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Inproceedings Reference The last 300 years of sedimentation in the Fuji Five Lakes: the impact of natural disasters with a special focus on earthquakes
Within the framework of the QuakeRecNankai project, which focuses on the geological record of paleoearthquakes rupturing the Nankai-Suruga subduction zone, we sampled bottom sediments of the Fuji Five Lakes at the foot of Mount Fuji. In October 2014, we acquired 23 short gravity cores from Motosu, Sai, Kawaguchi and Yamanaka Lakes. We focus on investigating the sensitivity of each lake for recording natural hazards (storms, floods, volcanic eruptions, earthquakes). Recent natural hazards impacting the Fuji Five Lakes area are expected to be recorded as rapidly deposited layers within the background hemipelagic sediments. We seek to identify event deposits in the collected short cores based on visual identification combined with high resolution analyses, comprising geophysical and geochemical properties, grain size and X-ray images. We establish an age-depth model by combining radionuclide (14C,137Cs,210Pb) dating with the identification of historical tephra layers, in particular the one deposited during the Hoei eruption (AD 1707) of Mount Fuji. The sedimentary events in each lake are compared to a historical catalogue of natural hazards in the Fuji Five Lakes area, including historical records of megathrust earthquakes rupturing the Nankai subduction zone and other earthquakes occurring along the inland active faults that produced significant shaking (MKS intensity >7) in the Fuji Five Lakes area. The preliminary sedimentary study highlights the high sensitivity of Motosu Lake compared to the very shallow Yamanaka and Kawaguchi Lakes, which we attribute to its specific geomorphology. Motosu Lake is characterized by a deep basin, surrounded by very steep slopes. The generation of earthquake triggered mass transport deposits/turbidites and the preservation of the deposits are favored due to the architecture of the basin. The Fuji lake sensitivity to megathrust events will be the target of a future coring campaign to retrieve a longer geological record.
Located in Library / No RBINS Staff publications
Inproceedings Reference The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs in Russia
Located in Library / RBINS Staff Publications
Inproceedings Reference The last polar dinosaurs: high diversity of latest Cretaceous arctic dinosaurs in Russia
Located in Library / RBINS Staff Publications
Proceedings Reference The last supper: multiproxy analyses of a Gallo-Roman votive meal in Belgium
Located in Library / RBINS Staff Publications
Proceedings Reference The LASUGEO project:monitoring LAnd SUbsidence caused by Groundwater exploitation through gEOdetic measurements.
In the last decades, rapid urbanization, global climate change and uncontrolled anthropogenic transformations of the territory caused a relevant increase in geo-hazards events with huge economic and social consequences. The dramatic increase of these events with environmental degradation highlights the importance of improving ground monitoring and natural resources management with a continuous exchange of knowledge between the scientific community and authorities in charge of environmental risk management. Since the late 1990s, SAR (Synthetic Aperture Radar) data allow measuring slow-moving ground deformations. In the last decades, the use of spaceborne InSAR (Interferometric SAR) has increased significantly thanks to the availability of large-area coverage, millimetre precision, high spatial/temporal data resolution and good cost-benefit. For the last 3 decades, the development of Multi-Temporal Interferometric SAR techniques (MT-InSAR), commonly grouped into PSI-like (Persistent Scatterers Interferometry) and SBAS-like (Small BAseline Subset) algorithms, has changed the way radar images can be exploited for geohazard monitoring (natural gas extraction, mining activities, groundwater overexploitation, karst or landslides processes, etc.). Most of the subsidence bowls mapped by the PSI technique in Belgium have been related to strong fluctuations of an aquifer implying at the surface ground deformations (Declercq et al., 2017; 2021). Besides, the recent dry years are related to ground stability problems in large areas of Flanders. Land subsidence poses significant problems. The most affected regions lie on compressible loose sediments. Any change in the piezometric heads modifies the pore pressure, which may induce consolidation if the geological formations are compressible. Geomechanical aspects are fully coupled to groundwater flow equations. If groundwater levels and pressures are restored, a partial rebound (uplift) corresponding to the elastic part of the geological formations is observed. Consolidation and elastic rebound processes occur in confined and unconfined conditions. The most sensitive parts of the concerned aquifers contain clay, loam or peat lenses but consolidation may occur mostly in the underlying and overlying layers that are often less permeable and more compressible than the aquifer itself. In this case, it is largely a delayed process occurring as far as the pore pressure variation slowly propagates in the low permeability (aquitard) layers. We propose to confront the results of the PSinSAR technique data with hydrogeological groundwater models and two other geodetic techniques: GNSS and gravimetry. LASUGEO Geologica Belgica Meeting 2021, September 15-18, Tervuren, Belgium – Abstract Book, p. 75 focusses on ground deformations in different areas in Belgium: the deep aquifer system of western Flanders, the Tertiary aquifer system in Central Flanders, the Antwerp area, the Leuven area and the Brussels Region. The possible groundwater overexploitation needs to be established through a transient hydrogeological model considering all the stress factors applied to the aquifers. The estimated compaction in the subsiding bowls will be compared with 1D geomechanical model results. The latter will be performed using geotechnical effective stresses as deduced from the pore pressure distribution from the hydrogeological model (Dassargues et al., 1989). These different steps will be done by the partners of the LASUGEO project that are involved in the different case study areas.
Located in Library / RBINS Staff Publications 2021
Proceedings Reference The Late Devonian spermatophytes: what about the male organs ?
The spermatophytes first evolved by the end of the Middle Devonian, some 390 million years ago. The Famenian deposits record what has been interpreted as the first seed plant radiation. In these levels, a surprisingly large seed plant diversity is observed. Indeed, up to seventeen ovule species are found occupying a wide morphological spectrum. In Belgium, ovules are associated in nearly all localities to sporangiate axes presenting a very similar vegetative morphology. They consist un a dichotomous branchin system bearing terminally a group of sporangia. Sporangia are small and round to oval in shape. They are borne on the recurved tips of a small dichotomous organ. This communication will focus on the description and discussion of the evolutionary implications of these sporangia that we consider as the microsporangiate organs of Late Devonian spermatophytes.
Located in Library / RBINS Staff Publications
Article Reference The latest Cretaceous hadrosaurid dinosaurs from Heilongjiang Province (China) and Amur Region (Russia)
Located in Library / RBINS Staff Publications
Article Reference The Latest Danian Event along a paleobathymetric gradient in the Nile Basin (Eastern Desert, Egypt).
Located in Library / RBINS Staff Publications
Inproceedings Reference The map of the Brabant Massif for offshore Belgium
The cartographic boundary of the Brabant Massif in the northwest is the North Sea, which is an observational limit. Nevertheless the Lower Palaeozoic rocks continue as part of a larger unit, referred to as the Anglo-Brabant Deformation Belt. Maps of the Brabant Massif largely rely on borehole data. The latest map of the Brabant Massif (Piessens et al., 2005) uses structural concepts and direct information, rather than geophysical information. Nevertheless, an aeromagnetic survey and gravimetric data corroborate the large scale distribution of the units. This map is extrapolated to the off-shore territory of Belgium. Direct information from drillings is not available for the off-shore region, and it is therefore not possible to draw this map at the same stratigraphic resolution. The formations are therefore grouped into Cambrian, Ordovician and Silurian units. Magnetic susceptibility is high for the Cambrian, which allows tracing their continuation from on-shore to off-shore. The formations at subcrop level along the central axis of the Brabant Massif are on-shore Cambrian in age, but young in a WNW direction. Also the magnetic pattern becomes less intense, likely corresponding to an increasing depth of the more magnetic lower Cambrian units. This trend continues off-shore, indicating that the Cambrian units disappears at subcrop level. Superimposed on this general trend an aeromagnetic anomaly about 15 km off-shore of Ostend marks the probable local reappearance of the Tubize Formation. A secondary and less continuous Cambrian axis passes near Diksmuide. A second isolated off-shore aeromagnetic anomaly, indicative of the Cambrian unit, lies along the trace of this secondary axis. The gravimetric map shows a low gravimetric anomaly of which the circular shape suggests a genetic link with the chain of gravimetric lows that underlie the southern part of the on-shore part of the Brabant Massif. The higher densities in the northern part of the off-shore territory confirm, in continuation of the on-shore formation boundaries, the presence of the Silurian unit. The validity of the inferred distribution of the stratigraphic units was verified with the structural 3D concept that was developed for the on-shore part of the Brabant Massif, concluding that the inferred distribution of the geological units is in agreement with the structural model derived on-shore. It for example explains the positions of the two magnetic anomalies relative to each another. A central element in the structural model is the Asquempont Detachment System of which a limited number of possible traces is possible.
Located in Library / RBINS Staff Publications 2016
Inproceedings Reference The massive Mousny Quartz Occurrence (High-Ardenne slate belt, Belgium), a late-orogenic dilatational jog?
Located in Library / RBINS Staff Publications