O património geológico-mineiro da região de Barrancos (Sul de Portugal)

A região de Barrancos apresenta património geológico-mineiro que tem sido objecto de estudo desde o final do século dezanove. São vários os locais de elevado interesse geológico, particularmente de natureza paleontológica, relacionados com os materiais do Paleozóico. A sua divulgação, protecção e conservação tem sido feita por entidades públicas e privadas

Graptólitos do Silúrico do Sinclinal de Buçaco : paleontologia e biostratigrafia = Graptolite faunas from Silurian of the Buçaco Syncline : paleontology and biostratigraphy

Estudaram-se exemplares de Graptólitos do Silúrico do sinclinal de Buçaco proveninentes de colecções de Nery Delgado e de amostragem recente. Foi realizada a actualização taxonómica das colecções antigas. Determinaram-se novas espécies e biozonas. Os novos resultados permitem precisar o Silúrico do Buçaco que tem muitas características estratigráficas e sedimentológicas em comum com o de outras áreas da parte sul da Zona Centro Ibérica

Three-dimensionally preserved graptolites from the Silurian of the Central Iberian Zone (Spain and Portugal)

[ES] Los graptolitos silúricos de la Zona Centroibérica suelen conservarse aplastados en pizarras negras, pero en algunos yacimientos los rabdosomas pueden retener parte de su relieve original o conservarse incluso en tres dimensiones. La mayoría de las veces existe una piritización temprana de los rabdosomas por la acción de bacterias sulforreductoras en ambiente anóxico, a la que se suma la génesis de nódulos. La alteración posterior de la pirita deja los graptolitos en forma de moldes, que pueden ser estudiados mediante vaciados en látex. Otros fenómenos de piritización multifásica en sedimentos gruesos conducen a la formación de nódulos de pirita que incluyen en su interior graptolitos huecos y en tres dimensiones, con el peridermo replicado delicadamente en óxidos de hierro. En otras ocasiones, los graptolitos preservados en nódulos generados en sedimentos pelágicos incluyen el recrecimiento de fosfatos sobre el peridermo de los graptolitos, que llegan a conservarse huecos y con estructuras de rellenos geopetales. Finalmente, se presenta el único caso de calizas con graptolitos conocido en el Silúrico centroibérico.[EN] Silurian graptolites form the Central-Iberian Zone are often preserved as flattened moulds in black shales, but in some cases rhabdosomes can maintain a part of its original relief, and even can appear three-dimensionally preserved. The majority of these cases can be related to an early pyritisation of the periderm favoured by bacterial activity under anoxic conditions, which also led to the genesis of nodules on the same beds. Further oxidation and dissapearance of iron minerals limited the preservation of graptolites to external moulds, that can be studied through latex casts. A different way of preservation of 3-D graptolites occurs in coarse sandstone that enhanced multiphase pyritisation fenomena, where ferruginous nodules enclosing rhabdosomes reveal that the framboidal pyrite that mineralized the periderm during very early diagenesis was remarkably resilient not only to subsequent deformation, but also to the differential weathering of the massive overpyrite that constitute the nodules. The pyritised graptolite periderm was finally replicated by iron-oxides with a minor proportion of phyllosilicates. The occurrence of “hollow” graptolites is also known from silico-phosphatic nodules, where the organic periderm was finely replicated by phosphatic overgrowths that coated the inner and outer surfaces of the rhabdosome. Occasional pseudostalactites of phosphatic minerals and colloidal silica partially occupied the empty spaces. Graptolite internal moulds occurring in limestone are very rare and are restricted to a single locality within the studied region.Peer reviewe

Conodontos del Ordovícico Superior (Ashgill) en la Serra do Buçaco, Portugal

Se describen los primeros conodontos ordovícicos de Portugal, que fueron obtenidos en el Miembro Poiares de la Formación Ferradosa, aflorante en el sinclinal de Buçaco (Zona Centroibérica portuguesa). La mayor parte de los taxones de conodontos se han identificado en nomenclatura abierta debido a las condiciones de conservación que presentan. De las observaciones tafonómicas del material estudiado, se infieren condiciones de metamorfismo de grado bajo (epizonal) para las rocas de las cuales fueron extraídos. La asociación de conodontos está integrada por taxones representativos de la Biozona de Amorphognathus ordovicicus (Ashgill) en la Provincia Mediterránea del Dominio Nordatlántico

Lower Devonian faunas and palynomorphs from the Dornes Syncline (Central Iberian Zone, Portugal): stratigraphical and paleogeographical implications

International audiencen the Dornes syncline, southern Central Iberian Zone, Portugal, the uppermost levels of the Serra do Luação Formation up to now have been considered to be of Pridoli-Lochkovian? age because they lie immediately under the Dornes Formation, which is of Pragian age and is well defined stratigraphically. New paleontological elements including benthic faunas and palynomorphs allow us to confirm that the top of the Serra do Luação Formation is securely Lochkovian, for upper Lochkovian strata are present although relatively thin. The transition from the Serra do Luação to the Dornes formations and their lithostratigraphical relationship are now clear: the terrigenous succession belongs to the Serra do Luação Formation and the limestones represent the Dornes Formation. The benthic faunas clearly have North-Gondwanan affinities

Silurian stratigraphy and paleontology of the Valongo anticline and Arouca-Tamames syncline, Central-Iberian Zone (Portugal and Spain)

2 páginas.-- Comunicación presentada en Time and Life in the Silurian: a multidisciplinary approach, Italy , June 4-11, 2009; (Subcommission on Silurian Stratigraphy Field Meeting 2009).-- Abstract.This work is a contribution to the projects CGL2006-07628/BTE (Spain) and PTDC/ CTE-GEX/64966/2006 (Portugal).Peer reviewe

Lower Devonian faunas and palynomorphs from the Dornes Syncline, Central Iberiam Zone, Portugal : stratigraphical and paleogeographical implications

In the Dornes syncline, southern Central Iberian Zone, Portugal, the uppermost levels of the Serra do Luação Formation up to now have been considered to be of Pridoli-Lochkovian? age because they lie immediately under the Dornes Formation, which is of Pragian age and is well defined stratigraphically. New paleontological elements including benthic faunas and palynomorphs allow us to confirm that the top of the Serra do Luação Formation is securely Lochkovian, for upper Lochkovian strata are present although relatively thin. The transition from the Serra do Luação to the Dornes formations and their lithostratigraphical relationship are now clear: the terrigenous succession belongs in the Serra do Luação Formation and the limestones represent the Dornes Formation. The benthic faunas clearly have North-Gondwanan affinities