water infiltration

Hi, I'm confused about what it says in the lab manual lab 1 section 2: 'On campus, the uppermost part of the parent material often consists of glacial till... Till deposits are the main source of inorganic particles in the surface mineral horizons of the campus soils. Since most of the particles in these deposits were relatively large (gravel and sand), most of the inorganic particles in the soils are also large, and the soils are coarse in texture. The pores between these relatively large particles are also large, and consequently soil horizons formed from these materials, unless cemented, are very permeable to air, water, and roots.' But then says: 'Many of the parent materials found on campus have very low permeability and water tends to accumulate and move laterally above them.' Is it just that both kinds are found, or a difference between higher and lower in the horizon?

Well there are two types of glacial till - ablation till (which is loose material comprised of particles of various sizes) and basal till (which is cemented, hard and of low permeability for water). And both types happen to be present on our UBC campus. When both types are present, ablation till is on the top of the basal till.