Paleomagnetic preliminary results from the Aptian-Albian Araripe Basin, northeastern Brazil

Tectonic opening of the Equatorial Atlantic Gateway (EAG) and its impact on Ocean–Atmosphere dynamics has global implications. Rifting between South America and Africa drove a transition from continental–lacustrine to evaporitic, and ultimately marine, environments, although the timing and duration of these changes remain debated. Over the same period, Earth’s magnetic field remained in a stable polarity state for ~38 Myr, a phase referred to as the Cretaceous Normal Superchron (CNS). In northeastern Brazil we have key sedimentary sections for this period, such as the Araripe Basin. The studied interval within the basin is notable for recording the evolution from restricted marine sequences to the complete opening of the EAG. Here, we present a preliminary paleomagnetic study of key sedimentary sections from Araripe Basin, in northeastern Brazil, covering the Aptian-Albian ages. Stepwise alternating field (AF) and thermal (TH) demagnetizations were used to isolate the primary remanent component. Magnetic remanence and rock magnetic parameters, such as magnetic susceptibility (χ), anhysteretic remanent magnetization (ARM) and isothermal remanent magnetization (IRM), were measured. Rock magnetic measurements indicate that the primary magnetic remanence carriers are low-coercivity magnetite and/or titanomagnetite and high-coercivity hematite. Our magnetoestratigraphy records reveal a long interval of normal polarities associated with the CNS, with isolated short intervals of reversed polarities that could be further investigated in the future. The results illustrate the potential of paleomagnetic records for best understanding the Earth’s magnetic field in the equatorial region during the Aptian-Albian to better understanding the age and tectonic evolution of the EAG.