Calcareous tufa as indicators of climatic variability: a case study from southern Tuscany (Italy) - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 272

This view is not shared by some authors who
postulate that tufa growth in the Mediterranean
area was limited to global warm climate and that
no carbonate deposition could occur during
glacial, stadial and interstadial periods (Vaudour
1988, 1994; Pe˜a et al. 2000; Horvatin ˇ i ´ et al.
2000; Soligo et al. 2002; Pedley et al. 2003).
Possible explanations of this contradiction are:
(i) the glacial period in the southern segment of
Valdelsa valley was not sufficiently cold to
prevent the deposition of carbonate; (ii) the rainfall
is arguably as a climatic factor affecting tufa depo-
sition more important than supposed before; and
(iii) the speculated low-thermal characteristics of
the issuing waters had a positive influence on the
production of carbonate deposits even during
cool/cold periods. The latter interpretation, even if
the climate-travertine relationships are not yet ade-
quately substantiated, is in agreement with several
authors which concur in the opinion that endogenic
groundwaters may be less dependent on climate,
since they have little opportunity to interact with
the atmosphere before resurgence (Sturchio et al.
1994; Pentecost 1995; Capezzuoli & Gandin 2004;
Faccenna et al. 2008).
More isotopic and geochemical data are necess-
ary for a comprehensive vision of this problem,
but at the moment they are not available.

controlled by the climatic variability of the
younger Late Pleistocene-Holocene. At least three
of the Valdelsa carbonate Synthems and the inter-
posed erosional phases can be correlated with
the major climatic changes recognized in the
European-Mediterranean area. The FOC Synthem
apparently coincides with the Last Glacial Inter-
stadial; the FOC/BEL erosional phase with the
Younger Dryas; the BEL Synthem with the
'Optimum Climatic' (Atlantic); the BEL/POG ero-
sional phase with the Sub-Boreal, and finally the
POG Synthem seems to summarize the deposition
of the last 2.5 ka (Sub-Atlantic).
This climatic correlation and the radiometric
data imply that the deposition of calcareous tufa in
Valdelsa was mainly dependent on the rainfall avail-
ability and, consequently, active even during
cold periods.
In this reconstruction, evidence of Late
Pleistocene-Holocene climatic variations in the
Central Apennine have been inferred for the first
time from terraced fluvial carbonates (calcareous
tufa) rather than from detrital lacustrine deposits.

This work has been financially supported by the University
of Siena PAR Grant (F. Sandrelli). The authors would like
to thank Susan Pedley for language ameliorations of the
text. We are grateful also to Brian Jones and to the
Volume Editor for critical reading of the manuscript and
constructive comments suggesting major improvements.

Conclusions

The southern segment of the Valdelsa Basin
(Tuscany) is characterized by the presence of a car-
bonate terraced succession developed in a limited
segment of the fluvial pattern. Sedimentological
and petrographic analysis shows that these carbon-
ates are mainly composed of calcareous tufa depos-
ited in a fluviatile-paludal environment.
Radiometric dates performed on organic-rich
material indicate that at least the older terraced
sequences were deposited during a cold climatic
interval. A scenario that cannot be discarded to
explain the occurrence of calcite precipitation
even during cold periods is that the carbonate
system could have been fed by slightly warm
waters, even during cold periods. This is speculated
on the presence of microbial laminated carbonate
facies locally exposed at the base of the apical
portion of these carbonates bodies and possibly
related to thermal springs.
Geomorphological and sedimentological analy-
sis supported by the results the radiometric data
show that the depositional/erosional evolution of
the Valdelsa succession is constrained by major
climate phases corresponding to those recognized
in the coeval detrital lacustrine successions of
Central Italy. Consequently, the evolution of the ter-
raced succession appears to have been directly

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