Turkish Journal of Earth Sciences Turkish J Earth Sci (2014) 23: 602-614 http://journals.tubitak.gov.tr/earth/ © TÜBİTAK Research Article doi:10.3906/yer-1311-14

Quaternary travertine ridges in the area: active extension in NW

1, 2 Mohammad MOHAJJEL *, Karim TAGHIPOUR 1 Department of Geology, Tarbiat Modares University, , Iran 2 Department of Geology, University of , Birjand, Iran

Received: 16.11.2013 Accepted: 16.07.2014 Published Online: 03.11.2014 Printed: 28.11.2014

Abstract: The Lake Urmia area is surrounded by several major active oblique-slip faults with dextral and normal offsets. Extensive travertine ridges were produced along the E-W up to NW-SE trending extension fractures in the Lake Urmia area, NW Iran. These fractures are parallel to subparallel with abundant normal faults. Pliocene-Quaternary volcanic domes occur in the area and their activities tend toward apparent distinction between colored travertine layers and ridges. Two different modes of banded travertine within the fissures and layered travertine on the surface are observed. Some banded travertines are not vertical and obviously were tilted. Layered travertines were cut, rotated, and displaced sequentially by NW-SE oriented normal faults. Local collapsed areas are produced subparallel to the extension fractures, implying that extension in the area has continued to recent time. We conclude that extensive deposition of travertine is produced along extension fractures with volcanic activity and active oblique-slip normal faults indicating regional extension in the Lake Urmia area. The Lake Urmia area in NW Iran is not only situated in an active tectonic region in junction with Anatolia, escaping to the west, and the Iranian microcontinent, escaping to southeast along the major strike-slip faults, but it is also located at the extension termination of the Main Recent .

Key words: Active extension, Main Recent Fault, NW Iran, travertine ridges, Lake Urmia

1. Introduction 2 km in length east of Lake Urmia (Figure 1). Abundant Travertine is attributed to out-flowing acidic groundwater Quaternary volcanic domes and basaltic and andesitic along the faults and fractures (Chafets and Folk, 1984; lavas are exposed in the Lake Urmia area of NW Iran Altunel and Hancock, 1993). Geometry and kinematics (Shahrabi et al., 1985; Kheirkhah et al., 2009). of the fissure-ridge travertines are well detailed in several In this study, the geometry and kinematic evidence studies (e.g., Altunel and Hancock, 1993, 1996; Mesci et of active extension fractures and synchronous travertine al., 2008, 2013; Mesci, 2012). Faults and fissures play a precipitation are documented in the eastern part of Lake major role in moving hydrothermal fluids to the surface. Urmia in the Azarshahr area. Extension directions have The relationship of travertine to active tectonics and the been determined from the orientation of fibers existing in role of faults and fractures in conducting hot water to the the banded travertines of vertical fractures. Their structural surface were examined in different cases (e.g., Altunel relations to regional extension in the Lake Urmia area in and Hancock, 1993; Ford and Pedley, 1996; Hancock et association with dextral, oblique-slip normal faults are al., 1999; Mesci et al., 2008). Timing of fissure generation attributed to the regional extension in NW Iran located in related to late Quaternary seismic events was also the extensional termination of the NW-SE oriented strike- documented (Uysal et al., 2007; Faccena et al., 2008). There slip active, Main Recent Fault of the Zagros suture zone, is an intimate tectonic relationship between active zones . and travertine formation. Tectonic deformation forming the fissure-ridge travertines results from extension (Mesci 2. Regional geology of the Lake Urmia area et al., 2008). Therefore, it is a good indicator for regional Lake Urmia is a very large (5000 km2), shallow (8–12 m), extension direction (Altunel and Hancock 1993, 2005; hypersaline lake with surface water salinities of more than Çakır, 1999; Mesci, 2012). 200 g/L, situated in a subsiding tectonic basin in NW Iran Extensive fissure-ridge travertines (Bargar, 1978; (Berberian and Arshadi, 1975; Kelts and Shahrabi, 1986). Chafets and Folk, 1984) occur in vast areas, each up to Palynological evidence from Lake Urmia indicates a late 150 m above the surrounding cultivated areas and up to Pleistocene to early Holocene history (Jamali et al., 2008). * Correspondence: [email protected] 602 MOHAJJEL and TAGHIPOUR / Turkish J Earth Sci

Figure 1. a) Some major active faults in Iran, including the Main Recent Fault. The study area is located in the NW of Iran. b) Shuttle Radar Topography Mission (SRTM) image from NW Iran and location of the Lake Urmia area. Fault plane solutions of recent are presented. Active major faults around the Lake Urmia area are shown by black lines (Main Recent Fault, North Fault, Fault, Serow Fault, Piranshahr Fault, Urmia Fault). Extension direction marked by white arrows parallel to the slip vector measured on the exposed normal fault planes and perpendicular to the travertine ridges. Fault plane solutions in black are from the Harvard CMT catalog (http:// www.seismology.harvard.edu/). Lighter-colored focal mechanisms are from EMSC, Vannucci and Gasperini (2004). c) Simple geology map of the Lake Urmia area (after Shahrabi et al., 1985 with changes).

A number of volcanic domes are exposed around and in part of Lake Urmia is about 41 km, and it increases to Lake Urmia. The Sahand volcanic complex is the largest about 48 km towards the east and west of the peninsula. to the east, while the Eslamy peninsula and Bezudaghi This may reflect more crustal thinning in the central part volcanos are situated at the central part (Figure 1). Basaltic of Lake Urmia and consequent mantle diapirism under the and andesitic lavas of these volcanoes are attributed to Eslamy peninsula (Moayyed et al., 2008). the Arabia-Eurasia collision active in Quaternary times (Kheirkhah et al., 2009). Volcanic ashes are identified 3. Quaternary travertine ridges in bore holes drilled through sediments covering the Travertine ridges are extensively exposed east of Lake basement rocks of Lake Urmia (Kelts and Shahrabi, 1986). Urmia (Figure 2). They are in contact with 2 different West of Lake Urmia, Paleozoic metamorphic rocks are rock types: Jurassic-Cretaceous carbonates and igneous exposed, whereas Mesozoic carbonate, sandstone, and rocks of the Sahand volcanic complex. It is proposed quartzite occur to the south and southeast (Figure 1). The that the travertine originated from an acidic solution of Early Miocene is represented by coralline limestone, which the Jurassic-Cretaceous carbonate. Since considerable crops out along the northwestern shores and on many of travertine has been produced in the study area, it implies the islands in the lake. The northern part comprises Eocene that abundant caves have been formed in the Jurassic- to Miocene evaporate-marl sequences and overlying red Cretaceous carbonates (Jalali et al., 2009). conglomerate. The acidity of the groundwater is caused by Investigation of the Burguer gravity field of NW Iran groundwater flowing through volcanic ashes towards Lake shows that the gravity increases from east to the west Urmia. Water dissolves carbonate rocks and forms soluble from –150 to –100 m Gal indicating a decreasing crustal bicarbonate. The dissolved bicarbonates are carried to the thickness (Dehghani and Makris, 1983). The thickness of surface through the opened fractures. Solid carbonate the crust under the Eslamy peninsula located in the central precipitates due to escape of carbon dioxide from the

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Figure 2. All small arrows with various colors on the map indicate the extension directions measured in the study area. Active ridges (red), central fractures of travertine ridges (gray), active liner springs (blue), and dykes (green) (see the location in Figure 1b). spring waters. The travertine has 2 distinct colors in the Travertine ridges are about 80 km2 and 39 ridges are study area: the northern travertines are red and yellow, observed in the study area (Table). The average height showing contamination by Fe ions possibly derived from of the ridges is about 120 m above the cultivated area the Sahand volcanic complex, and the southern travertine surrounding the ridges. The longest ridge is 1984 m. The are of cream color (Figure 2). width and height of the ridges change along the ridges and Fissure-ridge-type travertine formations are deposited are not the same in all places. Ridges are in various forms by Ca-bicarbonate waters rising through extension of early stage, mature stage, and eroded form. Travertine fractures and flowing to the surface around the fractures. ridges are exposed with variable sizes and with 2 different As a result, ridges are formed by the accretion of Ca- styles. Much of the travertine consists of subhorizontally bicarbonate deposits along the feeding fractures. precipitated layered travertine (Figure 3a), and the second

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Table. General average properties of travertine fissure ridges in the Azarshahr area.

Length Width Height (respective to Height (respective to Activity and Location No. Attitude (m) (m) adjacent layers) surrounding area) condition 1 1113 195 22 55 122 c 2 1016 190 11 63 120 a, b, and d 3 402 150 8 48 091 - 4 384 75 10 40 100 - 5 368 160 8 54 028 - 6 721 200 18 62 133 - Northern part 7 377 140 5 16 112 Totally eroded (Mount Qezeldagh) 8 1705 260 44 93 117 - 9 309 93 11 50 155 - 10 1053 280 38 85 124 a and b 11 1708 212 12 85 127 d 12 1984 250 52 115 113 a 13 1201 210 22 90 180 - 14 440 200 32 72 104 - 15 147 70 10 90 110 - 16 605 140 23 68 026 - 17 941 128 47 47 158 - 18 299 120 18 70 049 - 19 519 130 17 70 064 - Central part 20 720 200 23 75 098 - 21 832 200 25 80 020 - 22 1090 230 25 140 090 - 23 1358 235 40 155 137 - 24 1170 220 35 35 150 - 25 1089 160 32 140 121 - 26 456 95 15 160 070 - 27 333 90 15 160 070 - 28 450 95 20 160 077 - 29 1033 85 18 77 180 - 30 700 77 15 70 163 - 31 1905 165 38 130 153 c

Southern part 32 680 75 10 80 158 - 33 325 45 8 75 150 - (Dashkasan 34 964 68 12 105 153 - Assemblage ) 35 1715 60 7 110 150 - 36 1560 80 12 105 140 - 37 790 70 10 75 170 - 38 1243 115 15 120 177 c 39 578 70 8 75 153 c a- ridge comprises several fissures. b- upper parts of the ridge are eroded. c- ridge has active linear spring on its top. d- extension is currently active on the ridge.

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Figure 3. Different parts of a fissure-ridge type travertine in the Azarshahr area. a) Ridge, looking from top. b) Central part of the ridge containing vertical veins. c) Horizontal aragonite fibers in vertical veins in central part of the ridge (see the location in Figure 2). style consists of subparallel vertical veins located in the quantity of water supplied by springs. Field evidence central part of the ridges (Figure 3b) that represent the shows that some of the ridges stopped growing and source of the fracture-controlled ground waters. The veins the source fracture remained open (Figure 3a). An consist mostly of aragonite fibers that are perpendicular unconformity is observed between the upper and lower to the vein walls. This implies that when the extension parts of travertine in some ridges (Figure 5a). Paleosoil was wide enough for the water to get through, no vertical is found in places subparallel to bedding planes (Figure veins were produced, but when the extension was 5b). This evidence indicates that interruptions occurred synchronous with the intrusion of water with the same during travertine precipitation. Aragonite fibers were rate, the vertical veins were produced. The vertical veins produced perpendicular to the walls of the veins and are normally identical on both sides of the fissure (Figure no oblique fibers in veins were observed in the area. 3b) and fibers are of different sizes and scales (Figure 3c). The orientation of the fibers is used to determine the Fissure-ridge travertine in the study area is generated extension direction of the fractures. In addition to by the first-stage fractures in the basement rocks of the fibers measurements, trends of active faults, ridges, and region. Water with Ca-carbonate has come to the surface active travertine feeding springs in the area were also through basement fractures and precipitated as layered measured (Figure 6). travertine at the surface besides the fissures (Figure The subsurface geometry of travertine ridges in 4a). By the end of the first stage, the feeding fissure this area is not well known. Ground-penetrating radar is blocked because of low pressure of CO2. At the later has been normally used to examine the subsurface stage, by further extension in the area, both fractures geometry of fissure-ridge travertine and the central in the basement rocks and the layered travertine in fissure (Yalçiner, 2013). Restricted seismic cross- ridges are extended and new Ca-carbonate comes to the sections from the central part of Lake Urmia indicate surface again (Figure 4b). By decreasing the pressure that the basement is located 180–200 m below the water of the CO2 in the fractures, travertine produced the surface in Lake Urmia. Acoustic blanking anomalies fibers perpendicular to the fracture walls. This process were observed in the seismic cross-section and are happened several times and travertine was formed in seen through the entire section (Figure 7). They are vertical veins (Figure 4c). Vein width decreases upwards attributed to gas bubbles along the fissure that ends in (Figure 4d). Compound veins of up to 50 m wide are also a travertine ridge under the saline water inside Lake found in the central part of the ridges (Figure 4e). Urmia. Similar ridges of 20–30 m long, up to 10 m in Precipitation of travertine was not continuous but width, and 2 m in height were also documented by Kelts possibly was controlled by climate change and the and Shahrabi (1986).

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Figure 4. Schematic stages (left) and their equivalents in the field (right) presenting generation and development of a travertine ridge and its central vein. a) Initiation of extensional fracture and generation of travertine ridge (for location, see Figure 2). b) Travertine ridge with recent travertine layer in white (for location, see Figure 2). c) Travertine ridge with more than 100 m height and about 1 km length (Gezeldagh ridge looking to north). d) Open central fracture in a travertine ridge (for location, see Figure 2). e) Root of a travertine ridge containing vertical travertine (south of Gowgan village, looking to SE).

4. Relation of travertine ridges to active extensional travertine layers were broken by new extension and blocks tectonics were separated (Figure 8c) or rotated, and breccias along Travertine layers in the study area are cut by vertical and the extended fractures were cemented by new travertine subvertical fractures (Figure 8a). In some cases these (Figure 9a). Linear collapse in travertine ridges subparallel fractures are filled by newly generated travertine. As a to the trends of the ridges indicates active extension (Figure result, fractured and brecciaed travertine in the fractures 9b). In Figure 9a, 3 types of travertines with different was cemented by new travertine (Figure 8b). Consolidated colors exist. The banded travertines (white bands) are

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forming linear features on satellite images subparallel to the abundant active fault traces, which are mapped around the travertine ridges (Figure 10d). Relation of travertine oriented ridges to active extensional tectonics is documented in different areas (Altunel and Hancock, 1993, 1996; Mesci et al., 2008). Normal faults and rotation of the banded travertines indicate an extension event with normal faults after generation of ridges.

5. Discussion The Lake Urmia area is part of an active tectonic system due to the interaction between Arabia, Anatolia, and Eurasia including the North Anatolian Fault, the East Anatolian Fault, the Caucasus Mountains, and the Zagros Main Recent Fault, which bounds the Zagros Mountains. It accommodates both the northward motion of Arabia and the westward motion of Anatolia relative to Eurasia, both of which occur at 20–30 mm/year (Reilinger et al., 2006). The oblique orientation of the motion relative to the Zagros mountain range results in the partitioning of the motion between shortening in the Caucasus and right- lateral strike-slip motion along the Main Recent and North Tabriz faults (Copley and Jackson, 2006). The Lake Urmia area in NW Iran is situated in a junction with Anatolia escaping to the west and the Iranian microcontinent escaping to southeast. Active tectonics of NW Iran and SE Figure 5. a) Younger horizontal travertine layers cover the steeply involve a counterclockwise rotating array of NW- dipping travertine layers. Yellow arrows mark the unconformity surface. b) Paleosoil exists subparallel to the travertine layers. SE trending, right-lateral strike-slip faults (Copley and Jackson, 2006). The Lake Urmia area is situated among several steeply dipping SW, while thin-layered yellow travertines regional, seismically active faults (Figure 1a). The strike- between white bands and pink bedded travertines are slip Piranshahr segment of the Main Recent Fault is steeply dipping to the NE. The white banded travertines located to the SW (Mohajjel and Rasouli, 2014), the originally were produced vertically in the fissure when the Salmas and Serow oblique normal faults (Tchalenko and pink and yellow layered travertines were dipping towards Berberian, 1974; Berberian and Tchalenko, 1976) to the the SW. Meanwhile, the white banded travertines show west, and the WNW-ESE trending North Tabriz strike-slip about 45° clockwise rotation. The thin yellow layers were fault (Hessami et al., 2003; Siahkali Moradi et al., 2011) formed in a void between the banded travertines and pink to the north. Several recent earthquakes are documented layers and they were horizontal when they formed. This is from normal displacements of different faults in NW Iran unique evidence for tilting and later rotation. (Copley and Jackson, 2006) (Figure 1b). The general trend of the faults in the study area is NW- The NW-SE trending Main Recent Fault (Tchalenko SE. It is 120N–140E in the north and northwest of the and Braud, 1974) is an active, major dextral strike-slip region and 120N–160E in the central and southern part, fault generated by oblique continent–continent collision while orientation of the ridges are locally changed (Figure of the Arabian plate with the Iranian microcontinent 2). Directions of fibers are mapped in the area and, in spite during the last 5 Ma (Talebian and Jackson, 2002). It of local changes in orientation of the fibers, the main trend follows the Zagros suture and accommodates the strike- is E-W up to NE-SW (Figure 2). Travertine ridges are cut slip component of partitioned motion of oblique plate and displaced by younger active normal faults (Figure convergence in western Iran (Figure 1a). The fault consists 10a). Layered travertines were cut by younger normal of several en echelon segments, each over 100 km long. faults (Figure 10b) and in some cases faulted layered A horse-tail type of termination has been documented blocks were rotated due to further extension, resulting in in the SE of the Main Recent Fault (Authemayou et al., normal faults (Figure 10c). Travertine ridges are obvious, 2006). The Piranshahr fault located SW of Lake Urmia

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Figure 6. Rose diagrams show the strike of the measured data. Red open arrows present the extension directions (see the locations in Figure 2). is the NW segment (Mohajjel and Rasouli, 2014). displacement. Sedimentary basins are produced on the Several significant earthquakes occurred on or near hanging wall side of these faults (Figure 11). Slip vectors the Main Recent Fault and focal mechanisms of between 290 and 300 on the Serow fault planes suggest these earthquakes indicate mostly dextral strike-slip normal displacement (Copley and Jackson, 2006). The displacement (Tchalenko and Braud, 1974; Berberian, 1930 Salmas produced spectacular surface 1995; Talebian and Jackson, 2004). A slip vector of 250 faulting with a NW-SE strike and involved almost equal to 260 is measured on the Piranshahr segment of the components of normal and dextral slip (Tchalenko and Main Recent Fault planes SW of Lake Urmia, suggesting Berberian, 1974; Berberian and Tchalenko, 1976). This normal displacement (Copley and Jackson, 2006), and implies a slip vector between the E-W and NW-SE in several subparallel normal faults were produced NE NW Iran (Copley and Jackson, 2006). The extension of the Piranshahr fault (Mohajjel and Rasouli, 2014). direction measured by abundant travertine ridges with Right-lateral displacements of 10–50 km of geological the main trend of E-W up to NE-SW (Figures 2 and 6) marker beds are reported in the northwestern Zagros is concordant to regional extension concluded from the (Gidon et al., 1974; Talebian and Jackson, 2002; Copley normal faults in the Lake Urmia area, NW Iran. and Jackson, 2006). Even more displacement is reported from displaced markers in the collision zone (Berberian, 6. Conclusions 1995). The present day kinematics of the Zagros are Active extension in the Lake Urmia area is documented by characterized in the northern Zagros by 3–6 mm/year normal faults with right lateral components with N-S and of orthogonal shortening and 4–6 mm/year of orogen- NW-SE trending extension fractures forming travertine parallel right-lateral strike-slip motion (Tatar et al., ridges. The active oblique normal displacements of the 2002; Walpersdorf et al., 2006). Piranshahr, Serow, and Salmas faults in addition to A number of oblique-slip normal faults are mostly existing active volcanoes in the Lake Urmia area during documented to the south and west of the Lake Urmia the Pliocene-Quaternary and enormous travertine ridges area. The NW-SE trending active Salmas and Serow around the Lake Urmia area demonstrate regional active faults both display dextral oblique-slip normal extension in this region of NW Iran.

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Figure 7. a) Cross-section presenting the sediments deposited in the central part of Lake Urmia where a road cuts across the lake (see location in Figure 1c). b) ENE-WSW oriented seismic cross-section from the central part of Lake Urmia. Vertical fissure is identified by negative anomaly cutting the sediments in central part and travertine ridge is located at the top of the fissure (from Iran Marin Industrial Company, 2003).

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Figure 8. a) Subhorizontal layers of travertine are cut by subvertical fractures. b) Fractures are filled by travertine breccias cemented by younger aragonites (marked by white arrows). c) Subvertical open fractures are produced without considerable vertical displacement. See the location in Figure 2.

Figure 9. a) Flat layers of pink travertine (left) are cut by the stripped vertical white travertine veins (write) containing aragonite fibers perpendicular to the fracture. Later extension gash was produced between pink and white travertine (center). Consider the long fibers perpendicular to the wall and angular patches inside the gash. All are rotated 30° clockwise, possibly due to later extension and block rotations in the area. b) Travertine ridge is collapsed subparallel to the trend of the ridge (a man is marked inside the circle for scale). See the locations in Figure 2.

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Figure 10. a) Active travertine ridge is cut and displaced by younger active normal fault; the older ridge is seen to top of the ridge (see the locations of a–c in Figure 2). b) Layered travertines were cut by younger normal faults. c) Faulted layered blocks were rotated due to further extension resulting normal faults. d) Google Earth image presents the travertine ridges. Faults are shown with red arrows and travertine ridges are marked by yellow arrows (see the location in Figure 2).

Figure 11. 3D SRTM image of NW Iran. Lake Urmia area is surrounded by several major active oblique normal faults and fissure- ridge type travertines.

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Acknowledgments comments; G Seyitoğlu for expert editorial handling; We acknowledge Tarbiat Modares University for support; and Z Çakır and 2 anonymous reviewers for constructive Dr Christopher Fergusson for editing the manuscript; comments. Dr M Talebian from the Geological Survey of Iran for

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