Geological Features for Geotourism in the Zanjan and Hamadan Area, Northern Iran

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Article Geological Features for Geotourism in the Zanjan and Hamadan Area, Northern Iran

Ardalan Afrasiabian 1 , Siamak Mahmoudi Sivand 2, Dragana Doganˇci´c 3 , Lucija Plantak 3 and Bojan Ðurin 4,*

1 Institute of Applied Geosciences, Graz University of Technology, 8010 Graz, Austria; [email protected] 2 Water Research Institute, Tehran 1417466191, Iran; [email protected] 3 Faculty of Geotechnical Engineering, University of Zagreb, 42000 Varaždin, Croatia; [email protected] (D.D.); [email protected] (L.P.) 4 Department of Civil Engineering, University North, 42000 Varaždin, Croatia * Correspondence: [email protected]

Abstract: Iran is a land of complex geological past which reflects in its many natural wonders. There are more than 850 known caves in Iran with a total length not exceeding 1000 km, many of them not being properly explored. Two of the biggest and most famous caves are Ali-Sadr and Katale-Khor. The Katale-Khor cave has a simple maze anastomotic pattern. Ghar Ali-Sadr is an anastomotic type of cave located 75 km northwest of Hamedan in a village by the same name and circa 60 km south of Katale-Khor cave. Ali-Sadr cave is considered to be one of the most unique and scenic caves in the world. One of the features that makes Ali-Sadr cave special is a fact that it is the longest and the biggest water cave in the world (from the point of the boating course inside the cave). This natural wonders in Northern Iran are great base for developing a geotourism, as a form of tourism that specifically focuses on geology and landscape. Its purpose is to promote an understanding of Citation: Afrasiabian, A.; Mahmoudi earth sciences through appreciation and conservation of geodiversity. The best way to achieve this is Sivand, S.; Doganˇcić,D.; Plantak, L.; through visits to geological features and locations. Ðurin, B. Geological Features for Geotourism in the Zanjan and Keywords: Hamadan Area, Northern Iran. karst cave; passages; karst spring; talars; Iran Sustainability 2021, 13, 6587. https:// doi.org/10.3390/su13126587

Academic Editor: Dmitry A. Ruban 1. Introduction Caves have fascinated mankind from the earliest times. Caves provided shelter from Received: 16 April 2021 the elements and became home for the first humans. Evidence for that is seen in numerous Accepted: 2 June 2021 archeological remains found inside inhabitable caves. Cave drawings are both an evidence Published: 9 June 2021 of artistic aspirations of the first modern humans, and a testimony of past times by being the first documentary depictions of everyday events and immediate environment. Nowadays Publisher’s Note: MDPI stays neutral caves are a window to Earth’s interior and means to investigate unknown aspects of with regard to jurisdictional claims in underground dynamics. Caves can be defined as underground spaces created by natural published maps and institutional affil- geological and geomorphological processes which are large enough to be examined in iations. certain way by humans. The majority of caves have developed in the rocks which can be dissolved by a weak natural acid like carbonic acid which forms by absorption of CO2 by rainwater either in the air or in the upper layers of soil [1]. The growing interest of tourists to visit the caves and the development of speleology Copyright: © 2021 by the authors. make the caves an attractive natural asset today [2,3]. Even at the moment, the underground Licensee MDPI, Basel, Switzerland. world is still posing a mystery to most people who never visited it because it is believed to This article is an open access article be (and is to some extent) dangerous. The underground exploration requires both special distributed under the terms and equipment and knowledge of the speleological techniques. However, the fascination of a conditions of the Creative Commons strange and mysterious place, such as the underground, is the main impulse for people to Attribution (CC BY) license (https:// partake in underground geotourism. Process of transformation of the cave in a show cave, creativecommons.org/licenses/by/ suitable for visits of the tourists untrained in speleological techniques is complex and it 4.0/).

Sustainability 2021, 13, 6587. https://doi.org/10.3390/su13126587 https://www.mdpi.com/journal/sustainability Sustainability 2021, 13, 6587 2 of 15

requires modification of the underground space. The first step necessary to transform a natural cave into a show cave is to understand its unique significance from both aesthetic and scientific aspects. To enable entering visitors into the caves, one must ensure lights, ladders and staircases, bridges, handrails and pavements. Furthermore, sometimes it is necessary to widen the narrow passageways and to make connecting tunnels. All of these actions modify the natural arrangement of the cave in some extent [1]. Iran is a Middle East country with a rich cultural heritage and various natural beauties. Carbonate rocks cover about 185,000 km2 or roughly 11 % of Iran’s land area and present an important factor in water supply of many regions. Even though karst aquifers and springs are present in various carbonate formations, majority does not have a developed cave system. Arid climate was not a favorable condition for formation of mature karst and large well-developed cave systems. Rare multilevel caves have developed in some areas due to rapid tectonic uplift, folding and faulting of the terrain [4]. There are more than 850 known caves in Iran with a total length not exceeding 1000 km; many of them not being properly explored. Two of the biggest and most famous caves are Ali-Sadr and Katale-Khor (Figure1)[ 5]. Both of them are developed in areas with rare surface karst landforms and genesis of caves by meteoric sinking streams seems to be unlikely case [6]. Tourism still does not have a big role in Iran’s economy, with religious tourism being the most dominant type. Ecotourism and historical tourism gains momentum in some parts of the country but it is far from using its full potential. Iran is a country with exceptional history but also has the significant geological phenomena and diverse landscapes, thus giving a base for a broad range of tourism activities [1,7]. Geotourism is a new and innovative branch of tourism which promotes both environmental and social responsibility and is becoming more and more widespread [8]. One can define geotourism as a form of tourism that specifically focuses on geology and landscape. Its purpose is to promote an understanding of earth sciences through appreciation and conservation of geodiversity. The best way to achieve this is through visits to geological features and locations. Unlike other forms of tourism, geotourism takes place mainly in natural areas, wherever there is a geological site [9,10]. Herrera-Franco et al. [11] state that geotourism must fulfill five basic principles. It must be geologically based (geoheritage) and sustainable (geoconservation) with an educational purpose (geointerpretation). Furthermore, it must bring benefits at the local level and provide tourist satisfaction. However, it is imperative to consider that popular geotourism destinations face the same challenges as other tourism destinations, such as overcrowding and a wide range of negative impacts on geoheritage and on the vegetation and wildlife of these destinations [12]. The connection between tourism and geosites is definitely a multifaceted one, resulting from the economic focus of tourism on one side and the preservation efforts of protected areas on the other side [13]. Lately, a new concept arises, called cultural sustainability, which is the concept for the improvement and protection of cultural identities. It is in line with traditional practices and celebrates local and regional histories and passes down cultural values for generations to come. Geoparks represent an innovation in the protection of natural and geological heritage and play an important role in cultural sustainability in rural areas. Additionally, a geopark promotes local socio-economic and socio-cultural development by attracting an increasing number of visitors [14]. When we talk about tourism, it is very important to emphasize the importance of sustainability of all aspects of tourism activities. Caves are naturally very vulnerable environments, due to their isolated nature, their relatively stable environments and their direct reliance on the activities conducted at the surface directly above and in the recharge area of the caves. Rising number of visitors can pose a threat to sensitive parts of the landscape. Ahmadzade and Elmizadeh [15] found that maximum presence of tourists in the Katale-Khor and Saholan caves disrupted the formation of the speleothems due to change in the microclimate. Facilities that are an integral part of the tourist offer can often become a source of contamination. This is especially pronounced in the karst areas where a thin or non-existent ground cover facilitates the infiltration of water and contaminants Sustainability 2021, 13, 6587 3 of 15

to groundwater. This is particularly important nowadays when Iran is turning itself to possible usage of karst aquifers for water supply [15]. Show caves have a wide range of different management plans, from high-impact activities reserved for tourists in caves, to simple visits with minor changes to the natural environment [16]. Each cave has a specific flux (or number of visitors in time unit) tolerance limit. Nowadays, people are aware that show caves are impacted by tourist development and that they must be under constant monitoring in order to prevent any detrimental consequences of human activities. Geosites and geotourism have been the topics of a growing number of studies and articles [12]. Zgłobicki and Baran-Zgłobicka [17] found that landscape (aesthetic) values were the main motive for the tourist visits and the sites of great scientific and cognitive value did not stimulate the interest of tourists. Furthermore, authors found that the understanding of a given area results in a better rating given to it by tourists. These findings are similar to ones from [18] which observed that Iranian geotourists deemed the rarity of a geosite and the number and quality of viewpoints as most important reasons for visit. The promotion of valuable geological sites should be part of bigger projects meant to develop tourism in poorly developed areas. Geomorphological heritage sites are usually visited during visits to well-known tourist destinations. It often occurs that the interesting geomorphosites are little known, even though they are located quite close to the famous tourist centers because the wish to learn more about the assets of inanimate nature is seldom the main goal of the tourist visits. Geotourism, if established correctly, can also have a somewhat protective purpose on the environmentally sensitive areas, since it draws attention from well-known destinations making it “more eco-friendly than ecotourism per se” [19]. Experiences from areas with longer tradition in geotourism show that the distribution of discoveries and their scientific significance to local communities, combined with actions to raise perception of the need to safeguard natural and cultural sites leads to establishment of successful geosites. Further- more, it is very important to form a partnership between different groups within academia with diverse research interests and local authorities. The participation of numerous local stakeholders in geotourism projects which aim to conserve and capitalize upon the natural and cultural heritage of the region by means of education and tourism is essential [20]. Even though in terms of tourism both Ali-Sadr cave and Katale-Khor cave are very remarkable and popular, from the geological perspective there has been only few investigation of cave genesis and characteristics, other than detailed mapping, especially the role of hypogene processes in their formation [6]. In order to build a strong foundation for a thriving geotourism industry and make these geosites attractive to visitors it is important to understand all the aspects of the caves, the surrounding areas and the possible impact tourist can have on it [10]. Therefore, our main mission was to examine characteristics of the abiotic landscape in order to go form qualitative to quantitative understandings. This information is known for some geological environments, but for the majority, these research data are missing. Better understanding of the natural phenomenon and its presen- tation to visitors can promote these geosites outside the borders of the provinces Hamedan and Zanjan.

2. Materials and Methods 2.1. Geographical and Geological Characteristics of the Location Iran has a complex geological past that is reﬂected in the complex structure of the present geological formations. Southern and western parts of the Iran are parts of the Arabian plate, Cimmerian microplate makes northern and eastern parts and northeastern margin of Iran is a part of Eurasian plate [21]. Sustainability 2021, 13, 6587 4 of 15 Sustainability 2021, 13, x FOR PEER REVIEW 4 of 15

FigureFigure 1. 1.Map Map of of Iran Iran and and position position of of the the study study locations locations (adapted (adapted from from [22 [22,23]).,23]).

TheThe Central Central Iran Iran is is a complexa complex triangular-shaped triangular-shaped region region of theof the interior interior Iranian Iranian Plateau Plat- (Figureeau (Figure2). It is 2). consisted It is consisted of several of microcontinentalseveral microcontinental blocks and blocks is bounded and is by bounded the marginal by the fold-and-thrustmarginal fold-and-thrust belts of the Zagrosbelts of andthe MakranZagros inand the Makran south, thein the Alborz south, and the Kopeh-Dagh Alborz and inKopeh-Dagh the north, and in thethe Sistannorth, accretionaryand the Sistan wedge accret inionary the east wedge [24]. Asin the a result east of[24]. the As ongoing a result convergenceof the ongoing between convergence the Arabian between and Eurasianthe Arabian plates, and this Eurasian area is subjectedplates, this to area a constant is sub- continentaljected to a deformationconstant continen [25,26tal]. deformation In the basement [25,26]. of the In Centralthe basement Iranian of Provincethe Central lies Ira- a Cimmeriannian Province miniplate lies a whichCimmerian is overlain miniplate by late which Cretaceous is overlain to early by Miocene late Cretaceous magmatic to rocks early ofMiocene Urmieh-Dokhtar magmatic magmatic rocks of arc. Urmieh-Dokhtar Thick layers of volcanicmagmatic rocks, arc. evaporitesThick layers and of turbidites volcanic wererocks, formed evaporites during and Eocene turbidites back-arc were extension formed across during Central Eocene Iran. back-arc This sequence extension is usually across superimposedCentral Iran. byThis Oligocene sequence terrestrial is usually clastites, superi evaporitesmposed by and Oligocene volcanic rocksterrestrial of the clastites, Lower Redevaporites Formation. and Marinevolcanic deposition rocks of the continued Lower Red throughout Formation. larger Marine part ofdeposition Central Irancontinued with thethroughout carbonates larger of the part lower of Miocene Central QomIran wi Formationth the carbonates which is overlain of the lower by middle Miocene Miocene Qom terrestrialFormation clastites which andis overlain evaporites by middle of the UpperMiocene Red terrestrial Formation clastites [27,28 and]. The evaporites Central of Iran the isUpper dominated Red Formation by narrow [27,28]. mountain The rangesCentral and Iran intermontane is dominated depressions. by narrow mountain The mountain ranges rangesand intermontane and the lowlands depressions. of Central The Iran mountain are divided ranges by and deep-seated the lowlands reverse of Central and strike-slip Iran are faultsdivided [29]. by deep-seated reverse and strike-slip faults [29]. Sustainability 2021, 13, x FOR PEER REVIEW 5 of 15

Sustainability 2021, 13, 6587 5 of 15 The Qom Basin covers the western parts of central Iran and was formed in the Late Oligocene by marine transgression. The Qom Formation consists of a thick succession of marineThe marls, Qom Basin limestones, covers the gypsu westernm and parts siliciclastic of central Iran rocks. and It was overlies formed the in theLower Late Red For- Oligocenemation and by marineEocene transgression. volcanic rocks. The The Qom Qom Formation Formation consists is ofoverlain a thick by succession the Upper Red ofFormation marine marls, consisted limestones, of non-marine gypsum and siltstones siliciclastic and rocks.evaporite-dominated It overlies the Lower beds Red[4,30–32]. Formation and Eocene volcanic rocks. The Qom Formation is overlain by the Upper Red Southeastern region of Zanjan is part of the northwestern part of Central Iran. The Formation consisted of non-marine siltstones and evaporite-dominated beds [4,30–32]. average height of the province is about 1600 m with a total area of 22,150 km2.

FigureFigure 2. 2.The The structural structural map map of Iran of withIran thewith position the position of the investigated of the investigated caves (adapted caves from (adapted [18,33]). from [18,33]).Southeastern region of Zanjan is part of the northwestern part of Central Iran. The average height of the province is about 1600 m with a total area of 22,150 km2. AsAs stated, stated, only only 11 11 % of% theof the Iran Iran is underlain is underlain by carbonate by carbonate rock formations, rock formations, mainly in mainly in aa broadbroad western western belt, belt, in thein the northeast northeast and centraland ce parts.ntral parts. Geomorphological Geomorphological studies havestudies have determineddetermined evident evident differences differences between between the sizethe ofsize karst of landformskarst landforms in arid Centralin arid IranCentral Iran andand the the more more abundant abundant karst karst in more in more humid humid regions regions such assuch the Zagros.as the Zagros. Majority Majority of the of the famousfamous and and important important caves caves like like Ali-Sadr Ali-Sadr and Katale-Khorand Katale-Khor have developed have developed in areas within areas with rarerare surface surface karst karst landforms landforms where where cave cave genesis genesis by meteoric by meteoric sinking sinking streams streams seems to seems be to be improbable. Hypogene caves are found mainly in the Northwest, the Central and Eastern improbable. Hypogene caves are found mainly in the Northwest, the Central and Eastern zone, where they are associated with the igneous activity, and the Zagros zone. zone, where they are associated with the igneous activity, and the Zagros zone.

2.2. Climate Based on the data from 1990–2014, 9 out of 31 possible Köppen-Geiger climate types are present in Iran. Most parts of central, eastern, and southern Iran are classified as BWh and BWk climate types. The coastal areas next to the Caspian Sea and most parts of Sustainability 2021, 13, 6587 6 of 15

2.2. Climate Based on the data from 1990–2014, 9 out of 31 possible Köppen-Geiger climate types are present in Iran. Most parts of central, eastern, and southern Iran are classified as BWh and BWk climate types. The coastal areas next to the Caspian Sea and most parts of mountainous areas of Zagros and Alborz in west and north of Iran have moderate climate type (Csa). The eastern slopes of Zagros and southern slopes of Alborz that are connected to the central arid and semi-arid climate of central Iran are categorized as BSk climate. The southern parts of Zagros region are generally dominated by BSh climate. Dsa and Dsb climate types can be found in several parts of mountainous areas of Zagros and Alborz, while Csb and Cfa are the localized climate types that can be observed in coastal areas of the Caspian Sea [34]. Zanjan is one of the coldest regions in Iran with an average daily temperature during warm period of only 20 ◦C. According to Köppen-Geiger climate classification, this area is classified as DSa and DSb [35]. The Ds climate types are snow climate with dry summers. The third letter designates hot (a) or warm (b) summer. The Ds climate types are very vulnerable to change and shift. Lately, the Dsb climate type tends to shift into Dsa climate types. Furthermore, it was noticed that the Ds climate types in western Iran tend to be substituted by Csa climate type. The evident shift from Ds or Csa climate types into BSk climate type is seen in northwestern Iran. This indicates a rapid and extensive desertification in northwestern Iran due to global climate change [34]. The Zanjan region has a semi-arid climate, and the average annual rainfall is 300 mm [6]. Due to the warmer temperatures the best time for traveling and exploring geotourism locations is from June to September. According to [36], the northern and western mountainous areas have somewhat regular precipitation distribution during the year, while southern areas have a strong seasonality. The precipitation occurrences move back from south to north from April to September, being limited to the Caspian Sea region in August and September. What one might call the ‘wet season’ extends from November to April. Only one substantial flood event has been reported during the past twenty years. Vegetation is sparse, except around oases maintained by groundwater. Farms and small villages get water from historic systems of “qanats”, drainage capture tunnels dug long and deep into the alluvial fans and other deposits.

2.3. Methods For the purpose of the research, samples of the drip water from the Katale-Khor cave and Garmab spring waters were collected. Since the upper ﬂoors of the Katale-Khor cave are dry the samples were taken from the 4 permanent water drips. An automatic water sampler was designed for drip water collection in a 60 mL PVC bottle each hour. Every 24 h, the electrical conductivity (EC) and pH of the samples were measured by a WTW Multi 340i instrument and a WTW MultiCal pH-540 m on their arrival in the laboratory. Based on the variations in EC, some typical samples were chosen for chemical analysis by ion chromatography (Methrom 761 Compact IC) which included: K+, Na+, Ca2+, Mg2+, 2− − − SO4 , Cl and NO3 ions. Samples selected for chemical analyses of major ions were refrigerated at 5 ◦C and analyzed within 48 h after collection. X-ray diffraction analysis (XRD) is a very useful and rapid technique that provides information on phase composition and crystal structure of the material. Mineral identiﬁ- cation is based on d-spacing and relative peak intensities and is much easier if a sample contains only one type of the mineral. One of the major limitations of XRD technique is the detection limit, which is just about 1 % of weight [37]. The mineralogical composition of ground rock samples was determined by X-ray diffraction (XRD) analysis using a MAXima X XRD-7000 X-ray diffractometer. An internal standard was added to each of the samples. Internal standard materials include corundum, zincite or rutile and are selected according to which material yields the least interference with the sample mineralogy. Three grams of the sample/internal standard powder were placed in a McCrone Micronizing mill with 15 mL of 2-propanol and processed for 4 min. Sustainability 2021, 13, 6587 7 of 15

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The mill reduced the particle size to approximately 1 µm. The mixture was left to dry overnight,Data andprecipitation then the powdervalues were was collected forin available X-ray analysis. meteorological The mineralogical measurement identificationstations. Water was flow based values on the were comparison obtained with by measurement a database. instrument. Data precipitation values were collected in available meteorological measurement stations.3. Caves Water and Springs flow values Characteristics were obtained by measurement instrument. 3.3.1. Caves Katale-Khor and Springs Characteristics 3.1. Katale-KhorWith an explored length of 12,860 m, Katale-Khor cave is the longest cave in Iran. It is developedWith an explored mainly lengthwithin ofthe 12,860 Oligocene/Miocene m, Katale-Khor Qom cave islimestone the longest in cavethe northern in Iran. Itflank isof developed an anticline mainly of Saghez-lou within the Mountain Oligocene/Miocene (Figure 3). QomThe cave’s limestone mouth in thestands northern 6–8 m flank above a ofdry an anticlineriver (Figure of Saghez-lou 4). The name Mountain of the (Figure cave, 3Katale-Khor,). The cave’s mouthmeans stands“mount 6–8 of m the above Sun” in aPersian. dry river Katale-Khor (Figure4). The is a name multistage of the cave,cave with Katale-Khor, three levels means ranging “mount from of the1670 Sun” to 1742 in m Persian.above mean Katale-Khor sea level. is a There multistage are two cave visiting with three routes levels inside ranging the fromcave: 16703 km to open 1742 mto the abovepublic mean and seaanother level. 4 There km available are two visiting only for routes experienced inside the cavers. cave: 3 Tourists km open can to the visit public 2850 m andof the another cave 4on km the available first floor. only Cave for experienced levels have cavers.been developed Tourists can due visit to fluctuation 2850 m of the of the cavewater on table. the first The floor. cave Cave was levelsmainly have created been by developed phreatic duecorrosion to fluctuation in a still of water the water environ- table.ment. The The cave floors was of mainly the cave created are almost by phreatic horizontal corrosion and inare a stillconnected water environment. by relatively Thevertical floorswells. of the cave are almost horizontal and are connected by relatively vertical wells.

FigureFigure 3. 3.Geological Geological map map withwith positionposition ofof Katale-KhorKatale-Khor cave,cave, AliAli Sadr cave and Garmab spring spring (modiﬁed(modified after after [38 [38]).]).

The cave is famous for its beautiful cave deposits. Stalagmites, stalactites and limestone columns are found in abundance in the middle areas of the cave. Probably the most attractive part of the cave is the hall called Persepolis which contains many columns Sustainability 2021, 13, x FOR PEER REVIEW 8 of 15

with a diameter of more than one meter and a height of 10 m. In the Parvin hall, visitors can see curtains, shells and aragonite flowers. Calcite speleothems (stalactites, stalagmites, columns, flowstones and helictites) occur locally in the zones of water percolation Sustainability 2021, 13, 6587 from overlying formations. The fractures in the overlying limestone layers allowed8 of 15the entrance of the precipitation in the cave system. The changes in carbon dioxide concentrations caused deposition of stalagmites, stalactites, columns, etc.

Figure 4. The entrance of the Katale-Khor cave [39]. Figure 4. The entrance of the Katale-Khor cave [39].

TheKatale-Khor cave is famous cave has for itsdifferent beautiful origin cave than deposits. Ali-Sadr Stalagmites, cave. According stalactites to and previous lime- stonestudies, columns Katale-Khor are found cave in abundanceis an anastomoti in thec middle maze cave. areas The of the evidence cave. Probably demonstrates the most the attractivefloodwater part origin of the of cave Katale-Khor is the hall cave called [6]. Persepolis Rezaei et al., which as well contains as Mahmoudi many columns Sivand with and aBgherinejad, diameter of morehave thansuggested one meter an epigenic and a height speleogenesis of 10 m. In[40,41]. the Parvin Three hall,distinct visitors levels can of seecave curtains, passages shells have and formed aragonite during flowers. the lowering Calcite of speleothems the water-level. (stalactites, The drops stalagmites, of the wa- columns,ter levels flowstones were fast and and approximately helictites) occur 25 locally m each. in theIn the zones periods of water between percolation drops fromdevel- overlyingoped flat-roofed formations. passages, The fractures with V-shaped in the overlying cross sections limestone typical layers of allowedconvection the entrancealong the ofceiling the precipitation and the walls in theof galleries cave system. immersed The changesin CO2-riched in carbon solutions. dioxide The concentrations elliptical, rec- causedtangular deposition and T-shaped of stalagmites, sections indicate stalactites, the columns, saturation etc. conditions at first and then—with a decreaseKatale-Khor in water cave level—the has different channel origin conditions than Ali-Sadr at the time cave. of cave According formation. to previous Unlike in studies,Ali-Sadr, Katale-Khor the source caveof the is anCO anastomotic2 was meteoric maze water cave. that The recharged evidence demonstratesfrom the anticline the floodwaterrange. Ahmadzade origin of and Katale-Khor Elmizadeh cave [15] [6 propose]. Rezaei different et al., as theory well asof Mahmoudispeleogenesis. Sivand They andclaim Bgherinejad, that ascending have deep suggested waters an of epigenicmagmatic speleogenesis origin may have [40,41 played]. Three the distinct principal levels role ofincave the cave passages development. have formed After during a while, the th loweringe recharge of thefrom water-level. the magmatic The source drops was of theslowly water reduced levels wereand the fast succeeding, and approximately epigene processes 25 m each. created In the the periods current between form. drops developed flat-roofed passages, with V-shaped cross sections typical of convection along the3.2. ceiling Ghar Ali-Sadr and the walls of galleries immersed in CO2-riched solutions. The elliptical, rectangularGhar andAli-Sadr T-shaped is an sectionsanastomotic indicate type the of saturation cave located conditions 75 km northwest at first and of then—with Hamedan ain decrease a village in by water the same level—the name channel and circa conditions 60 km south at the oftime Katale-Khor of cave formation. cave.Ali-Sadr Unlike cave in is Ali-Sadr,considered the sourceto be one of theof COthe 2mostwas meteoricunique and water scenic that caves recharged in the from world. the anticlineOne of the range. fea- Ahmadzadetures that makes and Elmizadeh Ali-Sadr cave [15] proposespecial is different a fact that theory it is ofthe speleogenesis. longest and the They biggest claim water that ascendingcave in the deep world waters (from of the magmatic point of origin the boating may have course played inside the the principal cave) (Figure role in 5). the cave development.The cave After is 2500 a while, m long, the with recharge the depth from theof water magmatic reaching source 8 m was in slowlysome parts. reduced The andlake the water succeeding, is fresh epigeneand transparent, processes and created the thecave current has many form. cavernous phenomena to- 3.2.gether Ghar with Ali-Sadr a range of colorful stalactites. The tourists can explore the cave by pedal boat and on foot and the presence of nearby accommodation adds to this recognized ge- Ghar Ali-Sadr is an anastomotic type of cave located 75 km northwest of Hamedan otourism product [42]. The cave is developed in crystallized limestones and Jurassic in a village by the same name and circa 60 km south of Katale-Khor cave.Ali-Sadr cave is schists (Figure 3). The origins of the cave are not precisely identified but most likely cause considered to be one of the most unique and scenic caves in the world. One of the features for development of the cave lies in the differential solubility between the hard schists and that makes Ali-Sadr cave special is a fact that it is the longest and the biggest water cave in layers of soluble limestone. The length of the cave is about two kilometers. the world (from the point of the boating course inside the cave) (Figure5). The cave is 2500 m long, with the depth of water reaching 8 m in some parts. The lake water is fresh and transparent, and the cave has many cavernous phenomena together with a range of colorful stalactites. The tourists can explore the cave by pedal boat and on foot and the presence of nearby accommodation adds to this recognized geotourism product [42]. The cave is developed in crystallized limestones and Jurassic schists (Figure3) . The origins of the cave are not precisely identified but most likely cause for development Sustainability 2021, 13, x FOR PEER REVIEW 9 of 15

Ali-Sadr cave is located in a large anticline with a main axis orientation in a north-south direction. The layers in the cave are at 40 to 45 degrees. The maximum height of the Ali-Sadr field is 2180 m above sea level, and the cave entrance is at 1980 m. The development of both caves is affected by fractures and faults. Narrow karst passages developed along larger fractures. Their predominantly oval cross section indi- Sustainability 2021, 13, 6587 cates a karst dissolution during seasonal saturation or flooding. The existence9 of 15 of irregular surfaces in both caves implies that water has dissolved paths in the areas where the carbonate rock was weakened by fractures and had more impurities, like MgO, in composi- oftion. the cave Unlike lies in in the Katale-Khor, differential solubility caving between did thenot hard play schists an andimportant layers of solublerole in formation of limestone.Ali-Sadr The cave. length of the cave is about two kilometers.

FigureFigure 5. Inside5. Inside of the of Ali-Sadr the Ali-Sadr Cave [43 Cave]. [43].

Ali-SadrThe temperature cave is located of in the a large cave anticline water withis approx a mainimately axis orientation 12 °C, and in a north-with a pH value of 7, south direction. The layers in the cave are at 40 to 45 degrees. The maximum height of the Ali-Sadrthe water field is 2180nearly m above saturated sea level, with and calcite. the cave entranceThe water is at table 1980 m. varies every year by around 0.5–1The m, development with a maximum of both caves in late is affected spring by to fractures early summer and faults. when Narrow some karst water pas- can even spill sagesto a developedspring [6]. along larger fractures. Their predominantly oval cross section indicates a karst dissolutionAli-Sadr during Range seasonal is an isolated, saturation steep or flooding. ridge The in existencethe middle of irregular of alluvial surfaces fans and plains. It inis both part caves of impliesthe western that water structural has dissolved units paths of in the the areasCentral where Iran the carbonatezone. Horizontally rock bedded was weakened by fractures and had more impurities, like MgO, in composition. Unlike in Katale-Khor,limestones caving and didmarls not of play Eocene an important to Oligocene role in formation age overlay of Ali-Sadr the cave.folded Jurassic limestones andThe schists. temperature The main of the cavefracture water directions is approximately created 12 ◦ C,during and with the a uplift pH value of ofthe limestone se- 7,quences the water determine is nearly saturated the pattern with calcite. of cave The passages water table in varies Ali-Sadr every yearCave by which around follow the strike 0.5–1of the m, withvery a maximumsteeply indipping late spring beds. to early The summer beddi whenng planes some water and can joints even spillwere expanded by to a spring [6]. phreaticAli-Sadr solution Range is anbut isolated, due to steep continuous ridge in the uplift middle which of alluvial caused fans anddrainage plains. they remained Itsmall is part in of thesize western [6]. In structural the period units ofof thecave Central formation, Iran zone. circulation Horizontally of bedded groundwater in the limestonesAli-Sadr and cave marls aquifer of Eocene was to slow Oligocene to almost age overlay stagnant the folded circulation. Jurassic limestones The main and evidence for that schists.is the Thelack main of passages fracture directions with canyon-like created during or thetube-shaped uplift of the cross limestone sections sequences which form during determinevigorous the vadose pattern ofor cave shallow passages phreatic in Ali-Sadr water Cave whichflow follow[44]. Calcite the strike shelfstones of the very found un the steeply dipping beds. The bedding planes and joints were expanded by phreatic solution butAli-Sadr due to continuous cave suggest uplift 3 whichm of osci causedllation drainage of the they pool remained surface small over in sizethe [last6]. In 25,000 year or so. theReason period for of cave this formation, can be cooler circulation climate of groundwater conditions in thein the Ali-Sadr Pleistocene cave aquifer and was to some extent in slowhuman to almost regulations stagnant circulation. of a scarce The water main evidenceresource for [45]. that isNowadays, the lack of passages the only with recharge is occa- canyon-likesional rain or tube-shapedonto the limestone cross sections [46]. which According form during to vigorous [44], since vadose no or shallowspecific speleogenetic phreatic water flow [44]. Calcite shelfstones found un the Ali-Sadr cave suggest 3 m of oscillationstudies have of the been pool surface done overso far, the the last specific 25,000 year dissolution or so. Reason mechanism for this can beinvolved cooler is still elusive. climateBased conditions on current in the information Pleistocene and about to some cave extent morpho in humanlogy, regulations it is probable of a scarce that Ali-Sadr is of waterhypogenic resource [transverse45]. Nowadays, speleogenesis. the only recharge One is occasional of the rainnatural onto thephenomena limestone [46 ].in the area that Accordingsupports to [this44], sincethesis no specificis the speleogeneticGorgoloh, studiesa ma havejor spring been done approximately so far, the specific 20 km south of dissolution mechanism involved is still elusive. Based on current information about cave Ali-Sadr Cave. The spring is famous for the large amount of CO2 that emerges mixed morphology, it is probable that Ali-Sadr is of hypogenic transverse speleogenesis. One of thewith natural the phenomena water. The in thelarge area thatamount supports of thisautogenic thesis is theCO Gorgoloh,2 enables a majorgroundwaters spring to dissolve approximatelycarbonate rocks. 20 km Stream south of Ali-Sadrthat flows Cave. from The springthe Gorgoloh is famous spring for the largeprecipitates amount travertine, en- ofcrusting CO2 that moss, emerges cyanobacteria mixed with the and water. other The largeorganic amount material. of autogenic It is COa sign2 enables that cave formation groundwatersprocess continues to dissolve today carbonate and that rocks. the Stream acidic that wa flowsters fromform the new Gorgoloh cave systems spring at the present time by dissolving carbonate. Furthermore, aragonite mineralization is present inside SustainabilitySustainability 20212021, 13, 6587x FOR PEER REVIEW 10 of10 15 of 15

precipitatesAli-Sadr Cave travertine, [47]. Higher encrusting temperatures moss, cyanobacteria can promote and crystallization other organic of material. aragonite It is [48,49]. a signSince that the cave cave formation temperature process is continuesonly 12 °C, today higher and temperatures that the acidic watersneeded form for aragonite new cave for- systemsmation atcould the present be caused time by by ascent dissolving and carbonate.activity of Furthermore,deep hydrothermal aragonite waters. mineralization is presentClassic inside karstification Ali-Sadr Cave does [47 not]. Higher appear temperatures to have an can important promote role crystallization in the area of sur- aragonite [48,49]. Since the cave temperature is only 12 ◦C, higher temperatures needed for rounding the cave, since no epigene caves or karst features can be found above the aragonite formation could be caused by ascent and activity of deep hydrothermal waters. groundwater level. Possible reasons might be lack of substantial vegetation and thick soil Classic karstification does not appear to have an important role in the area surrounding thedue cave, to the since semiarid no epigene climate caves which or karst are featuresgenerally can the be main found source above of the CO groundwater2 for rainwaters level.that seep Possible into reasonsthe ground. might All be of lack this of makes substantial Ali-Sadr vegetation cave an and attractive thick soil scientific due to the object because it can be used to study cave formation under the influence of ascending CO2. semiarid climate which are generally the main source of CO2 for rainwaters that seep into the ground. All of this makes Ali-Sadr cave an attractive scientific object because it can be used3.3. Garmab to study Springs cave formation under the influence of ascending CO2. Garmab is a city in Khoda Bandeh county, in the south-eastern part of Zanjan 3.3. Garmab Springs province, with a population just over 3000 inhabitants. In the city and its vicinity there are twoGarmab karst is springs. a city in KhodaThe special Bandeh attraction county, in of the this south-eastern rural area partare the of Zanjan hot springs province, as well withas the a populationKatale-Khor just cave. over 3000The inhabitants.climate is a In mountainous the city and its with vicinity cold, there snowy are two winters karst and springs.moderate The summers. special attraction of this rural area are the hot springs as well as the Katale- Khor cave. The climate is a mountainous with cold, snowy winters and moderate summers. A karst aquifer has been formed in the Qom formation. The water level in this aq- A karst aquifer has been formed in the Qom formation. The water level in this aquifer uifer is currently lower than the level of the cave. The groundwater from the karst aquifer is currently lower than the level of the cave. The groundwater from the karst aquifer comes tocomes the surface to the atsurface two springs. at two The springs. Garmab The karst Ga springrmab karst emerges spring from emerges the eastern from end the of theeastern Qomend of Formation the Qom and Formation has an average and has discharge an average of 84 l/s.discharge The other of spring84 l/s. isThe located other inside spring is thelocated city ofinside Garmab the andcity hasof Garmab an average and discharge has an average of 30 l/s. discharge of 30 l/s.

4.4. ResultsResults FigureFigure6a 6a presents presents the chemical the chemical composition composition of drip water of sampleddrip water in the sampled Katale-khor in the caveKatale-khor while Figure cave6 bwhile presents Figure the chemical 6b presents composition the chemical of waters composition from Garmab of springs.waters from AllGarmab values springs. are expressed All values in meq/L. are expressed in meq/L.

FigureFigure 6.6. ((a)) TheThe chemical composition composition ofof dripdrip waterwater inin thethe Katale-KhorKatale-Khor cave, cave, ( b(b))The The chemicalchemical compositioncomposition of of waters waters from from Garmab Garmab springs springs in meq/Lin meq/L [50 [50].].

FigureFigure7 presents7 presents discharge discharge hydrograph hydrograph of the of Garmab the Garmab spring spring along withalong the with precipi- the pre- tationcipitation for the for two the consecutivetwo consecut monthsive months (August/September). (August/September). Sustainability 2021, 13, 6587 11 of 15 SustainabilitySustainability 2021 2021, 13, 13, x, xFOR FOR PEER PEER REVIEW REVIEW 1111 of of 15 15

200200 120120 Discharge Discharge (l/s) (l/s) Rainfall (mm) 180180 Rainfall (mm)

100100 160160

140140 8080

120120

100100 6060 Rainfall (mm) Discharge (l/s)

80 Rainfall (mm) Discharge (l/s) 80

4040 6060

4040 2020

2020

0 0 0 0 11 4 4 7 7 10 10 13 13 16 16 19 19 22 22 25 25 28 28 31 31 34 34 37 37 40 40 43 43 46 46 49 49 52 52 55 55 58 58 Days Days Figure 7. Discharge hydrograph of the Garmab spring for two months (August/September) [50]. FigureFigure 7. 7. DischargeDischarge hydrograph hydrograph of the Garmab spring for two months (August/September) [50]. [50].

FigureFigureFigure 88a a8a presentspresents presents resultsresults results ofof of thethe the XRDXRD XRD analysisan analysisalysis performedperformed performed onon on thethe the samplesample sample K-1K-1 K-1 takentaken taken fromfromfrom the thethe Katale Katale Katale Khor Khor Khor cave. cave. Figure FigureFigure 88b b8b showsshows shows thethe the samesame same analysisanalysis analysis performedperformed performed onon on samplesample sample A-2A-2 A-2 takentakentaken from from from Ali-Sadr Ali-Sadr Ali-Sadr cave. cave.

FigureFigureFigure 8. 8.8. ResultsResults Results of ofof the thethe XRD XRDXRD test testtest on onon the thethe sample sample K-1 K-1 ( a(a)) )and and and A-2 A-2 A-2 ( ( b(b))[ )[47]. 47[47].]. 5. Discussion 5.5. Discussion Discussion Better standard of life together with the increase of mobility, education and leisure, BetterBetter standard standard of of life life together together with with the the increase increase of of mobility, mobility, education education and and leisure, leisure, dramatically increased geotourism in the last two decades [17]. The main goal for a success dramatically increased geotourism in the last two decades [17]. The main goal for a suc- dramaticallyof geotourism increased is to reconcile, geotourism on the in one the hand,last two the decades conservation [17]. The of the main natural goal resourcesfor a success of geotourism is to reconcile, on the one hand, the conservation of the natural re- cessand, of on geotourism the other hand, is to supportreconcile, the on opportunities the one hand, for the the conservation development of of the recreation naturaland resources and, on the other hand, support the opportunities for the development of recre- sourcestourism. and, The on knowledge the other abouthand, allsupport the characteristics the opportunities of natural for the resource development is helpful of recre- when ation and tourism. The knowledge about all the characteristics of natural resource is ationestablishing and tourism. a suitable The product knowledge that takes about into all account the characteristics the needs of both of natural parties: resource the tourists is helpful when establishing a suitable product that takes into account the needs of both helpfuland nature. when Better establishing understanding a suitable of the product natural phenomenonthat takes into leads account to the the better needs preparation of both parties: the tourists and nature. Better understanding of the natural phenomenon leads to parties:of the geosite the tourists for the and tourist nature. ﬂow Better and unders also cantanding alter of the the perception natural phenomenon tourists have leads of the to the better preparation of the geosite for the tourist flow and also can alter the perception theproduct better [13 preparation]. of the geosite for the tourist flow and also can alter the perception tourists have of the product [13]. touristsWhen have we of talk the aboutproduct caves [13]. one of the most important factors is understanding of the When we talk about caves one of the most important factors is understanding of the processWhen of thewe cavetalk about formation. caves The one caves of the are most inseparable important part factors of their is understanding surroundings, of many the process of the cave formation. The caves are inseparable part of their surroundings, many processof them of being the cave part formation. of the much The larger caves and are more inseparable intricate part geological of their andsurroundings, hydrogeological many ofcomplex.of them them being being Tourists part part seeof of the onlythe much much one aspectlarger larger ofand and the more more cave–its intricate intricate aesthetics. geological geological In order and and forhydrogeological hydrogeological tourists to be complex.ablecomplex. to get Tourists Tourists acquainted see see only only with one one all aspect the aspect features of of the the ofca ca theve–itsve–its cave aesthetics. aesthetics. in an entertaining In In order order for for and tourists tourists interesting to to be be ableway,able to itto isget get necessary acquainted acquainted to constantly with with all all the the ﬁll features possiblefeatures of gapsof the the incave cave knowledge in in an an entertaining entertaining through detailed and and interesting interesting research. way,Oneway, ofit it theisis necessary necessary parameters to to thatconstantlyconstantly can shed fill fill apossible possible light into gaps gaps connection in in knowledge knowledge of the cavethroughthrough and detailed thedetailed surface re- re- search.issearch. a cave One One drip of of water. the the parameters parameters Chemical that compositionthat can can shed shed of a a thelight light cave into into drip connection connection water is of complexof the the cave cave due and and to the the surfacesurfacesurface is meteorologicalis a a cave cave drip drip water. water. circumstances Chemical Chemical composition andcomposition the heterogeneity of of the the cave cave ofdrip drip water water water movement is is complex complex in due thedue tokarstto the the unsaturatedsurface surface meteorological meteorological zone [51]. Watercircumstances circumstances conductivity and and isthe the directly heterogeneity heterogeneity related toof of thewater water concentration movement movement in of in thethe karst karst unsaturated unsaturated zone zone [51]. [51]. Water Water conducti conductivityvity is is directly directly related related to to the the concentra- concentra- Sustainability 2021, 13, 6587 12 of 15

ions in the water which comes from dissolved salts and inorganic materials such as alkalis, chlorides, sulfides and carbonate compounds. The EC of the drip water is 240 µm/cm. In the karst rock, drip water conductivity is controlled by the partial pressure of CO2 (pCO2) and the dissolution of bedrock. Within the cave, the partial pressure of CO2 in the cave air has the dominant effect. The drip water chemistry is a site-dependent characteristic based on the variants in water residence time inside the aquifer, the amount of water mixing inside the aquifer and prior calcite precipitation [52–54]. The upper floor of the cave is dry, the drip water and cold vapors being the only sources of the water. The pH of the drip water sample was 7.7 making it slightly alkaline. This is normal in karst areas due to the presence of carbonate and bicarbonate ions in waters. Total hardness is 105 mg/L making the water moderately hard. Elemental chemistry differentiates water sources and allows the reconstruction of the underground fracture network from the place where the water infiltrated to the outlets. The chemical analysis of drip water in the Katale-Khor cave and Garmab spring is shown in Figure6. As can be 2+ seen from the diagrams, dominant ions in the drip waters are Ca and HCO3− as is to be expected from the waters circulating through carbonate rocks. Smaller concentration of magnesium could be from dissolution of dolomite, a common mineral in carbonate rocks. Spring water, on the other hand, has a significant amount of sodium and chloride ion in its composition. Magnesium and calcium ions are present also, as well as hydrogen carbonate and sulphate ions. This could indicate a mixing of waters. Garmab spring water has pH 7.7, the same as drip water from Katale-Khor cave. Conductivity is significantly higher (2300 µS/cm). The total hardness is also higher (392 mg/L), making Garmab spring waters very hard [47]. Mohammadi et al. conducted chemical analysis of the water taken from Ali-Sadr cave [55]. The analysis revealed that the major cations in the water are Ca, Mg, − 2− − Na, Si, K and S and the main anions are HCO3 , SO4 and Cl . Water from Ali-Sadr cave is Ca-SO4 type. The data presented in Figure7 shows water discharge quantities at the Garmab spring for two months timespan (August and September). The ratio of flood discharge to baseline discharge reaches a maximum of 3. The discharge of these springs does not change much during rainfall. This means that below the current water table the karst features are not as developed as in the higher parts of the karst aquifer. Different hydrogeological parameters, such as recession coefficients at the surrounding springs, show low karstification of the aquifer. This is in dissonance with well-developed surface geomorphological phenomenon, like caves, shafts and big talars, which implicate higher degree of development of subsurface karst. Figure8 shows XRD results of samples of both presented caves. Both caves are developed in carbonate rocks and determination of dominant mineralogical composition can explain some aspects of cave development. X-ray diffraction allows a distinct differentia- tion between calcite CaCO3 and dolomite (Ca, Mg) CO3. XRD results show that samples taken from both caves have similar mineralogical composition. The dominant mineral in both samples is calcite which shows characteristic peak at 29.4◦ 2θ. Characteristic peak for dolomite is present at 30.9◦ 2θ. Smaller peak between 35◦ and 50◦ 2θ also peaks which originate from diffraction on calcite. Dominant peaks for quartz are at 26.6◦ and 20.8◦ 2θ. The peak area intensities indicate the amount of the present crystalline quartz since amorphous silica adds only to the diffuse scattering, which, is the part of the background noise. The amount of calcite is more than 50% and the amount of dolomite is less than 1% in both rocks. Since calcite has a better solubility than dolomite, higher amount of calcite in rocks makes them more prone to dissolution and karstification under influence of water. The analysis of stone rock sections shows that carbonate rocks around Ali Sadr cave are predominantly made of crystalized calcite and considered a weak marble but the rocks in the Katale-Khor cave are biomicrite wackstones. The limestones of Ali-Sadr cave are impure with many insoluble constituents, which possibly intensify the acidity of the percolating water [45]. Sustainability 2021, 13, 6587 13 of 15

Water absorption percentage and porosity of the rocks in Katale-Khor cave is 3 to 7 times more than water absorption percentage and porosity of the rocks in Ali Sadr cave [47]. This all implicates that Ali Sadr cave is a hypogenic cave while the Katale-Khor cave is epigenic. In comparison to epigene karst systems which form in close interaction with the landscape and have both surface and underground elements, hypogene karst evolves without direct genetic connection with the surface, being initially characterized solely by void-conduit systems at depth [6].

6. Conclusions Underground tourism is a relatively new and exotic form of geotourism. It enables untrained tourists to access before to them totally inaccessible areas of Earth’s interior. If performed correctly and in accordance with principles of sustainability, geotourism is a good candidate for economically balanced tourism. The authors collected information about possibilities for underground geotourism in areas of Zanjan and Hamedan though direct research of the cave characteristics, compared them to existing published data and consequently ﬁlled the gaps in available data [6,51,56]. The Katale-Khor cave is formed in the body of Saqiz-lo Daghi mountain and in the Qom limestones of Oligo-Miocene age. In terms of design and pattern, the cave is of simple and anastomotic type. Ali-Sadr cave is developed in crystallized limestones and Jurassic schists. Ali-Sadr cave is one of the most unique and scenic caves in the world. One of the features that makes Ali-Sadr cave special is a fact that it is the longest and the biggest water cave in the world from the point of the boating course inside the cave. The unique and attractive features of presented caves can make the local area very attractive for development of geotourism. In order to avoid serious and irretrievable damages of the phenomenon, detailed understanding of the phenomenon itself and the local geological conditions must be a priority. Better understanding of geological relations contributes to the establishment of better protective measures, which ultimately reﬂects on a better quality of life of the local population. All the activities should consider the need for sustainable development. Then again, resources should be made available in a such a way so that they serve both the local community and the region’s visitors during the next decades.

Author Contributions: Conceptualization, D.D. and L.P.; methodology, A.A.; software, S.M.S.; validation, A.A., L.P. and B.Ð.; formal analysis, S.M.S.; investigation, D.D.; resources, AA.; data curation, S.M.S.; writing—original draft preparation, A.A.; writing—review and editing, D.D.; visualization, D.D.; supervision, A.A.; project administration, B.Ð. All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Conﬂicts of Interest: The authors declare no conﬂict of interest.

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