Litho- and biostratigraphic data of lower-middle Miocene sections in the Transylvanian basin and SE Carpathian Foredeep (Romania)

Litho- and biostratigraphic data are provided of 5 stratigraphic sections in Romania covering the “Badenian” marine flooding that occurred in the Central Paratethys during the middle Miocene (Langhian). The dataset includes stratigraphic logs and descriptions of the profiles, and biostratigraphic analyses on calcareous nannofossils and foraminifera. In addition, characteristic stratigraphic features and representative fossils, including tiny Streptochilus foraminifera in the Campiniţa section in the SE Carpathian Foredeep, are presented in photographs. The data show that the flooding is characterized by the sudden abundance of Langhian calcareous nannofossils and foraminifera with a strong Mediterranean affinity.


Data
The litho-and biostratigraphic data from the sections document a shift from restricted brackishmarine deposits to open marine deposition by the sudden appearance of abundant Mediterranean planktonic foraminifera (Figs. 1 and 2). This transgressive interval was logged in detail in the Campinit¸a and Brebu sections, located in the Carpathian bend area in the East Carpathian Foredeep, where both intervals share similar features (CX, BX; Fig. 2., Fig. 3aec). In the SE Carpathian Foredeep, the onset of the open marine conditions is assigned to the planktonic foraminiferal zone MMi5b and calcareous nannofossil zones MNN4c-MNN5a. In the Transylvanian sections, the quality of the data is variable and the base of the flooding is in the range MMi4c to MMi5a (planktonic foraminifera) and MNN5a-MNN5b (calcareous nannofossils). The data can be used for a paleoenvironmental and chronostratigraphic interpretation of the research area.

Sampling and analysis
The stratigraphic profiles were logged at~0.5e1 m resolution during a fieldwork campaign in May 2015. Biostratigraphic samples were taken with a resolution of 1e2 m from the Valea Dracului (DV), Ciceu-Giurgest¸i (CG), Cepari (CP) and Campinit¸a (CA) sections. Additionally, biostratigraphic samples were taken at an approximately 25 cm resolution in the intervals just below the marine transgression Specifications  Stratigraphic logging Microscope: Zeiss Axioscope (nannoplankton), Nikon SMZ stereomicroscope (benthic foraminifera), Zeiss stereomicroscope (planktonic foraminifera) SEM:. JEOL JXA-8530 F field emission electron probe analyzer (benthic foraminifera), Jeol 6400 (planktonic foraminifera) Data format Raw and analyzed.

Experimental factors
Collection of data was focused on determining the age and mode of the Langhian marine flooding in the Transylvanian Basin and SE Carpathian Foredeep by litho-biostratigraphic constraints.

Experimental features
Documenting the lithology and fossils (planktonic and benthic foraminifera, calcareous nannofossils, ostracods) in five semi-parallel stratigraphic sections.

Data source location
Transylvanian basin and SE Carpathian Foredeep, Romania (see text for GPS coordinates of all localities).
Data accessibility Data are included in this article and supplemented Excel file. Value of the data The calcareous nannofossil and planktonic foraminiferal bio-events from the study area can be compared to dated bioevents in the Mediterranean region in order to provide an age framework for the Paratethys region. The litho-biostratigraphic data can be incorporated in future chronostratigraphic and paleoenvironmental studies in the Paratethys region. The data provide the first report of tiny Streptochilus/Bolivina spp. foraminifera in the sections in the SE Carpathian Foredeep in Romania, allowing comparison to similar blooming events in other parts of the Paratethys Sea, Mediterranean and Atlantic Ocean.
in Valea Dracului, Campinit¸a and Brebu. The resolution is lower (4 m or more) in intervals with a lot of coarse-grained material, such as sands and volcanic material. A total of 81 calcareous nannofossil smear slides were prepared for calcareous nannofossil analysis using standard methods [1,2] and analyzed with a Zeiss Axioscope microscope under magnification 1000Â at Catania University. According to the counting methodologies proposed by Refs. [2,3], targeted counts of biostratigraphically significant taxa were performed, in order to obtain relative abundances. Specifically, 30 and 50 specimens within the genera Sphenolithus and Helicosphaera were counted, respectively.
A total of 88 samples for the analysis of foraminiferal assemblages were prepared partly at the Geolab of the Faculty of Geosciences of Utrecht University and partly at the Micropaleontology Laboratory of the University of Parma. Samples (about 250 g) were dried in an electric oven at 40 C for approximately 2 days, were processed with H 2 O 2 (3%), and washed over 63 and 125 mm sieves. A qualitative analysis of planktonic foraminiferal assemblages was carried out on the >125 mm fraction of the washed residues focusing on the biostratigraphic marker species and on the >63 mm fraction specifically for Streptochilus spp; representative taxa were picked and mounted on micropaleontological slides. The biostratigraphic scheme for the Mediterranean by Ref. [4] emended in Ref. [5] was adopted. The foraminiferal content of the samples is highly variable, from (nearly) absent to very abundant. The preservation is also variable, from very poor to good. The samples containing benthic foraminifera (>125 mm size fraction) were qualitatively examined and representative taxa were mounted on micropaleontology slides for reference.

SE Carpathian Foredeep: Campinit¸a and Brebu
The Miocene sediments in the SE Carpathian bend area were deposited in a former piggyback basin and subsequently incorporated into the Tarc au nappe. Similar deposits are found in the Râmnicu Vâlcea -Câmpulung e Câmpina e Sl anic areas [e.g., 6,7]. In the study area, the Sl anic tuff with Globigerina Marls that mark the Badenian flooding are known as the Campinit¸a Formation [8].
The Campinit¸a (CA; 45.136799 N, 25.711042 E) section is 155 m thick and located on the southern flank of an anticline along the western bank of the Prahova river. The outcrop covers the upper part of the Doftana, Campinit¸a and Upper Evaporite Formations (Fig. 2). The lithology is dominated by brownand green-gray clays and silts with occasional wavy bedded sandy levels. Continental mottled red and green clays mark the basal part ( Fig. 3f. Thin gypsum levels appear from 60 m upwards. Around 80 m a prominent interval with wavy gypsum lamina intercalating with mm-scale organic rich shales is present, which likely represents the Cireş u gypsum [1] (Fig. 3). Thick yellow-gray fine to coarse micarich sand bodies stand out between 100 and 117 m (Fig. 3g. Some have current structures at their base and they often alternate with reddish marls in layers of 30e50 cm. Findings of vertebrate footprints and traces of raindrops suggest shallow water to intertidal conditions for part of the environment [9]. The base of the Campinit¸a Fm is at 138 m (Fig. 1). The formation is dominated by an about 10 m-thick sequence of gray tuffaceous marls with three biotite-bearing tuffs (5e10 cm thick) with large middle Miocene planktonic foraminifera. The section is sealed by a sequence of sapropels, gypsum-rich conglomerates and salt breccia.
The 400 m-thick Brebu (BR; 45.185498 N, 25.775669 E) profile is found along a NE striking tributary of the Doftana river and covers almost the complete early Miocene succession including the uppermost Lower Gypsum, Cornu(?), Brebu and Doftana Formations (Fig. 2). After a basal interval of gypsum and black shales (about 50 m; Lower Evaporite Fm), the lower part of the stratigraphy is dominated by conglomerates and sands (Brebu Fm) gradually passing into microconglomerates and clays of the Doftana Fm. Sands of the Brebu Fm are sourced from the Perş ani mountains, which currently form the internal part of the East Carpathians suggesting a low Carpathian topography at that time of deposition [6].
The upper part of the Brebu section is dominated by gray, green and red mottled clays and sandy silts including several gypsum layers (Doftana Fm). This part is poorly to non-exposed due to mudslides and vegetation, and was studied in more detail in the Campinit¸a section. Two notable evaporitic intervals could be recognized; the Perchiu gypsum at the base of the Doftana Fm, and the Cireş u gypsum towards the top, serving as regional evaporitic marker levels (Fig. 3b). Another notable feature is a biotite-bearing tuff layer (20e50 cm thick) followed by a prominent gypsum bed. The middle Miocene Sl anic tuff level is clearly visible in the top of the main Brebu profile. The transgressive boundary between the Doftana Fm and Campinit¸a Fm is exposed in a parallel section towards the west next to the Brebu Manastirei cemetery (Fig. 3b). It can be summarized by about 15 m of tuffitic clays and tuffites. The Brebu section is topped by a layer of salt breccia.
The transgressive intervals in Campinit¸a and Brebu sections both start with blue-gray clay and silt layers, followed by a dark sapropelic silt or clay interval full with orange-weathered iron oxides and barren in fossils. In both sections, this is followed by sands bearing water escape structures. The first rich planktonic foraminiferal assemblages appear within or just on top of these sand packages. In Brebu, the succession is followed by another resistant and prominent thick fine-to-medium greenwhite three-layered disturbed sand package with wavy lamination and iron coated 'knobs' at its base (Fig. 3b).

NW Transylvanian Basin: Valea Dracului, Ciceu-Giurgest¸i and Cepari
The Valea Dracului (DV), Ciceu-Giurgest¸i (CG) and Cepari (CP) sections cover (parts of) the upper Hida Fm and Dej Fm in the NW Transylvanian basin (Fig. 1). In this region, several studies defined the    .859869 E) is exposed on the flanks of a river canyon and covers the upper Hida and Dej Formations (Fig. 1). The upper Hida Fm (0e24 m) displays gray brown clays with cm-scale sand and coaly lenses. These are occasionally perturbed by yellow fine to medium sand beds that pinch out laterally (Fig. 3d). At 20 m, thick coarse to medium sand beds with basal clay with rip up clasts and coal chips appear. The facies reflect a distal fan delta environment with some gravity flow associated deposits.
The Dej Fm begins with a wedging conglomerate lens (0e5 m thick) cutting laterally into a finergrained succession with middle Miocene planktonic foraminifera. The basal part starts with orange fine sand grading first into slightly mottled brown-orange silt and later into gray brown silty clay. A horizontal layer of cm-scale iron nodules is present at the silt to clay transition. The brown clay is succeeded by distinct colored units: dark green bedded clay to sand, an orange clay level (1 cm), purple clay laminated with tuffites, gray marl with cm-lenses of tuffaceous sand, and green-white bedded tuffs (Fig. 1). This interval (24.3e28.7 m); DX in Fig. 2 is covered by massive volcanoclastics, towering high above the Dracului valley. The lowermost part is a tuffaceous sand with characteristic green elongated Dej tuff clasts with an erosive base, the middle part (~6 m) is coarse sand with large scale cross beds, and the top is a bedded alternation of silts and greenish tuff layers (Fig. 3d and e). The Dej Fm was deposited on the shelf margin or in deeper marine settings. The prominent coarse tuffites/ sands with basal rip-up clasts were interpreted as a submarine meandering channel reflecting high input of volcanic activity. This channel eroded into the underlying shelf deposits.
The 73 m thick Ciceu-Giurgesti section (CG; 47.241532 N, 24.032811 E) is exposed along a lowstanding river gully [14]. Published a log and planktonic foraminiferal bio-events for the lower part of the Ciceu-Giurgesti section covering the early-middle Miocene boundary. During the fieldwork campaign in 2015, however, the lowermost part of the section presented by [23] was covered by sediment and vegetation, and could not be studied. Therefore, the here presented section starts just above the First Occurrence (FO) of Praeorbulina glomerosa, and thus covers the Dej Fm only. Here, the Dej Fm is also known as the Ciceu-Giurgeş ti Fm, but this term is not used to avoid confusion with the other Transylvanian sections. The lowermost part of the profile (0e11 m) contains clays, silts and a thin conglomerate layer and is mostly unexposed (see [14] for details). Upwards a 5 m thick package of poorly sorted medium-coarse sand with elongated coarse greenish rip-up clasts and pebbles (<10 cm) stands out. The rip-up clasts are rich in tuffaceous material and occur in all sizes, the largest are 75 cm in length. The sand body is covered by an interval of silty clays and sands with (often) reworked green tuffs, and an~7 m interval dominated by volcanoclastic sands and cross-laminated layered tuffs. A tuff at~20 m stratigraphic height was dated at 14.38 ± 0.06 Ma [14]. The stratigraphy continues with dark gray clays intercalated with green tuff levels and an 1.5 m silty bed with algae mats and dark clay lenses. In the top of the CG section (>50 m) fine and medium grained sands with organic rich interbeds and some tuff intercalations stand out.
The 38 m thick Cepari section (CP; 47.242542 N, 24.425911 E) is well-exposed in a former quarry. Some authors infer a discontinuity at the base of the Langhian transgression in this region (~7 km NW of Cepari) based on lithostratigraphy and microfaunal analysis [15]. In most places, the transgression begins with a conglomerate level followed by characteristic Langhian microfauna. The basal part (0e4.5 m) of Cepari section contains gray brown silty clay with occasional yellow sands, and may be part of the Hida Fm. It is overlain by two discontinuous beds of dark gray and gray clay, that are laterally cut by a maximally 3 m thick coarse-to-medium poorly sorted sand with sand intraclasts. The beginning of the Dej Fm is marked by the first 4 m thick tuff bed. Silty clays with tuffs including a second thick (3 m) tuff package are positioned on top. The section ends with tuffaceous yellow gray clays intercalating with some fine sands, and one thick volcanoclastic sand.  (Figs. 4 and 7).
In the Brebu section, preservation is generally poor and calcareous nannofossil assemblages are often poorly preserved in the analyzed samples. However, in each sample the most relevant biostratigraphic markers were individuated, allowing to ascribe the deposits from the base to the top to the early Langhian MNN4b Subzone (BX1 and BX2 at 0 and 0.25 m), to the middle Langhian MNN5a Subzone (BX3 to BX10: 0.5e2 m), and to the late Langhian MNN5b Subzone (BX13, 2.4 m) ( Table 1, Fig. 7).
The preservation of the calcareous nannofossil assemblages in the Dracului Valley (DV) section is very poor in the low-intermediate portion of the sampled interval, between samples DV01 and DV17 (base of section to 21.8 m). Conversely, starting from sample DV19a (25.7 m), a good degree of preservation allows ascribing the deposits to the middle to late Langhian MNN5a (samples DV19a-DV21; 25.7e30.7 m) e MNN5b (sample DV22; 33 m) subzones. Sediments from Ciceu-Giurgest¸i Section are in general well-preserved. The bio-chronostratigraphic analysis allowed ascribing the samples between the early Langhian MNN5b Subzone (samples CG01-CG11; 6.5e33 m) and the late Langhian to early Serravallian MNN5c Subzone (samples CG12-CG24; 36.4e80 m). In the Cepari section, the preservation degree is very poor in the lowermost samples (CP01-CP3B; 0.1e3.4 m), and good in the upper part of the section (samples CP7b-CP10; 14.7e18.7 m). The bio-chronostratigraphic analysis allowed framing the deposition in the middle Langhian MNN5a Subzone (Fig. 7).

Planktonic foraminifera
Planktonic foraminifera from the lower part of the Campinit¸a section (up to sample CA08 at about 139 m, Doftana Fm) are generally absent or very diluted (Table 1). In a few stratigraphic levels (CA30 and CA29 at about 87 m) ill-preserved double-keeled planktonic specimens are evidence of reworking of Cretaceous sediments. Miocene planktonic foraminiferal assemblages are represented by rare and scattered occurrences of Dentoglobigerina spp., Globigerina praebulloides, Globigerinella spp., Globigerinoides trilobus and Paragloborotalia siakensis. In only two samples (CA44 at about 62 m and CA19 at about 102 m) a single occurrence of Praeorbulina glomerosa glomerosa has been found suggesting the attribution to Subzone MMi4c (Fig. 7). However, the biostratigraphic interpretation is weak because of the extreme rarity of planktonic foraminifera. In a few samples (CA12, CA11, CA10 and CA9B, 118e134 m) occurrences of Streptochilus spp./Bolivin spp. have been recorded in the >63 < 125 mm fraction of the washed residue (Table 1, Fig. 6).
In the Brebu section, most of the samples are barren in fossils or contain very rare planktonic foraminifera. Only the uppermost samples (BX10 and BX13) yield abundant and moderately preserved planktonic foraminifera. The most recurrent taxa are Dentoglobigerina altispira gr., Globigerina praebulloides, Globigerinoides sicanus, Globigerinoides trilobus, Globorotalia praescitula, Globoturborotalita woodi, Paragloborotalia siakensis, Praeorbulina glomerosa s.l. and Orbulina suturalis. Rare specimens of Praeorbulina glomerosa glomerosa and P. cf. glomerosa circularis occur in the lowermost sample (BX1) suggesting Subzone MMi4c/d?, while Orbulina suturalis has been found in the sample interval between BX06 and BX13 allowing the attribution of this interval to Subzone MMi5a. In the latter sample few specimens of O. suturalis show more evolved characters close to O. universa, whose first occurrence identifies the base of Subzone MMi5b (Table 1, Fig. 7).
Samples from the lower part of the Valea Dracului section, up to 25 m, are generally barren or nearly barren in foraminifera. In sample DV 17 (at~22.8 m) a single specimen of Praeorbulina glomerosa glomerosa has been found suggesting Subzone MMi4c? Note, however, that the reliability of this biostratigraphic attribution is weak since planktonic foraminifera are extremely rare in this sample.

Benthic foraminifera and ostracods
In the samples containing benthic foraminifera, the assemblages vary from extremely poor to relatively rich (Table 1). In the SE Carpathian Foredeep, in the Campinit¸a (CA) section, the interval below the open marine flooding (117.9e136.5 m; samples CA13, CA10 and CA9) is quartz-rich and the relatively rare hyaline taxa are poorly preserved. Grain size sorting suggests transport or winnowing. Plant remains in CA10 and CA13 indicate a near-coastal environment, possibly brackish and in the vicinity of a river plume. Most taxa in these samples are restricted to the inner-mid shelf; some taxa (miliolids, Hanzawaia boueana, Rosalina globularis) tolerate a certain degree of hypo-and hypersalinity. In sample CA09, preservation of fish remains suggests oxygen restriction (since phosphate is preserved under anoxic conditions), and a specimen of the planktonic foraminifer Morozovella sp. indicates reworking of Paleogene sediments. Sample CA08, located in the base of the flooding at 138.7 m, mainly contains diverse miliolids together with numerous, nearly monospecific smooth ostracods (Loxoconcha punctatella) pointing to an oxic, shallow-marine environment with deviating salinity (Table 1; Fig. 5).
In the Transylvanian Basin, the washed residue of the sample collected from the basal Dej Fm just above the flooding in the Valea Dracului (DV) section (DV19A; 25.7 m) is large, well-sorted and clean (mainly quartz, lithic fragments), suggesting a high-energy environment, possibly a beach. Absence of planktonic foraminifera and rare, recrystallized benthic foraminifera: miliolid, Elphidium sp. and Textularia sp. suggest shallow-marine waters. Higher up, the washed residue of sample DV19 (29.5 m) contains only two hyaline specimens (Cibicides -lobatulus and a C. cf. ungerianus?) which may be displaced or reworked. Planktonic foraminifera are relatively common and minor pyrite and fish remains are present. Together with the virtual absence of benthic foraminifera this might point to bottom-water oxygen deficiency in shelf waters of normal marine salinity.