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Geol. Surv. Iran, 39, 259-269, 1976
PRE-QUATERNARY FAULTS IN IRAN
M. BERBERIAN
GEOLOGICAL SURVEY OF IRAN
Abstract
Someof the pre-Quaternary Iranian faults, extracted from the extensive literature,
have been presented. The study of pre-Quaternay faults of Iran, mostly of late Alpine
origin, is as important as that of Quaternary faults. Faults of this category should not
necessarily be considered "dead."
1.
INTRODUCTION
The pre-Quaternary faults are mostly late Alpine faults. Somefaults shown as
bounding Quaternary and older rocks are included in this category, either because
the source of mapping used was of reconnaissance nature or because the mapping was
not done with the object of dating fault movements. Faults shown in this category
should not necessarily be considered "dead": evidence for recency of movementmight
not have been observed or it may be lacking because the fault has no contact with
Quaternary deposits. In manycases the evidence may have been destroyed by erosion,
or covered by vegetation or by works of man.
These faults may be capable of generating much larger and more damaging earthquakes, some of which could be accompaniedby sudden and extensive surface faulting.
The seismically quiet parts of these faults maypose an equal or greater potential risk.
2. IRANIAN PRE-QUATERNARY FAULTS
In this study Iranian pre-Quaternary Faults are presented in alphabetical order.
For location of the faults see the Seismotectonic Mapof Iran and the Generalized
Fault Mapof Iran.
2.1. Avaj Fault
This fault crosses the village of Avaj (N of Hamadan)and continues northwest
and southeast of the village. It is a facies divider fault separating the Central Iranian
and Sanandaj-Sirjan structural belts. It has been mappedby Bolurchi (1975), whence
the following has been taken. The Avaj fault-study shows that 50kmwest of Saveh the
fault has been displaced by a northwest younger fault (the offset area is covered by
younger sediments). The Avaj fault is the largest longitudinal fault in the area and
seems to have been formed during late Triassic (Early Kimmerian)orogenic movements,
and reactivated during younger orogenic and epeirogenic movements. It is partly a
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thrust fault involving the MioceneUpper Red Formation, all the older faults being
cut by the Avaj fault.
It seems that the main differences between the Sanandaj-Sirjan and Central Iranian
zones began to appear during the late Triassic orogenic movements. According to
Berberian (1973), Paleozoic sediments of the Sanandaj-Sirjan Belt were metamorphosed
during the Early Kimmerian orogenic movements, while the Paleozoic sediments of
Central Iran NEof the belt are not metamorphosed.In the investigated area the Early
Kimmerianmetamorphics are not exposed, but there are a few differences between the
two zones along the Avaj fault during the Jurassic period. The Rheato-Liassic sediments
are well developedwith substantial thickness south of the Avaj fault but have less thickness and development north of the fault. Thus it is clear that the fault was already
formed during the Early Kimmerian orogeny.
During and after the Laramidian orogeny, the Avaj fault was one of the faults
which had great importancein the volcani~ activity of the area. Reference to the geological map of the Avaj area (Kabudar Ahang Quadrangle , in preparation) shows
that the Eocene volcanics are related to the Avaj Fault, and are exposed along it at
Kuh-e-Goujeh Yoqquz, Kuh-e-Quraqash and Kuh-e-Qareh Torpaq. The fault suffered
a tensional force and the volcanics emerged from this weakline area.
During the Pyreneean and Laramidian orogenies similar reactivation of the Avaj
fault occurred, producing volcanics along a westward branch of the Avaj fault, at
Kuh-e-Panjeh Angosht, Kuh-e-Quravolkhaneh and Kuh-e-Boland. During the younger
movementsthe Avaj fault was reactivated, and in some places the Eocene pyroclastics
and metamorphosed Jurassic rocks were thrust over the Miocene Upper Red Formation along the fault.
It should be remarked that the Avaj fault has different movementsalong its respective sectors, for example, two thrust sections have been recognized along it. Thus
it seems that the Avaj fault is a Reverse fault with low and high angle effects. A few
epicentres have been recorded along the Avaj fault (1900-1976).
2.2. Attari Fault
The southern Alborz is limited to the south in the Semnan-Djam
area by the paleogeographic divide between the Alborz and Central Iran. This structure, named the
Attari accident by Alavi (1972) and Alavi and Flandrin (1970), has existed since
brian times and has been intermittently reactivated up to the Recent period. The direction of the fault is NE-SW.Only one important epicentre is located along the Attari
fault.
2.3. KandevanFault
The Kandevanfault is a persistent fault in the Alborz Mountains (SWAlamkuh),
striking WNW-ESE.
It is a steep southward reverse fault with some right-lateral slip
°movements, which amount to several kilometres. The fault dips north at 30°to 90
and has some associated mylonite zones. It has been partly mappedby Glaus (1965)
as the Kandevan fault and by Assereto (1966) as the Kandevan upthrust. Allenbach
(1966) mentioned that the Baidjan high angle reverse fault (Haraz Road, north
Gazanak) might be the eastern extension of the Kandevan fault.
According to Glaus (1965), the average dip of the fault in the Kandevanarea
PRE-QUATERNARYIFAULTS
261
30° to 60° towards the north, but towards the west the dip of the fault increases to
70° and 90° (southwest of Alamkuh). Near Anguran a vertical movementof 1000m
can be seen, while in the western part of Anguranthe horizonal displacement of the
fault is clear. It seems that the Kandevanfault marks the northern limit of the Eocene
sea.
Accordingto Assereto (1966) the fault is a fundamentalline in the upper Jajrud-Lar
area, which involves the Precambrian crystalline basement. It has a WNW-ESE
strike
and a steep dip to the north, and puts into contact two regions with differing structural
styles: the Paleozoic Central Zone to the north, characterized by a gentle fold style
and vertical block faulting, and the Tertiary Central Zone to the south in which a more
plastic style prevails, with isoclinal folds and overthrusts. The differences in the stratigraphic successions of the area to the north and south of this line seem to indicate that
the Kandevanis an old fault, which has been active since at least the early Cretaceous
and perhaps corresponds to an ancient Precambrian dislocation. No epicentre is located
on or along the Kandevan fault.
2.4. MainZagros Reverse Fault (the former MainZagros thrust)
The Main Zagros Reverse fault has a remarkably straight NW-SEalinement and
is a deep reverse fault, splitting a once-coherent Precambrianplatform into an Arabian
Fig. 1o MainZagrosReverseFault plane in Hadjiabad(180kin north of BandarAbbas). Looking
WeSt.
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and an Iranian fraction. The first evidence for the partition originated in Infracambrian
times, when a gentle, southwestfacing slope along the later reverse fault line limited
the Hormozsalt basin on the northeast (St6cklin 1968). The slope was smoothed out
during Paleozoic times but reappeared in more accentuated form in Rhaetic-Liassic
times, when the Zagros trough began to take shape and was bordered along the later
Main Reverse Fault line by the continental plrtteau of Central Iran. The Main Zagros
Reverse Fault was already an important tectonic divide during the Mesozoic. Along
the fault and in the southern part, the thickest development of the Zagros sediment
is found, together with a flyschlike facies in the youngest Mesozoicand older Tertiary.
These, as well as coloured m61angeof the Upper Cretaceous, indicate a markedunrest
not otherwise present in the Zagros range. A considerable amountof crustal shortening
must be assumed along this major tectonic trend.
Originally the Main Zagros Reverse Fault was identified with a simple thrust
line which had appeared on early geological maps and showed a conspicuous straight
alinement; faulting was thought to have been related to downwarpingof the Arabian
Plate margin, followed by its underthrusting below Central Iran (Falcon 1967, St6cklin
1968), Lees and Richardson (1940) namedthis fault zone the "zone of overthrusting"
and put a dashed line on their map, namingit the "approximate SWboundary of overthrust zone". Gansser (1955) used the term "Main Thrust Line."
Wellman(1966, 1969) included the Zagros fault line of Iran amongst the "major
wrench faults of the world" (mostly active). No evidence is given by Wellmanbut
reference is made to earlier papers by Pavoni (1961), and himself(1966). Pavoni
suggested by means of a dashed line on a small scale mapthat the Zagros fault line
might be a continuation of the Anatolian Fault line, although the largest tectonic map
of the world, based on all available geological maps, disagrees. Wellman’sconception
comes from a study of small scale aerial photograph mosaics and his evidence is
topographical rather than geological. In his own words evidence for horizontal movement along this 1200 kmfault line was found in three places only: "the best locality
shows tailing streams and three small streams that appear to have been displaced by
about 100m. At the other localities there are a possibly displaced spur and stream~.
All displaced features favour dextral displacement, but none is conclusive"
Falcon (1967) used the term "Zagros Thrust" and described it as a south-western
front of a belt of intense compression, over 800 miles long in Iran. He added that
"from late Triassic times until the onset of the Mio-Plioceneorogeny the facts of geology indicate that the Zagros thrust tectonic line separated a relatively stable Arabian
shield area from a mobile area north-east of it".
St6cklin (1968) stated that "the most important result of the late Triassic movements in Iran was the splitting of the Paleozoic platform into two parts, which subse..
quently took entirely different courses of structural development. The line separating
the two parts of the platform is the sameas that which was apparent as a facies divider
during the Infracambrian and which later, during the Alpine orogeny, developed into
the Main Zagros Thrust line".
A recent analysis of the Zagros line by Brand and Ricou (1971) has shown that
there are two major thrust faults, roughly parallel, sometimescoincident, but in places
departing from each other considerably. They are slightly different in age, but both
Fig. 2,3. MainZagros Reverse Fault in Hadjiabad. The Maestrichtian coloured m61angeof SanandajSirjan Belt (Central Iran; to the right) is thrust over the Plio-Pleistocene Ba!~htiari conglomerate of Zagros Active Folded Belt (left). Lookingwest.
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affect rocks as young as Miocene. The older, southwesterly, one is a low-angle thrust,
marking the actual southwestward overthrust of Central Iran on the Zagros, with a
horizontal displacement thought to be at least 40kin. The younger one is a steeply
northeast-dipping to subvertical reverse fault with a right-lateral componentof unknownmagnitude. There is no doubt, however, that the double line of faulting and
thrusting is but the reactivation of a mucholder rift (St6cklin, 1974).
Tchalenko and Braud (1974) named the younger fault the "Main Recent Fault",
a late Quaternaryright-lateral wrenchen 6chelon fault. In a discussion of the seismicity
of the MainRecent Fault between latitudes 33° and 35° N, they gave details of several
destructive earthquakes associated with the fault.
In Hadjiabad (180 km N of Bandar Abbas) the Main Zagros Reverse fault has
steep dip (Fig. 1) towards NEand in this area the Maestrichtian coloured m61ange
of Sanandaj-Sirjan Belt is thrust over the Plio-Pleistocene Bakhtiari congomerateof the
Zagros Active Folded Belt (Figs. 2 and 3). On the Main Zagros Reverse fault plane
a set of slickensides can be seen which indicates the latest movementof the fault
(Fig. 4). The reason for choosing the term "Main Zagros Reverse Fault" is that the
fault’s various segments have differing angles of dip.
Fig. 4. Slickensides over the MainZagros ReverseFault plane in Hadjiabad. Lookingsouth.
PRE-QUATERNARYFAULTS
265
2.3. MushaFault
The MushaFault is situated to the north of Tehran and is concave towards the
north. It was named the Musha-Fasham Fault by Dellenbach (1964) and Tchalenko
et al. (1974), the Southern Main Thrust by Lorenz (1964), the Mingun-MushaThrust
by Assereto (1966), and the Main Thrust by Allenbach (1966) and Cartier (1972).
fault extends from the edge of the mountain range in the west to the eastern Alborz.
Its trace is sinuous in plan, with an E-Wstrike in the west, and a WNW-ESE
strike
in the central sector, gradually bending to E-Win the east. Dips occur everywhere
to the north, varying between 35° and 70°. The thrust movementson this fault were
initiated before the Jurassic, and cumulative displacements amount to at least 4km
(Allenbach 1966, Steiger 1966, Tchalenko et al. 1974). Detailed mappingin the east
in the Musha-Mobarakabadvalley (Dellenbach, 1964) and in the extreme west near
Abeyek($ieber, 1970) indicates that the latest fault reactivation occurred sometime
after the Pliocene. Tchalenko(1974) stated that there is evidence for the fault having
been seismically active in ihistorical times as well as in the 20th century (Ah-Mobarakabad earthquake of 2 October 1930 and Musha earthquake of 24 November 1955).
Accordingto Stocklin (1964) the fault is steep (60°) and south-thrust in the west
and steep and north-thrust in the east. Movementscommencedin Pliocene or earlier
times and ceased in the Pliocene to Pleistocene interval. Displacement amounts to
several kilometres; Infracambrian is thrust onto Miocene.
According to Assereto (1966) the fault is one of the fundamental faults of the
central Alborz. Its trace can be followed for at least 170kmfrom Abeyekto Firuzkuh
and it has carried Infracambrian and Paleozoic sediments of the southern Paleozoic/
Mesozoic zone across intensely folded formations of the southern Tertiary zone.
The fault can be considered an upthrust in some places and an overthrust in others.
Significant facies differences on either side of the fault, in rocks as old as Cambrian,
indicated a very long history of movement,and for this reason Assereto believed this
fault to be fundamental in nature, deepseated and steep at depth.
2.6. Nainl Fault
This fault is situated in the western part of the Kalmardfault in East Central
Iran. The fault was mappedby Aghanabati (1975). According to him, the Naini fault
is covered by Quaternary deposits in the investigated area. The fault seems to be the
eastern limit of the Precambrian high grade metamorphics. The metamorphosedPrecambrian rocks face Jurassic sediments along this fault; thus vertical movementwas
important along it. During late Triassic movements, the reactivation of the Naini
fault recrystallized the Triassic sediments. No epicentre is located along the fault.
2.7. North Alborz Fault
This fault has a sinuous shape in plan and is concavetowards the north. It borders
the northern part of the Alborz Mountains, southwest of the Caspian Sea, but then
goes inside the mountains towards the east. Its total length is about 400km.The fault
is a steep, N-directed reverse fault with displacement exceeding 2kmalong it. Some
mylonite is present and movementsseem to have commencedin Pliocene or earlier
times and ceased in the Pliocene to Pleistocene interval (Stocklin 1960, 1974). A few
shallow earthquake epicentres are located on the North Alborz Fault.
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2.8. RudanFault
Rudan fault is situated northeast of Rudan (NE Minab), between Rudan and
Faryab. The trend of the fault is approximately NW-SE.Just east of the tunnel (south
of the road), metamorphic rocks of green schist facies are thrusted over coloured
m61ange(Fig. 5). The dip of the ault on the surface is 32 degrees towards NE, and the
northeastern block is thrusted over the southwestern block. Along the thrust, a crush
and mylonitized zone can be seen. A few epicentres are located along the Rudanfault.
2.9. Soltanieh Fault
The major part of the Soltanieh Fault (south of Zanjan) was mappedby St6cklin
et a1.(1965, 1969) and designated a border fault. The fault, whichis parallel to the Soltanieh Mountains and borders the northeast part of that range, separates the higher
mountains of Soltanieh (Precambrian, Paleozoic, Mesozoic) from the Eocene volcanic
belt in the northeast. The fault has a NW-SEtrend and is more than 150 km long.
Along this longitudinal fault the pre-Tertiary formations (Precambian-Mesozoic)
the Soltanieh mountains (horst) have been faulted against and partly thrust over the
Tertiary fill of the Zanjan-Abhar depression. This major fault is subvertical at the
Fig. 5. RudanFault. Themetamorphic
rocks of Paleozicage (?) are thrust over the colouredm61ange
(black) of Maestrichtianage. LookingNW.
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267
mountain border of Soltanieh but farther southeast, at Ardehin (east of Abhar),
changes into a thrust plane dipping 30° - 40° southwest. The fault was reactivated
by the Pliocene phase.
The Soltanieh Fault, however,loses its character as a border fault in the northwestern part of the range. There, at Gordanap, it turns from a northwestern into a westnorthwestern direction, is dissected by transversal faults near Qazavat and continues
as the thrust fault of Barut Aghaji in the interior of the range. In the southeastern sector
of the range, from Veyar southeastward, it gradually develops from a nearly vertical
border fault into a fiat border-thrust. This is well exposedat Alagozir, where the thrust
plane dips 30° to 40° southwest, with shales and dolomites of the Kahar Formation
over-riding subfolded tufts of the Karaj Formation. Generally the fault coincides with
the southwestern limit of the Eoceneformations, and it has certainly played its part in
the formation of the Eocenetrough itself. Its origin therefore dates back to pre-Eocene
time, and probably to some of the older, epeirogenic movements(Stocklin et al.
1965, 1969). No epicentre (1900-1976) is located on the Soltanieh fault.
2.10. TaleqanFault
This fault is situated in the southern part of the Kandevanfault with nearly E-W
direction. Parts of this fault were mappedas the Garmabdaroverthrust by Assereto
(1966), and the Taleqan thrust by Dedual (1967) and Meyer (1967). Allenbach
considered the Valar Rud fault (west of Damavand)and Shahan Dasht (east of Damavand) to be the eastern extension of the Taleqan fault (?).
According to Assereto (1966) the Garmabadar overthrust in the Jajerud-Lar
area has a trace which is more or less parallel to the Kandevanupthrust. It dips north
at a low angle, and has carried the strongly folded sediments of the Tertiary Central
zone across the more competent formations of the southern Paleozoic / Mesozoic
zone. The thrust movementmostly occurred at the level of the ShemshakFormation,
which, by virtue of its plasticity, favoured the movement.In the valley of the Jajerud
the distance of tectonic transport is estimated at morethan 5km.It is likely that the line
of Garmabdarinvolves only the sedimentary cover and does not reach into the crystalline basment. Assereto believed that the origin of this line is related to the tectonic
shortening to which the plastic Tertiary sediments have been subjected, as a result of
the formation of the Kandevan upthrust. One epicentre is located on the Taleqan
fault.
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