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Mount San Giorgio

A mountain of fossils

Svizzera, Cantone Ticino, RIVA SAN VITALE

Svizzera, Cantone Ticino, BRUSINO ARSIZIO

Svizzera, Cantone Ticino, MENDRISIO


Monte San Giorgio

(CH 1903) E   717620 N   83220 H   580.0
(WGS 84) Long.   8.954 Lat.   45.890
Stratigraphie, Sedimentology, Paleontology

Geo-mining, Hydromorphologie, Karst morphology
OTHER INTERESTS Naturalistic, Landscape, Didactic, Hiking
GEOSITE   PALEONTOLOGICAL - fossils of vertebrates


Seen from the north, the shape of Mount San Giorgio resembles a massive pyramid rising from the depths of Lake Lugano. Its sides, at first relatively steep, then descend rather more gently down towards Rancate and Ligornetto into hills and a small valley formed by the Gaggiolo River. The most interesting part of this vast geographical area, however, is roughly limited to the slope between the village of Meride and the summit of the mountain. That is, the relief is not particularly noteworthy except for the clear exception of the exciting panorama which may be enjoyed from the highest point. Hidden within the rocks there are preserved fossils of the rich marine life which thrived during the Middle Triassic Age in the basin of Mount San Giorgio. The rock strata deposited in the basin of the mountain, which also pertain to the Late Triassic Age, permit a further understanding of the important history of this basin, which constitutes a part of the history of the Southern Alps.


The paleontological wealth of the period between 242 and 235 million years ago is such that it has even earned the designation of the entire district of Mount San Giorgio as a UNESCO World Heritage Site. For the past 150 years, Mount San Giorgio has been the focus of research in the field of paleontology. Historically, the stratigraphic level of excavations is that of the Besano Formation, also called the Bituminous Zone Limit or, in German, Grenzbitumenzone. This is defined as a succession of sedimentary strata which contains an alternation of dolomite, volcanic tuff and bituminous schist formed from the remains of the rich fauna which inhabited the surface sea water of a basin, all arising as a result of the influx of the sea which characterizes the Middle Triassic Period. The isolated situation which the basin was in during the period between the Anisic and Ladinian Stages severely restricted the rate of sedimentation, so that the bodies fallen to the bottom accumulated, resulting in the formation of rock. Consequentially, circulation was restricted within the enclosed basin. This led to a scant replacement of water at the bottom of the sea, resulting in long periods without oxygen (i.e. a completely anoxic environment), thus excluding any necrophagic organisms. These conditions therefore guaranteed a perfect preservation of the skeletons which lay on the seabed. Reptiles, fish and invertebrates have been discovered in large quantities and varieties in just 16 metres of strata in the Besano Formation. Other types of fossils such as insects, plants and microfossils are rather more rare, which is why nowadays the research conducted by the Cantonal Museum of Natural History of Lugano has led to the carrying out of new excavations in the upper levels of the Saint Giorgio Dolomites and the Limestones of Meride.


Schist of the Besano Formation was also exploited for its bitumen content. Among the numerous mines there is the Tre Fontane, which until the 1940s included 1700 metres of development. The extracted bitumen was used to produce “saurolo”, a medicinal oil sold to pharmaceutical companies in Basel and Milan.
scala temporale periodi geologici


Along the A2, take exit 52 Varese-Mendrisio-Stabio and head towards Varese-Stabio for about 1 kilometre, turning towards Genestrerio-Novazzano-Rancate-Arzo. Follow the signs for Arzo, reached by passing through the villages of Rancate and Besazio. From Arzo turn right towards Meride and continue for 1 kilometre.


Between Meride and Serpiano you can follow various paths which lead into the geological site.


ANTONIETTI A. et al. (1978): Sentiero naturalistico del Monte San Giorgio. Guida, commento e note. Ente ticinese per il turismo. Bellinzona. 163 pp.
COTTI G. et al. (1990): Introduzione al paesaggio naturale del Cantone Ticino.Vol. 1, Le componenti naturali, Bellinzona, 484 pp.
DECUYPER H. & ANTOGNINI M. (2008): Magie di pietra. Locarno. Armando Dadò.
FELBER M. & TINTORI A. (2011): Geoguida del Monte San Giorgio. Geologia insubrica.



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Programma di cooperazione transfrontaliera Italia - Svizzera 2007 - 2013 Progetto cofinanziato dal Fondo Europeo Sviluppo Regionale (FESR)
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