Holy Cross Mountains, Central Poland)

Acta Geologica Polonica, Vol. 52 (2002), No. 2, pp. 217-238

Stratigraphic and biogeographic significance of Late Cambrian trilobites from ¸ysogóry (Holy Cross Mountains, central Poland)

ANNA ˚YLI¡SKA

Department of Geology, University of Warsaw, Al. ˚wirki i Wigury 93, PL-02-089 Warszawa. E-mail: [email protected]

ABSTRACT:

˚YLI¡SKA, A. 2002. Stratigraphic and biogeographic significance of Late Cambrian trilobites from ¸ysogóry (Holy Cross Mountains, central Poland). Acta Geologica Polonica, 52 (2), 217-238. Warszawa.

Revision of the Late Cambrian trilobites from ¸ysogóry in the Holy Cross Mountains, central Poland, enabled the application of a modified version of the Upper Cambrian biostratigraphic zonation established for the Baltica palaeocontinent. The following zones and subzones were recognised: Olenus scanicus and Parabolina brevispina subzones, Leptoplastus − Protopeltura praecursor Zone, Peltura minor Zone (Ctenopyge tumida and Ctenopyge affinis subzones), Peltura scarabaeoides Zone (Ctenopyge linnarssoni and ?Parabolina lobata subzones) and the Acerocare Zone sensu lato. Biogeographically the trilobites of ¸ysogóry show a distinct change, from a low diversity fauna with a predominance of Avalonian forms in the early Late Cambrian, to more diversified assemblages, characterised by the constant increase to dominance of Baltic elements by the end of the Cambrian.

Key words: Late Cambrian, Holy Cross Mountains, Trilobites, Biogeography, Biostratigraphy, ¸ysogóry Block.

INTRODUCTION The stratigraphy of the Upper Cambrian of the ¸ysogóry region of the Holy Cross Mountains presented The present study documents the stratigraphic and in this paper is based on rich and well documented trilo- biogeographic significance of Late Cambrian trilobites bite material (over 1300 specimens). Their revised sys- from the Holy Cross Mountains, central Poland. The tematic analysis was published recently (˚YLI¡SKA 2001). importance of this area stems from the fact that it is the Previous papers on the taxonomy and stratigraphy of the only Palaeozoic structure exposed in the direct vicinity of Late Cambrian trilobites (OR¸OWSKI 1968b; TOMCZY- the East European Craton. The Holy Cross Mountains KOWA 1968) indicated the presence of mainly endemic are a part of the Trans-European Suture Zone (TESZ), species in ¸ysogóry, and consequently local zonations one of the main geotectonic domains in Europe were applied hitherto. (BERTHELSEN 1992), the formation of which still remains highly controversial. The restudy of the biostratigraphy and biogeographic affinities of the Early Palaeozoic of GEOLOGICAL SETTING AND LOCALITIES the Holy Cross Mountains might thus be of crucial importance in deciphering the assembly of Laurussia during The Palaeozoic of the Holy Cross Mountains (Text- this interval. fig. 1a) consists of the Lower Cambrian up to and includ- 218 ANNA ˚YLI¡SKA

Fig. 1a. Geological sketch-map of the Holy Cross Mountains (distribution of Cambrian deposits after OR¸OWSKI 1992b), with location of studied outcrops and boreholes. 1b. Topographic sketch-map with location of outcrops and boreholes in the western part of ¸ysogóry. 1c. Location of the Wàworków quarry ing the Lower Carboniferous. On the basis of different The trilobite-bearing sections with trilobite ranges facies development, stratigraphy and tectonic evolution, and zonation are briefly characterised below (from west they are divided into two regions (recognised first by to east) (Text-figs 2-10) and their correlation is shown in CZARNOCKI 1919): the southern Kielce region and the Text-fig. 13. The lithological columns are generally after northern ¸ysogóry region, separated by the WNW-ESE OR¸OWSKI (1968a) and TOMCZYKOWA (1968). trending Holy Cross Dislocation. The ¸ysogóry region is generally the equivalent of the ¸ysogóry Block, whereas the Kielce region is considered to be the northern part of WiÊniówka Du˝a Quarry the Ma∏opolska Massif (see PO˚ARYSKI 1990). The Upper Cambrian is known exclusively from the ¸ysogóry region; WiÊniówka Du˝a is one of the quarries in the western in its southern part, along the Holy Cross Dislocation, the part of ¸ysogóry (Text-fig. 1b). The Upper Cambrian of Upper Cambrian crops out in a ca. 70 km long, 3-5 km the section (Text-fig. 2) is composed of thick-bedded, wide belt. Lithostratigraphically it belongs to the hard sandstones, light grey to bluish in colour, with WiÊniówka Formation and the Klonówka Formation numerous intercalations of siltstones and silty and clayey (sensu OR¸OWSKI 1975). The Klonówka Formation was shales, representing the WiÊniówka Formation, as well as also found in boreholes situated farther to the north shales and siltstones with sandstone intercalations of the (TOMCZYKOWA 1968). The WiÊniówka Formation ranges Klonówka Formation (OR¸OWSKI 1968a, 1975; equiva- in thickness between 400 and 1400 m, whereas the lents of the Êwi´tokrzyskie, màchocickie and ∏ysogórskie Klonówka Formation is about 400 m thick (OR¸OWSKI beds of TOMCZYKOWA 1968). Trilobites are very rare in 1975, KOWALCZEWSKI 1995). both formations. However, the original abundance of var- STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 219

ious organisms in the early Late Cambrian sea of the area is testified by the rich ichnocoenosis (e.g. RADWA¡SKI & RONIEWICZ 1963, 1972; OR¸OWSKI & al. 1970, 1971; OR¸OWSKI 1992a; OR¸OWSKI & ˚YLI¡SKA 1996).

Lisie Jamy

The exposure lies on the eastern slopes of Klonówka Hill, ca. 50 m to the west of the mouth of a narrow gorge, which lies perpendicular to the Lubrzanka river valley, opposite the red tourist route towards Radostowa Hill

Fig. 3. Lithological column of the Lisie Jamy section, based on OR¸OWSKI

(1968a); brachiopod data from JENDRYKA-FUGLEWICZ (1992)

(Text-fig. 1b). The ca. 10 m thick succession (Text-fig. 3) belongs to the Klonówka Formation, represented here by grey and greenish claystones with small sandstone-con- glomerate concretions in the lower part and thin intercalations of fine-grained reddish and brownish sandstones in the upper part. Trilobites are rather rare and poorly preserved throughout the succession, although complete specimens were also encountered.

Chabowe Do∏y

The Chabowe Do∏y section is situated on the eastern slopes of Klonówka Hill along the road in the Lubrzanka river valley (Text-fig. 1b). The whole succession belongs Fig. 2. Schematic lithological column of the WiÊniówka Du˝a Quarry section to the Klonówka Formation and is ca. 80 m thick. Its

(after ˚YLI¡SKA 1992), with brachiopod record from JENDRYKA-FUGLEWICZ & lower part, referred to in the literature as Chabowe Do∏y

MALEC (1997) and location of ‘Peytoia’ sp. after MASIAK & ˚YLI¡SKA (1994). Mill and Ravine, was first reported by GÜRICH (1896), 220 ANNA ˚YLI¡SKA who found specimens of Olenus sp. in it. Its upper part, able sandstone with abundant trilobites [referred to by devoid of trilobites, was uncovered by roadworks about OR¸OWSKI (1975) as the Chabowe Do∏y Bed]. Its upper ten years ago. part, known as Chabowe Do∏y Ravine, is composed of The Chabowe Do∏y Mill and Ravine section (Text- claystones and siltstones, with thin intercalations of hard fig. 4) is ca. 33 m thick and is composed of grey, bluish, bluish quartzitic sandstones passing into brown, more brown and yellow quartzitic sandstones and grey and friable sandstones in its upper part. Trilobites are not as brown claystones and siltstones of the Klonówka numerous as in the Chabowe Do∏y Bed. Formation. Its lower part (about 13 m thick), known as The upper part of the Chabowe Do∏y succession com- Chabowe Do∏y Mill, composed predominantly of sand- prises ca. 46 m of claystones and siltstones with rare inter- stones with thin claystone and siltstone intercalations, calations of hard bluish sandstones. So far, no trilobites contains an approximately 60 cm thick lens of yellow, fri- were encountered in this part of the succession.

Fig. 4. Lithological column of the Chabowe Do∏y Mill and Ravine section, modified from OR¸OWSKI (1968a); the Chabowe Do∏y Bed is arrowed STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 221

Fig. 5. Lithological columns of the a. Brzezinki 1 and b. Brzezinki 2 borehole sections; modified from TOMCZYKOWA (1968)

Brzezinki boreholes lain unconformably by claystones with carbonate concretions with Rhabdinopora sp., indicative of the Lower The three boreholes were drilled near the village of Tremadocian (TOMCZYKOWA 1968). Brzezinki (CZARNOCKI 1957; TOMCZYKOWA 1968) on the northern slopes of Klonówka Hill, ca. 1 km northwards from Chabowe Do∏y (Text-fig. 1b). Relying on archival Brzezinki 2 Borehole [50o55’05”N, 20o47’20”E] data and cores, TOMCZYKOWA (1968) redrew the lithological columns of the individual sections. The specimen The Upper Cambrian occurs between 7.5 and 120 m of Peltura sp. mentioned by TOMCZYKOWA (1968) from (Text-fig. 5b). The series is composed of grey to almost the Brzezinki 3 Borehole was not found in her collection black claystones, enriched with mica, with rare siltstone and therefore the borehole is excluded here from intercalations in the lower part of the succession and detailed biostratigraphic and biogeographic analysis. belongs to the Klonówka Formation. Trilobites are rare and poorly preserved.

Brzezinki 1 Borehole [50°55’10”N, 20°47’30”E] B´czkowska Ravine The Upper Cambrian occurs between 91.7 and 216.2 m (Text-fig. 5a). The series is composed mainly of grey to The ravine separates the southern slopes of the almost black claystones with thin mica-rich siltstone inter- Radostowa and B´czkowska hills (Text-fig. 1b). The calations of the Klonówka Formation. The trilobites are exposed up to 10 m thick series belongs to the Klonówka rare and poorly preserved. The Upper Cambrian is over- Formation and is composed of clayey and silty shales 222 ANNA ˚YLI¡SKA

(Text-fig. 6). The strata comprise ca. 7 m of grey quartzitic sandstones intercalated with grey to dark grey siltstones with mica in the lowermost part, followed by 166 m of grey to dark grey claystones with numerous mica and sporadic siltstone intercalations in the middle part. Trilobites are rare in the ca. 173 m succession.

Jeleniów boreholes

The boreholes were located in the eastern part of the Jeleniów village at the base of the northern slopes of the Jeleniów Hill (Text-fig. 1a). A rich trilobite assemblage was found in the Jeleniów 3 Borehole.

Fig. 7. Lithological column of the Jeleniów 2 borehole section; modified

from TOMCZYKOWA (1968)

Fig. 6. Lithological columns of the Wilków IG-1 borehole section; Jeleniów 2 Borehole [50o50’15”N, 21o07’20”E]

modified from TOMCZYKOWA (1968) The Upper Cambrian occurs between 183.2 and 241 m with intercalations of yellow and brown sandstones (see (Text-fig. 7). The succession belonging to the Klonówka OR¸OWSKI 1968a, fig. 6 for a detailed lithological col- Formation is composed of ca. 58 m of grey to dark grey umn). Although SAMSONOWICZ (1916), CZARNOCKI claystones, enriched with mica, with siltstone intercala- (1919) and OR¸OWSKI (1968a) noted the occurrence of tions in the lowermost part. Trilobites are very rare. Three rare trilobites, only one specimen from this locality was specimens of undetermined Ceratopygidae and two frag- traced in OR¸OWSKI’s collection. ments of Rhabdinopora sp. (TOMCZYKOWA 1968) indicate the Lower Tremadocian age of the overlying claystones with carbonate concretions (between 183.5 and 190 m). Wilków IG-1 Borehole [50o54’30”N, 20o50’45”E]

The borehole was drilled in 1961 in the Wilków valley Jeleniów 3 Borehole [50o50’10”N, 21o07’10”E] at the western end of the village of Wilków (TOMCZYKOWA 1968) (Text-fig. 1b). The Upper Cambrian belonging to The Upper Cambrian occurs between 11 and 185 m the Klonówka Formation occurs between 785 and 957.8 m (Text-fig. 8). This trilobite-rich succession belonging to STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 223

Fig. 8. Lithological column of the Jeleniów 3 borehole section; modified from TOMCZYKOWA (1968) the Klonówka Formation is composed of siltstones and (TOMCZYKOWA 1968). The Upper Cambrian was stated claystones, with frequent intercalations of grey to occur between 198.8 and 292.5 m (Text-fig. 9) and is quartzitic sandstones in the lowest part, followed by composed of fine-grained grey sandstones with mica, grey to dark grey claystones with siltstone intercala- followed by claystones with rare sandstone and siltstone tions, more common in the lowest part. Trilobites are intercalations. Trilobites are particularly common common in the interval between 106 and 160 m. between 238 and 243 m.

Bukowiany 1a Borehole [50o48’30”N, 21o19’15”E] Wàworków Quarry

The borehole was located near the village of This abandoned quarry is located along the valley of Bukowiany, ca. 4 km from the Truskolaska Hill the river Opatówka, ca. 2 km south-east of Opatów 224 ANNA ˚YLI¡SKA

Fig. 9. Lithological column of the Bukowiany 1a borehole section;

modified from TOMCZYKOWA (1968); P. (N.) stands for Parabolina (Neoparabolina)

(Text-fig. 1c). The exposed succession (Text-fig. 10), belonging to the WiÊniówka Formation, is ca. 30 m thick and includes thick- and medium-bedded quartz sandstones, white, grey, bluish and reddish in colour, with intercalations of claystones and siltstones. The numeri- cally rich fauna is limited to a 1 m thick sandstone bed in the lower part of the succession (SAMSONOWICZ 1934; OR¸OWSKI 1968b; DZIK & OR¸OWSKI 1993, figs 1b-c).

BIOSTRATIGRAPHY

Because the Late Cambrian trilobite fauna of ¸ysogóry is represented mostly by forms known from Scandinavia (see discussion on biogeography), the biostratigraphic zonation applied here (Text-fig. 11) is a slightly modified version of the zonation used in the Baltic region (e.g. GEYER & SHERGOLD 2000). The bio- zones are assemblage zones, whereas the subzones are defined as range subzones (WESTERGÅRD 1922, 1947; HENNINGSMOEN 1957; MARTINSSON 1974; GEYER & SHERGOLD 2000). The trilobite zonation applied to the Upper Cambrian of ¸ysogóry is discussed below in ascending stratigraphical order. The ranges of the trilobite taxa are shown in Text-fig. 12. The biostratigraphic value of non-trilobite fossils (brachiopods, acritarchs, Fig. 10. Lithological column of the Wàworków quarry section; modified trace fossils) is also discussed. from OR¸OWSKI (1968a). STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 225

Olenus scanicus Subzone and Parabolina brevispina interval encompassing the Olenus scanicus Subzone Subzone and the Parabolina brevispina Subzone. The acritarchs documented from the WiÊniówka Trilobites characteristic of the subzones of Olenus Du˝a Quarry (KOWALCZEWSKI & al. 1986, KOWAL- scanicus and Parabolina brevispina are: Aphelaspis rara CZEWSKI 1995) are represented exclusively by long- (OR¸OWSKI, 1968), Olenus solitarius (WESTERGÅRD, ranging forms (Middle Cambrian − Early Tremadocian) 1922), Protopeltura aciculata (ANGELIN, 1854) and and do not permit a precise dating. Early Tremadocian Solenopleuridae gen. et sp. indet. The first three taxa acritarchs were noted in the northern (stratigraphically are known from rare specimens from the WiÊniówka youngest) part of the WiÊniówka Du˝a Quarry Du˝a Quarry (Text-fig. 2). Aphelaspis rara, Protopeltura (KOWALCZEWSKI & al. 1986). This part of the sequence aciculata and Solenopleuridae gen. et sp. indet. are also yielded a mouth-piece of an anomalocaridid common in Wàworków, in a bed in the lower part of (MASIAK & ˚YLI¡SKA 1994). Anomalocaridids and the section (Text-fig. 10), where they are accompanied related forms occur in Lower, Middle and very rarely by various brachiopods, including Orusia cf. lenticularis Upper Cambrian strata in different parts of the world (OR¸OWSKI 1968b, JENDRYKA-FUGLEWICZ 1992). In (CONWAY MORRIS 1989, DZIK 1993, MCHENRY & YATES Scandinavia, and in England and Wales Orusia lenticu- 1993) and their occurrence in the Lower Tremadocian is laris marks the base of the Parabolina brevispina highly improbable. Recent data on acritarchs from Subzone (RUSHTON 1983). Aphelaspis rara was report- samples collected from the trilobite-bearing beds from ed from the Olenus cataractes Subzone of the the central part of the WiÊniówka Du˝a Quarry indicate Maentwrog Formation of North Wales (ALLEN & al. concordance between the trilobite and acritarch ages. 1981, ALLEN & JACKSON 1985). The Olenus cataractes The acritarch assemblages indicate an interval not older Subzone represents the upper part of the Olenus and than the Olenus Zone and not younger than the lower Homagnostus obesus Zones of Eastern Avalonia and is part of the Parabolina spinulosa Zone (Z. SZCZEPANIK, an equivalent of the Olenus scanicus Subzone of the personal communication). So far, the presence of Early upper part of the Olenus Zone in Baltica (e.g. GEYER Tremadocian forms has not been confirmed at this & SHERGOLD 2000). Olenus solitarius occurs in the locality. Parabolina brevispina Subzone of Sweden (WESTERGÅRD Based on the occurrence of the trace fossil Cruziana 1922). Olenus cf. solitarius is known from the upper barbata SEILACHER in the southern (stratigraphically old- part of the Olenus cataractes Subzone in North Wales est) part of the WiÊniówka Du˝a Quarry, OR¸OWSKI (RUSHTON 1983). The vertical range of Protopeltura (1992a, b) suggested a Middle Cambrian age for the old- aciculata encompasses the Parabolina brevispina and est deposits in the quarry. The use of Cruziana barbata as Parabolina spinulosa subzones of Norway, Sweden and an index fossil of the uppermost Middle Cambrian has England; in Sweden and England Protopeltura aciculata already been questioned by KOWALCZEWSKI (1995). aciculata (ANGELIN) occurs in the Parabolina brevispina Recently, Cruziana barbata was found in higher parts of Subzone, and in Norway and Sweden Protopeltura the WiÊniówka Du˝a succession (˚YLI¡SKA 1992). It thus aciculata pusilla WESTERGÅRD is common in the definitely possesses a much wider stratigraphic range and Parabolina spinulosa Subzone (HENNINGSMOEN 1957; should not be regarded as an indicative taxon of the late MORRIS 1988). The co-occurrence of Aphelaspis rara Middle Cambrian. and Protopeltura aciculata in Wàworków indicates the The interpretation of the stratigraphic range of the presence of the Parabolina brevispina Subzone. WiÊniówka Du˝a section became even more confusing Solenopleuridae range from the Middle Cambrian to after the publication of JENDRYKA-FUGLEWICZ & MALEC the Lower Ordovician, whereas Andrarina? pusilla (1998), who, based on brachiopods, suggested a (WESTERGÅRD), to which the specimens from Tremadocian (!) age for the oldest strata in the quarry. Wàworków are provisionally referred, comes from the The brachiopods were provisionally referred to Obolidae; Parabolina brevispina Subzone (WESTERGÅRD 1922). however, their poor preservation does not allow accurate In the case of the WiÊniówka Du˝a Quarry the abun- assignment, and the supposed Tremadocian age cannot dances of trilobites are very low. The Parabolina be confirmed. brevispina Subzone is indicated only by three speci- The trilobites from the WiÊniówka Du˝a Quarry indi- mens of Protopeltura aciculata. Moreover, the assem- cate that at least part of the sequence represents the blage lacks representatives of Orusia cf. lenticularis or lower Upper Cambrian (Olenus scanicus and Parabolina Solenopleuridae gen. et sp. indet. Thus it is not clear brevispina subzones or only the Parabolina brevispina whether the succession from WiÊniówka Du˝a belongs Subzone). Analysis of trilobites from the Wàworków to the Parabolina brevispina Subzone or to a wider Quarry, assigned by SAMSONOWICZ (1934) to the genera 226 ANNA ˚YLI¡SKA

Fig. 11. Correlation of the zonal scheme applied in this paper with schemes presented by OR¸OWSKI (1968b, 1988) and TOMCZYKOWA (1968) for the Upper Cambrian of the Holy Cross Mountains. The vertical bars show intervals directly documented by trilobite fauna. Parab. spin. stands for Parabolina spinulosa, P. brevispina stands for Parabolina brevispina, S. alatus stands for Sphaerophthalmus alatus

Peltura, Cyclognathus and (in part) Parabolina, clearly Do∏y Mill and Ravine section (Text-fig. 4) (see below for demonstrates that most of those forms belong to discussion). Brachiopods (Eoorthis sp.) from Lisie Jamy Aphelaspis rara (˚YLI¡SKA 2001). The remaining speci- (JENDRYKA-FUGLEWICZ 1992) have no stratigraphic mens should be assigned to Protopeltura aciculata. Thus, value. Based on the fact that the representatives of the the trilobites in Wàworków are indicative of the genera Leptoplastus and Eurycare are encountered in Parabolina brevispina Subzone. Scandinavia, England and Wales in the Leptoplastus Zone and range upward to the Protopeltura praecursor Zone (WESTERGÅRD 1922, 1947; HENNINGSMOEN 1957; TAYLOR Leptoplastus − Protopeltura praecursor Zone & RUSHTON 1972), it is assumed that the Lisie Jamy section represents an interval spanning the Leptoplastus − Trilobites indicative of this interval are represented by Protopeltura praecursor Zone. Leptoplastinae gen. et sp. indet. − Leptoplastus or Eurycare − from Lisie Jamy (Text-fig. 3); their poor preservation does not allow definite taxonomic determi- Peltura minor Zone nation. Additionally, this section yields Leptoplastides irae (OR¸OWSKI, 1968), which is also present in the Peltura The Peltura minor Zone in ¸ysogóry is characterised minor and Peltura scarabaeoides zones of the Chabowe by Trilobagnostus rudis (SALTER, 1864), Peltura acutidens STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 227

Fig. 12. Range chart of the Late Cambrian trilobites from ¸ysogóry

BRØGGER, 1882, Peltura protopeltorum OR¸OWSKI, 1968, also known. The species Sphaerophthalmus alatus found Sphaerophthalmus alatus (BOECK, 1838), Ctenopyge in Scandinavia (Norway, Sweden and Denmark), and in (Mesoctenopyge) tumida WESTERGÅRD, 1922, and England (HENNINGSMOEN 1957, RUSHTON 1968) both Peltura scarabaeoides scarabaeoides (WAHLENBERG, in the Ctenopyge tumida and the Ctenopyge affinis sub- 1818), found in the Chabowe Do∏y Bed from the zones, ranges higher, to the lower part of the succeed- Chabowe Do∏y Mill section (Text-fig. 4). Trilobagnostus ing Peltura scarabaeoides Zone in Sweden and in stink- rudis occurs in Sweden and North Wales in the Peltura stone boulders in northern Germany (WESTERGÅRD minor Zone (MORRIS 1988, AHLBERG & AHLGREN 1947, SCHRANK 1973). 1996). In Sweden it is associated with Peltura minor The subspecies Peltura scarabaeoides scarabaeoides, (BRØGGER), Ctenopyge (Mesoctenopyge) tumida, although regarded commonly as a Peltura scarabaeoides Parabolinella laticauda WESTERGÅRD and Sphaero- Zone taxon, first appears already in the Ctenopyge affinis phthalmus alatus (WESTERGÅRD 1922, HENNINGSMOEN Subzone. It is well known from Sweden (Öland, 1957), and thus is characteristic of the Ctenopyge tumida Västergötland − WESTERGÅRD 1922), where it co-occurs Subzone, from which the species Peltura acutidens is in its lower range with Peltura minor and Ctenopyge 228 ANNA ˚YLI¡SKA

Fig. 13. Tentative trilobite-based correlation scheme of the sections with Upper Cambrian strata from the Holy Cross Mountains. For detailed position of the trilobites in particular sections see Text-figs 2-10 STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 229

(Ctenopyge) affinis WESTERGÅRD*. Thus most of the men- by the occurrence of Peltura scarabaeoides scarabaeoides, tioned taxa are characteristic of the Ctenopyge tumida and Ctenopyge (Ctenopyge) fletcheri, Ctenopyge (Ctenopyge) Ctenopyge affinis subzones. cf. linnarssoni WESTERGÅRD, 1922, Sphaerophthalmus Additionally, the Chabowe Do∏y Mill section is humilis (PHILLIPS, 1848) and Sphaerophthalmus major characterised by Parabolina (Neoparabolina?) lapponica LAKE, 1913 in the Chabowe Do∏y Ravine section (Text- WESTERGÅRD, 1947, which was described originally from fig. 4). Peltura scarabaeoides scarabaeoides ranges from the Peltura scarabaeoides Zone, but judging by the the Ctenopyge affinis Subzone of the Peltura minor Zone material from ¸ysogóry, has a much longer range (from to the upper part of the Ctenopyge linnarssoni Subzone the Peltura minor Zone to the Acerocare Zone sensu lato), (defined by the total range of its index taxon) of the as well as by Acerocarina klonowkae (OR¸OWSKI, 1968), a Peltura scarabaeoides Zone (WESTERGÅRD 1922, dominant form of the Peltura scarabaeoides Zone at HENNINGSMOEN 1957). Ctenopyge (Ctenopyge) fletcheri Chabowe Do∏y Ravine (Text-fig. 4). The assemblage also also has the same vertical range. Sphaerophthalmus contains Parabolina (Neoparabolina?) dawsoni MATTHEW, humilis occurs in the Ctenopyge bisulcata and Ctenopyge 1901, a species described from the Peltura Zones (s.l.) of linnarssoni subzones in Scandinavia and Wales Newfoundland, where it is associated with Ctenopyge (HENNINGSMOEN 1957, RUSHTON 1968). Sphaero- (Ctenopyge) fletcheri (MATTHEW, 1901) and Peltura phthalmus major is found in the Ctenopyge linnarssoni scarabaeoides scarabaeoides (HUTCHINSON 1952), indi- Subzone in Scandinavia and England. Consequently, the cating the Peltura scarabaeoides Zone. Its presence in the association from the Chabowe Do∏y Ravine indicates Peltura minor Zone of Chabowe Do∏y Mill section indi- the Ctenopyge linnarssoni Subzone. cates its much longer vertical range. Peltura protopeltorum Slightly younger strata are indicated by the pres- OR¸OWSKI, 1968 is known exclusively from Chabowe Do∏y ence of Peltura scarabaeoides cf. westergaardi Mill. It is inferred therefore that this species is restricted HENNINGSMOEN, 1957, accompanied by Nericiaspis to the upper part of the Peltura minor Zone. Leptoplastides robusta (TJERNVIK, 1953), in the Wilków IG-1 Borehole irae ranges from the Leptoplastides or Protopeltura (Text-fig. 6). Peltura scarabaeoides westergaardi charac- praecursor zones to the Peltura scarabaeoides Zone and is terises mainly the Parabolina lobata Subzone, but thus of low stratigraphic value. appears already in the uppermost part of the Ctenopyge Summing up, the assemblage from the Chabowe linnarssoni Subzone (HENNINGSMOEN 1957). In Do∏y Mill section is considered to represent the Scandinavia Nericiaspis robusta is known exclusively Ctenopyge tumida and Ctenopyge affinis subzones of the from a few cranidia from the Ctenopyge bisulcata and Peltura minor Zone. It is worth noting, however, that Ctenopyge linnarssoni subzones (TJERNVIK 1953, 1955), the fauna indicative of both subzones is limited to the and Nericiaspis cf. robusta is noted from stinkstone 60 cm thick lens comprising the Chabowe Do∏y Bed. boulders in northern Germany, where it is accompa- Although this is a thickness comparable to the thickness nied by taxa characteristic of the Ctenopyge linnarssoni of the zone in Scandinavia, where the Upper Cambrian Subzone (SCHRANK 1973). Therefore, the strata strata are represented by condensed alum shale facies between 856 and 847.8 m in the Wilków IG-1 Borehole (BERGSTRÖM & GEE 1985, THICKPENNY 1987), such an represent the uppermost part of the Ctenopyge lin- occurrence is extremely unusual in ¸ysogóry, where the narssoni Subzone. If, however, the vertical range of Upper Cambrian succession is greatly expanded, pre- Nericiaspis robusta is extended, the strata in question sumably up to 1800 m thick (see OR¸OWSKI 1975, 1988, would represent the Parabolina lobata Subzone. 1992b; KOWALCZEWSKI 1995). The Chabowe Do∏y Bed, with a randomly distributed fauna characteristic of both the Ctenopyge tumida and Ctenopyge affinis subzones, Acerocare Zone sensu lato thus suggests strong condensation. In ¸ysogóry, this zone is characterised by both long- ranging inter-regionally distributed taxa (in Scandinavia, Peltura scarabaeoides Zone England and Wales, Argentina and Bolivia) and short- ranging taxa, characteristic of this interval. For this rea- In ¸ysogóry, the lower part of this zone is indicated son, this part of the Upper Cambrian, corresponding to

* According to HENNINGSMOEN (1957, p. 232), the vertical range of Peltura minor overlaps that of Peltura scarabaeoides scarabaeoides in the lower part of the

Peltura scarabaeoides Zone; this, however, does not find confirmation in the sections from Öland and Västergötland in Sweden (WESTERGÅRD 1922, pp.31,

34, 51, 71), where Peltura scarabaeoides scarabaeoides co-occurs also with Ctenopyge (Ctenopyge) affinis. If HENNINGSMOEN’s view is to be accepted, the range of the index fossil for the Ctenopyge affinis Subzone would be wider than the range of this subzone. This is assumed to be incorrect. 230 ANNA ˚YLI¡SKA the zones of Peltura transiens, Peltura costata, proving its occurrence also in at least the lower part of Westergaardia and Acerocare ecorne (GEYER & SHERGOLD the Acerocare Zone sensu lato. Leptoplastides was long 2000) is referred to here as the Acerocare Zone sensu lato considered as a Tremadocian genus, but NIKOLAISEN & (Acerocare Zone of HENNINGSMOEN 1957 and AHLBERG HENNINGSMOEN’s (1985) revision of the genus shows & AHLGREN 1996). that it appears already in the Late Cambrian, which is The zone is present in the Brzezinki 1 and 2, Wilków also confirmed here. Leptoplastides ulrichi is a charac- IG-1, Jeleniów 2, Jeleniów 3 and Bukowiany 1a boreholes teristic species of the Parabolina argentina Zone in (Text-figs 5-9). Parabolina (Neoparabolina) frequens Argentina and Bolivia (HARRINGTON & LEANZA 1957, (BARRANDE, 1868), Leptoplastides latus (TOMCZYKOWA, PRˇIBYL & VANEˇK 1980), but because of its association 1968) and Leptoplastides ulrichi (KAYSER, 1897) dominate there with Parabolina (N.) frequens (synonym of among the long-ranging taxa. They are accompanied by Parabolina argentina) and various agnostid species (e.g. rare Parabolina (Parabolina) heres BRØGGER, 1882, Gymnagnostus thoas PRˇIBYL & VANEˇK or Gymnagnostus Acerocare sp., Peltura cf. costata (BRØGGER, 1882), Peltura bolivianus HOEK), the ranges of which are partly within cf. transiens (BRØGGER, 1882), Angelina cf. hyeronimi the Late Cambrian (NIELSEN 1999), it can also be con- (KAYSER, 1876), Plicatolina sp., Parabolina (Parabolina?) sidered as Late Cambrian in age. Leptoplastides cf. latus jemtlandica WESTERGÅRD, 1922, Parabolinella sp. and and Leptoplastides cf. ulrichi have been recognised in the Leptoplastides coniunctus (TOMCZYKOWA, 1968). Also Protopeltura praecursor Zone, and most probably also present is Parabolina (Neoparabolina?) lapponica, known higher in the Kistedal Formation of the Digermul from the underlying Peltura minor and Peltura Peninsula, Norway (NIKOLAISEN & HENNINGSMOEN scarabaeoides zones. 1985). The Acerocare Zone sensu lato is also indicated by Parabolina (N.) frequens, long considered an Early Parabolina (P. ) heres. The range of Angelina hyeronimi is, Tremadocian species (SDZUY 1955; HENNINGSMOEN 1957; similarly to that of Parabolina (N.) frequens, considered HARRINGTON & LEANZA 1957; PRˇIBYL & VANEˇK 1980), is to span the Cambrian − Ordovician boundary, and its now recognised to range down into the Late Cambrian Late Cambrian occurrences were recognised e.g. in the (RUSHTON 1982; ACEN~OLAZA 1983; SHERGOLD 1988; Cordylodus proavus Zone in Mexico (ROBISON & LANDING & al. 2000; FRANCO TORTELLO, personal com- PANTOJA-ALOR 1968) and in the Cardonal Formation of munication). Its occurrences are inferred from its appear- Jujuy in Argentina (TORTELLO & al. 1999). Rare speci- ance well below the entrance level of Rhabdinopora fla- mens of Plicatolina SHAW and Parabolinella BRØGGER belliformis (e.g. in Argentina − HARRINGTON & LEANZA from ¸ysogóry are not specifically determined, but rep- 1957; SHERGOLD 1988, and Wales − RUSHTON 1982; resentatives of both genera occur also in the Acerocare SHERGOLD 1988; LANDING & al. 2000); and its association Zone of Wales (RUSHTON 1982). Peltura cf. costata from with the conodont Cordylodus proavus MÜLLER, the first the Brzezinki 1 (Text-fig. 5a) and Jeleniów 3 (Text-fig. 8) appearance of which coincides with the base of the boreholes, as well as Parabolina (P. ? ) jemtlandica from Symphysurinid biomere in Laurentia, and the last the Jeleniów 2 Borehole (Text-fig. 7), represent proba- appearance of which is below the Cambrian − Ordovician bly slightly younger horizons of the Acerocare Zone boundary (BRUTON & al. 1988; COOPER & NOWLAN 1999; sensu lato. Parabolina (P. ? ) jemtlandica is known from PUURA & VIIRA 1999; GEYER & SHERGOLD 2000; Sweden and probably from Wales (WESTERGÅRD 1922, LANDING & al. 2000; COOPER & al. 2001). ALLEN & al. 1981), and in both areas it is regarded as an In ¸ysogóry Parabolina (N.) frequens first appears Acerocare Zone species. well below the occurrence of Rhabdinopora sp. in the At present no detailed subdivision is possible for the Brzezinki 1 Borehole (Text-fig. 5a), and in the Jeleniów Acerocare Zone sensu lato, as proposed herein for 3 and Bukowiany 1a boreholes (Text-figs 8-9), where it is ¸ysogóry (Text-figs 11-13). This is caused by the rather associated with Parabolina (N.?) lapponica, Lepto- poor representation of biostratigraphically important plastides, Acerocare sp., as well as with Peltura cf. tran- taxa, above all of Peltura, which gives a series of good siens. In Scandinavia, Acerocare and Peltura transiens are index species in other areas. restricted to the Acerocare Zone sensu lato, with the latter taxon limited to the lowermost part of this zone (HENNINGSMOEN 1957). Parabolina (N.?) lapponica, BIOGEOGRAPHY known from the Peltura minor Zone in ¸ysogóry (Chabowe Do∏y Mill) and from the Peltura scarabaeoides Palaeogeographic reconstructions for the Late Zone of Scandinavia and ¸ysogóry (Chabowe Do∏y Cambrian are still very controversial, mainly because of Ravine), co-occurs in the topmost part of its ¸ysogóry the lack of good quality palaeomagnetic data. For Baltica, range with Acerocare sp. and Peltura cf. transiens, thus for instance, the scarcity of reliable palaeomagnetic data STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 231 is caused by inappropriate lithologies (deposits with low the Alum Shale Formation and in the Kistedal Formation or unstable natural remanent magnetisation) or by the of the Digermul Peninsula, Finnmark (Norway), as well frequent remagnetisation of the deposits during as in the clastic deposits from the Polish part of the East Caledonian deformations and/or Variscan igneous activi- European Craton; ty (TORSVIK & REHNSTRÖM 2001). In many cases the – endemic fauna − occurring only in ¸ysogóry; thermal overprint and the complex subsequent tectonic – Gondwanan fauna − known also from the Angosto, history is a reason of unequivocal palaeomagnetic data Santa Rosita and Volcancito Formations of Argentina, (LEWANDOWSKI 1993). The existing biogeographic inter- Taraya Formation of Bolivia and lower Tiñu Formation of pretations of the ¸ysogóry Upper Cambrian suggested Mexico; the presence of totally endemic faunas (OR¸OWSKI 1968b; – mixed Avalonian-Baltic fauna; TOMCZYKOWA 1968) or their close relationship to – mixed Baltic-Gondwanan fauna; Avalonia (see in BELKA 2000; BELKA & al. 2000). Recent – mixed Avalonian-Baltic-Gondwanan fauna. revision of the trilobite fauna (˚YLI¡SKA 2001) showed The spectra of particular biogeographic groups repre- that the biogeographic relationships of the studied area sented in the studied material are analysed for the fol- are more complex. lowing intervals*: – Olenus scanicus Subzone and Parabolina brevispina Subzone; Affinities of the Late Cambrian trilobites from ¸ysogóry – Peltura minor Zone; – Peltura scarabaeoides Zone; Thirty-seven trilobite taxa are recognised in the – Acerocare Zone sensu lato. Upper Cambrian of ¸ysogóry (˚YLI¡SKA 2001); twenty- The species-level analysis demonstrates that the bio- eight at species level, seven at generic level, and two at geographic relationships of the Late Cambrian ¸ysogóry family level. At generic level (Text-fig. 14), the fauna has trilobites are much more complex than inferred from a mixed Avalonian-Baltic character, i.e. it is dominated generic level analysis, and moreover, that they underwent by genera occurring in both Avalonia and Baltica. It also a distinct change during that interval (Text-fig. 16). The contains some exclusively Baltic genera (Acerocare Baltic fauna, including faunas occurring also in other ANGELIN, Acerocarina POULSEN and Nericiaspis areas, is present in all of the intervals. Its diversity and TJERNVIK), as well as some genera unknown from abundance increases towards the top of the Cambrian. Baltica, but occuring widely in other areas: Aphelaspis The Avalonian fauna is common only in the lowermost RESSER, known from Laurentia and Avalonia; part of the sequence. In the Peltura minor Zone it is rep- Plicatolina SHAW, reported from Laurentia, Avalonia resented by a single taxon, and above this zone it com- and Gondwana; and Angelina SALTER, noted from the pletely disappears. On the other hand, the Gondwanan Upper Cambrian of Gondwana, and also from the fauna appears only in the uppermost part of the Tremadocian of Avalonia. sequence. Towards the top there is also a constant The species-level biogeographic analysis of the decrease in species diversity and abundances of the ¸ysogóry Late Cambrian focuses on Baltica, Avalonia endemic fauna. The mixed Avalonian-Baltic fauna is pre- and part of Gondwana proper (South America), that is sent in all of the intervals, although decreasing distinctly areas dominated by the presence of olenid trilobites in the Acerocare Zone sensu lato, both in species diversity (Baltic province sensu SHERGOLD 1988). and in abundances. In this interval it is replaced by the Among the Late Cambrian trilobite species from mixed Avalonian-Baltic-Gondwanan fauna and by the ¸ysogóry the following biogeographic groups have been mixed Baltic-Gondwanan fauna. distinguished (Text-fig. 15): The biogeographic analysis shows that in different – Avalonian fauna − known also from the upper part stratigraphic intervals of the Late Cambrian the of the Maentwrog, Ffestiniog Flags and Dolgellau ¸ysogóry Block shares up to 80% of trilobite species Formations of North Wales, and the Outwoods Shales, with Baltica, including mixed Avalonian-Baltic species, Monks Park Shales and White-Leaved-Oak Shales of whereas up to 40% comprises solely Baltic species. England, as well as from maritime eastern North Avalonian species in contrast never exceed 33%, and America (Nova Scotia, New Brunswick, eastern their number decreases rapidly in the Peltura minor Newfoundland in Canada); Zone, to disappear completely above. The endemic – Baltic fauna − known also from Scandinavia within fauna appears in the Peltura minor Zone and comprises

* Fauna recognised in the Lisie Jamy exposure is excluded from this analysis. It is represented by a very small number of specimens, including a long-range endemic species and a form assigned only at family level; furthermore, the stratigraphic horizon cannot be precisely defined. 232 ANNA ˚YLI¡SKA

Fig. 14. Distribution of trilobite genera in the Upper Cambrian of ¸ysogóry and in other biogeographic areas (based on HENNINGSMOEN 1957a, HARRINGTON

& LEANZA 1957, SHERGOLD 1988 and MORRIS 1988)

Fig. 15. Distribution of the ¸ysogóry trilobite species in particular biogeographic groups

30% of the species with regard to the taxonomic con- the ¸ysogóry Block maintained constant and increasing tent, and over 50% with regard to the abundances. proximity to Baltica in the Late Cambrian. The domi- Towards the top of the Cambrian the endemic fauna nance of the Avalonian fauna in the lower part of the decreases in diversity and abundances. sequence might suggest that this area was much closer to The trilobite diversity in ¸ysogóry varied from a low Avalonia than to Baltica in the early Late Cambrian. diversity assemblage in the early Late Cambrian, with the Later on, the migration of trilobites between Avalonia predominance of the Avalonian fauna, to more diversified and the ¸ysogóry Block was impeded. The appearance of assemblages in the late Late Cambrian with a constant endemic taxa in the Peltura minor Zone may be a result of increase in the Baltic fauna, and a parallel decrease in the geographic isolation. On the other hand, the appearance endemic fauna (Text-fig. 16). It is inferred therefore that of the Gondwanan fauna as well as the mixed Baltic- STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 233

Gondwanan fauna at the end of the Late Cambrian sug- al. 1981; RUSHTON 1983), and the Polish part of the East gests exchange of faunas between the ¸ysogóry Block and European Craton (BEDNARCZYK 1972, 1984; LENDZION the South American part of Gondwana. Low abundances 1976, 1982, 1983, 1988), the faunas from the Acerocare of mixed Avalonian, Baltic and Gondwanan species Zone sensu lato are different. The Alum Shale fauna is [Parabolina (Neoparabolina) frequens – RUSHTON 1982, poorly represented in this zone in ¸ysogóry. The com- LANDING & al. 2000] and the lack of mixed Avalonian and monest taxa here are Leptoplastides RAW and Parabolina Gondwanan genera (e.g. Angelina SALTER) before the (Neoparabolina) frequens, the forms known from shaly- Tremadocian in Avalonia suggest its isolation during this arenaceous sediments (READING 1965) of the Kistedal interval. and Berlogaissa Formations of the Digermul Peninsula, It is also notable that whereas the Baltic and mixed Finnmark (Norway) (NIKOLAISEN & HENNINGSMOEN Avalonian-Baltic faunas recorded from ¸ysogóry in the 1985), deposited at the margin of Baltica (BERGSTRÖM & Peltura minor and Peltura scarabaeoides zones are identi- GEE 1985, COCKS 2000). These taxa also occur in cal with those from the Alum Shale Formation in Avalonia: in the Upper Cambrian of England, Wales and Scandinavia (WESTERGÅRD 1922, 1947; HENNINGSMOEN maritime eastern North America (RUSHTON 1982; 1957; MARTINSSON 1974; BERGSTRÖM & GEE 1985), SHERGOLD 1988; LANDING & al. 2000), as well as in Wales, England (e.g. TAYLOR & RUSHTON 1972, ALLEN & Gondwana: in Argentina and Bolivia (PRˇIBYL & VANEˇK

Fig. 16. Composition of the Late Cambrian trilobite fauna of ¸ysogóry with respect to its biogeographic affinities. Note the distinct change in the composition towards the dominance of Baltic forms in the latest Cambrian 234 ANNA ˚YLI¡SKA

1980; ACEπOLAZA 1983; FRANCO TORTELLO, personal adapted to the oxygen-depleted environments communication). It is quite possible that the trilobites (THICKPENNY 1987) of the ‘Alum Shale’ sea (see from Finnmark and ¸ysogóry could represent forms JENDRYKA-FUGLEWICZ 1992). poorly adapted to the extreme conditions of the ‘Alum The muscovites and zircons from the lower part of the Shale’ sea (NIKOLAISEN & HENNINGSMOEN 1985; Cambrian clastics of ¸ysogóry (WiÊniówka Du˝a and CLARKSON & TAYLOR 1995), that is disaerobic environ- Wàworków quarries) suggest more than one source of ments which could have been dominated by chemoau- clastic material. The possible source areas include a totrophic symbionts from the olenid family (FORTEY Cadomian (Gondwanan) provenance and detritus from 2000). The trilobites in question probably flourished on the Svecofennian basement of Baltica (BELKA & al. 2000, the margins of Baltica, from where they could be distrib- VALVERDE-VAQUERO & al. 2000). These conclusions are uted onto the Avalonian and South American segment of thus in concordance with the trilobite-based biogeo- Gondwana, for instance by changing current patterns graphic results inferred for this interval, suggesting (SHERGOLD 1988). Avalonian and mixed Avalonian-Baltic affinities. Previous biogeographic interpretations based on trace fossils (SEILACHER 1983; see in BELKA 2000; Palaeogeographic position of the ¸ysogóry Block during VALVERDE-VAQUERO & al. 2000) pointed to the the Late Cambrian Gondwanan and Peri-Gondwanan provenance of the ¸ysogóry Block. The trace fossil in question, Cruziana The ¸ysogóry Block was regarded either as a part of semiplicata SALTER, was most probably made by Baltica (DADLEZ 1983, TOMCZYK 1988, DADLEZ & al. Aphelaspis rara (˚YLI¡SKA 1999), which is an Avalonian 1994, MIZERSKI 1995, COCKS 2000), or as an exotic ter- species characteristic of the early part of the Late rane (PO˚ARYSKI 1990, PO˚ARYSKI & al. 1992, BELKA & Cambrian. Thus again, there is a strong evidence that the al. 2000, TOMCZYKOWA & TOMCZYK 2000, VALVERDE- early Late Cambrian history of the ¸ysogóry Block was VAQUERO & al. 2000). In the latter case the time of its connected closely with Avalonia. On the other hand, the accretion to Baltica, similar to that of other exotic ter- distribution of Cruziana trace fossils was probably not ranes of the TESZ (e.g. Ma∏opolska Block), remains restricted to the Gondwanan realm, as suggested by unknown. However, the event certainly took place SEILACHER (1983). Similar specimens were recognised on before the Devonian (e.g. LEWANDOWSKI 1987, 1993; the margin of Baltica within the Upper Cambrian strata NAWROCKI 2000). of the Digermul Peninsula (STRAND 1935). Recent geophysical soundings show that the ¸ysogóry As discussed above, the Late Cambrian trilobite Block is a narrow, ca. 30 km wide zone, separated from assemblages in ¸ysogóry are dominated by the Baltic the East European Craton (Baltica in the early fauna, which indicates the location of the ¸ysogóry Block Palaeozoic) by an almost vertical, deep fault (SEMENOV & close to Baltica. However, the observed trends of biogeo- al. 1998). Its basement, of unknown provenance, is sup- graphic changes and the dominance of the Avalonian posed to lie at depths of about 6-7 km (SEMENOV & al. fauna at the beginning of the Late Cambrian point to a 1998). GUTERCH & al. (1986) postulated that the Moho more complex scenario. It is possible that the ¸ysogóry underneath this unit lies at much greater depths in com- Block was isolated from Baltica at the beginning of the parison to that of the Palaeozoic platform, being other- Late Cambrian (dominance of the Avalonian fauna). wise similar to the Moho depth of the East European Later on it moved away towards Baltica, but was in some Craton. Palaeomagnetic data obtained from the Upper way isolated (low and decreasing content of the Cambrian sandstones of ¸ysogóry are most probably of Avalonian fauna, low but increasing content of the Baltic secondary origin, and are thus inconclusive for determin- fauna, high but decreasing content of the endemic fauna), ing the position of the ¸ysogóry Block in the Late to attain very close connections (enabling mixing of fau- Cambrian (LEWANDOWSKI 1993). nas) with Baltica by the end of the Cambrian (high con- Brachiopods recognised in ¸ysogóry do not confirm tent of the Baltic fauna, low content of the endemic fauna, the biogeographic conclusions based on trilobites. no Avalonian fauna). However, palaeogeographical However, according to FORTEY & COCKS (1992), in the reconstructions (MCKERROW & al. 1992, TORSVIK 1998, early Palaeozoic brachiopods reacted with delay to conti- TORSVIK & REHNSTRÖM 2001) indicate that Avalonia nental separations, and thus their affinities do not neces- (which during the Late Cambrian was still incorporated sarily reflect true biogeographic relationships. Long-rang- into the North African – South American part of ing mixed Avalonian-Baltic and Avalonian brachiopod Gondwana) was constantly in the vicinity of the shelf of taxa recognised in the area (BIERNAT & TOMCZYKOWA southern Baltica (present-day co-ordinates). In this case, 1968, JENDRYKA-FUGLEWICZ 1992) were probably poorly the significant decrease in the Avalonian faunal content in STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 235

¸ysogóry towards the end of the Late Cambrian may not Micha∏ POROS lent his specimens of Protopeltura aciculata from necessarily be a result of geographic isolation of the two the WiÊniówka Du˝a Quarry. The research was supported by the areas linked with the width of the Tornquist Sea (COCKS Institute of Geology, Department of Geology, University of & FORTEY 1982), but may have resulted from other fac- Warsaw (individual BW grants in 1996-2000), the European tors, e.g. oceanic currents, environmental factors or the Commission (Tempus Phare Individual Mobility Grant in 1998), recently recognised rapid counter-clockwise rotation of the Paleontological Society of America (PALSIRP grant in 1999) Baltica during the Late Cambrian and the Early and the International Subcommission on Cambrian Ordovician (TORSVIK & REHNSTRÖM 2001). The latter Stratigraphy. The financial support of the KOPIPOL event, combined with simultaneous counter-clockwise Foundation is acknowledged with many thanks. This paper is a rotation of Gondwana, led to the juxtaposition of differ- contribution to the project “Palaeozoic Accretion of Poland”, ent shelves on both palaeocontinents in Early Ordovician Polish Committee for Scientific Research Grant no. PCZ 07-21. time, the Avalonian shelf being shifted westwards.

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Manuscript submitted: 10th December 2001 Revised version accepted: 15th April 2002 STRATIGRAPHY AND BIOGEOGRAPHY OF LATE CAMBRIAN TRILOBITES 239