Search publications of the members of the Royal Belgian institute of natural Sciences
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A complete insect from the Late Devonian period
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First occurrence of the lungfish Sagenodus (Dipnoi, Sarcopterygii) from the Carboniferous lagerstätte of Montceau-les-Mines, France
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New data on the Silurian-Devonian palaeontology and biostratigraphy of Bolivia
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Geoarchaeological Research in Lower Khuzestan: State of the Art
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L’hématite abrasée : usages et fonctions dans le Néolithique ancien d’Europe du Nord-ouest
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Studying the Influence of Landscape Changes on the Late Bronze Age Abandonment of the Harbour Town HST: Unravelling the Sedimentary Record of the Larnaca Salt Lake, Cyprus
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Site Saint-Lambert, à Liège : Datations Carbone 14 par A.M.S. des occupations mésolithiques et néolithiques (secteur DDD et SDT)
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3. Les occupations pré-romaines
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Annexe I. Datation radiocarbone des niveaux pré-romains du site de Bruyelle
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Using Historical Imagery and GIS for Reconstructing the Ancient Landscapes of Khuzestan (SW Iran)
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Ostracodes et lithologie du stratotype de la Formation du Mont d'Haurs (Givétien)
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L'altération des briquets en «marcassite» du «Trou de Chaleux» (Fouilles d’Édouard Dupond) : identification de phases minérales primaires et secondaires
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The role of rivers in ancient societies, or how man transformed the alluvial landscapes of Khuzestan (SW Iran)
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Studying the driving forces of landscape change in the surroundings of the Late Bronze Age harbor town Halla Sultan Tekke, Cyprus
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Intra- and Intertaxon stable O and C isotope variability of fossil fish otoliths: an early Eocene test case
- Knowledge of basic data variability is essential for the interpretation of any proxy-based paleotemperature record. To evaluate this for δ18O stable isotope paleothermometry based on early Paleogene fish otoliths from marginal marine environments, an intra- and interspecific stable O and C isotope study was performed at a single locality in the southern North Sea Basin (Ampe Quarry, Egem, Belgium), where shallow marine sands and silts are exposed. The age of the deposits is early late Ypresian (ca. 50.9 Ma) and falls within the early Eocene climatic optimum (EECO) interval. In each of four fossiliferous levels sampled, the same three otolith species were analyzed (Platycephalus janeti, Paraconger papointi and “genus Neobythitinorum” subregularis). Intrataxon stable isotope spread amounts on average 2.50-3.00‰ for all taxa and is present in all levels. This implies that each sample level comprises substantial variability, which can be attributed to a combination of temporal and taphonomic effects. More importantly, intertaxon offsets of 4.60‰ in δ13C and 2.20‰ in δ18O between the mean values of the three otolith species are found, with “N.” subregularis representing more positive values relative to the other species. We hypothesize that freshwater influence of coastal waters is the most likely cause for these discrepancies. Similar analyses on two coastal bivalve species (Venericardia sulcata and Callista laevigata) corroborate this hypothesis. Accordingly, δ18O values measured on “N.” subregularis otoliths probably represent a more open oce- anic signal, and therefore seem well-suited for δ18O stable isotope paleothermometry. This study highlights the importance of investigating data variability of a biogenic carbonate paleotemperature proxy at the species level, before applying paleotemperature equations and interpreting the outcome.
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Updating the theories on ammonoid extinction
- Since Alvarez et al. (1980) found new evidence for the impact of catastrophic events on earth’s biota, hypothesis and theories explaining the fossil record (re)gained a lot of attention. The extraterrestrial origin of the anomalous iridium concentrations seemed highly controversial at first, but nowadays the Chicxulub ‘accident’ has become the marker for the start/base of the Paleogene. Its pivotal role in the Mesozoic-Cenozoic faunal turnover cannot be refuted (Schulte et al 2010). However, alternative theories remain being published. Of these, the Deccan volcanism with its widespread flood basalts stepped prominently forward as one of the main triggers, especially when trying to explain the gradual diversity decline within the fossil record. The inconsistencies between the proposed theories generally root in too narrowly geographically and geologically spread datasets. This applies to most fossil groups, and especially to the ammonoids (Class Cephalopoda, °Early Devonian – †Late Cretaceous). A compilation of ammonoid occurrences of Late Maastrichtian age published by Kiessling & Claeys (2002) evidenced the lack of a globally well distributed dataset. In this compilation, North Africa was left as a blind spot, while Tunisia had been the centre of the K/Pg mass extinction debate for almost three decades, e.g. with the definition of the GSSP for the base of the Paleogene at El Kef. Both at the GSSP and several other sections in the Tunisian Trough Basin, ammonoids were found within the topmost meters of the Maastrichtian, until very close to the K/Pg boundary level. About 900 uppermost Maastrichtian ammonoids were collected, all from within the last 420.000 years of the Cretaceous. With 22 species on record, belonging to 18 genera and 10 families, and with representatives of each of the four large ammonoid suborders (Phylloceratina, Lytoceratina, Ammonitina and Ancyloceratina), the Tunisian fauna demonstrates that ammonoids were both taxonomically and morphologically diverse until their very end. An updated version of the compilation of latest Maastrichtian ammonoid occurrences documents at least 53 species, 29 genera and 13 families in the ultimate half million year of the Cretaceous, in many more localities and occurring in a wide variety of settings. When the Tunisian ammonoid species richness data are plotted next to all time constraints of the possible causes, the possibility of Deccan flood basalt volcanism negatively influencing ammonoid diversity must be refuted. A major extinction caused by the Chicxulub impact seems the most plausible theory at present. Through inducing a mass kill of the marine plankton, the juvenile ammonoids lost their primary food source leading to their final extinction. Alvarez, L.W., Alvarez, W., Asaro, F., Michel, H.V., 1980. Extraterrestrial cause for the Cretaceous-Tertiary extinction. Science, 208, 1095-1108. Kiessling, W., Claeys, P., 2002. A geographic database approach to the KT Boundary. In Buffetaut, E., Koeberl, C. (Eds), Geological and Biological Effects of Impact Events, Springer-Verlag Berlin, 83-140. Schulte, P. & 40 authors, 2010. The Chicxulub Asteroid Impact and Mass Extinction at the Cretaceous-Paleogene Boundary. Science 327, 1214-1218.
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Fish otolith stable isotope paleothermometry in the early Paleogene: limitations and future directions
- The climate of the early Paleogene is characterized by short-scale temperature variations which are superimposed on a general trend of rising temperatures culminating during the late early Eocene (early Eocene climatic optimum, EECO). These include several transient periods of abrupt climate warming or ‘hyperthermals’, such as the PETM (~55 Ma). Profound proxy development is needed to successfully extract shorter-scale variability from suitable records and unravel its underlying mechanisms. This study assesses and extends the use of fossil fish otolith O and C stable isotopes as a paleotemperature and seasonality proxy for early Paleogene marginal marine sedimentary environments. Well-known limitations include the lack of accurate estimates for the oxygen isotope composition of ambient water, and potential bias when applying paleotemperature equations. Moreover, taxon inconsistencies for both O and C were observed, complicating data interpretation (Vanhove et al., 2011). A single locality test case in the southern North Sea Basin has been performed to address this observation (Egem, Belgium, coastal sands). In each of four fossiliferous levels sampled, the same three demersal otolith species were analyzed (Platycephalus janeti, Paraconger papointi and “genus Neobythitinorum” subregularis). Cross-plots of δ18O and δ13C isotopes show three statistically different data clouds, corresponding to the three taxa. Several processes can cause such discrepancies. The most likely option is the influence of freshwater influx. According to this interpretation, Paraconger sp. and Platycephalus janeti lived in coastal areas prone to freshwater influx, while “genus Neobythitinorum” subregularis inhabited more distal realms. This is confirmed by similar analyses on Callista sp. and Venericardia sp. bivalves of the same locality, because these were deposited relatively in situ compared with otoliths, which predominantly arrive in the sediment after post-mortem predation-related transport. Taxon-sensitive differential diagenesis is disproved by SEM, cold cathodoluminescence and X-ray diffraction investigations, revealing the presence of pristine aragonite in all cases. Bias resulting from variability in the amount of summer or winter carbonate deposition is contradicted by visual inspection of growth ring thicknesses, and cyclical incremental stable isotope patterns of individual growth bands. Taxon inconsistencies were not described previously by authors working on the same taxa and in the same area, hence the paleoecological interpretation of this data could indicate enhanced runoff and freshwater influx during the EECO relative to later time intervals, or the presence of a large river mound close the investigated location. Temperature calculations based on “genus Neobythitinorum” subregularis reveal mean annual temperatures around 27.5 °C and a seasonality of 9 °C for the EECO interval. Given the mentioned assumptions, future directions should include other quantitative, preferably salinity-independent paleotemperature proxies to test these data interpretations. VANHOVE D., STASSEN P., SPEIJER R. P. and STEURBAUT E., 2011. Assessing paleotemperature and seasonality during the early Eocene climatic optimum (EECO) in the Belgian Basin by means of fish otolith stable O and C isotopes. Geologica Belgica, 14(3-4): 143-158.
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Variable benthic foraminiferal ecosystems responses to the PETM in shelf environments
- The Paleocene-Eocene thermal maximum (PETM) is characterized by a worldwide 5-8 °C warming of Earth’s surface as well as the deep oceans, major global faunal and floral turnovers and large changes in ocean chemistry. In order to establish clear biogeographic patterns of how shallow benthic foraminiferal communities responded to these climate changes, we compare shallow marine ecosystems in three separated regions and provide a synthesis of the short-term biotic responses. These regions are located in Tunisia (Northern and Gafsa Basin), Egypt (Nile Basin) and the North Atlantic Coastal Plain (Salisbury Embayment, United States). In Egypt, widespread anoxia during PETM peak warming led to the collapse of Paleocene deep shelf communities and a basin-wide downslope migration of pioneering shallow water taxa (A. aegyptiacus) during the initial recovery phase. In the shallower Tunisian settings, the PETM is marked by dysoxia, increased water depth and an elevated sedimentation rate. This resulted in the migration of deeper-dwelling species (lagenid and buliminid fauna) at the onset of the PETM, replacing the former shallow water community. At the onset of the PETM in the North Atlantic Coastal Plain, deposition occurred in a basin-wide mud belt, inhabited by opportunistic deep shelf taxa. Increased eutrophication, high sedimentation rates and widespread hypoxia are linked to the establishment of a river-dominated shelf during the PETM. As a result, in shallow and deep shelf settings, diverse Paleocene assemblages were replaced by characteristic river-outflow assemblages (P. prima, A. acutus, T. selmensis), either by upslope migration or increased abundances of these background taxa. Due to the magnitude and tempo of global warming, the PETM exerted worldwide environmental stress on benthic foraminiferal communities, triggering prominent transient changes in population structure and biodiversity, yet the evolutionary impact was minor compared to the deep-sea extinction event. This implies the existence of refugia on the shelves. In general, stable latest Paleocene benthic foraminiferal assemblages were abruptly replaced by more stress-tolerant faunas, reflecting stressed dysoxic to anoxic eutrophic environments, due to higher nutrient delivery (increased runoff and upwelling) and stratification. These hypoxic conditions occurred in the early stages of the PETM continually or with high frequencies and evolved towards periodic (seasonal?) oxygen depletion during the latter stages of peak warming or initial recovery. The final recovery phase reflects a reoxygenation of the sea floor and a distinctive buliminid bloom (B. callahani) occurred at both sides of the Atlantic Ocean. These eutrophic conditions remained stable and continued in the aftermath of the PETM, yet the oxygenation of bottom waters became restored. The PETM sequences thus document a progression of environmental regimes that is somewhat similar in all studied settings, indicating a widespread mutual response to the massive injection of carbon dioxide at the onset of the PETM.
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The onset of the negative Carbon Isotope Excursion on dispersed organic matter as criterion of the Paleocene-Eocene boundary: uses, biases and limits
- The primary criterion ratified by the International Subcommission on Paleogene Stratigraphy (ISPS) to define the Paleocene-Eocene (P/E) boundary, and the beginning of the Paleocene-Eocene Thermal Maximum (PETM), is the onset of a prominent negative Carbon Isotope Excursion (CIE; Aubry et al., 2007), located in the lower to middle part of Chron C24r, in calcareous nannofossil Zone NP9 and at the base of planktonic foraminiferal Zone E1 of Berggren & Pearson, 2005 (see also Wade et al., 2011), also termed Zone P5 in Aubry et al. (2007). Based on cyclostratigraphy, the CIE is estimated to have spanned 150 ± 20 kyr and would reflect a major perturbation of the global carbon cycle. Organic matter (OM) may be judged as a (very) reliable material for isotopic chemostratigraphy, in both marine and terrestrial settings. Here we show several examples of successions (Belgium, Egypt, France, Spain, Tunisia, USA-Wyoming) where: isotopic analyses on OM are necessary to define the P-E boundary (lack of carbonates and/or diagenetic 1. alteration of the isotopic signal on carbonates, including calcitic shells, bulk rocks and pedogenic nodules), organics are probably not the best material to precise the P-E boundary,2. geological processes, such as hiatuses, and potential reworking of OM in channels and turbidites, may per3. turb the reliability of the carbon isotope results (on both organics and carbonates). Aubry, M.P. et al., 2007. Episodes, 30, 271-286. Berggren, W. A., and Pearson, P. M., 2005, J. of Foraminiferal Research, 35/4, 279–298. Wade, B.S. et al. 2011, Earth Science Reviews 104, 111-142.
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Biotic and lithologic expressions of lower Paleogene hyperthermals in the Nile Basin, Egypt.
