Palynological and paleoenvironmental analyses of selected shale samples from Orange basin, South Africa

Abstract

Core and ditch cutting of shaly samples were selected from 5 wells within the Orange Basin, South Africa. It was with a view to studying the palynological contents of the samples and to also delineate the  environment and condition in which the samples were formed. The samples were prepared for palynological studies using standard extraction techniques involving HCL, HF treatments, wet sieving with 10 μm polyester sieve and mounting of samples on glass slides using glycerine jelly. The samples were moderately abundant and diversified in pollen and spores. Sixty-eight palynomorphs species were identified and were used for biozonation. Two biozones were identified in this study. These were SI in Wells A_C2, A_U1 and top of Well O_A1 and SII in Wells K_BI, A_F1 and base of Well O_A1. The SI with interval between 2030 m and 4170 m was characterized by acme of Inaperturopollenites sp at 2697 m in Well O_A1. Other palynomorphs identified within the zone were Anglatisporites sp, Triporites sp and Polypodiaceoisporites retirugutus with age range of possibly between Valanghian- Barremian. The SII zone at interval of between 1330 m and 2030 m and with age range of Aptian to Albian at the base was defined by Antulsporites baculatus at 2030 m at the top of Well A_O1. This zone was further characterized by the occurrence of Klukisporites sp and Taurocusporites sp at depths of 1330 m and 1690 m in Well A_F1, respectively. The few counts of Bacutriporites sp, Classopollis sp, Polyangulatisporites sp were also recorded within the zone. The palynoflora assemblages were quantitatively dominated by brackish to fresh water swamp species such as Laevigatosporites sp, Polypodiaceoisporites sp with moderate counts of forest species such as Saptaceoideapollenite sp. The environment of deposition of the sediments was brackish to fresh water.

Keywords: Palynology, Paleoenvironment, Biozonation, Orange Basin, Palynoflora