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See detailEarthquake imprints on a lacustrine deltaic system: the Kürk Delta along the East Anatolian Fault (Turkey)
Hubert, Aurelia ULg; El Ouahabi, Meriam ULg; Garcia-Moreno, David et al

in Sedimentology (2016)

Deltas contain sedimentary records that are not only indicative of water level changes, but also particularly sensitive to earthquake shaking typically resulting in soft-sediment-deformation structures ... [more ▼]

Deltas contain sedimentary records that are not only indicative of water level changes, but also particularly sensitive to earthquake shaking typically resulting in soft-sediment-deformation structures. The Kürk lacustrine delta lies at the south-western extremity of Lake Hazar in eastern Turkey and is adjacent to the seismogenic East Anatolian Fault (EAF), which has generated earthquakes of magnitude 7. In this paper we have reevaluated water level changes and earthquake shaking that have affected the Kürk Delta combining geophysical data (seismic-reflection profiles and side-scan sonar), remote sensing images, historical data, onland outcrops and offshore coring. The history of water level changes provides a temporal framework for the depositional record. In addition to the commonly soft-sediment-deformation documented previously, onland outcrops reveal a record of deformation (fracturing, tilt and clastic dykes) linked to large earthquake-induced liquefactions and lateral spreading. The recurrent liquefaction structures can be used to obtain a paleoseismological record. Five event horizons were identified that could be linked to historical earthquakes occurring in the last 1000 years along the EAF. Sedimentary cores sampling the most recent subaqueous sedimentation revealed the occurrence of another type of earthquake indicator. Based on radionuclide dating (137Cs and 210Pb), two major sedimentary events were attributed to the 1874-1875 EAF earthquake sequence. Their sedimentological characteristics were determined by X-ray imagery, XRD, LOI, grain-size distribution and geophysical measurements. The events are interpreted to be hyperpycnal deposits linked to post-seismic sediment reworking of earthquake-triggered landslides. [less ▲]

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See detailInfluence of sedimentary setting on the use of magnetic susceptibility : examples from the Devonian of Belgium
Da Silva, Anne-Christine ULg; Mabille, Cédric ULg; Boulvain, Frédéric ULg

in Sedimentology (2009), 56

Bulk magnetic susceptibility measurements on sedimentological samples from all geological periods have been used widely in the last two decades for correlations and as a proxy for sea-level variations ... [more ▼]

Bulk magnetic susceptibility measurements on sedimentological samples from all geological periods have been used widely in the last two decades for correlations and as a proxy for sea-level variations. This paper explores the link between magnetic susceptibility, depositional setting and environmental parameters. These environmental parameters include distal–proximal transects, microfacies successions and fourth-order trends on different carbonate platform types (platform, ramp, carbonate mound or atoll) during different Devonian stages (Eifelian, Givetian and Frasnian). Average magnetic susceptibility values over a distal–proximal-trending facies succession vary markedly with depositional setting. On carbonate platforms, average magnetic susceptibility generally increases towards the top of shallowing-upward sequences. On a distal–proximal transect, average magnetic susceptibility is intermediate for the deepest facies, decreases for the reef belts and increases to a maximum in the back-reef zone. In ramps and atolls, magnetic susceptibility trends clearly differ; average magnetic susceptibility generally decreases towards the top of shallowing-upward sequences and is highest in the deepest facies. The strong relationship between magnetic susceptibility, facies and sequences implies a strong environmental influence. However, the different responses in the different latform types suggest that sea-level changes leading to variation in detrital input is not the only parameter controlling average magnetic susceptibility values. Other primary or secondary processes also probably influenced magnetic mineral distribution. Primary processes such as carbonate production and water agitation during deposition are probably key factors. When carbonate production is high, the proportion of magnetic minerals is diluted and the magnetic susceptibility signal decreases. High water agitation during deposition will also selectively remove magnetic minerals and will lead to low average magnetic susceptibility values. These parameters explain the lowest values observed on the reef platform, inner ramp and atoll crown, which are all in areas characterized by higher carbonate production and greater water agitation during deposition. The lowest values observed in the lagoon inside the atoll crown can be related to detrital isolation by the atoll crown. However, other parameters such as biogenic magnetite production or diagenesis can also influence the magnetic signal. Diagenesis can change magnetism by creating or destroying magnetic minerals. However, the influence of diagenesis probably is linked strongly to the primary facies (permeability, amount of clay or organic matter) and probably enhanced the primary signal. The complexity of the signal gives rise to correlation problems between different depositional settings. Thus, while magnetic susceptibility has the potential to be an important correlation tool, the results of this investigation indicate that it cannot be used without consideration of sedimentary processes and depositional environments and without strongbiostratigraphical control. [less ▲]

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See detailUn curieux phénomène d'érosion famennienne: les "pains de grès" de Chambralles (Ardenne belge)
Macar, Paul; Ek, Camille ULg

in Sedimentology (1965), 4

Les carrières de Chambralles, ouvertes dans les bancs de grès verticaux du Famennien supérieur, montrent une grande variété de structures péné-contemporaines de la sédimentation. On y note en particulier ... [more ▼]

Les carrières de Chambralles, ouvertes dans les bancs de grès verticaux du Famennien supérieur, montrent une grande variété de structures péné-contemporaines de la sédimentation. On y note en particulier, sur un banc largement dégagé, des îlots souvent limités par des micro-falaises et de petites masses de grès isolées, de forme arrondie ("pains de grès"). [less ▲]

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