Bol. R. Soc. Española Hist. Nat. (Geol.), 79: 277-286 (1981). Fossils from the basal leveis of the Pedroche Formation, Lower Cambrian (Sierra Morena, Córdoba, Spain) por Eladio Lifiáu (*), Elena Moreno-Eirii (*5), Antonio Perejón (*5*) y Michael Scbmitt (****) RESUMEN. Este trabajo constituye un avance de 7los primeros resultados obtenidos del estudio de los trilobites, arqueociatos, algas s. s. y estromatolitos de los niveles basales de la Formación Pc- droche, así como la distribución estratigráSica (le cada uno de los grupos fósiles. ABSTRACT. Tlus paper constitutes an advance of the results obtained from the study of, trilobites, ar- chaeocyathans, algae s. s. and stromatolites from the basal leveis of the !'eclroche Formation and also the stratigraphic (listrihution of each fossil groups. 1. INTRODUCTION. The Biostratigraphy of the Lower Cambrian base of the Iberian Peninsula is not yet known precisely because, Wi a local scale, facies show little variety and therefore the fossil groups found are not diverse. This rneans that the Biostrati- graphy has to be identifieci, so far by one fossil group and also; on a regional basis, facies cliffer depending on location. From this ve can deduce that reliable cor- relations are very difficult to determine. In the Sierra of Córdoba, important outcrops of basal Cambrian rocks are found, with a cyclical successiOns of facies of carhonatic and terrigenous materials, which, favourable to evolution and uf e record, thev mark at the sanie time a paleoenviro- ment whose conílitions are more or less steady throtigh the years. The repetition and alternation of these facies allow a simultaneous classification of fossils froni different comrnunities, consisting of trilobites, arcliaeocvathans, stroniatolites, algae (*) Departamento de Paleontología. Facultad de Ciencias. Universidad de Zaragoza. (5*) Departamento de Paleontología. Facultad de Ciencias Geológicas. Instituto de Geo- logía Económica. C. S. 1. C. Universidad Complutense. Citiclad Universitaria. Madrid-3. (***) U. E. 1. y Departamento de Paleontología. Instituto (le Geología Económica. C. S. 1. C. Facultad de Ciencias Geológicas. Universidad Complutense. Ciudad Universitaria. Ma- drid-3. (5*5*) Institut für Paliiontologisches der Universitiit. Würzburg, Pleicherwall 1 D-8700 Würzburg; Bundesrepuhlik Deutschland. 278 REAL SOCIEDAD ESPAÑOLA DE HISTORIA NATURAL and trace fossils, which interrelate in space and time, and make possible the es- tablishment of a more accurate date by comparison and contrast of ages deduced from the study of taxa in the different groups and also by their evolution in space and time. These aspects come together arici can be observen in the series which break out in Arroyo of Pedroche, located along the road Córdoba-Badajoz between 1,9an1 2,5 km (fig. 1). CARBONELL published jo 1926 the first (lates about the materials in Arroyo of Pedroche and he put them in the Carboniferous strata because of the similarity of facies. Later on, in 1929 CARBONELL found archaeocvathans on the same leveis and he dated those beds to the Cambrian age. lo 1930 CARBONELL mapped these leveis in his fieldwork on El Majanillo ami Mirabueno. CABANAS (1964) found 0 2 4 6 8 10 km. 11 Trilobites » Algae s.s. Á Microfossils ® Archoeocyotho t1 Stromotolites Troce fssiIs Hg. 1.—Geographic distribution of studied fossils Jocalities and other near Córdoba. archaeocyathans aboye the strearn, under the ¡ron bridge of the Córdoba-Almorchón raiiway. PEREJÓN (1974-1977) discovered new localities ami studied the fauna of archaeocyathans previously found. LIÑÁN (1974) proposed the Cambrian type- section of the Sierra of Córdoba establishing three formations. LIÑÁN & DABRIO (1974) drew up in detail the lithologic section of the lower member of the Pedroche Formation, ZAMARREÑO (1977) studied sorne leveis with aigae on the Córdoba- Badajoz roaci. LIÑÁN (1978) carried out the cartography in the Sierra of Córdoba and made a study of the discovered trilobites. LIÑÁN & SDZUY (1979) published a systematic study of sorne genera of trilobites in Arroyo of Pedroche. SECCIÓN GEOLÓGICA 279 ARROYO PEDROCHE SECTION z 2 —i RILOL A RCHAE0CYATHA ALGAE s.l. w — wu z > uj 12 - o o o__j ' o O 16 15 Z 14 13 :---- - - u 12 - a ----- -í0 - a 10 E 9 a U 1 U 1 UI II IJ.LL 8: er 11111 ii:i' 40 O o _ o 4 —J 2 er CO VE RED ? "Trilobites Archoeocyotho Argüe ss. 0 Stromotolites £Microfossils —Trace fossils - L_J I?I Andesits Dolomitic Limestones Shoes rones E:Sondstones Fig. 2.—Biostratigraphic section oí Pedroche Formation (Member 1) oí early Lower Cambrian. 280 REAL SOCIEDAD ESPAÑOLA DE HISTORIA NATURAL Each author is responsible for a part of the study: E. LIÑÁN, for the date concerning trilobites, microfossils and ichnofossils; E. MoRENo-EIRIs, for the algae s. s.; M. ScI-IMIrr, for the stromatolites, and A. PEREJÓN, for the archaeo- cyathans. The aim of this paper is to present the stratigraphic distribution of the taxa of trilobites, archaeocyathans, stromatolites and algae s. s., found in the Meniber 1 of Pedroche Formation. II, STRATIGRAPHIC NOTIONS. The Cambrian Series of the Sierra of Córdoba consists of three different for- rnations: Pedroche, Santo Domingo, and Los Villares, in ascending stratigraphic order. This study is centred on the lower member of Pedroche Formation. The detailed lithologic column of the type section of this member was carried out by LIÑÁN & DABRIO (1974) and it has served as the basis for the present study. As these authors have pointed out, concerning this series a certain repetition of carbonatic and terrigenous rnaterials is noticed. Each sequence starts in theory with facies of sandstones and shales with trace fossils, then oolitic and onclithic lirnestones facies in hecis of clecirnetric thickness, followed by algae limestones and sornetimes by archaeocvathans. In the upper part, microfossils, brachiopods, and trilobites are ussually found. The cvcle ends with new deposits of sancistones, and shales with trace fossils. In each cycle, algae limestones can he sustituted by strornatolitic limestones and algae rnats -limestones, depending on the geographic point where the series is cut. The usual lenticular shape of the carbonatic layers implies that they appear on a regional scaie as (liscontinuous levels which are repeated in space and time. The base of the series cannot be observed since it is covered in its last metters by the terraces of the Guadalquivir river. At 40 metres from the base andestic materials from San Jerónimo Formation (Upper Proterozoic) are found. III. TAXA SRATIORAPHIC DISTRIBUTION. Although sorne other groups with problernatic microfossils, brachiopods and ostracodes have seen recognized we shall only (leal with the taxa distribution of trilobites, archaeocvathans strornatolites, ami algae s. s. TR1LoBITEs.—These are located in the calcareous leveis, ni its upper part or in the contact between the lirnestone and terrigenous rnaterials: jo this case the ori- ginal carapace is not usually preserved. Thev are associated with archaeocyatharis and algae s. s. at the calcareous ievels; at terrigenous leveis it is more frequently associated with brachiopods, pelagiellids, ostracodes and Chancelloriida in variable proportions, according to the level considered. By rneans of .limestone attack with formic acid 10 % diluted, several specimens of opistoparian trilobites have heen extracted, rather scarce ami incomplete. The distribution of classified genera can he seen in fig. 2. The Bigotina genus appear in the base of level 9 and are replaced by Lenidaa'ella with which they coexist. Between one genus and another a progressive evolution is observed, ami so there are intermediate forms which are difficult to include in one or other genus. The studied species are new, but given that the record of this section is continuous, it SECCIÓN GEOLÓGICA 281 is ver)- difficult to estahlish their boundaries and because of this it has been (lecided to ieave, for the moment, their specific systernatiC study. Alioli- with this tran- sition, several crarildli of a new genus were found, but it vas imposible tu define such genus, because of the feiv specirnens studied. ARcHEocYvri-1,\ —This fossil group is well represented in nearly every calca- reotis stretch of Member 1 of the Pedroclie F'orrnation, this is due as mucli to the number of differcnt gener.i, as to the quantitv of specimens found. Fig. 2. Archaeocyathans are alway; associated with algae forrning the fundamental organic body of ca]careous beds; when there are coluninar stroniatolitic structures the cups are arranged either in the inner ernpty spaces or on top of tliern. Onlv at the base of level 9 do the archaeocvathans constitute the niain component of a bioherni 1,50 ni thick and 2 ni long, where algae are second to them iii importance. Wc have determined 267 speciniens corresponding to 16 genera of the Class Regular and 490 specirnens corresponding tu 7 genera of the Class Irregular, scat- tered in levels 1, 5, 6, 7, 9 and 13. As can be observed en fig. 2, in each level there are one or sorne places where ve have found archaeocvathans. aud in all of thern ve can find genus of the Regular, vhile the Irregular are missing ni foui- of them. The relation between the number uf genera of each Class in cadi level is ver)' variable but the proportion alwavs favour the Regular, except for the basal bed of level 9. Qn dic other hand, the arnount of Irregular specimells is higher than that of Regular, although in sorne places there are no Irregulares at al!. Consideiing the great quantitv of Irregular specimens studied, especiallv those from level 9 base, we want to point out that in man' longitudinal sections we have observed a gradual progression among the characteristic structures of genera Bic'aíJi us-;i rc/tacopharc/ra-Protopliarefra-Ardrossac yafli os-fi gastrocvatli os. Tuis proh!em wili be consiciereci ni a future studv. So as not to coniplicate this, we have considered each one of this genera to be separate and inclepenclent. Generallv, (lepending on the place of appearance in the stratigraphic section, dic archaeocvathans can he grouped in three units. The first une will include genera appearing ni the lower levels of Member 1 (1 to 4) and arnong them can he found onlv Ah/anoc'athus, SibirccvatJins ami Profopharcfra associated with algae from genus Epiphvfon, fragments of opistoparian trilobites and trace fossi!s. The second archaeoeyadians group appearing in the intermediate levels of Member 1 (5 to 9) vould be constituted liv 16 Regular genera, Capsulocvaflius, Tumuiiolynthis, Dokidocvafhus, 4idanoca.fhus, Robustocyathus, Rol undocatJius, Sibirccvathus, Afiacyatlnis, Terraccyathus, Tavlorcvathus, Gordon ifungia ?, Pre- fiosoci'athus, Tumuloc'vatli os, Retecoscinus, Coscin ocyafhis and Axiculifungia, froni which we llave studied 258 specirnens, 91 % of them failing between 0-6 mm in ha- meter ami 7 Irregular genera, Bicvafhus, Arcliacopharctra, Dictyoc','athus, Froto- pharcfra, Agaslrocvathus. Andalusic'vatJíus, and Flindersicoscinus, with 489 speci- mens, 57 % of thern, failing between 0-6 mm and a 11,5 7o fal! between 9-15 mm. In these levels dic arcliaeocvathans are associated with trilobites of dic genera Bigo tina and I,emdadeila, with the stroniatolites T7efelia and Charaiilaciva with manv algae and Chancelioriida and sume traces fossils. The third group is located in the upper levels (10 to 15) and it consists of two genera of Regular. Rotundocvathus and Retecoscinus with 6 specimens, 3 of them measuring from 0-6 mm diarneter and 3 other between 6 and 9, none of dic Class Irregular were foi.md. Tu these level archaeocyathans are associated with trilobites uf Leindadella and algae. 282 REAL SOCIEDAD ESPAÑOLA DE HISTORIA NATURAL If we analize the appearing of the different morphologic structures of the ar- chaeocyathans, we find the following: In level 5 we find Capsulocyathtis, with only one wall; genera with both simple was appear in this and in every leve!, and among them, there is Aidanocyathus which is only missing in level 13. The inner wall with pore-tubes is found with Afiacyathus, restricted to the base of this level. The annulate inner wall is found in Tayiorcyathus and Gordonifwzgia ? also present in level 7, and genera with tabulae like Coscinocyathus and Axiculifungia. Arnong the Irregular ve find Andalusi- cvathus seen again in level 6 and F11.ndersico.scinus with tabulae restricted to this level only. Ja leve! 7, we find the last specimen with annulate inner wall and genus Pre- tiosocyathus with double outer wall; and also cups whose outer wall presents tumuli, as in Tumulocyathus also present in level 9, and for the last time Regular genera are found with tabulae. In leve! 9, we find Tunzuiioiynthus with only one wall with ttimuli, and Terrae- cyathus with unconnected pore-tubes in the inner wall. Retecoscinus shows tabulae. In leve! 13, only Regular genera Rotundocyaíhus with simple walls, and Rete- coscinus with tabulae and no Irregular genus. ALGAR S. s.—In every one of the carbonatic leveis of the Member 1 of Pedroche Formation, algae rernains are present, sorne of them are associated with strornato- litic structures as in leveis 5 and 6 (fig. 2) and also with trilobites and microfossils remains. But those organisrns with wliicb they are frequently associated are the archaeocyathans and they forrn organic buildings with a variable arrangement either in space or time. Therefore, within the same carbonatic level we can observed facies characteristic of bioherm and biostrorn; only in the basal limestone of leve! 9 do we find a bioherm with a considerable volume and whose morphological features can be observed in field. In this carbonatic stretch both algae and archaeocyathans show a reduced generic variahility, since it is in a bioherm that specific genera predominate. As for the algae (fig. 2) they are Epiphyton, Tubomorphophyton, Renaicis and Gir- vaneila; and for fue archaeocyathans there are the specirnens belonging to this Class Irregular, with five genera, those which predominate netly upori the Regulars, with three genera. In contrast, there is mentioned leve! 7, where ve find alternating facies be- longing to bioherm and hiostrom, with a great generic variability of archaeocyathans and algae. Genus Epiphyton BORNEMANN, 1886, is one of the most frequent algae existing in the Pedroche Formation in its Member 1. It is found scattered along fue whole section from the lower leveis, and constitutes together with the genera Girvanella and Renaicis the rnost abunclant forrn. These organisrns show a great morphological variety whose specific classification we shall cleal with in a future stuciy. This genus is mainly found in those leveis where archaeocyathans exist, as it is one of the main elements of the organic limes- tones; it is also associated wiLh strornatolites, trilobites and microfossils. The Epiphyton genus has heen refered by the specialists to different algae types, to Chlorophyta (GORDON. 1921; MASLOV, 1956), to Cyanophyta (LucHININÁ, 1971, 1975; WRAY, 1977), and to Rhodophvta (KORDE, 1955, 1958, 1959, 1961, 1969, 1973; VOLOGDIN, 1962; VORONOVA. 1976; DROZDOVA, 1980) and its inciusion SECCIÓN GEOLÓGICA 283 within Rhodophyta in the Epiphytaceae family (KORDE, 1959) is now accepted by most authors. Tu the Rhodophyta, besicles Epipliyton, we have recognized two other genera, Kordephyton RADUGIN & STEPANOVA, 1964, and Tub omorph opityton KORDE, 1973, the latter showing a great amount oí specimens in the basal limestones oí level 9. Genus Renalcis VoLoGnIN, 1932. foun(1 scarcelv is from level 5 to 8 oí the section, vhilst jo level 9 it is very abundant with a great morphologic variety; it is worth pointing out that in sorne cases ve observe a very intirnate spatial relation among the forms Renalcis, Girvanella and Epiphyton. This organism which appears froni the Canibrian to the Upper Devonian aoci shows a branched multilocular shape with thick caicareous Nvalls, has heen usuaily consiciered as an a]gae by severai authors (KoRnE, 1961, 1965; VOLODGIN, 1962; JOHNSON, 1966; LuciliNINa, 1971, 1975 VoRoNov, 1976; Wv, 1977; DRoz- 1)0VA, 1980) and it is included by most in Cyanophvta. However o;her authors have refered to it as a henthic Foraminifera, ELIAS, 1950; KLOVAN, 1964; RIDING & BRasIER, 1975. Genus Girvanella NicrIoLsoN & ETuERIoGE, 1878, in Member 1 oí Pedroche Formation is distri)utecl along the whole section; it is characterized bv its tubular ami non-branched calcified filamentous. lo level 5 and 6 is scarcelv founil. while in leveis 7 and 9, it is very abunclant showing great morphological variety from isolated nodular forms, scatterecl in the rnicrosparitic matrix, to elongated fornis which surrouncl aocI colonize the outer waiis oí the archacocvathans cups. This genus has now heen reconsiclered by DaNIELr,I, 1981 aoci he inciudes it in the Family Porostrornata Pia, 1927, inside Cyanophyta, in this work the author offers a complete research mi all the Girvaneila specimens so for descrihed. Genus Bija VOLOGDIN, 1932 shows an irregular celiular structure oí polygonal to rounded celis, considered by VOLoGDIN. 1962 aoci KORDE, 1969 as Rhodophyta; by Lucr-IINrNA, 1971 as Cvanophvta and by VORONOVA, 1976 as incertac seclis. In the section oí Memher 1 we find it onlv in level 5, in its lower part it is asscciatech with Epiphton, Turbomorphoph'yton, Renalcis, and Girvanclia, in the midcile part only to Kora'cphvton and on the uppel- ve fincl oniy Bija. Genus Botrnnaella KORDE, 1958 alga Cvanophyta (KORDE, 1958, 1961, 1969; LUCIIININA, 1971; DROZDOVA, 1980) constitutes with Girvanelia the most abundant form oí the upper stretches oí level 7; it is founcl associatecl with Epiphvton, Kor- dephvton, and Renalcis genera whose appearances are soinewhat sporachic jo this level. S'rRoMA'roLrTEs.—Strornatolites coexist with algae s. s., microfossiis and archaeo- cyathans (this rarely) 'locateci between the cohumnar structure in facies oí greater terrigenous upbringing, where cups are oí a srnahi size. In level 5 Vetelia is found, Charaulachia in level 6. lo level 9 a new form oí Vete/la is found coexisting with the olcier Bigotina species found, so that in the section, the columnar strornatolites are onlv seen below L,e;ndade!la. IV. STRARIGRAPHIC CONSIDZRATIONS. This preliminary studv allo\vs us to propose the division oí the Lower Carnhrian base jo the Sierra oí Córdoba in tliree clearly differentiated parts, according to the ciifferent fossiis groups fotind. 284 REAL SOCIEDAD ESPAÑOLA DE HISTORIA NATURAL The lower part would include the iowest leveis of Member 1 from 1 to 4 and it is characterized by remains of opistoparian trilobites, archaeocyathans of the genera Aldanocyathus, Sibirecyathus and Protopliareira, aigae from genus Bpiphy- ton and traces fossils Monocraterion type. The rnidclle part includes from level 5 to 9 inclusive cont.ains trilobites of genera Bigotina and Lemdadella, although the appearance moment of Bigotina is not well-known, besides the species of both genera overlap in time for a short period. Also all genera of archaeocvathans found: Capsulocyathus, Tuniulioiynthus, Do- kidocyalhus, Alclanocyathus, Robustocyathus, Rotundocyathus, Sibirecyalhus, Afia- cyathus, Terraecyathus, Tayiorcyathus, Gordonifisngia ?, Pretiosocyathus, Tumu- Iocyathus, Retecoscinus, Coscinocyathus, Axiculifungia, Bicyathus, Archaeophare- tra, Dictyocvathus, Agastrocyathus, Andalusicyathus anci Flindersicoscinus; the stromatolites forms Vetella aoci Charaulachia; abundant algae with the presence of iipiphyton, Kordephyton, Tuboniorphophyton, Renalcis, Girvanella, Bija, Bo- tornaL'lla; traces fossils, Plan olites, Monocraterion and Cruziana ? and Chancellorii- da very much frequent. The upper part mcludes leveis 10 to 15 it is characterizeci by presence of L.em- dadella, the Regular archaeocyathans: Rotundocyathus, and Retecoscinits and ah algae genera except Bija and Botomaella. V. CORRELATIONS. In Spain, Lenidadella and Bigotina have only been found up to now in Sierra Morena, so that correlations with other series are not very accurate. LIÑÁN & SDZUY (1979) have pointed out that for northern Spain the horizon with Parared- lichia, aoci Bigotinops of Concha of Artedo can probably be correlated with the upper leve!s containing the Leindadella fauna, and for this reason the Bigotina fauna is older than any other in Spain. The group of archaeocyathans genera found shows many resemblances to those of Las Ermitas, although up to now the genera Terraecyathus, Gordonifungia ?, Pretiosocvathus, and Axiculifungia have only been found in this localities and, on the o:her hand we have to take into account that genus Andalusicyathus jo poorly represented here. Jo Morocco, Lemdadella is found in Ounein and Tiout (SDZUY, 1978; LIÑÁN & SDZUY, 1979) in this ilast place this genus coexist with specimens which cou!d well be refered to Bigotinops and so, its age must be the Zone 1 of Hupe, the same as the lower horizon of Concha of Artedo. The stromatohites found also show a low age in the Lower Cambrian. By the place they occupy in the Tiout series, Veteila should be more recent than the species of this genus appearing jo Córdoba. The archaeocyathans we have studied in this locality present a very similar genera association to that found in Tiout (DEBRENNE & DEBRENNE, 1978) except by Tuinulifungia and Neoloculic'vathus which are missing in Córdoba, therefore we think they must have a similar age. Jo the French loca!ity of Carteret, trilobites of genus Bigotina are also found whose age shouid not be very different to that of the Córdoba fauna and there are archaeocvathans of the genera Aldanocvathus, Sibirecyat/ius, Retecoscinus and Pro- topharetra (DEBRENNE & DEBRENNE, 1978) which are also present here. These SECCIÓN GEOLÓGICA 285 discoveries allow the comparison and correlation of these series with those of Mo- rocco. In Siberia there are oniy known species of Bigotina and this is the main reason for the difficulty experienced in correlating date with the Peninsula up to now. The discovery of associated faunas of L,cmdaclella and Bigotina, as well as the exis- tence of 6 genera of comrnon archaeocyathans in both regions: Do/eidocyathus, Aldanocyathus, Retecoscinus, Coscinocyathus, Taylorcyathus, Gordonijungia ?, well be of great importance in future correlations with the siberian and the moroccan faunas ni which Spain can represent an intermediary point of connection. (Recibido el 23 de abril de 1982.) (Aceptado el 30 de abril de 1982.) REFEIiENCES. BORNEMANN, J. G. 1886. Die versteinerungen des Cambrischcn Schichtensystems der Insel Sardinien nebst vergleichenden Untersuchungen über analoge vorkommnisse aus andern Lb.ndern. Nova Acta Acad. Cacsar. Leop. Caro!., Halle, 51, págs. 1-148. CAnANAS, R. 1964. Notas estratigráficas de la provincia de Córdoba. Not. y Com. I. G. M. E., 74, págs. 69-74, 2 figs. CARBONELL, A. 1926. Nota sobre los yacimientos de Arqueociátidos de la Sierra de Córdoba y deducción para el análisis tectónico. Com. Mali. G. Esp. Bol. I. G. M. E., 47 (7) 3.a serle, 2.1 part., págs. 311-315. 1929. Un nuevo yacimiento de Archaeocyathidae en Córdoba. Consecuencias tectónicas. Mcm. R. Soc. Española Hist. Nat., 15(1), págs. 271-274. 1930. Un nuevo yacimiento de Archaeocyathidae en Córdoba. Consecuencias tectónicas. Rey. Min. Met. y de Ing., 3.204, págs. 73-74. DANIwI, H. M. C. 1981. The fossil alga Girvanella Nicholson & Etheridge. 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