زمین گاه‌نگاری پیدایش اشکال ژئومورفولوژی در قلمروهای کوهستانی به روش سازندی - ساختاری (مطالعه موردی: غار کرفتو، استان کردستان)

Given the unique characteristics of the Karaftou cave, it appears that it can serve as a suitable case study for understanding the karstification process and its influence by geological conditions. This research can achieve two objectives: first, to identify the geological processes involved in the formation and extent of the Karaftou cave, and second, to allow for the dating and determination of the period of its formation concerning geological eras and epochs in history of the Earth. Geological evidences include the presence of major and minor faults within the Karaftou cave, the performance of the fault in the wall of the outer and inner spaces of cave and the development of its natural indicates that the cave is in structural form and relevant with semi fault function that existing in that place. Cutting of upper units of the Qom Formation by mentioned network fault and its discontinuity in Plio-Quaternery units has made it possible to chronology and dating it with the “Comparative Method" or "Formation-structural Method". Since the network of the mentioned fault cuts off the last limestone unit of the Qom Formation and does not continue in the Pleiocene-Quaternary units, it seems that their active age is related to the impact of the Oligocene orogenic phase at the beginning of the Middle Miocene and the Langhian stage. As a result, the main process of cave formation likely began after these events, so the maximum age of cave formation can be attributed to this period, and on the other hand, its minimum age can be assigned to the early Pleiocene.
 
Extended Abstract
 
Introduction
The formation mechanism of caves or developed karst cavities in limestone rocks is generally based on two geological processes: first, the formation of fault caves (structural caves), where water infiltration and dissolution expand through the main fault surfaces and fracture networks cutting across rock bedding; second, the formation of interlayer caves (stratified caves), in which water infiltration and karstification progress through meteoric waters penetrating stratigraphic surfaces or limestone bedding. A less common third process, known as hypogenic cave formation, results from the ascent and activity of deep hydrothermal waters, with Ali-Sadr Cave in Hamedan as a notable example. Considering the complexity of natural environments, a combination of these processes can influence cave development. For instance, in Khasheh Tarash Cave in Isfahan, tectonics is the primary factor in cave formation, while subsequent architecture results from dissolution processes, leading to the creation of multiple passages and halls. Karstification or dissolution of carbonate rock units is widespread across Iran; in the northeastern Kurdistan Province, between Divandarreh and Takab, thick to massive limestone layers of the upper Qom Formation on the western margin of the Central Iran zone have created favorable conditions for cave formation. with Karaftou Cave as a prominent example. Accordingly, the main research questions of this study are: (1) from a geological standpoint, is Karaftou Cave a stratified or structural cave? (2) What role has the regional fault network played in the formation of Karaftou Cave? and (3) What is the geochronology of Karaftou Cave’s formation?
 
Methodology
The present study is based on the integration of two methods: 1) field investigations and 2) theoretical studies. In the first stage, based on fieldwork, the internal space of Karaftou Cave, including the main corridor and its subsidiary branches, was examined, and the evidence of existing geological processes within the cave was studied. Then, the external and surrounding environment of the cave was considered, including: a) the main entrance wall of the cave and its lateral extensions, and b) the exposed geological layers and formations of the region, which encompass the cave and adjacent villages. In the second stage, by combining previous geological maps and reports of the area with field observations, the functioning of the geological phenomena under study was analyzed.
 
Results and Discussion
Geological evidence, including the presence of major and minor faults within the Karaftou Cave area, fault-related features on the outer cliff walls and inside the cave, and the natural development patterns of the cave, indicate that this cave is structural in nature and linked to the activity of the local fault network. The disruption of the upper units of the Qom Formation by this fault network, along with its absence in the Plio-Quaternary units, allows for relative dating or “stratigraphic-structural” dating. Since the fault network cuts through the upper limestone units of the Qom Formation but does not continue into the Pliocene-Quaternary units, it is likely that its activity dates back to the strain phase of mountain building at the beginning of the Middle Miocene and the Langhian stage. Therefore, the main process of cave formation likely began after these fault activities, placing the maximum age of cave formation in this time interval, while the minimum age can be assigned to the early Pliocene.
 
Conclusion
Field investigations and observations of the speleogenesis process within the main passage of Karaftou Cave indicate that water infiltration occurred from above through the main fault plane and its subsidiary branches on both sides. This has led to the longitudinal expansion of the cave space, the development of lateral chambers connected to these branches, and severe fracturing of the limestone walls in many areas of the Oligo-Miocene limestone unit (unit F) of the Qom Formation. In other words, a dense fault network, as a continuation of the regional faults adjacent to the overall cave area, has disrupted the upper limestone and marl units of the Qom Formation in the Se-Khaharan Mountains and the cave walls of Karaftou. These faults generally trend northeast–southwest, aligning with the main axis of the cave. However, since the overlying sedimentary units of Pliocene-Quaternary age are unaffected by these faults, it appears that the fault activity dates back to the strain phase of mountain building in the early Middle Miocene during the Langhian stage. The primary cave formation process likely began after these fault events, roughly between the Middle Miocene and the Late Miocene, with a relative age range of approximately 15 to 5 million years ago.
One of the most significant limitations of the present study is the difficulty of applying absolute dating methods within the sedimentary deposits related to the cave and on the structural forms associated with it, particularly the early-formed speleothems, which could play an important role in refining the timing of the onset of cave formation in Karaftou. Considering this limitation, along with the field observations made within the Karaftou Cave area and a review of existing literature and satellite imagery, it appears that a more comprehensive understanding of the cave formation mechanisms requires further detailed studies.