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Field sampling data in the Vocontian Basin (southeastern France) and Mallorca (Spain), at the transition between the lower and upper Barremian (upper Moutoniceras moutonianum Zone and lower Toxancyloceras vandenheckei Zone), provides new information about the early representatives of the ammonite family Ancyloceratidae. Several successive species o...
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... Building on the body of stratigraphic observations generated by Crough (1983), Ziegler et al. (1985) and others, Fernandes et al. (2019) compiled 339 locations where such stratigraphic transitions are observed in outcropping stratigraphy of the North American Western Interior. Stratigraphy from these locations typically feature as part of well-established chronostratigraphic frameworks that include radiometric dating (Cobban et al., 2006;Lynds & Slattery, 2017;Merewether & McKinney, 2015;Merewether et al., 2011;Obradovich & Cobban, 1975). Thicknesses and distributions of Cretaceous rocks from outcrop and well data (e.g., Mancos Shale) are of special importance because of their role in defining when marine conditions likely last prevailed across large tracts of the continental interior (Bond, 1976;Cross & Piliger, 1978;Li & Aschoff, 2022;L. ...
... Regressive stratigraphic sequences were identified from published facies interpretations (e.g., Gani et al., 2015;Johnson et al., 2002;L. N. R. Roberts & Kirschbaum, 1995), and ages were tied using published regional chronostratigraphy (Figure 1d; Cobban et al., 2006;Lynds & Slattery, 2017;Merewether & McKinney, 2015;Merewether et al., 2011;Obradovich & Cobban, 1975). Particular care was taken to identify lateral and temporal variability in the depositional facies sequences. ...
Mantle convection plays a fundamental role in driving evolution of oceanic and continental lithosphere. In turn it impacts a broad suite of processes operating at or close to Earth's surface including landscape evolution, glacio‐eustasy, magmatism, and climate. A variety of theoretical approaches now exist to simulate mantle convection. Outputs from such simulations are being used to parameterize models of landscape evolution and basin formation. However, the substantial body of existing simulations has generated a variety of conflicting views on the history of dynamic topography, its evolution and key parameters for modeling mantle flow. The focus of this study is on developing strategies to use large‐scale quantitative stratigraphic observations to assess model predictions and identify simulation parameters that generate realistic predictions of Earth surface evolution. Spot measurements of uplift or subsidence provide useful target observations for models of dynamic topography, but finding areas where tectonics have not also influenced vertical motions is challenging. To address this issue, we use large inventories of stratigraphic data from across North America with contextual geophysical and geodetic data to constrain the regional uplift and subsidence history. We demonstrate that a suite of typical geodynamic simulations struggle to match the amplitude, polarity and timing of observed vertical motions. Building on recent seismological advances, we then explore strategies for understanding patterns of continental uplift and subsidence that incorporate (and test) predicted evolution of the lithosphere, asthenosphere and deep mantle. Our results demonstrate the importance of contributions from the uppermost mantle in driving vertical motions of continental interiors.
... (Tibert et al. 2003), roughly between 94 and 90.5 Ma Albright et al. 2007b). In the BRCA region, the ammonites indicate that the Tropic Shale here was deposited after approximately 94 Ma and before 92.5 Ma (Bowers 1991;Cobban et al. 2006). The Tropic Shale is roughly equivalent to the lower Mancos Shale found to the east (Leckie et al. 1997;Tibert et al. 2003), correlating to the Tununk Member of eastern Utah (Elder andKirkland 1993, 1994;Albright et al. 2007a). ...
Bryce Canyon National Park Paleontological Resource Inventory
... F. Liu et al., 2005;Peyton et al., 2011). The chronology of the Western Interior Cretaceous basin is cited from Obradovich (1993), Cobban et al. (2006), and Gradstein et al. (2020Gradstein et al. ( ). et al., 2014Miall & Catuneanu, 2019). Notably, the abundant ammonite fauna found throughout the strata of this period provided precise age data (with an accuracy of 0.3-0.5 Myr; Minor et al., 2022), serving as the foundation for dating the strata and analyzing basin subsidence (Cobban et al., 2006;Obradovich, 1993). ...
... The chronology of the Western Interior Cretaceous basin is cited from Obradovich (1993), Cobban et al. (2006), and Gradstein et al. (2020Gradstein et al. ( ). et al., 2014Miall & Catuneanu, 2019). Notably, the abundant ammonite fauna found throughout the strata of this period provided precise age data (with an accuracy of 0.3-0.5 Myr; Minor et al., 2022), serving as the foundation for dating the strata and analyzing basin subsidence (Cobban et al., 2006;Obradovich, 1993). Although brackish-water and non-marine strata lack ammonites, frequent marine flooding events in a landward direction led to ammonite occurrences above and below non-marine strata. ...
... The excellent, pre-existing ammonite-zonation age control of the Upper Cretaceous strata and its calibration with a series of absolute age dates (Cobban et al., 2006) in the WIB are widely used and provide the reasonably precise data needed for quantitative subsidence studies. Some of the biostratigraphic data were selected to form Table S1 for subsidence analysis in this study. ...
Variability in subsidence rates within Upper Cretaceous strata of the Western Interior Basin offers crucial insights into the response of surface sedimentation styles to Sevier‐to‐Laramide tectonics and related deep mantle processes. The formation mechanisms of the Late Cretaceous Western Interior Basin in North America have long been a subject of debate. A re‐evaluation of the basin's subsidence history reveals rapid subsidence pulses lasting ca. 2 Myr within longer‐term (average 5.7 Myr) progradational or aggradational clastic wedges. The timing of these wedges, especially the widespread marine flooding resulting from subsidence, is constrained through the calibration of ammonite zonation with absolute dates. Sevier wedges exhibit a different architecture compared to the Laramide wedges. The former recorded initial rapid and widespread marine transgressions followed by long‐term coastal progradation, whereas the latter developed by initial erosional and progradational growth followed by aggradation and long‐term coastal transgression. The Sevier clastic wedges, initially accumulated within a N‐S elongated, long‐wavelength tectonic subsidence zone close to the thrust belt, gradually migrated cratonward. Starting in the early Campanian (ca. 82 Ma), the Laramide Orogeny developed along a NW‐SE trend and then migrated northeastward, roughly consistent with coeval long‐wavelength frontal basin subsidence. The spatio‐temporal variations in long‐wavelength tectonic subsidence indicate a shift in the dynamic subsidence's migration direction from eastward to northeastward, driven by changes in Farallon subduction direction and mode. Our work shows how repeated subsidence behavior in the Sevier‐to‐Laramide transition records evolving architectural responses and the trajectory of coeval dynamic topography.
... So, not even with ammonites or any other marine fossil group has the official boundary been defined. Those authors commented, "probably placement would be near the Dunveganoceras pondi Zone of the Western Interior, the base of which Cobban et al. (2006) used for their Upper/Middle substage boundary." ...
The Arlington Archosaur Site (AAS) between Dallas and Fort Worth, Texas, is known as a rich fossiliferous section. The age of these rocks is generally considered to be mid Cenomanian, but conflicting evidence suggests the age may be as young as the late Cenomanian early Turonian. To address the issue, a palynological study was designed and conducted based on the close sampling of the lithofacies. Palynological samples were processed according to the standard acid preparation. The study was quantitative and focused on associations to determine the paleoenvironment, paleoclimate, biostratigraphy, and age of exposure. The rich palynological assemblages comprise spores from seedless plants, gymnosperms, angiosperms, fungi, algae, and dinoflagellate cysts. Bryophytes were abundant mainly in Facies A and B, with Zlivisporis cenomanianus taking over the bryophytes' habitat in Facies D. Lycophytes abundant in the alluvial and coastal plains are considered to have been transported. Conifers were the predominant group of gymnosperms, also mainly transported into the section. Freshwater algal remains include Schizophacus laevigatus/Ovoidites parvus, Schizosporis reticulatus, Botryococcus sp., and Pediastrum sp. Acanthomorph acritarchs present in low abundance and diversity appear following shallow marine dinoflagellates' spikes and before freshwater colonial algal spikes. The vegetation signal at Noto's Facies A and B indicates tropical to subtropical shallow marine to coastal plains, while Noto's Facies D indicates tidally influenced areas. Also, picks of the diversity and abundance of dinoflagellate cysts are interpreted as an increased marine influence and proposed as possible flooding surfaces. The results support the alternation of marine incursions within deltaic and floodplain sequences, related to regional climate oscillation that affected the vegetation on the upland drainage area. Key palynological markers point to an early Late Cenomanian age, and the presence of the Cyclonephelium compactum - C. membraniphorum (Ccm morphological plexus) signals that the incursion of boreal waters during the Plenus Cold Event of the Ocean Anoxic Event 2 may have reached as far south as the AAS area. This coincides with vegetation trends that suggest a cooler and less humid climate at the start of Facies A, where Ccm is more abundant.
... The curve of 87 Sr/ 86 Sr through time for the Coniacian is based in sparse data from the U.S. Western Interior and data from the Trunch borehole (McArthur et al. 1993a;. The base of the C. d. erectus Zone in the U.S. Western Interior coincides with the base of the Scaphites preventricosus ammonite Zone (Cobban et al. 2006). The 87 Sr/ 86 Sr value of that level is 0.707 314 ± 0.000 002 (2 s.e., n = 14). ...
... In the U.S. Western Interior the base of the Campanian has been traditionally set at the base of the Scaphites Leei III ammonite Zone (Cobban 2006) or some 20% up from the base (Fig. 27.9 in GTS2020). The base of the zone has an 87 Sr/ 86 Sr value of 0.707 454 ± 0.000 002 (2 s.e.. n = 6) based on the data of McArthur et al. (1994); the value for the base of the overlying zone of Scaphites hippocrepis I is 0.707 465. ...
This contribution outlines the methodology of strontium-isotope stratigraphy, and reviews the information that underpins the calibration curve of ⁸⁷ Sr/ ⁸⁶ Sr against time for the Cretaceous.
... The Santonian-Campanian succession in the Western Interior Basin of the USA has been documented by Cobban (1952Cobban ( , 1969, Scott and Cobban (1964) and Cobban et al. (2006). The stratigraphy, sedimentology and palaeoecology of the Smoky Hill Chalk Member of the Niobrara Formation of Kansas was described by Hattin (1982), who provided detailed logs. ...
... Locally there have been problems with the incorrect identification of the C34n-C33r boundary, most notably in the English Chalk (Barchi, 1995;Montgomery et al., 1998), which led to a significant misinterpretation of the biostratigraphical age of the reversal as falling within the U. socialis Zone of the Santonian (Gale et al., 1995), corrected by Thibault et al. (2016). A parallel situation occurred in the northern part of the Western Interior Basin, where Lerbekmo (1989), Lerbekmo and Braman (2002), Leahy and Lerbekmo (1995) and Lillegraven (1991) identified the C34n-C33r boundary as falling within the "smooth Baculites Zone" of Cobban et al. (2006), 5 zones above the D. bassleri Zone, and well above the base of the Campanian as now defined. This was corrected by Kita et al. (2017), who reported the chron boundary close to the base of the Scaphites leei III ammonite zone within the Upper Chalky Shale (Fig. 20). ...
Following the unanimous vote of the Executive Committee
of International Union of Geological Sciences in
October 2022, the Global boundary Stratotype Section
and Point for the base of the Campanian Stage is confirmed
as the magnetic polarity reversal from Chron 34n
(top of the Long Cretaceous Normal Polarity–Chron) to
Chron C33r at the 221.53 m level in the Bottaccione Gorge
section at Gubbio, Umbria–Marche Basin, Italy. This event
has been widely identified in oceanic settings and in widespread
onshore outcrops. Sedimentation across the Santonian–
Campanian boundary interval in the proposed
GSSP appears to be continuous, supported by evidence
from the carbon isotope record and complete micro– and
nannofossil biostratigraphy. The succession comprises
deep–water cherty limestones (mudstones and foraminiferal
wackestones) which provide a detailed record of
calcareous nannofossils and planktonic foraminifera and
yields an excellent palaeomagnetic record. The high–resolution
carbon isotope record, derived from bulk sediment,
provides an important additional means of correlation to
other regions.
... The stratigraphic position of the type locality is within that portion of the Pembina Member that correlates with the upper portion of the Burning Brule Member (Sharon Springs Formation, Pierre Group) in central South Dakota Bertog et al., 2007;Bertog, 2010). That correlation places the type locality within either the Baculites obtusus or Baculites mclearni ammonite range zones (e.g., Gill and Cobban, 1965;Bertog et al., 2007;Bertog, 2010), which are the two oldest range zones within the middle Campanian (Cobban et al., 2006). A sample taken from the Q3 bentonite (sensu Bamburak et al., 2013) at the study area was dated at 80.04 ±0.11 Ma (U-Pb zircon age: Bamburak et al., 2016), which is consistent with dates obtained elsewhere from bentonites within the Ardmore bentonite succession (e.g., Obradovich, 1993;Hicks et al., 1999) and provides a lower bound on the age of the type locality. ...
Mosasaurs are large, carnivorous aquatic lizards with a global distribution that lived during the Late Cretaceous. After 200 years of scientific study, new mosasaur species are still being discovered as new localities are explored and specimens collected long ago are reevaluated using modern standards of species delimitation. Even so, the phylogenetic positions of many key taxa are unresolved and therefore our understanding of mosasaur macroevolution is muddled. Here, we describe a new genus and species of mosasaurine mosasaur comprising a partial skull and skeleton from the Pembina Member of the Pierre Shale Formation in Cavalier County, North Dakota. The lower bound on the age of the specimen is 80.04 ±0.11 Ma, provided by the underlying bentonite bed. Its skull and jaws are nearly complete, and the postcranial skeleton preserves seven cervical vertebrae with three hypapophyseal peduncles, 11 ribs, and five anterior dorsal vertebrae. The new specimen was scored into a modified version of an existing phylogenetic matrix of Mosasauroidea and was recovered in a polytomy with Clidastes; however, given that its morphology is significantly different from that of Clidastes, we refer it to a new genus and species, Jormungandr walhallaensis. Notably, this new taxon shares a mosaic of features seen in both basal (e.g., Clidastes; high dental counts) and derived (e.g., Mosasaurus; subrectangular quadrate) mosasaurines, in addition to possessing its own unique suite of autapomorphies. Given that it possesses morphology intermediate between Clidastes and Plotosaurini, we suspect that future analyses of mosasaur phylogeny, following the addition of new characters and taxa, will recover Jormungandr as transitional between them. Its occurrence increases the known diversity of mosasaurs from the Pembina Member and is the earliest mosasaur to possess autapomorphies of Plotosaurini. Finally, we also analyzed the matrix using different outgroups to test their effect on tree topology and resolution, and found that including multiple nonmosasauroid anguimorphs increased resolution, but not support, of mosasaurid ingroup relationships.
... Remarks: Forresteria (Forresteria) hobsoni (Reeside, 1932), compared to F. (F.) peruana, is more evolute and less compressed with stouter whorls throughout its ontogeny and consistently coarser ribs (Kennedy and Cobban, 1991, p. 29 Cobban et al. (2006Cobban et al. ( , 2008, Merewether et al. (2011, fig. 2), Slattery et al. (2015, fig. ...
... It is worth noting that Walaszczyk and Cobban (1998, p. 495) clarified the position of F. (F.) peruana, stating: "First "Coniacian" ammonite, Forresteria peruana, appears in the indisputable Turonian, in the zone of M. scupini, and the reference to Forresteria in the boundary definition should be rejected." Walaszczyk and Cobban (2000), Cobban et al. (2006) and Walaszczyk et al. (2010) show F. (F.) peruana only in the upper Turonian M. scupini Zone. ...
A low diversity fauna of upper Turonian ammonites and inoceramids occurs in the Montezuma Valley Member of the Mancos Shale and the overlying Gallup Sandstone near Herrera in Bernalillo County in west-central New Mexico. The ammonites Forresteria (Forresteria) peruana (Brüggen, 1910), Baculites yokoyamai Tokunaga and Shimizu 1926 and Scaphites (Scaphites) corvensis Cobban, 1952 and the inoceramid Mytiloides scupini (Heinz, 1930) are present in the Montezuma Valley Member. Mytiloides scupini, F. (F.) peruana and B. yokoyamai also occur at the base of the Gallup Sandstone and above, at a stratigraphically higher position. The M. scupini inoceramid zone is equivalent to the Prionocyclus germari ammonite zone, which establishes a late Turonian age for these strata.
... Eutrephoceras sp. Walaszczyk and Cobban (2000), Cobban et al. (2006Cobban et al. ( , 2008, Merewether et al. (2011, fig. 2), Slattery et al. (2015, fig. ...
Reports of Turonian occurrences of Eutrephoceras in North America, which are the oldest reports of the genus from the continent, are exclusively from New Mexico, and these reports as well as global reports of that age are rare. The oldest Eutrephoceras previously reported from New Mexico were from the Prionocyclus quadratus Zone. We document here two specimens of Eutrephoceras from the Scaphites ferronensis Zone in the D-Cross Member of the Mancos Shale in Socorro County, New Mexico, which is three ammonite zones lower than the P. quadratus Zone. They are thus the oldest record of Eutrephoceras from North America.
... Lucas (2017, p. 465) defined the best sections as those that were "abundantly fossiliferous, well studied, stratigraphically dense and temporally extensive records from a single depositional basin or geographically restricted outcrop area" or, put another way, as those sections "that have the most continuous and extensive fossil record that encompasses the extinction being studied." Because of their utility in high-resolution biostratigraphy (e.g., Klinger and Kennedy, 2001;Cobban et al., 2006;Slattery, 2019), the fossil ammonite genus Baculites Lamarck, 1799 may represent a prime case study for the effects of the CCE on patterns of extinction. ...
... In view of this revitalization and the fact that Baculites traditionally has been seen as an exemplar of Cope's (1896) concept of taxon senescence or overspecialization (Hyatt, 1872(Hyatt, , 1889(Hyatt, , 1893Cope, 1896;Lull, 1926;Schindewolf, 1993), it is interesting to question whether the ideas of these researchers can be justified by analyzing the fossil record of Baculites. In contrast to many other fossils, the fossil record of Baculites, particularly in the North American Western Interior, is regarded to be exemplary (Klinger and Kennedy, 2001;Cobban et al., 2006;Slattery, 2019). Therefore, this investigation analyzes the fossil record of Baculites from two perspectives: first, a "best sections" approach (cf. ...
... At first glance, these observations are consistent with the taxon senescence or weak directionality hypothesis. For example, the extinction of a relatively diverse and apparently entirely endemic clade, which culminated in Baculites eliasi Cobban, 1958, effectively marks the Campanian/Maastrichtian stage boundary within the Western Interior of North America (Cobban et al., 2006;Ward et al., 2015;Slattery, 2019). Within the Paleobiology Database or Fossilworks: The Gateway to the Paleobiology Database, two major fossil databases typically used for diversity analyses (Prothero, 2015), the stratigraphic distribution of Campanian Baculites characteristic of the Western Interior is given simply as Campanian, 83.6-72.1 Ma or 84.9-70.6 ...
The concept that taxon senescence led to the extinction of the heteromorph ammonite genus Baculites Lamarck, 1799, has a long intellectual pedigree dating to E. D. Cope and the neo-Lamarckian period of American paleontology. Revivified versions of Cope’s basic concept emphasize a unimodal or hat-like, five-phased pattern of diversification among fossil taxa: origination, expansion, peak, decline, and extinction. Extinction is driven primarily by negative density-dependent effects in sympatry during the peak of diversification, when Van Valen’s law of constant extinction (i.e., the Red Queen effect) is observed, competition among a large number of closely related congeners is most acute, and the so-called “seed-of-decline” is planted. However, these modern versions of Cope’s taxon senescence concept do not take into account the possibility that these fundamental patterns may be artifacts of data compilation—that is, the compiled correlation effect (CCE).
An archetype of Cope’s taxon senescence concept, the Late Cretaceous heteromorph ammonite Baculites superficially appears to adhere to several of these key predictions: a unimodal, hat-like pattern of diversification, a high degree of spatiotemporal overlap among congeners during peak diversification, and an apparently constant extinction rate during peak diversification. However, this is only the case when poorly resolved, stage-level distribution data are analyzed from the Paleobiology Database and Fossilworks. Once high-resolution phylogenetic and biostratigraphic data are taken into account, multi-modal fluctuation in standing diversity over the course of the Campanian conforms to a random walk coupled with a stochastically constant extinction rate. The extinction of Baculites appears to have been both age and density-independent, invalidating the taxon senescence concept and providing critical support for the CCE, which must now be expanded beyond alleged mass extinction to include patterns of background extinction.
