Early Chattian Research Articles

Porcelaneous larger foraminiferal responses to Oligocene–Miocene global changes

Sea surface temperatures (SST) have been identified as a main controlling factor on larger benthic foraminifera (LBF) living in tropical to sub-tropical shallow-water carbonate and mixed siliciclastic‑carbonate platforms. Changes in SST, along with those in ocean acidification and nutrient content recorded in the global oceans throughout their history will not only continue but also be amplified in the future at an unprecedented rate of change possibly reaching levels found in the geological record. This study focuses on the Oligocene (mean SST 8 °C higher than present) and the Miocene (SST 5–8 °C higher than present) epochs which were characterized by a higher richness in porcelaneous LBF (pLBF) than today. A systematic re-assessment and comprehensive literature survey of stratigraphic ranges and palaeogeographic distribution in the Western Tethyan (Mediterranean) and Indo-Pacific regions are used to evaluate the impact of changes in SST, seawater pCO2 and pH on the biodiversity of the Oligocene–Miocene pLBF Alveolinella, Austrotrillina, Borelis, Bullalveolina, Flosculinella, and Praebullalveolina. Two peaks in species richness were identified during the Aquitanian and Langhian–Serravallian. These peaks occurred when SST was ∼29 °C, with pCO2 of ∼400 ppm and pH > 7.8. These values are comparable to those of today. The minima in species richness recorded in the Rupelian–early Chattian, in the Burdigalian and from the Tortonian onward can be correlated to the detrimental effects of both minimum (< 26 °C) and maximum (> 31 °C) SST thresholds. High pCO2 (> 600 ppm) values, which are limited to the Rupelian–early Chattian, are also detrimental to species richness. Seawater pH higher than 7.7 did not negatively affect species richness. These historical trends have serious implications for the future diversity of pLBFs with the increasing likely scenario of rising SST and pCO2 and lowering of pH values in the near future. These developments can potentially lead to diversity decrease and even extinction of pLBFs. However, the resilience of present-day pLBF species to rising SST and pCO2 levels is underpinned by the evolutionary histories of their fossil counterparts during climate variations, albeit at much different rates of change.

MIDDLE EOCENE IN THE ALPINE RETROFORELAND BASIN (NORTHERN ITALY): SEDIMENTARY RECORD OF A “MESO-ALPINE” ARC-TRENCH SYSTEM IN THE ALPS

The middle Eocene Cibrone Formation of Brianza (central-western Lombardy) represents an important stratigraphic record to understand a key step of the tectonic evolution of the Alpine range poorly recorded elsewhere. Quantitative petrographic analysis of turbidite arenites, well-constrained in age by the biostratigraphy of interlayered marlstones based on calcareous foraminifera and nannoplankton, allowed us to identify a possible vertical compositional trend within the Cibrone Fm. and to document the NP17 nannofossil Zone (Bartonian) in central Lombardy exposures, east of the Ternate Formation outcrop area. Variable arenite compositions are interpreted to reflect contributions from different source areas, i.e., recycled orogen, island arc, and starved continental shelf. In a paleogeographic scenario still open to different interpretations, the proposed reconstruction supports a classical plate tectonics model for arc-trench systems. The stratigraphic gap, recorded everywhere in Lombardy, between the Eocene succession and the base of the Gonfolite Lombarda Group (upper NP24 nannofossil Zone, early Chattian), corresponds to the earliest stage of continental collision, uplift and erosion that climaxed in the Neo-Alpine Phase.

Evolutionary trends in the Mediterranean Nephrolepidina: new chronosubspecies and biostratigraphic constraints

ABSTRACT The mean values of the grade of enclosure of the protoconch by the deuteroconch (Ai), the number of adauxiliary chamberlets (C), the number of annuli within 0.5 mm from the embryonic apparatus (N05) and the degree of stolonic distalization (FD5) were evaluated for several Nephrolepidina populations from the western Mediterranean. Data from two new populations were added to the various populations biometrically investigated in the last decades. The routinely employed Ai and C indexes alone seem to be not sufficient to provide biostratigraphic constraints for each Nephrolepidina chronospecies, whereas N05 appears to be dependent to the embryonic size. By including the index FD5, and thus the concept of neanic acceleration, it becomes possible to clearly separate the different chronosubspecies of Nephrolepidina from the Mediterranean bioprovince. Nephrolepidina praemarginata praemarginata is restricted to the late Rupelian SBZ22A. N. pramarginata elenamoroi n. ssp. is erected for those early Chattian (SBZ22B) populations with 32%<FD5mean <42%. N. morgani, characterised by 42%<FD5mean <50%, stands as a long-ranged species, spanning from the whole Chattian to the lowermost Aquitanian. N. tournoueri antonioi n. ssp. marks the Aquitanian (SBZ24) and is characterised by Aimean >45% and 50%<FD5mean <55%. N. tournoueri tournoueri characterises the Burdigalian (SBZ25), with Aimean >45% and FD5mean >55%.

Biostratigraphy, microfacies, paleoenvironment, and paleoecological study of the Oligocene (Late Rupelian–Early Chattian) Baba Formation, Kirkuk area, Northeastern Iraq

Biostratigraphy, microfacies, paleoenvironment, and paleoecological study of the Oligocene (Late Rupelian–Early Chattian) Baba Formation, Kirkuk area, Northeastern Iraq

Paleo-facies distribution and sequence stratigraphic architecture of the Oligo-Miocene Asmari carbonate platform (southeast Dezful Embayment, Zagros Basin, SW Iran)

A facies and sequence stratigraphic analysis was made of the Oligo-Miocene Asmari carbonate platform situated in the east and southeast of the Dezful Embayment (Zagros Basin, SW Iran). This study provides new paleofacies and depositional sequence distribution models for the eastern part of the Dezful Embayment and discusses the impact of the factors controlling sediment deposition being eustatic sea-level changes and tectonic processes. The petrographic study reveals that the variations in facies cover three depositional settings, e.g. open marine, lagoon and tidal flats. In total, six depositional sequences (DS) were identified within the sedimentary sequence of the Asmari Formation. DS1 and DS2 were deposited during the Rupelian (Oligocene) within deeper open marine platform settings. Sediments forming DS3 and DS4 were deposited during the Chattian in a carbonate platform environment within an open lagoon to protected lagoon setting. The Miocene DS5 and 6 sequences, Aquitanian and Burdigalian in age, were deposited in shallower environments compared to other DS's, within protected lagoon to tidal flat settings. A comparison with the sedimentary development in other parts of the Dezful Embayment showed that the deposition of the Asmari strata started earlier (Early Rupelian) in the eastern, south-eastern and north-eastern part of the basin. In the western and central parts of the Dezful Embayment it began in the Late Rupelian or even Rupelian/Chattian. The eastern and south-eastern parts of the Dezful Embayment displayed a platform margin setting during the Rupelian while the north-eastern and central areas showed a basin setting. During the Early Chattian, clastic sediments originating from the Arabian Plate were deposited in the west, southwest, northwest and centre of the basin in response to a sea-level lowstand. The two very thin sandstone units occurring in the Late Aquitanian succession across the west of the Bibi Hakimeh oilfield are the only sandstone layers related to a sea-level lowstand throughout E/SE of the Dezful Embayment. During the Chattian the sediments in the eastern parts of the Dezful Embayment were deposited in a proximal inner ramp setting, and corals and coralline red algae (mainly Lithophyllum sp. and Lithothamnion sp.) dominated the carbonate platform in the east, while imperforate benthic foraminifera (e.g. Peneroplis sp., Archaias sp.) and rare perforate benthic foraminifera (e.g. Neorotalia sp., and Amphistegina sp.) were the most frequent sediment contributors in the southeast of the basin (Bibi Hakimeh area). At the same time, sedimentation occurred on a distal inner to mid-ramp settings through the central areas of the Dezful Embayment. A eustatic fall in sea-level and tectonic processes resulted in the isolation of the basin. During the Aquitanian two exposure horizons formed in the western and central Dezful Embayment basin while the eastern part only displays one. During the Burdigalian, sedimentation in the entire Dezful Embayment occurred within an innermost, very shallow ramp setting. The current study shows that sea-level fluctuations and sometimes combined with regional tectonic processes controlled the variability in platform geometry and paleofacies distribution of the Oligo-Miocene sediments across the basin.

The Oligocene to Lower Miocene depositional sequences of the Zagros Basin, SW Iran

This research assesses the Oligocene to Lower Miocene Asmari and Pabdeh formations characteristics and depositional sequences in the Zagros Basin (south‐west Iran). A regional stratigraphic transect is selected including the Persian Gulf Foreland Basin, Dezful Embayment, and the Zagros Simple Folded sub‐zones of the Zagros Basin. Five major depositional sequences have been distinguished by major changes in facies and stratal architecture. The spatial and temporal distribution and evolution of the five third‐order sequences identified show a strong progradation system from the Zagros Simple Folded Belt (N/NE) towards the Persian Gulf Foreland Basin, especially during the Rupelian, while geometric intricacy and significant facies changes are less developed in the Late Chattian and Early Miocene. According to the sequence stratigraphy correlation, two tectonic pulses are proposed for the Asmari deposits in the Dezful Embayment and Zagros Simple Folded Belt during the Rupelian to Early Chattian. During the Burdigalian, the series drastically thickens northward, so that the greatest sediment thickness occurred in the Zagros Simple Folded Belt. There is probably a connection between the structural closure of the Neo‐Tethys and the continuous uplift of the Zagros fold belt in the study area.

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.

A New Specimen of Xiphiorhynchus sp. cf. aegyptiacus (Istiophoriformes, Xiphioidei, Xiphiidae) and Billfish Diversity in the Oligocene of South Carolina

A partial billfish rostrum from the Chandler Bridge Formation (Early Chattian, Oligocene) near Ladson, South Carolina, U.S.A., is described and identified as Xiphiorhynchus sp. cf. aegyptiacus. The angle of taper, depth to width ratio of the cross section, and other morphological features (including dorsolateral grooves and a planoconvex cross-section), indicate that this specimen (and an earlier published speccimen) is closest in morphology to X. aegyptiacus from the Eocene Birket Qarun Formation of Egypt. This confirms the presence of a second xiphiid in the Chandler Bridge Formation besides the well-documented giant swordfish X. rotundus. This is an unusual example of two Xiphiorhynchus species existing in known sympatry, and strongly contrasting morphologies and morphometrics may point to niche partitioning between the two forms. The occurrence of specimens strongly resembling X. aegyptiacus in the western Atlantic also further substantiates past arguments that easy dispersal across the Atlantic was possible for this genus, and, by extension, that it shared the open-sea, migratory epipelagic lifestyle of modern swordfish. Moreover, the Chandler Bridge Formation boasts the most diverse billfish assemblage in the world, including Xiphiorhynchus sp., cf. X. aegyptiacus, X. rotundus, an early istiophorid, and 4-7 species of blochiid billfish in the genera Aglyptorhynchus and Cylindracanthus.

The Oligocene/Miocene boundary in the ON-Mol-1 and Weelde boreholes along the southern margin of the North Sea Basin, Belgium

Based on palynologic interpretations, the Oligocene/Miocene boundary was identified in the cored samples of the ON-Mol-1 and Weelde boreholes in the southern North Sea Basin. In both boreholes, the presumed location of the Oligocene/Miocene boundary is marked by a thin gravel bed, which testifies of a hiatus, within a continuation of shelly, dark green to black fine glauconitic sands. In the Weelde borehole, the hiatus is relatively short as the dinocysts under- and overlying the gravel bed suggest a late(st) Chattian and early Aquitanian age. This study thereby for the first time indicates the presence of Aquitanian strata in the area. In the ON-Mol-1 borehole, located south of the Weelde borehole, the hiatus is longer as dinocysts under- and overlying the gravel bed suggest an early Chattian and late Aquitanian age. The wider ranges of the hiatus might be the result of the combination of erosion/non-deposition of late Chattian strata and the gradual transgression of the southern North Sea Basin from north to south after the Oligocene/Miocene sea-level fall. The sampled interval around the Oligocene/Miocene boundary contains a lot of reworked Paleogene (including irregular upper Oligocene species occurrences) and Mesozoic taxa, which explains why the Miocene strata in the ON-Mol-1 and Weelde boreholes were dated as Chattian by previous studies.

Biometric study of late Oligocene larger benthic Foraminifera (Lepidocyclinidae and Nummulitidae) from the Qom Formation, Central Iran (Tajar-Kuh section)

AbstractThe Oligocene strata of the Qom Formation from the Tajar-Kuh section, Central Iran, are rich in various Larger Benthic Foraminifera (LBF). Morphometric studies of the internal features of the LBF tests were carried out based on matrix-free specimens from seven samples. The LBF assemblage studied in 24 populations mainly contains representatives of two nummulitid (the reticulateNummulites bormidiensisTellini, 1888, only in the lower three samples, and the radiateNummulites kecskemetiiLess, 1991 in all samples) and of two lepidocyclinid lineages. Of the latter,Nephrolepidina praemarginata(R. Douvillé, 1908) occurs in all the samples, whereasEulepidina formosoidesH. Douvillé, 1925 is present in the lower six samples. In the upper sample, the slightly more advancedEulepidinaex. interc.formosoidesH. Douvillé, 1925 etdilatata(Michelotti, 1861) is recorded. Due to the very similar taxonomic composition of the Tajar-Kuh section with their coeval faunas of the Mediterranean, the age was evaluated in the frame of the Western Tethyan Oligo-Miocene shallow benthic zonation (SBZ). Although the presence ofE. formosoidessuggests late Rupelian (SBZ 22A Zone) age, the occurrence ofHeterostegina assilinoides,N. kecskemetii,N. bormidiensis, andPlanolinderinasp. preferably represents the SBZ 22B Zone of the early Chattian. Based on the obtained results, at least the lower six samples can indicate the very basal part of the Chattian. More advancedEulepidinafrom the uppermost sample suggests a slightly younger but still early Chattian age.

LA "GONFOLITE LOMBARDA": STRATIGRAFIA E SIGNIFICATO NELL'EVOLUZIONE DEL MARGINE SUDALPINO

The Oligocene-Miocene succession of the "Gonfolite Lombarda" outcrops in Western Lombardy and is largely represented in the subsurface of the northern PO Plain. In the this group was considered as a typical example of post- orogenic molasse deposit. The new data suggest that it represents a clastic wedge infilling a deep foreland basin flanking a zone of continental collision. The stratigraphic evolution of the succession strictly reflects the tectono-sedimentary evolution of the basin.&#x0D; The succession (almost 3000 m thick) between Como and Varese covers a time span from late early Oligocene (late Rupelian) at least to early Miocene (Burdigalian). It consists of clastic sediments deposited in a deep-sea environment. Both the benthic Foraminifera and the macrofossil assemblages indicate that these sediments were deposited in the epibathial zone (from 500-700 m to 1000-1300 m) throughout all the time span considered. The succession can be splitted in two main segments based on their different sedimentary characters and because they are separated by a regional unconformity corresponding to a hiatus of several million years. The lower one is represented by the Chiasso Formation (about 170m thick) and the upper one by the Gonfolite Group s. Str. (about 2800 m thick).&#x0D; The Chiasso Formation is a depositional sequence late Oligocene (late Rupelian to early Chattian) in age. It consists of mudstones and rare thin-bedded turbidites, representing slope or slope-base deposits. The overlying Gonfolite Group represents the build-up of several deep sea fan systems one on top of the other during the very late Oligocene (late Chattian) to the early Miocene (Aquitanian- Burdigalian) and perhaps to the middle Miocene. Resedimented conglomerates infilled deeply incised canyons confined by natural levees in their distal part. The canyons evolved laterally and distally to still partly confined sandy depositional lobes during the early Miocene.&#x0D; In the Gonfolite Group three depositional sequences could be recognized. The first one is represented by the Como Conglomerate (800-1500 m thick) and of some heteropic formations, covering a time span from late Chattian to early Burdigalian. This depositional sequence represents an asymmetric megacycle with an initillly very rapid progradation of the conglomeratic system followed by its gradual regression and, in the Como area, by a westward shift of the system axis. Moreover, it is worth mentioning that pebbles of granodiorite-diorite called "ghiandone and serizzo" of the Val Masin0-Val Bregaglia Massif make their appearance already in the basal part of the Como Conglomerate.&#x0D; The second depositional sequence consists of the Lucino Conglomerate (800-1000 m thick) and of some heteropic formations. It represents a gradual progradation of the whole deep sea fan system during the late earIy Miocene (Burdigalian).&#x0D; In the Varese area, the Gurone Sandstone (120 m thick) may represent a third depositional sequence, which because of its stratigraphic position is younger than the late Burdigalian, and it appears to be deposited prior to the late Miocene (Tortonian).&#x0D; The "Gonfolite Lombarda" basin was interested by an intense and continue tectonic activity with at least two periods of "crisis" occurring in the late Chattian and in the early Burdigalian. Because of the strong tectonic Control it's difficult to correlate the "Gonfolite Lombarda" depositional sequences with the generalized sea level curves.

NICHE PARTITIONING OF THE EUROPEAN CARNIVOROUS MAMMALS DURING THE PALEOGENE

We here describe the first partial cranium of Hyaenodon leptorhynchus, the type species of the taxonomically diverse and widely distributed hypercarnivorous genus Hyaenodon (Hyaenodonta). The cranium is from the Seon Saint-Andre deposits (Marseille, France; Chattian, MP26). It is preserved in a dense red marl matrix that obscures key morphological features. CT-scans were used to reconstruct the specimen. The morphology of the cranium reinforces the homogeneity previously observed in Hyaenodon despite its specific diversity. The fossil represents a juvenile: it preserves its deciduous canines and the P3 is almost fully erupted. This pattern of delayed canine eruption is a trait shared among North American and European Hyaenodon. This discovery is the third occurrence of this species in the early Chattian: indeed, over a period of 5 My (from MP24 to MP27), only two occurrences (Rigal-Jouet and Saint-Martin de Casselvi, MP25) have been reported. Based on body mass and the general Hyaenodon body plan, we confidently identify H. leptorhynchus as a cursorial hypercarnivorous predator, hunting prey such as small artiodactyls. In order to understand the evolution of the European carnivorous faunas, we compared taxonomic diversity and the evolution of body mass in Hyaenodon and amphicyonids: this reveals stasis in Hyaenodon through the late Eocene and Oligocene, while amphicyonids show an extensive ecological diversification, especially during the Chattian.

The Rupelian–Chattian transition in the north-western Transylvanian Basin (Romania) revealed by calcareous nannofossils: implications for biostratigraphy and palaeoenvironmental reconstruction

AbstractSediments belonging to the Oligocene Vima Formation (located in the north-western part of the Transylvanian Basin, Romania) have been investigated for calcareous nannofossils content. Biostratigraphically, the sedimentary succession is late Rupelian–Chattian in age, belonging to the NP24 —Sphenolithus distentusand NP25 —Sphenolithus ciperoensisbiozones, to CP19a —Cyclicargolithus floridanusand CP19b —Reticulofenestra bisectaSubzones and to the interval from CNO4 —Sphenolithus distentus/Sphenolithus predistentusCRZ to CNO5 —Sphenolithus ciperoensisTZ. The palaeoenvironment of the Fântânele section was reconstructed by means of calcareous nannofossils and statistics. Multivariate statistics were applied to the composition of autochthonous assemblages and the obtained clusters were used to assess the palaeoecological preferences of the nannofossils. We document changes from more stable open-marine regime, with temperate sea-surface temperatures interfering locally with influx of cooler water and enriched cool-nutrient supply for the late Rupelian–earliest Chattian (NP24), to shallower and possibly warmer near-shore marine eutrophic environment, with salinity fluctuations, increased terrigenous material run-off and freshwater influx for the remaining early Chattian (NP25).

A new archaic baleen whale Toipahautea waitaki (early Late Oligocene, New Zealand) and the origins of crown Mysticeti.

A new genus and species of extinct baleen whale †Toipahautea waitaki (Late Oligocene, New Zealand) is based on a skull and associated bones, from the lower Kokoamu Greensand, about 27.5 Ma (local upper Whaingaroan Stage, early Chattian). The upper jaw includes a thin, elongate and apparently toothless maxilla, with evidence of arterial supply for baleen. Open sutures with the premaxilla suggest a flexible (kinetic) upper jaw. The blowhole is well forward. The mandible is bowed laterally and slightly dorsally; unlike the Eomysticetidae, there are no mandibular alveoli, and the coronoid process is tapered and curved laterally. Jaw structure is consistent with baleen-assisted gulp-feeding. The age of early Chattian makes †Toipahautea a very early, if not the oldest named, toothless and baleen-bearing mysticete, suggesting that the full transition from toothed to baleen-bearing probably occurred in the Early Oligocene. Late Oligocene mysticetes vary considerably in jaw form and kinesis, tooth form and function, and development of baleen, implying a wide range of raptorial, suctorial and filter-feeding behaviour. More study may elucidate the function of jaws, teeth and baleen in terms of opportunist/generalist feeding, as in modern gray whales, versus specialized feeding. We here propose that early mysticetes, when transitioned from toothed to baleen-bearing, were generalists and opportunists instead of specializing in any forms of feeding strategies. In addition, two different phylogenetic analyses placed †Toipahautea either in a polytomy including crown Mysticeti, or immediately basal to the crown, and above †Eomysticetidae in both cases. Because the †Toipahautea waitaki holotype is an immature individual, it may plot more basally in phylogeny than its true position.

New data on the biostratigraphy (charophytes, nannofossils, mammals) and lithostratigraphy of the Late Eocene to Early Late Miocene deposits in the Swiss Molasse Basin and Jura Mountains

In the northern Swiss Plateau and Jura Mountains, non marine Paleogene and Neogene deposits of the Swiss Molasse Basin or linked to the Upper Rhine Graben are examined in detail. The Late Eocene (Middle–Late Priabonian) is characterized by charophytes of the Vasiformis–Tuberculata Zone (Diegten Susswasserkalk) and Vectensis Zone (lower Tuberculata Superzone, Oberdorf Susswasserkalk, Terre jaune). The Rupelian and Early Chattian appear as little developed and extended. The Rupelian is characterized by charophytes of the Pinguis Zone (upper Tuberculata Superzone, basal Conglomerat de Porrentruy) and Major Zone (Conglomerat de Porrentruy, lower “Molasse alsacienne”, Marnes rouges). In the Neuchâtel region of central Jura, a paleokarst marine filling of UMM (Montmollin) yielded nannofossils of Early Rupelian (NP 21) age. Early Chattian sediments are for the first time precisely dated by small mammals (MP 25–26a) and typical charophytes of the Microcera Zone (Calcaire d’eau douce de Trois-Rods). The biostratigraphy of charophytes for the Early Miocene to early Late Miocene (MN 1–9) can also be defined more precisely ranging from Nitida Zone to Etrusca Zone. The biozonation of charophytes for the Swiss Paleogene and Neogene (SPN) is revised and completed by the creation of 11 assemblage zones SPN-EC 1–2 (Eocene charophytes, Late Eocene), SPN-OC 1–2 (Oligocene charophytes, Rupelian), SPN-OC 3–5 (Chattian), SPN-MC 1–2 (Miocene charophytes, Aquitanian), SPN-MC 3 (Burdigalian) and SPN-MC 4 (Langhian–Early Tortonian).

Oligocene and early Miocene mammal biostratigraphy of the Valley of Lakes in Mongolia

The Taatsiin Gol Basin in Mongolia is a key area for understanding the evolution and dispersal of Central Asian mammal faunas during the Oligocene and early Miocene. After two decades of intense fieldwork, the area is extraordinarily well sampled and taxonomically well studied, yielding a large dataset of 19,042 specimens from 60 samples. The specimens represent 176 species-level and 99 genus-level taxa comprising 135 small mammal species and 47 large mammals. A detailed lithostratigraphy and new magnetostratigraphic and radiometric datings provide an excellent frame for these biotic data. Therefore, we test and evaluate the informal biozonation scheme that has been traditionally used for biostratigraphic correlations within the basin. Based on the analysis of the huge dataset, a formalised biostratigraphic scheme is proposed. It comprises the Cricetops dormitor Taxon Range Zone (Rupelian), subdivided into the Allosminthus khandae Taxon Range Subzone and the Huangomys frequens Abundance Subzone, the Amphechinus taatsiingolensis Abundance Zone (early Chattian), the Amphechinus major Taxon Range Zone (late Chattian), subdivided into the Yindirtemys deflexus Abundance Subzone and the Upper Amphechinus major T. R. Z., and the Tachyoryctoides kokonorensis Taxon Range Zone (Aquitanian). In statistical analyses, samples attributed to these biozones form distinct clusters, indicating that each biozone was also characterised by a distinct faunal type.

UPPER CRETACEOUS-TERTIARY GEOLOGY/STRATIGRAPHY OF PERTEK AND ITS VICINITY (TUNCELİ, TURKEY)

The basement units of the study area are Paleozoic-Mesozoic Keban metamorphics and Late Cretaceous Elazig magmatics. As a result of tectonic events caused by final collision in Middle Maastrichtian, all these basement units were juxtaposed, uplifted, eroded and acted as a source area for the Maastrichtian-Paleogene basins. Upper Cretaceous Paleogene deposits were systematically sampled in order to determine their ages and lithologies. Due to new age findings and stratigraphical positions the marine units were identified as; Harami, Seske and Kirkgecit formations. Late Oligocene-Early Miocene Alibonca formation and Pliocene Karabakir formation are the other units of the study area. Maastrichtian-Thanetian Harami formation is formed by grainstone intercalated with sandstone at the bottom and white limestone at the top. Early Lutetian Seske formation consists of conglomerate at the bottom and much nummulitic, carbonate cemented sandstone with ophiolitic fragments at the top. Kirkgecit formation consists of sandstone-siltstone-limestone intercalation, and it is early Bartonian early Chattian. Late Chattian-middle Burdigalian Alibonca formation consists of conglomerate at the bottom, reefal limestone in the middle and clayey limestone intercalated with algal limestone at the top. Pliocene Karabakir formation is formed by conglomerate-mudstone and locally by intercalations of pyroclastics and lavas. Pertek Andesite and Basalt Members are both vertically and laterally transitional with sedimentary lithologies of the Karabakir formation. There is no data to date the lithology; however, it was assumed that it had been Pliocene in age according to the lithostratigraphical succession. In the study area, macrotectonic events were experienced in Late Cretaceous, Early Eocene, middle-late Lutetian, Middle?-Late Miocene and in the Latest Pliocene. During the last tectonic phase, the Anatolian plate bounded by the East Anatolian Fault (EAF) in E-SE began to move westward, and the right lateral strike slip Pertek Fault activated in the study area.

MALATYA OLİGO-MİYOSEN İSTİFİNİN BENTİK FORAMİNİFER BİYOSTRATİGRAFİSİ (DOĞU TOROSLAR, DOĞU TÜRKİYE)

The benthic foraminiferal biostratigraphy of Oligo-Miocene aged Muratli and Petekkaya formations which crop out over wide regions around Akcadag town, west of Malatya province in Eastern Taurids were revealed in this study. Systematical sampling was carried out in measured stratigraphical sections in four locations in order to perform stratigraphical and paleontological investigations. Benthic foraminifera taken from 182 hard rock samples were defined and three biozones were determined as; SBZ 21-22, belonging to Oligocene (Rupelian - Early Chattian), SBZ 23 (Late Chattian) and SBZ 25 belonging to Lower Miocene in shallow marine deposits in the region. It was stated that the assemblage of planktic foraminifer and nannoplankton which stratigraphically detected within Chattian - Burdigalian units in the succession most probably indicated Aquitanian age. Besides; Oligo-Miocene transition in the region was approved with this study based on biostratigraphical locations of benthic foraminiferal taxa

Parallelism in the evolution of dental pattern and systematic implications: The case of Protechimys major Schlosser, 1884 (Theridomyinae, Rodentia, Mammalia) and its associated rodents

Abundant remains of Protechimys major Schlosser (1884) (Rodentia, Theridomyinae) from Mas-de-Pauffié (Lot, France; standard–locality MP26, e.g., BiochroM’1997; Early Chattian) are described and their morphological and dimensional variability are analyzed. At this locality, and also at Les-Milles (Bouches-du-Rhône), P. major is associated with a few teeth of Archaeomys-Blainvillimys sp. Due to this scarcity and to similar evolutionary trends in the pattern of lower molars, it is not possible to find accurate features likely to distinguish Protechimys from Archaeomys or advanced Blainvillimys, but lines of research are given. Their co-occurrence with Issiodoromys pauffiensis Vianey-Liaud (1976) is documented at localities with different depositional conditions; together with the analysis of precise and focused samples made in the limited outcrop, it contributes to demonstrate the temporal homogeneity of the MP26 rodent assemblage from Mas-de-Pauffié.

BENTHIC FORAMINIFERAL BIOSTRATIGRAPHY OF MALATYA OLIGO-MIOCENE SUCCESSION (EASTERN TAURIDS, EASTERN TURKEY)

The benthic foraminiferal biostratigraphy of Oligo-Miocene aged Muratli and Petekkaya formations which crop out over wide regions around Akcadag town, west of Malatya pro- vince in Eastern Taurids were revealed in this study. Systematical sampling was carried out in measured stratigraphical sections in four locations in order to perform stratigraphical and paleontological investigations. Benthic foraminifera taken from 182 hard rock samples were defined and three biozones were determined as; SBZ 21-22, belonging to Oligocene (Rupe- lian - Early Chattian), SBZ 23 (Late Chattian) and SBZ 25 belonging to Lower Miocene in shallow marine deposits in the region. It was stated that the assemblage of planktic forami- nifer and nannoplankton which stratigraphically detected within Chattian - Burdigalian units in the succession most probably indicated Aquitanian age. Besides; Oligo-Miocene transition in the region was approved with this study based on biostratigraphical locations of benthic foraminiferal taxa.