 |
Geoconservation Research
2021, Volume 4 / Issue 1 / pages(93-103)
European UNESCO Geoparks: Original Article
1 Centro de Geociências, Universidade de Coimbra, Rua Sílvio Lima, 3030-790 Coimbra, Portugal
2 Department of Geology, Ghent University. Krijgslaan 281, S8. 9000 Ghent, Belgium
3 Instituto Dom Luiz, Departamento de Geologia, Faculdade de Ciências da Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
4 Geopark Naturtejo Meseta Meridional. Centro Cultural Raiano. Avenida Joaquim Morão, 6060-101, Idanha- a-Nova, Portugal
Sofia Pereira Centro de Geociências, Universidade de Coimbra,
Rua Sílvio Lima, 3030-790 Coimbra, Portugal.
Abstract
Middle Ordovician successions occur at Naturtejo UNESCO Global Geopark in five Variscan-folded, kilometer- to tens of kilometer-long structures. Four of them revealed to be fossiliferous in the different recognized lithostratigraphic units, middle- to-uppermost Darriwilian in age, with particular emphasis for Brejo Fundeiro (Oretanian regional chronostratigraphic stage) and Fonte da Horta (Dobrotivian regional stage) formations. Recent paleontological and biostratigraphic works have detected most of the previously recorded and new fossil sites, improving the Middle Ordovician biostratigraphy of this region and updating the knowledge of its fossil assemblages, which are fairly more diverse than previously considered. The good preservation of the fossils and their relevance to understanding the climax of the Global Ordovician Diversification Event at high paleolatitude shallow marine environments, as well as the protection or identification of some of the fossil sites as UNESCO Geopark’ geosites, make certain their interpretation and use in already existing geotrails and new interpretation centers and school programs.
Keywords: Naturtejo Geopark, Brejo Fundeiro Formation, Fonte da Horta Formation, Oretanian, Dobrotivian, Central Portugal
Article information | |
Received: 2020-10-26 Accepted: 2020-12-22 DOI: 10.30486/gcr.2020.1913411.1054 How to cite: Pereira S, Colmenar J, Esteves CJP, Dias da Silva I, Pires M & Neto de Carvalho C (2021). Paleobiodi- versity in the Darriwilian (Middle Ordovician) of the Naturtejo UNESCO Global Geopark (Portugal). Geoconservation Research.4(1):93-103. doi: 10.30486/gcr.2020.1913411.1054 Geoconservation Research e-ISSN: 2588-7343 p-ISSN: 2645-4661 © Author(s) 2020, this article is published with open access at http://gcr.khuisf.ac.ir
|
Naturtejo UNESCO Global Geopark joined the European and Global Geoparks networks under the auspices of UNESCO, in 2006. It was includ- ed in the International Geosciences and Geoparks Programme of UNESCO in 2015 as a territory of 5067 km2, covering the municipalities of Castelo Branco, Idanha-a-Nova, Nisa, Oleiros, Penama- cor, Proença-a-Nova, and Vila Velha de Ródão, located in Central Portugal. Represented by de- posits from the Neoproterozoic to the Quaternary, the Ordovician successions are among the main features of the Naturtejo geological heritage, ex- posed in large, kilometers to tens of kilometers long, Variscan-folded structures, forming Appa- lachian-type landforms and representing some of its most famous geosites (e.g., the Penha Garcia Ichnological Park and the Portas de Ródão Natural Monument).
The Middle Ordovician is the most fossiliferous Ordovician series across the Central Iberian Zone. The so-called “tristani beds” (Born 1916), due to the abundance of the trilobite Neseuretus tristani in these shallow marine deposits, represents the Oretanian-Dobrotivian interval (correlated with most of the global Darriwilian Stage), which hosts the most classical Portuguese Ordovician fos- sil sites (e.g. Valongo, Arouca and Buçaco; e.g., Romano 1982; Couto et al. 1997; Guy & Lebrun 2010). While in Northern Portugal these stages are represented by a homogeneous succession of shales and siltstones (Valongo and Moncorvo formations) overlying the ‘Armorican Quartzite’ (Santa Justa and Marão formations, Romano & Diggens 1974; Sá et al. 2005), in central Portu- gal this interval is represented by intercalation of mudstones and sandstones units: Brejo Fundeiro, Monte da Sombadeira, Fonte da Horta, and Cabril formations (Cooper 1980; Young 1988). Among these, the lower Dobrotivian Fonte da Horta For- mation is the most fossiliferous unit, providing highly diverse assemblages (mainly brachiopods, trilobites, ostracods, molluscs, hyolithids, bryozo- ans, and crinoids), with fewer but frequent fossils
also reported from the Brejo Fundeiro and the Ca- bril formations (e.g., Delgado 1908; Young 1985). Finally, the paleontological record of the Monte da Sombadeira Formation is sparse, but documented (e.g., Delgado 1908; Cooper 1980; Romão 2006).
Within the Naturtejo Geopark area, fossiliferous Oretanian and/or Dobrotivian units are represent- ed in four of its five structural Variscan-folded structures: the Fajão-Muradal, the Vila Velha de Ródão, and the Penha Garcia synclines plus the Monforte da Beira folded structure. During the first decades of geological studies in Portugal, the Middle Ordovician of these sectors was consid- ered poorly fossiliferous, bearing solely rare and badly preserved remains, what was interpreted as being related to deeper environments (Delga- do 1908). During the second half of the twenti- eth century, the discovery of Middle Ordovician fossiliferous levels in Fajão-Muradal, Vila Velha de Ródão and Penha Garcia synclines changed somewhat this interpretation (e.g., Thadeu 1951; Ribeiro et al. 1965, 1967; Perdigão 1971; Young 1988), but their paleontological record was rarely figured (e.g., Neto de Carvalho et al. 2014), and the idea of a low potential for this paleontological heritage remains.
In this work, we show this potential through a se- lection of specimens from old and new fossil sites, improving the Middle Ordovician biostratigraphy of this region and updating the knowledge of its fossil assemblages, which are fairly more diverse than previously considered.
The studied area belongs to the Central Iberian Zone (CIZ) of the Iberian Massif, corresponding to post-Cambrian metasedimentary sequences that lie in angular unconformity on the Beiras Group (upper Ediacaran -?lower Cambrian). Five NNW- SSE to WNW-ESE major Variscan-folded struc- tures, preserving lower Paleozoic successions ranging in age from Lower Ordovician (Tremado-
cian) up to, at most, lower Silurian (Llandovery), occur within the Geopark: Fajão-Muradal, Vila Velha de Ródão, Penha Garcia, Castelo Branco – Unhais-o-Velho and Monforte da Beira sectors (Fig. 1). Only the southern half of the 32 km-long Fajão-Muradal Syncline lies within Naturtejo area, roughly south of the Zêzere River (Fig. 1). For this reason, herein we will focus only on the Muradal sector when referring to Fajão-Muradal Syncline.
The Oretanian/Dobrotivian (middle to upper Darriwilian) succession among the Naturtejo area starts with the Brejo Fundeiro Formation (20-120 m), conformably overlying the Serra do Brejo and Penha Garcia formations (‘Armorican Quartzite’, Cooper 1980; Bayet-Goll & Neto de Carvalho 2020). This metapelitic unit is recog- nized throughout all Naturtejo sectors, thickening southwards, from solely 20 m in southern half of the Fajão-Muradal Syncline to 120 m in Vila
Figure 1. Simplified geological map of the Naturtejo UNESCO Global Geopark (adapted from the 1:500000 map published by Serviços Geológicos de Portugal, Oliveira et al. 1992) with the location of the four sectors indicated in the text: 1 – Fajão-Muradal Syncline; 2 – Vila Velha de Ródão Syncline; 3 – Penha Garcia Syncline; 4 – Monforte da Beira folded structure.
Velha de Ródão, and eastwards, to about 80 m. The Brejo Fundeiro Formation is assigned to the regional Oretanian stage (middle to upper Darri- wilian). In Castelo Branco – Unhais-o-Velho and Monforte da Beira exposures, the lower Paleozo- ic succession is preserved only up to part of the Brejo Fundeiro Formation, being impossible to estimate its original thickness. A sudden change in lithology marks the base of the following unit, the Monte da Sombadeira Formation (5-50 m), a
regressive storm-generated sandstones sequence of lower Dobrotivian age (ca. uppermost Darriwil- ian). Its thickening and coarsening tendency south and eastwards in Portuguese Central Iberian Zone (Young 1985), is also verified in the studied area, being only 5 m thick in Fajão-Muradal, 20 m in Vila Velha de Ródão and 50 m in the Penha Garcia Syncline. Conformably overlying these micace- ous sandstones is the Fonte da Horta Formation (20-65 m), consisting of mudstones with rare
sandstone beds, also of lower Dobrotivian age. It was recognized throughout the synclines of Fajão-Muradal, Vila Velha de Ródão and Penha Garcia. The Fonte da Horta Formation rapidly thins southwards, from 55-65 m in Fajão sector (Young 1988; Metodiev et al. 2009) to solely 10- 15 m in Muradal and Vila Velha de Ródão areas, thickening eastwards in Penha Garcia to about 50 m. Finally, this mudstone-dominated unit is overlaid by the Cabril Formation, composed of siltstones and sandstones beds exhibiting hum- mocky cross-stratification within a background of laminated siltstones and mudstones. This unit is assigned to the base of the upper Dobrotivian (global uppermost Darriwilian), being less than 30 m thick and poorly characterized in the Penha Garcia Syncline (Young 1985). In its type area (Buçaco Syncline) and the Amêndoa-Carvoe- iro Syncline (located westwards of the studied sequences), the top of the Cabril Formation is marked by a persistent phosphatic conglomerate, not represented in any of the Naturtejo’ sectors. Likewise, the following unit in the Buçaco and Amêndoa-Carvoeiro synclines, the Carregueira Formation, is also absent in the studied sequenc- es. Deposition conditioned by eustatic events and an erosive episode that preceded the depo- sition of the Upper Ordovician (probably related to the Sardic phase, a deformation event along the northern Gondwana margin; e.g., Puddu et al. 2019) may justify the incompleteness of the Ca- bril Formation and the absence of the Carregue- ira Formation in Naturtejo sectors. Furthermore, Young (1988) recognized a maximum shoaling during the deposition of the upper part of the Ca- bril Formation and concluded that Carregueira Formation, which shows marked thickness varia- tions, may be absent in the “rise” areas. Accord- ing to the stratigraphic data presented herein, the Fajão-Muradal Syncline marks the belt of maxi- mum condensation of the sequences during the Middle Ordovician. Thus, the sedimentary model suggested by Young (1988) supports and justifies the verified sedimentary hiatus for this sector and south-eastwards areas.
Fajão-Muradal Syncline (southern sector) The first Middle Ordovician fossils from the Fa- jão-Muradal Syncline were reported by Thadeu (1951, pp. 38-39), but all the occurrences are from the northern part of the syncline (outside the stud- ied area). Besides graptolites in the Brejo Fundeiro Formation, this author recovered numerous frag- ments of the trilobite Neseuretus tristani, two in- determinate orthid brachiopods and one ostracod from the mudstones of the Fonte da Horta Forma- tion. Two decades later, Perdigão (1971) present- ed the only previously reported fossil occurrences from the Middle-to-Upper Ordovician of the Mu- radal sector. Several fossil sites for the Brejo Fun- deiro Formation were documented, yielding the characteristic graptolite Didymograptus (Sarnadas de S. Simão, Picoto, Candal, Zebro and Orvalho). In the Fonte da Horta Formation, Perdigão (1971) identified one single fossil site (Candal at Sarna- das), yielding the trilobite Neseuretus tristani and indeterminate crinoids. One single specimen of a graptolite from the Muradal sector was figured (‘D. bifidus’: Perdigão 1971, pl. 1, fig. 6) and up to now, this was the only Middle Ordovician fossil ever published from there. The recent geo- logic mapping survey conducted by Metodiev et al. (2010) did not provide fossil remains from the southern sector of the syncline. From a paleonto- logical point of view, the Middle Ordovician of the Muradal region is fairly fossiliferous (Fig. 2), and the present work revealed several new fossil sites, increasing the total number of known spe- cies from three to almost 30. The Brejo Fundeiro Formation provided three fossiliferous horizons in the lower part of the unit containing an assem- blage representative of the Oretanian age, yielding graptolites (Didymograptus murchisoni and Did- ymograptus cf. artus), echinoderms (Calix sp.), trilobites (Neseuretus cf. avus and Asaphellus sp.), bivalves (Redonia deshayesi, Praenucula? sp.), brachiopods (Orthidae indet.) and hyolitids (Figs. 2A-E). No fossils were found up to the mo- ment in the Monte da Sombadeira Formation. The mudstones of the Fonte da Horta Formation are
very fossiliferous, like in other geographic sectors of central Portugal. Its fossil assemblage is typi- cal of lower Dobrotivian age, yielding abundant trilobites (Neseuretus tristani, Kerfornella brev- icaudata, Crozonaspis cf. struvei, Plaesiacomia oehlerti, Isabelinia? sp., Phacopidina micheli, Selenopeltis sp. and Eccoptochile sp.), ostracods (Lardeuxella bussacensis, Reuentalina ribeiriana, Quadritia tromelini, Medianella sp., Quadrijuga- tor marcoi), bivalves (Cardiolaria beirensis), bra- chiopods (Crozonorthis musculosa, Heterorthina sp. and Horderleyella sp.), indeterminate crinoids and the ichnospecies Tomaculum problematicum. The Cabril Formation did not provide fossils up to the moment.
The Geological Survey of Portugal had developed some work in the Ordovician sequence of this structure during the second half of the nineteenth century, but Delgado (1908, p. 70) considered its Middle Ordovician units to be sparsely fossilif- erous, bearing rare and poorly preserved fossils, which he interpreted as related to deeper sedi- mentary settings. Nevertheless, there is a good, although poorly diverse, collection recovered by that author, housed in the National Laboratory of Geology and Energy (eight Oretanian/Dobrotivian species) which, together with additional materials collected during the twentieth century, were listed and taxonomically updated by Neto de Carval- ho et al. (2009). In a preliminary study, Thadeu (1951) found some fragments of trilobites and bra- chiopods in the Middle Ordovician mudstones of the Fonte da Horta Formation. Some years later, Ribeiro et al. (1965, 1967) reported Didymograp- tus, Neseuretus tristani, ‘Dalmanella testudinar- ia’ (probably Horderleyella sp.), ostracods and in- determinate bivalves. Furthermore, they described some levels as bearing abundant fossils, although poorly diverse (e.g., Barroca da Senhora and Quin- ta da Carga). By the same time, Romariz & Gaspar (1968) published an important graptolite fossil site yielding Didymograptus amplus, a species previ- ously unknown in Portugal but later considered
to be a junior synonym of D. murchisoni (Jen- kins 1987). Our prospection work corroborates what was previously considered: although bearing highly fossiliferous levels, the Middle Ordovician assemblages of the Vila Velha de Ródão Syncline are poorly diverse and only a few new occurrences are herein reported (including new fossil sites in the vicinities of Perdigão village). Nevertheless, the Brejo Fundeiro Formation hosts good fossil localities, yielding complete and well-preserved specimens with geoheritage potential (Fig. 3A- G), some of them protected as geosites under the Portas de Ródão Natural Monument. On the other hand, it is expected that increasing the prospection works will lead to a higher diversity: the identified taxa correspond to the most abundant species oc- curring in coeval levels from other CIZ sectors and in those regions many of the less common species were only discovered due to decades of intense fossil collecting (e.g., Buçaco and Amêndoa-Car- voeiro synclines). So far, the Oretanian Brejo Fun- deiro Formation provided trilobites (Neseuretus tristani, Ectillaenus giganteus and Eodalmanitina destombesi), pelagic graptolites (Didymograptus murchisoni, Didymograptellus bifidus), bivalves (Redonia deshayesi), brachiopods (Sivorthis noc- tilio), echinoderms (Calix cf. sedgwicki) and os- tracods (Lardeuxella bussacensis), besides the ichnofossil Arachnostega gastrochaenae which usually infests internal molds of trilobites. In the Fonte da Horta Formation, several fossiliferous levels contain Dobrotivian assemblages yielding trilobites (Neseuretus tristani, Colpocoryphe cf. rouaulti and Plaesiacomia oehlerti), ostracods (Lardeuxella bussacensis, Quadrijugator marcoi and Reuentalina sp.), bivalves (Glyptarca sp.) and brachiopods (Heterorthina kerfornei and indeter- minate orthids). No fossils were recovered from the Monte da Sombadeira Formation, and only few trilobite remains (Neseuretus tristani) were found in the Cabril Formation.
As for the previous structures, the early decades of geologic studies (Delgado 1908) did not detect
Figure 2. Fossils from the Oretanian (A-E) and Dobrotivian (F-S) of the southern half of the Fajão-Muradal Syn- cline. A-E, Brejo Fundeiro Formation at Orvalho Village; F-S, Fonte da Horta Formation at Orvalho Village (F,G,- J-S) and Sobral do Queixo (Vilar Barroco) locality (H,I). A) The bivalve Redonia deshayesi (internal mold, right valve). B) The trilobite Neseuretus cf. avus (internal mold of a pygidium). C) The trilobite Asaphellus sp. (internal mold of a pygidium). D) The diploporite echinoderm Calix sp. (latex cast of an external mold). E) The lopho- phorate Hyolithidae indet. (Longitudinal section). F) Trilobites Neseuretus tristani and Phacopidina micheli (the former, yellow color: Internal mold of an exuvium; the latter, white color: internal mold of a cranidium); G, I, J, the trilobite Phacopidina micheli. ((G) Internal mold of a librigenal, preserving the eye surface with lenses. I) Internal mold of a cranidium. J) Internal mold of a pygidium)). H), Tomaculum problematicum (fecal pellets accumulated on sediment surface)). K) The trilobite Kerfornella brevicaudata (internal mold of a cranidium). L) Neseuretus tristani and the bivalve Cardiolaria beirensis (latex cast of an external mold of a pygidium and an articulated specimen, respectively). M) Plaesiacomia oehlerti and Lardeuxella bussacensis (internal mold of a cranidium and an isolated valve, respectively). N) The crustacean ostracod Quadrijugator marcoi (internal mold of a right valve).
O) The ostracod Lardeuxella bussacensis (internal molds of several valves). P) Ostracods accumulation (mainly internal molds of Lardeuxella bussacensis and external molds of Quadritia tromelini). Q) Cardiolaria beirensis (internal mold of a left valve). R) The brachiopods Crozonorthis musculosa and Heterorthina sp. (internal molds of ventral – the former, and dorsal – the latter, valves). S) The brachiopod Horderleyella sp. with Quadrijugator marcoi (latex cast of an internal mold of a dorsal valve and internal mold of a left valve, respectively). All scale- bars = 5mm, except G, M, O (= 2 mm) and N (=1 mm). All photographs from the authors.
Figure 3. Fossils from the Oretanian (A-D, H) and Dobrotivian (E-G) of the Vila Velha de Ródão Syncline (A- G) and Monforte da Beira folded structure (H). A-D, Brejo Fundeiro Formation at M1373 road; E-G, Fonte da Horta Formation at Barroca da Senhora (E) and Perdigão surroundings (F-G); H, Brejo Fundeiro Formation at NW of Monforte da Beira. A) The pelagic hemichordate graptolite Didymograptus murchisoni (several stipes). B) Neseuretus cf. tristani (internal mold of an exuvium). C) Calix cf. sedgwicki (external mold of plates with detail of tubercles and diplopores). D) Ectillaenus giganteus (internal mold of a complete exoskeleton). E) accumulation of (mainly) Neseuretus tristani sclerites. F) Trilobites Plaesiacomia oehlerti (left) and Neseuretus tristani (right) (internal molds of cranidia). G) Neseuretus tristani (internal mold of a cranidium). H) Ogyginus forteyi (external mold of a pygidium). All scale-bars = 5 mm. All photographs from the authors.
paleontologic potential in the Middle Ordovician sequence of the Penha Garcia Syncline. Later, Thadeu (1951) reported the trilobite Neseuretus tristani and two indeterminate brachiopod spe- cies, probably from the Dobrotivian Fonte da Horta Formation. A slightly higher, but still low, diversity was reported by Perdigão (1971) who identified one bivalve (Ctenodonta sp.), brachio- pods (‘Harknessella cf. vespertilio’ and ‘Orthis’ sp.) and indeterminate crinoids in the Oretanian/ Dobrotivian mudstones, figuring only two speci- mens (Perdigão 1971, pl. 1, figs. 5,7). The import- ant lithostratigraphic work performed by Young (1985) improved the Dobrotivian biostratigraphic
knowledge of the Penha Garcia Syncline, docu- menting the occurrence of the brachiopods Het- erorthina kerfornei, H. morgatensis, Crozonorthis musculosa (figured on op. cit., pl. 19, figs. 13,15) and Aegiromena mariana (first occurrence in Por- tugal, figured on op. cit., pl. 28, figs. 18-19), plus few trilobites (Neseuretus tristani, Prionocheilus mendax, Ectillaenus sp., Colpocoryphe sp. and Placoparia sp.) in Monte da Sombadeira and Fonte da Horta formations. By the end of the last century, the geologic mapping surveys of Sequeira et al. (1999) provided few trilobites (non-identi- fied) in the Brejo Fundeiro Formation. More re- cently, Neto de Carvalho et al. (2014) presented
an update of occurrences and fossil sites in the Middle Ordovician of the Penha Garcia Syncline (e.g., Ribeira do Reca, Fonte do Cuco), including the complete revision of the existing collections from the National Laboratory of Geology and Energy. These authors identified six trilobites, three brachiopods, plus bivalves, crinoids, ostra- cods, orthocerids and the ichnofossils Arachno- stega gastrochaenae and Planolites montanus. Part of this material is here revised, together with a few new specimens (Fig. 4), demonstrating the potential for future paleontologic works in the Middle Ordovician of the Penha Garcia Syncline, where fossil heritage from both the Lower and Upper Ordovician is also outstanding (Neto de Carvalho et al. 2014). The Brejo Fundeiro For- mation yields a typical Oretanian assemblage of trilobites (Neseuretus tristani, Eodalmanitina destombesi, Colpocoryphe cf. rouaulti, Ogyginus sp.), brachiopods (Cacemia cf. ribeiroi, Sivorthis noctilio and Paralenorthis sp.), bivalves (Redo- nia cf. deshayesi, Hemiprionodonta lusitanica and Praenucula costae), rostroconchs (Tolma- chovia sp.), graptolites (Didymograptus mur- chisoni, D. cf. artus, Didymograptellus bifidus, Hustedograptus cf. teretiusculus, Diplograptus sp.) and indeterminate orthocerids. The Monte da Sombadeira Formation only provided the bra- chiopod Heterorthina morgatensis in its upper ferruginous beds (Young 1985), an index-species of uppermost Oretanian-lowermost Dobrotivian in Ibero-Armorica (Gutiérrez-Marco et al. 2016). The Fonte da Horta Formation yields a low-di- versity assemblage of lower Dobrotivian age, containing trilobites (Neseuretus tristani, Pri- onocheilus mendax, Placoparia cf. tournemini, Ectillaenus giganteus and Colpocoryphe sp.), brachiopods (Apollonorthis cf. bussacensis, Het- erorthina morgatensis, H. kerfornei, Aegiromena mariana and Crozonorthis musculosa), ostracods (Lardeuxella bussacensis and Medianella sp.) and trepostomate bryozoans. The Cabril Forma- tion did not provide fossils up to now.
The first and only Oretanian fossil assemblage reported from this complex structure was found by Delgado (1908, p. 71), who reported a pygidi- um of an asaphid trilobite, orthocerids, a lingulid brachiopod and an indeterminate bivalve, com- ing from mudstones he assigned to his ‘Schistes à Orthis Ribeiroi’, currently the Brejo Fundeiro Formation. This is the only Ordovician litho- stratigraphic unit recognized by us above the ‘Ar- morican Quartzite’, and the limited exposure area may justify not having been detected in the recent geological map published for this region (Romão et al. 2010). Nevertheless, no additional materi- al was found. Thadeu (1951) also recognized this Oretanian succession of purple micaceous mud- stones, but part of his selected sections corre- sponds to the Neoproterozoic Beiras Group. The revision of Delgado’s (1908) material allowed the identification of the trilobite Ogyginus forteyi (Fig. 3H), characteristic of Oretanian in Iberia and thus confirming the representation of this stage in the Monforte da Beira structure.
Figure 4. Fossils from the Oretanian (A-J) and Dobrotivian (K-M) of the Penha Garcia Syncline. A-J, Brejo Fundeiro Formation at Fonte do Cuco (A), Serra do Ramiro (B), Barragem (C,D,H), Ribeira do Reca (E,F,I,J) and Arraial da Antónia Tomé (G) localities; K-M, Fonte da Horta Formation at Ribeira da Nave locality. A) Didy- mograptus murchisoni (one rabdosome). B) The cephalopod nautiloid Orthocerida indet. (Internal mold). C) The trilobite Colpocoryphe cf. rouaulti (internal mold of an exuvium). D) Ogyginus sp. (internal mold of an exuvium).
E) Neseuretus tristani (internal mold of a cranidium). F) The brachiopod Paralenorthis sp. (internal mold of a ven- tral valve). G) The mollusc rostroconch Tolmachovia sp. (internal mold of the right side of the shell). H) Redonia cf. deshayesi (internal mold of a left valve); I, Hemiprionodonta lusitanica (internal mold of a left valve partially preserving the mineralized shell). J, the bivalve Praenucula costae (internal mold of a left valve). K) A brachiopod Orthidae indet. (Internal mold of a valve). L) The trilobite Placoparia cf. tournemini and Orthidae indet. (Internal mold of a complete exoskeleton and external mold of a valve, respectively). M) The brachiopods Apollonorthis cf. bussacensis, Heterorthina sp. and a bryozoan Trepostomata indet. (external and internal, respectively, internal molds of dorsal valves). All scale-bars = 5 mm. All photographs from the authors.
Fundeiro, Fonte da Horta and Cabril formations at Portas de Ródão are protected under the national law for nature conservation, some of them includ- ed in the Master Plan of the municipality of Vila Velha de Ródão. The main road that crosses the Monument also intersects the entire Ordovician succession cropping out in this Variscan structure and has been successfully used for training uni- versity students in geosciences. Finally, the fos- sil sites of Ribeira do Reca and Fonte do Cuco,
in the Penha Garcia Syncline, are geosites under the Geopark list; these and the other fossil sites, including the Vale Feitoso Estate, are located close to Penha Garcia Ichnological Park, the most important geotourism destination at Naturtejo Geopark. Also, an important Interpretative Centre of the Ordovician Paleobiodiversity is under con- struction and the studied fossils will be included and showcased from a paleoecological perspec- tive in the permanent exhibition.
The trilobite-dominated, high paleolatitude ma- rine assemblages from the Middle Ordovician, whose recent works increased the number of known species from 20 to over 40 in the Oretani- an/Dobrotivian of Naturtejo Geopark area, includ- ing the first report of several genera (the trilobites Selenopeltis, Eccoptochile, Ogyginus, Asaphellus, Kerfornella, the bivalve Cardiolaria, the ostracod Quadritia, the rostroconch Tolmochovia, among others), reveal higher biodiversity than previously documented. This fossil record is representative of the High Latitude peri-Gondwana Realm for this period of time and, therefore, must be deeply an- alyzed at a regional level under the Global Ordo- vician Biodiversification Event and introduced to schools and public, through effective exhibitions and school programs, as one of the main examples of animal evolutionary radiation in the Phanero- zoic.
The ongoing fieldwork is partially supported by Naturtejo, EIM under its program Geopark Science for Development. The authors also express their gratitude to the Municipality of Oleiros (Paulo Ur- bano) and the authorities of the village of Orval- ho (Luis Roque) for their support; to Herdade de Vale Feitoso for the permit to work in this private property; to Ana Medeiros and Frederico Ferreira for helping in fieldwork at Vila Velha de Ródão and giving specimens for study; to Ana Jacinto and Francisco Piçarra for helping in fieldwork at Oleiros municipality, and Tim Young (Cardiff Uni- versity) for sharing his data and knowledge. We thank Helena Couto (Universidade do Porto) and an anonymous reviewer for manuscript revision. This work was supported by Fundação para a Ciên- cia e a Tecnologia under the UID/Multi00073/2019 Project framework, Portugal.
The authors declare to have no conflict of interest
Bayet-Goll A & Neto de Carvalho C (2020). Architec- tural evolution of a mixed-influenced deltaic suc- cession: Lower-to-Middle Ordovician Armorican Quartzite in the southwest Central Iberian Zone, Penha Garcia Formation (Portugal). International Journal of Earth Sciences. 109: 2495-2526. https:// doi.org/10.1007/s00531-020-01915-8
Born A (1916). Die Calymene Tristani – Stufe (mit- tleres Untersilur) bei Almaden, ihre Fauna, Glie- derung und Verbreitung. Abh. Senckenberg. Natur- forsch. Ges. 39: 309-358.
Cooper AH (1980). The stratigraphy and palaeontolo- gy of the Ordovician to Devonian rocks of the area north of Dornes (near Figueiró dos Vinhos), central Portugal. PhD Thesis, University of Sheffield.
Couto H, Piçarra JM & Gutiérrez-Marco JC (1997). El Paleozoico del Anticlinal de Valongo (Portugal). [In A Grandal d’Anglade, JC Gutiérrez-Marco, L Santos Fidalgo (Eds.) XIII Jornadas de Paleontolo- gia “Fósiles de Galicia” y V Reunión International Proyecto 351 PICG “Paleozoico Inferior del No- roeste de Gondwana”, Libro de Resúmenes y Ex- cursiones (pp. 270-290) ]. Sociedad Española de Paleontologia. A Coruna.
Delgado JFN (1908). Système Silurique du Portugal. Étude de stratigraphie paléontologique. Memórias da Commissão dos Serviços geologicos de Portu- gal. 1-245.
Gutiérrez-Marco JC, Sá AA, García-Bellido D & Rába- no I (2016). The Bohemo-Iberian regional chronos- tratigraphic scale for the Ordovician System and palaeontological correlations within South Gond- wana. Lethaia. 50(2): 258-295.
Guy PM & Lebrun P (2010). Les trilobites de l’Ordo- vicien du Portugal. Fossiles, hors-serie. 1: 41-88.
Jenkins CJ (1987). The Ordovician graptoloid Didy- mograptus murchisoni in South Wales and its use in absolute strain analysis. Transactions Royal Society of Edinburgh, Earth Science. 18: 105-114.
Metodiev D, Romão J, Dias R & Ribeiro A (2009). Sin- clinal de Vila Velha de Ródão (Zona Centro-Ibéri- ca, Portugal): litostratigrafia, estrutura e modelo de evolução da tectónica Varisca. Comunicações Geológicas. 96: 5-17.
Metodiev D, Romão J, Dias R & Ribeiro A (2010). Sinclinal Varisco de Serra do Moradal-Fajão (Zona Centro-Ibérica, Portugal Central): padrões es- tratigráficos e estruturais. E-Terra. 11(1): 1-4.
Neto de Carvalho C, Rodrigues J & Metodiev D (2009). Inventário do Património geológico do Concelho de Vila Velha de Ródão: Contributo para a caracteri- zação do Geopark Naturtejo da Meseta Meridional. Açafa. 2: 1-53.
Neto de Carvalho C, Rodrigues J & Baucon A (2014). “Fossil Art”: the importance and value of the palae- obiodiversity in the Naturtejo Global Geopark, un- der UNESCO (Portugal). Comunicações Geológi- cas. 101(1): 91-99.
Oliveira JT, Pereira M, Ramalho M, Antunes MT & Monteiro JH (1992). Carta geológica de Portugal à escala de 1/500 000. Lisboa: Serviços Geológicos de Portugal.
Perdigão JC (1971). O Ordovícico de Fajão, Un- hais-o-Velho, Salgueiro do Campo e Penha Garcia. I Congresso Hispano-Luso-Americano de Geologia Económica, Madrid/Lisboa. 2: 525-541.
Puddu C, Álvaro JJ, Carrera N & Casas JM (2019). Deciphering the Sardic (Ordovician) and Variscan deformations in the Eastern Pyrenees, SW Europe. Journal of the Geological Society. 176: 1191-1206.
Ribeiro O, Teixeira C, Carvalho H, Peres A & Fer- nandes HP (1965). Carta Geológica de Portugal na escala 1:50.000. Notícia explicativa da folha 28-B (Nisa). Lisboa: Serviços Geológicos de Portugal.
Ribeiro O, Teixeira C, Ferreira CR & Alves CAM (1967). Notícia Explicativa da Carta Geológica de Portugal Folha 24 ‐ D Castelo Branco. Lisboa: Serviços Geológicos de Portugal.
Romano M (1982). The Ordovician biostratigraphy of Portugal – A review with new data and re-appraisal. Geological Journal. 17:89-110.
Romano M & Diggens JN (1974). The stratigraphy and structure of Ordovician and associated rocks around Valongo, north Portugal. Comunicações Serviços Geológicos de Portugal. 57: 23-50.
Romão JMC (2006). Carta Geológica de Portugal na es- cala de 1:50.000. Notícia explicativa da folha 28-A (Mação). Lisboa: Serviços Geológicos de Portugal.
Romão J, Cunha PP, Pereira A, Dias R, Cabral J & Ribeiro A (2010). Carta Geológica de Portugal na escala de 1:50.000. Notícia Explicativa das Folhas 25-C, Rosmaninhal, 25-D, Segura e 29-A, Retorta. Lisboa: Laboratório Nacional de Energia e Geolo- gia.
Romariz C & Gaspar A (1968). Notas sobre graptol- óides portugueses. II – A fauna dos xistos de Ródão. Boletim da Sociedade Geológica de Portugal. 16(3): 203-209.
Sá A, Meireles C, Coke C & Gutiérrez-Marco JC (2005). Unidades litoestratigráficas do Ordovícico da região de Trás-os-Montes (Zona Centro-Ibérica, Portugal). Comunicações Geológicas. 92: 31-74.
Sequeira AJD, Proença Cunha P & Ribeiro ML (1999). Carta Geológica de Portugal na escala de 1:50.000. Notícia explicativa da folha 25-B (Salvaterra do Ex- tremo). Lisboa: Serviços Geológicos de Portugal.
Thadeu D (1951). Geologia e jazigos de chumbo e zin- co da Beira Baixa. Boletim da Sociedade Geológica de Portugal. 9(1-2): 1-144.
Young TP (1985). The Stratigraphy of the Upper Ordo- vician of Central Portugal. PhD. Thesis, University of Sheffield.
Young TP (1988). The lithostratigraphy of the Upper Ordovician of Central Portugal. Journal of the Geo- logical Society. 145:377-392.
