Magmatic activity in the Sakarya Zone, an important segment of the Alpine orogenic belt, continues intermittently from the middle Carboniferous to Miocene. In this study, we provide geochronological and geochemical data from the Dağdibi Pluton in the eastern Sakarya Zone to present some inferences on the source region and petrogenesis of the middle Eocene magmatism. U–Pb zircon geochronology from two granodiorite samples gives middle Eocene ages of 44.75 ± 0.92 and 45.01 ± 0.59 Ma. The pluton is mainly composed of K-feldspar, plagioclase, quartz, Mg-hornblende/actinolite, Fe–Ti oxides and small amounts of biotite, and secondary chlorite and epidote. Parental magma of the intrusive rocks has a high-K calc-alkaline affinity with metaluminous character. The oxygen fugacity values vary between −18 and −17. The rocks show slightly radiogenic 87Sr/86Sr(i) (0.704845–0.705726) ratios and ϵNdi values between −0.96 and +0.52. Pb–Pb isotope ratios are typical for those of the lower continental crust. ϵHf(i) values of the zircons range from 0.14 to 10.26. The geochemical and isotopic features of the pluton point to a parental magma derived from a depleted mantle that was metasomatized by fluids during previous subduction events. The volumetric abundances of the rock types are decreased as the silica content increase, implying that the fractional crystallization is the most important process during the formation of the present compositional range of the pluton. Amphibole, plagioclase and Fe–Ti oxides are the fractionated phases while K-feldspar is largely accumulated. In the light of the data presented above, slab breakoff is regarded as the geodynamic process responsible for the formation of the Dağdibi Pluton in the middle Eocene.

The Palaeocene–Eocene Thermal Maximum (PETM) is one of the most important Cenozoic climatic events shaping modern biodiversity, yet reconstructions of its palaeobiomes remain controversial. Here we describe Gesomyrmex gallicus sp. nov., a new, extinct species of the ant genus Gesomyrmex Mayr, 1868, based on minor and major workers preserved in the early Eocene amber of Oise, France. Although there are only seven known extant species in the genus, all confined to warm and humid forests of SE Asia, the fossil record of Gesomyrmex indicates that the genus once radiated across Eurasia. The new species therefore provides direct evidence that this radiation likely co-occurred with the PETM. This observation constrains palaeoclimatic reconstructions of the Early Eocene by requiring the presence of an extensive, homogeneous and interconnected rainforest-like biome across palaeo-Eurasia, a scenario otherwise corroborated by pollen assemblages. The phases of regression of warm and humid forests and the widening of dry biomes probably occurred later during the Eocene, in between hyperthermals, and were probably less extensive than some computer models predicted.

In this study, we present apatite fission-track results obtained for ten rock samples collected from three different areas across the Sierra Madre del Sur, southern Mexico. The central objective of our study is the timing of the exhumation event that took place in southern Mexico during Late Cretaceous–Palaeogene time. The thermochronometric data obtained during this work indicate that a Late Cretaceous–Eocene cooling is recorded within the Sierra Madre del Sur, and this is interpreted as resulting from exhumation, an orogenic event that is contemporaneous with the Laramide sensu lato (or the Mexican Orogeny). The fission-track ages become younger from west to east across the Sierra Madre del Sur, whereas the cooling rates also increased in the same direction approximately during Campanian–middle Eocene time. Here, we suggest that the activity of the major fault systems of southern Mexico, such as the Caltepec and the Oaxaca faults, played a primary role in the development of geological structures and the exhumation of the Sierra Madre del Sur. Active magmatism during the evolution of the Mexican Orogen implicates the subducted Farallon slab as the main driver of crustal thickening. Moreover, the possible influence of the eastward movement of the Chortis Block on the deformation of the Sierra Madre del Sur cannot be ruled out.

Dinoflagellate cyst assemblages recovered from the La Meseta Formation cropping out in Seymour Island, Antarctic Peninsula, are studied herein and their distribution is compared with the biostratigraphic scheme available for the Palaeogene of the Southern Ocean and other high-latitude regions. In this way, the La Meseta Formation is dated as middle Lutetian to Priabonian (46.2–36 Ma), which differs from the age provided by other fossils, isotopes and also with the magnetostratigraphic scheme recently performed for the unit. The dinoflagellate cyst data support the proposal of ocean circulation patterns on the South American Shelf prior to the opening of Drake Passage. Assemblages from the La Meseta Formation contain Antarctic-endemic taxa which are also dominant in several circum-Antarctic sites, located south of 45° S. Their distribution reflects an ocean-circulation scheme with wide clockwise gyres surrounding Antarctica that were disrupted as a consequence of the deepening and definitive apertures of the Tasmanian Gateway and Drake Passage towards the Eocene/Oligocene transition. The palaeoenvironmental inference based on the S/D ratio (sporomorphs versus dinoflagellate cysts) and the P/G ratio (peridinioid versus gonyaulacoid dinoflagellate cysts) suggests an overall trend through the section from marine-dominated assemblages with poorly productive waters in the lower part of the section to more terrestrially dominated assemblages with increasing productivity in the upper part of the unit, reflecting a shallowing trend to the top.

K-Ar ages of Eocene glauconite pellets from the Isle of Wight are related to quantified amounts of older glauconite pellets and to occurrences of detrital mica/illite particles that might have been added to synsedimentary pellets during reworking processes. Addition of older glauconite did not significantly bias the K-Ar dates, as the results most often provide the expected stratigraphic reference ages or even significantly lower ages. Alternatively, K-Ar dates significantly greater than those suggested by the stratigraphy appear to result from non-glauconized detrital mica in the pellets which is not always removable, even by high-gradient magnetic separation.

Unexpected ‘old’ K-Ar glauconite ages do not result from misapplication of the method, but from inability to systematically identify and remove the `contaminant' particles from glauconite splits. Analysis of highly evolved glauconite separates is definitely appropriate for reliable isotopic age determinations, but it might not be enough for the final selection, as long-lasting diagenesis might have taken over the synsedimentary process. Much if not all depends on the separation and characterization of the separates, but also on the completion of the glauconitization process which effects cannot always be anticipated.

Clay mineral associations of Palaeocene and Eocene age, with special attention to the late Palaeocene thermal maximum, have been examined in ten sections from the Tethys (Egypt, Israel, Tunisia, Spain and Kazakhstan) and Atlantic (England). A widespread abundance of kaolinite in marine sediments at all locations suggests a warm and humid climate with high rainfall in the Tethys region during the early Palaeocene. In the coastal basins along the southern margin (Israel and southern Tunisia), kaolinite disappears gradually giving way to palygorskite and sepiolite, suggesting the progressive development of arid climatic conditions in this part of the Tethys from the late Palaeocene to the early Eocene. Remarkably, kaolinite increases strongly throughout most of the Tethys during the late Palaeocene thermal maximum (LPTM) reflecting an episode of humidity and warmth and coincident with a global maximum warmth of seawaters inferred from oxygen isotopic data.

The genus Neomonoceratina, which dominated the ostracod assemblage in the uppermost part of the Akasaki Formation (Miroku Group) of the Kyushu Island, Japan, is associated with the benthic foraminifer Ammonia cf. beccarii, mollusca Terebralia? sp. and Anomia sp., and the oogonium of Charophyceae, indicating a marine-to-brackish estuarine environment involving inflowing freshwater. This is the first record of Eocene coastal-estuarine ostracods from the eastern margin of the Eurasian continent and demonstrates that different pre-Neogene coastal-estuarine ostracod assemblages flourished in this region. The assemblages comprised five ostracod species (including one novel species) assigned to the genera Neomonoceratina, Paijeiborchella, Propontocypris and Parakrithella. These species exhibited genus-level links with the Eocene borehole cores along the continental shelf of the East China Sea and other areas of Kyushu. Fossil data of characteristic Eocene coastal-estuarine genera collected worldwide indicate that different characteristic genera inhabited each region. For example, Neomonoceratina originated on the Indian subcontinent by the Early Paleocene period at the latest, along with the northern drift of the Indian subcontinent. These species subsequently diversified west and east with the equatorial current and counter-current via the Tethys and reached the eastern margin of the Eurasian continent among the various eastwards-migrating species, where one genus ultimately adapted to the coastal-estuarine environment. Notably, the coastal-estuarine ostracod assemblage of the eastern margin of the Eurasian continent differs completely from that of the Tethys during the Eocene period. Our results suggest that coastal-estuarine ostracod assemblages are a powerful tool for palaeogeographic reconstruction.

The well-exposed marine Eocene units from southwestern Patagonia, Argentina, contain useful information for reconstructing regional climate and oceanographic patterns in an area adjacent to the Drake Passage. The aim of this paper is to integrate dinoflagellate cyst data from three sections of the southwestern Austral Basin (Río Turbio Formation) to propose a zonation scheme, which can be applied to other southwestern Atlantic Ocean sites. Assemblages of organic walled dinoflagellate cysts have been analysed in different cropping-out sections and cores, showing the high potential of this fossil group as biostratigraphic markers. Comparison of dinoflagellate cyst events of the upper member of the Río Turbio Formation with calibrated biostratigraphic ranges in the Palaeogene South Pacific Ocean allowed us to date and correlate these sedimentary sections. The resulting zonation consists of four dinoflagellate cyst zones labelled RTF 1 to RTF 4, between the middle Lutetian and late Priabonian. As a final point, we applied dinoflagellate cyst species with importance as palaeoenvironmental markers to assess long-term climatic and oceanographic evolution for the area. This study shows that the endemic–Antarctic dinoflagellate cyst assemblage is dominant during the middle to late Eocene (RTF 1 to RTF 3), while a significant replacement of these taxa by cosmopolitan species characterizes the upper part of the upper member of the Río Turbio Formation (RTF 4). This turnover seems to be a consequence of changes in the ocean circulation patterns forced by deepening of the southern Atlantic gateways (the Drake Passage and the Tasman Gateway).

The family Achilidae (Hemiptera, Fulgoromorpha, commonly called planthoppers) is one of the least known and least understood groups, due to their cryptic lifestyle. They appear in the fossil record in the Lower Cretaceous, with a single genus and two species from the Crato Formation of Brazil. The oldest amber inclusion is reported from the earliest Late Cretaceous amber of Burma. Surprisingly, Achilidae are relatively common among the larger inclusions that can be found in Eocene Baltic amber. The first description of a fossil species was in the mid-19th Century. Currently, there are 13 genera and 16 species known from fossils, of which nine genera and 11 species are from Baltic amber. However, many of them need reconsideration, revisionary studies and placement in the phylogenetic context of the family. Former studies on inclusions in this amber revealed several unique forms (extinct tribes Ptychoptilini and Waghildini), or taxa ascribable to the sparse Recent tribe Achilini. This paper provides an overview of the knowledge of fossil Achilidae, particularly those from Baltic amber. The Eocene appears to be the heyday of the family; however, this hypothesis should be tested with further detailed studies.

Based on two well-preserved specimens from late Eocene Baltic amber, a new fossil species belonging to the family Trogossitidae, Seidlitzella hoffeinsorum sp. nov., is described. This is the second known fossil species of the tribe Gymnochilini and the second known species of the genus Seidlitzella. The systematic and biogeographical relations of the genus to other members of the Gymnochilini are discussed. It is hypothesised that the extant eastern Mediterranean species Seidlitzella procera may be phylogenetically related to the genus Phanodesta, today distributed in New Zealand, New Caledonia, Lord Howe Island, Juan Fernandez Island and Sulawesi.

The present study consists of a synthesis of the lithostratigraphy, geotechnical properties, geometry and distribution of Eocene and Quaternary deposits of the Belgian continental shelf. It is based on available large datasets (seismics, cores, cone penetration tests) and their interpretations synthesised from numerous studies from the last 20 years. A significant effort has been focused on data digitisation and integration into appropriate GIS software packages in order to compare the data in a much more dynamic and flexible way. New insights have been proposed on the lithostratigraphy and geotechnical properties of offshore and onland deposits.

An application is presented for the selection of wind farm implantation sites. Geological and geotechnical aspects of direct interest for wind farm implantation site selection have been focused on, such as the stability of the offshore wind turbine structures and the minimization of environmental impacts on the seabed. Sites suitable for wind turbines using monopile structures on the Belgian continental shelf are proposed.

The Geiseltal fossil collection from southern Sachsen-Anhalt Germany contains remarkably well-preserved fossils of middle Eocene age. These include several crocodylian skulls, representing at least four different genera with a fifth genus represented by two mandibular rami. As sites with this many crocodylian genera are unknown in modern ecosystems, it has been hypothesized that these crocodylians may have differences in habit as compared to living crocodylians. In order to test similarities between the Geiseltal crocodylians and extant species, an analysis was conducted using geometric morphometrics to quantify shape in crocodylian skulls of all living species (n = 218) and all well-preserved crocodylian skulls of the Geiseltal fauna (n = 28). A relative warps analysis was used to quantify and compare skull shape, revealing Allognathosuchus and Boverisuchus to be very distinct from each other as well as from Asiatosuchus and Diplocynodon. Overlap in shape alone exists between some Diplocynodon and some Asiatosuchus, but there was significant difference in adult size. When compared with extant crocodylians, three Geiseltal genera occupied distinctly non-modern morphospace in the first two relative warps axes. Comparison of the diets of living crocodylians with similarly shaped skulls was used to reconstruct the prey preferences of the Geiseltal crocodylians, revealing differences in specialization. During the middle Eocene high global temperatures, partitioning of prey preference may have allowed this group to attain its higher than usual diversity, reducing the amount of direct competition.

Three isolated limestone deposits and their fauna are described from a middle Eocene Flysch succession in northwestern Istria, Croatia. The limestones are identified as ancient methane-seep deposits based on fabrics and characteristic mineral phases, δ13Ccarbonate values as low as −42.2 ‰ and 13C-depleted lipid biomarkers indicative of methane-oxidizing archaea. The faint bedding of the largest seep deposit, the great dominance of authigenic micrite over early diagenetic fibrous cement, as well as biomarker patterns indicate that seepage was diffusive rather than advective. Apart from methanotrophic archaea, aerobic methanotrophic bacteria were present at the Eocene seeps as revealed by 13C-depleted lanostanes and hopanoids. The observed corrosion surfaces in the limestones probably reflect carbonate dissolution caused by aerobic methanotrophy. The macrofauna consists mainly of chemosymbiotic bivalves such as solemyids (Acharax), thyasirids (Thyasira) and lucinids (Amanocina). The middle Eocene marks the rise of the modern seep fauna, but so far the fossil record of seeps of this age is restricted to the North Pacific region. The taxa found at Buje originated during the Cretaceous Period, whereas taxa typical of the modern seep fauna such as bathymodiolin mussels and vesicomyid clams are absent. Although this is only a first palaeontological glimpse into the biogeography during the rise of the modern seep fauna, it agrees with biogeographic investigations based on the modern vent fauna indicating that the dominant taxa of the modern seep fauna first appeared in the Pacific Ocean.

We investigated the Quaternary lithological succession and faunas in a borehole near Moriaanshoofd (Province of Zeeland, SW Netherlands), in order to improve our understanding of the depositional context of classical Gelasian mammal faunas from the region. The fossils mostly derive from the base of a fossil-rich interval between 31 m and 36.5 m below the surface, that was initially interpreted as a Middle or Late Pleistocene interglacial marine unit, but turned out to be a Late Quaternary fluvial unit with large amounts of reworked fossils and sediments. Eocene mollusc taxa pinpoint Flanders (Belgium) as the source region for this river. Within the base of this paleo-Schelde River fossil material of various stratigraphic provenance became incorporated.

We focus on an active continental margin related to northwards subduction during the Eocene in which sedimentary melange (‘olistostromes’) forms a key component. Maastrichtian – Early Eocene deep-marine carbonates and volcanic rocks pass gradationally upwards into a thick succession (<800 m) of gravity deposits, exposed in several thrust sheets. The lowest levels are mainly siliciclastic turbidites and debris-flow deposits. Interbedded marls contain Middle Eocene planktonic/benthic foraminifera and calcareous nannofossils. Sandstones include abundant ophiolite-derived grains. The higher levels are chaotic debris-flow deposits that include exotic blocks of Late Palaeozoic – Mesozoic neritic limestone and dismembered ophiolite-related rocks. A thinner sequence (<200 m) in one area contains abundant redeposited Paleogene pelagic limestone and basalt. Chemical analysis of basaltic clasts shows that some are subduction influenced. Basaltic clasts from unconformably overlying alluvial conglomerates (Late Eocene – Oligocene) indicate derivation from a supra-subduction zone ophiolite, including boninites. Taking account of regional comparisons, the sedimentary melange is interpreted to have formed within a flexurally controlled foredeep, floored by continental crust. Gravity flows including large limestone blocks, multiple debris flows and turbidites were emplaced, followed by southwards thrust imbrication. The emplacement was possibly triggered by the final closure of an oceanic basin to the north (Alanya Ocean). Further convergence between the African and Eurasian plates was accommodated by northwards subduction beneath the Kyrenia active continental margin. Subduction zone rollback may have triggered collapse of the active continental margin. Non-marine to shallow-marine alluvial fans prograded southwards during Late Eocene – Oligocene time, marking the base of a renewed depositional cycle that lasted until latest Miocene time.

The types and undescribed material of the hymenopteran fossils of the Insect Bed of the Bembridge Marls from the Isle of Wight (UK) are critically revised and studied. A total of 1460 fossils are recorded and attributed to 20 families: Gasteruptiidae s.l. (1); Proctotrupidae (3); Diapriidae (24); Cynipidae (7); Figitidae (6); Pteromalidae (1); Agaonidae (3); Scelionidae (12); Platygastridae (2); Ichneumonidae (32); Braconidae (75); Bethylidae (3); Crabronidae (2); Sphecidae (1); Apidae (2); Scoliidae (1); Tiphiidae (2); Vespidae (4); and Formicidae (1220). Described as new are 51 species, 13 genera, two tribes and two subfamilies. Minimum number of species recorded (either as described species or representing higher taxa with no described species in the assemblage) is 118. The composition of the hymenopteran assemblage is most similar to that of Baltic amber and indicative of a well forested territory, as well as of a humid, equable (aseasonal but not very hot) climate, more typically equable than in the Baltic amber source area, judging from the absence of Aphidiinae and scarcity of aphids.

Batfishes of the family Ogcocephalidae are derived lophiiform fishes characterized by having a dorsoventrally depressed body and a distinctive series of morphological features. A new genus and species of batfish, Tarkus squirei gen. et sp. nov., is described from the Eocene (Ypresian) limestone of the celebrated locality of Monte Bolca, Italy. It is based on five well-preserved specimens that display a unique combination of characters (body moderately depressed; disk rounded in outline; caudal peduncle thick and stout; frontals with median groove for the illicium; teeth present on jaws and palate; illicial bone pitted and trilobate; body covered with thick slightly overlapping tubercles) that support its recognition as a new genus of the family Ogcocephalidae. Tarkus gen. nov. is also characterized by having distally branched pectoral-fin rays, a condition unique within the family, and by a peculiar structure of the axial skeleton, which possibly represents the plesiomorphic state for the ogcocephalids. Tarkus gen. nov. shows a certain degree of phenetic affinity with the extant shallow-water batfish genera Halieutaea and (more particularly) Halieutichthys. The specimens of this taxon are the first articulated skeletal remains of the Ogcocephalidae ever recorded as fossils, also representing the oldest members of the family known to date. The general structure of the skeleton of Tarkus gen. nov. provides unambiguous evidence that the existence of the modern ogcocephalid body plan was already established in the early Eocene, and probably originated well before that period. Palaeoenvironmental considerations suggest that Tarkus gen. nov. was a tropical batfish that inhabited the inner-shelf palaeobiotopes of the central-western Tethys.

An integrated bio-, magneto- and cyclostratigraphic study of the Ypresian/Lutetian (Early/Middle Eocene) transition along the Otsakar section resulted in the identification of the C22n/C21r chron boundary and of the calcareous nannofossil CP12a/b zonal boundary; the latter is the main correlation criterion of the Lutetian Global Stratotype Section and Point (GSSP) recently defined at Gorrondatxe (Basque Country). By counting precession-related mudstone–marl couplets of 21 ka, the time lapse between both events was calculated to be 819 ka. This suggests that the age of the CP12a/b boundary, and hence that of the Early/Middle Eocene boundary, is 47.76 Ma, 250 ka younger than previously thought. This age agrees with, and is supported by, estimates from Gorrondatxe based on the time lapse between the Lutetian GSSP and the C21r/C21n boundary. The duration of Chron C21r is estimated at 1.326 Ma. Given that the base of the Eocene is dated at 55.8 Ma, the duration of the Early Eocene is 8 Ma, 0.8 Ma longer than in current time scales. The Otsakar results further show that the bases of planktonic foraminiferal zones E8 and P10 are younger than the CP12a/b boundary. The first occurrence of Turborotalia frontosa, being approximately 550 ka older that the CP12a/b boundary, is the planktonic foraminiferal event that lies closest to the Early/Middle Eocene boundary. The larger foraminiferal SBZ12/13 boundary is located close to the CP12a/b boundary and correlates with Chron C21r, not with the C22n/C21r boundary.

Recent field work in the southern Moroccan Sahara (‘Western Sahara’), south of the city of ad-Dakhla, has led to the discovery of several new fossiliferous sites with fossil vertebrates in sedimentary deposits previously reported for the Mio-Pliocene. The sedimentology and geological setting of the studied area are briefly reported here, and at least three units have been identified in successive stratigraphical sequences according to their fossil content. The first preliminary list of vertebrate associations is reported and consists mainly of isolated teeth belonging to selachian and bony fishes, a proboscidean tooth currently assigned to ?Numidotherium sp. and many remains of archaeocete whales (Basilosauridae). At least 48 species of selachians are presently identified; many of them are new and others are recorded in the late Middle Eocene (Bartonian) and Late Eocene (Priabonian) of Wadi Al-Hitan (Egypt) or Wadi Esh-Shallala Formation (Jordan) as in other African localities (e.g. Otodus cf. sokolowi, ‘Cretolamna’ twiggsensis, Xiphodolamia serrata, Misrichthys stromeri, Hemipristis curvatus, Galeocerdo cf. eaglesomi, Propristis schweinfurthi), probably indicating a Late Eocene age for unit 2 of the bedrock successions. The evolutionary trend noticeable on the proboscidean tooth is in agreement with such an assumption, by comparison with the close relative species known from the Eocene of Egypt, Libya and Algeria. Indeed, the faunal associations from the Dakhla area clearly demonstrate the erroneous age of these deposits, previously thought to be Mio-Pliocene. It suggests a correlation in age (late Middle Eocene–Late Eocene) and a similar environment with the famous marine deposits from Egypt and Jordan. It opens new opportunities to understand the biogeography and the surprising similarity of landscape between West and Northeast Africa during the Bartonian–Priabonian period.

The genus Diplocynodon is widely recorded in Europe from Early Eocene up to Middle Miocene times. A fragmented but almost complete skull of a new species of Diplocynodon is reported from the Late Eocene locality of Domérat, northern border of the Massif Central (Allier), France. The present skull provides an important basis for comparison with other members of the genus and complements a fossil record full of gaps despite the large number of vertebrate localities spanning the Cenozoic. The new taxon occurs at a key period for climate evolution with conditions marking the transition from a greenhouse to an icehouse world. The response of crocodylian assemblages to this climatic shift is discussed in light of evidence for their decline in diversity from the Eocene period onward.