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The sedimentation of Makran flysch continued until
Oligocene time (Fig. 16). According to Ahmed (1969)
the Oligocene Epoch marked the beginning of the final
regression covering the margins of the Makran basin and
a fundamental change in sedimentation, with an absence
of carbonates and the deposition of thick sandstone and
shale units. It is known that a substantial thickness of
Paleogene and Neogene sediment is present off the
Oman coast, where refraction profiles in the westcentral
Gulf of Oman are interpreted to indicate 3.7 km
of sediments on oceanic crust (Closs et al 1969; Gealey
1977).
Towards the end of the Middle Alpine, the Zabol-
Baluch flysch basin progressively dried up, and the
sediments were folded, thrusted, and uplifted by the end
of the Oligocene Epoch. Absence of Tertiary arcmagmatism
in Makran may indicate a very low angle
descending oceanic crust.
H.6d--Kopeh Dagh basin during Middle Alpine time
In the Kopeh Dagh basin, like the Zagros, Eocene
volcanic rocks are absent, indicating a non-volcanic
basin in which marine sediments were deposited (Fig.
15). In late Paleocene to early Eocene time, the last
marine transgression covered the northern and eastern
part of the Kopeh Dagh basin. The Middle-Upper
Eocene to Lower Oligocene Khangiran Formation
(shale, gypsiferous mudstone with limestone concentrations,
and siltstone) is the youngest shallow marine or
brackish water deposit in the eastern and central Kopeh
Dagh (Afshar Harb 1969, 1979; see Table 3). After the
deposition of the Khangiran Formation the last epeirogenic
movement occurred in late Eocene - early Oligocene
time (37 Ma), uplifting the entire region, and
causing the last regression of the Tertiary sea. The
regression started in late Middle Eocene time, from west
Kopeh Dagh, and reached the east at the end of the late
Eocene or probably in early Oligocene time (Afshar
Harb 1969, 1970, 1979). Therefore the Kopeh Dagh
formed a mountain belt since early-to-middle Oligocene
time (Fig. 16). The post-Lower Oligocene (probably
Miocene) continental red beds (similar to the Upper Red
Formation of Central Iran) conformably overlie the
Khangiran Formation in Sarakhs and Daregaz areas
(Table 3).
II.7--LATE ALPINE MOVEMENTS (