lower cretaceous calcareous algae and foraminifera from trbušnica
Transcript of lower cretaceous calcareous algae and foraminifera from trbušnica
ACTA PALAEONTOLOGICA ROMANIAE (2014) V. 10 (1-2), P. 95-104
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1 Babeş-Bolyai University, Department of Geology and Center for Integrated Geological Studies, str. M. Kogălniceanu nr. 1,
400084 Cluj-Napoca, Romania. [email protected] 2 Faculty of Ecology and Environmental Protection, Department of Geology, Union-Nikola Tesla University, Cara Dusana 62-64, 95
11 000 Beograd, Serbia. [email protected] 3 Kralja Petra I, 38, 11158 Beograd, Serbia. [email protected]
LOWER CRETACEOUS CALCAREOUS ALGAE AND FORAMINIFERA FROM
TRBUŠNICA (VARDAR ZONE, SERBIA)
Ioan I. Bucur1, Svetlana Polavder2 & Rajka Radoičić3
Received: 15 September 2014 / Accepted: 12 November 2014 / Published online: 18 November 2014
Abstract The basal part of the Miocene sedimentary deposits from Trbušnica region (south-west of Belgrade, Serbia,
Vardar zone) consists of conglomerates containing pebbles of Mesozoic limestones. The study of two of these
pebbles led to the identification of an interesting assemblage of dasycladalean calcareous algae with Andreiella
rajkae, Montiella elitzae, Neomeris sp., Salpingoporella muehlbergii, Salpingoporella gr. pygmaea, Salpingoporella
sp., Suppiluliumaella gr. polyreme, ?Suppiluliumaella sp., Suppiluliumaella sp., Triploporella sp. and Zittelina
hispanica. Foraminifera accompany this algal association: in one of the samples Montseciella arabica is dominant,
while the other one contains orbitolinid fragments (possibly Palorbitolina lenticularis). The two orbitolinids point to
a Late Barremian – earliest Aptian (early Bedoulian) age for the studied limestone pebbles.
Keywords: orbitolinids, dasycladaleans, Lower Cretaceous, Serbia
INTRODUCTION AND GEOLOGICAL SETTING
The study area is located southwest of Belgrade, between
Rudovci and Trbušnica localities where Neogene deposits
(Middle Miocene and Pliocene) crop out (Fig. 1, based on
Filipović et al., 1976, geological map 1: 100000, sheet
Obradovac). In the area located between the Bistrička
River and Trbušnica Upper Cretaceous (“Senonian”)
rocks are topped by basal Miocene conglomerates.
These conglomerates contain numerous calcareous
pebbles assigned to the Jurassic or Cretaceous, besides
Paleozoic metamorphic ones. Locally, the composition of
the pebbles is dominated by gabbro, diabase, pyroxenite
and serpentine, imprinting a characteristic feature of these
deposits. The conglomerates are overlain by coarse or
fine sandstones, and rarely by marls with coal interbeds
(Fig. 2).
The conglomerates cropping out in the Trebušnica area
Fig. 1 Geological map of the Trbušnica area (modified from Filipović et al., 1976). The star indicates the location
of the samples; 1. Igneous rocks; 2. Metamorphic rocks; 3.Upper Cretaceous (“Senonian”); 4.Middle Miocene;
5.Pliocene; 6.Fault
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contain numerous limestone pebbles of Early Cretaceous
age, some with microfossil content that can be identified.
We have studied 10 thin sections obtained from two
samples (sample RR013234, thin sections RR4523,
RR4524, RR4525, RR4527, and sample RR013205, thin
sections RR4516, RR4517, RR4518, RR4519, RR 4520
and RR4521). The present paper briefly describes the
calcareous algae and the foraminifera identified in this
material, in order to more closely understand the age
relationships of the pebbles. The samples are part of
Rajka Radoičić’s private collection.
Fig. 2 Succession of the Miocene rocks from Trbušnica area
(modified from Filipović et al., 1976).
MICROFACIES
Three microfacies types have been defined in the
investigated pebbles.
1. Bioclastic coarse grainstone/rudstone with
Montseciella (Fig. 3 a-c). Fragments of corals, bivalves,
gastropods and echinoderms, calcareous algae and
foraminifera are the main biogenic components.
Additionally, rivulariacean-type cyanobacteria,
Bacinella-type structures, oncoids with micritic cortex
and neoformed quartz – the latter mainly located in the
oncoids' cortexes – were also identified. They are
accompanied by dasycladalean algae, rare udoteacean
algae (Arabicodium sp.) and foraminifers – among which
Montseciella is dominant. Locally, lithoclasts of
sandstones, crystalline limestones or siliceous rocks are
present.
2. Bioclastic rudstone with Zittelina (Fig. 3 d). It contains
large coral fragments, sclerospongia fragments, bivalves,
gastropods and echinoderms, dasycladalean algae,
Bacinella-type structures and orbitolinids, which
agglutinate large amounts of terrigenous quartz.
3. Bioclastic rudstone/floatstone with Triploporella (Fig.
3 e, f). It includes fragments of corals, sponges, bivalves
and echinoderms. The corals are sometimes encrusted by
red algae (Polystrata alba and Sporolithon rude).
Besides, we have identified encrusting foraminifers,
fragments of orbitolinids, nodosariids, dasycladalean
algae and the microproblematicum Carpathoporella.
FORAMINIFERA
The studied Lower Cretaceous pebble samples contain
numerous sections of the orbitolinid Montseciella arabica
(sample RR013235). Additionally, rare specimens of
Charentia cuvillieri, Everticyclammina sp.,
?Palorbitolina lenticularis (sample RR013234),
miliolids, nodosariids and other non-identified
foraminifers were found.
Genus Montseciella Cherchi & Schroeder, 1999
Montseciella arabica (Henson, 1948) Schroeder et al.,
2002
Fig. 4 a-l.
Description. Conical test (Fig. 4 a-e), 1.0-2.3 mm in
diameter and 1.0-1.8 mm in height, displaying about 14
chamber layers per millimeter in the axial-sub-axial
plane. We did not observe embryos, with the possible
exception of the specimen illustrated in Fig. 4 l where the
presence of an eccentric one might be assumed. An
eccentric embryo location is also suggested by the overall
configuration of the apical area of the specimen in Fig. 4
e.
One of the typical features for this species is represented
by the rudimentary radial partitions in the external part of
the central area, as extensions of the marginal chambers'
separating walls (Fig. 4 g, h, k) (Schroeder & Cherchi,
1979; Baud et al., 1994; Cherchi & Schroeder, 1999;
Maksoud et al., 2014). Especially based on this feature,
Schroeder et al. (1968) have assigned this species
originally ascribed to Dictyoconus by Henson (1948) to
the genus Paleodictyoconus. Subsequently, Schroeder et
al. (2002) have transferred it to the genus Montseciella.
The inner part of the central area is separated by pillars
displaying vermicular or pillar-like structures (Fig. 4 g,
k). The pillars alternate from one chamber layer to
another (Fig. 4 a-f). The chamberlets from the marginal
area are subdivided by one rather short horizontal plate
(Fig. 4 a-f) and one or two vertical ones (Fig. g-i, k), the
result being the formation of sub-epidermal chamberlets
(Fig. 4 j). The apertural pores with diagonal display are
visible in the subaxial (Fig. 4 a-f), as well as in the
oblique (Fig. 4 h) or the transversal-oblique sections (Fig.
4 g, k).
Remarks. In a recent publication, Schroeder et al. (2010)
have summarized the existing data and revised the
biostratigraphical zonation based on orbitolinids, as well
as on the phyletic lineages of Barremian-Aptian
orbitolinids. Accordingly, the Barremian-Aptian interval
was divided into six zones and three subzones.
Montseciella arabica is present in deposits covering
Lower Cretaceous calcareous algae and foraminifera from Trbušnica (Vardar zone, Serbia)
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Fig. 3 Microfacies of the Lower Cretaceous limestone pebbles from Trbušnica. a-c Coarse grainstone to rudstone
containing bivalve, gastropod and echinoderm fragments, rare coral fragments, cortoids and bacinellid oncoids as well
as rare metamorphic, siliceous and sandy lithoclasts. Neoformation quartz is preferentially located in the micritic
cortex of some oncoids. Large dasycladaleans (Andreiella, Suppiluliumaella) and orbitolinid foraminifera
(Montseciella) are present; a, thin section RR4516; b, c, thin section RR4518. d Bioclastic rudstone with bivalve,
gastropod, echinoderm, sponge and rare coral fragments. Reworked orbitolinids agglutinating terrigenous quartz
(?Palorbitolina), as well as large dasycladaleans (Zittelina) are present. Thin section RR4524. e, f Rudstone/floatstone
with coral, bivalve, sponge and echinoderm fragments, large dasycladaleans (Triploporella) and foraminifera. The
large bioclasts are encrusted by foraminifera and red algae (Polystrata and Sporolithon); e, thin section RR4525; f,
thin section RR4527. Scale bar = 1 mm.
Ioan I. Bucur, Svetlana Polavder & Rajka Radoičić
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almost the whole Late Barremian to earliest Aptian
interval. This species is extremely abundant in the Late
Barremian, where it represents the index species for the
M. arabica subzone.
DASYCLADALEAN ALGAE
The dasycladalean algae assemblage identified in the
studied samples includes: Andreiella rajkae, Montiella
elitzae, Neomeris sp., Salpingoporella muehlbergii,
Salpingoporella gr. pygmaea, Salpingoporella sp.,
Suppiluliumaella gr. polyreme, ?Suppiluliumaella sp.,
Triploporella sp. and Zittelina hispanica. A brief
description of these species in alphabetical order follows.
We used the following symbols for the measured size
parameters: D = external diameter of the thallus; d =
diameter of the axial cavity; l = length of the primary
laterals; p = width of the primary laterals; l’ = length of
Fig. 4 Foraminifera from the limestone pebbles of Trbušnica. a-l Montseciella arabica (Henson); a-f, l, subaxial
sections; g, k, transverse-oblique sections; h, i, obliques sections; j, tangential-oblique section. a, c, f, g-j, thin section
RR4518; b, e, k, l, thin section RR4521; d, thin section RR4516. Scale bar = 0.25 mm.
Lower Cretaceous calcareous algae and foraminifera from Trbušnica (Vardar zone, Serbia)
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the secondary laterals; p’ = width of the secondary
laterals; h = distance between two successive verticils; w
= number of primary laterals in a verticil; w’ = number of
secondary laterals per primary one.
Genus Andreiella Bucur, 2014
Andreiella rajkae Bucur, 2014
(Fig. 5 e)
Andreiella rajkae was recently described by Bucur (2014)
from Upper Barremian – lowermost Aptian (lower
Bedoulian) limestones in the Hăghimaş Mountains
(Eastern Carpathians, Romania). It is characterized by a
cylindrical thallus with a narrow main stem and two
orders of laterals. The first order laterals, large and club-
shaped, gradually broaden from the proximal to the distal
part where they slightly narrow towards the exterior. The
secondary laterals are short and vesiculiform to ovoid in
shape. Calcification forms an irregular sleeve around the
distal end of the primary laterals, embedding the
secondary ones.
A single specimen was identified in the studied samples
from Trbušnica (Fig. 5 e), however it is very
representative for the species. Until this study, A. rajkae
has been identified in only three sites: Mount Rujen
(Vardar zone, Macedonia) (Radoičić, 2002), Bicaz
Gorges (Hăghimaş Mountains, Eastern Carpathians,
Romania) (Bucur & Săsăran, 2011; Bucur, 2014), and
Munella Platform (Albania) (Schlagintweit, unpublished;
Bucur, 2014). Thus, Trbušnica represents the fourth
location for this species.
Dimensions (mm): D = 2.60; d = 0.60; p (distal) = 0.30;
p’ = 0.07.
Genus Montiella L. Morellet & J. Morellet, 1922
Montiella elitzae (Bakalova, 1971) Radoičić, 1980
(Fig. 5 d)
Only one specimen, cut in tangential-oblique-longitudinal
section revealing only partly the axial cavity, was
identified. Nevertheless, it displays the typical
arrangement of the fertile and sterile secondary laterals.
Dimensions (mm): D = 1.0; d = 0.11; Diameter of the
fertile ampoules = 0.26.
Genus Neomeris Lamouroux, 1916
Neomeris sp.
(Fig. 5 g, h)
We have identified two specimens in sub-transversal
section, both showing secondary laterals and ovoidal
fertile ampoules similar to those of Neomeris cretacea
Steinmann. However, while oblique or longitudinal
sections are missing, a species assignment cannot be
without doubt.
Dimensions (mm): D = 1.30-1.50; d = 0.65; l’ = 0.20-
0.32; length of fertile ampoules = 0.15-0.20; width of
fertile ampoules = 0.07.
Genus Salpingoporella Pia in Trauth 1918, emend.
Carras et al., 2006
Salpingoporella muehlbergii (Lorenz, 1902) Pia in
Trauth, 1918
(Fig. 6 a, b)
Only a few specimens were identified in thin section
RR4518 that display the typical shape and size features
for the species Salpingoporella muehlbergii. This is one
of the most frequent dasycladaleans found in Barremian –
Aptian deposits in the Tethys area.
Dimensions (mm): D = 0.37-0.50; d = 0.15-0.20; p
(distal) = 0.08-0.10; h = 0.10.
Salpingoporella gr. pygmaea (Gümbel, 1891) emend
Carras et al., 2006
(Fig. 6 d)
Also in the case of this species, only a few specimens
were identified – mainly cut in oblique sections.
Dimensions (mm): D = 0.78; d = 0.35; l = 0.25-0.30.
Salpingoporella sp.
(Fig. 6 c, e)
We have identified a few larger specimens in a poorer
preservation state than that of S. muehlbergii, showing
about eight phloiophorous laterals per verticil and a thick
calcareous wall; however, a distinct species assignment is
difficult.
Dimensions (mm): D = 0.62-0.77; d = 0.15-0.32; l = 0.22;
p (distal) = 0.10-0.15.
Genus Suppiluliumaella Elliott, 1968
Suppiluliumaella gr. polyreme Elliott, 1968
(Fig. 6 f, h)
The specimens identified in the Trbušnica samples are
present in transversal-slightly oblique sections. The
primary laterals are originally tubular but then they
broaden distally, giving rise to 4-6 secondary laterals
directly connected to the distal part of the primary
laterals, without constrictions (like the fingers of a glove).
Dimensions (mm): D = 1.20-2.10; d = 0.80-0.95; l =
0.30-0.65; p’ (distal) = 0.15-0.20; l’ = 0.15-0.20.
Remarks. Bakalova (1971) has described two new species
of Suppiluliumaella: S. praebalcanica and S. elliotti. The
difference between the first and S. polyreme is
represented by the presence of third order laterals, a
feature that still needs to be documented. S. elliotti differs
from S. polyreme …”par l’absence de parois autour de la
cellule axiale” [while it shows no wall around the axial
cell] (Bakalova, 1971: 125). Table A (in Bakalova, 1971)
summarizing the size differences recorded for the three
species (S. polyreme, S. praebalcanica and S. elliotti)
shows little discrimination, being mainly a proof for
some dimensional overlaps. Some of the apparent
differences may be the result of different sectioning
angles: most of the specimens described by Bakalova
(1971) are present in oblique and transverse sections, in
which the inclination of the primary laterals, their length,
the length of the secondary laterals etc. are more difficult
to evaluate. One cannot exclude that the two species
identified by Bakalova (1971) are recent synonyms for
the species S. polyreme. More samples, including
topotype material, need to be studied in order to confirm
this assumption.
Dimensions (mm): D = 2.10-2.10; d = 0.80-0.95; l =
0.35-0.65; l’ = 0.15-0.20; p (distal) = 0.15-0.20; p’ =
0.05-0.07; w = 18-20.
?Suppiluliumaella (Fig. 6 g, j, k)
Ioan I. Bucur, Svetlana Polavder & Rajka Radoičić
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Fig. 5 Dasycladalean algae from the limestone pebbles of Trbušnica. a-c, f Zittelina hispanica Masse, Arias & Vilas.
Transverse-slightly oblique (a, b) and oblique (c) sections; f, enlargement of the lower part of the specimen in b. a, c,
thin section RR4524; b, thin section RR4523. d Montiella elitzae (Bakalova) in longitudinal-subaxial section; thin
section RR4521. e Andreiella rajkae Bucur in oblique section; thin section RR4516. g, h Neomeris sp. in transverse
sections; thin section RR4518. Scale bar = 0.25 mm.
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Fig. 6 Dasycladalean algae from the limestone pebbles of Trbušnica. a, b Salpingoporella muehlbergii (Lorenz);
longitudinal-oblique (a) and transverse-oblique (b) sections; thin section RR4518. c, e Salpingoporella sp. in transverse
section (c) and oblique section (e); thin section RR4518. d Salpingoporella gr. pygmaea (Gümbel) in oblique section; thin
section RR4518. f, h Suppiluliumaella gr. polyreme Elliott; transverse-slightly oblique sections; e, thin section RR4516; h,
thin section RR4517. i ?Triploporella sp.; longitudinal-oblique section, thin sectionRR4518. g, j, k ?Suppiluliumaella sp.
in oblique sections (g, j) and longitudinal-oblique (k) sections; g, thin section RR4519; j, k, thin section RR4521. Scale
bar = 0.25 mm.
Ioan I. Bucur, Svetlana Polavder & Rajka Radoičić
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Present as fragments of relatively large thallus with
ovoidal to ovoidal-elongated-cylindrical primary laterals
that are approximately perpendicular to the axial cavity to
which they are connected through a short peduncle, and
with Suppiluliumaella-type secondary laterals.
Dimensions (mm): D = 1.80-2.50; d = 0.60-0.80; p
(maximum) = 0.30; l = 0.55; p’ = 0.08-0.10; l’ = 0.20; h =
0.10-0.12.
Remarks. Similar specimens were identified in Upper
Barremian – basal Aptian limestones from Bicaz Gorge
(Eastern Carpathians, Romania) (Bucur & Săsăran, 2011:
60-61, Plates 10-11). In spite of the similitude of the
laterals' morphology between this form and genus
Dissocladella, the authors (Bucur & Săsăran, 2011) have
considered that they represent sections through the lower
part of the Suppiluliumaella elliotti thallus (see also
Barattolo, 1983, with a reconstruction of
Suppiluliumaella showing different morphologies and
different inclination of laterals along the axis).
Unfortunately, no section illustrating the continuity
between the two parts of the same algae was identified:
thus, this assignment is still questionable.
Genus Triploporella Steinmann, 1880
?Triploporella sp.
(Fig. 6 i)
We have identified a longitudinal-oblique section through
a specimen that shows well-preserved primary laterals.
They are slightly inclined in respect to the axial cavity.
The distal, probably broadened part of these laterals, as
well as the secondary laterals, are not clearly visible.
Dimensions (mm): D = 1.94; d = 0.64; l = 0.60; p (distal)
= 0.22; h = 0.20.
Triploporella sp.
(Fig. 7 a-g)
In three of the studied sections obtained from sample
RR013234 we have identified the rests of a large
Triploporella species present in transversal-oblique
sections (Fig. 7 a-d); one fragment is present in a
longitudinal-oblique section (Fig. 7 b).
The two transversal sections differ in the size of the axial
cavity and in the display of the laterals. The specimen in
Fig. 7 a shows a broad axial cavity, while that in Fig. 7 d
shows a narrower one. Also, the laterals seem to be less
inclined in the first specimen (Fig. 7 a) and more inclined
in the second one (Fig. 7 d). These features point to the
fact that the alga may display a claviform thallus with a
narrower external diameter and axial cavity in the lower
part (Fig. 7 d) broadening towards the upper part (Fig. 7
a). Secondary laterals are not visible (possibly they are
primarily not-calcified). Typical for the specimens from
Trbušnica are the very small cyst-containers (Fig. 7 b, c,
e-g) as compared to those in other Triploporella species
(e.g. Bucur et al., 2013). At a first glance, they seem to be
simple cysts; when investigated in detail, some show
inner round, micritic corpuscles, and can be considered
intracellular receptacles-type reproducing organs – cyst-
containers that are typical for the genus Triploporella and
are present in most species of this genus (Barattolo, 1980,
1981; Barattolo et al., 2013). Such small cyst-containers
were recently noticed also in other Triploporella
specimens identified in Upper Aptian limestones from the
Apuseni Mountains (Romania) (Bucur et al., 2013).
Dimensions (mm): D = 5.60-6.60; d = 2.00-4.20; l =
1.40-1.50; p = 0.25-0.30; w = 45-70; diameter of cyst-
containers = 0.050-0.090/0.040-0.070; cyst diameter =
0.020-0.030.
Genus Zittelina L. Morellet & J. Morellet, 1913
Zittelina hispanica Masse, Arias & Vilas, 1993
(Fig. 5 a-c, f)
Three specimens of a large dasycladalean alga were
identified in transverse-slightly oblique (Fig. 5 a, b) and
oblique (Fig. 5 f) sections. The thallus is calcified only
around the central stem and at the distal end of the
laterals. The area between the two calcified zones is filled
with calcified and partly cement-bound cyst-containers,
around the original area of the primary laterals (Fig. 5 f).
Two Zittelina species are known in Lower Cretaceous
deposits: Z. hispanica and Z. massei (Bucur et al., 2010).
Based on their overall appearance, mainly on the width of
the axial cavity and the d/D ratio, we consider that the
Trbušnica specimens correspond to species Zittelina
hispanica.
Dimensions (mm): D = 5.10-5.90; d = 2.90-3.50; l =
1.10-1.30; cyst-container diameter: 0.10-0.12/0.18; cyst
diameter: 0.06-0.08.
Remarks. The dimensions of our specimens are slightly
larger than those indicated by Masse et al. (1993) for the
type-specimens. However, a specimen that one of the
authors (I.I.B.) has collected from the type-locality and
that was illustrated in Bucur (2002) shows an external
diameter of 6.8 mm – thus, the Trbušnica specimens fall
in the dimensional range of Z. hispanica.
ACKNOWLEDGEMENTS
Rajka Radoičić thanks her colleague Ivan Filipović who
kindly showed the outcrop of Lower Miocene
conglomerates overlying Cretaceous succession in
Trbušnica area. We thank the two reviewers, Felix
Schlagintweit and Bruno Granier for their critical
remarks, and Stephen Kershaw for English corrections
and further suggestions on the text.
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