Paleoenvironments and Sequence Development of the Miocene succession , Western and Southern Iraq

Abstract

The Miocene succession of western and southern Iraq is represented by the
Euphrates, Ghar, Jeribe, Nfayil, Fatha, and Injana formations. The Euphrates
Formation (Early Miocene) consists mainly of shallow marine facies; it`s equivalent
the Ghar Formation (Early- Early Middle Miocene) is represented by continental
clastic facies. The Jeribe Formation (Early Middle Miocene) represents shallow
marine environment. The Nfayil Formation (Middle Miocene) also of shallow marine
environment, it`s equivalent the Fatha Formation is represented mainly by supratidal
marine environment. The Injana Formation (Late Miocene) represents the clastic
continental facies.
The studied succession was highly affected by many diagenetic processes such as
dolomitization, dedolomitization, dissolution and cementation with less effective
micritization, neomorphism, and compaction.
Four third order cycles were recognized in the studied sections, These include:
cycle A of the Miocene Euphrates Formation and it`s equivalent the lower part of the
Ghar Formation, cycle B of the Early Middle Miocene Jeribe Formation and it's
equivalent the upper part of the Ghar Formation, cycle C of the Middle Miocene
Nfayil Formation and it`s equivalent the Fatha Formation, and cycle D of the Late
Miocene Injana Formation. Each third order cycle can be subdivided into a number of
fourth order cycles. All of the fourth order cycles are assymmetrical reflecting an
imbalance between the relative sea level and carbonate production. A variation
between the different sections in nature of cyclic deposition reflects the difference of
local tectonic effect on the sequence development.