HYDROCARBONS IN CARBONATE ROCKS OF THE NEOPROTEROZOIC ALTO PARAGUAI BASIN, MATO GROSSO, BRAZIL * * Supported by: FAPESP. E-mail: acrnogue@usp.br
AFONSO C. R. NOGUEIRA1,2, CLAUDIO RICCOMINI3, ALEXEI KERKIS2, THOMAS R. FAIRCHILD3AND RENATA L. HIDALGO2
1Departamento de Geociências, FUA, Manaus, AM.
2Programa de Pós-Graduação em Geologia Sedimentar, Instituto de Geociências, USP, São Paulo, SP.
3Instituto de Geociências, USP, São Paulo, SP.
Presented by ANTONIO C. ROCHA-CAMPOS
A singular occurrence of hydrocarbons (bitumen) was found in Neoproterozoic carbonate rocks of the Araras Formation (Alto Paraguai basin) in the Terconi quarry (Mirassol d'Oeste, Mato Grosso, Brazil). The bitumen occurs in a transgressive carbonate succession overlying Varanger tillites, that consists of two facies associations: (1) lagoon complex, with pink parallel-laminated dolomicrites and fenestral stromatolitic biostromite, and (2) tidal-flat complex, represented by terrigenous gray micrites and pseudosparites, with parallel lamination, asymmetric ripple marks, tepee breccia, planar stromatolites and evaporites. When fresh, the bitumen is compact and vitreous, filling fractures, stylolites and dissolution cavities, generally associated with calcite cement and euhedral dolomite crystals. Microscopic examination shows the bitumen filling pores of primary (fenestral) and secondary (moldic and intragranular) origins. As the first record of hydrocarbon in Neoproterozoic rocks of the Paraguai Belt, this occurrence opens a new perspective for the evaluation of oil potential in Precambrian rocks of Central Brazil. ( December 8, 2000 )
Publication Dates
-
Publication in this collection
08 Oct 2001 -
Date of issue
Sept 2001
