Palynocycles, Palaeoecology and Systems Tracts Concepts: A Case Study from the Miocene Okan-1 Well, Niger Delta Basin, Nigeria

Abstract

Palynocycles are recurrent palynological sequences reflecting vegetational changes determined by cyclic sea level oscillations and the associated climatic variations. This study presents the results of a study on Okan - 1 well from the Niger Delta. This study utilised new ecological indicators established according to their palaeocliamtic and sea level signal. The main aim is to identify the different species of sporomorphs (pollen and spores) present in the sample for the recognition of sea level and climate change during the Miocene as well as their biostratigraphic significance. The biostratigraphic age control of the study location was identified based on the first and last appearance datum of Verrutricolporites rotundiporus (BZ6), Racemonocolpites hians (BZ4), Operculodinium centrocarpum (BZ2), and Magnastriatites howardi (BZ1). The Nine climatic cycles were recognised and used to infer the depositional cycles that indicate recurrent palynogical sequences and vegetation changes based on the sea level change. The wet - dry cycles inferred indicates the fluctuation of the climate and sea level change during the Miocene, thus the use of the variation of vegetation at the different depth intervals as a proxy for the recognition of palaeoenvironmental change (palynocycles 1, 2, 3, 4). The wet cycle suggest highstand / transgressive systems tracts. While on the other hand, the dry cycle indicate lowstand systems tracts. We therefore present this model as a yardstick for the use of pollen and vegetation signals in the recognition of sequences stratigraphy, sea level and climate change.