Palaeomagnetic directions of the volcanic rocks from Gramado Xavier, Rio Grande do Sul State, South Brazil: implications for time duration of the volcanic activity.

M Irene B Raposo1, Edgardo Canon-Tapia2, Letícia Freitas Guimarães1 and Valdecir A Janasi1, (1)USP University of Sao Paulo, São Paulo, Brazil, (2)Center for Scientific Research and Higher Education at Ensenada, Ensenada, Mexico