132 



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



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Fig. 12 Selected chitinozoan distribution at La Vid. Chitinozoan zonation after Verniers et al. ( 1995): su: superba, ele: elegans. ko: kosovensis. 



LVl and LV2 (42 m and 38.8 m below the base of the San Pedro 

 Formation) suggests an Upper Llandovery age for the Formigoso 

 Formation. Angochitina echinata Eisenack ( 1931 ) anAAngochitina 

 r/jfli/e/// Paris (1981) (PI. 12, fig. 1 1 ) were recovered from LV 5a. The 

 latter has been reported from strata assigned to Graptolite Biozones 

 32 and 33 (Homerian to Lower Gorstian) of Elles & Wood ( 1 90 1 -1 8) 

 by Schweineberg (1987: 59). A Llandovery age is also supported by 

 the presence of C. elenitae in LVl. The recovery of this species (39 

 metres above the base of the San Pedro Formation at the level of 

 sample LV 7b) is probably the result of reworking. A. echinata is a 

 common species in the Middle Gorstian to Lower Pfidoli (Verniers et 

 al. 1995). 



Typical Pfi'dolichitinozoans (e.g. Urnochitinaiirna -PI. 12, fig. 4), 

 associated with Plectochitina ( PI . 1 3, fig. 8 ), are not recovered until LV 

 10, 102.2 metres above the base of the San Pedro Formation. 

 Margachitina elegans (PL 1 2, fig. 5), used as an index species for the 

 mid-Pfidoli by Verniers et al. ( 1995), is first encountered in LVl 1, 

 107.8 m above the base of the San Pedro Formation. Ancyrochitina 

 fragilis brevis Taugourdeau & de Jekhowsky (1960) was recovered 

 from LV 1 ( PI . 1 3 , fig . 5 ). This species was regarded as a iate Ludlow ' 

 species by Crainer & Diez (1978a). Samples LV 10, 1 1, and 12 are 

 regarded as lowermost Devonian based on the spores but no chitinozoans 

 were recovered that could be positively identified as Devonian. The 

 spores in sample LV 1 3, r. 1 m above LV 1 2, are typical of the lower 

 MN Biozone (NA Subzone) of Lower Lockhovian age. 



Stage and Series boundaries 



No Devonian chitinozoans were recovered from La Vid and typical 

 Pfidoli forms such as P.seudoclathrochitina cannenchiii and M. 



elegans were still recovered from the top of the section. However, the 

 first appearance of Aneumspora is used tentatively to place the base 

 of the Devonian below LVIO (see also Richardson, Rodriguez & 

 Sutherland. 2000). The base of the Pridoli is placed somewhere 

 below LVIO with the first occuirence of U. iinui. As with Argovejo, 

 the presence of Upper Llandovery chitinozoans in the Formigoso 

 Formation may suggest the presence of a disconformity or the 

 reworking of Lower Silurian faunas. The spacing of some samples, 

 because of unsuitable lithology and poor recovery from others, 

 makes a more precise biostratigraphy difficult at this time. 



La Peral (Fig. 13) 



Because Spinachitina has not been reported above the Llandovery, 

 the presence of Spinachitina sp. in LP2 (PI. 11, fig. 4) 18 meters 

 above the base of the San Pedro Formation may suggest either a 

 pre-Wenlock age for this part of the section or possibly evidence 

 for reworking. Conochitina nidda Sutherland (1994), present in 

 LP3, 24.6 metres above the base of section, has been described 

 from the Upper Wenlock/Lower Ludlow of the type area in the 

 Welsh Borderlands (Sutherland, 1994: 48). Conochitina 

 pachycephala Eisenack 1964, present in LP3 (PI. 11, fig. 1), is 

 used as an index species for the mid-Upper Wenlock but also 

 ranges well into the Gorstian (Verniers et al. 1995). The presence 

 of Cyathochitina elenitae (PI. 1 1, fig. 3) in the same sample may 

 be the result of reworking. The recovery of Angochitina echinata 

 (PI. 12, fig. 10) suggests an age of at least Middle Gorstian to 

 Lower Pfidoli (Verniers et al., 1995) for LP 8, 77.5 m above the 

 base of section. A. elongata. recovered from the same sample, was 

 used as a mid-Ludlow zonal indicator in the biozonation of 



