학술논문

Paleomagnetic constraints on the age of the Botucatu Formation in Rio Grande do Sul, southern Brazil
Document Type
article
Source
Anais da Academia Brasileira de Ciências. September 2006 78(3)
Subject
paleomagnetism
Botucatu Formation
magnetostratigraphy
magnetic anisotropy
Late Jurassic
Language
English
ISSN
0001-3765
Abstract
Paleomagnetic and rockmagnetic data are reported for the aeolian Botucatu Formation, in the southern Brazilian State of Rio Grande do Sul. Oriented samples were taken from a section located between the cities of Jaguari and Santiago. After thermal and alternating field demagnetization, both normal and reversed characteristic remanent magnetizations were found. These results yielded 13 reversed and 5 normal polarity sites, composing a magnetostratigraphic column displaying a sequence of reversed-normal-reversed polarity events. The paleomagnetic pole calculated for 18 sites is located at 114.7ºE, 78.5ºS (dp=8.1º; dm=1.2º), after restoring the strata to the paleohorizontal. This paleomagnetic pole indicates a Late Jurassic-Early Cretaceous age to the Botucatu Formation in the investigated area, and places the sampling sites at paleolatitudes as low as 21ºS.