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was undergoing calc-alkaline magmatic activity, deformation,
and simultaneous sedimentation. This is completely
different from the sediments of the stable platform
(of Arabia and Iran) in the south. Therefore two
completely different tectonic and sedimentary regimes
are represented (Fig. 10).
Thus there is evidence that in this period, Iran, southeastern
Turkey, Iraq, Syria, and parts of Afghanistan
and Pakistan were connected (via Arabia) to Africa, and
the Hercynian Ocean was to the north. This stratigraphic
evidence is consistent with the paleomagnetic data (discussed
in Section II).
1.2.2--Late Paleozoic and Middle Triassic orogenic
movements
The Late Paleozoic (Hercynian) orogenic belt is presumably
associated with the closure of the ’Hercynian
Ocean’ (we choose to name oceans after the orogenic
episode caused by their closure). The ocean was to the
north of lran (as indicated by the foregoing stratigraphic
evidence). It seems clear that subduction was restricted
to the northern side of the ocean in the Middle East
region and resulted in prolonged deformation, metamorphism,
and magmatism.
The deformation apparently started during Carboniferous
time (about 330 Ma) and finished during the Triassic
Period (about 220 Ma). Most of this deformation
appears to be associated with the northward subduction
and closure of the Hercynian Ocean. Towards the end of
the period Iran apparently moved as one or a few continental
fragments across the Hercynian Ocean, leaving
new oceanic crust behind to form the ’High-Zagros
Alpine Ocean’ in the south (Fig. 4). There is stratigraphic
evidence (continental rift volcanism and sedimentation
consistent with stretching along the Sanandaj-
Sirjan belt; Fig. 11; Section II.2.2b) that Iran and
BERBERIAN AND KING 213
some surrounding countries were becoming detached
from Arabia in Permian time (possibly around 240 Ma).
However, paleomagnetic poles indicate that lran remained
close to Arabia during at least the early part of
this period. The Upper Triassic - Jurassic pelagic sediments
along the active Central Iranian and the passive
Zagros continental margins provide the first sedimentary
evidence for the appearance of a true oceanic environment
(Table 2).
Sometime prior to the Middle Triassic orogenic phase
(210 Ma), the late Paleozoic ophiolites were emplaced
in the north, presumably at the time of the collision of
the continental fragments with Asia (Section II.2.2a).
By Middle to Late Triassic time (200 Ma) a major
difference in sedimentary environment between [ran and
Arabia on either side of the High-Zagros Alpine Ocean
is evident. While marine carbonates continued to be
1.2.l--Early Paleozoic movements (450-370 Ma)
Because of the deficiency of data, no reconstruction is
given for the time of the Early Paleozoic (Caledonian)
movements. The deposition of Upper Silurian (395 Ma)
continental sediments together with the lack of Lower
deposited in a passive environment on the Arabian foreland,
shallow lagoonal coal-beating detrital sediments
Devonian rocks in Central Iran may indicate a Late
Silurian movement (see Section II.2.1), the cause were deposited in Iran (Table 2). Furthermore, these
which is not yet understood.
were apparently continuous with similar deposits in
southern Asia (Kopeh Dagh - Turan) suggesting that
Iran and southern Asia were connected and formed a
single sedimentary province by that time (Fig. 5).
It is therefore concluded that the late Paleozoic - early
Mesozoic phase in Iran and surrounding countries was a
period when continental fragments travelled across the
Hercynian Ocean to become attached to Asia (Fig. 5).
The time taken does not appear to be greater than 40 Ma
and, based on paleomagnetic data and our reconstructions,
the continental fragments covered a distance of
about 4000 km. The necessary rate of movement of I0
cm/year is reasonable, since India split from Africa and
formed parts of the Indian Ocean at a rate of 18 crn/year.
There is some evidence of late Paleozoic low-grade
metamorphism along the Sanandaj-Sirjan belt at a time
when the paleomagnetic data indicate that the High-
Zagros Alpine Ocean had not formed in the south (Section
II.2.2b). This could be interpreted as an error in the
paleomagnetic data, with some subduction occurring on
the southern part of Central Iran along the Sanandaj-
Sirjan belt, prior to the Middle Triassic orogenic movements.
Alternatively it could be associated with the late
Paleozoic closure of the rifts formed in the second Palmrlange
belts (65 Ma), with outcrops indicated in black. The southeastern parts of the Middle Cretaceous (110 Ma) Sevan-Akera
and Vedi ophiolites of the Little Caucasus are shown in the northwestern part of the country. The extensive belts of ophiolites
mark the original zone of convergence between different blocks. The positions of ophiolites are modified by post-emplacement
convergent movements. 8. Major facies dividing basement faults, bordering different tectono-sedimentary units. Contrasting
tectono-sedimentary regimes, belts of ophiolites, and associated oceanic sediments, together with paleogeographicontrasts
along the Main Zagros (MZRF) and the High-Zagros (HZRF) reverse faults in the southwest, and the South Kopeh Dagh fault
(SKDF) in the northeast indicate the existence of old geosutures along these lines. The Chapedony and Posht-e-Badam faults
delineate the possible Precambrian island arc in eastern Cental Iran. SJMF: South Jaz Murian Fault in the southeast. 9. Late
Alpine fold axes. 10. Postulated active subduction zone of Makran in the Gulf of Oman. 11. Province boundary.
(Figure based on Berberian (1980a). Lambert Conformal Conic Projection.)