Search publications of the members of the Royal Belgian institute of natural Sciences
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EMODnet Data Ingestion Portal Project - WP4.1: Identification of potential data sources
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EMODnet Data Ingestion Portal Project - WP4.3: Promotion activities
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Dealing with historical data and making it accessible.
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Coastal lake sediments reveal 5500 years of tsunami history in south central Chile
- We present an exceptionally long and continuous coastal lacustrine record of ~5500 years from Lake Huelde on the west coast of Chiloe Island in south central Chile. The study area is located within the rupture zone of the giant 1960 CE Great Chilean Earthquake (MW 9.5). The subsequent earthquakeinduced tsunami inundated Lake Huelde and deposited mud rip-up clasts, massive sand and a mud cap in the lake. Long sediment cores from 8 core sites within Lake Huelde reveal 16 additional sandy layers in the 5500 year long record. The sandy layers share sedimentological similarities with the deposit of the 1960 CE tsunami and other coastal lake tsunami deposits elsewhere. On the basis of general and site-specific criteria we interpret the sandy layers as tsunami deposits. Age-control is provided by four different methods, 1) 210Pb-dating, 2) the identification of the 137Cs-peak, 3) an infrared stimulated luminescence (IRSL) date and 4) 22 radiocarbon dates. The ages of each tsunami deposit are modelled using the Bayesian statistic tools of OxCal and Bacon. The record from Lake Huelde matches the 8 regionally known tsunami deposits from documented history and geological evidence from the last ~2000 years without over- or underrepresentation. We extend the existing tsunami history by 9 tsunami deposits. We discuss the advantages and disadvantages of various sedimentary environments for tsunami deposition and preservation, e.g. we find that Lake Huelde is 2-3 times less sensitive to relative sea-level change in comparison to coastal marshes in the same region.
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Larger earthquakes recur more periodically: New insights in the megathrust earthquake cycle from lacustrine turbidite records in south-central Chile
- Historical and paleoseismic records in south-central Chile indicate that giant earthquakes on the subduction megathrust – such as in AD1960 (Mw9.5) – reoccur on average every ∼300yr. Based on geodetic calculations of the interseismic moment accumulation since AD1960, it was postulated that the area already has the potential for a Mw8earthquake. However, to estimate the probability of such a great earthquake to take place in the short term, one needs to frame this hypothesis within the long-term recurrence pattern of megathrust earthquakes in south-central Chile. Here we present two long lacustrine records, comprising up to 35 earthquake-triggered turbidites over the last 4800yr. Calibration of turbidite extent with historical earthquake intensity reveals a different macroseismic intensity threshold (≥VII1/2 vs. ≥VI1/2) for the generation of turbidites at the coring sites. The strongest earthquakes (≥VII1/2) have longer recurrence intervals (292 ±93 yrs) than earthquakes with intensity of ≥VI1/2 (139 ±69 yr). Moreover, distribution fitting and the coefficient of variation (CoV) of inter-event times indicate that the stronger earthquakes recur in a more periodic way (CoV: 0.32 vs.0.5). Regional correlation of our multi-threshold shaking records with coastal paleoseismic data of complementary nature (tsunami, coseismic subsidence) suggests that the intensity ≥VII1/2 events repeatedly ruptured the same part of the megathrust over a distance of at least ∼300km and can be assigned to Mw≥8.6. We hypothesize that a zone of high plate locking – identified by geodetic studies and large slip in AD 1960 – acts as a dominant regional asperity, on which elastic strain builds up over several centuries and mostly gets released in quasi-periodic great and giant earthquakes. Our paleo-records indicate that Poissonian recurrence models are inadequate to describe large megathrust earthquake recurrence in south-central Chile. Moreover, they show an enhanced probability for a Mw7.7–8.5 earthquake during the next 110 years whereas the probability for a Mw≥8.6(AD1960-like) earthquake remains low in this period.
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Distinguishing megathrust from shallow intraplate earthquakes using lacustrine turbidites (Laguna Lo Encanado, Central Chile)
- One of the main challenges in seismically active regions is differentiating paleo-earthquakes resulting from different fault systems, such as the megathrust versus shallow intraplate faults in subductions settings. Such differentiation is, however, key for hazard assessments based on paleoseismic records. Laguna Lo Encanado (33.7°S; 70.3°W; 2492 m a.s.l.) is located in the Central Chilean Andes, 50 km east of Santiago de Chile, a metropole with over 5,000,000 inhabitants. During the last century the study area experienced 3 large megathrust earthquakes (1906, 1985 and 2010) and 2 intra-continental plate earthquakes (1942 and 1958) (Lomnitz, 1960). While the megathrust earthquakes cause Modified Mercalli Intensities (MMIs) of VI to VII at the lake (Van Daele et al., 2015), the shallower intraplate earthquakes cause peak MMIs up to IX (Sepulveda et al., 2008). Here we present a turbidite record of Laguna Lo Encanado going back to 1900 AD. While geophysical data (3.5 kHz subbottom seismic profiles and side-scan sonar data) provides a bathymetry and an overview of the sedimentary environment, we study 15 short cores in order to understand the depositional processes resulting in the encountered lacustrine turbidites. All mentioned earthquakes triggered turbidites in the lake, which are all linked to slumps in proximal areas, and are thus resulting from mass wasting of the subaquatic slopes. However, turbidites linked to the shallow intraplate earthquakes are additionally covered by turbidites of a finer-grained, more clastic nature. We link the latter to post-seismic erosion of onshore landslides, which need higher MMIs to be triggered than subaquatic mass movements (Howarth et al., 2014). While shallow intraplate earthquakes can cause MMIs up to IX and higher, megathrust earthquakes do not cause sufficiently high MMIs at the lake to trigger voluminous onshore landslides. Hence, the presence of these post-seismic turbidites allows to distinguish turbidites triggered by shallow intraplate earthquakes from those triggered by megathrust earthquakes. These findings are an important step forward in the interpretation of lacustrine turbidites in subduction settings, and will eventually improve hazard assessments based on such paleoseismic records in the study area, and in other subduction zones.
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Geological evidence for extreme wave events on a coastal lowland facing the Tokai segment of the Nankai-Suruga Trough
- Located close to Japan’s densest concentrations of people and industry, the easternmost region of the Nankai-Suruga subduction zone has long been the focus of attempts to forecast and even precisely predict future earthquakes. While historical records attest to the occurrence of great earthquakes and subsequent tsunamis that may have originated from the Tōkai segment, past rupture zone extents and recurrence intervals remain poorly understood. Coastal stratigraphy has the potential to record the occurrence of both tsunami inundation and coseismic vertical land-level change over timescales far exceeding the historical record, with important implications for refining understanding of future hazards (Garrett et al., 2016). Here we present initial results from an extensive coring survey of the lower reaches of the floodplain of the Sagara River, close to the town of Sagara, Shizuoka Prefecture. The site lies at an altitude of ~1 – 5 m and is within the anticipated inundation zone of future worst-case tsunami scenarios. Typhoon-driven storm surges and river floods are also likely to have inundated the site, complicating the interpretation of potential tsunami deposits. Using CT scans, multi-sensor core logs, diatom assemblages and radiocarbon dates, we evaluate sedimentary processes and make the distinction between extreme wave events and fluvial deposits. Where possible, we assess methods to differentiate between storm surges and tsunami deposits. Finally, we evaluate the potential for the site to provide a long and continuous record of extreme wave events and highlight the probable influence of changing thresholds of evidence creation and preservation over time.
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Partial revision of the genus Dorysthenes (subgenus Paraphrus ) Thomson, 1861 with overall review of the species planicollis (Bates, (Coleoptera, Cerambycidae, Prioninae, Prionini )
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Critical analysis of carnivoran mammal success in Europe during the Paleogene
- Why are we surrounded by only one group of placental carnivorous mammals (Carnivora: the present-day lions, dogs, bears, and seals among others) today, while at least three other groups of placental mammals (Hyaenodonta, Mesonychia, Oxyaenidae) were in competition with carnivorans 50 million years ago? Since the 1990s, palaeontologists have investigated the success of carnivoraform mammals (including Carnivora) and their crucial adaptations in detail. Analysis of the taxonomic and morphological diversification of these groups in the North American fossil record clearly showed that carnivoraforms outcompeted hyaenodonts and oxyaenids during the Eocene, specifically from around 50 Ma when carnivoraforms began to dominate. It has been suggested that the evolutionary success of carnivorans may have resulted from the broad range of dental adaptations (i.e., a broad variety of diets) conferred by the particular position of their carnassial teeth. Here we document the evolutionary history of the taxonomic diversity as well as the evolution of the body mass of carnivorous mammals that lived in Europe during the Paleogene (66–23 Ma). The results suggest that this competition was diametrically opposed in North America and Europe. Carnivoraforms actually did not become diversified in Europe during the Eocene and thus were not as taxonomically successful in Europe as in North America during that period. Moreover, when one considers body mass, the European hyaenodonts were distinctly more diversified than the carnivoraforms. The situation dramatically changed during the 'Grande Coupure' (around Eocene–Oligocene boundary; ca. 33.9 Ma). This transition corresponds to a major faunal turnover in Europe: during the earliest Oligocene global cooling (Oi-1) event, the Eocene endemic carnivorous fauna were replaced by immigrant taxa (hyaenodonts and carnivorans), mainly from Asia. The Oligocene fossil record shows a diversification of the carnivorans, whereas hyaenodonts were almost only represented by the hypercarnivorous genus Hyaenodon. However, two distinct periods can be discriminated in the Oligocene: the Rupelian was dominated by the Nimravidae and feliforms, while the Chattian was dominated by the caniformians (especially the Amphicyonidae and Ursidae). This turnover seems to be concomitant with the Latest Oligocene Warming and Microbunodon Event. Based on these results, one can hypothesize that the evolution of the European carnivorous mammals might have been profoundly driven by climate modifications (abiotic factors). Grant Information: This abstract is a contribution to the Belspo Brain Pioneer project BR/175/PI/CARNAGES funded by the Belgian Science Policy Office.
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Additional contribution to the knowledge of Asian Aegosomatini with the description of a new species in the genus Aegosoma Audinet-Serville, 1832 (Coleoptera, Cerambycidae, Prioninae)
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Macrodontia crenata (Olivier, 1795) au Suriname (Coleoptera, Cerambycidae, Prioninae)
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Hybotidae (Diptera) of the Botanic Garden Jean Massart (Brussels-Capital Region, Belgium) with description of two new Platypalpus species and comments on the Red Data List
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From a pair to a dozen: the piscivorous species of Haplochromis (Cichlidae) from the Lake Edward system
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Co-introduction of Dolicirroplectanum lacustre, a monogenean gill parasite of the invasive Nile perch Lates niloticus: intraspecific diversification and mitonuclear discordance in native versus introduced areas
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Species depauperate communities and low abundances of monogenean gill parasites at the edge of the natural distribution range of their cichlid hosts in northern Africa
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Le mobilier lithique du site préhistorique de Sirault Couture des Anglés (Saint-Ghislain, Hainaut).
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Les matières premières argileuses en région andennaise : de l’extraction des terres crues aux terres cuites.
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[Ath] Les fouilles préventives du site des « Haleurs » à Ath.
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Ath « Les Haleurs », deux villages Rubané et Blicquy/Villeneuve-Saint-Germain (Néolithique ancien) : mécanismes de transition culturelle par l’étude intégrée des productions.
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Ghislenghien (Ath). Vestiges protohistoriques mis au jour lors des fouilles menées en 2019 et 20220 dans la zone d’activité économique de Ghislenghien « Orientis III-extension ouest ».
