Dinoflagellate cysts stratigraphy and paleoecology from some Lower Miocene rocks, GS9-1X well, northern Gulf of Suez, Egypt

Abstract

Palynological analysis of a Lower Miocene section from the GS9-1 well, northern Gulf of Suez, Egypt, has yielded significant dinoflagellate cysts of stratigraphic significance such as Exochosphaeridium insigne, Sumatradinium soucouyantiae and Hytrichokolpoma rigaudiae, which enabled age dating of the well section as Lower Miocene. Two distinct palynofacies are recognised. Palynofacies “A” was recovered from the basal part of the section from the Nukhul Formation. It is dominated by amorphous organic matter (AOM) and contains frequent translucent and opaque phytoclasts indicating a kerogen type II. Palynofacies “B” was recovered from the overlying interval of the well from the Rudeis Formation. It shows an inverse pattern, where phytoclasts are the main components and AOM declines markedly indicating a kerogen type III. Palynomorphs (mostly dinoflagellates) occur in both facies but with lesser percentages than palynodebris. Paleoenvironmental implications are inferred in the light of the recently established information from the distribution of modern-day dinoflagellate cysts (e.g. Zonneveld et al. 2013) since many of the recovered dinoflagellate cysts from the investigated well section still thriving today. A normal (shallow) marine environment is generally inferred for the studied Miocene section, with more peridinioid dinoflagellate cysts than gouyaulacoids. Higher up in the section, terrestrial palynomorphs dominate the dinoflagellate cysts; the latter are rare or missing. This suggests development of a marginal basin that is probably connected to local uplift or sea regression.