Miocene biofacies development and geological history of the Gulf of Suez, Egypt

Abstract

Miocene sediments of the Gulf of Suez were deposited in a rapidly subsiding rift which became active during Late Oligocene and Early Pliocene tectonic episodes. Complex lithological variations associated with the variable submarine structure commonly preclude detailed correlation of drilled subsurface successions. Thick Middle to Late Miocene evaporites and their geometry obscure seismic interpretation of prospective sub-evaporitic Early and Middle Miocene sequences. The thick Miocene sediments are believed to have significantly furnished the source, as well as the reservoirs and seals for the oil discovered in the Gulf of Suez. Over four billion barrels of oil have been established as recoverable reserves in Miocene reservoirs. A new Gulf-wide detailed correlation scheme is established based upon a series of newly defined microfaunal assemblage zones. These zones are based on holistic analysis of microfauna utilizing planktonic and benthonic foraminifera, diatoms, otoliths and pteropods. Dating by planktonic foraminifera and calcareous nannofossils indicates the zones are isochronous. Vertical and lateral variations in assemblage characteristics have been identified, mapped and are concluded to be the results of vertical and lateral differences in salinity, water depth, water clarity, lithological variation and oxygen availability. The correlative applicability of this scheme within the Gulf of Suez provides potential for it to serve as a reference for drilled sequences in the Red Sea, where thicker evaporite sequences make sub-evaporitic stratigraphic correlation even more difficult owing to the greater seismic attenuation. Isochronous palaeoenvironmental variations are detected, utilizing the zonation scheme, both within the Gulf of Suez and the Red Sea region, which will assist in the correlation and mapping of stratigraphic sequences of hydrocabon potential. Detection, confirmation and the degree of displacement of faults is also improved by the application of the scheme.