“…Interpolating the age of ''Glyptops'' pervicax Hay 1908, which may be conspecific with T. hiatti (Ostrom 1970), from the Cloverly Formation of Montana, yields an age of at least 101.6 Ma. Neurankylus wyomingensis, reported from the Colorado shale near Cody, Wyoming, was likely recovered from the Cody Shale of current usage, which in that region contains the biostratigraphic zones of Scaphites ventricosus Meek and Hayden 1862, and Schaphites depressus Reeside 1927(Dyman et al 1997, giving a conservative age estimate of middle to late Coniacian (87.88-85.85 Ma;Gradstein et al 2004). Arundelemys dardeni, here provisionally hypothesized to be a basal neurankyline, occurs in the Arundel Clay facies of the Potomac Group, which was dated to middle Aptian by palynological biostratigraphy (Doyle 1992).…”
A new species of Neurankylus (N. lithographicus sp. nov.) is described on the basis of skull and shell material from the Santonian-aged Milk River Formation, Alberta, Canada. The genus Neurankylus is also rediagnosed on the basis of the Milk River material and on new material pertaining to the type species N. eximius. N. eximius previously was considered to be a long-lived and cosmopolitan taxon. New Neurankylus material provides insights into the range of morphological variation present in the genus and indicates that many specimens previously referred to N. eximius may belong to different species. The congeners recognized in this chapter have a more restricted geographical and temporal range than has been suggested previously. A new phylogenetic analysis of all known baenid taxa, including all described species of Neurankylus and several basal paracryptodiran taxa of uncertain affinities, yields two important results: a monophyletic Neurankylus is recovered as a basal radiation within Baenidae and parallel evolution is identified among many features previously regarded as synapomorphies for Baenidae. In light of this study and other recent work on turtle systematics, it is now apparent the biogeography and biostratigraphy of Cretaceous turtles may have been more complex than previously appreciated.
“…Interpolating the age of ''Glyptops'' pervicax Hay 1908, which may be conspecific with T. hiatti (Ostrom 1970), from the Cloverly Formation of Montana, yields an age of at least 101.6 Ma. Neurankylus wyomingensis, reported from the Colorado shale near Cody, Wyoming, was likely recovered from the Cody Shale of current usage, which in that region contains the biostratigraphic zones of Scaphites ventricosus Meek and Hayden 1862, and Schaphites depressus Reeside 1927(Dyman et al 1997, giving a conservative age estimate of middle to late Coniacian (87.88-85.85 Ma;Gradstein et al 2004). Arundelemys dardeni, here provisionally hypothesized to be a basal neurankyline, occurs in the Arundel Clay facies of the Potomac Group, which was dated to middle Aptian by palynological biostratigraphy (Doyle 1992).…”
A new species of Neurankylus (N. lithographicus sp. nov.) is described on the basis of skull and shell material from the Santonian-aged Milk River Formation, Alberta, Canada. The genus Neurankylus is also rediagnosed on the basis of the Milk River material and on new material pertaining to the type species N. eximius. N. eximius previously was considered to be a long-lived and cosmopolitan taxon. New Neurankylus material provides insights into the range of morphological variation present in the genus and indicates that many specimens previously referred to N. eximius may belong to different species. The congeners recognized in this chapter have a more restricted geographical and temporal range than has been suggested previously. A new phylogenetic analysis of all known baenid taxa, including all described species of Neurankylus and several basal paracryptodiran taxa of uncertain affinities, yields two important results: a monophyletic Neurankylus is recovered as a basal radiation within Baenidae and parallel evolution is identified among many features previously regarded as synapomorphies for Baenidae. In light of this study and other recent work on turtle systematics, it is now apparent the biogeography and biostratigraphy of Cretaceous turtles may have been more complex than previously appreciated.
“…Dyman et al . [] reported palynological data indicating a Coniacian (89.3–85.8 Ma) depositional age for the middle to upper Frontier Formation in the nearby Centennial Range. These data correlate well with existing geochronological and palynological data from the Frontier Formation in the extreme southwestern Lima Peaks region, which encompasses the bulk of the Montana samples.…”
[1] We present a compilation of 8717 U-Pb analyses from 95 detrital zircon samples of Jurassic-Eocene North American Cordillera foreland basin strata. Of these samples, 30 are new and previously unpublished. Variation in detrital zircon age spectra between samples records erosion or recycling of basement and cover rocks within the Cordilleran orogenic wedge. Each sample can be classified into one of six major provenance groups, whose age spectra suggest derivation from (1) Mesozoic eolianites of the western United States, (2) Paleozoic passive margin strata of the western United States, (3) Paleozoic passive margin strata of western Canada, (4) the Mogollon Highlands, (5) the Cordilleran magmatic arc, or (6) Yavapai-Mazatzal Province crystalline basement rocks. Referencing these provenance interpretations to their location and stratigraphic deposition age produces a detailed spatial and temporal record of sediment dispersal within the foreland basin system. Late Jurassic provenance is dominated by recycling of Mesozoic eolianites from sources in the Sevier thrust belt. Cretaceous-Eocene provenance is dominated by recycling of the passive margin, with increasing complexity upsection. We interpret that this provenance transition records a basin-wide unroofing sequence. A composite age-probability plot of 1539 young (<250 Ma) detrital zircons reveals at least four age-abundance peaks that we interpret to represent periodic high-flux magmatism in the Cordilleran arc.
“…3B,C) briefly explained above, and it is also guided by: (1) the results of the first-arrival seismic tomography, which provides complementary information near the surface (Fig. S2); (2) the surface geology 51 and an exploration well drilled into the Centennial fault footwall 50 ; and (3) geomorphic analyses of stream channels and Quaternary deposits 60 .Figure 4Main facies characteristics of the seismo-stratigraphic units.…”
Section: Methodsmentioning
confidence: 99%
“…The definition of seismic stratigraphic packages is also guided by a line drawing of industry seismic data constrained by a well that penetrates the footwall of the Centennial Fault south of the terminus of our line 50 . Our correlation of lithostratigraphic units in Figs 2 and S1 to unconformity-bound seismic stratigraphic packages in Figs 5–7 is based on this line drawing and the regional geology.…”
Section: Methodsmentioning
confidence: 99%
“…These Mesozoic rocks are thickest in the western Centennial Mountains where the Cretaceous Frontier Formation composes the bedrock. Across the valley to the north and at the foot of the Snowcrest Range, basal conglomerates of the late Cretaceous-early Tertiary Beaverhead Group unconformably cover Paleozoic and older Mesozoic rocks 50 . Folds in the Beaverhead Group are evidence for syn-deformation deposition during the Sevier orogeny 43 .…”
We acquired a ~9-km long, high-resolution reflection seismic profile in the Centennial Valley, Montana, to better understand the kinematics of basin bounding faults and their role in accommodating proposed right-lateral shear in the Northern Basin and Range adjacent to the Yellowstone hotspot. In pursuing these goals, our findings have also shed light on the development of hanging wall stratigraphy and seismic hazards for this part of the SW Montana seismic belt. Here we present the profile and a working interpretation that identifies fault inversion, and an oblique, anticlinal accommodation zone linking the Centennial and Lima Reservoir faults in the Centennial Valley. These interpretations are consistent with seismicity and GPS-geodetically observed right-lateral shear aligned with the Centennial Valley north of the Yellowstone hotspot. Data were acquired using dense, wide-aperture arrays and illuminate the subsurface stratigraphy and faults down to ~1200 m, showing that the basin is a half-graben with a southern depocenter driven by the listric geometry of the north-dipping Centennial fault. Reflectors onlap basement highs with growth geometry against these faults. Our interpretation of a bright basal reflection as the Timber Hill Basalt (~6 Ma) or related flow, is consistent with a late Miocene – Pliocene inception of the basin proposed by other research. We also note a small inversion structure that we interpret as local evidence of transpression in the shear zone. This transpression is part of the accommodation zone and seismogenic faults including the Lima Reservoir fault that has well-expressed Holocene surface ruptures a few kilometres west of the seismic line along the northern edge of the Centennial basin.
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