Frasnian reefs, mounds and atolls from Belgium: sedimentology and magnetic susceptibility – A FIELDTRIP GUIDEBOOK

in Geologica Belgica (2010), 13(4), 483-496

The stratigraphical architecture of the Quaternary deposits as support for hydrogeological modelling of the central zone of Hanoi (Vietnam)

in Geologica Belgica (2010), 13(1-2), 77-90

The Quaternary deposits of the Hanoi area have been investigated in order to provide information required for the design of a groundwater-flow model. Limited sedimentological data exist from 32 ... [more ▼]

The Quaternary deposits of the Hanoi area have been investigated in order to provide information required for the design of a groundwater-flow model. Limited sedimentological data exist from 32 destructive drillings carried out previously in the study area. The data base contains hydrographical and hydrogeological observations, but few sedimentological details. This is in contrast with the more seaward regions of the area where the Holocene deposits of the Red River plain has previously been studied. However, a comparison of the results obtained in this study with the previous studies indicates that the Hanoi sediment succession developed in an incised valley under conditions of rapid relative sealevel rise until ca. 7-6 a cal BP. The succession consists initially of alluvial floodplain deposits conformably overlain by mud deposited at the head of an estuary which filled with continuing rapid sea-level rise. Once the relative sea-level rise stabilized, fluvial deposition prograded over the adjacent estuarine mud. The development of a groundwater-flow model requires knowledge of the three-dimensional distribution of the various deposits. Despite the paucity of information with respect to sediment description, a model of the entire Quaternary sequence is presented in several lithostratigraphic crosssections and a panel diagram. The latter forms the basis for the construction of a contour map of the base of the Pleistocene and Holocene deposits, and for a sequence map of the Quaternary deposits in the study area. [less ▲]

A magnetic susceptibility curve for the Devonian Limestone from Belgium

in Geologica Belgica (2010), 13

This paper proposes a first magnetic susceptibility (MS) curve for the Devonian Limestone from Belgium. A comparison with a large scale depositional model shows the complex relations between MS and ... [more ▼]

This paper proposes a first magnetic susceptibility (MS) curve for the Devonian Limestone from Belgium. A comparison with a large scale depositional model shows the complex relations between MS and paleoenvironments. Other Devonian-scale MS curves from other parts of the world are necessary to constraint these relations. [less ▲]

Towards a palaeogeographical and sequential framework for the Givetian of Belgium

in Geologica Belgica (2009), 12

This paper starts with a review of facies and reef morphologies from the Givet Group in the Ardenne area. Platform initiation and evolution are analyzed and related to external factors at a global scale ... [more ▼]

This paper starts with a review of facies and reef morphologies from the Givet Group in the Ardenne area. Platform initiation and evolution are analyzed and related to external factors at a global scale (sea level changes, climate changes), at a regional scale (local subsidence, change in detrital supply) and to internal factors like organic communities composition. More specifically, the location of reef barriers are related to sea level changes and a sequence stratigraphic canvas is proposed. [less ▲]

Detailed sedimentological study of a non-classical succession for Trois-Fontaines and Terres d'Haurs formations (Lower Givetian, Marenne, Belgium)- Introduction of the Marenne Member

in Geologica Belgica (2008), 11

This work details for the first time the sedimentology of the Marenne quarry. It exposes a remarkable succession of strata from the Trois-Fontaines Formation and the base of the Terres d’Haurs Formation ... [more ▼]

This work details for the first time the sedimentology of the Marenne quarry. It exposes a remarkable succession of strata from the Trois-Fontaines Formation and the base of the Terres d’Haurs Formation. Two sections (Marenne East and Marenne Centre) are investigated within the quarry. The first one (115 metres) covers both formations and is characterized by a mixed carbonate-siliciclastic succession replacing the classical base of the Trois-Fontaines Formation. We propose here to include these particular facies into a new member of the Trois-Fontaines Formation, the Marenne Member. The second one (48 metres) exposes a reefal lens also attributed to this new Marenne Member. Magnetic susceptibility was used to confirm geometric correlations previously obtained between these two sections. Petrographic study leads to the definition of 14 microfacies which are integrated into three palaeoenvironmental models. The first model (six microfacies) is proposed for the Marenne Member. In this ramp model, terrigenous inputs are particularly important. The mid-ramp is composed of four microfacies more or less influenced by storm events. The inner ramp (limited to the FWWB vicinity) is characterized by the development of the reefal lens and by peloidal microfacies. The upper part of Trois-Fontaines Formation is depicted by a back-reef model (three microfacies) which is mainly dominated by lagoons. However, intermittent agitation and non-restricted settings allow the local development and the reworking of branching organisms. The last model proposed (five microfacies) concerns the Terres d’Haurs Formation and corresponds to a ramp profile with the development of shoals. Those shoals locally protect semi-restricted lagoons. Algal mats are also observed. The last part of the work concerns the sedimentary dynamics and proposes sea level variations as the key parameter probably responsible for the succession of these three depositional settings. [less ▲]

Sedimentology and magnetic susceptibility of the Couvin Formation (Eifelian, South Western Belgium): Carbonate platform initiation in a hostile world

in Geologica Belgica (2007), 10(1-2), 47-67

The Eifelian of Belgium is mainly characterised by a mixed siliciclastic-carbonate sedimentation on a ramp profile. In this context, the Couvin Formation is the more important and remarkable exception. It ... [more ▼]

The Eifelian of Belgium is mainly characterised by a mixed siliciclastic-carbonate sedimentation on a ramp profile. In this context, the Couvin Formation is the more important and remarkable exception. It represents a carbonate platform initiation in a hostile environment. This work is mainly based on the stratotype, corresponding to two stratigraphic sections located in Couvin, along the southern border of the Dinant Synclinorium. These sections are the Eau Noire and Falaise de l'Abime sections. Unfortunately, they are discontinuous. To allow a better understanding of the sedimentary dynamics, the data are complemented by a shorter but continuous section located in Villers-la-Tour (3.5 km West of Chimay). Petrographic study leads to the definition of 14 microfacies which are integrated in a palaeogeographical model. It corresponds to a platform setting where the reef complex is mainly constituted by an accumulation of crinoids, stromatoporoids and tabulate corals. The microfacies evolution is interpreted in terms of bathymetrical variations. It shows a general shallowing-upward trend encompassing the vertical succession of fore-reef settings, reef development, back-reef and then lagoon environment. This interpretation is supported by trends in mean magnetic susceptibility data, providing a better understanding of the sedimentary dynamics. Moreover, these data show positive correlation with concentrations of detritic minerals, but an inverse relationship with well washed skeletal limestones. The comparison of the three studied sections leads to considerations concerning the lateral variability in the Couvin Formation indicating more agitated conditions in the Abime Member in Villers-le-Tour section. [less ▲]

Frasnian

in Geologica Belgica (2006), 9(1-2), 19-25

The name Frasnian, which comes from the locality of Frasnes near Couvin in Belgium, was introduced by Gosselet in 1879 and was formally retained for the lower stage of the Upper Devonian by the ... [more ▼]

The name Frasnian, which comes from the locality of Frasnes near Couvin in Belgium, was introduced by Gosselet in 1879 and was formally retained for the lower stage of the Upper Devonian by the Subcommission on Devonian Stratigraphy in 1981. The modern definition of the Frasnian is based on conodonts and the historical background of the stage is developed in detail herein. Data about the lithostratigraphy, sedimentology, biostratigraphy, chronostratigraphy and absolute age of the Frasnian can also been found in this contribution. [less ▲]

Disused Palaeozoic regional stages from Belgium: Devillian, Revinian, Salmian, Gedinnian and Burnotian.

in Geologica Belgica (2006), 9(1-2), 191-197

Frasnian carbonate buildups of southern Belgium: the Arche and Lion members interpreted as atolls

in Geologica Belgica (2005), 8(1-2), 69-91

The facies architecture, sedimentary dynamics and paleogeographic evolution were reconstructed for a number of Frasnian buildups developed on a carbonate platform on the south side of the Dinant ... [more ▼]

The facies architecture, sedimentary dynamics and paleogeographic evolution were reconstructed for a number of Frasnian buildups developed on a carbonate platform on the south side of the Dinant Synclinorium (Belgium). Bed-by-bed sampling and detailed petrography were complemented by magnetic susceptibility analysis, allowing for high-precision lateral correlation. Six facies were recognised in the buildups, each characterized by a specific range of textures and assemblage of organisms: grey, pinkish or greenish limestone, with stromatactis, corals and stromatoporoids (facies A3-L3); grey limestone with corals, peloids and dasycladales (facies A4-L4); grey, microbial limestone (facies A5-L5); grey limestone with dendroid stromatoporoids (facies A6-L6); grey, laminar fenestral limestone, (facies A7-L7); grey, bioturbated limestone (facies A8-L8). The time-equivalent off -buildup sediments include a large amount of transported material that originally came from the buildups. Sedimentological evidence suggests that facies A3-L3 developed between the storm wavebase and the fairweather wavebase, in a oligophotic environment. This facies contains lenses of facies A5-L5, with stromatolitic coatings and Renalcis-rich thrombolitic bushes. These lenses were developed in greatest abundance closest to the fairweather wavebase, and they became anastomosing. Facies A6-L6 was developed in an environment with slightly restricted water circulation; there is a steady transition between this facies and the fenestral limestone A7-L7, which were deposited in a moderately protected subtidal to intertidal area. Facies A8-L8 developed at subtidal depths in a quiet, lagoonal environment. The buildups started with the development of facies A3-L3, with microbial lenses and algal facies becoming progressively more abundant upwards. Above about 20m in each buildup, more protected facies are found in the buildup’s central part. This atoll-like geometry suggests the development of restricted sedimentation in this central area, sheltered by bindstone or floatstone facies. The initial development of the lower part of a buildup during a transgression and subsequent highstand would have been followed by reefal growth along the edge of the buildup during the succeeding lowstand; an atoll crown would then have started to develop during the following transgressive stage. The presence of restricted facies can be seen as the consequence of the balance between sea level rise and reef growth. [less ▲]

A Psammosteid Heterostracan (Vertebrata: Pteraspidomorphi) from the Emsian (Lower Devonian) of the Grand Duchy of Luxembourg

in Geologica Belgica (2004), 7(1-2), 21-26