Burdigalian Research Articles

BIOSTRATIGRAPHY AND PALEOENVIRONMENTAL ANALYSIS OF THE LOWER MIOCENE QOM FORMATION (JAAM AREA, CENTRAL IRANIAN BASIN)

Lower Miocene sediments from a previously not investigated outcrop of the Qom Formation (Central Iranian Basin) were studied for their foraminiferal and calcareous nannofossil content. The studied stratigraphic record is assigned to the upper part of calcareous nannofossil NN2 Zone/CN1c Subzone and to the benthic foraminiferal Borelis melo melo Zone of Burdigalian age. The diversity indices, benthic foraminiferal morphogroups, and quantitative analyses of assemblages (principal component and cluster analysis) suggest an overall shallow-marine depositional environment. This interpretation is well constrained based on the dominance of the B1 benthic foraminifera morphotype with biconvex, trochospiral calcareous test, and epifaunal habitat. The identified six cluster groups of benthic foraminiferal assemblages are confirmed by the principal component analysis too, and their distribution along the studied section argue for dynamic changes of the environment. This is well exemplified by a more or less constant shallowing, then deepening trend of the environment as revealed by the shifting from the high diversity, shallow-shelf assemblages of Cluster 5 and 6 toward the low diversity, near-shore Ammonia tepida and Porosononion subgranosus assemblage (Cluster 1), and back.

Foraminiferal distribution and biostratigraphy of the Lower Miocene Qom formation, north of Bijar, NW Iran

This study is based on larger benthic foraminifera that dominate the Lower Miocene shelf carbonates of the Qamcheqai section, NW Iran. During the time of deposition, the investigated area was positioned on the Eurasian side of the Tethyan Seaway between the Eastern and Western Tethys. Seven porcelaneous and hyaline perforated species were determined, including Praebullalveolina curdica, Peneroplis evolutus, Androsina cf. diyarbakirensis, Sivasina egribucakensis, Miogypsina cf. intermedia, Operculina complanata, and Amphistegina bohdanowiczi. The presence of Miogypsina cf. intermedia, and Praebullalveolina curdica allowed to correlate the assemblage with SBZ 25 Zone, indicating a Burdigalian age. The results of this study extend the paleogeographic distribution of the endemic taxa Androsina and Sivasina eastwards as far as Central Iran.

Insights into the palaeoenvironments, structure and stratigraphy of the lower Miocene of the Eastern Carpathians Bend Zone, Romania

The ages of several Oligocene to Miocene sedimentary formations from the Eastern Carpathians Bend Zone are poorly constrained due to palaeoenvironmental factors, reworking of fossils, structural complexity and limited exposure. To help overcome these issues, this study integrates calcareous nannoplankton and foraminifera biostratigraphy with isotopic age dating (U-Pb) of volcaniclastic zircons, and sedimentological and structural observations/interpretations. Our study was carried out along an ~6-km-long section made from a series of outcrops along the Bizdidel River which exposes several formations such as the Pucioasa, Fusaru, Vinețișu, Starchiojd and Slon. We show that the Fusaru Formation consists of coarse-grained rocks deposited as confined longitudinal channel successions that migrated laterally. It is bounded by the mud-rich Pucioasa and Vinețișu formations which are lateral equivalents of the Fusaru confined channels deposited as levee/overbank units. These genetically related formations appear to reach younger ages – of the lower to middle Burdigalian based on calcareous nannoplankton and foraminifera biostratigraphy – than previously thought (upper Oligocene to lower Burdigalian). The dominant organic-rich mudstones of the Starchiojd Formation represent pelagites/hemipelagites deposited in anoxic conditions. Their middle Burdigalian age is established by a 17.41 ±0.27 Ma zircon U-Pb age of zircons from the Bătrâni Tuff in the Starchiojd Formation. Based on the similar phenocryst content, zircon U-Pb age and zircon trace element composition, the source of the tuff is suggested to be the 17.3 Ma Eger ignimbrite-forming eruption, which has proximal, near-caldera deposits in the Bükkalja Volcanic Field, Hungary. The mud-rich Slon Formation seems to be related to shelf edge/upslope failure that formed cohesive debrite avalanches resulting from foreland propagation of compression. The Slon Formation extends in this area to at least the upper part of the lower Miocene to middle Miocene. These results highlight the need to revise ages of those parts of the sequence which are poorly constrained or different in other parts of the Carpathian Basin. Such revised ages help to better constrain the understanding of the deformation history of the Carpathians.

Distribution and abundance of early Miocene foraminifera in the Qom Basin of Central Iran

The Oligo-Miocene sediments of Central Iran were deposited in part of the Tethyan Seaway connecting the Mediterranean Sea (western Tethys) to the Indian Ocean (eastern Tethys). The Qom Formation sediments were deposited in the northeastern part of the Tethyan Seaway. For analyzing the depositional environments of the Qom Formation in the Tigheh Reza Abad section (type area of the Qom Formation) samples through 967 m thickness were studied which yielded 64 genera and 106 species of benthic and planktic foraminifera, including index species indicative of Aquitanian to Burdigalian age. Five faunal associations (I-V) are recognized on the basis of foraminiferal diversity and abundance. The faunal associations indicate different paleoenvironments along a gradient from inner to outer shelf in the warm, shallow-marine Qom Basin.

A synthesis of fauna, palaeoenvironments and stratigraphy of the Miocene Tagay locality (Olkhon Island, Lake Baikal, Eastern Siberia)

We report about the Early Miocene Tagay fauna of Olkhon Island, the largest island of the Baikal Lake. The Tagay fauna is of high scientific importance because of the diversity of fishes, amphibians, lizards, snakes, turtles, manifold birds and mammals. The lithology, geochemistry and the fossil record along the Tagay-1 section allow reconstruction of various palaeoenvironments, i.e. open water, shallow lakes with adjacent wetlands, riverine woodlands, and also forested and dry habitats. The fossil record, lithology and geochemical sediment-analyses suggest a temperate palaeoclimate with short humid and dry periods. The small mammal record and the magnetic polarity pattern of the upper part of section Tagay-1 correlate with the subchrons C5Cn.2r – C5Cn.1r of Chron C5C and the late Burdigalian Stage of the Geologic Time Scale (GTS2000). The corresponding age range of the Tagay fauna is ~16.5 to ~16.3 Ma.

A new volute, Ericusa ngayawang sp. nov. (Gastropoda: Volutidae), from the Miocene of South Australia.

Ericusa ngayawang sp. nov. is described from shells preserved in the Middle Miocene Cadell Formation in the western Murray Basin of South Australia. At the time the Murray Basin was part of the Southeastern Australian Marine Biogeographic Province. Ericusa ngayawang is a small heavily costate species of Ericusa with clear affinities to the Early Miocene E. atkinsoni of Victoria and Tasmania but can be distinguished from it by its smaller size, more slender proportions and its heavily costate body whorl. Ericusa atkinsoni and its relative, E. macroptera, inhabited the basins to the east of the Murray Basin during the Late Oligocene and Early Miocene but were extinct there before the end of the Burdigalian Stage of the Early Miocene. The persistence of E. ngayawang into the Langhian Stage of the Middle Miocene is another piece of evidence for partial biogeographic isolation of the western Murray Basin from the rest of the Southeastern Australian Province during the Miocene.

First records of extinct kentriodontid and squalodelphinid dolphins from the Upper Marine Molasse (Burdigalian age) of Switzerland and a reappraisal of the Swiss cetacean fauna.

The Swiss Upper Marine Molasse (OMM) documents a transgression event dated to around 21 to 17 million years in which dolphin and other vertebrate remains have been reported. We revised the whole cetacean (whales and dolphins) OMM assemblage available in main collections, focusing on the identification and interpretation of periotics (bone that contains the inner ear). Periotics are rare, but they provide the richest taxonomic information in the sample and hint to environmental associations. Micro-computerized tomography allowed the reconstruction of bony labyrinths for comparisons and environmental interpretations. Three families are represented by periotics: Kentriodontidae, Squalodelphinidae and Physeteridae. The cetacean taxonomic composition of the Swiss OMM reinforces biogeographical patterns reported for the Mediterranean and Paratethys during the Burdigalian at a regional scale and the Calvert cetacean fauna of the northwest Atlantic at oceanic scale.

3D models related to the publication: First records of extinct kentriodontid and squalodelphinid dolphins from the Upper Marine Molasse (Burdigalian age) of Switzerland and a reappraisal of the Swiss cetacean fauna.

3D models related to the publication: First records of extinct kentriodontid and squalodelphinid dolphins from the Upper Marine Molasse (Burdigalian age) of Switzerland and a reappraisal of the Swiss cetacean fauna.

Systematic of the Early-Miocene (Burdigalian) Ostracoda from Northeastern Semnan, Central Iran

Seven genera and seventeen species of marine Ostracoda are reported for the first time from the Attari section (Qom Formation), northeast of the Semnan, Central Iran. In this section, the Qom Formation outcrops with 280 m thickness lies on the Eocene volcanic and under the Upper Red formation. According to the distribution of index foraminifera, there is conspicuous similarity between larger bentic foraminifera assemblages of the Qom Formation foraminifera and those of the Zagros basin, such as Borelis melo curdica the age of Qom Formation in the Attari section is Early Miocene (Burdigalian). The Miocene and even Oligocene Ostracoda fauna, relatively similar to the Attari section, have been reported from the Mediterranean area and the Proto- Indo- Pacific Ocean. The presence of one species with Paratethian origin in the Qom Formation is strong evidence that during the Burdigalian stage, the sea way between Central Iran and Paratethys basin still existed.

Burdigalian-Langhian foraminifera of the northwest High Zagros Thrust Belt, southwest Iran

Abstract The foraminiferal contents of the lower–middle Miocene succession exposed in three sections in north Nur Abad on the northwestern side of the High Zagros Thrust Belt were studied. Assemblages of larger foraminifera from these sections can be referred to Zone SBZ 25 (and the Miogypsina globulus and Miogypsina intermedia subzones), which correlates with the Burdigalian Stage. For the first time, planktonic foraminifera documented from the Nur Abad area document Lang-hian deposits in the High Zagros, the upper 20 metres of the upper Sayl Cheshmeh section being characterised by the occurrence of planktonic foraminifera such as Globigerina concinna (Reuss), Globigerina diplostoma (Reuss), Globigerinoides obliquus (Bolli), Orbulina bilobata (d’Orbigny) and O.universa (d’Orbigny). This association characterises the Orbulina suturalis Interval Zone.

Micro biostratigraphy and paleo environment of Oligo-Miocene deposits in north of central Iran

Oligo-Miocene rocks are deposited between Pyrenean and Pasadenian orogenic phases. This rocks in central Iran back arc deposits are named Qom formation. There are well developed outcrops of Qom formation at the North of Central Iran zone. In order to study microbiostratigraphy of the formation, Three sections, north west of Darjazin town , Bonak mount and Arvaneh were selected. In these sections Qom formation with discontinuity overlays the Lower Red formation and with the same quality under the Late Miocene Conglomerate with intercalations of Sandstone, which is equivalent to the Upper Red Formation is placed. The main lithological composition of the Qom Formation in the study area alternates between layers of limestone and Marl with intercalations of siliciclastic rocks. Members and submembers of the Qom formation type area are not visible in this area and can only based on the lithological characteristics divide to local units. Based on bentic foraminifera and other microbiostratigraphical data, Qom Formation age in north west-west of Semnan (Darjazin-After zone), which is located in the Central Alborz structural- sedimentary zone, is early Miocene epoch and Burdigalian stage, which is the equivalent of Borelis melo curdica-Borelis melo biozone.

A high-resolution timescale for the Miocene Shanwang diatomaceous shale lagerstätte (China): development of Wavelet Scale Series Analysis for cyclostratigraphy

The Miocene aged Shanwang Formation from the Shanwang National Geopark in China represents a succession of lacustrine diatomaceous shales containing an abundant and diverse biota with lagerstatte fossilization of soft tissues. To date, the Shanwang Formation has not been investigated for cyclostratigraphy nor has it been dated with high precision methods. Now we use thorium data as a paleoenvironmental and paleoclimatic proxy to conduct a detailed cyclostratigraphic analysis. A new and simple cyclostratigraphic method, Wavelet Scale Series Analysis (WSSA) is developed to recognize Milankovitch cycles. A total of three short eccentricity and fifteen precession cycles are identified; obliquity cycles are not apparent. In the sedimentary succession, the corresponding precession and short eccentricity cycles are 1.17 m and 4.98 m thick respectively, with this verified by Correlation Coefficient (COCO) analysis and Multitaper-Method (MTM) spectral analysis. We estimate the studied interval was deposited over a duration of 0.3 Myr with a depositional rate of c. 5.7 cm/kyr. Paleomagnetic and radio isotope dating data shows that the diatomaceous shale was deposited during Chron C5En, which places it at approximately 18.5 Ma during the Burdigalian stage of the Early Miocene, rather than in the Middle Miocene as previously thought. The Shanwang lagerstatte biota therefore predates the Middle Miocene Climate Optimum (MMCO) and did not form within it. The geological time scale with a high resolution of 20 kyr was set accordingly.

BIOSTRATIGRAPHIC ANALYSIS OF THE OLIGOCENE-EARLY MIOCENE SUCCESSIONS FROM SULAIMANI AREA, KURDISTAN REGION, IRAQ

Three sections (Darzila, Hazar Kani and Basara) of the Oligocene –Early Miocene successions from Sulaimani area, Kurdistan region-NE Iraq, were measured and studied in order to interpret the biostratigraphic zonations at the Low and High Folded Thrust zones boundary, Low Folded Thrust zone, which are integrated with strontium stratigraphic dating. Accordingly, five biozones have been identified and they are:1- Nummulites vascus- Nummulites intermedius- Nummulites fichteli Assemblage Zone (Shallow Benthic Zone, SBZ 22A) represents the Rupelian age, 2- Lepidocyclina dilatata- Nummulites vascus - Nummulites fichteli Assemblage Zone (SBZ 22B-Early Chattian), 3- Praerhapydionina delicata- Archaias kirkukensis Assemblage Zone (SBZ23) representing the Late Chattian age, 4- Austrotrillina howchini- Peneroplis evolutus Assemblage Zone (SBZ24), almost point to the Aquitanian age and finally 5- Austrotrillina asmariensis- Dendritina rangi Assemblage Zone (equivalent to SBZ25) representing the Burdigalian age. Based on the distribution of the larger foraminifera and strontium stratigraphic dating, the Baba Formation is of Early to Late Oligocene age (Rupelian- Early Chattian), while the Bajawan Formation is of Chattian age, in addition to that, the Anah Formation is of Early Miocene age (Aquitanian) and the Jeribe Formation is of Burdigalian age. It is worthy to mention that the Oligocene-Miocene boundary has been identified in the studied area as well as, the gap duration between different formations of the Kirkuk Group, and the gap durations due to the absences of Serikagni, Euphrates and Dhiban formations.

Early Miocene squamate assemblage from the Mokrá-Western Quarry (Czech Republic) and its palaeobiogeographical and palaeoenvironmental implications

Two fossiliferous karstic fissures from the Mokrá-Western Quarry, MWQ (1/2001 Turtle Joint; 2/2003 Reptile Joint) provided a diverse vertebrate fauna from the early Miocene (Burdigalian, MN 4) including squamates. The rather warm climatic conditions during the Miocene Thermal Maximum (17.8-17.7 Ma) enabled dispersal of thermophilic lizards and snakes throughout Central Europe. In total, ten major clades have been identified in MWQ localities, including: Lacertidae (Lacertidae indet., Lacertidae tooth morphotype 1 and 2); Amphisbaenia (Amphisbaenia indet.); ? Scincoidea (? Scincoidea indet.); Anguidae (Pseudopus laurillardi (Lartet, 1851), Pseudopus sp., Ophisaurus sp., and Anguinae indet.); Varanidae (Varanus mokrensisIvanov, Klembara, Ruta & Böhme, 2018); Boidae (Bavarioboa cf. hermiSzyndlar & Schleich, 1993); Pythonidae (Python sp.); Colubridae (Colubridae gen. et sp. indet., Coluber [s.l.] sp., and “Colubrinae” indet., type 1), Natricidae (Natrix sp. and “Natricinae” indet.); Viperidae (Viperinae [‘Oriental vipers' group], Vipera sp. [‘European vipers' group]); and Elapidae (Elapidae gen. et sp. indet.). Python sp. from the MWQ represents the first known occurrence of this most thermophilic Neogene squamate taxon within the area of Central Paratethys and we assume that MAT did not fall below 18-19 °C in the vicinity of this locality during the late Burdigalian stage. These humid subtropical to paratropical climatic conditions, also documented by several full-aquatic and semi-aquatic amphibians and reptiles, were suitable for the occurrence of other thermophilic lizard and snake taxa reported from MWQ, including Varanus mokrensis, Pseudopus laurillardi, Bavarioboa, large Elapidae and ‘Oriental vipers'.

CAVOLINIDAE DEL MIOCENE INFERIORE Dl CASTELSARDO (SARDEGNA SETTENTRIONALE)

In this paper are described and illustrated Pteropoda coming frorn two Lower Miocene sections exposed near the village of Castelsardo (Norhern Sardinia). The sampled sections cover a stratigraphic range which extends from the basal part of zone N4 to uppermost N6 (after Blow's planktonic foraminiferal zonation), that means an Aquitaman—Burdigalian age.

Depositional and diagenetic history of limestones and dolostones of the Oligo‐Miocene Kujung Formation in the Northeast Java Basin, Indonesia

AbstractLithological and geochemical features of platformal carbonates record the signatures of the global climates and the regional environmental settings and also reconstruct the diagenetic history and porosity evolution, which are essential to evaluate the potential of hydrocarbon reservoirs. This study investigates the platformal carbonates of the Oligo‐Miocene Krunji Formation of North East Java Basin, which are potentially significant hydrocarbon reservoirs. The carbonate sequence in a 283 m thick section at Kranji in East Java is subdivided into three lithological units: limestone unit 1, dolostone unit 2, and limestone unit 3, in ascending order. The strontium‐isotope ratios of well‐preserved calcite samples indicate the depositional period from Chattian (late Oligocene) to Burdigalian (early Miocene), which is consistent with ages of the foraminifer assemblages. Unit 1 consists of low‐porosity limestone, in which two horizons of subaerial exposure are recognized by the occurrence of red‐colored matrix and lower δ13C values. Unit 2 consists of dolomitic rock and exhibits coarse‐grained calcitic grains and cross‐stratified structure. Considering that this unit has been subject to dolomitization, the sediment of unit 2 was initially permeable and was likely deposited in a shoal setting. The overlying unit 3 of Aquitanian–Burdigalian age is characterized by a highly granular texture. High porosity and uniformly low δ13C and δ18O values indicate that Unit 3 was subjected to more intense meteoric diagenesis than the Chattian unit 1. This was likely a consequence of the Antarctic ice‐sheet expansion during the Oligocene/Miocene transition, which amplified sea level change. The unit 2 dolomite has high δ13C and δ18O values and a high 87Sr/86Sr ratio which resulted from the reflux of seawater into permeable the sediment body in middle‐late Miocene (Burdigalian Tortonian) following the deposition of unit 3. The porosity and permeability of the Kujung Formation were initially controlled by sedimentological processes, but largely modified by later diagenetic processes.

Depositional cycles of the Lower Miocene Rudeis Formation (southwestern offshore margin of the Gulf of Suez, Egypt): Implications for reservoir evaluation

The Lower Miocene Rudeis Formation in the Zeit Bay Field (Gulf of Suez, Egypt) has been studied by analysis of cores from six boreholes. The objective was to detail the sedimentary cycles in the formation and their implications for the reservoir characteristics, as well as to obtain a more detailed insight into the precise age by establishing a foraminifer zonation. The formation, which was found to be some 60–191 m thick, is composed almost exclusively of various types of carbonates. These contain foraminifers that prove a Burdigalian age, and that also provide insight into the depositional environments, which turned out to form three belts. These belts represent an intertidal lagoon, barrier shoals, and a reef complex, respectively, indicating a down-dip depositional profile of a shallow marine rimmed carbonate shelf. Analysis of the cyclicity pattern of the Rudeis Formation, supported by facies analysis and CycloLog curves, makes it possible to distinguish three superimposed 3rd-order depositional cycles, which are subdivided into several higher-order cycles that are strongly controlled by eustatic sea-level fluctuations. A set of lithofacies isopach maps has been constructed for these cycles with the objective to facilitate interpretation of the spatial distribution of the reservoir quality for hydrocarbons. The maps show that the reservoir quality of the Rudeis Formation is heterogeneous because of the highly variable characteristics of the various lithofacies types.

An example of evolutionary trends in the Miogypsinidae (Foraminiferida) from Turkey

ABSTRACTThe objectives of the study are to establish evolutionary trends in the miogypsinid foraminifera from Mediterranean Tethyan carbonates in Turkey. Taxa classified under the genera Miogypsinella, Postmiogypsinella and Miogypsina and their assemblages closely resemble the fauna described from European marine sequences. The foraminiferal assemblages, studied in thin sections, are interpreted as representative of the Shallow Benthic Zones (SBZ) 21–22, of Rupelian-early Chattian age, and include Archaias kirkukensis, Austrotrillina asmariensis, Nephrolepidina praemarginata, Nummulites cf. vascus, Heterostegina assilinoides, Borelis pygmaea, Neoplanorbulinella malatyaensis, N. matsumarui, Risananeiza crassaparies, Neorotalia lithothamnica, Nephrolepidina sp. and others. The late Chattian SBZ 23 is represented by Miogypsinella borodinensis, M. akcadagensis, M. cf. complanata, Postmiogypsinella intermedia and Nephrolepidina morgani. SBZ 25, of Burdigalian age, includes Miogypsina globulina, M. cf. polymorpha, M. cf. thecideaeformis, Borelis curdica, Austrotrillina howchini, Planorbulinella caneae and Dendritina cf. rangi. A depositional hiatus in the Aquitanian SBZ 24, is also recorded using planktonic foraminifera and nannoplankton assemblages. Miogypsina globulina, widely reported from Central America, Mediterranean Tethys and Indo-Pacific areas, is a key species for the Burdigalian but Miogypsina cf. polymorpha is only reported from Indo-Pacific. A marine connection between the Indo-Pacific and Mediterranean Tethys is supported by these Burdigalian two species in the Malatya Basin. This study, which was carried out in Mediterranean Tethys, in the eastern part of Turkey could reveal an example of polyphyletic origin and geographical speciation or a local evolution during the migration of miogypsinids. The phylogenetic hypothesis in this study imply that Miogypsina is polyphyletic genus, originated twice (Miogypsinella-Postmiogypsinella-Miogypsina // Miogypsinoides-Miogypsinodella-Miogypsina).

Foraminiferal biostratigraphy of the lower Miocene Hamzian and Arashtanab sections (NW Iran), northern margin of the Tethyan Seaway

Lower Miocene strata exposed in the Khoy-Bostan Abad area (NW Iran) document marine platform environments. Paleontological and lithological characteristics of these deposits were investigated to develop detailed bio- and lithostratigraphic frameworks. The shallow marine units, composed of bioclastic carbonates in Bostan Abad and mixed siliciclastic carbonates in Khoy area, were deposited under different local tectonic regimes. Relatively diverse assemblages of benthic foraminifera from these shallow marine units were studied to establish a high resolution biostratigraphy in the context of the standard shallow benthic zonation of Western Tethys. The co-occurrence of Miogypsina intermedia Drooger and Borelis melo curdica (Reichel) characterizes Zone SBZ25, indicating a Burdigalian age as also indicated by planktonic foraminifera.

Foraminiferal biostratigraphy of the Miocene Qom Formation, northwest of the Qom, Central Iran

Near Dochah, in the type area of the Qom Formation, Central Iran, the Miocene is partly developed in pelagic facies. From the 894.1 meter thick, ‘a to e’ members of this section, 152 samples were collected. Abundant planktonic foraminifera let us correlate the study section with the global planktonic foraminifera biozonations. High diversity of foraminifera in the study section allow us to adapt the study succession to global biozonations. Twenty-seven genera and thirty-four species are reported for the first time from the Dochah section. First reports of Praeorbulina sicana and Praeorbulina transitoria in the upper part of this section led to recognition of the Praeorbulina sicana lower occurrence subzone (M5a) biozone with a late Late Burdigalian age.