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Description:
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Extensional stresses caused Africa and South America to break up about 130
Million Years . When Africa rifted away from South America , a large onshore triple
junction began at about 13° S and propagated northward . This triple junction failed and
created the Reconcavo -Tucano -Jupato rift (R -T -J ) , located in northeastern Brazil (north
of Salvador ) . The extensional stress that created this rift was caused by a change in the
force acting on the plate during the Aptian .
A series of offshore rifts also opened at this time , adjacent to the R -T -J rift ; this
series of basins are referred to as Jacuipe , Sergipe , and Alagoas (J -S -A ) . The basins are
separated by bathymetric highs to the north and the south of the Sergipe -Alagoas basin .
The Sergipe -Alagoas basin has a Bouguer gravity anomalies more negative than -35
mGal , and the other two basins have values more negative than -100 mGal ; the total
magnetic intensity is also about 60 -80 nT higher in the Sergipe -Alagoas basin than the
surrounding basins . The gravity and magnetic values in the Sergipe -Alagoas basin ,
when compared to the Jacuipe and the Sergipe -Alagoas basins , indicate that the depositional history and /or the formation of the Sergipe -Alagoas basin is different from
the other two basins .
This study was done by analyzing the gravity and magnetic anolamies in the
region , and comparing these anomalies to the stratigraphy of the basin . This research
has allowed the stratigraphy and structures of the Sergipe -Alagoas basin to be better
understood - the location of the Sergipe fracture zone will also be outlined . This study
provides a comprehensive view of the Sergipe -Alagoas basin and outlines a method for
using Gravity and Magnetics to better understand the stratigraphy and structure of the
Sergipe -Alagoas basin . |