlying Pliocene sands,
and resulted in an inverted relief in this area
(Bartolini & Peccerillo 2002) and a new hydro-
graphical pattern.
Along this renewed fluvial network, four sub-
sequent fluvial-palustrine episodes gave rise to
the sedimentation in the river valleys, of four
unconformity-bounded units composed of detrital,
alluvial materials (sands, silts and pebbles) locally
replaced by fresh water carbonates.
The four synthems (Fig. 2b): Abbadia (ABB),
Calcinaia (CAL), Torrente Foci (FOC) and Bella-
vista (BEL), are represented by terraces located on
the slopes of the main valleys of the area (Capez-
zuoli & Sandrelli 2004), that can be easily identified
in the landscape on the basis of their elevation
above the present thalweg position (þ20-30 m/
ABB, þ12-25 m/CAL, þ8-15m/FOC, þ2-
8m/BEL). The younger alluvial deposits locally
well-developed in the valley floors of several
rivers, form the present Poggibonsi Synthem
(POG). In discrete/specific segments of Elsa River
and its tributary valleys, the detrital alluvial deposits
of the four terraced systems are replaced by carbon-
ates in an area of over 50 Km
2
(Fig. 1). Tufa bodies
have been deposited in tracts of Elsa River (between
Gracciano and Poggibonsi) and Staggia Creek
(between Castellina Scalo and Poggibonsi) about
8-9 km long, while their extension along Foci
Creek (between San Gimignano and Campiglia dei
Foci) and Imbotroni Creek is shorter, no more
than 4 km long.
Reduced calcareous crusts are currently forming
locally, around few active small springs of low
thermal water (Capezzuoli et al. 2007). The four
calcareous bodies, previously described as 'recent
Geological setting
The southern Elsa River Valley, a NW-SE tectonic
depression known as Valdelsa Basin (Bossio et al.
1995b), filled up by late Miocene and Pliocene
continental and marine sediments (up to 2000 m;
Ghelardoni et al. 1968) is bounded by the Middle-
Tuscan Ridge to the West and South and by the
Chianti Ridge to the East (Bossio et al. 2000)
(Fig. 1). While the Chianti Ridge is mainly com-
posed of detrital-carbonate flysch successions per-
taining to the Late Cretaceous-Eocene Ligurian
tectonic units, the Middle-Tuscan Ridge is com-
posed of formations of the Tuscan Nappe resting
on the metamorphic Middle Triassic Verrucano
red beds through the 'Calcare cavernoso', a karsti-
fied tectonic breccia (Rauhwacke) derived from
Late Triassic evaporites (Gandin et al. 2000). It
constitutes the carbonate rich, catchments basin of
the main aquifer that supplies the base flow of the
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