GeolCarp_Vol63_No1_33

www.geologicacarpathica.sk

GEOLOGICA CARPATHICA

, FEBRUARY 2012, 63, 1, 33—48 doi: 10.2478/v10096-012-0003-9

Introduction

The  Vâlcan  Mountains  are  located  in  the  Southern  Car-
pathians between the Jiu Valley (to the east), the Petro ani Ba-
sin (to the north), the Motru Valley (to the west) and the Getic
Depression  (to  the  south).  The  Upper  Jurassic—Lower  Creta-
ceous limestones crop out on the southern border of the Vâl-
can Mountains and they were studied in stratigraphic sections
along  the  Cheii,  Pocuia,  Sudoie ului,  Valea  lui  Mare ,
Cire ului, Albului, Pârgavului, Bistri a, and Sârbului Valleys.
More than 800 samples have been collected and analysed.

In spite of the large number of previous regional geology

studies on this area, there are only a few data regarding the
biostratigraphy and lithology of the local sedimentary depos-
its. This is due to the scarcity of biostratigraphic markers
within these deposits and to their recrystallization caused by
late Senonian tectonics (Pop & Bucur 2001). This study repre-
sents a synthesis of the data obtained from a vast area in the
Vâlcan Mountains. It aims to describe the facies and microfa-
cies, to reconstruct the paleoenvironments and their evolution
in time, and to bring some new biostratigraphical data.

Geological setting

The structure of the western part of the Southern Car-

pathians is represented by three groups of tectonic units. The
lowermost unit is the Danubian Nappes, also called Danubi-
an Euxinides (Balintoni 1997), the Danubian Domain or
Danubian Autochthonous. This unit is overlain by the Sever-
in Nappe, representing the suture between the Danubian

An Upper Jurassic—Lower Cretaceous carbonate platform

from the Vâlcan Mountains (Southern Carpathians,

Romania): paleoenvironmental interpretation

MIHAI MICHETIUC

, CAMELIA CATINCU

and IOAN I. BUCUR

1,2

Babe -Bolyai University, Department of Geology, M. Kogălniceanu Str. 1, 400084 Cluj-Napoca, Romania;

m.michetiuc@yahoo.com; camelia0409@yahoo.com

Babe -Bolyai University, Centre for Integrated Geological Research, M. Kogălniceanu Str. 1, 400084 Cluj-Napoca, Romania;

ioan.bucur@ubbcluj.ro

(Manuscript received January 10, 2011; accepted in revised form June 9, 2011)

Abstract: The results of a biostratigraphic and sedimentological study of the Upper Jurassic—Lower Cretaceous limestones
cropping out in the southern sector of the Vâlcan Mountains in Romania are presented, including the definition of microfacies
types, fossil assemblages and environmental interpretation. Six microfacies types (MFT 1—MFT 6) have been identified,
each of them pointing to a specific depositional environment. The deposits are characteristic of a shallow carbonate platform.
They contain normal marine or restricted marine facies deposited in low or high energy environments from the inner, middle
and outer platform. The age attribution of these deposits (Late Jurassic to Berriasian—Valanginian—?Hauterivian, and Barremian)
is based on foraminiferal and calcareous algae associations. The micropaleontological assemblage is exceptionally rich in the
Vâlcan Mountains and brings new arguments for dating the Upper Jurassic—Lower Cretaceous limestones in this area.

Key words: Upper Jurassic—Lower Cretaceous, Vâlcan Mountains, paleoenvironment, carbonate platform, carbonate
sedimentology, microfacies.

Nappes  and  the  Getic  Nappe,  which  is  the  uppermost  unit.
Except for some thin strips belonging to the Getic Nappe, the
Vâlcan Mountains are dominated by the crystalline and vol-
canic  rocks  of  the  Lower  Danubian  Nappes  (Berza  et  al.
1983),  and  by  their  Mesozoic  cover  (Fig. 1).  The  Mesozoic
deposits  belong  to  the  sedimentary  cover  of  the  Lainici
Nappe (Berza in Balintoni et al. 1989).

The succession of the Mesozoic deposits in the area starts

with  Liassic  deposits  in  Gresten-type  Facies,  followed  by
carbonate  deposits  of  variable  thickness  (1—20 m),  Middle
Jurassic  in  age.  The  Upper  Jurassic  is  represented  by  three
formations: the Valea Pragurilor Formation (Oxfordian) – a
calcarenitic  sequence,  often  consisting  of  dolosparites;  the
Valea Cheii Formation (Upper Oxfordian—Lower Kimmerid-
gian)  –  a  siliciclastic  formation  with  regressive  character
(1—20 m thick); and the Tope ti Formation (Kimmeridgian—
Tithonian) – consisting of shallow-water carbonate deposits
dominated  by  blackish,  fine  to  coarse  stratified  calcarenites
and calcilutites. On the top of the Upper Jurassic deposits, a
40 m thick Neocomian limestone succession crops out. The
Izvarna Formation (Barremian—Aptian) is the last carbonate
formation developed in this region and it consists of Urgonian
limestones,  followed  transgressively,  and  sometimes  uncon-
formably,  by  Upper  Cretaceous  clayey  marls,  marly-lime-
stones and clays (Pop 1973; Pop & Bucur 2001) (Fig. 2).

New biostratigraphic data

In a previously published study (Michetiuc et al. 2008) we

performed a micropaleontological study concerning only the

MICHETIUC, CATINCU and BUCUR

GEOLOGICA CARPATHICA

GEOLOGICA CARPATHICA, 2012, 63, 1, 33—48

Lower  Cretaceous  deposits  from  several  sections  (Cheii,
Sudoie ului,  Cire ului,  Albului,  Pârgavului)  in  the  Vâlcan
Mountains. We combined here the micropaleontological data
published earlier with new ones, in order to provide a synthet-
ic image of the stratigraphic succession (Fig. 3). The studied
deposits can be assigned to the Upper Jurassic—Lower Creta-
ceous (Oxfordian—Barremian) with some uncertainties regard-
ing  the  Hauterivian  deposits  which  were  not  documented
paleontologically  due  to  a  lack  of  reliable  biostratigraphic
markers.  Here  we  focus  on  our  new  findings  which  are  dis-
cussed in order to stress their biostratigraphical significance.

The Late Jurassic age attribution is based on foraminifera:

Alveosepta jaccardi (Schrodt) (Fig. 4.1), Parurgonina caelin-
ensis Cuvillier, Foury & Pignatti Morano (Fig. 4.2), Kurnubia
palastiniensis Henson (Fig. 4.3), Protopeneroplis striata
Weyschenk (Fig. 4.4), Neokilianina sp., Verneuilina sp., and

on several dasycladalean algae: Megaporella boulangeri
Deloffre & Beun (Fig. 4.5), Clypeina sulcata (Alth) (Fig. 4.6),
and Salpingoporella annulata Carozzi.

Among the foraminifera, the most significant species is

Alveosepta jaccardi (Schrodt). It was first described by Schrodt
(1894, as Cyclammina jaccardi) from Upper Oxfordian—Mid-
dle Kimmeridgian deposits in Switzerland. It was subsequent-
ly reported from Upper Oxfordian—Lower Kimmeridgian
formations in France and in Romania (Pelissié & Peybern

1982; Cociuba 1997; Pop & Bucur 2001). Septfontaine (1981)
proposed an A. jaccardi Biozone, ranging from Middle
Oxfordian to Early Kimmeridgian. The species was also de-
scribed from Kimmmeridgian rocks in Turkey and Mexico
(Altiner 1991; Oma

a & Arreola 2008).

Parurgonina caelinensis Cuvillier, Foury & Pignattti Morano

was first described from Kimmeridgian—Portlandian forma-

Fig. 1. Location of the studied area (simplified map after Berza et al. 1994). 1 – Upper Danubian Nappes, 2 – Lower Danubian Nappes,
3 – Jurassic—Cretaceous cover, 4 – Getic Nappe, 5 – Severin Nappe, 6 – Pre-Alpine granitoids, 7 – Cenozoic basins, 8 – Fault, 9 – Over-
thrust. a—h – studied sections: a – Cheii, b – Pocuia, c – Sudoie ului, d – Valea lui Mare , e – Pârgavului, f – Albului, g – Cire ului,
h – Bistri a, i – Sârbului.

PALEOENVIRONMENTAL INTERPRETATION OF THE J/K CARBONATE PLATFORM (ROMANIA)

GEOLOGICA CARPATHICA

GEOLOGICA CARPATHICA, 2012, 63, 1, 33—48

tions by Cuvillier et al. (1968). The species was placed either
in the Lower Kimmeridgian (Pelissié et al. 1984; Tasli
1993), the Kimmeridgian—Lower Tithonian (Pop & Bucur
2001; Bucur & Săsăran 2005; Velić 2007), or the Oxfordian—
Middle Tithonian (Bassoullet 1997a).

Kurnubia palastiniensis Henson is another typical fora-

minifer from Upper Jurassic deposits. It was found in Lower
Oxfordian (Pelissié & Peybern

s 1982), Oxfordian—Kim-

meridgian (Peybern

s 1976; Clark & Boudagher-Fadel

2002), Kimmeridgian (Hottinger 1967; Altiner 1991; Oma

&  Arreola  2008),  Kimmeridgian—Lower  Tithonian  (Pop  &
Bucur 2001; Schlagintweit et al. 2005) or in Oxfordian—Mid-
dle  Tithonian  (Bassoullet  1997a;  Bucur  &  Săsăran  2005;
Velić  2007)  formations.  To  summarize,  the  distribution  in-
terval for this species is Oxfordian—Middle Tithonian.

The same time interval is indicated by the calcareous algae

assemblage.  Megaporella  boulangeri  Deloffre  &  Beun  was
described  from  the  Kimmeridgian  of  Morocco  (Deloffre  &
Beun  1986).  Recently,  Bouaouda  et  al.  (2009)  revised  the
distribution of this alga in the Moroccan Atlantic basin; they
assigned  it  to  the  Callovian—Oxfordian  interval.  In  the
Tethyan  area,  the  species  was  identified  by  Pop  &  Bucur
(2001) in Kimmeridgian—Tithonian deposits from the South-
ern Carpathians, Romania. Clypeina sulcata (Alth) is typical
for the Kimmeridgian—Berriasian interval (Granier & Deloffre
1993; Bassoulet 1997b; Bucur 1999).

In the Berriasian—Valangian—?Hauterivian deposits, a mi-

cropaleontological  association  consisting  of  foraminifera:
Haplophragmoides joukowskyi  (Charollais, Broennimann &
Zaninetti),  Andersenolina  cherchiae  (Arnaud-Vanneau,
Boisseau  &  Darsac)  (Fig. 4.7),  Montsalevia  salevensis
(Charollais, Broennimann & Zaninetti) (Fig. 4.8), Bramkam-
pella arabica Redmond, Vercorsella camposaurii (Sartoni &
Crescenti) (Fig. 4.9), Mohlerina basiliensis (Mohler), Mayn-
cina  sp.,  and  calcareous  algae:  Clypeina  parasolkani  Fari-
nacci  &  Radoičić,  Clypeina  sp.,  Salpingoporella  circassa
(Farinacci  &  Radoičić),  Salpingoporella  annulata  Carozzi,
and Macroporella praturloni Dragastan has been identified.

Andersenolina cherchiae (Arnaud-Vanneau, Boisseau &

Darsac)  has  been  frequently  reported  from  Berriasian—
Valanginian  deposits  (Arnaud-Vanneau  1980;  Neagu  1994;
Bucur  et  al.  1995;  Mancinelli  &  Coccia  1999;  Pop  &  Bucur
2001). Velić (2007) considered  H. joukowskyi,  M. salevensis
and V. camposaurii to be index fossils for the Valanginian of
the Adriatic carbonate platform.

The Barremian—Aptian foraminiferal association consists

of  the  following  species:  Paracoskinolina?  jourdanensis
(Foury & Moullade) (Fig. 4.10), Montseciella arabica (Hen-
son)  (Fig. 4.11),  Orbitolinopsis  sp.?,  Paracoskinolina  sp.?,
Paracoskinolina cf. maynci (Chevalier) (Fig. 4.12), cf. Palaeo-
dictyoconus  actinostoma  Arnaud-Vanneau  &  Schroeder
(Fig. 4.13),  ?Palorbitolina  sp.  (Fig. 4.14),  Vercorsella  scar-
sellai  (De  Castro)  (Fig. 4.15),  Everticyclammina  hedbergi
(Maync),  Pseudolituonella  gavonensis  (Foury),  Debarina
hahounerensis  (Fourcade,  Roul  &  Vila),  Neotrocholina
friburgensis Guillaume & Reichel, Sabaudia minuta (Hofker),
Pseudocyclammina lituus Yokoyama, Nautiloculina broenni-
manni  Arnaud-Vanneau  &  Peybern

s, Everticyclamina sp.,

Vercorsella sp., Nautiloculina sp., Charentia sp. and Comma-
liama sp. The association of calcareous algae includes: Salpin-
goporella  muehlbergii  (Lorenz),  Salpingoporella  melite
Radoičić, Salpingoporella cf. cemi Radoičić, Salpingoporella
sp., Clypeina solkani Conrad & Radoičić, Clypeina cf. solkani
(Conrad  &  Radoičić),  Suppiluliumaella  tuberifera  (Sokać  &
Nikler), Milanovicella sp., Clypeina sp., Pseudoactinoporella
fragilis  Conrad,  Similiclypeina  conradi  Bucur,  Salpingopo-
rella  cf.  genevensis  (Conrad),  Salpingoporella  heraldica
Sokać, Salpingoporella urladanasi Conrad & Peybern

s, and

Falsolikanella danilovae (Radoičić).

As a whole, this association is characteristic of the Barremian

interval in the Mesogean area. Among the species in this asso-
ciation, the most important biostratigraphically are the orbito-
linids such as Paracoskinolina? jourdanensis (Foury &
Moullade). It represents clear paleontological evidence for the

Fig. 2. Stratigraphic succession of the Jurassic—Cretaceous deposits
from the Vâlcan Mountains (after Pop & Bucur 2001).

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GEOLOGICA CARPATHICA, 2012, 63, 1, 33—48

presence of Lower Barremian in the studied limestone succes-
sion (Michetiuc et al. 2008). The orbitolinids Paracoskinolina
cf. maynci (Chevalier) and cf. Palaeodictyoconus actinostoma
Arnaud-Vanneau & Schroeder, encountered in the upper part
of the succession from Sârbului Valley, have also been identi-
fied in the interval between the upper part of Lower Barremian
and  the  Lower  Aptian  (Masse  1976;  Arnaud-Vanneau  1980;
Bucur 1997). Clavel et al. (2010) revised the biostratigraphic
distribution  of  the  orbitolinids  by  correlation  with  ammonite
zonations  placing  the  first  occurrence  of  Paracoskinolina
maynci  (Chevalier) in the Upper Hauterivian and that of the
Palaeodictyoconus actinostoma Arnaud-Vanneau & Schroeder
in the lowermost Barremian. The calcareous algae assemblage
characterizes  the  Barremian—Aptian  time  interval  (Granier  &
Deloffre 1993; Bucur 1999).

Microfacies analysis

We have identified six main microfacies types (MFT) with-

in  these  successions.  Microfacies  types  (sensu  Flügel  2004)
are defined according to criteria that allow attribution of spe-
cific environmental factors and specific depositional settings.
The  microfacies  criteria  used  here  include:  depositional  tex-
ture  and  fabric,  grain  composition  and  early  diagenetic  fea-
tures.  Each  MFT  and  its  occurrence  is  described  and  the
environmental interpretation is discussed.

MFT 1: non-fossiliferous, fenestral, laminated mudstone/
wackestone and subaerial exposure facies

This facies type is scarcely represented in the stratigraphic

succession, but is more frequent in the lower part. The most
typical diagnostic features are the presence of non-fossilifer-
ous (or poorly fossiliferous), unstructured or finely-laminated,
fine  granular  micrites,  locally  including  cryptomicrobial
(Fig. 5.1,2)  or  Rivularia-type  structures.  Scattered  dolomite
rhombs are locally present in the micritic matrix and grains.
Sometimes the original structure is obliterated by mosaics of
euhedral to subhedral dolomite crystals. Biodiversity is very
low,  microfossils  being  mainly  represented  by  ostracods,
rare foraminifera and gastropods (Fig. 5.3). Charophyte frag-
ments  (stems  and  gyrogonites)  are  also  locally  present  in  a
homogeneous or fenestral matrix (Fig. 5.4). Some reworked
bioclasts from the subtidal area may also occur.

Also included in this facies association are sediments that

have undergone subaerial exposure. Exposure features in-
clude desiccation cracks, paleosols and paleokarst. They are
more common in the lower parts of the profiles from the
Sârbului and Bistri a Valleys.

Interpretation: Non-fossiliferous, finely laminated carbon-

ate muds and cryptalgal fabrics are common constituents of
supratidal  or  upper  intertidal  environments  with  low  water
energy.  In  these  areas  the  fluctuating  salinity  and  frequent
subaerial exposures do not permit proliferation of infauna or
browsing  organisms  that  homogenize  the  primary  sedimen-
tary structures (Shinn 1983). The presence of charophyte re-
mains  is  usually  regarded  as  good  indicator  of  freshwater
environments (Tucker & Wright 1990), but salinity-tolerant

forms  were  also  reported  from  recent  and  ancient  brackish
environments  (e.g.  Burne  et  al.  1980;  Feist  &  Grambast-
Fessard  1984;  Climent-Dom

nech & Martín-Closas 2009).

In the studied area the charophyte remains appear along with
a brackish fauna of ostracods, and some are impregnated
with Fe-oxides. The preferential staining of bioclasts is proba-
bly similar to the preferential blackening of Pleistocene corals
in Florida, attributed by Strasser (1984) to the percolation of
staining fluids through their skeletons. The red pigmentation
is probably related to subaerial alteration (Wright et al. 2000;
MacNeill & Jones 2006).

Evidence of pedogenic influence such as desiccation-brec-

ciation, mottling, glaebule development, black pebbles, root
structures and microkarst (Esteban & Klappa 1983; James &
Choquette 1984; Demicco & Hardie 1994), are all common
features of this facies association.

The in situ brecciation of muds has led to the formation of

polygonal fracture networks filled with sparite or with sedi-
ment  containing  peloids  and  pisoids  (Fig. 5.5).  Brecciation
can be induced by desiccation (Fig. 5.6), displacive crystalli-
zation  of  calcite,  root  activity  and/or  dissolution  (Flügel
2004). Carbonate nodules (or glaebules in soil terminology,
see Esteban & Klappa 1983) are also frequent constituents of
caliche  profiles,  but  their  origins  are  not  fully  understood
(Wright & Tucker 1991). Circum-granular cracks, filled with
spar  cement,  usually  develop  around  glaebules  (Fig. 5.7).
They  are  formed  by  alternate  shrinkage  and  expansion  in-
duced by seasonal drying/wetting cycles (Esteban & Klappa
1983).  Mottling  from  red-brown,  yellow  to  grey  is  also
present (Fig. 5.8). This pedogenetic process may develop as
a result of fluctuating Eh—pH conditions or through redistri-
bution of iron oxide and iron hydroxide particles (Buurman
1980). The presence of black pebbles ‘floating’ in this type
of matrix is probably related to the burning of organic matter
because features like the gradation of blackening and the an-
gular  nature  of  the  pebbles  (Fig. 5.9),  seen  here,  are  argu-
ments  cited  by  Shinn  &  Lidz  (1988)  as  characteristic  of
subaerial  blackening  by  fire.  Other  interpretations  include
impregnation by dissolved, colloidal or finely particulate or-
ganic matter (Strasser 1984) or the blackening by finely dis-
seminated pyrite (Wright 1986a).

No rhizocretions have been encountered but some alveolar-

septal  structures  were  found  (Fig. 5.10).  Similar  structures
have been reported from ancient and recent paleosols (Adams
1980; Klappa 1980; Wright 1986b; Wright et al. 1988). They
have  been  interpreted  by  Wright  (1986b)  as  resulting  from
fungal  activity  around  roots.  Root  traces  represented  by
rounded or irregular voids lined with dense micritic coatings
(Fig. 5.11) are interpreted as being the products of void lining
biofilms or calcitic cutans (MacNeil & Jones 2006).

Microkarstic products represented by collapse breccias,

solution voids, and some speleotems (flowstone) (Fig. 5.12)
are also present. Such structures probably represent the up-
per vadose zone (Esteban & Klappa 1983).

MFT 2: fenestral wackestone/packstone-grainstone

This MFT is interlayered at different levels within the whole

stratigraphic succession and is characteristic for the intertidal

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GEOLOGICA CARPATHICA, 2012, 63, 1, 33—48

dal wackestone (formed in low-energy hydrodynamic condi-
tions) and b) fenestral peloidal packstone-grainstone (formed
when the hydrodynamic energy was intermittently high).

MFT 2a

The first subtype (Fig. 6.2,3) is commonly associated

with  microbial  bindstones  and  wackestones.  The  biodi-
versity is still low; sometimes inside the fenestrae one can
find  charophyte  oogones,  probably  reworked.  Gyrogo-
nites are easily transported, especially if they are desiccat-
ed (Wright 1990). Small gastropods are locally present in
the microbial mats (Fig. 6.4). Sometimes intensely biotur-
bated micrites, containing many Favreina-type coprolites
and  rare  ostracods,  are  grading  into  fenestral  microbial
mats (Fig. 6.5). The fenestrae associated with this subfa-
cies are of laminoid-fenestral and irregular type.

MFT 2b

These deposits are moderately to well sorted, some-

times displaying bimodal sorting; the particles are repre-
sented  by  well-sorted  and  well-rounded  peloids,  micritic
intraclasts and oncoids. Bioclasts are relatively rare, they
are  represented  by  foraminifera  (miliolids,  textulariids,
Sabaudia  minuta  (Hofker),  Vercorsella  sp.)  sometimes
showing  a  micritic  envelope,  bivalves,  gastropod  molds,
algae,  or  Rivularia-type  structures  (Fig. 6.6—8).  The
fenestral pores within these deposits are of spherical to ir-
regular types, and keystone vugs are also locally present.

Interpretation: As many authors mentioned (e.g. Tucker &

Wright  1990;  Flügel  2004)  the  assignment  of  ancient  lime-
stones to the intertidal environment is a difficult task. This is
due to the lack of reliable diagnostic features, and to the sim-
ilarities with the adjacent supratidal environments. Fenestral
structures in ancient and recent carbonate deposits are usual-
ly regarded as good indicators of upper intertidal to supratid-
al  settings  (Shinn  1983;  Tucker  &  Wright  1990).  Shinn  &
Robbin (1983) showed that open fenestrae are destroyed by
mechanical compaction so that the preservation of fenestrae
of  all  types  in  mudstones  signifies  that  the  host  sediments
were cemented before even shallow burial. Such an early ce-
mentation  is  a  characteristic  feature  of  peritidal  deposits
(Grover  &  Read  1978;  Shinn  1983;  James  &  Choquette
1984; Tucker & Wright 1990). Fenestrae have polygenic ori-
gins and may be caused by wetting and drying of carbonate
mud,  by  degassing  of  decaying  organic  material,  by  drying
out of the surface of cyanobacterial mats (in case of laminoid
and  irregular  fenestrae),  or  by  air  and  gas  bubbles  trapped
during deposition of the host sediment or generated by post-
depositional decay of organic matter (in the case of spherical
fenestrae) (Demicco & Hardie 1994). Keystone vugs present
in  the  grain-supported  facies  are  probably  the  result  of  air-
bubble  trapping  during  storm  deposition  in  the  swash  zone
on  beaches  or  in  the  sheetwash  zone  on  tidal  flats  (Shinn
1986;  Demicco  &  Hardie  1994;  Flügel  2004).  Irregular
fenestrae associated with cyanobacterial mats can be the re-
sult of irregular growth of these mats (Săsăran 2006).

Other characteristic features of the intertidal regime are ero-

sion alternating with deposition, as well as rapid changes in
current and wave velocity (Ginsburg 1975).

Fenestral limestones containing abundant fenestrae, associ-

ated with distinctive early diagenetic features (crystal silt,
leached fossils, micritization of bioclasts originating from nor-
mal marine environments), erosional surfaces, cryptalgal sedi-
ments, and a restricted fauna (ostracods and gastropods)
suggesting periodic emergence and desiccation, point to an in-
tertidal environment of formation in the case of these deposits.

MFT 3: peloidal bioclastic packstone/grainstone

These limestone types are interlayered at several levels

within the stratigraphic succession. The granular facies mainly
consists  of  moderate-  to  well-sorted  peloids  with  subangular
to  rounded  morphologies  (Figs. 6.9,10),  besides  rare  superfi-
cial  ooids,  micritic  intraclasts  and  oncoids.  Micritized  bio-
clasts  are  common.  Skeletal  grains  appear  in  various
quantities and are represented by gastropods, fragments of bi-
valves and echinoderms, benthic foraminifera (Fig. 6.11), and
dasycladalean algae. The foraminifera include: Kurnubia pa-
lastiniensis  Henson,  Protopeneroplis  striata  Weyschenk,
Andersenolina  cherchiae  (Arnaud-Vanneau  &  Boisseau),
Mohlerina basiliensis (Mohler), Paracoskinolina? jourdanen-
sis  (Foury  &  Moullade),  Pseudocyclammina  lituus  Yokoya-
ma,  Sabaudia  minuta  (Hofker),  Vercorsella  sp.  The
dasycladalean algae are represented by Clypeina parasolkani
Farinacci  &  Radoičić,  Pseudoactinoporella  fragilis  Conrad,
Salpingoporella  sp.  Also  microbial  nodules  (of  Rivularia-
type) occur.

Interpretation: The non-skeletal components, such as pe-

loids, intraclasts, ooids, cortoids and oncoids, and mostly
sparitic, or at least partly sparitic groundmass indicate an agi-
tated subtidal environment. The diverse skeletal components,
such as larger and smaller benthic foraminifera and calcareous
algae point to normal-marine, well-oxygenated conditions.
These deposits were formed in shallow subtidal environments
above the fair-weather wave base.

MFT 4: packstone-grainstone with rudists and wackestone/
packstone with green algae and foraminifera

These deposits, characteristic of the middle and upper part

of  the  section,  consist  of  wackestone/packstone,  and  pack-
stone-grainstone  with  highly  diversified  paleontological  as-
semblages:  molluscs,  benthic  foraminifera,  and  green  algae.
At certain intervals, rudists took part to the colonization of the
substrate  building-up  a  typical  Urgonian-type  facies  (Masse
1979, 1995; Gili et al. 1995) (Fig. 7.1,2). The rudists charac-
terizing  this  facies  have  a  patchy  distribution,  thick  shells,
large sizes, and they show no signs of perforation, micritiza-
tion or encrustation. The sediment associated with this facies
is usually represented by poorly washed packstone-grainstone
with small and very diverse foraminifera (especially miliolids,
cuneolinids and textulariids) and peloids (Fig. 7.3).

Another microfacies, associated with the rudistid one, is

represented by wackestone-packstone with green algae and
large benthic foraminifera (Fig. 7.4,5). The main characteristic

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of this microfacies is the diversification of organisms in mud-
supported,  sometimes  bioturbated  matrix.  Dasycladalean  al-
gae  are  very  frequent  (Clypeina  solkani  Conrad  &  Radoičić,
Salpingoporella  melite  Radoičić,  Salpingoporella  muehl-
bergii  (Lorenz),  Similiclypeina  conradi  Bucur),  along  with
benthic foraminifera (Montseciella arabica (Henson), Neotro-
cholina  friburgensis  Guillaume  &  Reichel,  Vercorsella
scarsellai  (De  Castro))  and  other  skeletal  grains  similar  to
those of the high-energy environment (MFT 3).

Interpretation: The Lower Cretaceous rudists are usually re-

garded as characteristic inhabitants of very shallow waters and
are especially linked to the inner, more or less protected parts
of the Urgonian platforms (Masse 1976, 1979, 1992; Masse &
Philip  1981;  Skelton  &  Gili  1991).  Their  association  with  a
grainy-muddy  substrate  containing  abundant  small  foramini-
fera  also  suggests  inner  platform  (lagoonal)  conditions  with
moderate to low-energy conditions.

The intensely bioturbated bioclastic wackestone microfacies

types containing normal marine fauna dominated by dasycla-
dalean algae besides foraminifera with complex tests, rudist
fragments, and gastropods have been interpreted as being
formed in the lower subtidal environment with low hydrody-
namic energy. The presence of dasycladalean algae points to
warm, relatively shallow waters (Bucur & Săsăran 2005).

Some of the beds containing microfacies types 3 and 4

show traces of subaerial exposure, such as dissolution and
recrystallization of bioclasts, or voids filled with vadose-silt
(Fig. 7.6).

MFT 5: wackestone/packstone with rudist fragments and mi-
croencrusters, and packstone-grainstone with microbialite

This MFT is associated with the subtidal marine facies pre-

sented  above  and  it  is  represented  by  peloidal  wackestone/
packstone with abundant microencrusters and bioclastic pack-
stone-grainstone with microbialite. The diversity of flora and
fauna is low, bioclasts being mainly represented by problem-
atic microencrusters of Bacinella- (very abundant) or Lithoco-
dium-type and Rivularia-type organisms (Fig. 7.7).  Bacinella
is present either in the matrix of these deposits, or inside and
around the bioclastic fragments forming oncoids (Fig. 7.8,9).
The bioclastic fragments are mainly represented by bored and
micritized  rudist  fragments  (Fig. 7.10)  but  never  by  whole
rudist shells. The sediment is inhomogeneous, suggesting in-
tensive burrowing.

Some of these deposits may contain a normal-marine fauna

with foraminifera, green algae, echinoids or rudists, associated
with  peloids  and  intraclasts.  This  association  witnesses  an
original  normal-marine  environment  later  grading  into  a  re-
strictive one, a change leading to the colonization of the sub-
strate by calcimicrobial structures (Fig. 7.11) and finally even
to the subaerial exposure of the sediment, with related dissolu-
tion,  reprecipitation  and  micritization  processes  affecting  the
bioclasts (Fig. 7.12).

Interpretation: This association is characterized by the pres-

ence  of  Bacinella  and  Lithocodium  along  with  fragmented
rudist  shells.  The  systematic  position  of  Bacinella  and
Lithocodium was intensely disputed; the first one being usual-
ly  interpreted  as  a  cyanobacterium  (Schäffer  &  Senowbari-

Daryan 1983; Maurin et al. 1985; Camoin & Maurin 1988)
while the second one was regarded as a Codiacean alga, lituolid
foraminifer, or cyanobacterium (for a comparison of different
taxonomic interpretations see Schlagintweit et al. 2010). Re-
cently, Schlagintweit et al. (2010) re-interpreted these organ-
isms as being ulvophycean green algae.

Regardless of their taxonomic position, most authors regard

the two microproblematic organisms as being characteristic of
very shallow, well-oxygenated and relatively oligotrophic en-
vironments  (Leinfelder  et  al.  1993;  Dupraz  &  Strasser  1999,
2002; Pittet et al. 2002; Reolid et al. 2009). The large oncoids
with lobate outlines, dominated by microencrusters (Bacinella
and Lithocodium), correspond to oncoids of types 3 and 4 de-
scribed  by  Védrine  et  al.  (2007)  or  to  the  organism-bearing
oncoids of Dahanayake (1977). The above-mentioned authors
ascribed  these  types  of  oncoids  to  the  low-energy  open-la-
goonal  environments,  where  the  microbial  meshwork  had
time to grow. In contrast, the smaller, spherical oncoids, with
micritic, homogeneous cortex (type 1 oncoids of Védrine et al.
2007) are often associated with packstone-grainstone and rep-
resent higher energy conditions.

Encrustation, borings, breakage, burrowing and micritiza-

tion  are  common,  indicating  low  accumulation  rates  (Enos
1983).  Oncoid  growth  also  requires  low  sedimentary  rates
(Peryt 1981; Flügel 2004; Védrine et al. 2007). The presence
of  abundant  oncoids  in  the  Oxfordian  of  the  Swiss  Jura  was
correlated (Védrine et al. 2007) with the beginning of a long-
term  sea-level  rise.  Furthermore,  the  authors  correlated  the
different types of oncoids with small-scale sea-level fluctua-
tions.  Consequently,  this  facies  was  probably  formed  in  a
subtidal lagoonal environment characterized by reduced accu-
mulation rates and was mainly controlled by water depth.

MFT 6: bioclastic packstone/ grainstone

This facies dominates the upper part of the succession. The

most typical carbonate particles included are bioclasts, repre-
sented  by  echinoid  plates  (sometimes  comprising  more  than
50 % of the total) of arenitic sizes and recrystallized fragments
of molluscs (Fig. 7.13). Most bioclasts either exhibit construc-
tive micritic envelopes, or are marginally or completely micri-
tized (Fig. 7.14). Besides, well-rounded to subangular peloids,
micritic  intraclasts,  microbial  nodules,  bryozoans,  brachio-
pods,  foraminifera  (Montseciella  arabica  (Henson),  Palorbi-
tolina  sp.,  Palaeodyctioconus  actinostoma  Arnaud-Vanneau
& Schroeder), and dasycladalean algae are present. The echi-
noid  fragments  are  well-rounded  and  locally  show  syntaxial
overgrowth cement. Some bioclasts are affected by processes
of micritization, dissolution and recrystallization under the ef-
fect of meteoric waters.

Interpretation: These deposits showing evidence of intense

reworking and containing a predominantly open marine fau-
na imply a formation in a marine environment with high hy-
drodynamic  energy;  they  represent  bioclastic  shoals  on  the
platform  margin  or  on  highs  in  the  platform  interior  (corre-
sponding to FZ 6 sensu Wilson 1975 and Flügel 2004). This
microfacies  is  sometimes  associated  with  wackestones  and
packstones containing angular bioclastic fragments and repre-
senting the perishoal offshore environment (Fig. 7.15).

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GEOLOGICA CARPATHICA, 2012, 63, 1, 33—48

Paleoenvironmental reconstruction and evolution

The detailed microfacies study allows the differentiation of

several facies belts. In a transect from the shoreline to the plat-
form margin the following facies zones occur: (1) inner plat-
form, (2) middle platform and (3) outer platform (Fig. 8). For
a better understanding of the depositional facies belts, com-
parisons with modern settings have been used.

1. Inner platform. In most of the studied sections the periti-

dal deposits dominate their lower parts, although some thin in-
tercalations  exist  in  the  whole  section.  The  supratidal  facies
belt  was  dominated  by  fine,  non-fossiliferous  muds  (MFT 1)
representing the result of sedimentation on the vast, protected
supratidal  marshes  that  were  subject  to  periodic  flooding  by
sea  water  during  spring  tides  and  storm  events.  The  charo-
phyte  remains  in  some  of  these  supratidal  deposits  suggests
the presence of freshwater ponds.

No well-developed caliche profile or karstic features have

been encountered in these deposits, but some evidence of sub-
aerial exposure and pedogenesis do exist. In contrast, the su-
pratidal deposits from the lower part of Sârbului section show
greater  thickness,  no  marine  influence  and  more  pronounced
pedogenic features. Such deposits were defined by MacNeil &
Jones (2006) as “disconnected palustrine deposits”. Their lo-
cal  presence  suggests  lateral  facies  variability,  probably
caused  by  the  inherited  paleotopography  or  by  differential
subsidence. A modern example of such deposits are the Flori-
da Everglades showing that the climate and topography were
important  controls  of  the  marginal  marine  settings  (e.g.  Platt
& Wright 1992).

The supratidal environments are good indicators of climat-

ic  conditions:  even  without  having  any  clay-mineralogical
data, but by virtue of sedimentological and early diagenetic
data  (lack  of  evaporites,  paleosoil  characteristics,  meteoric
water input) humid to sub-humid climatic conditions can be
assumed,  similar  to  those  of  the  modern  Andros  Island
(Ginsburg & Hardie 1975).

As already mentioned, recognition of the intertidal facies

belt and its subenvironments in ancient carbonates is a diffi-
cult task. Based on the energy of the environment we distin-

Fig. 8. Schematic reconstruction of the distribution of paleoenvironments of the Vâlcan car-
bonate platform.

guished  a  low-energy  and  a  high-energy  sub-environment.
The first one contains cryptalgal fabrics associated with lam-
inar-fenestral  or  irregular  fenestral  fabrics  (MFT 2a).  They
contain  a  restricted  fauna  and  were  deposited  on  intertidal
flats  with  shallow  ponds.  In  recent  intertidal  environments,
situated especially in more humid climates, ponds are a very
common  feature  (Pratt  et  al.  1992).  The  presence  of  abun-
dant crustacean coprolites and burrows and their association
with  microbialites  are  also  indicative  for  intertidal  environ-
ments. In recent environments, burrows by fiddler crabs are
abundant  in  the  lower  intertidal  flats  and  subtidal  ponds
(Shinn 1983, 1986).

The granular subfacies (MFT 2b) contains light grey intrac-

lasts and rounded peloids, suggesting reworking of an early
lithified sediment from the tidal flats. Some of them may rep-
resent high-energy events affecting the flats, while those con-
taining keystone vugs might represent poorly developed beach
ridges generated seaward of the tidal flats in the zone of break-
ing waves. Bimodal sorting is also a characteristic of beach
foreshores or beach storm layers (Taira & Scholle 1979).

In the studied sections, the peritidal deposits could not be

individualized  into  cycles  with  clearly  visible  deepening-
shallowing  facies  trends.  This  can  be  explained  by  lateral
migration  of  tidal  flat  subenvironments  (facies  mosaic;
Wilkinson & Drummond 2004; Wright & Burgess 2005).

2. Middle platform. The winnowed packstones and grain-

stones (MFT 3) rich in peloids, cortoids and intraclasts, con-
taining  different  amounts  of  reworked  benthic  foraminifera
and  green  algae,  reflect  deposition  under  high-energy  condi-
tions. Moderate turbulence is indicated by high packing densi-
ty, good sorting and roundness of particles (Bauer et al. 2002).
They represent subtidal sand bars moved by bottom currents.
In  some  cases,  especially  in  the  lower  parts  of  the  sections,
where they are associated with intertidal deposits, they might
represent tidal channel infillings. Unfortunately, the presence
of tidal channels can only be assumed because bipolar (her-
ringbone) cross-stratification is not present,  possibly having
been destroyed by intense bioturbation.

The low-energy subtidal environments (MFT 4) dominate

the middle—upper parts of the sections and were deposited in

protected or semi-protected parts of the
platform.  The  protection  was  ensured
by the bioclastic shoals on the platform
margin  (see  discussion  below).  The
ecological  requirements  of  fauna  and
flora  (especially  benthic  foraminifera
and  green  algae)  suggest  a  shallow-
marine  environment.  The  same  envi-
ronment  is  inferred  for  the  rudists
assemblages,  which  were  compared
(Masse  1976;  Masse  et  al.  2003)  with
the  Pinna—Pinctada assemblages thriv-
ing in the shallow-waters of Shark Bay
or the Arabian Gulf. Such shallow-wa-
ter environments were very sensitive to
bathymetric  changes  that  could  either
open or isolate the carbonate platform.

These middle platform deposits show

meter-scale cycles, each displaying a

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GEOLOGICA CARPATHICA, 2012, 63, 1, 33—48

shallowing-upward trend. At one end of the spectrum are the
mud  dominated  algal,  foraminiferal  wackestone—packstones,
representing the deeper, protected environments of the photic
zone.  They  are  followed  by  packstones—grainstones  with
small foraminifera, associated with rudists, representing shal-
lower and more energetic environments. The lack of micritiza-
tion, borings and encrustation on rudists shells suggests high
depositional  rates.  In  the  middle  part  of  the  sections  (Lower
Barremian) the cycles are predominantly composed  of rudist
fragments  and  microencrusters  (MFT 5).  They  also  show  a
shallowing-up  trend  from  deeper,  low-energy  environments,
to shallower and more energetic  environments. The presence
of  oncoids,  intensive  burrowing,  perforations  and  micritiza-
tion  suggest  lower  sedimentary  rates.  The  fragmentation  of
rudists  is  probably  the  result  of  intensive  in-situ  bioerosion
(Gili 1992; Gili et al. 1995) or of periodic reworking by high-
energy episodes.

Sometimes the cycles are capped by thin fenestral wacke-

stones and mudstones of the intertidal zone. The superim-
posed meteoric diagenesis (grain dissolution, recrystallization,
vadose silt) especially affected the MFT 5 and to some extent
the MFT 4, suggesting frequent subaerial exposures.

Such shallowing-up sequences in peritidal settings can

form through allocyclic or autocyclic processes (Strasser
1991). Autocyclic processes can be created by progradation
or migration of sedimentary systems (e.g. Ginsburg 1971;
Pratt & James 1986; Strasser 1991) without being related to
a sea-level fall. Allocyclic control mechanisms are indepen-
dent of the depositional processes and are commonly related
to different orders of eustatic sea-level fluctuations (e.g. Vail
et al. 1991; McLean & Mountjoy 1994; Strasser et al. 1999).

In our case, because of the bad outcrop conditions and the

effects  of  late  Senonian  tectonics,  a  correlation  of  meter-
scale cycles between sections is not possible, making it  dif-
ficult  to  determine  which  of  the  two  mechanisms  (or  a
combination  of  both)  was  involved.  Still,  in  some  of  these
cycles vadose diagenesis directly overprints the subtidal fa-
cies,  suggesting  that  allocyclic  processes  played  an  impor-
tant role in the formation of these sequences (Strasser 1991;
Strasser & Hillgärtner 1998; Burgess 2006).

3. Outer platform. The great thickness of the deposits,

predominance  of  echinoderm  fragments  along  with  other
stenohaline organisms, and the early diagenetic features sug-
gest the existence of bioclastic shoals situated at the platform
margin. These shoals were probably the main cause of plat-
form  restriction,  separating  the  inner  and  middle  platform
from the open ocean (Fig. 8). The closest recent counterpart
is represented by the bank-margin shoals of the Great Bahama
Bank (Rankey & Reeder 2011). Even though this facies was
encountered only in the Upper Barremian, the existence of a
high-energy barrier at the platform margin before this period
can  be  inferred  from  the  prevailing  restricted  conditions.
Likewise, in a section situated westward of the studied zone
(Mehedin i Plateau), belonging to the same limestone forma-
tion, we encountered a Tithonian—Berriasian reef barrier rep-
resented by coral-microbial boundstones.

The shallowing-up trend of the meter-scale cycles is still

maintained in the upper part of the sections, with the high-en-
ergy open marine shoals being covered by lagoonal environ-

ments.  The  great  thickness  of  the  high-energy,  open  marine
deposits, and the abrupt backstepping of facies (migration of
the platform rim toward platform interior) in the upper part of
the  sections,  implies  a  rapid  growth  of  the  accommodation
space.  This  may  be  related  to  a  maximum  flooding  on  the
long-term  sea-level  evolution  (Strasser  &  Hillgärtner  1998).
The  upward  shallowing  indicates  that  sedimentation    kept
pace with the created accommodation space.

Conclusions

The carbonate deposits from the Vâlcan Mountains have

been analysed from a sedimentological and biostratigraphic
point of view; lithofacies types, fossil assemblages, and their
vertical distributions have been defined.

We have identified six microfacies types (MFT 1—MFT 6)

within  these  deposits,  based  on  biotic  and  abiotic  compo-
nents,  sedimentary  structures  and  textures,  and  early  diage-
netic  features  with  an  environmental  significance.  The
deposits  are  characteristic  of  a  shallow  carbonate  platform
that can be further subdivided into an inner, middle, and outer
platform.

The inner platform deposits are represented by tidal flat

deposits  and  were  best  developed  during  the  Late  Jurassic.
Deposition  on  the  tidal  flats  occurred  in  a  great  variety  of
low-  and  high-energy  sub-environments  represented  by  su-
pratidal marshes and disconnected palustrine deposits, inter-
tidal  flats,  ponds,  beaches  and  possibly  channels.  They
reflect tropical humid to sub-humid climatic conditions.

These deposits were followed by predominantly middle

platform deposits, developed during the Early Cretaceous.
They were deposited in high-energy and low-energy envi-
ronments formed in protected or semi-protected shallow sub-
tidal conditions. Rudists and small benthic foraminifera were
the main sediment producers during the Early Cretaceous.

The middle platform deposits interfinger, in the upper

parts of the sections, with the outer platform deposits repre-
sented by high-energy bioclastic shoals and their associated
open-marine deposits.

The vertical succession of microfacies reflects cyclic

changes in water depth. They are more visible in successions
from the middle and outer platform where they are arranged
in shallowing-up cycles. These cycles are superimposed on
an overall transgressive trend, testified by the predominance
of the inner platform facies in the Upper Jurassic and the
transition to middle and outer platform facies during the Early
Cretaceous. This long term transgressive trend can be related
to the second-order tectono-eustatic cycle (Vail et al. 1991),
while the superimposed high frequency cycles can be the re-
sult of lower amplitude sea-level oscillations.

Following the micropaleontological study of some new sec-

tions, new biostratigraphic arguments have been added, com-
pleting  and  improving  the  few  data  available.  Three
associations  of  algae  and  foraminifera  have  been  identified.
The first association is characteristic of the Late Jurassic, the
second  points  to  Berriasian—Valanginian  (possibly  also  Hau-
terivian) age, while the third one indicates the Barremian in-
terval.  The  identified  micropaleontological  assemblages  can

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GEOLOGICA CARPATHICA, 2012, 63, 1, 33—48

also serve comparisons with other Tethyan regions contain-
ing Upper Jurassic—Lower Cretaceous deposits (e.g. Jaffrezo
1980; Soták & Mišík 1993; Bassoulet 1997a).

Acknowledgments: The study is a contribution to the CNC-
SIS Project BD 413. We thank Jean-Pierre Masse for his valu-
able suggestions on the first draft of this manuscript. We are
also grateful to André Strasser and an anonymous reviewer for
their constructive remarks.

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