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Decoding tufa and travertine (fresh water carbonates) in the sedimentary record: The state of the art

November 2013
Sedimentology 61(1)

November 2013
61(1)

DOI:10.1111/sed.12075

Authors:

Enrico Capezzuoli

University of Florence

Anna Gandin

Università degli Studi di Siena

Martyn Pedley

University of Hull

Traditionally, fresh water carbonate research has focused on the sedimentology and palaeontology of ancient lacustrine deposits. Lithofacies in such low-energy deposits are typically fine-grained, developed uniformly in a generally concentric distribution (‘bulls-eye’ pattern) and are predictable even when preserved imperfectly. In contrast, because of their local lithofacies and palaeontological complexities, fluvial carbonates were either delegated to a status of ‘minor geomorphological features’ or barely considered prior to the 1970s. This viewpoint was based on the depositional record of fluvial and spring-fed fresh water carbonates, which were considered to be restricted generally to localized karstic areas. Such deposits are often preserved as scattered patches of ambient temperature tufa. Occasionally, however, in active tectonic areas, localized travertine deposits are also developed from deeply circulating hydrothermal waters. With a few exceptions (for example, basins with high subsidence rates or in arid climate zones), these fresh water carbonates are prone to erosion from continuing river incision and thus may not be preserved in the geological record. A partial record of fluvial and spring-deposited carbonates is often preserved in Quaternary deposits, but the record in older deposits is typically fragmentary and often diagenetically modified. Yet once their unique facies architecture (and specialized nomenclature) is understood, these carbonates provide an important record of past sedimentological cycles of great value in palaeoenvironmental landscape modelling. The emphasis of modern research is to acquire information that explains how active systems function. In this respect, tufas reveal much of how carbonate precipitation is a shared product of physico-chemical and microbiological biomediation processes. Likewise, travertines not only show an intimate interrelation with active tectonism but also hold great potential as monitors of past volcanic carbon dioxide emissions. In addition, both tufas and travertines contain palynological records that can be used as proxy indicators of climate change. Perhaps no other field of sedimentology has witnessed more developments and applications over such a brief period of study.

Examples of travertine vent morphologies: (A) linear fissure ridge (Kamara ridge, Turkey), ca 40 m long; (B) linear ridge (ca 20 m long) formed by coalescent, aligned cone vents (Terme San Giovanni, Rapolano Terme, Italy); (C) high relief, circular mound (Castel di Luco, Italy - the mound is ca 10 m high); (D) low relief, circular mound with bubbling pool (Bullicame Spring, Viterbo, Italy - the pool is ca 7 m wide); (E) unusual mound at a triple fault junction (Cambazli, Turkey).

…

Examples of tufa morphologies: (A) cascade (ca 50 m high) at Monastiero de Piedra Natural Park (Zaragoza – Spain); (B) lakes and cascade (ca 15 m high) at Plitvice Jezera (Croatia); (C) fossil tufa cliff (ca 20 m high) at Antalya (Turkey); (D) small barrages (ca 50 cm high) at Diborra Gorge (Siena, Italy); (E) small cascades (ca 2 m high) below Lagunas Redondilla, Ruidera Pools Natural Park (Spain).

…

Diverse (in colour) microbial communities and changes in their relative lateral position between thermophyllic and photosynthesizing bacteria in several thermal systems. Examples from: (A) Egerszalok (Hungary; 60°C - the channels are ca 10 m long); (B) Bagni San Filippo (Italy; 52°C - the pool is ca 2 m long); (C) Karahayt (Turkey; 58°C - the thermal system is ca 4 m high); and (D) Castelnuovo Berardenga (Italy; 39°C - the pool is ca 10 m long).

…

A) The Holocene perched springline tufa body of Mai-Makden (Ethiopia). The gorge is ca 10 m deep. (B) Detail of phytohermal framestones in the upper portion of its frontal part typifying a densely vegetated cascade environment very different from the present-day arid environment (man for scale, ca 1.8 m tall).

…

A) Fissure ridge (ca 10 m long) at Bagni San Filippo (Italy). This travertine deposit is located at the tip zone of a strike-slip to oblique-slip fault along which eruptions of the Late Pleistocene volcano, Mount Amiata, occurred. Gas emissions and hot waters are issuing actively from this geothermal area, forming spectacular travertine bodies [the so-called ‘White whale’ slope travertine, ca 10 m high in (B)] and related macrocrystalline lithofacies [examples of thick crystalline crusts in (C)].

…

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Decoding tufa and travertine (fresh water carbonates) in the

sedimentary record: The state of the art

ENRICO CAPEZZUOLI*, ANNA GANDIN* and MARTYN PEDLEY†

*Department of Physical, Earth and Environmental Sciences, University of Siena, Via Laterina 8,

Siena 53100, Italy (E-mail: capezzuoli@unisi.it)

†Department of Geography, Environment and Earth Sciences, University of Hull, Hull HU6 7RX, UK

ABSTRACT

Traditionally, fresh water carbonate research has focused on the sedimento-

logy and palaeontology of ancient lacustrine deposits. Lithofacies in such

low-energy deposits are typically ﬁne-grained, developed uniformly in a gen-

erally concentric distribution (‘bulls-eye’ pattern) and are predictable even

when preserved imperfectly. In contrast, because of their local lithofacies and

palaeontological complexities, ﬂuvial carbonates were either delegated to a

status of ‘minor geomorphological features’ or barely considered prior to the

1970s. This viewpoint was based on the depositional record of ﬂuvial and

spring-fed fresh water carbonates, which were considered to be restricted gen-

erally to localized karstic areas. Such deposits are often preserved as scattered

patches of ambient temperature tufa. Occasionally, however, in active tec-

tonic areas, localized travertine deposits are also developed from deeply cir-

culating hydrothermal waters. With a few exceptions (for example, basins

with high subsidence rates or in arid climate zones), these fresh water carbon-

ates are prone to erosion from continuing river incision and thus may not be

preserved in the geological record. A partial record of ﬂuvial and spring-

deposited carbonates is often preserved in Quaternary deposits, but the record

in older deposits is typically fragmentary and often diagenetically modiﬁed.

Yet once their unique facies architecture (and specialized nomenclature) is

understood, these carbonates provide an important record of past sedimento-

logical cycles of great value in palaeoenvironmental landscape modelling.

The emphasis of modern research is to acquire information that explains how

active systems function. In this respect, tufas reveal much of how carbonate

precipitation is a shared product of physico-chemical and microbiological

biomediation processes. Likewise, travertines not only show an intimate

interrelation with active tectonism but also hold great potential as monitors

of past volcanic carbon dioxide emissions. In addition, both tufas and traver-

tines contain palynological records that can be used as proxy indicators of

climate change. Perhaps no other ﬁeld of sedimentology has witnessed more

developments and applications over such a brief period of study.

Keywords Calcareous tufa, fresh water carbonate, sedimentology, terrestrial

carbonate, travertine.

INTRODUCTION

Terrestrial carbonates comprise a wide spectrum

of lithologies (speleothems, calcrete, lacustrine

limestone, travertines and tufas) which are

mainly precipitated under subaerial conditions

from calcium bicarbonate-rich waters in a large

variety of depositional and diagenetic settings.

These carbonates are characterized by a distinct

range of lithological, petrological and geochemical

Sedimentology (2014) 61, 1–21 doi: 10.1111/sed.12075

STATE OF THE SCIENCE

properties which clearly distinguish them from

their marine counterparts. Over the past 20 years,

they have risen in status from minor curiosities

to a major new research frontier. This interest

derives ﬁrst from their widespread distribution

in continental settings, and second because they

have long been recognized as important reposito-

ries of proxy-palaeoenvironmental information.

This has presented a spectrum of opportunities

ranging from the reconstruction of past ecosys-

tems and environments to analyses of tectonic

and sedimentary regimes. Recent developments

in analytical techniques have also shown that it

is possible to use travertine and tufa in several

new, unexpected ways that relate to elemental

biomediation processes, bioremediation, palaeo-

environmental markers, proxies for interpreting

climate change and even proxies for extraterres-

trial life. The present review aims to provide a

concise summary of the general aspects of

travertine and tufa, including classiﬁcation, mor-

phology and geochemistry, with a focus on their

main applications in past, present and future

research.

TRAVERTINE AND TUFA: A

CONTROVERSIAL NOMENCLATURE

The terms tufa and travertine are often used

indiscriminately as alternative names for the

same fresh water limestone material (Juli

a, 1983).

In particular, the term ‘travertine’ has been over-

used as a descriptive term for all crystalline varie-

ties of fresh water carbonate. Others have

distinguished powdery whitish tufa or calc tufa

varieties. The terms tufa and travertine have also

been applied indiscriminately to cave deposits

(see Pentecost, 1981). Others (Irion & M€

uller,

1968) use the term calc sinter as a term for fresh

water carbonates. Pentecost & Viles (1994) and

Viles & Goudie (1990) presented a range of other

terms and classiﬁcations, many of which lack pre-

cision.

Several recent articles have focused upon

genetic deﬁnitions, based upon, for example,

water temperature, source of carbon dioxide

(Pedley, 1990; Pentecost & Viles, 1994; Jones &

Renaut, 2010) or upon the chemical mechanism

involved in precipitation (Pentecost, 2005). Thus,

‘travertine’ has been reserved by many authors as

a term for warm to hot water hydrothermal pre-

cipitates whereas ‘tufa’ has been reserved for

ambient temperature (cool water) deposits

(Pedley, 1990). For temperature-based deﬁni-

tions, water temperatures have been measured

directly in active depositing sites, or estimated

indirectly from associated organisms and fossils

(Pedley, 1990; Koban & Schweigert, 1993).

Deﬁnitions of cool water tufa frequently refer to,

or even require, the presence of macrophytes in

addition to cyanobacteria, heterotrophic bacteria

and algae, the suggestion being that temperatures

must remain below 30°C for these organisms to

survive. However, Pentecost et al. (2003) dis-

cussed the difﬁculties in deﬁning what consti-

tuted a ‘hot’ spring in ancient deposits, while

Brasier (2011) reiterated how the terms ‘tufa’ and

‘travertine’, which imply circumstances that cannot

be veriﬁed easily in ‘deep time’, might be avoided in

favour of more descriptive terminology.

Without doubt, a water temperature classiﬁca-

tion as an indicator of shallow versus deep-cir-

culating ground waters (and consequently of

travertine or tufa) is oversimpliﬁed. In fact, low-

temperature fresh water carbonates, such as the

Chinese deposits of Huanglong [10°at 3500 m

above sea-level (asl); Zhang et al., 2012] and of

Baishuitai (7°at 3000 m asl; Liu et al., 2010),

might easily be attributed to travertines due to

their geochemical characteristics. Interestingly,

Keppel et al. (2011) described typical phyto-

hermal framestone tufa deposited from 20 to

27°C waters and interpreted them as super-

ambient temperature meteogene ground water in

origin, based on the lack of signiﬁcant chemical

or temperature variance between samples

collected at different times of the year.

When analysing travertine and tufa, an

integrated approach is critical to understanding

and accurately interpreting the depositional

environment. The textures, the mineralogy and

the geochemistry of the fossil deposits, the asso-

ciated biota and the chemistry of the waters

from which they formed, as well as the likely

geomorphological, hydrological and tectonic set-

tings in which the carbonates were deposited

must be considered. In addition, the identiﬁca-

tion of a clear modern analogue is needed in

order to understand the processes and controls

operating in these settings and also to better

understand their signiﬁcance in the ﬁll and evo-

lution of continental basins (Table 1).

For this reason, the term travertine must be

retained for continental carbonates mainly

composed of calcium carbonate deposits pro-

duced from non-marine, supersaturated calcium

bicarbonate-rich waters, typically hydrothermal

in origin. Travertine deposits are characterized

chieﬂy by high depositional rates, regular bedding

2E. Capezzuoli et al.

and ﬁne lamination, low porosity, low permeabil-

ity and an inorganic crystalline fabric. Bacteria

and cyanophytes typically are the only associated

organic constituents, due to the presence of

unsuitable factors (for example, high temperature,

high rates of deposition, pH and sulphur) for plant

and tree growth (macrophytes). Aragonite rather

than calcite may also be present and d

C is typi-

cally high (positive or slightly negative). Such

deposits are typical of tectonically active areas

where geothermal heat ﬂux (endogenic or volca-

nic) is high.

In contrast, the term tufa (Ford & Pedley, 1996;

Pedley, 2009) refers to continental carbonates,

composed dominantly of calcite and typical of

karstic areas. These are typically produced from

ambient temperature, calcium bicarbonate-rich

waters which are characterized by relatively low

depositional rates producing highly porous

bodies with poor bedding and lenticular proﬁles,

but containing abundant remains of microphytes

and macrophytes, invertebrates and bacteria. Sec-

ondary carbonate deposits (cements and speleo-

thems) may also be associated. Aragonite is

usually absent (except from peculiar high Mg/Ca

ratio spring waters; Owen et al., 2010) and d

Cis

always low (very negative).

The distinction between these two lithotype

associations is not always clear since some cool

water deposits can represent a lateral develop-

ment of cooled thermal waters. In fact, macro-

vegetation readily colonizes the cooler water

areas downstream from hydrothermal resurgence

points. Confusion in the ﬁeld is mainly encoun-

tered where tufa and travertine are interlayered,

such as in distal areas of travertine ﬂowstones

which have cooled sufﬁciently to permit coloni-

zation by microphytes and macrophytes (Ford &

Pedley, 1996; Evans, 1999; Capezzuoli et al.,

2008; Brogi et al., 2012). However, the sedimen-

Table 1. Main distinctive characteristics of travertine and tufa (numerical data mainly derived from Pentecost,

2005; Gandin & Capezzuoli, 2008 and references therein).

Travertine Tufa

Depositional processes Dominantly abiotic Dominantly biotic

HCO

3content (mmol/l) >7<6

C (PDB&)1to+10 <0

DIC (mmol/l) >10 <8

Water temperature Thermal, generally higher than

30°C

Ambient, generally lower than 20°C

Mineralogy Calcite, aragonite Calcite

Depositional rate Higher (cm to m/year) Lower (mm to cm/year)

Fabric Mainly regularly bedded to ﬁne

laminated

Mainly poorly bedded

Crystal calcite size Macro (dendritic, bladed or acicular)

to micritic crystals

Dominantly micritic to microsparitic

crystals

Primary porosity Generally low (less than 30%) Generally high (over 40%)

Biological content Low (bacteria and cyanophytes) Very high (micro to macrophytes)

Depositional morphologies Multi-symmetrical bodies

(mounds, ridges and slopes)

Axial-symmetrical bodies (cascade,

dams and barrages)

Distinctive lithofacies Coated bubbles, shrubs Phytoherms

Hydrological setting Regular, generally permanent ﬂow Variable, rainfall-dependent ﬂow

Climatic control on

deposition

Less dependent Strictly dependent

Anthropogenic inﬂuence

on deposition

Scarcely inﬂuenced Deeply inﬂuenced

Tectonic relation Always present Often absent

Decoding tufa and travertine 3

STATE OF THE SCIENCE

tary facies and geometry of these tufa deposits

in the ﬁeld and their incidental juxtaposition

with typical travertine facies, are sufﬁcient, in

most cases, to suggest the primary physical char-

acteristics of the water source. Consequently, it

is generally possible on ﬁeld evidence alone,

even in ancient deposits, to make a clear dis-

tinction between travertines and tufas and to

distinguish the origin of their water source (Ped-

ley, 2009). However, there are a group of tufas

characterized by a typical hydrochemical signa-

ture indicative of ambient temperature precipita-

tion from cooled, deeply cycled (geothermal)

waters that are more difﬁcult to interpret; they

are generally encountered in the peripheral sec-

tors of geothermal regions with a recently active

tectonic history (for example, Italy). The term

‘travitufa’ is suggested in order to distinguish

them from normal tufas.

SEDIMENTARY FACIES

Despite growing interest, the classiﬁcation of trav-

ertine and tufa facies has presented many prob-

lems due to the number of parameters that

inﬂuence the ﬁnal depositional product (for exam-

ple, chemistry, hydrology, morphology, micro-

biology and botany), and no clear classiﬁcation

scheme embracing both tufas and travertines has

yet been proposed. However, classiﬁcation

schemes based on facies types typical of cold,

warm and hot water systems have been designed

to facilitate identiﬁcation and discussion. Hence,

different schemes use different criteria related to

petrography, morphology, deposition rate, cli-

mate, geochemistry, etc. (Zamarre~

no et al., 1997;

Guo & Riding, 1998; Fouke et al., 2000; Carthew

et al., 2003; Gandin & Capezzuoli, 2008). Details

of the basin-scale processes at the time of deposi-

tion, however, are often masked or even lost by

later continental erosion, and the remaining frag-

ments are frequently insufﬁcient to provide a full

interpretation of depositional scenarios.

DEPOSITIONAL ENVIRONMENTS AND

MORPHOLOGIES

In contrast with most continental deposits, ter-

restrial carbonates are capable of constructing

rapidly lithiﬁed rocks with positive relief at the

time of deposition. The abiotic/bio-induced

build-up process is responsible for their rapid

depositional rate. In tufa, for instance, deposi-

tional rates have been calculated in fossil and

active deposits by several authors, ranging from

032 mm/year (Heiman & Sass, 1989), 08 mm/

year (Pe~

na et al., 2000), 12to24 mm/year

(Andrews et al., 2000) and 42 mm/year (Weijer-

mars et al., 1986). For a more detailed review, see

Gradzinski (2010) and V

azquez-Urbez et al.

(2010a). Travertine depositional rates can be even

higher. Comparatively few measurements have

been made but most attest to the rapid accumula-

tion of travertines. The data range between 1 mm/

year and 1000 mm/year with a mean of around

200 mm/year (Pentecost, 2005). Consequently,

even if fresh water carbonate events are of short

duration in the geological record (Ford & Pedley,

1996), travertine and tufa are capable of rapidly

transforming the landscape and may have a major

inﬂuence on its evolution.

Perhaps the most common manifestation of

fresh water carbonate deposition is the terrace.

Such surfaces may be inclined gently and cover

several square kilometres, as in the case of

geothermal hot spring sites. Tufa terraces may be

composed of tens of kilometres of near horizontal

sheets comprised of lacustrine, paludal and bar-

rage lithofacies; their modern distribution from

the tropics to the Arctic conﬁrms their signiﬁ-

cance in the continental geomorphological

record, and illustrates the importance of better

understanding depositional processes rooted in

ﬂuid dynamics, precipitation kinetics and crystal

growth dynamics (Goldenfeld et al., 2006; Ham-

mer et al., 2010).

Nonetheless, physico-chemical ground water

parameters and external biotic–abiotic mecha-

nisms directly determine peculiar travertine and

tufa morphotypes and these deserve detailed con-

sideration. In particular, microbial composition,

associated vegetation type, substrate topography

and ﬂuvial and ground water hydrochemistry

contribute signiﬁcantly to depositional style and

preservation potential. All of these factors inﬂu-

ence the ﬁnal carbonate morphology and provide

criteria for their classiﬁcation (Table 1).

Travertine

Depositional and morphological classiﬁcations

have been proposed by several authors (Altunel

& Hancock, 1993b; Guo & Riding, 1998; Fouke

et al., 2000; Veysey et al., 2008; Guido et al.,

2010; Guido & Campbell, 2011, 2012). Many

travertines are associated with ﬁssures

which vent hot, deeply circulated waters to the

surface.

4E. Capezzuoli et al.

Vent environments (proximal)

Travertine deposits are focused frequently

around discrete springs associated with convec-

tive hydrothermal systems, often under high

pressure, and enhanced by bedrock damage that

give rise to connected fractures and enhanced

permeabilities in the bed rock. Such scenarios

favour circulation and upwelling of hydrothermal

ﬂuids (Rowland & Sibson, 2004). Precipitation

events are triggered frequently by CO

pressure

ﬂuctuations (Uysal et al., 2009) and seismic

activity (Becken et al., 2011). The shallow

plumbing system, representing conduits for the

upwelling thermal water, is lined by variably

shaped calcite/aragonite crystals (sparitic, acicu-

lar, dendritic and platy) developed into non-por-

ous, sub-vertical crystalline laminated crusts

(banded travertine: Altunel & Hancock, 1993a,b,

1996; Uysal et al., 2007, 2009, 2011). These

sheets are best developed in the throat of the trav-

ertine vent system but commonly also extend lat-

erally into injection veins and sill-like structures

(De Filippis et al., 2012), and decrease in thick-

ness and frequency away from the vent conduits.

At the water surface, travertine rapidly deposits

and quickly develops into steep-sided construc-

tional morphologies. If this occurs in an unusual

subaqueous setting (travertine pipes and pinna-

cles, Hillaire-Marcel et al., 1986; Hillaire-Marcel

& Casanova, 1987), the resulting macrofacies are

more porous and are connected intimately with

algal-microbial interactions. In contrast, their

more commonly encountered epigean counter-

parts generally consist of ﬁnely laminated drapes

often composed of macrocrystalline precipitates

deposited from thin, laminar ﬂowing sheets of rap-

idly cooling water. Depending on the chemical

and physical characteristics of these thermal

waters, irregular masses of ﬁlamentous bacteria

may locally colonize pool and channel margins in

the vicinity of the vent (Fouke et al., 2000; Taka-

shima & Kano, 2008; Di Benedetto et al., 2011;

Fouke, 2011). Here, they are often associated with

microsparitic to micritic laminae which may build

up into small (millimetre to centimetre scale)

shrubby growths, especially in shallow pools.

Ultimately, ledges can develop along the pool

margins and larger domes may form around vent

resurgence points. These carbonates are character-

ized by a vast array of crystal forms, from coarse

dendritic to platy and spherulitic calcite (Jones &

Renaut, 1996, 1998, 2010).

The resulting macro-morphologies are repre-

sented by two end member types: circular

mounds and linear-to-arcuate ﬁssure ridges. As

discussed by several authors (Curewitz & Karson,

1997; Brogi & Capezzuoli, 2009), development of

each type is driven by substrate competence and

permeability. For example, travertine ﬁssure-

ridges mainly develop on brittle-fracturing bed-

rock exposed at the surface, while isolated ther-

mal springs, such as towers, pinnacles and

mounds, generally form on unconsolidated sedi-

ments (Hancock et al., 1999; Brogi & Capezzuoli,

2009) and are often point sourced (Fig. 1).

Slope environments (intermediate)

Thermal waters ﬂowing away from the resurgence

area rapidly cool and degas. As temperature falls,

the environment is more conducive to bacterial

colonization and a more varied range of precipi-

tates often develop. Altunel & Hancock (1993b)

distinguished two kinds of depositional systems

(terrace and range-front sheets) in the Pamukkale

deposits (Turkey). Their morphologies are con-

trolled by the underlying morphology being either

gently inclined slope deposits or steep slopes

around graben fault margins.

Guo & Riding (1998) suggested an alternative clas-

siﬁcation using a depositional systems approach

developed for the Rapolano Terme deposits of Italy.

The ﬁnal shape of the travertine slope system is con-

trolled in the short-term by underlying morphology

but high deposition rates rapidly bury it. This pro-

cess leads to the deposition of variably inclined

lobate bodies characterized by smooth to well-

developed terraced slopes in their frontal part

(Chafetz & Folk, 1984; Guo & Riding, 1998). Waters

generally ﬂow over the entire terrace surface in

laminar sheets. Interactions between the pre-exist-

ing and evolving morphology, ﬂow velocity and

the biological components lead to deposition of a

diverse range of travertine lithofacies (for example,

crystalline crust, shrubs, coated bubbles and paper

thin-rafts).

If discharge ﬂuctuates, portions of the surface

can become exposed to sub-aerial conditions

and, depending on the period of exposure, may

become partially cracked or pedogenically

altered (autobrecciated sheets and more mature

palaeosol horizons). When the free ﬂow of

thermal water becomes conﬁned, rapid vertical

travertine accretion occurs along the channel

margins. Here, turbulent ﬂow causes physico-

chemical degassing (calc lev

ee precipitation

along the channel margins and accreting laminar

sheet deposition along the channel base). This

degassing rapidly leads to the vertical growth of

Decoding tufa and travertine 5

STATE OF THE SCIENCE

elevated, low sinuosity channels which may

stand metres higher than the surrounding terrace

and be hundreds of metres long (‘self-built chan-

nels’, Altunel & Hancock, 1993b; or ‘catwalks’,

Violante et al., 1994).

Distal environments

Distal environments encompass all of the depo-

sits forming in low relief topography from near-

ambient water temperatures where hot ground

water has been mixed with surface rain water.

These settings, marshes (Guo & Riding, 1998),

shallow lakes (Sant’Anna et al., 2004) or alluvial

plains (Brogi et al., 2012), are typically transi-

tional environments where travertine fabrics

grade imperceptibly into tufa fabrics and biotic

controls on depositional processes progressively

increase (Rainey & Jones, 2009). Deposits are

often dominated by lithoclastic material (often

hillwash breccia), but coated grains, in situ

coated macrophyte stems and subordinate,

massive bedded layers of clotted peloidal mi-

crite may develop. Many of these deposits could

be classiﬁed as travitufa deposits.

Tufa

The classiﬁcation of tufa into depositional

models has been considered by several authors

(Pedley, 1990, 2009; Violante et al., 1994; Ford

& Pedley, 1996; Carthew et al., 2003, 2006).

Classiﬁcation is generally based on depositional

geometry, details within sedimentary proﬁles

and petrology (for example, perched springline,

cascade, ﬂuvial, lacustrine and paludal). In con-

trast, Arenas-Abad et al. (2010) reviewed previ-

ous schemes and selectively analysed their

vertical facies successions as representing the

sedimentary processes leading to their develop-

ment. This analysis resulted in the grouping of

ABC

Fig. 1. Examples of travertine vent morphologies: (A) linear ﬁssure ridge (Kamara ridge, Turkey), ca 40 m long;

(B) linear ridge (ca 20 m long) formed by coalescent, aligned cone vents (Terme San Giovanni, Rapolano Terme,

Italy); (C) high relief, circular mound (Castel di Luco, Italy - the mound is ca 10 m high); (D) low relief, circular

mound with bubbling pool (Bullicame Spring, Viterbo, Italy - the pool is ca 7 m wide); (E) unusual mound at a

triple fault junction (Cambazli, Turkey).

6E. Capezzuoli et al.

all previously recognized fresh water carbonate

facies into two process-related models: (i) low-

gradient, non-stepped ﬂuvial and ﬂuvio-

lacustrine conditions, generally with extensive

development of oncoid and paludal facies; and

(ii) high-gradient and stepped ﬂuvial conditions

typically with laminated ﬂuvial and lacustrine

facies and variable developments of barrages,

waterfalls and dammed areas.

Resurgence environments (proximal)

Physico-chemical deposition of terrestrial carbo-

nates is always associated with calcite crystal

growth from CO

-rich ground waters oversatura-

ted in calcium ions. As water ﬂows away from the

resurgence point, carbon dioxide escapes into the

atmosphere and tips the increasingly supersatu-

rated solution in favour of calcite precipitation.

However, calcite precipitated from microbial bio-

mediation is increasingly recognized as important

(Rogerson et al., 2008; Pedley et al., 2009). This

contribution is considerably greater in tufa systems

than in travertine systems because bioﬁlms are

able to biomediate calcite internally even where

surrounding waters are insufﬁciently saturated for

abiotic calcite precipitation. The combined result

of the two processes effectively strips calcite from

the ﬂuvial system quite proximal to the source;

hence, it is possible to recognize the inputs of mul-

tiple resurgences within a single river course.

These processes may cause tufa deposition near

a single subaerial resurgence point (for example,

perched springline, Pedley, 1990; mound springs,

Keppel et al., 2011) and the deposit may be com-

posed predominantly of highly irregular, very por-

ous macrobiota dominated, depositional fabrics

(phytohermal facies). Alternatively, tufa may

develop at multiple resurgence sites along a water-

course to produce barrage tufas (Pedley et al.,

1996; Pentecost, 2005). On steep subaerial slopes,

point sourced resurgences are invariably associ-

ated with lobate perched springline tufas (Pedley

et al., 2003), whereas valley bottom and artesian

resurgences lead to the development of spring

mounds with lower width to height ratios than are

found in lacustrine settings (Pedley & Hill, 2002).

Less commonly, tufas may develop at lake ﬂoor

resurgences within fresh water, hyposaline or

hypersaline water bodies (Kempe et al., 1991;

Larsen, 1994; Rosen et al., 2004; Jones & Renaut,

2010; Guo & Chafetz, 2012). In these subaqueous

situations, porous stromatolitic/thrombolitic

build ups are more usual and may give rise to

mound morphologies.

Intermediate environments

Intermediate environments cover those parts of

ﬂuvial systems located considerable distances

from resurgences. Waters here are generally

undersaturated; consequently, little carbonate

precipitation is to be expected. However, other

mechanisms encouraging precipitation within a

river system include evaporation within ponded

areas and extensive colonization both by bio-

ﬁlms and aquatic vegetation (Perri et al., 2011;

Manzo et al., 2012). In addition, morphological

steps along water courses also cause enhanced

turbulence and lead to further release of carbon

dioxide, thereby encouraging physico-chemical

precipitation. Small cascades and barrages are

the most representative morphotypes (for exam-

ple, Plitvice Jezero and Krka River barrages –

Croatia; Emeis et al., 1987; Lojen et al., 2004;

Fig. 2). Unfortunately, it is often difﬁcult to

distinguish barrages forming adjacent to resur-

gences from those developed at morphological

thalweg steps where physico-chemical processes

are more active.

Upstream areas of these cascades and barrages

are often characterized by low-energy/stagnant

water settings (paludinal marshes, ponds or small

lakes). Planktonic bacteria and algae abound in

these low energy, pool settings and there is often

a tendency, especially during the summer

months, for whitings to develop (Thompson

et al., 1997; Ohlendorf & Sturm, 2001; Dittrich

et al., 2004). These whitings are caused by plank-

tonic microbial metabolic process triggered pre-

cipitation of minimicrite crystallites, and

contribute considerable volumes of lime mud to

the pool ﬂoor. Evaporation also concentrates

cations close to the air–water interface, further

enhancing the carbonate precipitation process.

Extensive bioﬁlm colonization of marginal aqua-

tic vegetation is also capable of encouraging thin

laminar carbonate precipitation on detrital nuclei

(superﬁcial oncoids) and semi-aquatic macro-

phytes (cylindrical oncoids) in intermediate envi-

ronments.

Distal environments

In the downﬂow direction, waters progressively

lose their dissolved calcium carbonate and their

capacity to deposit calcite is reduced or

stopped. In distal riverine environments, detrital

tufa deposition dominates but may become pro-

gressively diluted with other clastic input (Ortiz

et al., 2009; Capezzuoli et al., 2010). Where

present, detrital tufas typically are developed

Decoding tufa and travertine 7

STATE OF THE SCIENCE

into braidplain valley ﬁlls. In proﬁle, the

deposits show interpenetrative channelling,

small-scale channel bar structures and occa-

sional ripple bedforms. Deposits typically are

well-sorted but grade rapidly downstream into

ﬁner particles because individual tufa clasts are

easily abraded, especially if there is a siliciclas-

tic component present. Where rivers enter lakes,

small detrital tufa deltas may form and medium

to ﬁne calciturbidite couplet sheets may develop

peripherally towards the depocentres. Many such

lakes, especially in relatively cool and humid

climates, are well-stratiﬁed meromictic water-

bodies (for a modern deﬁnition see Walker &

Likens, 1975; Hakala, 2004). In these stratiﬁed

waterbodies, the monimolimnion may remain

undisturbed for decades to centuries. These sites

slowly accumulate detrital organics which

survive as sapropel layers in the neutral to

acidic waters below the chemocline (Pedley,

1993). By contrast, in warmer climates, when

the sedimentation rate is not too high, organics

generally decompose or oxidize too rapidly for

sapropel accumulation to occur (Pedley et al.,

1996) and holomictic lakes are more typical. In

arid climates evaporation within the lake, with

or without the planktonic algal contribution

may give rise to micrite precipitation and

deposition of lacustrine limestone (Gierlowski-

Kordesch, 2010).

Tufa versus travertine and internal drainage

basins

Caution should be exercised when classifying

lacustrine mound and marginal carbonates in

areas of geothermal activity (for example, Wes-

tern USA hypersaline lakes, Scholl, 1960; Guo &

Chafetz, 2012; Northern Greece, Hancock et al.,

1999; Inner Mongolia, Arp et al., 1998; Eastern

Africa, Renaut et al., 2013). Some of these pre-

cipitates, whether physico-chemical or micro-

bial, are the product of carbonate precipitation

from springs issuing into lakes at temperatures

of more than 30°(and up to 90°) centigrade (for

example, Pyramid Lake, Arp et al., 1999; Mono

Lake, Dunn, 1953; Lake Bogoria, Renaut et al.,

2013). The clear implication here is that the lake

waters are derived from multiple origins which

have been modiﬁed by meteoric and geothermal

sourcing and by evaporation. Consequently, the

derived elemental and isotope signatures of any

carbonate precipitates (for example, mounds and

pinnacles) developed either proximal to the

hydrothermal vents or distally around the ambi-

ent temperature lake margins (for example,

microherms) are likely to be complex. Those

precipitates formed at the lake-geothermal

spring interface will have characteristics closely

comparable with travertines sensu stricto.

Importantly, however, hot spring waters will

ABC

Fig. 2. Examples of tufa morphologies: (A) cascade (ca 50 m high) at Monastiero de Piedra Natural Park (Zaragoza

–Spain); (B) lakes and cascade (ca 15 m high) at Plitvice Jezera (Croatia); (C) fossil tufa cliff (ca 20 m high) at

Antalya (Turkey); (D) small barrages (ca 50 cm high) at Diborra Gorge (Siena, Italy); (E) small cascades (ca 2m

high) below Lagunas Redondilla, Ruidera Pools Natural Park (Spain).

8E. Capezzuoli et al.

mix rapidly into the surrounding lake waters

and ambient temperature carbonate fabrics more

akin to tufas often form. Around lake margins

stromatolite laminites, thrombolites and even

phytoherms are frequently established. Never-

theless, the host ﬂuids from which they precipi-

tated will not be fresh water. The carbonate

deposits will show variable chemical and isoto-

pic characteristics set at the time of precipita-

tion by the degree of lake desiccation, and the

relative inputs of meteoric and geothermal

waters. Consequently, whether physico-chemical

or biomediated, the deposits merit their own

speciﬁc designation. In order to avoid confusion,

it is suggested that any carbonate precipitated

under playa lake conditions where resurgent

waters are geothermal should be designated as a

‘saline travertine’. Precipitates within playa

lakes where waters are at ambient temperatures

and derived from meteoric or mixed sources

should be designated as a ‘saline tufa’. Many of

the saline lakes containing these precipitates are

shallow and lie in tectonically active areas (for

example, Lake Bogoria; Renaut et al., 2013).

Such sites may show characteristics similar to

fresh water, meteoric dominated precipitate

phases during lake highstands, and both hyper-

saline, geothermal dominated precipitate phases

and true travertines during lowstands; these

may also be intercalated with evaporites.

NEW PERSPECTIVES

Thirty years after the carbonate petrological char-

acterizations of Chafetz & Folk (1984), travertines

and tufas provide a new frontier for future car-

bonate research. Innovative new research ﬁelds

are now pushing the frontiers back and revealing

unexpected clues, not only to crystal precipita-

tion and early diagenetic processes, but also to

past climatic, tectonic and hydrological regimes

and even to the origins of life.

Geomicrobiology in tufa and travertine

Geomicrobiology concerns the role of microbes

and microbial processes in geological and

geochemical processes and vice versa. The appli-

cation of geomicrobial processes, especially to the

cool water carbonate precipitation process, has

already been discussed brieﬂy here. Current

research is now investigating bioﬁlm microstruc-

ture and ultrastructure and the intercellular

processes leading to carbonate bioprecipitation

(see Pedley, 2013). In particular, Turner & Jones

(2005) and Pedley et al. (2009) have demonstrated

the close control on skeletal crystal triad precipita-

tion by microbial ﬁlaments. Pedley et al. (2009)

have highlighted the precipitation of ‘Swiss

cheese’ microspar crystals and nanospheres

within living fresh water prokaryote-microphyte

tufa bioﬁlms.

The ﬁeld has seen enormous advances in the

past three decades fundamentally changing

the understanding of how microbial life impacts

the Earth. This change is nowhere more so than

in the study of extremophile organisms, the

microorganisms that thrive in environments nor-

mally considered hostile (Konhauser, 2009).

Such locations may include extremely hot (hot

springs or mid-ocean ridge black smokers)

environments (Kerr & Turner, 1996), extremely

saline environments, or even extraterrestrial

environments.

Palaeontologists and biologists now employ

travertine deposits as analogue settings for early

life on Earth (Fig. 3; Walter & Des Marais, 1993;

Farmer, 2000; Riding, 2000; Fouke et al., 2000;

Fouke, 2011). By analogy to Earth, specialized

microbes may have also existed in the heated,

mineralized waters of extraterrestrial bodies.

Thermal deposits on Earth can rapidly entomb

individual organisms and even complete ecosys-

tems within spring-deposited minerals (Norris &

Castenholz, 2006). These often record physico-

chemical signatures of the original habitat (Cady

& Farmer, 1996; Trewin & Rice, 2004; Guido

et al., 2010). Since the geological relations which

produce hot springs can be recognized in extra-

terrestrial orbital imagery, directed searches for

microfossils in such deposits are deemed possi-

ble. For this reason, hot spring deposits have

been cited as prime locations for exobiological

exploration (NASA, 1995). This explanation is

due to the fact that a fossil hot spring deposit on

a desiccated extraterrestrial surface might reveal

evidence of biological weathering, or preserve

textures such as nanospheres (Jones & Peng,

2012) and ‘crystal shrubs’ (Chafetz & Guidry,

1999) that have been attributed on Earth to

biomineralization. This is a possibility on Mars,

where an active subsurface spring might still nur-

ture microorganisms adapted to dark, anaerobic

conditions. In any case, a Martian hot spring

would be a prime site in the search for past or

present extraterrestrial life (Allen et al., 2000;

Allen & Oehler, 2008).

Decoding tufa and travertine 9

STATE OF THE SCIENCE

Neotectonics and geothermal implications

The intimate connection between travertine and

active tectonics is a basic concept in neotectonic

and seismological studies, because the location of

travertine deposits is a very useful tool for identi-

fying active and potentially hazardous faults. In

some cases, travertine masses can also reveal

much about palaeoseismology (Sibson, 1987;

Muir-Wood, 1993; Martinez-Diaz & Hernandez-

Enrile, 2001; Piper et al., 2007; Nishikawa et al.,

2012), because of their potential for accurate dat-

ing. Improved knowledge of the palaeo-seismic

history of faults using the U-series dating tech-

nique provides valuable additional data with

which to constrain and improve simulations of

earthquake fault system dynamics (Uysal et al.,

2007; Brogi et al., 2010a).

The term ‘Travitonics’ emphasizes the close

relation between travertine deposition and

tectonics (Hancock et al., 1999). Travertines are

considered to be important tools for tectonic

investigations due to the fact that the fracture

network typifying the fault damage zones plays

an important role in the circulation and upwell-

ing of hydrothermal ﬂuids in geothermal areas

(Barbier, 2002). For this reason, travertine

masses deposited from thermal springs are

considered good indicators of tectonic activity

(Altunel & Hancock, 1993a,b; Hancock et al.,

1999; Altunel, 2005) and, consequently, a poten-

tial archive recording of the surface activity of

deep ﬂuid circulation in a geothermal reservoir

(Minissale, 2004; Crossey et al., 2006; Nelson

et al., 2009; Banerjee et al., 2011).

Good examples of this interaction are illus-

trated by the Jurassic hot spring deposits of the

Deseado Massif, Argentina (Guido & Campbell,

2009; Guido et al., 2010). Where there is lateral

evolution and cooling from thermal-derived

ﬂuids, some associated tufa deposits have been

Fig. 3. Diverse (in colour) microbial communities and changes in their relative lateral position between thermo-

phyllic and photosynthesizing bacteria in several thermal systems. Examples from: (A) Egerszalok (Hungary; 60°C

- the channels are ca 10 m long); (B) Bagni San Filippo (Italy; 52°C - the pool is ca 2 m long); (C) Karahayt

(Turkey; 58°C - the thermal system is ca 4 m high); and (D) Castelnuovo Berardenga (Italy; 39°C - the pool is ca

10 m long).

10 E. Capezzuoli et al.

used as indicators of tectonic activity in Brazil

(Corr^

ea et al., 2011) and in Italy (Brogi et al.,

2012). Active hydrothermal-derived carbonate

deposits represent some of the best surface mani-

festations of a deep-seated geothermal system, as

they provide information on water reservoir tem-

perature (Navarro et al., 2011; Pasvano

glu &

Chandrasekharam, 2011) and of its sustainability

(F

orizs et al., 2011; Carucci et al., 2012). Thermal

water depositional temperatures are also obtain-

able from ancient travertine deposits by using the

clumped-isotope thermometer method (Gosh

et al., 2006). Alternatively, when coupled with a

O water composition estimate, palaeotempera-

tures can be obtained from the water–bicarbonate

oxygen isotope equilibrium fractionation value

(Halas & Wolacewicz, 1982, as an alternative to

employing the water-travertine equilibrium frac-

tionation of Friedman & O’Neil, 1977). Recent

applications in Kele et al. (2008, 2011) show an 8

to 9°C difference with respect to previous palaeo-

temperature calculations.

Information about palaeoenvironmental condi-

tions and the geothermal characteristics of the

associated ﬂuids are potentially available from

ﬂuid inclusion analyses of ancient travertine

bodies. This method, mainly used for interpret-

ing the genesis of metamorphic and volcanic

rocks, has been applied in the study of Pleisto-

cene travertine in Argentina (Antuco travertine;

Gibert et al., 2005) and in recent laminar depo-

sits at Gordale, England and Bagno Vignoni,

Italy (Parnell & Baron, 2004).

Volcanoes and CO

emissions

Travertine deposits and volcanism are often

closely associated due to hot crustal-ﬂuid ﬂow,

active tectonism and related surface hot springs

(Crossey et al., 2006). Carbon dioxide is a com-

mon magma constituent and during magma

upwelling, pressure reduction leads to outgas-

sing and eventual CO

release.

Circulating ground waters are capable of dis-

solving large quantities of gas under high hydro-

static pressures. The resulting solutions dissolve

calcium carbonate at depth, providing highly

concentrated bicarbonate solutions that com-

mence degassing as the waters rise (Chiodini

et al., 1995; Frondini et al., 2008).

In active tectonic regions with extensional

regimes, this process may be encouraged by the

presence of deep faults that act as preferential

conduits for upwelling ﬂuids. For example, Brogi

et al. (2010b) investigated the kinematics of the

geological structures related to active evolution of

the Mt. Amiata volcano (Southern Tuscany, Italy)

from the tectonic deformation and structural

features affecting the local travertine deposits of

Bagni San Filippo (Fig. 4).

Because of the relatively high solubility of car-

bon dioxide in water, the occurrence of gas

emissions at the surface depends on the quanti-

tative ratio of ground water volumes circulating

in the sub-surface relative to the amount of gas

arriving from depth. Large volcanic CO

outputs

are very important in Earth history, due to the

fact that they may strongly inﬂuence climate

and contribute to the rapid passage from glacial

to interglacial periods (Huybers & Langmuir,

2009). By contrast, Uysal et al. (2009) proposed

a positive feedback between water availability

(rainfall) and surface discharge of carbon diox-

ide. Studies on Turkish travertine deposits

testify to host rock fracturing by seismic shaking

caused by ﬂuid overpressuring in geothermic

Fig. 4. (A) The Holocene perched springline tufa body of Mai-Makden (Ethiopia). The gorge is ca 10 m deep. (B)

Detail of phytohermal framestones in the upper portion of its frontal part typifying a densely vegetated cascade

environment very different from the present-day arid environment (man for scale, ca 1.8 m tall).

Decoding tufa and travertine 11

STATE OF THE SCIENCE

systems during dry climate periods. In this

sense, climate variability controls the availabi-

lity and quantity of geothermal waters, with rel-

atively wet climate events leading to CO

discharge and dissipation at the surface, which

may be associated with the deposition of ter-

race-mound travertines. In contrast, very dry cli-

mate events lead to CO

oversaturation in deep

reservoirs and promote rapid exsolving and

expansion of the dissolved gas leading to hydro-

thermal eruptions. Undoubtedly, the well-dated

evolution of volcano-related travertine deposits

offers the potential for deciphering links

between ancient volcanism, active tectonism,

hot crustal-ﬂuid ﬂow and the birth, growth and

death of ancient hot springs (for example, Italian

Mt. Etna area, D’Alessandro et al., 2007; Argen-

tinian San Agust

ın deposit, Guido et al., 2010).

Anthropogenic inﬂuence on natural

environments

Tufa and travertine depositional environments

provide favourable sites for human settlement

activities (Gonzalez et al., 2009). Consequently,

they are often associated with hominid remains

and traces of old civilizations (Kappelman et al.,

2008; Ashley et al., 2010). Human inﬂuence on

tufa deposition has been so profound during late

historical times that deforestation, improved

drainage and pollution are perceived as the most

common causes for their depositional decline

(Goudie et al., 1993; Taylor et al., 1998; Nyssen

et al., 2004). Recent case studies have docu-

mented a range of anthropogenic-associated

environments including Plitvice lakes –Croatia

(Horvatin

ci

cet al., 2006), coastal tufa of the

Leeuwin-Naturaliste geographic region –Wes-

tern Australia (Forbes et al., 2010), Huanglong

ravine and Xiangshui River –China (Liu et al.,

2011; Zhang et al., 2012). In all cases, carbonate

deposition rates have declined signiﬁcantly as a

result of phosphate pollution caused by tourism

and agricultural activities within the catchment

areas.

Landscape evolution

Fluvial deposits, and in particular the associated

detrital deposits, commonly have a low preserva-

tion potential owing to the erosive effect of ﬂow-

ing waters. However, terraced, ﬂuvial carbonate

deposits appear to be a particularly promising

tool for understanding the environmental and

palaeohydrographical evolution of an area, since

the morphology and depositional features of car-

bonate terraces are generally well-preserved by

early lithiﬁcation (Ord

nez et al., 2005; Schulte

et al., 2008; Zentmyer et al., 2008; Ortiz et al.,

2009; Capezzuoli et al., 2010). Although outcrops

are commonly poor, the internal architecture of

terrace deposits can be revealed by ground-pene-

trating radar, especially in areas where the water

table is low (Pedley et al., 2000; McBride et al.,

2012). Using this method, Pedley et al. (2000)

showed the former presence of an incised mean-

dering limestone gorge below a tufa terrace and

revealed details of a buried barrage-tufa succes-

sion. In a further example, within the Piedra

River catchment (Spain), V

azquez-Urbez et al.

(2010b) distinguished two distinctly different

episodes of ﬂuvial activity which were triggered

by a temporarily blocked river subsequent to tufa

barrage aggradation within the primary river

channel. In both episodes, channel avulsion

diverted ﬂow across a local divide and into a sec-

ond water course.

The geomorphological evolution of a river val-

ley can also reﬂect variations in palaeoclimate.

Golubic (1969) recognized the cyclic nature of

many deposits with each episode terminated by a

deep erosive event probably triggered by environ-

mental change. In particular, the downcutting of

a series of terraces can often be directly related to

tectonics or to major climate phases in the region.

It has been noted that many rivers formed new

terraces during warm periods or cold to warm

transitions. In contrast, the rivers seem to have

produced incised valleys following interglacial

periods. These changes reﬂect responses driven

by climate change, mainly at orbital (Milanko-

vitch) frequencies (Bridgland & Westaway, 2008;

Ortiz et al., 2009).

The travertine terraced deposits along the Dan-

ube River (Hungary) are good examples of such

interaction. Ruszkiczay-R€

udiger et al. (2005)

conclude that they resulted from the emergence

of the local mountain range during an epoch of

signiﬁcant climate changes and, as a conse-

quence, periodic terrace carving, valley widening

and terrace aggradation occurred.

Climate reconstruction

The importance of travertines and tufas for

Quaternary studies derives primarily from their

value as repositories of palaeoenvironmental

data, much of which can be dated using radio-

metric techniques such as

C radiocarbon

methods for Holocene–Late Pleistocene tufas

12 E. Capezzuoli et al.

(Srdo

cet al., 1980, 1983) or uranium series

(

230

Th/

234

U) and (

234

238

U) methods for the

older Quaternary (up to 400 ka and 1 Ma,

respectively; Soligo et al., 2002; Sierralta et al.,

2010; Brogi et al., 2010a). Most reliable dates are

obtained from autochthonous deposits such as

back barrage pool deposits or stromatolitic

crusts, but even these may possess contaminants

in sufﬁcient quantity to prevent reliable dating.

Other isotopes may also be used (

228

Ra/

226

Ra,

210

Pb) but all of these methods are prone to

error, caused by the presence of contaminants,

recirculation or diagenesis (Schwarcz, 1990;

Pentecost, 2005; Walker, 2005). Alternative tech-

niques for dating of tufa and travertine deposits

include thermoluminescence (Engin & Guven,

1997; Engin et al., 1999) and electron spin reso-

nance (ESR; Blackwell et al., 2012).

Many studies emphasize the close relation

between climate and tufa deposition (for reviews

see: Pentecost, 2005; Andrews, 2006; Pedley,

2009), with tufas occurring more abundantly

during humid and warm phases since they

favour forest development and associated soil

production. This close relation further

implies that, in dominantly humid and cold

environments (for example, middle-northern

latitudes), tufas may be used as proxies for

warm interglacial phases (Grifﬁths & Pedley,

1995; Limondin-Lozouet et al., 2010; Dom

ın-

guez-Villar et al., 2011). The former presence of

active tufas in arid to semi-arid and temperate

to tropical environments also testiﬁes to impor-

tant rainfall regime shifts in the geological

record. This shift has been demonstrated in

distal glacial transitional environments and for

glacial periods (South Europe, Capezzuoli et al.,

2010; Alexandrowicz, 2012) and in semi-arid

(Brazil, Auler & Smart, 2001; Spain, Luz

et al., 2011) and desert settings (Namibia, Viles

et al., 2007; Libya, Cremaschi et al., 2010; Ethio-

pia, Moeyersons et al., 2006), where tufa depos-

its are a direct record of the wetter phases.

Consequently, speciﬁcally in non-tectonically

inﬂuenced settings, tufas are proxies for water

availability and thereby vehicles for palaeohy-

drogeological studies. In contrast, the presence

of tufas in tropical and monsoon-dominated

settings testiﬁes to an absence of destructive

large wet season ﬂoods and, consequently, for

reduced periods of rainfall (Carthew et al., 2003,

2006; Fig. 5).

With regard to travertine deposition, many

authors (Pentecost, 1995; Mesci et al., 2008)

emphasize the fact that the inﬂuence of climate on

geothermal-related precipitation is generally less

obvious. Nevertheless, Sturchio et al. (1994) for

example, showed how travertine deposition in

Wyoming was profoundly affected by Pleistocene

glaciations. In that setting, prolonged freezing

conditions prevented inﬁltration of water by

blocking the hydrothermal circuit and modifying

the hydraulic head. Such a circuit response could

provide the perfect climate proxy. Climate change

could also be registered within travertines by

changes in

O ratios, while

C ratio

shifts could highlight changes in the source of CO

with associated input on the Milankovitch cycles.

More realistically, travertines are linked to the

availability of water, being inﬂuenced indirectly

by tectonically driven ground water ﬂow changes,

which directly reﬂects rainfall availability and an

elevated ground water table (Rihs et al., 2000;

Faccenna et al., 2008; Zentmyer et al., 2008). Geo-

chemical studies and absolute dating of terrestrial

carbonates in Central Italy (Minissale et al., 2002)

considered the effects of hydrogeology on ground

water ﬂow paths and resultant geochemistry.

These studies concluded that travertines preserve

a valuable record of palaeoﬂuid composition and

palaeoprecipitation.

In the same way, Liu et al. (2010) demon-

strated, from studies of travertine deposits in

south-west China, that rates of carbonate precip-

itation and the formation of lamination were

controlled principally by rainfall. This may

provide an additional approach for using

ancient travertine deposits to reconstruct the

climate in the past.

Macroﬂora and microﬂora

The analysis of palaeoenvironmental change

using fresh water carbonate fossil faunas is possi-

ble because of the rich communities present in

tufa, although this is less true for travertine (for a

complete review see Pentecost, 2005). Fossil ﬂora

is mainly represented by macroremains (leaf

impressions, fruits, moss cushions, twigs and

seeds) and microremains (diatoms, pollens and

algae). The analysis of these materials provides an

important additional research strand that can be

integrated with sedimentology for palaeoenviron-

mental analysis (for a complete review see Pente-

cost, 2005). Fresh water carbonate palynology has

been applied less commonly because many still

argue that pollen is poorly preserved in alkaline-

dominated depositional environments (Traverse,

2007). Nevertheless, there are some notable

successes, especially in Holocene ambient

Decoding tufa and travertine 13

STATE OF THE SCIENCE

temperature tufa deposits (Burjachs & Juli

1994; Taylor et al., 1994, 1998; Vermoere et al.,

1999; Makhnach et al., 2004; Pentecost, 2005;

Schulte et al., 2008; Curr

as et al., 2012). Despite

general misgivings, tufa carbonate palaeobotany

is quite feasible and can provide valuable ﬂoral

distribution data at local and regional scales, for

palaeoclimatic reconstructions. In particular,

vegetable macroremains from tufa deposits have

contributed signiﬁcantly to a better understanding

of the evolution of modern European forest

patterns, the past distribution of arboreal species

(Ali et al., 2003a,b; Fauvart et al., 2012) and the

effects of ﬁre on the distribution of Holocene

vegetation (Ali et al., 2005a,b).

Work has barely commenced on the palynology

of travertine deposits. Bertini et al. (2008) carried

out palynological analyses in the Italian Rapolano

and Tivoli sites, demonstrating that travertine

deposits can also yield pollen in sufﬁcient

quantity to be of signiﬁcant value in the investiga-

tion of late Quaternary palaeoclimates.

CONCLUSIONS

From humble beginnings, tufa and travertine

research has developed internationally over

three decades into a major ﬁeld of carbonate

sedimentology and palaeoenvironmental model-

ling. Tufa and travertine are continental carbo-

nates that can be treated as part of a complex

continuum of terrestrial deposits resulting from

combined chemical and bio-induced precipita-

tion processes. These extend from sub-terrestrial

ground water sites (speleothems and calcretes),

via subaerial ﬂuvial sites (perched springlines

and barrages) to perennially submerged

continental depressions (paludal and lacustrine

deposits). For these reasons, their classiﬁcation

Fig. 5. (A) Fissure ridge (ca 10 m long) at Bagni San Filippo (Italy). This travertine deposit is located at the tip

zone of a strike-slip to oblique-slip fault along which eruptions of the Late Pleistocene volcano, Mount Amiata,

occurred. Gas emissions and hot waters are issuing actively from this geothermal area, forming spectacular traver-

tine bodies [the so-called ‘White whale’ slope travertine, ca 10 m high in (B)] and related macrocrystalline lithofa-

cies [examples of thick crystalline crusts in (C)].

14 E. Capezzuoli et al.

must consider carefully the depositional setting

and a number of extra-sedimentological para-

meters, including the associated physico-chemi-

cal and biotic elements (mineralogy and

geochemistry, associated biota and chemistry of

the depositing waters).

The term travertine should refer to calcium car-

bonate deposits produced from non-marine,

supersaturated carbonate waters, typically hydro-

thermal in origin and chieﬂy marked by high

depositional rates, regular, ﬁne laminated bed-

ding, with a dominantly inorganic crystalline fabric

of low porosity and permeability. Microbial com-

munities may be associated with this deposit; arago-

nite as well as calcite may be present and the d

Cis

typically high (positive or slightly negative).

In contrast, the term tufa should be applied to

deposits consisting dominantly of calcite that are

produced from low depositional rate, shallow

cycled and karstic-derived, ambient temperature

waters which are characterized by poorly bedded,

highly porous fabrics. Microbiota and macrobiota

are very common, and d

C is always low, while

primary aragonite is typically absent except in

spring waters with a high Mg/Ca ratio.

In the case of tufa fabrics precipitated from

cooled thermal waters, the resulting deposits

should be identiﬁed as ‘travitufa’. These ambient

temperature deposits are characterized by their

deep-circulating hydrochemical signatures. Simi-

larly, playa lakes (Salinas) contain peculiar carbon-

ates that require special consideration. Those

precipitated directly from thermal waters at the

saline lake water-spring interface should be identi-

ﬁed as ‘saline travertines’, whereas those derived

from ambient temperature lake waters should be

designated as ‘saline tufas’. The strict application

of these deﬁnitions makes the terms travertine and

tufa useful indicators of speciﬁc hydrological and

environmental conditions. For example, the ‘tufa

towers’ mainly described from the Western USA

Great Basin region (Scholl, 1960) and which clo-

sely resemble the ‘travertine pipes’ from the East-

ern African rift lakes (Hillaire-Marcel et al., 1986;

Hillaire-Marcel & Casanova, 1987) would, on the

basis of water geochemistry and tectonic-related

characteristics, be described as saline travertines.

Consequently, the interpretation of deposi-

tional processes must be the initial procedure in

tufa and travertine analysis and decoding. How-

ever, additional regional or global factors, such as

biotic evolution, ground water circulation, global

climate change and local to regional tectonic pro-

cesses, must also be taken into consideration for

their full interpretation. Consequently, a full

understanding of these deposits necessitates a

diverse, multidisciplinary approach.

Tufa and travertine research has played a

pivotal role in the development of a number of

novel research areas:

Fresh water Geomicrobiology: A new sub-disci-

pline studying tufa and travertine generating bio-

ﬁlms and their role in the biomediation of

calcium carbonate and their control on carbonate

micro-fabrics.

‘Travitonics’: A new sub-discipline relating

neotectonics and fracture controlled travertine

development.

Fresh water Geochemistry: In particular, the

study of volcanic CO

emissions and geothermal

signatures preserved in travertine deposits.

Karst Geochemistry: The recognition and use of

fresh water carbonates as important repositories of

radiometric and stable isotope data in karstic regions.

Carbonate Geoarchaeology: A sub-discipline

involved with the interaction of anthropogenic

processes and carbonate environments.

Fresh water Carbonate Palynology:Anewsub-

discipline using fresh water carbonates as a proxy for

the reconstruction of climate change in karst regions.

There are further ﬁelds yet to be revealed,

which will undoubtedly shed considerable light

on diagenetic processes in carbonates, including

neodiagenesis (for example, the growth of nano-

spheres and microspar within bioﬁlms, and

related dissolution and precipitation processes)

and subsequent fresh water diagenesis in the

meteoric domain. The role of bioﬁlms in the

evolution of life on Earth is signiﬁcant and may

well have a direct bearing on the potential to

develop and preserve extraterrestrial life.

Finally, there are the potential economic aspects

of these deposits which range from consider-

ations of their value as building stones and

sources of high grade calcium carbonate, to their

potential as aquifers and recently as commercial

hydrocarbon reservoirs (Wright, 2012).

ACKNOWLEDGEMENTS

We warmly thank R. Riding, L. Pickett, T. Frank,

E. Richardson, S. Rice, P. Swart and two anony-

mous reviewers for handling our manuscript and

for very constructive comments. We also thank S.

Kele for help. EC is pleased to acknowledge a

P.O.R.-F.S.E. 2007-2013 (Regional Competitive-

ness and Employment) grant from the Tuscan

Regional Administration.

Decoding tufa and travertine 15

STATE OF THE SCIENCE

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Decoding tufa and travertine 21

STATE OF THE SCIENCE

Rise and decline of Holocene tufas across Europe: exploring east/west and north/south similarities and differences in their development

Article

Full-text available

Jun 2024

An extended inventory of 82 well‐dated European calcareous tufas is used to discuss the timing and amplitude of their onset, maximum and decline; in particular differences from east to west and between the Mediterranean area and the rest of Europe. Eastern deposits start to develop and reach their maximum slightly earlier than western tufas. Strong east–west differences in the timing and intensity of the climatic improvement during the first half of the Holocene explain the earlier development of eastern tufas compared with the west. The strongest differences are observed between Mediterranean deposits and other European tufas both in their development and decline, whether all or only fluvial deposits are considered, reflecting the important decoupling between Mediterranean and mid‐latitude climate records. During the Late Holocene, the earlier and more pronounced tufa decline observed in European mid‐latitudes is likely to result from more intense and rapid deforestation compared with the Mediterranean region.

بررسی ﺷﺮاﻳﻂ زﻣﻴﻦ‌ﺷﻨﺎﺳﻲ ﺗﺸﻜﻴﻞ ﺗﺮاورﺗﻦﻫﺎي منطقۀ منشگه- چاراویماق ﺑﺎ ﻧﮕﺮشی ﺑر ﻛﺎرﺑﺮد آن در ﺻﻨﻌﺖ سنگ‌های ﺗﺰﺋﻴﻨﻲ

Conference Paper

Full-text available

May 2024

Farhad Pirmohammadi Alishah

Investigating conditions of the geological formation of travertine in the Maneshgeh-Charoimag area with a special concentration, its consumption in ornamental stone industries

Article

Full-text available

May 2024

Introduction Continental carbonates comprise a wide range of lithologies including speleothem, calcrete, palustrine, travertine, and tufa. Travertine and tufa deposits are frequently associated with limestone dissolution in superficial (epigean) or deep (hypogean) hydrogeological reservoirs (Pentecost and Viles 1994; Pentecost 2005; Jones and Renaut 2010; Capezzuoli et al. 2014; Gandin and Capezzuoli 2014). However, a large variety of other rocks can occur as substratum and source of elements building these carbonates. Many studies have shown that igneous rocks (basalts, rhyolites, ultramafics, granites) and sedimentary rocks such as dolostones, evaporates and marls may constitute derivative sources for calcium and other elements required for travertine and tufa build-up and this can be determined by elemental geochemical studies. Travertine deposits cover a vast area in the southwest of Charoimag (East Azarbaijan province) and some parts, there are active springs (Ebrahimzadeh et al., 2019). The area has been studied, is centered in the province of East Azerbaijan province, Charoimag city and east of Maneshgeh village and located in western Alborz- Azerbaijan zone. The present research has clarified that for the first time introduce and determine conditions of these Travertines. the study is to emphasize the use of geochemical data in travertine classification, determination of the origin of elements building travertines, CO2 origin, and comparison of Maneshgeh-Charoimag region samples with global thermogenic and methanogens travertines. Material & Methods For petrographic studies on travertine samples deposited in Maneshgeh village, 20 samples of travertine sediments and old travertine rocks are collected. To compare the geochemical characteristics of samples, ten samples of travertine rock samples are also collected. Fifteen samples were examined for mineralogical composition using XRD analysis. For geochemical analysis (ICP-MS), ten travertine samples have been analyzed at the Zarazma Laboratory, Zanjan. Discussion According to the geochemical studies of the major elements on the travertine of the Maneshgeh, iron, sodium, and potassium elements clearly emphasize the thermogenesis of these travertines, but other trace elements cannot determine the type of travertine. The concentration of rare earth elements in samples is lower than that of samples, indicating a lower reaction rate of this spring with source rocks and its rapid ascent to Earth's surface. Due to high concentrations of strontium and low concentration of barium, the Maneshgeh travertine deposits plotted in the range of hypogean Calcite and Aragonite Travertine and Tufa (CATT) originated from limestone, evaporates, and dolostones. The origins of the samples using beryllium values indicate that the Maneshgeh travertine was similar to the values of this element in hypogean travertines with carbonate sources (Moosavizadeh et al., 2020). Based on this study, it seems that hydrothermal fluids may have initially taken the CO2 derived from magma, and during the upward movement with carbonate rocks, decarbonization has occurred. These fluids transport CO2 from carbonates, and then they appear as spring’s water at the surface and precipitate travertine due to the rapid release of CO2. Conclusions The area has been studied, is centered in the province of East Azerbaijan province, Charoimag city and east of Maneshgeh village and located in western Alborz- Azerbaijan zone. The present research has clarified that for the first time it introduces and determines the conditions of these Travertines. Information has been produced by providing the results of studies and geological information moreover, by integrating them precisely with satellite data, geological maps of 1: 1000 scale was overwrought, ultimately computerizing the data by arc GIS software. On this basis, it was revealed that an important relationship between two efficient items, region tectonics, and travertine deposits. Additionally, current morphology has been affected by active tectonics force in this area. Based on geochemical studies, it can be concluded that hydrothermal fluids may have initially taken the CO2-derived from magma, and during the upward movement with carbonate rocks, decarbonization has occurred. These fluids transport CO2 from carbonates, and then they appear as spring’s water at the surface and precipitate travertine due to the rapid release of CO2. Due to the direct non-slip weight of travertine blocks, their ability in the construction industry as an ornamental stone was investigated with the results of physical and chemical experiments, which clearly showed that travertine layers are not of good quality and can be used as carcass stone.

Palaeoenvironmental reconstruction of Holocene calcareous tufas distributed over a manganese deposit in Mexico

Article

Jun 2024

The Holocene calcareous tufa deposits are located in the north-central sector of the state of Hidalgo, Mexico. These deposits outcrop on the Upper Jurassic Chipoco Formation in the Molango Manganese District. Calcareous tufa deposits correspond to carbonate formations of inactive tufas disconnected from the current hydrological network. To better understand the textural, geochemical, and biological characteristics and environmental conditions during their formation, a detailed study involving field analysis, X-ray diffraction analysis, X-ray fluorescence analysis, and morphometric analysis with light microscopy, and scanning electron microscopy was carried out. Similarly, 14C analysis was undertaken to determine the age of the deposit. On this basis, two biofacies were defined, one with stem structures and the other with Phyto clasts, bryophytes (Plagiomnium cuspidatum), and copepods, limited both at the base and the top by lenticular-shaped erosive surfaces and sigmoidal clinoforms. These bio facies formed in lacustrine and paludal environments, and barrier waterfalls. From a geomorphological point of view, the accumulations of these calcareous tufas originated on slopes and/or at the foot of karstic springs, where the accumulation of material originated from the height of the spring with respect to the bottom of the valley, giving rise to a set of stepped tuffaceous plains with a wedge-shaped profile, colonized by important masses of bryophyte mounds, copepods, and vascular plants. This suggests a swampy environment where sedimentation took place in shallow water accumulations, where there is clear evidence of exposure and pedogenetic modification, indicating wet and dry episodes that translate into seasonal fluctuations in the water table. Six mineral phases were observed including silicates, carbonates and arsenates. The 14C analysis indicates that the plant found in the charcoal sample within the calcareous tufa deposit is of Holocene age.

Was fire use a cultural trait of the Gravettian? New micro-archaeological data from Fuente del Salín cave (Val de San Vicente, Cantabria)

Preprint

Full-text available

Jun 2024

Micro-archaeological data from sites located in central and eastern Europe show that, in comparison with other Upper Paleolithic hunter-gatherers, Gravettian foragers used re more intensively and for a wider range of purposes. In these regions, this shift in pyrotechnology overlaps with the onset of periglacial conditions and comparable micro-archaeological datasets from milder regions, such as Cantabria, remain scarce. As result, it is di cult to conclude whether these re behaviors were cultural traits of the Gravettian tradition, or whether they re ect adaptations to regional environments. To further investigate these hypotheses, we studied the sequence preserved at the cave of Fuente del Salín, in Cantabria, where previous excavations unearthed potential re residues of Gravettian age. Using micromorphology, µ-X-ray uorescence, and Scanning Electron Microscopy we reconstructed multiple phases of human visits to the site. Our results show that, during the main Gravettian occupation, foragers made intensive use of re, as indicated by abundant heated bones and seashells, charcoals, amorphous char, fat-derived char, and in situ remains of stacked open hearts as well as burnt grass beddings. The intensive burning, systematic reuse of combustion features, and multiple purposes of the res at Fuente del Salín are comparable with Gravettian sites from central and eastern Europe, indicating that these re-use traits were not related with periglacial environments but with lifeway aspects and traditions of Gravettian hunter-gatherers.

Strontium isotopes and rare earth elements in terrestrial hot-spring deposits: Characterization and geothermal implications

Article

May 2024
GEOL SOC AM BULL, GSA Bulletin

Identifying geothermal reservoir rock types is fundamental in geothermal exploration, but the absence of active surface geothermal manifestations (especially hot springs) in blind geothermal systems makes this identification difficult. Nevertheless, blind geothermal systems may develop early-formed hot-spring deposits. As (bio-)chemical precipitate, these deposits may retain geochemical signatures of spring waters and thus provide insights into reservoir rock types. To assess their geothermal implications, the 87Sr/86Sr and rare earth elements + yttrium (REE + Y) characteristics of hot-spring deposits in two geothermal systems were investigated and compared with those of their reservoir rocks. Results showed relatively uniform 87Sr/86Sr values in hot-spring deposits within each system, but occasional 87Sr/86Sr contamination induced by exogenous detritus input was also observed. The amount of detritus input relates to the potential for interaction with surrounding soils/rocks and is thus environmentally controlled. Hot-spring deposits with high Sr concentrations showed greater 87Sr/86Sr contamination resistance than those with low Sr concentrations, revealing the influence of Sr concentration in hot-spring deposits on detrital 87Sr/86Sr contamination. The detritus input also influenced the REE + Y signatures of the hot-spring deposits, underscoring the necessity of contamination assessment before geochemical interpretation. Excluding samples with significant 87Sr/86Sr and/or REE + Y contamination, the remaining samples closely mirrored their respective reservoir rocks in terms of 87Sr/86Sr, with partial overlap in REE + Y signatures. This suggests that the 87Sr/86Sr and REE + Y characteristics of hot-spring deposits provide valuable insights into reservoir rock types. However, variations in 87Sr/86Sr or REE + Y compositions between some hot-spring deposits and corresponding reservoir rocks indicate additional influencing factors beyond reservoir rock types. Therefore, a comprehensive understanding of reservoir rock types requires integrated geochemical characterization, probably including 87Sr/86Sr, REE + Y, and other parameters. These findings underscore the potential of geochemical characterization of hot-spring deposits for identifying geothermal reservoir rock types, and this geochemical approach can complement geological and geophysical data to improve exploration efficiency, especially in blind geothermal systems.

Microbially induced Ca-carbonate authigenic deposition in the Mercure palaeolake (Middle Pleistocene -Southern Italy)

Article

Apr 2024

The varved carbonates of the Mercure Basin are representative of a palaeolake basinal setting, where the normal pelagic sedimentation was interrupted by occasional sedimentary flows triggered by the intrinsic lake dynamics (river floods, storms, etc.). The presence of in place charophytes green algae oogonia testifies a limited lake depth that favored the necessary light filtration for this biota. In this environmental setting, micrite is the dominant component and it occurs with microbial aphanitic and clotted fabrics. At the nanoscale both micrite types are characterised by a tight aggregation of nanospheres forming irregular to globular major-size clots, spherical and semi-cylindrical aggregates with a common internal hollow structure, typical of microbial-induced mineralization processes. Moreover, the hollow structures of the nanospheres aggregates could be linked with green algae and bacteria cells whose blooms may cause whiting phenomena.

Depositional and Diagenetic processes in travertines: A comprehensive examination of Tocomar Basin lithotypes, Northwest Argentina

Article

May 2024
J S AM EARTH SCI

Anadolu’nun MIS 9 Karasal Karbonat Kayıtları ve Paleoiklimsel Çıkarımlar: Örtülü/Sarıkavak (Afyon), Karahallı (Uşak) ve Bahçecik (Gümüşhane)

Article

Mar 2024

Denizel izotop fazlarından biri olan ve buzul arası döneme karşılık gelen MIS 9 dönemi, günümüzdeki sıcak dönem için bir analog olarak görülmektedir. Ancak karasal karbonat çökellerinden bu döneme ait veriler oldukça sınırlıdır. Bu çalışmada, Anadolu’nun farklı bölgelerinde yüzlek veren traverten ve tufa gibi karasal karbonatların MIS 9 buzul arası dönemine ait kayıtları incelenmiştir. Bu amaçla, GB-Anadolu’dan iki lokasyona (Örtülü/Sarıkavak (Afyon) ve Karahallı (Uşak)) ve KD-Anadolu’dan bir lokasyona (Bahçecik, Gümüşhane) ait karasal karbonat çökellerinin MIS 9 verileri, ayrıntılı olarak incelenmiştir. Sedimantolojik, izotopik ve palinolojik verilerin ışığında, MIS 9 buzul arası dönemin ortamsal ve iklimsel koşulları ortaya konmuştur. MIS 9 döneminde çökelimine devam etmiş olan Örtülü travertenler, sığ bir göl ortamında çöküntü depolanma sistemi içinde çökelirken Sarıkavak tufaları ise orta-yüksek eğimli bir topoğrafyanın egemen olduğu, akarsu ortamında çökelmişlerdir. Karahallı travertenleri ise, tektonizmanın etkin olduğu sığ bir göl kenarı ortamında çökelmişlerdir. Bir diğer çalışma alanı olan Bahçecik travertenleri ise, çöküntü ve yamaç depolanma sistemi içinde çökelmiş traverten oluşuklarıdır. MIS 9 döneminde, GB-Anadolu’da yer alan Karahallı travertenleri ve Örtülü/Sarıkavak karasal karbonatlarında δ13C duraylı izotopları, pozitife yakın (‰ -0,47 ile ‰ 1,86) değerler sunarken δ18O duraylı izotop değerleri ise negatiftir (‰ -9,67 ile ‰ -8,72). Ancak KD-Anadolu’da MIS 9 dönemine ait duraylı izotop değerlerinde önemli bir farklılık gözlenmiştir. δ13C izotop değerleri daha pozitif (‰ 4,5 ile ‰ 5,0) iken, δ18O değerleri ise çok daha negatiftir (‰ -14,67 ile ‰ -14,6). Karbon ve oksijen izotop değerlerindeki bu belirgin farklılık, yağış/buharlaşma ile doğrudan ilişkilidir. Palinolojik kayıtlara göre, MIS 9e ve MIS9a arasında önemli bir farklılık kaydedilmiş ve nemlilikte göreceli bir değişim tespit edilmiştir. Elde edilen tüm veriler ışığında, Anadolu’da MIS 9 dönemi, belli dönemlerde yağışın azaldığı kuraklaşmanın hüküm sürdüğü iklimsel dalgalanmalar gösterse de genel itibariyle daha ılıman ve yağışlı bir dönem olduğu söylenebilir.

Last interglacial in western Europe: 20 years of multidisciplinary research on the Eemian (MIS 5e) calcareous tufa sequence at Caours (Somme basin, France) – a review

Article

Apr 2024

The calcareous tufa sequence and associated Palaeolithic site of Caours were discovered in 2002 during a test‐pit campaign aimed at identifying last interglacial (MIS 5e) archives in the fluvial terrace system of the Somme basin, northern France. The presence of an outstanding stratigraphical succession with four in situ Palaeolithic layers within the tufa sequence has motivated archaeological excavations of the site since 2005. The first malacological studies and U‐series ages quickly showed that the sequence was mainly deposited during the Eemian interglacial (MIS 5e). After 20 years of investigations, we propose here a summary of this multidisciplinary research project including stratigraphy, sedimentology, geochronology, geochemistry, malacology, mammals, palaeovegetation and archaeology. By combining 25 dates obtained by U‐series, ESR/U‐series, TL and OSL methods, the Caours calcareous tufa sequence is securely dated to the Eemian (123.1±2.8 ka). Based on the summary of the whole information, we propose a robust and detailed reconstruction of the modification of the valley environments between the Late Saalian and the Early Weichselian. At the scale of northwestern Europe, Caours provides a reference terrestrial molluscs record for the Eemian interglacial, including the climatic optimum, that is also described in the same layers by δ ¹⁸ O and δ ¹³ C analyses on calcite and by mammal remains. Moreover, the 300‐m‐long transect crossing the fluvial terrace covered by the tufa sequence and the bottom valley formation, combined with the chronology established from U‐series and OSL ages, shows that the incision of the present‐day valley, leading to the setting of the Very Low Terrace, was achieved during the first stages of the Early Weichselian (MIS 5d–5c). From an archaeological point of view, the configuration of the Caours site is unique at the scale of western Europe and demonstrates the adaptation of Neandertals to a forested environment and to fully temperate conditions during the Eemian.

Quaternary travertines at Rochetta a Volturno (Isernia, Central Italy). Facies analysis and sedimentary model of an organogenic carbonate system

Chapter

Full-text available

Jan 1994

The evolution of travertine masses in the Sivas area (Central Turkey) and their relationships to active tectonics

Article

Full-text available

Apr 2008

Sιcak Cermik, Delikkaya and Sarιkava are important travertine fields with active hot springs located 31 km west of Sivas. Based on their morphology, most of the travertines are classified as fissure-ridge travertines. Eroded sheet-type, terraced, and self-built channel types of travertine are also present at a few locations. Faults and fissures formed in the underlying Incesu Formation, and fissures developing in the fissure-ridge travertines are linked to one another. Tectonic deformation forming the fissure-ridge travertines resulted from NE-SW extension associated with a NW-SE compressional regime related to the Central Anatolian Thrust Belt and Sivas Backthrust. U/Th series age dating results indicate that the travertine deposition extends back to 400 ka and yields ages of 11.400 (±500) to 364.000 (+201.000/-76.000) from the fissure-ridge travertines. Age data and fissure width observations indicate that a ∼0.06 mm/year extension rate is associated with the compressional regime in the Sivas Basin. On average, fissure-ridge travertines formed over intervals of 56.000 years, and indicate that a major regional seismic event with a magnitude of 7.4 has occurred here with this order of frequency. The Pamukkale travertines in Western Turkey are one of the most spectacular natural heritage sites in the world, as well as a site of active tectonic studies, and are now protected for these reasons. As shown by this study, the Sιcak Çermik travertines are of comparable interest and should receive similar protection.

The experimental study of oxygen isotope exchange reaction between dissolved bicarbonate and water

Article

Jan 1981

The rate and equilibrium fractionation factor of oxygen isotope exchange between HCO3 and H2O were studied at 25, 35, and 45 °C. It was found that the exchange reaction is complete in 8.8 h (5τ) at 25 °C, 2 h at 35 °C, and in less than 1 h at 45 °C. The equilibrium fractionation factor as a function of temperature fits the equation 10 ³ ln α(HCO3⁻-H20)=(2. 92±0.07) (10⁶/T²)-(2.66±0.18). The CO 2 produced from rapidly precipitated BaCO3, to trap the HCO3⁻ ions maintained in isotopic equilibrium with water at 25 °C, is enriched in δ ¹⁸O by 0.73‰±0. 07‰ in comparison to CO2 directly equilibrated with the same water at 25 °C. This provides an alternate method for determining the oxygen isotopic composition of water.

Use of Quaternary travertine of central-southern Italy as archives of paleoclimate, paleohydrology and neotectonics

Article

Jan 2008

This paper reports how travertine of central-southern Italy, formed in response to the extensive circulation of waters inside the regional aquifer hosted in the Mesozoic carbonate sequences, can be used as a tool for paleoclimatic, neotectonic and paleohydrological investigations. CO2-rich thermal springs, CO2 vents and travertine are frequent occurrences of the peri-Tyrrhenian sector of central-southern Italy. In a crust affected by mantle magmas triggering fluids motion, among others CO2 from several horizons at variable depth, the δ¹³C of CO3-ions of dissolved travertine suggests the type of circulation and the prevalent CO2 source involved. More negative values suggest "normal" topographically driven circulation in karstic circuits, where CO2 derives from soil (bacteria); more positive values suggest the inflow into the karstic circuits of deep CO2. Such rising CO2, together with other acidic gases (e.g. H2S) greatly enhances limestone dissolution. Accordingly, the travertine formed at the surface (metheogene vs thermogene) reflects the type of "mother" CO2 involved in the dissolution process. In this way, travertine can be used to trace the evolution of paleohydrothermal systems in areas where there are no thermal features at surface. In terms of tectonic tool, since active and fossil travertine in the Apennines can be found at very different elevations, their formation age reflects the difference in elevation between the present and the past karstic circulation. Being the Apennines a young, very active orogen, the described methodology of using travertine as a benchmark for paleohydrology, suggests for a vertical isostatic rate of 0.7 mm/y. Being very sensitive to environmental conditions, travertine can also be used as a tracer for paleoclimate. The parallel investigation on the stable isotopic composition (δ¹⁸O, δ¹³C) of the dissolved CO3-ions, and palynological profiles in two Pleistocene deposits of central Italy (Serre di Rapolano and Tivoli, the latter in progress), allowed to describe variations in the last ca 120 kyrs. The correspondence between observed environmental fluctuations in pollen and isotopes, as well as with other proxies in nearby terrestrial deposits, and with more global proxies (ice-core and foraminifera) seems possible and demonstrates that travertine can be used to investigate the paleoclimate of the late Quaternary. This is in line with the observation that most of dated travertine in central Italy cluster in interglacial periods. This coincidence seems reasonable: 1) because the deposition of travertine is depending upon rainfall amounts, and 2) because in glacial periods, the lower level of the oceans also lowers the base level of karstic circulation.

Travertines: Neotectonic indicators

Article

Jan 2005

E. Altunel

The Rhynie Hot-Spring System: Geology, Biota and Mineralisation - Preface

Article

Jan 2004

Cyclic and noncyclic mechanisms in the formation of travertine

Article

Jan 1969

Stjepko Golubic

The chemistry of carbonate deposition in freshwater is relatively well understood. Chemical processes in nature, however, often occur combined in complex mechanisms. A variety of the fossil and recent sediment formations can thus be explained only within the context of particular ecological situations. The development of travertine dams causes the differentiation of a river profile into a series of lakes and waterfalls. Some mechanisms in the formation of travertine will be presented here as examples: one from the waterfalls and one from the lakes. The third section will deal with a complex of interactions within this entire ecosystem.

Neohydrotectonics

Article

Jan 1993

Robert Muir-Wood

Major earthquakes cause significant hydrogeological ("seismohydraulic') changes, some transient in nature, others long-lived or even permanent. The temporary changes include regional increases in groundwater discharge. The most significant permanent changes are those relating to hot springs, and can involve the staunching of pre-existing springs, changes in discharge rates and the creation of new springs. These phenomena can be recorded geologically in a variety of ways. Mineral precipitates can reveal transient changes in groundwater chemistry or temperature, and certain kinds of banded mineralisation are in effect earthquake varves. Some earthflows and craters may also provide geomorphic evidence of more dramatic but short-lived hydrogeological phenomena. Lastly, hot springs themselves can owe their very existence to the occurrence of certain styles of near-surface fault rupture. -from Author

Quaternary Dating Methods

Article

Apr 2005

Mike Walker

The tufa deposits of the Malham district, north Yorkshire.

Article

Jan 1981

Allan Pentecost

Tufa is a soft, porous, calcareous rock that forms in springs, waterfalls and lakes of limestone regions. The Malham district provides many examples from the thin films coating the surface of pebbles to complex screens. Deposition is a chemical process, assisted by the presence of certain mosses and algae, and typically occurs where subterraneanw ater, rich in carbon dioxide and supersaturated with calcite, issues onto the surface. The loss of carbon dioxide to the atmosphere alters the pH of the water and causes precipitation of calcium carbonate within about 80m of the feeder spring. The chemistry involved is explained in appendixes. Tufa is easily damaged by human interference. -from Author

Decoding tufa and travertine (fresh water carbonates) in the sedimentary record: The state of the art

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