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AN APPROACH TO GENESIS OF SEPIOLITE AND PALYGORSKITE IN
LACUSTRINE SEDIMENTS OF THE LOWER PLIOCENE SAKARYA AND PORSUK
FORMATIONS IN THE SIVRIHISAR AND YUNUSEMRE-BICER REGIONS
(ESKIS� EHIR), TURKEY
SELAHATTIN KADIR1 ,*, MUHSIN EREN
2, TANER IRKEC3 , HULYA ERKOYUN
1 , TACIT KULAH4, NERGIS ONALGIL
1 ,AND JENNIFER HUGGETT
5
1 Eskis� ehir Osmangazi University, Department of Geological Engineering, TR-26480 Eskis� ehir, Turkey2 Mersin University, Department of Geological Engineering, TR-33343 Mersin, Turkey
3 Anitta Park Sitesi, 2853. Cad. 32, Daire 3/15, TR-06810 Ankara, Turkey4 Dumlupınar University, Department of Geological Engineering, TR-43100 Kutahya, Turkey
5 Natural History Museum, Department of Earth Sciences, London, UK
Abstract—The Lower Pliocene lacustrine sediments of the Sakarya and Porsuk Formations in theSivrihisar and Yunusemre-Bicer regions consist of claystone, argillaceous carbonate, carbonate, andevaporites. No detailed studies of paleoclimatic conditions have been performed previously. The presentstudy aimed to determine the depositional environment and paleoclimatic conditions for the formation ofthese economically important sepiolite/palygorskite/carbonate/evaporite deposits based on detailedmineralogical, geochemical, and isotopic studies. Samples from various lacustrine sediments wereexamined using polarized-light microscopy, X-ray diffraction, scanning electron microscopy, andchemical and isotopic analysis methods. Dolomites are predominantly of micrite, which is partlyrecrystallized to dolomicrosparite/dolosparite close to desiccation fractures. The presence of ostracods anddacycladecean algae in the carbonates reflects a restricted depositional environment. The formation ofsepiolite and palygorskite fibers, either as cement between/enclosing dolomite and/or as calcite crystals,reflects occasional changes in physicochemical conditions provided by fluctuations in the lake-water leveland influx of groundwater in relation to climatic changes during and after dolomite precipitation. Thepositive correlations of SREE with Al2O3, Nb, high-field-strength elements, and transition elements aredue to alteration of feldspar and hornblende in the volcanic units. The high values of Ba and Sr relative toCr, Co, Ni, and V also indicate that felsic rather than ophiolitic rocks were the parent material. Thecrossplot of whole-rock SiO2 vs. Al2O3+K2O+Na2O and V/Cr ratio suggests deposition ofcarbonate�dolomitic sepiolite�sepiolitic dolomite under arid climate and oxic conditions, whereas theNi/Co and V/(V+Ni) ratios of the sediments indicate deposition of organic-bearing sepiolite/palygorskiteunder anoxic-dysoxic conditions. An enrichment in d13C and d18O values of dolomite with respect tocalcite is probably due to differences in mineral fractionations. The d34S and d18O values and 87Sr/86Srisotope ratios for gypsum suggest an intensely evaporitic lacustrine environment fed by an older marineevaporitic source. The Si, Al, Mg, Ca, and enhanced TOT/C required for periodic precipitation of organic-rich brown sepiolite/palygorskite characterize deposition in a swampy environment, while dolomiticsepiolite and sepiolitic dolomite formed in ponds by partial drying of the main alkaline lake.
Key Words—Dolomite, Gypsum, Lower Pliocene, Palygorskite, Sepiolite, Sivrihisar, Yunusemre-Bicer, Turkey.
INTRODUCTION
The widespread Neogene lacustrine claystone layers
that appear as brown, beige, and white colored sediments
in the Eskis� ehir region are either intercalated or overlain
by carbonate, argillaceous carbonate, and to a lesser
extent organic materials such as remnants of plant roots
and stems (Fukushima and Shimosaka, 1987; Irkec, 1988;
Irkec and Unlu, 1993; ITIT, 1993; Irkec and Gencoglu,
1994; Ece and Coban, 1994; Unlu et al., 1995; Karakaya
et al., 2004, Yeniyol, 2014). Changes in physicochemical
conditions are characterized by variations in concentra-
tions of Al+Fe, Mg, Ca, and S; by a pH range of 8 to 9,
which developed due to lithofacies, mineralogy, chemical
composition, and alteration process; and by controlled
periodic precipitation of sepiolite, palygorskite, carbo-
nates, and evaporites in the environment.
The geology, sedimentology, mineralogy, geochemis-
try, stable isotope composition, and 87Sr/86Sr ratios of
carbonate and gypsum in the Sivrihisar area were studied
by Bellanca et al. (1993), Karakas� and Varol (1994),
Altay (2004), Aydogdu (2004), Boyraz (2004), Gungor
(2005), Varol et al. (2005), Karakas� (2006), Altay et al.
(2007), Zeybek (2007), Yes� ilova and Tekin (2007), Kırtıl
(2008), and Altay (2011). Although Kadir et al. (2016)
studied the mineralogy, geochemistry, and genesis of
* E-mail address of corresponding author:
DOI: 10.1346/CCMN.2017.064067
Clays and Clay Minerals, Vol. 65, No. 5, 310–328, 2017.
sepiolite and palygorskite in the Neogene lacustrine basin
of the Eskis� ehir province, no information is available
concerning the general distribution of dolomite, sepiolitic
dolomite, sepiolite, and gypsum in the lake and related
environments. The purpose of the present study was to
investigate the sedimentological, mineralogical, and
geochemical characteristics of the sepiolite and palygors-
kite in lacustrine carbonate sediments of the Sakarya and
Porsuk formations and their relationships with paleocli-
mate and environmental conditions.
GEOLOGICAL SETTING AND DEPOSITIONAL
ENVIRONMENT
In central Anatolia, the Neogene tectonics character-
ized by extensional and strike-slip faulting caused the
development of the Miocene sedimentary basins in
depressional areas (Kahraman, 2010) such as
Yunusemre-Bicer sub-basin and Upper Sakarya basin
separated by a threshold of Paleozoic metamorphic and
Upper Cre taceous ophio l i t i c basement rocks
(Figures 1�3). The basement rocks are overlain uncon-
formably by Upper Miocene volcanics and sediments.
These units comprise continental clastics, volcanics,
volcanoclastics and carbonates, and thick gypsum layers
in the ‘Upper Sakarya Section’ (USS) of the extensive
‘Central Anatolian Neogene Basin’ (CANB) in the south
of Sivrihisar. In the Yunusemre-Bicer sub-basin in the
northern part of the study area, however, the Upper
Miocene sediments comprise continental carbonates and
clastics with discoidal and rosette-like gypsum crystals
(Figure 2). These units are overlain unconformably by
lacustrine sediments of the Lower Pliocene Sakarya
Formation which represents playa-lake environments
(ITIT, 1993; Irkec and Gencoglu, 1994; Figure 2). The
Lower Pliocene sediments in the Yunusemre-Bicer sub-
basin characterize marginal shallow-lake environments
which may be correlated with the Sakarya Formation.
This unit has been described as the Porsuk Formation by
Gozler et al. (1996), Karakas� (2006), and Zeybek (2007).
The Lower Pliocene lacustrine sediments within the
Eskis� ehir province are represented by argillaceous
carbonate, claystone, and gypsum deposited in fluvial
and lacustrine environments (Figures 1, 2). These
sediments have been deposited under alkaline environ-
mental conditions in the USS of the extensive CANB in
the south of Sivrihisar and within the Yunusemre-Bicer
sub-basin in the north (Figure 3).
Figure 1. Geological map of the USS of the CANB in the Sivrihisar and Yunusemre-Bicer regions (adapted from Konak, 2002;
Turhan, 2002). USS: Upper Sakarya Section; CANB: Central Anatolian Neogene Basin.
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 311
The organic-rich brown sepiolite occurs in anoxic
swamps in both the marginal zones and central playa lake
zone (ITIT, 1993; Irkec and Gencoglu, 1994; Unlu et al.,
1995; Figure 4a,b). The beige dolomitic sepiolite, with no
organic material, formed in small ponds of the playa lake
(ITIT, 1993; Irkec and Gencoglu, 1994; Unlu et al., 1995;
Figure 4a). Dissolution cavities are filled by beige colored
material in clay, silt, and sand size. The white, massive,
homogeneous, light sepiolitic dolomite generally grades
into brown and beige sepiolites (Figure 4c�f). The
uppermost part of the sequence comprises hard dolomitic
levels (Figure 4f,g). Silica bands and nodules together
with sepiolite lenses are present occasionally. Gypsum
crystals are observed in the lower part of the Sakarya
Formation in the CANB, and thick, massive gypsum
deposits of the Porsuk Formation in the Yunusemre-Bicer
sub-basin (ITIT, 1993). Gypsum/anhydrite occur either as
massive discoidal, swallow-tail, and rosette-shaped crys-
tals (Figure 4h,i) or as discoidal, swallow-tail, and rosette-
shaped crystals in silty claystone and in green smectitic
clays (Figure 4j). All the aforementioned formations are
overlain unconformably by Quaternary alluvium
(Figure 2).
Figure 2. Column sections of the study area showing vertical and lateral distribution of sediments in the USS of the CANB in the
Sivrihisar and Yunusemre-Bicer regions (after Irkec and Gencoglu, 1994; Zeybek, 2007).
312 Kadir et al. Clays and Clay Minerals
MATERIALS AND METHODS
Typical stratigraphic sections were measured to
determine vertical and lateral variations within the
Neogene lacustrine basin of the Eskis� ehir area.
Characteristic fresh and altered samples were collected
(Figures 1, 2, 4) and examined under a polarizing
microscope (Nikon-LV 100Pol). The mineralogical
characteristics of the samples were analyzed by powder
X-ray diffraction (XRD) (Rigaku D / Max � 2200 Ultia
PC, Japan). The XRD analyses were performed with
CuKa radiation at a scanning speed of 1º2y/min.
Samples for clay analysis (<2 mm) were dispersed in
distilled water overnight. These samples were dispersed
further using ultrasonic vibration for 15 min. The fine
silt and coarser materials were separated from the clay
fraction by timed settling. Several oriented mounts of the
<2 mm fractions were prepared from each clay fraction
by dropping a small amount of clay onto a glass slide
and drying in air. One oriented mount was solvated with
ethylene glycol vapor at 60ºC for 2 h to identify
smectite. Further oriented mounts were heated at 300
and at 550ºC for 2 h to detect chlorite. Semi-quantitative
amounts of rock-forming minerals were obtained using
the standard methods of Brindley (1980) and Eren and
Kargı (1995). The relative abundances of clay minerals
were determined using their basal reflections and
mineral-intensity factors (Moore and Reynolds, 1989).
Scanning electron microscopy and energy-dispersive
analyses (SEM-EDX) were performed on selected
samples to determine the micromorphological character-
istics of carbonate, argillaceous carbonate, and evaporite
samples. The analyses were carried out at The Natural
History Museum, London, UK, using an FEI QUANTA
SEM equipped with Bruker Esprit software and an EDX
detector (Berlin, Germany). For SEM-EDX analysis,
representative samples were prepared by adhering the
fresh, broken surface of the sample onto aluminum stubs
with double-sided carbon tape and adding a thin coat
(~350 A) of gold palladium using a Cressington 208 HR
coater (Watford, UK).
Chemical analyses of six carbonate, three argillac-
eous carbonate, and four evaporite whole-rock samples
were performed at Bureau Veritas Mineral Laboratories
(Vancouver, Canada) using inductively coupled plasma–
atomic emission spectroscopy (ICP-AES) (PerkinElmer,
Elan 9000, Waltham, Massachusetts, USA). The Spectro
XLAB-2000 PEDX-ray fluorescence spectrometer was
calibrated using USGS interlaboratory standards. The
Inductively Coupled Plasma Emission Spectroscopy
(ICP-ES) and Inductively Coupled Plasma Mass
Figure 3. Schematic cross-section of the overall depositional environment of USS of the CANB in the Sivrihisar and Yunusemre-
Bicer lacustrine sediments (see Figure 1 for route of the cross-section).
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 313
314 Kadir et al. Clays and Clay Minerals
Spectrometry (ICP-MS) analyses were carried out on
lithium metaborate/tetraborate fusions following dilute
nitric acid digestion. Loss on ignition (LOI) was
determined as the weight difference after ignition at
1000ºC. The detection limits for the analyses were
between 0.01 and 0.1 wt.% for major elements, between
0.1 and 5 ppm for trace elements, and between 0.01 and
0.5 ppm for the SREE. The accuracy and analytical
precision of the measurements of major elements, trace
elements, rare-earth elements (REE), and transition
elements (TRE) was measured against standard refer-
ences STD SO-18, STD SO-19, STD GS311-1, STD
GS910-4, STD DS10, and STD OREAS45EA (used by
the Bureau Veritas Mineral Laboratories, Vancouver,
Canada), and duplicate analyses for each samples.
Stable-isotope analyses (d13C and d18O) of ten
dolomite and four calcite samples were performed in the
laboratories of Iso-Analytical Ltd (Crewe, UK). Powdered
samples of 5�10 mg were reacted with 100% phosphoric
acid (H3PO4) at 50ºC. The powdered carbonate samples
were weighed into Exetainer1 vials and placed in an
oven for drying to ensure that no moisture remained in the
samples nor in the containers prior to sealing them and
carrying out the acid conversion to carbon dioxide. The
tubes were then flushed with 99.995% He. After flushing,
0.5 mL of phosphoric acid (H3PO4) was added to digest
carbonate phases (Coplen et al., 1983) by injecting
through the septum caps into the vials. The vials were
left for 24 h at room temperature in order to allow the acid
to react with the samples. After 24 h, the vials were heated
to 60ºC for 2 h to ensure conversion of all available
carbonate to carbon dioxide. The CO2 gas liberated from
the samples was then analyzed by continuous-flow
isotope-ratio mass spectrometry (CF-IRMS) (Europa
Scientific, 20-20 mass spectrometer, Crewe, UK).
Standards IA-R022 (ISO-analytical working standard
calcium carbonate), NBS-18, and NBS-19 were run as
quality-control check samples during analysis of the
samples. All isotopic data are reported in delta (%) vs.
V-PDB standard (Ratio sample/Ratio V-PDB) -1)61000.
The d34S and d18O values were determined on ten
gypsum and anhydrite samples which were selected
carefully by handpicking under a binocular microscope.
Stable-isotope analyses (d34S + d18O) were conducted at
the Department of Geosciences, University of Arizona,
USA, using a MAT 261-8 Mass Spectrometer (Finnigan
MAT, San Jose, California, USA).
d34S was measured on SO2 gas in a continuous-flow
gas-ratio mass spectrometer (ThermoQuest Finnigan
Delta PlusXL, Tucson, Arizona, USA). The samples
were combusted at 1030ºC with O2 and V2O5 using an
elemental analyzer (Costech, Tucson, Arizona, USA)
coupled to the mass spectrometer. Standardization was
based on international standards OGS-1 and NBS123
(Hosono et al., 2014), and several other sulfide and
sulfate materials for sulfur that have been compared
between laboratories. Calibration is linear in the range
�10 to +30%. Precision is estimated to be �0.15% or
better (1d) based on repeated internal standards.
The d18O of sulfate was measured on CO gas in a
continuous-flow gas-ratio mass spectrometer (Thermo
Electron Delta V, Tucson, Arizona, USA). The samples
were combusted with excess C at 1350ºC using a thermal
combustion elemental analyzer (ThermoQuest Finnigan,
Tucson, Arizona, USA) coupled to the mass spectro-
meter. Standardization was based on international
standard OGS-1. Precision was estimated to be �0.4%or better (1d), based on repeated internal standards.
The strontium isotopic analyses (87Sr/86Sr ratios) of
gypsum/anhydrite samples were performed using a Triton
Figure 4 (this and facing page). Field photographs of: (a) thick brown sepiolite overlain by beige and white sepiolites and dolomite in
the Yenidogan pit (Playa lake zone); (b) close-up view of brecciated, soapy, pure brown sepiolite in the Oglakcı pit; (c) close-up view
of brown sepiolite layers overlain by white sepiolite in the Yunusemre pit; (d) thin brown sepiolite band between beige sepiolite
layers in the Oglakcı pit; (e) carbonate-infill along the discontinuity surface between sepiolite and palygorskite layers in the
Yunusemre pit; (f) brown sepiolite band between beige sepiolite and dolomite layers in the Veletler pit; (g) thick, white dolomitic
bed intercalating thin sepiolite layers in the Yenidogan pit; (h) massive gypsum layer in the Mulk gypsum pit; (i) alternation of hard
and friable gypsum layers in the Bicer village; (j) rosette- and swallow-tail-type gypsum in mudstone (claystone) in the Bicer
village.
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 315
Multi-Collector Thermal Ionization Mass Spectrometer
(Thermo Fisher Scientific Inc., Waltham, Massachusetts,
USA) with static multi-collection. Analytical uncertainties
were given at the 2m level, and 87Sr/86Sr data were
normalized with 86Sr/88Sr = 0.1194. During the course of
the measurement, the Sr standard, NIST SRM 987, was
measured as 0.710245 � 0.000005 (n = 2).
RESULTS
Petrography
Petrographic determination of the thin sections
indicated that the dolomite and sepiolite-palygorskite-
bearing dolomite samples are micritic in character and
mostly non-fossiliferous (Figure 5a,b). The dolomicrite
was partly converted to dolomicrosparite (Figure 5a) and
dolosparite (Figure 5b) due to recrystallization.
Microbrecciation was observed in some samples.
Dacycladecean algae (Figure 5c) and ostracods
(Figure 5d) are common in some dolomicrite samples.
Gypsum was observed as euhedral to subhedral crystal
forms in some thin sections (Figure 5e,f).
XRD
The XRD data for bulk samples and their clay
fraction confirmed the presence of sepiolite, palygors-
kite, smectite, chlorite, illite/mica, dolomite, calcite,
gypsum, quartz, opal-CT, and feldspar (Table 1;
Figure 6). Dolomite is abundant and associated with
sepiolite, palygorskite, smectite, and chlorite. Dolomite
generally dominates toward the top of the sequence and
is associated with accessory calcite. Dolomite was
identified from sharp peaks at 2.88�2.89 A and calcite
by peaks at 3.87 and 3.04 A (Figure 6). Sepiolite and
palygorskite were identified by peaks at 12.51 and
10.50 A, respectively (figure 5, Kadir et al., 2016).
Gypsum was identified by sharp peaks at 7.66, 4.27, and
2.87 A (Figure 6).
SEM-EDX
The SEM analysis was performed on carbonate,
argillaceous carbonate, claystone, and gypsum samples
(Figure 7). Sepiolite occurs as interwoven and scattered
fibers (Figure 7a,b). Sepiolite and palygorskite either
enclose relicts of dolomite (Figure 7c) or occur as
cement in bridging form between dolomite crystals
(Figure 7d,e). Dolomite and calcite occur as masses of
anhedral to euhedral crystal forms, overlain by traces of
palygorskite (Figure 7f). Gypsum in the Sivrihisar region
occurs in platy, sheet-like, and massive forms
(Figure 7g,h). Gypsum crystals are 1�3 mm in diameter,
and are cemented locally by prismatic and platy fine-
grained gypsum with dimensions of 1 mm60.1 mm.
Chemical analyses
The carbonate and argillaceous carbonate samples are
characterized by high MgO (avg. 13.99% and 20.10% by
weight, respectively), CaO (avg. 20.51% and 31.87% by
weight, respectively), and LOI (avg. 26.63% and 41.5%
by weight, respectively) contents (Table 2; an extended
version of Table 2 has been deposited at http://
www.clays.org/Journal/JournalDeposits.html). Sepiolite
was characterized by the relatively large MgO/
Al2O3+SFe2O3 ratio and SiO2 and decrease in the
MgO/(Al2O3+SFe2O3) ratio in palygorskite.
The Ni+Co contents in the carbonate, argillaceous
carbonate, calcareous claystone, claystone, and evapor-
ite samples showed a positive correlation with both SiO2
(r = 0.781) and Al2O3 (r = 0.664) values increasing with
clay abundance (Figure 8a,b). The Cr/Ni ratio
(<0.68�2.39) reflects the availability of ferromagnesian
phases such as olivine and pyroxene derived from
ophiolitic basement units (Table 2 and the extended
vers ion thereof [ht tp : / /www.clays .org/Journal /
JournalDeposits.html]. The crossplot of Th/Co
(0.3�2.33) vs. La/Sc (0.3�4.46) ratios for carbonate,
argillaceous carbonate, calcareous claystone, and
claystone samples falls in the field of silicic rocks
(Figure 8c). Average Al2O3/TiO2 ratios >14 range
between 15.69 and 20.45 in carbonate, argillaceous
carbonate, calcareous claystone, and claystone samples.
In general, concentrations of Ba (avg. 170.7 ppm) and Sr
(avg. 2213 ppm) are greater than those of Cr (avg.
85.48 ppm), Co (avg. 3.45 ppm), Ni (avg. 76.64 ppm),
and V (avg. 42.01 ppm). Sr values in the carbonate and
argi l laceous carbonate (86.4�3539.1 ppm and
218 .9�5786 .4 ppm, respec t ive ly , excep t for
15967.9 ppm in sample VEL1-1, that is possibly due to
the presence of celestite) are high compared to the Sr
(avg. 423 ppm) in evaporites. Sr shows a negative
correlation with Ca (r = �4.53) (Figure 8d). The SREEshow positive correlations with each of Al2O3 (r =
0.9208), TiO2 (r = 0.8492), Nb (r = 0.877), high-field
strength elements (HFSE) (Hf+Nb+Ta+Th+Ti+Zr) (r =
0.8586), and TRE (Co+Cr+Cu+Ni+V+Sc+Zn) (r =
0.4264) (Figure 8e�i).SiO2 vs. Al2O3+K2O+Na2O data for the carbonate,
argillaceous sediments, and evaporites were plotted on a
paleoclimate discrimination diagram (Figure 9). The Ni/
Co (7.19�100), V/(V+Ni) (0.23�<0.72), and V/Cr
(0.13�<2.20) ratios for carbonate, argillaceous dolo-
mite, calcareous claystone, claystone, and evaporite are
listed in Table 2 (and in the extended version thereof).
Stable-isotope geochemistry
The d13C and d18O values of the dolomite samples
range from �2.98 to +1.73% PDB and from �5.59 to
�0.23% PDB, respectively, whereas those for calcite
range from �7.28 to �1.42% PDB and from �8.80 to
�7.03% PDB, respectively (Table 3; Figure 10).
The sulfur and oxygen isotope compositions of
gypsum and anhydrite range from 15.7 to 22.3% and
from 9.4 to 19.4%, respectively (Table 4; Figure 11).
These compositions are consistent with an evaporitic
316 Kadir et al. Clays and Clay Minerals
lacustrine environment (Onal et al., 2008). These data
also suggest a contribution from pre-Lower Pliocene
evaporite deposits similar to those reported by Garcıa-
Veigas et al. (2011).
87Sr/86Sr isotope geochemistry
The 87Sr/86Sr isotope ratios for gypsum and anhydrite
samples from different parts of the CANB around
Eskis� ehir range from 0.707579 to 0.708203 (avg.
0.70782) (Table 4).
Figure 5. Photomicrographs of: (a,b) dolomicrite showing microbrecciation caused by desiccation fracturing (Fr) and
recrystallization to dolomicrosparite (arrows) and dolosparite (arrow), respectively (crossed polars, YDN-9); (c) Dasycladecean
alga-bearing dolomicrite (crossed polars, YSE-5); (d) ostracod-bearing dolomicrite (crossed polars, IL-11); (e,f) replacement of
algal dolomicrite by gypsum. Arrow showing dasycladecean alga (plane and polarized light, respectively, YSE-5).
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 317
Table 1. Mineralogical variations through stratigraphic sections of the lacustrine sediments from the USS of the CANB in theSivrihisar and Yunusemre-Bicer regions.
Sep Plg Sme Chl Ilt/Mca Cal Dol Gp Anh Qz Opl Fsp
Yunusemre - Bicer Subbasin (Marginal sub-basin)YunusemreYSE-3 ++ ++ + acc accYSE-5 acc acc +++++YSE-4 ++ +++ accYSE-14 + ++++YSE-16 +++ ++
BicerBCR-2 +++++BCR-5 +++++
SazılarSZL-2 +++++SZL-6 +++++SZL-8 +++++
OglakcıOGL-6 +++++OGL-9 +++ ++
DemirciDMC-5 +++++
BabadatBBT-1 acc + ++ ++ accBBT-4 acc ++++ acc + acc
MulkMLK-1 + acc +++ + accMLK-5 +++++MLK-6 +++++ accMLK2-3 +++++MLK2-5 +++++
GunyuzuGNU-1 acc acc ++ acc ++++ acc + accGNU-2 acc acc ++++ acc acc
USS of CANB in the south of Sivrihisar (Playa lake basin)VeletlerVEL1-1 ++ +++VEL1-3 ++ +++VEL1-7 + + + acc acc + +VEL1-10 acc acc + acc +++ accVEL2-1 ++ +++ accVEL2-2 ++ +++ accVEL2-6 ++ +++
Kurts� eyh-Insustu TepeKRT-1 + acc acc +++ + accKRT-3 acc acc ++ + + accKRT-5 + ++ + +KI-1 ++ +++KI-6 +++++ acc accKI-11 +++ ++ accKI-12 + ++++KI-20 +++++KI-23 + ++++KI-26 + ++++
AhilerAHL-1 ++ acc +++AHL-2 ++++ acc +AHL-5 acc +++++AHL-7 acc +++++
318 Kadir et al. Clays and Clay Minerals
DISCUSSION
Neogene lacustrine sediments are widespread in the
Eskis� ehir area (part of the CANB) and consist of
alternation of claystone, argillaceous carbonate, and
carbonate beds indicating cyclical climatic conditions.
The sediments show vertical and lateral changes in
lithology and mineralogical and chemical composition.
The increased thickness and spread of carbonates in
swampy playa (dolomitic) lakes indicate formation by
drying of the extensive alkaline permanent lake, result-
ing in thick horizons of brown sepiolite similar to that
reported by ITIT (1993), Irkec and Gencoglu (1994), Ece
and Coban (1994), and Yeniyol (2014) (Figures 2�4).Increase in carbonate-bed thickness upward in the
sequence indicates increasing supersaturation caused
by evaporation, increased Mg/Ca ratio, and consequently
precipitation of dolomite or, where the Si/Mg ratio is
also increased, co-precipitation of dolomite and sepiolite
(Figure 4f,g; Tables 1, 2). The organic-rich brown
sepiolite (Figure 4a�g) in swampy ponds in marginal
zones of the lake formed during the seasonal transgres-
sions and regressions with low-energy conditions and
limited dimensions similar to those reported by Akbulut
and Kadir (2003), Irkec (2011), Celik Karakaya et al.
(2011b), Kadir et al. (2010), and Galan and Pozo (2011).
This interpretation is consistent with the presence of
~2.97 wt.% TOT/C in sample AHL-2 (Kadir et al., 2016)
(locally <7 wt.% TOT/C) in the samples studied. In the
predominant swamp facies, laminated or massive,
brecciated, soapy, pure sepiolites were deposited by an
influx of groundwater and frequent changes in the lake
volume.
Abundant dolomicrite, partly recrystalized into dolo-
microsparite, and locally associated with ostracods and
dacycladecean algae indicates a restricted environment
(Figure 5a�d; Braithwaite, 1979). Micromorphologically,
the occurrence of sepiolite fibers as interwoven aggre-
gates and discrete particles, frequently bridging individual
rhombohedric dolomite crystals, reflects the Si enrich-
ment of the precipitating solution (Figure 7c�f). This may
be derived from supersaturated groundwater, or a change
in the composition of existing pond water, as indicated by
dissolution of dolomite crystal surfaces, giving rise to
neoformed sepiolite and palygorskite fibers. Factors
conducive to sepiolite/palygorskite precipitation are a
pH range of 8�8.5, moderate salinity, and a high
concentration of Mg2+, Al3+, and Si4+; conditions that
are achieved in a semi-arid to arid climate as discussed
previously (Gehring et al., 1995; Jones and Galan, 1988;
Kadir et al., 2002; Akbulut and Kadir, 2003). The
paleoclimatic discrimination diagram plot of SiO2 vs.
Al2O3+K2O+Na2O (Chen et al., 2016; Figure 9) is
consistent with an arid to semi-arid climate during
dolomitization or precipitation of associated argillaceous
sediments in the basin. Development of sepiolite and
palygorskite fibers on dolomite and rarely calcite crystals
in dolomitic sepiolite/palygorskite and sepiolitic dolomite
implies precipitation as a result of decreased Ca/Mg ratio
during dolomitization.
The Ni/Co and V/(V+Ni) ratios of the sediments of
7.19�100 and 0.23�0.72, respectively, suggest anoxic
to suboxic conditions (Table 2 and the extended version
t h e r e o f [ h t t p : / / w w w . c l a y s . o r g / J o u r n a l /
JournalDeposits.html]; Jones and Manning, 1994;
Rimmer, 2004). In addition, V/Cr ratios of 2 in
carbonate, calcareous claystone, and claystone units are
consistent with precipitation in an oxic environment
(Celik Karakaya et al., 2011a,b). The local increase of
Ni up to <512 ppm values and positive correlation
between Ni+Co vs. each of SiO2 and Al2O3 in the
claystone and calcerous claystone suggest an ophiolitic
basement and volcaniclastic sediment source (Jaques et
al., 1983; Sharma et al., 2013; Kulah et al., 2014).
Average Al2O3/TiO2 ratios of >14 for carbonate,
Table 1 (contd.)
Sep Plg Sme Chl Ilt/Mca Cal Dol Gp Anh Qz Opl Fsp
YenidoganYDN1-1 +++++YDN-10 + + +++YDN-11 +++++YDN-12 +++++
Ilyaspas� a +++++IL-1 +++++IL-3 acc + ++++IL-8 +++++IL-12 +++++IL-15 ++++ acc +IL-16 acc acc +++++
Sep: sepiolite, Plg: palygorskite, Sme: smectite, Chl: chlorite, Ilt/Mca: illite/mica, Cal: calcite, Dol: dolomite, Gp: gypsum,Anh: anhydrite, Qz: quartz, Opl: opal-CT, Fsp: feldspar, and acc: accessory, +: relative abundance of mineral (mineral-nameabbreviations after Whitney and Evans, 2010).
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 319
argillaceous carbonate, calcareous claystone, and clay-
stone samples, and a crossplot of elemental ratios of Th/
Co vs. La/Sc indicate a felsic origin (Figure 8a; Hu et al.,
2015; Pozo et al., 2016) for the sediment. This
interpretation is consistent with the low concentration
of Cr, Co, Ni, and V values compared to those of high Ba
and Sr (Ahrari Rudi and Afarin, 2016). The positive
correlation of SREE with each of Al2O3, TiO2, Nb, high-
field-strength elements (HFSE), and TRE which are
transported in the terrigenous sediments also indicate
degradation of feldspar and volcanic glass derived from
volcanic materials (Figure 8c�g; McLennan et al., 1980;
Rollinson, 1993; Gonzalez-Alvarez and Kerrich, 2010;
Pozo et al., 2016).
The high Sr values in the carbonate (avg. 1452.1 ppm)
and argillaceous carbonate (avg. 7234.4 ppm) compared
to the evaporates (avg. 423 ppm) may be due to the
leaching of Sr from evaporites which show 87Sr/86Sr
isotope ratios ranging from 0.707579 to 0.708203 and the
association of Sr with carbonates during diagenesis
(Tables 2, 4; Lerouge et al., 2011). The Sr may be
exchangeable as in Callovian-Oxfordian evaporates (cal-
cite, dolomite, siderite, celestite, and detrital minerals) of
the Paris Basin (Lerouge et al., 2011). Degradation of
Figure 6. XRD patterns for: (a) claystone, (b) calcareous claystone, (c) argillaceous carbonate, (d,e) carbonate, and (f) evaporite
samples. Sep: sepiolite, Plg: palygorskite, Cal: calcite, Dol: dolomite, Gp: gypsum, Qz: quartz, and Fsp: feldspar (mineral name
abbreviations after Whitney and Evans, 2010).
320 Kadir et al. Clays and Clay Minerals
Figure 7. SEM images of: (a) sepiolite fibers forming an interwovenmass (OGL-4); (b) close-up view of sepiolite fiber mat (OGL-4);
(c) palygorskite fibers enclosing dolomite relic (BBT-4); (d) dolomite rhomb coated by sepiolite fibers (GNU-1); (e) close-up view
of d; (f) calcite rhombs on dolomite relic (GNU-1); (g) platy form of gypsum crystal (MLK-2); (h) blocky form of gypsum crystal
cemented by anhedral gypsum (DMC-5).
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 321
Table 2. Chemical compositions of the selected rock samples in the study area.
Major oxides(wt.%)
CarbonateAvg. (n = 6)
Argillaceous carbonateAvg. (n = 3)
Calcareous claystone+
Avg. (n = 7)Claystone+
Avg. (n = 7)Evaporite
Avg. (n = 4)
SiO2 9.79 17.57 39.66 53.65 1.18Al2O3 1.40 1.28 5.49 6.16 0.24SFe2O3 0.64 0.59 2.92 3.71 0.14MgO 13.99 20.10 15.16 16.04 0.32CaO 31.87 20.51 8.85 1.02 33.08Na2O 0.10 0.12 <0.23 0.16 0.03K2O 0.28 0.14 <1.08 0.99 0.07TiO2 0.07 0.06 <0.35 0.35 0.02P2O5 0.03 0.04 <0.09 <0.06 0.01MnO 0.02 <0.02 <0.06 <0.04 0.01Cr2O3 0.008 <0.006 0.03 <0.08 0.00LOI 41.5 26.63 26.09 17.40 22.18
Total 99.64 98.95 99.76 99.66 57.26TOT/C 11.03 9.14 3.75 0.93 0.70TOT/S <0.03 <0.25 <0.09 <0.10 16.10
Trace elements (ppm)Ba 278 170.1 144 117 30.75Be 1 <1 <2 <2 1.00Co 2.4 1.56 11.87 18.26 0.53Cr 57.02 <38.77 205.26 <543.35 18.82Cs 5.3 10.9 <21.62 32.07 0.40Ga <1.7 6.47 <6.8 26.67 0.50Hf <0.6 0.37 <1.97 1.91 0.13Nb 1.8 1.73 <8.35 10.16 0.45Ni 34 <37.7 238.86 <511.75 20Rb 13.3 11.1 <69.27 64.39 2.43Sc <1.7 <1.7 <8 <9.67 1.00Sn <1.2 <1 <1.33 <1.5 1.00Sr 1452.1 7234.4 567.19 249.91 423.0Ta <0.1 0.3 <0.55 0.66 0.13Th 1.8 2.5 <7.08 5.44 0.35U 7.8 6.1 <2.23 3.04 0.45V 23.5 36.3 <95.33 248.86 9.00W <0.7 <0.5 <1.42 <1.17 0.50Zr 21.8 14.4 64.39 73.13 4.20Y 3.4 2.5 8.9 7.37 0.58La 5.4 5.43 14.77 14.14 1.33Ce 8.7 9.0 29.91 25.20 1.43Pr 1.06 0.89 <3.39 2.72 0.18Nd 3.7 3.0 <12.38 9.99 0.70Sm 0.6 0.54 <2.35 1.89 0.10Eu 0.15 0.13 <0.53 0.38 0.04Gd 0.63 0.55 <2.2 1.56 0.12Tb 0.09 0.07 <0.34 0.23 0.02Dy 0.54 0.41 <1.92 1.38 0.11Ho 0.10 0.08 <0.38 0.25 0.03Er 0.33 0.22 <1.11 0.79 0.06Tm <0.05 0.03 <0.16 0.12 0.02Yb 0.30 0.24 <1.06 0.81 0.07Lu 0.04 <0.04 <0.16 0.12 0.01Mo 0.2 <0.3 <0.35 <0.30 0.15Cu 2.9 5.7 16.47 15.89 0.90Pb 2.0 2.5 6.76 6.19 0.93Zn 6 10 30.43 36 2.00As 7.2 14.3 <7.87 5.91 3.10Cd <0.1 <0.1 <0.2 <0.2 0.10Sb <0.1 <0.4 <0.43 <0.48 0.10Bi <0.1 <0.1 <0.14 <0.2 0.10Ag <0.1 <0.1 <0.5 <0.6 0.10Au (ppb) 1.7 <1.5 7.79 <1.57 0.78
322 Kadir et al. Clays and Clay Minerals
gypsum/anhydrite of the Upper Miocene continental
sediments and crystallization of Lower Pliocene gypsum
in an open hydrologic system may have resulted in the
leaching of Sr and substitution of Sr by Ca in calcite,
dolomite, and Ca-bearing silicate crystal structure, similar
to that reported by Jaworska and Ratajczak (2008).
The d13C and d18O values of dolomite (from �2.98 to
+1.73% PDB and from �5.59 to �0.23% PDB,
respectively) and calcite (from �7.28 to +1.73% PDB
and from �8.80 to �7.03% PDB) show a negative
correlation and suggest an evaporitic, hydrologically
closed system, as well as a meteoric origin of the
solutions and an edaphic source for the carbon. The
oxygen isotope fractionation value of 3 � 1% PDB
between dolomite and calcite (Figure 10) shows that the
d18O and d13C values of coexisting limestone and
dolomite are consistent with that stated by Land
(1980). In such an environment, the formation of
dolomite would correspond to periods of higher eva-
poration rates (Figure 10) similar to that reported by
Lopez-Galindo et al. (1996). The lake water would be
Hg 0.04 <0.02 <0.29 <0.03 0.01Tl <0.1 <0.1 <0.24 0.2 0.10Se <0.5 <0.5 <0.5 <1.6 0.50Ni/Co 33.15 <44.18 79.48 <18.25 70.24Cr/Ni 1.16 0.86 0.86 <1.07 0.94V/V+Ni 0.45 <0.52 <0.39 <0.56 0.31V/Cr 0.99 <1.36 <0.46 <0.46 0.50HFSE 425.58 358.89 2180.04 2189.00 110.13TRE 136.65 131.57 606.22 1387.78 52.24SREE 24.97 <23.11 <84.81 66.95 5.21
HFSE: Hf+Nb+Ta+Th+Ti+Zr; TRE: Co+Cr+Cu+Ni+V+Sc+Zn; n = number of samples; +Kadir et al. (2016).
Table 2 (contd.)
Trace elements(ppm)
CarbonateAvg. (n = 6)
Argillaceous carbonateAvg. (n = 3)
Calcareous claystone+
Avg. (n = 7)Claystone+
Avg. (n = 7)Evaporite
Avg. (n = 4)
Table 3. Stable-isotope compositions of dolomite and calcitefrom carbonates in the study area.
Sample d18O PDB (%) d13C PDB (%)
CalciteBBT-4 �7.03 �7.28MLK-6 �7.82 �5.79KI-20 �8.80 �4.91IL-1 �7.90 �1.42Avg. �7.89 �4.85
DolomiteKI-12 �0.23 �2.80YSE-5 �2.70 �1.94YSE-14 �4.42 +1.73YDN1-1 �4.52 �0.04YDN-11 �5.59 �0.88YDN-12 �4.28 +0.20AHL-5 �3.31 �2.98AHL-7 �3.13 �2.49IL-12 �3.22 �0.82IL-13 �3.09 �0.86Avg. �3.45 �1.09
Table 4. Sulfur-, oxygen-, and 87Sr/86Sr-isotopic composition of gypsum and anhydrite samples from the study area.
Sample Mineralogy d34S V-CDT*(%)
d18Osulfate
V-SMOW* (%)
87Sr/86Sr(�2s in 10�6)
Standard error
SZL-2 Gypsum 20.5 17.6 0.707855 � 0.000050SZL-6 Gypsum 22.2 19.4 0.707706 � 0.000050SZL-8 Gypsum 21.8 17.2 0.707825 � 0.000012MLK2-3 Gypsum 21.0 18.9 0.707579 � 0.000070BCR-2 Gypsum 22.3 17.8 0.708203 � 0.000015MLK2-5 Anhydrite 21.8 9.4 0.707751 � 0.000050BCR-5 Gypsum 15.7 11.3DMC-5 Gypsum 20.3 17.8MLK-5 Gypsum 19.8 14.9IL-8 Gypsum 20.3 16.7
*V-SMOW: Vienna Standard Mean Ocean Water, a standard defining the isotopic composition of fresh water*V-CDT: Vienna Canyon Diablo Troilite, a standard for reporting sulfur isotope ratios
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 323
Figure 8. Elemental variation diagrams for major oxides (wt.%) and trace elements (ppm) of the Eskis� ehir samples: (a) Ni+Co vs.
SiO2; (b) Ni+Co vs. Al2O3; (c) Th/Co vs. La/Sc; (d) CaO vs. Sr; (e) SREE vs. Al2O3; (f) SREE vs. TiO2; (g) SREE vs. Nb; (h) SREEvs. HFSE; (i) SREE vs. TRE.
324 Kadir et al. Clays and Clay Minerals
enriched in C and O even under humid conditions
(Talbot, 1990). The concentration of C is related to the
biological processes in the basin (McKenzie, 1985; Kelts
and Talbot, 1989; Talbot, 1990; Talbot and Kelts, 1990).
Carbon isotope systematics in these cases are indepen-
dent of the oxygen isotopic system, however (McKenzie,
1985; Faure, 1986; Kelts and Talbot, 1989; Talbot, 1990;
Talbot and Kelts, 1990). The oxygen and carbon isotope
systems are controlled by the lakewater evaporation rate
(Talbot and Kelts, 1990). The negative C and O values
also support the hypersaline water and bacterial sulfate
reduction which leads to precipitation of carbonates.
The d34S and d18O values for gypsum range from
15.7 to 22.3% and from 9.4 to 19.4%, respectively,
suggesting an evaporitic lacustrine environment
(Table 4). The shift of d18O in anhydrite to lower values
may reflect the effect of evaporation. These isotopic
compositions indicate a lacustrine origin for the
evaporites, implying that they were deposited in playa
or long-lived saline lakes (Onal et al., 2008). This
interpretation is consistent with the occurrence of
gypsum as beds in the Upper Miocene carbonate units.
Further evidence for this interpretation is the develop-
ment of secondary anhedral gypsum crystal cement
between euhedral and subhedral gypsum crystals
(Figure 7h) similar to that reported by Tekin (2001).
The wide range of d34S and d18O values may also reflect
a contribution from hydrothermal fluids and mixing with
meteoric water as reported by Rye (2005). The presence
Figure 9. Paleoclimate discrimination diagram of SiO2 vs.
Al2O3+K2O+Na2O in the USS of the CANB in the Sivrihisar and
Yunusemre-Bicer lacustrine sediment samples (after Suttner
and Dutta, 1986).
Figure 10. A crossplot of d13C vs. d18O compositions of dolomite and calcite from carbonate samples.
Figure 11. A crossplot of d34S vs. d18O compositions of gysum
and anhydrite samples.
Vol. 65, No. 5, 2017 Genesis of sepiolite and palygorskite in Turkish lacustrine sediments 325
of fault-controlled hot springs (Yuce et al., 2015) and
epithermal gold deposits in the vicinity support this
interpretation. Palmer et al. (2004) reported that marine
evaporites were the source of sulfate for non-marine
Miocene evaporite deposits in Turkey. They suggest that
the SO4 and sulfur isotopic compositions of non-marine
Miocene evaporite deposits have similar values to actual
geothermal fluids from western Turkey.
CONCLUSIONS
Dolomite, argillaceous carbonate, and claystone are
widespread in Neogene lacustrine sediments of the
Eskis� ehir province. Dolomites are micritic in character
and partly recrystallized to dolomicrosparite and dolos-
parite. The presence of ostracods and dacycladecean
algae reflects deposition within a restricted environment.
Sepiolite (�palygorskite) and palygorskite occur in many
places in the CANB-USS, and the Yunusemre-Bicer sub-
basin, as scattered fibers, fiber-mats, or bridging relicts
of dolomite crystals in dolomitic units. In swamp and
playa sediments, sepiolite (�palygorskite) and palygors-
kite formed by direct precipitation from saturated
solutions. Textural and morphological features suggest
precipitation from discharging groundwater, rich in Si,
Mg, and Al, during or following dolomitization which
took place at the time of diagenesis.
Contacts between dolomite, argillaceous carbonate,
and claystone may be transitional � especially in the
swampy ponds, or may be sharp and distinct such as in
the ponds of the playa lakes, formed through partial
drying under arid climatic conditions. Sharp contacts
between dolomite, argillaceous carbonate, and claystone
occur due to the precipitation of calcite and further
conversion into dolomite, and the association of these
carbonates with minor sepiolite (�palygorskite) were
controlled by lithology, Mg/Ca ratios, and the concen-
tration of Si and Al under alkaline physicochemical
conditions. The Si, Al, Mg, Ca, and S ions, required for
sepiolite, palygorskite, and associated dolomite, calcite,
and gypsum formation were provided by solution(s) that
percolated through the ophiolitic and volcanoclastic
sedimentary source rocks. Thus, Sr and Ba enrichment
in the carbonate and argillaceous carbonate is a
consequence of degradation of feldspar and hornblende
derived from volcanic units. The presence of Ni+Co in
claystone and calcerous claystone indicates a contribu-
tion by the ophiolitic basement.
The d13C and d18O values of dolomite and calcite are
interpreted as resulting from an increase in evaporation
from the marginal subbasin to the playa-lake environ-
ment, resulting in widespread dolomitization. The d34Sand d18O values for gypsum suggest an evaporitic
lacustrine environment. The low d18O values in anhy-
drite reflect the effect of evaporation. The 87Sr/86Sr
isotope ratios also indicate that Sr originated from a non-
marine source. The aridity and anoxic-dysoxic and oxic
conditions of the precipitation environment in the basin
are demonstrated by the discrimination plot of SiO2 vs.
Al2O3+K2O+Na2O and ratios of each Ni/Co, V/(V+Ni),
and V/Cr.
ACKNOWLEDGMENTS
The present study was supported financially by theScientific Research Projects Fund of Eskis� ehir OsmangaziUniversity under Project No 2014�487. The authors areindebted to the editors and to the anonymous reviewers fortheir extremely careful and constructive reviews whichimproved the quality of the paper significantly. Part of thiswork was presented during the 53rd Annual Meeting ofThe Clay Minerals Society, Georgia State University,Atlanta, Georgia, USA, in June 2016. Jennifer Huggettthanks the staff of the Natural History Museum, London,for assistance with the SEM work.
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