The Middle Palaeolithic site of Birzgane (Tebessa, Algeria): Rock magnetic property characterisation and past rainfall reconstruction

The magnetic fraction of the alluvial sediment contains mainly oxidised magnetite and smaller amounts of haematite and goethite; indicated by thermal demagnetisation curves of isothermal remanent magnetisation. Magnetic properties such as enhanced susceptibility, anhysteretic remanent magnetisation and frequency dependent susceptibility indicate that the upper part of the section was subjected to pedogenesis after deposition. A conceptual magnetic enhancement model was applied to reconstruct past rainfall quantities in the upper part, taking into account present day temperatures and rainfall, water saturation, soil moisture and magnetic susceptibility. A precipitation quantity of 560 ± 40 mm was estimated for the transition period from MIS 5 to 4, corresponding to the Saharan Pluvial, an extended humid climate period in northern Africa between 100,000 and 70,000 years before present.