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The Paleozoic succession in the Nevera inlier of the Molina-Alto Tajo UNESCO Global Geopark (Western Iberian Cordillera, NE Spain) includes an incomplete, richly fossiliferous Silurian succession, ca. 350‒400 m thick, at the locality of Checa, one of the geosites of international interest in the Paleozoic of Spain. The Checa section starts with quartzites (Los Puertos Formation: Rhuddanian to Aeronian) which rest unconformably on Late Ordovician glaciomarine diamictites (Orea Formation: Hirnantian) and are succeeded by graptolitic black shales (Bádenas Formation). The basal 60 m of the latter unit are of Telychian age and exhibit rich graptolite faunas of nine successive graptolite biozones and subzones, with more than 85 graptolite species identified of which four were new. Besides the scientific value of the fossil locality for paleontology and international correlation of the early Silurian, aspects of the promotion and preservation of its geological heritage have been enhanced by designation as a national and international geosite, as well as by the integration in a geo-trail for visitors to the park and the fencing of part of the fossil locality to avoid illegal digging and collecting.

The discovery of Didymograptus (Didymograptus) artus Elles and Wood in the Ordovician section of the Vidrias Cape (Atlantic coast of Spain), constitutes the first record of early Oretanian (= mid Darriwilian) rocks in the Cantabrian Zone of the Iberian Massif. The fossil locality lies in a shaly intercalation towards the middle part of an easternmost equivalent of the «Sabugo Quartzite» of the Navia Domain (West Asturian-Leonese Zone), so far unknown in the reference section for the Ordovician of the Cantabrian Zone of the nearby Peñas Cape. Correlations of the studied strata by previous authors are also reviewed, and the existence of a fault is suggested to occur between the «Peñas» and «Vidrias» members of the Luarca Formation on the famous section of the Peñas Cape

24 páginas, 4 figuras, 2 láminas, 1 tabla., [EN] New palaeontological data from Upper Ordovician formations of NW Spain (Caurel-Peñalba and Truchas synclines) are documented. The «Trigal limestones» of the Casaio Formation, the La Aquiana Formation and calcareous pebbles of the Rozadais Formation have yielded conodont assemblages indicating the Ashgillian Anzorphognathus ordovicicus Biozone. Scabbardella altipes (Henningsmoen), Panderodus gracilis (Branson & Mehl), Anzorplzognathus ordovicicus Branson & Mehl, Amorphogizatlzus sp., Sagittodontiíza robusta Knüpfer, Sagittodontina? sp., Icriodella sp. and Hamarodus europaeus (Serpagli) have been identified and described. Stratigraphic correlations between the different structural units are discussed, as well as the regional context of the Upper Ordovician sedimentation. According to a new model which conciliates the local geotectonic setting with the global paleoclimatic events, the Rozadais Formation underwent a glaciomarine influence during the Hirnantian, and is clearly younger in age that other Ashgill units which consist or include pre-Hirnantian limestones (La Aquiana and Casaio formations)., [ES] Se presentan las asociaciones de conodontos ordovícicos registradas en las «calizas del Trigal» de la Formación Casaio, en la Formación La Aquiana y en los cantos calcáreos englobados en la Formación Rozadais, pertenecientes a afloramientos del sinclinorio de Truchas (norte de la Zona Centroibérica) y del sinclinal del Caurel-Peñalba (sur de la Zona Asturoccidental-leonesa). Las formas identificadas son Scabbardella altipes (Henningsmoen), Paizdei~odus gracilis (Branson y Mehl), Amorphognathus ordovicicus Branson y Mehl, Anzorphognathus sp., Sagittodoiztiiza robusta Knüpfer, Sagittodontina? sp., Icriodella sp. y Hanzarodus europaeus (Serpagli), que corresponden a la Biozona de Aínorphognathus ordovicicus del Ashgill y se describen e ilustran en el apartado sistemático. En función de estos datos y sus circunstancias estratigráficas, se propone una correlación general de las unidades del Ordovícico Superior de la región, presentándose un nuevo modelo que armoniza el marco geotectónico local con los eventos globales del Ashgill comunes a la región nord-gondwaniense. En este sentido, se considera un influjo glaciomarino para la Formación Rozadais (Hirnantiense), cuyo depósito no sería coetáneo con las unidades calcáreas pre-Hirnantienses (Trigal y La Aquiana)., Este trabajo se inscribe en los proyectos PB94-1330 y PB96-0839 de la DGES, y sus resultados son también una contribución al Proyecto 410 del PICG (IUGS-UNESCO), así como al Proyecto «Iberia» del Programa EUROPROBE (European Science Foundation). La participación del primer autor fue posible gracias a una beca postdoctoral de la Comunidad de Madrid, que lleva por título «Aplicación de Conodontos en bioestratigrafía de alta resolución y geotermometría de materiales ordovícicos y silúricos de España» (1998-1999).

The first Silurian graptolites from NW Spain were discovered South of Brazuelo de Pradorrey (province of León) by Casiano de Prado in 1855. The locality lies in the core of the Castrillo syndine, where the Silurian succession is composed by a lower unit of ?Rhuddanian-Aeronian sandstones, gradually passing to an upper unit of black graptolitic shales. Aeronian graptolites (?D. triangulatus and D. convolutus biozones) were reported from the top of the sandy formation and from the transitional beds in the lower half of the overlying unit. The Brazuelo locality corresponds to the younger black shales, and includes three sucessive horizons with Telychian graptolites. The first one represents the upper part of the R. linnaei Biozone, followed up in the section by a second assemblage, which probably belongs to the M. griestoniensis 3¡ozone, and finally, by a third horizon also representative of the M. griestonensis or even the T. tulibergi Biozone. Craptolite assemblages are poor and bad preserved, but include some species of high palaeobiogeographic and palaeoenvironmental significance, as for instance Metaclimacograptus cf. asejradi Legrand or Paraclimacograptus? flamandi (Legrand), typical of shallow sapropelitic facies in peri- and intracratonic Gondwanan basins

The first Silurian graptolites from NW Spain were discovered South of Brazuelo de Pradorrey (province of León) by Casiano de Prado in 1855. The locality lies in the core of the Castrillo syndine, where the Silurian succession is composed by a lower unit of ?Rhuddanian-Aeronian sandstones, gradually passing to an upper unit of black graptolitic shales. Aeronian graptolites (?D. triangulatus and D. convolutus biozones) were reported from the top of the sandy formation and from the transitional beds in the lower half of the overlying unit. The Brazuelo locality corresponds to the younger black shales, and includes three sucessive horizons with Telychian graptolites. The first one represents the upper part of the R. linnaei Biozone, followed up in the section by a second assemblage, which probably belongs to the M. griestoniensis 3¡ozone, and finally, by a third horizon also representative of the M. griestonensis or even the T. tulibergi Biozone. Craptolite assemblages are poor and bad preserved, but include some species of high palaeobiogeographic and palaeoenvironmental significance, as for instance Metaclimacograptus cf. asejradi Legrand or Paraclimacograptus? flamandi (Legrand), typical of shallow sapropelitic facies in peri- and intracratonic Gondwanan basins

Upper Ordovician rocks have been characterized for the first time in the Cantabrian Zone of the Hesperian Massif. The sequence consists of a lower siliciclastic unit of Caradoc-(‘basal Ashgill age developed as an alternation of shales, siltstones and sandstones, overlain by an upper unit of fossiliferous limestones with marly intercalations, of pre-Hirnantian (mainly Cautleyan-Rawtheyan) age. Ashgill fossils are fairly abundant in the limestone unit, and there have been identified brachiopods of the «Nicolella fauna», echinoderms of the «Heliocrinites fauna» and trilobites of the Qvalocephalus biofacies

2 páginas.-- Comunicación presentada en el IV Congreso Nacional de Geología, Alcalá de Henares, 1996., This work deals with the stratigraphical and palaeontological study of the vulcanosedimentary Castro Formation in its type locality, close to Cabo Peñas (Asturias, Cantabrian Zone). The formation consists of three members: a lower member of alternating volcanoclastic and sedimentary rocks, a middle member, mostly basaltic, and an essentially upper calcareous member (Viodo Mb.). On the basis of the palaeontological data and the preliminary results from the correlation with Cabo Vidrias section (west of Cabo Peñas), a Middle Ordovician age is established for the lower member. The Viodo Mb. is Lower Silurian in age as shown by an abundant fossiliferous content. So far, fossils supporting the occurrence of the Upper Ordovician have not been found, although it could be represented in the middle member of the formation., Este trabajo es una contribución al proyecto "Bioestratigrafía del Ordovícico de la Zona Cantábrica y margen de la Asturoccidental-leonesa" (DGICYT, PB 91-0671).

Fossiliferous shales of the Luarca Formation are identified for the first time in the southern part of the Pliegues y Mantos domain of the western Cantabrian Zone. The outcrop consists of 10,6 m of dark shales and micaceous silts tones, tectonically intercalated between the La Matosa (Middle and Upper Cambrian) and Tanes (Arenig) members of the Barrios Formation, close to the classical section of this unit. The occurrence of a diverse assemblage of trilobites, graptolites, ostracods, brachiopods, echinoderms, molluscs and some acritarchs and chitinozoans confirms a Middle Ordovician age for the shales, whereas the age of the top of the Barrios Formation does not exceed the Arenig

A new continuous section with Aeronian to lower Telychian graptolites is described near Corral de Calatrava (province of Ciudad Real). The transition between the «Criadero Quartzite» and the overlying black shales is detailed. The section is correlated with another similar sucessions around the Ordovician/ Silurian boundary in the southern part of the Central Iberian Zone, and chronostratigraphic aspects are briefly analyzed and discussed. The sedimentation of the «Criadero Quartzite» took place during Rhuddanian to late Aeronian times; a minor hiatus was developed at the upper limit with the graptolitic black shales. The base of the latter is not older than the palmeus sub-biozone of the early Telychian

The Silurian sequence in the Herrera del Duque syncline (Southern Central Iberian zone) starts with 20 m of black shales (Guadarranquejo Formation) which lay disconformably upon the Hirnantian diamictites (Gualija Formation). Within the black shales, eight graptolite horizons have been recorded (A-H) and two (I-J) at the base of the overlying sandy alternances. A Telychian (post-Turriculatus Zone) age for the Guadarranquejo Formation has been suggested, the Llandovery/Wenlock boundary lying probably near its top, La secuencia silúrica en el sinclinal de Herrera del Duque (zona sur Centroibérica) empieza con 20 m de lutitas negras (Formación Guadarranquejo), las cuales se apoyan paraconformes sobre diamictitas del Hirnatiense (Formación Gualija). Dentro de las lutitas negras, se han encontrado ocho horizontes de graptolitos (A-H), y dos (I-J) en la base de las alternancias arenosas suprayacentes. Se ha sugerido la era Telychiense (zona post-Turriculatus) para la Formación Guadarranquejo. El límite Llandovery/Wenlock se encuentra, probablemente, cerca del techo.

[ES] Se analiza la distribución vertical de más de doscientas especies fósiles reconocidas en las «capas con Tristani» de España central, cuya estratigrafía también es objeto de una primera revisión. La fauna está compuesta principalmente por trilobites, moluscos, braquiópodos, equinodermos, crustáceos y graptolitos, entre los cuales algunos géneros y especies se citan por vez primera en España. La extensión vertical restringida de ciertos trilobites, braquiópodos y graptolitos permite la caracterización de algunas Biozonas que tienen grandes posibilidades de ser correlacionadas con otras áreas peninsulares y el Macizo Armoricano francés. En el trabajo empleamos la Serie Dobrotiviense de Bohemia como sustituto (aprox.) del Llandeilo de la escala patrón británica, ya que este último es muy difícil de caracterizar en el sector estudiado por corresponder a un contexto biogeográfico y paleogeográfico muy diferente del de las áreas-tipo del Ordovícico., [EN] The vertical distribution of more than two-hundred fossil species determined in the "Tristani beds" of Central Spain is analized. At the same time, their stratigraphy is reviewed. Its fauna is composed mainly by trilobites, molluscs, brachiopods, echinoderms, crustaceans and graptolites, some of whose species are listed for the first time in Spain. Ihe restricted vertical distribution of certain trilobites, brachiopods and graptolites allows the charachterization of several biozones with a high possibility of correlation with other peninsular areas and with the French Armorican Massif. In this study we make use of the Dobrotivian Series of Bohemia as a substitute of the Llandeilo of the British standard scale, as the latter proves to be exceedingly difficult to charachíerize in the studied region, because of its belonging to a biogeographic and palaeogeographic background very different from that of the Ordovician type-areas.