Depositional Environments and Petrography of Denizli Travertines

Mineral Res. Expl. Bul., 125, 13-29, 2002

DEPOSITIONAL ENVIRONMENTS AND PETROGRAPHY OF DENİZLİ TRAVERTINES

Mehmet ÖZKUL*, Baki VAROL** and M. Cihat ALÇİÇEK*

ABSTRACT- Quaternary to Recent travertines in the Denizli basin are distinguished in 9 lithofacies according tothe field and microscobic features. These are: 1) Crystalline crust, 2) Shrub, 3) Pisolith, 4) Paper-thin raft,5) Coated gas bubble, 6) Reed, 7) Lithoclast, 8) Pebbly travertines and 9) Palaeosols. Various combinations of thedistinguished lithofacies are deposited on slope, depression, mound, fissure ridge and channel depositional envi-ronments. In addition, these main depositional environments are divided into subenvironments. As to isotope analy-sis made of some travertine samples, d3C and d8O values show a wide distribution. The d13C values are between0.35%o and 6.70%o; d18O values are -6.47%o to -15.10 %o. Consequently, an isotopic grouping have been broughtup based on lithofacies variation and depositional environments.

INTRODUCTION

The Denizli basin is an important regionin sense of travertine formation both in Turkeyand the world. A part from modern Pamukkaletravertines where a lot of tourists visit everyyear, there are extensive travertine masses atdifferent parts of the basin, especially alongthe northern margin (fig. 1). The total areaoccupied by modern and old travertines ismore than 100 km2 in the basin and theirthickness is up to 60 m (fig. 2). Some of theold travertines have been quarriying by marb-le industry for a long time.

Travertines are limestones that formwhere hot ground waters, rich in calcium andbicarbonate, emerge at springs (Guo andRiding, 1998). CO2 outgassing causes rapidtravertine precipitation. Travertines have acomplex internal architecture frequentlychanging both in lateral and vertical directionsin short distance. This complexity is originat-ed from many factors such as spring position,underlying topography, chemical compositionof travertine depositing waters, organic activi-ty and surfacial waters. Recently, there areincrease in the studies made on geochem-istry, morphological types, macro- and'microorganic components, stable isotopevariations and dating of travertines both inTurkey and the world (i.e. Chafetz and Folk-1984; Pentecost and Tortora, 1989; Guo and

Riding, 1998, 1999; Guo et al.,1996; Srdoc etal., 1989, 1994). Most of the studies made onthe Denizli travertines are generally focusedon Pamukkale and related to hydrogeology ofthe hot waters, geothermal potential, wastingand conversation. (Koçak, 1971; Şentürk etal., 1971; Canik, 1978; Eşder and Yılmazer,1991; Gökgöz, 1994; Gökgöz and Filiz, 1998;Ekmekçi et al., 1995). Some studies havebeen subjected the stratigraphical position oftravertines in the basin, dating, morphologicalclassification, relations between travertineand neotectonics-seismicity of the region(Altunel and Hancock, 1993 a,b and Altunel,1996), travertine geochemisty and physico-mechanical features (Demirkıran and Çalap-kulu, 2001 and Özpınar et al., 2001). In theprevious works, depositional features (litho-types, facies, etc.), organic and inorganiccomponents, petrography of the travertineshave not been sufficiently investigated.Phototrophic microorganisms, their distribu-tion and influence on the travertine depositioninvestigated by Pentecost et al. (1997) areonly confined modern Pamukkale travertines.Aim of this study is to describe the differentlithofacies of recent and old travertines in thebasin context, according to field and petro-graphical features and to determine environ-ments where the lithofacies have precipitated.In addition, some stable isotope variationswere studied.

14 Mehmet ÖZKUL, Baki VAROL and M. Cihat ALÇİÇEK

GEOLOGICAL SETTING

The depression 50 km long, 25 km widelocated at the eastern end of junction localitywhere Büyük Menderes and Gediz grabenswas named as Denizli basin (Westaway,

1990, 1993). Pre-Neogene basement rocksof the basin that crop out at the horst areasare consisted of metamorp-hic rocks ofMenderes massif represented schist, marbleand allochthonous Mesozoic carbonates

PETROGRAPHY OF DENİZLİ TRAVERTINES 15

and ophiolites and Paleogene limestone,dolomite and evaporites. The basin filled byNeogene-Quaternary deposits was boundedby normal faults both in the north and southmargins (Fig. 1). The Neogene sequence,which are deposited lake and river environ-ments and Late Miocene (Meotian-Pontian) inage (as ascribed by Taner, 2001), exposescommonly at the basin margins and someuplifted areas in the middle. The basinextends in NE-SW direction. According toWestaway (1993), the extension has begun inthe Middle Miocene (ca 14 Ma. ago). Traverti-ne masses in the Denizli basin have deposit-ed where dip-slip normal fault segments dis-play step over along strike (Çakır, 1999). Thespring waters take required ions from thebasement carbonate rocks for the travertineaccumulation. The travertines deposited byemerging waters along the extentional fis-sures and normal faults rest on the Neogenesediments. Travertines at the quarries to thenorthwest of Kaklık (Fig. 1) are transitional inlateral and vertical directions with greenishgray, cream-coloured lake-marsh deposits,reddish-brown coloured alluvium, palaeosoland coarse-grained ephemeral river sedi-ments (Fig. 2). Travertines in this region havegained a stepped structure from north tosouth by normal faulting series. Nevertheless,age of first travertine accumulation in thebasin have not been clarified yet, the oldesttravertines at Pamukkale are at least 400.000years in age, as pointed out by Altunel (1996).During our study, some vertebrata teeth andjaws were found at the travertine quarries tothe northwest of Kaklık. By the preliminarydescription, it has been found out that thesevertebrata bones belong to Equus, who is anancestor of modern horse in Quaternary (Ş.Şen and G. Saraç, 2001; personal communi-cation).


METHODS

Samples are collected from the differenttravertine lithofacies, by investigating the fieldproperties. SEM analysis of the collectedsamples were made by using Jeol JSM-840type electron microscope in the TurkishPetroleum Corporation Laboratuary, Ankara.In order to perform that, polished surfaces ofthe rock samples were etched by %5 HCI dur-ing 3-5 seconds and than coated by gold in avacuum system, the images were taken.Stable isotope analyses were made at theIsotope Laboratory of Tubingen University.

PETROGRAPHY OF THE DENİZLİTRAVERTINES

Travertines precipitated at differentdepositional conditions display variations ofcolour, appearance, bedding, porosity, tex-ture, and composition. In this study, differenttravertine precipitates in the Denizli basinwere separated into the lithofacies based onfield scale and petrographical features of thesamples taken from each lithofacies wereinvestigated.

Mainly travertine lithofacies: 1)Crystallinecrust, 2) Shrub, 3) Pisolith, 4), Paper-thin raft,5) Coated gas bubble, 6) Reed, 7) Lithoclastand 8) Pebbly travertine. Paleosol horizons(9) are formations that point out erosion andnondeposition periods and frequently coin-cided with travertine sequences.

1) Crystalline crust travertine lithofacies

Crystalline crust travertines (Guo andRiding, 1992, 1998) commonly form as aresult of rapid precipitation from fast flowingwaters on smooth slope, rims and verticalwalls of terrace pools, cliff surface of waterfallsubenvironments and in extensional fissures(fig. 3). Crystalline crusts are commonlydense, crudely fibrous, light-coloured, con-sisting of elongated calcite feathers, devel-oped perpendicular to the depositional sur-face. The crystalline crusts change from a fewcentimeters to meter in thickness. The outer

crust surfaces are usually ornamented bymicroterrace pools.

Previously, the vertical crystalline crustsdeveloped in the extensional fissure ridges atPamukkale were named as bandedtravertines by Altunel and Hancock (1993a)and Altunel (1996). Crystals in the bandedstructure are perpendicular to the vertical fis-sure walls of which depositional surfaces. Byreason of that, the banded travertines precip-itated along the vertical walls of extensionalfissures (Plate I, fig. 1) also have beenaccepted as crystalline crust travertines in thisstudy. These vertical banded crusts filling thefissure space display slower and entirely inor-ganic precipitation by degassing of CO2.Crusts at the Kamara hot spring in the BüyükMenderes valley to the northwest of theDenizli basin and at Karahayıt nearPamukkale are consisted of alternation ofwhite, red, and brown colour layers due tohigh iron content of the hot spring waters.Guo and Riding (1998) determined that oldcrystalline crusts were compact and hard, butwhen young, as at Terme San Giovanni, nearRapolano Terme, Italy, they can be delicateand easily crushed.

In the microscopic appearances, it isseen that micrit and sparit laminae are alter-nated (Plate I, fig. 2). The micritic laminaecommonly are dark-coloured and in millimet-ric scale. In dark micritic laminae, the solutionpores have developed in places. The sparitelaminae, which are centimeter and decimeterin scale, may contain iron of various ratio. Thespar crystals have grown radially on themicritic basement and organised as bundlesin some places. Better development of oneside of the crystals gives a cedar tree appear-ance (Plate I, fig. 3) (Folk et al., 1985). Thesecrystals that are 10 micron in width and 100-200 micron in lenght are distinguished withthe smooth crystal boundaries from each oth-ers. In addition to unfractured crystals, frac-tured pieces are also fairly abundant. The


fractured crystals are seen as a fill of theinterspaces or randomly distributed in amicritic floor (Plate II, fig.1, 2). In SEMimages, calcite crystals forming the crust dis-play blade edge like appearances (Plate II,fig.1, 2).

Due to high flow velocity of water, thecrystalline crust develops where biogenicactivity is limited (Guo and Riding, 1998).Formation of the radial calcite crystals is aresult of direct crystallization from hot water.Any trace reflecting the microbial activity isnot coincided with the microscopic appear-ances of the samples. The alternation of lightand dark layers have been interpreted asdiurnal variation near spring area (Folk et al.,1985; Guo and Riding, 1998).

2) Shrub travertine lithofacies

Travertines represented by small bush-like growths are common deposites on hori-zontal-subhorizontal surfaces (Chafetz andFolk, 1984; Guo and Riding, 1994, 1998 andChafetz and Guidry, 1999). They are boundedby the micritic layers from both bottom andtop. The shrup lithofacies is the most commonone in the Denizli travertines. Individual shrublayers in the macro samples are light cream-coloured, 3-16 mm in thickness and seen asirregular horizons (Plate I, fig. 4).

Under the microscope, they are com-posed of the crystal associations of spar andmicrite organized in different ways. In gener-al, there is not a clear boundary between twokinds of crystal shapes. In thin sections, pre-pared perpendicular to the bedding, thespaces among the dark-coloured micriticshrub forms that expand upward were filledby secondary spar calcite mosaic (Plate I, fig.5). Whereas, in the thin sections, parallel orslightly oblique to the bedding, dark micriticclumps in the sparite constitute a mottled tex-ture as islands or patches. The densely andloosely packed micritic fields can be separat-ed in the shrub samples. Completely micritic

fields are observed where the shrub formshave densely packed. The densely packedshrubs consist of euhedral and subhedralcrystals, 5-10 urn in size, without having anyinternal architecture. These have been com-monly found in the shrub formations in mixedwith spar crystals.

Loosely packed micrites, in the form ofthin levels in places, comprise abundantdiatome (Plate III, fig. 1). The micritic clumpsare very common in the mottled texture andform the structures resembling bubble andpustule (Plate III, fig. 8). The cloudy micriteshave developed on the spar crystals. Theycompose of the micritic grains that are 5-15urn in size and wholly unhedral. In addition,the rod-shaped micrite crystals and calcifiedtubes are found within them (Plate II, fig. 3).The spar crytals followed in the form ofresidue under the micritic clumps support thatthose areas have become sparmicritization.Kahle (1977) has described this event asmicritization forming by dissolution-crystal-lization in spar crystals from the way of bioticand abiotic. In the samples, the bacterial fla-ments that is widely seen in the fields wherethe sparmicritization is present, supportingthe micrite has a biogenic origin.

According to Guo and Riding (1994,1998), shrub forms are ordinary componentsof terrace pools, but the shrubs in layers arethe most common and the thickest lithofaciesof shrub flats (shallow, extensive pools) andsubsequently marsh-like environments indepressions and on low angle slopes (fig. 3).In the studied travertines, the shrubs displaytransitions to the crystalline crust, reed,paper-thin raft and irregular radial pisoliths(bacterially mediated). According to Chafetzand Folk (1984), shrub layers represent grow-ing season (spring-summer), whereas micriticlayers represent the non-growing season(winter). Bacterial shrubs formed from heatedwaters, i.e., water temperatures were above


ambient water temperatures for a region(Chafetz and Guidry, 1999). For this reason,shrub forms are not observed in cool watertravertines (=tufas). Abiotic origin was alsoproposed for shrubs (Pentecost, 1990). Thiskind of shrubs display needle crystal shrubs'of Guo and Riding (1994) and 'crystal shrubs'and 'ray crystal shrubs' of Chafetz and Guidry(1999).

3) Pisolith travertine lithofacies

Coated grains as pisoliths are commonin travertines. (Chafetz and Meredith, 1983;Folk and Chafetz, 1983 and Guo and Riding,1998). Pisoliths form in small terrace pools ofthe steep slopes, and wide pools in depres-sion fields (fig. 3). In addition, pisoliths werefound in the self-built channels of Pamukkaleduring this study. Pisoliths occurred in thewide pools are generally associated withshrub form and micritic carbonate. Grainshape ranges from spherical to discoidal, incontrol of water agitation and microbial activi-ty (Folk and Chafetz, 1983). Previously, threetypes of pisoliths are distinguished based ontexture: 1) Concentrically laminated (Folk andChafetz, 1983), 2) Radial shrub (Folk andChafetz, 1983) and 3) Stromatolitic mammi-lated(Guo, 1993).

First two types are observed in theDenizli travertines. Concentrically laminatedpisoliths were originated from splashing andturbulent water in terrace pools and self-builtchannels. The grains size of spherical partic-les are up to a few cm (Plate I, fig. 6).Although their nuclei are always not clear,they have usually grown on a dark micriticnuclei. Crystals forming the nucleus arecoarser (10-15 mm ) than those in thin micriticlayers of the pisolith microstructure (Plate III,fig. 6). The thin micritic layers that cover theradial calcite crystals are entirely ksenotopic,consisted of grains of 3-6 mm in size. Thereare interfaces that have restricted the growthin pisolith microstructure. The interfaces are

microkarstification and dissolution structuresthat do not show lateral continuity (Plate III,fig. 2, 3) and also transform into a microstro-matolitic structure in some places. Themicrokarstification and dissolution structurespoint out most probably desiccation periods inthe terrace pools. Concentrically laminatedpisoliths have been accepted to be inorganic(Folk and Chafetz, 1983).

4) Raft travertine lithofacies

The rafts are thin, delicate and brittlecrystalline layers precipitated at the watersurfaces of pools and main fissure aper-tures filled by hot waters of the travertineridges (Plate I, fig., 7, 8). They are com-posed of calcite and/or aragonite crystalsand their extend quietly limited, in meterscale. Present day rafts are going on toprecipitate at the water surfaces of thepools located both on terraced steep slopeand near the hot spring orifices atPamukkale and Karahayıt respectively.Dense raft concentrations are commonlyassociated with coated gas bubbles at theÇukurbağ hot spring (Plate IV, fig. 8), ofwhich temperature is 58°C. The colours ofthe rafts range from white to brown, basedon chemical composition of the hot water.The horizontal rafts occurred in the mainfissure of an old travertine ridge near theKocabaş, village (Plate IV, fig. 7) are asso-ciated with lithoclasts and vertical crys-talline crusts (Plate I, fig. 7). The old exam-ples of the rafts are thickened a little due tosecondary encrustation in early diageneticstage, as exemplified by Guo and Riding(1998) from Rapolano Terme, Italy.Previously, the rafts are named as 'hotwater ice' (Allen ve Day, 1935), 'calcite ice'(Bargar, 1978), 'calcite rafts' (Folk et al.,1985) and 'paper-thin rafts' (Guo andRiding, 1998). The Similar occurrences arealso well known from cool water cave pools(Baker and Frostick, 1951; Black, 1953).


5) Coated bubble travertine lithofaciesThe coated gas bubbles are common in

depositional environments of travertine suchas terrace pools and extensive equivalents inthe depressions. The origin of the gas bub-bles is microbiologic activity in the base sedi-ments of the pools. They are mainly trappedbeneath the paper-thin rafts, among theplants and in the crystals and preserved byrapidly coating by calcium carbonate.Therefore, the coated gas bubbles are usual-ly observed together with the crystalline crust,raft (Plate I, fig. 8) and reed travertine lithofa-cies. The shape of the bubbles is sphericaland oblate and their sizes range from millime-ter to centimeter. Guo and Riding (1998)pointed out that some coated bubbles havegained a tubular appearance by joining eachother. Chafetz and Folk (1984) have termedthe coated bubbles as 'lithified bubbles' and'foam rock'. Coated bubbles have a similarstructure to that of paper-thin raft with aninner micritic layer and an outer (water side)veneer of euhedral, mainly aragonite crystals.The bimineralic wall structure has beenattributed to variation in supersaturation levelof the water (Chafetz et al., 1991 a).

6) Reed travertine lithofacies

Reed lithofacies are one of the promi-nent elements in the Denizli travertinesdeposited marsh-pool, mound and self-builtchannels. The travertines rich in molds ofreed and coarse grass were named 'reedtravertine' by Guo (1993) and Guo and Riding(1998). Reed, grass and similar water plantgrow in distal areas where hot spring waterscool and dilute due to rain influence. The plantclusters obstacles the water flow and theroots stabilize the sediments and encrustedmostly by micritic carbonate. The remainingspaces from the plants were partly or entirely,filled by the same material. The cylindiricalmolds up to 2-3 cm wide. The calcite crystalsof 20-150 mm that have form from space wallto the center are typical. The reed lithofacies

is usually associated with the rafts. The reedtravertine lithofacies are ordinary componentof both marsh-like shallow depressions dryingtime to time and reed mound. The organicmatter content and pore ratio of the reedtravertine are much more than the otherslithofacies. The lithofacies is seen at theupper levels of the quarries located to thenorthwest of Kaklık town.

7) Lithoclast travertine lithofacies

Lithoclasts are penecontemporaneous,angular to subangular travertine fragments indifferent size, by erosion of the upper slopesand collapse of waterfalls and terrace cliffs.The fragments derived from the slope arecommonly light-coloured. The fragments aresubsequently deposited at the lower slopeand in the depressions. In addition, morelocally, some fragments broken off from theupper part of fissure walls have fallen downinto the fissure apertures (Plate I, fig. 7). Thedark-coloured lithoclast interlayers in the hor-izontal travertines that have deposited in theshrub-flat and marsh-pool subenvironmentsof the depressions is 20-100 cm in thickness.This lithoclast interlayers show pedogenicalteration and caliche formation at the lowerand upper parts. The brecciation, colour andtexture variation are common in the lithoclasttravertine lithofacies that has been observedlocally.

8) Pebbly travertine lithofacies

Some travertines investigated in theDenizli basin contain sparse rounded pebblesof limestone, marble, chert, radiolarit and ser-pentinite. The pebbly travertines are seenaround the antique tombs betweenKüçükdere and Irlıganlı villages and somequarry fields located to the northwest ofKaklık. In addition, they have been observedas dropped down pebbles into the fissurespaces of the ridges. These rounded pebblesin the travertines have probably derived bythe ephemeral floodings from the basement


units of Neogene and the older sedimentaryrocks adjacent to the travertine depositionalenvironments. The pebbly travertine lithofa-cies described here may be partly correlatedwith 'cemented rudites' recognized in theBritish travertines by Pentecost (1993).

9) Palaeosol lithofacies

Decrease in water supply and diversionin flow direction result rapid exposure oftravertine surface to rain water, subaerial des-iccation, biological activities and soil forma-tion. Although palaesol formation is not direct-ly a travertine lithofacies, closely related tothe travertines precipitated especially indepressions and lower slopes. The palaesolinterbeds in the Denizli travertines are fre-quently seen at the quarries to the northwestof Kaklık. In the sequence logged at one ofthese quarries, four different brown-colouredpalaesol interbeds were separated rangingfrom 40 cm to 3 m in thickness (fig. 2). Thebed thickness increases from the slope to thedepressions. The each palaeosol bed hasconstituted a sequence boundary betweenthe two travertines. The thickness ofpalaeosol is related to how long the travertineis exposed.

TRAVERTINE DEPOSITIONAL ENVIRONMENTS

The lithofacies described above havebeen represented in state of various combi-nations in different depositional environ-ments. They are found mainly three deposi-tional environments: 1) Slope depositionalenvironment, 2) Depression depositionalenvironment; 3) Mound depositional environ-ments. This kind of classification was previ-ously made at the Rapolano Terme hot springtravertines (Italy) by Guo and Riding (1998).

In addition to the three environmentsexplained above, two additional main types ofdepositional environments were also definedin this study. One of them is fissure ridgeformed by emerging hot waters along the

extensional fractures and the other self-builtchannel called fourth and fifth depositionalenvironment respectively.

1. Slope Depositional EnvironmentSlope depositional environment are

divided into three subenvironment:a) Terraced slope, b) Smooth slope andc) Waterfall.

a) Terraced slope subenvironment.- Themost spectacular and present day examplesof the slope environment are formed atPamukkale (Plate IV, fig. 1). The terrace poolsare developed on the slope morphology. Theterraced slopes consist of vertical terracewalls, pools and rims confining the margins ofthe pools. The vertical terrace walls and rimsare composed of crystalline crust lithofacies.Paper-thin rafts, pisoliths and coated gas bub-bles are the additional lithofacies formed atthe base of pools. The terrace pools occur onthe prograding slope where waters flow turbu-lent.

b) Smooth slope subenvironment- Thesmooth slope forms where the slope dips arebetween 10-40°, on which the terrace poolshave not developed. The recent smooth slopesubenvironments at Pamukkale are transi-tional with terraced slope both in vertical andlateral direction (Plate IV, fig. 1). The domi-nant lithotype precipitating on the smoothslope is crystalline crust as seen on the wallsand rims of the terrace pools. The thicknessof crust is range from centimeter to a fewdecimeters. Feather crystals forming thecrusts are perpendicular to the slope surface.Smooth slopes develop where waters usuallyflow in laminar. Thicker crystalline crusts rep-resent rapid deposition under high flow rateswhereas thinner crust precipitated by slowerflow (Folk et al., 1985; Guo and Riding, 1998).But thin crystalline crusts were deposited byalternating with shrub layers on the low-angled slope where water supply and flowvelocity are low. Thin lithoclast levels areeven observed at lower parts of slope.



c) Waterfall subenvironment- Thewaterfall subenvironment is much more localand restricted than the others. An activewaterfall is located at the left slope of B.Menderes river valley, three kilometers southof Güney town in the northwest of Denizli (fig.1). It is forming by cool spring waters of 16°-18°C. Therefore, these porous travertines areconsidered as tufa that calcium carbonateencrusts the plants. At the same locality thereare inactive counterparts.

A second inactive example has beenformed on the steep slope facing to the northof Keltepe, along a fault scarp, near Dereköy(fig. 1). The waterfall travertines are deposit-ed on a vertical substrata, resembling anoverhanged curtain (Plate IV, fig. 3). Theoverhanged deposits have been mainly com-posed of crystalline crusts. The waterfalltravertines have been passed into the smoothslope at the lower altitudes in the time,towards north.

2- Depression depositional environment

These kinds of depositional environ-ments have been introduced during the stud-ies made on Rapolano Terme travertineslocating south of Florence, Italy (Guo, 1993;Guo and Riding, 1998). They are flats andhallows in areas of relatively low topographyand divided into two subenvironments:a) Shrub flat, b) Marsh-pool. The depressiondepositional environments are located in frontof the slopes and around of the fissure ridges(Plate IV, fig. 8).

a) Shrub flat subenvironment- Shrubflats are subenvironments in which the hori-zontal and subhorizontal, travertines havedeposited. The travertines deposited in theseenvironments are light-coloured, thin-beddedlaterally extensive and consist of mainly shrublithofacies (Plate IV, Fig. 5,6). The shrub flattravertines comprise some lithoclastinterbeds. Long-term erosion periods andshort-term precipitation interruptions result

palaeosols and desiccation surfaces respec-tively. In addition, red mudstones and con-glomerates interpreted as products of flood-

jngs and ephemeral streams are associatedwith the shrub travertines (fig. 2). In the stud-ied area, lower parts of the quarries in Beleviand northwestern of Kaklık (Killiktepe and justnorth of the Denizli Cement Factory) com-posed of the travertines of shrub flat subenvi-ronments (Plate IV, fig. 4,5,6). Transitionsfrom the shrub flats to marsh-pools subenvi-ronments are represented by alternation oflight and dark coloured layers in a travertineunit as seen on the wire-cut surfaces (PlateIV, fig. 6).

At the bottom of the Alimoğlu quarrylocated to the southern slope of the Killiktepe,a shrub flat travertine unit is up to 5 m thick.The thickness of 5 m at the north decreasesto 2.5 m in distance of 90 m. In the samedirection, the colour is become darker lateral-ly. The unit are underlain by a brown palaesolbed and overlain by gray, green-coloured thinmudstone deposited in the marsh. In the otherquarry near Alimoğlu, four different travertineunits have been observed from the bottom tothe top, which are precipitated in the shrub flatsubenvironments (fig. 2). Their thicknesseschange between 1.5 and 5 m.

b) Marsh-pool subenvironment. - Domi-nant rock types of the marshpool subenviron-ments are horizontal, gray, brown-colouredtravertines that are rich in reed lithofacies.The marsh-pool deposits are interbedded withlight-coloured travertines of the shrub flatsubenvironments and transitional in lateraldirection. They comprise lithoclastic interlay-ers and common pedogenic indications.Gastropod tests are locally abundant. Thetravertines near Kocabaş village deposited inthe marsh-pool subenvironments of thedepressions located around the fissure ridgeshave not been sufficiently consolidated yet.These are darker and more porous relative tothe slope travertines. Therefore, we think that


Kocabaş mass is younger than thetravertines at the quarries in the north, fourkm far from there.

On the other hand, these types oftravertines that are widespread at theHonaz, Karateke, Pınarkent and Gürlekareas have formed a plateau stepped fromthe south to the north (fig. 1). Thetravertines of these areas are darker, moreporous, rich in organic content, with highpedogenic effects and reed appearance inlithofacies and much more in tufa character.On the road cuts between the railway andthe highway near Pınarkent, angular traver-tine lithoclats in different sizes eroded fromsouthern part of the plateau were redeposit-ed as colluvium on a slope surface of 25-30°.

3- Mound depositional environment

Reed mound depositional environmentare those that the water plants denselylocated in depressions and near lowerslopes. The travertines of this environmentshave been previously introduced as 'mounddepositional system' and its reed moundfades by Guo and Riding (1998). In thestudied area, travertines of the mound envi-ronments have developed in associationwith the horizontally bedded travertines ofshrub flat and marsh-pool subenvironmentsbelonging to the depressions, at the upperparts of the quarries both around Killiktepeand just north of the Denizli Cement Factoryin the northwest of Kaklık (fig. 2). The mostprominent deposits of the environment isreed travertine lithofacies. The reed clustersin the growth position expand upward. Atthe slopes of the mound, the beds dip awayfrom the crest with angles of 10°-35°. Thesubsequent lithofacies such as micritic lam-inae, paper-thin rafts and coated gas bub-bles are accompanied by the reedtravertines. Some voids of the reeds werefilled by micritic laminae and paper-thinrafts.

4- Fissure-ridge depositional environment

Fissure ridges (Bargar, 1978) are narrowlinear mounds formed where hot springwaters emerge along a joint or fault on an ele-vation (Guo and Riding 1998). Fissure ridgesentirely have diverse depositional morphologyrelative to the slope environments. In theDenizli basin, both active and inactive exam-ples of the fissure ridges are observed(Altunel and Hancock, 1993a; Altunel, 1996;Çakır,1999; Özkul and Alçiçek, 2000; Özkul etal., 2001). The fissure ridges at Pamukkaleand Kocabaş have been investigated earlierin neotectonic and seismic aspects (Altuneland Hancock, 1993 a, b). According to Çakır(1999), fissure ridges occurred along thenorthwest margin of the basin are preferen-tially developed at the ends of the normal faultsegments or in step-over zones betweenthem. The most fissures are parallel to thefaults, but some are oblique. Although theridges are located along the northwest marginof the basin, there are a few examplesoccurred near the southern margin and incentral parts, as is well seen at the west endof the Honaz fault (Bozkuş et al., 2000) andaround Kocabaş respectively. B. Menderesvalley (near Yenice), Gölemezli, Pamukkale-Karahayıt, Akköy, Kocabaş and Honaz aremain locations where the ridge morphologiesare observed completely or partly, (fig. 1;Plate IV, fig. 7 and 8).

Both the Kamara ridge in the valley ofBüyük Menderes river and the Kırmızısu fis-sure ridge near Karahayıt are active and allthe others inactive. The ridges seen straightor sinuous in plan view are 100-1400 m long,up to 20 m high and 20-125 m wide at thebase. The width of individual fissures is maxi-mum in the middle and become narrowtowards both terminations. Fissure width ofeast-west trending Kuşgölü ridge is 7 m in themiddle, 5 m in the western end, at the north-west of Kocabaş village (Plate IV, fig. 7).Vertically banded crystalline crust lithofacies


are precipitated on the walls of fisures that thehot waters emerge (Plate I, fig. 1), The crys-talline crusts in some fissure fills are associat-ed with coarse-grained lithoclasts and crystalrafts and coated gas bubbles (Plate I, fig. 7).The fissure space that the hot water does notemerge are filled by red palaesol, angulartravertine lithoclasts, and gravels.

On the both slopes of the ridges, thebedded travertines are deposited in flankingaway from the main ridge axes. The dips ofthe bedded travertines range from almost ver-tical to 5°. The terrace pools in macro- andmicroscales have been formed on some ridgeslopes. The inclined travertine layers on thefissure slopes include almost all the travertinelithofacies. The most prominent lithofacies aremicritic laminae, crystalline crust, shrub, rafts,and lithoclast. The lithoclasts have beenresulted by both erosion of the upper slopesnear the crest and repeating extensional frac-turing in time. The inclined layers distally passinto the adjacent flats and depressionsaround the ridges (Plate IV, fig. 8). The faciesin the fissure slopes rapidly changes in shortdistances, even a few meters. Rapid faciesvariations in short distance are typical featurefor fissure ridges (Guo and Riding, 1999).

5- Self-built channel depositional environment

Self-built channels are linear travertinemasses built up by spring waters in flow direc-tion. Active and inactive examples of thechannels are common in Pamukkale andaround Kocabaş. The inactive channels arepartly destroyed, eroded and collapsed inplaces due to human activities and naturalprocesses, such as earthquake shaking, asseen in Pamukkale (Altunel, 1994). The chan-nel formation are realized either by naturalprocess or man-made for irrigation. Marginalslopes range from vertical to flanking sur-faces. Morphologic and structural propertiesand distribution of them have been previouslyinvestigated by Altunel (1994) and Altuneland Hancock (1993a). They have sinuous

shape in plan view and cut-cone or 'M'-shaped (term of Altunel and Hancock, 1993a)in cross section. The channel thalweg arerestricted by rims from the both sides. The

- rims have developed along the points whereprecipitation is maximum, similar to those thatin the terrace pools.

The self-built channels show lithofaciesvariations in a short distance as well as thefissure ridges and the terraced slopes. Thechannel thalweg grow as gradually upward intime by alternation of micritic laminae andcrystalline crusts. The pisolith clumpsobserved in some hollows placed along thethalweg are formed by agitated water. At thesame time, the channel slopes are developedin small scale on the both sides by overflow-ing and splashing water. The slopes are com-posed of inclined crystalline crusts, thin micrit-ic layers and reed lithofacies. The combina-tions and the ratios of the lithofacies changefrom place to place along the channels.

STABLE ISOTOPES

Oxygen and carbon stable isotope anal-yses were performed on the nine samples ofthe Denizli travertines. d3C isotope valueschanges between 0.35 and 6.7 %o while d18Ovalues varies from -6.47 to -15.10 %o (Table 1).Groundwater isotopic characteristics aremodified in case of water emerging fromspring. Main reasons of this event are intensi-ty of depositional rate and kinetic effect thataccompany to rapid degassing of CO2

(Usdovski and Hoefs, 1990).

Both biotically induced geochemical pro-cesses such as photosynthesis and decreas-ing of temperature on during flow process,evaporation, mixing from soil profile or sur-face waters effect the variations of isotopicvalues (Chafetz et al., 1991b; Guo et al.,1996).

d180 %o PDB and SMOW with d13C %oPDB values of the travertine examples ofDenizli basin and their bivariate distribution


show three different areas that indicateshrub+raft, pisolith+reed and crystalline crust(fig. 4).

The variations of stable isotope values in

the lithofacies deposited within the differentenvironments (i.e. smooth and terracedslopes, shrub flats and marsh-pools ofdepressions) under the various conditions


(i.e. water temperature, flow velocity and dis-tance from spring, surface area and biologicaleffects) are possible. Isotopic fractionationat the thermal waters going away from thesource cause a getting rich of d13C whenremoving of d12C together with continuous-ly degassing of CO2 from the thermalwaters at the orifices (Chafetz et al.,1991b). Similarly, the increasing of microbi-ologic and photosynthetic activities in poolsand depressions also result d13C enrich-ment of the system (Guo et al., 1996). Allthese data show that going away from thespring, travertines are enriched relatively interms of d13C. The same event is valid ford18O as well. Cooling of spring water in theflow direction and leaving of d16O from thesystem by evaporation increase d18O value.Linear relation of increasing of both thesetwo isotopes in relation with distance ofspring has been revealed in many studieson recent and fossil travertines (Chafetzand Lawrence, 1994; Guo et. al., 1996).

This linear relation could not beobserved at the isotope values at the litho-facies representing the Denizli travertines.The d13C values of the shrub, raft andpisolith lithofacies, precipitated in the poolsand flats away from the springs, display adistinct decrease unexpectedly (Table 1),although the expected increase of d18O val-ues has been appearantly realized.

CONCLUSIONSConclusions inferred in the study are

as follows:1- Hot water travertines of the Denizli

basin have been separated into lithofaciesin field scale. These are: Crystalline Crust,Shrub, Pisolith, Paper-Thin Rafts, CoatedGas Bubbles, Reed, Lithoclast, PebblyTravertine and Paleosol Horizons.Petrographical investigations (includingSEM studies) have also been made on therepresentative samples taken from eachlithofacies.

2- The travertine lithofacies are found indifferent rates in the depositional environ-ments. The crystalline crust lithofacies areseen commonly on the smooth slopes, rims ofthe terrace pools, vertical surfaces of thewaterfall subenvironments and in extensionalfissures of the travertine ridges. The light-coloured shrub lithofacies is the most com-mon and typical component in the shrub flatsof the depressions and comprises abundantdiatome and bacterial filaments.

3- The dark-coloured reed travertinesare particular to the reed mounds and marsh-pool subenvironments in the depressions.The reed travertines are the second orderlithofacies in widespread, in related to theshrub travertines. Pisolith, Paper-Thin Raft,Coated Gas Bubble, Lithoclast and PebblyTravertine Lithofacies are the local andrestricted occurrences. The solution cavitiesand microkarstic features seen in a pisolithinner structure reflect more probably desicca-tion periods in the terrace pools wherepisoliths formed.

4- The Travertines in the study area aremainly precipitated on the slope, depression,fissure ridge, mound and self-built channelenvironments. The slopes and the depres-sions are divided into smooth, terraced andshrub flat and marsh-pool subenvironments,respectively. Transitions in the vertical direc-tions have been observed usually from thedepression to slope or mound depositionalenvironments.

5- The travertine precipitation in thedepressions have been ceased by palaeosolformations, green mudstones and marl bedsdeposited in the marsh and shallow lakes.

6- According to the stable isotope analy-sis of the travertine samples, the values ofd13C and d18O changes between 0.35 to 6.7 %oand -6.47 to -15.10 %o, respectively. Whend18O %o PDB and SMOW and d13C %o PDBvalues are intersected with each other, the


clumping occurrences in three different fieldsrepresent shrub+raft, pisolith+reed and crys-talline crust lithofacies. Such a isotopic clump-ing supports that the travertines have precipi-tated in different depositional conditions andenvironments. d13C values are unexpectedlylow in the travertine lithofacies that character-ize the pools and stagnant water conditions.This statement means that the biologic induceof the CaCO3 precipitation in the environmenthave not been enough effective enough.

ACKNOWLEDGMENTS

The fieldwork and SEM analysis of thisstudy were supported by The Scientific andTechnical Research Council of Turkey(TÜBİTAK, project no: YDABÇAG-198Y100).The authors thank to Muharrem Satır(University of Tubingen, Germany) for isotopeanalysis. We are grateful to NizamettinKazancı (Ankara Univesity) who encouragedus to study the Denizli travertines and RobertRiding (University of Wales, Cardiff, UK) andAllan Pentecost (King's College London, UK)for some comments and literature support.During the fieldwork, the owners ofKömürcüoğlu, Mayaş, Alimoğlu, İlik, Çakmak,Emek and Ece quarries and the Kamara ther-mal hotel have provided logistic support.

Manuscript received November 2, 2001

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PLATES

PLATE -1

Fig. 1 - Light-coloured, vertical crystalline crust (cc) filled in a extensional fissure. Light and dark colouredtravertines on the right are deposited in the shrub flat (sf) and marsh-pool (mp) subenvironmentsrespectively. Kocabaş village, the Fidan travertine quarry. Marker as scale =13 cm

Fig. 2 - Thin section views of white, fibrous crystalline crust (cc) developed perpendicular to depositional sur-face and dark micritic interlayers (m).

Fig. 3 - Thin section view of the crystalline crust. Better development of one side of the clump of the calcitecrystals display a cedar three appearance.

Fig. 4 - Light-coloured, dendritic shrub layers (s) expanding upward in the growth position and dark micriticlaminae (ml). The wire-cut surface, the Ece subquarry, south of Belevi village.

Fig. 5 - Thin section views of dark and micritic shrub forms (s) expanding and branching upward in the growthposition. The peripheral voids between the shrubs are filled by sparite (sp).

Fig. 6 - Pisolith travertine. Thin section views of the pisolith grains composed of smooth concentric laminae.

Fig. 7- Paper-thin raft (r) travertine laminae precipitated in the space of an extensional fissure and the litho-clasts travertine (It) dropped down into fissure space. The Kuşgölü fissure ridge hot springtravertines, northwest of Kocabaş village.

Fig. 8 - Modern paper-thin raft (r) and coated gas bubbles (gb) formed together. The Çukurbağ hot spring,Pamukkale.

Mehmet ÖZKUL, Baki VAROL and M. Cihat ALÇİÇEK PLATE-I

PLATE - II

Fig. 1, 2- SEM photomicrographs of smooth-edged, elongated calcite crystals (Fig. 1) and crushed crys-talline crust (cc) in a micritic ground (Fig. 2).

Fig. 3- SEM photomicrographs of micrites (m) developed on the relics of spar crystals (sp), due to spar-micritization and calcified bacterial filaments (bf) at the upper left corner.

Fig. 4- SEM photomicrographs of alternation of the micrite interlayers (shown by rows) and calcite layers withradial growth in a pisolith grain. Microsolution pore (mp) on the upper right was filled by lightcoloured, secondary lime mud (Im).

Fig. 5, 6, 7- SEM photomicrographs of euhedral-subhedral spar crystals growing on the micritic ground.Rhombic edges of the crystals are preserved as seen in Fig. 7 or partly fractured or rounded(Fig. 6 and 7).

Fig. 8- Radial calcite crystals (cc) developed perpendicular to micritic ground (m).

Mehmet ÖZKUL, Baki VAROL and M. Cihat ALÇİÇEK PLATE-II

PLATE - III

Fig. 1- SEM photomicrograph of diatome relics (d) on a micritic ground of the dark coloured travertines pre-cipitated in a marsh-pool subenvironment.

Fig. 2- SEM photomicrograph of microkarstification (mk) in internal structure of a pisolith grain and microstro-matolith structure.

Fig. 3- SEM photomicrograph of close up view of a pore resulting from microkarstification between pisolithinterlayers.

Fig. 4- SEM photomicrograph showing radial calcite (rc) crystals covered by thin micritic interlayers (ml) in apisolith structure.

Fig. 5- SEM photomicrograph showing calcite crystals with radial/feathery growth in a pisolith structure.

Fig. 6- SEM photomicrograph showing the aggregate composed of ksenohedral coarser micritic grains (mg)in the nucleus of a pisolith.

Fig. 7- SEM photomicrograph showing the euhedral spar crystals as a pore fill.

Fig. 8- SEM photomicrograph showing probably bacteria-induced structure in the micritic levels of thetravertines.

Mehmet ÖZKUL, Baki VAROL and M. Cihat ALÇİÇEK PLATE-III

PLATE - IV

Fig. 1- Smooth and terraced slope subenvironments of a slope depositional environment at recentPamukkale travertines. ss= smooth slope, ts= terraced slope.

Fig. 2- Microterrace pools developing on a vertical wall. The Kırmızısu hot spring, Karahayıt, Scale:Marker=13 cm.

Fig. 3- Vertical travertines deposited a waterfall subenvironment resembling an overhanged curtain (ohc)and composed of mainly crystalline crust lithofacies, The northern slope of Keltepe, near Dereköyvillage.

Fig. 4- General view of bedded travertines deposited in shrub and marsh-pool subenvironments of depres-sional fields. Emek guarry, Kocadüz locality, northwest of the Denizli Cement Factory.

Fig. 5- Horizantal bedded, light coloured travertine deposited a shrub subenvironment, wire-cut surface, theİlik quarry, southern slope of Killiktepe, northwest of Kaklık.

Fig. 6- Horizontal, light coloured shrub flat (sf) and dark colured marsh-pool (mp) travertines deposited in thedepressional field neighbouring a fissure ridge and stratified layers of white crystalline crust litho-facies (arrowed).

Fig. 7- The view of the Kuşgölü fissure ridge from the west. E-W trending main fissure at the west part of theridge is 5 m in thickness.

Fig. 8- North-west trending the Çukurbağ fissure ridge (arrowed in the middle) and adjacent depressionaldeposition environments (de) with low topography lying on the each sides of the ridge. The Çukur-bag thermal spring located at the southern end of the ridge (arrowed in the lower left), Pamukkale.

Mehmet ÖZKUL, Baki VAROL and M. Cihat ALÇİÇEK PLATE-IV

Documents

Depositional Environments and Petrography of Denizli Travertines