geo-trails in the ordovician of portugal



geo-trails in the ordovician of portugal
M. Valério1,2, C. Neto de Carvalho3,4 & H. Couto5
Centro de Interpretação Geológica de Canelas, Canelas de Cima Cx 213, 4540-252 Arouca, Portugal, 2Ardósias
Valério & Figueiredo, Lda., 4540-252 Arouca, Portugal, 3 Geopark Naturtejo da Meseta Meridional – European
and Global Geopark, Geology and Paleontology Office, Centro Cultural Raiano, Av. Joaquim Morão, 6060-101
Idanha-a-Nova, Portugal, 4Municipality of Idanha-a-Nova, Av. Joaquim Morão, 6060-101 Idanha-a-Nova,
Portugal. 5Departamento de Geociências, Ambiente e Ordenamento do Território/Centro de Geologia, Faculdade
de Ciências, Universidade do Porto. Rua do Campo Alegre 687, 4169-007Porto, Portugal
*([email protected])
Keywords: Ordovician; geo-trails; geodiversity; environmental education; geotourism
Some north to south geo-trails have been established in the Ordovician of Portugal to reveal geological
heritage. There are examples of such in the Douro Internacional Natural Park, or in Beja–Barrancos.
However, we will emphasize the work developed in three areas where strategies involving
geoconservation have been applied since the 1980‘s. In Valongo Palaeozoic Park, in Geological
Interpretation Center of Canelas (Arouca Global Geopark) and in Penha Garcia Ichnological Park
(Naturtejo Global Geopark) there are Interpretative Circuits with implemented geo-trails that allow the
observation and interpretation of different particular aspects of the Ordovician of Portugal.
The Valongo Palaeozoic Park, a partnership between the Faculty of Sciences of the University of
Porto and the Municipality of Valongo, has since 1998 been an educative and environmental resource,
where the geology advertising and awareness of the natural environment is addressed for schools and
for the general public (Couto, 2005). The interpretative circuit has three footpaths trails (green, red and
yellow trails) that include tracks in the Ordovician showing different aspects of geodiversity (Fig. 1a).
More recently the Municipality of Valongo established an ―ecological corridor‖ gaining the green geotrail of Palaeozoic Park and linking the urban area to the outcrop. The geo-trails cover rocks of
Palaeozoic age and make it possible to observe the variation in sedimentary environments (marine and
continental) from nearly 540 to 300 million years ago. Some Ordovician lithologies provide evidence,
among other, for the existence of submarine volcanism during the Lower Ordovician, the great
biodiversity in the Middle Ordovician and of the great glaciation that occurred in the Upper
Ordovician. Gold exploited by Romans is in great part related to volcanism of Lower Ordovician.
Thus, the geomining heritage can be also be related with the period of Ordovician history. Evidences
of Roman mine works can be observed along the different trails. In red geo-trail, Fojo das Pombas, a
significant Roman mine can be visited. Interesting geomorphologic and tectonic aspects can also be
observed along the trails. Valongo Anticline is a significant geologic structure that extends for about
50 km from north Valongo to Arouca having suffered 350 million years of erosion along to create a
classic case of relief inversion as evidenced by Ordovician lithologies.
Geological Interpretation Center of Canelas (GICC) is situated in the heart of the rocks of the
Paleozoic Era, more precisely within Ordovician. The fossils of the so called "Pedreira do Valério",
are internationally famous particularly for the giant trilobites (Sá & Valério, 2005), and were studied
initially by Décio Thadeu during the 1950‘s. The resumption of exploration in 1988 allowed the
collection of thousands of specimens, the most emblematic are those displayed since 2006 in the
GICC. The opening of this private space to the public was complemented by the creation of an
approximately 5km circular footpath, called the "Route of the Palaeozoic." This trail allows visitors to
walk through several episodes of Earth‘s geological history (Fig. 1b). They also learn about the
"louseira" quarrying at different periods over nearly two centuries, when fossils never posed a barrier
to commercial activities. Now the giant trilobite fossils, which have been trapped in the slate for 465
million years, have become a tourist attraction. This trail, with several geological stops, highlights also
a number of historical and cultural sites, which include the exploitation of gold from the Roman
"Gralheira d‘Àgua" mine. There is evidence of the use of fire for breaking up the veins, as well as the
existence nearby of a primitive gravity ore wash. Besides GICC and Gralheira d‘Água three more sites
are included in the geosites inventory of Arouca Geopark (Upper Ordovician glaciomarine diamictites,
Lower Silurian graptolites and Carboniferous conglomerates). The "Route of the Paleozoic" is of great
interest to students at a more advanced levels of education, which came successfully to fill a priceless
asset for GICC activity. It is estimated that about half of a total 10000 visitors of CIGC opt to follow
this trail annually.
Among the trails which offer an interpretation of the Ordovician in Naturtejo Global Geopark (Secrets
of Almourão valley, Schist Path of the Griffon Vulture Flight and Orvalho Geotrail) the Fossils Route
is the most visited and best suited for educational activities (Rodrigues & Neto de Carvalho, 2009). A
circular path paved with local quartzite was created by the local community in the early eighties to
facilitate the visit to the watermills and the legendary ―painted snakes‖. The ―Fossils Route‖ was
formally established in 2003 according to the international rules for walking trails. As the structural
axis for disclosing Penha Garcia Ichnological Park, this 3 km long circuit starts and finishes in the
medieval part of Penha Garcia village. The viewpoints of the Mother Church and the Castle prepare
the visitor to dive in to the Ordovician sea. By crossing the major part of the Armorican Quartzite
Formation the trail exposes the different sub-environments that were present during deposition of the
sands and mud in the marine realm at this stage. Dozens of different primordial habits are interpreted
from well preserved trace fossil assemblages including different approaches to feeding from juvenile
(meraspid) to giant trilobites. Within a short walk there is so much to see in the rocky gorge of the
Ponsul river: different physical and biogenic sedimentary structures typical of sandflats in barrierisland systems, curious folds resulting from fault activity during the Variscan Orogeny, vertical
bedding planes equipped for climbing, watermills prepared for milling flour and a traditional bakery
with fresh bread always available. The trail also leads to the Pego swimming area, carefully cultivated
gardens along the river and even a bog in Mediterranean-type climate with dozens of minute species of
plants and insects. 11000 visitors enjoy the ―Fossils Route‖ every year, by just undertaking a short trek
or by participating in dozens of adventure sports activities and cultural events especially organized by
active tourism companies, such as Trilobite.Aventura or the local community with support of the
Municipality of Idanha-a-Nova (Fig. 1c).
Apart from regular self-guided visits, guided tours for schools (students at different educational levels)
and for the general public, formation courses for teachers and national and international scientific
meetings and outreach activities have been developed in these areas involving the geo-trails.
a Portugal: a) Green Geotrail; b) Palaezoic Route; c) Fossils Route.
Fig. 1 – Geo-trails in the Ordovician of
Couto, H. 2005. Parque Paleozóico de Valongo. Preservar porquê e para quê? In: Conservar para
quê?, Vítor Oliveira Jorge (coord.), pp.199-211. Faculdade de Letras da Universidade do Porto.
Departamento de Ciências e Técnicas do Património. Centro de Estudos Arqueológicos das
Universidades de Coimbra e Porto (Fundação para a Ciência e Tecnologia).
Rodrigues, J. & Neto de Carvalho, C. 2009. Geotourist trails in Geopark Naturtejo. In: New challenges
with Geotourism, Neto de Carvalho, C. & Rodrigues, J. (eds.), pp. 45-50. Proceedings of the 8th
European Geoparks Conference.
Sá, A.A & Valério, M. 2005. Uma jazida paleontológica excepcional no Ordovícico do SW da Europa:
a ―Pedreira do Valério‖em Canelas (Arouca, Portugal). In: Cruziana 05,Neto de Carvalho, C. (coord.),
pp. 23-25. Actas do Encontro Internacional sobre Património Paleontológico, Geoconservação e
Geoturismo, Idanha-a-Nova.