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EUROPEAN ASSOCIATION OF VERTEBRATE PALAEONTOLOGISTS 14th Annual Meeting – Teylers Museum, Haarlem (the Netherlands), 6-10 July 2016

Field guide

THE UPPER CRETACEOUS AND LOWER PALEOGENE IN THE TYPE AREA OF THE MAASTRICHTIAN STAGE (72.1–66 Ma) John W.M. JAGT1 and Elena A. JAGT-YAZYKOVA2

1 Natuurhistorisch Museum Maastricht, de Bosquetplein 6-7, 6211 KJ Maastricht, the Netherlands (john.jagt@maastricht.nl; www.nhmmaastricht.nl) 2 Opole University, Department of Biosystematics, Oleska 22, 45-052 Opole, Poland (eyazykova@uni.opole.pl)

INTRODUCTION Ever since the chance discovery (autumn 1992) of the spectacular Cretaceous–Paleogene (K/Pg) boundary section at the Geulhemmerberg underground galleries (Geulhem, Berg en Terblijt), a few kilometres east of Maastricht, there has been a renewed interest in the stratigraphy and faunal content of the type section of the Maastrichtian Stage (Fig. 1a-b). For the first time, isotope analyses (C, O, Sr) have been carried out (Vonhof et al., 2011), flint genesis and Milanković cyclicity documented in detail and a preliminary sequence-stratigraphic interpretation of the type Maastrichtian published. Added to that is an increase in faunal studies, both of bioclast assemblages (ecozonations) and of macrofossil associations, with the emphasis on their value for interregional correlations (Fig. 2) and palaeobiological/-ecological interpretations.

The ENCI-HeidelbergCement Group quarry (Sint-Pietersberg), just south of the outskirts of the city of Maastricht, is the most important of several key sections of the type area of the Maastrichtian Stage.

Fig. 1a. Extended type area of the Maastrichtian Stage (southern Limburg, the Netherlands) and contiguous areas in northeast Belgium and northwest Germany.

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Fig.1b. Lithostratigraphy of Cretaceous (Santonian-Maastrichtian) and lower Paleogene (Danian) strata in the area and key horizons used in regional correlations (W.M. Felder and Bosch, 2000).

Fig. 2. Correlation of Cretaceous-lower Paleogene strata with macrofossil zones of northwest Europe (northern Germany, Denmark; from Jagt, 1999).

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ENCI-HeidelbergCement Group quarry – Sint-Pietersberg, Maastricht (outcrop 61F-19)

Fig. 3. Log of the section (formerly) exposed at the ENCI-HeidelbergCement Group quarry, supplemented by borehole data (W.M. Felder and Bosch, 1998).

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The extensive quarry of ENCI-HeidelbergCement Group includes the type section of the Maastrichtian Stage (Dumont’s ‘système maestrichtien’, 1849) as currently defined, which comprises the steep rock face directly behind the main office building, and underneath the Lichtenberg farmstead. Conditions of exposure in the adjoining quarry change rapidly on account of ongoing quarrying activities, making virtually the entire section easily accessible. The current ‘Plan van Transformatie van het ENCI terrein’ works towards cessation of quarrying activities by the summer of 2018, and a ‘reshaping’ of quarry faces and creation of several isolated blocks illustrating various portions of local stratigraphy. Below only those lithostratigraphical units that have yielded notable and/or common vertebrate remains will be listed and briefly discussed, with ample reference to literature sources. 1. GULPEN FORMATION Lixhe 1-3 members Villain (1977) typified these units as biomicrites (wackestones), deposited in a setting with oceanic influence, as based on calcareous nannofossils and planktonic forams, but without transport or horizontal currents. Palaeowater depth was considered to have been between 80 and 150 m. Zijlstra (1994) interpreted the Lixhe 3 Member as a pure coccolithic wackestone, with silt-sized bioclasts, horizontal flint beds, and considered it to be homogeneously bioturbated (Planolites, Zoophycos, Chondrites, Bathichnus and Thalassinoides-type deep burrows). Since the Lixhe 3 Member occurs mostly below the present-day ground water table, it is (dark) grey in colour and still contains reduced iron (pyrite, smectite and glauconite).

Flint genesis was studied in detail by Zijlstra (1994) in the upper part of the Gulpen Formation (Lixhe and Lanaye members; Fig. 3), which shows a regular succession of c. 75 thickening-upwards, continuous flint levels. These nodule layers are considered to have formed when detrital skeletal opal dissolved during late diagenesis and concentrated in sites of relatively high early diagenetic authigenic silica polymorph concentration. These silica polymorphs precipitated in the anoxic redox zones of bacterial sulphate and/or carbon dioxide reduction, situated below and parallel to the sediment surface. The highest concentrations of authigenic silica occurred during periods when deposition rate was low, and when sediment resided for a relatively long period in the anoxic redox zone. The rhythmic vertical variation of the flint nodule concentration is held to reflect the influence of periodic variation of the earth's orbital parameters (precession index) on climate, oceanography and periodically varying deposition rates. Zijlstra (1994) also attempted to link the flint-rich sequence of the Lixhe and Lanaye members to Milanković rhythmicity. His conclusion: the chalk with flint contains 75 flint layers, with individual members containing 20, 15, 20 and 20 flint layers, respectively, and with flint levels forming bundles of 5, suggesting that this sequence may be interpreted as E4 (1,300 kyr), E3 (413 kyr), E2 and E1 (98 and 126 kyr) eccentricity cycles and P (20 kyr) precession cycles.

The Gulpen Formation as exposed south of Maastricht reaches a total thickness of some 40 m and contains about 75 precession-induced sedimentary cycles. Zijlstra (1994) assumed these cycles to have been deposited during approximately 75 x 20 = 1,5 million years. The increase of mean cycle thickness from 4 dm at the base to 1 m at the top of the Gulpen Formation sequence would then reflect an increase in mean deposition rate from 2 to 5 cm/kyr. To Zijlstra (1994), this fine-grained chalk with a high flint concentration and symmetrical thin-bedded eccentricity cycles reflected a low-energy environment with a low deposition rate. The coarser-grained (tuffaceous) chalk, on the other hand, with a lower flint concentration and asymmetrical, thick-bedded eccentricity cycles reflects a high-energy environment with high erosion/deposition rates.

On the basis of a quantitative palynological analysis of a section in the Lixhe 3 Member, P.J. Felder et al. (2003) recorded an obvious relationship between pollen content of the sediment and short-term climatic changes (cooling trends), as based on oxygen isotopes.

The Lixhe 1-3 members generally yield few macrofossils, with the exception of holasterid echinoids, coleoid cephalopods and various bivalves. Of note amongst the echinoids is the, apparently sudden, replacement in the Lixhe 3/Lanaye members of the cold-water genus Echinocorys (E. ex gr. conoidea) by the (sub)tropical Hemipneustes (H. striatoradiatus and H. oculatus). Coleoids are all assignable to the Belemnitella junior group, by definition the index taxon of the temperate/boreal upper Maastrichtian.

■ The find of mosasaur ‘Carlo’, a taxon held to be closely related to Prognathodon sectorius, in the upper Lixhe 3 Member (September 2012) came as a complete surprise (Schulp and Jagt, 2013). In all, some 30–40 per cent of the skeleton has been recovered, inclusive of a partial skull. Portions of dentary, maxilla and premaxilla and several vertebrae have been freed from the matrix, but more work is needed during the coming years. A pathology of the snout has been briefly described recently (Bastiaans et al., 2014). Although a handful of neoselachian teeth have been found close to the

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skeleton of ‘Carlo’, there is no evidence of scavenging (tooth marks) to date. For the time being, preparation of ‘Lars’, collected between April and September 2015, has been given precedence in the Sciencelab at the Natuurhistorisch Museum Maastricht.

Fig. 4. Local synsedimentary tectonics and sequence-stratigraphic interpretation of the section exposed at the ENCI-HeidelbergCement Group quarry (from Schiøler et al., 1997).

Lanaye Member This unit was interpreted by Villain (1977) as a compact biomicrite (with biomicrosparite patches), deposited in a setting with oceanic influence still, with horizontal transport of sediment particles by episodic currents, and a palaeo waterdepth of 40 and 80 m. Liebau (1978) characterised the depositional setting as a platform environment with minor open ocean influence (middle sublittoral) and subtropical temperatures.

Zijlstra (1994) considered this unit to represent a pure (97 per cent) coccolithic bioclastic silty, homogeneously bioturbated packstone, with large-scale wavy lamination preserved in places. Well-developed planar-parallel flint nodule levels occur at 0.5-1.5 m interspaces. Nodules are either tubular (formed around crustacean burrows) or platy, and traces of shallow bioturbation and sediment mixing are common but poorly preserved. The activity of deep burrowers is preserved as ghost structures in flint.

In this member there is a flint maximum (Figs. 3, 4), which Schulz and Schmid (1983) held to correspond to a similar maximum at Hemmoor (NW Germany). The first appearance datum (FAD) of the index nannofossil taxon Nephrolithus frequens seems to follow immediately upon this flint maximum at both localities. Present data, however, suggest this correlation to be erroneous; the level of correlation needs to be situated lower, i.e., within the Lixhe member complex.

The occurrence of the benthic foraminifera Reussella cimbrica, Coleites reticulosus and Bolivinoides decorata gigantea assigns an unequivocal early late Maastrichtian age to this unit. Amongst macrofossil of correlative value are mainly coleoid cephalopods, all assignable to the Belemnitella junior group, and ammonites comprise only poorly preserved, phosphatised baculitids. Hemipneustes is not the only 'southerly' echinoid genus to appear first in this member; it is accompanied by e.g., Oolopygus and Nucleopygus. The crinoid fauna does not comprise any isocrinids, which abound in the white chalk facies elsewhere in northwest Europe. Inoceramid bivalves comprise only 'tegulated' types (Walaszczyk et al., 2010), but poor preservation at

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times precludes definite specific assignment, particularly in friable biocalcarenites. Additional evidence amongst micro- and macrofauna for an increasing Tethyan/proto-Mediterranean influence during this interval is furnished by ostracods, mosasaurs and cheloniid turtles.

■ The first representatives of Mosasaurus hoffmanni, predominantly from the Eben Emael area (province of Liège, northeast Belgium; see Garcet, 1982; Lingham-Soliar, 1995; Cornelissen et al., 2011), are known from this member, although the underlying Vijlen Member (intervals 5 and 6) in the Haccourt-Lixhe area (province of Liège) has also furnished a few isolated tooth crowns/teeth that are closely comparable. Associated mosasaur taxa in the Lanaye Member include Carinodens belgicus and Plioplatecarpus marshi, generally in the upper part of the member (Lingham-Soliar, 1994, 1999; Jagt, 2005; Mulder et al., 2013). Flint level 18 of this unit at the ENCI quarry produced (August 1998) a partial skeleton, inclusive of a near-complete skull, of a new taxon, Prognathodon saturator (see Dortangs et al., 2002; Schulp, 2006). Associated is the cheloniid turtle Allopleuron hofmanni (see Mulder, 2003), the FAD of which is lower, in the Vijlen Member (interval 6), as determined on an isolated lower jaw from the Haccourt area.

2. MAASTRICHT FORMATION Valkenburg Member The base of W.M. Felder's (1975) Maastricht Formation corresponds largely to the original definition of the 'système maestrichtien' by Dumont (1849). The boundary (= Lichtenberg Horizon) between this formation and the underlying Gulpen Formation is an irregular, slightly undulating erosion surface.

Zijlstra (1994) noted the occurrence of several tens of metres wide and dm-deep depression at the top of the Lanaye Member, filled with coarse-grained phosphatic/glauconitic and pyritic bioclastic sand, representing the base of a fining-upward cycle. Depositional lamination was shown to be virtually entirely destroyed by bioturbation, and the sand to contain skeletal elements, reworked chalk and low concentrations of sand-sized extrabasinal quartz and heavy mineral grains.

The Valkenburg Member is 2.5 m thick, shows a fining-upward trend, with an upper cycle of 1.5 m thickness, with a rather fine-grained, slightly lithified (proto-hardground), pure carbonate top with poorly developed flint nodules around spreiten and Thalassinoides type burrows, as well as Teichichnus. The macrofauna comprises numerous crinoid ossicles, echinoid, craniid and thecideid brachiopods, cirripedes, coleoids, nautilid jaw elements, faecal pellets (hence Dumont’s name ‘Couche à coprolithes’, 1849) and numerous vertebrate remains (neoselachians [Herman, 1977], teleosts [Friedman, 2012; Taverne and Goolaerts, 2015], mosasaurs, cheloniid turtles). All of these taxa have also been recorded from the underlying Lanaye Member.

■ This particular level has produced the first (and so far, only) example of a mammal, Maastrichtidelphys meurismeti (Martin et al., 2005), in the area. The lowermost portion of this unit has also yielded a partial mosasaur quadrate (Schulp and Jagt, 2015) of a taxon closely related to Prognathodon saturator, but differing in details and perhaps best linked with P. sectorius, as well as a partial sawfish (batoid) snout with rostral and oral teeth of a species first described from the upper Maastrichtian of Morocco, Ganopristis leptodon.

Gronsveld Member According to Zijlstra (1994), the lower part of the Gronsveld Member also consists of fining-upward cycles with a phosphatic, glauconitic-pyritic, bioclastic sand at the base, the sand of the lowermost cycle being characterised by well-developed wavy lamination. Wavy laminated sediment at the base of these cycles changes upwards via (sub)horizontally laminated sediment towards lithified homogeneously bioturbated, fine-grained, purer carbonate sediment at the top. The upper part of this unit consists of well-sorted bioclastic, fine sand with low-angle, large-scale wavy lamination (hummocky stratification), with flint nodules forming laterally restricted curvi-planar levels (Zijlstra, 1994).

Of particular note is Zijlstra's (1994) observation that the glauconitic cycles of the Valkenburg Member at the ENCI quarry change laterally towards the south into cycles with flint nodule layers very similar to those of the Lanaye Member. This correlation is corroborated by analyses of bioclast assemblages. The same holds true for bourgueticrinid crinoids, ophiolepidid and ophiacanthid brittlestars, as well as a few asteroids. This occurrence testifies to a sudden burial (obrution) by clastic input (from the northeast?) and subsequent (near)absence of bioturbation.

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■ Mosasaur remains in this unit are few and far between, with only a handful of isolated vertebrae and tooth crowns (Mosasaurus hoffmanni, Plioplatecarpus marshi) known.

Emael Member Prior to 1975, W.M. Felder's Valkenburg, Gronsveld, Schiepersberg and Emael members (Maastricht Formation) were referred to as Ma and Mb. Villain (1977) considered the Ma/Mb interval to represent a gravelly intrabiomicrosparite, with regional currents constant enough to horizontally displace sediment particles over the entire platform, at shallow depths of 20 to 40 m, and free from oceanic influence. Sediment reworking result in homogenisation of sediments over a depth of some decimetres, resulting in a relatively solid sea floor and clear waters. Liebau (1978) typified the setting as middle sublittoral, with subtropical temperatures and characterised by the occurrence of sea grass communities.

■ This part of the sequence has yielded two mosasaur individuals in recent years: ‘Kristine’ (Plioplatecarpus marshi) and ‘Lars’ (a subadult individual of Mosasaurus hoffmanni; see Jagt et al., 2015a, b, 2016), both with traces documenting shark scavenging (compare Bardet et al., 1998), as noted previously for other mosasaur taxa in the area. Some authors (Street and Caldwell, 2016b) are of the opinion that an individual in the Brussels collections, from these levels at Zichen-Zussen (province of Limburg, Belgium), deserves description as a new species, different from co-occurring Mosasaurus hoffmanni. From these, and higher, levels isolated plesiosaur (elasmosaurid; see Mulder et al., 2000) remains (isolated vertebrae, teeth) have been recovered in several places. Of course, this material is insufficient to determine the impact of these forms on trophic structures, as has been done for the upper Maastrichtian of Morocco (Vincent et al., 2013). In all probability, these animals did not permanently inhabit the area but were swept in as floating carcasses. In addition, a handful of bird remains (Dyke et al., 2002, 2008) is known, some consisting of associated material, from this part of the section. Lesions and fractures in several mosasaur bones attest to run-ins with other mosasaurs or large sharks, such as documented for the ‘Bemelen’ specimen of Mosasaurus hoffmanni, for the type specimen of Prognathodon saturator and for ‘Lars’. Other palaeopathological features include fused vertebrae and bone infections of several kinds (Kruytzer, 1957; Mulder, 2001; Lingham-Soliar, 2004; Schulp et al., 2004, 2006).

Nekum Member The stratotype of this member is at the disused de Tombe quarry, to the northwest of the present-day ENCI quarry ; it comprises a poorly indurated, white-yellowish, coarse-grained homogeneous (hence its use for building purposes !) chalk, in the lower part with few, randomly distributed greyish brown flint nodules. Locally, coarse-grained fossil hash lenses and discontinuous beds occur. Total thickness varies between c. 7 and 15 m.

Villain (1977) typified these deposits as medium- to coarse-grained biocalcarenites (mainly packstones and grainstones; gravelly intrabiomicrosparite), with an indurated calcarenite, yielding innumerable serpulids, bivalves and gastropods as well as rare ammonites, resting directly upon the Laumont Horizon. Flint nodules, the stratigraphically youngest to occur in the type Maastrichtian, often are associated with concentrations of large skeletal grains, and are tubular when associated with bioturbation (decapod crustaceans, mostly callianassoids). The upper part of this member comprises porous, fine carbonate sands with undulating erosion surfaces. Sand lenticles resting on such erosional surfaces may show tangential cross bedding; the Kanne Horizon represents an undulating erosion surface overlain by very coarse bioclastic sand. Close to the Kanne Horizon, numerous chelipeds of callinassoids are found, at times with poorly preserved pereiopods associated.

Here too belemnites and a few ammonite species are amongst the interregionally important macrofossil taxa (e.g., Belemnitella gr. junior, FAD Sphenodiscus binckhorsti, FAD ‘Menuites’ fresvillensis, Hoploscaphites pungens, H. felderi, Glytoxoceras rugatum).

■ The upper third of this member comprises the ‘stratum typicum’ of the type specimen of Mosasaurus hoffmanni (Bardet and Jagt, 1996; P.J. Felder and Jagt, 1998). Another partial skull, from the Buch’oz Collection, was discovered in 1766, and is now part of the collections of Teylers Museum (Haarlem). The exact date of the discovery of the type specimen has always been contested (either 1770 or 1780), until Homburg (2015) showed it to be October 1778. The story of the French revolutionary troops taking Maastricht (1794) and the seizure of the mosasaur skull, then in the possession of canon Godding, has been told many times (Rompen, 1995; Pieters et al., 2011; Homburg, 2015). Part of the other material seized has been retraced in recent years in the Paris

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collections, mostly neoselachians and teleost fish (Brignon, 2015). The discovery of this ‘extinct’ animal heralded in a first period of Maastricht palaeontology, to be followed by a second surge during the mid-19th century with people such as Binkhorst van den Binkhorst, Bosquet and Ubaghs (see Crouzen and van Royen, 2011). In view of the fact that only this part of the section was exposed in the extensive subterranean galleries of the Sint-Pietersberg (Fig. 5A-E), material collected by Ubaghs (1879) must have originated from this unit. Of interest is the highest occurrence of Prognathodon saturator in the area, in co-occurrence with Mosasaurus hoffmanni (Schulp et al., 2013).

A

B

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C

D

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E

F Fig. 5A-E. Copies of several plates from Pasteur (1802), as follows: map of the Sint-Pietersberg in the late 18th/early 19th centuries (A); the main entrance to the underground galleries (B); quarrying activities underground (C); the skull of the later type specimen of Mosasaurus hoffmanni (D); isolated mosasaur tooth crowns and neoselachians (E). NOTE: added is a photograph of modern-day block extraction at Sibbe, near Valkenburg aan de Geul (the Netherlands) (F).

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Meerssen Member Within this member, Zijlstra (1994) observed that the upwards-coarsening of grain size and the increase of average bed thickness indicated a gradual increase of average hydrodynamic energy and deposition rates. The most strongly silicified/lithified layers formed when deposition rate was zero, thus when hydrodynamic energy increased and the consequent increase of erosion was equal to the relative sea level rise. During a further increase in hydrodynamic energy, previously lithified sediment was eroded during storms and wavy beds formed. A hardground, a bored, encrusted and mineralised rocky sea bottom, formed when the sediment that was eroded during a storm was not redeposited after the storm, so that the previously lithified layer was continuously exposed.

Villain (1977) described this unit as a gravelly intrabiomicrosparite, deposited in a shallow setting (2–15 m), with agitation having been able to displace larger sediment particles, deposited in oblique stratification under maximum energy conditions during the lower portion of this unit. Liebau (1978) typified these sediments as high-energy deposits, with a high production of carbonate detritus leading to the establishment of a broad, shallow, well-lot, warm carbonate platform with rich phytal associations. Water temperatures are held to have risen to 20–25 degrees Celsius, allowing the growth of solitary corals, especially in the lower and middle portions of this member. Traces of bioturbation include burrows which acted as fossil traps and from which exquisitely preserved bryozoans (Voigt, 1987) and other faunas are known. On top of hardgrounds and indurated beds occur concentrations of macro- and mesofossils (bioclasts), which comprise brachiopods, bivalves, corals, echinoids, crinoids, asteroids and ophiuroids. Reef-like structures (biohermal structures) occur in places, are of a lenticular nature, and yield many scleractinian and the last rudistid bivalves. Biostromes in this member occasionally yield interesting macrofaunal assemblages, e.g., exuviae of decapod crustaceans (Collins et al., 1995), diverse ophiuroid and asteroid faunules.

In an attempt to provide detailed correlations between the Meerssen Member as exposed at the Ankerpoort-Curfs, former Blom (Berg en Terblijt) and ENCI quarries, the section exposed at the last-named locality has recently been remeasured. It appears that the Meerssen Member at the ENCI quarry in places (southwestern corner) extends to (just) below the Berg en Terblijt Horizon as recognised at the Ankerpoort-Curfs quarry. This means that subunit IVf-7 of this member is not represented at the ENCI, and that, as a consequence, this section cannot furnish any details in the discussion on the K/Pg boundary in the Maastrichtian type area. But, broken and often worn specimens of typically Early Paleocene macrofossil taxa are occasionally found associated with latest Maastrichtian species, thus testifying to a former cover of strata correlatable with the Geulhem Member elsewhere in the area (Albertkanaal outcrops, Geulhem area).

Recent macropalaeontological studies have focused on determining the FAD of the coleoid index species Belemnella (Neobelemnella) gr. kazimiroviensis, the LAD of rudistid bivalves and the range of various ammonite species (e.g., Hoploscaphites constrictus, Menuites terminus).

■ The highest part of this unit is the level of Glyptochelone suyckerbuykii, of which merely two individuals and some isolated remains are known (Mulder and Jagt, 2016), and also documents the youngest occurrence of Mosasaurus hoffmanni in the type area, nicknamed ‘Curfske’ (Jagt et al., 2008). Mosasaurus hoffmanni thus shows an extensive geographical distribution (Mulder, 1999; Grigoriev, 2014; Street and Caldwell, 2016a), although it appears generally confined to strata of late Maastrichtian age. The handful of dinosaur remains, some of them representing historical specimens (Jagt et al., 2003; Mulder et al., 2005; Csiki-Sava et al., 2015), and crocodylomorphs (Mulder and Jagt, in press) generally stem from the upper portion of the Maastricht Formation, in particular the Nekum and Meerssen members.

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K/Pg boundary sections (Meerssen and Geulhem members)

Fig. 6. The combined sections at the former Ankerpoort-Curfs quarry and the nearby Geulhemmerberg subterranean galleries have been shown to comprise the most complete K/Pg boundary interval in the Maastrichtian type area (Smit and Brinkhuis, 1996).

Coleoid cephalopods of the Belemnitella junior group range throughout the entire Maastricht Formation, and are accompanied by the first representatives of the Belemnella (Neobelemnella) kazimiroviensis group from the top of section IVf-3/base of section IVf-4 of the Meerssen Member upwards (Christensen, 1996). The FAD of Bln. gr. kazimiroviensis in the type Maastrichtian thus appears to coincide with the demise of rudistid bivalves and the majority of hermatypic scleractinian corals in the area, and thus suggests a (?temporary) incursion of cold-water forms into a very shallow, subtropical setting. Of note is also that this 'faunal change' more or less matches the proposed rapid local subsidence to account for the extreme thickness of section IVf-6 of the Meerssen Member. This tectonic activity, dated at c. 100,000 yrs prior to the K/Pg boundary, if one accepts Vonhof and Smit’s (1996) estimate of c. 10 cm/kyr sedimentation rate, could have resulted in deeper waters and an increased depositional rate. Representatives of Bln. gr. kazimiroviensis range to the K/Pg boundary (= Berg en Terblijt Horizon). Reworked, but otherwise fairly well-preserved specimens have been collected from the base of section IVf-7, where occurrences of the 'resedimented accumulate type' may be noted. This suggests time-averaging to have taken place at this horizon.

The pachydiscid ‘Menuites’ terminus, currently known from the ENCI, former Blom and Ankerpoort-Curfs quarries, is known from the middle/upper portion of the Meerssen Member. In the Bay of Biscay sections (France, Spain), this short-ranging taxon first appears 30-40 m below the K/Pg boundary. It is also known from the uppermost Maastrichtian of Denmark, Bulgaria, Azerbaijan, central Poland, South Africa (KwaZulu-Natal) and Turkmenistan (pers. obs.). The ‘Tethyan’ pulses noted in the upper Maastricht Fm apparently have a (?combined) north African/southern European as well as a North Atlantic origin.

Brinkhuis and Schiøler (1996) have recently shown the uppermost Meerssen Member to contain Thalassiphora pelagica and Palynodinium grallator, which enable a correlation with the uppermost Maastrichtian in other parts of the North Sea basin. Their presence suggests that the type Maastrichtian is more complete than previously thought. Schiøler et al. (1997) provided a dinoflagellate zonation and sequence-stratigraphical interpretation of the Maastrichtian stratotype (Fig. 4). These authors documented a change

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from open marine to marginal marine conditions to have taken place at the Lixhe 3/Lanaye members boundary. In addition, they interpreted changes in lithology and palynological assemblages in the light of a sequence-stratigraphical scheme, noting that part of four cycles (UZA 4.5, TA 1.1, TA 1.2 and a fourth of probably higher order) could be recognised at the ENCI quarry.

The strontium isotope profile for the type Maastrichtian (Vonhof and Smit, 1996; Vonhof et al., 2011) has been shown to be a useful chronostratigraphical tool in correlating the type section with Bidart (France) and El Kef (Tunisia). Their estimate of depositional rates for the highest 30 m of the type section (c. 10 cm/kyr) provides a valuable tool for estimating faunal changeover patterns in the latest Maastrichtian of the type area.

Dinoflagellates and other palynomorphs (Brinkhuis and Schiøler, 1996) show the top of section IVf-6 to be of latest Maastrichtian age, and IVf-7 of early Paleocene date, the FAD of Senoniasphaera inornata more or less corresponding to the K/T boundary, when calibrated against the P0 zone.

On the basis of echinoids and asteroids, the Geulhem Member may be correlated with the lower to middle Danian oedumi, abildgaardi and bruennichi zones, as recognised in eastern Denmark (Stevns Klint, Sjælland). The correlative potential of neoselachians in the Geulhem Member was not realised until recently. It appears that quite a number of species may be used for interregional correlations and interpretation of faunal exchanges between northern Africa and Europe. The dasyatid ray Prosopodon assafai is just one example (Halter, 1989; Noubhani and Cappetta, 1995).

On the basis of strontium isotope analyses of heterohelicid foraminifers from the E Clay of the Geulhemmerberg section (Fig. 6), Vonhof and Smit (1996) confirmed the early Danian age assignment of other studies. In the absence of an iridium spike (Smit and Brinkhuis, 1996) at Geulhemmerberg, the planktonic foraminifer Heterohelix globulosa was assumed to have survived the K/Pg boundary for at least some 5-50 kyr. This corresponds to the duration of deposition of the iridium-bearing boundary clay interval elsewhere (northern Spain and Tunisia).

Smit and Brinkhuis (1996) reported briefly on geochemical studies which had revealed the presence of 'molecular fossils' in samples from just below the Berg en Terblijt Horizon (= top of section IVf-6). These are of bacterial origin, having been formed during massive anoxic fermentation, and are a valuable marker for the K/Pg boundary, since they are also known to occur at El Kef in the basal boundary clay interval. A combination of preliminary data obtained in a multidisciplinary study of the K/Pg boundary interval may be found in Fig. 6 and a proposed scenario of events in Fig. 7. Note that there are ammonite faunules well above the Berg en Terblijt Horizon (= K/Pg boundary as now understood); these comprise well-preserved specimens of baculitids (Baculites gr. anceps, Eubaculites carinatus) as well as the scaphitid Hoploscaphites constrictus johnjagti. In view of their often preserving apertural features, and considering the association of strombid, aporrhaid, naticid, cerithiid, turritellid and ?fusid gastropods as well as inoceramid/pteriid, nuculid, nuculanid, poromyid and other bivalves (often still articulated), these ammonites are considered to have survived K/Pg boundary perturbations in this area. This is in accord with occurrences in Denmark and New Jersey.

3. FUTURE WORK In the near future, we hope to refine the stratigraphic ranges of the various species of mosasaur and turtle, providing details of preferred diet and niche partioning (compare Schulp et al., 2013), provide more data on microwear of mosasaur teeth (see Holwerda et al., 2013), determine the impact of larger-sized neoselachian taxa in the area (compare Guinot, 2013) and document bone damage (both syn vivo and post-mortem) on cheloniid and mosasaur bones (see Janssen et al., 2013).

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Fig. 7. Favoured scenario across the K/Pg boundary in the type area of the Maastrichtian Stage (from Smit and Brinkhuis, 1996). Acknowledgements We wish to extend cordial thanks to all those amateur palaeontologists who have assisted during field work and supplied us with loads of interesting material over recent years – their role in 21st century palaeontology of a huge one (see Potter, 2010; Catalani, 2014).

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