Données palynologiques nouvelles dans l'Ordovicien inférieur du bassin de la Senne, Massif du Brabant, Belgique

The massive phyllites of Oisquercq in the Senne Basin are followed up by quartz phyllites which have yielded acritarchs of several different ages for the different localities, viz. Arenig or Llanvirn at Asquempont (Brussels-Charleroi canal section), lower Tremadoc at Virginal (railway cutting north of Virginal Station), Arenig or Lanvirn at Quenast (railway cutting east of Quenast). These new micropalaeontological data show the existence of two quartz phyllitic intervals in the Senne Basin, and suggest the correlation of the first with the " quartzophyllades" of Chévlipont, and the second with the "quartzophyllades" of the Abbey of Villers-la-Ville of the Dyle Basin. They thus provide support for Fourmarier's opinion that the grey, variegated and green rocks of Oisquercq would be the stratigraphie equivalent, in different facies, of the black rocks-of Mousty

Biostratigraphie par Acritarches du Cambro-Ordovicien de Belgique et des regions limitotrophes: synthese et perspectives d'avenir

The stratigraphic significance of Cambrian and Ordovician acritarchs in Belgium and adjacent areas is discussed. It now appears that the age of the Deville group in the Ardenne (more precisely the upper part of this group) should be broadened to include not only the middle and late Lower Cambrian, but also the early Middle Cambrian. The Revin group comprises several well dated levels between the middle late Middle Cambrian to the latest Upper Cambrian. The lower part of the Salm Group (the so-called Sm1) comprises strata of early and late Tremadoc age. The age of the uppermost part of the Salm group (Sm3b) lies between the Llanvirn and the early Caradoc. Within the Brabant Massif, recent investigations of several boreholes have enabled the relative ages of the Oisquercq and the Mousty «assises» to be reconsidered, and the problem of their synchronism or diachronism to be addressed. If the fossiliferous samples prove to belong to these «assises», acritarchs would indicate a Lower or early Middle Cambrian age for the Oisquercq (comparable to the age of the Deville group) and an approximately Middle to Late Cambrian age for the Mousty (comparable to that of the Revin group). Comparison of the different areas studied shows a probable synchronism of the Deville-Revin boundary, the later possibly coincident with that between the Oisquercq and Mousty; a likely unconformity in the Revin group of the Rocroi Massif; sedimentary variations in the Cambrian (Mousty lacking in some places) and the Ordovician (Tribotte facies restricted to the Dyle area) of the Brabant Massif comparable with block faulting phenomena; existence of? eustatic late Tremadoc regression and contemporaneous unconformities; a possible confirmation, by means of bathymetric criteria, of a subdivision of Lower Palaeozoic strata into 3 megasequences, and a correlation of this cyclicity with that observed in southern Great Britain

Critères palynostratigraphiques conduisant à la reconnaissance d'un pli couché Revinien dans le sondage de Grand-Halleux

The biostratigraphY based on palynology is given of the most important sections through the lower and middle Revinian of the Stavelot, Rocroi and Givonne massifs. Four assemblage-zones of interregional value are recognised. Assemblage-zone 4 (VANGUESTAINE, 1974) is subdivided into subzones 4a and 4b. The new biostratigraphic information confirms the earlier interpretation (VANGUESTAINE, 1968 and 1970) of black rocks recovered at the base of the Grand-Halleux borehole. They are of Revinian age and occur in a recumbent fold with a subdhorizontal axial plane.The palynological data combined with a lithological comparison of different sequences have shown that: 1.- there is a possible diachronism of lithofacies at the Rn1a-Rn1b boundary between the central part of the Stavelot massif and the overturned flank of the Revinian fold in the Grand-Halleux borehole; 2.- there may be diachronism of the quartzitic rocks at the base of Rn2a in the normal and overturned flanks of the same borehole; 3.- a condensed sequence or, possibly, even a stratigraphic gap exists at Revin (Rocroi massif) for the horizon corresponding to acritarch zone 3 and subzone 4a of the Stavelot massif; 4.- the Rv2b horizon is diachronous between the Rocroi and Givonne massifs. The stratigraphic distribution is given of several species selected on the basis of abundance, easily recognisable morphology and short ranges (Figs 3,6,8,9). Sorne species which are either rare, of undifferentiated morphology or long ranging, are treated separately in Annexe I. Four plates illustrate both common and rare species of the different zonal assemblages. Annexe II deals with two new genera: Cristallinium and Timofeevia, as well as one new species: Timofeevia phosphoritica; an additional two species, Hemisphaerium ? sp. A and Timofeevia sp. A, are newly described but left in open nomenclature. Four new specific combinations are proposed, viz. Cristallinium cambriense (SLAVIKOVA, 1968), Elektoriskos cerinus (VOLKOVA, 1968), Timofeevia lancarae (CRAMER et DIEZ, 1972) and Timofeevia pentagonalis (VANGUESTAINE, 1974)

New biostratigraphic and chronostratigraphic data from the Sautou formation and adjacent strata (Cambrian, Givonne inlier, Revin group, Northern France) and some lithostratigraphic and tectonic implications

In the western part of the Givonne Inlier, the “Falizette” and the “Claire-Terne de la Borne” rivers exhibit sections described as belonging, in ascending order, to the La Chapelle (Rv2), Illy (Rv3) and Sautou (Rv4) Formations. The “Falizette” section yielded acritarchs of zone 4 (locally 4b) similar to assemblages observed earlier (Vanguestaine, 1978) in the “Givonne” and “ Hatrelle” valleys of the Givonne Inlier. In the “Terne de la Borne” section, the strata described as belonging to the Illy Formation and most part of the Sautou Formation, the latter in its type locality, provided acritarchs of zone 2 (and possibly 1) and do not correlate therefore with the Rv3 and the Rv4 of the Rocroi Inlier but with Rv2 (and possibly Rv1) of the same area. This correlation is reinforced by the observation in the sequence of a roo? ng slate seam, previously undescribed, a possible equivalent of the Peureux Member, characterizing the upper part of Rv1 in the Rocroi Inlier. Besides specimens pointing to an acritarch biozone 2 assemblage, the richest sample of the Sautou Formation also yielded rare examples of acritarch species which have not previously been recorded in Belgium or the surrounding areas. They are Adara alea, Celtiberium geminum, possibly Eliasum llaniscum, Multiplicisphaeridium martae and Retisphaeridium postae. The probable metazoan Ceratophyton vernicosum has also been observed. Compared to the well dated Newfoundland Cambrian succession, acritarch biozones 2 assemblages indicates a mid Middle Cambrian age. This new chronostratigraphic result not only allows a better calibration of the Belgian acritarch zonation with respect to the acritarch and trilobite international zonations but also con? rms our interpretation of the lithostratigraphic succession

Decouverte d'un brachiopode inarticulé <i>Acrothele</i> cf. <i>Bergeroni</i> Walcott, dans le Revinien inferieur de trois-ponts, Cambrien du Massif de Stavelot, Belgique

The Revinian (Cambrian) of the Ardenne, from which no macrofossils have hitherto been recorded, has yielded two inarticulate brachiopods determined here as Acrothele cf. bergeroni WALCOTT. The specimens were found south of Trois-Ponts in the Stavelot Massif, at a horizon referred to division Rn1a. The stratigraphic age suggested by the brachiopods is compared with that indicated by acritarchs : a Middle Cambrian age seems probable

Acritarchs from the Abbaye de Villers and Tribotte Formations in their type section of the Thyle river valley (Middle Ordovician, Brabant Massif, Belgium) and their stratigraphic implications

Reinvestigation of the Thyle river section, in the southern part of the Brabant Massif, has led to a better understanding of acritarch distribution in the Middle Ordovician Abbaye de Villers and Tribotte formations, and their stratigraphical significance in the type localities of both formations. The middle and upper parts of the Abbaye de Villers Formation and the lower part of the Tribotte Formation yielded an acritarch assemblage corresponding to the Frankea hamata-Striatotheca rarirrugulata Acritarch Zone of the English Lake District, demonstrating a late Arenig (late Fennian, early Darriwilian) age. Two species, Adorfia firma and Arbusculidium filamentosum, not recorded in the overlying Rigenée Formation, probably have their last appearances below the Arenig-Llanvirn boundary. Acritarch (late Arenig, late Fennian) and chitinozoan datings (middle Arenig, Whitlandian pro parte) of the middle part of the Abbaye de Villers Formation suggest correlation with the older part of the Frankea hamata-Striatotheca rarirrugulata Acritarch Zone. The uppermost part of the Tribotte Formation shows palynological similarities with the overlying Rigenée Formation. The exact position of the Arenig-Llanvirn boundary in the Thyle river section is not yet known and does not necessarily coincide with the Tribotte-Rigenée lithostratigraphical boundary

Observations palynologiques dans le Couvinien (Emsien terminal et Eifelien) du bord oriental du synclinorium de Dinant, Belgique

The Couvinian (a chronostratigraphical unit equivalent to the Uppermost Emsian and to the Eifelian) was made the object of palynological studies concentrating as much on acritarchs as on spores in the eastern flank at the synclinorium of Dinant. The samples are located in a lithological sequence, certain of the units in which are new and defined here for the first time. Their biostratigraphical relations with the type sequence on the south side of the basin were established on the bases of brachiopods. Twenty-three spore species are recorded. Grandispora velata and hystricospores make their first appearance whithin the sequence studied, the first in the Upper Couvinian, the second probably in the Upper Emsian (pre-Couvinian). Their absence permits to date also part of the conglomerate beds which characterize the base of these sequences. Thirty-five species of acritarchs were recognized. Certain are reworked from sediments as ancient as the Cambra-Ordovician, the majority are ubiquitous and already known from the Lower Devonian and even from the Silurian. Some correspond to species already described from the Middle or Upper Devonian. On the basis of the latter, a subdivision of the Couvinian into 4 zones is proposed

Miospores et acritarches de la formation d'Hydrequent (Frasnien superieur à Famennien Inferieur, Boulonnais, France)

The upper part of the Hydrequent Shales, which are inserted between the last dolomite layer and the Ste Godeleine Sandstone, consists of at least 20 m of shaly sediments with thin sandy partings. The 44 samples studied have yielded numerous spore and acritarch species which permit a very detailed palynological zonation to be established, mainly corresponding to the upper Frasnian. The highest samples, 0.5 m below the Ste Godeleine Sandstone, can be correlated with the lower Famennian of the Belgian stratotype. The Frasnian-Famennian boundary thus falls within the Hydrequent Shales between 0.5 and 2.5 m below the Ste Godeleine Sandstone

Late Devonian and Carboniferous acritarch stratigraphy and paleogeography

Detailed analysis of literature on late Devonian and Carboniferous acritarchs learns that, up to now, late Devonian acritarch zonation has been proposed only for Algeria, U.S.A. and Belgium. These zonations comprise only part of the Upper Devonian sequence in U.S.A. and Belgium, whereas the complete Upper Devonian acritarch zonation for Algeria is not matched by a detailed chronostratigraphic subdivision for that last area. Upper Devonian and Carboniferous acritarchs have also been described from many other areas in North and South America, Africa, Europe, Asia and Australia, but the data are mainly based on spot sampling or these are restricted to rather reduced intervals.Comparison between the abundance of acritarchs in late Devonian sequences of Ohio and Belgium reveals consistent patterns of successive maxima and minima. They may reflect global changes in the environment and be related to worldwide events. Remarkable is the extremely low number of acritarchs throughout the Carboniferous succession. This forms a clear contrast with the relative abundance of acritarchs in marine Devonian sediments

Acritarches du Cambrien moyen de la vallée de Tacheddirt (Haut-Atlas, Maroc) dans le cadre d'une nouvelle zonation du Cambrien

The limestones and siltstones which crop out in the Tacheddirt Valley of the High Atlas Mountains (Morocco), have provided 13 acritarch localities yielding 16 species, including two new ones, viz. Multiplicisphaeridium chakor and Timofeevia tacheddirtensis. Two different associations have been distinguished. The older one is the most diversified and is characterised by the constant presence of Cristallinium cambriense (Slavikova) Vanguestaine, 1978, Eliasum llaniscum Fombella, 1978 and Timofeevia lancarae (Cramer & Diez) Vanguestaine, 1978. The younger one is only composed of sphaeromorphs and Micrhystridium. Trilobite remains reported in the present paper date the older association as the Paradoxides oelandicus "stage" or early Paradoxides paradoxissimus "stage" of the Middle Cambrian. The younger assemblage is also associated locally with Middle Cambrian trilobites.A biostratigraphic zonation for the entire Cambrian shows that 7 acritarch Zones or Superzones may be distinguished. This zonation allows the rocks at Tacheddirt to be assigned biostratigraphically. The chronostratigraphic implications are dealt with in the conclusions