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A plethora of names has been applied to upper Cambrian and Lower Ordovician lithostratigraphic units distributed from western Utah to southeastern and central Nevada. We report comprehensive stratigraphic analysis utilizing lithologic, conodont, brachiopod, sequence stratigraphic, and carbon isotope data from several ranges in southeastern Nevada. Those data demonstrate that upper Cambrian to Lower Ordovician strata in that area belong to a variety of depositional systems that can be integrated into a comprehensive and functional depositional model that span carbonate tidal flat to shallow marine carbonate ramp to shelf to deep marine settings. Most of these strata should be placed within a single lithostratigraphic nomenclature based on the well-known Notch Peak Formation and House Limestone of western Utah. Strata of the Whipple Cave Formation in the South Egan Range, Nevada are reassigned to the three members of the Notch Peak Formation. Strata assigned to the Nopah Formation and Pogonip Group by geologic mappers who worked in the Delamar Mountains, Meadow Valley Mountains, Sheep Range, and Arrow Canyon Range in Nevada are reassigned to the Notch Peak Formation and overlying House Limestone. Coeval strata farther west record a deeper marine depositional setting and are appropriately assigned to the Windfall Formation and Goodwin Limestone. Conodonts and sequence stratigraphic packages identified from slope deposits of the Hales Limestone at Tybo Canyon in the Hot Creek Range allow correlation to the Notch Peak Formation and House Limestone in western Utah. [ABSTRACT FROM AUTHOR]

Strophomenoid brachiopods had thin, concavo‐convex shells, were ubiquitous colonizers of Palaeozoic muddy seafloors, and are hypothesized to have filter‐fed in a concave‐upward orientation. This orientation would elevate their line of commissure out of potentially lethal lophophore‐clogging mud. The paradox is that epibiont distributions on strophomenoids support a convex‐upward life position, as do studies of strophomenoid stability and trace fossils formed by strophomenoid sediment‐clearing. A premise of the concave‐upward orientation hypothesis is a narrow gape, which causes narrow, high velocity inhalant currents, leaving strophomenoids vulnerable to sediment entrainment. Herein we investigate the gape angle of Rafinesquina using serial thin sections and peels, silicified specimens, computer modelling, SEM analysis, x‐ray microCT, and 3D printing. Hinge line structure suggests that, conservatively, Rafinesquina could gape 40–45°. Such a gape occurred when diductor muscle contraction could not cause any further rotation, hinge teeth and crenulations were disengaged, and interareas interlocked. In contrast, when closed, hinge teeth were locked in hinge sockets. This wide gape eliminates constraints on feeding orientation. In either convex‐up or concave‐up orientation, Rafinesquina could feed with slow, diffuse inhalant currents incapable of disturbing sediment, and could snap valves shut to forcefully expel enough water to clear sediment from the mantle cavity, explaining previously described moat‐shaped trace fossils associated with shells. Our findings demonstrate that Rafinesquina gaped at an angle approximately equal to the angle between the two interareas when the valves are closed. Our analyses hint that other strophomenoids with similar interarea angles also lived with their shells widely agape. [ABSTRACT FROM AUTHOR]

Abstract: The 'butter shale' Lagerstatten of the Cincinnati Arch have produced an abundance of articulated trilobites, along with assorted bivalves and cephalopods. These bluish gray shales are rich in clay, [...]

Abstract: Shell-bed development can be a product of complex sedimentological and biological factors. The Upper Ordovician sediments near Cincinnati, Ohio constitute a succession of thinly interbedded shelly carbonates and mudrocks. [...]

The Upper Cambrian sponge Wilbernicyathus donegani Wilson, 1950 was originally described as an archaeocyath. The original specimens were lost. Later, based on the original description and figures, this species was interpreted as an orchocladine lithistid, but family-level taxonomy has not been clear. A neotype is designated to help stabilize the taxonomy of this species. A redescription based on the neotype and other new material from the area of the type locality and elsewhere demonstrates that this species is an orchocladine lithistid sponge belonging to the family Anthaspidellidae. It has a regular skeleton consisting of dendroclones and trabs arranged in a ladderlike net, and radial canals are well organized. The species occurs within sponge-microbial and stromatolitic reefs in the Wilberns Formation of central Texas and possibly the Clinetop Bed of the Dotsero Formation of Colorado. Stratigraphically, it ranges from the Idahoia to the Saukia trilobite zones of the Upper Cambrian Ptychaspid Biomere. Ecologically, Wilbernicyathus Wilson, 1950 occupies a reefal niche and constitutes up to 30% of the reef volume. These Late Cambrian bioherms represent the initial Laurentian expansion in the sponge-microbial buildups that dominated reef environments worldwide during the Early Ordovician.

Three parallel, manus-only sauropod trackways from the Coffee Hollow A-Male tracksite (Glen Rose Formation, Kendall County, Texas) were studied separately by researchers from the Heritage Museum of the Texas Hill Country and the Houston Museum of Natural Sciences. Footprint and trackway measurements generally show good agreement between the two groups' data sets. Footprints appear to be shallowly impressed true tracks rather than undertracks. One of the Coffee Hollow trackways shows marked asymmetry in the lengths of paces that begin with the left as opposed to the right forefoot, and two of the Coffee Hollow trackways are unusually broad. The Coffee Hollow trackways differ enough from the manus portions of other Glen Rose Formation sauropod trackways to suggest that they were made by a different kind of sauropod. Greater differential pressure exerted on the substrate by the forefeet than the hindfeet probably explains the Coffee Hollow trackways, like other manus-only sauropod trackways, but the possibility that they indicate unusual locomotion cannot at present be ruled out. [ABSTRACT FROM AUTHOR]

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Diplocraterion, a U-shaped burrow attributed to infaunal invertebrates, is normally a shallow-marine trace fossil and not part of a continental vertebrate ichnoassemblage. Hence, the Glen Rose Formation (Aptian–Albian) of Texas (USA) presents an opportunity to studyDiplocraterionassociated with a world-class dinosaur tracksite. MostDiplocraterionare in a bioclastic wackestone–packstone bed just above the Taylor Tracklayer, a significant dinosaur track horizon.Diplocraterionare consistently sized, but with variable depths; most have protrusive spreiten and northeast–southwest trends. SmallerArenicolitesco-occur withDiplocraterion, and other trace fossils includeRhizocoralliumand a large theropod trackway. Based on our analysis, a sea-level rise buried the Taylor Tracklayer, with a shallow-marine carbonate mud colonised byDiplocraterionandArenicolitestracemakers. ProtrusiveDiplocraterion, eroded burrow tops,Rhizocorallium, and other criteria point towards firming and net erosion of the bed caused by a stillstand. The depositional environment of theDiplocraterionbed was possibly a subtidal lagoon that covered shoreward sediments impacted by large theropods. Burrow orientations suggest bidirectional currents consistent with trends of theropod trackways, implying each were controlled by a shoreline. The results of our study demonstrate how marine invertebrate and continental vertebrate trace fossils can be used together to define fine-scale changes in former carbonate shorelines. [ABSTRACT FROM AUTHOR]

Limestone and shale facies of the Upper Ordovician Grant Lake Formation (Katian: Cincinnatian, Maysvillian) are well exposed in the Cincinnati Arch region of southern Ohio and north-central Kentucky, USA. These rocks record a gradual change in lithofacies and biofacies along a gently northward-sloping ramp. This gradient spans very shallow, olive-gray, platy, laminated dolostones with sparse ostracodes in the south to offshore, nodular, phosphatic, brachiopod-rich limestones and marls in the north. This study uses facies analysis in outcrop to determine paleoenvironmental parameters, particularly those related to water depth (e.g., position of the photic zone and shoreline, relative degree of environmental energy). Within a tightly correlated stratigraphic interval (the Mount Auburn and Straight Creek members of the Grant Lake Formation and the Terrill Member of the Ashlock Formation), we document the occurrence of paleoenvironmental indicators, including desiccation cracks and light-depth indicators, such as red and green algal fossils and oncolites. This permitted recognition of a ramp with an average gradient of 10-20 cm water depth per horizontal kilometer. Thus, shallow subtidal ("lagoonal") deposits in the upramp portion fall within the 1.5-6 m depth range, cross-bedded grainstones representing shoal-type environments fall within the 6-18 m depth range and subtidal, shell-rich deposits in the downramp portion fall within the 20-30 m depth range. These estimates match interpretations of depth independently derived from faunal and sedimentologic evidence that previously suggested a gentle ramp gradient and contribute to ongoing and future high-resolution paleontologic and stratigraphic studies of the Cincinnati Arch region. [ABSTRACT FROM AUTHOR]

The Upper Cambrian sponge Wilbernicyathus donegani Wilson, 1950 was originally described as an archaeocyath. The original specimens were lost. Later, based on the original description and figures, this species was interpreted as an orchocladine lithistid, but family-level taxonomy has not been clear. A neotype is designated to help stabilize the taxonomy of this species. A redescription based on the neotype and other new material from the area of the type locality and elsewhere demonstrates that this species is an orchocladine lithistid sponge belonging to the family Anthaspidellidae. It has a regular skeleton consisting of dendroclones and trabs arranged in a ladderlike net, and radial canals are well organized. The species occurs within sponge-microbial and stromatolitic reefs in the Wilberns Formation of central Texas and possibly the Clinetop Bed of the Dotsero Formation of Colorado. Stratigraphically, it ranges from the Idahoia to the Saukia trilobite zones of the Upper Cambrian Ptychaspid Biomere. Ecologically, Wilbernicyathus Wilson, 1950 occupies a reefal niche and constitutes up to 30% of the reef volume. These Late Cambrian bioherms represent the initial Laurentian expansion in the sponge-microbial buildups that dominated reef environments worldwide during the Early Ordovician. [ABSTRACT FROM AUTHOR]

The 'butter shale' Lagerstätten of the Cincinnati Arch have produced an abundance of articulated trilobites, along with assorted bivalves and cephalopods. These bluish gray shales are rich in clay, poorly calcified, and show vague internal bedding in outcrop. Butter shales form a repetitive motif with similar lithological and paleontological characteristics, suggesting conditions existed that can be explained by the interference between different orders of sequence stratigraphic cyclicity. The characteristics that define butter shales include rarity of coarser interbeds, homogenous, fine grain size, and abundance of burial horizons. The overriding control is siliciclastic sediment supply. During third-order transgressions, sediment supply to the basin is too low to produce thick shale-prone intervals. Conversely, during third-order falling stages, sediment supply is generally too high to favor butter shale deposition. Butter shales formed preferentially during a third-order highstand systems tract, and two subtly different variants resulted from the superimposed effects of higher order cycles. Highstands moderated by small-scale transgressions are characterized by lower background sedimentation and fewer, thinner mud deposition events. Superposition of small-scale sea-level fall on highstands produced increased background sedimentation, higher silt, and patchy fossil occurrences. Juxtaposition of various scaled highstand systems tracts provided the optimal butter shale conditions, characterized by elevated mud influx and frequent episodic burial events, leading to abundant, articulated trilobites and associated fauna. In these scenarios, episodic events provide sufficient mud to smother local faunas and create a soft, fine-grained substrate that prohibited recolonization by taxa adapted to firm substrates. Each scenario differs from the others with respect to sedimentology and faunal composition. [ABSTRACT FROM AUTHOR]

Focuses on the crinoid columnals of interbedded shales and carbonates of the Upper Ordovician Kope to Fairview formations. Basis of distinctive morphological characters of the columnals; Correlation of crinoid taxa with hallowing depth; Characteristic of deeper water disparids.