Anatomy, internal heterogeneities, and early fracture network of a Pleistocene carbonate coastal dune (Rejiche Formation, southeastern Tunisia)

Although eolian deposits are known to record the dominant winds, secondary conditions such as wind reversals during wintertime can also be observed in the petrographic composition and facies succession. Thus, eolian deposits are used here as a local paleoclimatic proxy. The spatial distribution of the depositional facies, early diagenetic imprints, and early fracture network of a coastal Pleistocene eolian ridge in southeastern Tunisia is described using a small-scale GIS model. Facies analysis indicates that coastal dune systems record seasonal cycles. The fracture density and directions are strongly inXuenced by the depositional facies type. Laminated facies present a higher fracture density compared to more homogeneous facies and show only one major fracture direction, while the more homogeneous facies display a bimodal distribution. Such a diVerence between these two groups is explained by the heterogeneous distribution of the early calcite cement within the laminated facies. No tectonic activity or overlying strata have aVected the Pleistocene dunes under study. Therefore, the mechanism responsible for the fractures could only be related to the own weight of the eolianite and to its internal or underlying lithologic heterogeneity