Calcareous tufa as indicators of climatic variability: a case study from southern Tuscany (Italy) - Tufas and Speleothems: Unravelling the Microbial and Physical Controls - page 259

Calcareous tufa as indicators of climatic variability: a case study
from southern Tuscany (Italy)

ENRICO CAPEZZUOLI*, ANNA GANDIN & FABIO SANDRELLI
Dipartimento di Scienze della Terra, University of Siena, Via Laterina 8, 53100 Siena, Italy
*Corresponding author (e-mail: [e-mail])

Abstract: A carbonate terraced succession mainly consisting of fluvial/palustrine calcareous
tufa and of lacustrine limestone was deposited during recent Quaternary in a limited segment of
the Valdelsa fluvial pattern (southern Tuscany, Italy).
The radiometric data obtained from three carbonate terraces indicate that the depositional/
erosional history of the Valdelsa succession during Late Pleistocene-Holocene, has been con-
strained by the same cyclic events observed in coeval detrital lacustrine successions of Central
Italy. At least three of the Valdelsa carbonate Synthems and the interposed erosional phases can
be correlated with the major climatic changes recognized in the European-Mediterranean area,
from the Last Glacial Interstadial through the Younger Dryas to the Atlantic 'Optimum Climatic',
the Sub-Boreal and finally at 2.5 ka the last Sub-Atlantic oscillation.
This climatic correlation and the radiometric data imply that the deposition of calcareous tufa in
Valdelsa was mainly dependent on rainfall availability and, consequently, was active during the
milder oscillations within the cold periods.

(Ord ` ˜ez et al. 2005; Capezzuoli & Sandrelli 2006;
Ortiz et al. 2009).
Terrestrial carbonates comprise a number of
deposits formed on emerged land in a variety of
depositional settings where old carbonate rocks are
exposed. Their perceived importance has greatly
increased since it has been revealed that they are
particularly sensitive indicators of past environ-
mental conditions. Recent studies, in fact, have
demonstrated that extended and detailed palaeocli-
matic records can be obtained from the sedimentolo-
gical/stratigraphic and geochemical analysis of
speleothems, calcrete and lacustrine limestone
(Henning et al. 1983; Livnat & Kronfeld 1985;
Bar-Matthews et al. 1997; Von Grafenstein et al.
2000; Leng & Marshall 2004; McDermott 2004;
Fleitmann et al. 2004; Drysdale et al. 2004;
Dworkin et al. 2005). Comparable information
is now becoming available from the study of
travertines and tufas precipitated from calcium-
bicarbonate-rich stream waters flowing under sub-
aerial conditions, from thermal or karstic springs
(Andrews 2006; Andrews et al. 1993, 1994, 1997,
2000; Frank et al. 2000; Makhnach et al. 2000,
2004; Matsuoka et al. 2001; Soligo et al. 2002;
Ihlenfeld et al. 2003; Garnett et al. 2004; Smith
et al. 2004; Andrews & Brasier 2005).
The geomorphological evolution of a river
valley can also reflect the main palaeoclimatic vari-
ations. In particular the down cutting of a series of
terraces is generally related to major climate
phases in the region. It has been noted that many

Interest in the climatic oscillations on the Earth, and
the extent to which humankind is changing the bio-
sphere, has never been as great as at present since
climate controls all the surface processes on our
planet including the formation of sediments/rocks
(Pentecost 2005).
So far, acquisition of data on the climatic con-
ditions of recent terrestrial deposits has been gener-
ally performed in mainly terrigenous, lacustrine
sediments (Digerfeldt et al. 1997; Magri 1999;
Giraudi 2000, 2001; Magny et al. 2002, 2006;
Sadori et al. 2004; Wulf et al. 2004; Drescher-
Schneider et al. 2007). Actually the study of past
lake-level changes provides an excellent proxy for
palaeoclimatic reconstructions because of: (i) a
potentially continuous record covering a time span
from the present day back through several glacial/
interglacial cycles; (ii) a high temporal resolution
due to high sedimentation rates and the preservation
of annual laminations; and (iii) considerable poten-
tial for tephrochronological investigation, enabled
by contemporary volcanic activity (Wulf et al.
2004). Fluvial deposits have a lower potential for
preservation owing to the high-erosive potential of
the flowing waters and high erodibility of the associ-
ated detrital deposits. However, terraced, fluviatile
carbonate deposits appears to be particularly promis-
ing for the understanding of the environmental and
palaeoclimatic evolution of the area, since the mor-
phology of carbonate terraces and their depositional
features are generally rather well-preserved due
to early lithification of the carbonate sediments