CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM SEPTEMBER 2013 CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM SITUATION NORTH AMERICAN EURASIAN PLATE PLATE PACIFIC PLATE PACIFIC AFRICAN PLATE PLATE SOUTH AMERICAN PLATE INDO-AUSTRALIAN PLATE ANTARTIC PLATE Non-geoscientists may not be used to seeing the map shown on the figure above. It shows the earths surface divided according to the tectonic plates limits. It is used to think that the tectonic plates limits are the same as the continents, but in this map it is shown that actually the continents are located over the plates, which are also formed by the oceanic surface. CATALONIA Iberia is a small tectonic plate that has been moving between the Euroasiatic and African plates from the Lower Cretaceous (130 Ma) until the Eocene (45 Ma), when it was pinched out below the Euroasiatic during the Alpine orogeny. Catalonia is located in the NW limit of the Iberian microplate, forming part of the Alpine orogenic belt. It has represented on its rocks the history of the main geological events since the Carmbrian period (530 Ma). CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM Main morphounits AXIAL PYRENEES As a result of more than 500 million years of geological processes, Catalonia is divided today into three main morphounits. Parallel to the coast, there S O is the Catalan Coastal Range, which is a small range U ES T ENE that separates the coast from the inner country. In H ER N PYR the French border, there are the Pyrenees, which come all along the border from the NE Iberian plate Girona limit. And between those positive relief units, there is the Ebro Basin, which is the flattest zone of the Lleida E country. IN NG AS R A B L BR O T A E AS CO AN Barcelona AL A T C A E Sitges S N Tarragona A E N R A E R M E D I T Geological map Catalonias territory is mainly formed by sedimentary rocks, little deformed in the Ebro Basin and folded in the Catalan Coastal Range and Pyrennes. But there i i i i i i are igneous and metamorphic rocks in the Pyrennes i i central zone, called Axial Pyrennes. And it is also i i i i possible to find recent volcanism in some parts of the i country. i a a i a a a a a i i a a na E lfogo i a ncaval e Val a cament d i a Thanks to a large geological history, Catalonia has a i i i i a rich geological record. In its territory there are rocks a i i i a a MONTSERRAT from every geological period since the Cambrian (530 a i Girona Ma), and these are distributed according to the a a i i i i i Lleida i processes that have affected each zone. In the Catalan a GARRAF a i i i a Coastal Range rocks are mainly from the Paleozoic a a i i i a a (530 Ma 250 Ma) and the Triassic period (250 Ma), a a i i 1 i in the Pyrenees from the Paleozoic and from the a a a i MONTSANT i a a i i i a a Barcelona Cretaceous (60 Ma) and in the Ebro Basin from the i i i i a i i Eocene (45 Ma). i i 2 i i a i 3 Sitges a i 1- Qaternary 8- Early Cretaceous Tarragona 2- Volcanic (Qaternary) 9- Jurassic a i 3- Paleocene 10- Triassic a i 4- Oligocene 11- Paleozoic i 5- Late Eocene 12- Paleozoic 6- Paleocene and Early 13- Granitoid i Eocene 14- Gneiss i 7- Late Cretaceous CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM MONTSERRAT: THE EMBLEMATIC MOUNTAIN OF 1 CATALUNYA Montserrat is a special mountain, not only for its remarkable shapes and geological settings, but also because it is a sacred place for Catalans. The differential erosion of the Eocene (56 Ma 34 Ma) conglomerates through a dense net of joints that have made possible its characteristic spire shapes pointing to the sky above. Program FRANCE P Y R E N E E S CATALONIA Girona MONTSERRAT ARAGÓN Lleida 1 Barcelona A E Sitges S N A Tarragona E N R A E R M E D I T STOP 2 LUNCH Rellinars Castellvell i el Vilar STOP 1 STOPS 3-4-5 Can Massana MONTSERRAT STOP 6 Salnitre cave Collbató to Sitges from Sitges CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM STOP 1 Panoramic view of Montserrat Just seeing carefully the Montserrat massif rocks it is possible to deduce a lot of things about its origin. The stratification, which is horizontal despite the vertical appearance of the spires, is the key to understand Monteserrat. Anybody can see in the Southern side that the layers are thick, and towards the Northern side the layers turned gradually thin until they disappeared. Montserrat is formed by clastic rocks, and in sedimentology that thickness variation of the clastic rocks is caused mainly by the side of its grains. Then, in the Southern side the grains are bigger than in the Northern. Also, if it is looked at the middle part of the mountain (between Southern and Northern), it is possible to see that in the lowest part the layers are thin, and to the top the layers are thick. This is what is called a thickening and coarsening upward sequence, and this is the key observation to understand Montserrat. SN C A B + energy - FAN DELTA AA B CC STOP SEA C 1 In sedimentology, it is possible to associate these features to an alluvial-fan facies. BB Montserrat forms part of a big fan delta that extends more than 100 km2. The alluvial- fan is the continental part of the fan-delta A system, and offshore it is found the fan- delta front and the fan-delta slope, the A marine parts. LAND N RIVER CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM STOP 6 Salnitre Cave As it is has been said, Montserrat is formed mainly of conglomerates. These conglomerates are composed by two parts, which are the grains and the matrix. The grains are the smaller or bigger clasts that have been transported and accumulated by the streams, and the matrix is the fine side fraction that aggregates clast among them. The matrix could be made of lower side grains (in comparison to the main clasts) or by cement. The cement is a precipitation of some type of mineral among some particles that joint it. It could be made of silica or calcite, and the conglomerates in Montserrat are made of calcite. The calcite is a calcium carbonate made of 2- 2+ one Ca and one CO3 , which is very easily dissolved by acid waters. The normal rainfall pH is over 5.5, which is an acid pH, which means that if there are water and calcite Salnitre Cave together in nature it is normal that the mineral dissolves. The formations caused by the dissolution of carbonated rocks are called Karst entry chasms water table In Montserrat there is an aquifer system which has its 1 sinkhole recharge zone over the mountain. In this karst system it is posible to find deep chasms of more than 100 m, caves and srpings. One of this caves is the Salnitre Cave. It has been interpreted that many years ago, before the Llobregat River emplacament, this cave worked sometime as a sinkhole (input) and sometimes as a srping (output), depending of the water table level. 2 spring The circulation of acid waters among the calcite matrix of the conglomerates dissolved the rock and formed galleries which can collapse and produce big halls. The precipitation of the calcite mineral present in these waters produces stalactites and stalacmites. Once the Llobregat River had been emplaced in its Llobregat present position, the discharged zone was moved to the river NE side of the massif, which is lower, and it dried the Salnitre 3 Cave old discharged galleries transforming them into subaerial spring caves. CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM GEOLOGY AND ARCHAEOLOGY OF GARRAF 2 Garraf is a calcareous massif located at North of Sitges that has abrupt cliffs eroded by Mediterranean Sea. It is made of Triasic and Cretaceous rocks laying on unconformity above the Paleozoic basement. The humans have been interested on exploit its resources since the Paleolithic age, and there is the first Neolithic underground mine. Program FRANCE P Y R E N E E S CATALONIA Girona ARAGÓN GARRAF Lleida Barcelona 2 A E Sitges S N A Tarragona E N R A E R M E D I T Brugers STOP 1 STOP 3-4 Gavà STOP 2 GARRAF STOP 5 to Sitges CONFERENCE FIELD TRIPS GUIDE ITINERARIS GEOLÒGICS.COM STOP 1 Prehistoric variscite mines Regarded as one of our country's most relevant and unique heritage sites, mining began 6,000 years ago and subsisted for roughly one thousand years. Aside from their remote age, it is important to mention that these coetaneous mines are immensely complex structures and the only ones used to extract variscite, a decorative mineral held in great esteem. The archaeological park, created to help preserve and enhance awareness of this exceptional mining site, provides a unique experience in which the mining structures coexist with a modern museum display. Here, visitors can capture the site's immensity and come to comprehend the life system and beliefs of our ancestors via advanced audiovisual and multimedia technology. A sizeable portion of the original artefacts are on display in the Gavà Museum.