Geochemistry of the eocretacic basalt magmatism in the Piraju-Ourinhos region, SE Brazil, and implications to the stratigraphy od the Serra Geral Formation - Janasi, Valdecir de Assis; Negri, Francisco de Assis; Montanheiro, Tarcísio José; Freitas, Vivian Azor de; Rocha, Brenda Chung da; Reis, Pedro Morais (Revista Brasileira de Geociências, 2007)