The gilsonite outcrops of Gilangarb natural bitumen mines in Kermanshah province include three main groups:
1- Outputs that are being extracted or have already been extracted from them.
2- Protrusions that are widely exposed and can be identified.
3- Outgrowths that are very detailed and little outcrops, but the existing evidences and works prove that they are rooted.
Wherever these outcrops are exposed to sunlight for a long time, due to evaporation and volatility of hydrocarbon substances, weathered surfaces are seen in pea color.
And while weathered surfaces that are not exposed to direct sunlight are seen in gray colors or shades of gray.
Therefore, in the search for natural bitumen on the surface of the earth, the depth of weathering in rocks that are exposed to direct sunlight is taken into consideration.
In general, Gilsonite outcrops of natural bitumen mines in Gilangrab are relatively abundant in Gilangrab region.
And in any place where the conditions are suitable in terms of geology and topography, there is a possibility of outcropping of natural bitumen.
Although it seems that in addition to that, there are also a number of Andes that are not yet possible to emerge, or in other words, have not yet reached the surface of the earth.
The pattern of Gilsonite outcrops characteristic of natural bitumen mines in Gilangarb region shows that natural bitumen outcrops are under the influence or control of tectonic and stratigraphic factors.
In this range, on the levels of discontinuities, permeable layers of natural bitumen are usually folded, normal and inverted faults are seen.
The presence of natural bitumen in Qasrshirin and Gilangarb can be explained using plate tectonics.
Because this area is affected by the Arabian and Eurasian plates on the one hand, and on the other hand, it exists on the border of these plates.
In these tectonic conditions, which are caused by faults and joints, oil and gas move upwards from reservoirs.
Of course, we should pay attention to this point, the characteristic of natural bitumen mines in which Gilsonite is observed is more effective than small oil traps and natural bitumens.
which are mostly shallow, under the influence of construction activities, they manage to reach the surface of the earth.
In this way, the natural bitumen deposits in the West Gilan region and in the so-called Shak Maidan area and the West Gilan River are located in empty spaces and cracks due to the escape of petroleum materials and the settling of semi-solid and pasty petroleum materials.
Gilsonite is stored in gypsum and marl masses of Gachsaran Formation.
These natural bitumen deposits, the main feature of the natural bitumen mines of Gilan Gharb, are seen in the form of lens-shaped masses with thicknesses from a few centimeters to even 15 meters.
Some other natural bitumen deposits can be seen in Shek Maidan area in the form of streaks with different thicknesses and 20 meters long.