Trilobites from the Dinantian Tn2b-C of the Kastanjelaan-2 Borehole (Maastricht, the Netherlands) C
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51 Natuurhistorisch Maandblad 71 (3).1982 gedurende de laatste 500.000 jaren Dankbetuiging rous the Brabant Massif has been covered se- zocht de rivier zich een weg, die in veral times by a relatively thin and incomplete De schrijver is zeer erkentelijk voorde hulp, die hij sequence of sediments. These deposits disap- grote lijnen overeenkomt met haar mocht ontvangen van de zijde van Mevr. Th. Ver- peared almost completely as a result of subse- huidige loop. In het begin werden toen boekèt, die het manuscript meermalen moest uit- quent erosion phases. Thick, and more or less zanden en grinden afgezet op het ni- typen, en van Dhr. J.C. Franssen bij het afwerken complete sequences accumulated in the grabens veau van de huidige Pietersberg. Maar der figuren. to the north. This overall sedimentation pattern has been only interrupted during the Late Creta- naarmate de Maas zich verder in haar ceous and Early Tertiary when inversion move- huidige dal insneed werden de sedi- ments caused temporary uplift of the graben area. menten, die vanuit Noord-Frankrijk en Summary During that period the Brabant Massif was de Ardennen werden aangevoerd, op flooded by a shallow sea. lagere niveaus ("terrassen") afgezet. The paleogeographic evolution of the southern The boreholes Heugem and Kastanjelaan in Netherlands and northern Belgium since the Pa- Maastricht have proved that this area was located Pas in de laatste honderduizend jaar leozoic shows the continuous influence on the at the eastern flank of the Brabant Massif. During heeft het Maasdal haar huidige vorm sedimentation pattern of the two principal tectonic the Devono-Carboniferous a narrow graben or verkregen. elements in that area: the Brabant Massif in the depression existed between Vise and Maastricht. south and a complex graben zone to the north. This graben is characterized by rapid local chan- Presumably, during the Devonian and Carbonife- ges in the thickness and fades of the deposits. Trilobites from the Dinantian Tn2b-c of the Kastanjelaan-2 borehole (Maastricht, the Netherlands) C. Brauckmann Fuhlrott-Museum, Auer Schulstrasse 20, 5600 Wuppertal 1, Federal Republic of Germany The trilobites from the 335.10 - 335.25 m interval of the Kastanjelaan-2 Type horizon: The 335.10 - 335.25m level of borehole in the municipality of Maastricht (South Limburg, the Nether- borehole, Dinantian Tn2b-c (see BLESS et al., 1981, p. 348). lands) belong to four different genera: Cummingella maastrichtensis Distribution: Known only from the type loca- Brauckmann nov.sp., Phillipsia (Phillipsia) sp., Piltona? sp. and Archego- lity and the type horizon. nus? nov.sp. The conodonts and corals in this interval suggest a Dinantian Other specimens: Cranidium NHMM Tn2b-c age. 198244 (fig. 1a-b, 3a-c), and perhaps free cheek NHMM 198245 (fig. 5). Derivation of name: After the type locality. Up to present, Carboniferous trilobites ger strata (Tn3a-b) of the Tournai re- from the Netherlands have only been gion. Striking is the difference between Diagnosis: A species of Cummin- regarded by DORSMAN (1945), who the low number of specimens and the gella with the following characteristics. briefly described some fragments from high number of different taxa. Glabella very compact, subquadratic the marine Aegir level (base of Westp- in dorsal view, strongly convex both in halian C; Upper Carboniferous) as Family PHILLIPSIIDAE OEHLERT 1886 longitudinal and transverse section, Griffithides sp. (now probably better Subfamily CUMMINGELLINAE G. & R. scarcely contracted at mid-length; 4 determined as Paladin sp.). Lower HAHN1967 pairs of very shallow glabella furrows; Carboniferous (Dinantian) trilobites Genus Cummingella Reed 1942. anterior border covered by the over- were hitherto completely unknown hanging glabella. Pygidium with 11 Type species: Phillipsia jonesii The more surprising was the discovery rings on the rhachis and 11 pairs of ribs Portlock 1843. of trilobite fragments from several le- on the pleural fields; pleural furrows Diagnosis: G. & R. HAHN(1972), p. vels of the borehole Kastanjelaan-2 in broad (exsag.), reaching the border; 341-342 ("Beziehungen"). the municipality of Maastricht (cf. interpleural furrows passing onto the BLESSef a/., 1981). The better preser- Cummingella maastrichtensis border; anterior band of all ribs dis- ved ones, to be described in this paper, Brauckmann nov.sp. (fig. 1 -4, ?5). tinctly continuing on the border. Stein- are from the 335.10 - 335.25 m level, kern surface of the glabella densely Bollandia n. sp.?; BRAUCKMANN in: BLESSef a/., which is dated as Dinantian Tn2b-c by 1981, p. 352, pi. 15, (fig. 1). granulated, pygidial rhachis (stein- means of conodonts and corals. It kern) with well marked irregular, rather should be noted that in equivalent Holotype: Pygidium (steinkern) NHMM spinous nodes. 198243 (fig. 2a-b, 4a-c). strata in Belgium only different trilobite Description: Glabella (paratype Type location: Borehole Kastanjelaan-2 in taxa have been found yet, while com- the municipality of Maastricht (South Limburg, the NHMM 198244; other parts of the cra- parable species occur in slightly youn- Netherlands). nidium are not preserved). Lateral Natuurhistorisch Maandblad 71(3).1982 52 ribs; pleural furrows broad (exsag.), not deeply incised, reaching the con- T 0 vex, rather narrow and indistinctly marked border; interpleural furrows (= rib furrows) of all ribs weak, but pas- sing onto.the border; anterior bands of the ribs continuing on the border, breadth of the anterior and posterior 4mm bands of the ribs nearly the same (ex- sag.); steinkern of the rhachis with well marked, rather spinous irregular no- Figure 1. Cummingella maastrichtensis Brauckmann nov. sp. Reconstruction of paratype glabella, des. Lengths: pygidium 7.6 mm; rha- NHMM 198244. a: dorsal view, b: lateral view. chis 6.8 mm. Breadths: pygidium 10.6 mm; rhachis 4.2 mm. Remarks: Perhaps also to this spe- cies belongs an isolated free cheek (NHMM 198245; fig. 5) of nearly cum- mingelloid outline, which shows a sculpture very similar to that of the gla- bella described above. Unfortunately the poor preservation does not allow an exact identification. Discussion: Among the characte- ristic features of C. maastrichtensis the most important ones are (1) the very strong convexity of the overhan- ging glabella, in which this species Figure 2. Cummingella maastrichtensis Brauckmann nov. sp. Reconstruction of holotype pygidium, shows' quite un-cummingelloid, but NHMM 198243. a: dorsal view, b: lateral view (same scale as fig. 1). bollandoid tendencies, and (2) the prominent sculpture both on the gla- bella and on the pygidial rhachis, which is also very uncommon in Cum- view (fig. 1b, 3b): Scarcely curved then falling down steeply to the very mingella. Both features led to the pre- (nearly plain and horizontal) in poste- short (sag.), convex post-axial part of liminary determination as "Bollandia rior half, but frontal lobe strongly bent the pleural fields; rings moderately n. sp.?", based on the at that time un- down, distinctly overlapping the ante- prominent, with steep posterior slope; completely prepared specimens. But rior border. Very strongly arched in an- pleural field slightly inclined backward, mainly the configuration of the glabella terior view (fig. 3c). Dorsal view nearly plain beside the rhachis, but be- furrows and the outline and structure of (fig. 1a, 3a): Subquadratic, scarcely coming more convex against the pos- the pygidium (anterior bands of the ribs contracted at mid-length, frontal lobe terior border; ribs moderately promi- continuing on the border!) show that nearly truncate in outline. 4 pairs of nent; border convex. Posterior this species belongs to Cummingella. very shallow glabellar furrows; S1 and view (fig. 4c): Rhachis equally ar- There is no other known species within S2 beginning at the dorsal .furrow, ched; inner half of pleural fields direc- Cummingella with shows this kind of strongly curved backward (S1 perhaps ted horizontally, outer half strongly combination of characteristics. Most not reaching the occipital furrow, but bent downward to the convex border; closely related to C. maastrichtensis is the poor preservation does not allow a dorsal furrows only weakly incised. a still undescribed taxon from the definitive conclusion), S3 and S4 not Dorsal view (fig. 2a, 4a): Slightly Tn3a-b, collected in several speci- connected with the dorsal furrows, elongate; rhachis broader than one mens in the Tournai region (SW Bel- very weak, directed more transversely pleural field, nearly parabolic in outli- gium), which will be described in detail than S1 and S2. The whole surface of ne, long, with 11 rings; anterior 7-8 in one of the next parts of the mono- the steinkern is distinctly granulated. rings rather prominent, posterior ones graph on the trilobites of the Belgian Length 6.0 mm. Breadth at mid-length more indistinct, but visible; axial fur- Lower Carboniferous by G. & R. Hahn 4.0 mm. rows broad (sag.), weakly incised, di- and the present author. Pygidium (holotype NHMM 198243). rected nearly straight transversely, The main differences between these Lateral view (fig. 2b, 4b): Rhachis showing only very slight backward two taxa seem to be in the even much relatively low (ratio height of rhachis: curvature against the dorsal furrows; more spinous sculpture of the pygi- height of pleural field = 1:3), curving dorsal furrows rather distinct; pleural dium (both on the rhachis and the pleu- gently down backward to the last ring, fields with 11 ribs, no place for more ral fields) in the Belgian taxon, which 53 Natuurhistorisch Maandblad 71 (3).1982 reminds that of the fruit of the Erica- cean Arbutus and is comparable with the sculpture of the Japanese Carboni- ferous griffithidinid trilobite Parvidu- mus densigranulatus Kobayashi & Hamada 1980. At present, without ha- ving examined the Belgian specimens in detail, the preservation does not al- low an exact comparison, because the pygidium from Maastricht is exfoliated, while the Belgian ones are not. The differences in the sculpture could have been caused either by the different preservation or - perhaps more likely - by the more advanced development of Figure 5.