عنوان مقاله [English]
Caves are suitable places for recognizing the inner layers of the earth in which tectonic activities of the earth can be observed. Regarding the origin of the caves, the prevailing view has been the superiority of the role of dissolving the rocks.
Materials and Methods:
Books, articles, reports, geological maps, aerial photographs and satellite images for basic studies were used. The research method was based on field research, extent library, direct observation and measurement. GPS was used to obtain the mathematical coordinates of the mouth of caves, relative position and the route map. From VNIR images of ASTER sensor of TERRA satellite, which has a suitable spatial resolution of 15 meters and has Geology and Landuse-Landcover applications for discovering the relationship of caves with fault tectonics, identifying and detection of faults were used; From remote sensing techniques, image enhancement such as using Edgesenh Linear filter and Stretching by Histogram Equalization method were used. The compass was used to measurement the slope and extension of layers and faults, fold hinge, axial plate effect as well as orientation inside caves. From laser meter for estimate the distance and dimensions was used. A water test tube was used for water sampling. Plastic with zippers was used to place samples of stones, skeletons, fossils, etc. A questionnaire, checklist and identity card were used to record the characteristics of each cave. In addition, the wireless device was used to find team members, express the situation and inform each other.
Findings and discussion:
Considering the researchers opinions and concurrences, this section has been analyzed and discussed in three dimensions:
A) Sedimentary-structural features: Field studies, interpretation of geological maps and existing formations of each of the caves showed that North Khorasan in terms of sedimentary-structural features in the two zones of Kopet-dagh-Hezarmasjed and Aladagh-Binalood (Eastern Alborz) has expanded; The largest area is related to the Kopet-dagh-Hezarmasjed zone in the northern half of the province. That Kopet-dagh mountain range corresponds to Kopet-dagh-Hezarmasjed zone and Aladagh mountain range corresponds to Aladagh-Binalood zone. These two mountain ranges, despite the similarity in the construction process, have undergone different geological evolution. Most of the caves of this province (Bidak, Yayjat, Poostinduz, Kafar ghaleh, Ostad and Konehgarm) have been formed and developed in a clear orbitolithic calcareous formation called Tirgan (Ktr). From this perspective, limestone and dolomitic limestone called Lar Formation in Binalood zone (Eastern Alborz) (Jl) is in the second place and Armadloo, Kaftarak, Siahkhaneh and Gesk caves have been formed and developed in this formation. Gomnamane-Salug and Ganjkooh caves have also developed in light to pink limestone and dolomitic limestone called Mozdoran Formation in Kopet-dagh zone (JKmz).
B) Structural features: Structural evidences such as marbled rocks, fragmentation, displacement and discontinuity in the vicinity of the fault plane, possession of aragonite mineral, evidences of occurrence of major slope-slip, strike-slip ,combined faults and slip on the bedding plane, etc., indicate the superiority of the role of fault tectonics in caves formation and development. The Yayjat, Armadloo, Kafar ghaleh, Ostad, Siahkhaneh, Gesk and Noshirvan caves, due to normal slippery fault, The Khazinehrah, Kaftark and Ganjkooh caves, due to slippery fault, Poostinduz cave, due to reverse slippery fault and faulting on the bedding plane, Bidak cave, due to oblique thrust fault, Gomnamane-Salug cave, due to reverse fault and Noshirvan cave, due to thrust fault have been formed.
C) Morphogenetics and the role of tectonics in the formation of caves: North Khorasan province caves by one of the six mechanisms were evolved.
1. The Bidak, Gomnamane-Salug, Armadloo and Gesk caves have been formed due to fault tectonics and dissolution with fault superiority.
2. The Kaftarak and Ganjkooh caves were formed due to fault tectonics and dissolution with dissolution superiority.
3. The Yayjat and Ostad caves were created due to faulting and fault surface opening.
4. The Poostinduz and Konehgarm caves have been formed due to flexural-slip folding.
5. In the formation of the initial and final forms of Kafar ghaleh cave, the tectonic in the form of uplifting and neutral-surface folding mechanism has played a major role.
6. The Khazinehrah cave due to the dissolution of evaporative sediments along the joint system and microfaults has evolved.
7. The caves of Siahkhaneh and Noshirvan have natural and handmade origin.
8. The caves of Honameh and Babaghodrat are considered handmade.
In the formation and development of caves in North Khorasan province, seven factors Included: fault tectonics and dissolution with faulting superiority, fault tectonics and dissolution with dissolution superiority, faulting and fault surface opening, flexural-slip folding, neutral-surface folding and uplifting, dissolution along the joint system and micro-faults, natural and human and purely human factors have been effective, But the role of fault tectonics has a special advantage over dissolution.
Examination of cross section and profile of caves showed that in each cave where tectonic processes and faults have played a major role in its formation and development, its profile is irregular and has a classification.
Existing studies have shown that the terms cave and karst are not equal to each other due to their nature and how they are formed and developed, and there is a difference between them and not necessarily every cave is karst.
Due to the climatic conditions of North Khorasan region and the relative limitation of rainfall, many limestones do not have karst features and what is seen today as karst phenomena in this area, Except in a few cases, they are the result of Quaternary rainy periods.
Due to the tectonic origin of most caves in North Khorasan province, they can be used as indicators and Neotectonic evidence in the region.
Due to the high potential for falling, Konehgarm cave is considered as 1st degree with no access and Kafar ghaleh cave is 2nd degree with limited access.
Field studies and subsequent reviews indicate the large number of caves in North Khorasan province, which due to time, financial and technical constraints, only 16 caves were carefully studied and it is better to study the others at a more appropriate time.