DINOFLAGELLATE CYSTS AS PALEOCLIMATE INDICATORS IN THE PALEOGENE OF WEST AFRICA

The Cenozoic era is considered a very important and significant time in earth’s history because of natural climate change. The Early Paleogene (Paleocene-Eocene) represents a global transition in the climate system and carbon cycle perturbations. An abrupt rise in the temperature recorded at the Paleocene-Eocene Thermal Maximum (PETM) is considered to be one of the most dramatic events of the Cenozoic era. This rise in temperature resulted in a great turnover of both marine and terrestrial living organisms. Following the PETM and subsequent Eocene hyperthermals, cooling and a significant drop in sea level during the Oligocene epoch were characterized by low carbonate sedimentation rates, planktonic diversity and productivity.

A nearly continuous sedimentary record from Ocean Drilling Program (ODP) Site 959 (Hole 959A and 959D) in the Côte d’Ivoire-Ghana Transform Margin provides the opportunity to study dinoflagellate cysts in two significant paleoclimate intervals in the Paleogene of West Africa. Dinoflagellate cysts are very sensitive to changes in climate and depositional environment. In the Paleocene-early Eocene interval of ODP Hole 959D, the dominance of warm water species of dinoflagellate cysts, such as Apectodinium spp. and Tectatodinium spp., support warm climatic conditions. These species were consistent in their abundance especially during the Selandian and Thanetian.

Later in the sedimentary record, several dinoflagellate cyst taxa record a cold interval during the early Oligocene interval of ODP Hole 959A. This interval yielded an assemblage of good stratigraphic markers that are also present in the northern high latitudes. The taxa include Bitectatodinium spp., Filisphaera filifera, Habibacysta tectata and Nematosphaeropsis spp. The presence of these dinoflagellate cyst taxa in this tropical setting may be indicative of an arctic dinoflagellate migration to low latitude regions during a narrow interval during the Oligocene epoch.