- Department of Paleobiology
NMNH Smithsonian Institution
10th Street and Constitution Ave. NW
Washington, DC 20560-0121
- Paleontology, Paleoclimate, Paleoenvironment, Mass extinctions, Palynology, Sedimentology, and 20 morePaleobotany, Permian, Cretaceous, Geology, Taphonomy, Biostratigraphy, Microscopy, Microvertebrates Paleontology, Hell Creek Formation, Cretaceous-Tertiary boundary, Late Cretaceous, Autunian, Focus stacking, Fort Union Formation, Depth of field reconstruction, Walchia, Evolutionary Biology, Evolution, Stratigraphy, and Micropaleontologyedit
- Antoine Bercovici is a paleobotanist and sedimentologist, currently postdoctoral fellow at the Paleobiology departmen... moreAntoine Bercovici is a paleobotanist and sedimentologist, currently postdoctoral fellow at the Paleobiology department of the National Museum of Natural History, Smithsonian Institution, Washington DC, USA.edit
The fossil record and recent molecular phylogenies support an extraordinary early-Cenozoic radiation of crown birds (Neornithes) after the Cretaceous- Paleogene (K-Pg) mass extinction. However, questions remain regarding the mechanisms... more
The fossil record and recent molecular phylogenies support an extraordinary early-Cenozoic radiation of crown birds (Neornithes) after the Cretaceous- Paleogene (K-Pg) mass extinction. However, questions remain regarding the mechanisms under- lying the survival of the deepest lineages within crown birds across the K-Pg boundary, particularly since this global catastrophe eliminated even the closest stem-group relatives of Neornithes. Here, ancestral state reconstructions of neornithine ecology reveal a strong bias toward taxa exhibiting predominantly non-arboreal lifestyles across the K-Pg, with multiple convergent transitions toward predominantly arboreal ecologies later in the Paleocene and Eocene. By contrast, ecomorphological inferences indicate predominantly arboreal lifestyles among enantiornithines, the most diverse and widespread Mesozoic avialans. Global paleobotanical and palynological data show that the K-Pg Chicxulub impact triggered widespread destruction of forests. We suggest that ecological filtering due to the temporary loss of significant plant cover across the K-Pg boundary selected against any flying dinosaurs (Avialae) committed to arboreal ecologies, resulting in a predominantly non-arboreal post-extinction neornithine avifauna composed of total-clade Palaeognathae, Galloanserae, and terrestrial total-clade Neoaves that rapidly diversified into the broad range of avian ecologies familiar today. The explanation proposed here provides a unifying hypothesis for the K-Pg-associated mass extinction of arboreal stem birds, as well as for the post-K-Pg radiation of arboreal crown birds. It also provides a baseline hypothesis to be further refined pending the discovery of additional neornithine fossils from the Latest Cretaceous and earliest Paleogene.
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This paper provides the first palynological data from four Upper Cretaceous localities from the Islands of Hvar and Scedro (southern Croatia), in the central part of the Adriatic Carbonate Platform. Studied material represents... more
This paper provides the first palynological data from four Upper Cretaceous localities from the Islands of Hvar and Scedro (southern Croatia), in the central part of the Adriatic Carbonate Platform. Studied material represents palynomorphs produced by coastal vegetation and transported to the shallow marine platform areas. Determined vegetation includes diverse hygrophilous, understory vegetation, range of evergreen needle trees attributable to Pinaceae and Podocarpaceae, as well as Araucarian conifers; ginkgo, cycads and/or bennettites. Flowering plants were likely represented by herbaceous forms. The palynoflora is generally indicative of a temperate, warm and humid climate. The occurrence of the Normapolles group with the presence of Plicapollis sp. and Pseudoculopollis sp. point to Turonian or probable TuronianeConiacian age, and represent the southernmost record of occurrence within the Normapolles palynological province. Dominance of angiosperms and low abundance of ferns suggests an early-Late Cretaceous age. These findings are supported by the micropaleontological analyses and previously determined age of the sauropod dinosaur footprints described on the Island of Hvar. Based on the paleobotanical and palynological data, the dinosaur diet probably included araucarian conifers, ginkgo and angiosperms, and ferns to a lesser extent.
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Stable isotopes of inorganic and organic carbon are commonly used in chemostratigraphy to correlate marine and terrestrial sedimentary sequences based on the assumption that the carbon isotopic signature of the exogenic carbon pool... more
Stable isotopes of inorganic and organic carbon are commonly used in chemostratigraphy to correlate marine and terrestrial sedimentary sequences based on the assumption that the carbon isotopic signature of the exogenic carbon pool dominates other sources of variability. Here, sediment samples from four Permian–Triassic boundary (PTB) sections of western Guizhou and eastern Yunnan provinces in South China, representing a terrestrial to marine transitional setting, were analyzed for δ 13 C of organic matter (δ 13 C org). These values were subsequently compared to published δ 13 C values of carbonates (δ 13 C carb) from the Global Stratotype Section and Point at Meishan and many other marine and terrestrial sections. A similar isotopic trend evident through all four sections is characterized by a negative shift of 2–3‰ at the top of the Xuanwei Formation, where we tentatively place the PTB. This negative shift also corresponds to a turnover in the vegetation and the occurrence of fungal spores, which is generally interpreted as a proliferation of decomposers and collapse of complex ecosystems during the end-Permian mass extinction event. Moreover, the absolute values of δ 13 C org are more extreme in the more distal (marine) deposits. The δ 13 C org values for the studied sediments are more variable compared to coeval δ 13 C carb records from marine records especially in the interval below the extinction horizon. We contend that the deposi-tional environment influenced the δ 13 C org values, but that the persisting geographic δ 13 C org pattern through the extinction event across the four independent sections is an indication that the atmospheric δ 13 C signal left an indelible imprint on the geologic record related to the profound ecosystem change during the end-Permian extinction event.
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The Permian–Triassic boundary interval in China comprises a significant record of faunal and floral changes during this important extinction event. Here we discuss the details of palynomorph preservation at the classical Western Guizhou... more
The Permian–Triassic boundary interval in China comprises a significant record of faunal and floral changes during this important extinction event. Here we discuss the details of palynomorph preservation at the classical Western Guizhou and Eastern Yunnan sections in an effort to expand the stratigraphy and paleontology from these earlier studies.
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Because of their small size and vast abundance in various types of sedimentary rocks, microfossils have found a multitude of applications in geology, especially regarding biostratigraphy, correlations and paleoenvironmental analysis.... more
Because of their small size and vast abundance in various types of sedimentary rocks, microfossils have found a multitude of applications in geology, especially regarding biostratigraphy, correlations and paleoenvironmental analysis. Organic-walled microfossils such as pollen, spores, and various organic debris derived from terrestrial plants, are especially useful when studying terrestrial deposits. This chapter presents the many different groups of organic-walled microfossils, collectively called palynomorphs, and the different methods palynologists use to study and extract them from sediments and rocks. We present a biostratigraphic application, the use of the pollen and spore record across the Cretaceous–Paleogene boundary, which has proven to be one of the most precise and reliable means for pinpointing this major transition within terrestrial deposits.
Research Interests: Geology, Paleontology, Stratigraphy, Paleobotany, Palynology, and 17 moreBiostratigraphy, Dinoflagellates, Chitinozoans, Mass extinctions, Palynofacies, Cretaceous, Pollen, Fungal Spores, Mass Extinction, Pollen analysis, Dinoflagellate cysts, Palynostratigraphy, Spores, Acritarch, Palynology of spore and pollen of Cretaceous, Organic Matter, and Palynologie
Although it represents but one geographic data point, the uppermost Maastrichtian Hell Creek Formation (HCF), exposed in the upper Great Plains of the North American craton, remains the most studied source for understanding the final ~1.5... more
Although it represents but one geographic data point, the uppermost Maastrichtian Hell Creek Formation (HCF), exposed in the upper Great Plains of the North American craton, remains the most studied source for understanding the final ~1.5 Myr of the Mesozoic Era in the terrestrial realm. Because it lies conformably below the earliest Paleocene Fort Union Formation, and together these two units preserve a rich fauna and flora, much of what is understood about the terrestrial Cretaceouse-Paleogene (K–Pg) boundary comes from this sequence. The HCF has been reconstructed as an expansive, fluvially drained, low coastal plain, built out, to the west, against the Laramide Orogen, and to the east, against the ultimate transgression (Cannonball) of the Western Interior Sea. Its meandering rivers and moist soils supported a multi-tiered angiosperm-dominated flora and rich insect and vertebrate faunas, including dinosaurs, crocodilians, squamates, turtles, and mammals. A dramatic facies change representing the initiation of catastrophic flooding is preserved, within available levels precision, at the K-Pg boundary. High-precision stratigraphy has proven difficult in this lenticular fluvial system. Where present, the boundary can be recognized by the bipartite boundary claystone; otherwise, palynostratigraphy has proven a powerful tool. Numerical dates have been successfully obtained from in tonsteins at the boundary and above, in the Fort Union; however, these have proven elusive below the boundary within the HCF. The KePg boundary in this region is dated at 66.043 Ma (Renne et al., 2013). Magnetostratigraphic studies have been carried out in the HCF; although all but one have lacked numerical dates, these have been used for correlations of widespread, disjunct exposures and for the estimation of sedimentation rates. The palynoflora is largely homogenous through the HCF; at the KePg boundary, it shows an abrupt ~30% extinction. This makes it a powerful tool for identification of the KePg boundary, although because the boundary is identified on absence of Cretaceous taxa rather than presence of earliest Paleocene taxa, several competing methods have been applied to identifying the KePg boundary using pollen. The macroflora, consisting largely of leaves, consists of three successive floras, showing increasing diversity through the HCF. The ultimate of these three floras undergoes an abrupt 57% extinction; taken as a whole, however, the macroflora undergoes a 78% extinction at the KePg boundary. The best data available for dinosaurs - including archaic Aves - show an abrupt extinction. By contrast, salamanders and other lissamphibians, as well as chelonians, cross the boundary virtually without perturbation. Squamates appear to have suffered significant extinctions at the KePg boundary, as did euselachians (elasmobranchs) and insects. Mammals suffered a 75% extinction; however, some of this figure cannot be shown to have occurred in less than the last 500 kyr of the Cretaceous, and thus has been potentially attributable to causes other than a bolide impact. Taken together, the survivorship patterns are concordant with the catastrophic inception of ubiquitous flooding characterizing the KePg boundary. While the key K–Pg boundary question in the HCF was once the rate of the biotic extinction, it has moved to the distinction between single-cause scenarios, with the Chicxulub bolide as agent of extinction, and multi-cause scenarios, uniting habitat partitioning, Deccan flood-basalt volcanism, climate change, competition, and bolide impact. Not every potential environmental perturbation need be a mechanism for the extinction: parsimony and the data continue to be concordant with a bolide impact as the single agent of the terrestrial K–Pg mass extinction.
Research Interests: Paleontology, Sedimentology, Stratigraphy, Climate Change, Paleobotany, and 15 morePaleoenvironment, Palynology, Biostratigraphy, Vertebrate Paleontology, Mammalian Paleontology, Dinosaur Paleontology, Mass extinctions, Sedimentary geology and stratigraphy, Dinosaurs, Cretaceous, Fossils, Paleogene, Palynostratigraphy, Maastrichtian, and Palynology of spore and pollen of Cretaceous
Well-preserved marine fossils in carbonate rocks permit detailed studies of the end-Permian extinction event in the marine realm. However, the rarity of fossils in terrestrial depositional environments makes it more challenging to attain... more
Well-preserved marine fossils in carbonate rocks permit detailed studies of the end-Permian extinction event in the marine realm. However, the rarity of fossils in terrestrial depositional environments makes it more challenging to attain a satisfactory degree of resolution to describe the biotic turnover on land. Here we present new sedimentological, paleontological and geochemical (X-ray fluorescence) analysis from the study of four terrestrial sections (Chahe, Zhejue, Mide and Jiucaichong) in Western Guizhou and Eastern Yunnan (Yangtze Platform, South China) to evaluate paleoenvironmental changes through the Permian–Triassic transition.
Our results show major differences in the depositional environments between the Permian Xuanwei and the Triassic Kayitou formations with a change from fluvial–lacustrine to coastal marine settings. This change is associated with a drastic modification of the preservation mode of the fossil plants, from large compressions to small comminuted debris. Plant fossils spanning the Permian–Triassic boundary show the existence of two distinct assemblages: In the Xuanwei Formation, a Late Permian (Changhsingian) assemblage with characteristic Cathaysian wetland plants (mainly Gigantopteris dictyophylloides, Gigantonoclea guizhouensis, G. nicotianaefolia, G. plumosa, G. hallei, Lobatannularia heinanensis, L. cathaysiana, L. multifolia, Annularia pingloensis, A. shirakii, Paracalamites stenocostatus, Cordaites sp.) is identified. In the lowermost Kayitou Formation, an Early Triassic (Induan) Annalepis–Peltaspermum assemblage is shown, associated with very rare, relictual gigantopterids. Palynological samples are poor, and low yield samples show assemblages almost exclusively represented by spores. A ∼1 m thick zone enriched in putative fungal spores was identified near the top of the Xuanwei Formation, including diverse multicellular forms, such as Reduviasporonites sp. This interval likely corresponds to the PTB “fungal spike” conventionally associated with land denudation and ecosystem collapse. While the floral turnover is evident, further studies based on plant diversity would be required in order to assess contribution linked to the end-Permian mass extinction versus local paleoenvironmental changes associated with the transition between the Xuanwei and Kayitou formations.
Our results show major differences in the depositional environments between the Permian Xuanwei and the Triassic Kayitou formations with a change from fluvial–lacustrine to coastal marine settings. This change is associated with a drastic modification of the preservation mode of the fossil plants, from large compressions to small comminuted debris. Plant fossils spanning the Permian–Triassic boundary show the existence of two distinct assemblages: In the Xuanwei Formation, a Late Permian (Changhsingian) assemblage with characteristic Cathaysian wetland plants (mainly Gigantopteris dictyophylloides, Gigantonoclea guizhouensis, G. nicotianaefolia, G. plumosa, G. hallei, Lobatannularia heinanensis, L. cathaysiana, L. multifolia, Annularia pingloensis, A. shirakii, Paracalamites stenocostatus, Cordaites sp.) is identified. In the lowermost Kayitou Formation, an Early Triassic (Induan) Annalepis–Peltaspermum assemblage is shown, associated with very rare, relictual gigantopterids. Palynological samples are poor, and low yield samples show assemblages almost exclusively represented by spores. A ∼1 m thick zone enriched in putative fungal spores was identified near the top of the Xuanwei Formation, including diverse multicellular forms, such as Reduviasporonites sp. This interval likely corresponds to the PTB “fungal spike” conventionally associated with land denudation and ecosystem collapse. While the floral turnover is evident, further studies based on plant diversity would be required in order to assess contribution linked to the end-Permian mass extinction versus local paleoenvironmental changes associated with the transition between the Xuanwei and Kayitou formations.
Research Interests: Geochemistry, Paleontology, Sedimentology, Stratigraphy, Paleobotany, and 12 morePaleoenvironment, Palynology, Biostratigraphy, Mass extinctions, Sedimentary geology and stratigraphy, Triassic, Permian, Fluvial Sedimentology, Permian-Triassic transition, End-Permian extinction, End Permian, and Permian Triassic Boundary
Environmental conditions, dispersal lags, and interactions among species are major factors structuring communities through time and across space. Ecologists have emphasized the importance of biotic interactions in determining local... more
Environmental conditions, dispersal lags, and interactions among species are major factors structuring communities through time and across space. Ecologists have emphasized the importance of biotic interactions in determining local patterns of species association. In contrast, abiotic limits, dispersal limitation, and historical factors have commonly been invoked to explain community structure patterns at larger spatiotemporal scales, such as the appearance of late Pleistocene no-analog communities or latitudinal gradients of species richness in both modern and fossil assemblages. Quantifying the relative influence of these processes on species co-occurrence patterns is not straightforward. We provide a framework for assessing causes of species associations by combining a null-model analysis of co-occurrence with additional analyses of climatic differences and spatial pattern for pairs of pollen taxa that are significantly associated across geographic space.
We tested this framework with data on associations among 106 fossil pollen taxa and paleoclimate simulations from eastern North America across the late Quaternary. Th e number and proportion of significantly associated taxon pairs increased over time, but only 449 of 56 194 taxon pairs were significantly different from random. Within this significant subset of pollen taxa, biotic interactions were rarely the exclusive cause of associations. Instead, climatic or spatial differences among sites were most frequently associated with significant patterns of taxon association. Most taxon pairs that exhibited co-occurrence patterns indicative of biotic interactions at one time did not exhibit significant associations at other times. Evidence for environmental filtering and dispersal limitation was weakest for aggregated pairs between 16 and 11 kyr BP, suggesting enhanced importance of positive species interactions during this interval. Th e framework can thus be used to identify species associations that may reflect biotic interactions because these associations are not tied to environmental or spatial differences. Furthermore, temporally repeated analyses of spatial associations can reveal whether such associations persist through time.
We tested this framework with data on associations among 106 fossil pollen taxa and paleoclimate simulations from eastern North America across the late Quaternary. Th e number and proportion of significantly associated taxon pairs increased over time, but only 449 of 56 194 taxon pairs were significantly different from random. Within this significant subset of pollen taxa, biotic interactions were rarely the exclusive cause of associations. Instead, climatic or spatial differences among sites were most frequently associated with significant patterns of taxon association. Most taxon pairs that exhibited co-occurrence patterns indicative of biotic interactions at one time did not exhibit significant associations at other times. Evidence for environmental filtering and dispersal limitation was weakest for aggregated pairs between 16 and 11 kyr BP, suggesting enhanced importance of positive species interactions during this interval. Th e framework can thus be used to identify species associations that may reflect biotic interactions because these associations are not tied to environmental or spatial differences. Furthermore, temporally repeated analyses of spatial associations can reveal whether such associations persist through time.
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Changes in pollen and spore assemblages across the Cretaceous–Paleogene (K–Pg) boundary elucidate the vegetation response to a global environmental crisis triggered by an asteroid impact in Mexico 66 Ma. The Cretaceous–Paleogene boundary... more
Changes in pollen and spore assemblages across the Cretaceous–Paleogene (K–Pg) boundary elucidate the vegetation response to a global environmental crisis triggered by an asteroid impact in Mexico 66 Ma. The Cretaceous–Paleogene boundary clay, associated with the Chicxulub asteroid impact event, constitutes a unique, global marker bed enabling comparison of the world-wide palynological signal spanning the mass extinction event. The data from both hemispheres are consistent, revealing diverse latest Cretaceous assemblages of pollen and spores that were affected by a major diversity loss as a consequence of the K–Pg event. Here we combine new results with past studies to provide an integrated global perspective of the terrestrial vegetation record across the K–Pg boundary. We further apply the K–Pg event as a template to asses the causal mechanism behind other major events in Earths history. The end-Permian, end-Triassic, and the K–Pg mass-extinctions were responses to different causal processes that resulted in essentially similar succession of decline and recovery phases, although expressed at different temporal scales. The events share a characteristic pattern of a bloom of opportunistic “crisis” tax followed by a pulse in pioneer communities, and finally a recovery in diversity including evolution of new taxa.
Based on their similar extinction and recovery patterns and the fact that the Last and First Appearance Datums associated with the extinctions are separated in time, we recommend using the K–Pg event as a model and to use relative abundance data for the stratigraphic definition of mass-extinction events and the placement of associated chronostratigraphic boundaries.
Based on their similar extinction and recovery patterns and the fact that the Last and First Appearance Datums associated with the extinctions are separated in time, we recommend using the K–Pg event as a model and to use relative abundance data for the stratigraphic definition of mass-extinction events and the placement of associated chronostratigraphic boundaries.
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A palynological investigation of sedimentary rocks enclosing an exceptionally well-preserved fossil dinosaur (Hadrosauridae) discovered in the upper part of the Hell Creek Formation in south western North Dakota was conducted in order to... more
A palynological investigation of sedimentary rocks enclosing an exceptionally well-preserved fossil dinosaur (Hadrosauridae) discovered in the upper part of the Hell Creek Formation in south western North Dakota was conducted in order to document the immediate paleoenvironment of this dinosaur. The specimen, an Edmontosaurus annectens is remarkable in having exceptional three-dimensional preservation of soft tissue around the skeleton, indicating rapid burial. A well-preserved palynological assemblage dominated by fern and bryophyte spores, with lesser gymnosperm and angiosperm pollen was recovered. Sparse fresh-water algae and marine dinoflagellate cysts were also recorded. The palynofacies is dominated by wood fragments, including charcoal, with little amorphous organic matter. The presence of some typical pollen taxa of the Wodehouseia spinata Assemblage Zone including Striatellipollis striatellus, Tricolpites microreticulatus, Leptopecopites pocockii as well as a diverse suite of Aquilapollenites, is fully consistent with a Late Cretaceous (late Maastrichtian) age. The palynoflora indicates a local vegetation composed of a canopy of conifers dominated by Pinaceae and a minor sub-canopy of Taxodium and cycads, as well as an understory of hydrophilous ferns, mosses and herbaceous angiosperms, indicative of a warm and humid climate – an environment where this specific hadrosaur roamed over 66 million years ago.
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In South-East Asia, sedimentary basins displaying continental Permian and Triassic deposits have been poorly studied. Among these, the Luang Prabang Basin (North Laos) represents a potential key target to constrain the stratigraphic and... more
In South-East Asia, sedimentary basins displaying continental Permian and Triassic deposits have been poorly studied. Among these, the Luang Prabang Basin (North Laos) represents a potential key target to constrain the stratigraphic and structural evolutions of South-East Asia. A combined approach involving sedimentology, palaeontology, geochronology and structural analysis, was thus implemented to study the basin. It resulted in a new geological map, in defining new formations, and in proposing a complete revision of the Late Permian to Triassic stratigraphic succession as well as of the structural organization of the basin. Radiometric ages are used to discuss the synchronism of volcanic activity and sedimentation. The Luang Prabang Basin consists of an asymmetric NE-SW syncline with NE-SW thrusts, located at the contact between Late Permian and Late Triassic deposits. The potential stratigraphic gap at the Permian– Triassic boundary is therefore masked by deformation in the basin. The Late Triassic volcaniclastic continental deposits are representative of alluvial plain and fluvial environments. The basin was fed by several sources, varying from volcanic, carbonated to silicic (non-volcanic). U–Pb dating of euhedral zircon grains provided maximum sedimentation ages. The stratigraphic vertical succession of these ages, from ca. 225, ca. 220 to ca. 216 Ma, indicates that a long lasting volcanism was active during sedimentation and illustrates significant variations in sediment preservation rates in continental environments (from 100 m/Ma to 3 m/Ma). Anhedral inherited zircon grains gave older ages. A large number of them, at ca. 1870 Ma, imply the reworking of a Proterozoic basement and/or of sediments containing fragments of such a basement. In addition, the Late Triassic (Carnian to Norian) sediments yielded to a new dicynodont skull, attributed to the Kannemeyeriiform group family, from layers dated in between 225 and 221 Ma (Carnian).
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Los registros paleobotánicos en la cuenca de Cameros son escasos y se encuentran limitados a unas pocas localidades. Se presentan dos nuevos registros procedentes de depósitos del Barremiense en las cercanías de Salas de los Infantes y de... more
Los registros paleobotánicos en la cuenca de Cameros son escasos y se encuentran limitados a unas pocas localidades. Se presentan dos nuevos registros procedentes de depósitos del Barremiense en las cercanías de Salas de los Infantes y de Hortezuelos (Burgos). La nueva flora de Horcajuelos-1, cercano a Salas de los Infantes, se corresponde con los depósitos fluviales de la Formación Pinilla de los Moros.
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Resumen Los yacimientos de dinosaurio denominados" Vallazmorra-1" y" Vallazmorra-2" se encuentra al norte de los alrededores de La localidad de Santo Domingo de Silos entre los pueblos de Hinojar de Cervera y Hortezuelos cerca de la... more
Resumen Los yacimientos de dinosaurio denominados" Vallazmorra-1" y" Vallazmorra-2" se encuentra al norte de los alrededores de La localidad de Santo Domingo de Silos entre los pueblos de Hinojar de Cervera y Hortezuelos cerca de la carretera BU-911, en los terrenos comunales de Hortezuelos, en el sureste de la provincia de Burgos. Ambos yacimientos se encuentran al oeste de la Cuenca de Cameros en la parte más septentrional de la Cordillera Ibérica, en el noroeste de España.
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Palaeobotanical records of the Cameros basin are scarce and limited to a few localities. Two new records , mainly corresponding to Barremian deposits near Salas de los Infantes and Hortezuelos (Burgos) are presented. The new flora from... more
Palaeobotanical records of the Cameros basin are scarce and limited to a few localities. Two new records , mainly corresponding to Barremian deposits near Salas de los Infantes and Hortezuelos (Burgos) are presented. The new flora from Horcajuelos-1 near Salas corresponds to fluvial deposits of the Pinilla de los Moros Fm. A lower bed is dominated by Tempskya, while an upper layer includes abundant Onychiopsis cf. psilotoides, Regnellites, Ruffordia and Cladophlebis. The palynological records of the laterally equivalent lacustrine facies from the Hortezuelos Fm. are dominated by abundant and diverse fern spore assemblages (mainly Schizaeaceae) along with conifers (Classopollis and Araucariacites) and rare monosulcate angiosperm pollen.
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In Laos (Southeastern Asia), Late Paleozoic sediments were identified by early French explorations across Indochina during the late 19th century (Pavie missions), but little work was undertaken to characterize the sedimentological and... more
In Laos (Southeastern Asia), Late Paleozoic sediments were identified by early French explorations across Indochina during the late 19th century (Pavie missions), but little work was undertaken to characterize the sedimentological and stratigraphical context until now. From detailed sedimentological and paleontological studies, we propose an interpretation of the depositional environment and of the stratigraphic context of series located on the right bank of the Mekong River in the Luang Prabang Basin where three main formations were described. The silicoclastic Red Claystone Formation, attributed to alluvial plain environment, contains large fragments of unidentified dicynodonts. The Limestones and Sandstones Formation preserves a new macrofloral assemblage displaying affinities with Middle to Late Permian Cathaysian floras of South China. This assemblage occurs as an intercalation within marine calcareous sandstones that have yielded a marine fauna, including the ammonoid Pseudotirolites sp. which indicates a Late Permian (Changhsingian) age. The well-developed Purple Claystones Formation yielded an abundant and well preserved Late Permian fauna composed of a carnivorous amphibian and numerous Dicynodon cranial and postcranial elements. This formation shows a vertical evolution from braided river to alluvial plain with sheet-flood sand bed and bed-load rivers, with a constant supply of volcanic clasts. Results from the analysis of the paleontological associations in the Luang Prabang Basin suggest that a continental communication between Laurussia and the Indochina Block existed during the Permian, allowing for migration of the terrestrial Dicynodon fauna.
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The palynofloral changes around the Cretaceous-Paleogene (K-Pg) mass extinction event reveal the fine details of vegetation response to a global environmental crisis-in this case an asteroid impact in Mexico 65.5 million years ago. Due to... more
The palynofloral changes around the Cretaceous-Paleogene (K-Pg) mass extinction event reveal the fine details of vegetation response to a global environmental crisis-in this case an asteroid impact in Mexico 65.5 million years ago. Due to the extinction of several plant taxa at the K-Pg boundary, palynostratigraphy is a prime tool for localizing the Cretaceous-Paleogene boundary in non-marine successions. The Southern Hemisphere includes the tropical to sub-tropical Palmae Province, the high-latitude Nothofagidites/Proteacidites Province, and a transitional zone of mixed floristic composition. Maastrichtian key-species that go extinct at the Cretaceous-Paleogene boundary within the Palmae Province include Aquilapollenites magnus, Buttinia andreevi, Crassitricolporites brasiliensis, Proteacidites dehaani and Gabonisporis vigourouxii. In the Nothofagidites/Proteacidites Province, taxa such as Tricolporites lilliei, Triporopollenites sectilis, Quadraplanus brossus, Nothofagidites kaitangata, and Grapnelispora evansii have their last appearances at the boundary. It is obvious that more thorough analyses of the palynological signals across the K-Pg boundary in the Southern Hemisphere and China are required to elucidate the detailed patterns of vegetation response at different latitudes and at varying distances from the impact site in Yucatan, Mexico.
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Th is paper reports a new Early Cretaceous flora discovered recently near the village of Estercuel (Teruel province, northeastern Spain). Thee plant bearing beds belong to the uppermost part of the Early Cretaceous succession, at the top... more
Th is paper reports a new Early Cretaceous flora discovered recently near the village of Estercuel (Teruel province, northeastern Spain). Thee plant bearing beds belong to the uppermost part of the Early Cretaceous succession, at the top of the fluvial deposits of the Utrillas Formation. The site has yielded a diverse assemblage of plant compressions including lycopods and ferns, various gymnosperms as well as terrestrial and aquatic angiosperms. Leaves of aquatic lycopods (Isoetites sp.) constitute a minor component of the palaeobotanical assemblage. Filicales are not very common, with Dicksoniales (Onychiopsis sp.) and a few specimens of Cladophlebis type fronds. The gymnosperms are represented by fragmented remains of long parallel veined Desmiophyllum leaves as well as a great abundance of conifer axis corresponding to the form-genus Pagiophyllum and female cones. Terrestrial angiosperms include pinnately lobed leaves of the genus Myricompia, simple leaves with spatulate lamina and some petiolate leaves both corresponding to angiosperms of uncertain affinity. Aquatic angiosperms consist of Nelumbo-like floral receptacles (Nelumbonaceae, Proteales) and Aquatifolia cf. fluitans (Nympheales). The palynological assemblage is dominated by pollen of gymnosperms (mainly Taxodiaceaepollenites hiatus, Classopollis major and Araucariacites australis). It also includes many angiosperm grains (Afropollis jardinus, Clavatipollenites spp., Dichastopollenites spp., Liliacidites doylei, Monosulcites chaloneri, Penetetrapites mollis, Pennipollis spp., Phimopollenites augathellaensis, Retimonocolpites textus, Rousea spp., Senectotetradites varireticulatus, Stellatopollis barghoornii, Striatopollis spp., Transitoripollis sp. cf. T. similis, Tricolpites spp., Tricolporoidites sp.) and records the first occurrence of tricolporate forms in the uppermost part of the Utrillas Formation. Both macroflora and microflora assemblages present taxa similar to those of the uppermost Albian Shaftesbury Formation in northwestern Alberta in Canada, the uppermost Albian Denton Shale Member of Bokchito Formation in southern Oklahoma, the lower part of the Upper Albian Dakota Formation from the mid-west of North America, and Subzone II C of the Potomac Group, eastern United States. Both macro- and microflora assemblages display boreal influence with some similar taxa to those of the Upper Albian Kome Formation in western Greenland and some taxa as Afropollis jardinus and Stellatopollis barghoornii more frequently found in the tethyan and gondwanan realms. A gondwanan affinity is also indicated by the presence of Klitzschophyllites leaves.
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For a long time, debate has taken place regarding the trends and extinction rates associated with the Cretaceous-Paleogene (K-Pg) mass extinction event on land. While mainly focused on vertebrates and more particularly non-avian... more
For a long time, debate has taken place regarding the trends and extinction rates associated with the Cretaceous-Paleogene (K-Pg) mass extinction event on land. While mainly focused on vertebrates and more particularly non-avian dinosaurs, the dynamics of the plant cover remains nonetheless a major component of the biological response across the K-Pg interval and associated ecosystem destabilization. In this paper, we present a review of the late Cretaceous to Paleogene pollen and spore stratigraphy in the Northern Hemisphere Aquilapollenites paleophytogeographic province. In the United States of America, Late Cretaceous assemblages are marked by the appearance of a series of key taxa: the Santonian-Campanian transition is characterized by the appearance of Aquilapollenites and associated triprojectate genera, whereas the base of the Maastrichtian is marked by the appearance of the oculate genus Wodehouseia as well as Kurtzipites sp. The K-Pg extinction event remains easily identifiable in the palynological record with the disappearance of a series of angiospermous taxa, part of the Wodehouseia spinata Assemblage Zone, which are characterized by relatively large size and a complex wall structure. The recovery palynoflora in the Paleocene is represented by assemblages dominated by porate grains, with key species from the Momipites and Caryapollenites genera. As current data mostly cover the North American terrestrial record, more research efforts are needed in Chinese, European and Southern Hemisphere localities to provide for a better understanding of the global response of the terrestrial biosphere to the K-Pg impact event.
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This study documents the terrestrial palynological record at the John’s Nose section, a new Cretaceous–Paleogene (K–Pg) boundary site in North Dakota, USA. In addition to Mud Buttes and Pyramid Butte, John’s Nose represents the third K–Pg... more
This study documents the terrestrial palynological record at the John’s Nose section, a new Cretaceous–Paleogene (K–Pg) boundary site in North Dakota, USA. In addition to Mud Buttes and Pyramid Butte, John’s Nose represents the third K–Pg section in southwestern North Dakota that preserves direct evidence of the Chicxulub asteroid impact, allowing for direct comparison over the timing and trends of the palynological record in respect to this event. The palynological analysis of John’s Nose section reveals the presence of 68 pollen and spore taxa. Immediately above the boundary clay, a high abundance of fern spores of the genera Cyathidites and Laevigatosporites is recorded (with 59% of the assemblage being represented by Cyathidites). This very distinctive K–Pg ‘fern spike’ event is correlated with the devastation of land plants immediately following the asteroid impact and matches the composition generally reported from other sites in southwestern North Dakota. Palynostratigraphy demonstrates that the placement of the K–Pg boundary based upon the identification of the Last Appearance Datum (LAD) of typical Maastrichtian taxa (K-taxa) may be misleading. The presence of occasional K-taxa up to a few meters above the boundary clay at John’s Nose represents an important difference when compared to previous reports. In light of this observation, LADs should be used cautiously as the primary criteria to identify the boundary; some K-taxa may have a short-term presence in the earliest Paleogene, or be reworked. In the John’s Nose section, major changes and extinction in the palynological record occur at the geochemical K–Pg boundary, indicating that a catastrophic turnover took place over a short time.
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Modern debate regarding the extinction of non-avian dinosaurs was ignited by the publication of the Cretaceous–Tertiary (K–T) asteroid impact theory and has seen 30 years of dispute over the position of the stratigraphically youngest in... more
Modern debate regarding the extinction of non-avian dinosaurs was ignited by the publication of the Cretaceous–Tertiary (K–T) asteroid impact theory and has seen 30 years of dispute over the position of the stratigraphically youngest in situ dinosaur. A zone devoid of dinosaur fossils reported from the last 3 m of the Upper Cretaceous, coined the ‘3 m gap’, has helped drive controversy. Here, we report the discovery of the stratigraphically youngest in situ dinosaur specimen: a ceratopsian brow horn found in a poorly rooted, silty, mudstone floodplain deposit located no more than 13 cm below the palynologically defined boundary. The K–T boundary is identified using three criteria: (i) decrease in Cretaceous palynomorphs without subsequent recovery, (ii) the existence of a ‘fern spike’, and (iii) correlation to a nearby stratigraphic section where primary extraterrestrial impact markers are present (e.g. iridium anomaly, spherules, shocked quartz). The in situ specimen demonstrates that a gap devoid of non-avian dinosaur fossils does not exist and is inconsistent with the hypothesis that non-avian dinosaurs were extinct prior to the K–T boundary impact event.
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The main aim of this paper is to review Middle Permian through Middle Triassic continental successions in European. Secondly, areas of Middle–Late Permian sedimentation, the Permian–Triassic Boundary (PTB) and the onset of Triassic... more
The main aim of this paper is to review Middle Permian through Middle Triassic continental successions in European. Secondly, areas of Middle–Late Permian sedimentation, the Permian–Triassic Boundary (PTB) and the onset of Triassic sedimentation at the scale of the westernmost peri-Tethyan domain are defined in order to construct palaeogeographic maps of the area and to discuss the impact of tectonics, climate and sediment supply on the preservation of continental sediment.
At the scale of the western European peri-Tethyan basins, the Upper Permian is characterised by a general progradational pattern from playa-lake or floodplain to fluvial environments. In the northern Variscan Belt domain, areas of sedimentation were either isolated or connected to the large basin, which was occupied by the Zechstein Sea. In the southern Variscan Belt, during the Late Permian, either isolated endoreic basins occurred, with palaeocurrent directions indicating local sources, or basins underwent erosion and/or there was no deposition. These basins were not connected with the Tethys Ocean, which could be explained by a high border formed by Corsica–Sardinia palaeorelief and even parts of the Kabilia microplate. The palaeoflora and sedimentary environments suggest warm and semi-arid climatic conditions.
At the scale of the whole study area, an unconformity (more or less angular) is observed almost everywhere between deposits of the Upper Permian and Triassic, except in the central part of the Germanic Basin. The sedimentation gap is more developed in the southern area where, in some basins, Upper Permian sediment does not occur. The large sedimentary supply, erosion and/or lack of deposition during the Late Permian, as well as the variable palaeocurrent direction pattern between the Middle–Late Permian and the Early Triassic indicate a period of relief rejuvenation during the Late Permian. During the Induan, all the intra-belt basins were under erosion and sediment was only preserved in the extra-belt domains (the northern and extreme southern domains). In the northern domain (the central part of the Germanic Basin), sediment was preserved under the same climatic conditions as during the latest Permian, whereas in the extreme southern domain, it was probably preserved in the Tethys Ocean, implying a large amount of detrital components entering the marine waters. Mesozoic sedimentation began in the early Olenekian; the ephemeral fluvial systems indicate arid climatic conditions during this period. Three distinct areas of sedimentation occur: a northern and southern domain, separated by an intra-belt domain. The latter accumulated sediments during the Early–Middle Permian and experienced erosion and/or no-deposition conditions between the Middle–Late Permian and the beginning of Mesozoic sedimentation, dated as Anisian to Hettangian. At the top of the Lower Triassic, another tectonically induced, more or less angular unconformity is observed: the Hardegsen unconformity, which is dated as intra-Spathian and is especially found in the North European basins. This tectonic activity created new source areas and a new fluvial style, with marine influences at the distal part of the systems. During the Anisian and Ladinian, continental sedimentation was characterised by a retrogradational trend. In other words, the fluvial system evolved into fluvio-marine environments, attesting to a direct influence of the Tethys Ocean in the southern and northern domains. Both at the end of the Olenekian (Spathian) and during the Anisian, the presence of palaeosols, micro- and macrofloras indicate less arid conditions throughout this domain.
At the scale of the western European peri-Tethyan basins, the Upper Permian is characterised by a general progradational pattern from playa-lake or floodplain to fluvial environments. In the northern Variscan Belt domain, areas of sedimentation were either isolated or connected to the large basin, which was occupied by the Zechstein Sea. In the southern Variscan Belt, during the Late Permian, either isolated endoreic basins occurred, with palaeocurrent directions indicating local sources, or basins underwent erosion and/or there was no deposition. These basins were not connected with the Tethys Ocean, which could be explained by a high border formed by Corsica–Sardinia palaeorelief and even parts of the Kabilia microplate. The palaeoflora and sedimentary environments suggest warm and semi-arid climatic conditions.
At the scale of the whole study area, an unconformity (more or less angular) is observed almost everywhere between deposits of the Upper Permian and Triassic, except in the central part of the Germanic Basin. The sedimentation gap is more developed in the southern area where, in some basins, Upper Permian sediment does not occur. The large sedimentary supply, erosion and/or lack of deposition during the Late Permian, as well as the variable palaeocurrent direction pattern between the Middle–Late Permian and the Early Triassic indicate a period of relief rejuvenation during the Late Permian. During the Induan, all the intra-belt basins were under erosion and sediment was only preserved in the extra-belt domains (the northern and extreme southern domains). In the northern domain (the central part of the Germanic Basin), sediment was preserved under the same climatic conditions as during the latest Permian, whereas in the extreme southern domain, it was probably preserved in the Tethys Ocean, implying a large amount of detrital components entering the marine waters. Mesozoic sedimentation began in the early Olenekian; the ephemeral fluvial systems indicate arid climatic conditions during this period. Three distinct areas of sedimentation occur: a northern and southern domain, separated by an intra-belt domain. The latter accumulated sediments during the Early–Middle Permian and experienced erosion and/or no-deposition conditions between the Middle–Late Permian and the beginning of Mesozoic sedimentation, dated as Anisian to Hettangian. At the top of the Lower Triassic, another tectonically induced, more or less angular unconformity is observed: the Hardegsen unconformity, which is dated as intra-Spathian and is especially found in the North European basins. This tectonic activity created new source areas and a new fluvial style, with marine influences at the distal part of the systems. During the Anisian and Ladinian, continental sedimentation was characterised by a retrogradational trend. In other words, the fluvial system evolved into fluvio-marine environments, attesting to a direct influence of the Tethys Ocean in the southern and northern domains. Both at the end of the Olenekian (Spathian) and during the Anisian, the presence of palaeosols, micro- and macrofloras indicate less arid conditions throughout this domain.
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This paper focuses on the diversity and palaeontological significance of the Anisian floral record in the Triassic of the northeastern Iberian Peninsula. A summary of published information is followed by new records from macrofloral... more
This paper focuses on the diversity and palaeontological significance of the Anisian floral record in the Triassic of the northeastern Iberian Peninsula. A summary of published information is followed by new records from macrofloral localities at Rodanas (Aragonese Branch of the Iberian Range) and at Maya del Baztán (Basque–Cantabrian Domain, Pyrenees). Both of these new localities also yielded three Anisian microfloral assemblages. These records provide new evidence of Anisian (basal Middle Triassic) floras in Spain. They are found to be somewhat similar to the classical flora of the Grès à Voltzia Formation (Upper Buntsandstein) of the northern Vosges in north-eastern France, of whose age has been shown to be early Anisian.
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The Paleogene Order Taeniodonta Cope, 1876—peculiar heavy-bodied mammals, some with ever-growing cheek teeth—are grouped with the Late Cretaceous eutherian CimolestesMarsh, 1889, along with a host of other taxa in a superordinal group,... more
The Paleogene Order Taeniodonta Cope, 1876—peculiar heavy-bodied mammals, some with ever-growing cheek teeth—are grouped with the Late Cretaceous eutherian CimolestesMarsh, 1889, along with a host of other taxa in a superordinal group, the Cimolesta. Taeniodonts were thought to have arisen from Cimolestes indirectly, through Paleocene ProcerberusSloan and Van Valen, 1965. The recently described Paleocene AlveugenaEberle, 1999, until now known only from the upper dentition, has been put forth as a transitional form between cimolestids and taeniodonts on phylogenetic and biostratigraphic grounds. An older taeniodont, the Late Cretaceous SchowalteriaFox and Naylor, 2003, has since been described, complicating taeniodont origins. We describe here a lower jaw that we refer to Alveugena from the lower part of the Ludlow Member of the Fort Union Formation in North Dakota. The lower jaw comes from strata of early Early Paleocene age (Puercan 1 North American Land Mammal Age) 8.5 m above a Cretaceous-Paleogene boundary, identified using palynological criteria. A cladistic analysis is here presented using new data on Schowalteria and Alveugena, added to that of Cimolestes, Procerberus formicarumSloan and Van Valen, 1965, P. grandisMiddleton and Dewar, 2004, and Onychodectes. This analysis revealed Alveugena as the sister taxon of the taeniodonts but with a closer relationship to Cimolestes than Procerberus, suggesting that taeniodonts evolved from a Cimolestes-like ancestor. We discuss the age relations of early taeniodonts and related taxa and propose a scenario of ancestor-descendent relations that minimizes, but does not eliminate, implied stratigraphic gaps.
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“Vallazmorra-1” and “Vallazmorra-2” dinosaur bearing sites are located north of the vicinity of Santo Domingo de Silos between Hinojar de Cervera and Hortezuelos villages close to the road BU-911, in the communal terrains of Hortezuelos,... more
“Vallazmorra-1” and “Vallazmorra-2” dinosaur bearing sites are located north of the vicinity of Santo Domingo de Silos between Hinojar de Cervera and Hortezuelos villages close to the road BU-911, in the communal terrains of Hortezuelos, in the southeastern Burgos province. Both sites are located in the western Cameros Basin at the northernmost part of the Iberian Chain, in north-western Spain. The importance of this deposit is based on rare dinosaur remains described from the lowermost Cretaceous of the Iberian Peninsula. Beside these fossils, there is no other biostratigraphical control for this sequence. The studied palynological data come from two main levels located within a 24 m thick sedimentological sequence. The lower part corresponds to a succession of sandstones, mudstones and marls with bivalves, trunks, plant fragments and dinosaur remains. The upper part is mainly constituted by sandy limestones with bivalves, gastropods, ostracods and charophytes containing also fossil plants and dinosaur remains. Those deposits have been interpreted as lacustrine fluvial deposits in an endorheic basin. The palynological assemblage is characterized by a great abundance and diversity of sporomorphs. Fern spores and gymnosperm pollen grains dominate the palynological assemblage and, to a lesser extent, by freshwater algal spores. There is also present the stratigraphically important angiospermous-like pollen grains of Clavatipollenites type. The presence of this genus thorough all the sequence suggests a late Valanginian-Barremian age.
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Plant fossils are rarely preserved within the Upper Permian of western Europe as the majority of continental deposits consists of siliciclastic redbeds. Because organic matter such as plant debris and palynomorphs is destroyed by... more
Plant fossils are rarely preserved within the Upper Permian of western Europe as the majority of continental deposits consists of siliciclastic redbeds. Because organic matter such as plant debris and palynomorphs is destroyed by oxidizing conditions, these red sedimentary facies were often considered as “devoid of life”. This paper presents new palaeobotanical data from the Upper Permian strata of Minorca (Balearic Islands, Spain). In addition, a rich and diverse “Thuringian” palynoflora was recovered from the Permian sediments, and several megafloral taxa are recorded. Additionally, a detailed sedimentological analysis of the studied section is provided. The Permian succession shows a general evolution from a ponded floodplain environment to sand-sheet rivers flowing across a semi-arid alluvial plain. Additionally, new palaeobotanical elements, added to the study of palaeosols, allow reconstruction of Late Permian plant growth within the terrestrial environment, as well as a palaeoenvironment reconstruction of the preserved sedimentary interval. At the transition between ponds and alluvial plain deposits, root systems surprisingly similar to those known in extant mangroves are described for the first time within Permian deposits. As there are no other palaeobotanical remains preserved in association, the type of plant that inhabited this environment remains conjectural.
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Description of sedimentary sections and interpretations of sequence stratigraphic evolution of Permian–Triassic red beds of Minorca, allow a new proposal of palaeoenvironment reconstructions. The Permian sediments mainly correspond to... more
Description of sedimentary sections and interpretations of sequence stratigraphic evolution of Permian–Triassic red beds of Minorca, allow a new proposal of palaeoenvironment reconstructions. The Permian sediments mainly correspond to floodplain and pond deposits with sheetflood sand-bed rivers (environment DE 1), within a warm and semi-arid climate, and the preserved succession forms one complete stratigraphic cycle. The retrogradational phase of this cycle is represented by alluvial/colluvial deposits grading upwards to environment DE 1 and to extensive floodplain and pond deposits. The progradational phase is characterized by increasing fluvial influence (with palaeocurrent mainly oriented to the SW), palaeosol horizons, and preservation of a Late Permian palynoflora. The uppermost part of this succession is truncated by a major erosional surface. The sediments above this unconformity are characterized by braided river deposits (environment DE 2) with palaeocurrent oriented to the SSW within the more basal conglomeratic facies and to the WNW in overlying units. The absence of extensive floodplain deposits, a paucity of evidence for biogenic activity and palaeosols, together with the presence of ventifacts indicate an arid climatic setting for the succession. This environment evolved from braided rivers (palaeocurrents mainly oriented to the SE, environment DE 3) with in situ palaeosols and reworked breccias to fluvial–coastal and shallow marine deposits (environment DE 4) dated as upper Anisian to Ladinian. This succession characterizes a retrogradational trend. Although the transition between DE 2 and DE 3 was not observed, a switch in palaeocurrent directions may indicate a change in source area.
A comparison at a regional scale with other Peri-Tethyan basins allows the succession to be placed within a broader palaeoenvironmental and stratigraphic context during Late Permian to Middle Triassic. During the Late Permian, sedimentation occurred in alluvial, playa-lake or ponded environments where fluvial systems generally flowed southward, except in south-eastern France (oriented to the NE). Within these SW European basins, such as Minorca, the Late Permian succession shows a major retrogradational (evolution from fluvial or alluvial fan deposits to extensive lake, playa or floodplain deposits) and a progradational trend (fluvial or alluvial fan deposits). The Permian–Triassic transition corresponds to an unconformity overlain by braided river deposits with arid climate indicators (aeolian deposits: ventifacts and aeolian dune sedimentation). At the scale of western Europe, this arid episode is dated as Smithian and the Induan age sedimentation deposits seem to be preserved only in the central part of the Germanic Basin. As with all other Peri-Tethyan basins, environment DE 2 of Minorca (above the major erosional surface) is attributed to the Smithian. In the upper part of the studied succession, braided river deposits indicative of less arid climatic conditions are preserved. This succession contains the earliest Mesozoic palaeosols, dated as Anisian by palynomorphs, and expresses a vertical evolution from fluvial to open marine depositional environments attributed to the Muschelkalk transgression.
A comparison at a regional scale with other Peri-Tethyan basins allows the succession to be placed within a broader palaeoenvironmental and stratigraphic context during Late Permian to Middle Triassic. During the Late Permian, sedimentation occurred in alluvial, playa-lake or ponded environments where fluvial systems generally flowed southward, except in south-eastern France (oriented to the NE). Within these SW European basins, such as Minorca, the Late Permian succession shows a major retrogradational (evolution from fluvial or alluvial fan deposits to extensive lake, playa or floodplain deposits) and a progradational trend (fluvial or alluvial fan deposits). The Permian–Triassic transition corresponds to an unconformity overlain by braided river deposits with arid climate indicators (aeolian deposits: ventifacts and aeolian dune sedimentation). At the scale of western Europe, this arid episode is dated as Smithian and the Induan age sedimentation deposits seem to be preserved only in the central part of the Germanic Basin. As with all other Peri-Tethyan basins, environment DE 2 of Minorca (above the major erosional surface) is attributed to the Smithian. In the upper part of the studied succession, braided river deposits indicative of less arid climatic conditions are preserved. This succession contains the earliest Mesozoic palaeosols, dated as Anisian by palynomorphs, and expresses a vertical evolution from fluvial to open marine depositional environments attributed to the Muschelkalk transgression.
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Optical microscopy continues to be the preferred method for imaging in paleopalynology. While usefulness of other tools, such as the scanning electron microscope, is not questioned, the ease of use and timely results of optical microscopy... more
Optical microscopy continues to be the preferred method for imaging in paleopalynology. While usefulness of other tools, such as the scanning electron microscope, is not questioned, the ease of use and timely results of optical microscopy remains unsurpassed. However, obtaining good quality photomicrographs requires the use of the highest magnifying power objectives available, which are inevitably associated with very limited depth of field. To avoid the need for multiple photomicrographs in order to fully describe each palynomorph, a software solution for reconstructing depth of field is proposed. This solution allows for keeping the main advantages of high magnifying power objectives (better resolution and improved contrast) while suppressing their main weakness. In addition, photomicrographs published using depth of field reconstruction have a more natural appearance, similar to when directly viewed with the eye under the microscope. While this paper deals primarily with the usage of depth of field reconstruction for the enhancement of palynological photomicrograph, the technique can be applied similarly to many other paleontological and geological objects as well.
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The Cretaceous/Tertiary (K/T) boundary corresponds to one of the very few unique events in the geological record discovered to date, representing a single traceable timeline across the world. This timeline, coincident with the geochemical... more
The Cretaceous/Tertiary (K/T) boundary corresponds to one of the very few unique events in the geological record discovered to date, representing a single traceable timeline across the world. This timeline, coincident with the geochemical and mineralogical singularities caused by the impact of a large extraterrestrial body, is also coincident with the end-Cretaceous extinction event in North America. This precise timeline gives an ideal context for comparing the trends recorded by the different groups of the terrestrial fossil record during the K/T extinction event. However, in southwestern North Dakota, numerous studies conducted on excellent exposures of the K/T boundary showed that the geochemical and mineralogical criteria associated with the impact are rarely preserved. For that reason, palynology is preferred as a simple and efficient way for identifying the K/T boundary. In this context, a previously undescribed outcrop section from southwestern North Dakota was found to preserve an extensive record of the continental K/T boundary with miospores and plant megafossils, as well as microvertebrates and large vertebrate elements. Preliminary studies on the fossil associations recovered from this site showed an inconsistency between the Paleocene age given by the vertebrate and megafloral component and the Cretaceous age given by the palynological record. This issue is investigated in this paper, with a major emphasis on the description and analysis of the palynological record associated with sedimentological and paleoenvironmental data. Results shows that palynologically, the K/T boundary is placed more accurately using relative abundance variations of selected taxa.
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A stratigraphic section in the basal Fort Union Formation (Paleocene) in southwesten North Dakota was used to study in detail the post-crisis recovery as well as to reconstruct the local environment and its evolution using sedimentology,... more
A stratigraphic section in the basal Fort Union Formation (Paleocene) in southwesten North Dakota was used to study in detail the post-crisis recovery as well as to reconstruct the local environment and its evolution using sedimentology, palynology, fossil floras and vertebrate data. This report will focus on the flora from this site, corresponding to the first appearance data for Paleocene floral recovery, just above the Cretaceous-Tertiary (K/T) Boundary.
The studied flora consist of an assemblage of tightly stacked leaves preserved as carbon imprints (also called leaf mats), a preservation condition that makes the extraction of each individual leaf difficult to achieve directly on site. As a result, a new technique was tested, allowing the study of every leaf preserved, their sedimentological context as well as their position relative to each other. A large block of matrix including the leaf mat was jacketed in plaster and was taken to the museum laboratory for analysis under controlled conditions. Preparation consisted of removing sediments at a millimeter scale and recording of placement and orientation of all fossil materials for three-dimentional reconstructions. Using this technique, a description and census of more than 300 leaf specimens was possible within an area of only 0.5-square-meter.
The general sedimentological context indicates that the leaves were deposited in a near-stream environment associated with short-term flood events. Detailed information on depositional environment was gathered both by cutting a stratigraphic column from the Hell Creek/Fort Union formational contact up through the basal four meters of the Fort Union Formation and by studying sediments and leaf preservation mode in detail within the leaf mat. Significant changes in taxonomic abundances correlated with different lithologies was observed, and a leaf species new to the study area was reported. The new methodology proves to be an efficient way to recover additional taphonomic and paleonevironmental information from leaf mats necessary to understand the depositional dynamics of a fossiliferous leaf site, as well as to improve the record of taxonomic census.
In a biostratigraphical prospective, the specimens recovered represent a low-diversity Fort Union flora composed exclusively of dicots that do not exist in the Hell Creek Formation. Preliminary palynological analysis reveal a Cretaceous age for the entire stratigraphic section, implying that the studied leaf mat is part of the FU0 megafloral zone (as defined by the occurrence of a Fort Union flora with cretaceous palynomorphs). However, this Cretaceous age attribution for the entire section is questioned due to the occurrence of Paranymphaea crassifolia (part of the Paleocene FUI megafloral zone) within another leaf mat located 266 cm above the base of the coal representing the formational contact, and the occurrence of Paleocene PU1 mammals, reported from sediment within the leaf block interval.
The studied flora consist of an assemblage of tightly stacked leaves preserved as carbon imprints (also called leaf mats), a preservation condition that makes the extraction of each individual leaf difficult to achieve directly on site. As a result, a new technique was tested, allowing the study of every leaf preserved, their sedimentological context as well as their position relative to each other. A large block of matrix including the leaf mat was jacketed in plaster and was taken to the museum laboratory for analysis under controlled conditions. Preparation consisted of removing sediments at a millimeter scale and recording of placement and orientation of all fossil materials for three-dimentional reconstructions. Using this technique, a description and census of more than 300 leaf specimens was possible within an area of only 0.5-square-meter.
The general sedimentological context indicates that the leaves were deposited in a near-stream environment associated with short-term flood events. Detailed information on depositional environment was gathered both by cutting a stratigraphic column from the Hell Creek/Fort Union formational contact up through the basal four meters of the Fort Union Formation and by studying sediments and leaf preservation mode in detail within the leaf mat. Significant changes in taxonomic abundances correlated with different lithologies was observed, and a leaf species new to the study area was reported. The new methodology proves to be an efficient way to recover additional taphonomic and paleonevironmental information from leaf mats necessary to understand the depositional dynamics of a fossiliferous leaf site, as well as to improve the record of taxonomic census.
In a biostratigraphical prospective, the specimens recovered represent a low-diversity Fort Union flora composed exclusively of dicots that do not exist in the Hell Creek Formation. Preliminary palynological analysis reveal a Cretaceous age for the entire stratigraphic section, implying that the studied leaf mat is part of the FU0 megafloral zone (as defined by the occurrence of a Fort Union flora with cretaceous palynomorphs). However, this Cretaceous age attribution for the entire section is questioned due to the occurrence of Paranymphaea crassifolia (part of the Paleocene FUI megafloral zone) within another leaf mat located 266 cm above the base of the coal representing the formational contact, and the occurrence of Paleocene PU1 mammals, reported from sediment within the leaf block interval.
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This work presents the first analysis of the Martenet fossiliferous site in the Blanzy – Montceau-les-Mines basin, as well as a proposition for transport and fossilisation conditions based on the sole collection material. Description of... more
This work presents the first analysis of the Martenet fossiliferous site in the Blanzy – Montceau-les-Mines basin, as well as a proposition for transport and fossilisation conditions based on the sole collection material. Description of the megaflora revealed a classical « Autunian » flora of which 90% is dominated by Walchian conifers. The taphonomical and sedimentological prospective based on the collection specimens allowed to evaluate the transportation modalities of plant remains and to have an idea of the palaeoenvironment surrounding the Martenet fossiliferous site. Fragmentation is present on most plant remains, suggesting that a fair amount of transport has occured prior to final deposition. This implies the Martenet fossil site is the result of plant material accumulation sampled from a broad area. Comparisons done with previous palaeobotanical studies in other Permian basins show that even if all permian plant assemblages are conifer dominated, the dominant species is not the same. This suggests that within a similar sedimentological context, paleoecological and/or palaeogeographical preferences can be observed within « autunian » conifers