the beginning of the sixth sequence (top of d-Member).
Foraminiferal fauna and bioturbation in marls above the
gypsum (e-Member) documents reconstitution of fully
marine conditions with rising relative sea-level. The suc-
cession of benthic foraminiferal assemblages from the
e-Member marls (substitution of a shallow Textularia–
Spirorutilus–Baggina–Fontbotia assemblage by a deeper
Uvigerina–Cibicidoides–Heterolepa assemblage) displays
the deepening trend. In contrast, the overlying bioclastic
limestone succession of the lower subunit of the f-Member
(53–75) developed during the regressional stage of the
sixth sequence because of the dominance of light-depen-
dent biota. Corals are restricted to the uppermost part of the
sixth sequence (73) during which a suitable shallow water
depth was reached. The sixth sequence terminates with an
erosional surface that indicates emersion (base of bed 76)
and is interpreted as a sequence boundary.
The middle subunit of the f-Member includes the low- and
highstand deposits of a seventh sequence. With rising water
depth corallinacean limestones (76–101) developed in a
shallow to moderately deep environment as indicated by the
associated coral faunas. The above following marl interbeds
with plankton (102–108) indicate continued deepening.
A new shallowing trend is reflected by the corallinacean
limestone package in the upper subunit of the f-Member
(109–123). Fragmentation of skeletal grains and the pre-
dominantly grain-supported textures point to a turbulent
regime during deposition of these beds. Associated patch
reefs with Caulastrea and faviids also reflect a shallow
water depth. Their surrounding sediments are composed of
porcellaneous miliolid and soritid foraminifers, which
document seagrass vegetation in a shallow, restricted, inner
ramp environment (Fig.
10
b; Sen Gupta
1999
). The tran-
sition into the continental Lower Red Fm. is gradual and
without hiatus. Obvious is the drastic increase of fine si-
liciclastic material that interfingers with the bioclastic
limestone, which was formed in a low energy, marginal
marine environment (Harzhauser
2000
) as shown by
intercalated coquinas of the marsh clam Polymesoda aff.
brogniarti and an increasing terrigenous influx.
Chalheghareh section
Section Chalheghareh (Fig.
9
) contains four depositional
sequences. The mixed siliciclastic-carbonate sedimentary
succession at the base of the first sequence (1–28) indicates a
high-frequency oscillating relative sea-level. Cross-bedded
grainstones and siliciclastics with marine biota (1–3, 7–9)
refer to the shallow subtidal zone, while an intercalated
biolaminite (6) represents the intertidal zone, and a reddish
horizon (3) even indicates emersion and pedogenesis.
Upsection the decrease in grain size of terrigenous particles,
the loss of intertidal deposits, and the increase of marly
lithologies with plankton provide evidence for increased
water depth. Subsequently, decreasing water depth is rep-
resented by intercalations of bioclastic limestones that were
exported from a shallower source area, as indicated by the
mixture of deeper water (planktic foraminifers, delicate
branching bryozoans) and shallower water biota (corals,
mollusks, corallinaceans), and the high degree of fragmen-
tation of skeletal grains. One limestone bed documents a
high-energy regime due to a large-scale, cross-bedding
texture (40) and is therefore suggested to represent the rel-
ative sea-level lowstand of sequence two. In the marls above
the increase in quantity and diversity of bryozoans, espe-
cially of those with erect growth types, suggests an increase
in water depth. Bryozoan diversity and frequency is highest
in bed 58 and the large size of bryozoan colony fragments
points to a more or less in situ deposition. Floatstones with a
non-framework forming coral assemblage (65) are assigned
to moderately deep environments and imply an environ-
mental change back to shallower conditions.
During step-wise changes in sea-level, a turbulent regime
in the shallow subtidal was intermittently installed, as
indicated by the presence of cross-bedded (67–75) and
oolithic limestones (67–68). These coarser-grained units are
intercalated between marls containing planktic foramini-
fers. Terrigenous material occurring together with black
pebbles (79–83), and the first occurrence of evaporites (92)
characterize the relative sea-level lowstand at the beginning
of sequence three. Marls from above the lower gypsum unit
are interpreted to have formed in very shallow conditions
due to the occurrence of the benthic Jadammina–Ammo-
tium–Ammobaculites assemblage (93), which is typical for
coastal marshes (Sen Gupta
1999
), although planktic
foraminifers are also present, pointing to marine conditions
in the central basin. A bed containing gypsum intraclasts in
the upper gypsum unit (95) provides evidence for subaerial
exposure and reworking of previously precipitated material.
The upper gypsum unit is therefore interpreted as lowstand
deposit initiating the fourth sequence.
A thick marl unit (96–97) follows above the gypsum,
displaying onset of marine conditions by the presence of
planktic organisms. The overlying bioclastic limestone
succession again displays decreasing water depth. Rhodo-
lites, as well as the grain-supported texture and well
sorting, point to a turbulent water regime. Widely traceable
Kuphus-coquinas (103, 105) are interpreted as tempestites
and document deposition above the storm wave base. Karst
cavities on top of the bioclastic limestone package are
filled with sediments of the Upper Red Fm., documenting
emersion and erosion of the Qom Fm. sediments prior to
formation of the Upper Red Fm. (Fig.
5
f).
Int J Earth Sci (Geol Rundsch)
123