Organo-Geochemical, Petrography and Spectroscopy of Organic Matter Associated Ypresianphosphatic Series of the Maknassy-Mezzouna Basin Central Tunisia

The mineralogical and organo-geochemical analyses of borehole samples were carried out for the Ypresianphosphatic series of Jebel Jebbeus. This section corresponds to Chouabine Formation, which was deposited in Maknassy-Mezzouna Basin (central Tunisia) and is made up of three phosphatic layers alterned with dolomitic marls. Their thicknesses are 7, 2.3 and 6.1 m corresponding to the top, middle and the bottom layers. The aim of this study is to understand the nature, origin and preservation of organic matter (OM) within the phosphatic deposits of eastern basin. Three representative borehole sample of phosphate were investigated using Rock-Eval pyrolysis, X-Ray diffraction, Infrared analyses and the petrographic study of OM. This dataset shows that OM is immature. TOC contents slightly increases from the top to the bottom of the Chouabine Formation (0.33-0.51%), corresponding to increased contents of clay minerals content in the bottom of the formation. The clay fraction found in the middle and lower phosphate series is composed mainly of smectite. Petrography of the residual OM shows that the amorphous organic matter (AOM) is associated with land plant material. The orange AOM can be related to a high degree of aliphaticity, which is confirmed by predominatly of aliphatic bands of CH2 and CH3, likely by biochemical degradation by anerobic bacteria.