120 



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



into lower part of the Synorisporites libycus -Chelinospora 

 poecilomoipha (LP) Spore Biozone in the Anglo- Welsh area. Regard- 

 ing the age of the La Peral samples, there are two main possibilities: 

 the spores represent either an impoverished Gorstian (LP) assem- 

 blage with reworked fossils from the Homerian, or b, //; situ Homerian 

 spores. Since older spores may be reworked and deposited inside 

 clasts in younger rocks, they may be preferentially retained, whereas 

 the lower density of contemporary palynomorphs may cause them to 

 be selectively removed by currents. 



Occurence. Found only in the La Peral section. 



Age. Homerian. In the type Wenlock the brevicosta and lamontii 

 Sub-Biozones are more or less equivalent to the upper hmdgreni and 

 nassa to lower ludetisis Graptolite Biozones respectively. There is no 

 chitinozoan evidence for sample LP4 but in the underlying sample 

 (LP3) the chitinozoan species Conochitina rudda also indicates a 

 Upper Wenlock to Lower Ludfordian age. Therefore, the chitinozoan 

 evidence fits with an assignment to either the upper brevicosta - 

 verriicatus (BV) Biozone (Middle to Upper Homerian), or to the 

 succeeding spore zone in the Ludlow. 



Coronaspora reticulata - Chelinospora sanpetrensis 

 (RS) Spore Biozone (Figs 3-5) 



Nominal species 



Coronaspora reticulata sp. nov. Knoxisporites? riondae Cramer 



&Diez 1975 (pars): pi. l,fig. 17. 

 Chelinospora sanpetrensis (Rodriguez) comb. nov. Rodriguez, 

 1978c: pL l,fig. 13 (figs i. j, 1). 



Definition. Based on the incoming of either of the two nominal 

 species. In some sections the two species appear at the same horizon 

 (La Peral), in others C. sanpetrensis appears earlier. The zone 

 represents the interval between the first appearance of the nominal 

 species and the first occurrence of Chelinospora hemiesferica 

 (Cramer & Diez) comb. nov. 



Accessory species. Chelinospora poecilomorpha, Coronaspora 

 cromatica, Emphanisporites splendens, Chelinospora cantabrica. 



Remarks. This biozone is present in all four sections. In the La 

 Peral section the base lies above a thick sandstone in sample 6, c.71 

 m above the base of the San Pedro Formation. However, in the 

 Argovejo section several species that occur together in the lowest RS 

 Spore Biozone in the other samples follow one another in sequence. 

 This may mean that the oldest part of the zone is seen in the Argovejo 

 sequence. In all sections, however, Chelinospora cantabrica appears 

 a little above the first appearance of C sanpetrensis. which suggests 

 that all sections begin at a similar stratigraphical level. The concur- 

 rence of the two species may form a useful sub-biozone. 



Current data (see also Richardson & McGregor, 1986) indicate 

 that trilete spores, with a regular distal reticulum of even lacunae and 

 well-developed muri, first appear in the Pi'idolf. However, precise 

 corroboration is lacking, and spore/chitinozoan assemblages from 

 the lower parts of the Cantabrian Mountains sections studied are 

 often poor. Consequently, the exact relation of this sculptural event 

 to the Ludfordian/Pfi'doli boundary in the Cantabrian Mountains is 

 not clear. Distally reUculate spores first appear in the RS Spore 

 Biozone and the spore evidence indicates an Upper Gorstian age for 

 the base of the biozone. Other rare taxa include Insolisporites sp. (PL 

 3, fig. 3) and similar taxa are found in Britain in the Ludlow. 

 Chitinozoans in Ger 2A indicate an Upper Ludfordian age and 

 consequentely the upper part of the RS Spore Biozone is probably of 

 Pfidoli age. 



Reference section. La Peral, Cordillera Cantabrica, Province of 



Asturias, NW Spain. The 'base' of the zone is between 49 and 71 m 

 above the base of the San Pedro Formation. The strata in this 22 m 

 interval are dominated by red sandstones and were not sampled. The 

 zone is at least 22 m thick in the La Peral section. 



Distribution. La Peral, Geras, La Vid and Argovejo sections. In 

 the Argovejo sequence the thickness of the zone is uncertain due to 

 a 40 m interval where samples are barren. In the other sections the 

 thickness of the zone is around 15-25 m. 



Argovejo section. The lowest eleven samples are barren or do 

 not contain diagnostic palynomorphs. In sample ARG/4 

 poecilomorpha occurs with cf. sanpetrensis and may indicate the 

 presence of the upper part of the LP Biozone ( Upper Ludfordian in 

 England and Wales). Chitinozoa from the same sample are long 

 ranging from Upper Gorstian to Pindoli and therefore do not conflict 

 with the presence of the upper LP Spore Biozone but are insuffi- 

 ciently precise. 



Geras section. Chelinospora sanpetrensis, one of the nominal 

 species of the RS Spore Biozone, occurs in the basal sample (Ger 1) 

 of the Geras section. Chelinospora poecilomorpha and Stellatispora 

 inframurinatus var. cambrensis appear in the overlying samples (Ger 

 2A and Ger 3 respectively) and are also found in the upper Gorstian 

 and Ludfordian of England and Wales but are absent from the 

 succeeding Downtonian there. The presence of the chitinozoan 

 Ramochitina villosa indicates a Late Ludfordian age for sample Ger 

 2A within the RS Biozone. Emphanisporites splendens appears in 

 Ger2A to Ger6. This species is found in North Africa in association 

 with typical lower Downton (Lower Pfidoli ) species in the upper part 

 of its known range there. Thus, at least part of the RS Spore biozone 

 is of Upper Ludfordian age and, on present evidence, the Ludfordian/ 

 Pfidoli boundary probably occurs within the higher parts of the RS 

 Biozone. The Geras section is faulted at the base and no further 

 samples were collected below Ger 1. Coronaspora primordiale (PL 

 6, fig. 3) occurs rarely in samples Ger 2B and Ger 3, but in the 

 Argovejo and La Peral sections is found sporadically only in the 

 overlying H Biozone. Emphanisporites spp. (eg. PI. 2, fig. 9) occur 

 rarely in sample Ger 2B and also extend into the overlying H 

 Biozone in the La Peral section. Other species typical of the Homerian 

 and Gorstian occur erratically in this section and are most probably 

 reworked, eg. Hispanaediscus lamonti. 



La vid section. The lowest productive sample in the San Pedro 

 Formation is LV 6, which belongs to the RS Biozone. However, 

 spores similar to S. libycus and indistinguishable from C. 

 poecilomorpha (nominal species of the LP Biozone) occur. In 

 England and South Wales these species die out near the top of the 

 Ludfordian. Part of the RS Biozone is probably, therefore, Ludfordian 

 and may be equivalent to the libycus -poecilomorpha Biozone of the 

 Anglo- Welsh area. However, in the Cantabrian sections examined 

 the nominal species of the LP Biozone are erratically distributed. 

 Reworking is also evident in this part of the sequence and taxa typical 

 of the Homerian and Lower Gorstian occur there. These finds are 

 associated with an incursion of thick sandstones. 



Age. Ludfordian to lowermost Pfidoli. Chitinozoa in samples 

 from the RS Biozone in the Argovejo, Geras and La Peral sections 

 mainly have a long range, from Mid-Gorstian to Lower Pfidoli. 



Chelinospora hemiesferica (H) Spore Interval 

 Biozone (Figs 2-5) 



Nominal species 



Chelinospora hemiesferica (Cramer and Diez) comb, nov.; Cramer 

 and Diez 1975: pi. 2, figs 34-36, (PI. 9, figs 3, 5). 



