PDF COPY - Manuel berberian

Geirud Formation in the Alborz mountains (Assereto
1963; Sieber 1970), in the Khoshyeilagh Formation of
the Jajarm area, northeast Iran (Bozorgnia 1973), in the
Talesh mountains (Davies et al. 1972; Clark et al.
1975), and in the Anarak region in Central Iran (Reyre
and Mohafez 1972). Post-Silurian pre-Carboniferous
basic volcanics under a cover of Permo-Carboniferous
limestone, together with a Lower Carboniferous andesite,
are reported from the Talesh mountains, southwest
of the Caspian Sea (Clark et al. 1975; Table 1). The
Devonian-Carboniferous basalts along the Sanandaj-
Sirjan belt (Berberian and Nogol 1974; Berthier et al.
1974; Berberian 1977a; Alric and Virlogeux 1977) suggest
rifting during this phase. Subsequent closure of the
rift seems to be responsible for the late Paleozoic (Hercynian)
low-grade metamorphism along the belt (see
Section II.2.2b; and Fig. 11).
lI.2a.l.3--Permian-Triassic extensional phase--This
is an important rifting phase which apparently marks the
onset of the opening of the High-Zagros Alpine and the
narrow Central Iranian ocean belts (see Section 11.2.2,
and Figs. 4 and 11). No previous extensional phase left
any evidence of having produced oceanic crust. This
phase is mainly developed along the Sanandaj-Sirjan
belt with basic (basalt, diabase, and some intermediate)
volcanic activity (Thiele et al. 1968; Dimitrijevic 1973;
Berberian and Nogol 1974; Berthier et al. 1974; Berberian
1977a; Alric and Virlogeux 1977; Table 1). Some
Permian andesitic volcanics are reported from the Talesh
mountains of the southwest Caspian Sea (Davies et
al. 1972; Clark et al. 1975). Lower Permian basic volcanics
also occurred in the Dorud and Ruteh Formations
of the Qazvin area (Annells et al. 1975). There is only
one example of basaltic flow of Permian age reported
from the High-Zagros belt, west of Dehbid (Hushmandzadeh
1977).
H.2a.2--Paleozoic paleomagnetic data
The geological observations indicating a coherent
Iranian-Gondwanaland continental landmass during the
late Precambrian to Permian time interval are consistent
with the paleomagnetic results. Paleomagnetic evidence
from the Upper Precambrian rocks and iron ores of the
Central Iranian Bafq area (Becket et al. 1973), from the
Lower Paleozoic rocks of Kuh-e-Gahkom and Surmeh
of the Zagros belt (Burek and Furst 1975), from the
Cambrian Purple Sandstone of the Salt Range of Pakistan
(McElhinny 1970), from the upper Devonian
lower Carboniferous Geirud Formation of the Alborz
mountain in north Iran (Wensink et al. 1978), and from
the Upper Precambrian, Ordovician, and Permian rocks
of Central Iran (Soffel et al. 1975; Sorrel and Forster
1977) show similar virtual geomagnetic poles with those
of Afro-Arabia. This and the widespread similarity of
Paleozoic sedimentation (Table 1) indicate that during
BERBERIAN AND KING 231
the late Precambrian and Paleozoic, Central Iran, the
Alborz in northern Iran, the Salt Ranges of Pakistan in
the east, the Zagros in south Iran, and much of southeastern
Turkey, were parts of Gondwanaland (Fig. 3).
However, they do not eliminate the possibility of large
latitudinal differences.
H.2b--Asiatic northern Iran (Kopeh Dagh belt) during
the Paleozoic Era
There is a major difference between the Paleozoic -
early Mesozoic history of Iran in the south and that of the
Kopeh Dagh and Great Caucasus - Transcaucasian median
mass in the north. In contrast to the Iranian Paleozoic
stable platform-type shelf sedimentation (absence
of granitic intrusion or widespread volcanic activity and
unconformities), an eugeosynclinal regime with widespread
subsidence, uplift, granitization, volcanism, regional
metamorphism, and folding existed in the Caucasus
and Kopeh Dagh during Paleozoic time (Keller
and Predtechensky 1968; Nalvkin and Posner 1968;
Adamia 1968, 1975; Belov 1972; Khain 1975; Adamia
et al. 1977). The geosynclinal regime in the Great
Caucasus began in early Cambrian time. This Paleozoic
geosynclinal basin encompassed the areas of the Front
Range, the Main Range, and the South Slope of the
Great Caucasus. In the north, it was bordered by the
Cherkassy-Kislovodsk uplift and in the south by the
Transcaucasian median mass (Belov 1972). Adamia et
al. (1977) assumed that the axial part of the Tethys
Paleozoic and Mesozoic times ran across the Sevan-
Akera ophiolite belt of the Little Caucasus, northwest of
Iran (Fig. 1).
ll.2.1--Early Paleozoic (Caledonian) movements (450-
390 Ma)
During the Ordovician - early Devonian time interval,
the Caledonian orogeny affected the North Atlantic
region. The Caledonian fold belt in northwestern Europe
originated with the closure of the Caledonian (Iapatus)
Ocean. The Iapatus Ocean, which separated Laurentia
(North America) and Baltica (northern Europe), closed
along the Acadian-Caledonian eugeosynclinal belt of
northern Europe and eastern North America (Dewey
1969; Bird and Dewey 1970; Ziegler et al. 1979). North
America, Greenland, and the Russian platform were united
into a single continental mass, Laurasia. Farther
east, Hamilton (1970) suggested that the Russian plate
and an island arc collided in early Devonian time.
Iran being far from this collision zone suffered only
epeirogenic movements characterized by regional
regression of the Silurian sea (Table 1) and regional
disconformity and some local unconformities (in the
north) at the base of the Middle-Upper Devonian rocks
(Stocklin 1968a; Nabavi 1975, 1976; Berberian 1976a).
The large Silurian--Carboniferous sedimentary gap in
the Zagros (following the Ordovician and (or) lower