River Formation Research Articles

The “Judith River−Belly River problem” revisited (Montana-Alberta-Saskatchewan): New perspectives on the correlation of Campanian dinosaur-bearing strata based on a revised stratigraphic model updated with CA-ID-TIMS U-Pb geochronology

Terrestrial strata of the Judith River−Belly River wedge, widely exposed in the plains of north-central Montana, southern Alberta, and southwestern Saskatchewan, were pivotal in early stratigraphic investigations of the Western Interior of North America and are renowned to this day for their spectacular preservation of Late Cretaceous fossils, most notably dinosaurs. Correlation of the Judith River Formation in Montana with the Foremost, Oldman, and Dinosaur Park Formations (= Belly River Group) in Canada has been challenging for a variety of reasons, including lithostratigraphic complexities, legacy bentonite ages of limited comparability, and distinctly different stratigraphic models on opposite sides of the international border. An updated model calibrated with U-Pb zircon ages provides an improved framework for stratigraphic analysis. New geochronology indicates that the Oldman−Dinosaur Park discontinuity in Dinosaur Provincial Park correlates in age with the mid-Judith discontinuity in the Judith River Formation in Montana, which is interpreted as an expansion surface linked to a major pulse of accommodation and onset of the Bearpaw transgression at ca. 76.3 Ma. The regionally expressed shift in alluvial facies marking the mid-Judith discontinuity can be traced in well logs from Montana to southern Canada, where it loses distinction and transitions to a subsurface signature typical of the Oldman−Dinosaur Park discontinuity, which in turn can be traced north to Dinosaur Provincial Park and beyond. Across this expanse, both discontinuities parallel the Eagle/Milk River shoulder at approximately the same stratigraphic height, confirming their chronostratigraphic significance. These findings have clear implications for regional correlation and the evolution of alluvial depositional systems in a foreland basin setting, and they afford an opportunity to evaluate existing interpretations and advance understanding of the stratigraphy and paleontology of the Judith River−Belly River wedge. The term “Judith River−Belly River discontinuity” should be used henceforth to refer to the chronostratigraphically significant stratal discontinuity that subdivides the Judith River−Belly River wedge throughout the plains of north-central Montana, southern Alberta, and southwestern Saskatchewan.

Dolomite mineralogy as a proxy record for lake level fluctuations: a case study from the Eocene Uteland Butte Member of the Green River Formation, Uinta Basin, Utah, U.S.A.

ABSTRACT The Eocene Uteland Butte Member of the Green River Formation in the Uinta Basin is characterized by lacustrine carbonate depositional cycles consisting of calcareous shales, limestones, and dolomites that have been interpreted to reflect climatically driven lake level fluctuations. Previous work suggests that dolomitization of three distinct stratigraphic intervals in the Uteland Butte Member—the PZ-1, PZ-1′, and PZ-2—occurred during low lake levels and was driven by a combination of density-driven downward reflux and evaporative pumping of concentrated brines. The current study uses a novel high-resolution mineralogical dataset to evaluate these proposed dolomitization mechanisms. Mineralogical data from three drill cores show that the dolomitized intervals are characterized by variations in dolomite abundance (relative to calcite), dolomite stoichiometry, and cation ordering (015:110), all of which covary with depositional facies. In the near-basin margin core and near-basin center cores, the PZ-1 interval is characterized by a shallowing-upward facies trend that corresponds to an increase in stoichiometry, dolomite abundance, and cation ordering. In the PZ-1′ interval both the near-basin margin and near-basin center cores exhibit shallowing to deepening facies patterns up core that correspond to an increase and a subsequent decrease in dolomite stoichiometry. Similarly, dolomite abundance in this interval exhibits an increase then a decrease. The PZ-2 interval is also characterized by a shallowing to deepening facies pattern, which corresponds with an increase then a decrease in stoichiometry. Lateral trends between cores indicate that basinward facies have less dolomite, and that the dolomite is less stoichiometric compared to their more landward counterparts. Collectively, these observations argue against a simple model of top-down reflux dolomitization driven by evaporative pumping. Instead, the vertical and lateral relationships between depositional facies and mineralogical properties in the PZ-1′ and PZ-2 intervals suggest that dolomitization may have occurred syndepositionally, and that the observed mineralogical patterns were driven by differences in fluid chemistry associated with lake level fluctuations through time. These findings are broadly consistent with previous studies on peritidal marine carbonates showing that dolomite mineralogy can record temporal and spatial paleoenvironmental changes that can be utilized to evaluate dolomitization mechanisms.

Furcatoceratops elucidans, a new centrosaurine (Ornithischia: Ceratopsidae) from the upper Campanian Judith River Formation, Montana, USA

Although ceratopsian dinosaurs have been excavated from the Judith River Formation for more than a century, their diversity within the formation remains poorly understood due to the fragmentary nature of those specimens. Here, we describe Furcatoceratops elucidans gen. et sp. nov., a new centrosaurine ceratopsid, based on a nearly complete skeleton found in the upper Judith River Formation. F. elucidans is diagnosed by several unique characters such as anteriorly oriented supraorbital horncores with slight medial curvature and anteroventral process of the nasal that laterally covers the premaxilla. Cladistic analysis recovered F. elucidans as an early-diverging centrosaurine closely related to Nasutoceratops. The holotype is inferred to be a subadult individual based on its surface textures, histological features, size and suture obliteration patterns among bones, thus providing insights into the ontogeny of ceratopsid dinosaurs. The inferred ontogenetic sequence of F. elucidans suggests that the supracranial elements co-ossified earlier than narial elements, as in the chasmosaurine Triceratops but possibly unlike in derived centrosaurines. Because most bones such as cranial and vertebral elements are disarticulated and well preserved, the holotype will serve as a useful comparative specimen for future ceratopsian research.

Estimating formation and fracturing water production using simple diagnostic plots

The main goal of this paper is to evaluate the possibility of distinguishing between formation and fracturing water based on the water-flowback response without analyzing water chemical data. We analyze flowback production data of 100 multi-fractured horizontal oil wells completed in the Montney Formation and 89 oil and gas wells completed in the Duvernay and Horn River formations. We hypothesize that 1) the slope of water-flowback harmonic decline (HD) profiles (mHD) is proportional to the slope of rate-normalized pressure (RNP) plots (mRNP), and 2) both mRNP and mHD are inversely proportional to the amount of water influx from matrix into fractures. To verify our hypothesis, we 1) extend the previous HD and single-phase flowing material balance models by considering the water influx from matrix into fractures, 2) classify the studied wells based on observed trends, 3) construct RNP diagnostic plots of the studied wells, 4) investigate the relationship between mHD and mRNP, 5) analyze log data and estimate average initial water saturation (Swi) for the studied wells, and 6) investigate the relationship between of mHD and Swi. The results show that mHD for all the studied wells ranges from 0.00001 to 0.036 1/ m3 with a mean value of 0.0056 1/ m3. Wells with higher mHD have relatively higher mRNP values. In contrast, wells with very low mHD show no significant decline in water rate through the entire flowback process and relatively low or inconsistent mRNP values on the corresponding plots of RNP versus material balance time (MBT). We also observe a negative correlation between mHD and Swi obtained by analysis of wireline log data. This correlation and the positive correlation between mHD and mRNP indicate that as Swi increases, water influx from matrix to fracture increases, and thus, both mHD and mRNP decrease. Based on our modified models and the observed correlations, we develop a method to approximately differentiate between formation and fracturing water. The applications of our heuristic method on field data shows that 1) fracturing water production dominates the total water recovery for wells with higher mRNP, and 2) formation water production dominates the total water recovery for wells with lower mRNP.

Heritage Stone 9. Tyndall Stone, Canada’s First Global Heritage Stone Resource: Geology, Paleontology, Ichnology and Architecture

Tyndall Stone is a distinctively mottled and strikingly fossiliferous dolomitic limestone that has been widely used for over a century in Canada, especially in the Prairie Provinces. It comprises 6–8 m within the lower part of the 43 m thick Selkirk Member of the Red River Formation, of Late Ordovician (Katian) age. It has been quarried exclusively at Garson, Manitoba, 37 km northeast of Winnipeg, since about 1895, and for the past half-century extraction has been carried out solely by Gillis Quarries Ltd. The upper beds tend to be more buff-coloured than the grey lower beds, as a result of groundwater weathering. Tyndall Stone, mostly with a smooth or sawn finish, has been put to a wide variety of uses, including exterior and interior cladding with coursed and random ashlar, and window casements and doorways. Split face finish and random ashlar using varicoloured blocks split along stylolites have become popular for commercial and residential buildings, respectively. Tyndall Stone lends itself to carving as well, being used in columns, coats of arms and sculptures. Many prominent buildings have been constructed using Tyndall Stone, including the provincial legislative buildings of Saskatchewan and Manitoba, the interior of the Centre Block of the House of Commons in Ottawa, courthouses, land titles buildings, post offices and other public buildings, along with train stations, banks, churches, department stores, museums, office buildings and university buildings. These exhibit a variety of architectural styles, from Beaux Arts to Art Deco, Châteauesque to Brutalist. The Canadian Museum of History and the Canadian Museum for Human Rights are two notable Expressionist buildings. The lower Selkirk Member is massive and consists of bioturbated, bioclastic wackestone to packstone, rich in crinoid ossicles. It was deposited in a low-energy marine environment within the photic zone, on the present-day eastern side of the shallow Williston Basin, which was part of the vast equatorial epicontinental sea that covered much of Laurentia at the time. Scattered thin bioclastic grainstone lenses record episodic, higher energy events. Tyndall Stone is spectacularly fossiliferous, and slabs bearing fossils have become increasingly popular. The most common macrofossils are receptaculitids, followed by corals, stromatoporoid sponges, nautiloid cephalopods, and gastropods. The relative abundance of the macrofossils varies stratigraphically, suggesting that subtle environmental changes took place over time. The distinctive mottles—‘tapestry’ in the trade—have been regarded as dolomitized burrows assigned to Thalassinoides and long thought to have been networks of galleries likely made by arthropods. In detail, however, the bioclastic muddy sediment underwent a protracted history of bioturbation, and the large burrows were mostly horizontal back-filled features that were never empty. They can be assigned to Planolites. The matrix and the sediment filling them were overprinted by several generations of smaller tubular burrows mostly referrable to Palaeophycus due to their distinctive laminated wall linings. Dolomite replaced the interiors of the larger burrows as well as smaller burrows and surrounding matrix during burial, which is why the mottling is so variable in shape.

An intellectual optimization of k-anonymity model for efficient privacy preservation in cloud platform

Concerns of security as well as privacy are the chief obstacles which have prevented the public cloud’s extensive adoption in Intel IT as well as across the industry. Generally, IT organizations are quite reluctant to store sensitive as well as valuable data in infrastructures which are out of their control. The technique of anonymization is employed by enterprises to raise the security of the public cloud’s data whilst facilitating the data’s analysis as well as application. The procedure of data anonymization will modify how the data is either employed or published in such a way that it will prevent the key information’s identification. The privacy issues are addressed using k-anonymity. However, the issue of selecting the variables for anonymization and suppression of variables without the loss of knowledge is an optimization problem. To address the selection of variables for anonymization and suppression, metaheuristic algorithms are used. Diverse research groups have successfully utilized the River Formation Dynamics (RFD) metaheuristic to handle numerous problems of discrete combinatorial optimization. Even so, this metaheuristic has never been adapted for use in domains of continuous optimization. To mitigate the local minima problem, hybridization of the algorithms is proposed. In this work, a modified K-Anonymity technique’s proposal has been given by using the Modified Hill Climbing (MHC) optimization, the RFD-MHC optimization, the RFD-PSO optimization, the RFD-MHC suppression as well as the RFD-PSO suppression. Furthermore, proposal for a suppression technique has also been given in this work. Experiments demonstrated that the RFD-PSO optimization has higher classification accuracy in the range of 6.73% to 8.55% when compared to manual K-anonymization. The work has also given better trade off for security analysis and data utility effectiveness.

Anatomy of a fluvial paleo-fan: sedimentological and architectural trends of the Paleocene–Eocene Wasatch–Colton System (western Uinta Basin, Utah, U.S.A.)

ABSTRACT Recent developments in fluvial geomorphology and sedimentology suggest that fluvial fans (also known as distributive fluvial systems) could be responsible for the accumulation of great volumes of clastic successions in continental basins. A general depositional model based on sedimentological and architectural trends has been formulated for these fluvial systems, however, their recognition in the stratigraphic record often relies on partially preserved, discontinuous successions. This study provides a sedimentological and architectural characterization of Paleogene alluvial strata of the Wasatch and Colton formations in the southwestern Uinta Basin, central Utah (U.S.A.), following an ∼ 120-km-long outcrop belt which records deposition from an alluvial wedge that prograded to the north and northwest, from the basin margin to distal lake-dominated environments, preceding the onset of ancient Lake Uinta. Lateral and vertical distribution of facies associations are presented from a dataset of field observations (thirteen logged stratigraphic sections, for a total of ∼ 2400 m) and virtual outcrop models along the proximal-to-distal extent of the Wasatch–Colton alluvial system. Four sectors are defined (proximal, medial, distal, and terminal) to mark the longitudinal heterogeneity of alluvial stratigraphy. Noteworthy trends comprise a downstream decrease in the overall thickness of the alluvial stratigraphic column, a reduction in the relative volume, architectural complexity, and amalgamation of fluvial-channel bodies away from the apex, a weak downstream-fining trend in channel sandstones, and a down-system increase in preserved overbank and floodplain deposits accompanied by increasing volume and facies complexity of preserved lacustrine and palustrine facies associations. A proximal-to-distal change in fluvial-channel architecture is noted, with proximal sections characterized by vertically and laterally amalgamated sheet-like channel fills, transitioning to a lesser degree of amalgamation towards the medial sector, whereas distal and terminal sections are dominated by floodplain fines enveloping a subordinate volume of isolated, ribbon-shaped channel-sandstone bodies. The temporal development of the stratigraphic succession is observed in its entirety throughout the field area and, albeit localized, channel-scale erosion and potential depositional hiatuses punctuate the stratigraphy. Two major system-scale trends have been described in the Wasatch–Colton System (WCS). A first-order, long-term progradational trend, especially evident in proximal and medial sections, encompasses the large-scale vertical patterns in facies and architecture vertically through most of the stratigraphy of the WCS. In contrast, the uppermost part of the stratigraphic succession is characterized by a reverse, retrogradational trend, possibly associated with the early transgression of Lake Uinta's southern margin, marking the base of the overlying Green River Formation. Albeit expressed by different vertical succession of facies, proximal-to-distal processes, and stratal patterns documented along a longitudinal transect of the WCS mirror substantially identical vertical trends through the stratigraphy, which are interpreted as Waltherian superposition of distinct depositional domains during fluvial-fan progradation. Analyses of sandstone petrography and zircon geochronology suggest a unified source for the fluvial system, also supporting an interpretation as a distributive, rather than a tributive, fluvial system. This study enhances our understanding of the current depositional model for extensive fluvial-fan successions via a regional-scale stratigraphic analysis of a fluvial paleo-fan based on integrated characterization of both vertical and down-system patterns in facies distribution and fluvial architecture, providing key insights on useful criteria for recognizing fluvial-fan successions from the rock record.

Modeling the maturation history of the stacked petroleum systems of the Williston Basin, USA

A three-dimensional petroleum systems model was built to support U.S. Geological Survey assessments of undiscovered oil and gas resources in the Williston Basin of North Dakota, Montana, and South Dakota. Numerous Paleozoic source rocks have been proven or postulated in the basin, of which five were the focus of maturation and migration modeling: the Ordovician Icebox Formation, the kukersite beds of the Ordovician Red River Formation, the shales of the Devonian–Mississippian Bakken Formation, the Mississippian Madison Group, and the Pennsylvanian Tyler Formation. Calibration of the three-dimensional model to present-day temperature data indicates the existence of a north-south trend of high heat flow in western North Dakota, along with a region of high heat flow in eastern Montana. These high heat flow trends strongly control the maturity of all studied source intervals. A Bakken-specific hydrocarbon generation kinetic model was developed to match the calibrated time-temperature history of the basin to spatial trends in hydrogen index from programmed pyrolysis data. Generation of hydrocarbons occurred in the Cretaceous through Paleogene due to increased burial. Subsequent uplift and erosion in the Neogene cooled the basin, ending hydrocarbon generation for all source rocks. The cumulative volume of hydrocarbons generated by each of the source rocks was calculated and used to compare their relative robustness. The shales of the Bakken Formation are estimated to have generated approximately 460 billion barrels of oil equivalent (BBOE), while the Red River Formation generated approximately 130 BBOE, the Tyler Formation 94 BBOE, the Madison Group 44 BBOE, and the Icebox Formation 28 BBOE. Gross migration trends were analyzed with respect to historical oil and gas production in the basin and generally indicate segregation of petroleum systems throughout the stratigraphic column. However, most modeled scenarios indicated significant loss of Bakken oil to the Madison Group, suggesting that mixing of Madison and Bakken oils may be more prevalent than has recently been recognized in the U.S. portion of the Williston Basin and is particularly likely in fractured regions of the basin.

A new fossil katydid of the genus Arethaea Stål (Orthoptera: Tettigoniidae) with exceptionally preserved internal organs from the Eocene Green River Formation of Colorado

Orthoptera (grasshoppers, crickets, and katydids) are abundant and diverse in the lower–middle Eocene Green River Formation of the Piceance Basin in northwestern Colorado, though remain almost entirely unstudied. Here, we describe a new species of the katydid genus Arethaea Stål (Tettigoniidae: Phaneropterinae: Insarini) from the Parachute Creek Member at a locality near Meeker in Rio Blanco County. Arethaea solterae Heads, Thomas & Hedlund sp. nov. is the first fossil member of the genus and the first tettigoniid described from the Green River Formation. The holotype and only known specimen is remarkable for the exceptional preservation of internal organs including the anterior midgut (ventriculus) and what appear to be a testis, accessory glands, and possible fat body.

Walking in Social Groups: Role of Intra-Group Interactions

Interestingly, the interactions between members of a social group and across people of different social groups often happen through mutual understanding and reciprocate behaviour by means of gestures or eye contact. A controlled laboratory experiment is used to test the effect of interactions between members of a social group and across social groups on the walk dynamics of people. This study tries to discover the trade-off made by people between the need to communicate/interact between group members and the need to avoid collision with opposing pedestrians in a bidirectional flow. Thirty adults participated in a series of controlled experiments. The individuals and group characteristics were compared to study the effect of social groups. Spatial patterns/group formations, average walking speeds, and deviation from the desired direction of motion were assessed. The analysis shows that time to cross the platform is the least when triads adopt the river and inverted V group formations. In contrast, V and line-abreast group formations require slightly more time and are better suited to promote interactions between the group members. Irrespective of the initial formation adopted by participants, there is a higher tendency for the groups to shift to river formation or inverted V formations. This may be a result of the higher group speeds observed in the Inverted V and river formations, which accelerates their progress in the direction of motion. The understanding of walking dynamics of social groups from this study can enable better planning of pedestrian facilities and crowded events.

Optimization of Energy-Efficient Cluster Head Selection Algorithm for Internet of Things in Wireless Sensor Networks

The Internet of Things (IoT) now uses the Wireless Sensor Network (WSN) as a platform to sense and communicate data. The increase in the number of embedded and interconnected devices on the Internet has resulted in a need for software solutions to manage them proficiently in an elegant and scalable manner. Also, these devices can generate massive amounts of data, resulting in a classic Big Data problem that must be stored and processed. Large volumes of information have to be produced by using IoT applications, thus raising two major issues in big data analytics. To ensure an efficient form of mining of both spatial and temporal data, a sensed sample has to be collected. So for this work, a new strategy to remove redundancy has been proposed. This classifies all forms of collected data to be either relevant or irrelevant in choosing suitable information even before they are forwarded to the base station or the cluster head. A Low-Energy Adaptive Clustering Hierarchy (LEACH) is a cluster-based routing protocol that uses cluster formation. The LEACH chooses one head from the network sensor nodes, such as the Cluster Head (CH), to rotate the role to a new distributed energy load. The CHs were chosen randomly with the possibility of all CHs being concentrated in one locality. The primary idea behind such dynamic clustering was them resulted in more overheads due to changes in the CH and advertisements. Therefore, the LEACH was not suitable for large networks. Here, Particle Swarm Optimization (PSO) and River Formation Dynamics are used to optimize the CH selection (RFD). The results proved that the proposed method to have performed better compared to other methods.

Cimbicidae (Hymenoptera, 'Symphyta') in the Paleogene: revision, the new subfamily Cenocimbicinae, and new taxa from the Eocene Okanagan Highlands.

We erect the Cenocimbicinae, a new subfamily of Cimbicidae (Hymenoptera, Symphyta), restricted to the Selandian Menat Formation of France, the oldest occurrence of the family, and the Ypresian Okanagan Highlands of far-western North America. We describe new taxa from the Okanagan Highlands: Allenbycimbex morrisae gen. et sp. nov. and Leptostigma n. gen. with seven new species: L. alaemacula n. sp., L. brevilatum n. sp., L. fasciatum n. sp., L. longiclava n. sp., L. longipallidum n. sp., L. longitenebricum n. sp., and L. proxivena n. sp. We revise the Cimbicidae from the Ypresian Green River Formation and the Priabonian Florissant Formation, both in Colorado, USA. The oldest fossil of a modern cimbicid subfamily appears with a single pachylostictine specimen in the Green River Formation, and all Cimbicidae are in modern subfamilies after the Ypresian (we did not examine one larva known from Priabonian Baltic amber). Pseudocimbex clavatus Rohwer 1908 from the Florissant Formation is not a cimbicid; we treat it as Tenthredinoidea incertae sedis. We transfer Cimbex vetusculus Cockerell to Floricimbex n. gen.

Analysis of Langkolome River Flood, Wambona Village, Muna Regency (Case Study: Langkolome River, Wambona Village, Muna Regency)

Rivers are natural channels on the surface of the earth to drain water, apart from that, of course, interactions between discharges, other factors such as human activities along rivers give different characteristics of river formation. the largest portion comes from land clearing activities around the Langkolome river body located in Wambona Village, South Wakorumba District, Muna Regency. Based on the results of the calculation of the flood discharge of the Langkolome River in Wambona Village from 10 years of rainfall data, namely Q10 = 128,773 m3/sec, Q25 = 244,067 m3/sec. The capacity of the Langkolome river which has an impact on flooding Q = 158,063 m3/s. The maximum rainfall is greater than the capacity of the river, so this causes flooding in the Langkolome River, Wambona Village, Muna Regency

Multi-Mode Imaging of Ambient Background Noise for Karst Detection in the Limestone Area Based on Frequency-Bessel Transform

In response to the challenges of karst geophysical exploration in an environment with strong external interference, this paper proposes a new method, namely the frequency-Bessel transform method, for extracting multi-order dispersion curves of surface waves from background noise to characterize karst. The observation noise data of the Wuhan karst development area are used as an example, where the dolomitic limestone and limestone mixed with dolomite of the Jialing River Formation of the middle lower Triassic are widely developed in the observation area. The frequency-Bessel transform method involves performing a Bessel integral transformation on the cross-correlation coefficient of background noise in the frequency domain. Firstly, by synthesizing theoretical noise data and comparing it with the spatial autocorrelation method—which is currently the main method for extracting the fundamental dispersion curve of surface waves—it is verified that the frequency-Bessel transform method can extract the higher-mode dispersion curve. Then, by taking the actual measured single-point noise data as an example, the effect of applying the frequency-Bessel transform to the actual noise data is tested, and the inversion of the fine structure of the strata by the addition of higher-mode dispersion, the use of the damped least squares inversion method, and the joint inversion of fundamental and higher-mode dispersion curves are analyzed. The higher-mode dispersion curve of Rayleigh surface wave extracted by the frequency-Bessel transform is much clearer, and the 2D shear wave velocity structure profile obtained from inversion explains the karst development area, karst strip area, and thickness of the Quaternary overburden. The inferred results match with the actual borehole data. Multi-mode imaging of background noise based on the frequency-Bessel method can be applied to depict karst in complex backgrounds, and has significant potentiality in the field of ambient seismic noise tomography, providing a new idea and method for karst detection in near-surface engineering.

Environmental and microbial influence on chemistry and dolomite formation in an ancient lake, Green River Formation (Eocene), Uinta basin, Utah, U.S.A.

ABSTRACT Integrated stratigraphic, petrographic, and geochemical data allow interpretation of biogeochemical and mineralization processes in paleoenvironmental context of ancient lacustrine environments. These indicate that lake chemistry, microbial processes, and organic matter (OM) strongly influenced dolomite formation in near-surface environments throughout deposition of the Green River Formation (Eocene, Uinta basin, Utah). The lower Green River Formation consists of interbedded fluvio-deltaic siliciclastics, paleosols, carbonate mud, coated-grain carbonates, mollusk and ostracod limestones, and microbialites all landward of profundal OM-bearing illitic mudrocks. Calcite, dolomite, Fe-dolomite, and authigenic feldspars are common. Carbonate δ18O and δ13C are covariant, and positive excursions of carbonate δ13C (up to 6.9‰ VPDB) and organic-matter δ15N (up to 13.9‰ V-AIR) occur in profundal OM-bearing mudrocks. The upper Green River Formation consists mainly of laminated OM-lean and OM-rich dolomitic muds (i.e., “oil-shales”). Zoned dolomite crystals with Mg-calcite centers and Fe-dolomite rims are widespread in addition to authigenic feldspars and Na-carbonates. Carbonate δ13C-enrichment (up to 15.8‰ VPDB), and organic-matter δ15N-enrichment (up to 18.4‰ V-AIR) occur in these OM-rich dolomite muds. Organic-matter δ13C is relatively invariable (mean = –29.3‰ VPDB) and does not covary with carbonate δ13C. Trends in mineralogy, organic-matter abundance, and stable isotopes result from changing hydrologic systems, paleoclimate, lake chemistry and microbial processes coincident with the Early Eocene Climate Optimum. The lower Green River Formation paleo-lake was smaller in area and volume, heavily influenced by meteoric fluvial input, variably oxygenated, and ranged from neutral and fresh to alkaline and saline. Especially in littoral environments with abundant microbialites, dolomite formed through recrystallization of precursor carbonate involving both replacement of precursor carbonate and direct precipitation as cements and overgrowths. The upper Green River Formation paleo-lake was more expansive with widespread low-oxygen, nutrient-rich, and alkaline saline environments with increased planktic organic-matter productivity. Microbial decay of organic matter in low-oxygen environments produced alkaline lake waters through methanogenesis, possible denitrification, and bacterial sulfate reduction to a limited degree. This favored precipitation of widespread dolomite, as well as Na-carbonates, authigenic feldspars, and analcime from lake water and phreatic pore water. Extracellular polymeric substances (EPS) excreted by microbial communities provided favorable nucleation sites for Mg-carbonate, allowing kinetic barriers of low-temperature dolomite formation to be overcome. Cycling of pH due to turnover of organic matter and associated microbial processes potentially bolstered EPS generation and abiotic environmental conditions favorable to dolomite precipitation. It is likely that metastable precursor carbonate was recrystallized to ordered dolomite, but it is possible that direct precipitation occurred. Fe-dolomite overgrowths precipitated after dolomite where microbial Fe reduction occurred in stagnant, oxygen-depleted, alkaline pore waters.

The oldest known bat skeletons and their implications for Eocene chiropteran diversification.

The Fossil Lake deposits of the Green River Formation of Wyoming, a remarkable early Eocene Lagerstätte (51.98 ±0.35 Ma), have produced nearly 30 bat fossils over the last 50 years. However, diversity has thus far been limited to only two bat species. Here, we describe a new species of Icaronycteris based on two articulated skeletons discovered in the American Fossil Quarry northwest of Kemmerer, Wyoming. The relative stratigraphic position of these fossils indicates that they are the oldest bat skeletons recovered to date anywhere in the world. Phylogenetic analysis of Eocene fossil bats and living taxa places the new species within the family Icaronycteridae as sister to Icaronycteris index, and additionally indicates that the two Green River archaic bat families (Icaronycteridae and Onychonycteridae) form a clade distinct from known Old World lineages of archaic bats. Our analyses found no evidence that Icaronycteris? menui (France) nor I. sigei (India) belong to this clade; accordingly, we therefore remove them from Icaronycteridae. Taken in sum, our results indicate that Green River bats represent a separate chiropteran radiation of basal bats, and provide additional support for the hypothesis of a rapid radiation of bats on multiple continents during the early Eocene.

Fossil berries reveal global radiation of the nightshade family by the early Cenozoic.

Fossil discoveries can transform our understanding of plant diversification over time and space. Recently described fossils in many plant families have pushed their known records farther back in time, pointing to alternative scenarios for their origin and spread. Here, we describe two new Eocene fossil berries of the nightshade family (Solanaceae) from the Esmeraldas Formation in Colombia and the Green River Formation in Colorado (USA). The placement of the fossils was assessed using clustering and parsimony analyses based on 10 discrete and five continuous characters, which were also scored in 291 extant taxa. The Colombian fossil grouped with members of the tomatillo subtribe, and the Coloradan fossil aligned with the chili pepper tribe. Along with two previously reported early Eocene fossils from the tomatillo genus, these findings indicate that Solanaceae were distributed at least from southern South America to northwestern North America by the early Eocene. Together with two other recently discovered Eocene berries, these fossils demonstrate that the diverse berry clade and, in turn, the entire nightshade family, is much older and was much more widespread in the past than previously thought.

Astronomical and tectonic influences on climate and deposition revealed through radioisotopic geochronology and Bayesian age-depth modeling of the early Eocene Green River Formation, Wyoming, USA

The Wilkins Peak Member (WPM) of the Green River Formation in Wyoming, USA, comprises alternating lacustrine and alluvial strata that preserve a record of terrestrial climate during the early Eocene climatic optimum. We use a Bayesian framework to develop age-depth models for three sites, based on new 40Ar/39Ar sanidine and 206Pb/238U zircon ages from seven tuffs. The new models provide two- to ten-fold increases in temporal resolution compared to previous radioisotopic age models, confirming eccentricity-scale pacing of WPM facies, and permitting their direct comparison to astronomical solutions. Starting at ca. 51 Ma, the median ages for basin-wide flooding surfaces atop six successive alluvial marker beds coincide with short eccentricity maxima in the astronomical solutions. These eccentricity maxima have been associated with hyperthermal events recorded in marine strata during the early Eocene. WPM strata older than ca. 51 Ma do not exhibit a clear relationship to the eccentricity solutions, but accumulated 31%−35% more rapidly, suggesting that the influence of astronomical forcing on sedimentation was modulated by basin tectonics. Additional high-precision radioisotopic ages are needed to reduce the uncertainty of the Bayesian model, but this approach shows promise for unambiguous evaluation of the phase relationship between alluvial marker beds and theoretical eccentricity solutions.

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.