Burial history and thermal maturity assessment of Upper Cretaceous–Lower Tertiary formations in the Çankırı Basin, Turkey

www.elsevier.com/locate/ijcoalgeo

International Journal of Coal

Burial history and thermal maturity assessment of Upper

Cretaceous–Lower Tertiary formations in the CankVrV Basin, Turkey

Kemaleddin TokatlV a, Ismail H. Demirel b,*, Ali Ihsan Karayigit b

a Turkish Petroleum Corporation (TPAO), Exploration Group, Eskisehir Road/Ankara, Turkeyb Department of Geological Engineering, Hacettepe University, Beytepe, 06532 Ankara, Turkey

Received 1 March 2005; accepted 10 June 2005

Available online 26 September 2005

Abstract

A burial history and thermal maturity investigation has been carried out on Upper Cretaceous–Lower Tertiary deposits from

the CankVrV Basin. This basin, which contains post-deformational deposits of Campanian–Maastrichtian to Pliocene ages, forms

part of a rich hydrocarbon province defined by the presence of potential hydrocarbon source rocks. The stratigraphic sequence

was recorded at the CankVrV, Bayat areas and Topuzsaray-1 and Sagpazar-1 wells. At each area, the succession was found to be

incomplete and important unconformities were present indicating periods of non-deposition and/or erosion. These unconfor-

mities are of variable extent.

A potential source-rock interval of Upper Ypresian and Lutetian, the YoncalV Formation which has only the organic-rich

strata among the other formations in the CankVrV Basin, has been identified. It is composed of laminated dark gray shales

dominated by Type III kerogen with turbiditic sandstones, which were deposited in relatively deep water conditions. Total

organic carbon content values range from 0.5 to 1.0%. Assessments of time–temperature index (TTI) values indicate that the top

of the main zone of oil generation is at a depth of 3000–3250-m, and the onset of oil generation window, for the Bayat area,

took place in the Miocene (10.5 My ago) and continued into the present.

Coal samples collected from the KarabalcVk Formation of Lutetian age are high in ash and sulfur. Petrographic

identifications on the polished blocks in reflected light indicate that the coal samples include abundant huminite/vitrinite

group macerals. Mean random huminite/vitrinite reflectance values of the coal samples are between 0.51 and 0.53

%Rrandom oil (av. 0.52 %Rr oil), indicating low-rank coals (subbituminous A/high volatile C bituminous) according to

the ASTM classification.

D 2005 Elsevier B.V. All rights reserved.

Keywords: Burial history; Thermal maturity; Reflectance; Tertiary; CankVrV Basin; Turkey

0166-5162/$ - see front matter D 2005 Elsevier B.V. All rights reserved.

doi:10.1016/j.coal.2005.06.002

* Corresponding author. Tel.: +90 312 2977787; fax: +90 312

2992034.

E-mail address: [email protected] (I.H. Demirel).

1. Introduction

The CankVrV Basin (Fig. 1), one of the largest

Tertiary basins of Turkey, occupies an area of about

Geology 66 (2006) 35–52

DS

F

NAF

SaltLake Lake

VanAGS

EAF

Arabian BlockT A U R I D E S

Eurasian Block

P O N T I D S

WesternCentral

Eastern

BLACK SEA

MEDITERRANEAN SEA

NAF:AGS:EAF:DSF:KMM:

North Anatolian FaultAegean Graben SystemEast Anatolian FaultDead Sea Fault

Kırsehir Metamorphic Massif

MIOCENE THRUST FRONT

0 100 km

Study area

N

Syncline Anticline Thrust faul l

Anatolian BlockKMMIzm r-Ankara-Erzincan suture zone

t Wel

Çorum-Sungurlu

Topuzsaray-1

kKızılırmak

Yapraklı

ÇANKIRI

Sagpazar-1Ugurludag

Iskilip

Sungurlu

EldivanOphiolites

Bayat

1 2 3 4 5 6 7

(a)

(b)

.

˘˘

˘

Fig. 1. Location (a) and simplified geological map of the CankVrV and Bayat areas (b) (modifed from Ozcelik and Oztas, 2000). Abbreviations: 1,

Mesozoic (ophiolites); 2, Eocene (flysch); 3, Eocene (carbonate); 4, Eocene (volcanic); 5, Eocene–Oligocene (continental); 6, Miocene

(continental); 7, Quaternary (alluvium).

K. TokatlV et al. / International Journal of Coal Geology 66 (2006) 35–5236

K. TokatlV et al. / International Journal of Coal Geology 66 (2006) 35–52 37

22,500-km2, and is bordered by the North Anatolian

Fault and Pontids in the north, KVrsehir Meta-

morphic Massif in the south, Eldivan Mesozoic

Ophiolites in the west and Corum–Sungurlu Basin

in the east. The Upper Cretaceous to Lower Tertiary

lithostratigraphic units and geological evolution of

the investigated area have been studied by many

authors (for example Ayan, 1969; Norman, 1972,

1975; Akyurek et al., 1980; Senalp, 1981; Yoldas,

1982; Capan et al., 1983; YVlmaz and Sungurlu,

1991; Kocyigit, 1991; Tuysuz and Dellaloglu,

1992, 1994; Ozcelik, 1994; Ocakoglu, 1997;

KaymakcV, 2000). Previous studies show that the

first petroleum exploration in the northwestern part

of the CankVrV Basin (around Iskilip) was made by

Akkus (1962). Between 1974 and 2000, studies

focused on petroleum possibilities of the CankVrV–

Corum Basin have been documented by Dellaloglu

(1974), Birgili et al. (1975), Dellaloglu et al. (1992),

and Ozcelik and Savun (1993). In addition, some

authors such as Harput and Gurgey (1992), Ozcelik

and Oztas (2000), and Illeez and Tekin (2003)

evaluated organic geochemical analyses of core

samples from Topuzsaray-1 well (Fig. 1b), outcrop

samples, and oil seeps. They have shown that the

Lower Eocene YoncalV Formation, which has a con-

siderable high total organic carbon content, is an

important lithostratigraphic unit as a hydrocarbon

source rock in the CankVrV and Corum Basins. The

CankVrV and Corum Basins have been recognized as

a single basin by Birgili et al. (1975), Senalp

(1981), and Tuysuz and Dellaloglu (1994).

In this study, available geological and geochem-

ical studies and data about ages and thicknesses of

the stratigraphic units in the CankVrV Basin, for the

first time, have been evaluated for burial history and

the prediction of the thermal evolution of the Upper

Cretaceous and Lower Tertiary units, in order to

assess burial temperatures and, if present, timing

of hydrocarbon generation. For this purpose, this

study includes (1) a brief description of the geolo-

gical setting and depositional history of the CankVrV

Basin, (2) an evaluation of the analysis results of

coal samples collected from the Middle Eocene

KarabalcVk Formation, (3) the construction of burial

history diagrams for the CankVrV and Bayat regions

and the Topuzsaray-1 well, (4) measurement of sur-

face and borehole temperatures and the calculation

of present geothermal gradients, (5) calculation of

time–temperature index (TTI) values using equations

presented by Waples (1980), and (6) correlation of

these TTI values with measured random vitrinite/

huminite reflectance values. In addition, the

SagpazarV-1 well (see Fig. 1b for the location),

which only penetrated to shallow depths and thus

cut the relatively younger formations, was also used

for the calculation of surface temperature and pre-

sent geothermal gradients.

2. Lithostratigraphy

The CankVrV Basin is located in the Izmir–

Ankara–Erzincan suture zone, an approximately E–

W trending post collisional basin about 1500-km-

long and 100-km-wide containing a sequence of up

to 4.2-km of Upper Cretaceous–Tertiary mostly sedi-

mentary rocks, but north some igneous rocks. Fol-

lowing the closure of Neotethys at the end of the

Cretaceous, accretionary prism deposits were dis-

placed onto the Eurasian and Anatolian plates, result-

ing in subsidence of the CankVrV Basin. This basin is

part of the Central Anatolian sedimentation area and

contains post-deformational deposits of Campanian–

Maastrichtian to Pliocene ages.

The generalized stratigraphic succession of the

CankVrV area and its lithostratigraphic correlation

with the units identified in the Bayat area and Topuz-

saray-1 well, which are located within the CankVrV

Basin (see Fig. 1), are presented in Figs. 2–4. It is

clear that two non-depositional periods occurred in

the Upper Cretaceous and Paleocene successions in

the Bayat area (Fig. 3). The Topuzsaray-1 well has

penetrated a sequence extending from Senonian to

Oligocene (Fig. 4).

The basement in the study area is formed by the

Kosedag Melange (Fig. 2). The YaylacayV Formation

includes fine to medium grained sandstones inter-

calated with clayey limestones, marls and siltstones

at the top, and tuff, tuffite and agglomerate at the

base. The units above the YaylacayV Formation are

the MalbogazV, YapraklV, TaslVktepe and Gocuktepe

Formations, which pass laterally and vertically into

the CankVrV volcanites. The lower unit of the Mal-

bogazV Formation consists mainly of tuffs and

agglomerates of the CankVrV volcanites with lime-

Fig. 2. Generalized lithostratigraphic sequence of the CankVrV Basin (modifed from Ozcelik and Oztas, 2000).


ÇANKIRI AREA BAYAT AREA

Basal Age(My)

Basal Age(My)

Thickness(m)

Thickness(m)Formation Formation

0 0

1.64 1.64

5.2 5.2

10.3 10.3

23.3 23.3

29.3

38.0

40.0

42.0

45.0

54.0

57.0

62.0

65.0

66.0

70.0

74.0

88.5

26.3

33.5

38.6

41.0

50.0

56.5

66.0

70.0

74.0

88.5

0-500

300

?

Non-depositional Period(4.0 My)

Non-depositional Period(9.5 My)

20

50

150

150

300

1500

0-100

300-1000

1500

200

Kösedag Melange

Kösedag Melange

Yaylaçayı

Yapraklı

Hacıhalil

Yoncalı

Bayat

Kocaçay

Bayındır

Kızılırmak

Bozkır

Degim

AlluviumAlluvium

Degim

Bozkır

Kızılırmak

Bayındır

Incik

Kocaçay

Osmankahya

Karabalçık

Yoncalı

Hacıhalil

Dizilitaslar

Göçüktepe

Tasliktepe

Yapraklı

Malbogazı

Yaylaçayı

?

2500 ?

40-150

50-525

30-100

75-500

10-400

20-400

50-3000

100-400

170-250

65-350

135-2000

1500

100-330

60-500

30

5-30

AGE

QUATERNARY

PLIOCENE

MIOCENE

OLIGOCENE

EO

CE

NE

MID

DL

EU

PPE

RL

OW

ER

PAL

EO

CE

NE

UPP

ER

CR

ETA

CE

OU

S

SEN

ON

IAN

¸

¸

.

˘

˘

˘

˘

Incik.

˘

Fig. 3. Chronostratigraphic correlation of the Cretaceous–Tertiary rock units in the CankVrV and Bayat areas.


stone bands and lenses bearing Hippurites. Its upper

unit mainly contains quartz sandstones and white

limestones (Ozcelik and Oztas, 2000). The base of

the YapraklV Formation consists of conglomerates

passing into marl, siltstone, and sandstone alternat-

ing with 5 and 10-cm-thick clayey limestone beds.

The TaslVktepe Formation is composed of sand-

stones with shell fragments, sandy limestone, silt-

stone and marl. The Lower Paleocene sediments are

represented by the continental Gocuktepe Formation

composed of red-colored mudstone rich in organic

matter. The upper part of this formation is composed

of cross-laminated sandstones and conglomerates.

Lithologically, these pebbles consist of volcanic

Sandstone and shaleConglomerate

Mudstone

Conglomerate,sandstone,

mudstone, shale

0

725

929

2006.5

2907

3090

3568

Mal

boga

zıK

ocaç

ay

.

˘

Fig. 4. The identifiable formations in Topuzsaray-1 well, and their observed temperature values (Tsurface=13.6 8C, bottom hole tempera-

ture=102 8C; after PIGM, 1996).


rocks and were probably derived from the CankVrV

volcanites. The CankVrV volcanites are reported to be

generally tuff, tuffites, and agglomerates derived from

spilitic basalts and andesites. These sills in most

places have been recognized as volcanites intruded

into the rocks of the MalbogazV to the Gocuktepe

Formations during Uppermost Cretaceous–Lower

Paleocene (Ozcelik and Oztas, 2000).

The Uppermost Paleocene Dizilitaslar Formation

represents the beginning of a marine incursion into

the CankVrV Basin during the Paleocene, and was

deposited in a shallow-marine environment. It is

composed of reefal limestone at the base and alter-

nating gray sandstone and shale at the top. The

Ypresian HacVhalil Formation includes coaly mud-

stone at the base, conglomerate at the middle, and

sandstone and shale at the top. The YoncalV Forma-

tion represents a fully marine incursion into the

CankVrV Basin during Upper Ypresian and Lutetian.

Lithologically, the YoncalV Formation consists largely


of laminated dark gray shale rich in shallow marine

and terrestrial organic matter with sandstone depo-

sited as turbidites in relatively deep water. This

formation also contains conglomerates interpreted

as debris flow deposits associated with slump-type

folds. The shales of the YoncalV Formation are the

only potential hydrocarbon source rock among the

other formations of the stratigraphic succession in

the CankVrV Basin. Illeez and Tekin (2003) indicated

that its total organic carbon (TOC wt.%) values

range from 0.5 to 1.0 wt.% (av. 0.7 wt.%). The

KarabalcVk Formation was defined as fluvial fan

deposit at the base of the Lutetian succession (Del-

laloglu et al., 1992). The formation consists mainly

of conglomerate at the base, limestone with Num-

mulites in the middle, and sandstone and a coal

seam at the top. The coal seam is generally 0.50

to 1.20-m-thick but is 4-m-thick in the Bayat area.

The formation thins from 400 m in the east (Bayat

area) to 100 m in the northeastern part of the

CankVrV Basin (CankVrV and YapraklV areas, see

Fig. 1).

In the Bayat area, the Lutetian volcano-sedimen-

tary Bayat Formation (Fig. 3) is equivalent to the

upper part of the Osmankahya Formation and the

lower part of the Kocacay Formation in the CankVrV

area (Ozcelik and Oztas, 2000). This formation

is characterized by tuff, tuffite, agglomerate and

varicolored shale, marl interbedded with volcano-

clastics, and sandstone. In the CankVrV area, the

Osmankahya Formation which was deposited

between 40 and 42 My according to the strati-

graphic relations, consists of 3 and 4-m-thick red

cross-bedded conglomerate, and alternations of

sandstone with mudstone bearing plant and coal

fragments. The lower part of this formation is

intruded by the about 4-m-thick GozkayasV dyke.

The thickness of the formation varies between 170

and 250-m (Birgili et al., 1975; Ozcelik and Oztas,

2000). In general, the rocks of the Kocacay For-

mation reflect a change from shallow-marine to

terrestrial and fluvial deposition. Marine facies

represented by volcanites and cross-laminated con-

glomerates that grade upward into limestone bear-

ing Nummulites and Alveolina with green colored

marl and sandstone. The reef facies is about 15-m-

thick and occupies local basement highs in the

sequence.

As a result of the continuos gentle subsidence

with more or less constant sedimentation during the

Upper Eocene, the CankVrV Basin has become a shal-

low-marine to continental environment. The Upper

Eocene Incik Formation consists mainly of conglom-

erates, with 60 and 80-m-thick beds, sandstone and

organic-rich mudstone. The Incik Formation is

bounded conformably at the top by evaporites and

marls of the Oligocene BayVndVr Formation. Arid cli-

matic conditions at the end of the Eocene continued

during Oligocene and Miocene and resulted in the

deposition of marl containing porphyroblastic gyp-

sum and sandstone.

The Lower Miocene KVzVlVrmak Formation was

defined by Dellaloglu et al. (1992) as containing

red and orange fluvial conglomerate, sandstone and

mudstone. The Upper Miocene BozkVr Formation is

made up predominantly of white, thin bedded (0.5–2

cm) gypsum and alternations of green marl, siltstone

and sandstone. It is believed to ranging from 60 to

500-m-thick based on paleogeographic considera-

tions and facies correlation. The Pliocene Degim

Formation consists mainly of gray marl, mudstone,

and sandstone. The Quaternary alluvium and terrace

sediments unconformably cover all formations across

the study area.

3. Methods

3.1. Coal analysis

In order to enable the reconstruction of burial

histories, a total of 10 coal samples were collected

from the working mines in the KarabalcVk Formation

coals from the Bayat area. Standard proximate ana-

lysis and random huminite/vitrinite reflectance mea-

surements in the coal samples were carried out in the

Department of Geological Engineering at Hacettepe

University (HU), Ankara-Turkey, following the re-

commended guidelines of the American Society for

Testing and Materials (ASTM, 1991). Fifty random

reflectance values on the maceral huminite/vitrinite

for coal rank determination were measured on each

coal polished briquette using ordinary reflected light

with a petrological microscope (Leitz MPV II) with

a 32� oil-objective with immersion oil (noil=1.518).

Mean values (%Rr) for each sample were calculated.


3.2. Reconstruction of burial history curves and cal-

culation of geothermal gradients

Time-temperature index (TTI), Lopatin–Waples

type modelling, (Waples, 1980), was used to estimate

burial temperatures, the present level of the thermal

maturity and the timing of hydrocarbon generation.

0

500

1000

1500

2000

2500

3000

3500

3600

20 40 60

TEMPE

DE

PT

H (

m)

Presengradien

Fig. 5. Depth versus present measured temperature values for Topuzsaray-

8C/km; after PIGM, 1996).

However, the use of the TTI method alone to calculate

hydrocarbon generation and to match the measured

%Rr-trend can lead to an incorrect burial and thermal

history. This is because the TTI method was originally

developed to predict %Rr values of coals rather than to

predict hydrocarbon generation (Waples et al.,

1992a,b). However, using the details given in Waples

80 100 120Formation

Incik

Kocaçay

Bayat

Yozgat

Yaylaçay

RATURE (ºC)

t geothermalt: 24.7 ºC/km

.

g

1 well (Tsurface=13.6 8C, average present geothermal gradient=24.7


(1980), the TTI values in the present study were

adapted to predict kerogen maturity.

The burial history curves for the CankVrV and Bayat

areas and the Topuzsaray-1 well were constructed

using formation age, lithology, and thicknesses which

were taken from the measured outcrop sections by

previous workers and the well log data in Turkish

PetroleumCorporation unpublished reports of the Gen-

eral Directorate of Petroleum Works (PIGM). The sur-

face temperature values of the CankVrV and Bayat areas,

and the two wells (Topuzsaray-1 and SagpazarV-1)

were calculated using the values of longitude, latitude,

and elevation after Tezcan (1992). The present

Fig. 6. The identifiable formations in Sagpazar-1 well, and their observed

8C; after PIGM, 1997).

geothermal gradients used in the calculation of Lopatin

TTI values were calculated by employing the Bottom

Hole Temperature (BHT) data recorded on log head-

ings which were corrected using a Horner plot (Dow-

dle and Cobb, 1975) (Figs. 4–7). Present day

geothermal gradients range from 25 8C/km at Topuz-

saray-1 well (Fig. 5) to 30 8C/km at CankVrV and Bayat

areas and SagpazarV-1 well (Fig. 7), and in general the

geothermal gradients appear to decrease towards the

Topuzsaray-1 site. The relatively low geothermal gra-

dient at the latter site may result from the absence of a

thick Oligocene, Miocene and Pliocene cover in this

area, and therefore the paleogeothermal gradient has

temperature values (Tsurface=13.9 8C, bottom hole temperature=123


been assumed to have been 30 8C/km and was constant

during deposition of the CankVrV Basin rock units. The

measured random huminite/vitrinite reflectance values

and their paleotemperature conversions (Barker and

Pawlewicz, 1994) are mostly consistent with present

geothermal gradients.

0

500

1000

1500

2000

2500

3000

3500

3700

20 40 60

Present geothfor 0 - 1037 m

Presegradimete

Average present geothermgradient = 29.40 ºC/km.

T= 20 ºC

TEMPE

DE

PT

H (

m)

Fig. 7. Depth versus present measured bottom hole temperature values

gradient=29.4 8C/km; after PIGM, 1997).

The effects of the sedimentary hiatuses on the

burial history and thermal maturities were calculated

using the formula given by Dow (1977), and checked

using the equation for eroded thicknesses proposed by

Guidish et al. (1985). Calculated TTI values for the

Tertiary formations in the CankVrV and Bayat areas,

80 100 120 Formation

Incik

ermal gradienteters = 39 ºC/km

nt geothermalent for 1250 - 3700rs = 27.2 ºC/km.

al

RATURE (ºC)

.

for Sagpazar-1 well (Tsurface=13.9 8C, average present geothermal


and Topuzsaray-1 well were converted according to

the maximum vitrinite reflectance values (%Rmax)

using the conversion formula given by Kalkreuth

and McMechan (1988).

4. Results and discussion

4.1. Coal analysis results

Proximate analysis of ten coal samples, which were

collected from the KarabalcVk Formation of Middle

Fig. 8. Selected photomicrographs of macerals and minerals from the coals

and oil immersion: (a) typical cell structure form of huminite/vitrinite (H)

and funginite (Sc); (e–f) secondary pyrites (P) and carbonates (Cc) in frac

Eocene age, shows that the coal samples on an air-

dried basis average 3.12% moisture, 34.79% volatile

matter, 27.88% ash, 34.21% fixed carbon, 5.99% total

sulfur and 5211 kcal/kg gross calorific value. This

means that the coals are high in ash and especially

in total sulfur. Selected microphotographs of macerals

and minerals of the coal samples are given in Fig. 8.

Petrographic observations on the polished blocks in

reflected light indicate that the coal samples include

abundant huminite/vitrinite group macerals and pyrite

(Fig. 8). High pyrite contents, which were developed

in syngenetic and epigenetic forms (Fig. 8b–e), are in

in the KarabalcVk Formation of Middle Eocene age in reflected light

; (b–d) huminite/vitrinite (H), framboidal and crystalline pyrites (P)

tures of huminite/vitrinite (H).


agreement with the total sulfur contents. In addition,

some coal samples contain abundant carbonates,

formed epigenetically (Fig. 8f). This study shows

that the mean random huminite/vitrinite reflectance

values are between 0.51 and 0.53 %Rrandom oil

(av. 0.52 %Rrandom oil), indicating low-rank coals

(subbituminous A/high volatile C bituminous) accord-

ing to the ASTM classification given by Stach et al.

(1982).

4.2. Predicted thermal maturities

Fig. 9 is a burial history diagram of the Upper

Cretaceous–Pliocene sequence in the CankVrV area.

20

40

50

60

70

80

90

100

110

MESOZOIC CA

EoceneCamp. PaleoceneMaast.356.5

45 42 403880 74 70 66 65 6260 57 5414

30

50

120

A B C

Tsurface = 14 °C; Present geothe

A: YapraklıB: TaslıktepeC: GöçüktepeD: DizilitaslarE : HacıhalilF : YoncalıG: KarabalçıkH: OsmankahyaI : KocaçayJ : ncikK: BayındırL : KızılırmakM: BozkırN: DegimB

UR

IAL

TE

MP

ER

AT

UR

E (

°C) Formations:

¸

¸

I.

˘

Fig. 9. Burial history curves, maximum burial temperatures and the main z

the CankVrV area.

TTI values and vitrinite reflectance values were

calculated for only the Upper Cretaceous–Lower

Oligocene formations. The construction used bottom

boundaries and minimum formation thicknesses,

measured at outcrop. The total thickness of this

succession is 3750-m, and its maximum burial tem-

perature is between 111 and 126 8C. The total TTI

value is 33.2 and the calculated vitrinite reflectance

is 0.85% Rmax, indicating that the YapraklV Forma-

tion is in the oil generation window (Fig. 9 and

Table 1). The TTI values for the TaslVktepe, Gocuk-

tepe, Dizilitaslar, and HacVhalil Formations are 22,

19.5, 18, and 11.2, respectively. The maximum

burial temperatures to which these formations have

INOZOIC

Oligocene Miocene Plio.

3000

2500

2000

1500

1000

500

0

5.2

5.210.3

23.3

23.329.330

5.4

3500

3750

D E F G H I J K

rmal gradient = 30 °C/km

OilWindow

BU

RIA

L D

EP

TH

(m

)

LM N

ΣTTI=15

ΣTTI=75

one of oil generation of the Upper Cretaceous–Tertiary formations in

Table 1

Maximum burial temperature intervals, calculated time–temperature

index (TTI) and maximum vitrinite reflectance (%Rmax) values of

the Upper Cretaceous–Upper Eocene formations in the CankVrV area

Formations Maximum burial

temperature interval (8C)A TTI Calculated

%Rmax

(A) YapraklV 120–130 33.2 0.85

(B) TaslVktepe 110–120 22.0 0.79

(C) Gocuktepe 100–110 19.5 0.76

(D) Dizilitaslar 100–110 18.0 0.73

(E) HacVhalil 100–110 11.2 0.65

(F) YoncalV 100–110 8.2 0.59

(G) KarabalcVk 90–100 2.9 0.45

(H) Osmankahya 80–90 1.7 0.38

(I) Kocacay 80–90 1.3 0.35

(J) Incik 70–80 0.9 0.33


been exposed range from 104 to 111 8C, and the

calculated vitrinite reflectance values range from

0.79 to 0.65 %Rmax. Unfortunately, the organic geo-

chemical studies show that there is no hydrocarbon

source rock present in these formations. However, the

Lower Eocene YoncalV Formation shales have an

average TOC content of 0.7%, indicating a probable

source rock potential (Illeez and Tekin, 2003), and

kerogen in the YoncalV Formation is mostly Type III

material with calculated reflectance values (0.59

%Rmax) for this formation showing that it has not

quite reached the lower limit of the oil generation

zone, i.e., below a TTI value of 15 which indicates

the lower limit of the onset of oil generation (Waples,

1980). From the peak burial temperatures ranging

from 92 to 104 8C and reflectance values over 0.5

%Rmax, which is the threshold of the oil generation

window, it can be predicted that the YoncalV Forma-

tion is marginally mature. The total TTI value is 2.9

for the Middle Eocene KarabalcVk Formation, and the

maximum burial temperature is between 90 and 100

8C (Fig. 9). The calculated reflectance value is 0.45

%Rmax, indicating immaturity. However, as noted

earlier, measured random huminite/vitrinite reflec-

tance values of the coal samples taken from this

formation range from 0.51 to 0.53 %Rr (av. 0.52

%Rr). These reflectance measurements imply that

the KarabalcVk Formation has reached early maturity,

and therefore the calculated TTI values for this region

appear to be a slight underestimation of the degree of

thermal maturation (Table 1). The TTI values for the

Middle–Upper Eocene Osmankahya, Kocacay and

Incik Formations are 1.7, 1.3 and 0.9, respectively.

The maximum burial temperatures of these forma-

tions range from 77 to 84 8C (Fig. 9), and the

calculated vitrinite reflectance values range from

0.33 to 0.38 %Rmax. These three formations are there-

fore predicted to be immature.

In the Bayat area, the Paleocene TaslVktepe,

Gocuktepe and Dizilitaslar Formations were not

deposited and the Upper Paleocene–Lower Eocene

HacVhalil Formation presents an incomplete

sequence, therefore during reconstruction of the bur-

ial history diagrams, a non-depositional period of

these formations extending from 66.0 to 56.5 My

has been taken into account, and eight formations

from Lower Eocene to the end of Miocene in age

have all been modelled at this location (Fig. 10 and

Table 2). The HacVhalil and YoncalV Formations are

predicted to have reached the onset of the oil win-

dow, as indicated by TTI values ranging from 88.9

and 25.7, and calculated vitrinite reflectance values

ranging from 1.10 to 0.80 %Rmax. The earliest time

for the onset of oil generation is the Miocene (10.5

My ago) for the HacVhalil Formation, and the latest

time is Lower Pliocene (4.9 My ago) for the

YoncalV Formation. The main phase of oil genera-

tion occurs between depths of 3250- and 4270-m

(Fig. 10). The maximum burial temperature of the

HacVhalil Formation is about 142 8C. For the

YoncalV Formation, burial temperature values are

between 88 and 134 8C. The TTI values for the

Middle–Upper Eocene Bayat, Kocacay and Incik

Formations are 1.8, 1.0 and 0.4, respectively. Maxi-

mum burial temperatures of these formations range

from 74 to 88 8C. Calculated vitrinite reflectance

values of the Bayat and Kocacay Formations are

0.39 and 0.34 %Rmax. These three formations are

therefore predicted to be immature for oil genera-

tion. Predicted maturation data for the Bayat area

suggest that the YoncalV Formation, which is the

only formation displaying a hydrocarbon source

rock potential, has reached the oil generation win-

dow. However, its dominant organic matter content

is gas-prone Type III kerogen, and its total TTI

value of 25.7 is less than 75, below the threshold

for gas generation. These results show that the

source rock maturity level of this formation is not

sufficient for any hydrocarbon generation in eco-

nomic amounts.

CAINOZOIC

Eocene

Pal

eoce

ne

Oligocene

30

40

50

60

70

80

90

100

110

120

130

140

- 1000

- 2000

- 4000

- 4270

A B C D E

Miocene Plio.

56.5 50 41 38.6 33.5 26.3 23.3 10.3 0

35.4 23.3 5.256.5

20

- 3000

- 0

BU

RIA

L D

EP

TH

(m

)

BU

RIA

L T

EM

PE

RA

TU

RE

(ºC

)

F

G

H

Tsurface = 14 ºC; Present geothermal gradient = 30 ºC/km

OilWindow

A: HacıhalilB: YoncalıC: BayatD: KocaçayE: ncikF: BayındırG: KızılırmakH: Bozkır

ΣTTI=75

ΣTTI=15

Formations:

I.

Fig. 10. Burial history curves, maximum burial temperatures and the main zone of oil generation of the Upper Paleocene–Miocene formations in

the Bayat area.


Table 2



the Eocene formations in the Bayat area



%Rmax

(A) HacVhalil 140–150 88.9 1.10

(B) YoncalV 130–140 25.7 0.80

(C) Bayat 80–90 1.8 0.39

(D) Kocacay 80–90 1.0 0.34

(E) Incik 70–80 0.4* –

*A TTI=0.4b1, so it cannot be evaluated using logarithmic

transformation.


The Topuzsaray-1 well, the deepest well in the

region, is 3566-m deep and did not penetrate Oligo-

cene–Miocene and younger formations. The Mal-

bogazV, Yozgat, Bayat, Kocacay and Incik

Formations have all been modelled at this location

(Fig. 11 and Table 3). In this modelling, the Paleo-

cene–Lower Eocene Yozgat Formation comprises the

HacVhalil Formation at the base and the YoncalV

Formation at the top. Based on the burial history

diagram, the maximum burial temperature of the

MalbogazV Formation ranges from 90 to 97 8C,and the TTI value is 6.2 which is below the lower

limit of the onset of oil generation. The calculated

vitrinite reflectance value is 0.55 %Rmax, indicating

that the MalbogazV Formation is thermally early

mature. The TTI value of the Yozgat Formation

including the HacVhalil and YoncalV is 3.7 and the

maximum temperatures to which these formations

have been exposed ranges from 64 to 90 8C (Fig.

11). The calculated vitrinite reflectance value is 0.48

%Rmax, which appear to underestimate the degree of

thermal maturation, because measured reflectance

values of the core samples from the depths between

733–1074-m, corresponding to the Bayat and lower

parts of the Kocacay Formation, range from 0.45 to

0.65 %Rr (Illeez and Tekin, 2003). However, it

should be remembered that the main lithologies of

the Bayat and Kocacay Formations are tuff, tuffite,

agglomerate, limestones with Nummulites and marl,

and thus, the reflectance measurements might repre-

sent re-worked vitrinites. Maximum paleotempera-

tures for the Bayat, Kocacay and Incik Formations

range from 64 to 36 8C and the TTI values are equal

or less than 0.2 indicating that these formations are

immature.

In this location, it can be predicted that the upper

part of the Yozgat Formation, the YoncalV sediments,

which have potential hydrocarbon source rock cha-

racteristics, are marginally mature to mature.

5. Conclusions

Although the use of the Time Temperature Index

(TTI) method alone was originally developed to

predict %Rr values of coals (Lopatin, 1971; Waples

et al., 1992a,b), following Waples (1980) Lopatin–

Waples type modelling has commonly been used to

estimate the present level of thermal maturity and

the timing of hydrocarbon generation. The model-

ling in this study used data from previous studies

and two well logs for age, lithological distribution

and thicknesses of the formations. However,

although no effective sources of hydrocarbon have

yet been found in the CankVrV Basin, the Eocene

sediments are of special interest because of their

marine and terrestrial assemblages, relatively low

thermal maturity, and well-defined stratigraphic fea-

tures. Based on their burial history and calculated

present day geothermal gradients, predicted maturi-

ties for uppermost Cretaceous and Eocene forma-

tions in the CankVrV, Bayat areas and Topuzsaray-1

well suggest a general increase in maturity trend

from SE to NW in the CankVrV Basin. The TTI

maturity modelling trend is consistent with mea-

sured vitrinite/huminite reflectance data. Modelling

results indicate that the Lower Eocene YoncalV For-

mation shales, which are the only potential hydro-

carbon source rock in the CankVrV Basin, appear to

have the reached the onset of the oil generation

zone. In the CankVrV and Bayat areas, the calculated

vitrinite reflectance values for this formation range

from 0.59 to 0.79 %Rmax, indicating that this for-

mation is early mature to mature, whereas it is

thermally immature in the Topuzsaray-1 well. This

study also shows that measured mean random humi-

nite/vitrinite reflectance values of the Lutetian

KarabalcVk Formation that overlies the YoncalV For-

mation are between 0.51 and 0.53 %Rrandom oil

(av. 0.52 %Rr oil), indicating low-rank coals (sub-

bituminous A/high volatile C bituminous) according

to the ASTM classification. In the Bayat area, time

of hydrocarbon generation for the YoncalV Forma-

20

30

40

50

60

70

80

90

MESOZOIC CAINOZOIC

Maastrichtian Paleocene Eocene Oligo.65 56.5 35.4

74 70 66 45 40 38 29.30 m

1000

2000

30003090

A B C D E

Tsurface = 13.6 ºC; Present geothermal gradient = 24.75 ºC/km (~25 ºC/km)

BU

RIA

L T

EM

PE

RA

TU

RE

(ºC

)

BU

RIA

L D

EP

TH

(m

)

A: MalbogazıB: YozgatC: BayatD: KocaçayE: ncik

Formations:

˘

I.

Fig. 11. Burial history curves and maximum burial temperatures of the Upper Cretaceous–Upper Eocene formations in Topuzsaray-1 well.


tion can be assigned as; i) the main phase of oil

generation occurs between depths of 3250-m and

Table 3



the Upper Cretaceous–Middle Eocene formations in the Topuz-

saray-1 well



%Rmax

(A) MalbogazV 90–100 6.2 0.55

(B) Yozgat 80–90 3.7 0.48

(C) Bayat 60–70 0.2 0.22

4270-m, and ii) hydrocarbon generation was

initiated in the Lower Pliocene (4.9 My ago) and

continued into the present.

Acknowledgements

The authors are grateful to Y. Oztas (TPAO,

Ankara) and Dr. T.S. Yurtsever (MTA, Ankara) and

N. Varol (Dept. of Geol. Engineering, Hacettepe

University, Ankara) for their valuable contributions.

They wish to thank Dr. R. Gayer, Dr. J. Hower and


an anonymous referee who constructively reviewed

and improved the paper. Y. Bulut (Dept. of Geol.

Engineering, Hacettepe University, Ankara) is

thanked for his assistance.

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Documents

Burial history and thermal maturity assessment of Upper Cretaceous–Lower Tertiary formations in the Çankırı Basin, Turkey