Karst in Rila-Rhodopean Area

by Alexey Benderev in:

Caves and Speleology in Bulgaria

P Beron, T Daaliev, A Jalov

Publisher: Pensoft Publishers, BFS & NMNH

Publication date: 2006

Northern Pirin

Northern Pirin is the major part of the so-called Vihren-Sinanitsa Karst Region (Popov, 1976, Lichkov, Delchev, 2002). It is situated along the main ridge of the mountain and north of it, between the huts Vihren and Yavorov. The relief is typically mountainous, of alpine type, forming a central ridge with high summits, narrow ridges, deep valleys, above which summits over 2500 m high are situated. The first summit from east to west is Vihren (2914 m), followed by Kutelo I (2908 m) and Kutelo ІІ (2807 m), Banski Suhodol (2284 m), Bayuvi Dupki (2820 m) Каmenititsa (2726 m), Razlozhki Suhodol (2688 m). For the relief formation , the glaciations in Riss and Wurm were also important. During these glaciations the typical trog valleys and circuses were shaped. Because of the absence of water, they have got the local name of Suhodol (Dry valley). From SE to NW they are called Kazanite, Kutelo, Banski Suhodol, Bayuvi Dupki, Kamenititsa and Razlozhki Suhodol. In the upper parts of all of them relatively levelled areas, called “rigels” are formed, alternating with steeper sections. The valleys, starting from these circuses, descend towards Razlog Kettle, having an altitude of ca. 850-900 m.

The climate in the higher parts of Pirin is typically mountainous, while in the foothills (Razlog) it is of submediterranean influence. Precipitation, snow cover and the temperature have considerable influence on the formation of caves. Because of the considerable difference in the altitude, their values change very fast, the precipitation changing from 657 mm/a in Bansko to ca.1200 and more mm/a in the highest parts of the mountain. The considerable snowfall in the higher parts of the mountain and the long period of negative temperature contribute to the accumulation of a thick snow cover and to its slow melting in the spring. The perpetual snow formed by it remain up to early fall and serve as a source of very aggressive water, which also contributes to the karstification.

Along the main ridge of Pirin the water divide between the rivers Struma and Mesta goes. The karstic part is situated mostly in the water-collecting basin of the Mesta River and in it there are almost no surface waters. Almost the entire amount of rainwater, falling in this region, is immediately lost, re-appearing afterwards in the base area of the mountain as sources. Some rivers like Banderitsa and Bela Reka, starting outside this region, lose part of their water as soon as they reach the marble area. In the summer and autumn, smaller streams and rivers form out of the perpetual snow and are soon lost in some crevice or karstic form.

The karstic sector of Northern Pirin is build of Proterozoan age marble, massif or in bands, with muscovite-biotite and biotite gneiss, shists and amphibolites. In the contact areas with granites recrystalization and  skarn formation are observed, which is the result of contact-metasomatic processes. To the west, the boundary of the suitee can be followed between the summit Okaden and Yavorov Hut, it runs east of Butin Summit, then south of the main ridge of the mountain to the south to Vihren Peak, then turns NE, crossing the valleys of the rivers Banderitsa and Damyanitsa and goes further towards Bansko Town. The northern boundary is a tectonic one and runs at the base of the steeper part of the mountain slopes. In this part also relatively recent and karstified marble breccias are widespread. These boundaries determine the surface taken by the karst. The thickness of the suitee reaches 1000 m. The marble are bedding steeply to the northeast. Its situation is controlled by the tectonic frame. The main structure here is the Pirin Horst-Anticlynorium, the karstified rock having taken its northern part. It is separated from the Razlog Graben through Predel Zone of faulting. The marble is additionally broken up and fissured.

Considering the underground water, here a karstic basin of monoclyne type is formed.

The underground water is formed in the marble of Dobrostan Suitee, which is broken up in blocks and is considerably karstified. The gneiss of the Lukovishka Suitee serve as водоупор. To the south and south-east, the marble is in contact with Upper Cretaceous and Paleogenous intrusive rocks with fissure water in them. Northwards, the marble is covered with proluvial deposits in the outskirts of Pirin Mt. Underneath in the area of the sources, draining the basin, is the tectonic contact of the marble with the relatively water-resistant Pliocene material, filling the Razlog graben. The feeding of karstic underground water is done through rainfall. The amount of precipitation here is rather high, due to the high mountainous type of relief. Besides rainwater, karstic underground water is fed also through the river outflow, formed in the area of non-carbonate rocks. This is done in the peripheral sectors of the basin. In the western part, these are mainly the waters of Bela Reka river, in the eastern part – the water of Banderitsa River. Unconfined karstic flow, formed in the basin, moves from south to north – northwest, towards Razlog Kettle, surfacing along several parallel faults or through the proluvium. The impregnable barrier of Pliocene material pre- destine  barraging of the karstic ground waters and presence of a saturated (phreatic) zone in the basin. The biggest karstic sources, draining the basin, are: Yazo with an outflow of 440 to 2750 l/s, Кyoshka (15-2770 l/s) and Каlugeritsa (43-386 l/s). The maximum of the water quantities is at the beginning of the summer period (June – July), when intensive melting of the snow cover in the higher part of the mountain takes place, as well as in the rainy period of the year. The minimum of the water quantities is in February - April, most often in April, when considerable part of the catchment area of the source is frozen and the snow cover is not melted and the feeding of the underground waters has practically stopped.

The karstification of marble is considerable. It is defined by the high degree of tectonic and weathering fissurization. In the circuses, series of funnels are formed, usually distributed in lines along faults. Most of them are filled with rock blocks and angular gravel, while in some others there are fillings of firned snow and ice – the so called snow ploughs. Only few of them are opened and are followed by potholes. The tectonic crevices are widespread and karstified in different degree. The major negative surface karst forms are Golemiyat (the Big) and Malkiyat (the Small) Kazan under the summit Vihren. Because of the intense weathering processes typical karrens are almost missing. Along the edges of karstified fissures and potholes there are rillenkarrens. The high degree of karstification, especially in the peneplenized sectors above the rigels, contributes to the outflow of the rainwater in the depth, as well as the water of perpetual snows, melting in spring and summer. There are almost reduced to streams running on the surface for more than 100 m. Even the water of Banderitsa River disappears when the river enters the marble part.

For Northern Pirin, the potholes are typical, due to the considerable difference between the zone of sinking (usually at an altitude of 2000 to 2400 m and higher) and the sources (at ca. 900 m), horizontally, the potholes being rather close to each other – up to 5-6 km. This is also the reason for hoping to discover in Pirin the deepest potholes in Bulgaria - over 1000 m. Until the end of 2003, in Northern Pirin more than 120 potholes and caves have been discovered.

 

Some important potholes and caves in Northern Pirin

Name

Site

Depth, m

Length, m

1

System 9 –11

Banski Suhodol

- 225

311

2

Vihren

Vihren

- 170

396

3

Banderitsa

Banderitsa

- 125

243

4

К-18 Ledenata

Circus Kamenititsa

- 126

 

5

20 Godini Akademik

Circus Banski Suhodol

- 118

80

6

К-19

Circus Kamenititsa

- 118

 

7

Chelyustnitsa

Circus Bayuvi Dupki

- 107?

 

8

№14

Circus Kamenititsa

- 103

 

9

Spropadnaloto

Razlog

- 5

605

 

For most potholes, the presence of moving blockage and squeezes is typical, making it difficult to penetrate deeper. In some potholes (Vihrenskata Propast, Propast No9 – Banski Suhodol) there is permanent ice. One typical water pothole, containing waterfalls and ending in a siphon, is Banderitsa.

The biggest horizontal cave in the area – Spropadnaloto – is situated in the outskirts of the mountain, above the sources. In this cave part of the water, appearing in the resurgences, was followed. There are macadam roads to Vihren Hut and Yavorov Hut, situated along the periphery of the karstic region. An official authorization is needed to camp in the karstic region, as it is within the boundaries of Pirin National Park and the circus Bayuvi Dupki and the adjacent areas are within a Biosphere Reserve.

Rhodopes

Dobrostan Karstic Massif

The Dobrostan Karstic Massif is situated in the northernmost parts of the Rhodopes, bordering the Upper Thracian Lowland. It is a karstic region, outlined by Popov (1976). It is separated from the Prespa part of the Rhodopes by the locality Inkaya (Yanev & Popov, 1980). On the west it is limited by Chepelarska River and by the lower parts of Yugovska River, on the south – by the steep valley of Mostovska Sushitsa River, on the east – by Topolova River and the pass Topolovski, and to the north its ridges descend to the Upper Thracian Lowland. The southern part of the massif rises, plateau-like, with an average altitude of ca. 1300 m. Here, the highest summits in the region are found – Stariya Kladenets (1517 m) and Chervenata Stena (1504 m). In the south, west and north, steep slopes are formed, complicated by valleys, descending towards the rivers and the Thracian Lowland. The climate in the higher part is mountainous, with sharp daily fluctuations of temperature and an average amount of precipitation above 800 mm/a.

The Dobrostan Massif is built almost entirely by Precambrian metamorphic rocks from the so-called Rhodopean Supergroup. The massive and layered marbles of Dobrostan suite, which is of the biggest spreading, are subject to karstification. Their thickness is over 1600 m, in some places containing thin layers of various schists, gneiss and amphibolites. Under the marble, gneiss and schists of the Lukovishka suite lie. Tectonically, the region forms the eastern ending (periclyne) of the Northrhodopean Antycline, that is why the marble formations are inclined to 30-50° NE and SE. In NE, through a series of faults, coinciding with the base of the Rhodopean Mts., the Dobrostan massif is separated from the Upper Thracian Graben, filled with nonbound Pliocene and Quaternary materials. Several faults run through the massif as well, roughly directed to west-east. The karst waters in the marble are formed mainly by rainfall and temporary surface water, disappearing in the higher peneplenized and karstified parts of the massif. Occurring underground, they form underground streams, surfacing along the periphery of the massif in sources (Тroshanov, 1992). The biggest source – Chetiridesette Izvora (The 40 Sources) – is situated in the lowest part of the region, at the base of the Rhodopean slopes, and is determined by the contact of marble with the terrigenous sediments, filling the Upper Thracian Graben. Its outflow varies from 105 to 1439 l/s. Some other major sources are Varite (30- 50 l/s ) near Моstovo Village, Кluviyata (average 30 l/s) above Bachkovo Monastery, Каptazha (6-456 l/s), Маykite (about 5 l/s) near Oreshets Village and others.

The surface karstic forms have developed mainly in the higher plateau-like part. They are represented by many dolines and valogs. There are also several blind valleys. Because of the soil layer, karren and karren fields are absent or rarely met. The river Sushitsa, delimitating the Dobrostan massif from the south, has formed a picturesque canyon-like valley. Near the village Моstovo, the river forms a natural rock bridge, from which the name of the village comes.

The Dobrostan massif is rich in caves and potholes – ca. 90 of them (Pandev, 1993, 1994). Most of them, including the deepest, are situated in its higher part.

 

Major caves and potholes in Dobrostan Massif and the adjacent territories in the south

Cave

Site

Length, m

Denivelation, m

1

Topchika

Dobrostan Village

727

 61

2

Ivanova Voda

Dobrostan Village

695

113

3

Gargina Dupka (Garvanitsa)

Mostovo Village

524

+38

4

Vodnata Peshtera

Mostovo Village

450

53

5

Hralupa

Dobrostan Village

311

10

6

Zmiin Borun

v. Mostovo

242

+22 – 86

7

Ahmetyova Dupka

v. Dobrostan

44

 14

9

Druzhba

v. Dobrostan

 

130

 

From the caves indicated the pothole Druzhba, with the biggest cave vertical in Bulgaria, is of particular interest. The cave Ahmetyova Dupka is a show cave, while in the cave Topchika interesting archaeological items and new species of animals have been found.

Most of the bigger caves are situated near Martsiganitsa Hut, which is connected to Dobrostan Village through an asphalt road and further to Assenovgrad. Another hut in the area is Bezovo, situated in the northern part of the massif. Assenovgrad is the exit/staring point for it. Some caves can be reached starting from the village Mostovo.

Within this karstic region Chervenata Stena reserve is situated.

 

Trigrad Region

The karstic region of Trigrad is one of the most extensive in the Rhodopes. It is situated in the upper part of the basin of Vâcha river and its tributaries. In the inter-river basins, the higher parts have plateau – like relief. The river valleys are canyon-like, with steep rocky slopes.

In this part of the Rhodopes , mostly metamorphic and magma rocks are represented. In terms of karstification, most important are the marble rocks, which are widespread and thick up to 1600 m. They lie on gneiss and schists of Paleosoic age. In the western part on the marble, there is riolith from the effusion of the Oligocene. The whole rock complex contains granite bodies of different size, transient to the west into the pluton of Barutin-Buynovo.

Tectonically, the region falls within the South Rhodopean Syncline. On the north, it is limited by the fault of Shiroka Laka, the southern block of which has subsided by about 5000 m. The syncline is a big graben, complicated by many faults and other smaller structures, mainly of northwest – southeast direction (the direction of the Shiroka Lâka fault). Some graben-like low places exist, filled by lakes from the Paleogene and by aluvium – proluvium deposits.

Тrigrad Region is characterized by rainfall, which changes, according to altitude, from 692 to 1394 mm (average 953 mm – a value higher than the average for Bulgaria). In the marble terrains, one part of the rainfall drains superficially and takes part in the formation of the river outflow, while the bigger part infiltrates various karstic forms and replenishes the reserve of ground water. Besides, the rivers, which start outside the marble outcrops (Buynovska, Тrigradska, Chairska, Мuglenska – they all form Krichim River), enter karstified rocks and start losing water in sinks along the riverbeds. The most typical are the sinks of Muglenska River, where the entire outflow disappears. Entering underground, the water starts moving towards the sources (situated most often in tectonic faults), ponding of underground waters. The biggest karstic sources in the region are situated in the valleys of the rivers Кrichim and Shirokolashka, near the villages Nastan and Beden. These are the lowest points of marble outcrop on the surface. Its place is determined by the contact between marble and the Proterosoan non-karstified rocks. These rocks serve as a threshold, behind which a large saturated zone is formed. Here, the largest karstic sources (near the villages Nastan and Teshel, the source Vrissa near Beden and other sources near Shirokolashka River) are situated. There are also sources along Krichim River and its tributaries. They are situated at river level. The more important among them are the sources at Mugla Village, along Chairska River, the sources Каynatsite, situated along Buynovska River.

The varied geological structure has a considerable impact on the relief morphology in the region. Among the karstic formations worth noting are the karren and karren fields,  dolines, valogs and the karstic dolins/valleys (dry, blind and gorges). Around the villages Yagodina, Тrigrad, Zhrebevo and Chamla, typical uvalas are also formed. Here are the most picturesque karstic gorges in Bulgaria – these of Trigrad and Buynovo. The considerable vertical fragmentation of the relief and the presence of deep erosion base are the causes for some of the deepest potholes in the Rhodopes to have developed in Trigrad region. A total of over 85 caves and potholes have been recorded in the region, part of them quite sizeable.

Some important caves in Trigrad region

N

Name

Locality (village, area)

Length, m

Deniv., m

1

Yagodinskata Peshtera

Yagodina Village

8501

 60

2

Lednitsata

Gela Village

1419

 108

3

Izvora

Orpheus Hut

2480

 

4

Drangaleshkata

Mugla Village

1142

 255

5

Каmbankite

Chamla Village

 

 158

6

Dyavolskoto Gârlo

Trigrad Village

300

 85

7

Partizanskata

Orphey Hut

206

 80

8

Sanchova Dupka

Yagodina Village

888

 12

9

Haramiyskata

Trigrad Village

495

 48

 

Two of them are show caves and, together with the gorges in which they are situated, are particularly interesting for tourists. The pothole Dyavolskoto Gârlo is very impressive with its entrance 40-meter waterfall (the entire Trigrad River enters it, re-emerging some distance lower) and with its voluminous chambers. Nearby, the cave Haramiyska is situated (actually two caves, connected by 36 m vertical). Some of the caves of Trigrad Region contain important archaeological and paleontological sites.

The important settlements in Trigrad basin, except for Yagodina Village and Chamla Quarter, are situated in the river valleys.

The picturesque and almost virgin nature of Trigrad basin makes it attractive for tourism, together with the several mountain huts and hotels in Trigrad.

 

 

Caves on the territory of Smolyan municipality

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Caves on the territory of Smolyan municipality