Middle Eocene Time Research Articles

Paleogene paleogeographic reconstructions of the Kutai Basin: Refinement based on outcrop and subsurface data

The Kutai Basin is a Cenozoic sedimentary basin located in the eastern part of Borneo Island. Many studies were done on the eastern part of the basin, which is dominated by Neogene sediments. The west margin of the basin is outcropped onshore and to the east, the basin opens up to the Makassar Strait. Paleogene and older rocks outcrop in the west margin of Kutai Basin. The terrain and the access to the area are difficult and no significant hydrocarbon discovery was made in Paleogene sediments up to now.This study revisited the field works completed in the 1970s by a Shell team, which focused on the Paleogene section of the Kutai Basin. The result was integrated with later studies, and altogether were synthesized into a series of paleogeographic maps. A new set of paleogeographic maps is proposed in this paper, for Middle Eocene, Late Eocene, Early Oligocene, and Late Oligocene levels. The works included in this study comprised outcrop observations, biostratigraphy analysis of the samples and limited seismic in parts of the area. The results were integrated with other more recent work to build the new set of Paleogene paleogeographic maps.Outcrops data and well information show the distribution of shallow marine sediment in the Middle Eocene time with some fluvial input from the north and southwest of the basin. In the Late Eocene, some carbonates developed in the north of the basin. During Early Oligocene, the carbonate complex developed both in the south and in the north of the basin. In the Late Oligocene, the carbonate in the south became more stable. Through Paleogene time the center of Kutai Basin was dominated by the bathyal section.

Detecting the Laramide event in southern Mexico by means of apatite fission-track thermochronology

AbstractIn 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.

Denudation of the Cordillera and intraplate belt in central Patagonia inferred by detrital multi-dating of foreland basin deposits

The evolution of central Patagonia is associated with episodic shortening and extension that have greatly affected the topography of the Cordillera and intraplate belt. The San Jorge Basin is a site of sediment accumulation in the foreland that is surrounded by igneous and broken foreland relief. The latter originated from episodic deformation and reactivation of inherited structures associated with a period of slab shallowing that allowed the far-field transmission of Andean stresses to the foreland. Thus, due to of its location, the San Jorge Basin provides an exceptional opportunity to study the denudation of both Cordilleran and intraplate topography during the Cenozoic, particularly during the late Eocene–early Miocene interval of mild deformation. In this study, we use a single-grain geochronological approach combining apatite fission tracks and UPb dating on apatite, along with maximum deposition ages obtained from UPb zircon dating for Neogene foreland basin deposits, to distinguish between two distinctive sediment source regions in central Patagonia during the Cenozoic, despite the persistent volcanic signal. A compilation of previously published cooling ages combined with our new data define: (i) a dominant local source from the northern broken foreland from the late Eocene until the early Miocene; and (ii) a widespread source in the Cordillera during the Miocene based on a very uniform thermochronological signal observed throughout the entire foreland. Therefore, this study provides new insights into the variation in sediment sourcing in the central Patagonian foreland. This variation is primarily controlled by the decrease of post-orogenic erosional processes during a period of relative tectonic quiescence following the highly active Early Cretaceous–middle Eocene time interval.

Diachronous initiation of Arabia–Eurasia collision from eastern Anatolia to the southeastern Zagros Mountains since middle Eocene time

ABSTRACT The persistent debate over the timing of initial Arabia–Eurasia collision has eluded consensus for decades, with most estimates ranging widely from ~50 to 10 Ma along both the Anatolian and Zagros segments of the orogen. Here, we independently evaluate the timing and location of initial collision using a quantitative plate tectonic reconstruction that is the first to include the entire Arabian microcontinent and regions to the north in eastern Anatolia, northwestern Iran, and the Caucasus. The reconstruction combines new kinematic constraints from recent global plate models with a synthesis of available constraints on crustal shortening and continental and back-arc subduction to restore the pre-collisional geometries of the Arabian and Eurasian continental margins and to track their interaction through time. Our preferred model suggests that initial continental underthrusting, or soft collision, of the relatively thin Arabian passive margin with Eurasia occurred by ca. 42 Ma along the eastern Bitlis suture zone and began transmitting strain across central and eastern Anatolia, the Caucasus, and northwestern Iran. Collision inception then propagated westward into central Anatolia and southeastward into the northwestern Zagros Mountains by late Eocene time (ca. 40–35 Ma), the central Zagros by latest Eocene to early Oligocene time, (ca. 35–25 Ma), and finally the southeastern Zagros by latest Oligocene to middle Miocene time (ca. 25–15 Ma). The diachroneity of Arabia collision led to widespread upper-plate (Eurasian) contraction and a similarly time-transgressive magmatic lull that lagged behind the onset of collision by ~2–12 Myr. By incorporating the entire Arabian microcontinent and regions to the north, this new tectonic reconstruction highlights the diachronous nature of Arabia–Eurasia collision that occurred first along the Bitlis suture zone in eastern Anatolia during late middle Eocene time and became progressively younger to the southeast along strike of the Zagros suture zone.

Paleoclimate and changing composition of the Paleogene-Neogene shallow Molluscan Assemblages of Patagonia

A detailed compilation and updated taxonomy of the shallow molluscan assemblages of the Paleogene-Neogene of Patagonia was performed. Together with the Sr-chronostratigraphic framework developed during the last decade, five assemblages of Danian, late middle Eocene, latest Oligocene-early Miocene, middle Miocene and late Miocene ages were recognized. Temporal variation in the composition of these assemblages reflects the successive transient hyperthermal events superimposed to the global cooling trend in the sea surface temperatures during Cenozoic times. Tropical or warmest subtropical temperatures in the region during the Danian and late middle Eocene times coincide respectively with the Dan-C2 and the Latest Danian Event, and the Middle Eocene Climatic Optimum events. Tropical taxa, represented by Tethyan and warm-Cosmopolitan genera constitute 27.6% and 31.3% of the fauna respectively. The declining participation of Paleogene warm-genera, comprising just 15.3% of the fauna, coupled with the massive appearance of the subtropical Neogene Southern elements, reveals a decrease in sea surface temperatures during the latest Oligocene-early Miocene interval until the establishment of warm-temperate conditions in the area. Although lower than during the Paleogene, temperatures should have been higher than today, in coincidence with the late Oligocene warming and the multiple warming events in the early Miocene. The middle Miocene records the first large occurrence of Caribbean taxa that will be continue being important components of the fauna during the late Miocene. The contribution of warm-taxa to the faunas rose from 15.3% in the early Miocene to 23% and 22.8% in the middle and late Miocene respectively. Both faunas point to the development of subtropical conditions in the area and match with the record of three new warming peaks. One hyperthermal event is recognized at the Middle Miocene Climatic Optimum, and the other two increments coincide with the transient peaks occurring at ~11 Ma and ~9 Ma. Paleogene-Neogene heritage in modern faunas of the region is rather poor and comprises 36% of fossil survivor genera. Taxa that managed to survive are mainly Cosmopolitan, Neogene Southern and Endemic genera that mostly had appeared in the early Miocene and adapted to Recent cool and temperate-cool conditions of the Southwesten Atlantic Ocean.

Depositional environment of Eocene oil shales of Wadi Shallala Formation from northern Jordan

Oil shale deposits of the mid-Eocene Wadi Shallala Formation in northern Jordan consist of organic-rich limestones and chalks. These organic-rich deposits are exposed at the surface near Wadi Ash Shajara, in a 12-m-thick outcrop. For this study, a total of 21 oil shale samples were analysed for bulk elemental geochemistry, inorganic geochemistry, organic geochemistry and microfacies analysis. Three microfacies types were recognised: pelagic mudstone/wackestone, foraminiferal packstone and bioclastic packstone/wackestone. The observed cyclicity of these microfacies in the study area indicates fluctuations in depositional conditions in Neo-Tethys during the mid-Eocene. A shallow-water, calm, restricted marine environment with limited water circulation and low energy currents evolved into a deeper-water environment with open circulation at or just below the wave base. Wadi Shallala Formation in Wadi Ash Shajara composes mainly of chalk (CaCO3 = ~92 wt%) with a TOC of up to 5 wt % and comprises abundant calcareous nannofossils, foraminifera and ostracods as well as non-clastic components like calcitic fragments. The sulphur content of the analysed samples is significant (1.24 wt %) and is associated with the organic matter. Redox-sensitive elements (Fe, Ni, Zn, S and Zr) are enriched in the oil shale samples, indicating an anoxic depositional environment fluctuating between euxinic and sub-euxinic. These fluctuations in depositional conditions of the basin are a result of many factors such as climate, and tectonisms affected deposition of oil shales during Middle Eocene time.

Improved deep learning (inception) CNN for detecting small tectonic plates of broken Anatolian, Turkey

he Anatolian was at one time a single plate that is currently being turned into many small plates. The earliest separation stage occurred in the southeastern Anatolian from the Palaeocene to middle Eocene times. This study for the first time confirmed that the Anatolian plate was broken into a group of small tectonic plates with an area less than 1000 km2. We have called them nanoplates. We have detected formation of (9) nano plates in the East Anatolian region with (6) nanoplates in the West Anatolian region and single nanoplate in the central Anatolian region. The key geological feature that we targeted here to find these nano plate boundaries is the fault network. A network of deep fractures along the nano plates boundaries. This paper determined these boundaries by integrating and analysing huge remote sensing geophysical data. This paper ued for the first time the weights of filters in inception convolutional neural network (CNN) in Anaconda python Tensor Flow and Keras platform. Also used latest special scientific programming libraries of Python language like SciPy, Arcpy, NumPy and Pandas for data preparation. In addition, this study used ArcGis10.8 from ESRI foundation for GIS analysis beside PCI GEOMATICA 2020 for image analysis.

Geological structure and tectonic evolution of the Ukrainian sector of the Black Sea

The entire Ukrainian sector of the Black Sea, which occupies its northernmost part, was studied with the interpretation of the post-1990 seismic reflection data along seismic lines having a total length of some 30 000 km. In the northern Black Sea relatively low extension of the continental crust occurred in Albian-Cenomanian times and did not cause formation of deep (sub)-oceanic basins. Rift faults formed three major rift basins. One of the ENE-WSW oriented rift basins occupied areas of the present-day Karkinit Through, Krylov-Zmiiny Uplift, Gubkin Ridge and Sulina Depression within the Odessa Shelf. Another ENE-WSW oriented basin included areas of the present-day Tetyaev High, Sorokin Trough, Crimea Mountains and Marine Continuation of the Crimean Folds. The NW-SE oriented major rift basin occupied areas of the present-day Andrusov Ridge, Eastern Black Sea Basin, Shatskiy High and Euxinian Graben. Passive, thermal (post-rift) subsidence lasted in Turonian—Middle Eocene times and occurred in marine basins with a water depth that did not exceed a few hundred meters. A strong regional compression at the end of the Middle Eocene interrupted the post-rift (thermal) subsidence of rift basins, strongly deformed the sedimentary cover and formed a large NW-SE oriented landmass. This onshore terrain occupied the central and southern parts of the Odessa Shelf and the Crimean Peninsula, and deep-water area, including the Euxinian Graben, Marine Continuation of the Crimean Folds, Sorokin Trough, Tetyaev High, Andrusov Ridge, Shatskiy High and Eastern Black Sea Basin. Up to 5 km of sediments were eroded during the time of the existence of the emerged onshore terrain. Two subsequent S—N compressional events occurred at the end of the Late Miocene and invoked folding and thrusting of the sedimentary sequences in the originally ENE-WSW Cretaceous rift basins mainly. Anticlinal structures on the Odessa Shelf underwent additional growth and numerous new anticline folds were generated on the margins of the Western Black Sea Basin, including the Sorokin Trough and Marine Continuation of Crimean Folds. During both Late Miocene compressional events broad landmasses arose across the northern Black Sea region. These onshore terrains ran in a roughly E-W direction and occupied the present-day shallow shelves and northern part of the current deep water as well as almost the whole Crimea Peninsula. Like the Late Eocene landmass, the Late Miocene onshore terrains were evidently a source of sediments into marine basins that surrounded them. The first Late Miocene compression probably coincided in time with the Messinian Salinity Crisis and it was apparently accompanied by a sharp fall of the sea level. Prior to the second Late Miocene compressional event the sea level had risen sufficiently that a considerable part of the Odessa Shelf and other parts of the middle Pontian landmass were covered, at least periodically, by a shallow sea. The present-day deep-water part of the study area began to subside rapidly in the Pliocene. The mechanical response to this rapid subsidence appears to have reactivated normal faulting of the previously inverted south-dipping rift faults along the coast of the Crimean Mountains and in the eastern part of the Euxinian Graben during the Pleistocene and possibly Holocene. The very rapid subsidence and lack of sedimentary supply led to sub-oceanic water depth in the Western and Eastern Black Sea basins that had previously developed as relatively shallow seas.

Imaging the 2–D crust and upper mantle structure of the Iranian plateau resolved by potential field and seismic data

In this study, the crust and upper mantle density distribution across the Iranian plateau along a ~1500 km profile are investigated using an integrated modeling of potential field data (gravity, geoid and topography) and by assuming local isostatic equilibrium. Our profile is initiated in Arabian platform and running through the main geological structures of Iran including Zagros orogen, Sanandaj – Sirjan Zone (SSZ), Urumieh – Dokhtar Magmatic Arc (UDMA), Central Iran (CI) block, Tabas/Lut blocks, and East Iranian Range (EIR). In the second step, in order to verify the integrated model, the 1–D S–wave absolute velocities for the crust and upper mantle beneath 21 seismic stations which partially covered the density profile are obtained using the joint inversion of P–receiver function (PRF) and surface–wave dispersion data. Our results indicate a thick crust (~60 km) beneath the SSZ and UDMA which thinning toward the east and experienced its minimum value (~40 km) beneath the central Iran, as well as Tabas/Lut blocks. Moreover, a thick lithosphere (>150 km) is observed under the Zagros, SSZ and parts of the UDMA, whereas a thinner lithosphere (~120 km on average in velocity model) is presented under the most of our profile. Both density and velocity models indicate a lithospheric thinning toward the CI block which imply the slab breakoff or lithospheric delamination followed by the upwelling of the asthenosphere in the Neogene. The presence of a relative fast structure in the crust beneath the Tabas block which is coinciding with a shallow high velocity body in the uppermost mantle elucidates a signature of former oceanic crust, which disappeared after the collision of Lut and Afghan continental blocks and E-directed subduction of Neotethys under the Afghan microcontinent either in post-Albian or middle Eocene times.

Sensitivity of clumped isotope temperatures in fossil benthic and planktic foraminifera to diagenetic alteration

Applying the clumped isotope (Δ47) thermometer to foraminifer microfossils offers the potential to significantly improve paleoclimate reconstructions, owing to its insensitivity to the isotopic composition of seawater (unlike traditional oxygen isotope (δ18O) analyses). However, the extent to which primary Δ47 signatures of foraminiferal calcites can be altered during diagenesis is not well known. Here, we present Δ47 data as well as high-resolution (∼10 kyr) δ18O and δ13C middle Eocene time series, measured on benthic and planktic foraminifera from ODP/IODP Sites 1408, 1409, 1410, 1050, 1260 and 1263 in the Atlantic Ocean. The sites examined span various oceanographic regimes, including the western tropical to mid-latitude North Atlantic, and the eastern mid-latitude South Atlantic. Comparing data from contemporaneous foraminifera with different preservation states, we test the effects of diagenetic alteration on paleotemperature reconstructions for the deep and surface ocean. We find that overall, primary Δ47 signatures appear similarly sensitive to diagenetic overprinting as δ18O, with differences in sensitivity depending on pore fluid chemistry and the amount of secondary calcite. Where planktic foraminifera are significantly altered, sea surface temperatures derived from Δ47 and δ18O values are biased towards cool temperatures. In comparison, Δ47 and δ18O values of benthic and well preserved planktic foraminifera are less affected by diagenesis and thus likely to yield robust foraminiferal calcification temperatures. With independent estimates of diagenetic calcite fractions, secondary overprints could be corrected for, using end-member modeling and Δ47-based temperatures from benthic foraminifera.

The structure of the South-Central-Pyrenean fold and thrust belt as constrained by subsurface data

The interpretation of the available seismic lines of the South-Central-Pyrenean fold and thrust belt, conveniently tied with the exploration wells, define the main structural features of this realm of the Pyrenees. In particular, they define the geometry and areal extension of the autochthonous foreland underneath the sole thrust. The mapping ofseveral selected structural lines brings constraints for the structural interpretation of the South-Central Pyrenees, including the cut-off lines between selected stratigraphic horizons of the autochthonous foreland and the branch line between basement-involved thrust sheets and the sole thrust. The thrust salient which characterizes at surface the geometry of the South-Pyrenean fold and thrust belt contrasts with the linear trend of these structural lines at subsurface. This salient has been the result of a secondary progressive curvature developed since Middle Eocene times by thrust displacement gradients during verthrusting of the South-Pyrenean thrust sheets above a Paleogene autochthonous sequence. Displacement gradients resulted from the uneven distribution of weak salt layers, mostly the Triassic and the Upper Eocene ones. The minimum amount of South-directed displacement from early MiddleEocene times to Late Oligocene is 52km, which would be significantly higher if internal shortening by folding and cleavage/fracture development as well as hanging-wall erosion is added.

New Prespective Paleogeography of East Java Basin; Implicationrespond to Oil and Gas Eksploration at Kujung Formation Carbonate Reservoar

Paleogeography is one of critical points that always less considered by explorationist in the world. Almost all of the consideration is focused on trapping mechanism. Paleogeography is guidance in understanding both of physical and chemical of rock characteristic which will correlate with its depositional environment. Integration of various geological and geophysical data such as; tectonic, structural geology, stratigraphy, lithology, and biostratigraphy will lead us to a better understanding of rock characteristics. Six paleogeographic interpretations was made consist of; Early Tertiary (P5-56-55 ma), Middle Eocene (P14-41 ma), Late Oiligocene (P22-25.5 ma), Early Miocene (N7-16.5 ma), Middle Miocene (N9-14.5 ma), and Pleistocene (NN19-1.5 ma). That six paleogeographic interpretations are assumed represent the paleogeographic evolution of East Java Basin time after time. In Middle Eocene time, it would be more than hundred possibilities regarding the location where the formation deposited. This would be controlled by the existence of some local structural paleohighs and horsts which oriented NW-SE followed by their own sedimentary transportation path. With assumption that hydrocarbon generation was occurred in 15 Ma and the depth of maturation window lies on about 2,500 m depth. Therefore, the possibility of source rock maturation is high, due to almost of the clastics sediment of Ngimbang deposited into the series of grabens. The Kujung reef types simplified defines and categorize into; 1) Patch Reef 2) Berrier Reef 3) Pinnacle Reef Over Isolated Reef. Kujung Carbonates were deposited in Early Miocene when regional transgression occurred. The depositional environments were dominated by shallow marine littoral-sublittoral. Generally, the reservoir quality of this Kujung Carbonate shows fair to good quality, in range7-32% porosity, and 1-1400 mD permeability (internal SKK Migas data).

40Ar-39Ar geochronology and petrogenesis of postcollisional trachytic volcanism along the İzmir-Ankara-Erzincan Suture Zone (NE, Turkey)*

The obliteration of the Neo-Tethyan Ocean and collision of the microplates along the northern part of Turkey led to the development of the Izmir-Ankara-Erzincan suture zone (IAESZ). After the collision of Pontides with the Central-Anatolian Crystalline Complex (CACC) in the Paleocene, a new phase of extension and volcanism concomitantly developed along the northern (Almus; Pontides) and southern (Yildizeli; CACC) sides and along the IAESZ during the Middle Eocene time interval. The first products of the Middle Eocene volcanism in these areas are represented by calc-alkaline to alkaline (basic-intermediate) volcanic and volcanoclastic units together with late-stage trachytic dikes, plugs, and stocks. The mantle source area of both volcanic units displays a metasomatized character, which was dominantly fluxed by sediment-sourced melts. The partial melting of the metasomatized source area gave rise to first-stage basic-intermediate volcanism in the crustal levels. Simultaneously with the generation of the first-stage volcanism, basaltic trachyandesitic shallow-seated magma mushes were also developed. The reactivation of these shallow-seated mushes by late-stage extensional tectonics gave rise to the development of trachytic volcanism in both regions, which have a high-K to shoshonitic character. Almus trachytic lavas are phenocryst-poor and have differentiated Mg# numbers (avg. 26). On the other hand, Yildizeli trachytic lavas have a broad compositional range (benmoreite to latite); they are phenocryst-rich and show more basic character (Mg# avg. 40). Trachytic volcanism in both areas is largely controlled by fractional crystallization of similar basaltic trachyandesitic parental magma with minor assimilation of the upper crustal lithologies. 40Ar-39Ar ages from sanidine phenocrysts from both areas also confirm that trachytic volcanism in both regions developed nearly coevally in different tectonic blocks (~41?40 Ma). Generation of similar volcanism on the different tectonic blocks during the postcollisional stage was probably governed by a regional-scale delamination and/or lithospheric removal-related tectonomagmatic processes.

An overview on source rocks and the petroleum system of the central Upper Rhine Graben

The petroleum system of the Upper Rhine Graben (URG) comprises multiple reservoir rocks and four major oil families, which are represented by four distinct source rock intervals. Based on geochemical analyses of new oil samples and as a review of chemical parameter of former oil fields, numerous new oil–source rock correlations were obtained. The asymmetric graben resulted in complex migration pathways with several mixed oils as well as migration from source rocks into significantly older stratigraphic units. Oldest oils originated from Liassic black shales with the Posidonia Shale as main source rock (oil family C). Bituminous shales of the Arietenkalk-Fm. (Lias α) show also significant source rock potential representing the second major source rock interval of the Liassic sequence. Within the Tertiary sequence several source rock intervals occur. Early Tertiary coaly shales generated high wax oils that accumulated in several Tertiary as well as Mesozoic reservoirs (oil family B). The Rupelian Fish Shale acted as important source rock, especially in the northern URG (oil family D). Furthermore, early mature oils from the evaporitic-salinar Corbicula- and Lower Hydrobienschichten occur especially in the area of the Heidelberg-Mannheim-Graben (oil family A). An overview on potential source rocks in the URG is presented including the first detailed geochemical source rock characterization of Middle Eocene sediments (equivalents to the Bouxwiller-Fm.). At the base of this formation a partly very prominent sapropelic coal layer or coaly shale occurs. TOC values of 20–32 % (cuttings) and Hydrogen Index (HI) values up to 640–760 mg HC/g TOC indicate an extraordinary high source rock potential, but a highly variable lateral distribution in terms of thickness and source rock facies is also supposed. First bulk kinetic data of the sapropelic Middle Eocene coal and a coaly layer of the ‘Lymnaenmergel’ are presented and indicate oil-prone organic matter characterized by low activation energies. These sediments are considered as most important source rocks of numerous high wax oils (oil family B) in addition to the coaly source rocks from the (Lower) Pechelbronn-Schichten (Late Eocene). Migration pathways are significantly influenced by the early graben evolution. A major erosion period occurred during the latest Cretaceous. The uplift center was located in the northern URG area, resulting in SSE dipping Mesozoic strata in the central URG. During Middle Eocene times a second uplift center in the Eifel area resulted in SW-NE-directed shore lines in the central URG and contemporaneous south-southeastern depocenters during marine transgression from the south. This structural setting resulted in a major NNW-NW-directed and topography-driven migration pattern for expelled Liassic oil in the fractured Mesozoic subcrop below sealing Dogger α clays and basal Tertiary marls.

Post-Variscan basin evolution in the central Pyrenees: Insights from the Stephanian–Permian Anayet Basin

The Anayet Basin, in the central Pyrenees, records a Stephanian–Permian continental succession including three Permian volcanic episodes. The absolute chronology of these rocks has allowed us to better constrain the early post-Variscan evolution of the Pyrenees. The transtensional regime responsible for the formation of the pull-apart Anayet Basin began at least in Stephanian times, the age of the first post-Variscan deposits in the area, and lasted until Late Permian. During Middle Eocene times, the Alpine Orogeny inverted the Anayet Basin and led to the formation of south-vergent chevron folds and axial plane penetrative cleavage.

Revision of Oligocene Mediterranean meandroid corals in the scleractinian families Mussidae, Merulinidae and Lobophylliidae

Traditional morphology-based systematics indicates close evolutionary relationships between Caribbean and Indo-Pacific ‘faviid’ and ‘mussid’ reef corals. However, molecular phylogenies reveal three distinct family-level clades, which diverged by middle Eocene time: (1) Caribbean faviids + mussids; (2) Indo-Pacific faviids; and (3) Indo-Pacific mussids. During the early Cenozoic, members of these clades also occurred in a third geographical region, the Mediterranean, but became extinct in that region during the Miocene, as the Tethys broke up. We perform morphological phylogenetic analyses including Caribbean, Indo-Pacific and Mediterranean Oligocene and Recent taxa to reconstruct the pattern of divergence between the three regions, and examine how it was related to biogeography. First, fossil specimens were selected from museum collections, and a total of 13 species (three of which are new) were distinguished using nine morphological features. These 13 species were then added to a dataset with taxa consisting of 62 Recent plus one additional extinct species, and with 50 characters. In addition to traditional macromorphology, the characters include new micromorphological and microstructural features observed using electron microscopy and transverse thin sections. Phylogenetic analysis was performed on the dataset using parsimony. The results show that, contrary to traditional systematics, 11 of the 13 Mediterranean extinct coral species group more closely with Indo-Pacific taxa than they do with Caribbean taxa. Recent Caribbean taxa and Indo-Pacific ‘mussids’ form distinct clades; but Indo-Pacific ‘faviids’ form four poorly resolved subclades basal to the Caribbean clade. These results suggest that Mediterranean meandroid corals belong to a cosmopolitan pantropical fauna, from which modern Caribbean meandroid corals diverged as the Caribbean became isolated. Phylogenetic analyses including fossils have higher resolution than analyses including only modern corals. The systematics of the 13 extinct species are formally revised. Two new species – Variabilifavia ausuganensis sp. nov. and Echinophyllia sassellensis sp. nov. – and one new genus – Paraleptoria gen. nov. – are named, and one undescribed species is left in open nomenclature. Two previously synonymized genera are resurrected. http://zoobank.org/urn:lsid:zoobank.org:pub:A5731291-9792-464D-87CF-E1DED0C9057E

The fossil record and taphonomy of butterflies and moths (Insecta, Lepidoptera): implications for evolutionary diversity and divergence-time estimates.

BackgroundIt is conventionally accepted that the lepidopteran fossil record is significantly incomplete when compared to the fossil records of other, very diverse, extant insect orders. Such an assumption, however, has been based on cumulative diversity data rather than using alternative statistical approaches from actual specimen counts.ResultsWe reviewed documented specimens of the lepidopteran fossil record, currently consisting of 4,593 known specimens that are comprised of 4,262 body fossils and 331 trace fossils. The temporal distribution of the lepidopteran fossil record shows significant bias towards the late Paleocene to middle Eocene time interval. Lepidopteran fossils also record major shifts in preservational style and number of represented localities at the Mesozoic stage and Cenozoic epoch level of temporal resolution. Only 985 of the total known fossil specimens (21.4%) were assigned to 23 of the 40 extant lepidopteran superfamilies. Absolute numbers and proportions of preservation types for identified fossils varied significantly across superfamilies. The secular increase of lepidopteran family-level diversity through geologic time significantly deviates from the general pattern of other hyperdiverse, ordinal-level lineages.ConclusionOur statistical analyses of the lepidopteran fossil record show extreme biases in preservation type, age, and taxonomic composition. We highlight the scarcity of identified lepidopteran fossils and provide a correspondence between the latest lepidopteran divergence-time estimates and relevant fossil occurrences at the superfamily level. These findings provide caution in interpreting the lepidopteran fossil record through the modeling of evolutionary diversification and in determination of divergence time estimates.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0290-8) contains supplementary material, which is available to authorized users.

Additions to the Eocene Perissodactyla of the Margaret Formation, Eureka Sound Group, Ellesmere Island, Arctic Canada

We describe early Eocene (Wasatchian) occurrences of the isectolophid Homogalax, tapiroids Heptodon posticus, Heptodon cf. H. posticus, and Heptodon sp., as well as early middle Eocene (Bridgerian) fossils of the brontothere Palaeosyops from localities in the Margaret Formation of the Eureka Sound Group on Ellesmere Island, Nunavut, Arctic Canada. Their occurrence on Ellesmere Island considerably extends the geographic range of these taxa, previously known from mid-latitude localities in British Columbia (only Heptodon), the Western Interior of the United States, and Asia (Homogalax, Heptodon, and Palaeosyops). We also place the fossil localities near Bay Fiord on central Ellesmere Island into a refined lithostratigraphic framework based upon data from three measured stratigraphic sections. Our stratigraphic data confirm the presence of two, stratigraphically distinct fossil assemblages — a late Wasatchian-aged lower assemblage and a Bridgerian-aged upper assemblage that were previously hypothesized by others based on faunal differences — that are separated by a 478 m thick stratigraphic gap that appears to lack fossil vertebrates. From a paleoenvironmental perspective, occurrence of the tapiroid Heptodon in the Eocene Arctic corroborates an hypothesis put forward by others that tapiroids are proxies for densely forested habitats, although they were adapted to a range of temperatures including near (or at) freezing temperatures of Eocene Arctic winters. Further, Arctic occurrences of tapiroids and brontotheres imply that these typical mid-latitude ungulate mammals were adapted to Arctic environments, thereby increasing the probability of Trans-Beringian dispersal during early and middle Eocene time.

Paleogene rim gravel of Arizona: Age and significance of the Music Mountain Formation

The early Tertiary exotic rim gravel scattered across the Colorado Plateau in Arizona (USA) provides the only widespread evidence concerning the nature of the regional Paleogene drainage system that preceded the emergence of the modern Colorado River. The term “rim gravel” includes a wide range of Laramide (herein ca. 85–40 Ma) and younger reworked quartzite-dominated, arkosic sediments with diverse origins and ages that have been clarified only recently. The parent arkoses, with subordinate gravel lenses, contain volcanic clasts with ages ranging from Late Jurassic to early Eocene. The Laramide-age arkoses were shed off uplifted Precambrian terranes to the south and west; they are separated from their reworked derivatives and younger sediments by a disconformity that is best preserved in the structurally isolated paleocanyons of the Hualapai Plateau. Younger generations of reworked gravels continued to evolve during and following the widespread eruption of basalts of late Oligocene to Pleistocene age. Basaltic clasts in the reworked gravels attest to their much younger ages. Combined paleontologic, stratigraphic, paleomagnetic, K-Ar, U-Th/He, and zircon studies of the parent arkoses indicate that the tectonic framework corresponds to the Laramide orogeny, the concurrent regional erosion of the Colorado Plateau margin, and ensuing widespread deposition. The overall time frame coincides with the similar tectonic history recorded in the early Tertiary strata of southern Utah. Comparable but unrelated quartzite-dominated gravels, reworked southward from the Utah source rocks, are widespread on strath terraces north of the Colorado River. The Utah-derived gravels are products of the much younger Neogene incision of the modern Grand Canyon drainage system. The name Music Mountain Formation redefines the Laramide-age suite of the Arizona rim gravel parent sediments, best preserved on the Hualapai and Coconino Plateaus of northern Arizona, and distinguishes them from younger reworked gravels occurring both north and south of the Colorado River. A lacustrine mollusk assemblage collected from thin limestones intertonguing with Music Mountain arkose constrains the age of one Coconino Plateau exposure to early Eocene, whereas the association with the Laramide orogeny indicates that a Late Cretaceous to middle Eocene time frame comprises the broader geologic setting.

First record of eocene bony fishes and crocodyliforms from Canada's Western Arctic.

BackgroundDiscovery of Eocene non-marine vertebrates, including crocodylians, turtles, bony fishes, and mammals in Canada’s High Arctic was a critical paleontological contribution of the last century because it indicated that this region of the Arctic had been mild, temperate, and ice-free during the early – middle Eocene (∼53–50 Ma), despite being well above the Arctic Circle. To date, these discoveries have been restricted to Canada’s easternmost Arctic – Ellesmere and Axel Heiberg Islands (Nunavut). Although temporally correlative strata crop out over 1,000 km west, on Canada’s westernmost Arctic Island – Banks Island, Northwest Territories – they have been interpreted as predominantly marine. We document the first Eocene bony fish and crocodyliform fossils from Banks Island.Principal FindingsWe describe fossils of bony fishes, including lepisosteid (Atractosteus), esocid (pike), and amiid, and a crocodyliform, from lower – middle Eocene strata of the Cyclic Member, Eureka Sound Formation within Aulavik National Park (∼76°N. paleolat.). Palynology suggests the sediments are late early to middle Eocene in age, and likely spanned the Early Eocene Climatic Optimum (EECO).Conclusions/SignificanceThese fossils extend the geographic range of Eocene Arctic lepisosteids, esocids, amiids, and crocodyliforms west by approximately 40° of longitude or ∼1100 km. The low diversity bony fish fauna, at least at the family level, is essentially identical on Ellesmere and Banks Islands, suggesting a pan-High Arctic bony fish fauna of relatively basal groups around the margin of the Eocene Arctic Ocean. From a paleoclimatic perspective, presence of a crocodyliform, gar and amiid fishes on northern Banks provides further evidence that mild, year-round temperatures extended across the Canadian Arctic during early – middle Eocene time. Additionally, the Banks Island crocodyliform is consistent with the phylogenetic hypothesis of a Paleogene divergence time between the two extant alligatorid lineages Alligator mississippiensis and A. sinensis, and high-latitude dispersal across Beringia.