Geobios最新文献

The Lower Cretaceous carbonate successions of the Tauride Carbonate Platform(s) (TCP) are characterized by mostly restricted inner platform facies. The record of these stages is limited owing to frequent exposure of the platform to subaerial and supratidal settings during the Early Cretaceous. This study focuses on the Lower Cretaceous (Aptian–Albian) successions outcropping at two localities in the Geyik Dağı and Anamas Dağ areas, Central Taurides. These successions exhibit a peritidal shallowing upward trend evidenced by the dominance of mud-rich microfacies, lamination, fenestrae, oncoids, and changes in fossil content (benthic foraminifera, dasycladalean algae, rudists, etc.). The stratigraphic subdivisions of the studied successions utilize index taxa in the benthic foraminiferal assemblages which are documented and illustrated. Assemblage I (lower Aptian) is mainly characterized by Voloshinoides murgensis and Debarina hahounerensis; Assemblage II (upper Aptian) by Mesorbitolina parva, Carseyella tunesiana and “Arenobulimina” geyikensis; and Assemblage III (Albian) by Mesorbitolina gr. texana, Protochrysalidina elongata and Pseudonummoloculina heimi. Ranges and stratigraphic significance of some species through the Lower Cretaceous are discussed. Due to less favorable environmental conditions, the strata in the Anamas Dağ area have a low-diversity benthic foraminifera fauna and sparse macrofossils. In contrast, the strata in the Geyik Dağı area host rich and diverse larger benthic foraminifera as well as rudist bivalves and gastropods. A new species, “Palaeocornuloculina” taurica belonging to the family Ophthalmidiidae is described from these foraminifera-rich upper Aptian–Albian strata in the Geyik Dağı area.

An integrated stratigraphic study has been performed of the Lower Miocene deposits of the Poljanska and Mala sections (North Croatian Basin), coupled with ⁴⁰Ar/³⁹Ar dating, geochemical and mineralogical study of tuffitic and silty sand beds. The sedimentary record evidences deposition influenced by volcaniclastic input. The presence of marine, brackish and non–marine microfossils indicates complex palaeoenvironment, palaeoecology, and palaeobiogeography. Four different units were recognized based on their fossil content and sedimentological data. At the base of the Poljanska section (Unit P1), tuffitic sediments bear common endemic brackish, and rare marine to freshwater and terrestrial microfossils. Radiometric ⁴⁰Ar/³⁹Ar dating obtained on volcanic glass shards from this layer provided an age of 22.2 ± 1.9 Ma correlating with the earliest Early Miocene and indicating the existence of older volcanic activity in the NCB pro tempore. The succession transitions into the brackish-water lacustrine environments (Unit P2). This unit has two presumed different climatic events: a maximum temperature event in the lower part of the interval and one interruption with lower temperatures recognized in the upper part of the interval. The co-occurrence of limnic and marine species in the uppermost part of the investigated sediments (Unit P3) indicates a marine inflow into the coastal lake. It marks the beginning of a salina-type lake formation in Poljanska. In the Mala section (Unit M1), biostratigraphically dated to the NN4 Zone, a transgressive sequence is documented through the presence of marine calcareous nannoplankton, planktonic and benthic foraminifera, and ostracods.

New records documented here demonstrate that Palaeocaris Meek and Worthen, 1865 was the most cosmopolitan and longest ranging (earliest Bashkirian to Gzhelian) fossil syncarid genus. It contains three species that are primarily known from occurrences in Euramerican Carboniferous Lagerstätten. Two of these species, P. typus Meek and Worthen, 1865 and P. secretanae Schram, 1984, have previously been reported from North America. We add a third species to the North American fossil record, Palaeocaris retractata Calman, 1932, from the Manning Canyon Formation (Bashkirian) of north-central Utah, USA. This is the oldest geological record of Palaeocaris and extends the temporal range of P. retractata back from its appearance in the transitional Bashkirian to Moscovian Bickershaw Lagerstätte of England by at least 4 million years. The Manning Canyon Formation occurrence expands the paleogeographic distribution of P. retractata from western Europe (England) to the northeastern edge of the Great Basin, USA.

Well-documented, high-resolution sedimentary sections are critical to our understanding of the often eventful evolution of semi-isolated basins that form during the final stages of continent–continent convergence, as exemplified by the Mediterranean-Paratethys system. Due to its nearly land-locked position in the Late Miocene, the Mediterranean experienced the renowned Messinian Salinity Crisis. At the same time, the equally restricted Eastern Paratethys to the north-east evolved in a potentially related, but very distinctive way. The events of this period are fully recorded in the sediments deposited during the Pontian regional stage in the Dacian Basin, part of the Eastern Paratethys, which we here investigate in detail in the best available section. The studied interval of the Slănicul de Buzău section is more than 2 km thick and almost continuously exposed. It is analyzed for paleomagnetism, mollusks, microfauna and sedimentary facies. This allows us to refine previous results from nearby but less complete sections, with particular improvements concerning resolution, biostratigraphy and sedimentology. The marine incursion just below the base of the Pontian (6.1 Ma) is shown to significantly predate the early Pontian highstand. The biostratigraphically defined onset of the middle Pontian (6.0 Ma) coincides with the highstand and slightly predates the major regression (5.9–5.6 Ma) for which the middle Pontian is best known. In the here-investigated section, the transgression at the beginning of the late Pontian (5.6 Ma) is followed by a regressive trend culminating between 5.4 and 5.2 Ma around the Mio-Pliocene boundary (5.33 Ma). The late Pontian sedimentation then becomes relatively stable and the fauna gradually transitions (4.8 Ma) into assemblages characteristic for the Dacian stage of the Dacian Basin, while overall significantly diverging from the rest of the Eastern Paratethys. Finally, we discuss several factors that could affect accuracy and applicability of the updated chronostratigraphy, warranting some caution.

Three ichnospecies of the Late Jurassic trace fossil genus Rhamphichnus were first described and interpreted as the walking tracks of non-pterodactyloid pterosaurs like Rhamphorhynchus. This despite not resembling any previously identified pterosaur tracks and having a morphology unmatched by pterosaur skeletal elements. To fit the pterosaurian model, elongated imprints of R. pereiraensis and R. lafaurii, displaying four or five digit impressions were interpreted as manus prints, while shorter, five-digit prints were interpreted as imprints made by pedes with dislocated metatarsals and disarticulated phalanges. Comparison of published images and descriptions of Rhamphichnus ispp. to skeletal elements of six contemporaneous non-pterodactyloid taxa, skeletons and tracks from pterodactyloid pterosaurs, and modern and ancient lepidosaurs and crocodilians suggests an alternative interpretation. R. crayssacensis closely resembles crocodilian (Crocodylopodus (Sustenodactylus) isp.) and crocodylomorph (Batrachopus isp.) tracks; its holotype trackway was found 50 cm away from and parallel to a crocodilian swimming trackway with the same sized feet, possibly made by the same individual. R. pereiraensis and R. lafaurii strongly resemble lepidosaurian tracks and match the size and morphology of contemporary rhynchocephalians. Prints originally interpreted as manual and pedal in R. pereiraensis and R. lafaurii are reinterpreted and transposed in light of new data from pterosaurian, lepidosaurian, and crocodilian tracks and anatomy. Identification of fossil trackmakers depends on comparisons of a wide range of candidate taxa and elimination of those that cannot be considered further. With this reinterpretation of Rhamphichnus, there are no non-pterodactyloid pterosaurian tracks yet identified in the fossil record.

Some remains of suids were recovered during the second half of the 1800s from Quercia (Tuscany, Italy), at a close distance to, but from a lower stratigraphic position than the better-known mammal fauna of Olivola. Although they were collected a long time ago, Quercia suids are described for the first time in this work. This sample represents one of the earliest occurrences (middle Villafranchian) of Sus strozzii, a large-sized suid present in Europe during the Early Pleistocene, but only abundant ∼2.0–1.8 Ma. A biometric comparison with selected samples of Pliocene to early Middle Pleistocene European suids is carried out, showing some dimensional changes in S. strozzii as well as differences between S. strozzii and other species. Quercia has been somehow eclipsed by other historical samples from Tuscany, namely the extensive collection of the Upper Valdarno and the diverse fauna of Olivola, but it is a different and important palaeontological locality. Apart from S. strozzii, the local fauna of Quercia-Vaccareccia includes Anancus arvernensis, Canis sp., Stephanorhinus etruscus, Leptobos etruscus, ‘Pseudodama’ sp., and Castor sp., representing one of the few mammal assemblages referable to the Faunal Unit of Coste San Giacomo (late middle Villafranchian, MNQ 17b), corresponding to ∼2.2–2.1 Ma.

Central Asia is a region that, owing to its geographical position, has always been at the intersection of cultures. In the Fergana Valley, located in the very heart of Central Asia, the Late Pleistocene–Early Holocene is characterized by the expansion and intensification of human settlements. This cultural event has previously been linked to global climate changes that took place during the Pleistocene–Holocene transition. In order to reconstruct local climatic conditions in the area during this period, it is worth studying the fossil vertebrate faunas from late Quaternary sites in the Fergana Valley. The Obishir-5 rock shelter, dating to the Late Pleistocene–Early Holocene period, discovered in the middle of the 20th century, is a key archeological site in the valley. To date no thorough zooarcheological research has been done on the excavated faunal remains. Here we present the results of the first faunal analysis of the small vertebrates found at this site. We studied the taxonomic composition of remains, which was then used to make paleoenvironmental reconstructions. In total, we identified 13 small mammal species and three bird species. In addition, the assemblage contained one amphibian and two reptile taxa. The faunal composition suggests that during the final Pleistocene and Early Holocene the study area enjoyed a stable climate with vegetation dominated by open biotopes (alpine meadows, steppes, semi-deserts). Its location makes the Fergana Valley an example of a geographically isolated area for a terrestrial fauna which can exist for a long time without being influenced by biotic factors from neighbouring territories.

The Aïn Beni Mathar-Guefaït Basin, in the High Plateau Region (Morocco), is dissected by the Za River, the main eastern tributary of the Moulouya, which incises more than 150 m into Plio-Pleistocene sediments. The main goal of the present study is to provide an initial geochronologic framework for such basin infill based on a combination of magnetostratigraphy and electron spin resonance (ESR). The combined results have implications on the age of the paleontological record, the evolution of the Moulouya River, and the activity of the faults that delimit the basin. We have studied sedimentary rocks that are essentially flat-lying and of an alluvial and lacustrine/palustrine origin. An approximately 140 m-thick section has been sampled at an average of 2.5 m per site, allowing to build a local magnetic polarity stratigraphy that includes nine geomagnetic reversals. Although no fold test is available, the presence of dual polarities and rockmagnetic analysis give us confidence that magnetization directions are primary. We then anchored the obtained magnetozones to the Geomagnetic Polarity Timescale (GPTS) using the biostratigraphic data as well as local geological observations. Our proposed magnetostratigraphy-based chronology reveals a Plio-Pleistocene sedimentary infill spanning from Gauss to Olduvai Chrons. The lower, detrital formations mostly fall within the normal Gauss Chron, whereas the upper lacustrine and palustrine carbonates, which are almost widespread to the top of the sedimentary fill, are Olduvai in age. These results provide the first chronological constraints for the basin fill in one of the largest intermontane basins of the High Plateaus. The new magnetostratigraphy also reveals that the major environmental change that triggered a switch from alluvial to lacustrine-palustrine conditions in Northern Maghreb occurred near the Gauss-Matuyama reversal, ca. 2.6 Ma. In addition, it shows that the age of the paleontological site Guefaït-4 is approximately 1 myr older than the ESR ages obtained from the quartz grains. The possible sources for this underestimation are discussed. However, we also acknowledge and discuss other possible chronostratigraphic interpretations of the current data, although less likely.

The number of late Neogene Spanish micromammal-containing continental sections with a correlation to the Geomagnetic Time Scale is steadily growing. Nonetheless, well-calibrated sections with dense micromammal records are still rare, biostratigraphic correlations between basins are not straightforward, and ages of uncalibrated sites are poorly constrained. Here, we aim at improving the chronology of Iberian micromammal sections and sites for the interval 8.5–2 Ma by: (i) analyzing qualitative and quantitative similarities between rodent assemblages and turnover in the different basins, (ii) formulating a system of fifteen Iberian assemblage biozones, and (iii) constraining the ages of zone boundaries, assuming isochroneity across basins. Age uncertainty ranges for most known Iberian micromammal sites are obtained by combining regional biozone boundary ages with local magnetostratigraphic records, sedimentation rates and/or evolutionary rates. In addition, our results include new, integrated stratigraphic records from the Jumilla-La Celia and Teruel Basins, which are used to constrain the thus far poorly dated interval covering the latest Tortonian and earliest Messinian (8–7 Ma).

In this paper, we describe anatomical structures of 11 fossil wood samples collected from two localities (Brown Sands and Flat Sands) of the Usno Formation, in the Lower Omo valley, Ethiopia. On the basis of former stratigraphy and new investigation, notably Ar/Ar dating of intercalated tuffs and palaeomagnetic studies, the samples are dated between 3.33 and 3.21 Ma. The identified wood samples have been collected within two distinct stratigraphic layers deposited during this time range. The oldest one from Brown Sands includes Albizia sp., Entada sp. and a possible Combretaceae or Leguminosae. The youngest assemblage from White Sands includes many representatives of Combretaceae including Combretum molle and Terminalia sp. associated with Erythrina sp. These assemblages strongly differ from other Miocene and Pliocene wood assemblages known from Ethiopia. Palaeoenvironmental interpretation of the identified tree taxa support affinities with the extant mid-elevation Albizia forest replaced by Combretum/Terminalia woodland in about one hundred thousand years. In the Lower Omo valley, the more humid character of the Pliocene vegetation strongly contrast with the arid Acacia/Commiphora steppe widely spread over the region today. Such past vegetation attests to much wetter and favourable climatic conditions under seasonal climate. However significant changes in the floristic composition of tree cover occurring within a timespan of hundred thousand years, plays in favour of climatic and palaeo-environmental instabilities at a time when Australopithecus afarensis existed in the Turkana basin and flourished elsewhere in Ethiopia.