Early Tortonian Research Articles

Miocene sequences and depocentres in the Roer Valley Rift System

AbstractThe Miocene sequence in the Roer Valley Rift System consists of alternating open‐to‐shallow marine, coastal and fluvio‐deltaic deposits. In this study, well logs, bio‐chronostratigraphy and seismostratigraphy are used to characterize major units and their bounding unconformities and to infer sediment dispersal patterns. Three major unconformities occur in the sequence: the early, middle and late Miocene unconformities (EMU, MMU and LMU). The EMU formed due to tectonic motions related to the Savian phase. After formation of the EMU, a broad depocentre developed in the south‐eastern part of the Roer Valley Graben (RVG). Sediment accumulation increased during this period and peaked in the middle Langhian, after which it diminished again to a low level during the late Serravallian. The decrease in sediment accumulation coincided with a period of tectonic subsidence along the major bounding fault zones (i.e. the Peel Boundary Fault System, the Feldbiss Fault System and the Veldhoven Fault System). The resulting transgression caused sediment starvation in the central RVG. Subsequently, global sea‐level fall during the early Tortonian caused large‐scale erosion, and formation of incised valleys on the highs adjacent to the RVG (Peel Block and Campine Block), as well as the south‐eastern RVG, forming the MMU. However, sedimentation continued during this period in the central part of the RVG where no erosional hiatus developed. From the Tortonian onwards, accumulation rates increased again. The depocentre shifted towards the north‐west and clinoforms developed in the RVG. During the latest Miocene, the depocentre was concentrated along the south‐western margin of the RVG. Meanwhile, the depositional environment of the entire RVRS gradually shallowed as the LMU was formed.

Strontium Isotopic, Ostracod fauna, and Paleoenvironmental Features of the Late Miocene Sequence in Mut/Dağpazarı Region (Southern Turkey)

The primary focus of this study was the Dağpazarı village in the Mut region of Mersin, southern Turkey. In this research area, two stratigraphic sections were meticulously measured. The study conducted a comprehensive examination of the Middle-Late Miocene period in the Dağpazarı, Ballı, and Mut Formations by analyzing the ostracod fauna and utilizing strontium isotope chemostratigraphic dating. This research determined that the upper levels of the Mut/Köselerli formations, specifically from the Burdigalian to Serravallian, signify the commencement of the Miocene succession in the study area.The Dağpazarı Formation, characterized by abundant silty-clay, Ostrea fossils, and lignite layers, is deposited unconformably just above these levels.This formation contains the following ostracod taxa; Bairdia subdeltoidea, C. glypta, Cytheridea acuminata acuminata, Acanthocythereis hystrix, Krithe monosteracensis, Neomonoceratina mouliana, Hemicyprideis sp., Cistacythereis caelatura, Cyherella terguemi, T. prava, K. langhiana, A. ulicznyi, Pokornyella deformis minor, Loxoconcha alata, Tenedocythere salebrosa. Furthermore, the planktonic foraminifera species are; O. universa, Globigerinoides trilobus, Glb. ruber, Orbulina bilobata, Glb. sacculifer, O. suturalis, and the formation includes abundant bryozoa, echinoid spines, gastropods such as Terebralia at distinct levels, and fish otolith. The formation, dating from the late Serravallian to the early Tortonian, exhibits the shallow reef characteristics that continued to develop in the late Miocene.The formation consists of dark green, bulbous weathered claystone, Bairdia subdeltoidea and Ostrea which are reduced in size at the levels that pass into hard clayey sandstone, abundant benthic foraminifera with abundant echinoid spines. The formation consists of benthic foraminifera, hard clayey sandstone, and weathered dark green claystone, which contains numerous echinoid spines.Ostrea and Bairdia subdeltoidea are also present. The upper section of the analyzed succession concludes with silty, compact, clayey limestone layers and light-colored limestone bands. The Tırtar Ballı Formation, which conformably overlays the Dağpazarı Formation, signifies the culmination of a relatively recent reef formation during the Tortonian period.Ostracod species such as Aurila pigadiana, Thalmannia hodgii, Buntonia sublatissima dertonensis, Bairdia subdeltoidea, Aurila sp. Bassiouni have been defined. The limestones also contain abundant benthic foraminifera and echinoid spines. The 87Sr/86Sr ratio analyzed from the carbonate sample obtained from the Dağpazarı formation is 0.708920. Based on these isotope data, the age of the Dağpazarı formation was calculated to be 8.7 million years (Ma).

Oblique rifting triggered by slab tearing: the case of the Alboran rifted margin in the eastern Betics

Abstract. The tectonic evolution of highly oblique continental margins that result from extension above lithospheric subduction–transform edge propagator (STEP) faults is poorly understood. Here, we investigate the case of the Alboran margin in the eastern Betics characterized by crustal thinning of 15–10 km, oblique to the direction of slab retreat. The current deformation patterns indicate that oblique rifting is underway. However, it is unclear whether these conditions are those that prevailed during the formation of the metamorphic domes and intramontane basins. We review the temporal and spatial evolution of Neogene sedimentary basins and brittle deformation in the eastern Betics and exploit offshore seismic reflection lines to propose a crustal-scale section across the oblique margin. The history of sediment infill and rates of subsidence combined with the analyses of fault slip data confirm that brittle extension oriented from north 20∘ E to E–W occurred during an interval spanning from the Serravallian–early Tortonian to the late Tortonian (14–8 Ma). This extension is associated with both normal and strike-slip regimes and the evolution of the strike-slip fault zones flanking the metamorphic domes. The transtensional model forms a coherent scheme linking the ductile deformation associated with metamorphic domes and the formation of E–W- and NW–SE- or NNW–SSE-directed sedimentary basins in the brittle upper crust during the Tortonian. The oblique extension, which is closely associated with STEP faulting, occurred during the regional convergence between Africa and Iberia since the Miocene. Only recently, around 8 Ma, has slab detachment started to migrate westward, leading to tectonic inversion in the eastern Betics. Such a type of narrow oblique-rifted margin associated with transform-like plate boundaries is not unique but is expected to be hardly preserved in the geological record due to the transient nature of retreating subduction systems.

The Miocene record of the Betic Cordillera uplift in Los Guájares valley (Granada province, S Spain)

The Los Guájares valley is located about 35 km south of Granada in the Internal Zones of the Betic Cordillera. The Miocene deposits in this area consist of six sedimentary units separated by unconformities, which are exposed in small and laterally discontinuous outcrops overlying metamorphic rocks of the Alpujárride Complex. The lowest unit comprises upper Serravallian marls with planktonic foraminifera filling neptunian dykes and covering Triassic dolomitic marbles of the Alpujárride Complex. These marls reflect deep marine deposition on the Betic basement under a local extensional regime. Uplift of the region led to emergence and deposition of continental red alluvial-fan conglomerates and foothill breccias. The overlying unit, a shoreline conglomerate with small oyster banks, indicates relative sea-level rise. Shallow-marine conditions continued during the deposition of the following unit, early Tortonian in age, which consists of calcareous sandstones with hermatypic corals. Small patch reefs developed in the overlying unit composed of sandy limestones with corals (Porites, Tarbellastraea, Thegioastraea) and oysters, and sandy limestones with coralline algae in the most distal areas. The coral reefs in Los Guájares and some coral heads in Albuñuelas, a near locality, are the only record of early Tortonian coral buildups in the Mediterranean. The last marine unit comprises lower Tortonian conglomerates, sandstones and siltstones accumulated in the front of a small delta. Oyster banks and concentrations of Turritelines suggest high nutrient levels in the delta-front paleoenvironments. The Los Guájares valley area emerged afterwards, following the onset of a compressional geodynamic regime in the central Betic Cordillera and since the early Tortonian only small bodies of foothill and alluvial-fan deposits formed in a predominantly erosional context.

Using clay mineralogy and micropalaeontological observations to unravel Neogene climate variations in Northern Arabia

The Zagros Mountain belt in Iran comprises an extensive record of Mesozoic and Cenozoic deposits uplifted by collision of the Arabian and Iranian continental plates. This area has been shown to provide important information to decipher the climatic history of Western Asia, especially regarding the evolution of deserts in Mesopotamia and Northern Arabia. In a high-resolution geological record of 84 samples, we combine clay mineralogy and micropalaeontological observations to refine the late Neogene climate record in Northern Arabia. We investigated a 2.6-km-thick sedimentary profile from the Simply Folded Zagros Mountain belt spanning ca. 10.2 myrs from the late Middle Miocene (Serravallian) to earliest Pleistocene (Gelasian) comprising floodplain sediments and saline mudstones with a strong aeolian contribution. The clay fraction < 2 µm reveals palygorskite, smectite, illite, chlorite and the zeolite mineral erionite. Using clay mineralogy, arid conditions during the Serravallian and early Tortonian in Northern Arabia are identified, followed by semi-arid conditions during the late Tortonian. Clay mineralogy suggests a transition to sustained arid conditions during the early Messinian and provides a more complex picture on a previously proposed period of hyperaridity (NADX) in Northern Arabia penecontemporaneous with the apex of the Messinian salinity crisis.

Detrital zircon ages of Oligocene to Miocene sandstone suites of the Southern Apennines foreland basin system, Italy

U–Pb spot ages on detrital zircons from turbidite quartzarenites, quartz-feldspathic and volcaniclastic sandstones of the Tufiti di Tusa (TTF), Numidian Flysch (NF), Bifurto (BF), Gorgoglione (GF) and Serra Palazzo (SPF) formations, exposed in southern Italy, were detected to define their provenance signatures aiming to contribute to reconstructing the complex geodynamic evolution of the southern Apennine chain. The deposition ages of these sandstones range from Rupelian (TTF), Burdigalian p.p. -Early Langhian (NF and BF) and Langhian-Serravallian -Early Tortonian (GF and SPF). The detrital zircon ages in each deposit show different clusters. In TTF, the zircon age clusters are: 610 ± 6 Ma; 390 ± 4 Ma; 287 ± 3 Ma; 157 ± 2 Ma; 78 ± 1 Ma and 67 ± 1 Ma; 33 ± 1 Ma. In NF and BF formations, the prevalent zircon ages are clustered at 661 ± 10 Ma, 607 ± 8 Ma and 547 ± 8 Ma. In GF sandstones, the ages of detrital zircons are clustered around 672 ± 28 Ma, 458 ± 9 Ma, 297 ± 8 Ma and 24 ± 1 Ma. The sandstones of SPF contain zircons showing age clusters at 649 ± 10 Ma, 486 ± 7 Ma and 315 ± 5 Ma. Zircons and lithic fragments from TTF display a dominant provenance from Oligocene calc-alkaline effusive products located on western domains of the Mesomediterranean Microplate, and minor detritus from granitoids and metamorphic rocks of Variscan ages. Zircons of NF and BF indicate a provenance of detritus from the African Craton without evidence of Variscan or Alpine signatures. Zircons from GF and SPF show a provenance from both Variscan crystalline basement rocks forming the Alpine chain (Calabria-Peloritani Terranes) and Variscan magmatic and metamorphic rocks unaffected by Alpine tectonics, similar to Sardinia–Corsica (pro-parte) block. In addition, the Oligocene magmatic component dated at 24 Ma in GF sandstones is evidence for the maximum age of sedimentation for these deposits. In light of the recent and preliminary geochronological data acquired, a revised paleogeographic restoration could be inferred for the location of sedimentary basins during the Apennines tectonic evolution. The Rupelian sedimentation age of TTF suggests that the deposition domains of the Numidian sequences and the successive deposits of GF and SPF, were located in a more complex paleogeographic scenario along the orogenic system.

Sedimentary dynamics and topographic controls on the tidal-dominated Zagra Strait, Early Tortonian, Betic Cordillera, Spain

Abstract The approximately 350 m-thick stratigraphic succession of the Zagra Strait records an important oceanographic phase of basin interconnection between the Atlantic Ocean (Guadalquivir Basin) and the Mediterranean Sea through the Betic Cordillera (southern Spain) during the early Tortonian. The Zagra Strait developed as a narrow structurally controlled marine corridor. The sedimentary dynamics of the Zagra Strait were interpreted from the sedimentological features observed in six sections at well-exposed outcrops. Large-scale (&gt;10 m high) compound dunes and compound–dune complexes moved parallel to the strait margins under strong tidal currents generated by tidal amplification at the strait entrance and exit. Dune distribution can be divided into three sectors with different palaeocurrent migration, lithological and topographical characteristics. The northern and central sectors were separated by a deep depression (&gt;75 m water depth) where tidal currents were weaker and dunes were not generated. The southern sector records a relative decrease in current strength compared with the northern and central sectors, and a significant increase in the bioclastic content in the sediment. Terrigenous content generally increases towards the strait margins, and reciprocally, carbonates towards its axis. The closure of the Zagra Strait resulted from tectonic uplift of that part of the Betic Cordillera before the late Tortonian.

Palaeoenvironmental reconstruction of the late Miocene macroflora of La Bisbal d'Empordà (Catalonia, Spain). Comparison with small mammals

The late Miocene flora from La Bisbal d'Empordà (Catalonia, Spain) provides significant data for characterising the coastal vegetation from the north-eastern Iberian Peninsula during a key period in Neogene climatic evolution. To this end, a historical leaf collection from La Bisbal d'Empordà was re-examined, analysed from a palaeoenvironmental viewpoint and compared with data provided by the associated small mammal fauna. This flora dates from 9.6–9.7 Ma in age (early Tortonian) according to small mammal biostratigraphy.The fossil-bearing beds were deposited in the floodplain of a meandering river system. Three palaeoecological assemblages were recognized: 1) Helophytic plant stems related to a wetland community. 2) Torn leaves of Fraxinus sp., Ulmus sp., Zelkova sp., Cedrelospermum sp. Populus balsamoides, Alnus gaudinii, Carpinus sp., Platanus sp., Acer tricuspidatum, Daphnogene sp. and, Laurophyllum sp. which would have belonged to a riparian forest located beyond the wetland community, with Fraxinus being the plant growing in closest proximity; 3) Isolated complete Paliurus seeds, interpreted as mainly wind-transported, which provide evidence of an open and more arid landscape situated distally from the floodplain. The small mammal assemblages associated with this flora are consistent with this palaeoenvironmental interpretation. The paucity of small arboreal mammal taxa and insectivores suggests limited forested vegetation areas, while the more common terrestrial species indicate better developed open landscapes. Our results show a more heterogeneous environment than previously thought and that the riverine processes impinged the flora, somewhat limiting the climatic conclusions that might be derived from leaf physiognomic analyses such as CLAMP.

Palaeovegetation and paleoclimate in the SW Turkey – a study based on the early-middle Miocene coal-bearing sediments from the Büyük Menderes Graben

This study provides the age of coal-bearing sediments of the Büyük Menderes Graben (BMG) and palaeoclimatic and palaeovegetational change from the early to late Miocene. Two palynofloras, the Başçayır and Kızılcayer, are distinguished in the late Burdigalian-early Langhian, and Serravallian-Tortonian boundary. According to the microfloral composition of the Başçayır palynoflora is characterized by subtropical elements, and palaeoclimate is warm subtropical, with the coldest month mean temperature (CMT) 8–13 oC. Based on the palynoflora, the coal-bearing sediments were deposited in the fluvial-lacustrine environments. The abundances of gymnosperm species and the mean annual range of temperature (MART) point out high and middle altitude areas during the deposition of coal-bearing sediments. Based on the Kızılcayer palynofloral composition, palaeoclimate is the warm temperate (CMT: 3.1–13.3 oC), also the abundant presence of herbaceous species indicate open land areas in the Aydın-Kızılcayer area despite the existences of swampy-lowland environments.According to described palynofloral composition, the palaeotopographic conditions of the southern part of the BMG (Aydın-Kuloğulları) are generally higher than the northern parts (Aydın-Başçayır), and deposition areas in this graben are significantly uplifted from the late Burdigalian to early Tortonian. The regional palaeoclimatic condition from the early to late Miocene changed from warm subtropical to temperate in western Anatolia. The palaeotopographic changes related to the tectonic events and/or uplift of the Menderes Massive in western Anatolia could have been effective on regional paleoclimate during the deposition in the BMG, and this uplifting existed in the late Burdigalian and continued until the late Miocene.

Marine influence in western Amazonia during the late Miocene

The dynamic environments of western Amazonia during the Neogene (23 to 2.58 million years ago [Ma]) included continental-scale wetlands that were episodically influenced by marine incursions originating from the Caribbean. The nature and frequency of such events is highly debated, with a general consensus on short events during the early (23 to 16) and middle (16 to 11.6 Ma) Miocene. However, scattered evidence for more events up until the late Miocene (11.6 to 5.3 Ma) exists. Based on a palynological analysis of borehole 1-AS-9-AM from the Solimões Formation (western Amazonia, Brazil), we provide further support for late Miocene marine influence in the region. Comparisons with other sites in the Solimões Basin indicate an age of earliest Tortonian (~11–10 Ma) for an assemblage with foraminiferal linings, acritarchs and dinocysts, totalling ~17.3% of the palynological count ( n = 374 palynomorphs) at 34.10 m of depth. This is the topmost sample with a significant amount of marine indicators and its age is consistent even when different biostratigraphic interpretations are appreciated. Our data and comparisons also show that a larger proportion of sediments of the Solimões Formation should be placed within the late middle to early late Miocene. Our reconstruction of the Solimões deposits in the early Tortonian indicates intermintent low salinity regimes and a persistent connection with the paleo-Orinoco drainage until the closure of this connection in the late Miocene to Pliocene times. • New pollen data is presented from a borehole (1-AS-9-AM) in western Amazonia. • Graphic correlation was applied with two nearby sites, ages found from middle to late Miocene. • A thicker late Miocene section than previously interpreted is suggested. • A marine assemblage (~17% of the palynological count) at 34 m is composed of foraminiferal linings, dinocysts and acritarchs. • Regional comparisons support an early Tortonian episode of marine influence in a wide geographical area in western Amazonia.

The Scontrone turtles – A new insular testudinoid fauna from the late Miocene of the Central Mediterranean

We here describe a small turtle assemblage originating from the early Tortonian (late Miocene) palaeoisland of Scontrone, central Italy, a locality previously known mostly for its endemic mammals and giant birds, which were otherwise shared only with the Gargano localities, another fossiliferous area belonging to the same palaeobioprovince. The fossil turtle remains from Scontrone are referred to the geoemydid Mauremys sp. and a so far unidentified large-sized testudinid. The biogeographic origins of the Scontrone insular chelonians are discussed. The Scontrone geoemydid adds to the known occurrences of Mauremys in the late Miocene of the Mediterranean. The Scontrone large tortoise represents the oldest known Mediterranean insular testudinid, predating significantly the well-known Quaternary endemic island tortoises of the area.

Three (middle to) late Miocene plant macroremain assemblages (Pitsidia, Kassanoi and Metochia) from the Messara–Gavdos region, southern Crete

Based on macroremains, we describe three fossil plant assemblages from the Miocene of the Messara Basin (southern Crete) and the adjacent Gavdos Island. The palaeoflora of Kassanoi, which is the oldest (Messara Basin, Viannos Fm, Serravallian/early Tortonian), is documented mainly by leaf imprints, including a fern, a conifer (Tetraclinis cf. salicornioides) and 23 angiosperms. The assemblage is dominated by Daphnogene polymorpha, Podocarpium podocarpum and Myrica lignitum. The plant record from Pitsidia (Messara Basin, Ambelouzos Fm, early Tortonian) comprises thousands of specimens. The plant fossils are preserved as imprints often covered by an inorganic encrustation (replica). One alga, 2 ferns, at least 5 conifers and more than 45 woody angiosperms were identified. Dominant taxa are Myrica and Pinus pitsidiensis, documented by numerous vegetative and reproductive organs (Zidianakis et al., 2015, 2016). Leaves of oaks (Q. pseudocastanea, Q. kubinyii) and Daphogene polymorpha as well as twigs of Taxodium dubium are also fairly common. From the palaeoflora of Metochia, which is the youngest (Gavdos Island, Metochia Fm, middle Tortonian), (Mantzouka et al., 2015), we report further taxa, including Quercus mediterranea, Ziziphus paradisiaca and a palm (Sabalites sp.). The vegetation is assessed both empirically (phytosociologically) and by Integrated Plant Record (IPR) Vegetation Analysis. The reconstructed vegetation models are presented in detail and discussed in the context of the geological and palaeontological settings of the area. The climate is assessed based on the Coexistence Approach (CA) and the Climate Leaf Analysis Multivariate Program (CLAMP). The palaeoclimatic datasets reveal a warm temperate to subtropical climate, probably with a weak seasonal drought.

CLAMP-based palaeoclimatic analysis of the late Miocene (Tortonian) flora from La Cerdanya Basin of Catalonia, Spain, and an estimation of the palaeoaltitude of the eastern Pyrenees

We analyse the late Miocene (early Tortonian) climate of the La Cerdanya Basin (Catalonia, Spain) using the Climate Leaf Analysis Multivariate Program (CLAMP) based on an assemblage comprising twenty-nine dicot leaf taxa. Results show a mean annual temperature of 11.4 ± 2.1 °C. The coldest mean monthly temperature was 1.8 ± 3.4 °C while the warmest was 21.6 ± 2.5 °C. Growing season was 6.8 ± 1.1 months in duration. Precipitation during this period was 1082 ± 317 mm, reaching 661 ± 38 mm in the three wettest consecutive months, while in the three driest months it was 194 ± 229 mm. These results indicate a permanently humid temperate climate, with warm and wet summers. Compared with published palaeoclimatic results obtained using the Coexistence Approach method, our CLAMP analysis indicates lower temperatures and higher rainfall during the driest month. The climatic parameters are consistent with the occurrence of a temperate mixed evergreen and broadleaf deciduous fossil assemblage in the late Miocene of the La Cerdanya Basin. The assemblage contains more taxa in common with coeval localities from northern and central Europe than with Mediterranean sites; its closest modern analogue is with the montane flora from Honshu Island (Japan). Palaeoaltitudinal estimation using the terrestrial lapse rate method suggests that the La Cerdanya Basin was positioned at 1100–1550 m during early Tortonian times. These results challenge previous palynological and isotopic studies that inferred a palaeoaltitude of c. 600 m in early Tortonian-Messinian times.

Eustatic, Climatic, and Oceanographic Influences on Geomorphology and Architecture of Isolated Carbonate Platforms: Miocene, Northwest Shelf, Australia

Abstract The Miocene represents an interval of marked global change, and this evolution is reflected in carbonate platforms from this epoch. Seismic stratigraphic characterization of high-resolution (ca 60 Hz) 3D seismic data from the Browse Basin, offshore Australia, reveals a middle to upper Miocene three-part seismic stratigraphic subdivision. Each unit consists of several seismic sequence sets and their component sequences. Seismic stratal geometries and seismic facies define a prograding shelf (Langhian and older), a barrier-reef complex with scattered platforms (upper Langhian–early Tortonian), and aggrading and prograding isolated platforms (early Tortonian–Messinian). The data permit description and interpretation of high-fidelity stratigraphic details of the initiation, expansion, termination, and geomorphology of over 100 platforms in this interval. The results reveal that the isolated platforms initiated following the Middle Miocene Climatic Optimum. The succession includes major seismic stratigraphic boundaries and overall patterns of platform growth and demise that correspond roughly with periods of pronounced eustatic change associated with initiation of eastern Antarctic ice sheets. Although invoking a eustatic control for coarse trends may be tempting, mismatch between the numbers and ages of sequences, as well as the variable stacking patterns among contemporaneous platforms regionally, precludes such an interpretation; conversely, some globally recognized eustatic changes do not have a pronounced manifestation in this area. Thus, it appears that the eustatic signal combined with dynamic physical regional processes such as waves, currents, and variable subsidence creates the complex architecture and geomorphology of platforms. These results illustrate how global changes can interact with local controls to create diverse patterns of birth, growth, and demise of carbonate platforms and drive local stratal heterogeneity.

Sarmatian biostratigraphy of a marginal sea in northern Croatia based on calcareous nannofossils

Calcareous nannofossils of the Serravallian/Tortonian transition, known as the Sarmatian in the Paratethys were obtained from northern Croatia, Central Paratethys. The nannofossil biostratigraphy of the studied area included early Sarmatian biohorizons; the reliability of these and previous biohorizons was tested, and the known biostratigraphic and magnetostratigraphic datums of the Paratethys were compared with those from the adjacent Mediterranean and beyond. Six out of sixteen bioevents were selected to define five subzones (PNN6d-PNN8b) and crossover for the Badenian/Sarmatian boundary. Variations in the index fossil datums between the Paratethys and Tethys provide a broad perspective on local versus regional and global impacts on the nannofloras. The Paratethys/Tethys gateways (PTGs), and their progressive geodynamical closure, exerted a fundamental control on the salinity, circulation patterns and climate of the area. The global regression at the end of the Badenian, and the tectonic events associated with the Badenian/Sarmatian transition, also restricted the PTGs, initiating acmes of Calcidiscus pataecus and Reticulofenestra pseudoumbilicus, causing a small, early Sarmatian extinction event that occurred in coastal environments, which are the most affected by short-term environmental fluctuations. Stronger connections through the PTGs during the early/mid-Sarmatian transition induced a transgression that brought deep-dwelling Discoaster species into the area. The final closure of the PTG with the Mediterranean, which had been placed at the Badenian/Sarmatian boundary, actually occurred in the late Sarmatian as a result of tectonic movements that caused shallowing and a drastic reduction in nannofossil biodiversity. The PTG with the Indian Ocean existed until the early Tortonian, which allowed an early, but brief, occurrence of small, warm-water ceratoliths.

Evolution of the carnivoran (Carnivora, Mammalia) guild structure across the Middle/Upper Miocene boundary in Germany

We analyse the evolution of carnivoran guilds (body mass, locomotor pattern, and diet preference) across the Middle to Upper Miocene boundary based on a comparison of the carnivoran fauna from Steinheim (Mammal Neogene zone MN 7/8; Servallian to early Tortonian), and from the Eppelsheim Formation (Mammal Neogene zone MN 9/10; mid-Tortonian), Germany. Results reveal a massive faunal turnover between these two communties due to taxonomic differences up to the family level. Guild structures of both carnivoran faunas were similar, implying that Late Miocene taxa replaced Middle Miocene taxa in their respective niches rather than new ecological strategies being added to the guild. This is not surprising, as (1) the majority of Late Miocene taxa were derived from European Middle Miocene ancestors and mostly share their paleoecology, (2) of the few undisputed Late Miocene immigrant taxa (Eomellivora, Simocyon, Sivaonyx), only Eomellivora adds new ecological strategies to the guild, and (3) both faunas occupied the same kind of partly open woodland paleoenvironment. Our paper supports previous studies, suggesting that ecological diversity remains stable across the Middle to Upper Miocene boundary and that similar environments produce similar carnivoran guild structures irrespective of taxonomical composition.

Middle Miocene depositional evolution of the central Roer Valley Rift System

Correlations between bio‐ and/or lithostratigraphically analysed boreholes provide new insights on the late‐early to early‐late Miocene depositional evolution of the central Roer Valley Rift System (RVRS) as part of the southern North Sea Basin. This evolution started with a major regression that occurred in two steps, one during the late Burdigalian and another during the earliest Langhian. Each step coincides with a coarsening of the grain size, reduction in the content of glauconite and increase in the lignite content. The amount of open marine dinocysts also showed a strong decrease. Regression continued up to the middle Langhian as a large delta system builded out in the central RVRS. The main phase of regression ended in the late Langhian. Around the Langhian/Serravallian boundary, a major marine ingression drowned the former delta system. Transgression was evidenced by an increase in the content of glauconite and open marine dinocysts and a decrease in the lignite content. Maximum flooding occurred in the middle/late Serravallian and was followed by another regression. This regression ended in a regional latest Serravallian‐earliest Tortonian hiatus with locally deep erosion. During the early Tortonian, the whole region was transgressed again which was expressed by an increase in the content of glauconite and open marine dinocysts and decrease in the lignite content in the central RVRS. The late‐early to early‐late Miocene depositional evolution of the southern North Sea Basin corresponds very well with that previously described for the eastern and central (Danish) part of the North Sea Basin, but not with the global sea‐level curves, which show mainly the opposite trends. These mismatches could be explained by tectonics and/or changes in sedimentation rates.

Sedimentary Evidences for the Depositional and Environmental Changes Regarding to Regression during Mid to Late Miocene in the Neogene Adana Basin (Southern Turkey)

In this study we investigate sedimentary and stratigraphic characteristics of the Mid to Late Miocene deposits to better understanding of the Tertiary evolution of the Adana Basin (Southern Turkey). For this purpose, detailed mapping, sedimentary survey and interpretations were made considering the stratigraphic relations in the Middle-Late Miocene units in the region. The depositional evolution of the Adana Basin starts during the Early Miocene as a foreland basin within the Çukurova region. An extensive marine transgression during the Early Miocene commenced the filling of the basin. The pre-Miocene deposition area was a large platform with an adjacent depression area. This depositional environment widely controlled the Miocene sedimentation after the Aquitanian-Burdigalian transgression. The Miocene sequences in the Adana Basin were deposited due to the northward transgression. The northerly sourced deltaic and littoral-brackish Kaplankaya Formation and a slightly deeper reefal Karaisalı Formation were deposited in the areas close to the shore. Documented by shallow to deeper marine sedimentation, the marine inundation of the region occurred during Aquitanian-Burdigalian and continued into the Serravallian causing the former coastline to migrate north. Synchronously tectonic subsidence further south cause southward progressive deepening. Therefore, various facies types, ranging from deep marine turbidites to terrestrial, deposited in the basin. The northern margin of the basin was experienced normal faulting in consequence of progressive tectonic and subsidence events during this marine transgression in the Langhian-Serravallian. Mapped and interpreted within three facies types, Güvenç Formation include; i) deep marine sediments, ii) offshore sediments and iii) shallow marine sediments. Deep sea deposits were accumulated in the early stages of the Early-Middle Serravalian period in the deeper part of the basin. During the Mid-to Late Serravallian offshore sediments were deposited in the southern parts of the basin. Further south, due to the continued regression, the shallow marine sediments were deposited in the basin during the Serravalian. Related to the neotectonic period of Anatolia, the transgressive sequences deposited within the basin were tilted during Late Serravallian to Early Tortonian period. The marine regression towards the south was accompanied by tectonic re-organisation in the Early Tortonian. Consequently, regressive sequences of the Tortonian age, the Kuzgun member of Kuzgun Formation, which involve shallow marine (beach) sediments and meandering river deposits are resting on the tilted Güvenç Formation with low angle unconformity.

Sediment routing system and sink preservation during the post-orogenic evolution of a retro-foreland basin: The case example of the North Pyrenean (Aquitaine, Bay of Biscay) Basins

Abstract We investigated here the evolution of the sediment routing system, i.e. the sediment transport and deposition evolution along successive depositional topographies and environments, and the sink (i.e. deposited sediments) preservation in a foreland basin from the period of mountain belt shortening to its post-orogenic stage. The studied system is the North Pyrenean retro-foreland basin from 50 Ma to today which is, composed of a subsiding platform (the Aquitaine Basin) fed by the erosion of the Pyrenees passing laterally to a slope and a deep-sea plain (the Bay of Biscay deep basin), the ultimate area of deposition. This study is based on a double seismic stratigraphic and structural analysis of an extensive seismic dataset and on an age model of the sediments combining biostratigraphy, orbitostratigraphy and sequence stratigraphy with a time resolution of 0.1 Ma. Four major periods of deformation corresponding to a single or a set of stratigraphic sequence boundaries were characterized. The Pyrenean shortening decrease may be recorded by a basin-scale uplift at 49.8 Ma (Late Ypresian). The paroxysm of the piggy-back shortening and related uplift is dated at 35.8 Ma (Priabonian). The end of the Pyrenees shortening (transition to post-orogenic conditions) is well dated between 27.1 and 25.2 Ma (Chattian). A major West European scale deformation of possible mantle origin uplifted the basin from 16.4 to 10.6 Ma (Late Burdigalian to Early Tortonian). These major periods of deformations controlled the sink preservation at the first order through the ratio between the accommodation space created by subsidence on the Aquitaine platform (Asub) and the siliciclastic sediment supply coming from the erosion of the Pyrenees (Ssc). A general model is proposed. At the time of the foreland basin when ΔAsub ≤ ΔSsc, most of the sediments are preserved on the platform as a progradational-aggradational wedge (up to 25.2 Ma here). At the time of the post-foreland evolution when ΔAsub The continental sediment routing system is mainly provided along nearly flat alluvial plains with extensive lakes and/or humid zones, i.e. the local base levels of the alluvial fans. The Aquitaine retro-foreland was never overfilled.

The Libycosaurus (Hippopotamoidea, Artiodactyla) intercontinental dispersal event at the early late Miocene revealed by new fossil remains from Kasserine area, Tunisia

ABSTRACT Anthracotheres dispersed from Asia toward Africa at least three times: at the Eocene/Oligocene transition, during the early Miocene and later during the Miocene. Those dispersals are important datum events for African Tertiary biochronology. New fossil remains of early Libycosaurus, the genus implicated in the late Miocene dispersal, are described from a new Tunisian locality of the Kasserine area. The new fossils enhance the hypodigm of Libycosaurus algeriensis and increase the resolution of the phylogenetic position of this species using cladistics analysis. The inclusion of the genus Libycosaurus within the well-described Merycopotamus lineage allows us to constrain its dispersal time. Dispersal of this anthracothere from the Indian sub-continent to Africa was probably facilitated by sea level decrease during the early Tortonian, just preceding the Hipparion dispersal event. This new age estimation refines the resolution of the succession of late Miocene deposits in Maghreb and frames the date of the onset of the Sahara.