The sedimentology of the Upper Khami Group, Lower Cretaceous, in East Khuzestan Southwest Iran
The Lower Cretaceous Upper Khami Group is a widespread
stratigraphic unit in the Zagros Mountains of southwest Iran.
It is represented by two facies, the depostion of which was
influenced by a hinge line which trended northeast -
southwest. Shallow marine carbonates developed on the
platform to the east with a deeper water radiolarian facies to
On the platform the whole group comprises a megacyc10them
which can be divided into two shallowing-up (regressive)
The lower cyclothem is minor transgressive - major regressive,
and is deve~oped throughout the region. It records a
predominantly regressive sequence of carbonates which formed
in response to rapid sedimentation rates in excess of
subsidence. The minor transgressive phase which initiated
the cycle is thought to have been due to local fluctuations of
relative sea level. Shallow marine sub-tida1/inter-tida1
carbonate sediments together with more argillaceous deeper
water carbonates form the bulk of this sequence.
The upper. cyclothem is major transgressive - minor regressive,
and can only be recognised as a cycle in the eastern part of
the study area where the transgressive and regressive phases
can be identified. The transgression, believed to have been
caused by eustatic sea level rise, is suggested by the
dominance of argillaceous units with only minor carbonates.
All of these were deposited below wave base in environments of
wide lateral extent which ranged from open marine to distal
deeper marine. The regressive phase of shallow marine
carbonate sedimentation terminates this upper cyclothem in the
eastern part of the area.
Twelve lithofacies were recognised in the course of field work
and later petrographic studies. Features studied for
environmental subdivision include: sedimentary structures and
textures, composition, palaeoecology and early diagene~is,
combined with a review of similar features in Quaternary and
ancient carbonate sediments.