Calcareous tufa as indicators of climatic variability: a case study from southern Tuscany (Italy) - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 268

composition of wood and peat (226‰). With regard
to the dating of the sample of wood (Co2), it is poss-
ible to assume that the resulting measurement rep-
resents a maximum age, therefore including the
possible residence time in soil and/or reworking
of the wood, before C 14 clock started.
The 14 C chronological data combined with the
results of sedimentological analysis support a new
model of the geomorphologic evolution of the
valley network and the cyclic deposition of the
tufa systems. The depositional events recognized
in the Valdelsa terraced carbonates have been
correlated with the main Late Quaternary climatic
changes occurred in the European area and in
particular in Central Italy.
Discussion
The study of the terraced carbonate succession in the
southern Valdelsa Basin documents significant
changes of the landscape during Late Quaternary.
The four episodes of tufa development alternated
with stages of erosion that were followed by the
re-establishment of fluvial-palustrine conditions.
For a better understanding of the focal mechan-
ism triggering the erosional/depositional events in
this sector of Tuscany, we try to outline the likely
palaeoclimatic and/or tectonic regimes that con-
trolled the origin of the Valdelsa terraced succession
and related carbonate deposits.
Climatic conditions of deposition
In order to document the palaeoclimatic context in
which the calcareous tufa of the late Quaternary
Valdelsa carbonate synthems were developed, an
attempt has been made to correlate the deposi-
tional/erosional phases represented by the terrace
succession, with the coeval climatic changes
known to have occurred in Central Italy.
Palaeoclimatic data from Late Pleistocene-
Holocene lacustrine deposits of Central Apennine
(Fig. 1a) are available in the literature (Narcisi &
Anselmi 1998; Magri 1999; Magri & Sadori 1999;
Giraudi 2000, 2001; Narcisi 2001; Sadori et al.
2004; Magny et al. 2006; Drescher-Schneider
et al. 2007). Giraudi (2004) summing up the data
concerning the volcanic lakes of Mezzano and
Vico (northern Latium) and the drained tectonic
Fucino Lake (Abruzzo) (Fig. 1a), evidence an
unequivocal correspondence between the high and
low water levels of these lakes. According to
Giraudi (2004), the distribution of these Central
Apennine lakes implies that the key factor control-
ling the cyclical alternation of the lake levels
was conditioned by the hydrological balance (differ-
ence between precipitation and evaporation) and,
consequently, by climatic oscillations. Comparing