130 



J.B. RICHARDSON, R.M. RODRIGUEZ AND S.J.E. SUTHERLAND 



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H Sandstone _^ Phosphadc nodules 



Bshale g] Dolomites 



□ Sandstone & Shale Q Limestones 



■ sandstone /Oolites Quartz ites 

 H Ferrous Oolites 



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Ger 18 

 Ger 17 

 Ger 16 

 Ger 15B 

 Ger 15A 

 Ger 14 _ 

 Ger 13 " 

 Ger 12 

 Ger 11 

 Ger 10 

 Ger 9 

 Ger 8 

 Ger 7 

 Ger 6 

 Ger 5 

 Ger 4 

 Ger 3 _ 

 Ger2B 

 Ger2A 

 Ger 1 



•_ _ . Fault 



Fig. 10 Selected chitinozoan distribution at Geras. Chitinozoan zonation after Verniers et al. ( 1995): bo: bohemica, su: superba. ele: elegans, ko: 

 kosovensis, ba: barrandei, ph: philipi. 



Chitinozoan 



Spore 



Zonation 



Zonation 



Lodikov. 







MN 





bo 



Lochkov. 



(na) 



^ _i 



, 









Pridoli 



Vsu 



ele 







(a) 

 EC 





?ko 



Pridoli 



H 



?Pridoli 









?- -?. 



Ludlow 



?ba 



-?-?- 



RS 

 ■> 





?ph 



Ludford. 



^LP" 



(Schweineberg, 1987: 70). A similar species, Ancyrochitina sp. A, 

 was described by Paris from the Formation du Val in the section at 

 Heuze, Brittany (Paris, 1981) and is associated with Pterochitina 

 perivelata Eisenack (1937), a chitinozoan with a well established 

 range from the Upper Ludfordian to the Upper Pfi'doli (barrandei 

 Biozone to early part of the superba biozone of Verniers etal. (1995). 

 The presence of Angochitina elongata Eisenack (1931, figs 8h, i) in 

 sample Ger 9 may be the result of reworking. 



Uniochitina iirna (Eisenack, 1 934) is a very useful Pfidolf marker 

 in the stratotype area (Barandian region. Central Bohemia). U. iirna 

 occurs very close to (within 50 cm) or at the base of the Pfidoli 

 (although some atypical specimens do occur a few centimetres 

 below the first occurrence oi Monograptus parultimus (Kriz et al, 

 1986). U. uma is recovered from the Geras section at Ger 10, 55 

 metres above the base of the section in the San Pedro Formation. In 

 addition to U. uma, Pseudoclathrochitina carmenchui Cramer 

 (1964b) and Margachitina elegans (Taugourdeau & de Jekhowsky, 

 1960: pi. 7, figs 92, 93) also occur in Ger 10. Both species are 

 important markers for the mid-Pfidoli elegans Biozone of Verniers et 

 al. 1995. 



In Bohemia, Eisenackitina bohemica (Eisenack, 1934) occurs 

 50cm above the base of the Devonian at Klonk, the Silurian/Devonian 

 boundary stratotype, and Karlstejn (Paris et al, 1981). At Geras, E. 

 bohemica is recovered from Ger 14, 70 metres above the base of the 

 section in the San Pedro Formation (PI. 11, fig. 14). It is found 

 associated with Angochitina tsegelnjucki Paris & Grahn (1996, fig. 

 7r) (PI. 12, fig. 8). In Podolia this species is reported from the upper 

 part of the Mitkov Formation which, on the basis of its association 

 with E. bohemica and Margachitina catenaria Obut (1973), was 

 assigned to the Lochkovian by Paris & Grahn (1996). 



In the highest part of the secfion. between 74 and 76 m above the 

 base (samples Ger 16, 17 & 18). significant numbers of a species 

 resembling M. catenaria of Lochkovian age occur consistently (see 

 p. 134). However, only a tentafive assignment is made here to the 

 Cantabrian forms as no individuals were recovered that demon- 

 strated a convincing peduncle. 



Stage and Series Boundaries 



On the basis of chitinozoans the Silurian/Devonian boundary would 

 be placed below the first occurrence of £. bohemica at Ger 14. The 

 Ludlow/Pfi'doli boundary is less easy to define but will occur some- 

 where between the first occurrence of typical Pridoli chitinozoans 

 (U. uma, P. camienchui and M. elegans) in Ger 10 but above the last 

 occurrence of R. villosa in Ger 2b. 



Argovejo (Fig. 11) 



An Upper Llandovery age for the Formigoso Formation at Argovejo 

 (Argovejo 1-3; 21-10.5 metres below the base of the San Pedro 

 Formation) is suggested by the presence of Cyathochitina sp. B Paris 

 (1981: pi. 11, fig. 11) (PI. 11, fig. 12). This species is reported from 

 Upper Llandovery strata in the Massif Armorican by Paris (1981: 

 299). The discovery of the Llandovery chitinozoan Cyathochitina 

 elenitae Cramer ( 1 964b) in sample Arg 3 (PI. 11, fig. 6) supports this 

 age assignment. The latter species (PI. 1 1, fig. 5) was also recovered 

 with another Llandovery chitinozoan, Conochitina alagarda Cramer 

 1967 in Arg 4 (PI. 1 1, fig. 2). However, as both of these species are 

 found associated with spores from the RS Biozone (late Ludfordian- 

 Lower Pi'idolf) they may represent reworking. 



Ancyrochitina libyensis Jaglin (1986) was recovered from Arg 4, 



