Giant trilobites and biotite nodules in Portugal

Peter Perkins (UK) The generally accepted reason for the fame of Arouca is Princess Mafalda, born 1195, who was responsible for the convent becoming Cistercian. Here is an interesting story – she was beatified in 1793. However, I won’t go into that now, but it is well worth investigating. For this article, there are other reasons for its fame, at least among geologists. Arouca is 38km to the south east of Oporto, in northern Portugal, and gives its name to one of two geoparks in Portugal. In Arouca Geopark (Fig. 1), which has an area of 330km2 (just a little smaller than the Isle of Wight), there are two quite remarkable geological features, one palaeontological and the other concerning igneous petrology. Fig. 1. Map of Arouca Geopark. A geopark is an area of significant size that has a particular geological heritage, with a certain number of sites of special importance – scientific quality, rarity, aesthetic appeal and educational value. It must also have a sustainable strategy for development to be accepted as a member of the worldwide network of geoparks. There are 42 in Europe, in 16 countries. The other Portuguese Geopark is Naturtejo, through which the River Tagus flows. There are nine geoparks in the British Isles, for example, NW Highlands (Scotland), Copper Coast (Ireland), Fforest Fawr (Wales) and the English Riviera. The website, http://www.europeangeoparks.org, gives website addresses for all. The geology of Portugal is very complex. There are no strata younger than Triassic, except for Holocene deposits in … Read More

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Graptolites of Abereiddy Bay

Dr Neale Monks (UK) Graptolites are curious fossils that are common in Lower Palaeozoic rocks where other types of fossils are lacking. The word ‘graptolite’ comes from Greek words that mean ‘writing’ (graptos) and ‘stone’ (lithos), and refer to the fact that graptolite fossils look like pencil marks on stone, partly because they’re flat and partly because of the iridescence of many specimens when freshly exposed. It is generally assumed graptolites were planktonic organisms that occupied an ecological niche like that of modern jellyfish, drifting about the oceans feeding on algae or tiny animals harvested using some sort of filter-feeding mechanism. The impetus for this article was a quick but successful trip to Abereiddy in Pembrokeshire, Wales, about 2.5km from Britain’s smallest city, St Davids (population: 1,800). I had been to Abereiddy many years before on a geological field trip with Andy Gale, who is currently professor of geology at the University of Portsmouth, but I did not have any clear memory of where the fossils were to be found. But, as it happened, this locality is one of those where the fossils are abundant and easily collected – provided you look at the right sorts of rocks. Collecting at Abereiddy Bay Abereiddy is a tiny place, but the bay has become a popular tourist attraction because of a flooded quarry known as the Blue Lagoon. Quarrying for slate ended in 1901 and the sea eventually broke through to the quarry, creating what is, in effect, a small natural harbour. … Read More

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