FACIES, 3rd ORDER SEQUENCE STRATIGRAPHY AND HYDROLOGIC POTENTIAL OF SANDSTONES, MAFRA FORMATION (LATE PALEOZOIC), PARANÁ BASIN, BRAZIL* * Supported by FAPESP 97/13973-2. ** E-mail: jrcanuto@usp.br
CONRADO E.B. PICOLO AND JOSÉ R. CANUTO** * Supported by FAPESP 97/13973-2. ** E-mail: jrcanuto@usp.br
Instituto de Geociências, USP, São Paulo, SP.
Presented by ANTONIO C. ROCHA-CAMPOS
The middle part of the Mafra Formation shows, in Mafra and Rio Negro, a great thickness of diamictites, sandstones, shales, siltites and varvites.
According to Canuto's (1999) nomenclature, the following facies were recognized, in a general way: compacted massive diamictite, lenticular diamictite, cross-bedded and showing fining-upward sandstone, lenticular sandstone, massive siltite, massive siltite with dispersed clasts, laminated or massive shale with dispersed clasts, interlaminated (very fine sandstone intercalated with silty shale), and regular rhythmite, some of them corresponding to diagnostic (#) facies of facies associations.
Four facies associations were also recognized: A1, compacted massive diamictite#; A2, laminated or massive shale with dispersed clasts#; lenticular diamictite; cross-bedded and showing fining-upward sandstone, lenticular sandstone, massive siltite with dispersed clasts# and regular rhythmite#; A3, massive siltite, lenticular diamictite and cross-bedded and showing fining-upward sandstone; and A4, interlaminated#, lenticular sandstone and cross-bedded and showing fining-upward sandstone; they represent, respectively, lowstand, transgressive, highstand and regressive glacio-isostatic system tracts, forming a complete 3rd order sequence.
The alternation of psammitic and pelitic sediments identified sandstone porosities between 20 to 25% and the observed permeability of 10-3 cm/s indicate a good potencial as aquifers.
According to their great lateral extension, it can be expected that they can supply the local community even without a systematic exploration. Besides existing wells in the vicinity, water seeps in outcrops, directly used by the population have also been verified. (December 14, 2001).
Publication Dates
-
Publication in this collection
09 Oct 2002 -
Date of issue
Sept 2002
