Researchers complete geological inventory of São Paulo State

Researchers selected 142 geosites to be part of São Paulo State’s Geological Heritage, classifying them by scientific value and risk of degradation.

By Peter Moon  |  Agência FAPESP – During the Middle Permian, 260 million years ago, much of what is now São Paulo State in Brazil was covered by the waters of the Irati Sea. One of the most fascinating pieces of evidence of this prehistoric marine world can be found in Santa Rosa do Viterbo, near Ribeirão Preto, where limestone quarrying has revealed the existence of several giant stromatolites. 

Stromatolites are sedimentary layered deposits formed by the growth of microalgae in shallow water. The algae live in mats that expand vertically over thousands of years to form the calcareous structures in a process similar to the formation of coral reefs.

Stromatolites are found all over the world, but almost all of them are small. By contrast, Santa Rosa do Viterbo has an extraordinary field of giant stromatolites up to 3 m tall. As a unique site on Earth, it was one of 142 geosites selected to be part of São Paulo State’s Geological Heritage.

The selection of the geological sites took three years (2012-15) and was led by Maria da Glória Motta Garcia, a professor at the University of São Paulo’s Geoscience Institute (IG-USP) and principal investigator for the research project supported by FAPESP. She was assisted by José Brilha, a Portuguese geologist affiliated with the University of Minho’s Earth Science Institute in Braga, Portugal.

The survey was funded by the Special Visiting Researcher line of the Brazilian government’s Science Without Borders Program and coordinated by USP and the University of Minho with the collaboration of the firm Geodiversidade Soluções Geológicas Ltda. The study involved a team of 16 researchers comprising geoscientists affiliated with USP, the University of Campinas (UNICAMP), São Paulo State University (UNESP), the Federal University of São Carlos (UFSCar), the São Paulo State Forestry and Geological Institutes, and the Federal University of Paraná (UFPR), as well as 13 other geoscience professionals.

The inventory of São Paulo State’s geological heritage was published in the journal GeoHeritage.

The coordinators were responsible for surveying the sites that could potentially be included in the inventory, according to Garcia, who heads IG-USP’s Center for Research on Geological Heritage & Geotourism (GeoHereditas). “This gave a total of 193 geosites, and the 142 most relevant were selected,” she said.

“The sites were classified in terms of 11 geological reference frameworks, such as Precambrian terranes, continental rifts, geomorphological units and landforms, or caves and karst systems, among other categories.”

The main aim was to classify geological sites by scientific value and degradation risk “so as to establish priorities for management and geoconservation”.

The 142 geosites selected include important locations from the standpoints of science and tourism. Two caves combine both aspects, for example. One is Tapagem, which is popularly known as the Devil’s Cave. Tapagem is the largest cave in São Paulo State and is located in Jacupiranga State Park in the municipality of Eldorado, which is located in the southernmost part of the state.

The other is St. Anne’s Cave in the Upper Ribeira State Tourism Park (PETAR), which is also located in southern São Paulo. This cave is one of the most important caves in Brazil in terms of speleothems (stalagmites, stalactites and similar cave formations due to mineral deposits).

Another important geosite for geomorphology and tourism is Pico do Itapeva, which is located at an altitude of 2,025 m between Pindamonhangaba and Campos do Jordão. The mountain, which is part of the Serra da Mantiqueira range, comprises ancient granite and gneiss deposits dating from the Precambrian; thus, they are more than 550 million years old. The Paraiba Valley can be seen from the summit, with the Serra do Mar range in the background, making the geosite a tourist attraction.

The Paraiba Valley is a rift valley that opened due to tectonic forces that culminated in the formation of Serra da Mantiqueira and Serra do Mar. During the Oligocene, the entire valley was covered by a paleolake called Tremembé, so named because the terranes it comprises belong to the Tremembé geological formation.

In this case, the geosite to be protected is a montmorillonite clay quarry on Santa Fé farm near Tremembé.

This is the most important fossil site in Brazil that dates to the Paleogene, which was between 66 and 23 million years ago. It was here that, in 1982, Dr Herculano Alvarenga, Director of the Taubaté Natural History Museum, discovered an almost complete fossil of a terrorbird or teratorn classified in the orders Gastornithiformes and Cariamiformes. This animal was the top predator of the paleolake 22 million years ago.

Upper Cretaceous desert

Another lake record, much older in this case, is located in Itu. Varvite Park was created in a former quarry where slabs of varvite were extracted for over a century to pave the sidewalks of the city.

Varves represent annual seasonal deposits of siltstone and argillite. The quarry was once at the bottom of a glacial lake when São Paulo was covered by glaciers at some point during the Permo-Carboniferous.

In geomorphology, one of the selected sites is Devil’s Hill in Morro do Diabo Park, Teodoro Sampaio, which is located in far western São Paulo State on the border with Paraná State. This is a 600 m testimony hill formed by silicified sandstone deposits resulting from dunes of the ancient Caiuá Desert.

The enormous desert covered south-central Brazil in the Upper Cretaceous 170 million years ago, when South America and Africa were contiguous and Brazil was located in the heart of the supercontinent Gondwana.

According to Garcia, the survey followed a methodology created by Brilha and used to inventory Portugal’s geological heritage sites.

“Several European countries besides Portugal are inventorying their geological heritage or have already done so,” she said. “Portugal and Spain are now taking the additional step of selecting the best sites in their inventories to establish the geological heritage of the Iberian Peninsula.”

The Brazilian Commission on Geological & Paleobiological Sites (SIGEP) has published lists of over 100 geosites with recommendations by Brazilian researchers for classifying geologically important sites (Sítios Geológicos e Paleontológicos do Brasil, SIGEP, Brasília, 2002).

“This complete systematic inventory of geosites in São Paulo State, using well-defined methods, is the first of its kind in Brazil and South America. We hope other states survey their geological heritage in a similarly thorough manner, so that we can steadily build up a Brazilian inventory,” Garcia said.

The next steps include transferring the inventory database to the São Paulo State Geological Institute and creating a website with information on all 142 geosites.

“The complete list was delivered only as a technical report to CAPES [the Ministry of Education’s Office for Faculty Development]. It is important for this inventory to serve as a key input to land management policies that take geological heritage into account, in terms of the preparation of adequate laws for protection, geotourism, and science popularization,” Garcia said.

The article “The inventory of the geological heritage of the State of São Paulo, Brazil: methodological basis, results, and perspectives” (doi:10.1007/s12371-016-0215-y) by Maria da Glória Motta Garcia et al. can be retrieved from link.springer.com/article/10.1007/s12371-016-0215-y.

The article “Inventory and quantitative assessment of geosites and geodiversity sites: a review” by José Brilha can be retrieved from link.springer.com/article/10.1007/s12371-014-0139-3.