1. INTRODUCTION

The Sava depression represents the most southern part

of the Pannonian basin (Fig. 1). After the Middle

Eocene, a long continental phase started in the area rep-

resented by the present depression, during which tec-

tonic movements occurred and a fault network was cre-

ated along which the basin subsided by extension. The

oldest proven sediments belong to the fresh-water

Ottnangian deposits which are overlain by Carpathian,

Badenian and Sarmatian clastic marine sediments. Pan-

nonian and Pontian sediments were deposited in a

brackish to fresh water environment, while Pliocene

sediments represent fresh water-lacustrine deposits. The

thickness of this clastic complex exceeds 4,000 m in the

deepest parts of the depression. The complex was inter-

preted by FILJAK et al. (1969) as a single sedimentary

Facies and Facies Architecture of the IvaniÊ Grad Formation
(Upper Pannonian) - Sava Depression, NW Croatia

Boris VRBANAC

macro-cycle that can be subdivided in three distinct

parts. The oldest is composed of coarse clastics (brec-

cias, conglomerates and sandstones), overlain by clays,

marls, limestones and biogenic limestones deposited in

fresh-water and marine environments with occasional

intercalations of effusives. This part of the macro-cycle

comprises sediments of Ottnangian, Badenian and Sar-

matian age. The middle part of the complex is com-

posed of marls and sandstones that were deposited in a

brackish to fresh-water environment, and is of Pannon-

ian and Pontian age. These sediments represent several

turbidite cycles. The final part of the macro-cycle con-

stitutes Pliocene and Quaternary sediments of a mixed

lithological composition - sands, gravels, clays and lig-

nite. They were deposited in an alluvial environment,

either within the river bed or in the large swamps

extending along the rivers, following the elongation of

marginal depressions.

The studied sediments of the IvaniÊ Grad Formation

(Fig. 2) form part of this clastic complex. The Forma-

tion contains sandstone bodies in the central parts of the

depression, while the marginal and external parts are

represented exclusively by massive marls. The upper

boundary of the formation in the marginal parts of the

depression occurs at a depth of 300-400 m; in the cen-

tral parts this boundary is below 3,000 m. The total

thickness of this formation in the marginal parts is from

150-250 m, while in the central sections it reaches 800

m (Fig. 3). Part of the sedimentary body composed of

turbidite sediments has an elongated narrow fan mor-

phology extending NW-SE, 100 km long and 25 km

wide. Although the exact relationship between the

lithostratigraphic and chronostratigraphic units was not

determined, the fossil content shows that most of this

formation, if not the whole, is Upper Pannonian in age

(Fig. 4). 

The cored material from the central parts of depres-

sion, that coincide with the deepest parts of the deposi-

tional basin during the Late Pannonian, is, as a rule,

either barren of fossils, or contains fragments of

unidentifiable ostracods. In the cores taken from the

marginal parts of depression (which were the subsur-

face uplifts), the Upper Pannonian sediments are mostly

represented by marls occasionally interbedded with thin

sandstones. These marls were found to contain fossils.

The Upper Pannonian sediments were also investigated

Geologia Croatica 55/1 57 - 77 14 Figs. ZAGREB 2002

Key words: Facies, Facies association, Areal distribu-

tion, Turbidites, Massive marls, Upper Pannonian,

Sava Depression, Croatia.

INA - Naftaplin, Exploration Department, ©ubiÊeva 29, 10000
Zagreb, Croatia.

e-mail: boris.vrbanac@ina.hr

Abstract
Four facies were distinguished within the IvaniÊ Grad Formation of

the Sava Depression: massive marl facies (F1), thick-bedded to mas-

sive sandstone facies (F2), thin-bedded sandstone facies (F3) and thin-

bedded sandstone, siltite and marl facies (F4). Interpretation of the

depositional mechanisms confirmed the presence of two basic sedi-

mentary processes. Hemipelagic deposits are represented by fine-

grained detritus. The lithification of these produced a massive marl

(facies - F1). Sand detritus was transported into the depression by tur-

bidite currents (facies - F2- F4), and formed a narrow elongated sedi-

mentary body.

By comparing the facies defined on the basis of core samples, the

spontaneous-potential curve (SP) and the resistivity curve (Ra) of

identical intervals, four facies associations were defined on well log

diagrams: channel filling (FA), depositional lobe (FB), lateral and dis-

tal turbidites (FC) and massive marls (FD).



58 Geologia Croatica 55/1

at outcrop, on Mt. Medvednica, Mt. MoslavaËka gora

and elsewhere. The presence of macrofossils was also

determined. However, no publication describing this

Upper Pannonian fossil fauna, from either outcrops or

cores, explains the possible environment habitat of the

fauna. It is usually only stated that deposition took

place in a protected low-energy environment.

Over almost the entire area of the Sava depression,

the IvaniÊ Grad Formation overlies the Lower Pannon-

ian sediments of the Prkos Formation. Only in a narrow

strip of Dinaridic strike, located in the SW part of

depression, does the IvaniÊ Grad Formation directly

overlie the Badenian sediments. The lithological com-

position of the Prkos formation is mainly of shallow-

water thin or thick-layered marls, calcareous marls and

marly limestones. Sandstones are only rarely found in

the form of millimetre-thick layers or laminae. The

Lower/Upper Pannonian contact has not been precisely

defined, but it can be concluded that it roughly corre-

sponds with the contact between the lithostratigraphic

units. The Prkos formation is relatively easily identified

on the well logs, but its age is rarely palaeontologically

documented, due to the very scarce fossil content of the

cores. Nevertheless, the cored material of the Prkos

Formation contains a Lower Pannonian fauna without

exception, while the cores taken from the overlying

IvaniÊ Grad Formation mostly contain an Upper Pan-

nonian fauna, if any. Similarly, the sediments of the

Kloπtar IvaniÊ Formation, overlying the IvaniÊ Grad

Formation over the entire exploration area, exclusively

contain a Lower Pontian fauna. The Kloπtar IvaniÊ For-

mation bears lithological and depositional similarities

with the IvaniÊ Grad Formation which means that such

lithostratigraphic subdivision was conditioned by the

practical, petroleum-geological reasons.

Two basic concepts have been postulated to explain

the depositional environment of these sediments.

According to PLETIKAPI∆ (1965) the water depth was

shallow, and the cyclic character of the sediments was

due to frequent moving of the shore line and a high

energy area. Only in limited area and the constant sub-

sidence of blocks along active tectonic lines, could the

water depth have increased significantly in very narrow

channels where turbidite currents could have devel-

oped. According to MILJU© & VUGRINEC (1977) the

IvaniÊ Grad Formation was deposited during a regres-

sive phase. In zones of shallow water coasts pelites

were mostly deposited, while sandstones were deposit-

ed in the places of higher energy such as channels.

LU»I∆ (1994) interpreted the facies as coastal sedi-

ments, bar and beach sediments, interbar shoals, lagoon

sediments and tidal channel sediments of coastal plains.

The results of palynological analyses are contained in

an unpublished work (LU»I∆ & KRIZMANI∆, 19931).

The established palyno flora is composed of environ-

mentally different phytoplankton fossils. The genus

S p i n i f e r i t e s is very common and is characteristic of

shallow environments. Alternatively, Impaginidium and

G o n y a u l a x are phytoplankton that lived in deep water.

Despite the possibility that such an association can be

interpreted in terms of the deep water environment

wherein the shallow water organisms were transported

by resedimentation, the authors express the opinion

(after SÜTÖ-SZENTAI, 1982) that this was the case of

a shallow environment with occasional transport of the

deep water organisms by the sea currents, which means

that they were mixed with other fossils in the littoral

zone. There are significant differences in the age deter-

mination between the palynological analyses of the core

material from the three major oil fields - IvaniÊ, Æutica

and Okoli. These results remained unpublished in pro-

fessional studies within the Department of the Central

Laboratory. The samples from the IvaniÊ Grad Forma-

tion were found to pertain the Lower and Upper Pon-

tian, and Upper Pannonian. It has to be noted that not a

single sample with palynological findings has also been

documented by macrofossils. DALI∆ (1996) singled

out five different lithofacies - offshore homogeneous

marl deposits; well sorted marl intercalated with silt-

stones and marl deposited as progradational shoreface

and/or as barrier bar; marl with coal laminae and

lithoarenite layers deposited on tidal flat in estuaries;

marl intercalated with siltstone and fine grained sand-

stones were interpreted as shallow shelf deposits with

lagoonal characteristics; well sorted lithoarenites as a

subtidal barrier bar.

©IMON (1980) believed, on the basis of the geome-

try and lithological properties, that these sediments

belong to “the family of redeposited coarse clastics”.

He applied the concept of “submarine-sublacustrine

fan” to explain deposition. In defining the depositional

environment of the Okoli sandstones (the youngest

Fig. 1  Location map of the Sava depression.

1 LU»I∆, D. & KRIZMANI∆, K. (1993): Zavrπno izvjeπÊe, buπotina
Okoli-57, Biostratigrafska, litofacijesna i sedimentoloπka inter-
pretacija.- Unpubl. report, INA-Naftaplin Archive, Zagreb.



member of the IvaniÊ Grad Formation), in part of the

Æutica oil field, VRBANAC (1989, 1990) believed that

they belonged to the channelised part of a submarine

fan (to its middle proximal part). The detritus was car-

ried by gravitational flows which could be compared to

turbidity flows. In his later work VRBANAC (1996)

reconstructed a palaeogeographic view of the Sava

depression during the Upper Pannonian, and concluded

that it was a marked sub-sea (sub-lake) palaeorelief, the

major feature of which was a central tectonic graben

surrounded by submarine highs - the Medvednica horst

in the NE, MoslavaËka Gora horst in the north, Martins-

ka Ves horst in the south, and the Psunj-Prosara ridge in

the east (Fig. 2). The bottom of this graben was irregu-

lar and mildly inclined in a SE-E direction, with some

occasional steepening. He also concluded that this was

a calm, low-energy environment, with a sedimentary

basin large and deep enough to ensure a stable deposi-

tional environment, to compensate for the variations of

the factors that respectively influence depositional

mechanisms in a tectonically active basin.The source

area of the clastic material was N-NW from the area

named the “Alps mineral association”, and it can be

concluded that there was lengthy transport of the proba-

bly extensively resedimented material (©∆AVNI»AR,

1979).

Although they did not directly study the areas of the

Drava and Sava depressions, Hungarian authors also

think that during the Pannonian (Pannonian s.s.) a deep

water system existed with early turbidites, and later

59Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

Fig. 2  Location map of the explored area.



60 Geologia Croatica 55/1

delta slope sediments (MATTICK et al., 1985, 1988;

SZENTGYÖRGYI & JUHÁSZ, 1988; CLAYTON &

KONCZ, 1994; HÁMOR & BÉRCZI, 1999).

2. SEDIMENTOLOGICAL ANALYSES OF
CORE SAMPLES

Detailed sedimentological analysis, layer-by-layer, was

carried out on the cores from 29 wells distributed

throughout the Sava depression. The 61 cored intervals

were analysed with a total length of 569 m that covers

almost the entire interval of the studied formation. The

cores are mostly in isolated intervals that are not more

than 6 m length. Only 6 wells were found to have con-

tinuous coring ranging from 27-82.1 m in length. Since

most of the cores were taken 20 or more years ago, lots

of the core material was either missing or was found

fragmented in irregular small pieces that were unsuit-

able for sedimentological analysis.

2.1. Petrography

Sandstone, siltite and marl alternate with each other.

Data on the petrographic, mineralogical and physical

properties of the sediments are provided by experts

from INA-Naftaplin’s Central Laboratory.

Sandstones are present only in the central part of the

depression, pinching out towards the edges. They are

grey (mostly light grey) in colour, only those saturated

with oil are brown. Sandstone bedding is well ex-

pressed in parts where they are interbedded with marl;

bed thickness may reach several metres. They belong to

a group of very fine to fine-grained sands with average

grain size of 0.08-0.2 mm, rarely medium grained

(≤0.5mm). Roundness varies between 0.2-0.3, belong-

ing to the group of subangular grains. Sphericity grade

values are balanced and vary between 0.68-0.74, mak-

ing them highly spherical particles.

Sandstone porosity is 10-33%, with significant dif-

ferences in these values regarding the regional spatial

Fig. 3  Isopach map of the IvaniÊ Grad Formation.



61Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

distribution of sandstones in relation to the source area

of the detrital material and different facies. Parallel pre-

sentation data of porosity on several oil fields (BOKOR

et al., 1979) show a distinct decrease of these values

from northwest to southeast. Great differences in poros-

ity and permeability values are also statistically proven

in IvaniÊ Grad sandstones which belong to different

facies. Maximum values are determined in the distribu-

tory channel sandstones, while sandstones of levees and

lobes have considerably lower values (–UREKOVI∆,

1995).

The petrographic uniformity of the Upper Pannon-

ian sandstones has long been noted (©∆AVNI»AR,

1979). Quartz is the main component, together with

rock fragments, micas and feldspars. Quartz does not

exceed 60% of the detritus. Among rock fragments (18-

35% of composition), the most dominant are limestone

and dolomite, while grains of cherts, quartzite, clay

shale, chloritic and sericite shales, quartz-muscovitic

shale and gneiss, with rare fragments of granite and tuff

are also present. The clay mineral content is very low

(<5%, mostly 1-2%). Cement is formed by a mixture of

prevailing calcite and detritic silt-clayey matrix. The

detrital matrix contains illite, kaolinite, quartz, chlorite,

plagioclase and mica. Sandstone cementation is not

always complete, so many sandstone beds are poorly

cemented and friable. According to their composition,

they are litharenites, respectively calclithoarenites since

in rock cuttings carbonate sediments are dominant2.

Relatively large quantities of unstable grains indicate

the low maturity of sandstones (©∆AVNI»AR, 1979).

The best indicator of the petrographic uniformity of

this formation is the identical composition of accessory

heavy minerals, with the dominance of chlorite and gar-

net and to a lesser extent biotite, staurolite, disthene,

epidote, zoisite, apatite, tourmaline, zircon and rutile.

Such an association of heavy minerals indicates that the

source areas of the detritic material were probably the

Alps with metamorphic rocks of epi and mezzo zones,

as well as with limestones and cherts (©∆AVNI»AR,

1979).

A great number of sandstone beds contain dark grey

marl clasts. Clasts are mostly of an irregular and suban-

gular shape. Their dimensions vary considerably; more

often to 1-2 cm, very rare to 10 cm. They are found

either dispersed, scattared in great numbers, or massive-

ly. They can be scattered irregularly but mostly appear

so that their longer axis is parallel or subparallel to the

bedding plane. They are mostly found in the lower parts

of sandstone beds, although they can also be present in

the central and upper parts.

The mineralogical composition of siltites is identical

to that of the sandstones except for a higher mica con-

tent. Flat and/or cross-lamination is almost always pre-

sent, and visible due to presence of organic matter or

mica. Burrows of ichnofossils are frequently noticed, as

well as tiny marl clasts. Siltite porosity is mostly below

5%; permeability is also very poor, less then 10 µm-

2x10-3. 

Marls are grey brown, brown, dark grey and often

almost black in colour. They are mostly hard, fissile

and show parallel bedding planes where numerous car-

bonised plant remnants are frequently obseved. These

remnants are mostly particle-sized but can be larger

than 10 cm. Bioturbation is sporadically strongly

Fig. 4  Correlation table of the chronostrati-
graphic and lithostratigraphic units and
position of the EK markers.



62 Geologia Croatica 55/1

expressed. Ichnofossils look like winding tubes filled

with sand or marl material. Petrographic analyses show

that the marls consist of a clay-carbonate and cryp-

tocrystal base with more or less fine grained quartz and

mica of silt or sand dimensions. The CaCO3 content is

about 60%. 

2.2. Facies

According to the sedimentological properties of the

cored deposits (lithology, bedding, texture, relation

between lithological members) four facies were identi-

fied: massive marl facies (F1), thick bedded to massive

sandstone facies (F2), thin bedded sandstone facies (F3),

and laminated sandstone, siltite and marl facies (F4)

2.2.1. Massive marl facies (F1)

This facies consists of homogenous and massive, most-

ly unbedded marls, dark grey to almost black in colour

(Fig. 5a). Sporadically preserved signs of bedding and

lamination are mainly expressed by a colour change,

and occasionally by thin siltite or sandstone laminae or

beds. The massive homogenous appearance is sporadi-

cally disturbed by burrows, but those traces of organism

activities did not disturb rare primary internal structure

and textural properties. 

Massive marls are the “normal” basin deposit, as

hemipelagic muds which covered the basin floor relief

under stable conditions. The uniform petrographic

structure of detritical material indicates material trans-

ported by turbidity currents, but the transport mecha-

nism and mode of deposition is different. Thickness of

massive marls in the marginal, morphologically higher

parts of the depression, reaches 150-250 m, and up to

250 m in the central lower parts. Thin siltite and sand-

stone intercalations and laminae in the massive marl are

of turbidite origin, reflecting the enlargement of turbidi-

ty flow area in the direction of movement as well as in

their lateral spreading.

2.2.2. Thick bedded to massive sandstone facies (F2)

This facies is represented by thick-bedded to massive

homogenous sandstones with a few siltite and marl

intercalations which can be compared to massive sand-

stone facies (WALKER, 1978). The thickness of indi-

vidual sandstone beds from the cored intervals is from

0.5-6 m (Fig. 5b). Amalgamation is frequently present.

It is expressed by sharp changes in colour nuance with-

in homogenous sandstone beds, or by sharp changes in

grain size of sandstones. Frequently, several metre long

intervals of sandstone cores were broken into pieces

only a few cm long or even smaller, making sedimento-

logical analysis impossible. It is debatable whether

these significant thicknesses of sandstone beds could be

the consequence of amalgamation which, due to the

identical content and physical properties of sand detri-

tus, and broken of cores, can not always be determined.

This facies appears exclusively within distributory

channels where the energy of turbidity flows was the

highest and where the effects of erosion on the base by

mud flows were most strongly expressed.

Lower bedding planes are sharp and with more or

less expressed traces of erosion. Sandstones of this

facies can be of different structure. A lot of beds are

massive and homogenous. Normal gradation can be

noticed only in a few beds, in their upper part, while it

is less frequent in their lowest part or within the bed.

Even though there is usually no gradual transition

between a sandstone bed and overlying marl, some

sandstones gradually grade into siltite and marl. In such

beds horizontal and lateral siltite lamination can be

noticed, as well as convolution. The thickness of these

seal marls does not exceed several centimetres. Less

commonly there are cases of inverse gradation. Lami-

nation is very seldom present. Frequently, horizontal or

wavy lamination within sandstones which are abruptly

cut off on the upper side by a massive sandstone with

no texture, points to amalgamation, during which the

upper laminated part was carried away, probably

together with the capping marl. 

Deformed bedding and lamination, and convolute

bedding or lamination is common. This is the result of

hydroplastic deformation of unconsolidated deposits

over which strong water flows passed during sedimen-

tation (SANDERS, 1965), as well as in the post-sedi-

mentation phase as the result of the sudden displace-

ment of pore water (LOWE, 1975). In this way dish

structures and sand dikes are formed. Frequently, flame

structures occur on the lower surface of sandstone lay-

ers, and it could be established for some clasts that they

were formed by the breaking of thin marl beds due to

the sudden displacement of pore water, and their “intru-

sion” into overlying sandstone or even siltite beds.

Some deformations are probably the result of sliding of

poorly compacted material down the slope. Due to

expressed lamination, sinsedimentary faults of small

dimensions are often noticed, both normal and reverse.

On lower bedding surface visible traces were left by

erosion of the flow itself and/or traces of erosion by

objects moving over the bottom: clasts, plant parts etc.

Marl clasts of different dimensions and different round-

ness grades and carbonised plant remnants are quite

common. While carbonised plant remnants of different

dimensions originate from continental regions, marl

clasts were formed by the erosion of poorly consolidat-

ed sediments of the channel flanks and bottom, started

by turbidity flows. 

The estimated proportion of marl and siltite in this

facies does not exceed 10%.

The internal bed constitution and textural properties

are mostly the result of the final stage of transport and

2 Physical and petrographic data - Department of Central laboratory
INA-Naftaplin.



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64 Geologia Croatica 55/1

deposition (POSTMA, 1986), and are of special impor-

tance for the interpretation of environment and deposi-

tion conditions. Thick sandstone beds which are mas-

sive in their major part, and show a decrease in grain

size (gradation) in their top part, grading into thin, hori-

zontally laminated, and cross-laminated sandstone or

siltite covered by thin marl, could be compared to

Bouma sequence of Ta-e type (BOUMA, 1962). The

high quantity of sand (thick beds) indicates the

extremely high energy and capacity of these flows. The

presence of marl clasts in different parts of the bed and

the erosional base of the bed also suggests turbulent

flow. According to the above characteristics, they can

be compared with turbidites deposited from mud flows

of high concentration, where the detritus population I

and II (LOWE, 1982) was supported by upward turbu-

lence (MIDDLETON, 1970; LOWE, 1979, 1982). In

the flow base where slipping was the most intensive, it

was probably supported by dispersive pressure (MIDL-

LETON, 1967; LOWE, 1976, 1982). Namely, sedi-

ments deposited from liquid flows have flat bases due

to their laminar character and high density of flows

(LOWE, 1982), so these type of flows are not taken

into account. Sedimentation occurred by direct, rapid

and massive suspension sedimentation (WALKER,

1978), until the bedding plane did not reach the top of

the turbidite current cloud. The energy of such flows

was 5 Wm-2 (ALLEN, 1984). Deposits formed by direct

suspension sedimentation belong to poorly packed sedi -

ments (KOLBUSZEWSKI, 1950). These deposits are

poorly cohesive and strongly subject to liquefaction and

forming of secondary water escape pipes (LOWE &

LoPICCOLO, 1974; LOWE, 1975). It is considered

(LOWE, 1982) that at this development stage of mud

flows, a suspension mass of high density can almost

momentarily form an Ta interval Bouma sequence sev-

eral metres thick without any traction sedimentation

textures.

2.2.3. Thin-bedded sandstone facies (F3)

This facies is represented by sandstone beds several

centimeters to 0.5m thick (Fig. 5c). The proportion of

marl and siltite in this facies is 30-40%. Regarding

internal structure and gradation, the interval with hori-

zontal and lateral sandstone and siltite lamination, and

horizontal lamination in fine grained material is the

most frequent. Bouma sequences of type Ta-e, Tb-e and

Tc-e are all common. Some of these beds are parallel

laminated throughout their entire thickness, while in

their upper part they pass relatively suddenly into siltite

and marl. This facies can be found as the final beds in

the sediment sequence deposited in distribution chan-

nels, but are more characteristic as marginal channel

sediments.

The basal boundary is sharp, and very often strong

or weak erosion traces can be noticed on the upper bed-

ding plane of the underlying marl. Amalgamation was

not noticed or at least is not characteristic for sand-

stones of this facies. Convolution is very often present

in all parts of the bed, as well as dish structures. Small

marl clasts (<5 cm) are quite frequent, and are also

found in all parts of the sandstone bed. The thickness of

marl which appears among the sandstones varies from

several to tens centimetres. Marl bioturbation is well

expressed, especially in thicker intercalations.

The marl/siltite ratio is significantly higher in this

facies, and the estimated value is 30-40%.

This facies consists of repeated sandstone and marl

beds. Sharp lower bedding planes of the overlying

sandstone and the gradual upward passage into marl,

confirm spasmodic turbidite currents which, compared

with flows of the previous facies, are more diluted. On

the basis of their internal textures and their constant

succession, or similarity of these beds to a Bouma

sequence, they can be interpreted as turbidites, with a

lower proximity index than the previous facies, due to a

significantly lower proportion of the Ta interval.

2.2.4. Thin bedded sandstone, siltite and marl facies

(F4)

Facies four consists of very thin, thin -medium thick

sandstone beds in monotonous alternation, passing

upwards into siltite and marl, or there are thin siltite

intercalations that grade upward into marl (Fig. 5d)

They are mostly several centimetre thick beds that start

with a sharp bedding plane. On the upper bedding plane

of the marl, traces of weak erosion of the subsequently

developed mud flow are sometimes visible. Internal

textures are represented by horizontal and cross lamina-

tion, convolution, and structures developed by water

displacement - sand dykes. There is a rare occurrence

of uplifted beds, and deformed beds. Ta-e and Tb-e

type sequences occur being less numerous than Tc-e

and Td-e sequences. Beds of this facies are characteris-

tic for the marginal parts of the channel or prominent

parts of the bottom relief where the energy and influ-

ence of turbidity currents in the depositional processes

were distinctly weaker.

Marl clasts of 2 cm size are also present, as well as

carbonised plant remnants. In smaller sediment frac-

tions ichnofossils occur regularly, and are sporadically

visible in the coarser fractions. The traces of digging,

drilling and moving of organisms in the sediment are

occasionally so abundant that they disturb primary tex-

tures.

The proportion of marl and siltite in this facies is

estimated as between 50-60%.

Thin beds of well laminated fine-grained sandstone

and siltite in alternation with marl, frequently organised

in Bouma sequence Tc-e, suggest that at least a part of

these beds were formed by deposition from turbidity

currents of low concentration. In this regard, this facies

corresponds to thin bedded low energy levee deposits

(MUTTI & RICCI-LUCCI, 1975; WALKER, 1978) or

distal turbidite deposits. 



65Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

3. ORIGIN OF DETRITAL MATERIAL

The deposits are interpreted as sediments of moderate

water depth. Detrital material was brought into the

basin by turbidity flows or as normal basin deposit. The

constant sandstone type, uniform detrital content, con-

sistent structural characteristics and composition of

heavy minerals suggest Alpine metamorphics as the

source rocks. However, a significant part of the carbon-

ate detritus in the content of sandstone, as well as the

carbonate-clay content of siltite and marl and plant

remnants in marls, indicate more local sources of detri-

tal material. It can be assumed that the detrital material

has been reworked several times, the basis of which is

formed from an association of metamorphic minerals

and fragments of metamorphites of Alpine origin,

enriched with carbonate and clay material from local

sources.

The concept of the depositional environment of the

study area suggests that the present Sava depression

was part of the southern marginal part of the Pannonian

basin (lake) which extended southwards probably sig-

nificantly further from the presently determined bound-

aries. Prior to deposition in the Sava depression, the

detrital material was, after other probable multiple

episodes of deposition, deposited into the area of todays

Mura depresion, which represented a slope area - area

of material accumulation, from where it was occasion-

ally carried into the Sava depression. Coarse material

was brought by turbidity flows while pelitic material

was continuously brought and deposited by aggradation

in the basin regardless of its morphology. Since turbidi-

ty flows moved through the deepest parts of the basin, a

substantial mass of sand detritus was deposited in the

deepest parts of the basin.

4. FACIES ASSOCIATION ACCORDING TO SP
AND RA CURVES

SP and Gamma-ray curves reflect the change in grain

size in clastic sediments. This is why they are used for

the identification of lithologic structure/composition

and boundaries between formations, as well as for the

identification of depositional environments (e.g. GAL-

LOWAY, 1968, 1998; FISHER, 1969; PIRSON, 1970;

SELLEY, 1976, 1985).

The SP curve is the basic curve which defines facies

associations of the studied layers containing sandstones

(turbidite facies associations), while Ra curve deter-

mines the massive marl facies association. The SP

curve has values that are a function of the grain size of

sand detritus, and the relationship can be established

between the funnel or bell shape of these curves and the

tendency to coarsen or fine upward. With regard to the

sedimentological analyses which showed the structural

complexity of sedimentary bodies built of thin interca-

lations of sandstone and marl, it can be determined that

the thickness ratio in sandstone and marl intercalations

in alternation have a crucial influence on the final shape

of SP curve. A comparison of the SP curve and a litho-

logic column of the same interval in Gl-31 well (Fig.

6), shows that SP values depend on the relationship

between thicknesses of sandstone and marl intercala-

Fig. 6  Comparison between
lithologic column and corre-
sponding interval on the SP
curve.



66 Geologia Croatica 55/1

tions. Granulometric analyses performed on sandstone

intercalations indicate approximately identical values of

average grain diameter (Md). A tendency of upward

coarsening of sandstone beds on the SP curve is

expressed by a funnel curve shape. This symmetry/reg-

ularity was established in numerous examples of

upward coarsening of sandstone beds. A tendency of

upward fining of sandstone beds, noticed in cores,

results in a bell shape SP curve.

Taking into consideration the facies that were deter-

mined by sedimentological analyses (F1-F4), and the

defined depositional environment (©IMON, 1980;

VRBANAC, 1989, 1996), as well as the SP and Ra

curve shapes, four associations of facies were singled

out: channel filling facies association (FA), depositional

lobe facies association (FB), lateral or distal turbidites

facies association (FC), and massive marls facies associ-

ation (FD). Facies associations were recognized and

defined on well log diagrams (SP and Ra curves), which

enabled the reconstruction of their structure in space,

and mutual relationship. Since that relationship can be

best observed in oil fields - owing to a great number of

wells on a relatively small area, the Æutica oil field was

selected, where relationships of facies associations were

shown in detail, as an illustration of relationships in the

depression.

4.1. Channel filling facies association (F A)

This facies association consists of thick-bedded sand-

stone facies (F2) and thin-bedded sandstone facies (F3) .

The channel axis is characterised by thick sandstone

beds with sporadic marl intercalations. Sandstone beds

become thinner towards the channel edges, while marl

intercalations become thicker. It is important to empha-

sise that the expression “channel” does not imply the

type of channel which is forming within a classic fan

that occurred in the continental slope towards the open

sea. 

The depositional sequence of channel sediments is

represented on the SP curve by a bell shaped or cylin-

drical curve (PIRSON, 1970; SYED, 1979; GAL-

LOWAY, 1998). The thickness of some depositional

sequences is 10-20 m; most frequently, several

sequences are joined into one sandstone body (Fig. 7).

A depositional sequence is formed of sandstone beds

which are characterised by a certain shape on the SP

curve - bell, funnel or cylindrical shape. These shapes

reflect the tendency of the changing thickness of sand-

stone and marl beds in alternation. One depositional

sequence can be formed by one sandstone bed or there

can be several depositional sequences separated by

rather thick marl intercalations. Trends of particular

sequences may or may not correspond.

Bed erosion is strongest in the middle parts of the

channel, and weaker in the marginal parts, so that the

absence of marl intercalations, and numerous amalga-

mations undoubtedly suggest the position of the chan-

nel axis, or direction of the main flow of the turbidity

current in some phases of detrital deposition. So, chan-

nels were both depositional (HAMILTON, 1967) and

erosional (LAUGHTON, 1968). The main mass of tur-

bidity current passed through these channels. As turbid-

ity current energy weakened, particles carried in sus-

pension were deposited. Therefore, the thickest sand-

stone beds are related to the channels whose position, in

the deepest parts of the basin, depended on basin mor-

phology which was controlled by synsedimentary tec-

tonics.

The channel width for the member of Iva sandstones

on the Æutica oil field is about 250 m, possibly up to

1000 m. Some channels have a constant width; others

split into two arms or two channels merge into one. The

channel was probably not very deep, except where the

association of facies FA is laterally equivalent to the

association of facies FC or even FD, it probably con-

cerned a deeper channel of steep flanks which had a

narrow or non depositional area for facies associations

FB or even FC. Turbidity currents ran mostly through the

channel itself. Outside the channel only the marginal

parts of the turbidite cloud carried detritus depositing

associations of facies FB and FC.

On the SP curve diagram of the Iva-15 well (Fig. 7),

the channel filling facies association FA is expressed as

a succession of depositional sequences with a tendency

of upward fining of sandstone beds, composed of F2

and F3 facies sandstones. They were amalgamated by

stronger or weaker erosion into some 80 m thick sand-

stone bodies. On the SP curve, the association of chan-

nel sandstone facies is shown as a funnel shape, as the

result of the abrupt formation of a channel and deposi-

tion of thick sandstone beds. In the final phase, upward

fining sandstones and marls were deposited, depending

on the migration speed of the channel. If the migration

was abrupt, SP curve is of cylindric shape.

Although there was no statistical research of the

relationship between sandstone and marl within this

facies association, sandstone probably forms 90% of

the total.

4.2. Depositional lobe facies association (F B)

This association is composed of F3 facies in the lower

part and facies F2 in its upper part. They were deposited

outside and parallel to the distributary channels where

the power of turbidite currents is significantly weaker

so that erosional occurences, if any, are less expressed

than within the channel. As a consequence, amalgama-

tion is very rare. The total thickness of sandstone bod-

ies that belong to this facies association can exceed 30

m. Sandstone beds of this association show a tendency

to coarsen upward, while marl intercalations are usually

ten centimetres thick and more.

On the SP curve diagram of the Iva-15 well (Fig. 7),

the FB association of facies is expressed as a deposition-

al sequence of upward coarsening sandstone beds, and



67Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

by a funnel shaped curve. The depositional environ-

ment of this association of facies is parallel to channel

extension, it directly continues on channels and extends

for several to tens of kilometres in length and several

hundred metres to 1-2 km in width. In its narrowest part

this zone is less than several tens of meters wide. This

facies association is characteristic for a near channel

zone, or marginal parts of the channel, since turbidite

currents of great capacity did not move only through

channels but also in a wider channel zone. In this way,

from time to time, thick sandstone beds were deposited

outside the channel.

The estimated proportion of sandstone is 70 to 80%.

4.3. Lateral or distal turbidite facies
association (F C)

This association consists of a monotonous alternation of

very thin, thin and medium thick sandstone beds

(according to CAMPBELL, 1967) passing into siltites

and marls. They are represented by facies F3 and F2. On

upper bedding surfaces there is practically no erosion or

only very weak traces can be noticed. Alternation of

thin marl and sandstone intercalations cannot be regis-

tered by the logging tools, making the derived SP curve

a result of the relationships between final lithological

members (Fig. 7). This association of facies is charac-

Fig. 7  Vertical succes-
sion of the facies
associations.



68 Geologia Croatica 55/1

teristic for the areas of distal and lateral termination

extend of the turbidite currents, as well as the morpho-

logically higher interchannel areas. In a lateral direction

further from the channel, namely from the area of depo-

sition of channel sandstones, the share of sandstone

decreases with increasing share of siltite and marl. This

decrease of turbidite bed thickness continues until they

pinch out. The total bed thickness of this facies associa-

tion may be several tens of metres. In the north west

and central part of the depression, areas of turbidite

occurrences have a narrow elongated shape several

hundred metres wide, roughly following the channel

direction. They were formed by deposition of sandstone

and fine grained detritus in the lateral, transitional parts

of the basin, between the main current area and mor-

phologically higher zones. Therefore, deposition took

place in the area where the turbidite current travelled,

but were affected only by the upper part of the turbidite

cloud which is, in this part, thin and of low energy, and

capable of carrying only small quantities of sand. Distal

turbidites correspond to classic turbidites being deposit-

ed at the end of the basin plain, namely in the area of

termination of the turbidite current (WALKER, 1978).

The estimated sandstone ratio in the deposits of this

facies association is between 30 and 50%.

4.4. Massive marls facies association (F D)

This association is mostly represented by massive marl

facies F1 with rare intercalations of thin siltite or sand-

stone laminae or beds (Fig. 7). The depositional envi-

ronment of this facies association is the whole area of

the Sava depression; only in its central parts is this

association “masked” by turbidite associations. In the

lateral, morphologically higher parts of the basin, sedi-

ments of this association were exclusively deposited,

while in the central, morphologically deepest parts of

the basin, they only form a part of the depositional

sequence.

5. FACIES ASSOCIATIONS ARCHITECTURE

Depositional architecture in a basin reflects the interac-

tion of processes of sediment supply, relative subsi-

dence or uplifting and eustatic changes of sea level

(GALLOWAY, 1998). In addition, an important role in

depositional evolution are local factors: water depth in

the basin, palaeorelief, palaeoclimate, transport and

depositional mechanisms, quantity of transported detri-

tus and current velocity, local synsedimentary move-

ments, etc. The influence of each factor can significant-

ly vary in different parts of the basin, which additional-

ly makes the determination of relationships between

lithological members and facies in the basin more diffi-

cult. 

5.1. Lateral changes of facies associations

Determination of facies associations on well logs, more

particulary on SP and Ra curves, is especially reliable in

oil fields with many wells in a relatively small area. By

following lateral relationships on the favourably posi-

tioned profiles, perpendicular to the strike of distribu-

tary channels, the facies association of channel filling is

most frequently well noticed, as is their lateral transi-

tion into the depositional lobe facies association and

facies association of lateral turbidites, while beyond the

direction of turbidite currents the massive marls facies

association was deposited. Lateral spreading of the

channel filling facies association depends on the width

of the basin bottom and slope of the channel. There are

examples in the Æutica oil field where the facies associ-

ation of a several tens metres thick channel filling is lat-

erally continuous into a narrow zone of thin (∼10 m)

lateral turbidites facies association. This zone is fol-

lowed by the massive marl facies association (2-5 m

thick, Fig. 8). The association of massive marl facies

appears in all parts of the depression that were outside

the turbidite current direction, or in parts of the depres-

sion that are so far above the channel bottom that tur-

bidite currents could not or seldom reached them. The

morphologically higher parts of the bottom were also

found in the central part of the depression, so that the

facies association of massive marl was often surround-

ed by the association of facies containing sandstones

(Figs. 10 and 12). In observing the lateral succession of

facies associations, a general rule for their distribution

is noticed. Parallel with the spreading of channels in

which the channel filling facies association was

deposited, the lobe facies association most frequently

appears, followed by the association of lateral turbidite

facies which pass laterally into the association of mas-

sive marl facies (Fig. 8). This distribution of the facies

associations follows a general rule of the distribution of

facies in a fan (WALKER, 1978). Central deposition

occurs in the channels where thick-bedded to massive

sandstones were deposited. In near channel zones, thin

and thick bedded sandstones were deposited, while in a

more distal turbidite current direction, and lateral to the

channel axis, thin bedded turbidite sandstones and mas-

sive marls were deposited (Fig. 9).

Detailed distributional relationships between the

facies associations is shown in the example of a sand-

stone body member of the Iva sandstones of the Æutica

oil field. In this field a member contains ten sandstone

bodies. The lowest is γ8, followed by γ7, γ6, γ5, γ4, γ3, γ2,

γx, γ1 and γ0. Maps are given for γ4, γ3, γ2 and γ1. On the

maps, for each sandstone body, distributional channel

areas were marked where the deposited channel filling

facies associations (FA), other facies associations (FB-

FC), and the massive marl facies association (Figs. 10-

13) were deposited. On the maps, the form of the chan-

nel system, changes of channel position in space, and

changes in the shape and size of deposition surfaces of

sandstone detritus are easily observed. Within distribu-



69Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

Fig. 8  Correlation profile over the SW section of Æutica oil field.

, 
i --- 1S:llh:OJ.9mtWS 1'10JlO _ ........ , ---
i 

fI'.I 

~ 
"iii a "0 

Q ti ; 
~ "8 
"" ~ ra -,... 
u ~ 

1 d'3 rn 
U I1Il 

~ -e , ~ 
~ ~ ~ JLi 

~~ 
---+----~. ~~----,_--~!--~~~-r--­

! 
! 

0 



70 Geologia Croatica 55/1

Fig. 9  Facies associations distribution - upper part of Iva sandstone.

tary channels there are clearly marked areas where, due

to the erosional action of turbidite currents, a direct

contact between two or more sandstone bodies

occurred. The existence of three hydrodynamic units

which were determined during oil and gas exploitation

explain the erosional action of turbidity currents. The

sandstone bodies γ8, γ7 and γ6 form one hydrodynamic

unit, γ5, γ4, γ3 and γ2 form the second, and γx, γ1 and γ0

form the third, and it is obvious that the erosional action

of turbidite currents, which brought certain sandstone

bodies into direct contact, directly influenced the estab-

lishment of the hydrodynamic relationships.

5.2. Vertical succession of facies association

Most interpretations of depositional sequences are

based on facies sequence, namely on observation of

facies of the progradational and retrogradational move-

ments of lobes and channel filling (MUTTI &

GHIBAUDO, 1972). Let us consider the vertical rela-



71Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

tionships of the facies associations of the whole IvaniÊ

Grad Formation. The example of the Iva-15 well (Fig.

7) clearly illustrates the vertical succession of the facies

associations of the Iva-sandstone member that appear

over the whole area of the depression. The sequence

begins with the massive marls facies association as

basinal hemipelagics, followed by the facies association

of lateral (distal) turbidites represented by a serrated SP

curve. It is further followed by the depositional lobe

facies association (prograding lobe), which is obvious

Fig. 10  Distribution map of γ4 sandstone body (Iva sandstone) in Æutica oil field.

~ 

• 

~ 

• 
~, 

• 

DISTRIBtmON MAP OF "(. SANDSTONE OODY 
IN tl,rncA OIL FIELD 

.... -1;" 1,,-73 ... ,1 

pin<ll 0"' liM of sanditont 

_ fA • <b."".1 filii".: {xi .. OW>ciatioll 

_ FB · Ikpooilionallob< f.d", U>Ociariou 

_ Fe· IaIem IO>d di.lal _diI< ~,_ '_"'0' I 
I'D • __ i"" tnar1 fo<;os __ 

_ act""", or <"""'01 
J)"I<mJ (<If1 - y.'1"~) 

~" • 

1 ... )' i'»-'o' 
• • 

~. ~ 

• 

, 
.. ,. "'"'" 

z..111 
• • 

1.0-.. , 

• 



72 Geologia Croatica 55/1

by the tendency of upward thickening sandstone beds

(funnel shape of SP curve), and the channel filling

facies association marked by a bell shaped SP curve.

The depositional lobe facies association is repeated

marking side channel migration, followed by distal tur-

bidity facies association, and massive marl facies asso-

ciation.

The vertical succession of facies associations can be

well observed on the profile which shows the section

through the IvaniÊ Grad Formation of the Æutica oil

Fig. 11  Distribution map of γ3 sandstone body (Iva sandstone) in Æutica oil field.

~ . 
• 

r..", 
• 

• 

t..-Ill 
• 

~ 

• ~ 
• 

DlSTRlBtrrlON MAl' or y, SANDSTO.NE BODY IN 
2UTICA OIL FIELD 

piD<hO\ltUll< 0(_ 

_ FA • <h""",1 fillh •• ""in OHO<\afun 

_ Po _ deposi. iOO&lIobe facies oosoc\afun 

_ Fc _ ~I ODd distal turbidite foci .. ossociaIioo 

fD ...... iv. mart focies_iatioo 

::~r ",ntoc'aftaofchanncl 
'l"'=' (2I!l - ptyJ'1'+Y» 

~"' • 
~­• 

~, . 
• 

~ . 
• 

t..jf, 

• 
~, 

• 



73Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

field (Fig. 8). Not only is the vertical succession of

associations in each well obvious, but also the lateral

transitions of one facies association into the other, from

the channel filling facies association into the massive

marls.

If we summarize the experience obtained by such

analyses of SP and Ra curves, not only from the wells

on this profile, but from the wells in the depression, in

which all or most facies associations are well devel-

oped, certain conclusions can be reached. Vertical suc-

Fig. 12  Distribution map of γ2 sandstone body (Iva sandstone) in Æutica oil field.

• ,~ 

M <,'~ 

DISTRlSunON MAP orrl SANDSTONE BODY 
IN ZunCA Oil FlElO 

piO<h .... I;"" of_ 
_ fA · _I filii", (",i .. ","",,0000 

_ F1I • drpooiti .... 1 101:>< f>,ci .. __ 

_ Fe • 1.I<traI and <liltal t\lIIIidi .. faci ..... :.ciaIioo. 

Fl>. massive marl &.cia ...... ioIi"" 

«>IIIact m:. of_I 

a)'SI<!IU (V, - Y<'+rl"'Y'''P) 

~" • 



74 Geologia Croatica 55/1

cession of the explored deposits usually starts with the

massive marl facies association, followed by sandstone

beds of the distal turbidite facies assocciation, deposi-

tional lobe facies association and channel filling facies

association. This part of the succession would corre-

spond to the progradational phase. Then again follows

the facies association of depositional lobe, distal tur-

bidite facies association, and massive marl facies asso-

ciation. This part of the succession corresponds to a ret-

rogradational phase. These two phases form a cycle of

Fig. 13  Distribution map of γ1 sandstone body (Iva sandstone) in Æutica oil field.

, 
" ,', ..... 

DISTRIBUTION M"'1 OF i" SANDSTONE BODY 
IN tunC'" OIL fIElD 

P;"~ 0\11 line Of __ 

_ p", • 0 ........ 1 fiIIj". U<j .. _Wion 
_ I'D. oJ.epo<;liOll>! lob< U<io/. ___ 

_ PC · lalerol _ <ilitallllrlli4ito ,.;~ ,-."~, I 
I'D ...... ivc marl f .. d .. _ 

,(ij:; ,ontoctomoofchaoD<l 
~(OIX - Yo..y,..yJ 

~, 

• 

~ .. 
• 



75Vrbanac: Facies and Facies Architecture of the IvaniÊ Grad Formation...

sandstone material transport in the depression, compris-

ing the lithostratigraphic unit of the Iva sandstones.

After a longer period of time in which, over the whole

Sava depression, sediments of the massive marl facies

association were exclusively deposited, except in the

part of the Kloπtar IvaniÊ oil field where the distal tur-

bidite facies association was deposited, another rela-

tively long period of time occurred with numerous tur-

bidite currents that brought large quantities of sand-

stone detritus in the depression. This cycle of deposi-

tion of sandy detritus in the depression also consists of

progradational and retrogradational phases, and the sed-

iments of this cycle comprise the Okoli sandstones

lithostratigraphic unit. It can be concluded that sand-

stone material of the IvaniÊ Grad Formation was

brought during two cycles of turbidite current move-

ments. Each cycle had progradational and retrograda-

tional phases, and corresponds to an extending and nar-

rowing of the depositional area of detrital material (Fig.

14). The vertical succession of facies associations in

each well is subject to those occurrences of higher

order, and to its position in the depositional system. In

each member that contains sandstones, the vertical suc-

cession of facies associations was dictated mainly by

the lateral migration of channel, and afterwards by oth-

er numerous factors such as distance from the channel,

channel depth, density and size of turbidite cloud,

palaeorelief, etc. Proximity to distributional channels

determines thickness and number of sandstone beds

within a sandstone body, as well as the facies associa-

tion. In the channel, the thickness of sandstone beds and

bodies is maximal. It decreases with lateral distance

from the channel axis and southwards where the action

of turbidite currents gradually weakens.

6. CONCLUSION

(1) A double mechanism of transport and deposition of

the IvaniÊ Grad Formation was defined. Massive

marls represent “normal” basin hemipelagic deposi-

tion (F1 facies). Periodic turbidity brought coarser

sand-size detritus, as well as finer grained detritus

of siltite and mud size, lithification of which formed

turbidite facies (F2-F4 facies).

(2) Marginal parts of the research area were composed

exclusively of massive marls deposited in a calm,

low energy environment of moderate water depth.

However, since these marls are also present in the

central parts of the depression, in turbidite beds, it

Fig. 14  Schematic palaeogeographic section of
Sava Basin towards the end of Upper Pan-
nonian.



76 Geologia Croatica 55/1

can be concluded that the depositional environment

was calm and stable, owing to sufficient water depth

that compensated for all water level changes caused

by either tectonic movements or cyclic climate

changes. This calm environment was disturbed only

by temporary turbidity currents which deposited

most detritus in the depression.

(3) Understanding of the lateral and vertical relation-

ships of the four facies associations in the area (oil

and gas field) made it possible to understand deposi-

tional occurrences in other parts of the explored

basin.

(4) Reconstruction of the lateral extent of facies associ-

ation starts with channel filling facies association

which pass laterally into depositional lobe facies

association, and further from the channel axis into

the lateral turbidites facies association and finally

into the massive marl facies association. The same

regularity is noticed in the reconstruction of the ver-

tical succesion of facies associations.

(5) Detailed reconstruction of the distribution of sand

bodies - potential hydrocarbon reservoirs above all,

spatially defining channel position directs future

exploration activities to the most prospective parts

of the basin significantly diminishing exploration

expenses.

(6) Accurate understanding of the relationships of the

determined facies associations, which are charac-

terised by specific reservoir properties, contributes

to defining the strategy of locating development and

injection wells in previously discovered oil and gas

fields. This will result in the enhancement of recov-

erable hydrocarbon reserves.

Acknowledgements

An earlier version of this paper was critically read by

prof. Josip TI©LJAR, Faculty of Mining, Geology and

Petroleum Engineering, University of Zagreb, prof.

H.G. READING, the University of Oxford, and Dr sc.

Györgyi JUHÁSZ, Geological Institute of Hungary,

Budapest, who contributed extensive and valuable sug-

gestions. I am also grateful to Gordan BRZICA, Gor-

dana RAFFAEL-GUJI∆ and Neven BUTINA (INA-

Naftaplin) on graphic outfit of the paper.

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BOUMA, A.H. (1962): Sedimentology of some flysch

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BOKOR, N., DEVALD, M., LU»IN, J. & THALLER, J.

(1979): Usporedni prikaz naftnogeoloπkih odnosa u

“ I v a-pjeπËenjacima” polja IvaniÊ Grad-Æ u t i c a-O k o l i . -

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znan. umjetn. (Novi Sad), 2, 585-595, Zagreb.

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CLAYTON, J.L. & KONCZ, I. (1994): Petroleum geochem-

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Manuscript received September 1, 2000.

Revised manuscript accepted May 20, 2002.



78 Geologia Croatica 55/1