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Article Reference The genus Diplommatina Benson, 1849 (Gastropoda: Caenogastropoda: Diplommatinidae) in Nepal, with the description of seven new species
Located in Library / RBINS Staff Publications 2017
Article Reference The complexity of 3D stress-state changes during compressional tectonic inversion at the onset of orogeny
Compressional tectonic inversions are classically represented in 2D brittle failure mode (BFM) plots that illustrate the change in differential stress (σ1−σ3) versus the pore-fluid pressure during orogenic shortening. In these BFM plots, the tectonic switch between extension and compression occurs at a differential stress state of zero. However, mostly anisotropic conditions are present in the Earth's crust, making isotropic stress conditions highly questionable. In this study, theoretical 3D stress-state reconstructions are proposed to illustrate the complexity of triaxial stress transitions during compressional inversion of Andersonian stress regimes. These reconstructions are based on successive late burial and early tectonic quartz veins which reflect early Variscan tectonic inversion in the Rhenohercynian foreland fold-and-thrust belt (High-Ardenne Slate Belt, Belgium, Germany). This theoretical exercise predicts that, no matter the geometry of the basin or the orientation of shortening, a transitional ‘wrench’ tectonic regime should always occur between extension and compression. To date, this intermediate regime has never been observed in structures in a shortened basin affected by tectonic inversion. Our study implies that stress transitions are therefore more complex than classically represented in 2D. Ideally, a transitional ‘wrench’ regime should be implemented in BFM plots at the switch between the extensional and compressional regimes.
Located in Library / No RBINS Staff publications
Article Reference Stress-state evolution of the brittle upper crust during compressional tectonic inversion as defined by successive quartz vein types (High-Ardenne slate belt, Germany)
In the frontal part of the Rhenohercynian fold-and-thrust belt (High-Ardenne slate belt, Germany), two successive types of quartz veins, oriented normal and parallel to bedding respectively, are interpreted to reflect the early Variscan compressional tectonic inversion of the Ardenne–Eifel sedimentary basin. Fracturing and sealing occurred in Lower Devonian siliciclastic multilayers under very low-grade metamorphic conditions in a brittle upper crust. A geometrical and microthermometric analysis of these veins has helped to constrain the kinematic and pressure–temperature conditions of both vein types, allowing the reconstruction of the stress-state evolution in a basin during tectonic inversion. It is demonstrated that bedding-normal extension veins, which developed under low differential stresses and repeatedly opened and sealed (crack-seal) under near-lithostatic fluid pressures, reflect the latest stage of an extensional stress regime. Bedding-parallel veins, which developed at differential stresses that were still low enough to allow the formation of extension veins, cross-cut the bedding-normal veins and preceded the regional fold and cleavage development. These veins show a pronounced bedding-parallel fabric, reflecting bedding-normal uplift and bedding-parallel shearing under lithostatic to supra-lithostatic fluid pressures during the early stages of a compressional stress regime. This kinematic history corroborates that fluid overpressures are easy to maintain during compressional tectonic inversion at the onset of orogeny.
Located in Library / No RBINS Staff publications
Article Reference Linear to non-linear relationship between vein spacing and layer thickness in centimetre- to decimetre-scale siliciclastic multilayers from the High-Ardenne slate belt (Belgium, Germany)
Typical spacing distributions have frequently been described for fractures in thin sedimentary layers (<1 m). Regularly spaced fractures often result from saturation during fracture development. Spatial distribution of veins is less commonly studied although it also can show regular patterns. This study focuses on the spatial distribution of quartz veins in Lower Devonian siliciclastic multilayer sequences from the High-Ardenne slate belt (Belgium, Germany) and compares the observed vein spacing with published fracture spacing in order (i) to investigate the effect of the layer thickness to vein spacing and (ii) to understand the processes of early vein development during the late stages of burial in a sedimentary basin at the onset of orogeny. The results show that a quasi linear relationship between vein spacing and layer thickness in thin (<40 cm) competent sandstone layers, embedded in a pelitic matrix, becomes non-linear in thicker sandstone layers (>40 cm). Vein spacing tends to increase to a maximum value becoming more or less independent of layer thickness. The resemblance with fracture spacing suggests that in an unfractured rock vein saturation can occur. High fluid pressures are responsible for vein nucleation but the stress state around the initial veins controls the spacing pattern. Subsequently, in a vein-saturated rock, or the existing veins will thicken by the process of crack-sealing, or a new cross-cutting vein generation will develop in case the regional stress field changes relatively with respect to the existing veins.
Located in Library / No RBINS Staff publications
Article Reference Evidence of pressure fluctuations recorded in crack-seal veins in low-grade metamorphic siliciclastic metasediments, Late Palaeozoic Rhenohercynian fold-and-thrust belt (Germany)
Located in Library / No RBINS Staff publications
Article Reference Late burial to early tectonic quartz veins in the periphery of the High-Ardenne slate belt (Rursee, north Eifel, Germany)
A detailed structural mapping and geometrical analysis of distinct bedding-(sub)perpendicular and bedding-parallel quartz veins has been performed in the northeastern part of the High-Ardenne slate belt (Rursee, North Eifel, Germany), with the aim to reconstruct the local fracturing/veining history. The structural relationship of these two types of veins as well as their relationship with cleavage, folds and faults allows attributing a pre- to early-Variscan age to these veins. The first type of veins is oriented (sub)perpendicular to bedding and consists of several, mutual cross-cutting generations, which clearly predate Variscan deformation. The second type of veins, bedding-parallel veins, post-dates the bedding-(sub)perpendicular veins and reflects bedding-parallel thrusting at the onset of Variscan deformation, predating folding. Subsequently, during progressive Variscan compression both types of veins were passively folded within characteristic, NW-vergent, overturned folds. Locally, due to flexural slip folding, reactivation along the bedding-parallel veins may have taken place.
Located in Library / No RBINS Staff publications
Article Reference Chitinozoan biozonation and new lithostratigraphical data in the Upper Ordovician of the Fauquez and Asquempont areas (Brabant Massif, Belgium)
A chitinozoan biozonation is established for the Upper Ordovician rocks of the Sennette valley in the Fauquez area and the Asquempont area, revising the existing chitinozoan biozonation of the Brabant Massif. The chitinozoans of fi ve formations (the Ittre, Bornival, Huet, Fauquez and Madot formations) are studied from 70 samples. The chitinozoan biozonation is correlated with Baltoscandia and the Avalonian Upper Ordovician type sections in the U.K. This correlation provides an accurate dating of the studied formations. A megaslumping event, affecting a part of the Ittre and Bornival Formation and causing the overturning of a pile of sediments estimated at minimum 200 m thick, may be placed in the mid Oandu (Cheneyan, middle Caradoc, early “Stage 6”). The volcanic rocks in the Fauquez area, formally thought to be restricted to the Ashgill, are confi ned to the late Caradoc - early Ashgill timespan. In addition to this, this paper presents new lithostratigraphical data on the Ittre Formation and the lower member of the Bornival Formation.
Located in Library / No RBINS Staff publications
Article Reference Lessons from assembling UCEs: A comparison of common methods and the case of Clavinomia (Halictidae)
Located in Library / RBINS Staff Publications 2024
Article Reference The Megachilidae (Hymenoptera, Apoidea, Apiformes) of the Democratic Republic of Congo curated at the Royal Museum for Central Africa (RMCA, Belgium)
Located in Library / RBINS Staff Publications 2023 OA
Article Reference A new limestone-dwelling leaf-toed gecko (Gekkonidae: Dixonius) from coastal hills in Cha-am, peninsular Thailand
We describe Dixonius pawangkhananti sp. nov. from coastal limestone hills in Cha-am District, Phetchaburi Province, peninsular Thailand. The new species differs from all currently recognized Dixonius by the following combination of morphological characters and pattern: maximal known snout-vent length of 42.6 mm; 16 longitudinal rows of dorsal tubercles; 30 to 32 paravertebral scales; 16 longitudinal rows of ventral scales across the abdomen; six precloacal pores in males, no pores in females; a marked canthal stripe; and a sexually dimorphic dorsal pattern consisting of bands (males) or blotches (females). This description brings the number of Dixonius species to ten, with four species endemic to Thailand.
Located in Library / RBINS Staff Publications 2020