Characterization of geosites as a contribution to the valorization of geoheritage: migmatites from the Costeiro Complex in the Serra do Mar, São Sebastião - SP

Author(s)

Karina de Souza Ibanez

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Geociências (IG/BT)
• Defense date: 2024-04-25

Examining board members

Maria da Gloria Motta Garcia; Monica da Costa Pereira Lavalle Heilbron; Kátia Leite Mansur

• Advisor: Maria da Gloria Motta Garcia; Renato de Moraes

Abstract

This study brings new contributions to the understanding of paraderived migmatites of the Coastal Complex through the characterization of three geosites located in the city of São Sebastião, aiming to define their scientific value and valorize the geoheritage of the region. These geosites are rocky shores integrated into the geological and tectonic context of the Serra do Mar and the coastal ecosystems of the protected areas in the northern coast of the state of São Paulo, lacking specific geological data. Two new geosites were selected: the Stromatic Metatexite of Santiago and the Schollen Diatexite of Barra do Sahy, in addition to the already inventoried Boudins of the Camburizinho Islet geosite. The interpretation of the heterogeneous and complex evolution of granulite facies metamorphism was obtained from field data, petrography, and U-Pb zircon geochronology by LA-ICP-MS. The neosome presents various degrees of segregation and exhibits the paragenesis quartz + orthoclase + plagioclase + biotite ± ilmenite ± magnetite ± garnet, associated with an immature psammitic protolith. The residue is composed of residual minerals, biotite schlieren, and schollen consisting of deformed lenses of biotite amphibolite and metapsammitic metatexite. The structures indicate a high sin-anatectic deformation rate, associated with the Camburu Shear Zone. Geochronological analyses indicate the generation of Neoproterozoic metamorphic zircons over a continuous approximate temporal interval of 240 Ma, from ca. 770 Ma to ca. 530 Ma. The temporal variation from approximately 533 Ma to 627 Ma for the younger populations indicates the final cooling phase of a single metamorphic event within a tectonic switching model in a back-arc basin. This process led to high-temperature metamorphism over a protracted period during the post-extensional collisional phase, accompanied by intrusive basaltic magmatism in immature sedimentary rocks. UAV-derived geospatial products were used to develop an interactive virtual tour, aiming to enhance access to and understanding of the geoheritage and geodiversity of São Sebastião, with applications in geotourism and environmental education. The characterized geosites hold significance for understanding the Neoproterozoic evolution of the Central Ribeira Orogen and for elucidating the geological framework within the city\'s geoheritage inventory. Their unique geodiversity values are crucial for the sustainable management of these resources. The scientific value of the geosites provided a foundation for promoting their environmental, geotouristic, and educational significance, emphasizing the importance of geological characterization within the framework of Geoconservation strategies and for the valorization of the geoheritage in the Serra do Mar region. (AU)

• FAPESP's process: 20/16730-1 - Tectonic geoheritage in the central Ribeira Belt: analysis of boudins as records of the regional evolution, north coast of São Paulo
• Grantee: Karina de Souza Ibanez
• Support Opportunities: Scholarships in Brazil - Master