TEXTURE AND MINERAL CHARACTERISTICS OF THE SOILS OF NORTHERN TIKRIT, NORTH OF IRAQ

North of Iraq witnesses alternated continental and marine climatic regimes throughout the year in addition to diverse ways of sediment transportation and deposition. These variabilities affect the soil texture and mineral composition along horizontal and vertical soil profiles. Detailed investigation of the soil textures and mineral composition could provide a better understanding of the soil formation processes in the northern Iraq.

Grain size distribution analysis of 53 soil samples showed that sands represent the main constituent with 55.56% of the studied samples. The silty components represent 35.98% and the clays represent 8.46% of the studied samples. By plotting the results of the grain size distribution analysis on Folk triangle, we noticed that the studied samples can be represented as 41.5% silty sand, 41.5% sandy silt, 13.2% muddy sand and 3.8% sandy mud. In addition, values obtained from the cumulative curves ranged from (2.75 to 6.6Ø) for the median diameter and values of the standard deviation ranged from (1.47 to 3.09Ø), which indicates that all of the sediments are poorly to very poorly sorted. Stewart diagram showed that 70% of the soil sample is lacustrine in origin in addition to 30% of aeolian origin. Furthermore, results of the kurtosis rate showed that 67.9% of the samples have values ranged from (0.58 to 1.09) which indicates very platy kurtic, and meso platy kurtic, and 32.1% of the samples have values ranged from (1.21 to 2.40) which are within the types of lepto kurtic and very lepto kurtic. Results of the kurtosis rate confirm the inhomogeneous source areas of the soil profiles and the multiple processes involved during their formation.

Mineralogical analyses of the very fine sand extract showed that quartz is the most prevailing constituent in addition to gypsum, chert and carbonates in light minerals. Heavy minerals include opaque minerals as prevailing constitute, in addition to chlorite and zircon. This research has implications for understanding the formation processes and origin of the soil in the northern Iraq.