[en] Fresh shale samples taken from a well-known outcrop section of the Silurian Vila Maria Formation, located on the northeastern margin of the Parana Basin (Tres Barras Farm, Goias State, central-western Brazil), have been analysed for both palynological and radiometric age determinations. The rocks yielded a fairly diverse, age-definitive cryptospore assemblage, and the same samples proved suitable for Rb-Sr analysis, despite Silurian sedimentary rocks being rarely suited to radiometric dating techniques. This study thus introduces an alternative, independent method for estimating the minimum depositional age of the Vila Maria Formation. The Rb-Sr age value has been calculated via an isochron diagram that yields 435.9 +/- 7.8 Ma. Accordingly, the latter value is interpreted as the minimum depositional age of the analysed Vila Maria strata, implying their deposition during Llandovery times. This concurs with the palynological results, which indicate an age no older than Early Silurian and, more particularly, favour an Early to Middle Llandovery (Rhuddanian-Early Aeronian) attribution.
Disciplines :
Physical, chemical, mathematical & earth Sciences: Multidisciplinary, general & others
Author, co-author :
Mizusaki, A. M. P.
Melo, J. H. G.
Vignol-Lelarge, M. L.
Steemans, Philippe ; Université de Liège - ULiège > Département de géologie > Paléobotanique - Paléopalynologie - Micropaléontologie (PPM)
Language :
English
Title :
Vila Maria Formation (Silurian, Parana Basin, Brazil): integrated radiometric and palynological age determinations
Publication date :
July 2002
Journal title :
Geological Magazine
ISSN :
0016-7568
Publisher :
Cambridge Univ Press, New York, United States - New York
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