A brief history
As pointed out by Jagt (2001, p. 712), probably the most detailed account of the original meaning of the ‘système maestrichtien’ of Dumont (1849) was provided by van der Heide (1954). That author pointed out that the Rapport sur la carte géologique du Royaume, in which the term was first used, was in fact nothing more than a brief report given by Dumont during the presentation of the geological map to the ‘Académie’ in Brussels, and that additional notes were being prepared. However, Dumont’s untimely death in 1857 meant that these notes were not published until 1878 when Mourlon’s work came out (Mourlon, 1878). Apparently, Mourlon was aware of the ambiguity surrounding the meaning of the term ‘système maestrichtien’ and insisted that it was Dumont’s maps that provided the clues. In 1832, Dumont had referred the section exposed at the St Pietersberg, south of Maastricht, to the so-called ‘Craie’ and to the ‘Calcaire de Maestricht’. Van der Heide (1954) noted that in this ‘Calcaire de Maestricht’ was included a certain portion of what we now know as the Gulpen Formation (Lanaye Member).
In 1849, Dumont changed the ‘Calcaire de Maestricht’ into the ‘système maestrichtien’, which was characterised as follows, ‘Le dernier système, dont le nom rappelle celui de la ville de Maestricht, où il est depuis longtemps connu par les fossils qu’il contient, commence, dans quelques localités de la province de Limbourg, par de la glauconie sableuse ou du calcaire glauconifère; il comprend le calcaire grossier exploité aux carriers de Maestricht, celui de Folx-les-Caves et de Ciply, et correspond au calcaire pisolithique du basin de Paris.’ In the legend of the map, which did not appear in print until 1852 (see van der Heide, 1954), the above-mentioned glauconitic level is referred to as ‘Calcaire poudingiforme ou glauconifère ….’, which Mourlon (1878, p. 334) later described as, ‘… calcaire … renfermant … de petits corps ovoïdes de 1 à 2 millimètres de long sur 1/2 de large, d’un brun foncé ou clair, extrêmement luisants, translucides, irrégulièrement disséminés (Sluse, Nederheim, Maestricht)’ and ‘Cette couche, qui forme la base du système maestrichtien …’. Of note in the 1849 citation is the phrase, ‘… dans quelques localités …’. It is now well known that the coarse-grained phosphatic/glauconitic and pyritic, bioclastic sand resting directly upon the Lichtenberg Horizon at the base of the Valkenburg Member (Maastricht Formation) shows extreme variation in thickness and composition, even within a single quarry (e.g., ENCI-HeidelbergCement Group quarry; compare W.M. Felder, 1975a; Zijlstra, 1994).
B.J. Romein (1962, 1963) also pointed out that originally (that is, in 1849), Dumont referred to the upper part of the section exposed at the St Pietersberg as ‘partie supérieure du Système de Maestricht’ and to the lower, of which 5-6 m were accessible at that time, as ‘partie inférieure’, the boundary between these units being a ‘couche graveleuse, glauconifère’. Later, he appears to have changed his mind since his field notes dated July 13, 1850 (see Romein, 1963, fig. 4), show that he then considered this ‘couche’ to be the base of his système maestrichtien. Subsequently, Kedves & Herngreen (1980) have rightly remarked that, as Dumont’s field notes of 1850 have never been published, his 1849 interpretation has priority. This means that Dumont’s système maestrichtien corresponds not only to W.M. Felder’s (1975a, b) ‘Formatie van Maastricht’, but also comprises the highest member (Lanaye Member, ‘Kalksteen van Lanaye’) of the underlying ‘Formatie van Gulpen’. This interpretation is the one currently favoured by most members of the Maastrichtian Working Group.
Fig. 4. Litholog of the Vijlen Member (Gulpen Formation) as exposed at the ENCI-HeidelbergCement Group quarry (Maastricht), with indication (arrow) of the lower/upper Maastrichtian boundary on the basis of benthic foraminiferal analyses (modified after W.M. Felder & Bosch, 1998, fig. 5).
Jeletzky (1951, p. 15) opined that Leriche’s (1929) concept of the Maastrichtian corresponded entirely with Dumont’s original view, and that, to avoid further confusion, that term should be applied to all strata in the type area older than the Danian/Montian and younger than d’Orbigny’s (1842) Sénonien or Coquand’s (1857) Campanien. We now know that Jeletzky (1951) was right in assuming the Campanian/Maastrichtian boundary to occur within the ‘Gulpen Kreide’ (= Gulpen Formation) and in accepting an early Maastrichtian age for what he referred to as ‘oberste Schichten der Hervien-Grünsande’.
The first lithostratigraphical subdivision of Cretaceous strata in the study area is that by Uhlenbroek (1912), which W.M. Felder (1975a, b; see also Albers & Felder, 1979; W.M. Felder & Bosch, 2000) later considerably refined and formalised by introducing formations and members, and defining type sections for all of these. Flint genesis and Milankovitch rhythmicity, in particular within the middle and upper portion of the Gulpen Formation (Lixhe 1-3 and Lanaye members), was discussed in detail by Zijlstra (1994). Subsequently, the first sequence-stratigraphical interpretation of the type Maastrichtian, on the basis of palynomorph distribution and biozonation, was proposed by Schiøler et al. (1997). Additional work along these lines came from Vandenberghe et al. (2004), while Keutgen & Jagt (2009), Keutgen et al. (2010) and Walaszczyk et al. (2010) added estimated absolute numerical ages for sequence boundaries (see Table 2), proved that the great majority of early Maastrichtian coleoid taxa in the Vijlen Member (up to the base of interval 4) had been reworked and documented that inoceramid bivalves allowed correlation with central Europe (Poland), North America and South Africa, respectively. The most recent addition is a belemnite-based analysis of strontium, carbon and oxygen isotopes from the type section of the Maastrichtian Stage, which allows a more reliable, long-distance correlation to sections in northern Europe, North Africa and the South Atlantic (Vonhof et al., 2011).
Table 2. Estimated absolute numerical age for sequence boundaries based on the long (0.41 myr) eccentricity cycles and comparison with ages of biozone boundaries in northwest Germany (Kronsmoor and Hemmoor sections). MFm = Maastricht Formation; C/M boundary = Campanioan/Maastrichtian boundary (modified after Keutgen & Jagt, 2009, table 2).