Lithological properties and environmental importance of the Quaternary colluviums (Muğla, SW Turkey)

The colluviums are one of the common Quaternary deposits of the SW Turkey grabens. The protection of the colluviums is important for agriculture, ecology and safety of constructions. This study concentrates on the sedimentary properties of colluviums and environmental issues relating to them. The colluviums of the Muğla crop out in the northern-normal faulted margin of the Muğla Polje. These colluviums form wedge-shaped and narrow small strips (total 6 km in length, 250–300 m in width and 20 m thick), and contain four main facies delineated with respect to the field observations. These facies are A-Boulder facies, B-Cobble facies (gravel ≥94 % including cobble 10–46 %; mud + sand <6 %), C-Granule–pebble facies (gravel 83–94 %; mud + sand 6–17 %), and D-Fine-grained facies (matrix dominated; gravel <83 %; mud + sand >17 %). Three representative sections were measured and 14 sieve analyses were made during this study. These colluviums include poorly to very poorly sorted angular limestone fragments bearing breccia. The colluviums are underlain by crystallized Liassic limestone and laterally passing into the alluvial sediments in a downdip direction. Tectonic activity, climate, gravitational forces and host rock characteristics are the primary controlling factors in the development of colluviums in Muğla. Agriculturally fertile soil derived from colluviums has decreased due to new residential areas and road construction. Moreover, excavations due to urbanization are causing many stability problems (landslides, debris flows, and rock fall–slides). The heavy rainfall and seismicity of the area increase the effects of these stability problems.