Abstract

It is known that soils are broadly classified as (i) sedentary or in situ soils and (ii) drift or transported soils. The sedentary soils are distinguished by (1) the absence of any clear contact between the underlying bed and the top soil and (2) the existence of the fragments of the parent weathered rock mingled with the soil itself, as can be detected by the naked eye. A third test may be found in the close microscope. resemblance of the sandy fraction of the soil with the mineral constituents of the subjacent weathered rock, when examined under a petrological In the case of transported soils a clear distinct contact is seen between the soil and the subjacent geological formation. This contact by itself should in most cases be sufficient to decide the nature of the soil. It is needless to say that the other two conditions mentioned for sedentary soils. are absent. in this case. In addition all the circumstances which prove an unconformity between two geological sedimentary beds (e.g. change of fossils, denuded surface, change in the angle of dip) go to show the trans- ported nature of the soil.

Keywords: