Whatever caused this igneous intrusion occurred after the strata formed. The principle of superposition builds on the principle of original horizontality. These foreign bodies are picked up as magma or lava flowsand are incorporated, later to cool in the matrix. Thus, carbon has three isotopes: Keywords Keywords for this Article. Brongniart was the first to use fossils to date rock strata.
For instance, coarser grained sediments such as sand may be deposited at angles of up to 15 degrees, held up by the internal friction between grains which prevents them slumping to a lower angle without additional reworking or effort.
Physical Geology: Accumulating Glitches. Therefore, the piece, or inclusion, must be older than the material it is included in.