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S T U D I A G E O L O G I C A P O L O N I C AVol. 124, Kraków 2005, pp. 159–170.

Methods and Applications in MicropalaeontologyEdited by J. Tyszka, M. Oliwkiewicz-Miklasiñska,

P. Gedl & M. A. Kaminski

Tatiana WORONCOWA-MARCINOWSKA1

Middle Devonian conodonts from black shalesof the Œciegnia section, Góry Œwiêtokrzyskie Mountains,

central Poland

(Figs 1–8)

Abstract. The conodont fauna and conodont-based biostratigraphy of a part of the Devoniansuccession of the Œciegnia section (£ysogóry region, Góry Œwiêtokrzyskie Mountains [Holy CrossMountains]) are discussed. The studied strata are composed of rhythmically bedded black shales andmarly shales with intercalations of marly and coarse-grained limestones. They overlie the shales andsandstones of the Œwiêtomarz beds. This part of the shale-marly succession of the Œciegnia sectionrepresents the lower part of Nieczulice beds of the Devonian informal lithostratigraphical scheme forthe northern region of the Góry Œwiêtokrzyskie Mountains. The conodont assemblages indicate thatthe studied sequence ranges from the upper part of the Lower varcus conodont Zone to the Middlevarcus conodont Zone of the Givetian.

Key words: Góry Œwiêtokrzyskie Mountains, £ysogóry region, Devonian, Givetian, conodonts,biostratigraphy, Poland.

INTRODUCTION

The earliest basic papers on the stratigraphy of the Devonian in the £ysogóry re-gion were published by Gürich (1896) and Sobolew (1909). New important obser-vations (on the Devonian near the villages of W³ochy and Nieczulice) were addedmuch later by Czarnocki (1950). This author referred to the ‘coral limestones’ ofSobolew as the ‘Pokrzywianka beds’ and suggested their Frasnian assignment.Similarly, he attributed to the Frasnian the overlying shales, which he termed theNieczulice beds. The lower part of these shales were described already by Sobolew(1909) under the name ‘Œwiêtomarz Shales’. Subsequently, Czarnocki’s views onthe stratigraphy of the Pokrzywianka and Nieczulice beds were modified by

1 Polish Geological Institute, ul. Rakowiecka 4, 00-975 Warszawa, Poland: E-mail: [email protected]

Pajchlowa (1957). Based on observations in the Œwiêtomarz-Œniadka section, shereferred both units to the Givetian. According to Malec (1996) the lowermost partof the Nieczulice beds of the Ska³y section belongs to the Middle varcus conodontZone. Not acceptable is the subsequent statement in more recent report by Malec &Turnau (1997, Fig. 7 unit XXVIII, parts A-B), who refer this part of the successionto the stratigraphically younger, hermani-cristatus Zone. Namely, the specimen ofSchmidtognathus sp., indicative of the latter zone was found actually in part C ofunit XXVIII, i.e. distinctly above the conodont assemblage of the Middle varcus

Zone of the Ska³y section (Dr. Malec oral information from November 2004). Con-sequently, it cannot be taken as a date of the lowermost part of the Nieczulice beds.

In the western part of the £ysogóry region, the equivalent part of the Devoniansuccession was long known from the Œciegnia section (formerly known as theWzdó³ section), located in the western part of the Bodzentyn Syncline (see Fig. 1).According to Czarnocki (1950), Koœcielniakowska (1967), and Filonowicz (1962,1969) this section starts with the Givetian deposits of the Ska³y and the Œwiêtomarzbeds, which are overlain by Frasnian deposits, developed as shales and limestoneswith the brachiopod Leiorhynchus polonicus (Roemer) and tentaculitides, fol-lowed by limestones and shales with cephalopods (Filonowicz, 1969). Conse-quently, this could suggest a lack of the Nieczulice beds in the Œciegnia area.

During recent field works in the Œciegnia area a newly exposed part of the Devo-nian succession was found. Its lithological characteristics supported by biostra-tigraphical data suggest that this succession represents an equivalent of the lowerpart of Nieczulice beds. The present results seem to prove a much larger geographicextent of this lithostratigraphic unit than hitherto assumed.

160 T. WORONCOWA-MARCINOWSKA

Fig. 1. A – General map of Poland showing the location of the Góry Œwiêtokrzyskie Mountains;B – map of the Góry ŒwiêtokrzyskieMts showing location of the Œciegnia section (simplified afterRacki, 1993)

STRATIGRAPHICAL SETTING

The Œciegnia section, near Bodzentyn in the £ysogóry (northern) region (Fig. 1)is located in the western part of the Bodzentyn Syncline (Czarnocki, 1950). The De-vonian shales and limestones, dipping to the north, are exposed in the bank of astream, southwest of the exposures of shales and sandstones of the Œwiêtomarz beds(Fig. 2). The succession studied is composed of rhythmically bedded black shalesand marly shales, with intercalations of marl and coarse-grained limestone (Fig. 3).

MATERIAL

An eight metres thick part of the succession exposed in the Œciegnia section wassampled for microfauna. The studied sequence was accessible in two sections, withan observational gap in between estimated for about 20 m (Fig. 3). Among the 17samples analysed, 11 yielded relatively well preserved and abundant conodont ma-terial, with both juvenile and adult specimens represented (Fig. 3). The most abun-dant and fossiliferous material was found in sample 12.

Besides conodonts the samples yielded numerous dacryoconarids (Fig. 8A–F),leiospheres (Fig. 8G–H), globular microproblematica (Fig. 8I–N), resemblingthose described by Racki & Soboñ-Podgórska (1992, Fig. 9A–E), sclerites of thegenus Eocaudina (Fig. 8O–P), calcareous sponges (Fig. 8R), and fragments of fish(Fig. 8S, T). Most of dacryoconarid moulds and microproblematica are pyritized,

CONODONTS FROM DEVONIAN BLACK SHALES 161

Fig. 2. Geological uncovered map of the Œciegnia vicinities after O. Koœcielniakowska (1967)


Fig. 3. Distribution of conodonts in limestone layers or lenses of Œciegnia black shales

and then limonitized. Framboidal pyrite in the form of framboid-raspberries, con-sisting of densely packed spheroidal aggregates (Fig. 8K–N) is also present. Thespheroidal aggregates are 270–360 µm in diameter, which suggests that theyformed in conditions of a long-term euxinicity, interrupted by brief sea-floor oxy-genation events (Bond et al., 2004).

BIOSTRATIGRAPHIC RESULTS

Conodont assemblages found in the studied section include cosmopolitan Mid-dle Devonian taxa, characteristic of the upper Lower-Middle varcus zones. Cono-donts from samples 3–11 (Fig. 3), represented by Polygnathus varcus Staufer, P.

timorensis Klapper, Philip et Jackson, P. linguiformis linguiformis Hinde, P. lin-

guiformis weddigei Clausen, Leuteritz et Ziegler, Icriodus cf. excavatus Weddigeand Belodella resima (Philip), may indicate both the upper Lower varcus Zone andthe Middle varcus Zone (Figs 4–7). According to Ziegler et al. (1976) the base ofthe Lower varcus Zone, is defined by the lowest occurrence of P. timorensis Klap-per, Philip et Jackson, whereas the eponymous P. varcus Stauffer has the lowest oc-currence in the upper part of this zone. Similarly, P. linguiformis weddigei Clausen,Leuteritz et Ziegler has the lowest occurrence in the upper part of the Lower varcus

Zone and continues higher, into the Middle varcus Zone (Clausen, Leuteritz & Zie-gler, 1979; Bultynck, 1987; Uyeno, 1998).

Sample 12, containing the most abundant and diversified conodont assemblage,besides forms listed above also contains: Polygnathus linguiformis mucronatus

Wittekindt, P. rhenanus Klapper, Philip et Jackson. P. ansatus Ziegler et Klapper,Icriodus brevis Stauffer, I. cf. lindensis Weddige, and Tortodus sp. A gamma mor-photype (Sparling, 1999). Most of these taxa range higher, and were also found insamples 13 and 14, where they co-occur with representatives of the genus Neopan-

derodus (Figs 5–7).The assemblage from samples 12–14 characterises the Middle varcus Zone. It is

demonstrated by the presence of Polygnathus ansatus Ziegler et Klapper, the low-est occurrence of which defines the base of the zone, and the continuous occurrenceof P. linguiformis mucronatus Wittekindt and P. rhenanus Klapper, Philip et Jack-son, which do not range above its upper boundary (Klapper, Philip & Jackson,1970; Ziegler et al., 1976; Bultynck, 1987; Weddige, 1977). Worthy of note is thecommon occurrence in the Middle varcus Zone of juvenile Icriodus cf. lindensis

Weddige and of Tortodus sp. A gamma morphotype (Sparling, 1999). Usuallythese two forms disappear well below the base of this zone.

The specimen of Icriodus cf. lindensis (Fig. 5M) resembles I. brevis (Fig. 5N),from which it differs in the development of the three denticles of the posterior ex-tension of the middle row, which in the discussed specimen increase regularly inheight, similarly as in I. lindensis Weddige. The specimen of Tortodus, illustratedherein in Fig. 6E, possesses a well developed platform, with the margin bearingdelicate nodes. It closely resembles Tortodus sp. A gamma morphotype (Sparling,1999, fig. 5.7–5.9), known from the upper Middle varcus Zone of the Prout Dolo-mite Formation, Ohio, USA.



Fig. 4. Givetian conodonts from Œciegnia section. A – Polygnathus cf. varcus Stauffer, sampleŒ-3; B – Polygnathus linguiformis weddigei Clausen, Leuteritz et Ziegler, sample Œ-9; C – Poly-

gnathus varcus Stauffer, sample Œ-9; D – Polygnathus timorensis Klapper, Philip et Jackson, sampleŒ-11a; E–L – Polygnathus linguiformis linguiformis Hinde, E–H, K – juvenile specimens, E – sampleŒ-11a, F–H, I – sample Œ-11, J – sample Œ-12, K, L – sample Œ-14; A–L – Pa elements, upper views;length of scale bars: A – 10 µm, B, C, E – 30 µm, D, F, I, J – 100 µm, G, H, K, L – 20 µm


Fig. 5. Givetian conodonts from Œciegnia section. A – Polygnathus timorensis Klapper, Philip etJackson, sample Œ-12; B – Polygnathus rhenanus Klapper, Philip et Jackson, sample Œ-12; C–F, J, K– Polygnathus ansatus Ziegler et Klapper, D, F – juvenile specimens, sample Œ-12, C, E, – sampleŒ-12, J – sample Œ-14a, K – sample Œ-13; L – Icriodus cf. excavatus Weddige, sample Œ-11a; M –Icriodus cf. lindensis Weddige, juvenile specimens, sample Œ-12; N – Icriodus brevis Stauffer, sampleŒ-14a; A–N – Pa elements, upper views; length of scale bars: A–F, L – 30 µm, G, J – 10 µm, H, I, K, M,N – 20 µm


Fig. 6. Givetian conodonts from Œciegnia section. A, J–K – Polygnathus ansatus Ziegler etKlapper, sample Œ-12; B–D – Polygnathus timorensis Klapper, Philip et Jackson, B, C – sample Œ-12,D – sample Œ-14a; E – Tortodus sp. A gamma morphotype Sparling, sample Œ-12; F–I – Polygnathus

linguiformis mucronatus Wittekindt, sample Œ-12, G – lateral view; A–K – Pa elements, upper views;length of scale bars: A, B, E, F, H, I – 100 µm; C – 30 µm, D, G, J, K – 20 µm


Fig. 7. Givetian conodonts from Œciegnia section. A, B – Neopanderodus sp., A – sample Œ-14, B –sample Œ-14a; C – Neopanderodus transitans Ziegler et Lidström, sample Œ-14a; D–K – Belodella

resima (Philip), D, F – sample Œ-11, E, H, J, K – sample Œ-14a; I – sample Œ-12; A–K – lateral views;length of scale bars: A, C, I, K – 20 µm, B, D, F, G – 10 µm; E, H, J – 30 µm


Fig. 8. Givetian microfossils from Œciegnia section. A–F – dacryoconaryds: A – Viriatellina sp.,sample Œ-6, B–F – stylionids, B – sample Œ-6, C, D, F – sample Œ-14, E – sample Œ-13; G, H –leiospheres, sample Œ-11; I, J, M, N – pyritized globular microproblematica, I, J, M – sample Œ-12, N– sample Œ-14; K, L – framboids-raspberry, sample Œ-12; O, P – sclerites of the genus Eocaudina, O –sample Œ-6, P – sample Œ-11; R – calcareous sponges spicules, sample Œ-14; S, T – fragments of fishesskeletons, sample Œ-12; length of scale bars: A, F, P, T – 100 µm, B–E, I, J, O, R, S – 20 µm, G, H, N –10 µm

CONCLUSIONS

The studied part of the succession of the Œciegnia section (samples 3–14), justabove the shales and sandstones of the Œwiêtomarz beds, represents an intervalspanning the upper Lower varcus Zone to the Middle varcus Zone.

The conodont assemblage found is very similar to the assemblage reported fromthe Middle varcus Zone of the lower part of the Nieczulice beds of the Grzego-rzowice-Ska³y section, in the eastern part of the Góry Œwiêtokrzyskie Mountains(unit XXVIII, parts A-B in fig. 7 of Malec & Turnau, 1997).

The facies similarity of the studied succession to the Nieczulice beds of theGrzegorzowice-Ska³y section, supported by the biostratigraphical equivalence ofboth sections suggest, that the lower part of the shale and marly succession of thestudied section should be referred to the Nieczulice beds. However, the conodontassemblage of the Œciegnia section is a little older.

The black colour, the presence of the pyritized planktonic and nektonic fauna,and of framboidal pyrite (Fig. 8K–N), suggest dysoxic conditions in the bottom wa-ters and oxic conditions in the overlying water column during the sedimentation ofthe black clays.

Acknowledgements

I would like to thank K. Narkiewicz for comments, B. Giblewska, for computer drawings and L.Giro for SEM photographs of the microfauna (all from the Polish Geological Institute). Many thanksare also offered to Professor I. Walaszczyk, University of Warsaw, for his great help with the English.I would like to express many thanks also to Professor E. Turnau and Dr M. Oliwkiewicz-Miklasiñskafor valuable remarks during the review process.

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