GEOLOGICA CARPATHICA, 53, 3, BRATISLAVA, JUNE 2002
191 — 195
FORAMINIFERS AS AN INDICATOR OF PALEOBATHYMETRY
IN THE GOSAU GROUP OF EASTERN AUSTRIA
Czech Geological Survey, Klárov 131/3, 118 21 Praha 1, Czech Republic; email@example.com
(Manuscript received January 17, 2002; accepted in revised form May 9, 2002)
Abstract: Paleoecological studies indicate environmental changes during selected time horizons within the Upper Cre-
taceous sediments from three localities of the Gosau Group in Austria. Foraminiferal assemblages were studied from the
localities Grünbach-Neue Welt, Weissenbachalm and Spital am Pyhrn. Paleobathymetric changes have been recon-
structed using plankton/benthos ratio, percentual abundances of selected genera and species diversity. Three depth levels
with three groups of dominating species were recognized from the Late Turonian to Early Santonian sediments of the
Grabenbach Formation at Weissenbachalm locality. From the Grünbach-Neue Welt area the Grünbach Formation (Early
Campanian) and Piesting Formation (Late Campanian-Early Maastrichtian) comprise transitional assemblages from
shallow-water, neritic marls to bathyal hemipelagics and turbidites. The character of foraminiferal assemblages of the
Weisswasser Formation indicates shallow-water shelf conditions during Late Santonian and Early Campanian. The deeper
water Wurberg Formation contains richer foraminiferal assemblages with higher species diversity.
Key words: Austria, Northern Calcareous Alps, Gosau Group, Upper Cretaceous, paleoecological study, foraminifers.
Lee & Anderson (1999) wrote “The modern foraminifers are
one of the most important groups of marine protozoa on the
earth which play a significant role in the global biochemical
and ecological cycles of organic compounds. We can propose
that they have had the same position also during history of
earth as an indicator of paleoenvironmental changes.”. This pa-
leoecological study of foraminiferal assembages from the Gos-
au Group of the Northern Calcareous Alps shows, on the basis
of ecological data of selected genera by Murray (1991), Lom-
merzheim (1991) and Koutsoukos & Hart (1990) (Table 1) pa-
leobathymetric and paleotemperature changes during the Late
Cretaceous in the area of the Gosau Basin in Austria. Foramin-
iferal assemblages were studied from the localities Weissen-
bachalm, Grünbach-Neue Welt and Spital am Pyhrn (Fig. 1).
This study was done within the Visegrád 45-2001-IVF Project
and partly also within Grant Project No. 205/99/1551 support-
ed by the Grant Agency of the Czech Republic and the bilater-
al cooperation between the Czech Geological Survey, Praha
and Geologische Bundesanstalt, Vienna.
The characterization of studied localities
The small E-W striking Gosau deposits of the Weissen-
bachalm area (Lower Gosau Subgroup) is situated in the ex-
tremely tectonically deformed central part of the Northern Cal-
careous Alps. The deposits of the Gosau Group are
represented by an approximately 25 m high outcrop of grey
marls (Hradecká et al. 1999a). From the main profile of the
Weissenbachalm (Grabenbach Formation) five samples (WB4,
WB6, WB5, WB16) have been studied. Several other isolated
outcrops (WB1, WB2, WB9, WB10, WB21, WB3, WB8,
WB22, WB23, WB7, WB2, WB11, WB17) were sampled and
studied for additional information.
Grünbach-Neue Welt area
The classical area of the Grünbach-Neue Welt Gosau Group
is situated SE of the Hohe Wand mountain range, close to the
eastern margin of the Northern Calcareous Alps. From this
area only isolated samples from the Piesting Formation
(former “Inoceramus Marls”), (Summesberger et al. 2000)
from Grünbach, Zweiersdorf, Dörfles, (Grü8, ZW3-9, Dö1)
and the Grünbach Formation (former “Coal-Bearing Serie”),
the sample Mai1, have been collected (Hradecká et al. 1999b).
The samples of Gosau sediments from the region north of
Spital am Pyhrn belong to the marl-sandstones succession of
the fan delta complex of the Wurberg Formation and marl to
siltstone storm deposits of the Weisswasser Formation (Kreuss
1994; Hofmann, personal communication).
During these preliminary paleoecological interpretations in
the studied regions, only basic, classical methods such as the
plankton/benthos ratio, quantitative analyses – percentual
abundance of selected genera and the species diversity were
applied. Quantitative analyses were done from the identical
quarto of the size fraction > 0.063 cm. From a consistent vol-
ume unit of one cubic centimetre (1 cm
) a minimum of 200
specimens was counted. Diversity was determined using the
Fig. 1. The position of the studied localities of the Gosau Group in the Northern Calcareous Alps in Austria.
Table 1: Ecological data for selected genera according to Murray (1991), Lommerzheim (1991) and Koutsoukos & Hart (1990).
infaunal free; muddy sediment; detritivore; brackish-marine; temperate-tropical; brackish
marsches and lagoons; inner shelf – upper bathyal
infaunal-epifaunal free; muddy sediment; ?detritivore; marine; cold-warm; inner shelf – bathyal
epifaunal, attached; hard substrates; ?passive spension feeder; marine; warm-temperate;
50-500 m; shelf and upper bathyal
epifaunal, free; fine sands and mud; ?detritivore; marine; cold; shelf – bathyal
infaunal, free; mud-sand; ?detritivore; marine; 35 – 1235 m; temperate-cold; marshes – bathyal
infaunal, free; mud; ?detritivore; marine; temperate-cold; outer shelf – bathyal
epifaunal, free; mud; ?detritivore; marine; cold; outer shelf and bathyal
epifaunal, free; ?
infaunal, free; mud; detritivore; marine; cold; outer shelf to bathyal
epifaunal, free or clinging; plants or sediment; herbivore; marine-hypersaline; 32–65 ‰; cold-
warm; hypersaline lagoons, marine shelf, rarely bathyal
epifaunal, clinging; hard substrates; marine; temperate-cold; 1–100 m; inner shelf
epifaunal or infaunal, free; sediment; herbivore or detritivore; 0–60‰; cold-warm 0–30 ºC;
0 to 6000 m; intertidal shelf, bathyal, abyssal
FORAMINIFERS AS AN INDICATOR OF PALEOBATHYMETRY 193
Fig. 4. Plankton/benthos ratio of the foraminiferal assemblages
from the Grünbach-Neue Welt Gosau Group sediments.
Fig. 2. Plankton/benthos ratio of the foraminiferal assemblages
from the Weissenbachalm sediments.1 – plankton, 2 – benthos.
Fig. 3. The percentual abundances of selected genera from the
Weissenbachalm Grabenbach Formation (Lower Gosau Sub-
group). Legend same as Fig. 6.
On the basis of the studies of Butt (1981) and Wagreich &
Faupl (1994) in respect to foraminiferal paleoecology and pa-
leobathymetry in the Gosau Group, the following have been
recognized at the Weissenbachalm locality (Hradecká et al.
1 – Shallow-water conditions with water depths of about
10—20 m, pertaining to the inner neritic environment sensu
Wagreich & Faupl (1994), were determined in samples WB1,
WB4, WB9, WB10, on the basis of the abundance of benthic
foraminifers such as Quinqueloculina, Spirillina and Spiroloc-
ulina. These species tolerated not only cold but also warm wa-
ter. The plankton/benthos ratio is about 20—30 % (Fig. 2). The
genus Hoeglundina is characteristic for the shallow-water fa-
cies of these Gosau Group sediments.
2 – The second group of samples (WB3, WB6, WB7,
WB8) contains many calcareous species of the genera Praebu-
limina, Gavelinella and Gyroidinoides, nevertheless their tests
are smaller in size. The plankton/benthos ratio ranges between
40—60 %. Small juvenile tests of Globigerinelloides and Hete-
rohelix dominate the planktonic assemblages. The foramin-
iferal assemblage probably represents the middle neritic envi-
ronment with water depths of 30—100 m (Wagreich & Faupl
3 – The third group of samples (WB2, WB5, WB11,
WB16, WB17) belongs to the stratigraphic interval of the Late
Coniacian—Early Santonian. Rich plankton-dominated assem-
blages (about 70 %) also contain abundant benthic species be-
longing to the genera Gavelinella, Praebulimina, Dentalina
and Lenticulina. Where paleobathymetry is concerned, the
sedimentation took place in the deepest parts of the shelf sea,
which represents the outer neritic environment.
4 – All three foraminiferal assemblages from the Graben-
bach Formation of the Weissenbachalm locality show evi-
dence of the shallow-marine facies of the Lower Gosau Sub-
group as described by Wagreich & Faupl (1994) within the
Late Turonian—Campanian interval. Nevertheless, changes in
foraminiferal assemblages related to a gradual sea-level rise
were recorded during the Coniacian. The predominance of
Quinqueloculina (40—95 %) in samples WB21, WB22, WB23
suggests the occurrence of closed small basins with hypersa-
line conditions (Höfling 1985) (Fig. 3).
In the Grünbach-Neue Welt area two paleobathymetric
zones were determined on the basis of the plankton/benthos
ratio (Fig. 4).
1/ Outer neritic of Early Campanian age – sample Mai1
(Grünbach Formation) and samples Grü2,3,5 and Zw7 (Piest-
ing Formation) of Late Campanian age.
2/ Upper-middle bathyal in the Late Campanian—Early
Both facies belong to the transition between shallow-water
macrofossil-rich marls and bathyal hemipelagites and turbid-
ites (Piller et al. 1997; Wagreich & Summesberger 2001), (Fig.
5). Paleobathymetry based on the plankton/benthos ratio (40—
Fig. 6. The percentual abundances of selected genera from the Grünbach-Neue Welt Gosau Group (Piesting Formation + Grünbach For-
mation) and Spital/Pyhrn (Weisswasser Formation, Wurberg Formation).
Fig. 5. Upper Cretaceous lithostratigraphy of the Gosau Group in studied localities (based on Summesberger et al. 2000; Wagreich &
Summesberger 2001; Kreuss 1994).
60 %) indicates water depths of about 200 m, which implies an
outer neritic environment. The Late Campanian and Early
Maastrichtian sediments were probably deposited in a deeper
marine environment (upper-middle bathyal) dominated by
keeled planktonic species of the genera Globotruncana, Glo-
botruncanita and Globotruncanella (80—90 %).
The foraminiferal assemblages indicate a mixture of cold
and warm water-preferring taxa. Gyroidinoides, Haplophrag-
moides, Lenticulina etc. are present in an association of typical
Tethyan species, which suggests an influence of cold water
currents in the deeper water environment (Fig. 6). The change
in water temperatures from warm to cool-temperate during the
FORAMINIFERS AS AN INDICATOR OF PALEOBATHYMETRY 195
Campanian probably corresponds to a global climatic event
The washed material from the Weisswasser Formation at
Spital/Pyhrn locality contained poor foraminiferal assemblag-
es characterized by low diversity. Within the benthic species
specimens of the calcareous benthic genus Hoeglundina pre-
dominate (Fig. 6). This prevalence over planktonic species and
the presence of rather cold-preferring species may suggest
cooler temperate environments.
The content of planktonic species was 1—20 %. This differ-
ence is probably caused by sudden basin subsidence and the
local deepening of the basin (Wagreich 1989).
The character of foraminiferal assemblage indicates shal-
low-water shelf conditions (Fig. 7) with water depths probably
about 30—100 m (Wagreich & Faupl 1994).
The sediments from the Wurberg Formation (distal facies)
contain richer foraminiferal assemblages (Fig. 6). The diversi-
ty was slightly higher – 57 foraminiferal species were found.
The presence of Stensioeina as a representant of deeper water
depths (Wicher & Bettenstaedt 1957) may indicate fluctua-
tions of the sea level in an otherwise shallow-water environ-
ment. We interprete paleo-water depths of about 100—200 m
(Wagreich & Faupl 1994).
Paleoecological studies of the foraminiferal assemblages
from three localities of the Gosau Group showed environmen-
tal changes during certain stratigraphic levels of the Upper
During these first paleontological interpretations in the stud-
ied region, only basic ecological methods were applied. For a
more detailed study in the future the gained data based on mul-
tivariate methods such as cluster analyses, principal coordinate
Fig. 7. Reconstruction of the Late Santonian-Early Campanian pa-
leogeography of the Spital/Pyhrn locality (according to Kreuss
analyses etc. could be interesting for the paleoecological stud-
ies in this area.
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