The internal division of the Pliocene Lillo Formation : correlation between Cone Penetration Tests and lithostratigraphic type sections

The highly fossiliferous Lillo Formation (Pliocene, southern margin North Sea Basin) is formally subdivided in five lithostratigraphical members. While these members are generally relatively easily identifiable in outcrops, they are much more difficultly identifiable in boreholes, hampering geological studies. In the Port of Antwerp area, however, an already existing and dense network of Cone Penetration Tests (CPTs) provides an alternative and additional tool for the recognition of the different lithologies in the Lillo Formation. CPTs reveal a clear geotechnical threefold division of the Formation. The lower and upper intervals, herein named CPT units Li-A and Li-C respectively, are characterized by high q(c) and low R-f values and correspond to shell-bearing, sandy lithologies. CPT unit Li-A can further be divided in a shelly basal subunit Li-Al and an overlying sandy subunit Li-A2. CPT units Li-A and Li-C are separated by CPT unit Li-B characterized by low q(c) and high R-f values which correspond to more clayey lithologies. Four CPTs selected in close vicinity of four well-documented outcrops, some of them being formal stratotypes for the Formation and some of its members, allowed to correlate the geotechnical units with detailed lithological descriptions as well as the formal stratigraphy. CPT unit Li-Al can be correlated to the Luchtbal Member and the basal part of the Oorderen Member, whereas unit Li-A2 corresponds to the superjacent sandy body of the Oorderen Member. The overlying CPT units Li-B and Li-C seem to correlate differently in different outcrops to the clayey upper part of the Oorderen Member, Kruisschans and Merksem Members. This inconsistency hinders any direct correlation between the geotechnical stratigraphy and lithostratigraphy of the Members of the Lillo Formation. Further research is needed to find the reason(s) for this inconsistency

The Diest Formation : a review of insights from the last decades

Research conducted since the 1960s on the upper Miocene Diest Formation in NE Belgium is reviewed and integrated. Their lithology unites the deposits of the glauconiferous Diest Sand in one formation, though biozones and internal sedimentary structures strongly suggest the formation may agglomerate the deposits of two separate, successive sedimentary cycles. The lowermost cycle is thought to have deposited the "Hageland Diest sand" during the early or middle Tortonian. It contains the Diest Sand in the main outcrop area in Hageland, Zuiderkempen and central Limburg, and probably also the Deurne Member near the city of Antwerpen. It furthermore includes the lower part of the Dessel Member in the central Kempen and in the Belgian part of the Roer Valley Graben (RVG). The Hageland Diest cycle represents the infill of a large tidal inlet tributary to the southern North Sea bight, then situated over the southern Netherlands and the Lower Rhine embayment. The Hageland Diest sand has the composition of a marine deposit, yet the confined area of occurrence and the presence of tens of metres deep incisions at the base, set it apart. The confinement of the embayment, strong tides and a steady supply of coastal-marine sand arc invoked as the main driving forces that resulted in the distinctive geometry and internal architecture of the unit. The upper cycle is associated with the "Kempen Diest sand", which is found in the subsurface of the RVG and the Noorderkempen. It has a late Tortonian to earliest Messinian age with progressively younger ages occurring to the NW. It encompasses the upper part of the Dessel Member and the overlying, coarser Diest Sand, and correlates to most or all of the thickly developed Diessen Formation in The Netherlands. It is the deposit of a prograding marine delta, containing both marine components and continental components fed by the palaeo-Meuse/Rhine river mouths. Accommodation space kept increasing during deposition, due to subsidence of the deposition area, especially inside the RVG but also in the Noorderkempen. Although there is a fair consensus on the above, many concrete points about the geometry and depositional history of the Diest Formation and even a definitive decision on its single or dual character remain to be sorted out. In addition, this review excludes the Flemish Hills sand and the Gruitrode Member from the Diest Formation

Devonian and Carboniferous dendroid graptolites from Belgium and their significance for the taxonomy of the Dendroidea

peer reviewedDevonian and Carboniferous dendroid graptolites from Belgium are evaluated and partly revised. New finds in two different stratigraphic intervals of the ‘Carrière de Lompret’, an active quarry exploiting Frasnian limestones and shales east of Frasnes-lez-Couvin, allow the identification of Callograptus sp. and Dictyonema fraiponti, both belonging to the dendroid family Acanthograptidae. The relatively high diversity of the dendroid graptolite fauna from the Viséan Marbre noir de Denée, one of the few Carboniferous graptolite faunas in the world, can be shown to be based on astogenetic and preservational aspects. Nearly all known specimens can be included in the highly variable Dictyonema fraiponti, a fan-shaped large dendroid species with complex stipes formed from tubular thecae, possessing simple to complex bridges connecting adjacent stipes. Some of the graptolite material is well preserved and provides important information on the tubarium construction of Devonian to Carboniferous dendroid graptolites and, thus, is highly significant for a taxonomic and phylogenetic understanding of the youngest dendroid graptolite faunas worldwide. The genera Callograptus and Ptiograptus are revised based on their type species (Callograptus elegans from Quebec, Canada; Ptiograptus percorrugatus from the Silurian or Devonian of Kentucky, USA) and referred to the Acanthograptidae

Sclerochronological evidence of pronounced seasonality from the late Pliocene of the southern North Sea basin and its implications

Oxygen isotope (δ18O) sclerochronology of benthic marine molluscs provides a means of reconstructing the seasonal range in seafloor temperature, subject to use of an appropriate equation relating shell δ18O to temperature and water δ18O, a reasonably accurate estimation of water δ18O, and due consideration of growth-rate effects. Taking these factors into account, δ18O data from late Pliocene bivalves of the southern North Sea basin (Belgium and the Netherlands) indicate a seasonal seafloor range a little smaller than now in the area. Microgrowth-increment data from Aequipecten opercularis, together with the species composition of the bivalve assemblage and aspects of preservation, suggest a setting below the summer thermocline for all but the latest material investigated. This implies a higher summer temperature at the surface than on the seafloor and consequently a greater seasonal range. A reasonable (3 ∘C) estimate of the difference between maximum seafloor and surface temperature under circumstances of summer stratification points to seasonal surface ranges in excess of the present value (12.4 ∘C nearby). Using a model-derived estimate of water δ18O (0.0 ‰), summer surface temperature was initially in the cool temperate range (20 ∘C) before reverting to cool temperate values (in conjunction with shallowing and a loss of summer stratification). This pattern is in agreement with biotic-assemblage evidence. Winter temperature was firmly in the cool temperate range (<10 ∘C) throughout, contrary to previous interpretations. Averaging of summer and winter surface temperatures for the MPWP provides a figure for annual sea surface temperature that is 2–3 ∘C higher than the present value (10.9 ∘C nearby) and in close agreement with a figure obtained by averaging alkenone and TEX86 temperatures for the MPWP from the Netherlands. These proxies, however, respectively, underestimate summer temperature and overestimate winter temperature, giving an incomplete picture of seasonality. A higher annual temperature than now is consistent with the notion of global warmth in the MPWP, but a low winter temperature in the southern North Sea basin suggests regional reduction in oceanic heat supply, contrasting with other interpretations of North Atlantic oceanography during the interval. Carbonate clumped isotope (Δ47) and biomineral unit thermometry offer means of checking the δ18O-based temperatures

The upper Miocene Deurne Member of the Diest Formation revisited : unexpected results from the study of a large temporary outcrop near Antwerp International Airport, Belgium

A 5.50 m thick interval of fossiliferous intensely bioturbated heterogenous glauconiferous sand of the upper Miocene Diest Formation is documented from a very large temporary outcrop just southeast of Antwerp International Airport (northern Belgium), allowing to observe lateral variations over several hundreds of meters and to collect many vertebrate and invertebrate fossils. This paper documents observations on lithology, sedimentary and post-sedimentary structures, and discusses the results of the multi-proxy analyses of the sediment (granulometry, glauconite content, clay mineralogy, Fe content and Fe3+/Fe2+ ratios), the interpretation of the trace fossil assemblage and the sedimentary structures as well as of the large-scale samplings of micro-, meso- and macrofossils. We evidence that the Diest Formation in the Antwerp area consists of two different lithological entities, and that this twofold character can be extrapolated to all previously recorded Deurne Member outcrops. A revised lithostratigraphic scheme for the Diest Formation in the Antwerp area is proposed, with the new Borsbeek member at the base and a redefmed Deurne Member at the top

The fossil bivalve Angulus benedeni benedeni: A potential seasonally resolved stable-isotope-based climate archive to investigate Pliocene temperatures in the southern North Sea basin

Bivalves record seasonal environmental changes in their shells, making them excellent climate archives. However, not every bivalve can be used for this end. The shells have to grow fast enough so that micrometre- to millimetre-sampling can resolve sub-annual changes. Here, we investigate whether the bivalve Angulus benedeni benedeni is suitable as a climate archive. For this, we use ca. 3-million-year-old specimens from the Piacenzian collected from a temporary outcrop in the Port of Antwerp area (Belgium). The subspecies is common in Pliocene North Sea basin deposits, but its lineage dates back to the late Oligocene and has therefore great potential as a high-resolution archive. A detailed assessment of the preservation of the shell material by micro-X-ray fluorescence, X-ray diffraction, and electron backscatter diffraction reveals that it is pristine and not affected by diagenetic processes. Oxygen isotope analysis and microscopy indicate that the species had a longevity of up to a decade or more and, importantly, that it grew fast and large enough so that seasonally resolved records across multiple years were obtainable from it. Clumped isotope analysis revealed a mean annual temperature of 13.5±3.8°C. The subspecies likely experienced slower growth during winter and thus may not have recorded temperatures year-round. This reconstructed mean annual temperature is 3.5°C warmer than the pre-industrial North Sea and in line with proxy and modelling data for this stratigraphic interval, further solidifying A. benedeni benedeni's use as a climate recorder. Our exploratory study thus reveals that Angulus benedeni benedeni fossils are indeed excellent climate archives, holding the potential to provide insight into the seasonality of several major climate events of the past ∼25 million years in northwestern Europe

Late Cretaceous Ammonites from Tunisia: chronology and causes of their extinction and extrapolation to other areas.

This research focussed on achieving a better understanding of the evolutionary history and extinction of the ammonites, an extinct group of exclusively marine animals belonging to the Class Cephalopoda. Ammonites are the number one marine Mesozoic time clocks for geologists. Surprisingly enough, after a long history of being almost omnipresent in so many sediments, they vanished from the Earth s fossil record during the last ofthe big-five mass-extinctions life on our planet yet experienced. There are a lot of different and conflicting theories discussing the possible causes and mechanisms of mass-extinctions. Most of the controversies,however, primarily relate to the different possible interpretations of uncertainties caused by a biased sedimentary and palaeontological record. The present study is based on newly collected data from the thick, complete and well-exposed Upper Cretaceous sections of central Tunisia. The time span was narrowed down to the geological time periods Campanian andMaastrichtian, enabling to document the ultimate 18.5 million years of ammonite existence. In lithostratigraphical terms, this corresponds to the Abiod Formation (Assila, Haraoua, Mahdi, Akhdar, Gourbeuj, Ncham and Gouss Members) and lower part of the El Haria Formation (Mzita Marls andAïn Settara Marls). Four study areas were selected, from south to north: Kalaat Senan, Garn Halfaya, Ellès and El Kef. Several field campaigns were conducted in order to collect ammonites. All finds were placed in arefined stratigraphical and palaeo-ecological context. A collection of over 2000 specimens was gathered, and together with other accessible collections, the number of Campanian and Maastrichtian ammonites from Tunisia studied rose above 2350. Ammonites were found from within the top of the underlying Kef Formation to high within the Aïn Settara Marls. Theirdistribution, however, was highly unequal, with large parts of the studied interval covered by zero and low recovery rates. Three major types of preservation were observed, each with a different stratigraphical range and preserved set of taxonomic important characters. The ammonite fauna consists of 67 taxa, of which at least 6 are new to science, grouped into 11 families. Each taxon is described and figured in detail. The stratigraphical distribution of the different species led to construct an ammonite biostratigraphical scheme for the Campanian andMaastrichtian of Tunisia. It is integrated with the existing planktic foraminiferal and calcareous nannofossil zonations. In addition to that, cyclostratigraphical data allowed estimating the duration of the different zones and events. A detailed correlation and integration of the individual studied sections is accomplished. A revised correlation and integration of a published δ13C isotopic curve allowed a better correlation to Europe. Also, a comparison with European and Northern American biozonal schemes is established, and the positions of the chronostratigraphical boundaries are discussed. From an evolutionary point of view, the Tunisian Campanian to Maastrichtian ammonite fauna is diverse, with all four large Cretaceous suborderspresent till high up into the uppermost ammonite biozone, and thereforealmost up to the K/Pg boundary. Seemingly contradictory to old theorieson ammonite extinction, the highest diversity is found nearest to the K/Pg boundary. In addition to that, the uppermost Tunisian ammonite faunaseems by far the most diverse yet recognised uppermost Maastrichtian ammonite fauna of the entire world. Integrating all highest observed occurrences revealed that the observeddrop in species richness between 420.000 and 50.000 years prior to the K/Pg boundary, appearing from the literal reading of the data, was primarily related to collection failure rather than to true extinction. Thereremained, however, a gap of 50.000 years between the highest observedammonite and the boundary. A similar gap is present in all other K/Pg boundary sections in the world. A careful taphonomical investigation of the topmost metres of the Maastrichtian revealed slight changes, enlarging the possibility of collection failure, and therefore, this gap could not be directly related to an extinction event prior to the K/Pg boundary. It was concluded that the data of the present study, together with those from other sections, although in large part by indirect evidence, reveal that for the cause of the extinctions of the ammonites the finger has to be pointed to the instantaneous environmental perturbations generated by a large meteorite that struck the Earth about 65.95 million years ago near present day Mexico, Chicxulub!nrpages: XII + 220status: publishe

Shastasaurid ichthyosaurs and other lost critters from the French Rhaetian

Recent advances in the phylogeny and evolution of diversity of ichthyosaurs have recognized a smaller number of more intense turnovers compared to the previous understanding of their evolutionary history. One of these crucial turnovers occurred during the Late Triassic, when all ichthyosaur clades but a minor subset, the parvipelvians, went extinct. The timing and, hence, the severity of this event is however poorly understood and may have been protracted over the entire middle Norian–latest Rhaetian interval, more than 15 million years. The iconic, whale-sized shastasaurid ichthyosaurs are regarded as early victims of this turnover, disappearing by the middle Norian. In 1883, Henry Emile Sauvage (1842–1917), a famous French palaeontologist, described reptilian remains from a Rhaetian bonebed near Autun in eastern France. But this material was subsequently lost and disappeared from the literature. We have re-discovered most of this material in the fossil vertebrates collections of the Katholieke Universteit Leuven, Belgium. Reassessment of this material indicates the presence of very large shastasaurid ichthyosaurs (Ichthyosaurus rheticus, Rachitrema pellati [partim]), probable choristoderes (Actiosaurus gaudryi) and plesiosaurs (Plesiosaurus bibractensis). The occurrence of shastasaurids in Rhaetian strata is corroborated by recent findings in a new locality in southern France. This suggests that the final extinction of this important Triassic clade coincides with the rapid radiation of neoichthyosaurs, forming a short but extremely profound turnover that drastically impacted the evolutionary history of ichthyosaurs

&lt;i&gt;Oxyarietites boletzkyi&lt;/i&gt; n. gen., n. sp., nouveau genre et nouvelle espèce d&#039;ammonite dans le Sinémurien inférieur de Bourgogne (France) : un rare précurseur des morphologies oxycônes pour le Jurassique

L’une des toutes premières ammonites à coquille presque oxycône observée dans les séries fossilifères après la crise faunique de la limite Trias/Jurassique est décrite. Elle provient du Sinémurien inférieur (chronozone à Semicostatum ou à Turneri) de Bourgogne (Mavilly-Mandelot, Côte-d’Or, France). Cette nouvelle forme, Oxyarietites boletzkyi n. gen., n. sp., possède une coquille involute, comprimée et carénée dont le type clairement suboxycône est nouveau pour le Sinémurien inférieur. En raison de son aire ventrale carénée, ce taxon se rattache probablement à la super-famille des Arietitoidea Hyatt, 1875 sensu Guex (1995) mais son attribution familiale est incertaine et son origine évolutive reste énigmatique. Outre son intérêt taxonomique, cette découverte est importante car elle pose le problème de la valeur adaptative des caractères liés à la géométrie des coquilles d’ammonites. Il est actuellement admis que les coquilles involutes, comprimées et carénées de type suboxycône et oxycône favorisent significativement l’hydrodynamisme et donc la mobilité des espèces qui les possèdent. Il est surprenant que l’acquisition de ce probable avantage adaptatif n’ait pas favorisé l’implantation au sein des peuplements du nouveau taxon, qui reste une forme rare. Dans tous les cas, la découverte d’O. boletzkyi n. gen., n. sp. rajeunit d’environ 2 millions d’années la mise en place des morphologies oxycônes au cours de la phase de reconstitution de la biodiversité post-crise Trias/Jurassique.One of the very first quasi-oxycone ammonites following the Triassic/Jurassic boundary crisis is described. It was collected from the fossiliferous Lower Sinemurian (Semicostatum or Turneri Chronozone) strata of Burgundy (Mavilly-Mandelot, Côte-d’Or, France). The new taxon, Oxyarietites boletzkyi n. gen., n. sp., possesses an involute, compressed and keeled shell of suboxycone morphology, a shell type previously unknown for the Lower Sinemurian. The discovery makes younger by about 2 Ma the emergence of keeled (sub)oxycone shells following the Triassic/Jurassic boundary crisis. Its obviously keeled ventral area allows a probable assignation to the Arietitoidea Hyatt, 1875 sensu Guex (1995) superfamily, but family level assignation and its evolutionary origin remain obscure. Although, it is generally accepted that involute, compressed and keeled suboxycone and oxycone ammonite shells possess the best hydrodynamical abilities and mobility, the acquisition of this probable adaptive advantage in O. boletzkyi n. gen., n. sp. does not go together with abundancy in the fossil record.</p