Resumen de Dinoflagellate cyst biostratigraphy and paleoenvironment of the Lower-Middle Jurassic succession of Qatar, Arabian Gulf
M. I. A. Ibrahim, Hamad Al-Saad, S. E. kholeif
Dating of the Izhara and Araej formations in Qatar by 87Sr/86Sr gives an overall age range of 164.70 Ma (Bathonian/Callovian) to 202.40 Ma (Hettangian). Palynological analysis of these sediments is dominated by marine microplankton. The basal Izhara was found barren of index palynomorphs. Four informal dinoflagellate cyst assemblage biozones embracing the interval from Bajocian to Early Callovian are defined as follows: Mancodinium semitabulatum-Pareodinia ceratophora Assemblage Zone I (Early Bajocian), Gonyaulacysta pectinigera-Escharisphaeridia pocockii Assemblage Zone II (Late Bajocian), Ctenidodinium continuum-Dichadogonyaulax sellwoodii Assemblage Zone III (Bathonian), and Chlamydophorella ectotabulata-Rhynchodiniopsis cladophora Assemblage Zone IV (Late Bajocian-Early Callovian). These assemblages resemble those reported from Jurassic deposits elsewhere in the circum-Mediterranean region. The palynofacies and organic matter of these formations are almost exclusively of marine algal origin. The Izhara and Araej formations may have been deposited in shallow marine environment grading from the inner oxic shelf (Izhara) to middle dysoxic shelf (Araej) respectively.
