GEOL 102 Lecture 4: Geology102Lecture4Notes
Document Summary
Stratigraphic principles are very useful for figuring out the order in which rock layers were formed, folded, faulted, etc. Most of the geologic time scale was reconstructed this way. A branch of stratigraphy which uses features of rock layers to perform geologic correlations. Steno"s 3 laws, principle of cross-cutting relationships, principle of included. The layering of rocks (from old to new) A branch of stratigraphy which uses fossils to perform geologic correlations. Utilizes index fossils to define biostratigraphic units. Extrusive/ volcanic rocks also often form in layers. Intrusive/ plutonic rocks often follow cracks, voids, or other weakness in pre-existing rocks. Are created when pre-existing rocks are exposed to heat and pressure. Unconformities represent missing time in the rock record. A surface between two bodies of rock formed when. The rock that was there has eroded away. No rock formed during the period of time the surface represents. Occurs between parallel layers of sedimentary rock.
