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46 SOIL SURVEY
<br /> TABLE 3.Engineering test data for soil samples taken from selected soil profiles-Continued
<br /> Spc-
<br /> Percentage passing sieve'- Liq- Plas-
<br /> Classification
<br /> Soil name and location Depth from cific uid ticity
<br /> surface gray- No. 4 No. 10 No. 40 No. 200 limit index
<br /> ity (4.7 (2.0 (0.42 (0.074 AASHO Unified 9
<br /> mm.) min.) min.) min.)
<br /> Persayo silty clay loam: (Feel)
<br /> 1,000 feet E. and 1,320 feet S. of 1. 0 to 4. 0 2.71 99 98 97 96 46.5 21.9 A-7-6(15)-- CL.
<br /> W?4 corner sec. 23, T. 50 N., R.
<br /> 10 W., New Mex. P.M. (Sample
<br /> No.9A).
<br /> 700 feet E. and 400 feet S. of WY4 1. 0 to 3.5 2.70 96 91 82 64 33. 2 17.7 A-6(8)-____ CL.
<br /> corner sec. 23, T. 50 N. R. 10
<br /> W., New Mex. P.M. (ample
<br /> No. 10A).
<br /> 900 feet N. of WY4 corner sec. 23, 1. 0 to 3.5 2.54 97 94 92 85 39. 5 24. 9 A-6(10)---- CL.
<br /> T. 50 N., R. 10 W., New Mex.
<br /> P. M. (Sample No. 13A).
<br /> 300 feet S. and 1,300 feet W. of 8 to 4. 0 2.79 97 96 94 91 44. 8 21.3 A-7-6(14)__ CL.
<br /> NE. corner sec. 33T: 51 N., R.
<br /> 10 W., New Mex. VM. (Sample
<br /> No. 44A)._
<br /> 120 feet S. and 1,300 feet W. of 8 to 5.0 2.79 91 89 86 83 40.5 23.4 A-7-6(11)__ CL.
<br /> NE. corner sec. 33, T. 51 N., R.
<br /> 10 W., New Mex. P.M. (Sample
<br /> No. 45A).
<br /> Rock outcrop-Travessilla association:
<br /> 700 feet S. of WY4 corner see. 17, 1.0 to 3.0 ------ 100 100 99 93 32. 0 15. 0 A-6(10)_-__ NIL:
<br /> T.49 N., R. 9 W., New Mex.
<br /> P.M. (Test No.84).
<br /> Uncompahgre loam:
<br /> Near EY4 corner sec. 20, T. 51 N., .5 to 3.0 2.67 43 38 27 17 27.0 19.7 A-2-4(0)_-_ GM.
<br /> R. 10 W., New Mex. P.M.
<br /> (Test No. 60).
<br /> I According to Designation: T 88-57, "Mechanical Analysis of Soils," in "Standard Specifications for Highway Materials and
<br /> Methods of Sampling and Testing,"pt. 1,Ed.8(1961),published by AASHO. Results of this procedure may differ somewhat from results
<br /> obtained by the soil survey procedure of the Soil Conservation Service (SCS). In the AASHO procedure, the fine material is analyzed by
<br /> the hydrometer method, and the various grain-size fractions are calculated on the basis of all the material, including that coarser than 2
<br /> millimeters in diameter. In the SCS soil survey procedure, the fine material is analyzed by the pipette method, and the material coarser
<br /> than 2 millimeters in diameter is excluded from calculations of grain-size fractions. The mechanical analysis data used in this table are not
<br /> suitable for naming textural classes for soils.
<br /> 3 SCS and BPR have agreed to consider that all soils having plasticity indexes within two points of the A-line are to be given a border-
<br /> line classification. Examples of borderline classifications obtained by this use are SM-ML and ML-CL.
<br /> 3 NP=Nonplastic.
<br /> Genesis, Morphology, and have been acting upon the parent material. In many
<br /> Classification of Soils places, but not all, the activities of man have modified
<br /> the effect of the five major factors.
<br /> Soil is a natural body having characteristics developed The history of the development of soil characteristics
<br /> as the result of the action, over a period of time, of is called soil genesis. The characteristics themselves are
<br /> dynamic forces in the environment upon parent material. called, collectively, soil morphology. Although much is
<br /> The character of the soil in any landscape differs from known about soil genesis, it is not possible to recon-
<br /> place to place, depending upon the nature and intensity struct the precise history of a soils development from
<br /> of the factors that influenced its development. the data available to a soil scientist. Consequently, the
<br /> natural system of soil classification used in the United
<br /> Factors Affecting Soil Genesis States is based on morphologic features. It is possible
<br /> g to select morphologic features of soils known to result
<br /> Five major factors are influential in the development from ,given processes of soil genesis and, guided by an
<br /> of a soil at any specific location: climate, biological understanding of soil genesis, to use these features as
<br /> forces, time, relief, and parent materials. All of these the basis of a usable form of soil classification.
<br /> factors are highly complex. There are many kinds of The following sections give a general evaluation of
<br /> climate, and nâșany kinds and combinations of biological the factors influential in the development of the soils
<br /> forces. Parent materials vary widely in physical, chemi- of the Delta-Dsontrose Area and of the manner in which
<br /> cal, and mineralogical properties, and there are great the resulting soil morphology has been used to group the
<br /> differences in the length of time that the other factors soils into the units of the classification system.
<br /> 4 Q-F z i
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