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Gypsum karst and its evolution east of Hafik (Sivas, Turkey)
Geomorphology 71 (2005) 373 – 388 www.elsevier.com/locate/geomorph
Gypsum karst and its evolution east of Hafik (Sivas, Turkey) ¨ zel Ug˘ur Dog˘an*, Sadettin O Department of Geography, Faculty of Letters, Ankara University, 06100 SVhhVye, Ankara-Turkey Received 4 January 2004; received in revised form 25 May 2004; accepted 26 April 2005 Available online 13 June 2005
Abstract Sivas and its surroundings is the most important gypsum karst terrain in Turkey with a massive Lower Miocene gypsum formation 750 m thick. The region east of Hafik has a wide variety of well developed karstic features such as karrens, dissolution dolines, collapse dolines, blind valleys, karstic springs, swallow holes, caves, unroofed caves, natural bridges, gorges and poljes. The karstification started in the Early Pliocene. The piezometric level to the east of Hafik has lowered at least 200 m since the Early Pliocene and 90–100 m since the Early Pleistocene. There is a youthful karst (doline karst) on the Higher Plateau (1520–1600 m) and a mature karst on Lower Plateau (1315–1420 m). The mature karst evolved in two stages, first stage where excessively karstic paleovalleys, uvalas and collapse dolines appear and the second stage where poljes, collapse dolines and degraded collapse dolines dominated. D 2005 Elsevier B.V. All rights reserved. Keywords: Gypsum karst; Dissolution doline; Collapse doline; Polje; Mature karst; Hafik; Sivas; Turkey
1. Introduction Gypsum is about 10–30 times more soluble than limestone (Bo¨gli, 1980) and it commonly has a lower mechanical strength. Therefore karstic landscapes on gypsum terrains develop and are degraded much faster than they do on limestone or carbonate rocks (White, 1988; Ford and Williams, 1989). That is why the analysis of the geomorphological process in gypsum karst areas is very important both from scientific and applied points of view. The sudden generation of
* Corresponding author. E-mail address: [email protected] (U. Dog˘an). 0169-555X/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2005.04.009
collapse dolines in areas underlain by gypsum constitutes great danger for both lives and property. The maintenance of the water resources in these areas is also important. That is why the karstic and hydrogeological properties of gypsum terrains which cover great areas on the World have been the subject of extensive research (Alago¨z, 1967; Jassim et al., 1997; Kac¸arog˘lu et al., 1997, 2001; Benito et al., 1998, 2000; Gutierrez-Elorzo and Gutierrez-Santolalla, 1998; Calaforra and Pulido-Bosch, 1999, 2003; Cooper and Waltham, 1999; Pauksˇtys et al., 1999; Dog˘an, 2002; Gu¨nay, 2002; Waltham, 2002; Dog˘an and Yes¸ilyurt, 2004). Karstic terrains cover one third of the Turkish territory. The areas of gypsum outcrops are relatively
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small compared with carbonate rocks and occur in Central and Eastern Anatolia (Fig. 1). Although gypsum formations are found in Ankara, C ¸ ankVrV, C ¸ orum, KVrs¸ehir, Kayseri and Sivas regions (Alago¨z, 1967; Gu¨nay, 2002; Dog˘an and Yes¸ilyurt, 2004), the most important gypsum formation, around 750 m thick, crops out in Sivas region (Alago¨z, 1967; Aktimur, 1988; Kac¸arog˘lu et al., 1997; C ¸ ubuk and I˙nan, 1998; C ¸ iner et al., 2002; Dog˘an, 2002; Gu¨nay, 2002; Waltham, 2002, Dog˘an and Yes¸ilyurt, 2004).
In the gypsum areas outside Sivas the gypsum layers are associated with thick clay, marl, and sandstone layers. Except for some subsidence dolines at the east of C ¸ ankVrV (Dog˘an, 2002) there is no significant karstic development in these areas. Karst features are especially well represented in the Lower Miocene gypsum outcrops east of Sivas around Hafik, Zara and I˙mranlV. These include karrens, dissolution dolines, collapse dolines, blind valleys, karstic springs, swallow holes, caves, unroofed caves, natural
Fig. 1. A) Distribution of the main outcrops of evaporate rocks in Turkey (Gu¨nay, 2002). B) The rectangle indicates the location of the study area.
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bridges, gorges and poljes. Dissolution dolines are found in the youthful karst areas between Sivas and Zara at the north of KVzVlVrmak valley and south of ˙ImranlV and in the mature karst area between Hafik and Zara there are some of the most beautiful examples of poljes and collapse dolines (Alago¨z, 1967; Waltham, 2002; Dog˘an and Yes¸ilyurt, 2004). Despite the importance of the gypsum karst in Sivas region, the number of studies is limited. The first comprehensive geomorphological study in this area was carried out by Alago¨z (1967). Mayer (1974) carried out a cave survey in some parts of the karst region to the east of Sivas published in a short communication. Studies related to the hydrogeology were carried out by Kac¸arog˘lu et al. (1997) and Gu¨nay (2002). Karacan and YVlmaz (1997) and explained the formation mechanism of a collapse doline in Miocene gypsum to the southeast of Sivas. Waltham (2002) explained the general characteristics of the gypsum karst near Sivas and the karst landscape in the region. Finally, Dog˘an and Yes¸ilyurt (2004) investigated the properties of the gypsum karst to the south of I˙mranlV. Hafik, is located in one of the Central Anatolia Basins. The study area lies between the towns of Hafik and Zara, to the east of Sivas and is crossed by the KVzVlVrmak River and its tributary AcVsu River (Fig. 1). The area comprises the surroundings of KVzVlVrmak valley, a lower gypsum plateau (1315–1420 m) where mature karst is observed and an E-W trending higher gypsum plateau (1520–1600 m) to the north of KVzVlVrmak valley where youthful karst is present. The purpose of this study is to describe and analyze the karstic landscape developed in a sector east of Hafik, located in the most important gypsum karst area of Turkey and use it as a model to explain the evolution of a karstic system in gypsum areas with massive gypsum. Hafik has a continental climate with cold and snowy winters and hot dry summers. The average annual precipitation is 424 mm and rainfall generally occurs in autumn.
2. Geological setting The Sivas Basin is one of the largest Central Anatolia Basins which formed in the collision zone
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between the Pontide and Anatolide-Tauride belts (Cater et al., 1991; Gu¨rsoy et al., 1997; C ¸ iner et al., 2002; Gu¨nay, 2002). The basin was developed unconformably on a foundered Paleozoic–Mesozoic basement and on Eocene–Oligocene deposits (Fig. 2) (Kurtman, 1973; Poisson et al., 1997; Aktimur, ¨ zc¸elik, 1998; C 1988; Altunsoy and O ¸ iner et al., 2002; Gu¨nay, 2002; Kos¸un and C ¸ iner, 2002). The Sivas Basin was dominated by deep sea depositional environments during Paleocene and Eocene times (Kurtman, 1973; Kos¸un and C ¸ iner, 2002). During the Late Eocene–Oligocene, the basin became an uplifted foreland basin in which several kilometers of clastic-dominated marine sediments with subordinate evaporates accumulated. During the Late Oligocene– Miocene, the basin is considered to have evolved into a locally subsiding lagoonal and molassic basin (Poisson et al., 1996; C ¸ iner et al., 2002). Gypsum crops out in a large area in the Sivas Basin. The gypsum units in Sivas Tertiary Basin have a variable thickness and are present in formations formed in Eocene, Oligocene and Miocene times. The karst in a Hafik area has developed in a Lower Miocene gypsum unit. Different ages have been attributed to the Hafik gypsum unit: Oligocene (Poisson et al., 1996; C ¸ iner et al., 2002), Oligocene– Lower Miocene (Kos¸un and C ¸ iner, 2002), LowerMiddle Miocene (Kurtman, 1973) and Mid-Upper Miocene (Aktimur, 1988; Kac¸arog˘lu et al., 1997; Gu¨nay, 2002). Therefore a Lower Miocene age is ascribed to the Hafik gypsum in this study. Although Cater et al. (1991) correlated this gypsum with Eastern Mediterranean Messinian evaporates, C ¸ iner et al. (2002) and Poisson et al. (1997) proved it wrong as result of their investigations in the area. The Hafik gypsum formation overlies unconformably the Oligocene-aged Selimiye Formation. In this study area, near Hafik town, the thickness of this unit can reach a couple of hundred meters, even though a complete stratigraphic section cannot be reconstructed due to deformation within the gypsum (Kurtman, 1973; C ¸ iner et al., 2002). Hafik gypsum deposits are below the Lower Miocene marine units (Ag˘Vlkaya Formation), Lower-Middle Miocene river-playa and continental shelf units (Eg˘ribucak Formation) and Lower Pliocene continental units (I˙ncesu or Zo¨hrep Formations) (Fig. 2) (C ¸ ubuk and I˙nan, 1998; C ¸ iner et al., 2002; Kos¸un and C ¸ iner, 2002).
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Fig. 2. Generalized stratigraphy for the central part of the Sivas Basin (C ¸ iner et al., 2002).
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The massive Hafik gypsum 750 m in thickness (Aktimur, 1988; Tu¨tu¨ncu¨ and Aktimur, 1988) contains intercalations of thin clay and sandstone layers (Kurtman, 1973; Aktimur, 1988, C ¸ iner et al., 2002). In so many field, the rock salt or halite objectives interlayer to the gypsum formation. (Alago¨z, 1967; C ¸ ubuk and ˙Inan, 1998; Kac¸arog˘lu et al., 2001; Gu¨nay, 2002) (Fig. 2). In some regions such as the surroundings of East Lota Lake there are beds with selenite crystals up to 25 cm in length (Waltham, 2002). The Hafik Formation, which constitutes the thickest gypsiferous unit in the Sivas Basin, is affected by N-NW converging small thrusts (C ¸ iner et al., 2002). The basin which had been under the influence of an N-S compression regime until the Middle-Late Miocene, became under an extensional regime in neotectonic period as a result of the collision of the Anatolian–Arabian plates (Kos¸un and C ¸ iner, 2002). The faults and various folds are observed around Hafik and its surroundings (Alago¨z, 1967; Kurtman, 1973; C ¸ ubuk and ˙Inan, 1998; C ¸ iner et al., 2002; Gu¨nay, 2002; Kos¸un and C ¸ iner, 2002). The tectonic
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style of the Sivas Basin is characterized mainly by polyphase thrust systems (Poisson et al., 1997; C ¸ iner et al., 2002; Gu¨nay, 2002) developed along a regional NNW-SSE shortening direction (Gu¨nay, 2002). The central and southern parts of Sivas Basin are heavily faulted. The faults generally strike NE-SW and NWSE directions, and most of these faults are oblique with strike greater than the dip components (Kac¸arog˘lu et al., 1997; Gu¨nay, 2002). A few normal faults have short elongations. The E-W orientated longitudinal depressions (troughs) are formed in the gypsum in relation to this faulting. The linear depressions in the gypsum around KVzVlVrmak River valley and beneath the alluvium indicate linear extension of the faults (Kac¸arog˘lu et al., 1997). The most important fault line in the area is the fault line passing from the border of the higher gypsum plateau and northern parts of the To¨du¨rge Lake extending in E-W and NW-SE directions (Fig. 3). Hafik gypsum is highly jointed. The joints generally parallel the faults with a dominant NW-SE orientation. Most of the joints are vertical or nearly vertical, and
Fig. 3. Geomorphologic map of the study area. Legend: 1. Gypsum, 2. Quaternary, alluvium, 3. Fault, 4. Dissolution doline, swallow hole and uvala 5. Collapse doline, 6. New collapse doline, 7. Cave, 8. Paleokarstic valley, 9. Closed polje and open polje (or corrosion plain), 10. Cliff, 11. River, 12. Lake, 13. Temporal lake, 14. Height, 15. Town, 16. Village.
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solution cavities have developed along the joint zones (Kac¸arog˘lu et al., 1997; Gu¨nay, 2002).
3. Karstic features 3.1. Karrens Karrens develop much faster on gypsum rocks than on carbonate rocks. Gypsum is easily corroded by precipitation. Karrens form quickly, but because the gypsum is soft, they are soon destroyed (Kac¸arog˘lu et al., 1997, Dog˘an and Yes¸ilyurt, 2004). However poorly-preserved rinnenkarrens (Alago¨z, 1967) and rillenkarrens are encountered on the sides of a 60–708 slope, pits and tunnel karrens occur on some gypsum blocks. The karrens observed at the east of Hafik are not as developed as those seen at the southeast of ˙ImranlV (Dog˘an and Yes¸ilyurt, 2004). 3.2. Dissolution dolines Dissolution dolines are the main karst landforms on the higher gypsum plateau (1520–1600 m) to the north of KVzVlVrmak River (Fig. 3). The diameters of the dolines on the western sector of the higher plateau are 100–500 m. Some of the dolines have merged
with each other acquiring a blind valley character. The depths of some of the dolines and blind valleys are 50–100 m on the plateau. The eastern part of higher plateau is an exceptional doline karst area, and displays a truly outstanding karst landscape (Figs. 3 and 4). The number of dolines per km2 is higher, but these dolines are relatively shallow and smaller. The dolines are up to 20 m deep and up to 250 m in diameter. In this region the number of doline per km2 reaches values of 80–100. The dolines less than 10 m deep are not depicted in the geomorphologic map (Fig. 3) since they are not represented on the 1 / 25,000 topographic map used as a base for Fig. 3. Therefore we must emphasize that the actual number of dolines is much higher than the number of dolines marked on the geomorphological map. In the higher karstic plateau a polygonal net of low interfluve ridges encloses shallow depressions with internal drainage into small sinks. The dissolution dolines are seldom seen in the mature karst area between Hafik and Demiryurt to the south of KVzVlVrmak valley where the thickness of the gypsum is less. However large shallow dolines occur on the lower plateau to the southeast of Demiryurt where the thickness of the gypsum strata is greater than 100 m. They tend to be concentrated at the bottom of paleovalleys.
Fig. 4. Overview of the doline karst on the higher gypsum plateau. Agricultural activities carried out in the bottom of the doline.
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The clay and sandstone interlayers in the gypsum unit have led to the formation of 1–5 m thick residual soil at the base of the dolines (Fig. 4). The floors of some of the larger dolines with soil cover are used as agricultural land. The rainfall and the overland flow on the gypsum outcrops and the soil cover are quickly drained underground. The runoff is collected at the base of the dolines and disappears through swallow holes.
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Table 1 Diameter and depth of some collapse dolines in the east of Hafik Doline name
Diameter (m)
Deep (m)
Bu¨yu¨ko¨rmen C ¸ ukuru Kurudeniz C ¸ ukuru OvacVk KVrdavut C ¸ ukuru KVzVlc¸am C ¸ ukuru West Lota East Lota
700 500 500 750 300 300 425
90 50 40 55 50* 15* 5*
* The depth is indicated that up to the surface of doline lake.
3.3. Paleokarstic valleys Paleokarstic valleys are relatively frequent to the east of Hafik (Fig. 3). These valleys are rarely encountered on the Higher Plateau but they are common on the lower plateau. The surface drainage passed underground and way incorporated into the groundwater flow, due to the continuous incision of the KVzVlVrmak River and enlargement of the joint systems in the gypsum by dissolution. As a result, the tributaries of the river became karstified hanging valleys above the floors of KVzVlVrmak valley. 3.4. Collapse dolines There are examples of large collapse dolines in the Hafik area (Fig. 3). Collapse dolines are not seen on the Higher Plateau. However there is a large number of generally circular dolines with variable diameters and depths on the Lower Gypsum Plateau. Gypsum in this area has long nets of joint controlled cave passages and numerous collapse dolines. Collapse dolines in the study area play an important role in the groundwater flow system. There are permanent and temporary lakes in some of these collapse dolines. The formation of collapse dolines in this area is still continuing today. The biggest and the deepest collapse dolines are located to the east of To¨du¨rge Lake. Among them are; Bu¨yu¨ko¨rmen C ¸ ukuru, Kurudeniz C ¸ ukuru and OvacVk collapse dolines are ranging in N-S direction (Fig. 3; Table 1). There are several E-W trending collapse dolines between OvacVk collapse doline and To¨du¨rge Lake. some of these dolines have merged to form uvalas. The merging of some of the large dolines and their slope profiles indicate that their formation is very old. There are temporary lakes in the bottom of all these collapse dolines.
KVrdavut C ¸ ukuru located south of Demiryurt village, at the edge of KVzVlVrmak River (Fig. 3). It resembles an unroofed cave with NE-SW trending long-axis (Table 1). The difference of elevation between the Lower Gypsum Plateau and the regional base level decreases towards the west of Demiryurt village. In this region the water table crops out in the bottom of same dolines forming permanent lakes. KVzVlc¸am C ¸ ukuru collapse doline located to the south of Bulakbas¸V is one of them (Fig. 3). The funnel-shaped KVzVlc¸am C ¸ ukuru collapse doline with a regular circular rim is 300 m in diameter (Fig. 5; Table 1). The diameter of the lake in the doline is 220 m. Its depth is not known and the surface of the lake is 10 m above the KVzVlVrmak River floodplain located 3 km to the north. Apart from these there is large number of collapse dolines with lakes on the plateau between C ¸ imenyenice and Bulakbas¸V villages. Active enlargement processes still continuous due to with large and small fallen blocks of gypsum undermined by dissolution and cave roof collapse in the SarVtepe doline (Fig. 3). This feature has a small lake, ponded to the level of the adjacent river, only 10 m below the surrounding terrain. The south wall of the doline has larger block of gypsum that appear to have dropped into a cave perhaps 25 across (Waltham, 2002). This doline thought to have been formed by the gradual roof collapse of a cave passage and dissolution undercutting of the doline walls. To the north of KVzVlVrmak valley between DVs¸kapV and Yarhisar area are many collapse dolines, among them, West and East Lota collapse dolines are biggest (Fig. 3). The West Lota collapse doline is 300 m in diameter and 15 m depth. The diameter and the depth of the lake inside the doline are 250 m and 8.5 m
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Fig. 5. KVzVlc¸am collapse doline, one of the most beautiful features of mature karst area.
respectively (Alago¨z, 1967). At the south of the doline, the development of the doline still continues with rock-falls on the southern margin from steep gypsum walls. The East Lota doline has a diameter of 425 m and a depth of 5 m from the surface of the lake. The lake has a diameter of 325 m and a depth of 38 m (Alago¨z, 1967). New collapse dolines appear in the study area. A new collapse doline recently occurred on the karstic plateau to the south of East Lota Lake (Fig. 3). The doline is 30 m wide and 25 m deep and contains a pile of blocks derived from the collapsed roof. The underground water entering the base of the doline from the northeast continues its flow beneath the intact roof of the cave to the northeast. The latest collapse doline is located at the south of SarVtepe collapse doline (Fig. 3). The doline does not have a circular diameter and its bottom is covered with fresh broken blocks. Part of the collapsed cave passage is visible. There is a brown soil cover on the block pile formed by the blocks dropped from the roof (Fig. 6).
at or very close to base level (Fig. 7). Some of the poljes are completely open and drained by a fluvial network. The floors of some of the poljes locally host temporary and permanent lakes such as To¨du¨rge Lake, the biggest lake in the region, 3 km2 2500 and 2375 m in length. The lake is generally shallow but the deepest part reaches 28 m (Alago¨z, 1967). These poljes have formed by corrosional deepening and lateral planation along tectonic and structural lines. Some of the polje bottoms are around 5 m below the river floodplain and are drained underground. Among the closed poljes in the region the one located east of C ¸ imenyenice. The polje is 2.5 km2 an area and N-S orientation long axis 2.4 km. The closed polje south of DVs¸kapV village has an area of 2 km2 and a length of 2.5 km. The flat bottoms of the poljes are veneered by residual soil and alluvium derived from the sand and clay beds interlayered in the gypsum unit.
3.5. Poljes
KVzVlVrmak River and its tributary the AcVsu River flow in steep sided gorges in some parts of the area (Fig. 3). KVzVlVrmak River enters a narrow and deep canyon at As¸ag˘Vekinli village and flows in an 8 km long gorge to the west of Demiryurt. The depth of the
Poljes are located around To¨du¨rge Lake to the north of KVzVlVrmak valley and to the west of KVzVlVrmak River (Fig. 3). The bottoms of the poljes are situated
3.6. Gorges
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Fig. 6. The youngest collapse doline of the study area located to the south of SarVtepe doline.
gorge decrease from 90–100 m in the eastern sector to 40–50 m in Demiryurt area. The gorge excavated in gypsum rocks has a meandering trajectory and a 250 m wide bottom. The meandering KVzVlVrmak River is superimposed and entrenched into the gyp-
sum. West of Yarhisar the KVzVlVrmak River again enters a 2 km long and 60–70 m deep gorge with a NE-SW orientation. To the south the AcVsu River flows in a longer gorge. The depth of AcVsu gorge is approximately 100 m.
Fig. 7. The eastern view of an open polje between Lota lakes.
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KVzVlVrmak River appears to have incorporated some collapse dolines during entrenchment of its gorge upstream of the village of Demiryurt (Fig. 3). Two features in the south wall of the gorge, 4–5 km east of Demiryurt, resemble cut-off incised meanders (Waltham, 2002). 3.7. Caves Only a few of the many caves in the area east of Hafik have been investigated (Fig. 3) (Mayer, 1974; Waltham, 2002). Paleovalley surface flows incorporated into the groundwater flow has created a very suitable medium for the development of caves. There are collapses in the roofs of the caves related to the enlargement of the passages which have formed sequential collapse dolines. In addition to these dolines, the roof collapses at the entrance of the caves make their investigation very difficult. There are many cave entrances on the gypsum ridges between the poljes but these caves are not very long. The entrance of a cave on a steep gypsum side-slope located east of Mag˘ara Lake (Fig. 3). The cave entrance is 20 m wide, with a roof height of 15 m. The cave passage narrows after the first 40 m. The major portion of the cave (225 m) at south of the Lota Lake collapsed and turned into an unroofed
cave or a gorge. An underground river flows through the cave and feeds the Lota Lake. As a result of a roof collapse at the southern part of the cave a 20 m doline formed. The intact 50 m part of the cave remained as a natural bridge between this collapse doline and the unroofed cave (Fig. 8). The meandering passage has a width of 4–5 m and a height of 3–4 m. There is an accumulation 1 m thick of clay and silt at the base of the passage formed. Apart from these, there are caves up to of 300 m long to the east of Hafik investigated by Mayer (1974). On the other hand, no long cave has been explored in Hafik-Sivas gypsum karst (Waltham, 2002; Dog˘an and Yes¸ilyurt, 2004).
4. Evolution of the gypsum karst The evolution of the gypsum karst east of Hafik has been controlled by several factors: time of development; the lithologic–stratigraphic features of the gypsum; tectonic structure; climate; base-level changes. The marine sedimentation of the Sivas Tertiary Basin continued until the end of the Middle Miocene (Fig. 2) (C ¸ iner et al., 2002). As a result of uplift of the area in the Upper Miocene the KVzVlVrmak River sys-
Fig. 8. A northern view of the collapsed cave roof and natural bridge at the south of West Lota Lake.
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tem formed and the basin became an erosional area (Tu¨rkmen and Kerey, 1995). The Upper Miocene continental Eg˘erci Formation was deposited by this river system in the Upper KzVlVrmak Basin (Tu¨rkmen and Kerey, 1995). The Early Pliocene terrestrial ˙Incesu (Zo¨hrep) Formation (Fig. 2) was deposited in the Sivas Basin (Aktimur, 1988; C ¸ iner et al., 2002; Gu¨nay, 2002) and was correlative with Upper Miocene-Early Pliocene erosion in the study area. The cover formations over the gypsum to the east of Hafik were eroded in this period and exposed a Higher Gypsum Plateau at elevations of 1520–1600 m (Upper Miocene-Early Pliocene denudational surface) (Fig. 9.1). This is why the initial karstification of the gypsum east of Hafik started in the Early Pliocene.
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The Higher Gypsum Plateau is 230–300 m higher than the KVzVlVrmak River valley floor. The youthful karst or doline karst occurs on the Higher Gypsum Plateau north of the KVzVlVrmak River valley (Fig. 3) where the elevation above the baselevel and thickness of the gypsum is very high. The fact that the rivers incised their valleys deeper as a result of the tectonic activity which took place starting from the end of Early Pliocene resulted in the formation of this Higher Gypsum Plateau (Ozaner and Tu¨fekc¸i, 1988; Tu¨rkmen and Kerey, 1995). There was no possibility for the development of large-scale forms the formation such as poljes and collapse dolines on the Higher Gypsum Plateau due to continuously decreasing piezometric level in the Plio-Quaternary
Fig. 9. Schematic development stages of the gypsum karst at the east of Hafik (since the Early Pliocene) (P.L.:Piezometric Level).
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period. The surface waters join the underground waters and cause the formation of dissolution dolines. A thick impermeable unit crops out in a very narrow area around Gu¨nyamac¸ village on the western part of the Higher Plateau (Fig. 3). Although there are no data which can substantiate whether this impermeable formation is a thick unit in the gypsum or a formation carried here as a result of tectonics, the first alternative seems much more probable. In the western sector of the Higher Plateau, the doline diameters increase because the bottoms of some dolines reach the impermeable unit. Some of these dolines have been transformed into blind valleys due to lateral growth and coalescence (Fig. 3). That is why the depths and areas of the dolines in the western sector of the plateau are higher than in the polygonal karst area north and northeast of To¨du¨rge Lake where the gypsum is thicker, and lacks impermeable units. A new erosion process started in this area due to tectonic activity which took place from the end of the Early Pliocene. Erosion of a trough-shaped during Early Pleistocene denudational surface (the Lower Plateau 1315–1420 m elevation) fallowing an eastwest direction started to develop around the KVzVlVrmak River valley (Fig. 9.2) (Alago¨z, 1967). The slope of this denudational surface is towards the west, the direction of the flow of the KVzVlVrmak River. The elevation of the Early Pleistocene denudational surface above base level decreases from 100–120 m east of Hafik to 30–50 m to the west. The gypsum east of Hafik has been eroded by 230–300 m since the end of Early Pliocene. The piezometric level at the east of Hafik has lower at least 200 m since end of the Early Pliocene and 90– 100 m since the Early Pleistocene (Fig. 9). The levels of the denudation surface, depths of the Pleistocene canyon valleys and elevation of the terraces played a key role in the determination of the variation of the piezometric levels. The KVzVlVrmak and AcVsu rivers flow on the floor of the valley at elevations of 1285–1300 m. In contrast to the doline karst observed on the higher plateau on the gypsum karst to the East of Hafik, there are dominated mature karst formations, such as poljes and collapse dolines on the Lower Plateau at 1315– 1420 m around the KVzVlVrmak River valley (Fig. 3).
On the Early Pleistocene denudational surface to southeast of Demiryurt village where youth karst can be seen (Fig. 3). In this area was dominated by doline karst and paleokarstic valleys (Fig. 9.2). To the southeast of Demiryurt where collapse dolines are rarely seen and poljes are never encountered there are dissolution dolines in and around the paleovalley (Fig. 3). The presence of dissolution dolines and the absence of mature karstic features in the area indicate that the area belongs to the first stage of karstic development on the Lower Plateau (Fig. 3). The karstified hanging valleys in this area suggest that the surface drainage in the Early Pleistocene. The surface drainage passed underground and way incorporated into the groundwater flow, due to the continuous incision of the KVzVlVrmak River and enlargement of the joint systems in the gypsum by dissolution. As a result of this the tributaries of the river became karstified hanging valleys. The dolines in and around the paleokarstic valley started to lose their circular character and became uvalas. Mature karst on the lower plateau has evolved in two stages, controlled by the changes of the piezometric level and topographic elevation of gypsum. The first stage was characterized by intensively karstified paleovalleys and collapse dolines (Fig. 9.3). The second maturity stage was dominated by poljes, corrosion plains and degraded collapse dolines (Fig. 9.4). The first stage of the mature karst (Fig. 9.3) is represented by the west of Demiryurt (Fig. 3). In these areas the difference in elevation between the base level and the gypsum plateau is 50–90 m. Dissolution dolines are almost non existent and there are highly karstified and enlarged gutter-type paleovalleys and collapse dolines. The karstification in the paleovalleys is highly, developed compared with the area that represents the youth karst area of the Lower Plateau. There are no dissolution dolines but large shallow karstic depressions (uvalas) in west of the Demiryurt. The area has underground drainage. These dolines are the evidence for a well-developed endokarst system. Some of the dolines such as at KVzVlc¸am reach the water table and host permanent lakes. It is interesting that most of the collapse dolines bottoms are at or proximity the local base-level. This indicates that the cave systems which form the collapse dolines reach the base level. The formation of collapse dolines in this area is still continuing.
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The second and final stage of mature karst (Fig. 9.4) is seen at the junction of the rivers between Hafik and Bulakbas¸V, and around the To¨du¨rge Lake (Fig. 3). The second maturity stage was dominated by poljes, collapse dolines and degraded collapse dolines. The gypsum outcrops in this area were lowered to the base level in some regions and formed 20–30 m high gypsum hills in others. The poljes in the area extend in NW-SE and E-W directions in accordance with the tectonic and structural alignments. Some of the poljes in paleovalleys are in the form of closed depressions and their drainage is carried underground. Some of the poljes are in the form of corrosion plain (Ford and Williams, 1989) drain to by the river. The steep gypsum states are the rivers floodplains such as at KVzVlVrmak and AcVsu, are undermined by the rivers at retread by rock-fall. The base-level undercutting and collapse of the cliff is very conspicuous west of DVs¸kapV village (Fig. 3). Here a tilted block 100 m long is separated from the cliff by a canyon formed by a combination of mass movement, cave unroofing and massive blockfall (Waltham, 2002). The meanders of the rivers have a significant effect in the enlargement of open poljes or corrosion plains and there is an alluvial material in the bottom of these poljes. The residual hills on the floor of polje are indicative of the topography before the formation of the poljes.
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The ridges between the degraded collapse dolines have disappeared and the dolines have merged with each other east of To¨du¨rge Lake (Figs. 3 and 9). It is possible that the area of these merged collapse dolines will enlarge with time and join with To¨du¨rge Lake. This will enlarge the area of the lake towards the east. It is observed that cave-roof collapse and transformation into a gorge has an important effect in the enlargement of poljes or corrosion plains. The major portion of the cave roof at south of West Lota collapsed and turned into a gorge (Fig. 8). This gorge will cause the gypsum ridge at the west to remain as a gypsum hill between the poljes and it will be gradually destroyed with time (Fig. 3). Poljes enlarge as a result of the collapse of cave roofs or the merging or the destruction of collapse dolines. The collapse dolines, characteristic features of the mature karst area east of Hafik, show four stages of development (Fig. 10). The first stage is the collapse of a cavity roof and the formation of a collapse doline. The dimension of the collapse doline formed at this stage depends on the dimensions of the cave passage, and the doline generally has a non circular rim. There is a pile of blocks in the doline that have fallen from the roof. In some of these dolines a cave or an underground stream can be observed (Fig. 10.1). The newly formed doline south of SarVtepe is a good example of this (Fig. 6). In the second stage,
Fig. 10. Schematic development stages of collapse dolines.
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Fig. 11. Doline development south of west Lota Lake by undercutting of its steep sides. The photograph shows a 2 m wide block separated with a deep crack which is ready to fall 0.5 m wide.
with the collapses or block fallen are going on the slopes of doline continuous to enlarge. This kind of doline development results from either active cave roof collapse or undercutting of doline slopes. If there is a permanent lake in the doline the blocks that fall into the lake eventually dissolve. At least one of the sides of the doline still maintains its steepness (Fig. 10.2). This was the case in West Lota (Fig. 11) and SarVtepe dolines. In the third stage the doline reaches its maximum diameter and acquires a circular rim. The doline has sloping margins (Fig. 10.3). KVzVlc¸am doline is good example for this (Fig. 5). The final stage involves the retreat of the sides of the doline as a result of dissolution (Fig. 10.4). The doline may merge with the neighboring doline at this stage, its area increases and steepness of the side slopes decreases (as it’s the case of the OvacVk collapse doline: Fig. 3).
5. Conclusions Sivas and its surroundings is the most important gypsum karst terrain in Turkey with a massive Lower Miocene gypsum formation 750 m thick. The region
east of Hafik has a wide variety of well developed karstic features. Initial karstification of the gypsum east of Hafik started in the Early Pliocene. There is youthful karst (doline karst) on the Higher Plateau (Upper MioceneEarly Pliocene denudational surface) and mature karst on the Lower Plateau (Early Pleistocene denudational surface). East of Hafik the piezometric level has fallen at least 200 m since the Early Pliocene and 90–100 m from the Early Pleistocene. The continuous decrease of the piezometric level throughout Plio-Quaternary period made it impossible for the development of karstic formations such as poljes and collapse dolines upon the Higher Plateau. On the surface of Lower Plateau, while surface drainage was performed through valley, due to incision KVzVlVrmak, tributaries became hanging valley. Hence, on the surface of Lower Plateau in the Early Pleistocene occurred youth karst. Together with sequence going dissolution and erosion, this stem from the lowering of the plateau level towards KVzVlVrmak valley, let to a two-stage mature karst development, in areas where gypsum thickness on local base level (or piezometric level) is relatively more, enlarged, shallow paleokarstic valleys, uvalas and collapse dolines are found, whereas in areas where thickness decreased,
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poljes, collapse dolines and degraded collapse dolines are found. The formation of collapse doline goes on the mature karst area to the east of Hafik. It is possible that the catastrophic collapses in this area, great danger for both lives and property. Consequently, there are several control factors on gypsum karst. Among these factors on the development and evolution of massive Hafik gypsum karst, suitable precipitation condition for the gypsum karst, piezometric level change (or base level change) and areal change of gypsum thickness above piezometric level or relief configuration of the area are more considerable elements. Besides, this study is significant, it indicates that the process, which began with youth stage (doline karst) on gypsum karst in such a short period of time as the Quaternary, has reached maturity stage (polje and collapse doline) and further more in some mature karst features has started to degradation process.
References ¨ lc¸ekli Ac¸Vnsama Nitelikli Tu¨rAktimur, H.T., 1988. 1/100 000 O kiye Jeoloji HaritalarV Serisi Divrig˘i-F24 PaftasV. MTA, Ankara. 11 pp. Alago¨z, C.A., 1967. Sivas C ¸ evresi ve Dog˘usunda Jips KarstV ¨ niversitesi Dil ve Tarih-Cog˘rafya Faku¨ltesi OlaylarV. Ankara U YayVnV, Ankara. 126 pp. ¨ zc¸elik, O., 1998. Organic facies characteristics of Altunsoy, M., O the Sivas Tertiary Basin (Turkey). Journal of Petroleum Science and Engineering 20, 73 – 85. Benito, G., Perez-Gonzalez, A., Gutierrez, F., Machado, M.J., 1998. River response to Quaternary subsidence due to evaporite solution (Gallego River, Ebro Basin, Spain). Geomorphology 22, 243 – 263. Benito, G., Gutierrez, F., Perez-Gonzalez, A., Machado, M.J., 2000. Geomorphological and sedimentological features in Quaternary fluvial system affected by solution-induced subsidence (Ebro Basin NE-Spain). Geomorphology 33 (3-4), 209 – 224. Bo¨gli, A., 1980. Karst Hydrology and Physical Speleology. Springer-Verlag, Berlin. 284 pp. Calaforra, J.M., Pulido-Bosch, A., 1999. Gypsum karst features as evidence of diapiric processes in the Betic Cordillera Southern Spain. Geomorphology 29, 251 – 264. Calaforra, J.M., Pulido-Bosch, A., 2003. Evolution of the gypsum karst of Sorbas (SE Spain). Geomorphology 50, 173 – 180. Cater, J.M.L., Hanna, S.S., Ries, A.C., Turner, P., 1991. Tertiary evolution of the Sivas Basin Central Turkey. Tectonophysics 195, 29 – 46.
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Gypsum karst and its evolution east of Hafik (Sivas, Turkey) ¨ zel Ug˘ur Dog˘an*, Sadettin O Department of Geography, Faculty of Letters, Ankara University, 06100 SVhhVye, Ankara-Turkey Received 4 January 2004; received in revised form 25 May 2004; accepted 26 April 2005 Available online 13 June 2005
Abstract Sivas and its surroundings is the most important gypsum karst terrain in Turkey with a massive Lower Miocene gypsum formation 750 m thick. The region east of Hafik has a wide variety of well developed karstic features such as karrens, dissolution dolines, collapse dolines, blind valleys, karstic springs, swallow holes, caves, unroofed caves, natural bridges, gorges and poljes. The karstification started in the Early Pliocene. The piezometric level to the east of Hafik has lowered at least 200 m since the Early Pliocene and 90–100 m since the Early Pleistocene. There is a youthful karst (doline karst) on the Higher Plateau (1520–1600 m) and a mature karst on Lower Plateau (1315–1420 m). The mature karst evolved in two stages, first stage where excessively karstic paleovalleys, uvalas and collapse dolines appear and the second stage where poljes, collapse dolines and degraded collapse dolines dominated. D 2005 Elsevier B.V. All rights reserved. Keywords: Gypsum karst; Dissolution doline; Collapse doline; Polje; Mature karst; Hafik; Sivas; Turkey
1. Introduction Gypsum is about 10–30 times more soluble than limestone (Bo¨gli, 1980) and it commonly has a lower mechanical strength. Therefore karstic landscapes on gypsum terrains develop and are degraded much faster than they do on limestone or carbonate rocks (White, 1988; Ford and Williams, 1989). That is why the analysis of the geomorphological process in gypsum karst areas is very important both from scientific and applied points of view. The sudden generation of
* Corresponding author. E-mail address: [email protected] (U. Dog˘an). 0169-555X/$ - see front matter D 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.geomorph.2005.04.009
collapse dolines in areas underlain by gypsum constitutes great danger for both lives and property. The maintenance of the water resources in these areas is also important. That is why the karstic and hydrogeological properties of gypsum terrains which cover great areas on the World have been the subject of extensive research (Alago¨z, 1967; Jassim et al., 1997; Kac¸arog˘lu et al., 1997, 2001; Benito et al., 1998, 2000; Gutierrez-Elorzo and Gutierrez-Santolalla, 1998; Calaforra and Pulido-Bosch, 1999, 2003; Cooper and Waltham, 1999; Pauksˇtys et al., 1999; Dog˘an, 2002; Gu¨nay, 2002; Waltham, 2002; Dog˘an and Yes¸ilyurt, 2004). Karstic terrains cover one third of the Turkish territory. The areas of gypsum outcrops are relatively
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small compared with carbonate rocks and occur in Central and Eastern Anatolia (Fig. 1). Although gypsum formations are found in Ankara, C ¸ ankVrV, C ¸ orum, KVrs¸ehir, Kayseri and Sivas regions (Alago¨z, 1967; Gu¨nay, 2002; Dog˘an and Yes¸ilyurt, 2004), the most important gypsum formation, around 750 m thick, crops out in Sivas region (Alago¨z, 1967; Aktimur, 1988; Kac¸arog˘lu et al., 1997; C ¸ ubuk and I˙nan, 1998; C ¸ iner et al., 2002; Dog˘an, 2002; Gu¨nay, 2002; Waltham, 2002, Dog˘an and Yes¸ilyurt, 2004).
In the gypsum areas outside Sivas the gypsum layers are associated with thick clay, marl, and sandstone layers. Except for some subsidence dolines at the east of C ¸ ankVrV (Dog˘an, 2002) there is no significant karstic development in these areas. Karst features are especially well represented in the Lower Miocene gypsum outcrops east of Sivas around Hafik, Zara and I˙mranlV. These include karrens, dissolution dolines, collapse dolines, blind valleys, karstic springs, swallow holes, caves, unroofed caves, natural
Fig. 1. A) Distribution of the main outcrops of evaporate rocks in Turkey (Gu¨nay, 2002). B) The rectangle indicates the location of the study area.
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bridges, gorges and poljes. Dissolution dolines are found in the youthful karst areas between Sivas and Zara at the north of KVzVlVrmak valley and south of ˙ImranlV and in the mature karst area between Hafik and Zara there are some of the most beautiful examples of poljes and collapse dolines (Alago¨z, 1967; Waltham, 2002; Dog˘an and Yes¸ilyurt, 2004). Despite the importance of the gypsum karst in Sivas region, the number of studies is limited. The first comprehensive geomorphological study in this area was carried out by Alago¨z (1967). Mayer (1974) carried out a cave survey in some parts of the karst region to the east of Sivas published in a short communication. Studies related to the hydrogeology were carried out by Kac¸arog˘lu et al. (1997) and Gu¨nay (2002). Karacan and YVlmaz (1997) and explained the formation mechanism of a collapse doline in Miocene gypsum to the southeast of Sivas. Waltham (2002) explained the general characteristics of the gypsum karst near Sivas and the karst landscape in the region. Finally, Dog˘an and Yes¸ilyurt (2004) investigated the properties of the gypsum karst to the south of I˙mranlV. Hafik, is located in one of the Central Anatolia Basins. The study area lies between the towns of Hafik and Zara, to the east of Sivas and is crossed by the KVzVlVrmak River and its tributary AcVsu River (Fig. 1). The area comprises the surroundings of KVzVlVrmak valley, a lower gypsum plateau (1315–1420 m) where mature karst is observed and an E-W trending higher gypsum plateau (1520–1600 m) to the north of KVzVlVrmak valley where youthful karst is present. The purpose of this study is to describe and analyze the karstic landscape developed in a sector east of Hafik, located in the most important gypsum karst area of Turkey and use it as a model to explain the evolution of a karstic system in gypsum areas with massive gypsum. Hafik has a continental climate with cold and snowy winters and hot dry summers. The average annual precipitation is 424 mm and rainfall generally occurs in autumn.
2. Geological setting The Sivas Basin is one of the largest Central Anatolia Basins which formed in the collision zone
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between the Pontide and Anatolide-Tauride belts (Cater et al., 1991; Gu¨rsoy et al., 1997; C ¸ iner et al., 2002; Gu¨nay, 2002). The basin was developed unconformably on a foundered Paleozoic–Mesozoic basement and on Eocene–Oligocene deposits (Fig. 2) (Kurtman, 1973; Poisson et al., 1997; Aktimur, ¨ zc¸elik, 1998; C 1988; Altunsoy and O ¸ iner et al., 2002; Gu¨nay, 2002; Kos¸un and C ¸ iner, 2002). The Sivas Basin was dominated by deep sea depositional environments during Paleocene and Eocene times (Kurtman, 1973; Kos¸un and C ¸ iner, 2002). During the Late Eocene–Oligocene, the basin became an uplifted foreland basin in which several kilometers of clastic-dominated marine sediments with subordinate evaporates accumulated. During the Late Oligocene– Miocene, the basin is considered to have evolved into a locally subsiding lagoonal and molassic basin (Poisson et al., 1996; C ¸ iner et al., 2002). Gypsum crops out in a large area in the Sivas Basin. The gypsum units in Sivas Tertiary Basin have a variable thickness and are present in formations formed in Eocene, Oligocene and Miocene times. The karst in a Hafik area has developed in a Lower Miocene gypsum unit. Different ages have been attributed to the Hafik gypsum unit: Oligocene (Poisson et al., 1996; C ¸ iner et al., 2002), Oligocene– Lower Miocene (Kos¸un and C ¸ iner, 2002), LowerMiddle Miocene (Kurtman, 1973) and Mid-Upper Miocene (Aktimur, 1988; Kac¸arog˘lu et al., 1997; Gu¨nay, 2002). Therefore a Lower Miocene age is ascribed to the Hafik gypsum in this study. Although Cater et al. (1991) correlated this gypsum with Eastern Mediterranean Messinian evaporates, C ¸ iner et al. (2002) and Poisson et al. (1997) proved it wrong as result of their investigations in the area. The Hafik gypsum formation overlies unconformably the Oligocene-aged Selimiye Formation. In this study area, near Hafik town, the thickness of this unit can reach a couple of hundred meters, even though a complete stratigraphic section cannot be reconstructed due to deformation within the gypsum (Kurtman, 1973; C ¸ iner et al., 2002). Hafik gypsum deposits are below the Lower Miocene marine units (Ag˘Vlkaya Formation), Lower-Middle Miocene river-playa and continental shelf units (Eg˘ribucak Formation) and Lower Pliocene continental units (I˙ncesu or Zo¨hrep Formations) (Fig. 2) (C ¸ ubuk and I˙nan, 1998; C ¸ iner et al., 2002; Kos¸un and C ¸ iner, 2002).
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Fig. 2. Generalized stratigraphy for the central part of the Sivas Basin (C ¸ iner et al., 2002).
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The massive Hafik gypsum 750 m in thickness (Aktimur, 1988; Tu¨tu¨ncu¨ and Aktimur, 1988) contains intercalations of thin clay and sandstone layers (Kurtman, 1973; Aktimur, 1988, C ¸ iner et al., 2002). In so many field, the rock salt or halite objectives interlayer to the gypsum formation. (Alago¨z, 1967; C ¸ ubuk and ˙Inan, 1998; Kac¸arog˘lu et al., 2001; Gu¨nay, 2002) (Fig. 2). In some regions such as the surroundings of East Lota Lake there are beds with selenite crystals up to 25 cm in length (Waltham, 2002). The Hafik Formation, which constitutes the thickest gypsiferous unit in the Sivas Basin, is affected by N-NW converging small thrusts (C ¸ iner et al., 2002). The basin which had been under the influence of an N-S compression regime until the Middle-Late Miocene, became under an extensional regime in neotectonic period as a result of the collision of the Anatolian–Arabian plates (Kos¸un and C ¸ iner, 2002). The faults and various folds are observed around Hafik and its surroundings (Alago¨z, 1967; Kurtman, 1973; C ¸ ubuk and ˙Inan, 1998; C ¸ iner et al., 2002; Gu¨nay, 2002; Kos¸un and C ¸ iner, 2002). The tectonic
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style of the Sivas Basin is characterized mainly by polyphase thrust systems (Poisson et al., 1997; C ¸ iner et al., 2002; Gu¨nay, 2002) developed along a regional NNW-SSE shortening direction (Gu¨nay, 2002). The central and southern parts of Sivas Basin are heavily faulted. The faults generally strike NE-SW and NWSE directions, and most of these faults are oblique with strike greater than the dip components (Kac¸arog˘lu et al., 1997; Gu¨nay, 2002). A few normal faults have short elongations. The E-W orientated longitudinal depressions (troughs) are formed in the gypsum in relation to this faulting. The linear depressions in the gypsum around KVzVlVrmak River valley and beneath the alluvium indicate linear extension of the faults (Kac¸arog˘lu et al., 1997). The most important fault line in the area is the fault line passing from the border of the higher gypsum plateau and northern parts of the To¨du¨rge Lake extending in E-W and NW-SE directions (Fig. 3). Hafik gypsum is highly jointed. The joints generally parallel the faults with a dominant NW-SE orientation. Most of the joints are vertical or nearly vertical, and
Fig. 3. Geomorphologic map of the study area. Legend: 1. Gypsum, 2. Quaternary, alluvium, 3. Fault, 4. Dissolution doline, swallow hole and uvala 5. Collapse doline, 6. New collapse doline, 7. Cave, 8. Paleokarstic valley, 9. Closed polje and open polje (or corrosion plain), 10. Cliff, 11. River, 12. Lake, 13. Temporal lake, 14. Height, 15. Town, 16. Village.
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solution cavities have developed along the joint zones (Kac¸arog˘lu et al., 1997; Gu¨nay, 2002).
3. Karstic features 3.1. Karrens Karrens develop much faster on gypsum rocks than on carbonate rocks. Gypsum is easily corroded by precipitation. Karrens form quickly, but because the gypsum is soft, they are soon destroyed (Kac¸arog˘lu et al., 1997, Dog˘an and Yes¸ilyurt, 2004). However poorly-preserved rinnenkarrens (Alago¨z, 1967) and rillenkarrens are encountered on the sides of a 60–708 slope, pits and tunnel karrens occur on some gypsum blocks. The karrens observed at the east of Hafik are not as developed as those seen at the southeast of ˙ImranlV (Dog˘an and Yes¸ilyurt, 2004). 3.2. Dissolution dolines Dissolution dolines are the main karst landforms on the higher gypsum plateau (1520–1600 m) to the north of KVzVlVrmak River (Fig. 3). The diameters of the dolines on the western sector of the higher plateau are 100–500 m. Some of the dolines have merged
with each other acquiring a blind valley character. The depths of some of the dolines and blind valleys are 50–100 m on the plateau. The eastern part of higher plateau is an exceptional doline karst area, and displays a truly outstanding karst landscape (Figs. 3 and 4). The number of dolines per km2 is higher, but these dolines are relatively shallow and smaller. The dolines are up to 20 m deep and up to 250 m in diameter. In this region the number of doline per km2 reaches values of 80–100. The dolines less than 10 m deep are not depicted in the geomorphologic map (Fig. 3) since they are not represented on the 1 / 25,000 topographic map used as a base for Fig. 3. Therefore we must emphasize that the actual number of dolines is much higher than the number of dolines marked on the geomorphological map. In the higher karstic plateau a polygonal net of low interfluve ridges encloses shallow depressions with internal drainage into small sinks. The dissolution dolines are seldom seen in the mature karst area between Hafik and Demiryurt to the south of KVzVlVrmak valley where the thickness of the gypsum is less. However large shallow dolines occur on the lower plateau to the southeast of Demiryurt where the thickness of the gypsum strata is greater than 100 m. They tend to be concentrated at the bottom of paleovalleys.
Fig. 4. Overview of the doline karst on the higher gypsum plateau. Agricultural activities carried out in the bottom of the doline.
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The clay and sandstone interlayers in the gypsum unit have led to the formation of 1–5 m thick residual soil at the base of the dolines (Fig. 4). The floors of some of the larger dolines with soil cover are used as agricultural land. The rainfall and the overland flow on the gypsum outcrops and the soil cover are quickly drained underground. The runoff is collected at the base of the dolines and disappears through swallow holes.
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Table 1 Diameter and depth of some collapse dolines in the east of Hafik Doline name
Diameter (m)
Deep (m)
Bu¨yu¨ko¨rmen C ¸ ukuru Kurudeniz C ¸ ukuru OvacVk KVrdavut C ¸ ukuru KVzVlc¸am C ¸ ukuru West Lota East Lota
700 500 500 750 300 300 425
90 50 40 55 50* 15* 5*
* The depth is indicated that up to the surface of doline lake.
3.3. Paleokarstic valleys Paleokarstic valleys are relatively frequent to the east of Hafik (Fig. 3). These valleys are rarely encountered on the Higher Plateau but they are common on the lower plateau. The surface drainage passed underground and way incorporated into the groundwater flow, due to the continuous incision of the KVzVlVrmak River and enlargement of the joint systems in the gypsum by dissolution. As a result, the tributaries of the river became karstified hanging valleys above the floors of KVzVlVrmak valley. 3.4. Collapse dolines There are examples of large collapse dolines in the Hafik area (Fig. 3). Collapse dolines are not seen on the Higher Plateau. However there is a large number of generally circular dolines with variable diameters and depths on the Lower Gypsum Plateau. Gypsum in this area has long nets of joint controlled cave passages and numerous collapse dolines. Collapse dolines in the study area play an important role in the groundwater flow system. There are permanent and temporary lakes in some of these collapse dolines. The formation of collapse dolines in this area is still continuing today. The biggest and the deepest collapse dolines are located to the east of To¨du¨rge Lake. Among them are; Bu¨yu¨ko¨rmen C ¸ ukuru, Kurudeniz C ¸ ukuru and OvacVk collapse dolines are ranging in N-S direction (Fig. 3; Table 1). There are several E-W trending collapse dolines between OvacVk collapse doline and To¨du¨rge Lake. some of these dolines have merged to form uvalas. The merging of some of the large dolines and their slope profiles indicate that their formation is very old. There are temporary lakes in the bottom of all these collapse dolines.
KVrdavut C ¸ ukuru located south of Demiryurt village, at the edge of KVzVlVrmak River (Fig. 3). It resembles an unroofed cave with NE-SW trending long-axis (Table 1). The difference of elevation between the Lower Gypsum Plateau and the regional base level decreases towards the west of Demiryurt village. In this region the water table crops out in the bottom of same dolines forming permanent lakes. KVzVlc¸am C ¸ ukuru collapse doline located to the south of Bulakbas¸V is one of them (Fig. 3). The funnel-shaped KVzVlc¸am C ¸ ukuru collapse doline with a regular circular rim is 300 m in diameter (Fig. 5; Table 1). The diameter of the lake in the doline is 220 m. Its depth is not known and the surface of the lake is 10 m above the KVzVlVrmak River floodplain located 3 km to the north. Apart from these there is large number of collapse dolines with lakes on the plateau between C ¸ imenyenice and Bulakbas¸V villages. Active enlargement processes still continuous due to with large and small fallen blocks of gypsum undermined by dissolution and cave roof collapse in the SarVtepe doline (Fig. 3). This feature has a small lake, ponded to the level of the adjacent river, only 10 m below the surrounding terrain. The south wall of the doline has larger block of gypsum that appear to have dropped into a cave perhaps 25 across (Waltham, 2002). This doline thought to have been formed by the gradual roof collapse of a cave passage and dissolution undercutting of the doline walls. To the north of KVzVlVrmak valley between DVs¸kapV and Yarhisar area are many collapse dolines, among them, West and East Lota collapse dolines are biggest (Fig. 3). The West Lota collapse doline is 300 m in diameter and 15 m depth. The diameter and the depth of the lake inside the doline are 250 m and 8.5 m
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Fig. 5. KVzVlc¸am collapse doline, one of the most beautiful features of mature karst area.
respectively (Alago¨z, 1967). At the south of the doline, the development of the doline still continues with rock-falls on the southern margin from steep gypsum walls. The East Lota doline has a diameter of 425 m and a depth of 5 m from the surface of the lake. The lake has a diameter of 325 m and a depth of 38 m (Alago¨z, 1967). New collapse dolines appear in the study area. A new collapse doline recently occurred on the karstic plateau to the south of East Lota Lake (Fig. 3). The doline is 30 m wide and 25 m deep and contains a pile of blocks derived from the collapsed roof. The underground water entering the base of the doline from the northeast continues its flow beneath the intact roof of the cave to the northeast. The latest collapse doline is located at the south of SarVtepe collapse doline (Fig. 3). The doline does not have a circular diameter and its bottom is covered with fresh broken blocks. Part of the collapsed cave passage is visible. There is a brown soil cover on the block pile formed by the blocks dropped from the roof (Fig. 6).
at or very close to base level (Fig. 7). Some of the poljes are completely open and drained by a fluvial network. The floors of some of the poljes locally host temporary and permanent lakes such as To¨du¨rge Lake, the biggest lake in the region, 3 km2 2500 and 2375 m in length. The lake is generally shallow but the deepest part reaches 28 m (Alago¨z, 1967). These poljes have formed by corrosional deepening and lateral planation along tectonic and structural lines. Some of the polje bottoms are around 5 m below the river floodplain and are drained underground. Among the closed poljes in the region the one located east of C ¸ imenyenice. The polje is 2.5 km2 an area and N-S orientation long axis 2.4 km. The closed polje south of DVs¸kapV village has an area of 2 km2 and a length of 2.5 km. The flat bottoms of the poljes are veneered by residual soil and alluvium derived from the sand and clay beds interlayered in the gypsum unit.
3.5. Poljes
KVzVlVrmak River and its tributary the AcVsu River flow in steep sided gorges in some parts of the area (Fig. 3). KVzVlVrmak River enters a narrow and deep canyon at As¸ag˘Vekinli village and flows in an 8 km long gorge to the west of Demiryurt. The depth of the
Poljes are located around To¨du¨rge Lake to the north of KVzVlVrmak valley and to the west of KVzVlVrmak River (Fig. 3). The bottoms of the poljes are situated
3.6. Gorges
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Fig. 6. The youngest collapse doline of the study area located to the south of SarVtepe doline.
gorge decrease from 90–100 m in the eastern sector to 40–50 m in Demiryurt area. The gorge excavated in gypsum rocks has a meandering trajectory and a 250 m wide bottom. The meandering KVzVlVrmak River is superimposed and entrenched into the gyp-
sum. West of Yarhisar the KVzVlVrmak River again enters a 2 km long and 60–70 m deep gorge with a NE-SW orientation. To the south the AcVsu River flows in a longer gorge. The depth of AcVsu gorge is approximately 100 m.
Fig. 7. The eastern view of an open polje between Lota lakes.
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KVzVlVrmak River appears to have incorporated some collapse dolines during entrenchment of its gorge upstream of the village of Demiryurt (Fig. 3). Two features in the south wall of the gorge, 4–5 km east of Demiryurt, resemble cut-off incised meanders (Waltham, 2002). 3.7. Caves Only a few of the many caves in the area east of Hafik have been investigated (Fig. 3) (Mayer, 1974; Waltham, 2002). Paleovalley surface flows incorporated into the groundwater flow has created a very suitable medium for the development of caves. There are collapses in the roofs of the caves related to the enlargement of the passages which have formed sequential collapse dolines. In addition to these dolines, the roof collapses at the entrance of the caves make their investigation very difficult. There are many cave entrances on the gypsum ridges between the poljes but these caves are not very long. The entrance of a cave on a steep gypsum side-slope located east of Mag˘ara Lake (Fig. 3). The cave entrance is 20 m wide, with a roof height of 15 m. The cave passage narrows after the first 40 m. The major portion of the cave (225 m) at south of the Lota Lake collapsed and turned into an unroofed
cave or a gorge. An underground river flows through the cave and feeds the Lota Lake. As a result of a roof collapse at the southern part of the cave a 20 m doline formed. The intact 50 m part of the cave remained as a natural bridge between this collapse doline and the unroofed cave (Fig. 8). The meandering passage has a width of 4–5 m and a height of 3–4 m. There is an accumulation 1 m thick of clay and silt at the base of the passage formed. Apart from these, there are caves up to of 300 m long to the east of Hafik investigated by Mayer (1974). On the other hand, no long cave has been explored in Hafik-Sivas gypsum karst (Waltham, 2002; Dog˘an and Yes¸ilyurt, 2004).
4. Evolution of the gypsum karst The evolution of the gypsum karst east of Hafik has been controlled by several factors: time of development; the lithologic–stratigraphic features of the gypsum; tectonic structure; climate; base-level changes. The marine sedimentation of the Sivas Tertiary Basin continued until the end of the Middle Miocene (Fig. 2) (C ¸ iner et al., 2002). As a result of uplift of the area in the Upper Miocene the KVzVlVrmak River sys-
Fig. 8. A northern view of the collapsed cave roof and natural bridge at the south of West Lota Lake.
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tem formed and the basin became an erosional area (Tu¨rkmen and Kerey, 1995). The Upper Miocene continental Eg˘erci Formation was deposited by this river system in the Upper KzVlVrmak Basin (Tu¨rkmen and Kerey, 1995). The Early Pliocene terrestrial ˙Incesu (Zo¨hrep) Formation (Fig. 2) was deposited in the Sivas Basin (Aktimur, 1988; C ¸ iner et al., 2002; Gu¨nay, 2002) and was correlative with Upper Miocene-Early Pliocene erosion in the study area. The cover formations over the gypsum to the east of Hafik were eroded in this period and exposed a Higher Gypsum Plateau at elevations of 1520–1600 m (Upper Miocene-Early Pliocene denudational surface) (Fig. 9.1). This is why the initial karstification of the gypsum east of Hafik started in the Early Pliocene.
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The Higher Gypsum Plateau is 230–300 m higher than the KVzVlVrmak River valley floor. The youthful karst or doline karst occurs on the Higher Gypsum Plateau north of the KVzVlVrmak River valley (Fig. 3) where the elevation above the baselevel and thickness of the gypsum is very high. The fact that the rivers incised their valleys deeper as a result of the tectonic activity which took place starting from the end of Early Pliocene resulted in the formation of this Higher Gypsum Plateau (Ozaner and Tu¨fekc¸i, 1988; Tu¨rkmen and Kerey, 1995). There was no possibility for the development of large-scale forms the formation such as poljes and collapse dolines on the Higher Gypsum Plateau due to continuously decreasing piezometric level in the Plio-Quaternary
Fig. 9. Schematic development stages of the gypsum karst at the east of Hafik (since the Early Pliocene) (P.L.:Piezometric Level).
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period. The surface waters join the underground waters and cause the formation of dissolution dolines. A thick impermeable unit crops out in a very narrow area around Gu¨nyamac¸ village on the western part of the Higher Plateau (Fig. 3). Although there are no data which can substantiate whether this impermeable formation is a thick unit in the gypsum or a formation carried here as a result of tectonics, the first alternative seems much more probable. In the western sector of the Higher Plateau, the doline diameters increase because the bottoms of some dolines reach the impermeable unit. Some of these dolines have been transformed into blind valleys due to lateral growth and coalescence (Fig. 3). That is why the depths and areas of the dolines in the western sector of the plateau are higher than in the polygonal karst area north and northeast of To¨du¨rge Lake where the gypsum is thicker, and lacks impermeable units. A new erosion process started in this area due to tectonic activity which took place from the end of the Early Pliocene. Erosion of a trough-shaped during Early Pleistocene denudational surface (the Lower Plateau 1315–1420 m elevation) fallowing an eastwest direction started to develop around the KVzVlVrmak River valley (Fig. 9.2) (Alago¨z, 1967). The slope of this denudational surface is towards the west, the direction of the flow of the KVzVlVrmak River. The elevation of the Early Pleistocene denudational surface above base level decreases from 100–120 m east of Hafik to 30–50 m to the west. The gypsum east of Hafik has been eroded by 230–300 m since the end of Early Pliocene. The piezometric level at the east of Hafik has lower at least 200 m since end of the Early Pliocene and 90– 100 m since the Early Pleistocene (Fig. 9). The levels of the denudation surface, depths of the Pleistocene canyon valleys and elevation of the terraces played a key role in the determination of the variation of the piezometric levels. The KVzVlVrmak and AcVsu rivers flow on the floor of the valley at elevations of 1285–1300 m. In contrast to the doline karst observed on the higher plateau on the gypsum karst to the East of Hafik, there are dominated mature karst formations, such as poljes and collapse dolines on the Lower Plateau at 1315– 1420 m around the KVzVlVrmak River valley (Fig. 3).
On the Early Pleistocene denudational surface to southeast of Demiryurt village where youth karst can be seen (Fig. 3). In this area was dominated by doline karst and paleokarstic valleys (Fig. 9.2). To the southeast of Demiryurt where collapse dolines are rarely seen and poljes are never encountered there are dissolution dolines in and around the paleovalley (Fig. 3). The presence of dissolution dolines and the absence of mature karstic features in the area indicate that the area belongs to the first stage of karstic development on the Lower Plateau (Fig. 3). The karstified hanging valleys in this area suggest that the surface drainage in the Early Pleistocene. The surface drainage passed underground and way incorporated into the groundwater flow, due to the continuous incision of the KVzVlVrmak River and enlargement of the joint systems in the gypsum by dissolution. As a result of this the tributaries of the river became karstified hanging valleys. The dolines in and around the paleokarstic valley started to lose their circular character and became uvalas. Mature karst on the lower plateau has evolved in two stages, controlled by the changes of the piezometric level and topographic elevation of gypsum. The first stage was characterized by intensively karstified paleovalleys and collapse dolines (Fig. 9.3). The second maturity stage was dominated by poljes, corrosion plains and degraded collapse dolines (Fig. 9.4). The first stage of the mature karst (Fig. 9.3) is represented by the west of Demiryurt (Fig. 3). In these areas the difference in elevation between the base level and the gypsum plateau is 50–90 m. Dissolution dolines are almost non existent and there are highly karstified and enlarged gutter-type paleovalleys and collapse dolines. The karstification in the paleovalleys is highly, developed compared with the area that represents the youth karst area of the Lower Plateau. There are no dissolution dolines but large shallow karstic depressions (uvalas) in west of the Demiryurt. The area has underground drainage. These dolines are the evidence for a well-developed endokarst system. Some of the dolines such as at KVzVlc¸am reach the water table and host permanent lakes. It is interesting that most of the collapse dolines bottoms are at or proximity the local base-level. This indicates that the cave systems which form the collapse dolines reach the base level. The formation of collapse dolines in this area is still continuing.
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The second and final stage of mature karst (Fig. 9.4) is seen at the junction of the rivers between Hafik and Bulakbas¸V, and around the To¨du¨rge Lake (Fig. 3). The second maturity stage was dominated by poljes, collapse dolines and degraded collapse dolines. The gypsum outcrops in this area were lowered to the base level in some regions and formed 20–30 m high gypsum hills in others. The poljes in the area extend in NW-SE and E-W directions in accordance with the tectonic and structural alignments. Some of the poljes in paleovalleys are in the form of closed depressions and their drainage is carried underground. Some of the poljes are in the form of corrosion plain (Ford and Williams, 1989) drain to by the river. The steep gypsum states are the rivers floodplains such as at KVzVlVrmak and AcVsu, are undermined by the rivers at retread by rock-fall. The base-level undercutting and collapse of the cliff is very conspicuous west of DVs¸kapV village (Fig. 3). Here a tilted block 100 m long is separated from the cliff by a canyon formed by a combination of mass movement, cave unroofing and massive blockfall (Waltham, 2002). The meanders of the rivers have a significant effect in the enlargement of open poljes or corrosion plains and there is an alluvial material in the bottom of these poljes. The residual hills on the floor of polje are indicative of the topography before the formation of the poljes.
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The ridges between the degraded collapse dolines have disappeared and the dolines have merged with each other east of To¨du¨rge Lake (Figs. 3 and 9). It is possible that the area of these merged collapse dolines will enlarge with time and join with To¨du¨rge Lake. This will enlarge the area of the lake towards the east. It is observed that cave-roof collapse and transformation into a gorge has an important effect in the enlargement of poljes or corrosion plains. The major portion of the cave roof at south of West Lota collapsed and turned into a gorge (Fig. 8). This gorge will cause the gypsum ridge at the west to remain as a gypsum hill between the poljes and it will be gradually destroyed with time (Fig. 3). Poljes enlarge as a result of the collapse of cave roofs or the merging or the destruction of collapse dolines. The collapse dolines, characteristic features of the mature karst area east of Hafik, show four stages of development (Fig. 10). The first stage is the collapse of a cavity roof and the formation of a collapse doline. The dimension of the collapse doline formed at this stage depends on the dimensions of the cave passage, and the doline generally has a non circular rim. There is a pile of blocks in the doline that have fallen from the roof. In some of these dolines a cave or an underground stream can be observed (Fig. 10.1). The newly formed doline south of SarVtepe is a good example of this (Fig. 6). In the second stage,
Fig. 10. Schematic development stages of collapse dolines.
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Fig. 11. Doline development south of west Lota Lake by undercutting of its steep sides. The photograph shows a 2 m wide block separated with a deep crack which is ready to fall 0.5 m wide.
with the collapses or block fallen are going on the slopes of doline continuous to enlarge. This kind of doline development results from either active cave roof collapse or undercutting of doline slopes. If there is a permanent lake in the doline the blocks that fall into the lake eventually dissolve. At least one of the sides of the doline still maintains its steepness (Fig. 10.2). This was the case in West Lota (Fig. 11) and SarVtepe dolines. In the third stage the doline reaches its maximum diameter and acquires a circular rim. The doline has sloping margins (Fig. 10.3). KVzVlc¸am doline is good example for this (Fig. 5). The final stage involves the retreat of the sides of the doline as a result of dissolution (Fig. 10.4). The doline may merge with the neighboring doline at this stage, its area increases and steepness of the side slopes decreases (as it’s the case of the OvacVk collapse doline: Fig. 3).
5. Conclusions Sivas and its surroundings is the most important gypsum karst terrain in Turkey with a massive Lower Miocene gypsum formation 750 m thick. The region
east of Hafik has a wide variety of well developed karstic features. Initial karstification of the gypsum east of Hafik started in the Early Pliocene. There is youthful karst (doline karst) on the Higher Plateau (Upper MioceneEarly Pliocene denudational surface) and mature karst on the Lower Plateau (Early Pleistocene denudational surface). East of Hafik the piezometric level has fallen at least 200 m since the Early Pliocene and 90–100 m from the Early Pleistocene. The continuous decrease of the piezometric level throughout Plio-Quaternary period made it impossible for the development of karstic formations such as poljes and collapse dolines upon the Higher Plateau. On the surface of Lower Plateau, while surface drainage was performed through valley, due to incision KVzVlVrmak, tributaries became hanging valley. Hence, on the surface of Lower Plateau in the Early Pleistocene occurred youth karst. Together with sequence going dissolution and erosion, this stem from the lowering of the plateau level towards KVzVlVrmak valley, let to a two-stage mature karst development, in areas where gypsum thickness on local base level (or piezometric level) is relatively more, enlarged, shallow paleokarstic valleys, uvalas and collapse dolines are found, whereas in areas where thickness decreased,
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poljes, collapse dolines and degraded collapse dolines are found. The formation of collapse doline goes on the mature karst area to the east of Hafik. It is possible that the catastrophic collapses in this area, great danger for both lives and property. Consequently, there are several control factors on gypsum karst. Among these factors on the development and evolution of massive Hafik gypsum karst, suitable precipitation condition for the gypsum karst, piezometric level change (or base level change) and areal change of gypsum thickness above piezometric level or relief configuration of the area are more considerable elements. Besides, this study is significant, it indicates that the process, which began with youth stage (doline karst) on gypsum karst in such a short period of time as the Quaternary, has reached maturity stage (polje and collapse doline) and further more in some mature karst features has started to degradation process.
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