River Formation Research Articles

A well-preserved cranium from the Judith River Formation (Montana, USA) reveals the inner ear and neuroanatomy of a Campanian baenid turtle.

A cranium belonging to a baenid turtle was recently recovered from the lower half of the Judith River Formation, Montana. Badlands Dinosaur Museum (BDM) 004 is a well-preserved partial cranium that includes the posterior cranial vault, cranial base, and otic capsules. Based on diagnostic characters, the skull can be attributed to Plesiobaena antiqua, which has been previously reported from the Judith River Formation. It also shares with palatobaenines projecting posterior processes of the tubercula basioccipitale and a prominent condylus occipitalis with a deep central pit, demonstrating variation within the Pl. antiqua hypodigm. In a phylogenetic analysis, an operational taxonomic unit of BDM 004 was positioned within Baenodda in an unresolved polytomy with Pl. antiqua, Edowa zuniensis, Palatobaeninae, and Eubaeninae. Microcomputed tomographic (μCT) scans revealed morphology of the middle and inner ear and endocast that are largely unknown in baenids. Semicircular canals of BDM 004 are virtually identical to those of Eubaena cephalica and consistent in dimensions to those of other turtle taxa, including anterior and posterior semicircular canals that are robust and taller than the common crus and diverge from each other at an angle of approximately 90°. The digital endocast reveals a moderately flexed brain with rounded cerebral hemispheres and minimal separation between the metencephalon and myelencephalon. Its well-preserved columella auris (stapes) is gracile with a posterodorsally flared basis columella. It arcs across the middle ear and flattens near its terminus. This study adds to the understanding of baenid middle and inner ear and neuroanatomical morphology and expands the morphological understanding of Pl. antiqua.

Fossil Leaves and Fruits of Tetramelaceae (Curcurbitales) from the Eocene of the Rocky Mountain Region, USA, and Their Biogeographic Significance

Premise of research. Eocene sediments of Colorado, Utah, and Wyoming contain fossil leaves and infructescences that appear to represent Tetramelaceae (Cucurbitales). Today, this family consists of two genera (Tetrameles and Octomeles) of towering rain forest trees native to India, Southeast Asia, and Australia.Methodology. We examined the fruit, seed, and leaf morphology of extant Tetramelaceae as a basis for recognizing fossil representatives. Fossils were studied from localities in the Parachute Creek Member of the Green River Formation in Utah and Colorado and in the Bridger and Aycross Formations of western Wyoming. Extant and extinct material was studied by light microscopy and micro–computed tomography (micro-CT) scanning.Pivotal results. Infructescences of Parvaspicula lepidioidea (Cockerell) comb. nov. conform to Tetramelaceae in their spicate arrangement of helically arranged, capsular, ribbed fruits with inferior ovaries and parietal placentation. Each fruit typically has four styles and dehisces apically between the styles, reminiscent of extant Tetrameles, but they share an apical disk and the bulbous stigmas of extant Octomeles. Leaves of Punctaphyllum glandulosum (Brown) comb. nov. conform to Tetramelaceae in their long petioles, basal marginal and intramarginal veins, and regularly spaced circular laminar glands. These glands are small and cover the laminae or are larger and concentrated in a single file row along the lamina margin. Punctaphyllum glandulosum varies in its base shape, lobe number, and margin type, matching the variation seen in extant Octomeles leaves.Conclusions. The repeated co-occurrence of Parvaspicula and Punctaphyllum and the morphological similarities of both of these organs with extant Tetramelaceae lead us to infer that they represent parts of the same extinct plant. These records serve as the first documented leaf and infructescence fossils of Tetramelaceae and suggest that the family once lived in North America, indicating broader biogeographic distribution than previously recognized.

The earliest Pupipara (Diptera: Hippoboscoidea): A new genus and species from the lower Eocene of the Green River Formation

Eornithoica grimaldii gen. et sp. nov., the currently earliest Pupipara, is described from the lower Eocene of the Green River Formation. The previously oldest representative of this clade was from the Oligocene. The new fossil has some plesiomorphic character states, suggesting a ‘basal’ position in the clade. Its age, around 52 Ma, suggests that these epizooic ectoparasitic flies originated during the Paleocene or even the latest Cretaceous, prior to the first bats, if the latter. As is the case for several early diverging hippoboscids that feed on birds, E. grimaldii possibly victimized birds or terrestrial mammals. This study is a further example of the quantity of new information that can be obtained by the examination of fossil insects under UV light.

Simulating the source waters for the Wilkins Peak Member evaporite sequence with modern soda spring analogues

Chemical sediments of the lacustrine Wilkins Peak Member of the Eocene Green River Formation potentially preserve detailed paleoclimate information relating to the conditions of their formation and preservation within the lake basin during the Early Eocene Climatic Optimum. The Green River Formation comprises the world's largest sodium-carbonate evaporite deposit in the form of trona (Na2CO3⋅NaHCO3⋅2H2O) in the Bridger Basin and nahcolite (NaHCO3) in the neighboring Piceance Creek Basin. Modern analogues suggest that these minerals necessitate the existence of an alkaline source water. Detrital provenance geochronometers suggest that the most likely source for volcanic waters to the Greater Green River Basin is the Colorado Mineral Belt, connected to the basin via the Aspen paleoriver.Here, we test the hypothesis that magmatic waters from the Colorado Mineral Belt could have supplied the Greater Green River Basin with the alkalinity needed to precipitate sodium-carbonate evaporites that are preserved in the Wilkins Peak Member by numerically simulating the evaporation of modern soda spring waters from northwestern Colorado at various temperature and atmospheric pCO2 conditions. The resulting simulated evaporite sequence is then compared to the mineralogy and textures preserved within the Wilkins Peak Member. Simulated evaporation of Steamboat Springs and Mineral Spring waters produce a close match to core observations and mineralogy. These simulations provide constraints on the salinities at which various minerals precipitated in the Wilkins Peak Member as well as insights into the regional temperature (>15 °C for gaylussite and trona; >27° for pirssonite and trona) and pCO2 conditions (<1200 ppm for gaylussite and trona) during the Early Eocene Climatic Optimum.

The Amazon paleoenvironment resulted from geodynamic, climate, and sea-level interactions

The northern South American landscape evolved in response to complex interactions between geodynamic processes, climate, and sea-level oscillations, culminating in formation of the Amazon River. Although the history of this drainage basin was investigated in previous studies, the controlling factors on its depositional environment before Amazon River formation remain elusive. Based on existing sedimentologic and paleontologic observations and new numerical models, we show that Andean mountain building, evolving climate, and eustatic sea-level oscillations controlled the transition from intermittent marine to lacustrine environmental conditions in Amazonia before the onset of the transcontinental river. Our numerical simulations show that the incorporation of an evolving climate contributed to the shortening of the time interval between the end of marine influence in Western Amazonia and the onset of the transcontinental Amazon River during the late Miocene. Additionally, our numerical scenarios indicate that sea-level oscillations created intermittent marine incursions in central and western Amazonia only when negative dynamic topography induced by mantle convection was taken into account. After the establishment of the transcontinental river, the numerical scenarios produced no further marine incursions in central and western Amazonia, despite continued sea-level oscillation. We propose that this environmental evolution influenced regional biodiversity and the sedimentation history in northern South America, and explains the formation and disappearance of aquatic environments before the onset of the transcontinental Amazon River.

A new Eocene cockroach species from the Green River Formation of Colorado, U.S.A.

A new Eocene cockroach species from the Green River Formation of Colorado, U.S.A.

Carbon storage capacity of shale formations: Mineral control on CO[formula omitted] adsorption

When CO2 is injected into storage reservoirs, buoyancy drives flow upward towards overlying caprock layers that retard flow. Caprocks are commonly shale formations with extremely low pore connectivity, but they contain a large amount of nanopores (pore width < 200 nm). Nanopores with large surface area can potentially adsorb and store any CO2 molecules that manage to flow into the caprock. The heterogenous shale composition, with varying chemical and physical structures, controls both wetting and sorption properties. The goal of this study is to determine the extent to which mineral attributes affect CO2 accessible pore spaces, using low-pressure adsorption. We use pure clay samples and 55 shale samples that are from Bakken, Wolfcamp, Utica, Niobrara, and Green River formations in the US, and from Agardhfjellet and Rurikfjellet formations in Svalbard. We show that organic matter and clay groups are the primary drivers of CO2 adsorption. Organic matter has a large amount of micropores for storage and a natural affinity for CO2, while clay minerals store CO2 on the large specific surface area provided by the expandable clays (smectite-illite-mica), mostly in meso- to macropores. CO2 adsorption increases with thermal maturation of both organic matter and clay minerals. Inorganic minerals, such as carbonate, quartz, K-feldspar, plagioclase and pyrite, are non-sorbing minerals that have an inverse relation to CO2 adsorption. However, chemisorbed water in calcite mineral interlayers can dissolve CO2. Due to competing and complementing effects of mineral composition, correlations of CO2 storage capacity and lithology is best understood using multivariate analysis.

Prediction of Total Organic Carbon in Organic-Rich Shale Rocks Using Thermal Neutron Parameters.

Total organic carbon (TOC) content is one of the crucial parameters that determine the value of the source rock. The TOC content gives important indications about the source rocks and hydrocarbon volume. Various techniques have been utilized for TOC quantification, either by geochemical analysis of source rocks in laboratories or using well logs to develop mathematical correlations and advanced machine learning models. Laboratory methods require intense sampling intervals to have an accurate understanding of the reservoir, and depending on the thickness of the interested formation, it can be time-consuming and costly. Empirical correlations based on well logs (e.g., density, sonic, gamma ray, and resistivity) showed fast predictions and very reasonable accuracies. However, other important parameters such as thermal neutron logs have not been studied yet as a potential input for providing reliable TOC predictions. Also, different studies estimate the TOC based on the well-logging data for various formations; however, limited studies were reported to predict the TOC for the Horn River Formation. Therefore, the objective of this study is to estimate the TOC variations based on the thermal neutron logs using one of the largest source rocks in Canada: The Horn River Formation. More than 150 data sets were collected and used in this work. The parameters of the artificial neural network (ANN) model were fine-tuned in order to improve the model's prediction performance. Furthermore, an empirical correlation was developed utilizing the optimized ANN model to allow fast and direct application for the developed model. The developed correlation can predict the TOC with an average absolute error of 0.52 wt %. The proposed TOC model was able to outperform the previous models, and the coefficient of determination was increased from 0.28 to 0.73. Overall, the proposed TOC model can provide high accuracy for TOC ranges from 0.3 to 6.44 wt %. The developed model can provide a real-time quantification for the organic matter maturity, helping to allocate the zones of mature organic matter within the drilled formations.

Influence of lake-basin morphology on climate-sediment transfer functions: Early Eocene Wilkins Peak Member, Green River Formation, Wyoming

Lacustrine strata are often among the highest-resolution terrestrial paleoclimate archives available. The manner in which climate signals are registered into lacustrine deposits varies, however, as a function of complex sedimentologic and diagenetic processes. The retrieval of reliable records of climatic forcing therefore requires a means of evaluating the potential influence of changing sedimentary transfer functions. Here, we use high-resolution X-ray fluorescence core scanning of the Wilkins Peak Member of the Green River Formation to characterize the long-term evolution of transfer functions in an ancient lacustrine record. Our analysis identifies a shift in the frequency distribution of Milankovitch-band variance between the lower and middle Wilkins Peak Member across a range of temporally calibrated elemental intensity records. Spectral analysis of the lower Wilkins Peak Member shows strong short eccentricity, obliquity, precession, and sub-Milankovitch−scale variability, while the middle Wilkins Peak Member shows strong eccentricity variability and reduced power at higher frequencies. This transition coincides with a dramatic decline in the number and volume of evaporite beds. We attribute this shift to a change in the Wilkins Peak Member depositional transfer function caused by evolving basin morphology, which directly influenced the preservation of bedded evaporite as the paleolake developed from a deeper, meromictic lake to a shallower, holomictic lake. The loss of bedded evaporite, combined with secondary evaporite growth, results in reduced obliquity- and precession-band power and enhanced eccentricity-band power in the stratigraphic record. These results underscore the need for careful integration of basin and depositional system history with cyclostratigraphic interpretation of the dominant astronomical signals preserved in the stratigraphic archive.

Hybrid Recommender System Using Systolic Tree for Pattern Mining

A recommender system is an approach performed by e-commerce for increasing smooth users’ experience. Sequential pattern mining is a technique of data mining used to identify the co-occurrence relationships by taking into account the order of transactions. This work will present the implementation of sequence pattern mining for recommender systems within the domain of e-commerce. This work will execute the Systolic tree algorithm for mining the frequent patterns to yield feasible rules for the recommender system. The feature selection's objective is to pick a feature subset having the least feature similarity as well as highest relevancy with the target class. This will mitigate the feature vector's dimensionality by eliminating redundant, irrelevant, or noisy data. This work presents a new hybrid recommender system based on optimized feature selection and systolic tree. The features were extracted using Term Frequency-Inverse Document Frequency (TF-IDF), feature selection with the utilization of River Formation Dynamics (RFD), and the Particle Swarm Optimization (PSO) algorithm. The systolic tree is used for pattern mining, and based on this, the recommendations are given. The proposed methods were evaluated using the MovieLens dataset, and the experimental outcomes confirmed the efficiency of the techniques. It was observed that the RFD feature selection with systolic tree frequent pattern mining with collaborative filtering, the precision of 0.89 was achieved.

A new transitional ‘libelluloid’ family (Odonata, Cavilabiata) with Mesozoic affinities in the Eocene Green River Formation (Utah, USA)

A new transitional ‘libelluloid’ family (Odonata, Cavilabiata) with Mesozoic affinities in the Eocene Green River Formation (Utah, USA)

Hybrid Recommender System for Mental Illness Detection in Social Media Using Deep Learning Techniques.

Recommender systems are chiefly renowned for their applicability in e-commerce sites and social media. For system optimization, this work introduces a method of behaviour pattern mining to analyze the person's mental stability. With the utilization of the sequential pattern mining algorithm, efficient extraction of frequent patterns from the database is achieved. A candidate sub-sequence generation-and-test method is adopted in conventional sequential mining algorithms like the Generalized Sequential Pattern Algorithm (GSP). However, since this approach will yield a huge candidate set, it is not ideal when a large amount of data is involved from the social media analysis. Since the data is composed of numerous features, all of which may not have any relation with one another, the utilization of feature selection helps remove unrelated features from the data with minimal information loss. In this work, Frequent Pattern (FP) mining operations will employ the Systolic tree. The systolic tree-based reconfigurable architecture will offer various benefits such as high throughput as well as cost-effective performance. The database's frequently occurring item sets can be found by using the FP mining algorithms. Numerous research areas related to machine learning and data mining are fascinated by feature selection since it will enable the classifiers to be swift, more accurate, and cost-effective. Over the last ten years or so, there have been significant technological advancements in heuristic techniques. These techniques are beneficial because they improve the search procedure's efficiency, albeit at the potential sacrifice of completeness claims. A new recommender system for mental illness detection was based on features selected using River Formation Dynamics (RFD), Particle Swarm Optimization (PSO), and hybrid RFD-PSO algorithm is proposed in this paper. The experiments use the depressive patient datasets for evaluation, and the results demonstrate the improved performance of the proposed technique.

Revision of the two small damselflies Eopodagrion scudderi Cockerell, 1921 and Eopodagrion ‘Podagrion’ abortivum (Scudder, 1878) (Odonata, Zygoptera) from the lower Eocene of Green River Formation (USA)

Two early Eocene damselfly taxa Eopodagrion scudderi Cockerell, 1921 and Eopodagrion ‘Podagrion’ abortivum (Scudder, 1878) are redescribed and refigured. Their phylogenetic relationships are discussed. Although they could likely belong to the Coenagrionidae, their exact affinities remain uncertain because of the presence of homoplasies affecting crucial characters among the Zygoptera.

The second European representative of the epallagid genus Labandeiraia in the lowermost Eocene Oise amber (Odonata, Zygoptera)

Among the calopteran damselflies, the family Epallagidae was clearly dominating the diversity of the Holarctic Cenozoic (11 described species in eight extinct genera), while the Calopterygidae were extremely rare at the same time (six Cenozoic species in two extant and one fossil genera) (Fossilworks database at http://www.fossilworks.org/cgi-bin/bridge.pl?action=home, consulted 21/10/2022). They mainly belonged to the extinct subfamily Eodichrominae Cockerell, 1923, and their most diverse genus was the early Eocene genus Labandeiraia Petrulevičius et al., 2007, known from compression fossils from the lacustrine Green River Formation (USA) and the marine Fur Formation in Denmark (Petrulevičius et al., 2007; Bechly et al., 2020).

Biostratigraphy and taxonomy of polymerid trilobites of the Manuels River Formation (Drumian, middle Cambrian), Newfoundland, Canada

Biostratigraphie et taxonomie des trilobites polymères de la formation de Manuels River (Drumien, Cambrien moyen), Terre-Neuve, Canada. La formation cambrienne moyenne de Manuels River est renommée pour sa faune de trilobites bien préservés. Nous présentons ici un assemblage nouvellement collecté de 1184 spécimens provenant de la localité type de Conception Bay South, Terre-Neuve, Canada. L'assemblage faunique comprend des informations détaillées sur les aires de répartition précises de chaque espèce. Ainsi, les zones de polymérides Paradoxides davidis et Paradoxides hicksi précédemment établies pour la région et les zones d'agnostides Tomagnostus fissus, Hypagnostus parvifrons, Ptychagnostus atavus et Ptychagnostus punctuosus, reconnues mondialement, sont maintenant précisément corrélées. La faune de polymères est comparable à celle d'autres régions d'Avalonia, de Baltica et partiellement du Gondwana. Notre analyse de l'assemblage faunique démontre qu'il est nécessaire de procéder à des révisions complètes des faunes de trilobites du Cambrien, y compris des taxons importants et bien connus comme Agraulos Hawle & Corda, 1847 et Paradoxides sensu lato. Sao hirsuta Barrande, 1846 a été précédemment documenté de la République Tchèque, de l'Espagne et de l'Allemagne, et est maintenant décrit pour la première fois de l'ouest d'Avalonia, tandis que Bailiella aequalis (Linnarsson, 1882) est déjà mentionné pour l'est de Terre-Neuve et est maintenant illustré pour la première fois. Les spécimens présentés ici ont été assignés aux ordres Ptychopariida, Redlichiida et Corynexochida et comprennent Agraulos ceticephalus (Barrande, 1846); Jincella? applanata (Hicks dans Hicks & Salter, 1869); Sao hirsuta Barrande, 1846; Bailiella aequalis (Linnarsson, 1882); Bailiella tenuicinta (Linnarsson, 1879); Meneviella venulosa (Hicks, 1872); Paradoxides davidis Salter, 1863; Plutonides hicksii (Salter,1866b); Clarella venusta (Billings, 1872); et Acontheus inarmatus Hutchinson, 1962.

A transitional species of Daspletosaurus Russell, 1970 from the Judith River Formation of eastern Montana.

Here we describe a new derived tyrannosaurine, Daspletosaurus wilsoni sp. nov., from Judithian strata (~76.5 Ma) intermediate in age between either of the previously described species of this genus. D. wilsoni displays a unique combination of ancestral and derived characteristics, including a cornual process of the lacrimal reduced in height relative to D. torosus and more basal tyrannosaurines, and a prefrontal with a long axis oriented more rostrally than in D. horneri and more derived tyrannosaurines. The description of this taxon provides insight into evolutionary mode in Tyrannosaurinae, lending strength to previous hypotheses of anagenesis within Daspletosaurus and increasing the resolution with which the evolution of this lineage can be reconstructed. Cladistic phylogenetic methods, stratigraphy, and qualitative analysis of the morphology of relevant taxa supports an anagenetic model for the origin of morphological novelty in this genus, highlighting the predominance of anagenetic evolution among contemporary dinosaur lineages.

The Paleoproterozoic Amer supergroup, Amer Fold Belt, Nunavut: stratigraphy, structure, correlations, and uranium metallogeny

The Amer Belt, hosting eleven informal formations of the Amer supergroup, is proposed as type area for four regional Paleoproterozoic sequences (Ps1–Ps4) in central Rae Craton, western Churchill Province. The ca. 1.9–1.865 Ga Snowbird orogeny (DP1) affected only Ps1–Ps3, whereas the ca. 1.87–1.81 Ga Hudsonian orogeny (DP2) affected all four. Sequence Ps1 Ayagaq Lake formation (&lt;2.3 Ga quartzite) initiates as schistose basal polymict orthoconglomerate unconformably overlying paleoweathered Neoarchean rocks. It transitions upward to lower Ps2 Resort Lake formation: gossanous, recessive, graphitic, pyritic-metalliferous phyllite (Re–Os age: 2126 ± 24 Ma). Ps2 conductors beneath the &lt;1.74 Ga Thelon formation have been drilled for unconformity-related uranium. Gradationally overlying siliceous dolomitic marble (Aluminium River formation) completes Ps2. The gradationally overlying lower Ps3 is either foliated calcareous tholeiitic basalt (Five Mile Lake formation) or grey phyllite (Three Lakes formation). These lateral equivalents host strong linear aeromagnetic markers. The Oora Lake formation foliated feldspathic calcareous sandstone gradationally overlies only the Three Lakes formation and underlies the upper Ps3 Showing Lake formation (interbedded phyllite and foliated calcareous arkose) whose two arkose members host laterally continuous disseminated uraninite + magnetite forming linear aeromagnetic markers. Pristine sequence Ps4 molasse, deposited and weakly deformed during DP2, comprises four formations of rhythmically interbedded, deep maroon to pink and green, feldspathic-lithic arenite, conglomerate, and mudstone that unconformably overlie and include clasts of DP1-deformed Ps1–Ps3 + Neoarchean basement. Ps4 detrital zircon (3.05–1.90 Ga) suggests local + distal provenance from south Rae and Slave Cratons, and Taltson–Thelon magmatic zone.

Imaging geomechanical properties of shales with infrared light

Hyperspectral images are data cubes that associate with each pixel an infrared (IR) reflectance spectrum. We hypothesize there is an implicit but discernable link between IR spectra of rocks and their mechanical response that can be learned by a machine learning (ML) algorithm. Our rationale is that IR spectra are sensitive to both rock composition and microstructure, two attributes that determine all hydro-thermo-mechanical properties of the rock. To test this hypothesis, we confine ourselves to shale specimens from the Green River formation, Utah, US, and aim to map acoustic velocity (Vp), acoustic attenuation coefficient (Ap), and X-ray attenuation coefficient (µ) from hyperspectral images acquired in the near-, shortwave-, and mid-IR. We propose an experimental workflow that generates large quantities of labelled data needed to train supervised ML algorithms. The trained algorithms are shown to accurately predict Vp, Ap, and µ directly from pixelwise IR spectra. In some cases, even a 1% random sampling of pixels is found sufficient for training. While both artificial and convolutional neural networks are probed, performances are similar, but better than linear regression. More important is ensuring the training data are representative of all lithologies to be targeted during prediction. This work implies the feasibility of extrapolating beyond a handful of point or line measurements from indentation, scratch testing, or field surveys to, respectively, cm-scale, m-scale, and potentially outcrop-scale rock faces.

Bulk and intramolecular carbon isotopic compositions of hydrocarbon gases from laboratory pyrolysis of oil shale of the Green River Formation: Implications for isotope structures of kerogens

Evaluation of intramolecular isotope distributions within organic compounds can provide important insights into gas formation processes and structural properties of gas-generating precursors, such as kerogen, bitumen, and oil, in natural reservoirs. Until recently, little has been known about the intramolecular isotope distributions within kerogens. In this study, we conducted systematic pyrolysis experiments of gas generation from a lacustrine oil shale of the Eocene Green River Formation under hydrous and anhydrous conditions (equivalent maturity or Easy %Ro: 0.76 to 3.27 at 310 to 480 °C for 3 to 50 days), measuring gas yields and compositions, as well as bulk and position-specific (PS) carbon isotope compositions. Gas generation processes were investigated in combination with kinetic Monte Carlo (kMC) simulations on a model Type I kerogen based on the chemical structures of oil shale of the Green River Formation. The comparison of our experimental results with kMC modelling indicates a series of β-scission, radical isomerization, and recombination reactions better represent the bulk isotope compositions of propane in the pyrolysis of the oil shale of the Green River Formation, but the ΔCc-t (= δ13Ccen – δ13Cter) values of propane at Easy %Ro > 1.5 can be better simulated by a simple combination of propyl groups with H radicals. Combining our previous works on marine shale of the Woodford Formation and Springfield Coal Member of the Carbondale Formation, PS carbon isotopes of propane indicate that in the lacustrine shales of the Green River Formation and the marine Woodford Shale, propane is sourced from CC bond cleavage, while CO bond cracking generates propane from coal at the initial kerogen cracking stage. At high maturity, the differences of late-stage propane production among the source rocks lead to the different bulk and PS C kinetic isotope effects of propane. Our findings suggest that the δ13C at the terminal position of propane precursors is likely up to 3.6‰ higher than at the central position in the Green River kerogen, while they are similar in the marine shale of Woodford Formation. In addition, the δ13C at the central position of propyl groups attached to heteroatom compounds is relatively more positive in the Springfield Coal Member of the Carbondale Formation than in Green River kerogen. A comparison of intramolecular C isotopes of propyl groups in the kerogens with their bulk δ13C, based on the PS δ13C of early-generated propane, contributes to our understanding of heterogeneities of isotopic structures of sedimentary organic matter.

Description of the first definitive Corythosaurus (Dinosauria, Hadrosauridae) specimens from the Judith River Formation in Montana, USA and their paleobiogeographical significance.

Despite the long history of research in the late Campanian Judith River Formation in northern Montana, most of the vertebrate fossils are represented by fragmentary remains, making precise taxonomic identifications difficult. Contrary to this, the partially contemporaneous Dinosaur Park Formation, Alberta, Canada is known for its tremendous fossil preservation, permitting rigorous studies of dinosaur diversity, evolution, and biostratigraphy. Hadrosaurids comprise one of the most abundant dinosaur clades in the Dinosaur Park Formation, but taxonomic affinities of hadrosaurid specimens remain poorly understood in the Judith River Formation. Corythosaurus is the most common hadrosaurid in the Dinosaur Park Formation and, to date, has been restricted to this formation. This study reports the first definitive Corythosaurus specimens from the Judith River Formation, which were discovered on two private ranches in northern Montana. The attribution of the most complete skeleton to Corythosaurus is indicated by: wide crest-snout angle, presence of premaxilla-nasal fontanelle, dorsoventrally expanded nasal, laterally exposed ophthalmic canal of the laterosphenoid, and tall neural spines. A second specimen preserves a large ilium that can be positively identified as Corythosaurus based on its associated skull, which is now in private hands. The specimens were recovered from the Coal Ridge Member of the Judith River Formation, which is approximately time equivalent to the Dinosaur Park Formation. Thus, the discovery of Corythosaurus in the Judith River Formation extends the biogeographic range of this genus and establishes a framework for future interformational biostratigraphic studies of Late Cretaceous dinosaur faunas in North America.