A Study on the Sensivity of Geological Formations to Erosion in the Maharlou Basin

Maharlu basin with an area of 4274 km2 is located in Fars province. The Precambrian Hormoz series and the Quaternary units are the oldest and youngest rocks in the basin, respectively. Spans of outcropped rocks, covering from the Cretaceous to Quaternary, are carbonate sediments of deep to shallow marine facies. These sedimentary sequences include large and small stratigraphic gaps in the form of disconformity and sometimes nonconformity. More than 50% of the basin area is covered by the Quaternary sediments. The region is mainly composed of sedimentary deposits. Six factors of rock unit weathering: rock resistance, weathering condition, fissure and joints, slope, climatic conditions and vegetation covering are the main factors for estimation the sensitiveness of geological formation to weathering resulted from laboratory and field tests.‍‍ 12 formations Cropped out in the basin. To evaluate erodibility, BLM method is used to measure the weathering sensitivity of soft geological formations. The acquired data and the formations with their sensitivity to weathering are combined into GSI and finally the map of sensitivity of different geological formations to weathering of Maharlu basin was prepared. The data resulted from laboratory and field tests indicate that Asmari-Jahrum formation and the Quaternary alluvial fan possess lesser sensitivity and higher resistance to erosion and Hormoz series, Pabdeh-Gurpi formation, Razak formation and Aghajari formation are critical to weathering. Bakhtyari formation, Bangestan formation, Tarbur formation, Sachoun formation, and young and old Quaternary deposits can be placed in group of moderate to weathering.