Evidence of Saharan dust in Upper Pleistocene reworked palaeosols of Northwest Sardinia, Italy: Palaeoenvironmental implications

A multi-disciplinary approach was followed to investigate two thick palaeosol
strata that alternate with wind-blown dominated deposits developed along the Alghero coast
(North-west Sardinia, Italy). Optically stimulated luminescence ages reveal that both
palaeosols were developed during cooler drier periods: the first one at around 70 ka Marine
Isotope Stage 4 and the latter around 50 ka (Marine Isotope Stage 3). In contrast, the pedological
features indicate that the palaeosols underwent heavy weathering processes under warm humid to
sub- humid conditions, characteristic of the Sardinian climate during the last interglacial stage
(Marine Isotope Stage 5e). To reconcile this apparent data discrepancy, a range of
sedimentological and pedological analyses were conducted. These analyses reveal that the
palaeosols possess a complex history, with accumulation and weathering occurring during Marine
Isotope Stage 5e, and erosion, colluviation and final deposition taking place during the
following cold stages. Thus, even if these reddish palaeosols were last formed during the
glacial period, the sediments building up these strata probably record the climate of the last
interglacial stage (Marine Isotope Stage 5e). Trace element and X-ray diffraction analyses,
together with scanning electron microscope images, reveal the presence of Saharan dust in
the parent material of the palaeosols. However, no evidence of any far-travelled African
dust has been observed in the Marine Isotope Stage 4–3 aeolian deposits. It is possible to
conclude that in the West Mediterranean islands, Saharan dust input, even if of modest
magnitude, is preserved preferentially in soils
accumulated and weathered during interglacial stages.