Principles of relative dating in geology blake lively dating penn 2016
Principal of Superposition: - In an undisturbed sequence of rocks, each layer is younger than the one beneath it and older than the one above it. Faunal Succession: - Fossils as timepieces - Use of index fossils to correlate rocks (formations) from different locations. Unconformities: - Markers of missing time - (deposition of rocks isn’t continuous forever) a) Disconformity: an unconformity in which the rocks above and below the unconformity are parallel.
b) Angular Unconformity: not parallel due to folding and uplifting, erosion then takes part of the rock away, and new layers form on top of the unconformity.
Since we assume all the layers were originally horizontal, then anything that made them not horizontal had to have happened after the fact.
We follow this same idea, with a few variations, when we talk about cross-cutting relationships in rock.
Geologists establish the age of rocks in two ways: numerical dating and relative dating.