Litak, R. K., Barazangi, M., Brew, G., Sawaf, T., Al-Imam,
A., and Al-Youssef, W.
Structure and evolution of the petroliferous Euphrates graben system, southeast
Am. Assoc. Petr. Geol. Bull., 82, 1173-1190, 1998
The northwest-trending Euphrates graben system
is an aborted intracontinental rift of Late Cretaceous age that has subsequently
been hidden by Cenozoic burial. Approximately 100 km wide, the system comprises
an extensive network of grabens and half grabens extending some 160 km from the
Anah Graben in western Iraq to the Palmyride fold belt in central Syria, where
it becomes more subdued. The youngest prerift rocks are presently at a maximum
depth of about 5 km. Based primarily on interpretation of 1500 km of seismic reflection
profiles and data from 35 wells, we mapped a complex network of numerous branching
normal and strike-slip faults, generally striking northwest and west-northwest.
Both branched and single-strand linear normal faults of generally steep dip, as
well as positive and negative flower structures, are manifest on seismic sections.
No single rift-bounding fault is observed; instead, a major flexure coupled with
minor normal faulting marks the southwestern edge of the basin, with considerable
variation along strike. To the northeast, deformation diminishes on the Rawda
high near the Iraqi border. The Euphrates graben system likely formed in a transtensional
regime, with active rifting primarily restricted to the Senonian and with an estimated
maximum extension of about 6 km. Minor Cenozoic inversion of some structures also
is evident. Approximately 30 oil fields have been discovered in the Euphrates
graben system since 1984. Recoverable reserves discovered to date reportedly exceed
1 billion barrels of oil and lesser amounts of gas. Light oil is primarily found
in Lower Cretaceous sandstone reservoirs juxtaposed by normal faulting against
Upper Cretaceous synrift sources and seals.
Copyright 1998, AAPG. Reprinted by permission
of the AAPG whose permission is required for further use.
Association of Petroleum Geologists Bulletin online
Key Figures and Captions
Figure 5. Structural cross section across the Euphrates graben
system based on seismic interpretation constrained by well data. Location shown
in Figs. 2 and 4.
Figure 14. Series of schematic cross sections illustrating conceptual
evolution of the Euphrates graben system. Darkest shaded area represents most
recent sedimentation in each case.