GEOLOGICA CARPATHICA, 48, 6, BRATISLAVA, DECEMBER 1997
371–386
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC
CARBONATES OF THE PRE-NEOGENE VIENNA BASIN BASEMENT
PETER MASARYK
1
and OTÍLIA LINTNEROVÁ
2
1
VVNP, Research Oil Company, Votrubova 11/a, 825 05 Bratislava, Slovak Republic
2
Departrment of Mineral Deposits and Geology, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovak Republic
(Manuscript received March 18, 1997; accepted in revised form October 15, 1997)
Abstract
: The Upper Triassic carbonates of the Opponitz Formation and Hauptdolomit Formation represent reservoir
rocks of gas deposits in the basement of the Vienna Basin Neogene fill. During study of the reservoir rock properties of
dolomites in the well Kuklov-3 (K-3) significant variations in porosity as a result of late diagenesis processes in buried
sediment were found. On the basis of petrographical, SEM and mineralogical-geochemical methods, we identified neo-
morphic calcite layers, also found in the Kuklov-4 (K-4) well. Coarse crystallized calcite crystals are idiomorphic (e.g.
ditrigonal scalenohedron). They have a relatively high content of Sr, Fe and Na, and decreased isotopic ratio of O (
δ
18
O:
–6 to –9 ‰) or also C (
δ
13
C: –0.7 up to +1.8 ‰) in comparison with values in dolomites (
δ
18
O: –4.8 up to;1.3 or also
δ
13
C:
0.1 to +4.1 ‰) or also in limestones (mostly
δ
18
O: –3.9 to –3.6 ‰). Microstructural analysis indicates that they substi-
tute dolomites as a result of dedolomitization under conditions of deep burial. Diagenesis under conditions of deep burial
results in forming of new minerals such as kaolinite, pyrite and illite. The observed changes (increasing) of reservoir rocks
porosity of dolomites both in the well K-3 and K-4 (at the depth of 3660 to 3830 m) were caused by diagenetic processes
taking place in the deep burial environment and these processes were probably limited to a layer of (originally dolomitic)
breccias.
Key words:
Upper Triassic, carbonate reservoir, chemical and mineralogical composition, SEM, dedolomitization, stable
isotopes of O and C.
Geological and reservoir setting
Both, in the Austrian and the Slovak part of the Vienna Ba-
sin, three nappe zones (Bajuvaricum, Tirolicum and Juvavi-
cum) were interpreted separated from each other by Upper
Cretaceous and Paleogene sediments of the Gosau type (Wes-
sely 1983, 1988; Jiříček 1984). The most external, thrusted
over the Klippen Belt are the Bajuvaric nappes (Frankenfelds
and Lunz nappes). The Upper Cretaceous and Paleogene sedi-
ments of the Giesshübel Syncline have been deposited on
these nappes in a transgressive position. According to Wessely
(1983, 1988), Jiříček & Tomek (1981), Jiříček (1980, 1984),
Sauer et al. (1992) the Bajuvaric nappes are extended in the
belt Aderklaa–Schönkirchen–Prottes–Borský Jur–Kuklov-
Šaštín–Senica and are submerged under the Upper Cretaceous
and Paleogene sediments of the Myjavská pahorkatina Up-
land. They appear at the surface in form of isolated structures
southwards of the Klippen Belt between Podbranč and Lubina.
Well exploration into pre-Neogene basement of the Vienna
Basin was aimed at elevation structures (Šaštín, Závod, Stu-
dienka, Borský Jur, Kuklov, Senica) with a mean depth of the
Neogene basement in the interval of 3000 to 4000 m. In the
Slovak part of the basin two gas deposits — Borský Jur and
Závod were discovered in Upper Triassic dolomite sequences
of the Opponitz Limestone and Hauptdolomite Formations.
Both wells K-3 and K-4 were drilled into the marginal zone
of the Borský Jur reservoir (Fig. 1). The well K-3 is consid-
ered to have one of the most complete sections through the
Lunz Nappe sequence (the interval of 2700 to 5200 m). Be-
Introduction
The presented paper is aimed at the question of whether the
observed change in Upper Triassic dolomites of wells Kuk-
lov-3 (K-3) and Kuklov-4 (K-4) in the basement of the Neo-
gene fill of the Vienna Basin (Fig. 1) is a result of late-diage-
netic processes. Upper Triassic carbonates (Opponitz
Limestone Formation and Hauptdolomite Formation) repre-
sent reservoir rocks of gas deposits in the Slovak part of the
basin. The present burial depth of the Triassic sequence in the
Vienna Basin is predominantly more than 3000 m (in an in-
terval of 2000 to 3000 m, except near basin rims). The porosi-
ty values of the carbonate rocks are frequently below the lower
limit referred to good carbonate reservoir rocks (< 6 %). The
porosity record of the dolomite sequence in the well K-3
shows that the usual porosity reduction with increasing depth
reversed. We observed abnormal increased porosity values
(above 15 %) in this part of the well. Study of reservoir rocks
properties of dolomites was carried out in the framework of
the state research project „Evaluation of prospectivity of
searching for hydrocarbon in selected areas of the Western
Carpathians“ (Masaryk 1996 in: Janků et al. 1996). Preceding
results (Borza et al. 1985; Masaryk et al. 1988; Ostrolucký &
Jiříček 1986; Ostrolucký 1994) were supplied with other pet-
rographical, mineralogical and geochemical results (Lintner-
ová 1988; Masaryk 1990, 1996). It is becoming evident that
late-diagenetic alteration of a carbonate sequence affected
mostly parts built up by breccias and significantly influenced
their reservoir rock properties.
372 MASARYK and LINTNEROVÁ
sides the Upper Triassic dolomites (2700 to 3832 m), the well
also penetrated the Lunz-Reingraben Formation (up to 4758
m) and a part of the Reifling Formation (up to 5200 m). The
lithological nature and changes in reservoir rocks were
checked in logs (Figs. 2–3). Biostratigraphical subdivision of
the carbonate sequences was problematical because of the lack
of fossils.
The Uppermost layers of the Upper Triassic dolomites con-
tain foramifers Uppermost Norian to Rhaetian (Borza et al.
1985). It is possible to accept the lithofacial subdivision of
the Hauptdolomite Formation proposed by Scherreiks (1971)
and later made more precise by Fruth & Scherreiks (1982,
1984, 1985) also for sequences of the Vienna Basin base-
ment. On the basis of this subdivision, the well K-3 drilled
through the middle and basal part of the Hauptdolomit For-
mation and Opponitz Limestone Formation (Fig. 3). The Op-
ponitz Limestone Formation was also found in the well K-4,
but the Mesozoic sequences were drilled in an inverted ar-
rangement (Masaryk et al. 1988).
Methods
150 thin-sections were studied from the wells K-3 and
K-4. Some of them were coloured with alizarine red. The
porosity of well core rocks was evaluated by methods of
triple scaling, Hg-porosimetry and optical coloured poro-
simetry. We also utilized the results of processed logs of
the well K-3 (processed by computer). For all methods of
porosity measurements in details see Masaryk (1996). We
studied the fracture surfaces of dolomite and also etched
and polished rocks thin plates (0.5% formic and 1% hydro-
chloric acid, 15 sec. to 1 min.) under a scanning electron
microscope (SEM). The mineral composition of rock sam-
ples was studied by X-ray diffraction analysis (CuK
α
).
The dolomite stechiometry (mole calcite– dolomite ratios)
and the dolomite crystal ordering have been evaluated by
methods of Lumsden (1979). The calcium and magnesium
content of the carbonate parts of rock samples (HCl dis-
solved) were checked by chemical analysis. The calcite and
dolomite contents were corrected on the basis of insoluble resi-
due (IR) gravimetrical determination (Table 3). The elements
listed in Table 2 were determined by the AAS method in the
sample portions soluble in hydrochloric acid. The 67 whole-
rock analyses from both wells were done by the X-ray fluo-
Fig. 1.
Localization map of the Kuklov 3 (K-3) and Kuklov 4 (K-4)
boreholes.
WELL
DEPTH (m)
P HG
(%)
P HG
>20 nm (%)
TOP
(%)
VP(%)
LITHOLOGY
AGE
Kuklov 3
27083013
1.50
0.39
3.05
2.03
Grey-brown loferitic and
brecciated dolomites
Norian
Kuklov 3
30893238
1.33
0.45
2.10
0.64
Grey-brown laminated
dolomite with anhydrite
Norian
Kuklov 3
33903665
0.91
0.32
0.00
1.07
Grey-brown massive
limestone
Carnian
Kuklov 3
36763832
2.03
0.37
8.77
3.35
Grey-brown limy
dolomite and dedolomite
Carnian
Kuklov 4
33293573
0.30
0.10
0.00
0.40
Grey-brown massive
limestone
Carnian
Kuklov 4
36413644 10.42
6.72
13.00
11.75
Grey-brown porous
dolomite
Carnian
Kuklov 4
36973734
2.95
1.55
3.50
3.07
Grey-brown carbonate
breccia
Carnian
P HG (%) average of the total porosity measured by Porosimetro 2000, (Hg-porosimetry)
P HG >20 nm (%) average of the effective porosity measured by Porosimetro 2000
TOP(%) average of the total optical porosity (colour optical porosimetry)
VP (%) average of the total volume porosity (triple weight)
Table 1:
The results of porosity measurement by four methods.
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC CARBONATES 373
Fig. 2.
Borehole K-3: Lithological section and the values of log porosity.
rescence method. Some of them are listed in Table 2, but the
complete analyses are unpublished (Borza et al. 1985; Lint-
nerová 1988).
Powder specimens for isotopic analysis from analysed
cores were prepared. Samples were dissolved by the stan-
dard method (McCrea 1950), i.e. in 100% phosphoric acid
in vacuum at 25
o
C. In samples containing calcites and dolo-
mites, carbon dioxide has been separated step by step, ac-
cording to reaction time. The values of the isotopic ratio
were corrected (decreased by 0.8 ‰) in respect to a different
fractional factor of oxygen in reaction with the acid. The
quoted way of separation is favourable for samples with the
content of one component over 10 %. Results were quoted
as an isotopic ratio
δ
in per mile, related to the PDB standard
for both elements. The accuracy of the assurements is better
than 0.1 ‰ for both
δ
13
C and
δ
18
O.
374 MASARYK and LINTNEROVÁ
Fig. 3.
Upper Triassic carbonate cores in boreholes Kuklov 3 and Kuklov 4.
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC CARBONATES 375
Results
Petrographic characteristics of the specimens
Well Kuklov-3 (K-3)
The Upper Triassic carbonate rocks of the well K-3 were
subdivided into three lithological types (Figs. 2–3). The dolo-
mites of cores 6–11 represent the middle part of the Hauptdo-
lomit Formation sequence, while cores 12 to 14 were taken
from the basal dolomitic-anhydritic complex (after Scherreiks
1971; Fruth & Scherreiks 1982, 1984, 1985). The limestones
and dolomites of cores 15 to 22 (Fig. 3) belong to the Opponitz
Limestone Formation.
Cores 6 to 11 are formed by grey-brown tectonized lofer-
ite dolomites (Fig. 4: 1–2). The uppermost part of the dolo-
mites (cores 6,6a) are formed primarily by dolosparite
(grain size 200–250
µ
m,) and sporadically by microsparite.
In other cores recrystallization is not so intensive, and fine-
grained dolomitic matrix (5–25
µ
m in size) is partly recrys-
tallized into microsparite (30–100
µ
m in size). Initial sedi-
mentary textures and structures were almost completely
wiped away and are preserved only in the form of indistinct
ghosts (Fig. 4: 1). Fossil fragments (ostracods, foraminifers,
crinoids) occurred only rarely (Fig. 4: 2). The primary stro-
matolite structure is the most typical phenomenon in this part
of the sequence (Fig. 4: 3–4, 7). The dolomites were relative-
ly intensively fractured and the secondary joints are filled
primarily by calcite, less by dolomite and rarely by anhydrite
crystal aggregates. The open jointed network in tectonized
layers (tectonic breccia) wholly increase communication of
pore spaces. Locally, the rocks have the nature of pseudoru-
dite and are formed by lighter dolomicrosparitic clasts en-
closed by dark dolomitic matrix.
Cores 12 to 14 (Fig. 3) contain grey-brown brecciated do-
lomites with anhydrite. The dominant breccias have clasts
formed by laminated loferite dolomites (Fig. 4: 3–4, 7–8) and
matrix formed by laminated anhydrites with dolomite inter-
calations (Fig. 4: 5). The anhydrite of these layers is coarse
grained and tabular or needle-shaped crystal forms are char-
acteristic. The dolomite laminae are micritic, frequently with
a clay admixture. The dolomite clasts in the breccia are
formed by the same types of dolomites as described from
cores 6 to 11.
Cores 15 to 19 (Fig. 3) are formed by grey-brown laminat-
ed limestones. The matrix of the limestones is micritic with
an inexpressive fine lamination. The limestones (limy mud-
stones) are poor in organic remnants and other allochems.
Sporadic pellets, ostracods, crinoids, globochaetes and fora-
minifers are most frequently concentrated into thin laminae.
The matrix includes a finely dispersed clayey-silty admixture
(approx. 5 to 10 %) concentrated into stylolite surfaces that
represent a result of pressure dissolution. The limestones
were fractured by a relatively dense net of joints or veinlets
which were formed by secondary sparry calcite, seldom by
dolomite. Diagenetic dolomitization affected these lime-
stones only indiscernibly. Besides sporadic small rhombs in
the matrix of these limestones there are more abundant au-
thigenic pyrites and clay minerals. These limestone types
with a relatively high clayey-silty admixture also include
more intensively dolomitized limestones.
The rocks of cores 20 and 21 (Fig. 3) are formed by pale-
brown brecciated dolomite to dolomitic limestone. The ma-
trix is microsparitic to sparitic with relics of sporadically re-
crystalized foraminifers, ostracods, ooid relics and intraclasts
(Fig. 5: 1–2). The detritus content in dolomites reaches up to
10 % (wackestone type). The matrix has the typical granular
nature of dolomites, but locally with an increased calcite
content, fairly visible in thin sections coloured by alizarin
red and also according to the changes in size of crystals. Ir-
regular islands of dolomite (Fig. 5: 3) and relics of dolomite
(dolomitic ash) between and inside large calcite grains indi-
cate processes of a diagenetic alteration — dedolomitization.
The original laminated structure of dolomite is visible in
hand specimens but completely disappears in thin sections.
Dolomites were also strongly fractured and brecciated. A pri-
mary part of joints and pores is filled by neomorphic sparry
calcite, but part of the pores is free. This is very important for
reservoir rock properties (the increasing of the permeability).
Sample
CaO
MgO
CO
2
Fe
Mn
Na
Sr
wt. %
ppm
K3
6/2708
31.62
20.58
46.69
250
36
250
81
6a/2757
32.09
20.19
46.90
380
61
330
81
7/2704
32.19
19.92
46.93
300
44
460
75
8/2851
31.80
20.42
46.87
310
39
450
690
8/2853
32.29
19.83
47.07
290
39
440
71
10/2951
28.09
20.40
42.70
1550
74
650
96
10/2952
32.33
20.75
45.44
920
87
580
94
10/2953
24.66
16.58
36.36
2770
87
1050
94
11/3011
28.33
20.36
42.18
55
575
116
12/3090
3.72
2.51
5.66
108
738
995
13/3177
9.01
6.47
14.12
63
295
2218
14/3237
32.11
20.82
45.11
91
373
839
15/3391
53.64
1.31
42.54
20
330
800
15/3392
53.48
1.21
42.87
23
310
755
16/3421
51.84
2.70
42.45
910
195
701
17/3566
54.56
0.72
43.82
870
150
500
19/3663
42.45
4.43
37.48
328
475
443
20/3676
32.84
19.73
47.16
28
375
103
20/3677
32.41
19.60
47.03
32
388
100
21/3825
34.36
18.07
47.05
210
17
580
93
21/3826
55.48
0.59
43.09
455
10
128
378
21/3827
55.46
0.68
42.29
1330
14
113
228
22/3828
53.69
2.07
43.51
420
19
125
393
22/3829
50.00
4.71
44.48
420
22
125
231
22/3830
52.57
2.81
43.98
385
17
148
280
34/4902
48.72
0.95
41.17
29
890
K4
11/3699
53.42
1.21
42.59
80
260
325
11/cl
54.96
2.60
570
77
160
295
11/ce
53.14
0.15
760
82
310
309
11a/cl
52.57
1.61
580
45
190
305
11a/ce
38.27
0.71
1880
64
700
250
12/3732
46.83
1.41
68
450
230
12/cl
36.95
0.71
960
140
730
248
12/ce
38.55
0.50
690
55
720
203
Table 2:
Chemical composition of the rock samples. Sample 6/
2708 it is: 6-core number, 2708 = 2708 m in the borehole.
cl — clast, ce — cement
376 MASARYK and LINTNEROVÁ
We noticed a significant increase of calcite content in the
lower part of core 21 and in core 22, and although specimens
resembled dolomite by their appearance they are actually
formed by neomorphic calcite. The calcite crystals are sparit-
ic (Fig. 5: 3–8) with relics of dolomicritic matrix. Relics of
dolomicritic grains with their rims partially rhombohedrally
boundered as well as in form of large rhombohedral grains
were typical. Some core parts are formed by a carbonate
breccia with angular clasts with sizes of 0.1 mm to 4 cm.
Clasts were of a different nature, resembling the described
compact dolomites or limestones. The cement of these brec-
cias is formed by coarse-grained neomorphic calcite (Fig. 4:
6–7) and micritic parts (matrix), which are also calcitic.
Ghosts, remnants of tests probably from foraminifers and os-
tracods, appear locally.
Well Kuklov-4 (K-4)
The cores 11, 11a and 12 (Fig. 3) are formed by grey-
brown carbonate limestone breccias. Dolomites are present
only in core 10 (Fig. 3). The appearance and texture proper-
ties of them are very similar to those from well K-3, core 20.
The matrix of the limestone breccias is formed by mi-
crosparitic to sparitic calcite with a clayey admixture. The
matrix is relatively homogeneous without allochems. Be-
sides the matrix, a syntaxial calcitic cement is found at the
rims of some clasts. The clasts are dominantly angular to
subrounded with signs of corrosion. The contacts between
clasts and matrix are frequently obscured and rather resemble
to gradual transition. The breccia is distinctively polymodal,
clast sizes vary between 0.5 to 10 cm. Sporadically the clasts
show sedimentary structures, e.g. lamination, fenestral po-
rosity, loferite structure which are typical for (the described)
dolomites. They are formed by neomorphic calcite sparite
with small inclusions (relics) of dolomite. Micritic aggregate
grains with ghosts of a pseudo-oolitic texture can be ob-
served locally. In the sparite mosaic some grains thicken to-
wards rims, which are formed by completely pellucid rhom-
bohedral calcite grains. Generally recrystallization is
manifested by the presence of numerous inclusions and au-
thigenic minerals, e.g. pyrite. The breccias studied in the
well K-4 were gradually formed by leaching/dissolution and
neomorphic calcite grains substituted the original dolomitic
material.
Properties of the dolomite porosity
The comparison of measurement results gained by a few
methods (Table 1, Fig. 2) confirms a significant variability in
the dolomite porosity in the wells K-3 and K-4 or confirms
some increase of porosity towards depth. This increase at the
depth below 3600 m (Fig. 2) is connected with dolomites or
dedolomitized breccias, which is documented by porosity
based on logs processing of the well K-3 (Fig. 2). On this ba-
sis, it is impossible to make any statement as to the absolute
values of porosity, but the relative changes of reservoir rock
properties provide valuable information which shows that seg-
ments with an increased porosity coincide with intervals of
(late) diagenetic alteration. Apart from significantly (fracture)
porous and permeable dolomites in the beds directly underly-
ing the Neogene, which represent the old erosional surface of
the Triassic dolomites, and are associated with two known de-
posits in the Slovak part of the Vienna Basin, it is possible to
identify further important reservoir horizons. In both wells, K-
3 and K-4, reservoir rocks did not contain gas, but were filled
with salt water. For comparison Ostrolucký (1994) gives mean
porosities for the Opponitz Limestone Formation (K-3) of up
to 7.33 % and a permeability of 3.56 mD, simultaneously he
gives a mean value for the porosity of all the dolomites (reser-
voir rocks) of this well of 1.3 % and a permeability of 0.2 mD.
From the viewpoint of reservoir rock properties we can
classify the petrographic types as follows:
1. The coarse-grained dolosparites of a sugary appearance
are characterized by a predominantly planar polymodal coarse
crystalline mosaic with sizes of crystals above 100
µ
m (mean
250
µ
m in size). The extensive dolomitization resulted in a to-
tal destruction of the original rock and therefore we cannot ob-
serve any primary sedimentary textures and structures. Porosi-
ty values (Table 1) reach an average of 2.5 % (the interval
0–7.5 %), scanty communication — permeability of intercrys-
talline porosity represents a certain insufficiency.
2. The laminated muddy dolomites and dolomitic lime-
stones of mudstone type with anhydrite are characterized by
predominance of micritic, microsparitic types of the matrix
with sizes of dolomite crystals of up to 50
µ
m generally with-
out clasts or other allochems. The anhydrite formed synsedi-
mentary laminae, but was secondarily mobilized and repre-
sents fill of veinlets, stylolites and fractures. The original
sedimentary structural-textural elements are well preserved.
The values of the total porosity (Table 1) are low — 1 to 2 % ±
2 %, the rocks are, with exception of breccia layers, nearly im-
permeable.
The calcarenites of dolograinstone type with irregular clast
recrystallization and dolosparitic cement are characterized
by various stages of original sedimentary texture and struc-
ture preservation. Clasts are predominantly formed by pel-
lets, bio and lithoclasts. Dedolomitization results in a brec-
ciated to microsparitic nature with ghosts of clasts. The
porosity values of the original dolomites were low — 0–5 %,
but dedolomitized layers (Table 1) have higher porosity val-
ues — 5–12 % with a relatively good microfracture porosity.
These layers are some of the best reservoir rocks within the
whole carbonate complex.
Fig. 4.
Thin section photos of dolomites from well K-3 (cores 8 to
14). 1 — Coarse- to fine-grained dolosparite with relics of the dolo-
micrite in the pseudoclastic structure (2910 m, magnification 7
×
).
2
— Dolosparite with ghosts of bioclasts (ostracods, foraminifers)
and dolomicrite relics (2849 m, magnification 9
×
). 3–4 — Dolomite
with stromatolitic (loferite) structure (3091.8 m & 3235.5 m, magni-
fication 7
×
). 5 — Laminated finecrystalline anhydrite with thin lam-
inae of dolomicrite (3178.3 m, magnification 7
×
). 6 — Coarse crys-
talline anhydrite with dolomite relics (3089 m, magnification 7
×
).
7
–8 — Dolomitic breccia with a stromatolitic structure in the clast
(3237.4 m & 3012 m, magnification 7
×
).
→
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC CARBONATES 377
378 MASARYK and LINTNEROVÁ
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC CARBONATES 379
SEM
A total of 15 samples from the dolomite intervals (Fig. 3)
separated by limestone layers were selected from the well K-3
for SEM study. The first layer was caught by cores 6 to 14
(the interval 2708 to 3240 m), and the second one by cores
20–21 (the depth 3676 to 3830 m).
In the SEM micrographs it is possible to distinguish two
grain size classes in fine-grained dolomites (Fig. 6A–B). The
dolomite matrix is formed by grains below 10
µ
m in size and
a coarser grained crystalline phase, above 10 to 100
µ
m in
size. The grains reach in average around 50
µ
m in size and
are of typical rhombohedral morphology. These rhombs
grow partly into opened pores, partly replace matrix
(Fig. 6A–B). Their presence generally increases intergranu-
lar pore spaces most expressed in specimens of cores 6, 6a
(Fig. 6B). On rhombohedrons’ surfaces we can see intracrys-
talline pores and fractures, which were a result of proper re-
crystallization of the dolomite. Diagenetic dissolution by
Fig. 5.
Thin section photos of dedolomites from well K-3 (cores 20
to 22). 1–2 — Oolite dolograinstone with preserved interparticle
and intercrystalline porosity (3676 m, magnification 86
×
, 7
×
). 3–4
— Neomorphic sparry calcite replacing dolomicrite matrix with
vuggy macroporosity ( 3829 m, magnification 86
×
, 7
×
). 5 —
Pseudomorphic dolomitic texture of sparry calcite (3829.5 m,
magnification 86
×
). 6–7 — Neomorhic sparry calcite with relics
of dolomite (3827 m, 3831.5 m, magnification 86
×
). 8 — Pseudo-
morphose after dolosparite (the lower part) and neomorphic cal-
cite with relics of dolomicrite (the upper part), (3829.5 m, magni-
fication 45
×
).
Fig. 6.
Microphotographs (SEM) of the dolomites in K-3, cores 6 to 13. A — Microsparitic dolomite rhombs in the matrix replaced by
dolosparite rhombs. B — Large dolomite grains were dissolved and the new intragranular porosity was formed. C — Framboidal pyrite
aggregates were grown among dolosparite crystals. Dolomite grains were also partly dissolved. D — Sparry calcite grains were formed in
the pore space and also calcite filled fine veins. E — Dolomite matrix with siliclastic mineral coating (mica, illite), often on the stylolites.
F
— Large crystal aggregates of anhydrite in dolomite.
←
380 MASARYK and LINTNEROVÁ
pore solutions was indicated by disturbed rhombohedral
grains (Fig. 6B–C) and in places even by irregular residual
grains that were paler. The new phases in dolomites are rep-
resented by calcites (Fig. 6D) in joints as well as framboidal
pyrites (Fig. 6C) studied in specimens of cores 6 to 8. Anhy-
drites reduced by organic substances were probably the
source of the sulphur (Fig. 6F). The dolomite grains near the
framboidal pyrites were also (slightly) corroded (Fig. 6C).
The calcite crystals closely fill joints and are massive with-
out surface disturbance (Fig. 6D). Clastic minerals can be
seen at grain boundaries in typical laminae, deformed after
formation of carbonate grain. They were represented by mica
or chlorite grains pressed out by the dolomitization, but also
by (successive) pressure dissolution. Tiny dispersed particles
at grain surfaces (Fig. 6E) are probably authigenic illites.
The dolomite matrix of the core 20 is microsparitic and it
forms idiomorphic rhombic grains larger than 10
µ
m, in av-
erage 20 to 40
µ
m in size (Fig. 7A–C). SEM study showed
that specimens of the lower part of core 21 and in core 22
were formed by predominantly well crystallized, perfectly
limited crystals. We can recognize typical crystalline forms
of calcite, e.g. ditrigonal scalenohedral (Fig. 7C–F). We did
not notice rhombohedral neomorphic crystals. Neomorphic
crystals did not bear any signs of surface disturbance but
were strewn with residual (pale-dissolved) irregularly limit-
ed grains or dust (Fig. 7E–G). Grains frequently bear growth
defects or inclusions of smaller crystals. These crystals do
not fill only cavities but seem to substitute the essential
(large) volume of specimens. Locally grains were closely
crammed (Fig. 7D) but as a whole specimens seem to be rel-
atively loose, porous (Fig. 7E–G) for example in comparison
with calcitic cement in joints (Fig. 6B). We found authigen-
ic kaolinite in etched surfaces (Fig. 7H–I) and from these
parts of cores fluorite was also described (Mišík 1986). Ka-
olinite forms platy pseudohexagonally limited crystals. We
also sporadically observed grains of grown feldspar or
quartz, again in etched surfaces.
From the well K-4 we took 5 specimens from cores 10 to
12, depth interval of 3641 to 3734 m (Fig. 3). Dolomites
were found only in core 10 and they had increased calcite
content (Table 2). Calcite forms predominantly the fill of
cavities, pores and joints (Fig. 8A). Dolomitic micritic to mi-
crosparitic grains (up to 10
µ
m in size) bear quite apparent
traces of dissolution (Fig. 8B). Cores 11, 11A and 12 have
the appearance of a dolomitic breccia but they were proven
by chemical analysis to be actually limestones (Table 2).
These limestones displayed higher variability of grain size,
intercrystal porosity as well as of the surfaces disturbance
and presence of relic grains of the preceding phases. The
most important for us seemed to be the presence of „fresh di-
agenetic“ calcite grains (Fig. 8C–E) and crystals of clay min-
erals (Fig. 8E–F). These calcite grains were similar after
their morphology to grains studied in the core 22 of the well
K-3 (Fig. 7D–G). Crystals are without a surface dissolution
disturbance but they contain growth’s defects — pores, fre-
quently with crystalline negative morphology. Small relic
grains of the original phase are also present on the surface of
grains and in intercrystal spaces. Some of them have partly
rhombohedral limitation, similar to dolomite grains from the
core 10. Authigenic clay minerals, probably illites in their
typical fine grained form (Fig. 8F) cover the surfaces of cal-
cite grains and fill pore spaces between crystals. In speci-
mens from cores 11A and 12 distinctive signs of recrystalli-
zation and traces of dissolution were also observed
(Fig. 8H–I). On fracture surfaces we could observe preserved
isles of the original phase — fine-grained dolomite which
seems to be displaced towards crystal rims or into the inter-
crystal spaces of neomorphic calcites (Fig. 8H–I). According
to relations between grains, we can see that neomorphic clay
minerals were probably crystallized simultaneously with the
calcite grains formation (Fig. 8H) or later and grow into free
intercrystal spaces (Fig. 8F).
Geochemical-mineralogical analysis of specimens
We want to document by chemical analyses of specimens
that in cores 21 and 22 (Fig. 3) alteration of the chemical and
mineral composition of the rock arose. In one core (21) the
dolomite or dolomite breccia, has been altered into limestone
(limestone breccia) although the rock is of a dolomitic ap-
pearance. The neomorphic limestones are „pure“ and contain
hardly any aluminosilicate minerals. The limestone layers
continue into core 22 which also has a brecciated appear-
ance. Dolomite content slightly increased in specimens of
core 22 (Table 3). By analogy the breccia from K-4 was
formed by calcites (Table 3), but had an increased or more
variable content of clayey material, as well as of authigenic
material as it was documented also by SEM microphotogra-
phy. Their content in original clasts changed. Mineral com-
position was studied by X-ray diffraction. X-ray records
were assessed by a semi-quantitative method and the ob-
tained assessments correspond well to the mineral composi-
tion calculated from chemical analyses of rock specimens or
from the calcium and magnesium content determined by
classical chemical analysis (Tables 2–3).
Finer-grained, less crystallized dolomites from the well K-3
were close to stechiometric composition (50.5 to 52 mol. % of
CaCO
3
), coarse-grained (sparitic) reveal a slight content of
lime (53 to 56 mol. % of CaCO
3
). However, referred variabili-
ty could reflect alteration processes either in the topmost part
(disturbed rhombohedrons — core 6,6A and relatively little of
calcite cement) or in the lower part in cores 20 and 21. The ste-
chiometry differences were not clearly manifested in differen-
tiation of dolomite crystal ordering. The ratios of reflection in-
tensities 221 and 101 (Lumsden 1979; Hardy & Tucker 1988)
were relatively high in both dolomite grain size groups and
Fig. 7.
Microphotographs (SEM) of the dolomites and calcites
(dedolomites) in the K-3, cores 20 to 22. A–B — Dolomite mi-
crosparitic to sparitic matrix formed by idiomorphic rhombs. C —
Leaching or partly dissolved dolomite rhombs on both grain gen-
erations. D — Large neomorphic idiomorphic calcite crystals cov-
ered with dolomite ash. E — Neomorphic calcite in some part of
sample filling the space completely. F–G — Calcite crystals (ded-
olomite) with „open“ intercrystalline pores with residual dolomite
grains. H–I — Neomorphic platy kaolinite crystal on the calcite
surface (etched by acid).
→
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC CARBONATES 381
382 MASARYK and LINTNEROVÁ
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC CARBONATES 383
were in the range 0.6 to 1.0. Dolomites with evaporates and
specimens with quartz (cores 11 to 13) were not assessed by
this method. Contents of microelements in rock specimens
(Table 2) documented relative differences in composition of
dolomite/limestone layers. Analyses of separated parts of
breccias (Table 2), clasts and matrix/cements show partly
comparably high quantities of observed elements (Sr, Fe, Mg
or Na) in the observed parts, and also comparably higher con-
centrations than in the limestones. The neomorphic calcites
have a higher content of observed elements than the overlying
dolomites. Thus, if they originated by substituting dolomites,
then these alterations indicate buried diagenesis in a buried
sediment and the operation of diagenetic solutions. On the oth-
er hand fluids with a sufficient concentration of calcium or
brines could be obtained by dissolution of evaporite layers or
cements (Fig. 3; the well K-3, cores 12 to 14), although the
fluids could be originally of a meteoric origin (e.g. buried to-
gether with sediment below the Neogene fill, or descending to
depth along faults during different time periods). High con-
tents of Na could indicate the presence of sea water pore solu-
tions or rock brines in the recrystallization process.
Isotopic analysis
We can interpret two basic trends in the distribution of data
in both fields of isotopic data (Fig. 9) which reflect on the
one side preserved sedimentary or early diagenetic dolomiti-
zation distribution of values of isotopic ratios and on the sec-
ond later or deep burial diagenetic influences on isotopic ra-
tios of O and C. The specimens from the Hauptdolomite
Formation (cores 6 to 14, Fig. 9, field 1) have more positive
values of
δ
18
O than dolomites or calcites from the Opponitz
Limestone Formation and indicate the evaporitic type of do-
lomitizing solutions, probably the sabkha type of dolomitiza-
tion in strata overlying an evaporite sequence. The values of
δ
13
C for these specimens were in the range of normal sea val-
ues (0 to 4 ‰), however, they were slightly decreased (Ta-
ble 3). The specimen from core 6 is fairly shifted to lower
values both for
δ
13
C (+0.1 ‰) and
δ
18
O (–2.0 ‰). The dolo-
mites of this core were most tectonically disturbed, but cal-
cite content was low here. The values of couples calcite-do-
lomite were close though they were lower in younger
calcites. The calcites had to be formed in joints from pore so-
lutions which did not significantly differ in the origin of C
and O, but they could be formed at higher temperatures.
However, it could even be a case of mixing of (meteoric) so-
lutions/water dissoluing dolomites in surface (pre-Neogene)
conditions and calcites were formed from them. Limestones
and dolomites of the Opponitz Limestone Formation form
the second field (Fig. 9, field 2) and indicate a different sedi-
mentation or also a dolomitization environment. The values
of
δ
18
O were predominantly lower and
δ
13
C were predomi-
nantly higher than for the Hauptdolomite Formation speci-
mens. In dolomites (only 3 analyses) values of
δ
18
O were
considerably variable in comparison to limestones. The lime-
stones have preserved balanced original (sedimentary) high
values
δ
13
C which do not follow smaller variations in the
values for
δ
18
O in the set. In comparison of the couple cal-
cite-dolomite from core 20 we can see that dolomite has
higher ratios of C and also O than the neomorphic calcite
(Table 3) which indicates a (late) diagenetic origin of the cal-
cite (Fig. 9, field 2´). In the value set for the Opponitz Lime-
stone Formation specimens we can follow a more distinctive
diagenetic trend towards the basement (Table 3). The most
significant is the decrease of the
δ
18
O ratio and also a slight
decrease of the
δ
13
C ratio in the calcites. Changes of the
same nature were manifested in both ratios, but
δ
13
C re-
mained relatively small. An exception is represented by a
calcite specimen from the well K-4 (core 11) which has a
more significantly decreased carbon ratio (Fig. 9). The two
specimens were partly enriched in C
12
, and in both cases this
could be also the influence of carbon of an organic origin, for
example as a result of the decay of organic matter (reduction
of sulphates) as well as the influence of mixing of different
solutions. Our set also includes a specimen of the Reifling
Limestone Formation from a depth of 4902 m (i.e. approx.
100 m deeper). This limestone has no apparent signs of di-
Fig. 8.
Microphotographs (SEM) of the dolomite and the calcite in
the K-4, cores 10 to 12. A — Micrite to microsparite dolomite ma-
trix with large calcite grains in the join. B — Microsparite dolo-
mite rhombs were dissolved/leached (detail from A). C–D — New
generation of the idiomorphic calcites, with the characteristic cal-
cite crystal-morphology. E–F — Neomorphic illite particles cov-
ering calcite surface and also filling the open pore spaces between
grains. G — Siliclastic minerals mainly accumulated in the stylo-
lite were altered and form new mineral phases. H–I — Dissolution
and substitution of dolomite crystals by calcites. Small residual
dolomite rhombs were accumulated among large calcite grain.
Table 3:
Mineralogical composition and isotope analyses of the
rock samples.
←
cl — clast, ce — cement
Sample
calcite
dolomite
IR
calcite
dolomite
wt. %
per. mil PDB
δ
13
O
δ
18
O
δ
13
C
δ
18
O
K3
6/2708
6.67
91.67
1.66
0.1
-2.1
7/2704
8.15
90.80
1.05
3.0
1.3
8/2851
8.19
91.06
0.85
2.1
0.2
2.4
0.5
10/2952
12.05
84.08
3.78
1.2
0.6
1.4
0.9
11/3011
5.18
83.58
11.24
2.3
0.2
12/3090
0.39
11.50
88.11
0.5
-0.1
13/3177
29.58
70.11
1.8
-0.3
14/3237
14.30
79.22
6.48
2.9
-2.0
15/3391
94.72
1.88
3.23
3.8
-3.7
15/3392
93.43
3.73
2.67
3.7
-3.6
19/3663
66.32
17.41
16.27
2.5
-4.3
2.7
-4.8
20/3676
9.94
89.63
0.56
3.3
-2.1
4.1
-1.6
20/3677
8.71
90.50
0.46
3.9
-1.4
21/3825.5
81.20
17.75
1.05
1.5
-7.6
21/3825.8
90.32
8.86
0.92
1.4
-8.6
21/3826
95.11
4.68
0.21
1.5
-9.0
22/3827
90.11
9.47
0.42
3.5
-4.6
22/3827.5
85.92
12.90
2.18
2.0
-8.6
22/3828
92.73
5.71
1.56
1.8
-7.7
34/4902
86.96
3.42
9.16
1.7
-3.9
K4
11/3697
92.36
5.51
2.18
-0.7
-7.4
12/3730cl
90.26
5.00
4.74
1.1
-6.4
12/3730ce
90.26
21.68
1.4
-8.2
12/3732
80.08
6.43
10.87
12/3732cl
60.10
29.90
1.2
-8.0
12/3732ce
63.40
26.60
1.2
-8.2
384 MASARYK and LINTNEROVÁ
agenetic alteration, (Masaryk et al. 1993) as with limestones
from core 15. It differed rather by isotopic ratio of C than O
and the decreased ratio could be a reflection of an originally
deeper sedimentary environment.
Discussion
Taking into account microstructural properties as well as
changes of the chemical composition of dolomites or cal-
cites, from wells K-3 and K-4, we judged that dolomites
were also diagenetically altered under conditions of deep
(present) burial (Fig. 3). We described a diagenetic stratum
characterized by the presence of a new generation of coarse
grained, well crystallized calcites (Figs. 7–8) in the Opponitz
Limestone Formation at a depth of approximately 3660 to
3830 m with an observed significant increase of porosity.
These calcites substituted partially or totally the original sed-
imentary dolomite breccia in wells K-3 and K-4. In both
wells this layer is situated at an equivalent depth which itself
indicates that it was created under conditions of the deep
(present) burial, especially since we know that in spite of the
close position of these wells (Fig. 1), they did not penetrate
the same lithological succession. In well K-4 the Opponitz
Limestone Formation is in a reversed position indicating the
tectonic complications in the basin basement. Diagenetically
altered beds are joined rather to layers of original dolomite,
and or dolomitized breccias. As a matter of course, there was
a disadvantage in this comparison caused by the fact that we
could study only separated segments of sequence from the
well cores and the missing segments were much longer than
the available cores.
Based on our results we assume that the neomorphic cal-
cites were the result of the dedolomitization process in a
deeply buried sediment. Dedolomitization was originally de-
scribed as a close subsurface process, but later on also for
different conditions and depths (DeGroot 1967; Back et al.
1983; Land & Prezbindowski 1981; Stoessel et al. 1987;
Kastner 1982; Budai et al. 1984; Loucks & Elmore 1986 and
others). We noticed the disturbed, mostly dolosparitic grains
in the dolomites of the highest part of the basement (e.g.
cores 6, 6A, 8, Fig. 6). However calcite fills have mainly tec-
tonic joints (Figs. 4, 6D). The disturbance/dissolution of do-
lomites has a similar nature in a deeper part of the well sec-
tions (cores 20 to 21), but the neomorphic calcites are
entirely different. According to our observation, calcites
crystallized not only in joints, but they substituted a greater
volume of the dolomite or dolomitic breccia. A style of dolo-
mite rhombohedrons substitution is characteristic for the
dedolomitization (Rao 1969; Mišík 1988; Holail et al. 1988)
and can virtually be considered as a primary proof. We used
a SEM for the study of microstructures as well as an optical
microscope. The SEM microphotographs illustrated relations
between the new and preceding grains well. The neomorphic
calcites are different from calcites in joints and their mor-
phology is quite similar to laboratory evolved dedolomite
crystals (Stoessel et al. 1987). It is also possible to see the
presence of other mineral phases and judge the relative (tem-
poral) succession of the origin of phases. We could see the
presence of post-dedolomitization phases — illite, kaolinite,
pyrite or fluorite. Fluorite was described together with celes-
tine by Mišík (1986) in well K-3. The coexistance of these
phases documents the efficiency of diagenesis and the extent
of deep burial conditions. Neomorphic illites spreading to the
free spaces between calcites (Fig. 8) could be a good indica-
tor of such a process. Kaolinite with a platy-morphology
(Osborne et al. 1994) is also characteristic product of diagen-
esis in deep burial basin conditions (at least 2000 m).
Large, idiomorphic calcite crystals evidently needed a suf-
ficiently long time for their formation. The presence of im-
permeable beds (e.g. the Lunz Formation, Fig. 3) as well as
the actual depth (below 3 km) favours the lateral flow of the
solutions. However, it is impossible to exclude the role of
tectonic joints as ways for dedolomitizing solutions. In the
highest part of dolomites almost exclusively tectonic joints
are filled by calcite. It is evident that also in a dedolomitized
layer some calcites crystallized into free space (tectonic frac-
tures?). However, proper calcitized parts were frequently
packed, which was indicated by measured porosity data. The
first (principal) increase in porosity was attached to partly
substituted dolomites where there are many partially dis-
solved grains. The porosity was also decreased by a subse-
quent illite formation (mostly K-4, Fig. 8). The affect of so-
lutions rich in calcium and sulphates/chlorides was
considered in the interpretation of dolomite alteration. We
assume that, for example, dissolved anhydrite layers could
serve as the source of calcium. A sufficient amount of Ca
2+
is
a critical factor for the process of dedolomitization (Kastner
1982; Back et al. 1983; Stoessell et al. 1987), and not a high
content of sulphates (Katz 1968; Land & Prezbindowski
1981; and others). However, the composition of the solutions
is still not clear (Land & Prezbindowski 1981; Stoessell et
Moore 1985).
Dedolomites created under conditions of deep burial (Bu-
dai et al. 1984) differ from close subsurface ones by having a
relatively high content of elements such as Sr, Fe, but also
Na. Na indicates non-meteoric origin of solutions (of water)
leading to the formation of the neomorphic calcites. It is typ-
ical for Fe that it is joined to the carbonate and oxide or hy-
droxide minerals. Comparing the content of observed ele-
ments in dolomites, limestones and diagenetic calcites, we
can see that neomorphic, coarse grained calcites have rela-
tively high content of the above mentioned elements, higher
than dolomites.
The isotopic ratios of O and C in the neomorphic calcites
significantly decreased, especially that of
δ
18
O. The
δ
13
C is
shifted only relatively, and still represents values of marine
carbonates and such values Budai et al. (1984) mentioned for
a joint type of dedolomites. The isotope values of the studied
rock specimens are in general comparable with the previous-
ly studied Triassic carbonates (Lintnerová & Hladíková
1992; Soták & Lintnerová 1994), and with some ancient
sabkha facies (Tucker 1990). Calcites forming fill of joints in
tectonized dolomites have also relatively high isotopic ratios,
although relatively lower then adjacent dolomites. It is im-
possible simply to identify these conditions only as a reflec-
tion of the thermal differentiation of isotopes in respect to an
evaporite environment and enrichment of oxygen ratio in a
DIAGENESIS AND POROSITY OF THE UPPER TRIASSIC CARBONATES 385
heavier isotope connected with that. This process can also be
considered for late diagenetic (dedolomitization) fluids, al-
though in a longer transport (higher amount of water) this ef-
fect could become less important. The Vienna Basin is re-
garded as a „cold basin“ and the interpolated temperatures at
the depth of 3000 to 4000 m are 107 to 127
o
C (max. 150
o
C:
Franko et al. 1995). From diagenetic alteration of the organic
matter of the Lunz Formation (3940 to 4550 m) a tempera-
ture range of 100 to 120
o
C was deduced (Borza et al. 1985).
The process of dedolomitization could quite well operate at
such temperatures (Stoessell et al. 1987).
Conclusions
1. Diagenetic post-sedimentation processes influenced the
properties of the dolomite rocks to a different extent. Most ex-
tensively the breccia layers in the depth of 3660 to 3830 m
were altered, so that significant values of secondary porosity
(locally up to 15 %) appeared.
2. The top parts of the dolomite sequences forming the ero-
sive surface of the Mesozoic basement to a certain extent pre-
served their properties since they were formed by dolomitiza-
tion in a sabkha environment. This is indicated by their
relatively high (evaporitic) isotopic ratio of O and C. Values of
isotopic ratios of calcitic and dolomitic cements (tectonic
breccia) were at least lowered, which could have been affected
precisely by the evaporite participation in the sequence.
The porosity changes are found in the calcitic dolomite to
limestone layers where sparitic, idiomorphic calcites with re-
mains of preceding dolomite can be observed. The microstruc-
tural and also geochemical properties of these calcites indicate
their late-diagenetic origin in the buried sediment. The
δ
18
O
was significantly decreased, but the content of microelements
as well as values of
δ
13
C remained relatively high.
Acknowledgements
: The analyses of the carbonate rocks
were performed in the chemical laboratories of the Geological
Institute of the Slovak Academy of Sciences (Bratislava). We
are grateful to Dr. B. Toman, Dr. A. Čelková and Dr. E. Mar-
tiny, and also to Dr. I. Holický for helpful assistance during
SEM study. The porosity measurements were done in the labo-
ratory of VVNP, (Research Oil Company, Bratislava) and our
thanks are given to Dr. S. Jakubov, Mr. J. Valček. The optical
colour porosimetry analyses were performed by Dr. J. Bebej
from the Geological Institute of the Slovak Academy of Sci-
ence, Banská Bystrica. The isotopic analyses were performed
in the Laboratories of the Czech Geological Institute in Pra-
gue. We are grateful to Dr. J. Hladíkova for precise analyses of
calcites and dolomites. We would like to thank the head of
VVNP, (Research Oil Company), Dr. J. Kováč for financially
supporting of the porosity measurements and isotopic analy-
ses. This work was partially supported by the Scientific Grant
Agency (VEGA) of the Ministry of Education of Slovak Re-
public and the Slovak Academy of Science (GJA 1/4090/97).
We are very obliged to Dr. J. Zelman (VVNP, Research Oil
Company) for the translation of this paper and Mrs. V. Mak-
kyová for typing. We want to give thanks to all anonymous
reviewers for their critical comments on the manuscript and
their suggestions to improve the paper.
References
Back W., Hanshaw B.B., Plummer L.N., Rahn P.H., Rightmire C.T.
& Rubin M., 1983: Process and rate of dedolomitization: Mass
transfer and
14
C dating in a regional carbonate aquifer. Geol.
Soc. Amer. Bull.,
1415–1420 .
Borza K., Masaryk P., Jendrejáková O., Franců J. & Lintnerová O.,
1985: The borehole Kuklov 3: Geological interpretation of
the Neogene basement. Unpublished report, Geofond, Brat-
islava, 1–69 (in Slovak).
Budai J.M., Lohmann K.C. & Owen R.M., 1984: Burial dedolo-
mite in the Mississippian Madison Limestone, Wyoming and
Utah Thrust Belt. J. Sed. Petrology, 54, 276–288.
DeGroot K., 1967: Experimental dedolomitization. J. Sed. Petrol-
ogy,
37, 1216–1220.
Fruth I. & Scherreiks R., 1982: Hauptdolomite (Norian) — stratigra-
phy, paleogeography and diagenesis. Sed. Geol., 32, 195–223.
Fruth I. & Scherreiks R., 1984: Hauptdolomite—sedimentary and
paleogeography models (Norian, Northern Calcareous Alps).
Geol. Rdsch.,
73, 305–319.
Fruth I. & Scherreiks R., 1985: Zur Fazies, Diagenese und Paläo-
geographie der nordalpinen Hauptdolomit Formation. Jber.
Staatl. Naturwiss. Samlungen Bayerns, Munchen,
7–16.
Frank J.R., 1981: Dedolomitization in the Taum Sauk Limestone
(Upper Cambrian), south-east Missouri. J. Sed. Petrology, 39,
380–385.
Franko O., Remšík A. & Fendek M. ( Eds.), 1995: Atlas of geo-
thermal energy of Slovakia. Slovak Geological Survey, Brat-
islava, 1–145 (in Slovak, English resume).
Hardy R. & Tucker M.E.,1 988: X-ray diffraction. In: Tucker
M.E.(Ed.): Techniques in sedimentology. Blackwell, Oxford,
191–228.
Holail H., Lohmann K.C. & Sanderson I., 1988: Dolomitization and
dedolomitization of upper Cretaceous Bahariya Oasis, Egypt.
In: Holail et al. (Eds.): Sedimentology and geochemistry of do-
lostones. SEPM Special Publication No. 43., 191–207.
Jiříček R., 1980: The Alpine-type Mesozoic geology of SE part Vien-
na Basin. Conference book, (The serious topics of the structural
geology in the Czechoslovakia),
Bratislava, 123–140 (in Czech).
Jiříček R., 1984: The correlation of Northern Calcareous Alps and
Western Carpathians in the Vienna Basin basement. Zem.
Plyn Nafta,
29, 177–203 (in Czech).
Fig. 9.
Isotopic results in graph documenting the diagenetic trend
in both groups of carbonate. Squares — dolomite K-3, circles —
calcite K-3, triangle — calcite K-4, rhombs — sample of Reifling
Limestones.
386 MASARYK and LINTNEROVÁ
Jiříček R. & Tomek Č., 1981: Sedimentary and structural evolu-
tion of the Vienna Basin. In: Vogel A. & Shan H. (Eds): Earth
evolution sciences. 1, 3/4, 195–204.
Kastner M., 1982: When does dolomitization occur and what con-
trols it. 11th Int. Congress Sedimentology, Hamilton, Ontario,
Canada,
1–124.
Katz A., 1968: Calcian dolomites and dedolomitization. Nature,
217, 439–440.
Land L.S. & Prezbindowski D.R., 1981: The origin and evolution
of saline formation water, Lower Cretaceous carbonates,
south-central Texas, USA. J. Hydrology, 54, 51–74.
Lintnerová O., 1988: Geochemical study of carbonate rocks of
Malé Karpaty Mts. and Vienna Basin basement. Unpublished
PhD theses, Geol. Inst. Slovak Acad. Sci.,
Bratislava, 1–133
(in Slovak).
Lintnerová O. & Hladíková J., 1992: Distribution of stable O and
C isotopes and microelements in the Triassic limestones of
the Veterlín Unit, The Malé Karpaty Mts.: Their diagenetic
interpretation. Geol. Carpathica, 43, 203–212.
Loucks V. & Elmore R.D., 1986: Absolute dating of dedolomitization
and the origin of magnetization in the Cambrian Morgan Creek
Limestone, Central Texas. Geol. Soc. Amer. Bull., 486–496.
Lumsden D.N., 1979: Discrepancy between thin-section and x-ray es-
timates of dolomite in limestone. J. Sed. Petrology, 49, 429–436.
Masaryk P., 1990: Sedimentology and the microfacies of the Trias-
sic carbonate rocks in the NW part Malé Karpaty Mts. Unpub-
lished PhD theses, Geol. Inst. Slovak Acad. Sci.,
Bratislava,
1–119 (in Slovak).
Masaryk P. 1996: The carbonate reservoir rocks. In: Janků (Ed.):
The evaluation of the hydrocarbons exploration prospectivi-
ties in the selected parts of the Western Carpathians. Unpub-
lish. report., Geofond,
Bratislava, 1–85 (in Slovak).
Masaryk P., Lintnerová O. & Jendrejáková O., 1988: The borehole
Kuklov 4: Geological interpretation of the Neogene basement.
Unpublish. report., Geofond,
Bratislava, 1–30 (in Slovak).
Masaryk P., Lintnerová O. & Michalík J., 1993: Sedimentology,
lithofacies and diagenesis of the sediments of the Reifling in-
traplatform basins in the Central Western Carpathians. Geol.
Carpathica,
44, 233–249.
McCrea J.M., 1950: The isotopic composition of carbonate and
paleotemperature scale. J. Chem. Phys., 18, 849-857.
Mišík M., 1986: Fluorite and celestine originated from triassic car-
bonate rocks of the Vienna Basin basement. Miner. slovaca,
18, 259–266 (in Slovak).
Mišík M., 1988: Pebble dedolomitization in conglomerate of the
Pieniny exotic ridge and in other West Carpathian conglomer-
ates. Geol. Zbor. Geol. Carpath., 39, 3, 267–284.
Osborne M., Haszeldine R.S & Fallick A.E., 1994: Variation in kaolinite
morphology with growth temperature in isotopically mixed pore-
fluids, Brent Group, UK North Sea. Clay Miner., 29, 591–608.
Ostrolucký P., 1994: Geology and hydrocarbon accumulations in
the basement of the Slovak part of Neogene Vienna Basin.
Unpublished PhD theses. Comenius University,
Bratislava, 1–
169 (in Slovak).
Ostrolucký P. & Jiříček R., 1986: Borehole Kuklov 3, the finish
administrative report. Unpublish. report, Geofond, Bratislava,
9–63 (in Slovak).
Rao C.G., 1969: Dolomitization, dedolomitization and the dolo-
mite question in carbonaterocks. In: Selected lectures on pe-
troleum exploration. Institute Petrol. Explor. Oil Natural Gas.
Comm.,
Dehra Dun, India, Vol. 1, 209–216.
Sauer R., Seifert P. & Wessely G. (Eds.), 1992: Guidebook to excur-
sions in the Vienna Basin and the adjacent Alpine-Carpathian
thrustbelt in Austria. Mitt. Österr. Mineral. Gesell., 85, 1–258.
Scherreiks R., 1971: Stratigraphie und Faziesentwicklung der
Norischen Kalk-Dolomit - Folge (Hauptdolomit) der östli-
chen Lechtaler Alpen. Ph.Thesis, Univ. Munchen, 1–79.
Soták J. & Lintnerová O., 1994: Diagenesis of the Veterlín reef
complex (Malé Karpaty Mts., Western Carpathians): Isotope
geochemistry, cathodoluminescence and fluid inclusion data.
Geol. Carpathica
, 45, 239–254.
Stoessell R.K., Klimentidis R.E. & Prezbindowski D.R., 1987:
Dedolomitization in the Na-Ca-Cl brines from 100
o
to 200
o
C
at 300 bars. Geochim. Cosmochim. Acta, 51, 847–855.
Stoessell R.K. & Moore C.H., 1985: Chemical constraints and ori-
gins of four groups of Gulf Coast Reservoir Fluids: Reply.
AAPG. Bull.,
69, 122–126.
Tucker M. E., 1990: Dolomites and dolomitization models. In:
Tucker M. E. & Wright V. P. (Eds.): Carbonate sedimentology.
Blackwell,
365–400.
Wessely G., 1983: Zur Geologie und Hydrodynamik im südlichen
Wiener Becken und seine Randzone. Mitt. Osterr. Mineral. Ge-
sell.,
76, 27–68.
Wessely G., 1988: Structure and development of the Vienna Basin
in Austria. In: Royden L. H. & Horváth F. (Eds.): Pannonian
Basin, a study of basin evolution
. AAPG Memoir, 45, 333–346.