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BERBERIAN AND KING 225
TABLE 3. Correlation chart of the major Tertiary rock units, sedimentary gaps (blank areas), and unconformities (indented lines)
in Arabiand Iran. The Makran and Alborz units are divided into north (n) and south (s), and the Talesh into west (w) and east
S-S Central I. Lut Make’an Zabol-Ba
~b iJrnz ~ TaleShwl$ Caspian KopehD~
÷ ~ ._-..-.:..-~
Rb/Sr total-rock techniques have failed (Crawford
1977), and the Precambrian rocks remain geochronologically
unclassified. At this stage the Precambrian
metamorphic rocks of Iran can only be categorized into
high-grade (amphibolite facies) and low-grade (greenschist
facies) groups (Stocklin 1968a, 1974, 1977;
Hushmandzadeh 1973; Haghipour 1974, 1977).
After the metamorphism of the Precambrian formations
and the establishment of the Arabo-Iranian coherent
platform at the end of the Katangan orogeny (Fig. 3),
the compressional tectonic activity ended with granitic
intrusions and alkali volcanism (Fig. 10). The Upper
Precambrian alkali-enriched Doran granites of Iran
(Stocklin et al. 1964) seem to be equivalents of the 600
Ma Younger Granites of Arabia (Schmidt et al. 1973,
1978; Sillitoe 1979). The Doran granite cuts the Upper
Precambrian low-grade metamorphic rocks of the Kahar
Formation (Stocklin et al. 1964) and is covered by
Lower Cambrian sediments.
Late Precambrian post-orogenic volcanics, which are
partly the extrusive equivalents of the Doran granite,
and are mainly alkali rhyolite, rhyolitic tuff, and quartz
porphyry, form the Gharadash Formation in northwestern
Iran (Stocklin 1972), the Taknar Formation in the
Kashmar region, northeastern Iran (Razaghmanesh
1968), the Rizu-Desu Series (or Esfordi Formation)
......................, v U.R.~.,.~.~., **** k:::--:5:,’""~
~ ~- ~ ~. ~. ~- ~ ~- ~- ~- %* .....
::::::::::::::::::::::::::::::: - ÷ ¯ ~--:.!i
~::-’-’-’:-’-’: ~
- ÷i ::::::::::::::::::::::::::::"::’:’:"
"~ "" .....
-~.’° ,...:
............. .~.-~
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oo÷, .÷÷, ÷.. ÷÷’ ÷’
I
÷’ ::::::::::::::::::::::::::::
}::::::}::::}i
i Iil
}}}
¯ ....,÷÷o,°~a*’ ..............
~.÷++÷÷++÷~ .÷÷÷÷o÷÷,:i:~r":::i:i:i:!:~![
:::::2:: 2:::2::: ::::::::::::::::::::::::::::
’N
+ ,÷÷÷÷,,÷÷÷~
° ° ’°°*° ° ~ : *°°°...... .-.-,-.-.~v.v ,’:’:’:+~"~’~"v"’ ::::::::::::::::::::::
:::::::::::::::::::::::::::::::::::::::::::::::::::::
¯ ,~... o.o.~...-.......-.t:.............................,
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~ :-:-:-:-:-:-:-:-:-:
southeastern Central Iran (Huckriede et al. 1962; Forster
et al. 1973), and the Hormoz Formation in Zagros
(Stocklin 1972; Kent 1979). The late Precambrian volcanics
also include some andesite, basalt, and tuff.
These widespread ’post-orogenic’ volcanic rocks,
which overlie the Precambrian metamorphic rocks and
are overlain by the Upper Precambrian - Cambrian
sediments, may indicate the ’stretching’ of the Arabo-
Iranian coherent continental crust during an extensional
phase. This could have been associated with the formation
of the epicontinental platform from Arabia to A1-
borz prior to the deposition of the Upper Precambrian -
Cambrian sediments. Similar post-orogenic rhyolitic
pyroclastic rocks, lavas, and subordinate basaltic volcanics
of alkali affinity have been developed on the
Arabian-Nubian Shield (the Shammar Group) during
663 to 555 Ma (Brown and Coleman 1972; Sillitoe 1979;
Brown and Jackson 1979; Table 1). Although alkali
basalt is a typical member of the rifting magmatism,
extensional tectonics in the continental crust also permits
rapid rise of rhyolites and acid plutons (Bailey
1974; Eichelberger 1978).
During this general rifting and sinking phase of northeastern
Arabia, the Main Zagros, High-Zagros, Nayband,
and some other major faults appear to have acted
as facies dividers separating the main Hormoz evaporitic
Great Caucasian miogeosyncline). 10. Intrusive rocks. 11. Approximate boundary between different sedimentary facies. 12.
Subduction zone, with triangles on the upper plate. 13. Reverse faults, with bars on the upper plate. 14. Present continental
shorelines.
Principal sources of data: Reconstruction (Mercartor Conformal Projection) is modified from Smith and Briden (1977).
tectono-sedimentary data within the boundaries of Iran are based on our Fig. 15. Data outside Iran come from Grossheim and
Khain (1968), Ricou (1974), and Bij u-Duval et al. (1977) for the westernmost part, and Powell (1979) for the north Indian part.