Magnetostratigraphy and Environmental Magnetism of the Aptian--Albian
Boundary of a Sedimentary Core from the Sergipe-Alagoas Basin
The Early Cretaceous was dominated by greenhouse conditions coupled with
increased ocean crust production rate, which led to critical climate,
geographic and oceanographic changes and abrupt shifts in redox
conditions in the oceans. Regarding Earth’s magnetic field, the Aptian
time interval recorded a high rate of polarity reversals. However, after
121.4 Ma, a long period of polarity stability, known as the Cretaceous
Normal Polarity Superchron (CNPS), was established for
~38 Myr. Although, there is debate on the causes and
consequences of this extreme event, the exact behavior of the
geomagnetic field during the Aptian–Albian is still poorly understood,
and data from volcanic and sedimentary rocks are usually conflicting.
Here we integrate paleomagnetic and biostratigraphic data across the
Aptian–Albian transition in the Sergipe-Alagoas Basin (Brazil). Studies
suggesting the correlation between magnetostratigraphic and
biostratigraphic data for this interval in the Brazilian sedimentary
basins are rare, as well as for the South Atlantic marginal basins.
Additionally correlations with the Tethyan realm are still unclear.
Magnetic parameters, such as magnetic susceptibility, with a resolution
of 25 cm, and anhysteretic remanent magnetization (ARM), with a
resolution of 2.1 m, were collected over the ~200 m-long
succession of Core SER-03 in the Sergipe-Alagoas Basin. ARM acquisition
curves were separated into discrete coercivity components and they were
interpreted as related to detrital magnetite and/or eolian dust inputs.
The entire section spans 6 Myr, including the Aptian–Albian boundary.
Our interpretation of environmental magnetism parameter, therefore,
allow us to trace shifts between wet and dry climate conditions.
Therefore, these data will aid to develop an age model framework in
order to assist this uncovered region and future comparisons with
Tethyan sections (e.g., Vocontian Basin - France and Poggio Le Guaine -