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John W. M. Jagt - One of the best experts on this subject based on the ideXlab platform.
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A chemostratigraphic framework for the type-Maastrichtian
2020Co-Authors: Johan Vellekoop, Pim Kaskes, Sinnesael Matthias, John W. M. Jagt, Robert P. Speijer, Philippe ClaeysAbstract:<p>The youngest time interval of the Cretaceous Period is known as the Maastrichtian, a reference to the marine strata exposed in the area surrounding the city of Maastricht, in the Netherlands-Belgium border region. The stratigraphic succession at the original type-locality of the Maastrichtian (ENCI quarry, NL) only covers the upper part of the Maastrichtian Stage as it is nowadays defined. However, in combination with similar rock sequences in several other quarries (e.g. Hallembaye, Curfs) in the region, a substantial part of the Maastrichtian Stage is represented.</p><p>While the type-Maastrichtian strata have provided a wealth of paleontological data, comparatively little geochemical work has been carried out on this succession. So far, the age assessment of, and stratigraphic correlation with, the type-Maastrichtian has been largely based on biostratigraphy and preliminary attempts at cyclostratigraphy, techniques that are hampered by bioprovincialism and the presence of stratigraphic gaps in the succession. In recent years, stable carbon isotope stratigraphy has been proven to be a powerful tool for correlating Upper Cretaceous strata on a global scale. When calibrated with biostratigraphic events, carbon isotope stratigraphy can be used to test the synchroneity of bio-events and reconcile inter-regional biostratigraphic schemes. Therefore, we have generated the first high-resolution stable carbon isotope stratigraphy for the type-Maastrichtian, using the extensive sample set acquired in the context of the Maastrichtian Geoheritage Project. In combination with elemental data generated using &#181;XRF (e.g. Ca, Si, Al, Ti, Fe wt%), our record presents the first high-resolution chemostratigraphy for the type-Maastrichtian. This new chemostratigraphic framework enables us to refine the age-model for studied strata, and allows a better regional and global correlation with the type-Maastrichtian successions, placing the paleontological records from the type-Maastrichtian in a global context. &#160;</p>
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Stable isotopes, niche partitioning and the paucity of elasmosaur remains in the Maastrichtian type area
Netherlands Journal of Geosciences, 2016Co-Authors: Anne S. Schulp, John W. M. Jagt, Eric W.a. Mulder, Renée Janssen, Remy R. Van Baal, Hubert B. VonhofAbstract:Remains of elasmosaurid plesiosaurs are exceedingly rare in the type-Maastrichtian strata (Late Cretaceous, southeast Netherlands and northeast Belgium), in stark contrast to relatively common skeletal remains of mosasaurs. Here, we present an analysis of δ13C stable isotope values for tooth enamel of two elasmosaur teeth from the type Maastrichtian. The δ13C signal is a proxy for foraging area, trophic level and diving behaviour, the net value of which in these rare elasmosaurs turns out to be not noticeably different from that for the much commoner mosasaurs in the type Maastrichtian. Therefore, the rarity of elasmosaurs in the area probably reflects a primary near-absence of such reptiles during the latest Cretaceous, rather than a taphonomic artefact.
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Terminal Maastrichtian Ammonites from Turkmenistan, Central Asia
Acta Palaeontologica Polonica, 2012Co-Authors: Marcin Machalski, John W. M. Jagt, Alexander S. Alekseev, Elena A. Jagt-yazykovaAbstract:A complete uppermost Maastrichtian—Danian succession in the Sumbar River section, western Kopet Dagh (southwest Turkmenistan, Central Asia), constitutes one of the few instances in the world where the fossil record of the last ammonites can be directly positioned with respect to the iridium-rich, impact-related clay layer, which defines the Cretaceous—Paleogene (K—Pg) boundary. Two ammonite taxa, Baculites cf. vertebralis and Hoploscaphites constrictus johnjagti, range up to a level directly beneath the K—Pg boundary clay in the Sumbar River section. Thus, these two forms probably survived until the very end of the Maastrichtian in the western Kopet Dagh area. The terminal Maastrichtian ammonite records from the Sumbar River area represent the southeasternmost occurrences of these essentially Boreal taxa.
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Belemnite-based strontium, carbon and oxygen isotope stratigraphy of the type area of the Maastrichtian Stage
Netherlands Journal of Geosciences - Geologie en Mijnbouw, 2011Co-Authors: Hubert B. Vonhof, John W. M. Jagt, Adrian Immenhauser, Jan Smit, Y.w. Van Den Berg, Margot Saher, Norbert Keutgen, John J. G. ReijmerAbstract:Belemnitellid cephalopods from the Maastrichtian stratotype area (southeast Netherlands) are shown to be comparatively well preserved. Although partial diagenetic alteration has been observed, micromilling techniques have permitted the extraction of pristine belemnite calcite, suitable for the reconstruction of strontium (Sr), oxygen (O) and carbon (C) isotope variation of Maastrichtian seawater. A distinct Sr isotope pattern in the Maastricht record can be matched stratigraphically with records from Hemmoor (northern Germany), El Kef (Tunisia) and ODP site 690 (Maud Rise, Antarctica), leading to a new chemostratigraphical age model for the Maastrichtian stratotype section. Our data improve currently applied strontium isotope stratigraphical reference curves by revealing an Sr isotope inflection pattern near the lower/upper Maastrichtian boundary that is a potentially diagnostic feature for intra-Maastrichtian stratigraphical correlation between distant sections. Belemnites further show significant stratigraphical oxygen isotope variation through the Maastrichtian. We interpret this variation to have resulted from palaeoceanographic reorganisations in the Atlantic Ocean during this time interval.
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The phymosomatid echinoid Trochalosoma taeniatum from the Maastrichtian (Upper Cretaceous) of southeast Poland
Acta Geologica Polonica, 2010Co-Authors: John W. M. Jagt, Adrian KinAbstract:The phymosomatid Trochalosoma taeniatum (von Hagenow, 1840) is recorded for the first time from upper Maastrichtian strata exposed at Piotrowice, near Lublin, southeast Poland. Although fragmentary, the single, moderately preserved test is of note in representing one of the larger individuals of this species on record (estimated diameter > 60 mm), and in displaying crenulate ambulacral and interambulacral tubercles, at least adapically. Previous records of T. taeniatum include the lower and upper Maastrichtian of Denmark, northern Germany (Rugen), Alava (northern Spain) and Mangyshlak (Kazakhstan). Trochalosoma corneti (Cotteau, 1875), from the upper Maastrichtian of southern and northeast Belgium (Mons and Liege basins, respectively) and the southeast Netherlands (type area of the Maastrichtian Stage), synonymised by some authors with T. taeniatum, is considered to be distinct.
Nicolas Thibault - One of the best experts on this subject based on the ideXlab platform.
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Calcareous nannofossil response to Late Cretaceous climate change in the eastern Tethys (Zagros Basin, Iran).
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Mohammad J. Razmjooei, Nicolas Thibault, Anoshiravan Kani, Jaume Dinarès-turell, Emmanuelle Pucéat, Shamar ChinAbstract:Coniacian to Maastrichtian changes in calcareous nannofossil assemblages have been investigated in the eastern Tethyan Shahneshin section (central Zagros Basin, Iran). The nannofossil assemblages are mainly composed of Watznaueria spp. (avg. 54%), Retecapsa spp (avg. 7.9%), Cribrosphaerella ehrenbergii (avg. 7.7%) and Micula spp. (avg. 5.7%). Throughout the late Campanian, there is a trend to lower abundances in Watznaueria spp. together with increasing abundances of C. ehrenbergii and Arkhangelskiella cymbiformis, which are considered in this basin as the main cool-water taxa. Our results reveal that, despite a diagenetic impact on calcareous nannoflora, a number of primary paleoecological trends are preserved which depict well features of the progressive Late Cretaceous cooling. The first pronounced cooling episode occurs across the late Campanian to early Maastrichtian. The onset of pronounced cooling in the eastern Tethys appears to occur prior to the Campanian/Maastrichtian Boundary event (CMBE) δ13C negative excursion, in contrast with the Boreal realm where pronounced cooling only occurs in the early Maastrichtian, postdating the onset of the CMBE. The coincidence of this earlier cooling in the Zagros Basin with an interval characterized by a significant increase in benthic foraminifera suggests an amplified response of the assemblage due to a change to shallower environments. Hence, the late Campanian calcareous nannofossil assemblage turnover in central Zagros is either a response to an early cooling trend in the eastern Tethys or to sea-level fall or both. The mid-Maastrichtian warming and late Maastrichtian cooling episodes are also delineated in the nannofossil assemblage of Shahneshin and likely correlate with similar episodes in the Boreal Realm.
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upper campanian Maastrichtian chronostratigraphy of the skaelskor 1 core denmark correlation at the basinal and global scale and implications for changes in sea surface temperatures
Lethaia, 2015Co-Authors: Nicolas Thibault, Kresten Anderskouv, Morten Bjerager, Lars Ole Boldreel, Mads E Jelby, Lars Stemmerik, Finn SurlykAbstract:The lithostratigraphy, calcareous nannofossil biostratigraphy, carbon- and oxygen-isotope stratigraphy and gamma-ray profile are presented for the Skaelskor-1 core, eastern Denmark. The correlation of carbon isotopes to Gubbio (Italy) and ODP Site 762C (Indian Ocean) provides the chronostratigrahical framework of the core through a tie to magnetostratigraphy. Two new carbon-isotope excursions are defined for the uppermost Maastrichtian of the core and prove useful for long-distance correlation. Twenty stratigraphic tie-points are used for correlation of the upper Campanian–Maastrichtian interval by combining carbon-isotope and gamma-ray variations. Significant dissimilarities in the gamma-ray profiles of the Danish Basin cores preclude the sole use of this tool for basin-scale correlations. Bulk oxygen-isotopes and semi-quantitative abundance changes in the warm-water calcareous nannofossil Watznaueria barnesiae and the cool-water Kamptnerius magnificus highlight the following past changes in sea-surface temperatures (SSTs): relatively warm late Campanian SSTs, cooling across the Campanian–Maastrichtian boundary and through the early Maastrichtian, warming across the early–late Maastrichtian transition, cooling in the late Maastrichtian, intense warming in the latest Maastrichtian chron C29r, followed by a very short episode of cooling immediately before the Cretaceous–Palaeogene boundary. The late Campanian–Maastrichtian evolution in sea water temperatures inferred from the Danish Basin is similar to that delineated at tropical latitude oceanic sites.
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Astronomical calibration of upper Campanian–Maastrichtian carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C): Implication for the age of the Campanian–Maastrichtian boundary
Palaeogeography Palaeoclimatology Palaeoecology, 2012Co-Authors: Nicolas Thibault, Silvia Gardin, Bruno Galbrun, Dorothée Husson, Rikke Harlou, Emilia Huret, Fabrice MinolettiAbstract:Abstract An integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and δ13C stratigraphy is established for the upper Campanian–Maastrichtian of ODP Hole 762C (Exmouth Plateau, Northwestern Australian margin). Bulk-carbonate δ13C events and nannofossil bio-events have been recorded and plotted against magnetostratigraphy, and provided absolute ages using the results of the cyclostratigraphic study and the recent astronomical calibration of the Maastrichtian. Thirteen carbon-isotope events and 40 nannofossil bio-events are recognized and calibrated with cyclostratigraphy, as well as 14 previously published foraminifer events, thus constituting a solid basis for large-scale correlations. Results show that this site is characterized by a nearly continuous sedimentation from the upper Campanian to the K-Pg boundary, except for a 500 kyr gap in magnetochron C31n. Correlation of the age-calibrated δ13C profile of ODP Hole 762C to the δ13C profile of the Tercis les Bains section, Global Stratotype Section and Point of the Campanian–Maastrichtian boundary (CMB), allowed a precise recognition and dating of this stage boundary at 72.15 ± 0.05 Ma. This accounts for a total duration of 6.15 ± 0.05 Ma for the Maastrichtian stage. Correlation of the boundary level with northwest Germany shows that the CMB as defined at the GSSP is ~ 800 kyr younger than the CMB as defined by Belemnite zonation in the Boreal realm. ODP Hole 762C is the first section to bear at the same time an excellent recovery of sediments throughout the upper Campanian–Maastrichtian, a precise and well-defined magnetostratigraphy, a high-resolution record of carbon isotope events and calcareous plankton biostratigraphy, and a cyclostratigraphic study tied to the La2010a astronomical solution. This section is thus proposed as an excellent reference for the upper Campanian–Maastrichtian in the Indian Ocean.
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Bio-magnetochronology for the upper Campanian - Maastrichtian from the Gubbio area, Italy: new results from the Contessa Highway and Bottaccione sections
Newsletters on Stratigraphy, 2012Co-Authors: Silvia Gardin, Nicolas Thibault, Bruno Galbrun, Rodolfo Coccioni, Isabella Premoli-silvaAbstract:A new bio-chronostratigraphic framework is presented for the upper Campanian - Maastrichtian pelagic sediments of the Gubbio area (Bottaccione and Contessa Highway sections, Italy). New planktonic foraminiferal (FO of P. hantkeninoides), calcareous nannofossil (FO of M. prinsii, base acme of M. murus) and magnetostratigraphic data are provided and integrated to construct an age-depth curve based on the recent astronomical calibration of the late Campanian - Maastrichtian magnetic polarity time scale (Husson, D., Galbrun, B., Laskar, J., Hinnov, L. A., Thibault, N., Gardin, S., Locklair, R. E., 2011. Astronomical calibration of the Maastrichtian, Late Cretaceous. Earth and Planetary Science Letters 305, 328-340). All bio-horizons recorded in both sections fall on or are very close to the Line of Correlation (LOC), which testifies to the reliability of biochronologic studies in the Umbria-Marche basin. The proposed age model allows to estimate the sedimentation rates and the ages of calcareous nannofossil and planktonic foraminiferal bio-horizons in both sections. Also, it provides an excellent late Campanian - Maastrichtian reference for sections in the Umbria-Marche area and the entire Tethys. Due to the presence of a ∼425 kyr-long hiatus in Chron C31n of the Bottaccione section, the Contessa Highway section constitutes a more complete late Campanian - Maastrichtian reference for bio-magnetochronology in the Tethyan realm.
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Astronomical calibration of upper Campanian–Maastrichtian carbon isotope events and calcareous plankton biostratigraphy in the Indian Ocean (ODP Hole 762C): Implication for the age of the Campanian–Maastrichtian boundary
Palaeogeography Palaeoclimatology Palaeoecology, 2012Co-Authors: Nicolas Thibault, Silvia Gardin, Bruno Galbrun, Dorothée Husson, Rikke Harlou, Emilia Huret, Fabrice MinolettiAbstract:International audienceAn integrated framework of magnetostratigraphy, calcareous microfossil bio-events, cyclostratigraphy and δ13C stratigraphy is established for the upper Campanian–Maastrichtian of ODP Hole 762C (Exmouth Plateau, Northwestern Australian margin). Bulk-carbonate δ13C events and nannofossil bio-events have been recorded and plotted against magnetostratigraphy, and provided absolute ages using the results of the cyclostratigraphic study and the recent astronomical calibration of the Maastrichtian. Thirteen carbon-isotope events and 40 nannofossil bio-events are recognized and calibrated with cyclostratigraphy, as well as 14 previously published foraminifer events, thus constituting a solid basis for large-scale correlations. Results show that this site is characterized by a nearly continuous sedimentation from the upper Campanian to the K-Pg boundary, except for a 500 kyr gap in magnetochron C31n. Correlation of the age-calibrated δ13C profile of ODP Hole 762C to the δ13C profile of the Tercis les Bains section, Global Stratotype Section and Point of the Campanian–Maastrichtian boundary (CMB), allowed a precise recognition and dating of this stage boundary at 72.15 ± 0.05 Ma. This accounts for a total duration of 6.15 ± 0.05 Ma for the Maastrichtian stage. Correlation of the boundary level with northwest Germany shows that the CMB as defined at the GSSP is ~ 800 kyr younger than the CMB as defined by Belemnite zonation in the Boreal realm. ODP Hole 762C is the first section to bear at the same time an excellent recovery of sediments throughout the upper Campanian–Maastrichtian, a precise and well-defined magnetostratigraphy, a high-resolution record of carbon isotope events and calcareous plankton biostratigraphy, and a cyclostratigraphic study tied to the La2010a astronomical solution. This section is thus proposed as an excellent reference for the upper Campanian–Maastrichtian in the Indian Ocean
Shamar Chin - One of the best experts on this subject based on the ideXlab platform.
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Calcareous nannofossil response to Late Cretaceous climate change in the eastern Tethys (Zagros Basin, Iran).
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Mohammad J. Razmjooei, Nicolas Thibault, Anoshiravan Kani, Jaume Dinarès-turell, Emmanuelle Pucéat, Shamar ChinAbstract:Coniacian to Maastrichtian changes in calcareous nannofossil assemblages have been investigated in the eastern Tethyan Shahneshin section (central Zagros Basin, Iran). The nannofossil assemblages are mainly composed of Watznaueria spp. (avg. 54%), Retecapsa spp (avg. 7.9%), Cribrosphaerella ehrenbergii (avg. 7.7%) and Micula spp. (avg. 5.7%). Throughout the late Campanian, there is a trend to lower abundances in Watznaueria spp. together with increasing abundances of C. ehrenbergii and Arkhangelskiella cymbiformis, which are considered in this basin as the main cool-water taxa. Our results reveal that, despite a diagenetic impact on calcareous nannoflora, a number of primary paleoecological trends are preserved which depict well features of the progressive Late Cretaceous cooling. The first pronounced cooling episode occurs across the late Campanian to early Maastrichtian. The onset of pronounced cooling in the eastern Tethys appears to occur prior to the Campanian/Maastrichtian Boundary event (CMBE) δ13C negative excursion, in contrast with the Boreal realm where pronounced cooling only occurs in the early Maastrichtian, postdating the onset of the CMBE. The coincidence of this earlier cooling in the Zagros Basin with an interval characterized by a significant increase in benthic foraminifera suggests an amplified response of the assemblage due to a change to shallower environments. Hence, the late Campanian calcareous nannofossil assemblage turnover in central Zagros is either a response to an early cooling trend in the eastern Tethys or to sea-level fall or both. The mid-Maastrichtian warming and late Maastrichtian cooling episodes are also delineated in the nannofossil assemblage of Shahneshin and likely correlate with similar episodes in the Boreal Realm.
Mohammad J. Razmjooei - One of the best experts on this subject based on the ideXlab platform.
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Calcareous nannofossil response to Late Cretaceous climate change in the eastern Tethys (Zagros Basin, Iran).
Palaeogeography Palaeoclimatology Palaeoecology, 2020Co-Authors: Mohammad J. Razmjooei, Nicolas Thibault, Anoshiravan Kani, Jaume Dinarès-turell, Emmanuelle Pucéat, Shamar ChinAbstract:Coniacian to Maastrichtian changes in calcareous nannofossil assemblages have been investigated in the eastern Tethyan Shahneshin section (central Zagros Basin, Iran). The nannofossil assemblages are mainly composed of Watznaueria spp. (avg. 54%), Retecapsa spp (avg. 7.9%), Cribrosphaerella ehrenbergii (avg. 7.7%) and Micula spp. (avg. 5.7%). Throughout the late Campanian, there is a trend to lower abundances in Watznaueria spp. together with increasing abundances of C. ehrenbergii and Arkhangelskiella cymbiformis, which are considered in this basin as the main cool-water taxa. Our results reveal that, despite a diagenetic impact on calcareous nannoflora, a number of primary paleoecological trends are preserved which depict well features of the progressive Late Cretaceous cooling. The first pronounced cooling episode occurs across the late Campanian to early Maastrichtian. The onset of pronounced cooling in the eastern Tethys appears to occur prior to the Campanian/Maastrichtian Boundary event (CMBE) δ13C negative excursion, in contrast with the Boreal realm where pronounced cooling only occurs in the early Maastrichtian, postdating the onset of the CMBE. The coincidence of this earlier cooling in the Zagros Basin with an interval characterized by a significant increase in benthic foraminifera suggests an amplified response of the assemblage due to a change to shallower environments. Hence, the late Campanian calcareous nannofossil assemblage turnover in central Zagros is either a response to an early cooling trend in the eastern Tethys or to sea-level fall or both. The mid-Maastrichtian warming and late Maastrichtian cooling episodes are also delineated in the nannofossil assemblage of Shahneshin and likely correlate with similar episodes in the Boreal Realm.
Marcin Machalski - One of the best experts on this subject based on the ideXlab platform.
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late Maastrichtian cephalopods dinoflagellate cysts and foraminifera from the cretaceous paleogene succession at lechowka southeast poland stratigraphic and environmental implications
Cretaceous Research, 2016Co-Authors: Marcin Machalski, Zofia Dubicka, Danuta Peryt, Johan Vellekoop, Marian HarasimiukAbstract:Abstract The Lechowka section comprises the most complete Cretaceous–Paleogene (K-Pg) boundary succession in Poland and is among 29 sites worldwide with the youngest ammonite record. Here, cephalopods (ammonites and nautilids), organic-walled dinoflagellates (dinocysts) and foraminifera from the uppermost Maastrichtian interval are studied. In terms of ammonite biostratigraphy, the upper Maastrichtian Hoploscaphites constrictus crassus Zone is documented up to a level 120 cm below the K-Pg boundary. There is no direct, ammonite-based evidence of the highest Maastrichtian H . constrictus johnjagti Zone. However, the predominance of the dinocyst marker taxon Palynodinium grallator suggests the presence of the equivalent of the uppermost Maastrichtian Thalassiphora pelagica Subzone, which is correlatable with the H. c. johnjagti ammonite Zone. The planktonic foraminiferal assemblage is coeval with that from the H. c. johnjagti Zone as well. These data indicate that the top of the Maastrichtian at Lechowka is complete within the limits of biostratigraphic resolution, albeit slightly condensed. The dinocyst and foraminiferal assemblages are dominated by taxa that are characteristic of high-energy, marginal marine environments. A reduction in test size among the calcareous epifaunal benthic foraminifera is observed at a level 50 cm below the K-Pg boundary, which is possibly related to environmental stress associated with Deccan volcanism.
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Terminal Maastrichtian Ammonites from Turkmenistan, Central Asia
Acta Palaeontologica Polonica, 2012Co-Authors: Marcin Machalski, John W. M. Jagt, Alexander S. Alekseev, Elena A. Jagt-yazykovaAbstract:A complete uppermost Maastrichtian—Danian succession in the Sumbar River section, western Kopet Dagh (southwest Turkmenistan, Central Asia), constitutes one of the few instances in the world where the fossil record of the last ammonites can be directly positioned with respect to the iridium-rich, impact-related clay layer, which defines the Cretaceous—Paleogene (K—Pg) boundary. Two ammonite taxa, Baculites cf. vertebralis and Hoploscaphites constrictus johnjagti, range up to a level directly beneath the K—Pg boundary clay in the Sumbar River section. Thus, these two forms probably survived until the very end of the Maastrichtian in the western Kopet Dagh area. The terminal Maastrichtian ammonite records from the Sumbar River area represent the southeasternmost occurrences of these essentially Boreal taxa.
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The highest records of North American scaphitid ammonites in the European Maastrichtian (Upper Cretaceous) and their stratigraphic implications
Acta Geologica Polonica, 2007Co-Authors: Marcin Machalski, John W. M. Jagt, Neil H LandmanAbstract:The uppermost lower to upper Maastrichtian records of North American scaphitid ammonites in Europe are discussed in terms of taxonomy and significance for transatlantic correlation. A previous record of a U.S. Western Interior scaphitid ammonite, Jeletzkytes dorfi , from the lower part of the upper Maastrichtian in northeast Belgium, is demonstrated to have been based on specimens which reveal features typical of the indigenous European Hoploscaphites constrictus lineage. However, one of the individuals in this collection combines distinct mid-ventral swellings, characteristic of the H . constrictus stock, with irregular flank ornament, typical of J. dorfi . It is speculated that this specimen may be a product of interspecies hybridization. Hoploscaphites sp., allied to H. nicolletii or to H. comprimus , previously known only from the U.S. Western Interior, is recorded from the lower upper Maastrichtian of Austria, and Discoscaphites gulosus , hitherto regarded to be confined to the U.S. Western Interior, Gulf Coast, and Atlantic Seaboard, has been recognised in the upper Maastrichtian of Bulgaria. Additionally, poorly preserved material referred to as Discoscaphites ? sp. is recorded from the uppermost lower Maastrichtian of Denmark, and from the upper Maastrichtian of southern Sweden. These records of scaphitids support earlier conclusions that the base of the European upper Maastrichtian roughly corresponds to the base of the Hoploscaphites birkelundae Zone in the U.S. Western Interior.
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The youngest Maastrichtian ammonite faunas from Poland and their dating by scaphitids
Cretaceous Research, 2005Co-Authors: Marcin MachalskiAbstract:Abstract The youngest Maastrichtian ammonite faunas from Poland are discussed in terms of their taxonomic composition, dating and significance for the end-Cretaceous extinction debate. The fauna from the top of the classic Upper Maastrichtian succession at Nasilow comprises Baculites spp. (including B. anceps ), Hoploscaphites constrictus subsp. A, Menuites terminus , Pachydiscus jacquoti and Sphenodiscus binckhorsti . The commonest components of this fauna, i.e. Baculites spp. and H. constrictus subsp. A, occur also at the top of the Maastrichtian at Bochotnica, Prawiedniki, Metow and Klimusin. A distinctive fauna, identified for the first time in Poland, is present at the top of the Upper Maastrichtian at Melgiew. It is composed of H. constrictus subsp. B and Baculites sp. In the standard Upper Maastrichtian Boreal succession at Stevns Klint, Denmark, H. constrictus subsp. A is present in the white chalk and is replaced by H. constrictus subsp. B in the overlying Grey Chalk. Details of the evolutionary succession of H. constrictus as recorded at Stevns Klint allow for relative dating of the ammonite occurrences in Poland. The youngest ammonite faunas from Nasilow, Bochotnica, Prawiedniki, Metow and Klimusin, which include H. constrictus subsp. A are considered to be older than the ammonite fauna from the Grey Chalk in Denmark. In contrast, the topmost Maastrichtian fauna from Melgiew, with H. constrictus subsp. B, is thought to be coeval with that from the top of the Grey Chalk. The abundant occurrence of ammonite specimens at the top of the Maastrichtian successions at Stevns Klint and Melgiew supports some earlier views that the Boreal ammonites did not suffer any perturbations immediately prior to the end of the Cretaceous.
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Giant scaphitid ammonites from the Maastrichtian of Europe
1999Co-Authors: John W. M. Jagt, William James Kennedy, Marcin MachalskiAbstract:Giant scaphitid ammonites from the Maastrichtian of Europea have generally been assigned to Acanthoscaphites NOWAK, 1911. Prior to the present study, this genus comprised five species: A. tridens (KNER, 1848), A. varians (ŁOPUSKI, 1911), A. verneuilianus (D'ORBIGNY, 1841), A. sp. of KENNEDY (1987) and A. sp. of KENNEDY & CHRISTENSEN (1997). Of the first-named taxon, material from Aachen-Schneeberg of Early Maastrichtian age, including the specimen illustrated by HOLZAPFEL (1887-89) long thought to have been lost, is described. Recently collected topotype material from Kazimierz Dolny, and from Rejowiec (Poland), of latest Maastrichtian age (Belemnella karimiroviensis Zone), allows A. varians to be revised. Specimens from the late Early and early Late Maastrichtian of NW Europe, assigned to A. varians, differ consistently in details of ornament, and are assigned to a new subspecies, A. v. blaszkiewiczi n. subsp. Style of ribbing and tuberculation of the varians stock differs from that of A. tridens to such an extent that a new subgenus, Euroscaphites n. subgen., is erected, with varians as type species. The Late Maastrichtian Acanthoscaphites verneuilianus, only known from phragmocones, is provisionally assigned to the new subgenus. The other two species previously referred to Acanthoscaphites, viz. A. sp. of KENNEDY (1987) and A. sp. of KENNEDY & CHRISTENSEN (1997), both of Late Maastrichtian age, cannot be assigned confidently to either subgenus.
