GeolCarp_Vol56_No6_531

GEOLOGICA CARPATHICA, DECEMBER 2005, 56, 6, 531—543

www.geologicacarpathica.sk

The authigenic dolomite and smectite formations in the

Neogene lacustrine-fluvial Çaybaûô Basin (Elazôû, Eastern

Turkey)

DICLE BAL AKKOCA and AHMET SAGIROGLU

Fôrat University, Faculty of Engineering, Department of Geology Engineering, Elazôû, Turkey; dbal@fôrat.edu.tr

(Manuscript received October 8, 2004; accepted in revised form June 16, 2005)

Abstract: Mineralogical studies (XRD, SEM, EDS) and geochemical analysis (XRF) were applied to samples of the
Neogene Çaybaûô Formation representing different facies of lacustrine and fluvial lithologies. The bulk mineralogy of
the fluvial and lacustrine deposits comprises carbonate minerals (calcite, dolomite, aragonite), clay minerals (smectite,
illite, chlorite, mixed-layer clays S-C), nonclay silica minerals (quartz, feldspars, opal, cristobalite) and gypsum and
anhydrite. The smectite, calcite, dolomite and gypsum are generally authigenic. The quartz, feldspar, illite, chlorite,
detrital smectite probably derived from basement rocks. Major oxides and trace elements (SiO

, TiO

, Al

, Fe

, Cr,

Ni, Co, Cu) are present in high amounts in the fluvial formations and the marginal lacustrine facies, and these are
constituents of detritics transformed from the surrounding basement. The central facies of the lacustrine formations are
rich in Pb, Ba, Rb, Sr, CaO and K

O and composed of authigenic limestone, dolomite, gypsum, anhydrite and smectite.

The authigenic minerals are probably derivatives of the solutions solved from clastics and ash fall and moved towards the
central zones of the lake increasing pH, Mg / Ca ratios and thus leading to the precipitation of the carbonate. The high Ba / Sr and
Rb / Sr ratios in marginal lake facies are related to the presence of small amounts of carbonates, which incorporated Sr.

Key words: Neogene, Eastern Turkey, lacustrine and fluvial deposits, geochemistry, clay mineralogy.

Introduction

During the Neogene to Quaternary, several lacustrine ba-
sins were developed in Eastern Turkey (Fig. 1a). These
Neogene basins were filled up by clayey, carbonaceous
and sandy sediments, and also by pyroclastics of contem-
poraneous widespread basaltic, andesitic volcanism ( en-
gor & Yôlmaz 1981; aroglu & Yôlmaz 1986; Ercan et al.
1996). Çaybaûô is one of the many basins located east of
Elazôû (Fig. 1). Bulut (1973), Turkmen (1988), Unay & De
Bruijn (1997) studied the hydrogeological, sedimentolog-
ical paleontological characteristics of the basin. The aim
of this study is to present mineralogical and geochemical
variations in Çaybaûô formations and to describe authi-
genic mineral occurrences and their source, formation con-
ditions and environment.

Geological setting

The Elazôû Magmatics and Kôrkgeçit Formation consti-

tute the basement of the study area. Çaybaûô Formation un-
conformably overlies these basement rocks, and is covered
unconformably by the Palu Formation (Fig. 1b).

The Elazôû Magmatics which are widespread in the East-

ern Taurides, consist of andesites, basaltic lavas, pillow la-
vas, pyroclastics, and agglomerates of marine volcanism
association in the area. Pyroclastics and agglomerates are
composed of volcanic glass, volcanic rock fragments (andes-
ite, basalt, and diabase). Yazgan & Chessex (1991) gave the

age of the unit as Coniacian—Maastrichtian on the basis of
K / Ar age determination on sanidines.

The Kôrkgeçit Formation which is the other important unit

in Eastern Taurides is composed of sandstones, marls and
limestones. According to the paleontological studies of
Turkmen (1988), based on the fossils (Nummulites sp., Chap-
manina gassinensis, Rotalidae, Bryozoa, Asterigerina sp.,
Lithothumnium sp.) the age of the formation is Middle—
Upper Eocene.

On the basis of its sedimentary properties, ten lithofacies

are recognized and grouped as a lithofacies association in the
Çaybaûô Basin by Turkmen (1988). These lithofacies associa-
tions display characteristics of meandering river, braided
river and lake deposits (Turkmen 1988). The braided river
deposits consist of very coarse-grained, poorly cemented,
through cross-bedded sandstones, which bear red conglomer-
ate lenses in some places. Meandering river deposits contain
channel fill, point bar and flood plain subassociations up-
ward cycles and consist of limy sandy claystones, sandstones
and disorganized conglomerates. Detrital components of the
conglomerates and sandstones are composed of volcanic
rock fragments, quartz, feldspars, calcite, and mica. The lacus-
trine deposits comprise two sequences. The first sequence
consist of profundal, laminated limestones. The second se-
quence is formed by massive bioturbated limy sandy clay-
stones originated in a very shallow lacustrine-palustrine
environment. These lithologies are intercalated with soil
horizons, and with volcanoclastic materials which are main-
ly basic and intermediate in composition (Turkmen 1988).
The source of the volcanoclastics is Neogene volcanism.

532 BAL AKKOCA and SAGIROGLU

Upper Miocene-Lower Pliocene volcanisms are wide
spread on a regional scale in eastern Anatolia. Petro-
graphic and geochemical studies show that these volca-
nics are basaltic lava flows, tuffs and agglomerates
(Ercan et al. 1996).

Clayey limestones and limy claystones are pastel and

their colours vary from shades of white to buff. These
rocks are soft and contain fossils, peat, and red veinlets
or specks of Fe-oxides. Limestones consist of chert, cal-
cite and dolomite. Calcitic and dolomitic limestones
are dense and white, grey and pinky in colour. The do-
lomites deposited in the central part of the lake basin,
are harder than the limestone and pinkish grey. Because
of their hardness, dolomites form sharp topography in
the upper part of the Kirmizitepe section. The limy
claystones become more silty and sandy in the marginal
lake facies. These clays are hard with a conchoidal or
subconchoidal fracture or consist of unhardened sedi-
ments, and their colours are grey, red and green. The
age of the Çaybaûô Formation was defined as Upper Mi-
ocene—Pliocene (Turkmen 1988).

Fig. 1. Simplified location and geologic map of the study area. Modified from Bingöl (1984), Sungurlu et al. (1985), Turkmen (1988).

The Palu Formation consists of alluvial fan and braid-

ed river deposits. Alluvial fan deposits are conglomerates
and poorly sorted pebbly sandstones with muddy matrix
and showing normal and reverse grading. These facies
pass upward into the poorly sorted disorganized con-
glomerates and sandstone layers of braided river depos-
its. From its stratigraphic position in the section, the
formation is Pliocene—Quaternary in age (Cetindag 1985;
Turkmen 1988).

Material and methods

Fifty four samples representing lake and river (braided,

meandering) facies were collected from deposits (Fig. 1a)
along 4 vertical profiles traversing the Çaybaûô Forma-
tion. Details of the facies and their lithology along the
profiles are given in the next chapter. Each sample repre-
sents an interval approximately 10 m thick of same li-
thology. Samples were collected at a depth of 30—35 cm
from the surface to minimize the effect of weathering and

NEOGENE LACUSTRINE-FLUVIAL ÇAYBAƒI BASIN (EASTERN TURKEY) 533

contamination. The samples were dried and ground to
< 0.05 mm in grain size. Fifty four samples were used for
the mineralogical and 10 samples for geochemical studies.
Microscopic, X-ray powder diffraction (XRD), X-ray fluo-
rescence (XRF) and Scanning Electron Microscope (SEM)
techniques were used for the investigation of the samples.

For the XRD analyses of the bulk samples and clay

fractions a Rigaku DMAXXIIIC diffractometer, equipped
with a Cu tube, Ni filter, and slits, at Cumhuriyet Univer-
sity, Department of Geological Engineering Laborato-
ries, Sivas, Turkey, was used. The pulverized samples
were treated with 1 M HCl and NaCl solutions to dis-
solve carbonate and sulphate minerals respectively, and
then immediately were washed by centrifugation. The
2

µm fraction was isolated by normal sedimentation tech-

niques and concentrated by centrifugation. Suspensions
or smears of clay paste were dried on glass slides and
treated with ethylene glycol vapour for about 24 hours at
60 °C, then heated in an oven at 490 °C for four hours.
Clay minerals were examined by means of XRD patterns
on oriented plates (air-dried, heated, and glycol-treated)
on the basis of their (001) and higher-order reflections.
Semiquantitative ratios of minerals were estimated using
methods described by Temel & Gundogdu (1988). Their
methods are based on evaluating powder diffractograms
with the aid of the external standard method. The relative
error in this method is less than 15 %.

Fresh, broken surfaces of clay and carbonate samples

were placed on aluminum stubs coated with a thin film of
gold and examined with a JEOL JSM 840 A SEM at
Turkish Petroleum Corporation (TPAO), Ankara, Turkey.

For major and trace element analysis, X-ray fluorescence

(XRF) techniques were applied using a Rigaku 3270 model
spectrometer at Cumhuriyet University, Department of Geo-
logical Engineering Laboratories, Sivas, Turkey, applying
the calibrations of the U.S. Geological Survey (Flanagan
1976), and CRPG (Centre de Recherches Petrographiques et
Geochimiques) rock standards (Govindaraju 1989).

The loss of ignition (LOI) at 1000 °C was expressed as a

percentage of sample weight dried in an oven at 110 °C
overnight.

Results

Mineral assemblages and field relationships

The mineralogy of fluvial and lacustrine deposits from

the Çaybaûô Basin is variable and comprises carbonates,
sulphates, siliciclastics and clay minerals. Apparently, the
geochemical changes, tectonic evolution of the basin, and
amount and the nature of material transported by rivers to
the lake were the causes of mineralogical variations in the
lake sequences. These variations are well displayed in
mineral assemblages of samples from different sections
(Table 1, Fig. 2).

Nonclay silicates

Quartz, which is mainly detrital, is found in most sam-

ples, but only in small quantities, the largest amount in
the sandstone sample HK1 (21 %) from meandering river
and in clayey limestone sample C2 (9 %) from the lower
level of the lake sequence in the Çardakdivar section.
These two samples were collected from the area where flu-
vial and detritics sediments brought in to the lake basin.
In general, the amounts of quartz are the highest near the
edges of the lake basin and in the meandering river, and
gradually decrease towards the center of the lake basin.

Changes in source and volume of the incoming sedi-

ments due to cyclic sedimentation, could easily account
for this variation in the quantities of quartz (in general the
quartz ratio increases with increasing grain size) and
changes in lake water chemistry, perhaps due to water vol-
ume fluctuations, and tectonic development of the basin
may also have had some influence.

Table 1: The average mineralogical compositions were estimated from XRD profiles using the methods of Temel & Gundogdu (1988).
Note that totals do not sum up to 100 % due to average values. * – single sample (not mean) value; … – not analyzed for; ---- – not
detected; n – number of samples.

Uzunova Section

Kirmizitep Section

Çardakdivar Section

Hacisam Section

n = 1 0 n = 2

n = 8

n = 1 4 n = 3 n = 9 n = 8

Minerals

Lake River

Lake

Lake River Lake River

Calcite

Quartz

Feldspar

---

Clay

Opal Ct/A

---

43*

---

Cristobalite

---

Aragonite

---

Dolomite

---

Gypsum

---

Anhydrite

40*

---

Smectite

…

İllite
Chlorite

…

Mixed Layer

…

---

534 BAL AKKOCA and SAGIROGLU

Feldspars in the studied samples are potassium feldspar

with electron microscopic features indicating authigenic
origin (see Fig. 6d) and detrital plagioclase. Detrital pla-
gioclase is found as major constituent in most samples and
like quartz, the amounts of these minerals are the highest
in samples from the Hacisam section. These samples are
HK2 (68 %), representing sediments from meandering riv-
er, and HS10 (22 %), represent near points of entry into the
edge of the lake basin.

Fig. 2. Bulk mineral and clay mineral variations along studied sections. a – Uzunova-Kirmizitepe section, b – Çardakdivar section.
Continued on the next page.

Opal and cristobalite was detected in small or high

amounts (2—43 %) depending upon the locations in both
lake and river sediments. These amorphous materials dem-
onstrate that uncombined silica was present in the basin
and could be attributed to the volcanism, which occurred
at the same time with opal precipitation. The opal content
is the highest in sample K5 (43 %) from the lake sequence
of the Kirmizitepe section which must have been derived
from volcanic ash in various stages of devitrification. A mi-

NEOGENE LACUSTRINE-FLUVIAL ÇAYBAƒI BASIN (EASTERN TURKEY) 535

Fig. 2. Continuation from previous page. c – Hasicam section.

nor contribution to opal formation might come from the dia-
tom remains visible under the electron microscope (Fig. 3c).

Carbonates and sulphates

The carbonates are calcite, dolomite and aragonite. Cal-

cite is the predominant carbonate and comes from three
probable sources: biogenic (bioclasts of ostracod shells)
detritic and authigenic.

The total carbonate content in samples can reach up to

100 % in the Çardakdivar section. In that area the carbon-
ate-rich lake brines precipitated calcite. During the calcite
precipitation in the Çaybaûô Basin the chief inhibitor could
have been the Mg

ions. Kitano (1979) and Lippmann

(1973) found that Mg

2 +

controls the precipitation of the

calcite. XRD analysis has proved that sample U15, which
represents deep lake facies, contains Mg-calcite. For
Mg-calcite deposition the Mg / Ca molar ratios in the lake
water should be increased to more than 2 and at times they
can approach 100 (Last & Vance 2002). Probable sources
for the magnesium during the deposition of the Çaybaûô

Formation were the clayey carbonate Kôrkgeçit Formation,
basic magmatics rocks of Elazôû Magmatics and basic ash
falls. The Hacisam section where a meandering river en-
tered the lake and the edge of the lake basin, contains a
small amount of calcite. The Uzunova and Kirmizitepe
sections, which represent the central region of the lake,
have lower amounts of calcite and higher amounts of do-
lomite than the Çardakdivar section (marginal zone) due
to magnesium increase in the lake water from edges to-
wards the center of the lake basin. This phenomenon is
well described by Last & Vance (2002), Pimentel (2002), Ar-
ribas et al. (2004), and the driving force behind dolomitiza-
tion is the Mg / Ca ratio and its fluctuation.

Dolomite is absent from the Hacisam fluvial facies, but

high amounts occur in the middle—upper level of the Kir-
mizitepe lake facies. The dolomite content in some sam-
ples from Uzunova and Kirmizitepe sections can reach
99 %. Their presence would imply water conditions of the
highest salinity, high pH and high Mg / Ca ratios in water.
Jingquan (1998) describes polycrystalline dolomites as prob-
ably early diagenetic replacements and these are formed by

536 BAL AKKOCA and SAGIROGLU

contignuous growth of several rhombohedral dolomite
monocrystals. According to Wanas (2002) primary precipi-
tated dolomites are rose-like in shape. The studied samples
contain both secondary polycrystalline dolomite veinlets
and rhombohedral dolomites in clayey carbonaceous ma-
trix which are obviously of diagenetic replacement due to
calcite recrystallization (Fig. 3a,b,c) and rose-like dolomite
crystals (Fig. 3d) which are assumed to be primary precipi-
tates (Wanas 2002). Little detrital dolomite was found in
the sandstones in the Uzunova section (Fig. 2).

Aragonite is present at the all sections, except for the Kir-

mizitepe section. Its amount reaches up to 43 % in sample
U1 from the lake sequence of the Uzunova section. Arago-
nite may occur in hot water with sulphate minerals (Lipp-
mann 1973; Raiswell & Brimlecombe 1977; Last &
Schwegen 1983). The importance of SO

2—

(Kitano 1979),

high pH, Sr, Ba, Pb elements (Milliman 1974; Folk 1974) in
solution are emphasized. Gypsum and anhydrite are present
in the Uzunova limnic section. These minerals and aragonite
are available in a close vicinity and should have formed in
similar geochemical conditions. On the other hand, a small
amount of aragonite can be biogenic because aragonite mol-
lusc shells have been reported in the basin (Turkmen 1988).

The variations in Mg / Ca rates, high salinity, and

evaporation are important factors during gypsum pre-

Fig. 3. Microphotos of dolomites of different origin. a – Polycrystalline dolomite veinlets, b – Closer view of the veinlet, c – Rhom-
bohedral dolomite crystal of diagenetic origin, d – Rose-like dolomite crystals of primary precipitate.

cipitation (Berner 1971; Blatt 1982). Gypsum is present
in small amounts in sample U5 (5 %) and K4 (15 %)
from the lake environment of the Uzunova and Kirmiz-
itepe sections where the high salinity is estimated as
they represent central lake facies (Fig. 2a). On the other
hand, the occurrence of minor gypsum in these levels
indicate moderate salinities and this is supported by the
presence of metastable carbonates (aragonite, Mg cal-
cite), which can form in relatively dilute waters if a
high Mg / Ca ratio is achieved (Eugster & Kelts 1983;
Wright et al. 1997). Precipitation of gypsum may also
cause the increase of Mg / Ca ratio which induces dolo-
mitization (Arenas et al. 1999).

Correlation coefficients from bulk minerals and the Pear-

son coefficient (P) values are calculated using SPSS statisti-
cal program and given in Table 2. The level of significance
(

α) is 0.05, and data which have α values less than 0.05 are

accepted as significant. Negative correlations are estab-
lished between calcite and dolomite (probably due to dolo-
mitization), feldspar, quartz and dolomite with clay.
Positive correlation is present between quartz and feldspar.
This allows us to establish three main mineral assem-
blages: dolomite, calcite + clays, and feldspars + quartz,
which could have been seen in the different sections. In
general, feldspar and quartz are predominant in the fluvial

NEOGENE LACUSTRINE-FLUVIAL ÇAYBAƒI BASIN (EASTERN TURKEY) 537

formations and, at the edges of the lake basin represented
by the Hacisam section, lower level of the lake sequences
in Çardakdivar and Uzunova sections (Fig. 2a,b). The
calcite + clays assemblage generally makes up the highest
amount in lake facies of Hacisam and the lower levels of
the lake facies of all other sections. Dolomite is the most
common in the middle and upper level of the lake se-
quence at Kirmizitepe, Uzunova and Çardakdivar section.

Clay mineralogy

The clay minerals are smectite, illite, chlorite and

mixed-layer clays S-C (corrensite). The clay contents
range from 5 % to 69 % in the meandering river sequenc-
es, and from 32 % to 77 % in the lacustrine sequences.

The widespread and the dominant clay mineral in the

lake facies is smectite. It can be monomineral and reach up
to 100 % at K4, K6 and U22 from the lake facies in the
Kirmizitepe and Uzunova section. Intensities and
widths of the d-spacing 1.5 nm, (001) of the XRD pat-
terns are evaluated (Figs. 4—5). Low peak intensity of
(001) peak and broad (001) peak of smectite on XRD pat-
terns show a poor crystallinity which is attributed to the
alteration of amorphous silica and the authigenic origin
(Hem & Lind 1974; Jones 1986). This allows us to estab-
lish two smectite varietes in the basin.

Recent studies confirm the essentially detrital character

of fluvial clay suites (Konta 1985; Chamley 1989; Fagel
et al. 2003; Robert 2004; Suresh et al. 2004). Attempts
have been made to summarize the mineralogical composi-
tion of lutite suspensions in some of the largest rivers in
the world. The XRD patterns of smectites from meandering
river facies have high peak intensity and sharp (001)
peaks (Figs. 4—5).

Smectite at the edge of the lake basin can also be detri-

tal. A general correspondence exists between the mineral
composition of some lakes and the average clay mineralo-
gy of rocks and soil in the surrounding drainage basins
(Dean & Gorham 1976; Chamley 1989). For instance, in
Minnesota the silt- and clay-sized fraction of 46 lakes de-
pends mainly on the lithology of various crystalline and
sedimentary bedrocks. Numerous European examples also
indicate the close relation between lacustrine clays and de-

trital sources. The (001) peak intensity of smectites which
are taken from the marginal lake facies are higher and these
are detrital smectites (HS9-10, Ç3 in Fig. 5). Detrital smec-
tites of Çaybaûô could have been largely drained from ba-
saltic, andesitic rocks of the Elazôû Magmatics and marine
carbonate clay of the Kôrkgeçit Formation which form the
basement and surroundings of the basin (Fig. 1). Smectite is
one of the main component of the post Cenonian marine

Aragonite

Calcite

0.05

P=0.68

Dolomite

–0.67

P=0.62

–0.33

P=0.012

Feldspar

–0.22

P=0.10

–0.46

P=0.00

–0.15

P=0.16

Clay

–0.23

P=0.081

0.48

P=0.00

–0.39

P=0.003

0.18

P=0.17

Op-CT

0.19

P=0.14

–0.20

0.043

P=0.75

–0.47

–0.13

P=0.33

–0.11

–0.16

P=0.22

0.73

–0.18

P=0.75

0.19

–0.05

Quartz P=0.13

P=0.00

P=0.42

P=0.00

P=0.14 P=0.71

Aragonite Calcite Dolomite Feldspar Clay

Op-CT

Quartz

Table 2: Correlation analysis of the bulk minerals from the basin. The level of significance

α=0.05, valid coefficients with t-test are

given with bold characters.

Fig. 4. Representative XRD patterns of smectite. Low peak intensity and
broad (001) peak on smectite indicate its authigenic origin. High and
sharp (001) peak indicates its detritic origin.

538 BAL AKKOCA and SAGIROGLU

Fig. 5. The 001 peak intensity on XRD pattern of studied smec-
tite. Sample No, U – Uzunova section, K – Kirmizitepe sec-
tion, Ç – Çardakdivar section, HS – Hacisam section.

clays  (Bentor  1966)  and  Shoval  (2004)  determined  high
amounts  of  smectites  in  the  extensions  of  the  Kôrkgeçit  For-
mation  in  Israel.  However,  most  of  smectite  in  the  center  of
the  lake  basin  is  authigenic  in  origin  (Chamley  1989).  Authi-
genic  smectites  predominantly  in  the  center  of  the  lake  show
low  peak  intensity  and  broad  (001)  peaks  (Figs. 4—5).  Numer-
ous  descriptions  of  authigenic  clays  in  ancient  lakes  are  re-
ported  in  the  literature  (Chamley  1989).  Authigenic  smectite
can  be  formed  by  the  weathering  of  basic  igneous  rocks  (Vel-
de  1985).  Volcanic  ash  or  brines  can  react  with  water  to  form

Fig. 6. a – Typical honeycomb texture, formed by smectite crystals. b – Smectite flakes formed at the expense of volcanic glass,
which in places led to pseudomorphic replacement textures. c – Webby or highly-granulated pore lining and pore bridding authigenic
smectite. d – Highly-granulated authigenic smectite and authigenic K-feldspar.

smectite  minerals.  In  magnesium-containing  sediments,  a
smectite  may  be  derived  by  reaction  between  the  Mg  and  Si
of  silicified  rocks.  The  availability  of  sufficient  magnesium
and  basic  pH  conditions  are  the  most  important  factors  for  the
smectite-mineral  formation  (Harder  1971).  Authigenic  smec-
tites  which  combined  with  amorphous  silica  in  the  U22  sam-
ple,  taken  from  near  the  center  of  the  lake  basin,  were
distinguished  using  SEM  analysis.  Smectite  crystals  are
present  in  the  form  of  wavy  flakes,  forming  characteristic
honeycomb  textures,  which  might  be  due  to  dehydration  of
specimens  in  a  vacuum  (Fig. 6a).  The  smectite  flakes  formed
at  the  expense  of  volcanic  glass,  which  in  places,  led  to
pseudomorphic  replacement  textures  (Fig. 6b).

Chlorite, mixed layered clay (S-C) and illite show the

highest  content  in  the  meandering  river  of  the
Çardakdivar  section,  80  %  in  sample  Ç9,  82 %  in  sam-
ple  Ç10  and  38 %  in  sample  HK4  and  fluvial  sequences
of  other  sections.  These  indicate  the  detrital  character
of  these  minerals,  which  represent  characteristic  prod-
ucts  of  physical  and  chemical  weathering  from  basaltic
rocks  of  the  Elazôû  Magmatics,  and  marine  carbonate
clays  of  Kôrkgeçit.  In  sedimentary  rocks,  illite  is  usually
derived  from  the  mechanical  erosion  of  crystalline
rocks  (Deconinck  et  al.  2000).  Diagenetic  illitization
cannot  be  considered  in  Çaybaûô  Basin  as  K / Na  ratios

NEOGENE LACUSTRINE-FLUVIAL ÇAYBAƒI BASIN (EASTERN TURKEY) 539

are low which is also proved by the absence of analci-
me. In high salinity lakes, smectites are transformed to
illite following analcime formation (Stoffers & Hold-
ship 1975; Singer & Stoffers 1980).

Negative correlation between illite—smectite, chlorite—

smectite and (S-C)—smectite (Table 3), and a positive cor-
relation between illite—chlorite documented that they
were derived from the same source (Robert 2004). This
allows us to establish two main clay assemblages.
Smectite is dominant in the lake environment of the
Uzunova and Kirmizitepe sections and where it had an
authigenic character while illite, chlorite and S-C are
detrital in origin and their contents are high in the me-
andering river facies and in the places where the river
flowed into the lake basin.

Table 3: Correlation analysis of the clay minerals from the basin.
The level of significance

α=0.05, valid coefficients with t-test are

given with bold characters.

Table 4: Bulk geochemical analyses from the basin. U5,U15,U22 – Uzunova section (Lake); Ç10 – Çardakdivar section (River);
HS1,HS2,HS4, HK1,HK2 (River) HS14 (Lake) – Hacisam section. LOI — Loss of ignition.

Geochemistry

The bulk chemical compositions of the rocks are

shown in Table 4. The compositions of the studied rocks
vary in wide ranges due to three important factors (i)
differences in mineralogy (ii) variations of the environ-
mental constraints (pH, Eh) (iii) difference in the mobil-
ity of elements.

The samples from the meandering river facies of Haci-

sam and Çardakdivar sections contain abundant quartz,
feldspar and other detrital minerals such as chlorites, il-
lites, S-C and therefore contain high amounts of SiO

TiO

, Al

, Fe

and trace elements Cr, Ni, Co, Cu

are present at these levels, all indicating a detrital ori-
gin as the mobility of these elements and phases are
very low in solutions. Pb, Ba, Rb, Sr, Nb, Zr, Y are in
high amounts in samples from the lake facies of the
Uzunova section which has abundance of aragonite, dolo-
mite, gypsum and authigenic smectite minerals.

The negative correlation of SiO

with CaO and K

O is

due to most of the silica being sequestered in quartz which
is abundant at the edge of the basin, but CaO and K

O are

high at the center of lake because of their mobility (Ta-
ble 5). TiO

, Al

, Fe

, MgO, Na

O are well correlated

with each other, and Cr—Ni, Co—Cu, Co—Zn show positive
correlations. These elements are abundant where phyllo-
silicates are dominant, particularly illite and chlorite in
the basin. Positive correlations of P

with Mn, CaO; and

Smectite 1

Illite

–0.61
P=0.02

Chlorite

–0.58
P=0.04

0.36

P=0.035

S-C

–0.57

P=0.004

0.09

P=0.65

–0.28

P=0.19

Smectite Illite Chlorite S-C

Lake River

Lake

River

Major element (wt. %)

U15

U22

Ç10

HS1 HS2

HS4

HS14

HK1

HK4

SiO

46.76

40.69 56.89

50.14

48.9

46.86

52.68

47.74

46.69

66.39

TiO

0.76

0.56 0.64

1.37

0.99

0.88

1.09

0.99

0.49

0.70

13.33

11.4

14.92

14.54

15.15

14.18

16.61

14.87

10.25

13.07

5.78

5.92 5.12

13.48

10.06

8.83

10.84

10.79

2.52

4.01

MnO

0.13

0.06 0.12

0.17

0.12

0.18

0.09

0.18

0.07

MgO

6.89

3.61 2.7

7.70

6.26

6.63

6.12

6.19

2.61

2.97

CaO

10.85

17.48 6.17

2.96

6.48

10.1

3.4

6.77

18.8

4.54

1.05

0.43 2.38

1.81

0.77

0.74

1.13

0.69

2.65

3.27

2.12

1.55 2.48

0.57

1.49

1.42

1.59

1.41

1.64

1.63

0.13

0.13 0.12

0.09

0.11

0.12

0.18

0.11

LOI

12.46

19.4

8.94

5.76

10.08

10.6

6.48

10.55

14.44

3.57

Total

100.26

101.28 100.48

98.61

101.41 100.47

100.23

100.21

100.45

100.33

Trace element (ppm)
Cr

381

179

284

402

490

368

363

305

229

117

123

247

210

169

145

117

129

183

111

112

127

115

152

144

268

595

203

119

146

154

171

136

227

190

128

142

323

137

139

Ba/Sr

0.47

0.15 0.56

0.08

0.20

0.30

0.38

0.67

0.66

0.75

Rb/Sr

0.26

0.10 0.32

0.22

0.29

0.25

0.26

0.37

0.21

0.30

540 BAL AKKOCA and SAGIROGLU

Pb with Rb, Sr, Ba, Zr, Y, Th reflect the sequestration of
these elements in authigenic evaporite, carbonate and clay
minerals, which are abundant in the center of the lake.

The Ba / Sr and Rb / Sr ratios are higher in the deep lake

facies sample U15 than in the marginal lake facies U5 and
U22. Decrease in these ratios is due to the loss of Sr and
feldspar with an increased weathering and recycling. The
Sr content of sedimentary rocks varies because of the
many influences on Sr distribution in low temperature
depositional environment. These ratios may be reduced
due to additional Sr incorporated into calcite (Kinsman
1969; Bhatia 1985; Dimberline & Woodcock 1987). Ap-
parently Sr is also preferred by claystones, which have the
ability to concentrate Sr due to the ion exchange proper-
ties of clay minerals (Mc Cann 1991). Thus, Ba / Sr and
Rb / Sr ratios are low in the parts of the profiles where au-
thigenic carbonate and smectite are abundant.

Discussion and conclusions

During the Late Miocene, after the collision of the Anato-

lia-Arap platform, the Çaybaûô Basin was developed (Turk-
men 1988). Basin fills consist of lacustrine and fluvial se-
quences. The features of such basins were controlled by
subsidence rate (Basilici 1997). The Çaybaûô Basin was on
a very active fault zone which controlled subsidence. The
basin was filled up by clay, clayey carbonate, sandy sedi-

Table 5: The correlation analyses of a – Major oxide, b – Trace elements for bulk geochemistry.

ments, and also by products of contemporaneous wide-
spread volcanism.

The deposition of these clayey carbonate and sandy sedi-

ments was also interrupted periodically by ash falls. The ba-
sin was sometimes elevated and then paleosol horizons
formed. Fluvial and lake facies graded into each other dur-
ing basin development and in the meandering river, mar-
ginal lake and central lake facies each has its distinctive
mineral assemblages (Fig. 7). Quartz, feldspars, calcite, chlo-
rite, S-C and illite reach a high content in the meandering
river and lower lake levels of sections. As the lake enlarged
and deepened authigenic calcite, dolomite, smectite, gyp-
sum and anhydrite precipitated in the center of the lake
(represented by middle—upper levels of the Çardakdivar,
Kirmizitepe and Uzunova sections). These authigenic min-
eralizations were the consequence of Eh, pH and salinity
changes (Ingles et al. 1998).

The dissolution of volcanic ash, which was periodically

deposited in the lake, supplied the necessary silica to com-
bine with magnesium forming the smectites. Similar authi-
genic smectite formations originated from ash falls in lakes
are reported by many workers (e.g. Mackay et al. 1998; De-
coninck et al. 2000). At first, the calcite and smectites used
the Mg ions, and dolomite could not be precipitated at the
edge of the lake basin. The importance of relative increase
of magnesium ions at the formation of smectites (Harder
1971) and carbonates (Kitano 1979; Lippmann 1973) are
well established. On the other hand, Kahle (1965) and Gun-

SiO

TiO

0.02 1

0.28

0.68 1

–0.18

0.95

0.68 1

MnO

–0.09

0.37

0.16

0.25 1

MgO

–0.32

0.82

0.53

0.83

0.29 1

CaO

–0.62

–0.74

–0.84

–0.61

–0.11

–0.43 1

0.75

0.68

–0.28

–0.52

0.15

–0.6

–0.12 1

–0.66

–0.68

–0.12

–0.72

–0.19

–0.52

0.2

0.17 1

–0.31

–0.75

–0.72

–0.73

0.61

–0.57

0.83

0.21

0.38 1

LIO

–0.82

–0.56

–0.6

–0.66

–0.22

–0.21

0.89

–0.48

0.2

0.61

SiO

TiO

MnO MgO CaO Na

O K

O P

LIO

r 1

0.75 1

0.58

0.69 1

0.47

0.24

0.86 1

–0.56

–0.07

–0.77

–0.74 1

0.06

0.10

0.71

0.36

–0.34 1

–0.32

0.08

–0.68

–0.75

0.93

–0.45 1

0.51

–0.42

–0.88

0.87

0.71

–0.71

0.74

–0.38

–0.11

–0.41

–0.34

0.56

–0.24

0.92

0.26 1

–0.3

0.07

–0.04

–0.14

0.42

0.36

0.31

0.48

–0.42 1

0.53

–0.08

0.61

–0.68

0.82

–0.20

0.74

0.61

0.19

0.78

–0.69

–0.27

–0.54

–0.53

0.78

0.02

0.61

–0.71

0.20

0.89

0.93

–0.57

–0.20

–0.42

–0.43

0.71

0.12

0.58

0.47

0.81

0.97

0.05

–0.43

0.13

–0.31

–0.37

0.83

0.08

0.42

0.19

0.80

0.89

0.85

0.82

0.07

Cr Ni Co Cu Pb Zn Rb Ba Sr Ga Nb Zr Y Th

NEOGENE LACUSTRINE-FLUVIAL ÇAYBAƒI BASIN (EASTERN TURKEY) 541

dogdu (1985) determined the role of clay minerals in the
process of dolomite formation. The dolomite was formed
when the salinity, pH and Eh increased at the center of the
lake basin which are represented by middle—upper level of
the Çardakdivar, Kirmizitepe and Uzunova sections. As a
consequence, a mineralogical zonation of carbonate miner-
als, as calcite—calcite + dolomite—dolomite, from the edges
to the center of the lake basin was developed. In addition,
sulphate phases (gypsum and anhydrite) begun to precipi-
tate as soon as ion concentrations in solution reached
saturation. Consequently, some of the calcite, dolomite,
smectite and the large amount of illite and chlorite was de-
trital in origin. The mineral assemblage regarded as authi-
genic includes much of the calcite, aragonite, dolomite, K-
feldspars, smectite and sulphate minerals. A small amount

Fig. 7. Mineral distributions in different sections of the basin. Ar – Aragonite, Ca – Calcite, Do – Dolomite, F – Feldspar,
C – Clay, O – Opal-CT, Q – Quatrz, An – Anhydrite, Gyp – Gypsum, Cry – Cristobalite, S – Smectite, I – Illite, Chl – Chlo-
rite, S-C – Mixed Layer Clay.

of carbonate minerals could probably have been used in
the skeletons of the organisms seen as fossils.

Geochemical analysis supports the above outlined pat-

tern. The meandering river and marginal lake facies are
rich in SiO

, TiO

, Al

, Fe

, Cr, Ni, Co and Cu. These

are the constituents of detritics transported from the sur-
rounding basement. The high Ba / Sr and Rb / Sr ratios are
another indication of the abundance of detrital material.
The central parts of the lake are rich in Pb, Ba, Rb, Sr, CaO
and K

O which are constituted in authigenic calcite, dolo-

mite, gypsum, anhydrite and smectite, and could be trans-
ported in solutions to the central regions of the lake basin.

Acknowledgments:

This study was financially supported

by a grant from the Scientific Research Project Depart-

542 BAL AKKOCA and SAGIROGLU

ment of Fôrat Universty (FUBAP-671), Elazôû. We would like
to thank Prof. Dr. Huseyin Yalcin and Fatma Yalcin from
Cumhuriyet University for their help during laboratory works
at Cumhuriyet University, Sivas; to Abdullah Öner from
Turkish Petroleum Corporation (TPAO), Ankara, Turkey for
his assistance with the SEM microphotographs; Prof.
Dr. Muazzez Celik for critical reading of the manuscript. We
also sincerely thank Otília Lintnerová, Tadeusz Peryt for
their detailed critical reading and recommendations.

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