Sin-Conference Fieldtrip

Ancient roots of a cordillera of the Brasiliano Cycle:

the São Roque Group Raízes antigas de uma cordilheira do Ciclo Brasiliano: o Grupo São

Roque

Date: 27/07/2018

Route: Campinas- Cajamar-Pirapora do Bom Jesus municipalities, NW of São Paulo city

Minimum number of participants: 10

Maximum number of participants: 30

CELSO DAL RÉ CARNEIRO

University of Campinas, Graduate Program of Teaching and History of Earth Sciences,

Geosciences Institute, PO Box 6152, 13083-970 Campinas, SP, Brasil. Researcher of CNPq.

<cedrec@ige.unicamp.br>

Crossing geological history, mining and urban occupation

The reconstruction of the fascinating history of gold discoveries was the objective of a research

devoted to the preservation of some remarkable vestiges of ancient gold mines (Fig. 1). It is

probable that the first discovery of gold in Brazil occurred in 1560, by Brás Cubas, the founder

of the Santos city. In the 16th century the area was part of the Captaincy of São Vicente. The

Jaraguá caves (Fig. 2), next to the Jaraguá Peak, located in the close vicinity of São Paulo city,

represent the memory of the beginning of the mining of this metal in Colonial Brazil.

Figure 1. Dense tropical forest and grass around the protected Jaraguá State Park, which includes the urban Jaraguá peak (a). The Jaraguá Cave (b) can be seen from the Anhangüera Road, but it is hidden by a huge debris cover

The geological information gathered in the fieldtrip guide interconnects historical data,

methodological aspects of fieldwork practices and a view of the geology of the Neoproterozoic

unit called “São Roque Group”: rock types, magmatism, ductile folds, faults and fragile

structures. The collection helps to clarify the origin of some environmental problems found

nowadays.

a b

Figura 2. The urbanization of São Paulo city has restricted the ancient gold caves to narrow scattered remnants

(white bold lines). Source: satellite images from Google Earth 2008

On March 17, 2011, the Municipal Council for Preservation of the Historical, Cultural and

Environmental Heritage of the City of São Paulo (CONPRESP) has decided to protect the caves

(Fig. 2) (http://www.infopatrimonio.org/?p=17524). The geological framework records the

geological history of the Neoproterozoic Brasiliano Cycle and the origin of a large cordillera

whose roots composed the Gondwana supercontinent. Educational material based on regional

geological knowledge (Fig. 3a) makes it possible to integrate environmental issues that affect

the communities of this populous region with economic issues related to sustainable mining of

limestone for Portland cement (Fig. 3b), gravel and other mineral resources.

In august 1986, a geological hazard related to a doline collapse has occurred within the urban

area of Cajamar city (Fig. 3c). The consequences of the phenomena stimulates educational

research, seeking to broaden the available information for basic education teachers about

Geology, Geomorphology and Environmental Sciences.

Figure 3. Axial-plane tectonic foliation perpendicular to fine banded clay metasediments (a). General view of

limestone mining in Cajamar (b). Limits of risk zones in the urban area of Cajamar (c). Distribution of Neoproterozoic conglomeratic metamorphic rocks NW of São Paulo

The visited outcrops include a nice roadcut view of Neoproterozoic conglomeratic metamorphic

rocks situated NW of the São Paulo city (Fig. 3d, Fig. 4).

Figure 4. Neoproterozoic conglomeratic metamorphic rocks, NW of São Paulo

Complementary reading

CARNEIRO, C.D.R.; SANTOS, L.F.dos; SILVA, J.R.B.da. 2011. Cavas Históricas de Ouro do Jaraguá: o que resta para se preservar? Rev. Bras. Geoc., 41(1):108-120. URL: http://ppegeo.igc.usp.br/index.php/rbg/article/view/7818/7245. DOI: 10.25249/0375-7536.2011411108119. Acesso 24.01.2018.

HENRIQUE-PINTO, R.; JANASI, V.A. 2010. Metaconglomerados e rochas associadas do Grupo São Roque a norte da Cidade de São Paulo, Brasil. Rev. Bras. Geoc., 40(3):409-425. URL: ppegeo.igc.usp.br/index.php/rbg/article/download/7766/719. DOI: 10.25249/0375-7536.2011411108119. Acesso 24.01.2018.

HENRIQUE-PINTO, R.; JANASI, V.A.; TASSINARI, C.C.G.; SIMONETTI, A.; HEAMAN, L.M. 2012. Paleoproterozoic source contributions to the Sao Roque Group sedimentation: LA-MC-ICPMS U-Pb dating and Sm-Nd systematics of clasts from metaconglomerates of the Boturuna Formation. São Paulo. Geol. USP, Sér. cient. [online]. 12(3):21-32. URL: http://ppegeo.igc.usp.br/index.php/GUSPSC/article/view/3265/2823. Acesso 21.02.2018.