Sedimentological and Geochemical Aspects of the Late Paleocene-Early Eocene Phosphorites Cropping out in North Western Tunisia (sra Ouertane Basin)

The present work aims to reconstruct the paleoenvironments using a multidisciplinary approach including sedimentology, petrography, and geochemistry. These studies were undertaken on the late Paleocene–early Eocene succession of the Sra Ouertane area, Northwestern Tunisia. These deposits are mainly composed of phosphorites interbedded with limestones and marls. Phosphatised coprolites and indeterminate pellets contain a poorly preserved radiolarian assemblage, which can only be differentiated to the genus level. The presence of Calocyclas, Phormocyrtis, Lychnocanium, and Theocorysspp indicates a late Paleocene–early Eocene age. Geochemical study of major (Fe, Si, P, Ti, K) and trace (Zn, Y, Zr, Sr) elements reveals that the phosphorites at the base and top of the studied section, are characterized by high Sr concentration in addition to high P. In contrast, Zr, Ti, Si, and K are more abundant in samples from the middle part of the section. This enrichment of Zr, Ti, and K was favored by an efficient weathering of neighboring hinterlands during humid episodes, which favored the detrital inputs. This humid period was contemporaneous with the warmest global climate event.