in the process of burial, it is possible that siliciclastic deposits may subsequently be uplifted as a result of a mountain building event or erosion. when uplift occurs, it exposes buried deposits to a radically new environment. because the process brings material to or closer to the surface, sediments that undergo uplift are subjected to lower temperatures and pressures as well as slightly acidic rain water. under these conditions, framework grains and cement are again subjected to dissolution and in turn increasing porosity. on the other hand, telogenesis can also change framework grains to clays, thus reducing porosity. these changes are dependent on the specific conditions that the rock is exposed as well as the composition of the rock and pore waters. specific pore waters, can cause the further precipitation of carbonate or silica cements. this process can also encourage the process of oxidation on a variety of iron bearing minerals.