Microbiostratigraphy of the Gurpi Formation in Mook Area (South of Shiraz)

Abstract

The study of planktonic Foraminifera of the Gurpi Formation in Mook area (South of Shiraz) confirmed the presence of standard biozones defined in Tethyan realm. Seven biozones were identified as follows: Biozones I (Dicarinella asymetrica) and II (Rosita fornicata) indicate an age of Early to Late Santonian. The presence of Biozones III (Globotruncanita elevata), IV (Globotruncana ventricosa) and V (Globotruncanita calcarata) represent the Early, Middle and Late Campanian. Biozones VI (Globotruncana falsostuarti) and VII (Gansserina gansseri) suggest an age of Early and Middle to Middle Late Maastrichtian. The absence of Abathomphalus mayaroensis biozone is due to a sedimentary gap that occurred in the uppermost Maastrichtian. The gap can be identified by a glauconitic layer above the last biozone. This paraconformity is not recognizable in the field. The presence of the layer that contains glauconite in the lower parts of the Gurpi Formation and the red limestones in the upper parts of the Sarvak Formation are the evidences of disconformity between the Gurpi and its underlying Sarvak Formation. The thickness of the Gurpi Formation in Mook area is 287.6 m. The lithology of this sequence consists of shale, marly limestone and argillaceous limestone. Its contact with the underlying Sarvak Formation is disconformable while it is paraconformable with the overlying Pabdeh Formation. In this section, the Gurpi Formation is of Early Santonian to Middle Late Maastrichtian age.