Geomorphic Signatures of Active Tectonic in Drainage Basins in the

J Indian Soc Remote Sens DOI 10.1007/s12524-011-0145-8

RESEARCH ARTICLE

Geomorphic Signatures of Active Tectonic in Drainage Basins in the Southern Bolkar Mountain, Turkey Türkan Bayer Altın

Received: 8 October 2010 / Accepted: 17 June 2011 # Indian Society of Remote Sensing 2011

Abstract Bolkar Mountain forms the northeast extent of the Central Taurus Mountains, which are located north of the eastern Mediterranean Sea and consist of 3000 m or higher summits. The study area southern part of Bolkar Mt, has been investigated for geomorphic signatures of active tectonics using Geographical information system (GIS). The lower valley floor-towidth to height and elongation ratios, higher convexity, stream length-gradient (SL) indices, hypsometric integral and convex nature of the hypsometric curves and topographic asymmetry show that relative tectonic activity is greater in the eastern sector affected by Ecemiş fault. Spatial variations of tectonic activity along rivers studied point to a general trend of decreasing activity towards the west as well as tectonic activity again increase in the west. Westward migration of basin and range extension is consistent with the place of uplift in the southern Bolkar Mt. Topography of the southern sector is the result of Late Miocene-Early Pliocene extension related uplift. Drainage systems in the upper part of the central and western sectors are under the lithological control and karstic denudation; whereas the development of the drainage systems in the middle and outlet parts of all sectors depend on sea level

T. B. Altın (*) Department of Primary School Teaching, Faculty of Education, Niğde University, Niğde, Turkey e-mail: [email protected]

changes and Late Quaternary tectonism. The development of drainage systems of the eastern sector depends mostly on fault tectonism and climatic changes in the Late Quaternary. Keywords Bolkar Mountain . Taurus region . Drainage systems . Morphotectonic parameters . Quaternary

Introduction The Bolkar Mountain is the central part of the Taurus region which rises along the southern edge of the Anatolia Plateau. The convergence of Anatolian Plate with the Africa-Arabia Plate is accommodated by the active thrusts and faults (Şengör et al. 1985; Taymaz et al. 1991; Görür et al. 1995) and is expressed in the associated geomorphic features in this mountainous region. The displaced denudational accumulation surfaces, alluvial fans, topographic ridges, river and marine terraces are some of the potential indicators of active tectonics manifested along these thrusts and faults. Active tectonic movements along the tectonic thresholds and the thrusts have played an important role in the morphological evolution of the topographic features in the southern Bolkar Mt. An integrated multi-disciplinary approach using drainage, geomorphological and structural features is very useful in evaluation of active tectonics (Bhatt et al. 2008). The information about geomorphic indicators of active tectonics can be retrieved through analysis of topo-

J Indian Soc Remote Sens

graphic maps, aerial photographs, satellite data and quantification of morphotectonic indices (Keller 1986). Few researchers used GIS technique to identify and quantify morphostructural evidence of active tectonic. Bayer Altin (2008) identified structural extension and various geomorphic evidence of active tectonic using GIS technique along the southern Bolkar Mt. Dhont et al (1999) used Digital Elevation Model, satellite imagery and topographical maps supported by field checks to study extensional tectonic and its control on the uplift of the Bolkar Mt. In this paper, active tectonic movement will be focused along the southern Bolkar Mt. using morphotectonic indices with GIS techniques. Both geological and tectonic geomorphology features of the Bolkar Mt. have been confinedly studied (e.g., Tekeli et al. 1983; Özgül 1983; Akay and Uysal 1988; Erol 1991). Öner et al. (2005) investigated sea level changes during the Holocene in the tarsus delta plain situated within the Southern Bolkar Mt. Many workers studied glacial, periglacial and glacio-karst of the Bolkar Mt. (Birman 1968; Atalay 1973; Messerli 1980; Altin 1998; Çiner 2003; Altin and Bayer Altin 2005; Bayer Altin 2007). In the present study, an attempt has been made to identify and document various geomorphic indicators of active tectonic using topographic maps, supported by limited field check and through quantification of morphotectonic parameters, in the basins of the southern Bolkar Mt.

Geomorphology and Geology of the Study Area The study area consists of river basins situation within the southern Bolkar Mt. that overlooks the Mediterranean Sea (Fig. 1). This mountain forms a belt with peaks up to 3500 m, lying more or less parallel to the Mediterranean Sea coast. These summits exceed 3000 m, including Medetsiz H. (3524 m), Aydosdağ (dağ: mountain, 3430 m), Kekrecikdağ (3130 m) and Karayelekdağ (3069 m). As a result of the N-S compression that developed from the collision of the Arabian and Eurasian plates in Eastern Anatolia during Middle Miocene (Şaroğlu et al. 1983), Middle Miocene sediments are found at an elevation of 3000 m in Bolkar Mountain (Erol 1983, 1991, 2000). Following the collision phase, the Mediterranean Sea began to recede to the south

during the Lower to Middle Miocene, Upper Miocene, Pliocene, and Quaternary as a result of the different phases of uplift of Taurus Mountains (Erol 1997). A wide erosional surface system developed during the lower to middle Miocene (Erol 1997), which contains the rock units deposited from the Cambrian through the Tertiary (Özgül 1976). These erosional surfaces, which are located above 2000 m in elevation, correspond to rugged plateau areas in the Taurus orogenic belt that were dissected by rivers, uplifted, and dissected by faults during the Neotectonic (Erol 1999). From the headwater of the basins to the foot of the mountain, younger surfaces are lowland but consist of rugged morphologies (Öner et al. 2005). The deposits transported from Bolkar Mountain in violent uplift periods were deposited in basins that formed deep in front of the mountain. Because the edge of the basin was also uplifted during the later violent uplift period, former young units were included the new erosional area (Erol 2003). Thus, the sediments, which become younger from Bolkar Mountain to the Tarsus Plain, extend uninterrupted. The monocline blocks on these sediments form the main element of geomorphology of Bolkar Mountain (Öner et al. 2005). Bolkar Mountain has an asymmetrical appearance (Altın and Bayer Altın 2005): It is steep and narrow in the north, but it is wider and has plateaus in the south. Periglacial and glacial forms are found between 2500–3000 m in basins (Bayer Altın 2007) in the north (Fig. 2a, b), and fluvio-karstic forms are dominant in the southern part of the mountain. Vast formations of karst exist, as do landscapes that reveal the effects of glacial and fluvial erosion (Fig. 3). Additionally, deep karst and surface karst forms have developed on different ages and types of limestone (Altın 1998); these karstic forms contribute to the development of a drainage network. Furthermore, streams disappear into sink holes and karst pits, and karstic depressions extend through linear lines, capturing other neighborhood basins that are the consequence of the tectono-karstic development. Thus, in addition to structure and lithology, the effect of tectonic activity also is important in the development of the drainage network. The belt consists of carbonate and detrital rocks with variable age and kind (Fig. 4) affected by folds, thrusts and transcurrent faults resulting from two main tectonic events in the Late Cretaceous and Late EoceneOligocene (e.g., Özgül 1983). The Bolkar Mountain


Fig. 1 Location map of the study area

have raised since the Late Miocene (Özgül 1976) as attested by marine Lower to Middle Miocene sediments now at elevations more than 2000 m, unconformably overlying ophiolitic and platform carbonate rock units which were thrusted during the compressive events. The belt is interpreted as the northern uplifted shoulder of the Adana-Clicia basin situated within the eastern Bolkar Mt., due to thermal effects of Neogene lithospheric stretching and thinning (Dhont et al. 1999). The Late Neogene uplift has been interpreted as resulting from thrusting (Williams and Unlügenç 1992) or as a wide anticlinal fold (Şaroğlu et al. 1983). Some faults, which affected the morphology and lithological units, have been detected in several parts of the Bolkar Mt. The most important of these faults is the Ecemiş Fault, which cut the eastern part of the Bolkar Mt. This fault, striking NNE in its southern

part, which may have accommodated about 80 km of left-lateral slip motion since the Eocene (Özgül 1976; Scott 1981; Şengör and Yılmaz 1981; Yetiş and Uçar 2001).

Materials and Methods In this study, the basins, are situated within the southern Bolkar Mt, were investigated by using geomorphic indices. The study used SRTM data and GIS interpretive techniques to reveal the relationships between the morphometric parameters and the geologic, topographic and hydrologic features that have controlled the development of the basins. These features were overlaid on 1:25,000-scaled base maps. A quantitative data set and 3-D digital terrain models


Fig. 2 The simplified geomorphology map of the Kurtsuyu (a) and Tarsus basins (b)

were produced from mathematically defined data processed using GIS. In addition, digital elevation models (DEMs) were used to calculate the following geomorphic indices: valley floor width-to-height ratio (Vf), stream length-gradient index (SL), topographic symmetry factor (T), concavity index (CI), elongation ratio (Re), basin compactness (Bc), hypsometric curve Fig. 3 The simplified geomorphology map of the Mergin, Sorgun and Yumuk basins

and hypsometric integral (HI) (Table 1). Thus, a systematic geomorphological analysis of the drainage network was performed via a survey of the geomorphic indices of the individual basins. These indices are particularly related to anomalies in the longitudinal profiles and cross-sections of the basins (knickpoints, changes in the intensity of rejuvenated, headward and actual


Fig. 4 a Schematic presentations of the distribution of SL values along the rivers. b diagrams showing the distribution of SL values along the rivers. This map was compiled from 1/500.000 geological map of Turkey (MTA 2002). Faults from MTA (2002)

erosion). The study area was divided into four main basins and two sub-basins. From west to east, the main basins are the Mergin, Sorgun, Yumuk and Tarsus River basins. From west to east, the sub-basins are the Kurtsuyu and Cehennem subbasins. Downstream of the Göksu River investigated, because only this part of the Göksu River originates in the Bolkar Mt. The Tarsus Basin consists of the Tarsus River, the Cehennem Creek, and its other streams. These rivers discharge into the Mediterranean Sea.

Results and Discussion SL Index The high SL values are found on soft rock of Tertiary area. Anomalously high values of the SL index occur along fault trending NE-SW. This area of the high SL

values may indicate recent local tectonic activity. The low values are found at the confluence between the Kurtsuyu creek and main river, despite faults. Anomalously low values of the index may also represent tectonic activity (Keller and Pinter 2002). Along linear valley produced by fault trending N-S, low indices are found because the rocks in the lower reaches of the Kurtsuyu valley was crushed by fault movement. Thus Kurtsuyu creek flowing through valley has had lesser slope. Göksu River has low SL values along the valley, where the rock types are sediment and clastic rocks. The sensitivity of the SL index to rock resistance is illustrated on Fig. 4a, which shows the longitudinal profile of the Mergin and Sorgun rivers. SL values are relatively low in the lower and middle reaches of the Mergin River valley, where the rock types are Neritic limestone. The index increases at the resistant rocks in the higher reaches consisting of basic and ultrabasic rocks. SL values of

J Indian Soc Remote Sens Table 1 Explanation of morphometric indexes used in tectonic landform analysis (after Wells et al., 1988; Keller and Pinter 2002; Panek 2004; Bhatt et al. 2008). Morphometric parameter

Mathematical derivation

Explanation

Hypsometric integral (HI)

HI ¼ Hm Hmin=Hmax Hmin

Hmean: mean elevation of the basin.

Most tectonically active areas show high values of HI (usually HI > O,6) Stream length-gradient index(SL)

Disequilibrium conditions suggest tectonic disruption of the bed Valley floor width to height ratio (Vf)

Low values of Vf and Lwf show possible uplift tendency or zones of more resistant bedrock Concavity (CI)

Hmax: elevation of the highest point within the basin. Hmin: basin mouth

SL ¼ ðHmax Hmin=ΔLÞ L

ΔL is the length of the reach, L is the total channel length from the point of upstream to the highest point on the channel

Vfr ¼ 2Lwf =ðEl EsÞ þ ðEr EsÞ Lwf: valley floor width, El and Er are elevations of the left and right valley divides respectively. Es is the elevation of the valley floor

CI ¼ Ac=At

Equilibrium profiles have a lower concavity index, while rivers in tectonic regions have a higher concavity index T ¼ Da=Dd Topographic symmetry factor(T)

At is the fraction of the area onthe curve, Ac is the fraction of the area under the curve

Da is the distance from the channel to the basin midline. Dd is the distance from the 1ateral basin margin to the basin midline

T value can detect areas of lateral tilting For a perfectly symmetric basin, T = 0 As asymmetry increases, T increases and approaches a value of 1 Drainage basin elongation ratio (Re)

p p Re ¼ ð2 A= pÞ=L

The Re values less than 0.50, betmeen 0500.75 and more than 0.75 are characteristic of tctonically active, slightly active and inactive settings respectively Bc ¼ P=A Drainage basin compactness (Bc)

A:basin area, L: basin length

P:basin perimeter

High values of the Bc show long-term erosion activity or less resistant rocks

Sorgun River range low and high. The index begins the high value in the higher reach, and then decreases on relatively soft rocks of the Tertiary area. The index increases dramatically along the W-E trending faults. Finally, the index decreases again at the soft of the Tertiary and Quaternary areas. The high SL values on the soft rocks indicate recent tectonic activity in the higher reaches of the Yumuk River. The N-S trending faults and overthrust faults are cause of the high SL values. The index decreases dramatically again at the soft rocks of the Tertiary and Quaternary areas in the lower reaches of the river. The highest values in the study area are found in the higher reaches of the Tarsus and Cehennem

valleys (Fig. 4b). These values are 10500 gradient meters or greater and found between 3200 m and 2700 m where is impacted by Late Pleistocene glaciations. Moreover this area is affected by Ecemiş fault and other E-W trending faults. The sensitivity of the SL values to changes in channel slope due to glacial erosion is good example. Because the rocks in the valley were crushed by glacial body, low indices are expected. However, the existence of the important high values of the SL values in the higher reaches highlights the domination of the tectonic processes over the glacial erosion. Low indices are found in the belt of the rocks with low resistance in Tarsus canyon and Cehennem canyon. These rocks are clastic,


carbonate rocks and Quaternary fill. E-W trending faults are also found in area of low SL values. The high SL values in the higher reaches of rivers may indicate recent tectonic activity (probable Quaternary) of the Ecemiş Fault. Hypsometric Curve and Integral The main basins and the subbasins are identified by convex-up hypsometric curve with high HI value which is typical for youth and undissected landscape with disequilibrium stage. The HI values range between 0.49 and 0.51 (Fig. 5). The Cehennem Creek has the highest HI value. The HI value of the Kurtsuyu Creek is lower than others. The shapes of these curves indicate that basins are not very evolved, suggesting that the effectiveness of the fluvial and karstic processes are low. The convex curve of Mergin basin consisting of neritic limestone which is a less resistant lithology, has high hypsometric integral. Although the other basins all belong to the rocks with a varied lithology of limestone, clastic and carbonate rock, basic, ultrabasic, schist and marble, their curves are also convex-up shape. The relation between lithological resistance and hypsometric curve is not notable, but tectonic has also been a factor. The hypsometric integral increases progressively from west to east. Hypsometric curves of the eastern and central sectors are convex; Kurtsuyu subbasin in the Fig. 5 Hypsometric curves and hypsometric integral of the basins

west is slightly convex. Considering that the lithology is homogeneous and scale is minor influence, the only possible explanation for this is tectonics. The central and eastern sectors of the Bolkar Mt, as a consequence of the asymmetrical anticline development, have been more uplifted than western sector, and since the erosive agents in them are not yet effective the HI values are 0.50 or greater. The Tarsus and Cehennem basins—where the fluvio-karstic canyons are found—show HI values of 0.51, slightly higher than those in the western zone, showing a greater effect of the degradational processes, mainly fluvial erosion and glacio-karst evolution. Disparities seen in the hypsometric curves reflect the paleogeography of Bolkar Mountain. These basins formed during the humid climatic conditions of the Pliocene (Erol 1983, 1990) and were further affected by Pleistocene glaciation (Würm) (Birman 1968; Çiner 2003; Altın and Bayer Altın 2005). The area that was eroded by sub-glacial streams corresponds to a concave-up curve. Thus, the peak has moved further downwards due to the larger effects of karst erosion in this area. The area that consists of more resistant limestone or anticlines corresponds to a convex-up curve. The distribution of the values of hypsometric integral corresponds with tectonic structure of the region. High values above 0.50 can be found particularly on the forefront of the anticline in the Tarsus and Cehennem basins of a block-uplifted culmination part of the Bolkar


Mt, on this margin of the study area roughly along the line of the Ecemiş fault and other E-W trending faults which formed present elevation structure on the highest point of the region. The slightly low HI value observes in Kurtsuyu subbasin on the western side (0.49) can only be explained by the anticline configuration, which has uplifted its head water while depressing the lower part of the basin. Based on the morphometric parameters of the main basins and the sub basins, morphologic development of Bolkar Mountain can be explained by several different hypotheses: (1) Concave-up and convex-up curves indicate that after the basins reached a mature stage, they underwent rejuvenation and backward erosion. (2) These curves indicate that Bolkar Mountain was exposed to tectonic uplift several times. According to Akay and Uysal (1988), the Central Taurus uplifted during the post-Eocene period and was exposed to the effects of four different compression periods. The extension formed due to this compression trends in the N-S direction and progressively turns E-W in the northern portion of the belt (Şaroğlu et al. 1983). This change is related to the escape of Anatolia toward the Aegean domain from the late to Middle Miocene until today (Şaroğlu et al. 1983; Jackson and Mc Kenzie 1984; Akay and Uysal 1988; Dhont et al. 1999). According to these studies and hypsometric curve of the basins, after the LowerMiddle Miocene, this mountain uplifted in different phases, and the Mediterranean Sea began to recede towards the south as a result of this uplift. As such, different erosional surfaces developed, which extended along the southern feet of the Taurus Range (Erol 1997). (3) The existence of different curves might also be due to the structure of Bolkar Mt. For example, the convex curve of the Göksu Basin corresponds to an anticline in the headwaters. However, lithological variations also can affect the hypsometric curves of these basins. Longitudinal Profile and Concavity Index Two longitudinal profiles were extracted along channels in the Göksu River drainage. The mouth of the Göksu River is controlled by fault near the coast (Fig. 6). A profile of the westward-flowing Göksu River tributary Kurtsuyu Creek (Fig. 7) was also drawn. Both longitudinal profiles show a prominent concave upward section of the profile with the

Fig. 6 Longitudinal profiles of the Göksu River. Distances are measured downstream from the basin divide. Dashed lines show E-W trending faults and relative movement (U: upthrown block; D: ownthrown block)

knickpoints at the mountain front. Upstream from the concave upward section both profiles have a relatively convex upward shape, showing that at least 50 m of incision in the lower reaches. The Kurtsuyu Creek has an overall convex upward shape, but has a concave downward longitudinal profile. Knickpoints are found at the confluence with the main river, showing that at least 250 m of incision in this area and this creek is not completely in equilibrium. Mergin and Sorgun rivers have an overall convex upward profile (Fig. 7b, c), but concave profile is found between 1750 and 1500 m in Mergin basin, and 1500 m and 1250 m in Sorgun basin. These areas correspond to karstic erosion. These main basins have not prominent faults. The resistant lithology is the likely cause of the convex shape of the profile from 2000 m to 250 m. The convex shape at the mountain front shows that this is an area of rapid base level change near the mountain front. The slightly concave shape in some parts of these basins reflects low incision and slope and presence of exokarst. The concave and convex shape are successive along longitudinal of Yumuk River (Fig. 8a). The various resistance lithologies are cause of the convex and concave shapes of the profile. This river has concave profile between 500 m and 0 m, but several small knickpoints are found in these elevations. These knickpoints indicate at least 500 m of incision has occurred near the mouth of the river. Concave-up and convex-up curves suggest that the impact of sea level changes on the geomorphic evolution of the area should be considered. According to Erol (1990) and Öner et al. (2005), the Mediterranean Sea level was affected by glacial melt during the Pleistocene and the


Fig. 7 Longitudinal profiles of the Kurtsuyu Creek (a), Mergin (b)and Sorgun (c) rivers. Distances are measured downstream from the basin divide. Dashed lines show NE-SW trending faults and relative movement (U: upthrown block; D: ownthrown block)

Fig. 8 Longitudinal profiles of the Yumuk River (a), Cehennem Creek (b) and Tarsus River (c). Distances are measured downstream from the basin divide. Dashed lines show E-W trending faults and relative movement (U: upthrown block; D: ownthrown block)

Holocene, and this change is reflected in the 0–500 m portion of the hypsometric curves. Additionally, the Mediterranean Sea level retreated due to arid climates during the Messinian (late-upper Miocene) (Erol 1983, 1997). Thus, rivers eroded valleys depending on this general base level. The longitudinal profile of the Cehennem Creek (Fig. 8b) and Tarsus River (Fig. 8c) are o good example of the effects of glaciation. The prominent concave shape is the result of glacial erosion between 3000 m and 2700 m. Knickpoints are found near the faults and Tarsus River confluence. Either the faults (e.g., Ecemiş Fault

and E-W trending faults) or confluence could cause the gradient change. The low elevations suggest that the knickpoints are likely the result of glacial erosion. Knickpoints show 1300 m of incision because of these faults. The Tarsus River has several knickpoints at the confluence between the west (Cehennem Creek) and middle forks, showing that the river is in disequilibrium. These knickpoints are situated with in area corresponding to low elevation (between 1000 m and 50 m). The knickpoints are at such a low elevation that they are unlikely to be the result glaciation and are likely the result of an increase in


stream power due to Ecemiş Fault. Because this fault has totally 80 km of the left-lateral slip motion since the Eocene (Akay and Uysal 1988). This situation infers that slip on the Ecemiş Fault is the likely cause of the knickpoints. If 1000 m of uplift at the mountain front is subtracted from the longitudinal profile, the old mountain front may have been in equilibrium, with a convex profile, prior to a recent pulse of uplift at the mountain front. Moreover these knickpoints to be evidence of Quaternary tectonic activity of the Ecemiş Fault along the mountain front and show at least 1000 m vertical uplift of the basement because of this fault. Valley Floor Width to Height Ratio The cross channel profiles of the Tarsus River and Cehennem Creek, as well as the tributaries crossing the active fronts, are marked by deeply incised canyons showing “V-shaped” narrow valleys. The analysis reveals that the Vf values for the Tarsus River range from 0.01 to 5.16 and for Cehennem Creek from 0.01 to 0.15 (Fig. 9) which represent typically canyon valley. The mean Vf value of Tarsus River and Cehennem Creek 0.24 and 0.04, respectively (Table 2) The upper part of the canyon valley correspond to along front of the anticline which has experienced the most active tectonic uplift due to Ecemiş Fault and other E-W trending faults. Looking at the shape of the valley floors of the Tarsus River and the values of Vf, it appears that values of the Vf index 1 are observed along fronts of anticline where the highest point is found in the study area and near the coast. In other words, Tarsus River has broad U-shaped valleys with high Vf values >1. Existence of high Vf values of higher and lower parts of this valley indicate major glacial erosion and lateral karstic erosion, respectively due to the stability of base level or to tectonic quiescence especially in lower parts. Kurtsuyu Creek subbasin—where is found the eastern sector—has low values near the main river and high values in upper coarse. This river flows in deep canyon at the downstream with low Vf values develop in response to active uplift. This fact marks out that the tectonic activity is higher at the downstream than upstream where is presence of exokarst and low incision.

This index applied at a set distance from the mountain front (50 m) for every studied valley. The reason for working in this way is that valley floor of some rivers (Mergin, Sorgun and Yumuk) tend to be come gradually narrower middle part of valley from mountain front and wider in upper part of valley (Fig. 9). The broad valleys with high Vf values >1– 0.2 indicate major lateral karstic erosion, due to the stability of local base level or to tectonic quiescence. In addition, these broad valleys were developed by the lateral migration of channels in response to a stable local base level. These rivers have valley with low Vf values which are marked by deeply incised gorges (canyon) showing “V” shaped narrow valley. Existence of low Vf values at the low elevations show changes in sea base level. Concavity Index, Elongation Ratio (Re) and Basin Compactness (Bc) The concavity of the large river drainage basins vary from 0.28 to 1.15 (Table 2). The highest concavity is 1.15, 1.11 and 1.05 for the Kurtsuyu Creek, Mergin and Sorgun rivers, respectively. All the other rivers have concavities are 0.3 or greater. Although Tarsus River and Cehennem Creek are affected by Ecemiş fault, their concavity value is low, suggesting that rocks in the valleys were often crushed by glacial movement within the upstream. Resistant lithologies are cause of the high value of concavity in Mergin. The Kurtsuyu Creek has a higher concavity than the other rivers, which is interpreted as a greater rate of tectonic activity. The Sorgun, Yumuk, and Tarsus rivers are approximately the same distance from the mountain front but have varying concavities. The Sorgun and Yumuk have higher concavities than Tarsus River, suggesting that knickpoints have not migrated upstream and have had more recent uplift than Tarsus River. The values of Re vary from 0.37 up to 0.61 in the study area. According to Zuchiewicz (1989) the values of Re varying from 0.75 oscillate in the basins in tectonically active, slightly active and inactive areas. According to this ratio, five basins are situated in the zone with moderate tectonic movements; only two basins (e.g Sorgun and Yumuk) with their values approach the category manifesting low tectonic uplifts (Table 2).


Fig. 9 Mean Vf values of rivers along elevations

Bc value stands for a quantitative indicator of the segmentation of the basin groundplan (Panek 2004). High Bc values are observed particularly in Sorgun and Yumuk basins in less resistant rocks with longterm erosion activity (Table 2). Variations in the geomorphic indices along the southern Bolkar Mt suggest different uplift histories

and sea level changes in basins. Therefore the hypothesis that predicts block uplift of the southern Bolkar Mt, range extension fits the morphotectonic analysis. Extension in the southern Bolkar Mt supports uplift to the east at the Tarsus basin as documented by Dhont et al. (1999). Westward migration of the basin and range extension predicts

J Indian Soc Remote Sens Table 2 Concavity, T, Vf, Re and Bc values basins: basins are listed from west to east

River

Concavity

Tvalue

MeanVfvalue

Göksu

0.48

Kurtsuyu

Re value

1.15

0.68

0.27

Mergin

1.11

0.51

0.11

0.61

Sorgun

1.05

0.42

0.08

0.37

Yumuk

0.59

0.42

0.11

0.46

Cehennem

0.36

0.36

0.04

0.59

Tarsus

0.28

0.73

0.24

0.51

Fig. 10 Statistical diagram showing the distribution of T values in every basin

057

059

Bc value 0.19 0.21 0.18 037 0.34 0.25 0.17


that the greatest tectonic activity is found near the Tarsus River. E-W trending change in extension may be related to the Middle-Late Miocene to present westward escape of Anatolia toward the Aegean basin (Dhont et al. 1999). Topographic Symmetry Factor (T) Bolkar Mt. is deeply dissected by ‘V’ shaped valleys and gullies of relief exceeding at places 250 m. These valleys form a dendritic pattern and belong to several long and narrow, usually asymmetric, drainage basins. In general the calculated T values vary from 3.36 (roughly symmetric) to 0.73 (asymmetric). T values of the basins are 0.36, 0.42, 0.42, 0.58, 0.68 and 0.73 for the Cehennem subbasin, Sorgun Basin, Yumuk Basin, Mergin Basin, Kurtsuyu Subbasin and Tarsus Basin, respectively (Fig. 10). According to this analysis, eastern sector (except for the Cehennem subbasin) and western (Kurtsuyu Subbasin) sector of the study area have roughly asymmetric and asymmetric (Tarsus Basin) and the central sector have roughly symmetric (Mergin, Sorgun and Yumuk basins). Asymmetry of the Kurtsuyu and Tarsus basins could be interpreted as the result of tectonic tilting. T values indicate that the eastern and western sectors are more tilting than the central sector. Faults within the eastern sector bound north-dipping tilted blocks and are extensional (Dhont et al. 1999). Limitations on the Interpretation of Tectonic Geomorphology Tectonic activity is not the only factor that causes differential erosion within the southern Bolkar Mt. Bedrock type, glacial history and sea level changes all affect erosion rates and uplift. In the other words, the morphology of the basins with the calcareous platform in the southern Bolkar Mt was the result of the interaction between tectonic, fluvial, glacio-karstic processes and sea level changes. Glacial erosion could affect the interpretations of geomorphic indices because alpine glaciers increase mechanical and chemical denudation rates (Hallet et al. 1996). Bolkar Mt was glaciated in the Pleistocene (Çiner 2003; Messerli 1967). Glaciers have extended downvalley in the southern part of Bolkar Mt to elevations as low as 2800–3000 m (Altın 1998; Bayer Altın 2007). Thus Morphometric parameters were calculated at the

southern sector where lower elevations would be less affected by glaciation. In addition, gradient changes in longitudinal profiles were evaluated for the possibility that these changes resulted from glacial and galciokarstic erosion. The high Vf values proved this erosion in upper section of the Tarsus Basin and Cehennem subbasin. Resistant and less resistant bedrock type could effect erosion of the southern basins. There are low grade metamorphic rocks of Bolkar Mt and an Upper Cretaceous ophiolitic melange (Demirtaşlı et al. 1984). The sea level changes was established between the Göksu and Tarsus deltas during the Holocene (Erol 2003; Öner et al. 2005; Çiner et al. 2009). In addition, the Mediterranean Sea level retreated due to arid climates during the Messinian (late-upper Miocene) (Erol 1983, 1997). Thus, rivers eroded valleys depending on this general base level.

Conclusions The analysis of geospatial database using GIS helps identification of geomorphic indicators of active tectonics and quantification of morphometric parameters. The strong control exercised by the NE-SW and E-W trending faults on the drainage network is reflected by knicpoints, deep canyon valleys and abrupt changes in the flow direction. Variations in the geomorphic indices along the southern sector of Bolkar Mt suggest different uplift histories and sea level changes in basins. While tectonic uplift, structure, and karstic denudation affected the top of the longitudinal profile (from 1000 m), the Mediterranean Sea level changes that depended on climatic changes affected regions below 1000 m. Successive step-like strips of surfaces from 1000 m to 2500 m indicate that tectonic dynamism was rapid, and there was little time for the erosion of surfaces during tectonic uplift. In the central sector, the longitudinal profile of basins has concave shape in variation elevations (e.g. 1750–1500 or 1750–1250). Fluvial erosion increased toward the watershed and dominant karstification (exokarts), depending on fluvial erosion, occurred at these elevations. The formation of stepped surfaces towards to Mediterranean Sea indicates that tectonic uplift has been repeated several times, and the height of these basins significantly increases.


The morphotectonic indices show higher tectonic activity in four areas. High tectonic activity is found at the confluence with main river in Kurtsuyu subbasin (i), near the Göksu River mouth (ii), in the upstream of Tarsus (iii) and Cehennem (iv) basins where the greatest activity is found. Greater tectonic activity in the eastern and western sectors is coincident with the Ecemiş fault zone and NE-SW trending fault, respectively. The lower valley floor width-toheight and elongation ratios, higher concavity, SL indices, and hypsometric integral and convex nature of the hypsometric curves and interpreted to show greater tectonic activity in the western and eastern sector in the Southern Bolkar Mt. Although not as prominent, relatively greater tectonic activity is found in the Mergin, Sorgun and Yumuk basins compared to the other sectors. All drainage systems were primarily affected by local tectonism, sea level changes and secondarily by glacial erosion. The lower parts of all drainage systems are much younger than the in upper mountainous parts. Tectonic uplift was important especially in the eastern sector, and this phenomenon is still present. Tectonic uplift has been more important than river erosion, so that the southern rivers were not able to develop an equilibrium profile with a high concavity. In other words, the actual form of the longitudinal profiles of the rivers is the result of continuous adjustment since the Quaternary until the present day. A combination of the Middle-Late Miocene extension followed by Early Pliocene to present Ecemiş fault zone boundary deformation is most consistent with geomorphology of Bolkar Mt. Extension hypothesis explain the higher elevations in the eastern sector. Because extension occurred in the Miocene, the effects would again increase during Quaternary. This is consistent with uplift rates in the eastern sector. The higher tectonic activity in Tarsus valley is consequence NE-SW trending Ecemiş fault interactions beginning in the Miocene and continuing to the present. Spatial variations of tectonic activity along the studied basins point to a general trend of increasing activity towards the eastern sector. Acknowledgement The author wish to thank editor Vinay Kumar Dadwal and reviewer for their valuable comments and suggestions, which significantly helped to improve the manuscript.

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