January 2021 : Publication Mémoire du Service Géologique de l’Algérie

New chronological data on the moi-pliocene continental deposits of the Beni Fouda Basin (North Eastern Algeria) : small mammals and magnetostratigraphy

A combined magnetostratigraphic and small mammal investigation was carried out to acquire better age control on the sedimentary infill of the Beni Fouda basin in northeastern Algeria. In this work, we describe a new section located at 300m further north of the classic section described by Jaeger (1977). The present magnetostratigraphic investigation provides new elements with respect to discriminate against the absolute age of three fossil sites, Amama 1, 2, and 3.

The biochronological data obtained from the rodent fauna assemblage, combined with radiometric dating, allowed us to correlate the sequence of magnetic polarities of our section with the geomagnetic times scale of Gradstein et al., 2014. The paleomagnetic analyses show that the main minerals carriers of the magnetization in sediments are titanomagnetites, magnetite, and goethite. The directions of polarity sites are antipodal, and the reversing test is positive, indicating that the natural remanent magnetization is primary. Based on these data, the succession of the Miocene formation polarities (section 1) extends between C3.Br1n and C4r.1r. These results suggest that the sequence would be deposited between 8.2 and 7.3 Ma with an average sedimentation rate of 25.5 cm/ka. Our correlation places the Pliocene section (section 2) between C2An.1n and C2An.2r, showing a sedimentation rate of 10 cm/ka. This study evidenced a stratigraphic gap which is materialized by a deposits hiatus with 4 Ma estimated duration.

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References

Mahboubi Salamet, Benammi Mouloud – New chronological data on the moi-pliocene continental deposits of the Beni Fouda Basin (North Eastern Algeria) : small mammals and magnetostratigraphy – Mémoire du Service Géologique de l’Algérie n° 22, pp. 41 – 57, 10 fig.

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