چكيده لاتين :
Introduction
Relatively, sandstone rocks display landscape features obviously. Debris on the slopes is one of these landscapes, for example rock fall and rock topple are a kind of triggers for create these landscapes. Debris is characteristics of arid and semi-arid region. Geology and climate are the main mechanisms for generate of debris (Varnes1978). Rocky slopes mainly are formed by processes such as Rock falls. Weathering, gravity, earthquake, joints and temperature fluctuation are another mechanism. (Smith 2015, Alejanoa and et al. 2015, Babiker and et al. 2014, Luckman 2015). To be used Selby (1980) method, in order to determine the affective factor on debris. Also to determining of resistance rocks, Schmidt rebound hardness (SRH) is so practical. So far in the Geomorphology and geology, more than half a century used of SRH in its researches (Demirdag 2009). Type of stone with the porosity due to large differences in landforms (Yang, and et. al 2009), Porosity have occurred by dissolution of calcite cement, grains of feldspar and calcium carbonate sandstones. The increase pores, causing the rupture of the rock-forming particles (Bridge and Demicco, 2008; Khidir, and Catuneanu 2010). In addition to the Selby method, we used of porosity to determine of rock hardness in this paper. The aim of this study is the effect of rock hardness characteristics on generates of debris based on modified Selby method on Agha - Jari sandstone in southwest of Iran (Masjed - Soleyman).
Material and methods
In this study, in order to obtain samples and estimate of SRH, we took samples along eight layers which are named A to H. Samples A1 to A4 were taken from the oldest layer and samples H1 to H4 belonged to the youngest one. Because the thickness of layers varied from place to place, the sampling interval changes from 50 to 150 meters. Landforms geomorphic map of the study area was prepared by Freehand software via using 1:25,000 topographic maps of Iranian National Survey Organization. Geological data, such as lithology and contacts of the Aghajari sandstone layers, were derived from 1: 100,000 geological maps of Geological Survey of Iran. Also we estimate on the field some factors Selby method such as: Width of the joints, the spacing of joints, lateral or vertical continuity of the joints, Orientation of joints with respect to the slopes, State of weathering of the rocks. In following, thin section samples were prepared from fresh rock samples. After preparing thin sections, porosity was determined via point counting by counting 400 points in each sample.
Results
For understanding the effect of each Selby factors with debris, we comparing all factors to amount of debris on each layer, B, C, D and F have the most debris in throughout layers and A layer don’t any debris. Results showed have directly relationship by increasing between SRH and amount of debris with a high correlation (89%). Another factor showed respectively: Width of the joints: non correlation, the spacing of joints: low correlation (21%), weathering: high correlation (87%), lateral or vertical continuity of the joints: high correlation (83%), Orientation of joints with respect to the slopes: almost high correlation (63%) and porosity with mid correlation (56%).
Conclusion
Aghajari sandstone formation, due to the high percentage carbonate cement and grains, high porosity in some layers, folds in some of the layers and climate processes, have a unique landform such as kinds of debris slope. There are various sizes of debris across the layers of folded. The extent and size of debris in some of the layers is significant. Selby table parameters are appropriate indicator to measure the extent of this parameter. Results this paper showed respectively high relationship between debris and Schmidt rebound hardness (SRH), weathering and lateral or vertical continuity of the joints and low relationship between the spacing of joints and non-relationship between widths of the joints. Porosity and Orientation of joints with respect to the slopes have mid relationship with debris. Also A layer (the oldest layer) is weakest layer in through layers. B, C, D, E, G, F layers are resistances and H layer (the youngest) is mid hardness. Respectively Schmidt hammer hardness, weathering and continuity of joint, has the greatest impact on the creation of debris in Aghajary formation.
