Ihre Phylogenie und biostratigraphische Anwendung mit Hauptaugenmerk auf die Unterkreide des nordamerikanischen Western Interior Vorlandbeckens

Ostracods (aquatic microcrustaceans with a calcified, bivalved shell) are among the most common fossils in nonmarine deposits worldwide since the Middle-Late Jurassic. This dissertation deals with the taxonomy and systematics of Late Mesozoic nonmarine ostracods with emphasis on the Lower Cretaceous of the North American Western Interior Basin, and their utilization and application. The taxonomic revision of the genera Theriosynoecum Branson 1936 and Cypridea Bosquet 1852, particularly of taxa from the Lakota and Cedar Mountain formations and conducted from the perspective of application, resulted in a breakthrough in the consideration of their utility. Inconsistent taxonomy was determined to have been the main reason hampering their application. The understanding and verification that these ostracods are not as endemic to North America as erstwhile believed in combination with an upgraded taxonomic concept, is the key to their successful manifold application and the interpretation of their paleobiology, evolution, paleobiogeography, and paleoecology. The results of the revision signify considerable progress in the taxonomy and systematics of these ostracod groups, the supraregional correlation and Early Cretaceous North American biostratigraphy based on their representatives, and the assessment of the further application potential of the latter in the basin as well as worldwide. The timespan represented by the hiatus between nonmarine Upper Jurassic (to Early Berriasian?) and unconformably overlying Lower Cretaceous deposits throughout the North American Western Interior foreland basin has been under discussion for the entire 20th century and remains controversial to date. Ostracod correlations to well dated western European strata (Purbeck/Wealden of England and “German Wealden” of NW-Germany), mainly based on representatives of Cypridea, strongly suggest a much higher maximum age for some Lower Cretaceous formations of the Western Interior foreland basin, i.e., Berriasian to Early Valanginian instead of Barremian or Aptian. These biostratigraphic results have considerable consequences on a wide scope of basin-related geologic and paleontologic topics. The ostracods also help to expedite our understanding of animal (e.g. early mammals and dinosaurs) and plant (angiosperms) evolution on the North American continent. The research progress marks the advent of a refined ostracod-based biostratigraphy in the nonmarine Lower Cretaceous of the WI Interior Basin and the revival of the variegated application of these ostracods on regional to global scale.Ostrakoden (aquatische Kleinkrebse mit einer verkalkten, zweiklappigen Schale) gehören seit dem mittleren bis späten Jura zu den häufigsten Fossilien in nichtmarinen Ablagerungen weltweit. Die vorliegende Dissertation beschäftigt sich mit der Taxonomie und Systematik nichtmariner Ostrakoden des späteren Mesozoikums mit Schwerpunkt auf die Unterkreide des nordamerikanischen Western Interior Vorlandbeckens und ihrer Nutzbarmachung und Anwendung. Die anwendungsorientiert durchgeführte taxonomische Revision der nichtmarinen mesozoischen Ostrakodengattungen Theriosynoecum Branson 1936 und Cypridea Bosquet 1852, speziell von ausgewählten Taxa aus unterkretazischen Ablagerungen des nordamerikanischen Western Interior Vorlandbeckens (Lakota Formation und Cedar-Mountain Formation) hat zu deutlichen Fortschritten bezüglich der Einschätzung ihrer Verwendbarkeit geführt. Als Haupthindernis für eine Anwendung dieser Ostrakoden wurde ihre uneinheitliche Taxonomie ermittelt. Verständnis und Nachweis, dass die nichtmarinen Unterkreide- Ostrakoden Nordamerikas nicht so stark endemisch sind, wie früher angenommen, verbunden mit einem verbesserten taxonomischen Konzept, sind der Schlüssel zu ihrer vielfältigen Anwendung und der Interpretation ihrer Paläobiologie, Evolution, Paläobiogeographie und Paläoökologie. Die Ergebnisse der Revision bedeuten erhebliche Fortschritte in Taxonomie und Systematik dieser Ostrakodengruppen, überregionaler Korrelation und unterkretazischen Biostratigraphie Nordamerikas, basierend auf ihren Vertretern und der Beurteilung deren weiteren Anwendungspotentials im Vorlandbecken sowie auch weltweit. Über die Dauer der Zeitspanne, die im gesamten nordamerikanischen Western Interior Becken durch einen Hiatus zwischen Oberjura- (bis Unter- Berriasium?) und diskordant überlagernden Unterkreide-Ablagerungen repräsentiert ist, wurde durch das gesamte zwanzigste Jahrhundert debattiert. Sie ist bis heute umstritten. Auf Ostrakoden basierende Korrelationen mit gut datierten westeuropäischen Schichten (Purbeck/Wealden von England und „Wealden“ von Nordwestdeutschland), hauptsächlich mittels Vertretern von Cypridea, deuten nachhaltig auf ein wesentlich höheres Maximalalter einiger Unterkreideformationen des Vorlandbeckens hin, das heißt, Berriasium bis frühes Valanginium anstatt Barremium oder Aptium. Diese biostratigraphischen Ergebnisse haben erhebliche Auswirkungen auf eine große Bandbreite von beckenbezogenen geologischen und paläontologischen Themenfeldern. Die Ostrakoden helfen zusätzlich, unser Verständnis der Evolution von Tieren (z.B. Mammalia und Dinosauria) und Pflanzen (Angiospermen) auf dem nordamerikanischen Kontinent zu verbessern. Der Forschungsfortschritt leitet das Aufkommen einer weiterentwickelten Ostrakoden-Biostratigraphie in der nichtmarinen Unterkreide des Western Interior Vorlandbeckens ein und die Neubelebung der vielfältigen Anwendung der betreffenden Ostrakoden im regionalen und globalen Maßstab

An introduction to causes and consequences of Cretaceous sea-level changes (IGCP 609)

The International Geoscience Programme Project IGCP 609 addressed correlation, causes and consequences of short-term sea-level fluctuations during the Cretaceous. Processes causing several ka to several Ma (third- to fourth-order) sea-level oscillations during the Cretaceous are so far poorly understood. IGCP 609 proved the existence of sea-level cycles during potential ice sheet-free greenhouse to hothouse climate phases. These sea-level fluctuations were most probably controlled by aquifer-eustasy that is altering land-water storage owing to groundwater aquifer charge and discharge. The project investigated Cretaceous sea-level cycles in detail in order to differentiate and quantify both short- and long-term records based on orbital cyclicity. High-resolution sea-level records were correlated to the geological timescale resulting in a hierarchy of sea-level cycles in the longer Milankovitch band, especially in the 100 ka, 405 ka, 1.2 Ma and 2.4 Ma range. The relation of sea-level highs and lows to palaeoclimate events, palaeoenvironments and biota was also investigated using multiproxy studies. For a hothouse Earth such as the mid-Cretaceous, humid-arid climate cycles controlling groundwater-related sea-level change were evidenced by stable isotope data, correlation to continental lake-level records and humid-arid weathering cycles

Investigating Mesozoic Climate Trends and Sensitivities With a Large Ensemble of Climate Model Simulations

The Mesozoic era (∼252 to 66 million years ago) was a key interval in Earth's evolution toward its modern state, witnessing the breakup of the supercontinent Pangaea and significant biotic innovations like the early evolution of mammals. Plate tectonic dynamics drove a fundamental climatic transition from the early Mesozoic supercontinent toward the Late Cretaceous fragmented continental configuration. Here, key aspects of Mesozoic long-term environmental changes are assessed in a climate model ensemble framework. We analyze so far the most extended ensemble of equilibrium climate states simulated for evolving Mesozoic boundary conditions covering the period from 255 to 60 Ma in 5 Myr timesteps. Global mean temperatures are generally found to be elevated above the present and exhibit a baseline warming trend driven by rising sea levels and increasing solar luminosity. Warm (Triassic and mid-Cretaceous) and cool (Jurassic and end-Cretaceous) anomalies result from pCO2 changes indicated by different reconstructions. Seasonal and zonal temperature contrasts as well as continental aridity show an overall decrease from the Late Triassic-Early Jurassic to the Late Cretaceous. Meridional temperature gradients are reduced at higher global temperatures and less land area in the high latitudes. With systematic sensitivity experiments, the influence of paleogeography, sea level, vegetation patterns, pCO2, solar luminosity, and orbital configuration on these trends is investigated. For example, long-term seasonality trends are driven by paleogeography, but orbital cycles could have had similar-scale effects on shorter timescales. Global mean temperatures, continental humidity, and meridional temperature gradients are, however, also strongly affected by pCO2

Middle to late Eocene paleoenvironmental changes in a marine transgressive sequence from the northern Tethyan margin (Adelholzen, Germany)

The northern Tethyan margin is a key region for determining environmental changes associated with the collision of continental and oceanic tectonic plates and Alpine orogeny. Herein we investigated Middle to Late Eocene neritic to bathyal sediments deposited during an interval of unstable climatic conditions. In order to quantify paleoenvironmental changes, we developed a detailed age model based on biozonations of planktic foraminifera, calcareous nannoplankton, and larger benthic foraminifera. The section at Adelholzen covers the almost complete Lutetian Stage (calcareous nannoplankton zones NP15a-16, planktic foraminifera zones E8-11, shallow benthic (foraminifera) zones SBZ13-15) and large parts of the Priabonian Stage (NP18-20, E14/15), while the intermediate Bartonian Stage (NP17) is completely missing. Foraminiferal, calcareous nannoplankton, and macrofossil assemblages were analyzed for changes in paleo-water depth, mixing and stratification, paleo-primary productivity (pPP), food supply, and bottom water oxygenation. Paleo-water depth estimates range from 50 m (middle neritic, early Lutetian) to nearly 500 m (upper bathyal, late Priabonian). The combination of assemblage composition, planktic and benthic foraminiferal accumulation rates, and derived parameters (carbon-flux to sea floor, pPP) enabled us to identify a series of distinct paleoceanographic events of at least regional significance. Such events are characterized by considerable changes in primary productivity or reduced bottom water ventilation. Calculated pPP-values indicate oligotrophic conditions throughout

Site selective C–H functionalization of Mitragyna alkaloids reveals a molecular switch for tuning opioid receptor signaling efficacy

Mitragynine (MG) is an indole alkaloid from kratom plant that binds opioid receptors and as such presents a scaffold for the development of atypical opioid receptor modulators. Here, the authors report a synthetic method for selective functionalization of the C11 position of MG, and show that this position is essential for fine-tuning opioid receptor signaling efficacy

Aquifer-eustasy as the main driver of short-term sea-level fluctuations during Cretaceous hothouse climate phases

A review of short-term (<3 myr: c. 100 kyr to 2.4 myr) Cretaceous sea-level fluctuations of several tens of metres indicates recent fundamental progress in understanding the underlying mechanisms for eustasy, both in timing and in correlation. Cretaceous third- and fourth-order hothouse sea-level changes, the sequence-stratigraphic framework, are linked to Milankovitch-type climate cycles, especially the longer-period sequence-building bands of 405 kyr and 1.2 myr. In the absence of continental ice sheets during Cretaceous hothouse phases (e.g. Cenomanian–Turonian), growing evidence indicates groundwater-related sea-level cycles: (1) the existence of Milankovitch-type humid-arid climate oscillations, proven via intense humid weathering records during times of regression and sea-level lowstands; (2) missing or inverse relationships of sea-level and the marine δ18O archives, i.e. the lack of a pronounced positive excursion, cooling signal during sea-level lowstands; and (3) the anti-phase relationship of sea and lake levels, attesting to high groundwater levels and charged continental aquifers during sea-level lowstands. This substantiates the aquifer-eustasy hypothesis. Rates of aquifer-eustatic sea-level change remain hard to decipher; however, reconstructions range from a very conservative minimum estimate of 0.04 mm a−1 (longer time intervals) to 0.7 mm a−1 (shorter, probably asymmetric cycles). Remarkably, aquifer-eustasy is recognized as a significant component for the Anthropocene sea-level budget

A new diverse charophyte flora and biozonation of the Eocene bauxite cover-sequence at Gant (Vertes Hills, Hungary)

A diverse Eocene charophyte flora from a section at Gant (Vertes Hills), Transdanubian Central Range, north-western Hungary, provides significant new information building on previous studies based only on sub-surface data published from the mid-twentieth century. This newly acquired material facilitates the taxonomic revision and emendation of the species Raskyella peckii and thereby defines a new anagenetic lineage based on three successive varieties that were formerly considered as separate species or subspecies: Raskyella peckii var. peckii (early Lutetian-early Bartonian), Raskyella peckii var. caliciformis (early Bartonian), and Raskyella peckii var. vadaszii (late Bartonian). Based on this lineage, we propose a new local charophyte biozonation that consists of a 'Raskyella peckii Superzone' (Lutetian-Bartonian), sub-divided into three successive charophyte partial range zones: the 'Raskyella peckii peckii Zone' (Lutetian-lower-most Bartonian) characterized by an assemblage of R. peckii peckii, Gyrogona caelata forma caelata, G. caelata forma monolifera and Nitellopsis (Tectochara) aff. palaeohungarica, the 'Raskyella peckii caliciformis Zone' (lower Bartonian) characterized by the assemblage of R. peckii var. caliciformis, G. caelata forma caelata, G. caelata forma monolifera, G. caelata forma baccata, Nitellopsis (Tectochara) aff. palaeohungarica and Chara media, and the 'Raskyella peckii vadaszii Zone' (upper Bartonian) characterized by R. peckii var. vadaszii, G. caelata forma bicincta, G. caelata forma baccata, G. caelata forma fasciata, G. tuberosa, Psilochara polita, Psilochara sp., Chara media and Chara subcylindrica. Future research may show the new local biozonation as applicable to the whole of Europe and complementary to the current European charophyte biozonation. Our results show that the sequences from Gant, which were previously regarded as upper mid-Eocene (upper Lutetian-lower Bartonian) in age, appear to represent a longer chronostratigraphic interval: lower Lutetian to upper Bartonian. Our chronostratigraphic results imply a longer and more stepwise Eocene major transgression in the Transdanubian Central Range than previously thought